Incremental printing of symbolic information – Thermal marking apparatus or processes
Patent
1993-10-07
1996-07-16
Tran, Huan H.
Incremental printing of symbolic information
Thermal marking apparatus or processes
B41J 2325
Patent
active
055371388
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a recording and erasing system which records an image on a thermoreversible recording medium and erases such a recorded image therefrom by controlling a quantity of energy applied thereto.
BACKGROUND OF THE INVENTION
Up to now, efforts have been made to develop recording systems which can repeatedly record and erase an image on and from a thermoreversible recording medium which becomes black, or transparent and colorless depending upon quantities of thermal energy applied thereto.
Japanese patent laid-open publications No. Sho 57-77140 and Hei 2-188294 propose examples of thermographic materials for such a recording medium.
The former publication exemplifies a thermoreversible recording medium comprising layers of thermoreversible material of a whitening group applied on the surface of a glass or plastic substrate. This material inverts its state at two transition temperatures t.sub.1 and t.sub.2 (t.sub.1 <t.sub.2). When heated above the temperature t.sub.2 for a given period of time, the material becomes white. On the other hand, when heated above t.sub.1 but below t.sub.2 for a second given period of time, the material becomes transparent and colorless. Therefore, heating elements of a thermal head associated with an image to be recorded are heated above t.sub.2, while heating elements associated with an image to be erased are heated above t.sub.1 but under t.sub.2.
The latter publication discloses a thermoreversible medium including a thermoreversible material of a dye group. When the recording medium contains a dye whose transparency or color changes with temperatures, the medium can be repeatedly used for recording and erasing images such as letters and symbols thereon and therefrom, respectively, similarly to the foregoing thermoreversible medium of the whitening group.
The principle of the recording system will be described hereinafter. When a first energy (h.sub.1) is applied from a dynamic heat source such as a thermal head, the thermoreversible material is developed to form a first dark image (in black). The image is maintained as it is in a normal environment (temperature and humidity), but is erasable when a second energy (h.sub.2) is applied thereto. When the first energy (h.sub.1) is applied again, a second image can be formed. Thus, the recording and erasing can be performed repeatedly.
FIG. 1 of the accompanying drawings is a schematic view showing the configuration of the foregoing recording medium 1, which comprises a protective film 14, a recording layer 15 including materials such as a dye, an agent for making an image visible/invisible and a binder, and a substrate 16. When the first large energy (h.sub.1) of 200.degree. to 300.degree. C. is applied onto the recording medium 1 for a short period of time, e.g. 1 to 3 ms, in the direction shown by an arrow A, a black image is formed on the recording medium 1, for example. Conversely, when the second small energy (h.sub.2) of 80.degree.-160.degree. C. is applied to the recording medium 1 for a relatively long period of time, e.g. 5 ms to 2 sec, in the direction of the arrow A, the Image is erased from the recording medium.
Specifically, the recording layer 15 includes an agent for making the image visible/invisible which becomes acid and salt in response to an applied energy, and a leuco dye whose color changes with variations of acidity. FIG. 2 shows phenyl carbonate and organic amine salt as an example of the agent for making the image visible/invisible. FIG. 3 (a) shows a colorless leuco compound and FIG. 3 (b) shows a colored leuco compound.
The agent for making the image visible/invisible becomes acid when it is heated above the temperature t.sub.2, so that lactone rings of the leuco dye are opened. Thus, the leuco dye becomes colored. When heated above the temperature t.sub.1 but under the temperature t.sub.2, the agent for making the image visible/invisible changes to alkaline, so that the opened lactone rings are closed. Therefore, the leuco dye becomes colorless.
This record
REFERENCES:
patent: 4851924 (1989-07-01), Nakamura et al.
patent: 4965528 (1987-09-01), Dabisch et al.
Ohnishi Masaru
Yamada Keiki
Mitsubishi Denki & Kabushiki Kaisha
Tran Huan H.
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