Incremental printing of symbolic information – Thermal marking apparatus or processes – Having an intermediate medium for transferring ink
Reexamination Certificate
2003-03-31
2004-08-24
Feggins, K. (Department: 2861)
Incremental printing of symbolic information
Thermal marking apparatus or processes
Having an intermediate medium for transferring ink
C347S197000
Reexamination Certificate
active
06781615
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is a printing apparatus and a printing method for forming various information such as images and characters on a plurality of types of recording medium or transfer medium, and more particularly relates to a printing apparatus and a printing method that can accurately press against a plurality of types of recording medium or transfer medium having different degrees of hardness to form that information.
2. Description of the Related Art
Conventionally, thermal transfer method printing apparatuses that record desired images and characters by thermally transferring using a thermal head via a thermal transfer film to a recording medium are used to create card shaped recording medium, like credit cards, cash cards, license cards and ID cards. An example can be found in Japanese Patent Publication (Tokkai) 09-131930, which teaches a direct transfer method printing apparatus that directly transfers images and characters to a recording medium via thermal transfer film. The use of a thermal sublimate ink has the benefit of attaining high quality images because this type of ink is more expressive. However, a receptive layer to receive ink on the surface of a recording medium to which images, etc., are transferred is an essential element to make this method of printing possible. Therefore, there is the problem that the types of recording medium that can be used is limited, or else it is necessary to form a receptive layer upon the surface of a recording medium.
Generally, cards made of polyvinyl chloride (also known as PVC cards) are widely used as a recording medium because they can receive thermal sublimate ink. However, due to the fact that harmful substances are generated when these cards are burned, consideration is being given to switching to cards made of polyethylene terephthalate (also known as PET cards). However, because PET cards are made of a crystallized material, they are not only difficult to use in a thermal sublimate transfer process, but they are also difficult to use in embossing. For that reason, when it is necessary to emboss the recording medium, PCV will have to be used well into future.
Furthermore, in recent years, there are card shaped media that have IC chips or antennae embedded therein. Such IC cards are used in a variety of fields. Because there is an object embedded in the card, the surface of the card ends up being uneven which results in image transfer problems.
Japanese laid-open patent publication 8-332742 teaches the technology of a thermal transfer method printing apparatus that overcomes the aforementioned problems in an indirect transfer method printing apparatus that transfers an image to an intermediate transfer medium once, then transfers that image again to the recording medium. According to this method, it is possible to overcome the problems of the direct transfer method, such as the limit to the type of recording medium, related to the receptive layer, or the problem of the transferring of images to an uneven surface of the recording medium, both of which are considered to be demerits of direct transfer printing. Furthermore, this method has the advantage of being easier to printing to the entire surface of the card shaped recording medium compared to the direct transfer method.
Still further, Japanese laid-open patent publication 8-58125 discloses a thermal transfer printing apparatus that is structured to dually use a thermal head to transfer ink to an intermediate transfer film to transfer and form an image thereupon, then to retransfer that ink image to a recording paper using a heat roller, and to use a thermal head which is different to the aforementioned thermal head to transfer ink to the back side of a recording paper, to print to both the front and back sides of a recording paper.
However, running costs associated with the intermediate transfer method are higher than those for the direct transfer method because an intermediate transfer medium must be used. Printing also takes longer. Furthermore, depending on the design of the card, even if the entire front surface is required for printing, often times the back side is used only to print precautions for card use. Therefore, there are fewer cases requiring printing over the entire surface, so there are merits and demerits for both methods of printing. Therefore, if there were a printing apparatus that can switch between the printing methods of a direct transfer method and an indirection transfer method to print images to a recording medium according to the characteristic of a recording medium, including the quality of the material of the recording medium, like PVC or PET, or whether or not it is embossed or includes IC elements, and whether it is necessary to print to the entire surface of the recording medium, it would be possible to transfer (or print) using the method best suited that particular recording medium. This, in turn, would reduce the running costs that are associated with printing. Also, by sharing a part of the members between the direct transfer method and the indirect transfer method the entire printing apparatus can remain smaller and this would enable a printing apparatus with reduced running costs. Therefore, it is conceivable that an apparatus thus capable would become quite widely used. However, because there is a difference in hardness, caused by the thicknesses or structure comprised by each of a recording medium, such as a card formed with print information such as images by a thermal head and an intermediate transfer medium such a intermediate transfer film, it is difficult to attain high quality images under the same image transfer conditions.
Specifically, on printing apparatuses that comprise a thermal head, often times a platen roller is used to support a recording medium (or transfer medium) interposed therebetween a thermal head by an ink ribbon during printing. Rubber rollers are generally used for the platen roller, thus if the pressing force of the thermal head is constant when forming images onto a less-hard transfer medium with the pressing force having a value set for a harder transfer medium, the uneven surface of the platen roller can affect the less-hard transfer medium thereby causing transfer defects, or so-called insufficient or missing transfers onto the transfer medium. Needless to say, this notably reduces the quality of the image that is transferred. A relatively less-hard platen roller can also have an affect. It is conceivable to employ a platen roller with a higher degree of hardness, but if there is dirt or other foreign matter adhering thereto the surface, that area thereof cannot be reproduced, rather that hollowed area is supported which causes poor transfers, such as missing transfers when forming the next image. Therefore, it is necessary for the degree of hardness of a platen roller be lowered somewhat and to have some resilience. On the other hand, if an image is formed on a transfer medium that has a higher degree of hardness using a pressure set for a transfer medium that has a lower degree of hardness, with the pressure of the thermal head at a constant, this will hinder transport when forming an image onto the transfer medium because the pressing contact force for both is too large. This will speed up the wear-out of the thermal head or it can cause new problems such as scratching, cracking or otherwise degrading of the ink ribbon and making it difficult to achieve satisfactorily formed images.
For that reason, it is preferable to form images by changing the pressing force of the thermal head for a plurality of transfer medium types. Prior art, such as that disclosed in Japanese Patent Publication (Hei) 5-24305, teaches a technology of a head pressing apparatus on a printer to vary the pressing force of the thermal head. With this technology, the pressing force is set high for paper which is thicker than regular copy paper, such as a post card, and set slightly lower for such regular copy paper considering the amount to subtract according to the
Feggins K.
Nisca Corporation
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