JPH0940947A - Fluorescent display tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fluorescent display tube having a high luminance, a long lifetime and the capability of emitting a yellow light without causing any environmental problems by using a mixture of a (Zn, Mg)O:Zn phosphor with a conductive metal oxide as the material for forming the yellow-light- emitting phosphor layer. SOLUTION: A fluorescent display tube which performs display by utilizing the luminance of the phosphor layer by excitation with slow electron beams, wherein the phosphor layer is made of a mixture of a (Zn, Mg)O: Zn phosphor with a conductive metal oxide, is provided. When In2 O3 is used as the conductive metal oxide, it should have a median diameter of 10μm and is used in an amount of 0.01-20wt.% based on the phosphor. When a mixture of In2 O3 with WO3 is used as the conductive metal oxide, the mixture is used in an amount of 0.02-20wt.% based on the phosphor, and the In2 O3 is used in an amount to give an In2 O3 /Cn2 O3 +WO3 ) ratio of 0.01-1. Further, the surface of the phosphor is desirably coated with a silicone compound in a coating amount of 2,000ppm or below.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluorescent display tube that utilizes the light emission of a phosphor layer by low-speed electron beam excitation, and more particularly to a fluorescent display tube that improves the emission characteristics of a yellow light emitting phosphor layer. .

[0002]

2. Description of the Related Art Usually, a phosphor used in a fluorescent display tube is required to easily emit light by a low-speed electron beam. In order to obtain yellow emission, a (Zn, Cd) S system is used as a base material. (Zn, Cd) S: Ag, Cl phosphor, ZnS
The system is the base (ZnS: Mn, ZnS: Au, Al)
Phosphors or (Zn, Mg) O: Zn phosphors have been mainly used.

[0003]

However, (Z
In (n, Cd) S-based phosphors or ZnS-based phosphors, the phosphors are largely deteriorated by electron beam irradiation, and further, sulfur (S) generated by decomposition of the phosphors is scattered to the cathodes to cause electron emission of the cathodes. However, there is a problem in that the brightness is likely to be deteriorated by hindering the above.

Further, since the (Zn, Cd) S-based phosphor further contains Cd as a constituent element of the phosphor, it is difficult to dispose of it, which may cause pollution problems.

Furthermore, the (Zn, Mg) O: Zn phosphor is essentially resistant to the electron beam impact with respect to the (Zn, Cd) S: Ag phosphor and contains no sulfur (S). It has a long life because there is no deterioration factor of the cathode, and it has no pollution because it does not contain Cd, but the brightness is (Zn, C
d) It was a problem that it was as low as about 1/2 or less with respect to S: Ag phosphor and the like.

Therefore, the present invention has been made in order to solve the above-mentioned conventional problems, and an object of the present invention is to provide a fluorescent display tube capable of obtaining yellow light emission with high brightness and long life without causing pollution problems. To provide.

[0007]

In order to achieve such an object, the present invention provides a yellow light emitting phosphor layer (Zn, M
g) By using an O: Zn phosphor and mixing the phosphor with a conductive metal oxide, a current easily flows on the surface of the phosphor, so that high-luminance light emission can be obtained.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The inventors of the present invention repeatedly conducted various experiments on a yellow light emitting phosphor capable of achieving high brightness and long life of a fluorescent display tube, and as a result, found the following matters. . The conductivity of the (Zn, Mg) O phosphor was compared with other conductive phosphors with respect to the current value flowing through the anode. For example, as a typical example, for ZnO: Zn phosphor, (Zn, M
g) It was found that the O phosphor obtained only an anode current of about 80%.

That is, this means that the (Zn, Mg) O phosphor has a higher resistance value than the ZnO: Zn phosphor with respect to the conductivity of the phosphor, and a current can be easily applied to the phosphor. It was thought that high brightness could be achieved by doing so.

Fluorescent display tubes which are characterized by being excited by a low-speed electron beam are generally used at a voltage where the secondary electron emission ratio is <1, so that the resistance value of the matrix is high. The phosphor tends to be negatively charged, and it is desirable that the resistance value is low.

Therefore, in the embodiment of the present invention, (Z
n, Mg) O: Zn phosphor and In ₂ O ₃ , SnO ₂ , Zn
0.01w of transparent conductive material composed of metal oxide such as O
By adding in the range of t% to 20 wt% (Z
The surface resistance of the n, Mg) O: Zn phosphor is lowered to facilitate the flow of current.

[0012]

Embodiments of the present invention will now be described in detail with reference to the drawings. Example 1 First, the (Zn, Mg) O: Zn phosphor is
A synthetic product or a commercial product obtained by synthesizing ZnO and MgO by a known method is obtained. Next, In ₂ O ₃ was used as the conductive metal oxide. The In ₂ O _{3 used} was in the form of fine particles, and particularly had a median diameter (D50) of 0.2 μm.

Before the step of forming the phosphor screen, (Zn, Mg) O:
In ₂ O ₃ particles were added to the Zn phosphor in the range of 0.01 to 5.0 wt% to prepare a plurality of types of samples having different mixing amounts of In ₂ O ₃ particles. In this case, In ₂ O ₃ particles are sufficiently dispersed in the (Zn, Mg) O: Zn phosphor.

Next, a vehicle in which ethyl cellulose was dissolved in butyl carbitol acetate and a (Zn, Mg) O: Zn phosphor in which In ₂ O ₃ particles were dispersed were 40: 6.
Mix at a ratio of 0 and knead thoroughly to make a phosphor paste.

Next, this phosphor paste was applied onto the anode electrode of the fluorescent display tube by screen printing and dried to form a phosphor layer, and the fluorescent display tube was manufactured by a known method.

FIG. 1 is a diagram showing initial characteristics of a fluorescent display tube manufactured by using the (Zn, Mg) O: Zn phosphor layer formed by the above-mentioned method. As is apparent from FIG. 1, the maximum emission luminance was obtained when the amount of In ₂ O ₃ added was about 2.0 wt%, and the luminance could be improved about 1.6 times as compared with the non-added product. . In addition, FIG. 2 shows the result of a life test performed on the phosphor layer thus obtained.
As is apparent from FIG. 2, the (Zn, Mg) O: Zn phosphor layer to which In ₂ O ₃ was added according to the present embodiment has a conventional (Zn, Mg)
It was found that the Cd) S: Ag phosphor layer can have a long life.

The amount of In ₂ O ₃ added to the (Zn, Mg) O: Zn phosphor may be small if the particle size is small, and may be optimal as the particle size increases. Since the amount of In ₂ O ₃ increases, 0.0
It is preferable to select in the range of 1 to 20 wt%. In this case, if the minimum amount of addition is too small (0.01 wt.
% Or less) is insufficient to reduce the surface resistance of the phosphor, and if too much (20 wt% or more), In ₂ O _{3 to be} added is added.
Since the particles of In ₂ O ₃ are non-luminous substances, the brightness is lowered.
Those up to about m are suitable. When In ₂ O _{3 having} a particle size of 1 μm or less is used, the addition amount is 0.1.
A range of 1 to 5 wt% is suitable.

Here, the grain size of In ₂ O ₃ is 1 in terms of median diameter.
The particle size of the phosphor is 3 to 10 μm.
Considering the range of m, at least In larger than the phosphor is used.
_This is because the specific surface area of the ₂ O ₃ particles is small and the contact area with the phosphor for releasing the charged charge is small, so that it does not work effectively as a conductive treatment agent.
Therefore, In smaller than at least the particle size of the phosphor
Must select ₂ O ₃ particles, each particle size In ₂ O ₃
The relationship between the particle size and the maximum brightness when 0 to 20 wt% is added is as shown in FIG.

That is, even if the In ₂ O ₃ particles having a particle size of 10 μm or more are added, the brightness does not become higher than that without addition. Further, if the addition amount is 20 wt% or more, the non-emission I
Since n ₂ O ₃ covers the surface, the brightness does not become higher than that in the case of no addition. The (Zn, Mg) O: Zn phosphor, unlike other insulative phosphors, has conductivity in the host material, and thus basically emits light without adding In ₂ O ₃ . The conductive metal oxide such as In ₂ O ₃ exhibits the effect of improving the brightness by compensating the conductivity of the phosphor.

As another method of adding In ₂ O ₃ to the (Zn, Mg) O: Zn phosphor, a method in which an organic compound of In is dissolved in a solvent is added to the phosphor paste or in advance. (Zn, Mg) O: Zn phosphor particles may be coated. In addition, in these methods, In ₂ O ₃ is uniformly and film-likely attached to the surface of the (Zn, Mg) O: Zn phosphor, so that the addition amount thereof is 0.
The range of 01 to 2 wt% is preferable.

In addition, the compound containing silicon oxide as a main component, which is coated on the surface of the (Zn, Mg) O: Zn phosphor to improve electron beam impact resistance, has a silicon oxide addition amount of If it is too much, I as a conductive treatment agent
Since the effect of adding n ₂ O ₃ cannot be obtained, it is preferably 2000 ppm or less relative to the phosphor core as shown in FIG.

Further, in FIG. 5, In ₂ O ₃ was added (Z
It is a figure which shows the anode current retention rate with respect to the lighting time of the fluorescent display tube produced using the n, Mg) O: Zn fluorescent substance layer.
As apparent from FIG. 5, according to this embodiment (Zn, Mg)
The O: Zn phosphor layer contains sulfur (S) that deteriorates the cathode.
It was found that the anode current did not decrease, compared to the conventional (Zn, Cd) S: Ag phosphor layer, because the anode current did not include the above.

Example 2 ZnO particles as a conductive metal oxide were added to a (Zn, Mg) O: Zn phosphor in the same manner as in Example 1 described above. The result is shown in FIG.
When ZnO particles are added as apparent from FIG.
The optimum value of the emission brightness was obtained at wt%. In this case, the emission brightness could be improved about 1.3 times.

In Example 2 described above, ZnO
As shown in FIG. 1, since the effect of addition is less sensitive than that of In ₂ O ₃ , the effect of addition is less than 0.1 wt%. Also,
If the addition amount exceeds 18 wt%, the brightness becomes lower than that in the case where no addition is made. Therefore, in the case of adding ZnO, the range of 0.1 to 18 wt% is preferable.

Example 3 SnO ₂ particles as a conductive metal oxide were added to the (Zn, Mg) O: Zn phosphor in the same manner as in Example 1 described above. The result is shown in FIG. As is clear from FIG. 1, the amount of SnO ₂ particles added is about 7
The optimum value was obtained at wt%, and the emission brightness could be improved about 1.2 times.

In the third embodiment, SnO is used.
_As shown in FIG. 1, the effect of addition of ₂ is less sensitive than that of In ₂ O ₃ , so if the content is less than 0.1 wt%, the effect of addition is small. Further, when the addition amount exceeds 15 wt%, the luminance becomes lower than that in the case where no addition is made. Therefore, in the case of adding SnO ₂ , the range of 0.1 to 15 wt% is preferable.

Example 4 In the same manner as in Example 1 described above, WO ₃ particles and In ₂ O ₃ particles as conductive metal oxides were added to the (Zn, Mg) O: Zn phosphor as shown in the table below. 1 was added according to the ratio shown in Table 1, made into tubes by the same method as described above, and the luminescence brightness was measured. As a result, as shown in Table 1, higher brightness can be achieved by adding both WO _{3 and} In ₂ O ₃ together than by adding them alone.

[0028]

[Table 1]

In this case, In ₂ O ₃ compounded with WO ₃ is added.
And the total amount of WO ₃ and In ₂ O ₃ is (Zn, M
g) O: amount of Zn In ₂ O ₃ in a range not exceeding 20 wt% with respect to the _{phosphor, In 2 O 3 / (WO} 3 + In
₂ O ₃ ) = effective in the range of 0.01 to 1.

The wide range of the ratio of WO ₃ to In ₂ O ₃ means that the gas storage amount of the bulb or the anode fluorescence depends on the volume of the fluorescent display tube to be designed, the anode structure and the manufacturing conditions. This is because the conductivity of the body layer changes, and it is necessary to prescribe the amount of each added according to these changes.

This is an effect that is exhibited because WO ₃ and In ₂ O ₃ have different effects for improving the brightness, and WO ₃ is a harmful gas adsorbed on the phosphor surface. In ₂ O ₃ has a role of removing the phosphor and In ₂ O ₃ has a role of compensating the conductivity of the phosphor.

[0032]

As described above, according to the present invention,
Since high brightness of the (Zn, Mg) O: Zn phosphor layer can be achieved, high brightness is achieved in a fluorescent display tube that requires yellow light emission.
A long service life can be achieved, and an effect of improving quality can be obtained.

Further, according to the present invention, the conventional (Zn, C
d) Since the S-based phosphor does not contain Cd, there is no pollution problem that makes disposal difficult, and it is possible to contribute to the reduction of pollution of the fluorescent display tube.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the amount of conductive metal oxide added to a phosphor layer of a fluorescent display according to the present invention and the emission luminance.

FIG. 2 is a diagram showing a light emission luminance retention rate (lifetime characteristic) with respect to a lighting time of a phosphor layer related to a fluorescent display tube according to the present invention and a phosphor layer in a conventional fluorescent display tube.

FIG. 3 is a diagram showing the relationship between the amount of silicon compound coated on the surface of the phosphor of the fluorescent display according to the present invention and the emission brightness.

FIG. 4 is a diagram showing a relationship between brightness and median diameter.

FIG. 5 is a diagram showing a relationship between an anode current holding ratio and a lighting time of a phosphor layer according to the present invention and a conventional phosphor layer.

Claims (7)

[Claims] 1. A fluorescent display tube for displaying by utilizing light emission of a phosphor layer excited by a slow electron beam, wherein the phosphor layer comprises a (Zn, Mg) O: Zn phosphor and a conductive metal oxide. A fluorescent display tube characterized by being mixed with. 2. The conductive metal oxide according to claim 1, wherein the conductive metal oxide is In ₂ O ₃ , and the addition amount is 0.0 to the phosphor.
A fluorescent display tube, characterized in that the range is 1 to 20 wt%. 3. The conductive metal oxide according to claim 1, wherein SnO ₂ is added, and the addition amount is 0.1 to the phosphor.
A fluorescent display tube characterized by having a range of -15 wt%. 4. The conductive metal oxide according to claim 1, wherein the conductive metal oxide is ZnO, and the addition amount is 0.1 to the phosphor.
A fluorescent display tube characterized by having a range of 18 wt%. 5. The fluorescent display tube according to claim 2, wherein the In ₂ O _{3 has} a median diameter of 10 μm or less. 6. The fluorescent display tube according to claim 2, wherein the surface of the phosphor is coated with a silicon compound, and the coating amount is within a range of 2000 ppm or less. 7. The conductive metal oxide according to claim 1, wherein In ₂ O ₃ and WO ₃ are added, the addition amount is set to 0.01 to 20 wt% with respect to the phosphor, and In ₂ O _{3 is} added.
The addition amount of In ₂ O ₃ / (In ₂ O ₃ + WO ₃ ) = 0.01
A fluorescent display tube having a range of -1.