Record receiver having plural interactive leaves or a colorless – Having a colorless color-former – developer therefor – or... – Method of use – kit – or combined with marking instrument or...
Reexamination Certificate
1998-09-02
2002-03-26
Hess, Bruce H. (Department: 1774)
Record receiver having plural interactive leaves or a colorless
Having a colorless color-former, developer therefor, or...
Method of use, kit, or combined with marking instrument or...
C427S150000
Reexamination Certificate
active
06362130
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a reversible thermosensitive recording medium, more particularly to a reversible thermosensitive recording medium comprising a reversible thermosensitive recording layer of which transparency or color tone is reversibly changeable depending upon the temperature thereof, thereby recording information therein and erasing recorded information therefrom repeatedly as desired. The reversible thermosensitive recording may be used in information recording devices in any form, for instance, in the form of a card, a disk, a label, a disk cartridge or a tape cassette. The present invention also relates to a method of producing the above reversible thermosensitive recording medium. The present invention also relates to a method of recording images and erasing the same, using the reversible thermosensitive recording medium.
2. Discussion of Background
Recently attention has been paid to a reversible thermosensitive recording material capable of temporarily recording images therein and erasing the same therefrom when such images become unnecessary. For example, Japanese Laid-Open Patent Application 55-154198 discloses a representative example of a reversible thermosensitive recording material in which an organic low-molecular-wieght material such as a higher fatty acid is dispersed in a matrix resin such as a vinyl chloride—vinyl acetate copolymer.
However, such a conventional reversible thermosensitive recording material has a shortcoming that a temperature range in which the recording material exhibits light transmission or transparency characteristics or is in a transparent stare (hereinafter referred to as the transparentizing temperature width) is as narrow as 2 to 4° C., so that it is difficult to control the temperature for performing such image formation while utilizing the properties of reversibly becoming transparent or light shielding or opaque or milky white.
With this shortcoming of the above reversible thermosensitive recording material taken into consideration, the inventors of the present invention previously proposed to facilitate image erasure (making recorded images transparent) by using a mixture of a higher fatty acid and an aliphatic dicarboxylic acid to broaden the transparentizing temperature width to about 20° C. as described in Japanese Laid-Open Patent Applications 2-1363 and 3-2089.
In order to improve such erasability, it is also proposed to broaden the transparentizing temperature width by using a mixture of (a) a higher ketone or a fatty acid ester having a lower melting point than that of the higher fatty acid, and (b) an aliphatic dicarboxylic acid or a saturated aliphatic bisamide as described in Japanese Laid-Open Patent Applications 4-366682, 5-294062 and 6-255247. These methods are capable of broadening the transparentizing temperature width and accordingly capable of improving the erasability. However, due to the use of the higher ketone or fatty acid ester having a lower melting point than that of the higher fatty acid, the transparentizing temperature width is situated in a low temperature range, so that these methods have a shortcoming that the formed opaque or milky white images are erased when the ambient temperature thereof is high, for instance, when placed on a dashboard in midsummer.
It has been proposed to shift the transparentizing temperature width to a high temperature side by using a mixture of (a) an organic low-molecular-weight compound having a low melting point and (b) an alicyclic dicarboxylic acid having a melting point of about 200° C. which is significantly higher than the melting points of aliphatic dicarboxylic acids (as described in Japanese Laid-Open Patent Applications 5-139053, 6-48024 and 6-48025, or by using a mixture of (a) an organic low-molecular-weight compound having a low melting point and (b′) a low-molecular compound having a steroid skeleton having a melting point near 200° C. (as described in Japanese Laid-Open Patent Applications 8-20167 and 8-282131). However, despite the use of the above-mentioned compounds having such extremely high melting points, the upper-limit of the transparentizing temperature width is not shifted so much to a high temperature side and accordingly the erasability is not substantially improved. In order to improve the erasability, there is no choice but to use an organic low-molecular-weight compound having a low melting point, but when an organic low-molecular-weight compound having a low melting point is used, the heat resistance of images formed tends to be lowered.
Furthermore, the recording media disclosed in the above-mentioned Japanese laid-open patent applications have the shortcomings that the temperature difference between a transparentizing upper-limit temperature and an opaqueness initiation lower-limit temperature is so large that a significantly large amount of energy is required for the formation of milky white images, and that the durability of the media is lowered while in repeated use, with the surface of the recording media scratched, and the opaqueness of the image lowered in the course of repeated image printing and erasure.
When a large amount of energy is required for the image formation, a thermal head's pulse application time is required to be lengthened since there is a limit to a voltage that can be applied to the thermal head from a power source, or the recording speed has to be lowered. Furthermore, when the recording speed is lowered, or when the amount of energy applied to the thermal head is increased, the life of the thermal head is shortened. Thus, when the amount of energy required for the image formation is increased, the applied energy has adverse effects on an apparatus using the reversible thermosensitive recording medium. In this case, it is considered that the high opaqueness initiation temperature is caused by the use of the low-molecular weight compound having an excessively higher melting point.
Furthermore, there are proposed reversible thermosensitive recording media using a leuco dye and a color developer having a long chain alkyl group, capable of inducing a color in the leuco dye in Japanese Laid-Open Patent Applications 5-124360, 5-294063 and 6-171225. The recording media have an advantage over other conventional recording media that images can be developed in a variety of colors such as black and red, when the dye therefor is appropriately selected for use in the recording media, but have a shortcoming that the heat resistance of the images is inferior to that of image s obtained by the above-mentioned reversible thermosensitive recording media capable of forming milky white images with a transparent background or transparent images with a milky white background. It is considered that this shortcoming is caused by the vibrations of the long chain alkyl group of the color developer, initiated when heated to 50 to 60° C. even though the melting point of the color developer is as high as 150° C. or more, which vibrations cause the color developer to separate from the dye, and accordingly decolorize the images.
SUMMARY OF THE INVENTION
It is therefore a first object of the present invention to provide a reversible thermosensitive recording medium with an extended transparentizing temperature width, while maintaining the capability of producing images with high heat resistance, and with high repeated use durability, which is capable of producing images with high contrast and erasing the same with high erasability even when the ambient temperature is high.
A second object of the present invention is to provide a method of producing the above reversible thermosensitive recording medium.
A third object of the present invention is to provide an information recording device utilizing the reversible thermosensitive recording medium of the present invention.
A fourth object of the present invention is to provide a method of recording images in any of the reversible thermosensitive recording medium of the present invention and the information recording
Hosoda Kazuo
Hotta Yoshihiko
Kawai Koji
Kobori Hideyuki
Kokubo Katsuaki
Cooper & Dunham LLP
Hess Bruce H.
Ricoh & Company, Ltd.
LandOfFree
Reversible thermosensitive recording medium, card, label,... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Reversible thermosensitive recording medium, card, label,..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Reversible thermosensitive recording medium, card, label,... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2836733