FR2459498A1 - COMPOSITE PHOTOGRAPHIC STRUCTURES AND USES THEREOF - Google Patents

Abstract

Separably laminated composite photographic structure. A light sensitive element (21) is adhered to a transparent barrier foil (23), which in turn is removably adhered to a photographic carrier sheet (25). Adhesive layer (30) is firmly bonded to the outermost surface of element (21). After an image has been developed in element (21), adhesive layer (30) is adhered to a substrate (40). Carrier layer (25) is then stripped away, leaving imaged element (21) bonded to substrate (40) and protectively covered by barrier foil (23).

Description

"COMPOSITE PHOTOGRAPHIC STRUCTURES AND THEIR
USES "
The present invention relates to composite photographic structures, and more particularly to structures of this kind which can be used in the transfer of photographic images to supports.

 Photographic images can be applied to leather, fabrics or other media using a variety of different methods. For example, a photographic emulsion containing silver halide particles can be spread with a brush or otherwise applied to a canvas support under determined conditions of light, then exposed to radiation for the creation of an image through a photographic negative, the emulsion layer thus exposed is then subjected to developing solutions to form a positive image. Although this technique can be performed with a single layer to form a black and white image, the various manipulations greatly increase the cost and furthermore the preparation of color images is not possible in practice.

 The production of color photographs on a canvas support constitutes an interesting method for imitating an expensive portrait done in oil and it is thus that various techniques have been provided to achieve such an effect. For example, three emulsion layers can be prepared on a traditional support, each layer then being exposed to printing radiation through a mask of a different primary color (cyan, magenta or yellow) and the layers of emulsion are developed and transferred in turn to the desired support, ensuring that the three impressed layers are well in correspondence. High precision is required in handling the individual emulsion layers and it is extremely difficult to obtain high quality results, especially if the substrate is irregular or textured.

A fairly similar proposition has been described in U.S. Patent No. 3,721,557, according to which individual transparent positive images of different primary colors in a photopolymer supported by a film coating are in turn superimposed and brought to join together and in correspondence on a desired support. It is not only impossible to render a full range of colors with photopolymers, but in addition the various skin layers and adhesive layers tend to pocket making colors real unless each such layer is completely transparent.

 Prior to the present invention, the most popular method of transferring a color photographic image to a canvas or other medium was a process known as "splitting photographic paper". This process uses a photographic printing paper, available on the market and resistant to curling, this paper comprising a thin sheet of polyethylene laminated on each main face, the layers of photographic emulsions being applied to one of the sheet surfaces. . A color photographic image is developed in the emulsion layers and the opposite surface is temporarily caused to adhere to a support element. Taking great care, the paper layer is split as close as possible to the face polyethylene sheet coated with emulsion, which is in contact with the paper, the sheet and the developed image being carefully separated by wrapping them around a small cylindrical pin. The separate polyethylene sheet, carrying the layers of emulsions developed on one side, is then caused to adhere to the desired support and subjected to a pressure to conform it intimately to this support. Such a splitting process is not only difficult but also the rolled polyethylene sheet, carrying the emulsion, often withstands the efforts made to bring it flat. In addition, the outer photographic emulsion layer is subjected to damage, both during the process intended to apply it on a new support and when the laminate assembly is handled after the emulsion layer has been transferred.

The present invention provides a simple, uncoated method of applying high quality color or black and white images to canvas or other desired supports. The use of the product of the invention is simple enough for amateurs to be able to obtain excellent results, even without prior experience. A color image, thus transferred to a canvas support, not only closely resembles a portrait but also is protected from abrasion inadvertently made on the layers of photographic emulsions.

 According to its simplest embodiment, the new article according to the invention is constituted by a composite photographic structure comprising a flexible support sheet, atto-bearing, on which is arranged a phososensitive element, comprising at least one layer of emulsion photographic material containing dispersed silver halide particles. Between the support sheet and the photosensitive element, there is interposed a sheet forming a self-supporting barrier, polymer, thermoplastic, stretchable, flexible, light-transmitting, connecting the support sheet and the photosensitive element together. or the detachment existing between the barrier sheet and the support sheet is appreciably inferior either to the adhesion to the peeling existing between the barrier sheet and the photosensitive element, or to the cohesion resistance of the support sheet or of the barrier sheet. At the same time, the peel adhesion between the barrier sheet and the support sheet is sufficiently high to prevent separation during the manufacture of the composite structure and during subsequent manipulation during image creation, development and drying the photosensitive member.

A photographic image prepared in a composite photographic structure of the type described above is transferred to any desired medium by applying a layer of adhesive to the surface of the photosensitive element carrying the image, placing the surface of the adhesive in contact with a support to adhere thereto, and removing the support sheet to leave a photographic image adhering to the support and covered, as a protection, by the sheet forming a polymer barrier, transmitting light.

The product resulting from the operating phases described above is thus a photographic reproduction comprising in combination a support, an adhesive layer covering at least a part of this support, an element containing silver halide and comprising the image. , located over and bonded to the adhesive, and a light barrier, protective, flexible, self-supporting polymer barrier sheet lying over the element containing the silver halide and related to it.

 The invention will be described more fully below with reference to the accompanying drawings, the scale of which has been greatly enlarged for clarity.

 Figure 1 illustrates the simplest form of composite photographic structure according to the invention.

 Figure 2 is a cross-sectional view of a composite photographic structure according to the invention, showing several impressed layers of photographic emulsions containing dispersed particles of silver halide, as in the case where a color image is envisaged , an adhesive layer being applied to the exposed layer of silver halide.

Figure 3 shows the composite color photographic structure of Figure 2 during transfer to a support.

Figure 4 shows in perspective a portrait transferred to a support, as illustrated by the
Figure 3.

A composite photographic structure 10 includes a photosensitive member 11 formed from particles of silver halide dispersed in a photographic emulsion. The element 11 is closely linked to a transparent polymer barrier sheet 13 which, in turn, is removably linked to a support sheet 15. The adhesion of the photosensitive element 11 to the transparent barrier sheet 13, along the intermediate surface 12 is greater than the adhesion of the barrier sheet 13 to the support sheet 15 along the intermediate surface 14.

 Figure 2 shows a somewhat more complicated and currently preferred embodiment of a composite photographic structure 20 in the impressed state, i.e. in the ready state for transfer to a medium. The photosensitive element 21 is formed from impressionable layers 21a, 21b and 21c adhering to a transparent barrier sheet 23, an intermediate or primer layer 22 being interposed to improve the adhesion. The barrier sheet 23 is caused to removably adhere to a photographic support sheet 25, a peeling layer 24 being optionally interposed to obtain the desired degree of separability. The photographic support sheet 25 comprises a base layer of paper 26, on which is laminated a polymer sheet 27 serving to reduce any tendency of the sheet 25 to curl, for example when the layer of paper 26 expands during the development process (it will obviously be understood that, to improve the photographic yield of structure 20, there may be acuity dyes, filters, intermediate layers, antihalo layers, upper layers and other traditional layers and components).

In structure 20, each of the three impressionable layers 21a, 21b and 21c has been exposed to a desired pattern of actinic radiation, which gives respectively impressed areas 28a, 28b and 28c and unimpressed areas 29a, 29b and 29c. One of the three layers 21a, 21b and 21c contains a dye giving the color cyan or blue-green, while the other two layers contain respectively a dye giving the yellow and a dye giving the color magenta. As a result, an observer has the visual impression of a color representation. An adhesive layer 30 adheres firmly to the exterior surface of the photosensitive element 21.

FIG. 3 shows how the composite photographic structure 20, exposed and provided with an adhesive layer according to FIG. 2, is transferred to a surface of a canvas support 40, and how also the support sheet 25 is separated by peeling, by leaving the combined image of the layers 21a, 21b and 21c on the support 40, this image adhering thereto and being covered, for protection, by a sheet forming a transparent polymeric barrier 23. For convenience during the treatment of a photographic structure 20 and in order to obtain a transfer of the impressed photosensitive element 21 without deformation, it has been determined that the force necessary to separate the peelable layer 24 from the barrier sheet 23 should be between greater than 1 g / cm in width but less at 25 g / cm, the value of the adhesion to the coat preferably being between 6 and 10 g / cm in width. In most cases, in particular when the base layer 26 is formed by a photographic paper, the peelable or separating layer 24 can be omitted. If however the base layer 26 is a polymer sheet, the peelable layer 24 will probably be necessary to reduce the adhesion between the base layer 26 and the barrier sheet 24 in
desirable limits.

The barrier sheet 23 must be flexible and extensible enough to allow the transferred photographic structure to conform to the uneven surface of the canvas or other support to which this structure is applied. This sheet should furthermore be robust enough that the separation of the base layer 26 from its surface does not cause it to deform or break. Among the barrier sheets which are satisfactory, mention may be made of rubbery block copolymers of the AB type.
A and essentially non-oriented polyolefins, in particular low density polyethylene. To achieve the combination of appropriate robustness and good protection, while separating the photographic image from the observer at a minimum photosensitive element 21, the barrier sheet 23 is at least 10 microns thick but not more than 100 microns, this thickness preferably being of the order of 15 to 30 microns, which thus allows the sheet to be comply with irregularities of the underlying support.

 The layer 30, which can comprise a pressure-sensitive adhesive and normally tacky or activated by solvent, which can dry and harden, can be applied starting from organic solvents or in the form of melts or alternatively aqueous solutions and dispersions; alternatively, it can also be applied by a well-known transfer or transfer coating process. Excellent results are obtained using an emulsion of polyvinyl acetate ("white glue"), traditional pressure-sensitive adhesive transfer tapes, aerosol adhesives, etc. Application techniques can be roller application, brush application, transfer coating, etc. The adhesive layer 30 advantageously contains a sufficient quantity of titanium dioxide or of another pigment to make it opaque white, which thus creates the background necessary for the effective balance of the colors in the layer comprising the image 21 , that is, as in a color photograph. The flexibility of the adhesive layer 30 and its ability to conform to the element 21 should also be compatible with the properties of the barrier layer 23 and of the support 40.

 The presently preferred adhesive system according to the invention is a system which has adhesion characteristics with sensitivity to pressure at room temperature and comprises a hot melt adhesive, which can be activated with heat, containing microspheres of an elastomeric copolymer which is inherently tacky, as described in more detail in US Patent No. 4,049,483. An adhesive of this type is sufficiently tacky to allow the structure 20 to remain temporarily in a fixed position, the degree of sticking being however low enough that this structure 20 can be easily removed and replaced if desired. the structure 20 has finally been put in place, a sufficient amount of heat is applied to the surface 27 to activate the adhesive adhesive component of the layer 30, to create a sufficient flow so that there is an intimate conformation to the irregularities surface 40 of the support 40. Although a press comprising a heated plate is preferred for activating the melt component of the adhesive layer 30, it has been found that an ordinary pressing iron can also be used for this purpose.

 It will be readily understood that the image visible in the photosensitive element 11 or 21, exposed and developed, is reversed when the structure 10 or 20 is applied to a support. However, a positive can easily be obtained by simply reversing the negative through which the photosensitive element 11 or 21 is exposed to actinic radiation.

To allow a better understanding of the invention, various nonlimiting examples are presented below, all the parts mentioned being by weight unless otherwise indicated.

Example 1
A piece of biaxially oriented polyethylene terephthalate sheet is prepared, about 36 microns thick and comprising, on one side, a layer of peeling or separation of silicone. A sheet of high density polyethylene, about 15 microns thick, is placed on the silicone coated surface of the polyester sheet and the whole is placed in a dry mounting press at about 1500C for 3 minutes The laminated product is removed from the press and allowed to cool for 5 minutes at room temperature, then the exposed surface of the polyethylene sheet is subjected to a 2-crown discharge treatment at a rate of 54 dynes / cm and, using a rotogravure cylinder, apply a 1% solids undercoat solution, containing chromium alum, gelatin and a wetting agent.

To give more body to the structure which has just been described, an opaque white paper is then prepared on each side of which is laminated a sheet 2 of polyethylene, this paper weighing approximately 125 g / m. On an exposed surface of the polyethylene sheet, a layer of a 25% solids solution is applied, formed from an adhesive of isooctyl acrylate and acrylic acid copolymer (95.5 / 4, 5), the solvent then being evaporated in a hot air oven maintained at approximately 800C for 4 hours to leave a dry layer of adhesive, weighing approximately 12.5 g / m. On the surface coated with adhesive, then laminate the untreated side of the polyester sheet described in the previous paragraph, then apply three layers constituting a photographic emulsion element # of silver halide, entirely in color, over the surface previously furnished with an undercoat of the polyethylene sheet.

Each of the three layers of the photographic element contains a different chromogenic chemical, i.e. a dye giving the color cyan or blue-green, a dye giving the yellow and a dye giving the magenta. The composite photo-emulsion element is then impressed, developed by traditional photographic methods in the wet and dried state, then a layer, previously formed, of a hot melt adhesive, containing microspheres of an elastomeric copolymer inherently sticky (see the patent for
United States of America No. 4.049.483), supported by a removable liner, is placed in contact with the surface of the developed photo-emulsion and the rear side of this liner is actively rubbed to ensure proper bonding. is removed, the exposed surface of the adhesive is sufficiently sticky to allow the assembly to be mounted in a desired position while being able to be easily removed and replaced.

The adhesive coated surface of the structure which has just been described is placed in contact with a canvas fabric, comprising eight threads / cm in the warp direction and in the weft direction and the assembly is put on, for 1 minute. , in a press comprising a 2.5 cm foam pad, to which is opposed a plate heated to about 800C, so as to thus pour the hot melt adhesive component of the adhesive layer and to bind it securely to the support in canvas. The laminated product is then removed from the press and allowed to cool for 1 minute, then the photographic paper with a polyethylene surface is folded back on itself at 1800 and separated by peeling from the photographic layer. force required for removal at 30.5 cm / minute is 8.7 g / cm in width, when the measurement is made according to the specification ASTM n0
D903. There remains on the canvas a photograph which is the specular image of the one which appeared previously on the original photographic composite structure. The photograph is protected by the sheet of high density polyethylene, the surface of which shows an irregular appearance corresponding to that of the underlying canvas.

Example 2
A white base paper, of photographic quality, is prepared on the surface of which is laminated a sheet of polyethylene of a type which does not undergo deformation. A 5% solids solution in heptane is applied to the exposed surface of the paper, formed by a traditional peeling agent consisting of silicone ("Siloff" 23, product available on the market from the company Dow Chemical
Company), then the solvent is evaporated in an oven and the silicone is hardened by heating for 2 minutes at 930C, which leaves a layer of dry coat, thinking about 2230 mg / m
On the surface of the paper, coated with silicone, a 19 micron layer of high density polyethylene (DFD 3300, product of the company Union) is extruded.
Carbide, Inc.). The installation used is a 19 mm, four-zone laboratory extruder, with a length / diameter ratio of 25/1 and a screw speed of 20 revolutions per minute. The four zones are respectively heated to 2440C, 2540C, 2660C and 2710C, the temperature of the die being 258 C, while its second pressure is 42.8 kg / cm. The extruded polyethylene tape, in contact with the silicone-coated surface of the paper, then passes between a rubber cylinder and a chrome steel (82 C) cooling cylinder, the latter receiving contact with the extruded polyethylene. exposed surface of the extruded polyethylene is then subjected to a corona discharge treatment, then covered with an undercoat, and coated with a fully color photographic emulsion, all essentially as in the case of Example 1.

 The emulsion is impressed, developed, dried, covered with a layer of microspheres containing a hot melt adhesive, and then transferred to a canvas support, again according to the method of Example 1. The necessary force to separate the paper backing from the image protected by polyethylene is 5.4 g / cm in width.

Example 3
Example 2 is repeated except that a peeling agent formed from silicone is omitted. The force to separate the paper support from the image protected by polyethylene is 6.3 g / cm in width.

Example 4
Example 3 is repeated, except that the high density polyethylene resin is replaced by a transparent low density polyethylene resin ("PolyEth" 4516, product of the company Gulf Oil Chemical Co.) and that one uses a 51 mm extruder with a length / diameter ratio of 28/1. Satisfactory results are obtained when the operating conditions of the extruder are as follows: screw speed of 70 revolutions per minute; temperatures of the extruder zones: 2460C, 2600C, 2740C and 2740C respectively; die temperature: 2740C; pressure of 2 the die: 35.1 kg / cm; temperature of the cooling cylinder: 80C. The force required to separate the base piece from the exposed polyethylene-protected layer is 6.4 g / cm in width.

 Although, as mentioned, advantageous artistic effects can be obtained by transferring impressed photographic emulsion layers onto a canvas, the images can also be transferred to paper or cardboard materials for the preparation of packaging. aesthetic, on clear acrylic sheets that are used in backlit photographic displays, on steel plates that are used in graphics, on glass to create a non-storytelling imitation of tinted glass, on enamelled panels that are used for photographic transfers, on wooden panels for rustic effects, etc.

Claims (6)

1. Photographic reproduction, comprising a support, such as a fabric, steel, glass, wood, an enamelled panel or an acrylic sheet, a layer of an adhesive system over at least part of the support, and an impressed element containing silver halide, over the adhesive system layer being bonded thereto, characterized in that a sheet, barrier, light transmitting, flexible, self-supporting is provided over the element containing the silver halide and is linked to it, thus protecting the impressed element against abrasion.  2. Photographic reproduction according to claim 1, characterized in that the adhesive system is white and opaque, thereby creating the background necessary for a real balance of colors.  3. Photographic reproduction according to claim 2, characterized in that the adhesive system comprises a hot melt adhesive, which can be activated by heat, containing microspheres of an elastomeric copolymer which is inherently tacky.  4. Photographic reproduction according to any one of claims 1 S 3, characterized in that the barrier sheet is made of polyethylene.  5. Photographic reproduction according to any one of claims 1 to 3, characterized in that the barrier sheet is of a thickness of 15 to 30 microns and is formed of a high density polyethylene. 6. A method of preparing the photographic reproduction according to any one of claims 1 to 5, characterized in that it comprises: the rehabilitation of a composite photographic structure comprising a photosensitive element including at least one layer of emulsion photographic material containing dispersed silver halide particles, a flexible, self-supporting support sheet and, between this photosensitive element and this support sheet, a self-supporting barrier sheet, polymer, thermoplastic, stretchable, flexible, transmitting light, bonding together this photosensitive element and this support sheet, the peel adhesion between the barrier sheet and the support sheet being substantially lower or else the peel adhesion between the barrier sheet and the element photosensitive or to the cohesion resistance of the support sheet or of the barrier sheet; exposing the photosensitive member to radiation creating an image; the development of the image in this photosensitive element; applying a layer of adhesive to the surface of the photosensitive member; bringing the surface of the hesitant ad into contact with a support and creating an adherent bond between them; and removing the backing sheet to leave a photographic image which adheres to the backing and is covered by the barrier sheet which protects it.