Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Patent
1990-05-18
1993-02-16
Sluby, P. C.
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
428207, 428209, 428408, 428323, 428337, 428913, B32B 5116, B41M 526
Patent
active
051870029
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a thermal transfer sheet. More particularly, the present invention relates to an electrothermal transfer sheet utilized for the thermal transfer system of the electrical transfer process.
BACKGROUND ART
As the thermal transfer sheet utilized in the electrical transfer process where heat is generated by applying an electric current from an electrode head and the transfer is effected by this heat, there has been adopted a structure in which a resistor layer generating heat by an electric current supplied from an electrode head is formed on one surface of a substrate sheet and a dye layer containing a dye that can migrate under heating and can be transferred to a receipt sheet, such as a sublimable dye, is formed on the other surface of the substrate sheet, and a structure in which electroconductive fine particles are incorporated into a substrate sheet to cause the substrate sheet per se to act also as a resistor layer and a layer of a dye as mentioned above is formed on one surface of the sheet.
Most of resistance values of these resistor layers have, in general, a negative temperature coefficient or a temperature coefficient of zero, and even if the resistance values have a positive temperature coefficient, the value of the positive temperature coefficient is small. Accordingly, at the time of generation of heat by application of an electric current, with elevation of the temperature, the resistance value is reduced and super heating is caused by flowing of an increased electric current, or even if the resistance value is not reduced, an effect of controlling an excessive elevation of the temperature is insufficient. Therefore, problem such as fusion sintering of the thermal transfer sheet or breaking of the thermal transfer sheet are often occur.
Furthermore, in case of a thermal transfer sheet of this type, if long-run transfer is carried out, the electrode head is often deteriorated by the friction between the electrode head and the resistor layer. Moreover, a higher transfer energy is required for the thermal transfer sheet of the sublimation type than for a thermal transfer sheet of the fusion type, and therefore, the temperature of the resistor layer by generation of heat becomes much higher, with the result that heat fusion bonding is caused between the electrode head and the resistor layer, and insufficient transfer or insufficient running often occurs.
DISCLOSURE OF THE INVENTION
It is therefore a primary object of the present invention to provide an electrothermal transfer sheet in which the temperature of a resistor layer can be easily controlled, the heat resistance is high, heat fusion bonding to an electrode head is not caused, the slip to the electrode head is good and such troubles as insufficient transfer and insufficient running do not occur.
According to the present invention, this object can be attained by an electrothermal transfer sheet comprising at least one resistor layer formed on one surface of a substrate sheet and a dye layer comprising a heat-migratable dye and a binder, which is formed on the other surface of the substrate sheet, or comprising a substrate sheet acting also as a resistor layer and said dye layer formed on one surface of the substrate sheet, wherein at least one resistor layer has a positive temperature coefficient of the resistance, the ratio R.sub.100 /R.sub.25 of resistance value (R.sub.100) at 100.degree. C. to the resistance value (R.sub.25) at 25.degree. C. in said resistor layer is at least 1.2 and the ratio R.sub.200 /R.sub.100 of the resistance value (R.sub.100) at 100.degree. C. to the resistance value (R.sub.200) at 200.degree. C. in said resistor layer is at least 2.5.
Furthermore, in the present invention, by using a resin crosslinkable by ionizing radiation or heat as the resin constituting the resistor layer, the heat resistance of the resistor layer can be improved.
If the resistor layer has such resistance-temperature characteristics and heat resistance, heat fusion bonding is effectively
REFERENCES:
patent: 4103066 (1978-07-01), Brooks et al.
patent: 4684563 (1987-08-01), Hayashi et al.
patent: 4833021 (1989-05-01), Shimura et al.
Resistive Ribbon Thermal Transfer Printing, Ribbon and Head Requirements, W. Crooks et al., Journal of Imaging Technology, vol. 12, No. 2, Apr. 1986, pp. 106-110.
E-Beam Curable Formulations for the Resistive Ribbon of Thermal Transfer Printing, L. S. Chang et al., IBM Technical Disclosure Bulletin, vol. 25, No. 78, Dec. 1982, p. 3700.
Akada Masanori
Egashira Noritaka
Satake Naoto
Dai Nippon Insatsu Kabushiki Kaisha
Sluby P. C.
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