Abstract:
A film-mount structure comprises a relatively stiff face sheet and a backing sheet which can be peeled off to expose an adhesive for receiving, in a removable and replaceable manner, a film strip for retention and viewing. In order to protect the cellulose-based face sheet from partial separation when the radiographic film is peeled from the adhesive surface, a thin mylar sheet is adhesively attached in a substantially permanent manner to the face sheet, and the releasable adhesive is applied directly to the other side of the mylar sheet. In this way, the film mounts&#39; reusable feature is retained while maintaining the integrity of the face sheet.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to film mount structures and, more particularly, to structures for the convenient mounting, viewing, handling, and storing of exposed x-ray film strips. 
     In the medical field, it is common to record x-rays on photographic film, usually by way of a roll of film which is subsequently cut into a number of film strips, with each of those strips in turn having a number of frames. In order to accommodate the viewing, handling, and storing of those film strips, it is common to mount a number of these strips in a mounting device. Such device can be attached to the front of a uniform light source, or viewer, in order to view and analyze the films. After use, the mounting device, with its installed films, can be stored in the files for subsequent use. 
     One such mounting device is described in U.S. Pat. application Ser. No. 159,956, assigned to the assignee of the present invention and incorporated herein by reference. The film-mount structure described in that application comprises an apertured face sheet having an adhesive applied to the rear side thereof for receiving a backing sheet which, when removed in whole or in part, exposes the adhesive surface for receiving the film strips in a manner which allows them to be retained in position for subsequent handling. The type of glue, however, is carefully chosen, such that the relative bondings between the film and the adhesive and between the face sheet and the adhesive are such that the film can be removed and replaced without any significant damage to the integrity of the face sheet or to the adhesive coating thereon. 
     Because of cost considerations, it is desirable to fabricate the face sheet of a relatively inexpensive material such as &#34;tag board,&#34; a commonly available wood-pulp product. In accordance with the above-mentioned structure, the adhesive then is applied directly to one side of the tag board. If the removable/replaceable feature is to work, the adhesive chosen then has to be of a nature such that the bond between the film and the adhesive is less than that between the tag board and the adhesive. However, even if this condition is met, it may be that the internal bonding of the tag board itself is less than the bonding between the film and the adhesive, in which case the tag board will experience a partial, or possibly even total, separation. If this occurs, portions of the tag board will be torn off and will stick to the film by way of the adhesive, thereby possibly causing damage to the film and to the mount structure itself. 
     It is therefore the object of the present invention to provide an improved film mount which will overcome the deficiencies described hereinabove. 
     Another object of the present invention is the provison for a film mount having a cellulose-based face sheet. 
     Still another object of the present invention is the provision for a film mount which allows the repeated removal of film strips from an adhesive-laden, cellulose-based face sheet without incurring damage to the face sheet, adhesive, or the film. 
     Yet another object of the present invention is the provision for a film mount which is economical to manufacture and extremely functional in use. 
     These objects and other features and advantages become more readily apparent on reference to the following description taken in conjunction with the appended drawings. 
     SUMMARY OF THE PRESENT INVENTION 
     Briefly, and in accordance with one aspect of the invention, the face sheet of the film mount is protected from internal separation by the placing of a thin polyester sheet between the face sheet and the adhesive coating. The adhesive is then applied directly to the polyester sheet, rather than to the face sheet, and the polyester sheet is, in turn, attached to the face sheet in a substantially permanent fashion by way of an adhesive having a higher bonding characteristic than the adhesive on the other side of the polyester film. In this way, the integrity of the face sheet is not threatened by the removal of the film strip from the adhesive since the securely bonded polyester sheet protects it from any separation which might occur as described hereinabove. 
     In the drawings, as hereinafter described, the preferred emobodiment is depicted; however, various other modifications and alternate constructions can be made thereto without departing from the true spirit and scope of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the film-mount structure in accordance with the preferred embodiment of the invention; 
     FIG. 2 is an enlarged, fragmentary sectional view of a mount without the protective layer; and 
     FIG. 3 is an enlarged, fragmentary sectional view of a mount with the protective layer in accordance with the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention is shown generally in FIG. 1 and comprises a face sheet 11 and a backing sheet 12, with a protective polyester sheet, film, or layer 13 sandwiched therebetween. Particular types of adhesives are applied both between the polyester layer 13 and the face sheet 11 and between the polyester layer 13 and the backing sheet 12, as will be more fully described hereinafter. 
     It should be recognized that the particular design of the film mount, and that of its face sheet 11 and backing sheet 12, may take any of a number of forms. For example, the backing sheet 12 may be a single sheet which, when removed, will expose the entire adhesive-laden surface above the face sheet 11. In the preferred embodiment as shown, however, the backing sheet comprises, after selected die-cutting procedures have been performed, three parallel strips 14 disposed in close, adjacent relationship, such that any one or all can be individually removed to expose the relatively low-bond adhesive 15 for receiving a film strip 16 thereon. The term &#34;low bond&#34; as used with this adhesive shall mean, for purposes of this description, one which allows the peeling away of the backing sheet 12 and the subsequent application, removal, and reapplication, in a bonding manner, of a film strip 16. The film mount illustrated in FIG. 1 has two of its three backing sheet strips 14 removed and a film strip 16 placed in one of the two positions. 
     It will be seen that, in addition to the fact that the backing sheet 12 is die cut to provide three backing sheet strips 14, each of these strips is further die cut at two intermediate positions 17 and 18 so as to thereby provide three adjacent panels 19, any of which can be individually removed to provide an aperture for receiving a single radiographic film frame. Regardless of whether a single or a plurality of panels 19 are removed, a structural framework portion 21 of the backing sheet 12 is left to act as a guide for the placement of the film frames or strips 14 therein. 
     The backing sheet 12 is fabricated of a relatively light and flexible paper-based material which adheres to the low-bond adhesive 15 in such a manner as to allow for the easy removal of the individual strips 14 or panels 19 but, at the same time, allowing for the permanent adherence of the framework portion 21. A material which has been found to be suitable for use as this backing sheet is one which is commercially available and is described as 50 pound, clay-coated on one side, craft, silicone-release liner. Generally, this material can be described as being relatively granular and porous on its one side and relatively non-porous and &#34;slick&#34; on the side which attaches to the adhesive. 
     Referring now to the face sheet 11 portion of the mount structure as shown in FIG. 1, it is fabricated of a light-weight, relatively stiff material which acts to form the basic framework of the mount structure. The sheet has a plurality (nine in the embodiment shown) of apertures 22 formed therein as by die cutting of the included tabs 23 (three shown) to provide windows for the individual frames of the film strips. In the initial fabrication and cutting, the individual tabs 23 are left in their corresponding apertures 22 until such time as it becomes necessary and desirable to place a film strip therein for viewing. At that time, the tab or tabs are then removed, preferably along with the backing sheet as described in the above-referenced patent application. 
     In that application, one of the suggested materials for the face sheet 11 was tag board, which is a low-cost, light-weight material made from wood pulp. Although otherwise preferred, such a material has a tendency to internally separate when exposed to highly localized stresses. For example, when the low-bond adhesive 15 is applied directly to the tag board face sheet 11, as suggested in one embodiment of the above-referenced patent application, and as shown in FIG. 2 hereof, there is a tendency, when a film strip 16 is applied and subsequently peeled away, to pull or tear away a portion 24 of the face sheet 11 at points where the internal bonding of the face sheet is inadequate. This will occur if the adhesive bond between the film strip 16 and the adhesive 15 is sufficiently greater than that of the internal bond at a particular location within the face sheet 11. As a result, a hole 26 is left in the face sheet 11, and the face sheet portion 24, along with some of the adhesive 15, is left on the film 16, both conditions of which are highly undesirable. 
     The Applicants have recognized the above-described problem and, having a desire to continue use of a cellulose-based material, such as tag board, have devised the present protective structure for the face sheet 11 as shown in FIG. 3. 
     Disposed on the one side of the face sheet 11, in a substantially permanent manner, is the protective sheet, film, or layer 13 which acts to interface with the film strip 16 by way of the low-bond adhesive 15 in much the same way as the face sheet 11 interfaces with the film strip 16 as shown in FIG. 2. However, the internal strength of the protective sheet 13 is sufficient to prevent any separation as described hereinabove. Further, the protective sheet 13 and the manner in which it is applied to the face sheet 11 prevents any separation of the face sheet in that manner. This preventation is accomplished in two ways. First, the protective sheet 13 is applied to the face sheet 11 by way of a relatively high-bond adhesive 27 which is applied in liquid form and which dries to form a substantially permanent bond. Thus, the high-bond adhesive 27 tends to penetrate deeper into the face sheet 11 than does the so-called low-bond adhesive 15 and, when dried, it tends to lend strength to the face sheet 11 itself. Second, the presence of the protective sheet 13 between the face sheet 11 and the relatively high local stresses, which may occur when the film strip 16 is peeled away, tends to distribute the stresses over a wider area of the face sheet 11. 
     Whereas any type of polyester, plastic, foil, or other suitable material may be used for the protective layer 13 as described hereinabove, a preferred material is one which is commercially available under the name &#34;Mylar&#34; TM from E. I. DuPont de Nemour &amp; Co. The particular thickness of the material may be chosen to suit any of various other needs; however, a thickness of 0.0005 in. has been found to be satisfactory for purposes of economy, ease of application, and functionality. Similarly, any of a number of types of high-bond adhesives 27 may be used in the manner described hereinabove. 
     Other features and advantages characteristic of the film mount described in the above-referenced patent application are not substantially affected by the modification proposed in the present application. For example, the die-cut operations, which are performed on each side of the film mount to obtain the necessary cuts and perforations, are still possible with the present embodiment. This involves only two cutting operations, first, through a combination of the face sheet 11, the high-bond adhesive 27, the polyester film 13, and the low-bond adhesive 15, and second, from the other side, through the backing sheet 12, and the low-bond adhesive 15. 
     While the present invention has been shown and described in terms of a specific embodiment, it will be understood that other modifications and improvements will be apparent to those skilled in the art.