Compositions – Organic luminescent material containing compositions
Reexamination Certificate
2001-05-16
2002-10-29
Koslow, C. Melissa (Department: 1755)
Compositions
Organic luminescent material containing compositions
C252S301340, C252S301350
Reexamination Certificate
active
06471887
ABSTRACT:
FIELD OF TECHNOLOGY
The present invention relates to a fluorescent substance excellent in light emission, a method of preparing the fluorescent substance, a fluorescent composition such as, for example, an inking medium for use in an ink jet printer, containing the fluorescent substance, a fluorescent mark carrier such as, for example, postal envelopes, postal cards or postal parcels having a fluorescent mark formed by printing the fluorescent composition, and an optical reader and an optical reading system both operable to optically read the fluorescent mark at a high speed.
BACKGROUND ART
(Prior Art 1)
In various fields of industries including the distribution industry, bar codes are widely utilized to control the physical distribution of commodities. The bar codes are also utilized having been printed on various cards such as, for example, pre-paid cards, commutation cards and data cards. These bar codes are read by an optical reader such as, for example, an optical scanner which subsequently processes information represented by the bar codes. Most bar codes carried by surfaces of commodities or cards are in the form of a pattern of stripes printed by the use of a black inking medium against a white background and visible to human eyes under visible rays of light. This visible mark is printed directly on merchandise or printed on a shaped sheet-like carrier which is in turn affixed to merchandise.
On the other hand, attempts have been made to form a mark such as a bar code by the use of a fluorescent substance capable of emitting an infrared region of light so that the fluorescent mark can be identified by an optical reader. While the fluorescent mark is generally invisible to the human eyes, the fluorescent mark emits a fluorescent light when the fluorescent substance contained therein is excited upon irradiation of an external light of a particular wavelength and, therefore, by analyzing the fluorescent light with an optical reader, information represented by the fluorescent mark can be decoded or identified. Even the fluorescent mark is, as is the case with the visible mark, printed directly on merchandise or printed on a shaped sheet-like carrier which is in turn affixed to merchandise.
As compared with the system in which change in intensity of light reflected from the visible mark is read in handling merchandise, a system for handling merchandise, including an optical reader for reading the fluorescent mark, has numerous advantages, some of which are listed below.
(1) Reading of the fluorescent mark is seldom affected adversely by the color of the merchandise and, therefore, the reliability in reading the fluorescent mark is high with the reading error minimized.
(2) Even though the surface on which the fluorescent mark is formed becomes dirty, infrared rays of light emitted from the fluorescent mark has such a long wavelength that the reading error would seldom occur and the reliability is therefore high.
(3) Since the fluorescent substance is substantially colorless under visible rays of light, printing of the fluorescent mark on the merchandise will bring no adverse effect on the aesthetic appearance of the merchandise.
(4) Since the fluorescent substance is so invisible under visible rays of light that no one can recognize the presence of the fluorescent substance, it can provide security of information.
Particulars of interest in this connection are disclosed in, for example, the Japanese Patent Publications No. 55-33837, No. 60-29996 and No. 62-24024.
(Prior Art 2)
The fluorescent mark discussed above is formed by printing a fluorescent inking medium containing a fluorescent substance on a carrier such as, for example, a surface of the merchandise in a predetermined pattern. An infrared fluorescent inking medium has long been known and is disclosed in, for example, the U.S. Pat. No. 4,202,491. The infrared fluorescent inking medium disclosed therein is prepared from an inorganic fluorescent substance containing one or a mixture of neodymium (Nd), ytterbium (Yb) and erbium (Er). The inorganic fluorescent substance which utilizes Nd as an optically active element is known to emit a fluorescent light having a maximum intensity at about 1,050 nm in wavelength when irradiated with an exciting light of 800 nm emitted by a GaAlAs light emitting diode. The inorganic fluorescent substance containing a mixture of Nb and Yb as an optically active element is known to emit a fluorescent light having a maximum intensity at about 980 nm in wavelength when irradiated with an exciting light of 800 nm emitted by a GaAlAs light emitting diode. Similarly, the inorganic fluorescent substance containing a mixture of Yb and Er as an optically active element is known to emit a fluorescent light having a maximum intensity at about 1,050 nm in wavelength when irradiated with an exciting light of 940 nm emitted by a GaAs light emitting diode, and the inorganic fluorescent substance containing a mixture of Nd, Yb and Er as an optically active element is known to emit a fluorescent light having a maximum intensity at about 1,050 nm in wavelength when irradiated with an exciting light of 800 nm emitted by a GaAlAs light emitting diode.
(Prior Art 3)
The fluorescent substance disclosed in, for example, the Japanese Patent Publication No. 56-4598 makes use as the optically active element of Nd having a high absorption characteristic with respect to the infrared region of light, in combination with a fluorescent material capable of exhibiting a high intensity of light emission such as, for example, an alkaline metal salt (for example, Na
2
MoO
4
or the like) which is material for the matrix having a high efficiency of transmission of exciting energies from the optically active element to the emission center, or Yb having an emission center capable of favorably matching in wavelength with a Si photodetector.
(Prior Art 4)
For example, the Japanese Patent Publications No. 54-22326 and No. 61-18231 disclose a method of detecting the presence or absence of the fluorescent mark. In this known method, the fluorescent mark is prepared by the use of a fluorescent substance which emits a fluorescent light when irradiated with an exciting light within the infrared region of wavelength. This known method utilizes the difference between the center wavelength of the exciting light projected onto the fluorescent mark and that of the fluorescent light emitted from the fluorescent substance as a result of the irradiation of the exciting light and, for this purpose, only the fluorescent light is separated by an optical filter from rays of light reflected from the fluorescent mark so that the presence or absence of the fluorescent mark can be eventually detected.
The applicant has suggested a method of and an apparatus for detecting the position of a fluorescent mark by intermittently irradiating the fluorescent marking with the exciting light and then detecting the presence or absence of afterglow emitted from the fluorescent marking during the intermission of irradiation of the exciting light. (See, for example, the Japanese Laid-open Patent Publication No. 5-20512.)
(Prior Art 5)
FIG. 70
illustrates the prior art optical reading apparatus. The fluorescent mark shown therein is in the form of a fluorescent bar code
401
comprised of a pattern of parallel bars formed by printing the fluorescent inking medium on a sheet-like carrier
404
such as, for example, a label. The fluorescent inking medium used to form the bar code
401
contains fluorescent microparticles dispersed and retained in a binder, said fluorescent microparticles being of a kind which emit, when excited by an exciting light of a particular wavelength, for example, infrared rays of light
402
, a fluorescent light
403
of a wavelength different from that of the infrared rays of light
402
.
An optical reading apparatus for reading information from the fluorescent bar code
401
includes a light emitter
405
for emitting the infrared rays of light
402
, a light receiver
407
for detecting the fluorescent light
403
from the bar code
40
Kamoto Takanori
Nabeshima Tomio
Oshima Toshio
Saibara Shoji
Yamada Yukinori
Hitachi Maxell Ltd.
Koslow C. Melissa
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