JPS61243646A - Fluorescent character display tube - Google Patents

Abstract

PURPOSE:To obtain a fluorescent character display tube having excellent emission characteristic of cathode and long service life by providing a getter layer for effectively adsorbing the sulfide system gas produced from fluorescent material. CONSTITUTION:Upon driving to emit light from a fluorescent character display tube, thermions emitted from a cathode 30 are accelerated/controlled through a control electrode 29 to impinge against a fluorescent material layer 23. Since thin protection film of potassium silicate is applied onto the surface of said layer 34, the fluorescent material is hard to be decomposed even upon impingement of thermions to suppress production of sulfide system gas. It is assumed that the sulfide system gas is existing in the form of negative ions but since the getter layer 31 is maintained at positive potential, said negative ions are easily attracted and never separated. The gas is adsorbed reversibly with high efficiency through adsorbing function of potassium silicate. Consequently, the cathode 30 is scarcely deteriorated by the sulfide system gas resulting in lengthened service life of fluorescent character display tube 20.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a fluorescent display tube using a sulfide phosphor, such as a color fluorescent display tube, which has particularly excellent thermionic emission characteristics and a long life. This invention relates to a fluorescent display tube with a long filament cathode.

[Prior Art] Electrons emitted from a cathode are accelerated and controlled by a control electrode, and are caused to strike a phosphor layer in an anode section to produce a light-emitting display. Fluorescent display tubes are beginning to be adopted for multi-color displays that compactly combine display functions of two or more colors, and for multi-color or full-color graphics.

By the way, these types of fluorescent display tubes generally use sulfide, phosphor (for example, ZnS:Z,
n, ZnS: Ag+11 n203Zn5:C
u, AI+In 203. ZnS: 4u, Al
+In2O3(Zn,,Cd)S:Ag.

C1, Y 2. , o 3S: E u +s, n 0
2 etc.) are used.

However, when electrons from the cathode of a fluorescent display tube using the sulfide phosphor are made to collide with the anode to cause an anode current to flow. From sulfide phosphors H20, 02 and S, SO2, So,
Sulfide-based gases such as H2S are released, and the decomposition products of the sulfide phosphor itself are scattered.The oxide cathode is poisoned by these gas-splattered particles, and the electron emission characteristics of the cathode are
The so-called emission characteristics deteriorate significantly, the anode current decreases, and the brightness of the fluorescent display tube drops sharply.

Therefore, conventionally, methods as shown in FIGS. 5 and 6 have been proposed. That is, FIG. 5 is a cross-sectional view showing an example of a front-emitting fluorescent display tube, in which a transparent anode conductor formed in an arbitrary display pattern is provided on the inner surface of a transparent substrate l made of an insulating material. 2 is provided, and a phosphor layer 3 is thinly deposited on the surface of the anode conductor 2 to form an anode portion 4. The anode conductor 2 is connected to an external terminal 6 via a wiring conductor 5.
An insulating layer 7 is provided on the inner surface of the substrate l except for the anode section 4.

The anode section 4 faces the control electrode 9 and the cathode lO inside the envelope 8 maintained in a high vacuum, and the emitting phosphor layer 3 can be observed through the transparent substrate l. is configured to be

In addition to the above configuration, an adsorption layer 11 for gas generated from the sulfide phosphor is formed on the inner surface of the back plate 8a of the envelope 8. This adsorption layer 11 is formed by mixing carbon fine particles as a gas adsorbent with water glass as a binder, applying the mixture to the inner surface of the back plate 8a, and firing the mixture. Since this adsorption layer 11 has conductivity, it was configured to shield external electric fields by holding it at a negative potential.

Further, FIG. 7 is a sectional view showing an example of a type of fluorescent display tube in which the display is observed from the cathode side. A phosphor layer 14 is provided on the anode substrate 13 of the envelope 12 maintained in a high vacuum state.
An anode conductor 15 coated with is disposed to form an anode portion 16. A control electrode 17 and a cathode 18 are used above the anode section 16, and electrons emitted from the cathode 18 are accelerated and controlled by the control electrode 17 and impinge on the anode section 16, causing fluorescence. The body layer 14 is caused to emit light.

``The emitting phosphor layer 14 is observed through the transparent front plate 12a.

In addition to the above-mentioned second structure, a getter material 19 made of, for example, metal barium is provided at a corner of the envelope 12, facing the front plate 12a. The getter material 4
19 is vacuum-deposited on the inner surface of the front plate 12'a by heating after sealing to form a getter film 19a for adsorbing gas generated from the phosphor layer 14.

[Problem to be Solved by the Invention 1] However, the adsorption layer 11 provided in a front-emitting type fluorescent display tube is not very effective in adsorbing sulfide-based gas, and the cathode 10 is poisoned by the sulfide-based gas. There was a problem in that the emission characteristics of the cathode 1O deteriorated over time, and the luminance of the fluorescent display rapidly decreased.

Furthermore, in the fluorescent display tube having the structure shown in FIG. 7, the commonly used getter material 19 such as metallic barium is not very effective in adsorbing sulfide emitted from the phosphor when electricity is emitted, and the cathode Since the poisoning of sulfide phosphor cannot be prevented, the life of a fluorescent display tube using a sulfide phosphor is shortened.

[Purpose of the Invention] The present invention has been made to solve the above-mentioned problems, and is to provide a fluorescent display tube using a sulfide-based phosphor by efficiently discharging the sulfide-based gas generated from the phosphor. An object of the present invention is to provide a long-life fluorescent display tube with excellent cathode emission characteristics by providing a getter layer that can be well adsorbed. □ [Means for Solving the Problems] In order to achieve the above object, the present invention provides a cathode for emitting electrons in an envelope maintained in a high vacuum state, and a control device for accelerating the electrons. passing through the control electrode and the control electrode 1
．． In a fluorescent display tube, the anode portion is provided with at least a portion of a sulfide phosphor layer that emits light upon impingement of the electrons.
A getter layer containing at least one substance selected from the group consisting of potassium silicate, rubidium silicate, cesium silicate, and francium silicate is formed inside the envelope. do.

[Function] According to the configuration described in , the sulfide gas emitted from the sulfide phosphor layer is effectively adsorbed by the getter layer, and when the getter layer is heated, the getter layer is heated. The alkali metal silicate such as potassium silicate contained in the layer is deposited on the surface of the phosphor layer and serves as a protective layer, preventing the phosphor from being decomposed by electron bombardment and preventing sulfide-based Shows the effect of suppressing gas release itself.

[Example 1] Embodiments of the present invention will be described with reference to FIGS. 1 to 4.

Sulfide phosphor (for example, ZnS:Zn
ZnS:Ag+In 20:+ZnS:C
u, AI+In 20 3 ZnS:Au, AI
+In 20 3 (Zn,,Cd) S:A
g, CIY 203 S: E u + S n O
2), the getter layer that adsorbs gas is formed using various materials, but the inventor of the present invention particularly found that when the getter layer is formed using water glass graphite, It was discovered that the emission characteristics of fluorescent display tubes can be improved. It has also been found that when the potential of the getter layer is kept higher than that of the cathode, the emission characteristics are further improved. Therefore,
The inventors of the present invention further investigated which of the components constituting water glass graphite contributes to improving the emission characteristics.

Water glass graphite has graphite, water glass, Orca Seal (trademark), etc. as its main components. The main component of water glass is Na25iOa, and the main component of Orka Seal is K 2 Si O3.
It is a 28% aqueous solution of The water glass and Orca Seal have in common that they are both alkali silicate, but it was unclear which one contributes to improving the emission characteristics.

Therefore, an experiment was conducted in which a getter layer containing water glass and a getter layer not containing water glass were formed inside separate fluorescent display tubes, and the changes over time in the pulse emission values of the phosphor layers were measured and compared.

First, the following three types of fluorescent display tubes were manufactured as samples. Sample (A) is a fluorescent display tube having a getter layer formed of a material having almost the same composition as conventional water glass graphite, but configured so that the getter layer is held at a positive potential.

Sample (B) is a fluorescent display tube in which water glass is removed from the getter layer materials, and the getter layer is formed only of Habo graphite, Orca Seal, and alumina, and like sample (A), the getter layer is at a positive potential. configured to be retained. On the other hand, sample (C) is a conventional fluorescent display tube in which a getter layer formed of water glass graphite is maintained at a negative potential.

Next, the samples (A,), (B) and (C)
The lamp is driven to emit light and is left lit continuously for approximately 220 hours. During this time, the pulse emission values of the phosphor layers of each sample were measured at several points in time and plotted on a graph as shown in FIG. 3, which shows the change over time in the pulse emission values of each sample.

As shown in Figure 3, the sample with the highest pulse emission value is the sample (B) that does not contain water glass in the getter layer.
The next sample is sample (A), and both values are several times that of sample (C). From the above two results, it was found that Orcasil (potassium silicate) contributed to the improvement of emission characteristics. Furthermore, when comparing samples (A) and (B), it is found that holding the getter layer at a positive potential has a greater effect on improving the emission characteristics. This is thought to be because negative ions are formed within the getter layer, and if a positive potential is applied to the getter layer, the negative ions are easily attracted.

In addition, in the sample (B), when the content (weight %) of Orcaseal was changed, how the pulse emission value changed was measured, and the results shown in FIG. 4 were obtained. In other words, the content of Orcaseal is
It has been found that the emission characteristics are particularly improved when the amount is in the range of about 20% to about 43% of the total. Incidentally, even if the content is increased to the above-mentioned range -1-, the pulse emission value reaches an equilibrium state, so no more effect than the above can be expected.

Here, a fluorescent display tube according to an embodiment having a getter layer formed mainly of potassium silicate will be described.

FIG. 1 is a sectional view of a front-emission type fluorescent display tube. This fluorescent display tube 20 has an inner surface of a transparent insulating substrate 21.
A wiring conductor 25 is formed, and a pattern made of a transparent conductive film is formed on this wiring conductor 25 at least in the portion where the anode conductor 22 is divided according to the number of segments.

Further, a semi-transparent to opaque insulating layer 27 is formed on the surface of the substrate 21 on which the wiring conductor 25 is formed, leaving the anode conductor 22 in the segment shape.

Further, a thin phosphor layer 23 is applied to the -1- of the anode conductor 22 on which the insulating layer 27 is not applied, and the anode part 24 is
is formed. Note that this phosphor layer 23 is assumed to contain a whole sulfide-based phosphor at least in part. Further, the wiring conductor 2 covered with an insulating layer 27
5 is connected to the lead wire 26a and led out to the terminal connection portion of the external terminal 26. Further, a conductive film 27a for static prevention is applied to the insulating layer 27, if necessary. A control electrode 29 is provided below the anode portion 24, and a filament-shaped cathode 30 is stretched under the control electrode 29.

These control electrodes 29 and cathodes 30 are housed inside an envelope 28 composed of a substrate 21, a back plate 28a, and a side plate 28b, and the inside of the envelope 28 is kept in a high vacuum state. Retained.

A getter layer 31 is formed on the inner surface of the back plate 28a. To form this getter layer 31, first add about 20% alumina and about 30% graphite to potassium silicate of about 20 to 40% by weight, and then add an organic adhesive such as glycerin as a viscosity modifier. Add to make a paste. Then, this paste may be applied by a printing method to the inner surface of the back plate 28a before assembly, and then baked in the atmosphere at a temperature of about 50° C. to remove the organic adhesive. Note that since the gas generated when the adhesive material is fired evaporates from between the alumina particles, the gas does not remain in the getter layer 31 of the back plate 28a.

Then, as described above, the getter layer 31 is formed, the envelope 28 is assembled, and a fluorescent display tube is formed through a sealing process and a sealing process.

A portion of the potassium silicate contained in the getter layer 31 is evaporated by the heat within the fluorescent display tube or by electron bombardment, and adheres to the surface of the phosphor layer 23 to form a protective layer.

In the following configuration, when the fluorescent display tube 20 is driven to emit light, the thermoelectrons emitted from the cathode 30 are accelerated and controlled by the control electrode 29 and impinge on the phosphor layer 23. Since there is a thin protective film of potassium silicate on the surface of the phosphor layer 23, the phosphor is difficult to decompose even when bombarded with thermionic electrons, and the generation of sulfide gas is less than before. Become. Further, the generated sulfide gas is considered to exist in the form of negative ions, but since the getter layer 31 is held at a positive potential, the negative ions are not easily attracted and separated. Gas is reversibly and efficiently adsorbed by the adsorption action of potassium silicate and the like. Therefore, the cathode 30 is hardly poisoned by sulfide gas, and the life of the fluorescent display tube 20 is extended.

Next, the side in which the aforementioned getter layer is provided on the control electrode will be explained. FIG. 2 is a sectional view showing an example of a type of fluorescent display tube in which the display is observed from the cathode side. An anode conductor 36 coated with a phosphor layer 35 is disposed on the anode substrate 34 of the envelope 33 maintained in a high vacuum state, and the anode part 3
7 is formed. Note that this phosphor layer 35 contains at least a portion of the sulfide phosphor described above. □ Above the anode part 37, a control electrode 38 made of metal formed into a mesh shape and a filament-shaped cathode 39 are provided, and the electrons emitted from the cathode 39 are accelerated and controlled by the control electrode 38. , is configured to strike the anode portion 37 and cause the phosphor layer 35 to emit light. The emitting phosphor layer 35 is attached to a transparent front plate 40.
observed through.

Getter layers 41 are deposited on both sides of the control electrode 38, respectively. The constituent materials and deposition method of the getter layer 41 are the same as those described in the example of the front-emitting display tube 20. Therefore, the getter layer 41 contains not only potassium silicate, which is an insulator, but also graphite, which is a conductive material, and exhibits conductivity as a whole, which has an adverse effect on the electrical function of the control electrode 38. will not be given. At the same time, the getter layer 41 is always held at a positive potential during light emission display. Note that the control electrode 38
The structure can be such that the getter layer 41 is provided only on the anode part 37 side, but in that case, there is no need to particularly improve conductivity, so graphite may be omitted from the constituent materials of the getter layer 41. can.

The effect of the above configuration is that the front-emitting type fluorescent display tube 2
However, in this embodiment, the getter layer 41 is provided closer to the phosphor layer 35, so that the sulfide gas can be adsorbed more quickly. It will be.

[Example 2] Next, an example in which rubidium silicate (Rb2SiO3) is used instead of the potassium silicate will be described.

An experiment substantially similar to that in Example 1 was conducted using rubidium silicate instead of potassium silicate as the constituent material of the getter layer, and a sample fluorescent display tube was manufactured. As a result, it was found that rubidium silicate contributes to improving the emission characteristics of fluorescent display tubes.

Therefore, in a fluorescent display tube using a sulfide-based phosphor, a getter layer can be formed using substantially the same composition ratio and manufacturing method as in Example 1, except that potassium silicate is replaced with rubidium silicate.

Alternatively, rubidium silicate may be dispersed in water or an organic solvent to form a low-viscosity liquid, and the resultant layer may be applied to the anode side of the control electrode by spraying or coating, and then baked in the atmosphere to form a getter layer. can.

[Example 3] Next, an example in which cesium silicate (C32Si03) is used instead of the potassium silicate will be described.

An experiment substantially similar to that in Example 1 was conducted by using cesium silicate instead of potassium silicate as the constituent material of the getter layer, producing a sample fluorescent display tube. As a result, it was found that cesium silicate contributes to improving the emission of fluorescent display tubes.

Therefore, in a fluorescent display tube using a sulfide-based phosphor, the getter layer can be formed using substantially the same composition ratio and manufacturing method as in Example 1, except that potassium silicate is replaced with cesium silicate.

In addition, since cesium silicate is often obtained in a water-soluble state, fine particles of cesium silicate and graphite can be mixed and dispersed in water or an organic solvent to form a low viscosity liquid, and then applied to both sides of the control electrode using a spraying method. It is also possible to form a getter layer by depositing each by a coating method and then baking in the atmosphere.

In the embodiments described above, the getter layer can be constructed by replacing a substance such as potassium silicate with francium silicate, and in this case, the same effect as in Examples 1 and 2.3 can also be obtained. effect can be obtained.

Further, in the above embodiments, the getter layer was provided on the back plate or the control electrode, but it may be provided anywhere inside the envelope, for example, it may be formed on the inner surface of the side plate. .

[Effects of the Invention] As explained above, the present invention provides a fluorescent display tube having a triode structure having a sulfide phosphor layer.

A getter layer containing at least one substance selected from the group consisting of rubidium silicate, cesium silicate, and francium silicate is formed inside the envelope. Since the substances such as potassium silicate efficiently adsorb sulfide gases, poisoning of the cathode is prevented and a long-life fluorescent display tube with excellent emission characteristics can be realized.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a main part showing one embodiment of the present invention, FIG. 2 is a cross-sectional view of a main part showing another embodiment of the present invention, and FIG.
FIG. 4 is a table created by the present inventors showing the change over time in the pulse emission value of the fluorescent display tube according to the present invention in comparison with other fluorescent display tubes. In the embodiment, Orca Seal (
Figure 5 is a cross-sectional view of the main parts of a conventional front-emitting type fluorescent display tube, and Figure 6 is a table showing the relationship between the ratio of silicate (potassium silicate) and the pulse emission value of the fluorescent display tube of the example. , a perspective view of a back plate provided with a conventional getter layer, seventh
The figure is a sectional view of a main part of a conventional back-emitting fluorescent display tube. 20.32... Fluorescent display tube, 23.35... Fluorescent layer, 24.37... Anode part, 28.33... Envelope, 29.38... Control electrode, 30. 39... cathode,
31.41...Getter layer.

Claims (3)

[Claims] (1) In an envelope maintained in a high vacuum state, there is a cathode that emits electrons, a control electrode that accelerates and controls the electrons, and a sulfide that emits light when the electrons that have passed through the control electrode collide. In a fluorescent display tube having an anode portion in which a phosphor layer is disposed at least in part, a material selected from the group consisting of potassium silicate, rubidium silicate, cesium silicate, and francium silicate is contained inside the envelope. A fluorescent display tube comprising a getter layer containing at least one substance. (2) The fluorescent display tube according to claim 1, wherein the potential of the getter layer is maintained at a positive potential. (3) The fluorescent display tube is a front-emission type in which observation is made through a substrate of a luminescent display of a phosphor layer, and the getter layer mixed with a conductive material is an insulator on the inner surface of the envelope excluding the substrate. A fluorescent display tube according to claim 1, which is provided on a face plate.