US3156565A

US3156565A - Photographic stripping film

Info

Publication number: US3156565A
Application number: US223366A
Authority: US
Inventors: James R Sinclair
Original assignee: Minnesota Mining and Manufacturing Co
Current assignee: 3M Co
Priority date: 1962-09-13
Filing date: 1962-09-13
Publication date: 1964-11-10
Anticipated expiration: 1981-11-10

Description

Nov. 10, 1964 J. n. slNcLAlR 3,156,565

PHOTOGRAPHIC STRIFPING FIL Filed sapt. 1s, 1962 United States Patent O 3,156,565 PHOTOGRAPHIC STRIPPING FILM James R. Sinclair, Mayfield Heights, Ohio, assgnor, by

mesne assignments, to Minnesota Mining and Manufacturing Company, a corporation of Delaware Filed Sept. 13, 1962, Ser. No. 223,366 9 Claims. (Cl. 96-83) This invention relates to photography and to photographic film. In one aspect, this invention relates to an improved photographic stripping film.

In the graphic arts field and particularly in ph-otoengraving and similar processes, the conventional ph-otographie stripping film construction comprises a temporary `support of a suitable transparent film `base material. One side of the temporary support carries, in order, a release layer, a membrane, a subbing layer and a photosensitive emulsion. The release layer permits the membrane bearing the photosensitive emulsion to be removed from the temporary support at an appropriate time after exposure. The release layer must therefore serve to adhere the membrane to the temporary lsupport sufficiently to prevent the premature displacement of the membrane but must permit the membrane to be readily and cleanly separated from. the temporary support by peeling, without the use of solvents to alter the physical nature of the release composition. An anti-halation layer is generally provided on the other side of the temporary support and usually is 'bonded thereto 1by means of an intermediate suhstratum. When polystyrene film is employed as the temporary support, 'appropriate adhesion and release properties of the respective layers are particularly difficult problems. Moreover, the plurality of layers are undesirable not `only for achieving optimum photographic results but also for reducing the cost of manufacturing the film.

It is therefore an object of this invention to provide an improved photographic stripping film.

Another object of this invention is to provide a photographic stripping film which can be manufactured at reduced cost compared to the abovementioned conventional stripping films and which can be cleanly stripped or peeled apart mechanically without the need for a solvent treatment.

Still another object of this invention is to provide a photographic stripping hlm having a polystyrene temporary support and a minimum of layers thereon.

A further object is to provide a photographic stripping film which may be inspected during processing by both reflected and transmitted light land which has a greater cllectivc speed than thc abovementioned conventional stripping film.

Other objects and advantages will bc apparent from the following description.

ln accordance with this in-vention the foregoing and other advantages are achieved by providing a polystyrene tzmporary support, a rcleasable membrane 4supported thereon and comprising a minor amount of an acrylic polymer and a major amount of a cellulose ester or cellulose ether, and a photosensitive layer superimposed on the relcasable membrane. In a preferred embodiment a subbing layer is interposed between the rcleasable membrane and the photosensitive layer. as illustrated in the figure, the several layers depicted therein being exaggerated in thickness and the relative thicknesses being not necessarily in correct scale.

ln the most preferred embodiment shown in the figure, temporary support l comprises a clear polystyrene film, preferably 'biaxially oriented, containing anti-halation pigment or dye uniformly dispersed therein. The resulting support is translucent rather than opaque and preferably transmits about 22% to 24% of the incident light, based on a density of about 0.64 as determined by a photoelect 3,156,565 Patented Nov. 10, 1964 tric densitiometer. Particularly preferred is an orange colored dye or pigment which permits the thin temporary isupport to transmit the spectrum from a wave length of about 6000 A. to about 8000 A. An orange dye pigment of this type, e.g., cadmium orange, is suiciently absorptive of the light to which normal stripping film emulsions are sensitive and thus permits the temporary support to serve effectively as an anti-halation layer. When a clear, non-pigmented polystyrene sheet is used -as temporary support, it may be provided on the reverse side from the releasable membrane with =a separate anti-halation layer, which can :be firmly attached to the support by a cellulosic gelatin subbing layer 'and an anchoring layer containing a major amount of an yacrylate. ester polymer and a minor amount of a cellulose ester in the manner described in United States Patent Number 2,972,534.

The releasable membrane 2 must not only adhere to the polystyrene temporary support l and be readily releasable therefrom but also must maintain its integrity as membrane upon release. Because of these requirements and because of the problems associated with their attainment in association with polystyrene film, the composition of the releasable membrane must be maintained within the hereindefined limits. It has lbeen lfound that such `a membrane is provided by a layer containing from about 10 to about percent by weight of l.an acrylate ester polymer and from about to about 90 percent by weight of a cellulose ester or a cellulose ether, with from 0 to about 25 weight percent of a pla'sticizer, such as dibutyl phthalate, if desired. The preferred acrylate ester polymers are the 'binary polymers of methyl and ethyl acrylate or methacryl'ate. An illustrative acrylate ester polymer is the copolymer of ethyl methacrylate and methyl acrylate, c g., Acryloid B-72 (Rohm and Haas). Such polymers may be prepared by the eopolymeriz'ation of methyl or ethyl acrylate and methyl or ethyl methacrylate in the presence of an organic peroxide with the application of light and heat, as described in United States Patents 1,937,323 and 2,123,- 599. Those preferred acrylate copolymers are prepared from mixtures having :from about 10 to about 40 percent of ethyl methacrylate and from about to about 9() percent methyl acrylate. The cellulose ether polymers are preferably a lower alkyl celluose ether, such 'as methyl cellulose and ethyl cellulose. The cellulose ester polymers are preferably the cellulose esters of aliphatic carboxylic acids having from 2 to 4 car-bon atoms, such as cellulose acetate, cellulose propionate, cellulose butyrate and the mixed esters thereof, e.g., cellulose acetate butyrate.

The abovementioned proportion of the acrylate polymers and the cellulose derivative is critical for the production of a releasable membrane which can be adhered to the polystyrene temporary support during manufacture without intervening adhesive or anchoring layers and without separate release layers. The adhesion of the releasable membrane of this invention to the polystyrene temporary support is suicient to prevent premature peeling or separation of the film construction during processing and handling. Yet the releasable membrane can lbe cleanly stripped or mechanically peeled away from the polystyrene support without impairment of its integrity as a smooth and dimensionally uniform support for the photosensitive emulsion carried on its other side. It is a particular advantage that no special solvents are required to soften the membrane for the release step, since the use of solvents can reduce the cleanness of the release and can result in a stripped membrane of non-uniform thickness and light transmissive properties. When the releasable membrane contains more than about 45 weight percent of the acrylate ester polymers, the desirable release or strip-apart properties are adversely affected, and the membrane becomes tightly bonded or anchored to the polystyrene support. When the releasable membrane contains less than about weight percent of the acrylate ester polymers, the membrane tends to peel away from the polystyrene support during manufacture, handling and preliminary processing.

The substratum 3, if needed to adhere the photosensitive layer to the releasable membrane, preferably comprises a very thin coating of nitrocellulose and gelatin, although other suitable substrata may be employed to anchor the photosensitive layer 4 securely to releasable membrane 2.

The photosensitive layer 4 may be any silver halide gelatin emulsion of the type suited for stripping films. Since high contrast and excellent definition are generally required, orthochromatic emulsions are frequently ernployed.

In an illustrative and particularly preferred embodiment, a translucent, cadmium oxide pigmented polystyrene film having a thickness of about 0.005 inch and having the color and light transmission properties noted above is used. Such pigmented polystyrene film is available under the name Lustrex from Plax Corporation. This film base is coated with the following solution (25% solids) to provide the releasable membrane.

Non-volatile: Percent by weight Cellulose acetate butyrate second, Eastman Chemical EAB 381-20) 64 Copolymer of ethyl methacrylate and methyl acrylate (Acryloid B-72) 16 Dibutyl phthalate 20 Volatile:

Ethyl acetate 3.33 Butyl acetate 11.67 Isobutyl alcohol Toluene 10 Ethyl alcohol 50 Although various other solvent systems which do not cause etching or fogging of the temporary support may be employed, the preferred solvents systems, including the particularly preferred ranges in parentheses, are:

Wt. percent Ethyl, butyl or isopropyl acetate 0-20 (l0-20) Butyl or isobutyl alcohol 0-3 (l0-25) Toluene 0-15 (5-15) Ethyl or isopropyl alcohol -80 (40-65) Ethyl cellulose can be substituted for cellulose acetate butyrate in the above formulation.

The membrane, after drying, is coated with the following subbing composition:

Parts by Weight Preferred Range Gelatin 3 0. 5-4 Water 2 0. 5-5 Glacial acetic acid.- 6 1-8 Nitrocellulose (S55/2 8 0. 5-10 Acetone 18 5-25 Methanol 63 25-75 ping film of this invention can be manufactured at significantly lower cost than conventional stripping film. The elimination of a separate anti-halation layer and its associated subbing layers further reduces the cost. Moreover, the elimination of additional coatings brings the antihalation layer into closer proximity to the photosensitive layer and improves its effectiveness, particularly the speed of response, which can be as much as 50% faster than a conventional stripping film having a separate anti-halation coating. Furthermore, when the temporary support is translucent rather than transparent, the operator may visually inspect the exposed stripping film during development or processing by reflected light as well as transmitted light. This is in contrast to paper-backed stripping films which can be visually inspected only by refiected light. These advantages in cost, increased speed and definition are of great benefit to photoengravers and other users of photographic stripping film.

A further advantage of the stripping film construction of this invention is the added utility of the cleanly stripped temporary support, which is an ideal material for masking in layout and makeup work by photoengravers. With the pigmented, translucent polystyrene film the absence of further coatings on the stripped support is an added advantage.

Those skilled in the art will appreciate that various changes and modifications can be made in the preferred forms of the invention disclosed herein without departing from the spirit and scope of the invention.

It is therefore claimed:

1. A stripping film comprising a polystyrene temporary support, a releasable membrane on one side thereof consisting essentially of between about 10 and about 45 weight percent of acrylate ester polymer and between about 55 and about 90 weight percent of a member of the group consisting of a lower alkyl cellulose ether and a cellulose ester of an organic carboxylic acid having from two to four carbon atoms, said membrane being adhered to said polystyrene support and cleanly strippable therefrom by mechanical peeling, and a photosensitive silver halide layer carried by said releasable membrane on the side opposite the polystyrene support.

2. The stripping film of claim 1 in which an antihalation layer is carried by the temporary support on the side opposite the releasable membrane.

3. The stripping' film of claim 1 in which the temporary support is a translucent polystyrene film incorporating an anti-halation material therein.

4. A stripping film comprising a translucent polystyrene temporary support incorporating an anti-halation pigment, said temporary support transmitting from about 22% to about 24% of light incident thereon and being substantially opaque to light having a wave length of less than about 6000 A., a releasable membrane on one side thereof consisting essentially of between about 10 and about 45 weight percent of acrylate ester polymer and between about 55 and about 90 weight percent of a member of the group consisting of a lower alkyl cellulose ether and a cellulose ester of an aliphatic carboxylic acid having from two to four carbon atoms, said membrane being adhered to said polystyrene support and cleanly strippable therefrom by mechanical peeling, and a photosensitive silver halide layer carried by the releasable membrane on the side thereof opposite said polystyrene support.

5. A stripping film comprising a translucent polystyrene temporary support incorporating an anti-halation pigment, said temporary support transmitting from about 22% to about 24% of light incident thereon and being substantially opaque to light having a wave length of less than about 6000' A., a releasable membrane on one side thereof consisting essentially of between about 10 and about 45 weight percent of acrylate ester polymer and between about 55 and about 90 weight percent of a member of the group consisting of a lower alkyl cellulose ether `and a cellulose ester of an aliphatic carboxylic acid hav' ing from two to four carbon atoms, said membrane being adhered to sai-d polystyrene support and cleanly strippable therefrom by mechanical peeling, a cellulosic-gelatin subbing silver halide layer on said membrane, and a photo- `sensitive layer carricd by the releasable membrane on the side thereof opposite said polystyrene support.

6. The stripping film 0f claim 5 in which said releasable membrane also contains an organic plasticizer.

7. The stripping lm of claim 5 in which said releasable membrane contains ethyl cellulose.

8. The stripping lm of claim 5 in which said releasable membrane contains cellulose acetate butyrate.

9. The stripping lm of claim 5 in which said releasable membrane contains a copolymer of a lower alkyl acrylate and a lower alkyl methacrylate.

References Cited in the le of this patent UNITED STATES PATENTS UNITED' STATES PATENT OFFICE 'i CERTIFICATE 0F CORRECTION Patent No, 3,156,555 November 10, 1,964

James RfSinclaiT it is hereby certified that error appears in the above numbered patent'requiring correction and that the Said Letters Patent should read as corrected below.

Column 5, lines 4 and 5, for "silver halide layer on Ead membrane, and a photosensitve layer" read layer on said membrane, and a photosenstive silver halide layer Signed and sealedthis 24th day of August 1965.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents

Claims

1. A STRIPPING FILM COMPRISING A POLYSTYRENE TEMPORARY SUPPORT, A RELEASABLE MEMBRANE ON ONE SIDE THEREOF CONSISTING ESSENTIALLY OF BETWEEN ABOUT 10 AND ABOUT 45 WEIGHT PERCENT OF ACRYLATE ESTER POLYMER AND BETWEEN ABOUT 55 AND ABOUT 90 WEIGHT PERCENT OF A MEMBER OF THE GROUP CONSISTING OF A LOWER ALKYL CELLULOSE ETHER AND A TWO TO FOUR CARBON ATOMS, SAID MEMBRANE BEING ADHERED TO SAID POLYSTYRENE SUPPORT AND CLEANLY STRIPPABLE THEREFROM BY MECHANICAL PEELING, AND A PHOTOSENSITIVE SILVER HALIDE LAYER CARRIED BY SAID RELEASAB LE MEMBRANE ON THE SIDE OPPOSITE THE POLYSTYRENE SUPPORT.