JP2001192654A - Low-speed electron beam excited fluorescent substance and fluorescent display tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a CaS-based fluorescent substance, slightly negatively affecting emission to a cathode and providing a practically necessary brightness in a fluorescent display tube at about 100 V acceleration voltage. SOLUTION: This fluorescent substance is constituted of calcium, sulfur, europium and lithium in the ratio of 1 mol sulfur, >=0.0001 mol and <=0.1 mol europium and lithium based on 1 mol calcium. Otherwise, the fluorescent substance is constituted of calcium, sulfur, europium, lithium and chlorine in the ratio of 1 mol sulfur, >=0.0001 mol and <=0.1 mol europium, lithium and chlorine based on 1 mol calcium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phosphor which emits light by being excited by a slow electron beam, and a fluorescent display tube using the phosphor. More particularly, the present invention relates to a CaS-based phosphor having improved luminance characteristics and a CaS-based phosphor. The present invention relates to a fluorescent display tube used.

[0002]

2. Description of the Related Art Conventionally, a fluorescent display tube, which is one of electronic display devices, is often used as a display component of a dashboard of an audio device or an automobile. The fluorescent display tube is composed of an anode with a phosphor attached thereto and a cathode facing the anode arranged in a vacuum vessel, and the emitted light from the cathode collides with the phosphor to emit light. Generally, a triode type in which a grid for controlling the flow of electrons is provided between a cathode and an anode to selectively emit light from a phosphor is most often used. The phosphor used in such a fluorescent display tube is a phosphor called a low-speed electron beam-excited phosphor, which can obtain a practical luminance by an acceleration voltage of about 100 V.

[0003] In recent years, with the expanding use of fluorescent display tubes, demands for multicolor display have increased. In the early days of flat-type fluorescent display tubes, as a phosphor that can obtain practically sufficient luminance with a low-speed electron beam with an operating voltage of about 10 to 50 V,
There was no other than green-emitting ZnO: Zn. However, since the technology for reducing the resistance of the phosphor using a conductive material such as indium oxide (In ₂ O ₃ ) was developed, multicolor light emission using a sulfide phosphor has become possible. Examples of such a phosphor include ZnS: Cl + In ₂ O ₃ , which emits blue light,
There are yellow-green emitting ZnS: Cu, Al + In ₂ O ₃ and red-emitting ZnCdS: Ag, Cl + In ₂ O ₃ .

[0004]

However, in a fluorescent display tube using these sulfide phosphors, the sulfide phosphor is decomposed by electron beam irradiation, and the scattered sulfur (S) adheres to the cathode. There is a problem in that the oxide which is an electron source material is deteriorated, and the luminance is reduced. Therefore, there is a need for a ZnCdS-based phosphor and a sulfide phosphor that is more stable than the ZnS-based phosphor against electron beam irradiation. A condition for a stable sulfide phosphor is that the melting point of the sulfide serving as a base is high. This is because it is considered that the higher the melting point, the stronger the bonds between atoms are, and the more stable it is to electron beam irradiation.

As a ZnCdS-based phosphor or a sulfide phosphor having a higher melting point than that of a ZnS-based phosphor, calcium sulfide (Ca
A CaS-based phosphor having S) as a host is known. Ca
Since S has a melting point of 2000 ° C. or more, the melting point is 1600 ° C.
It is considered to be more stable to electron beam irradiation than CdS of a certain degree or ZnS which sublimates without melting. However, the conventional CaS-based phosphor has excellent luminous efficiency in a high voltage region, but has a low luminous intensity with a low-speed electron beam. For example, the relative luminance of a CaS: Eu phosphor that emits red light also emits red light. ZnCdS: It was １ ／ or less of the Ag, Cl phosphor, and only about １ ／ of the luminance required for practical use was obtained.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and provides a practically necessary luminance at a low accelerating voltage of about 100 V. CaS with little adverse effect
It is another object of the present invention to provide a fluorescent display device using the CaS-based fluorescent material and a long-life fluorescent display tube with reduced luminance reduction.

[0007]

Means for Solving the Problems To solve the above-mentioned problems, the inventors of the present invention have conducted various experiments on CaS: Eu phosphors to achieve the above-mentioned object, and as a result, calcium sulfide was doped with europium. In this case, it was found that when lithium was simultaneously doped, the emission intensity was higher than when only europium was doped. It has also been found that when doping calcium sulfide with europium, doping lithium and chlorine at the same time further enhances the emission intensity. In addition, it has been found that when these CaS-based phosphors are used for a phosphor film of a fluorescent display tube, by mixing indium oxide, they emit light with a practically sufficient luminance even at an excitation voltage of 26V. Further, other than europium, a rare earth element such as cerium has been found to similarly increase the emission intensity, and the present invention has been achieved.

[0008] The low-energy electron beam-excited phosphor of the present invention is characterized in that it is composed of lithium and one element selected from calcium, sulfur and rare earth elements. In one configuration example of this slow electron beam excitation phosphor, one element selected from rare earth elements is formed of europium. In this case, as for each component element of the phosphor, it is desirable that sulfur is 1 mol per 1 mol of calcium and that europium and lithium are each 0.0001 mol or more and 0.1 mol or less.

Another constitutional example of the low-energy electron beam-excited phosphor of the present invention is characterized by being composed of one kind of element selected from calcium, sulfur and rare earth element, lithium and chlorine. In one configuration example of this slow electron beam excitation phosphor, one element selected from rare earth elements is formed of europium. In this case, each of the constituent elements of the phosphor has 1 mol of sulfur per 1 mol of calcium, and europium, lithium and chlorine each contain 0.1 mol of sulfur.
It is desirable that the amount be from 0001 mol to 0.1 mol.

[0010] The fluorescent display tube of the present invention comprises:
An anode with a phosphor film attached thereto and a cathode are provided, and the electrons emitted from the cathode collide with the phosphor film to emit light. The phosphor film is composed of the aforementioned low-speed electron beam excited phosphor and indium oxide. Characterized by being composed of a mixture of In the phosphor film of the above-described fluorescent display tube, indium oxide exceeds 5 wt% with respect to the phosphor and is 30 wt%.
% Is desirable.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. In the slow electron beam excited phosphor according to the first embodiment of the present invention, the phosphor matrix is calcium sulfide (CaS), and the phosphor matrix includes europium (Eu), which is one of rare earth elements, and an alkali metal. Lithium (Li), which is one of the elements, is doped. Hereinafter, this phosphor is referred to as CaS: Eu, Li phosphor. In this embodiment, the addition amounts of Eu and Li are each 0.001 mol per mol of CaS.

The phosphor of CaS: Eu, Li is manufactured as follows. First, 99.99% pure CaS, 99.9% pure Eu ₂ O _3, and 99.9% Li ₂ C
And O _3, per CaS1 mol, Eu ₂ O ₃ and Li ₂ CO ₃
Are weighed so that both become 0.0005 mol, and then put into an alumina mortar and mixed well. Next, the mixed powder was put into an alumina crucible, and 1000 to 1000
Heat to 1300 ° C. and bake for 1-4 hours. Thereby, Eu and Li are each 0.0 mol per mol of CaS.
A 01 mol of CaS: Eu, Li phosphor is produced. The atmosphere at the time of firing is not limited to a nitrogen atmosphere, but may be an inert gas atmosphere such as argon or a weak reducing atmosphere such as a mixed gas of nitrogen and hydrogen.

Next, FIG. 1 shows the result of comparing the luminance of the CaS: Eu, Li phosphor with the CaS: Eu phosphor and the ZnCdS: Ag, Cl phosphor. FIG. 1 shows CaS: E
CaS when the luminance of u, Li phosphor is 100%:
It is a graph which shows the relative brightness of Eu phosphor and ZnCdS: Ag, Cl phosphor. Here, the CaS: Eu, Li phosphor contains Eu and Li each in an amount of 0.1 mol / mol CaS.
001 mol, and the CaS: Eu phosphor is
Eu is 0.001 mol per mol of CaS. The CaS: Eu, Li phosphor and the CaS: Eu phosphor are excited by a slow electron beam and have a peak wavelength of 640.
Emit red light at nm. Further, ZnCdS: Ag, Cl phosphor emits Zn _0.3 at a peak wavelength of 635 nm.
Cd _0.7 S: Ag, Cl was used.

In FIG. 1, when the luminance of the CaS: Eu, Li phosphor is 100%, the relative luminance of the CaS: Eu phosphor is 33%, and the relative luminance of the ZnCdS: Ag, Cl phosphor is 176%. , CaS: Eu, Li of the present invention
The brightness of the phosphor was improved about three times that of the conventional CaS: Eu phosphor. Here, the luminance required for practical use is about 60% of FIG.
, And the CaS: Eu, Li phosphor of the present invention obtained a luminance higher than this. Note that the luminance of these phosphors is such that 20 wt% to 25 wt% of In ₂
O ₃ was mixed and applied to the anode of a fluorescent display tube, and the measurement was performed by applying an anode voltage of +26 V at a duty ratio of 1/16.

Next, the effect of increasing the luminance of a CaS-based phosphor by adding lithium will be described with reference to a CaS: Eu, Li phosphor as an example. When Li is added to the CaS: Eu phosphor, the conductivity of the parent CaS is improved, so that the negative charges on the surface of the phosphor particles under electron beam excitation are easily released, and the negative potential on the surface decreases. As a result, it is assumed that the substantial anode voltage applied to the phosphor is increased, the energy of the colliding electrons is increased, the excitation is facilitated, and the luminance is improved.

Next, Ca for obtaining the luminance necessary for practical use is obtained.
S: Eu, Li The amount of Eu and Li added to the phosphor will be described. In order to obtain the luminance required for practical use, the amount of Eu added to CaS should be 0.0001 per mole of CaS.
In the range of not less than 0.1 mol and not more than 0.1 mol, the added amount of Li is 0.0001 mol or more and 0.1 mol per mol of CaS.
Desirably, the range is not more than mol. Here, the reason why the lower limit of the added amount of Li is set to 0.0001 mol or more per 1 mol of CaS is that if the added amount of Li is less than 0.0001 mol, the effect of improving the conductivity of the phosphor is small. This is because the luminance required for practical use may not be obtained depending on the amount.

The reason why the upper limit of the amount of Li added is set to 0.1 mol or less per 1 mol of CaS is that the amount of Li added is 0.1 mol.
If the amount is more than 1 mol, the luminance decreases, and depending on the amount of Eu, the luminance required for practical use may not be obtained. It is presumed that the reason why the luminance is lowered when the amount of Li added is too large is because the influence of lattice defects generated by the addition of Li increases. When the addition amount of Li is constant, the luminance is higher by 20% or more when the addition amount of Eu is between 0.001 mol and 0.01 mol than in the vicinity of 0.0001 mol or 0.1 mol. Therefore, L
Even when the amount of i added is less than 0.0001 mol or more than 0.1 mol, practically necessary luminance may be obtained. Therefore, the amount of Eu added is 0.001 mol to 0.1 mol.
When the molar ratio is between 01 mol, the range of the added amount of Li can be widened.

When the amount of Eu added is constant, L
When the addition amount of i is between 0.001 mol and 0.01 mol, the luminance is 10% or more higher than the vicinity of 0.0001 mol or 0.1 mol.
Even when the amount is less than 0.1 mol or more than 0.1 mol, practically necessary luminance may be obtained. Therefore, when the added amount of Li is between 0.001 mol and 0.01 mol, the range of the added amount of Eu can be widened. Also,
In order to further improve the luminance, the amount of Eu added is set to 0.0
It is preferable that the amount be from 0.01 mol to 0.01 mol and the amount of Li added be from 0.001 mol to 0.01 mol.

In this embodiment, CaS: Eu, Li
Although the description has been given by taking the phosphor as an example, the present invention is not limited to this. For example, the rare earth element cerium (Ce)
It may be applied to a phosphor that emits yellow-green light, such as a CaS: Ce phosphor using, to obtain a CaS: Ce, Li phosphor. Further, the present invention can be applied to other phosphors having CaS as a base material and a rare earth element as a light emission center.

Next, a second embodiment of the present invention will be described. In the slow electron beam excited phosphor according to the second embodiment of the present invention, the base material of the phosphor is calcium sulfide (Ca).
S), the phosphor matrix contains europium (Eu), one of the rare earth elements, lithium (Li), one of the alkali metal elements, and chlorine (C), one of the halogen elements.
l) is doped. Hereafter, this phosphor will be referred to as Ca
S: described as Eu, Li, Cl phosphor. This CaS: E
The u, Li, and Cl phosphors are the same as those described in the first embodiment.
aS: Luminance further improved as compared with Eu, Li phosphor. In this embodiment, Eu, Li, and Cl are used.
Was set to 0.001 mol per 1 mol of CaS.

This CaS: Eu, Li, Cl phosphor is
It is manufactured as follows. First, 99.99% pure C
aS, 99.9% pure Eu ₂ O ₃ and 99.9% pure L
i ₂ CO ₃ and NH ₄ Cl were mixed with Eu ₂ O per mole of CaS.
₃ and Li ₂ CO ₃ are both 0.0005 mol, and NH ₄ C
After weighing each such that 1 becomes 0.001 mol,
Place in alumina mortar and mix well. Next, the mixed powder was put into an alumina crucible, and then put in a nitrogen atmosphere at 1000 to 13 g.
Heat to 00C and bake for 1-4 hours. Thereby, C
Eu, Li and Cl are each 0.1 mol / mol of aS.
A 001 mole of CaS: Eu, Li, Cl phosphor is produced. The atmosphere at the time of firing is not limited to a nitrogen atmosphere, but may be an inert gas atmosphere such as argon or a weak reducing atmosphere such as a mixed gas of nitrogen and hydrogen.

Here, the Cl source is not limited to NH ₄ Cl, but is a chloride of an alkali metal element (NaCl, K).
Cl, RbCl, CsCl) and chlorides of alkaline earth metal elements (MgCl ₂ , CaCl ₂ , SrCl ₂ , BaC)
l ₂ ) can also be used. In this manufacturing method, Eu
Since the source, Li source and Cl source are added as separate compounds, the Eu concentration in the CaS: Eu, Li, Cl phosphor and L
i concentration and Cl concentration can be independently changed,
The optimum concentration can be selected depending on the use conditions.

Next, the luminance of the CaS: Eu, Li, Cl phosphor is compared with that of the CaS: Eu phosphor and CaS: Eu, Li.
FIG. 2 shows the result of comparison with the phosphor. FIG. 2 shows CaS:
Ca when the luminance of the Eu and Li phosphors is 100%
It is a graph which shows the relative brightness | luminance of S: Eu fluorescent substance and CaS: Eu, Li, Cl fluorescent substance. Here, CaS: Eu, L
The i, Cl phosphor is composed of Eu, Li and C per mole of CaS.
1 and 0.001 mol, respectively, and Ca
The S: Eu, Li phosphor is composed of Eu and L per mole of CaS.
i is 0.001 mol each. Also,
The CaS: Eu phosphor has a Eu content of 0.1 per mole of CaS.
001 mol.

The luminance of these phosphors is 20 W
A mixture of t% to 25% by weight of In ₂ O ₃ was applied to the anode of the fluorescent display tube, and an excitation voltage of +26 V was applied to the anode at a duty ratio of 1/16 for measurement. In FIG. 2, Ca
S: C when brightness of Eu, Li phosphor is 100%
The relative luminance of aS: Eu, Li, Cl phosphor is 117%,
The relative luminance of the CaS: Eu phosphor is 33%, and the CaS: Eu, Li, Cl phosphor of the present embodiment has
It can be seen that the luminance is 17% higher than that of the S: Eu, Li phosphor.

Next, the effect of improving the luminance by adding chlorine will be described with reference to CaS: Eu, Li, Cl phosphor. The mechanism of the luminance improvement by chlorine addition has not been elucidated yet, but it is speculated that Cl may have a function of stabilizing Eu in CaS to a +2 (Eu ²⁺ ) state in CaS. Eu emits red light when it is in a +2 valence (Eu ²⁺ ) state in CaS, but Eu has a valence of +2 valence and +3 valence.
In order to obtain a valence state, the doped Eu is composed of Eu ²⁺ and Eu
^Since it is divided into ³⁺ , the luminous efficiency is poor and the luminance is low. It is considered that, when doping Ca, which is the base, with Eu, which becomes the emission center, simultaneously doping Cl, the ratio of Eu ²⁺ is increased, the luminous efficiency is improved, and the luminance is improved.

Next, the amounts of Eu, Li, and Cl of the CaS: Eu, Li, Cl phosphor will be described. This Ca
The S: Eu, Li, Cl phosphor is obtained by improving the luminance of the CaS: Eu, Li phosphor shown in the first embodiment, and the amounts of Eu and Li added are each 0.1 mol per mol of CaS. In the range of 0001 mol or more and 0.1 mol or less, the amount of Cl added is 0.000 mol per mol of CaS.
It is desirable that the content be in the range of 1 mol or more and 0.1 mol or less. Here, the reason why the lower limit of the amount of Cl added is set to 0.0001 mol or more per 1 mol of CaS is that the amount of Cl added is 0.1 mol.
This is because the luminance is improved at 0001 mol or more. Further, the upper limit of the amount of Cl added is set to 0.1 mol or less,
This is because if the amount of Cl added exceeds 0.1 mol, the deterioration of the filament-shaped oxide cathode used in the fluorescent display tube due to Cl becomes large.

This CaS: Eu, Li, Cl phosphor is also
As in the case of the CaS: Eu, Li phosphor, when the added amounts of Li and Cl are constant, when the added amount of Eu is between 0.001 mol and 0.01 mol, around 0.0001 mol or 0.1 mol.
The luminance is higher by 20% or more than in the vicinity of 1 mol. Also,
Assuming that the addition amounts of Eu and Cl are constant, if the addition amount of Li is between 0.001 mol and 0.01 mol, 0.000 mol
The luminance is increased by 10% or more as compared with around 1 mol or around 0.1 mol. Therefore, in order to further improve luminance, E
It is desirable that the addition amount of u be 0.001 mol or more and 0.01 mol or less, and the addition amount of Li be 0.001 mol or more and 0.01 mol or less.

In this embodiment, CaS: Eu, L
As the method for producing the i, Cl phosphor, the method using Eu ₂ O ₃ , Li ₂ CO ₃ and NH ₄ Cl described above has been described.
The present invention is not limited to this, and Eu ₂ O ₃ and LiCl may be used. In this case, Eu ₂ O ₃ per mole of CaS
Is 0.0005 mol and LiCl is 0.001 mol, respectively, and then put in an alumina mortar and sufficiently mixed. Then, the mixed powder is put in an alumina crucible and then put in a nitrogen atmosphere at 1000 to 1300. Heat to ℃ 1
Bake for ~ 4 hours. Thereby, per mole of CaS,
A CaS: Eu, Li, Cl phosphor containing 0.001 mol of each of Eu, Li, and Cl is manufactured. According to this manufacturing method, the ratio of Li and Cl is fixed at 1: 1. However, it is not necessary to separately prepare the LI source and the Cl source, and there is an effect that the procedure can be simplified.

In this embodiment, CaS: Eu, L
Although the i and Cl phosphors have been described as examples, the present invention is not limited to this. For example, CaS: Ce, Li
A CaS: Ce, Li, Cl phosphor may be applied to the phosphor. In the case of Ce, the valences are +3 and +4. However, Ce emits yellow-green light in the +3 (Ce ³⁺ ) state in CaS.
Is believed to stabilize Ce to a +3 (Ce ³⁺ ) state. Further, the present invention can be applied to other phosphors having CaS as a base material and a rare earth element as a light emission center.

Next, an embodiment of a fluorescent display tube using the low-speed electron beam excited phosphor of the present invention will be described. FIG.
1 shows a configuration of a fluorescent display tube according to the present embodiment. In this fluorescent display tube, a wiring layer 2 having a predetermined pattern is formed on a glass substrate 1, and a through hole 3a is formed on the wiring layer 2. Is formed. A wiring layer 2 is formed on the surface of the insulating layer 3 through a through hole 3a.
The anode 4 having a predetermined pattern electrically connected to the anode 4 is formed, and a phosphor film 5 in which a CaS: Eu, Li, Cl phosphor and indium oxide (In ₂ O ₃ ) are mixed is deposited on the anode 4. Is formed.

Above the phosphor film 5, a grid 6 is arranged, and above the grid 6, a filament-shaped oxide cathode 7 in which tungsten thin wires are coated with (Ba, Sr, Ca) O is arranged. ing. A translucent face glass 9 is arranged above the filament-shaped oxide cathode 7, and is held at a predetermined distance from the glass substrate 1 by a frame-shaped side wall 8. The glass substrate 1, the side walls 8 and the face glass 9 are sealed with a low melting point frit glass 10,
A vacuum vessel is formed and kept at a vacuum of 10 ^-3 to 10 ^-5 Pa. A plurality of leads (not shown) are provided through the contact portion between the side wall 8 and the glass substrate 1, and an electric signal is externally applied to the cathode 7, grid 6, and anode 4 by these leads. ing.

Here, the method of depositing and forming the phosphor film 5 on the anode 4 may be the same as that of the conventional manufacturing method.
A phosphor paste obtained by mixing u, Li, Cl phosphor and In ₂ O ₃ with an appropriate organic binder is screen-printed on the anode 4, and then heated to about 500 ° C. in air and fired. It is formed by decomposing an organic binder present in the phosphor film 5. As a result, a phosphor film 5 in which the CaS: Eu, Li, Cl phosphor and In ₂ O ₃ are mixed is formed on the anode 4. When the organic binder is decomposed in the firing process, it becomes CO ₂ or CO and burns, so that the surrounding atmosphere is made neutral or reducing, so that oxidation of the phosphor can be suppressed. Therefore, when using a phosphor that is easily degraded by oxidation, such as CaS, it is desirable to increase the amount of the organic binder in the phosphor paste.

In this case, the addition amounts of Eu, Li, and Cl of the CaS: Eu, Li, Cl phosphor were 0.001 mol each of Eu, Li, and Cl per mol of CaS. Further, the addition ratio of In ₂ O ₃ is 20 to the phosphor.
wt% to 25 wt%. In addition, as shown in FIG. 4, the mixing amount of In ₂ O ₃ is
Since the luminance is reduced by 20% or more in the region exceeding wt%,
It is desirable that the content be in the range of 5 wt% or more and 30 wt% or less.
% To 25 wt%. 5 wt% decrease in brightness
In the region less than 30 wt%, the conductivity of the entire phosphor screen is insufficient, and in the region exceeding 30 wt%, the non-light emitting substance In
_It is considered that the ratio of ₂ O ₃ is increased. Note that the method of manufacturing the fluorescent display tube is the same as that of a known fluorescent display tube, and a description thereof will be omitted.

In the fluorescent display tube of this embodiment, the phosphor used for the phosphor film is exemplified by the CaS: Eu, Li, Cl phosphor, but is not limited to this, and the above-mentioned CaS: Eu is used. , Li phosphor, CaS: Ce, L
i, Cl phosphor, CaS: Ce, Li phosphor, Li and C
Other phosphors that use CaS to which l is added as a host and a rare earth element as a luminescent center, and other phosphors that use Ca as a host to which Li is added as a host and a luminescent center of a rare earth element can be used in the same manner.

Next, using the fluorescent display tube of the present embodiment, CaS: Eu, Li, Cl phosphor and CaS: Eu, L
FIG. 5 shows the result of comparing the luminance characteristics of the i phosphors. FIG.
Is the excitation voltage of CaS: Eu, Li, Cl phosphor 100
CaS: Eu, when the luminance at V is 100%
5 is a graph showing the relative luminance of a Li phosphor, wherein CaS: E
The u, Li, Cl phosphor is shown in (a), and the CaS: Eu, Li phosphor is shown in (b). Here, CaS: Eu, Li, C
The 1 phosphor has 0.001, mol of Eu, Li and Cl per mol of CaS, and CaS: E
The u and Li phosphors are each 0.001 mol of Eu and Li per mol of CaS. The luminance of these phosphors was determined by mixing 20 wt% to 25 wt% of In ₂ O ₃ with the phosphor, applying the mixture to the anode of the fluorescent display tube, and applying an excitation voltage to the anode at a duty ratio of 1/12. Measured.

In FIG. 5, CaS: Eu, Li, Cl
Assuming that the luminance of the phosphor at an excitation voltage of 100 V is 100%, the relative luminance of the CaS: Eu, Li phosphor is 85%.
From the start of light emission, the luminance of the CaS: Eu, Li, Cl phosphor is higher than the luminance of the CaS: Eu, Li phosphor, indicating that the addition of Cl is effective. Thus, C
aS: Eu, Li, Cl phosphor is CaS: Eu, Li
The effect that the luminance can be higher than that of the phosphor can be obtained. On the other hand, CaS: Eu, Li phosphor is CaS: E
Although the luminance is lower than that of the u, Li, Cl phosphor,
Is advantageous because it does not cause deterioration of the oxide cathode because it does not contain any.

Further, the embodiment of the fluorescent display tube of the present invention has been described with the fluorescent display tube having a structure in which the light emission of the phosphor film 5 is observed through the translucent face glass 9 as shown in FIG. The structure is not limited to this, and other structures may be the same as those of a known fluorescent display tube as long as the fluorescent film 5 contains the fluorescent material according to the present invention.

[0038]

As described above, the low-energy electron-beam-excited phosphor of the present invention is composed of calcium, sulfur, one kind of element selected from rare earth elements, and lithium. This has an effect that a luminance higher than that of a phosphor composed of one kind of element selected from rare earth elements can be obtained. Further, another low-speed electron beam-excited phosphor of the present invention is composed of one kind of element selected from calcium, sulfur and rare earth elements, lithium and chlorine, so that the luminance can be further improved. There is. In addition, the fluorescent display tube of the present invention is provided with a phosphor film in which the above-mentioned low-speed electron beam-excited phosphor and indium oxide are mixed. There is little effect on the emission of the cathode due to the decomposition of the body, and the service life can be extended.

[Brief description of the drawings]

FIG. 1 is a graph comparing the luminance of a phosphor according to a first embodiment and the luminance of a conventional phosphor.

FIG. 2 is a graph comparing the luminance of the phosphor according to the second embodiment and the luminance of the phosphor according to the first embodiment;

FIG. 3 is a cross-sectional view illustrating a configuration of a fluorescent display tube according to an embodiment of the present invention.

FIG. 4 is a graph showing a change in luminance due to a difference in the amount of In ₂ O ₃ added to the fluorescent display tube according to the present invention.

FIG. 5 is a graph showing a relationship between an excitation voltage and luminance of the fluorescent display tube according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Glass substrate, 2 ... Wiring layer, 3 ... Insulating layer, 3a ... Through hole, 4 ... Anode, 5 ... Phosphor film, 6 ... Grid, 7
... a cathode, 8 ... side walls, 9 ... face glass, 10 ... frit glass.

Claims (8)

[Claims] 1. A low-energy electron-beam-excited phosphor characterized by comprising lithium and one kind of element selected from calcium, sulfur and rare earth elements. 2. The slow electron beam excited phosphor according to claim 1, wherein one kind of element selected from the rare earth elements is europium. 3. The amount of sulfur is 1 mol, the amount of europium is 0.0001 mol or more and 0.1 mol or less, and the amount of lithium is 0.000 mol per mol of the calcium.
3. The low-energy electron beam excited phosphor according to claim 2, wherein the amount is 1 mol or more and 0.1 mol or less. 4. A low-energy electron-beam-excited phosphor comprising one kind of element selected from calcium, sulfur and rare earth elements, lithium and chlorine. 5. The slow electron beam excited phosphor according to claim 4, wherein one kind of element selected from the rare earth elements is europium. 6. The amount of sulfur is 1 mol, the amount of europium is 0.0001 to 0.1 mol, and the amount of lithium is 0.000 mol per mol of the calcium.
1 mol or more and 0.1 mol or less, and the chlorine is 0.00
The low-energy electron-beam-excited phosphor according to claim 5, wherein the molar ratio is from 01 mol to 0.1 mol. 7. A fluorescent display tube in which an anode and a cathode each having a phosphor film attached thereto are installed in a vacuum vessel, and wherein the phosphor film emits light by colliding electrons emitted from the cathode with the phosphor film. 7. A fluorescent display tube, wherein the film is formed of a mixture of the low-speed electron beam excited phosphor according to claim 1 and indium oxide. 8. The fluorescent display tube according to claim 7, wherein said indium oxide is mixed in a range of 5 wt% or more and 30 wt% or less with respect to said slow electron beam excited phosphor.