Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Radiation sensitive composition or product or process of making
Reexamination Certificate
2000-02-17
2001-08-28
Angebranndt, Martin (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Radiation sensitive composition or product or process of making
C430S945000, C430S019000, C365S119000, C365S107000, C365S120000
Reexamination Certificate
active
06280904
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of optical recording materials, in particular, fluorescent compounds and matrices suitable for use in optical memory systems, including three dimensional optical memory systems for READ ONLY MEMORY (ROM).
BACKGROUND OF THE INVENTION
Information storage and optical recording systems are of rapidly increasing importance in the modern society in view of the exponential rise in the number and complexity of the data which must be recorded and be retrievable so as to handle the increasing everyday business workload, and to assist efficiently enough in scientific development. Many optical information storage systems, including those based on silver halide emulsions and the like, have contributed significantly to this development, generally because of the high packing density combined with good resolution of information retrieve inherent to such systems. The advantage of READ ONLY MEMORY devices, based on photochemical generation of fluorescent compounds lies in the fact that storage of information in such systems is rapid and accurate, and there is no fixing required. Reading is also rapid, exceptionally sensitive and accurate and is not accompanied by degradation. At the same time there is another requirement the modern optical storage systems should comply with. The reading process should be non destructive for the memory material so as to enable repeating of reading thousands of times without detectable deterioration of the medium material. The reading process, can be carried out either by scanning point by point of the same layer, i.e. bit by bit of information, or by simultaneous reading from a 2-D layer carrying a medium material with the data recorded therein. In this manner a very fast access time to the stored information can be achieved. Reading of this type can be implemented by illumination of a 2-D layer by a fiber optics means. The intensity of illumination radiation should be sufficient for triggering fluorescence within the medium material accompanied by subsequent fluorescent photo-emission from all sites of the layer where the data have been stored.
Various methods and systems of recording of information based on generation of fluorescent compounds obtained from non-fluorescent precursor have been proposed.
The known methods include, for example, UV irradiation of bis-diarylchloromethyl-1,3,4-oxadiazoles as described by Singh in U.S. Pat. No. 3,869,363, herein incorporated for reference. There are known also many others systems as described by Zweig in the paper “Photochemical Generation of Stable Fluorescent Compounds”, Pure and Applied Chemistry, vol. 33, pages 389-410 (1973), herein incorporated for reference.
The main common feature of the prior art optical memory systems is associated with the fact that reading in those systems can be implemented only by lasers having wavelength shorter than 500 nm. It can be appreciated that this requirement prevents employing of modem lasers with longer wavelength.
Furthermore, there exists another requirement to the optical memory systems. This requirement is associated with the fact that the intermediate photo-induced fluorescent product should be thermally and photo-chemically stable otherwise it can be destroyed by the reading process itself. Unfortunately the known in the art materials employed in optical memory systems are not sufficiently stable.
OBJECTS AND SUMMARY OF THE INVENTION
It is therefore the primary object of the present invention to provide a method of recording of information within a 3-D Read Only Memory devices enabling high efficiency of writing in terms of quantum yield of the photo-transformation and in terms of quantum yield of the fluorescence produced by the photo-induced form of the medium material.
The other object of the present invention is to provide for a medium material suitable for use in an optical storage memory system, which is defined by high thermal and photochemical stability.
SUMMARY OF THE INVENTION
Rhodamine B lactams have been known for a long time for use as coloring element in thermo- and piezo-sensitive papers, as described in U.S. Pat. No. 3,922,283 by M. Iahargi, S. Horiuchi and in Japanese patent 11660 (1972) by M. Sadao, O. Misaoki and F. Mitsuru and in U.S. Pat. No. 4,599,630 by K. Ohtaki and H. Sakamoto herein incorporated for reference.
The Rhodamine-B lactams have been recognized as suitable coloring additive for chemical sensors however they were not considered in connection with optical recording of information. Despite the fact that Rhodamine B lactams are well known compounds there was not known about their ability to undergo photo-transformation under illumination by long wave electromagnetic radiation with subsequent formation of fluorescent derivatives and therefore about their suitability for optical storage memory systems.
In accordance with the present invention it has been surprisingly discovered that the transformation of a Rhodamine-B lactam into respective Rhodamine derivative can be successfully implemented for recording of information in various optical memory systems by virtue of the fact that Rhodamine derivatives exhibit induced fluorescence when illuminated by a long wave radiation. The induced fluorescence can be detected for example by a CCD camera.
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Knauer et al., “photochromism or rhodamine derivatives”, Angew. Chem. vol. 89(2) pp. 116-117, 1977.*
Willwohl et al., “Kinetics and mechanism of the photochromism of n-phenyl rhodmainelactame”, Laser Chem., vol. 10. pp. 63-72, 1989.
Levich Eugene B.
Malkin Jacob N.
Shubin Vladimir V.
Sokoluk Natalia T.
Angebranndt Martin
Blank Rome Comisky & McCauley LLP
TriDStore IP LLC
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