Note: Descriptions are shown in the official language in which they were submitted.
108;~445
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to novel fluorescent compositions
and low-velocity electron excited fluorescent display devices
5 . utilizing the same, and more particularly is concerned with novel
fluoroescent compositions which can display emission having high
luminance in a high state of color purity under low-velocity
electron excitation, and low-velocity electron excited fluorescent
display devices containing as a fluorescent screen these fluore-
scent compositions.
Description of the Prior Art
, As is commoniy known, a low-velocity electron excited
I fluorescent display device (which is abbreviated as a "Fluorescent
~ display device" hereinafter) may be employed as a display device
¦ 15 for desk top electronic calculators and various kinds of measur-
ing instruments . Demand for such fluorescent display devices is
¦ great because ofthe remar~able popularization in recent years of
calculators and instruments in which they are employed. The
fluorescent device of this kind in general has a fundamental
. :;` 20 structure such that both an anodic plate having a fluorescent
:
screen on one side thereof and a cathode standing face to face
,
: ~ with the above-described fluorescent screen are enclosed in an
. ~ evacuated tube wherein the fluorescent screen placed on the anodic
~ : plate is excited by low-velocity electrons emitting from the
J~
~:` 25 cathode to result in amission of light of certain wavelengths.
. ~
Both Figure 1 and Figure 2 give outlines of typical structures
. ~ of fluorescent display devices, and they show a diode type display. ~ 2 -
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~08'~445
tube and a triode type display tube, re~*ively. As s ~ n in both Figure
1 and Figure 2, one side of an anodic plate 11 made of, e.g., an al ~ num
plate, has a fluorescent screen 12 thereon. me other s~e of the anodic
plate 11 is supported by a ceramic base plate 13. The diode type
display tube is equipped with a cathode standing face to face with
the above-described fluorescent screen 12 placed on the one side
of the anodic plate 11, and emission occurs by excitation of
the fluorescent screen 12 which arises from low-velocity electrons
emitted from the cathode 14. In particular, the triode type
display tube shown in Figure 2 additonally has a grid electrode
15 between the cathode 14 and the fluorescent screen 12 so as to
control or diverge low-velocity electrons emitted from the cathode
14. Moreover, when the surface of the fluorescent screen 12 has
wide area, two or more cathodes may be additionally placed in both
fluorescent display tubes shown in Figure 1 and Figure 2 wherein
only one cathode is placed, and there is no particular limit to
the number of cathodes that can be placed therein. The aforesaid
anodic plate 11 having a fluorescent screen 12 on one side thereof,
the ceramic base plate 13 and the cathode 14 (which are shown in
Figure 1), or the aforesaid anodic plate 11 having a fluorescent
, screen 12 on one side thereof, the ceramic base plate 13, the
cathode 14 and the grid electrode 15 (which are shown in Figure 2)
are enclosed in a transparent container 16, made of, for example,
t glass, the pressure inside which is held at a high vacuum of 10 5
to 10 g Torr.
Zinc activated zinc oxide phosphors (ZnO:Zn) have ~een
commonly ~nown as phosphors employed for the above-described
. .;1
~ fluorescent display devices which can emit light of high
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~082445
luminance under low-velocity electron excitation occurring under
certain conditions, particularly under acceleration potential
below 100V. Phosphors of this kind can be prepared by firing
zinc oxide ~ZnO) alone in a reducing atmosphere, or by firing
ZnO contaminated with a slight amount of a certain zinc compound
other than ZnO such as zinc sulfide ~ZnS) or the like in air,
and they can give forth greenish white emission of high luminance
when excited by low-velocity electrons. Fluorescent display
devices havinq the fluorescent screen made of the aforesaid
~ZnO:Zn) have been commercially used as display devices for, e.g.,
desk top electronic calculators and various kinds of measuring
instruments. However, aside from ~ZnO:Zn) almost no phosphors
are known which can emit light under low-velocity electron
; excitation, and therefore, fluorescent display devices equipped
with fluorescent screens containing phosphors other than (ZnO:Zn)
are rare at the present stage of this art. Emission color of
~ZnO:Zn) is greenish white as described above, and therefore a
fluorescent display device utilizing ~ZnO:Zn) has inadequate
I color purity as a green emitting display. Accordingly, the
20 present invention is aimed at providing green emitting composi-
tions and fluorescent display devices using them which can emit
i~ green light in a high state of color purity. In addition, the
present invention is also aimed at providing fluorescent composi-
tions capable of emitting light of specific wavelengths, other
than greenish ones, in high luminance and at providing fluorescent
display devices utilizing them.
SUMMA~Y OF T~.E INVENTION
One object of the present invention is to provide novel
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108'~445
fluorescent compositions which can give forth emission of high
luminance in a high state of color purity under low velocity
electron excitation which occurs under certain conditions,
particularly under acceleration potential below lOOV.
S Another object of the present invention is to provide
novel green emitting compositions which can give forth green
emission of high luminance in a high state of color purity under
low-velocity electron excitation occurring under certain condi-
tions, particularly under acceleration potential below lOOV.
A further object of the present invention is to provide
novel blue emitting compositions which can give forth blue
emission of high luminance in a high state of color purity under
low-velocity electron excïtation occurring under certain condi-
tions, particularly under acceleration potential below lOOV.
Still another object of the present invention is to
provide novel red emitting compositions which can give forth red
emission of high luminance in a high state of color purity under
low-velocity electron excitation occurring under certain condi-
tions, particularly under acceleration potential below lOOV.
Another object of the present invention is to provide
fluorescent display devices which can display emission having b~th high
luminance and high color purity.
A further object of the present invention is to provide
fluorescent display devices which can display green emission hav-
2S ing both high luminance and high color purity.
Still another object of the present invention is to
provide fluorescent display devices which can display blue
~; emmission having both high luminance and high color purity.
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Another object of the present invention is to provide
fluorescent display devices which can display red emission hav-
ing both high luminance and high color purity.
Other objects of the present invention will become
apparent from a consideration of the following description and
examples.
These objects can be attained with fluorescent composi-
tions containing zinc oxide and one phosphor selected from the
following group in a weight ratio ranging from 1:9 to 9:1, said
group consisting of a copper and aluminium activated zinc cadmium
sulfide phosphor [(Znl x' Cdx)S:Cu, Al, wherein 0~x~0.1], a
cerium activated yttrium aluminium gallate phosphor [Y3(All y,
Gay)5Ol2:Ce, wherein 0Cy~0.5], a manganese activated zinc silicate
phosphor (Zn2SiO4:Mn), a terbium activated yttrium lanthanum oxy-
sulfide phosphor [(Yl z, Laz)2O2S:Tb, wherein 0~z~1], a europium
activated strontium gallium sulfide phosphor (SrGa2S4:Eu2 ), a
silver activated zinc sulfide phosphor (ZnS:Ag), and a europium
activated yttrium oxysulfide phosphor ~Y2O2S:Eu).
Moreover, some objects of the present invention can be
attained.with fluoresaent display devices having the above-
described fluorescent compositions as a compound of a fluorescent
screen.
When x equals zero in the aforesaid formula 1(Znl x' Cdx)
S:Cu, Al], this formula represents the copper and aluminium acti-
...... 25 vated zinc sulfide phosphor, but in the present discussion these
. are dealt with as the special cases of copper and aluminium
activated zinc cadmium sulfide phosphors.
Although the formulae ~Y3(All_y, ~ay)512
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108'~45
[(Yl z, Laz)2O2S:Tb] under the conditions of y=0, z=0 and z=l
represent a cerium activated yttrium aluminium phosphor, a
terbium activated yttrium oxysulfide phosphor and a terbium
activated lanthanum oxysulfide phosphor, respectiveLy, the former
is dealt with as the special case of cerium activated yttrium
aluminium gallium phosphor, and the latter two phosphors are
dealt with as the special cases of terbium activated yttrium
lanthanum oxysulfide phosphors analogous to the way mentioned
above.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 and Figure 2 are structural outlines of typi-
. cal examples of fluorescent display devices wherein a diode type
display tube is shown in Figure 1 and a triode type display tube
is shown in Figure 2,
Figures 3A to 3J illustrate the dependence of luminance
of emission on the mixing weight ratio of the amount of ZnO to
that of the phosphor contained in a fluorescent composition pro-
vided in the present invention under low-velocity electron exci-
tation,
Figures 4A to 4J are diagrams illustrating the relation-
ships between brightness of emission, which each of the fluore-
~ ~ scent compositions of the present invention and the phosphor
s' alone comprised therein give forth, and the acceleration potential;l applied to each of them,
t ~ 25 Figures 5A to 5K are emission spectra of the respective
fluorescent compositions of the present invention and the conven-
~ tional one, and
~ Figure 6 is a CIE standard chromaticity diagram plotted
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108;~445
against the emission chromaticity under low-velocity electron
excitation of the fluorescent compositions of the present inven-
tion and the known fluorescent composition.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
All the fluorescent compositions provided in the present
invention which contain a certain composition capable of emitting
green, blue or red-light under low-velocity electron excitation
are characterized by containing ZnO as an essential component.
Commercially available reagent grade ZnO (termed as
"reagent ZnO" hereinafter), for example, Sazex 2000* manufactured
by Saikai Chemicals, may be used as the ZnO which is one of the
important components of the present invention without any purify-
ing treatments. Besides reagent ZnO, zinc oxides produced by
firing in air zinc compounds of the kind which can easily be
converted to zinc oxide at high temperature, such as zinc carbon-
ate, zinc sulfate, zinc oxalate, zinc hydroxide, etc., (termed as
"fired ZnO" or "heat treated ZnO" hereinafter) can also be
employed. Appropriate firing temperatures for producing fired
ZnO were found to be below 1200C. Temperatures higher than
1200C were undesirable because ZnO commences sintering.
' The phosphors which correspond to the other component
-~ of the fluorescent compositions provided in the present invention
including phosphor (1) having the formula l(znl x' Cdx)S:Cu, Al],
phosphor 12) having the formula [Y3(all_y, Gay)5O12:Cel, phosp
~3) having the formula-[Zn2SiO4:Mn], phosphor (4) having the
formula l~Yl z, ~az)2O2S:Tbl, phosphor (5) having the formula
(SrGa2S4:Eu 1, phosphor (6) having the formula [ZnS:Agl and
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108'~445
phosphor (7) having the formula [Y202S:Eu] can, in general, be
produced in accordance with the following process.
Phosphor (1) may be prepared as follows: Chemically
precipitated zinc sulfide (ZnS) and chemically precipitated
cadmium sulfide (CdS) are mixed in a molar ratio of (l-x) mole
of the former to x mole of the latter (, wherein the value x is
within the range of O~x~0.1). To the resulting sulfide mixture
there are added both the prescribed amount of a copper compound
such as copper sulfate (CuSO4 5H2O) or the like and the pre-
scribed amount of an aluminium compound such as aluminium sulfate
[A12(SO4)3 18H2O] or the like, and they are mixed thoroughly.
Then, they are fired at a temperature ranging from about 900DC to
about 1200C for periods of about one hour to about five hours
in a sulfuric atmosphere such as an atmosphere of hydrogen sulfide,
sulfure or the like to produce phosphor (1). The preferred amount
of an activator corresponding to either Cu or Al which is suitable
for phosphor ~1) is within the range of 10 5 to 10 3 gram, and
more preferably 5 x 10 5 to 5 x 10 4 gram, per one gram of a host
material (Znl_x, Cdx)S.
When the affix x has a value larger than 0.1, the
phosphor (1) emits light of longer wavelength, from yellow to red,
with increasing value of x. Therefore, those compositions are
unsuitable for those of components which constitute fluorescent
compositions employed for green emitting fluorescent display
devices of the present invention.
Phosphor (2) may be prepared as follows: Yttrium oxide
-~ (Y2O3) or an yttrium compound easily alterable to Y2O3 at a high
- temperature, alluminium oxide (A1203) or an aluminium compound
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.
iO8;~445
easily alterable to A12O3 at a high temperature are mixed with
Ga203 or a gallium compound easily alterable to Ga203 in a molar
ratio of 5 moles of an oxide mixture, one mole of which is
represented by the formula (All y Gay)203 wherein Y mole of Ga2O3
is mixed with (l-y) mole of A12O3 under the condition of 0~y~0.5,
to 3 mole of Y203, and the prescri~ed amount of a cerium ion which
is suitable for the phosphor (2) is further added to and mixed
with the resulting oxide mixture in the form of cerium oxide
(Ce203) or a cerium compound easily alterable to cerium oxide at
a high temperature. The mixture is fired at a temperature within
the range of about 1200C to about 1700C, and preferably about
1400C to about 1600C, for about one hour to about five hours in
an air or in a weak-reducing atmosphere. It is preferred that the
above-described firing treatment be repeated not less than twice.
The preferred amount of the activator Ce appropriate to the
phosphor (2) is within the range of 10 4 to 10 1 gram atom and
more particularly 10 3 to 5 x 10 2 gram~atom, per mole of a host
3 1 Y y 5 12- Among the compositions included
within the scope of phosphor (2), those which have the affix y
equal to a value larger than 0.5 were not suitable as a component
of a fluorescent composition employed for the fluorescent display
device of the present invention because of the fluorescent
luminance decreases with increasing the value y.
Phosphor (3) may be prepared by mixing zinc oxide (ZnO)
or a zinc compound easily alterable to ZnO at a high temperature
with silicon dioxide (SiO2) or a silicon compound easily alter-
able to SiO2 at a high temperature in a molar ratio of 2 mole of
ZnO to 1 mole of SiO2, additionally mixing the resulting mixture
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108~44S
oxide with the prescribed amount of manganese ion, an activator
for the phosphor (3), in the form of manganese oxide (MnO) or a
manganese compound easily alterable to MnO, and then firing them
in air at a temperature within the range of about 10~0C to about
1400C, and more particularly about 1200C to about 1300C, for
about one hour to about five hours. The above-described firing
process should be repeated not less than 2 times. The preferred
amount of the activator Mn suitable for the phosphor (3) was
within the range of 10 4 to 10 1 gram atom, and more particularly
10 3 to S x 10 2 gram-atom, per mole of host material Zn2SiO4.
Phosphor (4) may be prepared by mixing yttrium oxide
(Y2O3) with lanthanum oxide (La2O3) in a molar ratio of (l-z)
mole of the former to z mole of the latter (wherein the value z is
present within the range of 0~z~1), additionally mixing them with
the prescribed amount of terbium oxide (Tb2O3), adding to the
resulting rare earth oxide mixture 20 to 40 weight % of sulfur (S)
and 20 to 40 weight % of sodium carbonate (Na2CO3) to act as a
flux thereon, mixing them thoroughly, and firing the resulting
mixture in air at a temperature within the range of about 1200C
to about 1300C for about one hour to five hours. The aforesaid
rare earth oxide mixture group consisting of Y2O2, La2O3 and Tb2O3
may be produced simply by physically mixing these ingredients, but
it should, in general, be prepared by once dissolving these
ingredients in a mineral acid with the intention of improving
2~ upon the miscibility thereof, adding in aqueous solution of oxalic
acid thereto to coprecipitate yttrium oxalate, lanthanum oxalate
and terbium oxalate, and then pyrolyzing the resulting coprecipi-
tated rare earth oxalate mixture. The preferred amount of the
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iO8'~445
activator Tb suitable for the phosphor (4) is within the range
of 10 2 to 1.5 x 10 1 gram, and more particularly 5 x 10 2 to
6 x 10 gram, per 1 gram of host material (Yl z, Laz)2O2S.
Phosphor (5) may be prepared by adding gallium oxide
(Ga2O3) of high purity to a strontium compound which is easily
- alterable to the sulfide by heating in a sulfuric stream, such
as strontium sulfate, strontium carbonate or strontium chloride,
all of which must be of high purity, in equimolar amounts, addi-
tionally adding as an activator the prescribed amount of europium
ion in the form of europium sulfate [Eu2(SO4)3~, europium nitrate
[Eu(NO3)3] or europium oxide [Eu2O3] to the aforesaid oxide mix-
ture, thoroughly mixing the resulting mixture, and then firing
it at a temperature within the range of about 700C to aboùt
1000C, and more preferably about ~00C to about 900C, for
about 3 to about 5 hours in a sulfuric stream of such as sulfur
vapor, hydrogen sulfide gas, carbon disulfide gas or the like.
The preferred amount of the activator Eu suitable for ISrGa2S4:
Eu2+] was within the range of 10 4 gram-atom to 5 x 10 1 gram atom,
and more particularly 5 x 10 3 gram-atom to 10 1 gram.atom, per
mole of host material SrGa2S4.
Phosphor (6) may be prepared by adding an appropriate
amount of a silver compound such as silver nitrate or the like
to reagent grade zinc sulfide (ZnS) and then ~iring the resulting
mixture in a weak-reducing atmosphere at a temperature within the
2~ range of about ~OO~C to about 1200DC for about one hour to about
five hours. The resulting IZnS:Ag~ is known to have two crystal
systems; i.e., a cubic system and a hexagonal system. The
phosphor [ZnS:Ag] crystal of the hexagonal system can be obtained
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~08'~445
by firing the aforesaid starting material at a temperature higher
than about 1020C, and that of a cubic system can be produced by
firing the aforesaid starting material at a temperature lower
than about 1020C. [ZnS:Ag] of either the cubic crystal system
or the hexagonal crystal system can be used as the component of
the fluorescent composition. The preferred amount of the activa-
tor Ag suitable for [ZnS:Ag] was within the range of 10 5 to 10 3
gramt and more particularly 5 x 10 5 to S x 10 4 gram, per gram
of host material ZnS.
10Phosphor (7) may be prepared by adding the prescribed
amount of europium oxide ~Eu2O3) to yttrium oxide (Y2O3), and
then mixing them thoroughly to make a rare earth oxide mixture,
further mixing the resulting mixturewith 20 to 40 weight % of
sulfur (S) and 20 to 40 weight % of sodium carbonate (Na2CO2) to
act as a flux, and then firing them in air at a temperature of
about 1200C to about 1300C for about one hour to about five
hours. The preferred amount of the activator Eu suitable for
[Y2O2S:Eu] was within the range of 10 2 to 1.5 x 10 1 gram, and
more particularly 5 x 10 2 to 6 x 10 2 gram, per gram of host
material Y2O2S.
Fluorescent compositions of thepresent invention can be
produced by mechanically mixing ZnO and one of the above-descri~èd
phosphors (1) to (7). The mixing process may be carried out by
use of a conventional mixing instrument such as a mortar, a ball-
mill, a mixer-mill or the like.
~`~The two components are mixed in a weight ratio of the
amount of zinc oxide to that of phosphor ranging from 1/9 to 9/1.
~Nhen~zinc oxide is present in an amount under the mixing weight
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108'~45
ratio of 1/9, characteristics of the resulting composition are
akin to those of the phosphor used. Therefore, substantially no
emission is observed under low-velocity electron excitation. On
the other hand, when zinc oxide is present in an amount in excess
of the mixing weight ratio of 9/1, the resulting composition
gives rise to very weak emission because of the small amount of
phosphor. Accordingly, the mixing ratio of these two components
isrequired tobe within the range of 1/9 to 9/1. This factis illustra-
tedby thegraphs inFigures3A to 3Jas follows: Each of Figures
3A to 3J shows the relationship between the ZnO/phoshpor ratio
(by weight) of one of fluorescent compositions to be examined
in the present invention and the luminance of emission achievable
under low-velocity electron excitation. Figures 3A to 3H each
corresponds to the luminance of emission achieved under the
acceleration potential of ~OV, while Figures 3I and 3J correspond
to that achieved at 100V. Figures 3A, 3B, 3C, 3D, 3E, 3F, 3G,
3H, 3I and 3J show the results obtained using as phosphors (I)
ZnS:Cu, A1 (pho5phor (1)-1), (II) (Zn0 95, Cdo 05)S:Cu, Al
(phosphor (1)-2), (III) Y3A15O12:Ce (phosphor (2)-1), (IV)
Y3(A10;6, GaO 4)5O12:Ce (phosphor (2)-2), (V) Zn2SiO4:Mn (phosphor
(3)), (VI) Y2O2S:Tb (phosphor (4)-1), (VII) La2O2S:Tb (phosphor
(4)-2), (VIII) SrGa2S4:Eu2+ (phosphor (5)), (IX) ZnS:Ag (phosphor
(6)) and (X) Y2O2S:Eu (phosphor (7)), respectively. The curve
a and the curve b in each of Figures 3A to 3H and Figure 3J
~5 show the case in which reagent ZnO is used and the case in which
fired ZnO produced by firing at the temperature of 1000C is
`~ used, respectively. The curve a, the curve ~ and the curve _ in
~igure 3I show the case wherein reagent ZnO is used, the case
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1~82445
wherein fired ZnO produced by firing at 700~C is used and the
- case wherein fired ZnO produced by firing at 1000C is used,
respectively.
It is apparent from the aforesaid figures that the
values of the luminance corresponaing to the values of the ZnO/
phosphor ratio smaller than 1/9 and larger than 9/1 were extremely
small in all fluorescent compositions. The value of the ZnO/
phosphor ratio which provides the maximum luminance depends upon
the kind of ZnO used. Namely, in each of Figures 3A to 3H and
Figure 3J, maximal luminance is obtained with the ZnO/phosphor
ratio of abour 1/1 when reagent ZnO is used and whatever kind
of phosphor may be used therein ~as shown on the curve-a). How-
ever, when fired ZnO is used, the ZnO/phosphor ratio capable of
providing maximal luminance is gradually shifted to larger
values than 1/1 (i.e., in the direction of increasing amount of
ZnO) with rising firing temperature. For example, in the case
where fired ZnO produced by firing at 1000C is employed, maximal
luminance is obtained with a ZnO/phosphor ratio of about 7/3
whatever kind of phosphor may be used therein (as shown on the
curve-b). A similar tendency to the above-described one can also
be observed in Figure 3J which shows that maximal luminance is
obtained with the ZnO/phosphor ratio of about 3/7 when reagent
ZnO is used (as shown on the curve-a). However, when fired ZnO
is used, the ZnO/phosphor ratio capable of providing maximal
2~ luminance is gradually shifted to larger values than 3/7 (i.e., in
the direction of increasing amount of ZnO) with rising firing
temperature. For example, in the case of a firing temperature
, ~ .
of 700~C (curve-b), maximal luminance is obtained with a ZnO/
- 15 -
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108'~4~5
phosphor ratio of about 1/1, and in the case of a firing tempera-
ture of 1000C (curve-c), maximal luminance is obtained with a
ZnO/phosphor ratio of about 7/3.
In addition, the fluorescent composition containing a
combination of two or more kinds of phosphors selected ~rom the
group consisting of the aforesaid phosphors (1) to (5) give
results similar to the above, and it goes without saying that
fluorescent compositions containing the combined phosphor in the
ZnO/phosphor ratio in the range of 1/9 to 9/1 fall under the
category of the present invention.
The fluorescent compositions of the present invention
are characterized by producing emissions having high luminance
and excellent color purity under low-velocity electron excitation.
Of the fluorescent compositions proposed in the present invention,
those compositions containing the phosphors (1) to (5) emit green
light, those compositions containing the phosphor (6) emit blue
light and those compositions containing the phosphor (7) emit red
llght. These results are particularly surprising in view of the
fact that the phosphors comprised in the fluorescent compositions
of the present invention themselves display emission at high
luminance under electron excitation at an acceleration potential
of several KV, ~ut display almost no emission under low-velocity
electron excitation, particularly under an acceleration poten~ial
below 100V.
Although the reason why compositions preparea from Zno
~ and phosphor of the ~ind which display hardly any emission under
;S ~low-velocity electron excitation by mixing them thoroughly can,
when mixed thoroughly, display some emission under low-velocity
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108Z4~5
electron excitation has not been clarified at the present, it is
thought that the aforesaid phenomena occurs predominantly because
of the improved excitation efficiency which becomes possible
because the electric conductivity of the composition is raised
S as a whole by the addition of ZnO having higher electric conduc-
tivity than the phosphors (1) to (7), so that the charge-up
phenomenon does not occur on the occasion of excitation.
~ he differences between the emission characteristics of
the fluorescent compositions of the present invention and those of
of phosphors present as a component therein are illustrated in
detail with reference to Figures 4A to 4J. These figures show
the dependence of luminance upon acceleration potential. In each
figure, curve-a corresponds to the result for the fluorescent
composition prepared in the present invention, while curve-b
corresponds to that for the phosphor comprised therein itself.
That is to say, the curve-a in Figure 4A shows the result for the
fluorescent composition prepared by mixing reagent ZnO with the
phosphor (1)-l lZnS:Cu, Al], which contains both activators Cu
and Al in the amount of 10 4 g/g, in an amount of an equivalent
mixing ratio by weight in accordance with one of the examples
hereinafter described, while the curve-b shows the result for the
aforesaid phosphor (1)-l alone. The curve-a in Figure 4B shows
the result for the fluorescent composition prepared by mixing
reagent ZnO with the phosphor (1)-2 {(Zn0 95, Cdo 05)S:Cu, Al],
which contains both activators Cu and Al in the samé amount of
--4
g/g, in an amount of an equivalent mixing ratio by weight in
accordancewith another example hereinafter described, while the
1'
. curve-b shows the result for the aforesaid phosphor (1)-2 alone.
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108'~445
The curve-a in Figure 4C shows the result for the fluorescent
composition prepared by mixing reagent ZnO with the phosphor
(2)-1 1Y3A15O12:Ce], which contains the activator Ce in the
amount of 10 2 gram-atom/mole, in an amount of an equivalent mix-
ing ratio by weight in accordance with a further example herein-
after described, while the curve-b shows the result for the
aforesaid phosphor (2)-1 alone. The curve-a in Figure 4D shows
the result for the fluorescent composition prepared by mixing
reagent ZnO with the phosphor (2)-2 [Y3(Alo 6~ Ga~ 4)512 Ce3,
which contains the activator Ce in the amount of 10 2 gram-atom/
mole, in an amount of an equivalent mixing ratio by weight in
accordance with still another example hereinafter described, while
~he curve-b shows the result for the aforesaid phosphor (2)-2
alone. The curve-a in Figure 4E shows the result for the fluor-
escent composition prepared by mixing reagent ZnO with the phos-
phor (3) lZn2SiO4:Mn], which contains the activator Mn in the
; amount of 2 x 10 2 gram-atom~mole, in an amount of an equivalent
` mixing ratio by weight in accordance with another example herein-
after described, while the curve-b shows the result for the
aforesaid phosphor (3) alone. The curve-a in Figure 4F shows
the result for the fluorescent composition prepared by mixing
reagent ZnO with the phosphor (4~ Y2O2S:Tb], which contains
~ the activator Tb in the amount of 5 x 10 2 g/g~ in an amount of¦ an equivalent mixing ratio by weight in accordance with a further
example hereinafter descri~ed, while the curve-b shows the result
for the aforesaid phosphor (4)-1 alone. The curve-a in Figure
3 4G shows the result for the fluorescent composition prepared by~ .
mixing reagent ZnO with the phosphor (4)-2 [La2O2S:Tb~, which p
~i' ' ;'- -
,~ ~ - 18 -
-1:~ . .
,, ~ , , , . . . .. , _ _ _ _ _ . . . . . . .
': - , . . .. ..
:, '- ' ' ' , . .
: . . . . .
.. . - : . . : . .- -
' , ' ., - ~- . .~ ,. . .. :
.. . . . . . . .
~,~, ~, - . ,
108'~445
contains the activator Tb in the amount of 5 x l0 g/g, in an
amount of an equivalent mixing ratio by weight in accordance with
a still another example hereinafter described, while the curve-b
shows the result for the aforesaid phoshpor (4)-2 alone. The
curve-a in Figure 4H shows the result for the fluorescent compo-
sition prepared by mixing reagent ZnO with the phosphor (5)
(SrGa2S4:Eu2+], which contains the activator Eu2~ in the amount
of 3 x l0 2 gram.atom/mole, in an amount of an equivalent mixing
ratio by weight in accordance with another example hereinafter
described, while the curve-b shows the result for the aforesaid
phosphor (5) alone. The curve-a in Figure 41 shows the result
for the fluorescent composition prepared by mixing heat treated
ZnO produced by firing at 1000C with the phosphor (6) [ZnS:Ag],
which contains the activator Ag in the amount of l0 4 g/g, in the
mixing ratio of 7 weight parts of the former to 3 weight parts of
the latter in accordance with a further example of the present
invention hereinafter described, while the curve-b shows the
result for the aforesaid phosphor (6) alone. The curve-a in
Flgure 4J shows the result for the fluorescent composition pre-
pared by mixing reagent ZnO with the phosphor (7) lY2O2S:Eu],which contains the activator Eu in the amount of 5 x l0 2 g/g~
in an equivalent mixing ratio by weight in accordance with still
another example of the present invention hereinafter described,
¦ while the curve-b shows the result for the aforesaid phosphor (7)
` 25 alone.
It is apparent from Figures 4A to 4~ that the fluor-
escent compositions ofthe present invention emit green, blue or
red light even under conditions that cause the luminance of the
,lg -
.. . .
'': . : ' - ~ :
.- .- : - , :. , , ,,- . ~ :............ . .
108'~'~45
phosphors contained in the respective fluorescent compositions
as essential components thereof, to decrease rapidly; i.e., under
low-velocity electron excitation induced by acceleration poten-
tials below 100V. For example, the luminance of each of the
S fluorescent compositions shown in Figure 4A, 4B or 4F is about
several hundred times that of said respective phosphors alone
under low-velocity electron excitation induced by application of
acceleration potential of 100V, and the luminance of each of the
fluor~scent compositions shown in Figure 4C, 4D, 4E, 4G, 4H, 4I
or 4J is about one thousand times that of said respective phos-
phors alone under the same conditions as mentioned abo~e.
The excellent emission spectrum characteristics of
the fluorescent compositions of the present invention can be seen
from Figures 5A to 5I. Among the fluorescent compasitions pro-
posed in the present invention, all green-emitting compositions
emit green light in a higher state of color purity that the well-
known fluorescent composition lZnO:Zn3. Namely, Figures 5A to 5
and Figure 5I are graphs representing the emission spectra of
fluorescent compositions of the present invention and tZnO:Zn],
respectively, under low-velocity electron excitation. Figure SA
shows the emission spectrum of a fluorescent composition prepared
by mixing ZnO and the phosphor (1)-1, Figure 5B shows the emis-
sion spectrum of a fluorescent composition prepared by mixing ZnO
and the phosphor (1)-2, Figure 5C shows the emission spectrum of
25 a fluore9cent composition prepared by mixing ZnO and the phosphor
(2~-1, Figure 5D shows the emission spectrum of a fluorescent
¦~ composition prepared ~y mixing ZnO and the phosphor (2)-2, Figure
5E shows theemission spectrum of a fluorescent composition
, - 20 -
.~,...~... .
~08~445
prepared by mixing ZnO and the phosphor (3), Figure 5F shows the
emission spectrum of a fluorescent composition prepared by mix-
ing ZnO and the phosphor (4)-1, Figure SG shows the emission
spectrum of a fluorescent composition prepared by mixing ZnO and
the phosphor (4(-2, Figure 5H shows the emission spectrum of a
fluorescent composition prepared by mixing ZnO and the phosphor
(5) and Figure 5I shows the emission spectrum of the conventional
fluorescent composition [Zno:Zn} alone.
All of the emission spectra in the aforesaid green
emitting compositions of the present invention indicate a main
peak at a wavelength closer to green than that ~f a well-known
composition [ZnO:Zn3, and the h~lf-value width of each emission
spectra is narrower than that of [ZnO:Zn]. Therefore, the emis-
sion color of each green emitting composition of the present
, 15 invention is a green of a higher color purity than the emission
color of [ZnO:Znl.
Figure 6 shows CIE standard chromaticity diagrams where-
in chromaticity points of the emission spectra obtained under low-
l velocity electron excitation relating to the fluorescent composi-
!; 20 tions ~llustrated in the examples of the present invention and
¦ lZnO:Zn], the emission spectra of which were shown in Figures 5A
, to 5I, are plotted. The chromaticity points A, B, C, D, E, F, G,
. ~ H and I correspond to the emission spectra shown in Figures 5A,
. ~ 5B, 5C, SD, 5E, 5F, 5G, 5H and 5I, respectively. As can be seen
~:~ 25 from Figure 6, the emission color-obtained for each of the fluor-
:, ~,
: ::
.~ escent compositions of the present invention (chromaticity points
.' 5',~ A, B, C, D, E, F, G and H) is also a green of much more excellent
color purity than that of lZnO:gn]. The fluorescent compositions
A~ . 21
~. . ; - ,. , ~ . . . , -- - .
,., . ~ ~ .
108Z445
prepared in accordance with the present invention and having
emission spectra as shown in Figures 5A to 5H each contains a
single phosphor. It is, however, possible to produce other
fluorescent compositions capable of emitting green light of
higher color purity than [ZnO:Zn] by combining two or more
phosphors selected from the aforesaid phosphors (l) to (S).
In addition, a fluorescent composition containing the
phosphor (6) prepared in accordance with the present invention
can give forth blue emi~sion of high luminance in a high state of
color purity, and another fluorescent composition containing the
phosphor (7) prepared in accordance with the present invention
can give forth red emission of high luminance in a high state of
color purity. Almost no fluorescent components of the kind which
can emit blue or red light of high luminance and high color
purity under low-velocity electron excitation have been know up
to naw. The emission spectra of the above-described fluorescent
compositions of the present invention are shown in Figure SJ and
ln Figure 5X, respectively. As clearly shown in these figures,
the emission spectrum of the fluorescent composition containing
the phosphor (6) has a peak at about 450nm, and the resulting
emission is blue of excellent color purity. On the other hand,
the emission spectrum of the other fluorescent composition con-
taining the phosphor (7) has a peak at about 625nm, and the
~ . .
resulting emission is red of excellent color purity. The fluor-
i 25 escent compositions provided by the present invention are very
i useful as phosphors for making fluorescent display devices, and
each can retain its above-mentioned excellent inherent character-
istics without impairment when employed as a fluorescent screen
- 22 -
,.
, ., . ~ . . : ~ .
- . . .,: . ; , . -
. " .:, ~ - . , : - -
~., . ~ .
.. ... . . , . . , , ~ .. ~ - .
.: .' . ., : - . :, . . - .. : ,
1~824~5
enclosed in a fluorescent display tube.
The fluorescent display device provided in accordance
with the present invention has essentially the same structure as
the known fluorescent display tube described earlier. Namely,
its basic structure includes an anodic plate having a fluorescent
screen on one side thereof and a cathode standing face to face
with the aforesaid fluorescent screen.
'1`
..
,
s
'
i~
- 23
., ,
,
, .
. ,~,. .
. , ~ ,
:. ' , ' ' ': '
.
.: -
. ~ , ' - .' . ', ~ ~ ,
., ,. ~ ~
~08'~445
both of which are enclosed in an evacuated tube. The fluorescent
display devicc of the present invention is characterized by the
fluorescent composition which forms the fluorescent screen on
the anodic plate. Therefore, aside from the fluorescent screen,
all elements constituting th~ fluoresccnt display device of the
present invention can be conventional ones as used in ordinary
fluorescent display devices. Moreover, conventional techniques
employed ~or producing conventional fluorescent display devices
can be applied to the production of the fluorescent display
devices of the present invention without modification. A concrete
illustration of a typical method for manufacturing the fluorescent
display device according to the present invention is given below.
First an anodic plate supported by a conventional
ceramic base plate is coated with the above-described fluorescent
; 15 composition in accordance with the sedimentation coating method
in order to make a fluorescent screen. Namely, an anodic plate
is placed in an aqueous suspension of the fluorescent composition
and the fluorescent composition is allowed to deposit on one
side of the anodic plate as it settles because of its own
i 20 weight, and then the water is removed from the aqueous suspension.
The resulting coated layer is then dried. In such a process,
a small amount of water glass (about 0.01 to about 1~) may be
added to the aforesaid suspension for the purpose of increasing
the adhesive property of the resulting fluorescent screen to
the ano~ic plate. The preferred ~mount of fluorcsccnt
composition applied to the anodic plate is within the range of
about 5 mg/cm to about 30 mg~cm2.
The above-described sedimentation coating method has
been commonly and widely applied in making fluorescent screens.
24
... , 1 ......... . . , ,........ , . . ........ . . . ~
. .. . ; . . .; ..... .. ., . . . . , , -
.. , . - . .. . . ... . .. . . . .... .
108'~445
l~owever, the method for making a fluorescent screen in accordance
with the present invention is not to be interpreted as being
limited to the aforesaid sedimentation coating method.
~ cathode made of a wire-heater covered with an oxide
such as BaO, SrO, CaO or the like is placed opposite the
fluorescent screen on the anodic plate at an interval of about
5mm, and then the resulting pair of electrodes is set in
a transparent container made of ~lass or the like and air
present in the containcr is cvacuated. After the pressure
inside this container reaches a pressure of 10 5 Torr or less,
the evacuation is stopped and the container is sealed. After
sealing, the pressure inside the resulting container is
additionally reduced by sputtering a getter. By the method
; described, a fluorescent display device capable of attaining
the objects of the present invention can be obtained. Further,
as shown in Figure 2, it is desirable to place a mesh-like
control grid between the cathode and the fluorescent screen
to function as a diverging electrode. Such an electrode is
useful in diverging low-velocity electrons emitted from the
cathode because the fluorescent screen on the anodic plate is
flat while the cathode is a wire. In this case, better results
are attained by using as fine a mesh as possible since a smaller
mesh results in a smaller loss in emission and in better
efficiency in the divergence of low-velocity electrons.
, 25 Specifically, meshes of below 500 micron and having an aperture
ratio of not less than 50% are preferred. (Where the aperture
ratio refers to the area of the holes capable of passing low-
velocity electrons divided by the total area of the grid).
., I
'' , 1
`. .. . ..
.
:. . . - , - ~ . ~ . : .
. : : , : : ,.,
.. . . . . . . . .
108;~4~5
A charact~r, numbcr or l~atterns can be displayed by cutting
the anodic plate in the form of the character, number or
pattern to be displayed and selectively applying the acceleration
potential suitable for the particular pair of separated anodes.
Moreover, multicolor fluorescent display devices can be
produced by cutting the anodic plate into a desired form; e.g.,
the form of an array of dots or lines, applying a fluorescent
screen which contains a first fluorescent composition consisting
of ZnO and one phosphor onto some portions of the separated
anode, and applying onto other portions of the anode a fluorescent
screen comprising other phosphors which, under low-velocity
electron excitation, can emit light of a color different from
that of said first composition.
In accordance with the present invention, it is possible
to provide fluorescent display devices which can display green
emission of higher color purity than conventional devices
having a fluorescent screen made of lZnO:Zn] and is further
I possible to provide devices which can display blue emission or
¦ red emission. The present invention has very large utility
value from a industrial point of view because almost no blue
I or red emitting fluorescent display devices have been known up
¦ to now. It has further been found in accordance with the
present invention that it becomes feasible to produce multicolor
~; low-velocity electron excited fluorescent display devices by
using a fluorescent screen consistin~ of various kinds of
fluorescent compositions suitable for low-velocity electron
excitation which can display emissions of different colors
~,
~1~ -~ from one another.
~i -; ,
~ ~ - 26
~., , . ., , :
. , : ' ,' '; ' ' , ': ' ' ' '
,. :- . , , , ,. . ,., . .: . . : .
''', ' ' ' ",' ... , ' ' .'". .; . ~
~08'~4S
The present invention will now be illustr~ted in
greater detail by refcrence to the following examples.
Example l
B One weight part of reagent ZnO (Sazex 2000 manufactured
by Sakai Chemicals) and one weight part of LZnS:Cu, Al]
(phosphor (l)-l) containing as an activator Cu and Al in the
equivalent amount of 10 4 g/g were mixed thoroughly by using
a mortar. A fluorescent composition capable of displaying green
emission having high luminance and hi~her color purity than
thàt of [ZnO:Zn] under low-velocity electron excitation was
obtained. In the same manner as the above, other fluorescent
compositions having different mixing ratios within the range of
l:9 to 9:1 (by weight) were prepared.
Example 2
lS Reagent ZnO (Sazex 2000 manufactured by Sakai Chemicals)
was placed in an alumina crucible and fired at 1000C for one
i hour in air. The resulting heat treated ZnO w~s fully ground
i I to a fine powder by means of a ball-mill. 7 weight parts of
this heat treated ZnO and 3 weight parts of [(Zn0 95, Cdo 05)S:Cu,
Al] (phosphor (1)-2) containing as an activator both Cu and Al
, in the equivalent amount of 10 4 g/g were thoroughly mixed by
using a mortar. A fluorescent composition capable of displaying
green emission having high luminance and higher color purity
~i I than that of ~ZnO:Zn~ under low-velocity electron excitation
i 25 was obtained. In the same manner, fluorescent compositions
having differcnt mixing ratios within the range of l:9 to 9:1
(by weight) were prepared.
'
- 27
-:: .
.'~
. ' ' '"'' ' ;' ' ' ' . - ~ : . .. ...
10~ 445
~xample 3
B One weight part of reagent ZnO (Sazex 2000 manufactured
by Sakai Chemicals) and one weight part of [Y3A15O12:Ce~
~phosphor (2)-1) containing Ce in the activating amount of
gram-atom/mole were thoroughly mixed by using a mortar.
Thus, a fluorescent composition capable of displaying green
emission having high luminance and higher color purity than
that of [ZnO:Zn] under low-velocity electron excitation was
obtained. In the same manner, fluorescent compositions having
different mixing ratios within the range of 1:9 to 9:1 (by
weight) were prepared.
Example 4
Zinc oxalate (ZnC2O4) was placed in an a~umina crucible
and fired at 1000C for one hour in air. The resulting heat
~15 treated ZnO was fully ground to a fine powder by means of
a ball-mill. 7 weight parts of the thus obtained heat treated
ZnO and 3 weight parts of [Y3(Alo.6, GaO.4)512 p
(2)-23 containing cerium in the activating amount of 10 2
gram~atom/mole were well-mixed by using a mortar. The thus
obtained fluorescent composition could display green emission
having high luminance and higher color purity than that of
' l [ZnO:Zn] under low-velocity electron excitation. In the same
manner, fluorescent compositions having different mixing ratios
within the range of 1:9 to 9:1 (by weight) were prepared.
Example 5
Zinc carbonate ~ZnCO3~ was placed in an alumina crucible
I and fired at 1000C for one hour in air. The resulting heat
i treated ZnO was well-ground to a fine powder by means of
~ a ball-mill. 7 weight parts of the thus obtained heat treated
,.;:: I
~ 28
` ~1
~ !
, ,, i ~ , , . ~ .
,
~ ~ . . . .
.
, . . . . . . . .
, . . ~. . . : : . .
,. . . . . . ;. .
1~38'~445
ZnO and 3 weig~lt parts of [Zn2SiO4:Mn~ (phosphor (3)) containing
manganese in the activating amount of 2 x 10 2 gram atom/mole
were fully mixed by using a mortar. Thus, a fluorescent composition
capable of disylaying green emission having high luminance and
higher color purity than that of ~ZnO:Zn] under low-velocity
electron excitation was obtained. In a similar manner,
fluorescent compositions having different mixing ratios within
the range of 1:9 to 9:1 (by weight) were prepared.
Example 6
1 B One weight part of reagent ZnO (Sazex 2000 manufactured
by Sakai Chemicals) and one weight part of [Y2O2S:Tb] (phosphor
(4)-1) containing tcrbium in the activating amount of 5 x 10 2
I g/g were thoroughly mixed by using a mortar. Thus, a fluorescent
- composition capable of displaying green emission having high
luminance and higher color purity than that of IZnO:Znl under
low-velocity electron excitation was obtained. In a similar
manner, fluorescent compositions having different mixing ratios
within the range of 1:9 to 9:1 (by weight) were prepared.
I Example 7
¦ 20 Reagent ZnO (Sazex 2000 manufactured by Sa~ai Chemicals)
was placed in an alumina crucible and fired at 1000C for one
¦ hour in air. The resulting heat treated ZnO was well-ground
I to a fine powder by means of a ball-mill. 7 weight parts of
j I the thus obtained heat treated ZnO and 3 weight parts of
¦ 25 ~La2O2S:Tbl (phosphor (4)-2) containing as an activator Tb in
the amount of 5 x 10 2 g/g were fully mixe~ by using a mortar.
~ Thus, a fluorescent composition capable of displaying green
¦ emission having high luminance and higher color purity than
- 29
... ., ~ . . . . .
-,: .. ,., . ~ : ..
. . : . : . ., . ~ . , - .
, ~ .
':
108~445
that of [ZnO:Zn] under low-velocity electron excitation was
obtained. In a similar manner, fluorescent compositions having
different mixing ratios within the range of 1:9 to 9:1 (by
wcight) were prepared.
Ixalnple ~
B Two weight parts of reagent ZnO (Sazex 2000 manufactured
by Sakai Chemicals), one weight part of [Zn2SiO4:Mn~ (phosphor (3))
containing as an activator Mn in the amount of 2 x 10 gram atom~mole
and one weight part of [Y3(Alo 6~ GaO 4)512 Ce] (phosphor (2)-2)
containing cerium in the activating amount of 10 2 gram-atom/mole
were fully mixed by using a mortar. Thus, a fluorescent composition
capable of displaying green emission having high luminance and
higher color purity than that of [ZnO:Zn] under low-velocity
electron excitation was obtained. In a similar manner,
fluorescent compositions differing from one another in composition
~ were prepared by changing the weight ratio of the amount of
I reagent ZnO to the total amount of the combined phosphors (2)-2
and (3) within the range of 1:9 to 9:1.
Example 9
Zinc carbonate (ZnCO3) was placed in an alumina crucible
I and fired at 1000C for one hour in air. The resulting heat
treated ZnO was well-ground to a fine powder by means of
a ball-mill. Two weight parts of the thus obtained heat treated
,~ ZnO, one weight part of IZnS:Cu, Rl] ~phosphor (1)-1) containing
as an activator both Cu and ~1 in the equivalent amount of
10 g/g and one weight part of 1Zn2SiO4:Mn~ (phosphor (3))
containing as an activator Mn in the amount of 2 x 10 2 gram~atom/mole
~¦ were fully mixed by using a mortar. Thus, a fluorescent composition
~1 .
- 30
. .
.:: : - , - .~
~ ~ `' : ` ; " '
:i, , .
~108;~'}45
capable of displaying green emission having high luminance and
higher color purity than that of [ZnO:Zn~ under low-velocity
electron excitation was obtained. In a similar manner,
fluorescent compositions differing from one another in composition
were prepare~ by changing the weight ratio of th~ amount of
the heat treated ZnO to the total amount of the combined
phosphors (1)-1 and (3) within the range of 1:9 to 9:1.
Example 10
Reagent ZnO (Sazex 2000 manufactured by Sakai Chemicals)
and [SrGa2S4:Eu2 ] containing europium in the activating amount
of 3 x 10 2 gram-atom/mole were well-mixed in equivalent weight
parts by using a mortar, Thus, a fluorescent composition
capable of displaying green emission having high luminance and
higher color purity than that of ~ZnO:Zn] under low-velocity
electron excitation was obtained. In a similar manner,
i fluorescent compositions differing from one another in
composition were prepared by changing the mixing weight ratio
of the amount of reagent ZnO to that of the phosphor [SrGa2S4:Eu2+].
Example 11
Reagent ZnO (Sazex 2000 manufactured by Sakai Chemicals)
was placed in an alumina crucible and fired at 1000C for one
I hour in air. The resulting heat treated ZnO was well-ground
I to a fine powder by means of a ball-mill. 7 weight parts of
; I the thus o~tained heat treated ZnO and 3 weight parts of
~SrGa2S4:Eu ~ containing europium in the activating amount
of 3 x 10 2 gram-atom/mole were fully mixed by using a mortar.
Thus, a fluorescent composition capable of displaying green
emission having high luminance and higher color purity than
- 31
' ~ , ' .,.' : ' ' ' -:
44$
that of [ZnO:~n] under low-velocity electron excitation was
obtained. In a similar manner, fluorescent compositions
differing from on~ another in composition were prepared by
changing the mixing ratio.
~xa.nplc 12
Zinc oxalate (ZnC2O4) was placed in an alumina crucible
and fired at 1000C for one hour in air. The resulting heat
treated ZnO was well-ground to a fine powdcr by means of a ball-
mill. 7 weight parts of the thus obtained heat treated ZnO
and 3 weight parts of 1SrGa2S4:Eu2+~ containing europium in the
activating amount of 3 x 10 2 gram atom/mole were mixed thoroughly
by using a mortar. Thus, a fluorescent composition capable of
displaying green emission having high luminance and higher color
purity than that of [ZnO:Zn] under low-velocity electron
lS excitation was obtained. In a similar manner, fluorescent
compositions differing from one another in composition were
prepared by changing the mixing ratio.
Example 13
Zinc carbonate (ZnCO3) was placed in an alumina crucible
and fired at 1000C for one hour in air. The resulting heat
treated ZnO was wcll-ground to a fine powder by means of a ball-
I mill. 7 weight parts of the thus obtained heat treated ZnO
¦ and 3 weight parts of ~SrGa2S4:Eu 3 containing europium in the
activating amount of 3 x 10 2 gram-atom/mole were fully mixed
by using a mortar. Thus, a fluorescent composition capable of
disp7ayins green emission having high luminance and higher color
i purity than that of ~ZnO:Zn~ under low-velocity electron
excitation was obtained. In a similar manner, fluorescent
compositions differing from one another in composition were
. .
7 I prepared by changing the mixing ratio.
, , - 32
, . ~
~o8~,~,4~5
Example 14
B Thr~e weight parts of reagent ZnO (Sazex 2000 manufactured
by Sakai Chemicals) and seven weight parts of [ZnS:Ag] containing
silver in the activating amount of 10 4 g/g were well-mixed by
using a mortar. ~hus, a fluoresccnt composition capable of
displaying blue emission having high luminance and higher color
purity was obtained. In a similar manner, blue emitting
fluorescent compositions differing from one another in composition
could be obtained by changing the mixing ratio.
Example 15
I Reagent ZnO (Sazex 2000 manufactured by Sakai Chemicals)
was placed in an alumina crucible and fired at 700C for one
hour in air. The resulting heat treated ZnO was well-ground
to a fine powder by means of a ball-mill. One weight part of
the thus obtained heat treated ZnO and one weight part of
[ZnS:Agl containing silver in the activating amount of 10 g/g
were fully mixed by using a mortar. The thus obtained blue
emitting fluorescent composition had high luminance and high
color purity under low-velocity electron excitation. In a
similar manner, fluorescent compositions differing from one
another in composition could be obtained by changing the mixing
ratio.
Example 16
' I ~eagent ZnO (Sazex 2000 manufactured by Sakai Chemicals)
was placed in an alumina crucible and fired at 1000C for one
hour in air. The resulting heat treated ZnO was well-ground
to a fine powder by means of a ball-mill. 7 weight parts of
¦ the thus obtained heat treated ZnO and 3 weight parts of tzns:Ag3
- 33
1 .
. . , ' ' ' . , ' ' . .
', ,. :, .: ., ,, , ,,', ., ' , ' , ' ' ' : '
,,
. ~ ' ' ' ' ' ' ' ..' ' . '
.. ', . ,, ., . , ' , . ', , . . . .. . . ' .
' '~ ' ' " " ~ '' '' . ' ~ ". ' " ' ', ' ' '
108~4~5
containing silver in the activatinc~ amount of 10-4 g/g were
fully mixed by using a mortar. Thus, a fluorescent composition
capable of emittin~ blue li~ht having high luminance and high
color purity under low-velocity electron excitation could be
obtained. In a similar manner, fluorescent compositions
differing from one another in composition were preparcd by
changing the mixing ratio.
Example 17
Zinc oxalate (ZnC2O4) was place~ in an alumina crucible
; 10 and fired at 1000C for one hour in air. The resulting heat
treated ZnO was well-ground to a fine powder by means of a ball-
mill. 7 weight parts of the thus obtained heat treated ZnO
and 3 weight parts of lZnS:Ag] containing silver in the activating
amount of 10 4 g/g were fully mixed by using a mortar. Thus,
lS a fluorescent composition capa~lc of displaying blue emission
having high luminance and high color purity under low-velocity
I electron excitation was obtained. In a similar manner, fluorescent
; I compositions differing from one another in composition were
prepared by changing the mixing ratio.
, 20 Example 18
Zinc carbonate (ZnCO3) was placed in an alumina crucible
i 1 and fired at 1000C for one hour in air. The resulting heat
treated ZnO was well-ground to a fine powder by means of a ball-
I mill. 7 weight parts of the thus obtained heat treated ZnO
and 3 weight parts of ~ZnS:Ag) containing silver in the activating
amount of 10 g/g were fully mixed by using a mortar. Thus,
a fluorescent composition capable of displaying blue emission
having high luminance and high color purity under low-velocity
~;
~ 34
. ~.
iO8;~445
electron e~citation was obtained. In a similar manner,
fluorescent compositions differing from one another in composition
were prepared by changing the mixing ratio.
Example l9
Reagent ZnO (Sazex 2000 manufactured by Sakai Chemicals)
and lY2O2S:~u] containing europium in the activating amount of
5 x 10 2 g/g were well-mixed in equivalent weight parts by using
a mortar. Thus, a fluorescent composition capable of displaying
red emission having high luminance and high color purity under
low-velocity electron excitation was obtained. In a similar
manner, fluorescent compositions differing from one another in
composition were prepared by changing the mixing ratio of the
amount of reagent ZnO to that of the phosphor [Y2O2S:Eu~.
, Example 20
Reagent ZnO (Sazex 2000 manufactured by Sakai Chemicals)
was placed in an alumina crucible and fired at 1000~C for one
hour in air. The resulting heat treated ZnO was well-ground
to a fine powder by means of a ball-mill. 7 weight parts of
the thus obtained heat treated ZnO and 3 weight parts of
[Y2O2S:Eu] containing europium in the activating amount of
5 x 10 2 g/g were fully mixed. Thus, a fluorescent composition
capable of displaying red emission having high luminance and
high color purity under low-velocity electron excitation was
obtained. In a similar manner, fluorescent compositions
differing from one another in composition were obtained by
changing the mixing ratio of the amount of fired ZnO to that
~ of the phosphor [Y2O2S:Eu~.
i ~
~,
- 35
I
:, . , . . . , ~ - .
. , , , ., . - :
. ~ , , . , , ,: , .
445
~xample 21
Zinc oxalate (ZnC2O4) was placed in an alumina crucible
and fired at 1000C for one hour in air. The resulting heat
treated ZnO was wcll-ground to a fine powder by means of a ball-
mill. 7 weight parts of the thus obtained heat treated ZnOand 3 weight parts of [Y2O2S:~u] containing europium in the
activating amount of 5 x 10 2 g/g were fully mixed by using
a mortar. Thus, a fluorescent composition capable of displaying
red emission having high luminance and high color purity under
low-velocity electron excitation could be obtained. In a similar
manner, fluorescent compositions differing from one another in
composition were prepared by changing the mixing ratio of the
amount of fired ZnO to that of the phosphor [Y2O2S:Eu].
Example 22
Zinc carbonate (ZnCO3) was placed in an alumina crucible
, and fired at 1000C for one hour in air. The resulting heat
; treated ZnO was well-ground to a fine powder by means of a ball-
mill. 7 weight parts of the thus obtained heat treated ZnO
and 3 weight parts of [Y2O2S:Eu] containing europium in the
activating amount of S x 10 2 g/g were fully mixed by using
a mortar. Thus, a fluorescent composition capable of displaying
red emission having high luminance and high color purity under
, , low-velocity clectron excitation could be obtained. In a similar
manner, fluorescent compositions differing from one another in
composition were prepared by changing the mixing ratio of the
amount of heat treated ZnO to that of the phosphor ~Y2O2S:Eu~.
; - 36
'~ : .
~. ~ ~ - , . . ~ ., ~
~ . .
: ' . . .
' " .' . .
- :'~ . ,, . :
-
108;~445
Example 23
One weiqht part of reagent ZnO (Sazex 2000 manufactured
by Sakai Chemicals) and one weight part of the phosphor (1)-1
containing both copper and aluminium in the activating amount
of 10 4 g/g w~re well-mixed by using a mortar. A 200mg portion
of the resulting mixture was dispersed into 100ml of distilled
water containlng water ~lass in the concentiation of 0.01~.
The resulting suspension was applied to a 2cm x lcm alminium
anodic plate supported on a ceramic base plate in accordance
with the sedimentation coating method to ma~e a fluorescent
screen. The amount of the fluorescent composition applied was
about 10mg/cm2. Next, a cathode made of a tungsten wire-heater
covered with an oxide was placed across from the fluorescent
screen on the aluminium anodic plate at the interval of about
5mm. Then this pair of electrodes was set in a hard glass
container and air present in thc container was evacuated,
After the pressure inside the container reached 10 5 Torr or
so, the evacuation was stopped and the container was sealed.
Next, the pressure inside the evacuated container was additionally
reduced by sputtering a getter. Thus, a fluorescent display
device having the structure as shown in Figure ~1) was obtained.
The resulting fluorescent display device displayed green
emission having a luminance of 8.2 ft-L under an anodic plate
potential of 80V, a cathode potential of 0.6V and a cathode
current of 4OmA.
Example 24
, Reagent ZnO (Sazex 2000 manufactured by Sakai Chemicals)
was placed in an alumina cruci~le and fired at 1~00C for one
hour in air. The resulting heat treated ZnO was well-ground
- 37
: I .
<! 1
.
~ ... . . . . . . ..
., , . .. . . .. ... . " - .
... . ... . . . . . . . . . . ...... .
. .
108;~4~
to a fine powd~r by mean~ of a ~all-mill. 7 weight parts of
the thus obtained heat treat~d ZnO and 3 w~ight parts of the
pllosphor (l)-2 containing both coppcr and aluminium in the
activating amount of 10 4 g/g were fully mixed by using a mortar.
~ fluoresccnt display d~vice was prepared in the same manner as
in ~xample 23 exccpt that thc thus obtained fluorescent composition
was employed. This fluorescent display device displayed green
emission having a luminance of 9.0 ft-L under an anodic platc
potential of 80V, a cathode potential of 0.6V and a cathode
current of 40mA.
Example 25
B One weight part of reagent ZnO ISazex 2000 manufactured
by Sakai Chemicals) and one weight part of the phosphor (2)-1
containing cerium in the activating amount of 10 2 gram-atom/mole
were fully mixed by using a mortar. A fluorescent display
device was prepared in the same manner as in Example 23 except
that the thus obtained fluorescent composition was employed.
This fluorescent display device displayed green emission having
¦ a luminance of 2.0 ft-L under an anodic plate potential of 80V,
a cathode potential of 0.6V and a cathode current of 40mA.
~xample 26
j I Zinc oxalate (ZnC2O4) was placed in an alumina crucible
! I and fired at 1000~C for one hour in air. The resulting heat
~ treated ZnO was well-ground to a fine powder. 7 weight parts{ 25 of the thus obtained heat treated ZnO and 3 weight parts of
~ the phosphor (2)-l containing cerium in the activating amount
t of 10 2 gram~atom/mole were fully mixed by using a mortar.
~r~ i A fluorescent display devices was prepared the same as in
t~ 38
`f
-' ' ' .- ' ' ' :
, `-- ,' , '
,, '-
~ ' ,, , ' , ' ' .
44S
Example 23 e~cept that the thus obtained fluorescent composition
was employed. This fluorescent display devices displayed green
emission having a luminance of 2.5 ft-L at an anodic plate
potcntial of 80V, a cathode potential of 0.6V and a cathode
current of 4OmA.
Example 27
Zinc carbonate (ZnCO3) was placed in an alumina crucible
and fired at 1000C for one hour in air. The resulting heat
treated ZnO was well-ground to a fine powder by means of a ball-
mill. 7 weight parts of the thus obtained heat treated ZnO and
3 weight parts of the phosphor (3~ containing manganese in the
activating amount of 2 x 10 2 gram atom/mole were fully mixed
by using a mortar. A fluorescent display device was prepared
in the same manner as in Example 23 except that the thus obtained
fluorescent composition was employed. This fluorescent display
device displayed green emission having a luminance of 5.0 ft-L
under an anodic plate potential of 80V, a cathode potential of
0.6V and a cathode current of 40mA.
Example 28
0 One weight part of reagent ZnO (Sazex 2000 manufactured
I I by Sakai Chemicals) and one weight part of the phosphor (4)-1
containing terbium in the activating amount of 5 x 10 2 g/g
¦ were fully mixed by using a mortar. A fluorescent display
device was prepared in the same manner as in Example 23 except
that the thus obtained fluorescent composition was employed.
This fluorescent display device displayed green emission having
a luminance of 1.8 ft-L under an anodic plate potential of 80V,
a cathode potential of 0.6V and a cathode current of 40mA.
- 3g
'
: . . . : ; - -
i . . , - .. ,' .. - : -
: . , ., :: . :
: .. - . . , ., : .. . . - .
4~5
~xample 29
12 ~
~L~ Reagent ZnO (Saz~x 2000 manufactured by Sa~ai Chemicals)
was plac~d in an alumina crucible and fired at 1000C for one
hour in air. 'l'he resulting heat treated ZnO was well-ground
to a fine powder by means of a ball-mill. 7 weight parts of
the thus obtained heat treated ZnO and 3 weight parts of the
phosphor (4) containing t~rbium in the activating amount ~f
5 x 10 2 g/g were fully mixed by using a mortar. A fluorescent
display device was prepared in the same manner as in Example
23 except that the thus obtained fluorescent composition was
employed. This fluorescent display device displayed green
emission having a luminance of 5.0 ft-L under an anodic plate
potential of 80V, a cathode potential of 0.6V and a cathode
current of 4OmA.
! 15 Example 30
- ¦ Two weight parts of reagent ZnO (Sazex 2000 manufactured
¦ by Sakai Chemicals), one weight part of the phosphor (3) containing
¦ manganese in the activating amount of 2 x 10 2 gram atom/mole
and one weight part of the phosphor (2)-2 containing cerium in
the activating amount of 10 2 gram atom/mole were fully mixed
by using a mortar. A fluorescent display device was prepared
in the same manner as in Example 23 except that the thus obtained
fluorescent composition was employed. This fluorescent display
¦ device displayed green emission having a luminance of 4.5 ft-L
;¦ 25 under an anodic plate potential of ~0V, a cathode potential of
~l 0.6V and a cathode current of 40mA.
~` 1
:fi'~
~ 40
,,i 1 1
. ~ ,,~ . . .. . .
108~445
Example 31
Zinc carbonate (ZnCO3) was placed in an alumina crucible
and fired at 1000C for one hour in air. The resulting heat
treated ZnO was well-ground to a fine powder by means of a ball-
mill. Two weight parts of the thus obtained heat treated ZnO,one weight part of the phosphor (1)-1 containing both copper and
aluminium in the activating amount of 10 4 g/g and one weight
part of the phosphor (3) containing manganese in the activating
amount of 2 x 10 2 gram atom/mole were fully mixed by using
a mortar. A fluorescent display device was prepared the same as
in Example 23 except that the thus obtained fluorescent composition
was employed. This fluorescent display device displayed green
emission having a luminance of 6.8 ft-L under an anodic plate
potential of 80V, a cathode potential of 0.6V and a cathode
current of 40mA.
Example 32
! B Reagent ZnO (Sazex 2000 manufactured by Sakai Chemicals)
; and lSrGa2S4:Eu ~ containing europium in the activating amount
of 3 x 10 2 gram~atom/mole were well-mixed in equivalent weight
parts by using a mortar. A fluorescent display device was
3~ ¦ prepared in the same manner as in Example 23 except that the
thus obtained fluorescent composition was employed. This
fluorescent display device displayed green emission having
~; ~ a luminance of 6.6 ft-L under an anodic plate potential of 80V,
~; ~25 a cathode potential of 0.6V and a cathode current of 40mA.
~xample 33
Reagent ZnO ~Sazex 20~0 manufactured by Sakai Chemicals)
was placed in an alumina crucible and fired at 1~00C for one
hour in air. The resulting heat treated ZnO was well-ground
- 41
, : . ~ . ,
~. ' - . ': - . '
~8Z445
to a fine powd~r by means of a ball-mill. 7 weight parts of
the thus obtained heat treated ZnO and 3 weight parts of
~SrGa2S4:Eu ] containing europium in the activating amount
of 3 x 10 2 gram-atom/mole were fully mixed by using a mortar.
A fluorescent display device was prepared in the same manner as
in Example 23 except that the thus obtained fluorescent composition
was employed. This fluorescent display device displayed green
emission having a luminance of 7.2 ft-L under an anodic plate
` potential of 80V, a cathode potential of 0.6V and a cathode
Z 10 current of 40mA.
Example 34
I Zinc oxalate (ZnC2O4) was placed in an alumina cruclble
I and fired at 1000C for one hour in air. The resulting heat
Zl treated ZnO was well-ground to a fine powder by means of a ball-
mill. 7 weight parts of the thus obtained heat treated ZnO
and 3 weight parts of lSrGa2S4:Eu2 ] containing europium in the
activating amount of 3 x 10 2 gram atom/mole were fully mixed
by using a mortar. A f luorescent display device was prepared
in the same manner as in Example 23 except that the thus obtained
fluorescent composition was employed. This fluorescent display
device displayed green emission having a luminance of 7.0 ft-L
~ under an anodic plate potential of 80V, a cathode potential of
Z 0.6V and a cathode current of 40mA.
Example 35
2S Zinc carbonate (ZnCO3) was placed in an alumina crucible
and fired at 1000C for one hour in air. The resulting heat
¦ ~ treated ZnO was well-ground to a fine powder by means of a ball-
mi~11. 7 weight parts of the thus obtained heat treated ZnO
- 42
,:
, ~ , , : .
~," . , ~ . ~ -
` 108'~445
and 3 weight parts of ~SrGa2S2:Eu2 ] containing europium in
the activating amount of 3 x 10 2 gram atom/mole were fully
mixed by using a mortar. A fluorescent display device was
prepared in the same manner as in Example 23 except that the
thus obtained fluorescent composition was employed. This
fluorescent display device displayed green emission having
a luminance of 6.8 ft-L under an anodic plate potential of 80V,
a cathode potential of 0.6V and a cathode current of 40mA.
Example 36
Bl Three weight parts of reagent ZnO ~Sazex 2000 manufactured
by Sakai Chemicals) and 7 weight parts of [ZnS:Ag] containing
silver in the activating amount of 10 4 g/g were fully mixed by
using a mortar. A fluorescent display device was prepared in
the same manner as in Example 23 except that the thus obtained
fluorescent composition was employed. This fluorescent display
I device displayed blue emission having a luminance of 4.0 ft-L
¦ under an anodic plate potential of 80V, a cathode potential of
¦ 0.6~ and a cathode current of 40mA.
Example 37
1 20 Reagent ZnO (Sazex 2000 manufactured by Sakai Chemicals)
¦ was placed in an alumina crucible and fired at 700C for one
~ hour in air. The resulting heat treated ZnO was well-ground
¦ to a fine powder by means of a ball-mill. One weight part of
~, the thus obtained heat treated ZnO and one weight part of
~ZnS:Ag] containing silver in the activating amount of 10 g/g
were fully mixed by using a mortar. A fluorescent display
~ device was prepared in the same manner as in Example 23 except
,~ ~- that the thus obtained fluorescent composition was employed.
:
~ ~ '
; ~
- 43
. ~: .
,: . , . , ~ , , ,: -
- -
. .. : . , ~ ,. , ~ ,., ,, :
, . . . , . : , . . .
108;~445
This fluoresc~nt display device displayed blue emission having
a luminance of 5.3 ft-L under an anodic plate potential of 80V,
a cathode potential of 0.6V and a cathode current of 40mA.
Example 38
B Reagent ZnO (Sazex 2000 manufactured by Sakai Chemicals)
was placed in an alumina crucible and fired at 1000C for one
~ hour in air. The resulting heat treated ZnO was well-ground
; to a fine powder by means of a ball-mill. 7 weight parts of
the thus obtained heat treated ZnO and 3 weight parts of ~ZnS:Ag]
containing silver in the activating amount of 10 4 g/g were fully
I mixed by using a mortar. A fluorescent display device was
prepared in the same manner as in Example 23 except that the
thus obtained fluorescent composition was employed. This
fluorescent display device displayed blue emission having
1 15 a luminance of 6.0 ft-L under an anodic plate potential of 80V,
s ¦ a cathode potential of 0.6V and a cathode current of 40mA.
Example 39
Zinc oxalate (ZnC2O4) was placed in an alumina crucible
and fired at 1000C for one hour in air. The resulting heat
treated ZnO was well-ground to a fine powder by means of a ball-
mill. 7 weight parts of the thus obtained heat treated ZnO
and 3 weight parts of IZnS:Ag] containing silver in the activating
amount of 10 4 g/g were fully mixed by using a mortar.
, A fluorescent display device was prepared in the same manner
J 25 as in Example 23 except that the thus obtained fluorescent
composition was employed. This fluorescent display device
,.. ~
displayed blue emission havinq a luminance of 5.5 ft-L under
, an anodic plate potential of 80V, a cathode potential of 0.6V
~ :
and a cathode current of 4On~.
- 44
1.~-- - . . , ........... -
-, , -,
. . . ~ ,.. ,. , ,, , ~ ,
1~8;~45
Example 40
Zinc carbonate (ZnCO3) was placed in an alumina crucible
and fired at 1000C for one hour in air. The resulting heat
treated ZnO was w~ ground to a fine powder by means of a ball-
mi]l. 7 weight parts of the thus obtained heat treated ZnO
and 3 weight parts of [ZnS:Ag] containing silver in the
activatinq amount of 10 4 g/g were fully mixed by using a mortar.
A fluorescent display device was prepared in the same manner as
in Example 23 except that the thus obtained fluorescent
composition was employed. This fluorescent display device
displayed blue emission having a luminance of 5.7 ft-L under
an anodic plate potential of 80V, a cathode potential of 0.6V
I and a cathode current of 4OmA.
I Example 41
¦ ~ ~eagent ZnO ~Sazex 2000 manufactured by Sakai Chemicals)
and IY2O2S:EU3 containing europium in the activating amount of
5 x 10 2 g/g were mixed thoroughly in equivalent weight parts
l by using a mortar. A fluorescent display device was prepared
1 in the same manner as in Example 23 except that the thus obtained
fluorescent composition was employed. This fluorescent display
device displayed red emission having a luminance of 1.5 ft-L
under an anodic plate potential of 80V, a cathode potential of
O.6V and a cathode current of 40mA.
¦ Example 42
¦ 25 Reagent ZnO (Sazex 2000 manufactured by Sakai Chemicals)
~¦ was placed in an alumina crucible and fired at 1000C for one
~- ¦ hour in air. The resulting heat treated ZnO was well-ground
to a fine powder by means of a ball-mill. 7 weight parts of
1: :
,.~
- 45
!-
`,''',"'` ''''"`, ''" '' ''`~` '' '~'''. " "" ' ''' ' ' " "'. `',''''' ' ` . `
108A~445the thus obtained heat treated ZnO and 3 weight parts of [Y2O2S:Eu]
containing europium in the activating amount of 5 x 10 2 g/g
were fully mixed by using a mortar. A fluorescent display device
was prepared in the same manner as in Example 23 except that
the thus obtained fluorescent composition was employed. This
fluorescent display device displayed red emission having
a luminance of 3.0 ft-L under an anodic plate potential of 80V,
a cathode potential of 0.6V and a cathode current of 4OmA.
Example 43
10Zinc oxalate (ZnC2O4) was placed in an alumina crucible
; and fired at 1000C for one hour in air. The resulting heat
treated ZnO was well-ground to a fine powder by means of a ball-
mill. 7 weight parts of the thus obtained heat treated ZnO
and 3 weight parts of [Y2O2S:Eu] containing europium in the
activating amount of 5 x 10 2 g/g were fully mixed by using
a mortar. A fluorescent display device was prepared in the same
manner as in Example 23 except that the thus obtained fluorescent
¦ composition was employed. This fluorescent display device
displayed red emission having a luminance of 3.1 ft-L under
¦ 20 an anodic plate potential of 80V, a cathode potential of 0.6V
and a cathode current of 4OmA.
¦ Example 44
Zinc oxalate (ZnC2O4) was placed in an alumina crucible
and fired at 1000C for one hour in air. The resulting heat
treated ZnO was well-ground to a fine powder by means of a ball-
¦ mill. 7 weight parts of the thus obtained heat treated ZnO
, , and 3 weight parts of [Y2O2S:Eu] containing europium in the
~;~ , activating amount of 5 x 10 2 g/g were fully mixed by using
~,' j
` - 46
.~1 .,, .. 1
- :.
~, . . . .:: . - . . ,., : .
. ~ .: : ,
:
, .. . . .. .. . .
~08;~445
a mortar. A fluorescent display device was prcpared in the
same manncr as in Example 23 exccpt that the thus obtained
fluorescent composition was employed. This fluorescent display
device displaycd rcd emission having a luminance of 2.7 ft-L
under an anodic platc pote~ntial of %OV, a cathod~ potential of
0.6V and a cathode current of 4OmA.
:`t'~
~ I - 47
~ !
,.. ~. . .. . - .... . . ... .. . ~. ~ .. . . . - . . .
, - . . . . .. . . ... . .. . . .
~,` . . . ' . ~ . . . . ... . . ..
... .. .. .. .. .. . . . . .
