Appeal No. 1996-2769
Application 08/270,089
The appellant’s invention is directed to a method of making improved phosphors
having a uniform, spherical shape and particle size below one micron. According to the
specification
Phosphors typically comprise one or more rare earth metals in a host
material. Up-converter phosphors emit light in the visible wavelength radiation
range (550-800 nanometers) when excited by long wavelength radiation, e.g., light
in the infrared wavelength spectrum. This is accomplished by multiple absorption of
infrared photons and energy transfer between the absorbing and the emitting ions.
For example, it is known that yttrium oxysulfide, Y O S, gadolinium oxysulfide,
2 2
Gd O S, and lanthanum oxysulfide La O S, doped with certain activator couples, will2 2 2 2
be excited by 0.96 micron wavelength radiation. Such radiation can be provided by
semiconductor lasers [specification , p. 1].
The phosphors of the present invention are said to be useful in biological assays for
detecting compounds such as proteins, drugs, and polynucleotides. Specification, p. 1.
The specification indicates that the phosphors “can be used as immunoassay labels by
attaching them to one or more probes, such as antibodies, protein A, polypeptide ligands
of cellular receptors, polynucleotides, drugs, antigens, toxins and the like.” Id., p. 2.
The examiner’s findings of fact and conclusion(s) of obviousness were set forth in
the Answer as follows. The examiner first applied Royce, a patent which was said to
disclose a process of heating a “mixture of rare earth oxides and a flux of sulfur and at
least one alkali metal salt at a temperature of 700-1250EC in the absence of oxygen,” as
the primary reference. Answer, p. 4. The examiner acknowledged that Royce did not
teach “the specifically claimed oxysulfide nor the claimed activator couples because they
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