US2392503A - Temporary support for photographic gelatin layers and method of transferring same to permanent supports - Google Patents

Description

8, 1946. s. POTTER ILITAL 2,392,503

TEMPORARY SUPPORT FDR PHOTOGRAPHIC GELATIN LAYERS AND METHOD OF TRANSFERRING SAME TO PERMANENT SUPPORTS Filed Sept. 28, 1942 LIGHT SENS/Tl VE /6ELAT/N LAVER- ATTACH/N6 LAYER OF CELLULOSE lY/TRATE 0R ZE/N.

PAPER SUPPORT.

4 g 2 BY g Robert 1 Brown ATTORI'QEY.

Patented Jan. 8, 1946 TEMPORARY SUPPORT FOR PHOTOGRAPH- IC GELATIN LAYERS AND METHOD OF TRANSFERRING SAME T PERMANENT SUPPORTS Rowland S. Potter, Brightford Heights, and Robert F. Brown, Rochester, N. Y., assignors, by mesne assignments, to E. L du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware Application September 28, 1942, Serial No. 459,898

' This invention relates to a temporary support for a photographic gelatin layer and method of transferring the gelatin layer to 'a permanent gelatin solution or the like, and thoroughly drying before removing the temporary support. This is known as dry-stripping.

support, and has for its'purpose to afford a practical, economical and emcient structure by which a photographic light-sensitive or-other gelatin layer can be readily transferred from a term porary paper or other porous light weight, flexible support and aflixed to a glass, plastic, metal, wood, or other permanent surface or support before exposure and before developing and fixing the image, without requirin an additional layer to hold the gelatin layer on the permanent support. thus enabling manufacturing such a product by applying a gelatin layer on a temporary support of paper and transferring only the gelatin layer quickly and easily to a metal, glass, plastic, wood, or lacquered surface to which it becomes permanently attached and-making it possible to expose and process the light-sensitive gelatin layer after its transfer to the permanent support.

In a more particular aspect, the invention has for its object to attach a, light-sensitive gelatin layer temporarily to a porous, light weight, flexible support of paper or other suitable material through the instrumentality of an intermediate retaining layer or coatin that is water permeable but insoluble in water or in any of the liquid mediums used in effecting the transfer and remains permanently attached to the paper support, the intermediate layer possessing a quality which enables it to retain the gelatin layer attached to the paper support while dry and until it is desired to separate them and readily to release the gelatin layer when the latter is to be attached to the permanent support such as glass, plastic, meta1, orwood, upon applying a water solution to such surface and squeegeeing the paper support and gelatin layer thereagainst with the gelatin layer adjacent to the water covered surface and then wetting. the back of the paper support, after which the paper support with the permanently attached retaining layer can be removed from the gelatin layer which remains firmly secured to the permanent support without requiring any additional layer or coating and can thereafter be exposed and processed, without having to remove any adherent partially dissolved material of an intermediate layer.

Heretofore all methods of photographic layer stripping and transfer have depended upon dissolving the attaching layer, or else included an attaching layer affording only limited adhesion with the gelatin layer when dry, the transfer being effected by firmly cementing the gelatin layer to the permanent supp rt by means of a weak Of the types of layers which permit stripping by dissolving are those soluble in hot or cold water, and those soluble in alkali or acid baths such as used in photographic processing solutions.

An example of a photographic transfer layer which is held by a soluble interlayer is disclosed in U. S. Patent No. 2,207,388 to Gerhard von is coated over a water-permeable but water-insoluble layer which in turn is coated on a paper support. The water-permeable layer is soluble in weak alkali, an acid, or neutral salt bath, and must be dissolved to release the light-sensitive gelatin layer from its temporary paper support when it is desired to transfer it to a permanent support. It is necessary, therefore, to expose the light-sensitive layer before transfer since it is well known that the light-sensitiveness of such layers is easily affected by such In photome'chanical processes, especially in making templates from drawings in the aircraft industries, it is necessary to make absolutely accurate reproductions and to scrupulously avoid distortions. Such distortions and inaccuracies cannot be avoided where the light-sensitive layer is exposed before transfer.

The present structure differs from all prior stripping films in that the sensitive gelatin layer can be stripped while wet from its temporary support and attached to the permanent support without the need of a collodion or other supporting layer that would remain attached to the gelatin layer, and may be exposed and processed after transfer to the permanent support. This enable a substantial saving where large sized sensitized glass plates'are required, since instead of carrying stocks of such sensitized plates in many sizes, the sensitized product is made in the form of paper, or other light weight, porous, flexible sheets from which the gelatin layer can readilyebe transferred to a glass plate of any selected size, and after use the gelatin can be removed from the glass plate and the latter employed again for another gelatin layer. The invention also possesses great advantage in making large sized templates such as required in the airplane manufacturing industry and in other lofting operations where it is desirable to attach a sensitized layer to a metal surface and expose it after attachment, which eliminatesthe obvious difilculty of dimensional change which is undesirable where accurate drawings are neces The drawing is a sectional view of a photo! graphic paper made in accordance with a preferred embodiment of the invention.

Referring more particularly to the drawing, in

carrying out the invention according to one possible procedure, a support I of paper or other porous, light weight, flexible ,material is first coated in any well known manner with a thin and to release the gelatin layer when it is treated in the manner to be described presently to permit its transfer to the permanent support. The

photographic light-sensitive gelatin layer 8 isapplied by any of the conventional coating methods and any gelatin layer other than a photographic light-sensitive layer, such as one adapted for drafting operations, may be similarly applied, where it may be desirable to transfer such a gelatin layer from a temporary support to a permanent support.

Any suitable material having the necessary qualities may be employed for this purpose, and it has been found that a thin layer of a cellulose ester such as cellulose nitratecontaining a suitable porosity-giving agent when thoroughly dry, is water-permeable and also insoluble in water or in any of the liquid mediums used in cfunprocessed, is then firmly squeegeed against the latter. Water is applied to the back of the paper support, preferably after the squeegeeing operation, and the back of the paper is kept thoroughly wet thereafter. The sensitive gelatin layer will firmly and quickly adhere to the liquid-covered supporting surface after which the temporary or paper support can be pulled away andthe gelatin layer alone remains attached to the permanent support, while the retaining layer of cellulose nitrate or other cellulose ester, zein, or other prolamine, remains permanently attached to the temporary or paper support as it is pulled away from the gelatin layer. The lightsensitive gelatin layer can then be exposed, and

processed in a manner well known in the photographic art with or without the intermediate step of drying. 'Anyother gelatin layer can be transferred as described and used in-the manner for which it is intended.

. to produce, and more practical than any of the fecting the transfer, and will function properly to retain the sensitive gelatin layer temporarily attached to the paper support and to release the "gelatin layer when it is to be transferred. any suitable porosity-giving agent such as urea may be incorporated in the cellulose nitrate layer.

A prolamine can also be employed for the purpose and one that has been used successfully is zein which is a protein derived from corn and marketed by the Corn Products Refining Company under the name Maaein." The zein is coated on the paper support as a solution which contains a suitable solvent mixture such as alcohol and water and which falls within the following general formula:

- Zein, 5% to by weight of total solution Alcohol, 85% to 95% by volume of solvent mixture Water, 5% to by volume of solvent mixture.

This solution may contain a small quantity 'of wax, such as beeswax, carnauba, paraifin, or.

' supporting surface and then exposed and processed.

- To effect the separation-and transfer of the gelatin layer, the glass, plastic, metal, or other permanent surface is covered with water, which may or may not contain gelatin, gelatin chrome known types of photographic stripping layers.

While the invention has been described with reference to a certain structure and procedure,

- the scope ofthe following claims.

alum, or chrome alum, in solution in a concentration generally usedin the art as a cementing layer to the permanent support. The gelatin layer, preferably We claim:

l. The combination with a temporary flexible paper support, of a photographic light-sensitive gelatin layer which'can be transferred from the temporary support to a liquid-coated surface of a permanent support by squeegeeing it thereon and applying water to the back of. the paper support, and a retaining layer consisting of a prolamine between the temporary support and the gelatin layer, said retaining layer being insoluble in water and the solutions used in transferring said gelatin layer and acting to retain the gelatin layer on the temporary support until it is to be transferred therefrom and then operable upon application of water to release it for attachment to the permanent support without adherence of any part of the retaining layer to the gelatin layer.

on the temporary support until it is to be transferred therefrom and then operable upon application of water to release it for attachment to the permanent support without adherenceof any part of the retaininglayer to the gelatin layer.

ROWLAND s. roam. ROBERT F. snows.

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