JPS6219475B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a yellow-emitting phosphor and a low-speed electron beam-excited fluorescent display tube (hereinafter abbreviated as "fluorescent display tube") using this phosphor. More specifically, the present invention relates to a lanthanum-activated tin oxide yellow-emitting phosphor and a fluorescent display tube using this phosphor as a fluorescent film.

As is well known, a fluorescent display tube has an essential structure in which an anode plate having a fluorescent film on one side and a cathode facing the fluorescent film are enclosed in a vacuum container. A low-speed electron beam emitted from the cathode excites the fluorescent film on the anode plate, causing it to emit light. 1 and 2 are schematic diagrams of typical examples of fluorescent display tubes, with FIG. 1 showing a diode tube and FIG. 2 a triode tube. As shown in FIGS. 1 and 2, a fluorescent film 12 is provided on one side of an anode plate 11 made of an aluminum plate or the like. Anode plate 11 is supported by ceramic substrate 13. Anode plate 11
A cathode 14 is provided opposite the phosphor film 12 provided on one side of the phosphor film 12, and the phosphor film 12 is excited by the low-speed electron beam emitted from the cathode 14 to emit light. In particular, in the triode shown in FIG. 2, a grid electrode 15 is provided in the gap between the cathode 14 and the fluorescent film 12 for controlling or diffusing the low-speed electron beam emitted from the cathode 14. Although one cathode 14 is used in the fluorescent display tube shown in FIGS. 1 and 2, two or more cathodes may be provided when the fluorescent film 12 has a large area. There is no particular limit to the number. The anode plate 11 having a fluorescent film 12 on one side, and a ceramic substrate 13
and a cathode 14 (FIG. 1), or an anode plate 11 with a fluorescent film 12 on one side, a ceramic substrate 13, a cathode 14 and a grid electrode 15 (FIG. 2).
is sealed in a transparent container 16 made of glass or the like, and its interior 17 is maintained at a high vacuum of 10 ^-5 to ^{10 -9} Torr.

Conventionally, zinc-activated zinc oxide phosphor (ZnO:Zn) has been well known for a long time as a phosphor that emits high-brightness light under slow electron beam excitation at an accelerating voltage of 1KV or less, especially 100V or less. There is. This ZnO:Zn phosphor exhibits high-brightness green light emission under slow electron beam excitation.
Green-emitting fluorescent display tubes with ZnO:Zn phosphor as the fluorescent film are widely used as display elements in portable computers, various measuring instruments, etc., but recently fluorescent display tubes have become more versatile. As a result, phosphors that emit light in colors other than green when excited by slow electron beams have become desirable.

Phosphors that emit high-intensity non-green light under slow electron beam excitation at accelerating voltages of 1KV or less, particularly 100V or less, include the recently invented indium oxide (In ₂ O ₃ ) and a specific red-emitting fluorescein. A red luminescent composition (Japanese Patent Publication No. 52-23916) in which In ₂ O ₃ is mixed with a specific blue luminescent phosphor (Japanese Patent Publication No. 52-23911), a blue luminescent composition in which In 2 O 3 is mixed with a specific blue luminescent phosphor, A red-emitting composition (Japanese Patent Publication No. 46912, 1983), which is a mixture of ZnO and a specific red-emitting phosphor;
25719), europium activated tin oxide (SnO ₂ :
Eu) red-emitting phosphors (Japanese Patent Publication No. 54-238) are known, but their number is small, and in particular, phosphors that emit high-intensity yellow light under slow electron beam excitation are hardly known. Not yet.

Therefore, the present invention has an acceleration voltage of 1KV or less, especially
The object of the present invention is to provide a phosphor that emits high-intensity yellow light under slow electron beam excitation of 100 V or less.

Another object of the present invention is to provide a fluorescent display tube that emits yellow light with high brightness.

The present inventors have conducted various studies to achieve the above object. As a _result , a phosphor made of lead oxide (SnO ₂ ) and activated with an appropriate amount of lanthanum (La) has a high accelerating voltage.
The present inventors have discovered that they exhibit high-intensity yellow light emission under slow electron beam excitation of 1KV or less, particularly 100V or less, and have completed the present invention.

The phosphor of the present invention is a lanthanum-activated tin oxide phosphor whose composition formula is SnO ₂ :xLa (where x is a number satisfying the condition 0.001≦x≦0.5).

Further, the fluorescent display tube of the present invention has a structure in which an anode plate having a fluorescent film on one side and a cathode facing the fluorescent film are enclosed in a container having a vacuum inside. The display tube is characterized in that the fluorescent film is made of the lanthanum-activated tin oxide phosphor of the present invention.

The phosphor of the present invention is manufactured by the manufacturing method described below. First, as a raw material for the phosphor, (i) one or more compounds selected from the group consisting of SnO ₂ and tin compounds that can be easily converted to SnO ₂ at high temperatures, such as chlorides, nitrates, oxalates, and hydroxides; 2 or more types, and (ii) lanthanum oxide (La ₂ O ₃ ) and chlorides, sulfates, oxalates, hydroxides, etc. that easily transform into La ₂ O ₃ at high temperatures.
One or more compounds selected from the group of compounds consisting of lanthanum compounds that can be used are used. Weigh the above two phosphor raw materials so that the stoichiometry becomes SnO ₂ :xLa (where x is a number that satisfies the condition of 0.001≦x≦0.5), and use a ball mill, mixer mill, or milk needle. Mix thoroughly. Next, the obtained phosphor raw material mixture is packed into a heat-resistant container such as an aluminum crucible or quartz crucible, placed in an electric furnace, and fired in air (in an oxidizing atmosphere) at a temperature of 1200 to 1400°C for 1 to 5 hours. do. Although this may depend on the amount of phosphor raw material mixture packed into a heat-resistant container, generally speaking, if the firing temperature is lower than 1200°C or the firing time is shorter than 1 hour, the resultant phosphor will be The luminescent color becomes yellowish white and the color purity deteriorates. On the other hand, if the firing temperature is higher than 1400°C or the firing time is longer than 5 hours, the particle size of the resulting phosphor becomes too large and the luminescence is reduced. Brightness also decreases. Note that instead of firing the phosphor raw material mixture obtained by mechanically mixing each phosphor raw material as described above, aqueous ammonia or the like is added to a solution in which the two phosphor raw materials are dissolved. Adding an alkaline aqueous solution or an oxalic acid aqueous solution
Sn and La may be co-precipitated as hydroxide or oxalate, and the precipitate may be filtered and dried to obtain a phosphor raw material mixture, which may then be fired. After firing, the fired product is washed, dried, and sieved to make the particle size uniform.
A phosphor of the present invention is obtained.

The phosphor of the present invention obtained by the above-mentioned manufacturing method exhibits high-intensity yellow light emission under slow electron beam excitation at an accelerating voltage of 1 KV or less, particularly 100 V or less. Further, the phosphor of the present invention exhibits high-intensity yellow light emission even under excitation with electron beams, ultraviolet rays, etc. at accelerating voltages of several KV to several tens of KV.

FIG. 3 is a graph showing the emission chromaticity points of the phosphor of the present invention on the CIE color system chromaticity coordinates, and points A, B,
C and D each have La activation amount (x value)
The emission chromaticity points of the phosphor are 0.005, 0.01, 0.02 and 0.1. As is clear from FIG. 3, the luminescent color of the phosphor of the present invention is yellow, and the color purity of the yellow color tends to deteriorate gradually as the x value decreases. It depends on the manufacturing method, but generally x
When the value is smaller than 0.001, the color purity of the emitted light deteriorates significantly (it becomes significantly whiter), and the emitted color cannot be called yellow.

FIG. 4 is a graph showing the relationship between acceleration voltage and luminance when the phosphor of the present invention is excited with a slow electron beam, and curves a and b are SnO ₂ :
This is the case for a 0.02La phosphor and a SnO ₂ :0.06La phosphor. As is clear from FIG. 4, the phosphor of the present invention has a low emission starting voltage, and sufficient luminance can be obtained even under slow electron beam excitation at an accelerating voltage of 20 V or less. Furthermore, the phosphor of the present invention exhibits a saturation phenomenon of luminance in the acceleration voltage region of 60 V or more, as seen in the above-mentioned SnO ₃ ;Eu red-emitting phosphor that uses the same SnO ₂ as the matrix. figure,
The accelerating voltage-emission brightness characteristics are good. In addition,
When the La activation amount x value is smaller than 0.001 and larger than 0.5, the emission brightness under slow electron beam excitation decreases significantly. Further, among the phosphors of the present invention, those having an x value in the range of 0.01 to 0.06 emit light with particularly high brightness.

The fluorescent display tube of the present invention is manufactured by the method described below. First, the above-mentioned phosphor of the present invention is coated by a precipitation coating method onto an anode plate, which is usually supported by a ceramic substrate, to form a phosphor film.
That is, an anode plate is placed in a suspension of phosphor dispersed in water, and the phosphor is deposited on one side of the anode plate by its own weight, and then the water is removed. Allow the paint film to dry. In order to improve the adhesion of the resulting fluorescent film to the anode plate, a small amount (0.01 to 0.1%) of water glass may be added to the suspension. Also, the coating density is 3 mg/cm ³
~30mg/ ^cm3 is suitable. Although the above-mentioned precipitation coating method is generally used as a method for forming a fluorescent film and is widely practiced, the method for forming a fluorescent film in the fluorescent display tube of the present invention is not limited to this precipitation coating method. . Next, a cathode made of a linear heater coated with oxides such as BaO, SrO, CaO, etc. is placed facing the fluorescent film on the anode plate with an interval of about 1 mm to 5 mm, and this pair of electrodes After placing it in a transparent container such as glass, the inside of the container is evacuated. After the inside of the container reaches a vacuum level of at least 10 ^-5 Torr, stop the exhaust and seal it. After sealing, the getter is removed to further increase the vacuum inside the container. In this manner, the fluorescent display tube of the present invention can be obtained.

The phosphor film on the anode plate is flat and the cathode is linear, so in order to diffuse the low-speed electron beam emitted from the cathode, a phosphor film is placed between the cathode and the phosphor film as shown in Figure 2. It is desirable to install a mesh-like grid electrode as the diffusion electrode. In this case, better results can be obtained if the mesh is as narrow as possible so that the loss of the amount of light emitted by the fluorescent film is small and the low-velocity electron beam is well diffused. Specifically, the mesh diameter is 500μ
It is desirable that the aperture ratio (the area of the hole through which the low-velocity electron beam passes relative to the total area of the grid electrode) be 50% or more. The anode plate can display any character or figure if the electrode form is divided into the required character or figure shapes and the required voltage can be selectively applied to each electrode. I can do it. Alternatively, the anode plate is divided into dots or lines, and a fluorescent film of the phosphor of the present invention is formed on some of the electrodes, and a fluorescent film of the phosphor of the present invention is formed on the other electrodes. By forming a fluorescent film made of different low-speed electron beam phosphors, a fluorescent display tube capable of displaying multiple colors can be obtained.

As described above, the present invention provides a phosphor that emits high-intensity yellow light under slow electron beam excitation at an accelerating voltage of 1 KV or less, particularly 100 V or less, and a yellow-emitting fluorescent material that has a fluorescent film made of this phosphor. It provides a display tube, and its industrial utility value is great.

Next, the present invention will be explained with reference to Examples.

Example 1 Stannous chloride SnCl _{2.2H 2} O
225.6 (1 mol) Lanthanum oxide La ₂ O ₃ 8.33 g (0.03 mol) An oxalic acid aqueous solution containing 100 g of oxalic acid (C ₂ H ₂ O ₄ ) was added to a solution of the above two phosphor materials dissolved in hydrochloric acid to form Sn. and La oxalate were coprecipitated. The obtained precipitate was separated and dried, then packed into an alumina crucible, placed in an electric furnace, and fired in air at a temperature of 1250°C for 3 hours. After firing, the alumina crucible was taken out of the furnace and cooled, and the fired product was taken out from the alumina crucible, washed with water, dried, and then sieved to make the particle size uniform. In this way, a SnOB:0.06La phosphor was obtained. When this phosphor was excited with a slow electron beam at an accelerating voltage of 50 V, it emitted yellow light with a chromaticity point of (x=0.51, y=0.44) on the CIE color system chromaticity coordinates.

100 mg of the above phosphor was added to 100 c.c. of distilled water and subjected to ultrasonic dispersion. A 2 cm x 1 cm aluminum anode plate supported by a ceramic substrate was placed in this dispersion, and after being left for 30 minutes, the supernatant liquid was removed and the coating film on the anode plate was dried to form a fluorescent film. . Next, a cathode made of a tungsten wire heater coated with oxide is placed facing the fluorescent film on the anode plate with an interval of approximately 5 mm, and this pair of electrodes is placed in a hard glass container. ,
The inside of the container was evacuated. The degree of vacuum inside the container
After reaching a vacuum level of about 10 ^-5 Torr, the exhaust was stopped, the container was sealed, and the getter was blown off to further increase the vacuum inside the container. In this way, a fluorescent display tube having the structure shown in FIG. 1 was obtained. This fluorescent display tube has an anode plate voltage of 50V and a cathode voltage of 1.2V.
Then, a yellow luminescence with a luminance of 8 ft-L was exhibited.

Example 2 Tinnic oxide SnO ₂ 150.7 g (1 mol) Lanthanum chloride LaCl ₃ 2.45 g (0.01 mol) The above phosphor raw materials were thoroughly mixed using a ball mill, and the obtained phosphor raw material mixture was It was packed in an aluminum crucible, placed in an electric furnace, and fired in air at a temperature of 1300°C for 2 hours. After firing, the alumina crucible was taken out of the furnace and cooled, and the fired product was taken out from the alumina crucible, washed with water, dried, and then sieved to make the particle size uniform. In this way _SnO2 :
A 0.01La phosphor was obtained. This phosphor has an accelerating voltage of 50V
When excited with a slow electron beam, it exhibited yellow light emission with a chromaticity point of (x=0.49, y=0.44) on the CIE color system chromaticity coordinates. Using this phosphor, a fluorescent display tube having the structure shown in FIG. 1 was obtained in the same manner as in Example 1.
This fluorescent display tube emitted yellow light with a luminance of 7 ft-L when the anode plate voltage was 50V and the cathode voltage was 1.2V.

Example 3 Tin hydroxide Sn(OH) ₄ 186.7g (1 mol) Lanthanum oxide La ₂ O ₃ 2.78g (0.01 mol) 1.5 at a temperature of 1400°C using each of the above phosphor raw materials
Same as Example 1 except for baking for a certain time.
A SnO ₂ :0.02La phosphor was obtained. When this phosphor was excited with a slow electron beam at an accelerating voltage of 50 V, it emitted yellow light with a chromaticity point of (x=0.49, y=0.44) on the CIE color system chromaticity coordinates. Example 1 using this phosphor
In the same manner as above, a fluorescent display tube having the structure shown in FIG. 1 was obtained. This fluorescent display tube has an anode plate voltage of
When the voltage was 50V and the cathode voltage was 1.2V, yellow light was emitted with a luminance of 6f-L.

[Brief explanation of the drawing]

1 and 2 are schematic diagrams of typical examples of fluorescent display tubes, with FIG. 1 showing a diode and FIG. 2 showing a triode. FIG. 3 is a graph showing the emission chromaticity points of the phosphor of the present invention on the CIE color system chromaticity coordinates. FIG. 4 is a graph showing the relationship between acceleration voltage and luminance when the phosphor of the present invention is excited with a slow electron beam. 11... Anode plate, 12... Fluorescent film, 13
... Ceramic substrate, 14 ... Cathode, 15 ... Grid electrode, 16 ... Container, 17 ... Inside of display tube kept in high vacuum.

Claims (1)

[Claims] 1. A lanthanum-activated tin oxide phosphor whose compositional formula is SnO ₂ :xLa (where x is a number satisfying the condition 0.001≦x≦0.5). 2. The phosphor according to claim 1, wherein the x is a number satisfying the condition 0.01≦x≦0.06. 3. In a low-speed electron beam-excited fluorescent display tube having a structure in which an anode plate having a fluorescent film on one side and a cathode facing the fluorescent film are enclosed in a vacuum container, the above-mentioned A slow electron beam-excited fluorescent film characterized in that the fluorescent film is made of a lanthanum-activated tin oxide phosphor represented by the composition formula SnO ₂ :xLa (where x is a number satisfying the condition 0.001≦x≦0.5). light display tube. 4. The low-speed electron beam excited fluorescent display tube according to claim 3, wherein the x is a number satisfying the condition 0.01≦x≦0.06.