Stock material or miscellaneous articles – Structurally defined web or sheet – Edge feature
Patent
1988-10-19
1991-01-15
Schwartz, Pamela R.
Stock material or miscellaneous articles
Structurally defined web or sheet
Edge feature
428195, 428208, 428211, 428486, 428913, 428914, B41M 526
Patent
active
049852922
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to thermal transfer type recording sheets or strips of roll form which are used with, typically, heat-sensitive facsimile recorders, and to an apparatus for the manufacture of such recording sheets More specifically, the invention pertains to a strip or roll of thermal transfer type recording sheet bearing an end mark for enabling the detection of the fact that the strip or roll is drawing to its end in use, as well as to an apparatus including means for printing such an end mark in a preassigned position on the recording sheet.
BACKGROUND ART
The facsimile recorder has been known and used extensively which employs a roll of thermal transfer type recording sheet, known as a donor roll, through which the subject copy is thermally transferred to paper. Some facsimile recorders on the market are further equipped to detect the fact that the roll is being used up, and to visually or audibly forewarn the user of the end of the, roll.
In order to make possible the automatic detection of the fact that the recording sheet is coming near to its end, it has been practiced to provide an end mark having a reflective surface on the sheet, in a position spaced a prescribed distance from its end anchored to the roll shaft. The end mark may be formed either directly on one side of the base film of the recording sheet or on the hot melt ink layer on the other side of the base film. The end mark is optically detected by a sensor comprising a source of infrared radiation and a photodetector responsive to such radiation. Flexography and brushing represent two typical conventional measures for creating such end marks.
Such conventional methods of forming end marks are objectionable for several reasons. First, for flexographic production of end marks, the printing ink of reflective material is pressed against the recording sheet by a rubber-made relief plate. The recording sheet is so thin, however, that the relief plate tends to wrinkle the sheet when pressed against the same via the reflective material. At the same time, moreover, the reflective ink easily oozes out from between the recording sheet and the plate, thereby forming undesired bulges beyond the due boundaries of the end marks. Such bulges not only blur the bounding edges of the end marks but also make their thickness uneven.
Additional disadvantages of flexography arise from the fact that before printing, the reflective ink on the rubber plate is in the form of a film overlying the protuberant parts of the relief plate. The ink film tends to develope unevenness on its transfer from the plate to the recording sheet, and it is difficult to control the amount of the ink so transferred and, therefore, the thickness of the end mark so printed. The composition of the ink is also subject to the restriction that it should contain no such solvent as will attack the rubber plate. This restriction imposes additional limitations on the choice of resins to be contained in the ink as a binder. Accordingly, the desired dispersion characteristics of the pigment or powdered metal contained in the ink are not easy to realize, with a consequent decrease in the quality of the printings. It is a still further weakness of flexography that the rubber plates are susceptible to deformation and poor in durability.
The production of end marks by brushing is also objectionable because of the poor quality of the markings so produced. What is worse, this conventional method is very time-consuming and not suitable for mechanized production of the recording sheets on a large scale.
For the reasons set forth in the foregoing, the end marks produced in accordance with the prior art, either by flexography or by brushing, have often been of uneven thickness and have not been defined clearly enough. Such defective end marks have often invited misdetection by infrared sensors, with the result that no warning is generated at the required time before the roll of recording sheet is used up.
Known apparatuses for the manufacture of rolls of recording sheets with e
REFERENCES:
patent: 4720480 (1988-01-01), Ito et al.
Imamura Hirokatsu
Umise Shigeki
Dai Nippon Insatsu Kabushiki Kaisha
Schwartz Pamela R.
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