JPS585221B2 - Luminescent composition and slow electron beam excitation fluorescent display tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel luminescent composition that emits red light and a low-speed electron beam excited fluorescent display tube using the luminescent composition.

More specifically, the present invention uses tin oxide (5n02) and a europium-activated yttrium oxysulfide phosphor (Y2O2S:
Eu), europium-activated yttrium oxide phosphor (Y
2O3:Eu) and a rare earth phosphor that is at least one of europium-activated yttrium vanadate phosphor (YVO4:Eu); This invention relates to a low-speed electron beam-excited fluorescent display tube using a film.

As is well known, a low-speed electron beam-excited fluorescent display tube (hereinafter abbreviated as a "fluorescent display tube") has an anode plate having a fluorescent film on one side, and a cathode facing the fluorescent film. The device essentially has a structure in which it is sealed in a vacuum container, and the fluorescent film on the anode plate is excited by the low-speed electron beam emitted from the cathode, 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.

A cathode 14 is provided opposite the fluorescent film 12 provided on one side of the anode plate 11, and the fluorescent 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, the ceramic substrate 13 and the cathode 14 (FIG. 1) having the fluorescent film 12 on one side, or the anode plate 11, the ceramic substrate 13, the cathode 14 and the grid electrode 15 (the second one) having the fluorescent film 12 on one side. In the figure, the device is sealed in a transparent container 16 made of glass or the like, and the interior 17 thereof is maintained at a high vacuum of 10' to 10@-9 Torr.

A zinc-activated zinc oxide phosphor (ZnO:Zn) is conventionally known as a phosphor that emits high-intensity light by excitation with a slow electron beam.

This phosphor exhibits high-intensity, festival-colored luminescence when excited by a slow electron beam with an accelerating voltage of several tens of volts to a few volts at most.

Fluorescent display tubes having the above-mentioned structure and having a fluorescent film made of ZnO:Zn are widely used industrially as display elements for, for example, desktop electronic computers and various measuring instruments.

Fluorescent display tubes using ZnO:Zn as a fluorescent film have been put into practical use, but there are almost no known phosphors other than ZnO:Zn that emit light through slow electron beam excitation. A fluorescent display tube in which a fluorescent film is made of a fluorescent material other than Zn has not been known in the past.

An object of the present invention is to provide a novel phosphor that emits high-intensity red light by excitation with a slow electron beam.

Another object of the present invention is to provide a novel fluorescent display tube that emits red light.

The present inventors have conducted various studies with the aim of obtaining a phosphor that emits high-intensity light by excitation with a slow electron beam and a fluorescent display tube using the phosphor.

As a result, SnO2 and Y2O□S:Eu, Y2O3:
A composition formed by mixing appropriate amounts of Eu and a rare earth phosphor that is at least one of YVO4:Eu has a voltage of several tens of V.
Discovered that high-intensity red light was emitted under slow electron beam excitation accelerated with an accelerating voltage of several hundred volts at most, and invented a red light-emitting fluorescent display tube using this luminescent composition as a fluorescent film. I ended up doing it.

That is, the luminescent composition of the present invention contains SnO2 and Y2O□S.
:Eu, Y2O3:Eu and YVO4:Eu, the mixed weight of 5n02 and at least one of Y2O2S:Eu, Y2O3:Eu and YVO4:Eu. It is characterized in that the ratio is in the range of 1:4 to 4:1.

Further, the fluorescent display tube of the present invention 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 container having a vacuum inside. In the tube, the fluorescent film is 5n02 and Y2O2S:E
The present invention is characterized by comprising a luminescent composition formed by mixing at least one of u, Y2O3:Eu, and YVO4:Eu at a weight ratio in the range of 1:4 to 4:1.

As 5n02, which is a component of the luminescent composition of the present invention, the general reagent SnO□ (hereinafter referred to as 5n02 raw powder) or the above-mentioned Sn02 raw powder or sulfate, nitrate, chloride, hydroxide, etc. can be easily used at high temperature. ni5n0
5nO2 obtained by firing a tin compound that can be converted into 2 in air, a neutral atmosphere, or a weakly reducing atmosphere.
(hereinafter referred to as calcined SnO2) is used.

The firing temperature for obtaining fired 5n02 may be any temperature below the melting point of SnO□ (approximately 1127° C.).

Note that SnO2 raw powder may contain tin oxides other than SnO□ such as SnO, but the presence of tin oxides other than SnO□ in small amounts will not have a negative effect on the luminescent properties. do not have.

On the other hand, Y which is the other component of the luminescent composition of the present invention
2O□S: Eu, Y2O32Eu and YVO4: Eu
is generally produced by the method described below.

First, Y2O2S: Eu is yttrium oxide (Y2O3)
20 to 40% by weight of sulfur (S) and 20 to 40% by weight of sodium carbonate (Na2OO3) as a flux are added and mixed to a mixed rare earth oxide obtained by mixing a predetermined amount of europium oxide (Eu2O3) with , 1200 in air
It is obtained by firing at a temperature of 1 to 1300° C. for 1 to 5 hours.

The preferred amount of the activator Eu in this Y2O2S:Eu is 10-2 to 1.5X10 to 1g of base Y2O2S.
'P, more preferably 5×10-2 to 6×
It is 1O-2P.

Next, Y2O3Eu is a mixed rare earth oxide made by mixing Y2O3 with a predetermined amount of Eu2O3, and 0.0% as a flux.
1 to 1% by weight of boric acid (H2BO3), potassium tetraborate (Ni2B+07), sodium tetraborate (Na2
B40□) and other boron compounds are added and mixed, and 13
It is obtained by firing at 00 to 1400°C for 1 to 5 hours.

The preferable amount of activator Eu for this Y2O3:Eu is the base Y
The amount is 10-2 to 1.5 x 10"g, more preferably 5 x 10-2 to 6 x 10"g per 2O3g.

YVO4: Eu is a mixed rare earth oxide prepared by mixing a predetermined amount of Eu2O3 with Y2O3, and further adding vanadium pentoxide (V2O6) in an equimolar amount to the mixed rare earth oxide, and heating the mixture at 1000 to 1100°C in air. It is obtained by baking for 1 to 5 hours.

The amount of the activator Eu in this YVO4:Eu is preferably 10-2 to 1.5X10''g, more preferably 7X10-2 to 8x10-2g based on the base YVO41P.
It is.

In addition, in the above three types of phosphor manufacturing methods, Y2O3
To obtain a mixed rare earth oxide consisting of Y2O3 and Eu2O3, it is possible to simply physically mix Y2O3 and Eu2O3;
2O3 and E u 20 s are once dissolved in nitric acid, an oxalic acid aqueous solution is added thereto to coprecipitate yttrium oxalate and europium oxalate, and this coprecipitated rare earth oxalate is thermally decomposed to form a mixed rare earth oxide. method has been adopted.

Y2O2S obtained by the above production method: Eu, Y
203: Eu and YVO4: Eu has an accelerating voltage of several K
When excited by an electron beam of V, these phosphors emit high-intensity red light, and these phosphors are in practical use as phosphors for the red light-emitting component of color television cathode ray tubes.

However, the luminescence of these phosphors under slow electron beam excitation is very weak, and especially under slow electron beam excitation at an accelerating voltage of 100 V or less, the brightness rapidly decreases and almost no light is emitted.

The luminescent composition of the present invention comprises the above-mentioned 5uO2 and Y2O2S:E.
It can be obtained by sufficiently mixing a rare earth phosphor that is at least one of u, Y2O3:Eu, and YVO4:Eu in a mortar, ball mill, mixer mill, or the like.

Both are mixed in a weight ratio such that the value of S n 02 /rare earth phosphor ranges from 1/4 to 4/1.

When the value of 5n02/rare earth phosphor is less than 1/4, the resulting composition has properties close to those of the rare earth phosphor and does not emit light under slow electron beam excitation.

On the other hand, when the value of SnO2/rare earth phosphor is greater than 4/1, the resulting composition has a small amount of rare earth phosphor and therefore emits very weak light.

From the viewpoint of brightness, the value of the SnO□7 rare earth phosphor is more preferably in the range of 3/7 to 7/3.

There are various possible reasons why a composition obtained by adding and mixing Sn02 to a rare earth phosphor that hardly emits light under slow electron beam excitation exhibits light emission under slow electron beam excitation, but the main reason is that Y2O □S:Eu,
This is because by adding and mixing 5n02, which has better conductivity than Y2O3:Eu and YVO4Eu, the conductivity of the entire composition is improved, and as a result, the charge-up phenomenon during excitation is eliminated, and the excitation efficiency is improved. I think that the.

The fluorescent display tube of the present invention is manufactured by the method described below.

The luminescent composition described above is first coated by precipitation coating onto an anode plate, usually supported by a ceramic substrate, to form a phosphorescent film.

That is, the anode plate is placed in a suspension of the composition dispersed in water, and the composition is applied by settling on one side of the anode plate by its own weight, and the water is removed and the coating is dried. let

In order to improve the adhesion of the fluorescent film obtained in this case to the anode plate, a small amount (0.01 to 0.1%) of water glass may be added to the suspension.

Further, the appropriate coating density is 5η/cm' to 30η/cm'.

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 an oxide such as BaO1SrO1Ca0 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 is After installing it in a transparent container, the inside of the container is evacuated.

After the inside of the container reaches a degree of vacuum of at least 10-5 Torr or more, the exhaust is stopped and the container is sealed.

After sealing, the getter is removed to further increase the degree of 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 diffusion electrode is placed between the cathode and the phosphor film as shown in Figure 2. It is desirable to install a mesh-like grid 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, it is desirable that the diameter of the mesh is 500 microns or less, and the aperture ratio (the area of the holes through which the low-speed electron beam passes, relative to the total area of the grid electrode) is 50% or more.

The anode plate can display arbitrary characters and figures by dividing the electrode form into the required character and figure shapes and making it possible to selectively apply the required voltage to each electrode. I can do it.

In addition, the anode plate is divided into dots or lines, and a phosphor film of a light-emitting composition made of a mixture of Sn02 and a rare earth phosphor is formed on some of the electrodes, and the above-mentioned phosphor is formed on the other electrodes. A fluorescent display tube capable of displaying multiple colors can be obtained by forming a fluorescent film made of a phosphor for slow electron beam excitation whose emission color is different from that of the composition.

Figure 3 shows the value (weight ratio) of SnO2/Y2O2S:Eu in a luminescent composition prepared by mixing SnO2 raw powder and Y20□S:Eu, which is the fluorescent film of the fluorescent display tube of the present invention, and the anode plate. Relationship with luminescence brightness when voltage (acceleration voltage) is 60V (curve a) and SnO2/Y2O2S:Eu
2 is a graph showing the relationship (curve b) between the value of and the acceleration voltage at which the luminescent composition starts to emit light, that is, the threshold voltage.

As is clear from the curve a in Figure 3, SnO2/Y2O2S
: Fluorescent display tubes whose fluorescent films are made of luminescent compositions with Eu values in the range of 3/7 to 7/3 have particularly high brightness (approximately 7/3).
ft-L or more).

Furthermore, as is clear from the curve in FIG. 3, it can be seen that the greater the amount of SnO2 mixed, the lower the threshold voltage becomes.

As mentioned above, FIG. 3 is a graph showing the relationship between the Sn02/Y202S:EuO value and the luminescence brightness and the relationship between the SnO2/Y2O2S:Eu value and the threshold voltage when SnO2 raw powder is used. However, almost the same results as in FIG. 3 can be obtained when calcined SnO2 is used instead of raw SnO2 powder.

It was also confirmed that the same tendency as shown in FIG. 3 was obtained when Y2O3:Eu or YVO4:Eu was used instead of Y2O□S:Eu.

FIG. 4 shows the emission spectrum of the fluorescent display tube of the present invention.
A is the emission spectrum of a fluorescent display tube whose fluorescent film is a luminescent composition formed by mixing SnO□ and Y2O2S:Eu;
B is the emission spectrum of a fluorescent display tube whose fluorescent film is a luminescent composition made by mixing SnO2 and Y2O3:Eu, and C is
This is an emission spectrum of a fluorescent display tube whose fluorescent film is a luminescent composition formed by mixing SnO2 and YVO4:Eu.

Figure 4 - The emission spectra of A, B and C are all E
It is a linear spectrum in the red region unique to u3+, and its emission color (emission chromaticity point) is only slightly different.

Therefore, the rare earth phosphor which is one component of the luminescent composition used in the fluorescent film of the fluorescent display tube of the present invention is Y2O2S.
:Eu, Y2O3:Eu and YVO4:Eu, the emission color of the resulting fluorescent display tube is different from that of the rare earth phosphor: Y202S:Eu, Y20
The color of the luminescence is almost the same as that of a fluorescent display tube whose fluorescent film is a luminescent composition composed of one of 3:Eu and YVO4:Eu.

As described above, the present invention provides a fluorescent display tube that emits high-intensity red light, and such a red-emitting fluorescent display tube has never existed before, and its industrial use is Value is great.

Next, the present invention will be explained by examples.

Example I S n02 raw powder (reagent manufactured by Shuzuihikotabe Shoten) 1 part by weight and E
Y2O2S with a u activation amount of 5 x 10-g/g and 1 part by weight of Eu were thoroughly mixed using a mortar.

A suspension of 200 mg of the resulting composition in 100 cc of distilled water containing 0.01% water glass was applied to a 2 cm substrate supported by a ceramic substrate by the sedimentation coating method.
A fluorescent film with a coating density of approximately 8 mg/cm' was formed on a ×1 cm aluminum anode plate.

Next, a cathode made of a tungsten wire heater coated with oxide was placed facing the fluorescent film on the anode plate for approximately 5 m.
After placing the pair of electrodes in a hard glass container with an interval of m, the inside of the container was evacuated.

After the degree of vacuum in the container reached about 10' Torr, the exhaust was stopped and the container was sealed, and then the getter was blown off to further increase the degree of vacuum in the container.

In this way, a fluorescent display tube having the structure shown in FIG. 1 was obtained.

This fluorescent display tube emitted red light with a luminance of 12 ft-L when the anode plate voltage was 60 V, the cathode voltage was 0.6 V, and the anode plate current was 2 mA.

Example 2 Sn (NO3)4 (reagent manufactured by Shuzuihikotabe Shoten) was packed in an alumina crucible and fired in air at 500°C for 1 hour.

After the obtained calcined SnO
0'' g/g of Y2O3:Eu (1 part by weight) was thoroughly mixed using a mortar.

A fluorescent display tube was produced in the same manner as in Example 1 except that the composition thus obtained was used.

This fluorescent display tube emitted red light with a luminance of 10 ft-L when the anode plate voltage was 60 V, the cathode voltage was 0.6 V, and the anode plate current was 1.5 mA.

Example 3 Sn (N03) 4. (Reagent manufactured by Shuzuhikotabe Shoten)
was packed in an aluminum crucible and fired at 600° C. for 1 hour in a weakly reducing atmosphere consisting of 98% nitrogen and 2% hydrogen.

After sufficiently pulverizing the obtained calcined SnO2 using a ball mill, 3 parts by weight of this calcined 5nO2 and the Eu activation amount were 7×1.
7 parts by weight of YVO4:Eu at 0-2 g/g were thoroughly mixed using a mortar.

A fluorescent display tube was produced in the same manner as in Example 1 except that the composition thus obtained was used.

This fluorescent display tube emitted red light with a luminance of 4.5 ft-L when the anode plate voltage was 60 V, the cathode voltage was 0.6 V, and the anode plate current was 2.5 mA.

Example 4 7 parts by weight of SnO2 raw powder (reagent manufactured by Shuzuihikotabe Shoten) and Eu
Y2O2S:Eu3 with an activation amount of 5 x 10-2 g/g
Parts by weight were thoroughly mixed using a mortar.

A fluorescent display tube was produced in the same manner as in Example 1 except that the composition thus obtained was used.

This fluorescent display tube emitted red light with a luminance of 6 ft-L when the anode plate voltage was 60 V, the cathode voltage was 0.6 V, and the anode plate current was 2.5 mA.

[Brief explanation of the drawing]

FIGS. 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. Figure 3 shows the value of SnO2/Y2O2S:Eu in a luminescent composition prepared by mixing raw SnO2 powder and Y2O2S:Eu, which is the fluorescent film of the fluorescent display tube of the present invention, and the luminescence when the anode plate voltage is 60V. Relationship with luminance (curve a) and S
nO2/Y2O2S: This is a graph showing the relationship (curve b) between the value of Eu and the threshold voltage. FIG. 4 shows the emission spectrum of the fluorescent display tube of the present invention.
is the emission spectrum of a fluorescent display tube whose fluorescent film is a luminescent composition formed by mixing SnO2 and Y2O2S:Eu, and B is the emission spectrum of a fluorescent display tube whose fluorescent film is a luminescent composition formed by mixing SnO2 and Y2O3:Eu. The emission spectrum of the fluorescent display tube, and C
is a graph showing the emission spectrum of a fluorescent display tube whose fluorescent film is a luminescent composition formed by mixing SnO2, YVO, and Eu. 11... Anode plate, 12... Fluorescent film, 13... Ceramic substrate, 14...
Cathode, 15... Grid electrode, 16...-- Container, 17...- Inside the display tube kept at high vacuum.

Claims (1)

[Claims] 1. Tin oxide (SnO□) and europium-activated yttrium oxysulfide phosphor (Y20□S: Eu), europium-activated yttrium oxide phosphor (Y203: Eu)
) and at least one of europium-activated yttrium vanadate phosphor (YVO4:Eu).
: A luminescent composition formed by mixing at a weight ratio of 4 to 4:1. 25uO2, Y2O2S:ELl, Y2O3:Eu
and YVO4: at least one of Eu
2. The luminescent composition according to claim 1, wherein the mixing weight ratio of the luminescent composition to the luminescent composition is in the range of 3 to 7:3. 3. A 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, in which the fluorescent film is made of tin oxide. (SnO
A low-speed electron beam-excited fluorescent display tube, characterized in that it is made of a luminescent composition prepared by mixing at least one of the following: 4: Eu at a weight ratio of 1:4 to 4:1. Claim 3, characterized in that the mixing weight ratio of 45n02 and at least one of Y20□S:Eu, Y2O3:Eu and YVO4:Eu is in the range of 3nia to 7:3. Slow electron beam excitation fluorescent display tube.