Record receiver having plural interactive leaves or a colorless – Having a colorless color-former – developer therefor – or...
Reexamination Certificate
2002-06-25
2004-03-23
Edwards, N. (Department: 1774)
Record receiver having plural interactive leaves or a colorless
Having a colorless color-former, developer therefor, or...
C503S207000, C503S226000
Reexamination Certificate
active
06710015
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to a thermosensitive recording material and, more specifically, to a thermosensitive recording material having an intermediate layer (undercoat layer) between a support and a thermosensitive recording layer.
With diversification of information and expansion of needs therefor in recent years, various types of recording materials have been developed and put into practice in the field of information recording. Especially, thermosensitive recording materials are widely used in various fields such as information processing (output of a desk-top calculator, computer or the like), recorder for a medical measurement device, low- or high-speed facsimile, automatic ticket machine (railway ticket, admission ticket or the like), thermal copying machine, label of a POS system, and luggage tag because of the following advantages:
(1) an image can be recorded with ease only by applying heat;
(2) recording can be conducted with a simple mechanism, so that it is possible to downsize the device, and a recording material is easy to handle and inexpensive; and
(3) a recording material consists of one component of a thermosensitive paper.
With a trend toward smaller and faster recording devices in recent years, demands for a high sensitive recording material capable of recording with low printing energy of a small-sized, high-speed machine are increasing.
A thermosensitive material is generally produced by applying a thermosensitive coloring liquid containing a coloring component which undergoes a coloring reaction upon application of heat on a support such as a paper or a synthetic resin film and drying the same. By applying heat with a thermal pen or a thermal head, a colored image is formed on the thermosensitive recording material. As known examples, there are thermosensitive materials disclosed in Japanese Laid-Open Patent Publication No. S43-4160 and Japanese Examined Patent Publication No. S45-14039. Such conventional thermosensitive recording materials have low thermal responsiveness and thus cannot obtain a sufficient coloring density in high-speed recording. As a method to overcome the drawback, thermosensitive recording materials having an intermediate layer containing hollow resin particles between a support and a thermosensitive recording layer are disclosed. For example, Japanese Laid-Open Patent Publication No. H01-113282 discloses a method in which spherical hollow particles having a Tg of 40 to 90° C., an average particle diameter of 0.20 to 1.5 &mgr;m, and a hollowness of at least 90% are used. However, this thermosensitive recording material has a drawback that the particles, when softened by the heat from a thermal head in printing, are likely to cause sticking. Also, the hollow particles do not have an effect of improving the sensitivity of the thermosensitive recording material up to a satisfactory level,
Japanese Laid-Open Patent Publication No. H04-241987 discloses a thermosensitive recording material having an intermediate layer containing hollow thermoplastic resin particles having an average particle diameter of 2 to 10 &mgr;m and a hollowness of at least 90%. Japanese Laid-Open Patent Publication No. H05-309939 discloses a thermosensitive recording material having an intermediate layer containing hollow particles having a particle diameter in the range of 2 to 20 &mgr;m and a specific gravity of not greater than 0.21. Japanese Laid-Open Patent Publication No. H08-238843 disclosed a thermosensitive recording material having an intermediate layer containing hollow particles having a hollowness of at least 90% and a block copolymer of ethylene oxide and propylene oxide. However, the hollow particles used in the above thermosensitive recording materials include particles with a large diameter of 10 to 30 &mgr;m and, when a thermosensitive recording layer is provided over the intermediate layer containing the particles, no thermosensitive layer is formed on parts where there are the particles of large diameters. This causes white void when a solid image is formed. Also, the hollow particles contain vinylidene chloride, which contains chlorine atoms that can contaminate the environment in incineration disposal of the thermosensitive recording material.
Japanese Laid-open Patent Publication No. H03-147888 disclosed a thermosensitive recording material having an intermediate layer containing hollow particles of a synthetic resin having a hollow volume rate of 35 to 60 vol. % and an average particle diameter of 0.4-1.5 &mgr;m. Japanese Laid-Open Patent Publication No. H02-214688 disclosed a thermosensitive recording material having an intermediate layer mainly composed of non-foamed microhollow particles having a hollowness of at least 30%. However, the particles used in the above thermosensitive materials, which have a low hollowness of not greater than 60%, do not have a sufficient thermal insulating property. Thus, the above thermosensitive recording materials are insufficient in sensitivity. As above, hollow particles having a diameter of not greater than 10 &mgr;m and a hollowness of at least 60% simultaneously have not been realized yet.
There has been proposed a method in which a binder resin is used together with hollow particles in an intermediate layer. For example, Japanese Laid-Open Patent Publication No. H06-247051 proposed the use of 10 to 40%, based on the amount of the hollow particles, of a binder in the intermediate layer. Japanese Laid-Open Patent Publication No. H02-214688 proposes the use of 2 to 50%, based on the amount of the hollow particles, of a binder in the intermediate layer. However, it is known that the rate of the binder is insufficient to improve the sensitivity of the thermosensitive recording material and definition of an image recorded thereon,
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a thermosensitive recording material with an intermediate layer containing hollow particles, which has overcome the drawbacks of the prior arts, having high sensitivity and free from a white void and sticking and capable of forming a uniform image.
Another object of the present invention is to provide a thermosensitive recording material having no possibility of environmental contamination in incineration disposal due to chloride.
In accordance with one aspect of the present invention, there is provided a thermosensitive recording material comprising a support, an intermediate layer provided on said support, and a thermosensitive recording layer provided on said intermediate layer and containing a leuco dye and a color developer for developing said leuco dye upon application of heat, wherein said intermediate layer contains a binder and hollow particles made of a crosslinked polymeric material and having a hollowness of not lower than 60% but not higher than 98%, a maximum particle diameter (D100) of 5.0 to 10.0 &mgr;m and a ratio D100/D50 of said maximum particle diameter (D100) to the median volume equivalent particle diameter (50) in the range of 1.5 to 3.0.
In another aspect, the present invention provides a thermosensitive recording material comprising a support, an intermediate layer provided on said support, and a thermosensitive recording layer provided on said intermediate layer and containing a leuco dye and a color developer for developing said leuco dye upon application of heat, wherein said intermediate layer comprises a binder and hollow particles of a crosslinked polymeric material which does not contain a halogen atom, said hollow particles having a hollowness of not lower than 60% but not higher than 98%.
Other objects, features and advantages of the present invention will become apparent from the detailed description of the preferred embodiments to follow.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
A thermosensitive recording material according to the present invention comprises a support, an intermediate layer provided on the support and containing hollow particles, and a thermosensitive recording layer provided
Hayakawa Kunio
Kaneko Yoshikazu
Mori Yasutomo
Morita Mitsunobu
Naruse Mitsuru
Edwards N.
Ricoh & Company, Ltd.
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