Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Patent
1985-05-31
1987-08-04
Herbert, Thomas J.
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
427262, 428337, 4284231, 4284237, 4284884, 428913, B32B 516, B32B 2706
Patent
active
046845631
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to an electrothermal transfer recording sheet having at least an ink layer and a resistance layer integrally bound so that the ink layer is melted to be transferred to a given substrate by virtue of joulean heat generated by flow of electric current through the resistive layer.
BACKGROUND OF THE INVENTION
In recent years, the thermal transfer recording has come to draw attention in numerous fields specializing in facsimile devices, computer terminal devices, and recorders because it possesses numerous features including freedom from impact and noise, necessity for no maintenance, low cost, feasibility of reduction in size and weight, and adaptability to color recording. Among other methods, the method which effects electrothermal transfer by the use of a current-passing head suits a full-color recording containing intermediate gradation and deserves the keenest attention as a most promising approach to production of hard copies.
FIG. 1 is a diagram of operating principle illustrating passage of electric current through an electrothermal transfer recording sheet 1 by the use of a recording electrode 5 and a returning electrode 6. In this arrangement, thermal transfer recording on a given blank sheet for recording (not shown) is accomplished by pressing the recording head into contact with a resistive layer 2 of the recording sheet thereby starting flow of current therethrough and causing the resistive layer to generate and assumulate heat until an elevated temperature, and causing a support layer 3 to conduct heat to the ink layer 4 thereby enabling the ink layer 4 to be heated, melted, and made to flow.
The most important quality which the resistive layer in the electrothermal transfer recording sheet is expected to possess is such as to fulfil the requirements (1) that the magnitude of resistance should be lowered to about 10.sup.2 to 5.times.10.sup.5 ohms, (2) that the resistive layer should be given an ability to withstand heat above at least 300.degree. C. for a brief period, and (3) that the tight adhesion of the resistive layer to the support layer should be enough against the shear friction due to the forced contact made by the curring-passing head.
The resistive layers so far proposed invariably fall short of fulfilling these requirements.
Various devices which have been heretofore contemplated to fulfil these requirements will be described below.
The first problem concerns a reduction in the magnitude of resistance. In this case, for the resistive layer to generate heat by the flow of electric current therethrough, the magnitude of resistance offered by the resistive layer is required to an intermediate between the magnitudes of resistance offered by an insulating material and a good conductor. The magnitude of resistance is fixed by the balance of various factors such as the amount of power supplied, the thermal conductivity of the recording sheet, and the energy spent in melting the ink layer. As means to impart the resistive layer an ability to generate heat, a method which forms a resistive layer by dispersing powder of aluminum, copper, iron, tin, zinc, nickel, molybdenum, or silver as electroconductive particles in a resin binder, a method which effects the production of a resistive layer by dispersion of precipitated copper in a resin binder, a method which produces a resistive layer by dispersing zinc oxide or titanium dioxide in a resin binder, a method which obtains a resistive layer by applying an electroconductive polymer on a substrate layer, and a method which prepares a resistive layer by dispersing graphite or acetylene black in a resin binder have been proposed.
The inventors have studied all these methods. They have consequently found that relatively inexpensive electroconductive particles which exhibit high affinity for the resin binder enough to be uniformly dispersed in the form of finely divided particles within the binder and also exhibit high affinity for the solvent used in solving the binder resin and, therefore, are satis
REFERENCES:
patent: 4100087 (1978-07-01), Takayama et al.
patent: 4479997 (1984-10-01), Masterson et al.
patent: 4510206 (1985-04-01), Shuman
patent: 4554562 (1985-11-01), Afzali-Ardakani et al.
Hayashi Sei-ichi
Takei Katsumori
Yamaguchi Yoshitaka
Herbert Thomas J.
Seiko Epson Kabushiki Kaisha
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