Abstract:
A method for creating a scratch-off document, the method includes the steps of providing a substrate with an image; covering the image with a scratch-off toner; sintering the scratch-off toner; wherein an amount of the sintering of the scratch-off toner is determined from a group consisting of pressure, speed, and mass of the scratch-off toner so that the scratch-off toner is sintered at a level which permits removal.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    Reference is made to commonly-assigned U.S. patent application Ser. No. ______ filed concurrently herewith, entitled “Method For Creating A Scratch-Off Document With Low Energy Components” by Dinesh Tyagi et al, the disclosure of which is incorporated herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention generally relates to scratch-off documents having an image covered by a scratch-off layer and more particularly to sintering the scratch-off layer that is easily removed during scratch-off. 
       BACKGROUND OF THE INVENTION 
       [0003]    Currently, scratch-off documents are used for a variety of applications. One of the most commonly used applications is the use of scratch-off documents for creating lottery tickets. In this application, a person purchases a lottery ticket and uses a hard object to scratch off the portion of the ticket covering hidden information such as a particular number. The use of scratch-off documents has vastly increased over the past years and several prior art documents address creating scratch-off documents. 
         [0004]    In this regard, U.S. Patent Application Publication 2007/0281224 is directed to a scratch-off document in which a first layer of toner forms an image which is first fixed to the substrate. An optional barrier layer, typically clear, is deposited and then affixed hereon. The first layer is well adhered to the substrate and the barrier layer is well adhered to the first layer. A second removable layer of toner is imaged and adhered to the first layer or the barrier layer in a second fixing step. The second toner layer is incompatible with the first toner layer and the barrier layer and can be removed when scratched using a hard object, leaving the first layer intact on the substrate. The application of the barrier layer is carried out offline and the document is reprinted with the scratch-off layer. 
         [0005]    U.S. Patent Application Publication 2008/0131176 is directed to an apparatus and method for producing a scratch-off document in which front side information containing the information to be hidden prior to scratch-off is first fused or otherwise well adhered to the base material prior to the printing of a removable scratch-off layer. 
         [0006]    U.S. Patent Application Publication 2009/0263583 is directed to a scratch-off document in which the information layer includes both an indicia and a noise component of varying height. A scratch off layer is deposited over the noise component. This variable height functions to obscure the indicia so that it is not easily seen until scratched off. 
         [0007]    U.S. Pat. No. 8,342,576 is directed to a scratch-off document having a first toner layer containing hidden information (i.e., the image that will eventually be revealed to the user after scratch off). The first layer is fixed to the substrate and then covered by a printed, removable, waxy scratch-off layer having a distraction pattern. 
         [0008]    Although each is satisfactory, cost efficiency improvements are always needed, as is the need for simple, but efficient scratch-off documents. 
       SUMMARY OF THE INVENTION 
       [0009]    A method for creating a scratch-off document, the method comprising the steps of: providing a substrate with an image; covering the image with a scratch-off toner; sintering the scratch-off toner; wherein an amount of the sintering of the scratch-off toner is determined from a group consisting of pressure, speed, and mass of the scratch-off toner so that the scratch-off toner is sintered at a level which permits its removal. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter of the present invention, it is believed that the invention will be better understood from the following description when taken in conjunction with the accompanying drawings, and wherein: 
           [0011]      FIG. 1  is a block diagram of an electro-photographic reproduction apparatus suitable for use in the practice of the present invention; 
           [0012]      FIG. 2  is a side view in cross section illustrating a substrate having underlying toner deposited thereon according to one embodiment of the present invention; 
           [0013]      FIG. 3  is a side view of  FIG. 2  after the underlying toner is fixed to the substrate forming a fixed image layer; 
           [0014]      FIG. 4  is a side view illustrating scratch-off toner deposited onto the underlying fixed image layer; 
           [0015]      FIG. 5  is a side view of  FIG. 4  after the scratch-off toner is sintered forming a fixed scratch-off layer; 
           [0016]      FIG. 6  is a side view after the scratch-off layer is removed by the scratch-off tool revealing the hidden information; 
           [0017]      FIG. 7  is a top view of  FIG. 6  along line  6 - 6  with the scratch off tool removed from view for illustrating the hidden information, the letter “K” in this example; and 
           [0018]      FIG. 8  is an alternative embodiment of  FIG. 2  having an indicia image printed on the substrate before depositing the scratch-off toner and an optional non-image toner. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    Before turning to the description of the present invention, it is important to note terms as used herein. In this regard, “sintering” means to form a continuous or substantially continuous mass without melting or without substantially melting. In sintering, the toner particles coalesce into a continuous mass through the application of pressure resulting in cold flow and cohesion of the particles. When a toner image is “fixed” to a substrate by fusing, sufficient heat is provided to cause a melt flow of the toner melt to penetrate into the substrate structure or to simply provide mechanical interlocking with the substrate. Thus the final image is well adhered to the substrate and cannot be removed easily. The resulting well adhered images do not lend themselves to provide a suitable scratch off document. However, by using the “sintering” process, the toner mass can be made to flow at ambient or very low temperatures. This can be achieved by making the toner particles to undergo cold flow. Cold flow can be described as the distortion, deformation, or dimensional change which takes place in materials under load at temperatures within the working range. In other words, cold flow is described as flow of thermoplastic materials that occurs at less than the optimum melt temperatures. Cold flow can also be described in terms of plastic flow under severe friction conditions. Therefore, cold flow is not due to heat softening or a melt process in which the materials has to undergo a phase transition. It is sometimes described as creep or compression set of the polymer that occurs at ambient temperature and is related to the viscoelastic flow of polymers under applied pressure. 
         [0020]    It is understood by those skilled in the art that partial melting can occur as a result of imprecision of the devices used or melted intentionally to a partial degree that still achieves the result of permitting scratch-off. 
         [0021]    Referring to  FIG. 1 , there is shown a block diagram of a scratch-off document apparatus  9 . The scratch-off document apparatus  9  includes an image forming unit  10  into which a substrate  2  is input. The image forming unit  10  deposits an underlying toner  20  (as shown in  FIG. 2 ) onto the substrate  2 , as is well known in the art, and passes the substrate  2  to an image fixing unit  11 . The image fixing unit  11  functions to adhere the underlying toner  20  to the substrate  2  which transforms the underlying toner  20  into a fixed image layer  30  (as shown in  FIG. 3 ) on the substrate  2 . The fixed image layer  30  is well adhered to the substrate  2  by any suitable mechanism such as two nip forming heated rollers, vapor fusing, flash fusing, infrared radiation fusing, or microwave, all of which are well known in the art. The substrate  2  with the fixed image layer  30  is passed to a scratch-off image forming unit  12 , which deposits a scratch-off toner  40  (as shown in  FIG. 4 ) onto the fixed image layer  30  and also onto the substrate  2  not covered by the fixed image layer  30 . A sintering unit  13  receives the substrate  2  with the fixed image layer  30  and scratch-off toner  40  from the scratch-off image forming unit  12  and sinters the scratch-off toner  40 . This sintering transforms the scratch-off toner  40  into a sintered scratch-off layer  50  (as shown in  FIG. 5 ). This produces a scratch-off document  68  (see  FIG. 5 ) in which the sintered scratch-off layer  50  is mechanically removed (as shown in  FIG. 6 ). A logic and control unit  14  controls the scratch-off document apparatus  9  and in particular it controls the pressure, speed, and temperature of the scratch-off document apparatus  9  and mass of the scratch-off toner  40 . 
         [0022]    Referring to  FIG. 2 , there is shown a side view of the substrate  2  having the underlying toner  20  applied thereon by the image forming unit  10 . The substrate  2  is preferably, but not limited to, paper or any suitable printing media receptive to toner printing. It is noted that the underlying toner  20  is patterned in a predetermined shape on the substrate  2 . This predetermined shape is representative of, but not limited to, symbols, numbers, letters and other symbols used in writing, art and the like. Referring to  FIGS. 2 and 3 , the substrate  2  with the underlying toner layer  20  is passed through the image fixing unit  11  so that the underlying toner  20  is fixed to the substrate  2  which results in the fixed image layer  30 . It is understood by those skilled in the art that the underlying toner  20  can be fused to the substrate  2  by the image fixing unit  11 . 
         [0023]    Referring to  FIG. 4 , a scratch-off toner  40  of opaque composition is applied by the scratch-off image forming unit  12 , and the scratch-off toner  40  covers and abuts the fixed image layer  30 . The scratch-off toner  40  also extends beyond the fixed image layer  30  so that it abuts the substrate  2  in areas not covered by the fixed image layer  30 . The scratch-off toner  40  functions to ensure that the predetermined shaped formed by the fixed image layer  30  (hidden information) is obscured from view until it is scratched off. The substrate  2  having the scratch-off toner  40  and fixed image layer  30  is then passed through the sintering unit  13  for sintering the scratch-off toner  40  onto the fixed image layer  30  and the substrate  2 . Referring to  FIG. 5 , the sintering causes the scratch-off toner  40  to become a sintered scratch-off layer  50 . The combination of the substrate  2 , the fixed image layer  30  and the sintered scratch-off layer  50  forms the scratch-off document  68  (see  FIGS. 5 and 7 ). 
         [0024]    Referring to  FIG. 5 , it is noted that the fixed toner layer  30  is fixed to the substrate  2  at a sufficient level which permits the fixed toner layer  30  to stay intact during scratch-off of the sintered scratch-off layer  50 . However, the sintered scratch-off layer  50  is sintered onto the substrate  2  and the fixed image layer  30  at a level which permits scratch-off. The amount of the sintering of the scratch-off toner  40  is determined from a group consisting of pressure, speed, and mass of the scratch-off toner. It is understood that the logic and control unit  14  controls the pressure, speed and mass of the scratch-off toner  40  that is applied by the scratch-off document apparatus  9  to achieve the desired sintering, as understood by those skilled in the art. The pressure, speed, and mass of the scratch-off toner  40  can be applied individually or in any combination to achieve the desired level of sintering. It can also be advantageous to raise the temperature during the sintering process to help with the sintering but care must be taken to ensure that increased temperature should not cause a heat softening or a melt process in which the materials undergoes a phase transition. 
         [0025]    The scratch-off toner  40  preferably has properties that permit it to scratch-off optimally. In this regard, the scratch-off toner  40  includes particles at least 10 microns larger than the underlying image toner  20 . The scratch-off toner  40  also has a molecular weight of between 2,000 and 100,000 and a glass transition temperature, Tg, between 50 degrees Celsius and 80 degrees Celsius. 
         [0026]    The scratch-off toner  40  can also be heated up to a temperature less than 10 degrees below the glass transition temperature during sintering. In another embodiment, the scratch-off toner  40  further includes a semi-crystalline additive, which has a melt temperature, Tm, of between 60 degrees Celsius and 120 degrees Celsius. Amount of the optional semi-crystalline additive can range from 10 to 60% by weight of the total scratch-off toner composition. The degree of the semi-crystalline additive can range from 60 to 90% by weight of the total weight of semi-crystalline additive. The scratch-off toner  40  can also be heated up to a temperature less than 10 degrees below the melt temperature during sintering. Lastly, the mass of the scratch-off toner  40  is preferably greater than 0.7 mg/cm 2 . 
         [0027]    Referring to  FIG. 6 , there is shown a scratch-off tool  65 , such as a hard rigid object, fingernail or any object suitable for scratching off the sintered scratch-off layer  50 . The sintered scratch-off layer  50  is removed thereby revealing the hidden information formed by the fixed image layer  30 . Referring to  FIG. 7 , there is shown the letter “K” formed by fixed image layer  30 , as an example. 
         [0028]    Referring to  FIG. 8 , there is shown an alternative embodiment of the present invention. In this embodiment, the predetermined shaped or image, indicia  70 , is pre-printed on the substrate  2  and consists of any suitable printing output such as ink, dyes, toner or the like. The devices used for depositing the indicia  70  on the substrate  2  are well known in the art. Thereafter, the substrate  2  is put into the scratch-off image forming unit  12  and the underlying toner  20  is deposited and sintered. In this embodiment, this sintered underlying toner  20  is scratched off to reveal the indicia  70 . Alternatively, the scratch-off toner  40  can be deposited on the underlying toner  20  for providing an additional layer for hiding the indicia  70 . For the purpose of hiding the indicia  70 , it would be advantageous for the underlying toner  20  to be opaque and nearly the same color as the indicia  70 . The underlying toner  20  could be formed using one or more color toners and imaged over the informational area to be hidden until mechanically removed. Since the underlying toner  20  does not form the image as in the previous embodiment, for purposes of term differentiation, the underlying toner  20  is referred to as the non-image toner  20  in this embodiment. After sintering, the non-image toner  20  forms a sintered non-image layer  30  (as opposed to a fixed image layer  30  as in the previous embodiment) which would be similar to  FIG. 5  except that the indicia  70  lies between the substrate  2  and the sintered scratch-off layer  50 . The combination of the substrate  2 , the sintered non-image layer  30  and the sintered scratch-off layer  50  forms the scratch-off document  68  in this embodiment. In this embodiment, the both sintered non-image layer  30  and sintered scratch-off layer  50  would be scratched off. It is noted that any height difference due to the indicia  70  is imperceptible to the touch so that the outline of the indicia  70  is not revealed. 
         [0029]    The present invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention. 
       PARTS LIST 
       [0030]      2  substrate 
         [0031]      9  scratch-off document apparatus 
         [0032]      10  image forming unit 
         [0033]      11  image fixing unit 
         [0034]      12  scratch-off image forming unit 
         [0035]      13  sintering unit 
         [0036]      14  logic and control unit 
         [0037]      20  underlying toner or non-image toner 
         [0038]      30  fixed image layer or sintered non-image layer 
         [0039]      40  scratch-off toner 
         [0040]      50  sintered scratch-off layer 
         [0041]      65  scratch-off tool 
         [0042]      68  scratch-off document 
         [0043]      70  indicia