Improvements in the Manufacture of Photographic Sensitized Materials.
Year: 1899

page_text: Date of Application, 17th Mar., 1899
Complete Specification Left, 9th Dec., 1899-Accepted, 3rd Feb., 1900
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Photographic Sensitized
Materials.
I, Jous EDWARD THORNTON, Rokeby, Oldfield Road, Altrincham, in the County
of Chester, Manufacturer, do hereby declare the nature of this invention to be as
follows:-
The object of this invention is to provide improved methods of manufacture of
photographic sensitized materials such as films, papers, and plates, and relates
more particularly to the process of coating same with the sensitizing material.
Sensitizing materials of various kinds are used according to the desired result,
but a gelatino-bromide or gelatino-chloride emulsion is most frequently used,
and therefore in describing this invention I hereinafter adopt the term emul-
sion" as sufficiently descriptive of any sensitizing material.
Similarly, various supports are used for the emulsion, such as celluloid or other
films, papers, glass plates, sheet metal, cardboard, and the like. Hereinafter
I use the term support to include any support.
"
In the manufacture of sensitized materials as hitherio carried out, it is the
custom to coat the support with a coating of emulsion of the requisite thickness
at one operation (by machine or hand): then to allow the coating to "set," which
process is often accelerated by passing the coated support into a chilling chamber,
suitably cooled by ice, mechanical, or other means; and then to pass it into a drying
chamber, which may be a room or chamber kept at a suitable higher temperature,
and fed with warm dry air on the one hand whilst the moist air is removed
on the other hand, by any suitable means, the means most commonly adopted
being to use air propellers, hot water pipes, and such like well known aids.
Now the thickness of coating necessary, and the results required in the finished
product (that is to say the condition of the dried coating), are such that the process
of drying is a very lengthy one, involving the necessity for the sensitized coating
being exposed to the air of the drying chamber for a number of hours. It is for
instance quite usual to.leave the coated material to dry all night and to remove it
the following morning. It has been found that any attempts to hasten this
drying process, beyond very narrow limits, produce such an effect upon or change
in the nature of the coated product as to render it unsuitable for use, such as
for instance as by rendering the top of the coating more insoluable than the other
parts. Moreover, the length of time necessary for drying of the coating is also
liable to cause defects in the finished product, as, if there are injurious gases.
in the air of the drying room, or too great a degree of moisture, the coating is
liable to partially decompose, fog, or produce insensitive patches, and other
faults.
Now it is evident that if the coating could be dried quickly the faults caused
by prolonged exposure to the atmosphere of a drying room would eliminated,
and that if no other defects (such as partial or unequal insolubility) were caused,
such quick drying would be a distinct and valuable improvement in the manu-
facture of sensitized products, and would also have the further advantage of
causing a corresponding increase in the output with the same coating plant.
This invention provides for accomplishing the end sought, and is very simple.

page_text: It consists essentially in applying a great number of exceedingly thin coats in
succession until the requisite thickness of coating has been built up, and in drying
very rapidly (in some cases almost instantaneously), by means of a blast of
heated air for instance, between each coat.
It has been found that if a blast of air sufficiently hot to dry quickly enough
is applied to a coating of the usual thickness, it only has the effect of melting the
coating, causing it to run, and yielding an absolutely useless result. But if the
heated air blast is applied to an exceedingly thin coat the result is quite different,
for the moisture is removed almost instantaneously, according to the thickness of
coat and temperature and quality of air.
The process is repeated until the finished coating is the desired thickness. I
find that it is often necessary to apply some 10 or 20 coats to obtain a thickness
equal to that usually applied at one operation. The sum total of the length of
time taken to dry the successive coats, however, is infinitely less than the time
taken to dry a single coating having the same finished thickness.
I find no defects or practical objections to a sensitized coating built up from a
number of successively dried coatings in the way described.
Any suitable means may be used for applying the coatings to the support,.
many of which are well known. As an illustration of a suitable apparatus I may
instance the following:-The material to be coated (for example a paper or
flexible film web) may be drawn off a spool and passed round or against a roller
or rollers fed with emulsion from a trough or other feeding apparatus, the supply
or thickness of emulsion applied to the web being regulated by scrapers or other
suitable means. The web, after receiving its coating, is drawn forward, passing
during its travel against a nozzle delivering beated compressed air; or through a
chamber or chest heated by hot air or steam; or against or around a drying
cylinder or drum, likewise heated by hot air or steam. The time of drying may
be varied from seconds to minutes, as desired, by adjusting the thickness of each
coating, the temperature of the drying air or apparatus, and the rate of travel of
the web or other coated surface.
The web may be reeled after each coat, and passed through the apparatus
repeatedly until the requisite thickness of coating has been obtained, but I prefer
to complete the finished coating at one operation, before the web leaves the
machine, by combining, in one machine, as many coating and drying sets of
apparatus as there are coatings to be applied.
The method of manufacture hereinbefore described is of enormous value when
dealing with gelatino-bromide emulsions of a very high degree of sensitiveness
such as are used for extremely rapid instantaneous work. The difficulties in
producing uniformity of results with such emulsions hitherto, have been greatly
increased owing to the delicate state of such emulsions, and the changes set up
therein during the process of drying, and due largely to atmospheric and other
conditions almost impossible to deal with or overcome when dealing with such
large volumes of air as it was. requisite to pass through the drying rooms.
These difficulties are practically removed by adopting the system of manufacture
herein described, and it is possible to dry the coatings by a very much smaller
quantity of air, and to keep such air at a more uniform temperature, freer from
impurities, and otherwise in better condition for the purpose; and to do this
at less expense than hitherto possible. The same air may be used over and over
again, the moisture being removed therefrom as the air circulates.
Dated this 16th day of March 1899

page_text: Improvements in the Manufacture of Photographic Sensitized
Materials.
I, JOHN EDWARD THORNTON, of Rokeby, Oldfield Road, Altrincham, in the
County of Chester, Manufacturer, 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:-
This invention relates to an improved process or method of coating photographic
films papers and plates with a sensitized emulsion during their manufacture.
Sensitized materials of various kinds are used according to the desired results,
but a gelatino-bromide of gelatino-chloride emulsion is most frequently used
and therefore in describing this invention I hereinafter adopt the term emul-
sion as sufficiently descriptive of any sensitizing material.
Similarly various supports are used for the emulsion such as celluloid or other
films papers glass plates sheet-metal cardboard and the like. Hereinafter I use
the term " support" to include any support.
In the manufacture of sensitive films papers and plates it has hitherto been the
custom to coat the support with a coating of the emulsion of the desired thickness
at one operation either by hand or by machine and then to allow the coating to set.
This process is often accelerated by passing the support after coating into a chilling
chamber suitably cooled by ice, mechanical or other means and then into a drying
chamber kept at a suitable temperature with a current of warm dry air passing
through it the dry air entering at one side and the damp or moistened air being
drawn off at the other. The means ordinarily employed for the purpose being air
propellers or fans hot water pipes and other similar appliances.
The present process of drying is a very lengthy one on account of the thickness
of the film of emulsion necessary upon the support and it involves the necessity
of the sensitized coating being exposed to the air of the drying chamber for a
number of hours. For example it is quite usual to leave the coated support in the
drying chamber from one day to the next.
Attempts have been made to hasten or shorten the drying process but it has
been found impracticable to do so beyond very narrow limits such a change in
the nature of the coated product being the result as to render it unsuitable for
use by making the top less soluble than the other parts and the expansion and
contraction has been unequal through out the films.
Defects are caused by the length of time now occupied in drying, injurious
gases in the air of the drying room cause the coating to partially decompose fog
or produce insensitive patches. Prolonged exposure to air charged with moisture
(especially in warm weather) causes the growth of fungus or germs which destroy
the gelatine and any change of temperature in the drying room produces drying
marks frilling" and uneven density in the negatives.
"
I have found that if the sensitive coating could be dried quickly the faults or
defects caused therein by long exposure to the atmosphere of the drying room
would be eliminated and provided other defects did not arise quick drying would
be a distinct and valuable improvement in the manufacture of sensitive papers
films and plates and would have the further advantage of increasing the speed of
manufacture.
This invention consists essentially in applying the sensitive emulsion to the
support in a great number of exceedingly thin or fine coats (each too thin for
photographing upon) and immediately without setting or solidifying drying each
successive coat or layer rapidly or instantaneously by a blast of heated air
It has been found that a blast of heated air sufficiently hot to dry quickly

page_text: applied to a coating of sensitive emulsion of the usual thickness melts the coating
and causes it to run yielding an absolutely useless result. I find however that the
heated air blast applied to an exceedingly thin or fine coat or layer of the sensitive
emulsion produces an entirely different result the moisture being almost instantly
removed.
The invention will be fully described with reference to the accompanying
drawings.
Fig. 1. Sectional elevation of apparatus for coating continuous films with the
sensitive emulsion.
Fig. 2. Modified arrangement of same.
Fig. 3. Apparatus for coating plates.
Fig. 4. Sectional elevation of apparatus for applying and drying a number of
coats of the sensitive emulsion without removing the film from the machine.
For applying the invention to the coating of a sensitive emulsion upon a
support of thin flexible material A such as paper celluloid or other web material
a suitable machine is constructed with a roller B to apply the emulsion to the
film A a jacketed or heated trough Ca ductor roller 1 rotating in the trough to
convey the emulsion to the coating roller B and enclosed chamber E through
which the web support when coated passes air ducts F through which heated air
is forced and caused to impinge upon the travelling web support A and guide
rollers G placed to conduct the material over the coating roller and through the
drying chamber E.
A straight drying chamber E as shown in Fig. 1, or a curved or cylindrical
drying chamber E as shown in Fig. 2 may be employed.
For the coating of a stiff or rigid support H such as plates of glass celluloid
mica or the like the machine is constructed with a travelling carrying band K
passing over guide rollers L and provided with a number of transverse ribs by
which the plates H are held in position thereon. Above or in close proximity to
the travelling carrier band K is placed the trough or box M for containing the
emulsion and over the travelling carrier band K is formed the drying chamber N
with the air ducts O through which the heated air is forced upon the coated
plates as they are carried through.
In the emulsion box or trough M is placed a revolving silver gauze cylinder P
which rotates in the emulsion and inside the gauze cylinder is placed a flat air
tube or nozzle R the width of the plates through which a blast of air is forced.
In the side of the trough or box M opposite the air tube a slit is formed through
which the emulsion adhering to the silver gauze of the cylinder P is blown in a
fine spray on to the plates H carried by the travelling carrier band K.
An exceedingly fine layer or coating of the emulsion is deposited on the sup-
port A or H and dried as such pass through the machine and the process is
repeated again and again until the finished coating of the sensitive emulsion is the
desired thickness. It will be necessary in this manner to apply about from 10 to
20 coats to obtain a thickness equal to that usually applied at the one operation.
The whole length of time taken to successfully apply and dry the successive thin
coats of the sensitive emulsion is infinitely less than the time now taken to dry
a single coating having the same finished thickness. In fact I find that the film
can be completed in a few minutes where it has hitherto occupied many hours.
Any other suitable appliance may be employed for applying the very thin
coating to the support and the sensitive film may be dried either by heated air or
by contact with a steam heated cylinder or hot rollers. The time of drying
may occupy seconds or minutes according to the thickness of coating applied the
temperature of the air and apparatus employed and the rate of travel of the
support.
The paper or flexible film support may be reeled as shown after each coat and
passed repeatedly through the apparatus or a number of coating rollers and
drying chambers or cylinders may be arranged in one machine see Fig. 4, so that

page_text: the support may be fully coated with the requisite number of fine coats at one
operation.
In Fig. 4, the apparatus is made up of any number of sections comprising a
coating roller B₁ trough C ductor roller D' to apply the emulsion to the coating
roller drying chamber E into which the heated blast of air is injected by the
nozzle on the perforated pipe F and guide rollers G¹ and G the roller G2 may
be heated if desired. Likewise a number of spraying apparatus may be used
for plates.
This method of manufacturing sensitive films upon flexible or rigid supports
will be found to be of enormous value when dealing with gelatino-bromide emul-
sions of a high degree of sensitiveness such as are used for extremely rapid
instantaneous work."
The difficulties in producing perfect results and products with good keeping
qualities with these delicate emulsions have hitherto been greatly increased by
the changes set up therein during the hitherto lengthy process of drying thick
coatings such as have always been used which was due largely to atmospheric con-
ditions producing chemical changes in the sensitive coating.
By my invention these difficulties are practically removed the coatings being
rapidly dried so as to prevent the aforesaid chemical changes accompanied as they
are by decomposition of the gelatine taking place.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed I declare that what
I claim is:
1. In the manufacture of photographic sensitized films plates or papers the
formation of the sensitive portion thereof by applying to the support a number
of very thin coats of the sensitive emulsion and without setting rapidly (almost
instantaneously) drying each successive coat by a blast of heated air.
2. In the manufacture of photographic sensitized films plates or papers the
formation of the sensitive portion thereof by applying to the support a number
of relatively very thin coats of the sensitive emulsion, and rapidly (almost instan-
taneously) drying each successive coat by a blast of heated air, immediately after
coating, and without any intermediate setting or chilling of each coat between
the coating and drying thereof.
3. The manufacture of sensitized photographic films plates or papers in the
manner and by the means and method described for the purpose of obtaining
improved results and for quickening the process of manufacture.
4. A photographic sensitized film plate or paper, having the sensitive portion
thereof, formed or built up to the necessary thickness by a great number of very
thin layers or coats of sensitive material successively applied to a support and
rapidly (almost instantaneously) dried thereon without previous setting sub-
stantially as described.
5. The apparatus for spreading or coating the photographic supports with a
number of very thin coats of sensitive emulsion to obtain the requisite thickness
and rapidly (almost instantaneously) drying same without intermediate setting
constructed substantially as described and shown in either of the figures of the
drawings.
Dated this Q1 1. € 1
1
1000
WM. P. THOMPSON & Co..
6, Bank Street, Manchester, Patent Agents.