Abstract:
A transparency is disclosed, which is suitable for use in a multicolored xerographic reproduction process comprising a transparent, thermoplastic film sheet having at least one surface treated with organic amine compounds or salts thereof. The treated transparency, when used in a multicolored electrostatic copying process improves adhesion of the multicolored image thereon and permits reproduction of colors and color densities in said image which correspond well enough to the multicolored original copied.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to xerographic reproduction and specifically to transparencies which are suitable for use in a xerographic reproduction process. 
     Transparencies are a highly useful product in visual education since an image on a transparency may be projected with the necessary degree of magnification onto a screen where it may be viewed by a large number of persons. Transparencies have heretofore been made by photographic reproduction of the desired image and accordingly have required the skill of an individual who is familiar with complex photographic reproduction processes. Photographic reproduction of transparencies also requires the expenditure of a large amount of time and money and is thus undesirable for this reason. Therefore, an easy and inexpensive means for the production of transparencies has been sought whereby transparencies could be conveniently and economically imaged and then used an unlimited number of times in visual education programs. 
     The advent of xerography and electrostatic copying as generally disclosed by Carlson in U.S. Pat. No. 2,297,691 has proven to be a highly successful process for reproduction with the inherent advantages of speed and reliability. In a usual xerographic process, an electrostatic image of an object is formed on a recording member such as a xerographic plate or drum. The xerographic plate may comprise a layer of photoconductive material, such as selenium on a conductive metal backing. The latent electrostatic image which is formed on the photoconductive material is developed into a powder image which is then subsequently transferred to a sheet of paper and affixed thereon to form a permanent print. 
     The xerographic process has therefore proven to be an easy and reliable means for the production of transparencies. Transparencies made by a xerographic process are produced by forming an electrostatic image of the desired object, developing it, and then transferring it to a transparent sheet material with the image being permanently affixed or fused thereto by either the application of heat or by the action of a solvent vapor. In either case the toner which is used to develop the powdered image is coalesced on the sheet material by the fusing technique to form a permanent image thereon. Solvent fusion techniques, for transparent materials made by a xerographic process, for example, are illustrated in U.S. Pat. Nos. 3,049,810 and 3,148,078. 
     While the xerographic reproduction process is an apparent solution to the problem of economical and efficient production of transparencies, other problems have also been encountered with its use in the production of transparencies. One of the most pronounced problems with producing transparencies by an electrostatic copying process is to get the powdered or developed image to adhere well to a transparent film material before the image is permanently affixed thereto by fusing. Failure to achieve this results in partial or &#34;cracked&#34; images. A further problem encountered is obtaining proper and uniform density of the image after fixing or fusion and without resultant damage to the transparent film material either in the fusion process or in the transfer system employed within the machine. For this reason, various coating and combinations thereof with various types of transparent sheet materials have been previously proposed to obviate some of these difficulties. Included are various single component polymeric coatings such as are exemplified in U.S. Pat. Nos. 3,539,341 and 3,535,112. 
     The above coatings, while of some assistance in improving adhesion of the developed electrostatic image to a transparent film material, nevertheless, are not entirely suitable when transparencies are produced by a multicolored xerographic imaging process. The difficulties encountered with a multicolored imaging process and transparencies produced thereby are due in part to the multicomponent pigment developers required in the multicolored imaging process and their varying degree of attraction for the transparent sheet material. Furthermore, the problem of getting the correct degree of coalescence of the toner particles in the permanent image is an even more critical matter with multicolored imaging than with single color image development. This increased criticality is due to the fact that single color transparent images only require complete opaqueness or nonopaqueness of varying degrees to produce a transparency which has images suitable for projection. 
     Multicolored transparency images, on the other hand, must allow for a certain degree of color density for each color or color combination in the image which is sufficient and uniform enough to allow projection of a uniform and true color. This, therefore, requires a different and unique combination of materials being employed and more critical controls being imposed upon the transparent materials which are used in a multicolor xerographic imaging process to obtain the correct degree of attraction of toner to the transparent sheet as well as proper coalescence of toner particles for good color density. 
     The instant invention relates to a transparency which fulfills all the requires for use in the production of multicolored electrophotographic images. The subject invention is particularly suited to overcome difficulties associated with the projection of color xerographic images which are formed on transparencies. In addition, the instant invention utilizes materials which are readily available and are relatively simple to work with. By means of the subject invention effective transparencies for use in a xerographic color process are easily prepared. 
     It is an object of the present invention to provide a transparency which is permanent in nature and having the sheet strength necessary to allow repeated use thereof for visual education purposes. 
     It is also an object of the present invention to provide for production of a color transparency by a xerographic multicolor imaging process which in turn eliminates the skill of a technician who is trained in reproduction photographic processing. 
     These and other objects, as well as the scope, nature and utilization of this invention will be apparent by the following detailed description and appended claims. 
     SUMMARY OF THE INVENTION 
     It has now been determined that the general objective of producing a transparency which will permanently hold a true and consistent multicolor xerographic image may be best achieved by utilizing a transparent, thermoplastic, film sheet such as a polysulfone, polycarbonate, or polyester sheet material, which has been chemically treated prior to xerographic imaging with an organic amine compound such as methyl amine or salts thereof. It is this treatment which has been found to insure that all colored pigments required in the multicolored reproduction process are properly attracted to and held by the transparent sheets during imaging and sheet so that a permanent image having a uniform and accurate color densities may be then fused on the transparent sheet. This treatment overcomes the previously noted difficulties with producing a transparency by a multicolored electrostatic copying process, among which are poor adherence of the developed xerographic image on the transparent film, as well as difficulty in insuring that a consistent and true color density is developed from the colored original which will also be suitable for projection or magnification on a screen. As indicated, these problems while existing with single color xerographic imaging, are even more pronounced when a multicolored xerographic process is employed. 
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In the process of multicolored xerographic reproduction, a subtractive color to color reproduction technique is used to develop images formed on the photoconductive layer. Furthermore, a multicolor xerographic imaging process may also employ multiple scanning of the colored original at different wavelengths of light to produce multiple images corresponding to each primary color involved in the original. These primary color images may be then recombined to form a single multicolored image corresponding to the original by using a multicomponent or multicolored toner in a subtractive color to color reproduction process. A subtractive color to color reproduction process is illustrated in U.S. Pat. No. 3,057,720. 
     Toners which are employed in multicolor xerography use subtractive primary colors, yellow, cyan (blue green) and magenta. These in turn are used to reproduce a wide gamut of colors normally found in the colored original. For the purposes of illustration, when subtractive mixing of the yellow and cyan colorants take place, greens are obtained. Likewise, the mixing of magenta and yellow colorant in varying amounts reproduces reds, while combining the cyan with magenta results in the reproduction of blues. Mixtures of equal amounts of each toner, of course, will produce a black image. 
     Production of the multicolored copy from the colored original may be appropriately achieved by any multicolored xerographic imaging process. It is not intended that this invention be limited by particular variations in the multicolored xerographic imaging processes that might be employed or with the equipment used in said process. Nevertheless, for the purposes of illustration, a suitable process for color imaging begins with proper discernment of the color composition of the original subject matter and recording thereof. This may be conveniently accomplished by sequential optical scanning of the color original a number of times to formulate a sequence of the latent electrostatic images which correspond to the primary colors in the original. This is accomplished by the light image passing through an appropriate color filter so that the latent image is then in effect, color separated according to the various primary colors. Theoretically, the latent image which is formed by passing the light image through a green filter should require the magentas (the complementary color) as areas of relatively high charge density on the drum surface, while the green (the separated color) should cause a low-charged density level. The magentas are then made visible by applying a green absorbing magenta toner to the image bearing member. By the same token, a blue separation is developed with a cyan toner. The three developed color separations are then brought together in registration upon the final sheet of support material to produce a multicolored facsimile of the original colored document copy. 
     It is this multicomponent developer system used in a subtractive color to color reproduction process which presents numerous problems when, for example, a color transparency is produced thereby which will reproduce, with uniform and accurate consistency the color densities which correspond to the colored original. 
     In the production of transparencies by a multicolored xerographic imaging process according to the present invention, a transparent, thermoplastic film sheet is selected as the support material upon which the multicolored xerographic image is to be developed. Although the sheet material may be any suitable thermoplastic film material which has the clearness, strength and heat resistance to allow repeated projection thereof, materials which are particularly preferred for the present invention include thermoplastic resins such as polysulfones, polycarbonates, or polyesters. 
     Thermoplastic sheet material which may be conveniently utilized in the present invention includes polysulfone sheet material which are commercially available from Rowland Products Inc., Kensington, Conn. and Instar Supply Co., Inc., New York, N.Y. under the name Folacron PSN, as well as polycarbonate sheet materials commercially available from General Electric Corp., Waterford, N.Y. under the names LEXAN SL1007 (a tetrachloro-polycarbonate) and LEXAN DL616 (a tetrabromo polycarbonate). These materials may be selected from any thickness range desired, although in selecting film thickness, the films should be thick enough to have the necessary strength but still be thin enough to remain flexible throughout continuous use thereof. A suitable thickness of the film suitable for use in xerographic imaging, will generally be 3 to 8 mils. 
     Within the purview of the present invention, the thermoplastic film material is chemically treated with an organic amine compound by applying said amine to the surface of the film and thereafter washing said surface. The chemical treatment is carried out by immersing the films in the respective solution of solvent and organic amine for a specific temperature and time. Washing takes place with the same or additional solvents and subsequently dried. The amine compound treatment has been found to increase the compatibility between the toner and transparency surface thereby resulting in a smoother interface and a more transparent (projectable) image. 
     The treating composition developed herein comprises a mixture of an organic amine or the salt thereof and a suitable solvent for treating purposes. While any and all organic amines fall within the purview of the present invention, preferred compounds include methyl amine, ethylenediamine, ethanolamine, octylamine, diamino octane and salts and mixtures thereof. Films treated with these particular compounds have been found to give optimum results. 
     The applied mixture will be normally coated on the transparent film material in the form of a solution and because of this, the choice of solvents to provide the solution is important, relative to the coating composition, since it must not cloud or change the film material and it must at the same time provide enough solubility for the amine compound to provide a clear uniform coating on the transparency with no evidence of component insolubility. 
     Suitable solvents for the organic amines of the present invention are those organic liquids which will dissolve the compounds but which are nonsolvents for the substrate material. The solvent composition found to be suitable for use with the present compounds and for their application to transparencies produced therewith are hydrocarbon solvents such as hexane. Additionally, alcohols such as ethanol and isopropanol can be used. And further, mixtures of conventional solvents may be employed to attain the requisite coating on the transparency. Aside from the selection features mentioned above, the particular solvent utilized is not considered critical to the ultimate transparencies formed within the purview of the present invention. 
     The organic amine materials which may be used in the treatment composition of the present invention may be any commercially available form of these materials. Most of the amine compounds mentioned above are supplied by the Armour Industrial Chemical Co. of Chicago, Ill. 
     The treatment compound after dissolution in the appropriate solvent mixture is applied to the transparent thermoplastic film by techniques which are well known to those skilled in the art of coating. Various techniques which are suitable for coating could be by roll, air knife, or any other uniform application means used in paper coating. For instance, the film may be simply passed (or dipped) through a hopper containing the coating composition in liquid form, which is provided by a doctor blade or the coating may be applied by use of a more precise coating apparatus such as a gravure press. After coating the organic amine compound the film is then washed with an appropriate solvent to remove the amine and thereafter the film is allowed to dry. Alternatively, a curing step may be employed to hasten reaction of the amine with the film. The time of reaction of the instant amine materials with the thermoplastic film should be up to about 10 minutes. 
     The following represents a specific illustration of the present invention although it should be understood that the invention is not intended to be limited to specific details to be set forth thereon. 
    
    
     SPECIFIC EMBODIMENTS OF THE INVENTION 
     In the following illustrations two film types were used, LEXAN DL616 (a tetrachloro polycarbonate) and LEXAN SL1007 (a tetrabromo polycarbonate). The amine treated films were made by immersing the transparencies in the respective amine solutions at about 50° C for the designated times. Copies were made in a Xerox Model D processor (flat plate) using a premixed developer containing 10 g. of Xerox Cyan Toner, internally designated as XT 1318C-13, and 500 g. of carrier material, internally designated as XC910-20. Print fixing was accomplished in a Xerox Model D fuser which had temperatures ranging between 150°-170° C. The resulting transparencies were judged by projection using a &#34;Telegraph-Resolute&#34; mode 21105 overhead projector and rating on a transparency scale of from 1 to 10. Therefore, a rating of 1 indicates that no color whatsoever was visible on the projection screen while a rating of 10 indicates complete transparency. 
     As can be seen from the data in Table 1, all the amine treated films exhibit a transparency of 5 or better. Particularly satisfactory results occur with the ethanolamine treatment of the films. It is to be noted that the HCl catalysed amines are the salts of the particular amines. 
     The amine treated transparent sheet material was subjected to a colored xerographic imaging process, as outlined above, with resultant heat fixing of the adherent image. It was observed that superior image adhesion occurred both before and after the fusion step. In addition, the colors reproduced were uniform, with consistent color density and with no evidence of toner &#34;spotting.&#34; Additionally, the treated transparencies of the instant invention exhibited lower frictional and static properties when compared with the uncoated transparencies. 
     It can be seen from the data set forth that the transparencies which are treated with the instant organic amine compounds exhibits improved toner adhesion properties and therefore are capable of better color image projection than the untreated transparencies. 
     
                                           TABLE 1__________________________________________________________________________           REACTION                  PRINT FUSETREATMENT       TIME/MIN                  TIME/MIN                         TRANSPARENCY__________________________________________________________________________Immersed in 6.7 % Aqueousmethyl amine    1      0.5    5Immersed in 6.7 % Aqueousmethyl amine    2      0.5    5As above with HCl catalyst           1      0.5    6As above with HCl catalyst           3      0.5    5Immersed in 20 % ethylenediamine         15     0.5    5Immersed in pure ethanol-amine           2      0.5    6Immersed in 50 % Aqueousethanolamine    3      0.5    8Immersed in 50 % Aqueousethanolamine    5      0.5    6Immersed in 2.5 % octyl-amine/hexane    5      1.0    5Immersed in 2.5 % octyl-amine/hexane    3      1.0    6Dipped in 0.4 % 1,8-diaminooctane/hexane   1      0.5    7Dipped in 0.2 % 1,8-diaminooctane/hexane   1      0.5    7__________________________________________________________________________