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
2002-02-26
2004-08-03
Hess, B. Hamilton (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...
C503S200000, C503S226000
Reexamination Certificate
active
06770592
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a reversible thermosensitive recording medium, and particularly a reversible thermosensitive recording material in which information on primarily a thermosensitive (recording) layer can repeatedly be written and erased by reversibly changing the transparency or the color tone of image information subjecting to the change of temperature.
2. Description of the Related Art
Reversible thermosensitive recording materials have recently been focused where image information is temporarily recorded or written and when not needed, erased or eliminated. For example, there is known a characteristic reversible thermosensitive recording medium, in which a particles of an organic monomeric material such as higher molecular weight of fatty acid is dispersed into a matrix resin having a low glass transition temperature (Tg) such as vinyl chloride-vinyl acetate copolymer which have a glass transition temperature (Tg) from 50 or 60° C. to lower than 80° C. (as disclosed in Japanese Unexamined Patent Publications of Tokkai Shou 54-119377 and Tokkai Shou 55-54198).
Also, there is known another thermosensitive recording composition, and recording material using it as disclosed in Japanese Unexamined Patent Publication of Tokkai Hei 5-124360, where a color developing action is effected using a coloring reaction between an electron-donor as a coloring compound (referred to as a colorant or leuco dye hereinafter) and an electron-acceptor compound (referred to as a developer hereinafter), in which, as the developer to be used in combination with the leuco dye as the colorant, an organic phosphoric compound, an aliphatic carboxyllic acid compound, or a phenollic compound, those all have a long chain fatty acid hydrocarbon group or groups, are employed, thereby an easy development and erasing of color image are realized, and as a result, both coloring and de-coloring actions can easily be performed under given heating and cooling conditions, also, both colored and de-colored states can be held stable at the normal temperature. Moreover, the coloring and the de-coloring courses can be repeated in stable cycles. Subsequently, of such phenol compound having long chain aliphatic acid hydrocarbon group or groups, a particular compound having specific constitution was proposed for actual utilizing (by Japanese Unexamined Patent Publication of Tokkai Hei 6-210954).
However, when the conventional reversible thermosensitive recording mediums being capable of repeating the coloring and the de-coloring are used under the actual operating conditions for printing and erasing, they often are likely to produce print blanks or erasing stains and fail to provide a satisfactory level of coloring and de-coloring performance. This results from sticking phenomenon and the like which caused by poor head matching of the recording layer of the recording medium to heating members such as thermal head or heat block, thereby allows no uniform heat supply to the all area to be heated of recording layer through the heating members. Also, there may be developed a gap of air between the thermal member and the surface of the reversible thermosensitive recording medium, and the gap interrupts the uniform heating.
Disclosed in Japanese Unexamined Patent Publication of Tokkai Shou 63-221087 is an improvement for eliminating the foregoing drawbacks of the conventional recording medium where an over-coating layer of silicon resin or silicon rubber is over-coated onto the surface of the recording medium to minimize the friction coefficient thereof. The over-coating layer is however insufficient in the bonding strength for the thermosensitive recording layer and may peel off the recording layer through a series of mechanical movements thus declining the quality of reproduced images. Also, other designs are disclosed in Japanese Unexamined Patent Publications (Tokkai Hei)5-092658 and (Tokkai Shou)63-317385 where a protective layer impregnated with a phosphazene resin or a silicon resin is used for improving the resistive to wear and lowering the friction coefficient or in Japanese Unexamined Patent Publication (Tokkai Hei)5-092658 where the protective layer contains long chain fatty acid or its alkyl ester, long chain dibasic fatty acid and its alkyl ester which serve as a lubricant. Each design however fails to improve the head matching of a reversible thermosensitive recording medium at high temperatures and may hence be disadvantageous in that the recording layer is injured when the image-erasing action is repeated a number of times and thus enables no uniform erase.
Disclosed in Japanese Unexamined Patent Publication (Tokkai Hei)8-156410 is a protective layer having a defined level of glossiness and a defined degree of surface roughness for improving the head matching and thus minimizing the injury throughout a series of the erasing actions. This however increases the gap of air developed between the thermal printing head and the surface of the reversible thermosensitive recording medium, thus permitting no uniform thermal printing. Particularly, if the temperature rising is limited to a given range, more erasing errors may be developed during the erasing action.
SUMMARY OF THE INVENTION
It is hence an object of the present invention to provide a reversible thermosensitive recording medium having improved characteristics in thermal head matching which minimize the erasing faults and ensure the stable erasing actions, and an excellent storage capability.
We have studied for overcoming the foregoing disadvantages and developed a novel reversible thermosensitive recording medium in which the gap of air between the thermal printing head and the surface of the recording medium is eliminated thus heat conductivity is improved allowing uniform application of thermal energy during the erasing action thereby erasing property is improved, while the surface smoothness is improved as for as during the heating action at high temperatures, resulting an excellent thermal head matching, and the storage capability therefor is improved too.
Above and other objects of the present invention are achieved by: (1) a reversible thermosensitive recording medium comprising at least a reversible thermosensitive recording layer provided on a supporting substrate and, a protective layer provided on the recording layer, wherein the recording layer is arranged so as to develop a first color therein when it is heated to a specific temperature level between a second temperature and a third temperature which is higher than the second temperature and then cooled to a first temperature level between normal temperature and the second temperature which is higher than the normal temperature, while so as to develop a second color therein when it is heated to another temperature level higher than a fourth temperature which is higher than the third temperature and then cooled to a particular temperature which is lower than the first temperature, and the protective layer contains at least a lubricant showing the melting point ranging from higher than or equal to the first temperature to lower than or equal to the second temperature and has a surface roughness (Rz) (where Rz represents an average rise on the surface by ten measurements) of 1.2 &mgr;m or more;
(2) a reversible thermosensitive recording medium according to the paragraph (1) wherein the protective layer is being crosslinked;
(3) a reversible thermosensitive recording medium according to the paragraphs (1) or (2), wherein the lubricant is particles having particle size smaller than or equal to the thickness of the protective layer;
(4) a reversible thermosensitive recording medium according to any one of the paragraphs (1) to (3), wherein the content (percent by weight) of the lubricant in the protective layer is higher than or equal to 0.1 and lower than 10.0;
(5) a reversible thermosensitive recording medium according to any one of the paragraphs (1) to (4), wherein the protective layer contains a filler having an oil absorption ca
Hotta Yoshihiko
Morohoshi Kunichika
Sampei Satoru
Sugiyama Nobuyoshi
Suzuki Kazumi
Cooper & Dunham LLP
Hess B. Hamilton
Ricoh & Company, Ltd.
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