Electrophotography – Image formation – Transfer
Reexamination Certificate
1998-05-14
2001-03-06
Pendegrass, Joan (Department: 2852)
Electrophotography
Image formation
Transfer
C156S235000, C156S240000, C430S047300
Reexamination Certificate
active
06198898
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
This invention is concerned with improvements in or relating to the formation by printing of images on diverse media, including paper, card, cardboard, glass, wood, metal, metallised materials, plastics materials, film form materials and fabrics and textile materials including closely-woven and knitted materials whether or not the surfaces of those materials are plain or have existing artwork thereon.
Attempts to transfer and so print images have been made previously but until now there has not been a successful attempt to transfer full colour images from one surface to another without the use of intermediate means such as adhesive materials and without loss of definition or colour tones or image quality.
UK patent specification no. 1215599 discloses a method of reproducing images on objects unsuitable for passage through an electrostatic copying machine, comprising: passing a sheet of material through a xerographic copying machine so that charged particles are distributed over the sheet of material in a pattern corresponding to the image to be reproduced; heating the sheet to cause the particles to adhere to the sheet; and subsequently placing the image-bearing surface of the sheet in contact with a further surface on which the image is required to be reproduced and applying heat and pressure to the said contacting surfaces until the particles transfer from the said sheet to the said further surface and fuse to the latter whereby on separation of the surfaces the fused pattern of particles is exposed on the said further surface. The method is said to be useful in forming images on surfaces of metal, glass, tiles, wood and fabric, and for forming transparencies such as overhead projection (OHP) foils.
The specific description refers to the use of a film material which may be a triacetate film or a proprietary film known as ‘Melinex’ film (MELINEX is a Registered Trade Mark of ICI Ltd.), heated during image transfer to a temperature between 80° C. and 100° C.
On page 2 at liens 4 to 8 of the aforesaid UK patent specification, it is stated that ‘It is of course unnecessary for all the particles on the sheet to transfer to the surface on which the image is to be reproduced; it is sufficient if a substantial proportion of the particles is transferred’, which is, of course, suitable for the purposes for which the invention was intended, namely the production of acceptable monochrome images in cases where the precision of image is not critical, but not for the clarity and definition of full colour images such as can be achieved by the present invention.
In U.S. Pat. No. 4,006,267, the invention is concerned with a method of colour highlighting an image on a xerographically produced copy by superimposing a colourant layer onto a monochrome image from a transfer donor, of Mylar film (MYLAR is a Registered Trade Mark of du Pont Corporation) or Lexan film (LEXAN is a trade mark of General Electric Company).
This disclosure describes the addition of colour to an existing monochrome image to provide background colour only. It does not teach the transfer of full colour images such as can be achieved by the present invention.
European patent application no. 191592 discloses a process of transferring metallic foils onto xerographic images which comprises a selective transfer process characterised by the steps of: providing a receiving substrate comprising xerographic images and a foil transfer sheet; placing the receiving substrate comprising xerographic images in face-to-face contact with the foil transfer sheet, to form a sandwich with the xerographic images on the inside; applying heat and pressure to at least one of the receiving substrate and the foil transfer sheet to cause the xerographic image to become tacky and the foil to selectively adhere to the images, resulting in a decorated receiving substrate; and stripping the foil transfer sheet away from the decorated receiving substrate.
In carrying out a process according to the invention disclosed in this European patent application, adhesive material is employed to transfer the xerographic images formed on paper to a receiving substrate which comprises a multi-layer assembly which may include a layer of metallic foil and/or a coloured layer so that the transferred images are positioned on a decorative background (ie. the receiving substrate). The use of adhesive material normally creates a ‘frame’ which is undesirable where a clean image is required.
However, there is no disclosure which teaches the transfer of full colour images as taught by the present invention.
Polyethylene naphthalate (PEN) film has existed for a number of years and was developed in film form for use in a number of applications including uses such as overhead projection foils or films and insulation on printed circuit boards.
In European patent application no. 222374, there is disclosed such an application of the use of PEN film. In this particular publication, there is described and claimed a film form polyethylene 2,6-naphthalate film, of thickness 0.5 to 6 microns, which has a thermal transfer layer coated on one of the surfaces of the film. The film is described as being dimensionally stable. The method of printing using this film form material is that referred to as thermal transfer printing in which the thermal transfer layer is placed while supported by the PEN film against a paper sheet while a thermal head is used to soften the material of the layer to an extent that it is transferred to the paper sheet thereby to form characters or images.
This European patent application further states (q.v. page 4) that by using three separate PEN films each having a layer of a primary colour thereon, it would be possible to build up an image on the paper sheet which is in full colour.
However, the specification of this application does not say how this would or could be achieved and the specific examples to which reference is made refer only to a typewriter ribbon made from material as claimed (q.v. p.15). Certainly, if a full-colour and complete image transfer could have been achieved on a commercial scale, then it would, because there always has been a demand for a solution to full colour transfer even if it had been a multi-stage operation of laying down each primary colour in turn.
In Japanese published application no. 62-11695, filed on Nov. 16, 1985 by Diafoil Kabushiki Kaisha, there is disclosed film for use in electronic photography which is provided by polyethylene-2,6-naphthalate film described as having a maximum specific shrinkage factor and a minimum lengthwise and transverse Young's modulus. The film is claimed to have a thermal stability and other properties which permit it to be used to form over head projection (or OHP) films which can be fed from a stack into a photocopier. In the published application the OHP film is described as being either a transparent film on its own or, when transfer qualities are required, as being coated by application of ‘a water system dispersing agent or water soluble resin having adhesive qualities . . . ’. It is further stated in relation to the Practical Embodiment 1 disclosed in this publication, that a PEN film of 50&mgr; thickness was evaluated using a Canon pc-10 dry electronic monochrome photographic copier (q.v. page 4). As recounted from the results of Table 2, where the film was fed through the copier from a stack, on a scale of 0 to 5 where 5 represents optimum results, toner transfer was rated as 4 (q.v. page 5). Such results do not indicate the way to full colour, complete, image transfer.
More recently than any of the above prior publications, a recent development by Minolta has been announced in which it is alleged that colour pictures and illustrations can be transferred onto ‘virtually any material’. This development relies upon the forming of an original image on a ‘special transparent plastic sheet’ onto which a bonding agent is sprayed over the image and the surface of the transparent plastic sheet. The image is then transferred by pressure onto the surf
ISO Developments Limited
Pendegrass Joan
Wilson Sonsini Goodrich & Rosati
LandOfFree
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