Incremental printing of symbolic information – Ink jet – Medium and processing means
Reexamination Certificate
2003-02-12
2004-12-21
Meier, Stephen D. (Department: 2853)
Incremental printing of symbolic information
Ink jet
Medium and processing means
C101S424100, C101S488000
Reexamination Certificate
active
06832831
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming apparatus including a print head for applying ink to a surface layer of a recording medium transported thereto and a heating unit for heating this recording medium for fixing the ink applied to the surface layer by the print head onto its fixing layer.
2. Description of the Related Art
An exemplary conventional technique relating to the above field of art is disclosed in Japanese patent application “Kokai” No: Hei. 10-297197. According to this, a metal substrate includes a coloring ground layer acting also as a rust-preventive layer, a transparent resin layer as an optical transparent resin layer formed over the coloring ground layer, the resin layer being made of acrylic resin, polyester resin, urethane resin etc., and an inkjet receiving layer formed over the resin layer and made of e.g. porous alumina. After application of a sublimating ink or pigment on the inkjet receiving layer by an inkjet printing, the sublimating pigment is heated in a heating furnace or by a hot press, whereby the sublimating pigment in the inkjet receiving layer is sublimed into the transparent resin layer. Then, the inkjet receiving layer is removed to obtain an ornamental metal body having a colored pattern fixedly formed within the transparent resin layer.
According to further art disclosed by Japanese patent application “Kokai” No: 2001-105638, sublimating ink is transferred from an ink ribbon onto a surface of a recording sheet. In order to heat and fix the ink on the sheet, the sheet is charged into a heater box, in which the sheet is advanced and heated between a press roll and a heat roll opposed to each other with a small gap therebetween or between a heat roll and a conveyer belt disposed along a portion of the peripheral face of the heat roll, and then the sheet is discharged from the heater box immediately.
Further, in the field of textile printing, according to an exemplary technique disclosed by Japanese patent application “Kokai” No: Hei. 08-311782, dye is applied to a textile by the inkjet printing method. Then, in order to reinforce the fixing of the dye and also to improve its color development, the textile is charged into a heater device to be heated therein. Then, the textile is discharged from the device immediately to be cooled at the normal temperature.
Still further, Japanese patent application “Kokai” No: Hei. 10-16188 discloses an image forming apparatus. According to this, first, a primary image is formed on a thermal transfer sheet by e.g. an inkjet printer. Then, this thermal transfer sheet having the image formed thereon is laid over a recording sheet and these sheets are pressed and heated together, whereby the image (ink) formed on the thermal transfer sheet will be sublimed by the heat and transferred onto an ink fixing layer of the recording sheet, thus forming a secondary image thereon. With this, a finished printed product is obtained.
Another image forming apparatus is known from Japanese patent application “Kokai” No: Hei. 10-230589. According to this, a laminated material layer is provided in advance on an ink fixing layer of a recording sheet. Then, an image is formed on the laminated material layer by e.g. an inkjet printer. Then, the resultant sheet is pressed and heated by heat rolls, thereby to make the laminated material layer transparent and also to fix the ink pigment on the fixing layer. With this, a finished printed product is obtained.
With these image forming apparatuses, sublimating ink is discharged against the recording medium which usually is being transported along a sub-scanning direction, so that an image is formed thereon with ink droplets (here, these will be referred to as “un-sublimated print dots”). Then, during the subsequent heat fixing process, these ink droplets are heated to sublime, so that the sublimed ink pigment (referred to here as “sublimed print dots”) is fixed in the fixing layer of the recording medium, whereby a final printed image formed of the sublimed print dots with vivid color development is obtained.
In order to maintain good quality of printed product as a finished product regardless of the print size, it is essential that the heating process be effected on the recording medium applied with the ink at an appropriate timing and with appropriate heating pattern. In this regards, it should be noted that these types of image forming apparatuses are often installed in a printing service shop or a photography shop, so the apparatus needs to be formed as compact as possible.
SUMMARY OF THE INVENTION
In view of the above-described state of the art, with the image forming apparatus described at the onset as being its starting technique, a primary object of the present invention is to provide a compact image forming apparatus capable of effecting an appropriate heating process in a smooth manner on various kinds of recording media transported from the printing unit, including a recording media of the standard poster size to a very long recording medium having a length of over 10 meters for production of a huge commercial advertisement billboard or the like.
For accomplishing the above-noted object, according to the present invention, an image forming apparatus comprises a printing unit having a print head for applying ink to a surface layer of a recording medium transported thereto; a loop-forming unit capable of temporarily storing the recording medium discharged from the printing unit; and a heating unit for heating the recording medium fed from the loop-forming unit for fixing the ink applied to the surface layer onto its fixing layer; wherein said heating unit includes at least two heating areas which are adjusted to heating temperatures different from each other.
With the above construction, the recording medium introduced into the heating unit is heated in the at least two heating areas adjusted to different heating temperatures. Hence, the recording medium is subjected to a main heating condition in which the medium is heated at the ink fixing temperature for sublimation of the ink (generally at 150° C. or higher) and a supplementary heating condition in which the medium is heated to a temperature lower than this ink fixing temperature. Namely, by appropriately avoiding rapid cooling or rapid heating, it becomes possible to alleviate thermal load to which the recording medium is exposed. Especially, when the heating unit is adapted for effecting a supplementary heating prior to the main heating, the recording medium is to be heated first to the lower temperature than the ink fixing temperature and then heated to the ink fixing temperature, whereby rapid increase in the temperature may be avoided when the recording medium is heated to the fixing temperature. As a result, with effective elimination of disadvantage due to rapid heating, a finished printed product having high quality may be obtained.
Further, according to one preferred embodiment of the invention, in order to create an advantageous heating condition within the heating unit, the heating unit includes a preliminary heating subunit for heating the recording medium from a normal temperature level to a ink fixing temperature level, a main heating unit for heating the recording medium at the ink fixing temperature level and a slow cooling subunit for slowly cooling the recording medium to the normal temperature level. With this construction, the recording medium which has been heated in the heating units is slowly cooled from the ink fixing temperature (generally 150° C. or higher) to the normal temperature (room temperature) by the slow cooling subunit. As a result, it is possible to restrict occurrence of deformation such as wrinkles in the recording medium which would occur otherwise if the medium were discharged suddenly from the heating unit to the outside due to rapid cooling thereof from the ink fixing temperature to the room temperature. Consequently, there is obtained a finished printed product of high quality with minimum wrinkles.
Preferably, said
Arai Kiyotaka
Funase Masasuke
Inoshita Masanori
Ishikawa Masazumi
Nagaosa Kazuo
Fulbright & Jaworski L.L.P.
Meier Stephen D.
Noritsu Koki Co., Ltd.
Tran Ly T
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