JPS6264030A - Fluorescent character display tube - Google Patents

Abstract

PURPOSE:To improve the emission characteristic of a cathode thus to achieve long service life by arranging Ag getter film mainly composed of Ag in addition to conventional Ba getter film. CONSTITUTION:An anode conductor 9 mainly composed of graphite and sulfide system fluorescent material layer 10 applied onto said anode conductor 9 are arranged in an enclosure 1. A control electrode 14 is arranged above the anode 11 while a cathode 8 is stretched between the cathode supporters 7a, 7b further above. In order to absorb gas produced in the enclosure 1, getter 12 of Ba metal and a getter 13 containing Ag are arranged. Since sulfide system gas can be adsorbed efficiently, poisoning of filament cathode is prevented to improve the emission characteristic and the service life.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to displaying numbers, letters, figures, etc. by the light emitted from a phosphor disposed in an envelope, and to use the light emitted as a light source. The present invention relates to a fluorescent display tube capable of producing a fluorescent display tube, and particularly relates to an improvement of a getter film capable of adsorbing sulfide gas to the phosphor.

[Prior art]

In general, the fluorescent display tube 100 has a substrate 101, a side plate 102, and a front plate 103 bonded to each other using a sealing material 104, as shown in FIG.
An anode conductor 106 disposed on the substrate 101 and an anode conductor 1 are placed in an envelope 105 adhesively assembled by
Anode 108 consisting of a phosphor layer 107 deposited on 06
to be placed. A mesh-like control electrode 109 is provided above the anode 108, and a filament-like cathode 110 is stretched above the anode 108.

An electric field shielding film 111 made of a transparent conductive film is formed on the inner surface of the front plate 103, and a Ba getter film 112 is deposited near the end. 113 is a support portion for getter material.

Further, an exhaust pipe 114 is provided on the side plate 102, and an exhaust pipe 114 is provided on the side plate 102.
All the gas in the envelope 105 is exhausted by the exhaust pipe and then sealed, and the inside of the envelope 105 is maintained at a high vacuum state of about I x 10-' Torr.

115 is a contact lead of the electric field shielding film 111, and applies a negative voltage to the electric field shielding film 111.

When the cathode 110 of the fluorescent display tube 100 configured as described above is heated by applying electricity, electrons are emitted from the electron emissive coating layer on the surface of the cathode 110. In this state, the control electrode 109,
When a positive voltage is applied to the anode 108, the emitted electrons are controlled by the control electrode 109, and those that have passed through the control electrode 109 are absorbed into the phosphor layer 1.07 of the anode 108.
The phosphor is excited and emits light.

When the fluorescent display tube 100 is turned on in this way, the cathode 110
decomposition and release of gas absorbed by the phosphor layer 107 occur.

In addition, adsorbed and occluded gas is ejected from the inner wall of the envelope, internal parts, anode conductor 106, and insulating layer. If such gases exist and accumulate in the envelope, they can poison the surface active layer of the cathode, contaminate the surface of the phosphor, and deteriorate the thermionic emission characteristics of the cathode. This is one of the causes of deterioration of the display tube characteristics, such as a decrease in the luminance of the phosphor.

Therefore, conventionally, a getter material of Ba metal is disposed in the support part 113 in the envelope in order to adsorb and remove the gas generated by lighting after sealing, and after sealing, the getter material of Ba metal is flashed to remove the getter film 112 of Ba metal. The Ba getter film 112 was deposited near the end of the front plate 111, and the gas inside the envelope 105 was removed by adsorption to the Ba getter film 112.

Further, the structure shown in FIG. 5 is a front-emission type, that is, a phosphor layer 207 is deposited on a transparent anode conductor 206 disposed on a substrate 201, and the phosphor layer 207 emits light. This is a type in which the images are observed through the anode conductor 206 and the substrate 201. In this front-emission type fluorescent display tube, a getter support portion 213 was similarly provided, and a getter film 212 of Ba metal was formed on the back plate 203.

Incidentally, recently, fluorescent display tubes have also been used for display devices on the front panel of cars, and the display in the normal state is green.
A multi-color display having two or more display colors, such as a yellow display for a warning state and a red display for a dangerous state, or one pixel composed of three segments of red, green, and blue, Color fluorescent display tubes with full-color graphics that can express all colors are beginning to be adopted.

The phosphor used in this color fluorescent display tube is often a sulfide phosphor containing S atoms.

- For example, ZnS:Zn (blue), ZnS:Ag+I
n203 (blue), ZnS:Cu*A1”InzOi (
green), ZnS:Au, AI+In203 (yellow), ZnS
:Mn+In203 (orange), (ZnCd)S:Ag,C
1 (red), (ZnCd)S:Ag+In203 (red),
(ZnCd)S:Ag-Al (green to red), etc.

When a color fluorescent display tube using a sulfide-based phosphor as described above is turned on, electrons from the cathode 110 are transferred to the phosphor layer 1.
07, the phosphor is excited and emitted light, and the phosphor decomposes, releasing sulfide-based gases such as s, so, so□, and H2S, and the decomposition products of the sulfide-based phosphor itself become neutral. and dispersed in the form of ions.

In addition, H,0102,C, etc. may be removed from the decomposition of the cathode in the fluorescent display tube, parts such as the wall of the envelope, control electrodes, insulating layer, anode conductor, etc.
01CO2 gas etc. are released, but these gases are Ba
There is a high possibility that it will be adsorbed and removed by the metal getter film 112.

However, since the sulfide gases and ions are unlikely to be adsorbed by the Ba metal getter films 112 and 212, these sulfide gases accumulate in the envelope 105 and adhere to the cathode 110. Ba on the surface of the cathode 110,
It reacts with oxides of Ca and Sr, significantly deteriorating the emission characteristics, and as a result, the anode current decreases and the brightness of the fluorescent display tube decreases rapidly, resulting in a shortened lifespan.

[Purpose of the invention]

Therefore, the present invention has been made to solve the above-mentioned problems, and provides a method for efficiently adsorbing sulfide-based gases in addition to a Ba metal getter film in a fluorescent display tube using sulfide-based phosphors. The purpose of the present invention is to provide a fluorescent display tube with a long life by improving the emission characteristics of the cathode by providing a getter film that can be used as a getter film.

[Structure of the invention]

In order to achieve the above object, the present invention includes a cathode that emits electrons and an anode coated with a phosphor that emits light when the electrons collide, in an envelope maintained in a high vacuum. , in the fluorescent display tube having a getter film that adsorbs gas generated in the envelope and maintains a high vacuum state, a part of the getter film provided inside the envelope contains Ag. shall be.

[For production]

The fluorescent display tube of the present invention is provided with a getter containing Ag. The chemical properties of this Ag are S, 5O1SO
It is known that silver sulfide is formed by reacting with sulfide gas such as 2,11□S. Therefore, A in the getter film
By containing g, S generated in the envelope can be reduced.
, 5O1SO□, H, S, etc., and converts the sulfide gases into stable compounds such as silver sulfide AgS.

Furthermore, since there is a high probability that the sulfide gas is negatively ionized like S-, the effect of attracting and removing the sulfide gas can be made more efficient by applying a positive voltage to the getter layer.

[Example 1] An embodiment of the present invention will be explained with reference to the drawing shown in FIG.

FIG. 1 is a sectional view of a conventional type fluorescent display tube that displays color.

In the figure, 1 is an envelope of a fluorescent display tube. It is composed of a front plate 5 having translucency and provided facing the front plate 5. A glass plate is used as a material for the envelope 1, and is hermetically sealed by adhering it with a glass sealing material.

Since the gas inside the envelope 1 is sealed after being exhausted from the exhaust pipe 6, the inside of the envelope is maintained in a high vacuum state.

Inside the envelope 1, there is an anode 11 consisting of an anode conductor 9 mainly composed of graphite disposed on a substrate 2 and a sulfide-based phosphor layer 10 deposited on the anode conductor 9. It is arranged. A mesh-like control electrode 14 is arranged above the anode 11, and further above a filament-like cathode 8 is stretched between the cathode supports 7a and 7b. In addition, a Ba metal getter 1 is used to adsorb the generated gas in the envelope 1.
2 and a getter 13 containing Ag of the present invention are provided.

The cathode 8 has Ba, Sr, Ca on the surface of wmIw.
It is coated with alkaline earth metal oxides such as

At least a portion of the phosphor layer 10 is made of sulfide-based phosphors such as (ZnCd)S:Ag, C1
(red) is coated.

Further, the getter 12 is a conventional Ba metal getter, and is a Ba-A1. A Ba alloy such as Ba-Mg is formed into a ring shape as the getter material 17 and is called a getter ring. This getter ring is fixed to the getter support part 18. After sealing, the envelope 1 is heated from the outside by high-frequency induction heating to evaporate the getter material 17 and form a Ba film getter 20 near the end of the front plate 5. Since this Ba getter film 20 contains Ba, it has the effect of adsorbing gases such as H2, CO, CO, 02, etc.

Further, the getter 13 of the present invention includes a getter support part 16, a getter material 15 of an intermetallic compound containing Ag fixed on the getter support part 16, and an Ag containing Ag.
It is composed of a getter film 19 and contact leads 21.

The getter support portion 16 is made of a metal material having a higher melting point than the getter material, for example, T4. It is formed into a disk shape of Ta, Mo, etc., and supports the getter material 15.

The getter material is an intermetallic compound containing Ag, for example AgTi, AgT as a compound of Ag and Ti.
i, AgMo is a compound of Ag and Mo, and AgAl, AgA1... are compounds of Ag and Al. There are also compounds of Ag and Ni, compounds of Ag and Cr, etc.

In this example, a ring-shaped getter ring was molded using AgTi and fixed to the getter support portion 16. After the inside of the envelope 1 is evacuated, the exhaust pipe 6 is sealed, and the inside of the envelope 1 is brought into a high vacuum state of about 1X10-' Torr. Then, the conventional Ba getter is evaporated from the outside of the envelope 1 by high-frequency induction heating, and gases other than sulfide are adsorbed.
gTi, the getter material is heated to a temperature at which Ag is particularly selectively evaporated, so that Ag is deposited on the inner surface near the end of the front plate 5.
A getter film 19 is formed. Further, a contact lead 21 is provided in advance at a position where the Ag getter film 19 is to be formed, and its end is electrically connected to an external terminal.
The structure is such that a positive voltage can be applied to the g getter film 19.

In addition, the front plate 5 has a transparent conductive film 2 for shielding external electric fields.
2 is formed, and an Ag getter film 19 and a Ba getter film 20 are formed on this transparent conductive film. Therefore, the contact unique to the transparent conductive film 22 is omitted,
The configuration is such that the same voltage as that for the Ag getter film 19 can be applied.

Therefore, the Ag formed within the hermetically sealed envelope 1
The getter film 19 has S, 5O1S0 due to the getter action.
2.1 (23, etc.) is actively and irreversibly adsorbed to maintain the degree of vacuum in the outer chamber 1 at a high vacuum state.

Similar to the Ag getter 13, the Ba getter 12 is heated and evaporated to form a Ba getter film 20, and then adsorbs molecules such as 2, N2.02, H2O, etc. by getter action.

As described above, in addition to the remaining various gases inside the envelope 1, the sulfide gas generated after sealing is completely adsorbed and removed by the Ba getter film 20 and the Ag getter film 19. Therefore, the inside of the envelope 1 is maintained in a high vacuum state with few harmful gases, so the probability that the filament-shaped cathode 8 is contaminated is reduced, and deterioration of the thermionic emission characteristics of the cathode 8 is extremely effectively prevented. The brightness of the fluorescent display tube can be maintained for a long time.

Here, in the first embodiment described above, the Ba getter 12 and the Ag
Although an example in which one getter 13 is provided has been described, depending on the size of the envelope 1 and the usage ratio of the sulfide-based phosphor, there may be two Ba getters 12 and two Ag getters 13.
By providing a plurality of these, the effect becomes even greater.

[Embodiment 2] In this embodiment, in addition to the conventional Ba getter 22,
As shown in FIG. 4, in the case where an Ag getter is provided, an external terminal 27 is connected to the support part 26 of the Ag getter 23, and the current is formed so as to flow through the support part 26. to be called.

The material of the support portion 26 may be any material that has a large resistance and generates heat when energized, and may be metals such as Fe, Ti, Ta, Mo, or alloys containing these metals.

In the illustrated embodiment, Fe material is used to form a band-shaped groove 26a, and a getter material AgTi3 is placed in this groove. An external terminal 27 is welded to the support part 26, and the end thereof is led out to the outside of the envelope 1.

Since the current-carrying getter 23 of this embodiment is configured as one or more, after the air in the envelope 1 is evacuated from the exhaust pipe and sealed when a high vacuum state is achieved, the getter terminal z7 is When a current of about 8 A is applied to heat the support part 26, the Ag getter material in the band-shaped groove is heated and evaporated, and an Ag getter film 29 is formed on the facing front plate. 32 is a transparent conductive film for electrostatic shielding.

Since this current-carrying getter is constructed in this manner, the getter area can be freely increased.

Therefore, the adsorption area of sulfide-based gases such as s, so''-1SO, and H2S can be increased, making it possible to further enhance the effect.

〔effect〕

As explained above, the present invention provides a fluorescent display tube having a sulfide phosphor in at least a portion of the anode, in which an Ag getter film containing Ag as a main component is disposed in addition to the conventional Ba getter film. This configuration has the following effects.

(1) In a fluorescent display tube coated with sulfide phosphor, everything except the getter is formed under the same conditions.In the conventional product, only the Ba getter film is formed, and the Ba getter is the same as the transparent conductive film for preventing electric fields. Forming an Ag getter film together with the fluorescent display tube A to which a negative voltage has been applied and the Ba getter film of the present invention,
A negative voltage was applied to the Ba getter, and a negative voltage was also applied to the Ag getter film.A positive voltage was applied to the Ba getter film, and a positive voltage was also applied to the Ag getter film. A fluorescent display tube C including the fluorescent display tube C and the current-carrying getter of the second embodiment was formed. All Ag getter materials are AgTi3.

The graph in FIG. 7 shows the time-dependent changes in pulse emission measured by lighting the fluorescent display tubes A, B, C, and D under the same conditions.

From this result, the conventional product A had the worst initial value of pulse emission, which was around 34+nA. And it got worse as time passed, and after 100 hours it was 15m.
A: After 300 hours, the voltage dropped to 2mA, close to 0.

The next best is B, with one Ba getter and one Ag getter.
These are the cases where negative voltage is applied to each case.
The initial pulse emission is about 47 mA, and after 100 hours it drops to about 40 mA, but after that it does not drop to 300 mA.
Even after the lapse of time, the voltage remained at 40mA.

The next best option is C, which has the same structure as B and has a positive voltage applied. The initial value is also good, 60mA, 1
Even after 00 hours have passed, the emission value remains at 52 mA, and even after 300 hours, the emission value does not drop and remains at 50 mA or more.

The best thing was the energization getter. This is thought to be due to the fact that the area of the getter film is several times larger than in the case of the fluorescent display tubes B and C, so the effect is greater.

As can be seen from the above data, the fluorescent display tube of the present invention is provided with a getter containing an Ag getter, so even if a sulfide-based phosphor is provided, it can efficiently adsorb sulfide-based gas. As a result, the residual sulfide gas in the envelope is reduced, and the filamentary cathode is prevented from being poisoned, resulting in the effect of improving emission characteristics. Furthermore, it has a great practical effect in that a fluorescent display tube with a long life can be provided because of little emission deterioration.

In addition, Figure 1 shows that by applying a positive voltage to the Ag getter film, negatively charged sulfide gas can be absorbed more effectively. 2 is a longitudinal sectional view taken along line I-I in FIG. 1, and FIG. 3 is a partially cutaway front view showing a second embodiment of the present invention. FIG. 4 is a vertical cross-sectional view of the same embodiment, FIGS. 5 and 6 are vertical cross-sectional views of the conventional fluorescent display tube, and FIG. 7 is the emission of the conventional fluorescent display tube and the embodiment of the present invention. It is a figure which shows the relationship between continuous lighting time and continuous lighting time.

1... Envelope 8... Cathode 1o... Phosphor layer 11... Anode 19... Getter film 13...
- Getter patent applicant Futaba Electronics Co., Ltd. Figure 1 Figure 2 Figure 3 Figure 5 Figure 6

Claims (4)

[Claims] (1) A cathode that emits electrons, an anode coated with a phosphor that emits light when the electrons collide, and a gas generated in the envelope that is kept in a high vacuum. A fluorescent display tube having a getter film that adsorbs and maintains a high vacuum state, wherein a part of the getter film provided inside the envelope contains Ag. (2) The fluorescent display tube according to claim 1, wherein at least a portion of the phosphor is sulfide-based. (3) The fluorescent display tube according to claim 1, wherein the getter film is maintained at a positive potential directly or indirectly through another conductive film or component. (4) The fluorescent display tube according to claim 1, wherein the getter material is an intermetallic compound containing Ag.