PROCESS FOR MANUFACTURING A PLASTIC TOKEN, AND TOKEN MANUFACTURED BY SAID PROCESS

Abstract: Method for manufacturing a plastic token or chip by producing a hologram (3) of a typical representation and separately producing two plastic overlays (1, 2) each com­ prising a raised outer edge (6, 7) and being transparent at least inside said raised outer edge, subsequently bonding said hologram inbetween said two overlays and finishing the resulting assembled body. A token or chip thus produced is distinct in that it displays in the light over a gaming table a sparkling pattern.

Description: A PROCESS FOR MANUFACTURING A PLASTIC TOKEN OR CHIP AND TOKEN OR CHIP MANUFACTURED BY SAID PROCESS. The invention relates to a process for manufacturing a plastic token or chip. Such a process, at least the product thereof is generally known. The tokens or chips produced have for example a coloured plastic body wherein a denomination is pressed and coloured in contrast to the body. Counterfeiting is a problem that may arise with these securities. The process according to the invention provides a token or chip being highly secured against counterfeiting. According to the present invention the process for manufacturing the plastic token or chip is characterized by procuding a hologram of a typical representation and separately producing two plastic overlays, each comprising a raised outer edge and being transparent at least inside said raised outer edge, subsequently bonding said hologram in between said two overlays and finishing the resulting assembled body. The tokens or chips manufactured according to the present process, offer the advantage that the raised edges contribute to conveniently stacking the tokens or chips as a result of a drastic reduction of the interface area of the tokens or chips in a stack. Hereafter the invention is illustrated with a description of a preferred embodiment including some variations thereof. The description refers to a drawing. The only figure shows in cross-section a token or chip that is the product of a process according to the present invention. In the figure the vertical dimensions are exaggerated compared with the approximately full-sized horizontal dimensions. In the figure an overlay 1 is bonded to an overlay 2, a hologram 3 being interleaved in between these overlays. The overlays 1 and 2 each comprise at least one transparent layer 4 a & d 5 respectively, displaying the hologram in the center portion 8 within their raised edges 6 and 7 respectively. The hologram is recorded on a flexible substrate using a conventional holographic facility. This substrate comprises a dichromate sensitized gelatin. Said gelatin is applied on a flexible carrier, preferably a polyester film or a polyvinyl acetate film. The gelatin layer is sensitized by immersing the layer into a solution of a dichromate compound, such as potassiumdichromate, ammonium dichromate or the pyridine dichromate complex. During an imagewise exposure of the gelatin layer the hexavalent chromium ion Cr is converted by photo-induction into trivalent Cr . This trivalent chromium ion is capable of cross-linking juxtaposed gelatin molecules, so that the gelatin is hardened where being exposed. The resulting differences in hardness between the exposed and non-exposed portions of the gelatin layers make up the latent representation of the hologram. By swelling the gelatin layer in a solvent, e.g. water, said latent representation is developed. The exposed portions of the gelatin layer that is to say the hardened portion thereof, absorb water to a considerably lesser degree than the non-exposed portions, so that the hardened representation is converted into a swelling representation. In this manner stress differentials are set up in the gelatin layer between the exposed and the non-exposed portions thereof. These stress differentials cause differences in density and thus result in differences in refractive index of the gelatin. The subsequent fixation of the swelling representation by means of dehydration is effected by immersing the gelatin layer into a solvent for water, such as alcohol, which removes the water from the said layer. The refractive index differentials corresponding with the initial representation form a phase hologram in the first instance. However, it is possible that with appropriate stress differentials and differences in hardness cracks arise in the gelatin layer, said cracks following the stress gradients. By this causing a so-called reticulation the refractive index differentials will be maximal, as they relate to the gelatin/air interface tAn about 0.5). After fixation by dehydration the gelatin layer is forcibly dried. Therefor the fixation is usually finished with a more or less long after-treatment of the gelatin layer at a higher temperature than room temperature, to remove the water remained behind and harden the gelatin layer by the heat treatment. The flexible substrate may be made to be a carrier of a representation being applied with a printing technique before and/or after the holographic recording. Accordingly a combination in register of a graphic representation or print and a holographic representation is optional. The detailed example of recording a hologram on a flexible substrate is as follows. The substrate is sensitized in a 5% ammonium dichromate solution in distilled water including a wetting agent in a proportion of 1 : 200 parts. The substrate is kept in the solution at room temperature for ten minutes. Subsequently the sensitized substrate is dried at room temperature, and optionally forcibly dried in a stream of hot air for some time. The sensitized substrate is thereafter imagewise exposed in a holographic facility using light having a wave-length of 514.5 nm. Subsequently the gelatin layer for developing the latent representation is caused to swell in a 5% aqueous solution of potassium hydroxide to which 1 : 200 parts of a wetting agent are added, at a temperature between 200 and 450C for three minutes. After removal of adhering potassium hydroxide solution by rinsing in water at a temperature between 600 and 750C for some minutes, gradual dehydration is effected in isopropyl alcohol. This step is finished by immersion in pure and concentrated isopropyl alcohol for some minutes. Finally the substrate is forcibly dried in a stream of hot air. The two overlays between which the resulting imagewise exposed and developed substrate is finally cemented, are manufactured by printing and stacking dully finished films of polyvinyl acetate or polyacrylate having a thickness of about 0.2 mm. The printed representation is carried out such that the joined films after stacking produce the lay-out of the token or chip. The film or films adjoining the substrate 3, are made of a transparent material, so that the center portion 8 of a token or chip displays the hologram on the substrate. After stacking up, the films are 0 laminated at a temperature of about 150 C and a pressure of about 2 50 MPa (500 kgf/cm ). One press plate is flat and the opposite plate has such recesses that after lamination the raised edges 6 and 7 respectively are produced. Each of the flat surfaces of both overlays is suitable for application of a printed representation. This print can be applied before the lamination, if use is made of a laminable ink or of laminable inks, such as a HSV type ink (HSv = heat set vinyl ink) for printing. In the printed representation register marks can be caused to register with register marks in the moulding la;nation press plate for example. Such register marks also may be put to use as aids when assembling the token or chip whereby the hologram is cemented inbetween the two overlays. A cyano acrylate cement is used to bond the two overlays 1 and 2 respectively on opposite sides of substrate 3. After bonding the assembled token or chip body and in particular the outer edge of the substrate is brought into the shape as corresponds with the shape of the overlays 1 and 2. Finishing the assembly is done mechanically. When using a token or chip made in the above manner a green gaming- table provides a dark background and any lamp over the table acts as a satisfactory white light source. Consequently the hologram can be observed in a wide viewing angle as is typical for a white-light hologram, whereby the hologram can always be perceived by the croupier at the gaming-table. The sparkling flashes occurring when stacking and selecting the tokens or chips carrying white light reflection holograms provide the croupier with a substantially automatical device to differentiate between genuine and counterfeit tokens or chips.

Claims: CLAIMS: 1. A process for manufacturing a plastic token or chip characterized by producing a hologram of a typical representation and separately producing two plastic overlays, each comprising a raised outer edge and being transparent at least inside said raised outer edge, subsequently bonding said hologram in between said two overlays and finishing the resulting assembled body. 2. A process according to claim 1, characterized by recording said hologram on a flexible substrate comprising a dichromate sensitized gelatin layer being arranged on a flexible film and finished after exposure, development and fixation by forcedly drying said gelatin layer on said film. 3. A process according to claim 1 or 2, characterized by printing a first representation on the said substrate before or after elaborating said hologram, whereby said hologram is arranged in register with said first representation or vice versa. 4. A process according to claim 1, 2 or 3, characterized by printing a further representation comprising register marks on the transparent portion of each of said overlays, said register marks being used in the bonding step. 5. A process according to claim 2, 3 or 4, characterized in that said film is selected from a group comprising polyester and polyvinyl films. 6. A process according to claim 5, characterized by manufacturing said overlays by laminating films selected from a group comprising PVC and polyacrylate films and having a thickness of about 0.2 mm and the said at least partially transparent film between a plane press face and a press face carrying an engraving for moulding said raised outer edge, said bonding being accomplished using a cyano acrylate cement. 7. A process according to claim 6, characterized in that a laminable ink (HSV-i-,k - Heat Set Vinyl ink) is used for producing ttlE- representation on an overlay. 8. Plastic token or chip manufactured with a process according to one of the preceding claims.

Inventors: SCHELL, KAREL JOHAN, TIJHOF, JOHAN
Applicants: JOH. ENSCHEDE EN ZONEN GRAFISCHE INRICHTING B.V.
Application year: 1982
Main classification: A44C21
IPC codes: B32B33, A44C21, G06K19, G07F1