JPS60101175A - Green light-emitting phosphor for projection type color television - Google Patents

Abstract

PURPOSE:To provide the titled green light-emitting phosphor which does not cause brightness saturation even in a highly excited state, exhibits high brightness, does not have a problem of quenching by temperature and suffer little variation in brightness caused by variation in the composition, consisting of Y3AlxGa5-x)12:Tb which has a composition satisfying specified conditions. CONSTITUTION:Y2O3, Al2O3, Ga2O3 and Tb4O7 are mixed together. The mixture is fired at 1,500 deg.C for 2hr to obtain a green light-emitting phosphor of the Y3Al5Ga5-xO12:Tb having a composition present in an inside region which is surrounded by a closed curve and does not include the boundary of the curve, said closed curve being obtd. by connecting the points A to H to each other in order under conditions of exciting voltage of 30KV and current density of 90muA/cm<3>, each of A to H being the values of the molar ratio of Al/Ga and mol% of Tb/(Y+Tb) given in the table. In the Fugure, the abscissa represents the molar ratio of Al/Ga, the ordinate represents mol%(=Tb concn.) of Tb/(Y+Tb), the point S represents Y3Al5O12:Tb which represents the point of the reference value 100 of the brightness of Tb concn. of 5mol%, broken lines represent lines of equal brightness, and the figure of each line represents relative brightness.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a projection type used in the fluorescent surface of a cathode ray tube (CRT, so-called cathode ray tube), which is a projection tube of a projection type television receiver. Regarding the green phosphor for television, especially Y3A7XGas-xOo
z: Relates to a green phosphor for projection televisions consisting of 'rb.

[Background technology and its problems]

CRTs (so-called cathode ray tubes) used as projection tubes for projection televisions include:
Generally, extremely high brightness is required. Conventionally, green phosphors for such projection tubes include GdzOzS:
Tb was used, but its temperature quenching and current brightness saturation characteristics were unsatisfactory, and currently Y3All
sO1z: Tb is now used. This Y, +AAsO1z :TI) solves the color shift caused by temperature quenching, so-called white balance shift, and significantly improves the brightness of the projection tube. However, in order to realize even brighter projection televisions, the excitation is strengthened (for example, by increasing the beam current from several times to several tens of times by creating multiple beams from an electron gun). It is necessary to emit light with even higher brightness, and in this case, the Y3A6s (J+2
Even if :Tb is used, the influence of brightness saturation appears. In other words, in the CRTs for projection televisions that have been put into practical use to date, the current activity is 5μA/c1#
~20μA/aA, and brightness saturation will not be a problem even if the above YaAgs01z:'rb is used as a green phosphor. For example, set the density to 20 pA/clr.
~80 μA/c, PL, even 100 E A/c4
If an attempt is made to increase the brightness to a certain level, brightness saturation becomes noticeable, and a green phosphor that does not undergo brightness saturation even in such a highly excited state and has stable light emission characteristics is required.

By the way, Y3A71! sO+z: Y3AlxGa 5-XO12 in which part of A4 of Tb is replaced with Ga: T
b provides even better brightness saturation characteristics than the above Y3AJlsO+z:Tb, but it is difficult to sinter to obtain a single phase, and the phosphor hardens after sintering, making it time-consuming to obtain powder. There is a problem that it takes. Also, A
It is known that even if the l/Ga ratio changes, a large difference may occur in the brightness, and furthermore, even if the firing temperature changes, the brightness will fluctuate greatly.

[Purpose of the invention]

The object of the present invention is to provide a green phosphor that solves the problem of brightness saturation and has stable luminescent characteristics.

[Summary of the Invention] That is, the green phosphor for projection television according to the present invention has the following characteristics: Y3A#aOxz :Tb(1) Ag C1)
Y3A-gXGas-xo+z partially substituted with Ga
: In a green phosphor made of Tb, the molar ratio of Al/Ga and the molar percentage of Tb/(Y+Tb) are A 3.3/1.7 and 10.0 molar ratio, respectively. 4
/2.6, 7.0 mole ratio C3,0/2.0, 5.0 mole% D 3.0/2.0, 2.5 mole ratio E 1.6/3.4, 2.5 mole ratio 1” 1.0/4.0, 3.2 molar ratio (J O, 9/
4.1, 5.0 molti H1,0/4.0, IO
, Al/G corresponding to the internal region that does not include the boundary line of the polygon formed by sequentially connecting points A-H with 0 molar coefficient.
The conditions for the a ratio and the Morch value of Tb/(Y+Tb) are to be satisfied. In this case, it is preferable that the temperature at the time of manufacturing the phosphor is 1500° C. in order to obtain the maximum brightness.

According to the green phosphor that satisfies the above conditions, Y
3AlsOu: Compared to Tb, approximately 60% to 90% in a highly excited state, e.g., current density 90 μA/c
Not only can higher brightness be obtained and brightness saturation does not occur, there is little brightness variation even with changes in composition, making it easy to mix raw materials during production, and moreover, stable light emission characteristics can be obtained.

〔Example〕

First, as the most preferred embodiment of the green phosphor for projection television according to the present invention, the molar ratio of Al/Ga is % and '
The phosphor Y3AlzGa 30+2 in which the molar ratio of , [' b / (Y+T I) ) is 5 molar ratio will be explained in detail together with the manufacturing method for Tb.

Cocote, above YzAl! z(Ja30+z: 't'
The raw materials necessary to obtain the composition ratio of b ('rb is 5 mol%) are Y2O3 (purity 4N) 32.18g Al+03 (pure f4N) lo, 20.9GazO3 (
Purity 4N) 28.12. ! i''I''t) 40' (purity 4~) 2.80g However, purity 4N is 99.99%
, indicating the so-called four nines.

Prepare a powder of 1 JaFz (
Add 3.51 g of reagent (special grade) and mix using a ball mill using 70 square meters of Equinol as a solvent. This ball mill mixture has a diameter of approximately 511 IJ+1. Alumina balls with a purity of about 99.8% or more, about 2 to 3 times the weight of the above raw materials, e.g. about 200 g, are put into an alumina container and heated at a rotation speed of 30 to 100 r, e.g. about 15° with a 3° decoy. This is done by time-rotating mixing. Thereafter, the alumina balls and the mixed raw materials are separated by one sieve or the like, and the ethanol is removed through a drying process.

Next, a crucible with a lid made of high-purity (for example, 99.8% or more) alumina is filled with the mixed and dried raw materials, and the lid and the crucible body are bonded together using a heat-resistant adhesive, such as Toagosei's [
Seal with adhesive called "Aron Ceramic D".

Next, this crucible is placed in a furnace and the temperature is raised to 1500°C at a rate of 200°C per hour, held at this temperature for 2 hours for firing, and then cooled in the furnace. .

Next, to remove any residual flux in the fired phosphor material, 1.5N (1.5N) nitric acid was added to the phosphor I.
Wash with a stirrer for 30 to 60 minutes using 1 Qcc per I, filter and dry.

YsAffl aGa301 obtained as above
2: A C1t'F (projection tube) for a projection type television is manufactured using a Tb (Tb is 5 mol %) phosphor, and its brightness and thermal characteristics are measured.

Furthermore, Ysl
'JxGas-xotz: 'rb fluorophore (7, J
Projection tubes were manufactured with various values in the range of Al/Ga strength 510 to 015 and Tb/(Y+Tb) 2.5 moltl 1O60 moltch, and the brightness and temperature characteristics were measured.

The excitation voltage of each projection tube in which these phosphors were used was set to 30
The cathode current IK at kV and raster size 100cJ is 9. (177LA (current ff1i 9071A/
d), and Y31'JsOrz: Tb (Figure 1 shows the relative luminance when the luminance of Tb concentration 5 lulu is taken as the reference value 100. The horizontal axis of the graph in Figure 1 shows Al/
The molar ratio of Ga is taken, and the vertical axis shows the Tb concentration and falsehood, that is, the Tb
/(Y + Tb), and the point S is the above reference tonal Y3A# 6012: T b (Tb
(concentration: 5 mol%). The broken line in the diagram is
Similar to so-called contour lines, it shows iso-brightness lines connecting points of equal relative brightness, and the numerical value attached to each broken line shows the relative brightness. Note that this relative brightness has been corrected for visibility.

As is clear from FIG. 1, the relative brightness changes from 100 to a high brightness of 190, despite the same excitation conditions (voltage 3QkV, current density 90μA/c+#). And the Al/Ga ratio is %, t Nawachi Y3A
e2Qa 3012: T b te, Tb'a degree is 5
The relative luminance near the molar point Q is the highest at 190, and is most preferable as a phosphor for a projection television. here,
Practical Al/Ga ratio as a phosphor for projection televisions
The area on the Tb concentration coordinate is the shaded area in the figure where the relative brightness is greater than 160. This is the area where the density of contour lines (isoluminance lines) is high, for example, Al in the figure.
/Ga ratio in the range of 1/4 to 015, l?
Even if the /Ga ratio slightly deviates, the brightness changes greatly, and it is difficult to stabilize the brightness because high-precision forging is required in the raw material preparation during phosphor manufacturing. (line) A region with a relative brightness greater than 160 where the interval is relatively thick is extracted.

Furthermore, if the Tb concentration is less than 2.5 molar, the emission color of the phosphor becomes whitish, and the color balance with other red and blue phosphors, so-called white balance, is deteriorated, which is not preferable. Furthermore, even if the Tb concentration is increased to 1000 mol or more, the relative brightness will not further improve, and the expensive Tb
Considering that it is not practical to increase the product price by using more b than necessary, and that the Tba degree at which the maximum brightness is obtained is around 5.0 molar coefficient, the upper limit of the Tb concentration is set to 10.0.
It is preferable to use a molar ratio.

To summarize the above, the A4/Ga ratio and Tb of the inner area (hatched area in the figure) that does not include the boundary line in the hexagon formed by sequentially connecting each point A-H in Figure 1 with a straight line. Y31'Jx (Ja6-xo
12: Tb phosphor is suitable as a green phosphor for projection mTV. Here, Al/
Oa ratio, and Tba degree, that is, Tb/(Y + Tb
) is as shown in the table below.

Furthermore, most preferred within this region is Ag
/ (3a power 2 / 3 T:, Tba degree power 50 mo/
This is a region where the luminance changes slowly around the l/ZOJ point (point Q in Figure 1), for example, when the Al/Ga ratio is 2.
5/2.5~1.5/3.5 Te, TbaK Ka3.
Y3A with conditions of 5 mo/l/% to 10.0 mo
fflxQas-xOlz: 'i'b fluorophore.

By the way, high excitation (voltage 30 kV) as mentioned above.

At a current density of 90 pA/c4), the temperature of the fluorescent surface of a 4T green phosphor for projection televisions is between 80°C and 100°C even when cooled by the currently mainstream liquid cooling method.
℃, temperature quenching becomes an important issue. Here, Figure 2 shows the change in relative brightness as the temperature of the phosphor surface increases. The relative brightness decreases slightly as the temperature rises, but even if the temperature reaches 10℃1℃, the relative brightness decrease of a phosphor that satisfies the above conditions is at most (1) 3.0% to 5.0%. %, which is extremely small and poses no problem in practice.

Next, FIG. 3 shows that the excitation voltage is 30 kV and the cathode current IK is 1.0 mA, that is, the raster size is 10.
The relative brightness when the current density in 04 is 10 μA/7 is shown on the Al/Ga ratio-Tb concentration coordinate, and the Y a A65012: T under the same excitation conditions.
b (7J4 degrees wo 100 c!: 0 when doing) A versus luminance is illustrated by contour lines (equal luminance m). As is clear from FIG. 3, the relative brightness is 12 (more than 1, especially 130
．． The region above 140 is in the highly excited state (voltage 3 (
There are many areas where the relative luminance of lkV and current density (i90 μA/cJ) is 160 or more.

Next, the relative brightness when the firing temperature during the production of the green phosphor as explained above is 1400 ° C, 1500 ° G, 1600 ° C (100 ° C when the firing temperature is 1500 ° C)
%. ) is shown in Figure 4.

In this FIG. 4, Y3A1. xGa5-xOl
z: Al/Ga molar ratio of Tb is 015.1/4
．． It shows the relative brightness of six types of phosphors, 2/3, 3/2.4/I, and 510, and for all except A6/Ga = 0'15, when the firing temperature is 1500 ° C. It is clear that the highest brightness can be obtained. Therefore, when manufacturing the green phosphor according to the present invention, it is preferable to set the firing temperature to 1500°C as in the above-mentioned example, and furthermore, the temperature increase rate and firing temperature holding time in the heat treatment step at this time are Preferably, the embodiments described above are followed.

Furthermore, regarding the phosphor immediately after firing, the present applicant previously proposed Japanese Patent Application No. 56-155084 (Japanese Unexamined Patent Publication No. 58-1989)
57491), cleaning with acid or alkali to remove residual fluxes such as BaF2 is preferred in order to prevent the phosphor from "gliding".

It should be noted that the present invention is not limited to the above-mentioned embodiments. For example, BaFz
In addition, BaCl2 or a mixture thereof may also be used, and the amount added is not limited to the proportions shown in the examples.

Furthermore, as a cleaning solution for removing flux after firing the phosphor, hydrochloric acid, sodium hydroxide solution, etc. may be used in addition to nitric acid.

〔Effect of the invention〕

As is clear from the above description, according to the green phosphor for projection television according to the present invention, the current density of the CRT serving as the projection tube is 20 ph/cji to 80/'A/C.
a. Furthermore, when increasing the current to about 100 μA/cA, brightness saturation does not occur even if there is a person, and temperature quenching is suppressed to a level that does not pose a practical problem, making it possible to achieve extremely high brightness using a multi-beam electron gun, etc. Not only can the projection C1 (T) be achieved, but even if the mixing ratio of raw materials during phosphor manufacturing is slightly off, the brightness will not be affected significantly, making it easy to manufacture and disrupting stable light emitting characteristics. It is possible to provide a green phosphor that

[Brief explanation of the drawing]

Figure 1 shows an excitation voltage of 30 kV and a current density of 907°C.
Graph showing relative brightness at 4A/c4 with contour lines,
Figure 2 is a graph showing the change in relative brightness as the temperature of the phosphor surface increases. FIG. 4 is a graph that does not show the change in relative brightness depending on the firing temperature during the production of the phosphor. Patent applicant Sony Corporation representative Patent attorney Kodo Koike 1) Sakae Mura - Figure 2 Y3A (!sO+z :'rb o-< Y3At3Ga20+2:TbY3GasCh
2: Tb Figure 3 8ru 6a cup 11c h

Claims (1)

[Claims] Y3AlX(las-x 012: molar ratio of Ad/Ga in a green phosphor consisting of Tb, and Tb/(
The molar coefficient values of A 3.3/1.7 and 10.0 molar coefficient 8 2.4/
2.6, 7. U mole ratio C3, 0/2.0, 5.0
Mol% D 3.0/2.0, 2.5 Mol%E 1.6/
3.4, 2.5 mole F 1.0/4.0, 3.2 mole GO, 9/4.
1, 5.0 molar ratio 8 1.0/4.0, 10.0 molar ratio each point A
1. A green phosphor for a projection television, characterized in that it has a composition that satisfies the condition of an internal region not including the boundaries of a closed curve formed by sequentially connecting the curves 1 to 1.