JP2004146074A - Electron beam excited light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluorescent display tube for extending the life of a phosphor with an SrTiO3 red phosphor as a parent body by using a non-evaporation type getter without using any evaporation type Ba getters. <P>SOLUTION: The non-evaporation getter containing at least one type out of Zr, V, Fe, Ti, Mg, Mn, La is used for the getter of the fluorescent display tube using a phosphor with an SrTiO3 as a parent body is used, thus removing a carbon-based residual gas in the tube, and providing the fluorescent display tube or an electric field discharge type display, where a decrease in brightness is small and life characteristics have been greatly improved. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electron-beam-excited light-emitting device such as a fluorescent display tube (VFD) or a field emission display (FED) that is driven at a low voltage of 1 KV or less, and in particular, uses SrTiO3 as the anode phosphor. The present invention relates to the improvement of the luminance lifetime characteristic of an electron beam excited light emitting device using a phosphor as described above.
[0002]
[Prior art]
A fluorescent display tube, which is an example of a conventional electron beam excited light emitting device, is provided with an anode substrate formed of a sheet glass, a front plate disposed to face the anode substrate, and between the anode substrate and the front plate. Electrodes are formed in an envelope having a flat box-shaped structure composed of a frame-shaped side plate. The electrode includes an anode conductor formed on the inner surface of the anode substrate, an anode composed of a phosphor layer adhered to the surface of the anode conductor, a mesh grid above the anode, and a filament shape above the anode. Are disposed.
[0003]
Further, the inside of the envelope is evacuated by a vacuum pump from an exhaust hole or an exhaust chip provided in the envelope, and then sealed to form a high vacuum state. Then, when the fluorescent display tube is driven to emit light, that is, when electrons are emitted from the cathode, the electrons are accelerated and controlled by the grid, and are projected on the phosphor layer of the anode, the phosphor emits light. . However, the electrons also strike other than the phosphor. For example, when it collides with the space between phosphor particles, the inner surface of a mesh-like metal grid, or an envelope, the residual gas adhering thereto is blown out. A getter is provided in the envelope to absorb the residual gas and maintain a high vacuum state in the envelope.
[0004]
In a conventional getter, a getter material such as Ba or Al alloy is put in a getter container made of metal, and the getter container is fixed by welding to a getter mounting tab provided on a cathode support in an envelope. Then, the gas in the envelope is evacuated by the vacuum pump, and the carbon dioxide gas generated by the flushing of the filament cathode is evacuated, followed by sealing. After sealing, the getter container is heated by a high-frequency heater to evaporate Ba of the getter material in the container to form a Ba getter film in the envelope. The residual gas was adsorbed on the getter film. As described above, the getter of the conventional fluorescent display tube is called an evaporation type getter because the getter material is evaporated to form a getter film on the wall surface inside the envelope.
[0005]
On the other hand, various types of phosphors that emit light at a low voltage are used as the phosphors attached to the anode. Green ZnO: Zn phosphors are generally widely used, and as the red phosphors, phosphors based on SrTiO3 invented by the present applicant, for example, SrTiO3: Pr, Al phosphors are known. . (For example, refer to Patent Document 1.)
[0006]
When the SrTiO3: Pr, Al phosphor is used for a fluorescent display tube, the initial luminance shows a high value, but the luminance gradually decreases when driving continuously for several tens of hours, causing a luminance deterioration phenomenon. I know that. However, it has also been found that when a continuous lighting test is performed in a vacuum chamber test apparatus that is constantly evacuated by a vacuum pump, the above-described luminance deterioration phenomenon does not occur. Therefore, it is considered that one of the causes of the luminance degradation phenomenon is the influence of the residual gas in the fluorescent display tube. Therefore, as a measure against the luminance degradation, it has been proposed to form a protective film of a metal oxide on the surface of the phosphor to prevent the influence of residual gas. (For example, see Patent Document 2.)
[0007]
[Patent Document 1]
JP-A-8-85788 [Patent Document 2]
JP-A-8-283709
[Problems to be solved by the invention]
However, in the conventional countermeasures against luminance degradation, it is difficult to control the thickness of the protective film because a metal oxide protective film is formed on the surface of the phosphor. And the brightness is reduced. In addition, it is easy to apply a uniform film thickness to the phosphor in the laboratory when a small amount of the phosphor is used. Did not go to production.
[0009]
In order to elucidate the cause of the luminance degradation, the inventors of the present invention, in a fluorescent display tube, continuously illuminated SrTiO3: Pr, Al phosphor and non-illuminated SrTiO3: Pr, Al phosphor surface Was analyzed. The analysis was performed by X-ray photoelectron spectroscopy (ESCA). The result is shown in FIG.
As shown in FIG. 1, the peak of the phosphor in the non-lighting portion is 285 to 286 eV, which indicates a CH bond and a CO bond. The illuminated phosphor has a peak at 285 eV, indicating a CC bond. That is, it was found that carbides such as CO, CO2, C2H2, and CH4 existed on the surface of the phosphor in the non-lighted portion, but amorphous carbon C existed on the surface of the continuously lit phosphor.
[0010]
Furthermore, gas analysis was performed to determine what kind of gas would be generated when the fluorescent display tube was energized. FIG. 2 is a graph showing an analysis of residual gas in the tube before driving the fluorescent display tube and an analysis value of gas in the tube when the tube is energized. From this graph, the SrTiO3: Pr and Al phosphors show that carbon compounds such as CO, CO2 and CH4 and H2 and H2O are increased from the residual gas in the tube when the electron beam is irradiated. Was found to be released.
[0011]
From the above results, the mechanism of luminance degradation due to the residual gas of the SrTiO3: Pr, Al phosphor was considered as follows.
The residual gas CO, CO2, H2O in the fluorescent display tube is adsorbed on the Ba getter film. Then, the residual gas reacts with Ba by a reaction formula (primary reaction) shown in the following (1), (2) and (3) to synthesize a Ba compound such as BaO and BaC2, and is chemically adsorbed to the getter. .
2CO + 3Ba → 2BaO + BaC2- (1)
2CO2 + 5Ba → 4BaO + BaC2- (2)
H2O + Ba → BaO + H2 ↑ − (3)
[0012]
However, if there is residual H2O in the tube, C2H2 is synthesized from BaC2 synthesized by the reactions (1) and (2) according to the reaction formula (secondary reaction) shown in (4). Further, C2H2 reacts with H2 according to the reaction formula (tertiary reaction) shown in (5) to synthesize CH4.
BaC2 + H2O → BaO + C2H2 ↑ − (4)
C2H2 + 3H2 → 2CH4 ↑-(5)
As described above, even if a Ba getter exists in the fluorescent display tube, a carbide-based gas such as CO, CO2, or CH4 exists, and this gas is combined with Sr on the surface of the SrTiO3 phosphor of the anode. This bond is not a strong bond such as a chemical bond that forms a compound with Sr, but seems to be physically adsorbed. Then, when driving is performed, the electron beam from the cathode is irradiated to the SrTiO 3 phosphor, and the physically adsorbed carbide-based gas is decomposed by the energy of the electron beam, and amorphous carbon is formed on the surface of the phosphor. As a result, it was presumed that since the carbon forms a bypass in the electron beam excitation energy transfer mechanism, the electron beam excitation energy is not easily transmitted to the phosphor itself, and the luminous efficiency is reduced.
[0013]
Therefore, the present invention finds a getter capable of adsorbing a carbide-based gas in a tube without using the Ba getter, which causes the generation of a carbide-based gas, in an electron-beam-excited light-emitting device using a SrTiO3 phosphor. It is an object of the present invention to provide an electron-beam-excited light-emitting device having no deterioration in luminance life.
[0014]
[Means for Solving the Problems]
The electron beam excited light emitting device according to claim 1, wherein a getter for maintaining a degree of vacuum, a cathode for emitting electrons, and a phosphor for emitting light by projecting the electrons are provided in a vacuum envelope. In the electron-beam-excited light-emitting device having an anode as described above, the phosphor is a phosphor based on SrTiO3, and the getter is at least one selected from the group consisting of Zr, V, Fe, Ti, Mg, Mn, and La. It is characterized by containing a kind.
[0015]
An electron beam excited light emitting device according to a second aspect is characterized in that the phosphor based on the SrTiO3 according to the first aspect is SrTiO3: Pr.
[0016]
An electron beam excited light emitting device according to a third aspect is characterized in that the phosphor based on SrTiO3 according to the first aspect is SrTiO3: Pr, Al.
[0017]
An electron beam excited light emitting device according to a fourth aspect is characterized in that the getter according to the first aspect is a non-evaporable getter.
[0018]
An electron beam excitation light emitting device according to a fifth aspect is characterized in that the electron emitting cathode according to the first aspect is a filament-shaped oxide cathode.
[0019]
An electron beam excited light emitting device according to a sixth aspect is characterized in that the electron emitting cathode according to the first aspect is a field emission type cathode.
[0020]
An electron-beam-excited light-emitting device according to claim 7, wherein the electron is emitted between a cathode that emits the electron according to claim 1 and an anode on which a phosphor that emits light by projecting the electron is attached. It has a grid for acceleration and control.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Therefore, attention was paid to metals of Zr, V, Fe, Ti, Mg, Mn, and La as getters used in the present invention. It is known that a simple substance or an alloy of these metals adsorbs a gas when the surface is activated by applying heat. The shape is formed into various shapes such as a plate shape and a ring shape, and the present invention uses a plate-shaped getter.
[0022]
The activation can be sufficiently activated by heating at 500 ° C. for 10 minutes in a vacuum maintained at a vacuum degree of 10 −4 or less in the tube. When the temperature is lower than 500 ° C., activation can be performed by increasing the time. As described above, the getter function is performed only by heating without evaporating in a vacuum, and is called a non-evaporable getter.
[0023]
The method of heating the getter may be a method using high-frequency induction heating, a method using an electric current flowing through the metal base of the getter, or a method using a laser beam or an infrared lamp from outside the envelope. In the manufacturing process of the fluorescent display tube, heat is applied from the outside during sealing to make it easier to release gas, and this heat can be used. In either case, the degree of vacuum in the envelope is maintained at 10-4 torr or less to activate the getter.
[0024]
As described above, these non-evaporable getters are heated to activate the surface of the getter, so that residual gases such as CO, CO2, CH4, H2, and H2O in the tube are chemically adsorbed to the getter.
[0025]
The position where the getter is attached may be anywhere within the envelope, but in the case of the present invention, it is preferable to attach the getter in the vicinity of the anode in order to allow the residual gas to be chemically adsorbed to the getter before being attached to the anode. .
[0026]
Example 1
The present invention will be described in detail with reference to the embodiment shown in FIG.
A wiring conductor 2 is formed of an aluminum thin film in the form of a wiring pattern on the inner surface of an anode substrate 1 made of sheet glass, which is a part of a flat box type envelope, by photolithographic means. The insulating layer 4 formed with 3 is laminated by a thick film printing method. Next, after the conductive paste 5 is filled in the through holes 3 by a thick film printing method, an anode conductor 6 is formed by a thick film printing method. Further, SrTiO3: Pr, Al phosphor 7 is applied to the surface of the anode conductor 6 by screen printing.
[0027]
A mesh grid 8 is arranged on the anode substrate 1 at a position where the grid 8 is electrically connected to the wiring conductor 2. A cathode support 9 made of a metal plate is provided at both ends of the anode substrate 1. An anchor and a support for stretching the filament cathode 10 are fixed to the cathode support 9.
Further, a getter mounting tab 11 for mounting a getter is mounted, and a getter 12 is welded and fixed to the getter mounting tab 11. A box-shaped full-surface container comprising a side plate 13 and a front plate 14 was covered on the anode substrate 1 and sealed with a glass adhesive, and the inside of the envelope was evacuated to form a vacuum.
[0028]
Next, the getter will be described in detail.
The getters focused on SAES St121 and St122. St121 is composed of Ti and a Zr-Al alloy, and St122 is composed of Ti and a Zr-V-Fe alloy.
In any case, the residual gas such as CO, CO2, CH4, H2, and H2O in the tube can be removed by chemisorption, but the feature is that St121 is less likely to be damaged even when heated in air. . In the manufacturing process of the fluorescent display tube, after a getter is attached, a heating process such as a sealing process and an exhaust process is performed. St121 is suitable for a fluorescent display tube because once it is heated, if it is activated again, the same adsorption characteristics as an unused one can be obtained. Therefore, this St121 getter was used for a fluorescent display tube using SrTiO3: Pr, Al phosphor. If a getter containing at least one kind of Zr, V, Fe, Ti, Mg, Mn, La is used, the same effect as that of the St121 getter can be expected.
[0029]
As a comparative example, a fluorescent display tube using a conventional Ba getter as a getter was manufactured in the same manner as in the example of the present application except for the getter among the preparation conditions.
[0030]
The life test of the fluorescent display tubes of this example and the comparative example was performed. FIG. 3 is a graph showing the continuous lighting time and the luminance remaining ratio. After lighting for 1000 hours, the fluorescent display tube using the conventional Ba getter has a luminance remaining ratio of 30%, but the fluorescent display tube using the Ti and Zr-V-Fe getter of this embodiment is The luminance residual ratio was 65%, which was more than twice the conventional ratio.
[0031]
As described above, the present invention has been described in the embodiment of the fluorescent display tube. However, in a field emission display (FED) using a field emission cathode (FEC) as a cathode, similarly to the fluorescent display tube, SrTiO3: Pr, Al phosphor is used. By using a getter containing at least one of Zr, V, Fe, Ti, Mg, Mn, and La, a long-life FED can be formed.
[0032]
【The invention's effect】
As described above, the present invention includes at least one or more of Zr, V, Fe, Ti, Mg, Mn, and La in a fluorescent display tube or a field emission display using a phosphor having SrTiO3 as a base. The use of the getter has the effect of providing a fluorescent display tube or a field emission display with a reduced luminance and a greatly improved life characteristic even when continuously lit.
[Brief description of the drawings]
FIG. 1 is a graph showing ESCA analysis results of a non-lighted portion and a continuously lighted portion of a SrTiO3 phosphor.
FIG. 2 is a graph showing analysis values of residual gas in a fluorescent display tube using a SrTiO3 phosphor and gas released during energization.
FIG. 3 is a graph showing a conventional example of a fluorescent display tube using a SrTiO3 phosphor and a result of a life test of the present application.
FIG. 4 is a sectional view showing a main part of the fluorescent display tube of the present example.

Claims (7)

An electron beam-excited light-emitting device having a vacuum envelope, a getter for maintaining a degree of vacuum, a cathode for emitting electrons, and an anode on which a phosphor that emits light by projecting the electrons is attached. Is a phosphor having SrTiO3 as a base material, wherein the getter contains at least one selected from the group consisting of Zr, V, Fe, Ti, Mg, Mn, and La. Light emitting device. 2. The electron beam excited light emitting device according to claim 1, wherein the phosphor having SrTiO3 as a matrix is SrTiO3: Pr. 2. The electron beam excited light emitting device according to claim 1, wherein the phosphor having SrTiO3 as a base is SrTiO3: Pr, Al. 2. The electron beam excited light emitting device according to claim 1, wherein the getter is a non-evaporable getter. 2. The electron beam excited light emitting device according to claim 1, wherein the cathode that emits electrons is a filament-shaped oxide cathode. 2. The electron beam excited light emitting device according to claim 1, wherein the cathode that emits electrons is a field emission cathode. 2. The electron beam excited light emitting device according to claim 1, further comprising a grid for accelerating and controlling the electrons between a cathode that emits the electrons and an anode on which a phosphor that emits light by projecting the electrons is attached.

Images