JPS62147633A - Fluorescent character display tube - Google Patents

Abstract

PURPOSE:To improve the emission of a cathode and increase its life by providing a getter film which can efficiently adsorb a sulfide-system gas in addition to a Ba getter film in the fluorescent character display tube using a sulfide- system phoshor. CONSTITUTION:Ba-system getter material for general gases is heated by high-frequency induction heating from outside of an envelope 1. Then, a Ba getter film 13 is formed to adsorb general gases such as H2, O2, Co, CO2 or the like. Next, a Ca-, Mg- or Mn-system getter material for a sulfide-system gas is heated to form a getter film 14 composed of at least one element selected from among Ca, Mg and Mn on the inner wall of the envelope 1. This getter film 14 positively and irreversibly adsorbs sulfide-system gases such as S, SO, SO2 or H2S to maintain high vacuum in the envelope 1. Therefore, the possibility of the cathode 10 being contaminated by the sulfide-system gases is reduced, thereby effectively preventing any deterioration of thermionic emission. Consequently, the luminance of the fluorescent character display tube can be maintained for a long time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fluorescent display tube that can be used as a display device for various electronic devices, household electrical appliances, computer terminals, car front panels, etc.

In particular, the present invention relates to a color fluorescent display tube using a sulfide phosphor as a phosphor used in the fluorescent display tube.

[Prior art]

Display devices using fluorescent display tubes generally use ZnO
: There were many devices that only emitted green light using Zn phosphors, but in recent years, as mentioned above, they have been used as display devices for various devices, and the data displayed has also become more diverse, so the display color has also changed to green. There is also a growing demand for display in colors such as not only red, blue, and yellow.

In addition, color graphic displays have become possible with fluorescent display tubes, and all colors can now be expressed by configuring three segments of red, green, and blue into one pixel.

The following color phosphors are generally well known as color phosphors used in these color fluorescent display tubes.

ZnS: ^g + In2O, ZnS: (Zn) Blue emission ZnS: Cu, A Q + In2O, green emission Z
nS: Au, A Q + In2O, lemon color luminescence (Z
no, gCdo, )S: Au, A Q + In2O
, yellow luminescence (Zno, sccio, )S: Ag
+ In2o3 Yellow-orange luminescent ZnS: Mn +
In2O, orange emission (7, no, 2Cdn, e) S:
Ag+In, 04 (ZnCd) S: Ag, AQ Red light emission (Zn, -2Cdx) S: Ag, A Q Green to red light emission However, the color phosphors already in use all contain sulfur in their components. Contains S. Therefore, these phosphors are collectively referred to as sulfide-based phosphors.

It has been found that when a color fluorescent display tube using such a sulfide-based phosphor is turned on, the following problems occur.

A conventional fluorescent display tube has a substrate 101 as shown in FIG.
Then, an anode conductor 106 is placed in an envelope 105 in which the side plate 102 and the front plate 103 are assembled by adhesively bonding the side plate 102 and the front plate 103 with a sealing material 104.
and a phosphor layer 107, a control electrode 100 disposed above the anode 108, and a filament-shaped cathode 110 stretched above the control electrode 109. Further, an electric field shielding film 111 is formed on the inner surface of the front plate by a transparent conductive film, and near the end,
A getter film 112 of Ba is deposited.

The filament-shaped cathode 110 has an oxide of an alkaline earth metal such as Da, Sr, Ca, etc. deposited on the surface of a thin wire of tungsten W in the form of a solid solution represented by (Ba, Sr, Ca)O, so that it can conduct electrons. Forms a release layer. When a voltage is applied to this filamentary cathode 110, electrons are emitted. The emitted electrons are accelerated and controlled by the control type [109] and impinge on the phosphor layer 107 of the anode 108, exciting the phosphor and producing a light-emitting display. but,
When the phosphor layer 107 is composed of a sulfide-based phosphor,
When the phosphor is excited, a part of the surface of the phosphor decomposes, and sulfide-based gases such as S, 5O1SO□, 11□8 are released from the phosphor layer 107, and the sulfide-based phosphor itself decomposition products may be scattered.

After sealing, the gases generated by lighting the fluorescent display tube generally include Co, C, etc., in addition to the sulfide gases mentioned above.
Although these gases are likely to be adsorbed and removed by the Ba getter film 112, the sulfide gases and decomposition products are also adsorbed and removed by the Ba getter film 112. Since there is a low possibility that it will accumulate in the envelope as the lighting time increases. When this sulfide-based gas adheres to the filamentary cathode, Ba, Sr, and C in the electron-emitting material layer are removed.
Since sulfides are formed by reacting with a, the emission characteristics of the cathode are significantly deteriorated. This phenomenon is generally referred to as the surface of the cathode being poisoned (voisoned).

When the filamentary cathode becomes poisoned, electrons are no longer efficiently emitted to the anode, resulting in a decrease in anode current and a sharp drop in the luminance of the phosphor layer, shortening the lifespan of the fluorescent display tube. It had some problems.

[Purpose of the invention]

Therefore, the present invention was made to solve the above problems, and in addition to the conventional Ba getter film, it efficiently adsorbs sulfide gas in a fluorescent display tube using a sulfide phosphor. 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]

To achieve the above object, the present invention includes a getter film on the inner wall of an envelope maintained in a high vacuum.

In a fluorescent display tube with a cathode formed with an electron emission layer and a phosphor layer of an anode that emits light due to the collision of electrons emitted from the cathode (some of which are partially sulfide-based phosphor), the getter film A part of the material contains at least one element selected from Mg, Ca, and Mn.

Here, it is preferable that the getter material disposed within the fluorescent display tube to form the getter film is a silicon compound of Mg, Ca, and Mn.

[For production]

The fluorescent display tube of the present invention is provided with a getter film containing at least one element selected from Mg, Ca, and Mn. It is known that the chemical properties of Mi Ca and Mn react with sulfide gases such as s, 'so, so, , 11□3, etc. to form sulfides. Therefore, by containing at least one element among Mg, Ca, and Mn in the getter film, it adsorbs and reacts with sulfide-based gases such as S-5O1SO2 and H2S generated in the envelope, and the sulfide-based gas This removes the ions and prevents them from reacting with the cathode.

Since the getter material that forms the getter film is installed in the envelope before the envelope is assembled and sealed, it is a necessary condition that it does not decompose at the heating temperature of 400 to 500°C during sealing. Become. Therefore, as a result of investigating each compound of MfC, Ca, and Mn by differential thermal analysis, it was found that CaSi, Mg
It was found that silicon compounds such as 2Si, MgSi, MnSi, MnSi2, etc. do not undergo deterioration and are stable. In addition, these silicon compounds are used as getter materials and heated in vacuum to utilize the difference in vapor pressure to obtain Ca, M[, M
It evaporates n-metal to form a getter film and has the function of adsorbing sulfide gas.

[Embodiment 1] The present invention will be described below with reference to embodiments shown in the drawings. 1st
FIG. 1 is a longitudinal sectional view of a fluorescent display tube according to the present invention.

In the figure, reference numeral 1 denotes an envelope, which includes an anode substrate 2 formed of a flat glass plate, a side plate 3, and a front plate 4, which are sealed with a glass sealing material. The gas inside the envelope 1 is evacuated through the exhaust pipe 5 and then sealed to maintain the inside of the envelope in a high vacuum state.

Further, an anode 8 consisting of an anode conductor 6 which is electrically connected to the wiring pattern and a sulfide-based phosphor layer 7 deposited on the anode conductor 6 is disposed on the anode substrate 2 in the envelope 1. ing.

A mesh-like control electrode 9 is disposed above the anode 8 as required, and further above a filament-like cathode 10 is stretched between cathode supports 11 and 11.

Further, a plurality of getter holding parts 12 are arranged at the end inside the envelope 1, and one of the getter holding parts 12a has a
Occurred inside envelope 1! A Ba-based getter material that adsorbs 1□, N2.02, H, 0, etc. is provided.

A Ba getter film 13 is formed on the inner wall surface of the envelope 1.

The other getter holding portion 12b is provided with a silicon compound containing at least one element selected from Mg, Ca, and Mn, which are getter materials of the present invention. - Examples are CaSi, Mg2Si, MgS
i, MnSi, MnSi2, etc., each of which uses the difference in vapor pressure to release Ca under appropriate getter scattering conditions.
, ME, and Mn can be formed on the inner wall surface of the envelope. This is the getter material.

It is molded by a press and fixed to the getter holding part 12b. The getter holding portion is made of a getter material of a metal material 1 having a high melting point, such as Ti, Ta, No, or the like.

In this embodiment, a link-shaped getter material is formed into a ring shape by press molding using Ba-A Q alloy and CaSi, and is fixed to getter holding parts 12a and 12b.

Inside the envelope 1 are an anode 8 and a control electrode 9. When installing the cathode 10, a getter holding part is also installed at the same time, and the envelope 1 is hermetically sealed with a glass sealing material. In the sealing step of fixing the sealing material, heating is performed at 400 to 500° C. in a carbon dioxide atmosphere, but the getter material [1a-A Q is not present]. After sealing, the inside of the envelope 1 is evacuated from the exhaust pipe 5, and the inside of the envelope 1 is
It is formed in a high vacuum state of about 0-' hr. Then, a Ba-based getter material for general gases is first heated by high-frequency induction heating from the outside of the envelope 1 to form a Ba getter film 13, and then a Ba-based getter material for general gases is formed. Adsorb gas. Next, Ca for sulfide gas,
Mg, Mn-based getter material is heated to produce Cci, Mg,
A getter film 14 of at least one type selected from Mn is formed on the inner wall surface of the envelope 1.

In this way, the Ca, Mg, and Mn getters 11 and 14 formed on the inner wall of the sealed envelope 1 are as follows:
The getter action actively and irreversibly adsorbs sulfide-based gases such as s, so, so, 112S, and maintains the degree of vacuum in the envelope 1 at a high vacuum state. Therefore, since the inside of the envelope 1 is maintained in a state where there are few harmful gases, the probability that the filament-shaped cathode 10 is contaminated with sulfide-based gas is reduced, and the deterioration of the thermionic emission characteristics of the cathode 10 is extremely reduced. It can be effectively prevented.

Therefore, it is possible to maintain the brightness of the fluorescent display tube for a long time.

In this embodiment, one Ba-based getter film 13 and one Ca-, Mg-, and Mn-based getter film 14 for sulfide-based gas are used.
Although an example in which they are formed at each location has been described, the effect will be greater by providing two or more locations depending on the size of the envelope 1 and the area in which the sulfide-based phosphor is used.

Further, as shown in FIG.
When a getter film is formed by a method called energized getter, in which a getter material is formed into a long and narrow groove using a material such as Fe, Ti, Ta, Mo, etc., a getter material is placed there, and an electric current is applied to heat the getter material, a getter film is formed. It is possible to freely increase the getter area.

By increasing the getter area, the adsorption area for sulfide-based gas increases, so it is possible to further increase the effect.

- FIG. 4 is a graph showing the relationship between cumulative lighting time and emissions of a fluorescent display tube when the Ca, Mg, Mn getter of the present invention is used in combination with a Ba getter and when only a conventional Ba getter is used.

The sulfide-based phosphor used was a blue-emitting phosphor of ZnS:Zn, and the lighting conditions were as follows: a cathode voltage of 2.5V, an anode voltage of 20V, and a grid voltage of 20V, and the lamp was continuously lit for 1000 hours.

The data indicated by A in the figure is when a Ca getter is used in combination with the Ba getter, and the getter material of the Ca getter is CaSi. The number of getters is one each.

The data indicated by B in the figure is when a Mg getter is used in combination with a Ba getter, and the getter material of the Mg getter is
It is MgSi. The number of getters is one each.

The data indicated by C in the figure is when a Mn getter is used in combination with a Ba getter. The getter material is MnSi.

The number is also one each.

The data shown in the figure is only for one Ba getter.

As can be seen from this graph, the emission characteristics are better when the Ca, Mg, and Mn getters of the present invention are used in combination than when the conventional Ba getter is used alone.

Especially the segments near the Ca, Mg, and Mn getter films.

The brightness does not drop and there is no uneven light emission.

〔Effect of the invention〕

As explained above, the present invention provides a fluorescent display tube using a sulfide-based phosphor with Mg, C, in addition to the conventional Ba getter.
Since a getter film containing at least one selected from a and Mn is formed, it becomes possible to adsorb sulfide gas generated from the phosphor layer during lighting. Therefore, the sulfide gas does not react with the alkaline earth metal of the filamentary cathode, and emission deterioration is reduced, resulting in an effect of lengthening the life of the fluorescent display tube.

Furthermore, since the getter material is a silicon compound of Mg, Ca, and Mn, it is not decomposed by the temperature and atmosphere of the sealing and exhaust steps, and a high-quality getter film can be formed, which has a great practical effect.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a fluorescent display tube of the present invention, FIG. 2 is a partially cutaway plan view of another embodiment of the present invention, FIG. 3 is a sectional view of a conventional example, and FIG. 4 FIG. 2 is a diagram showing the relationship between cumulative lighting time of a fluorescent display tube and emissions.

Claims (2)

[Claims] (1) A cathode that has a getter film on the inner wall of an envelope maintained in a high vacuum and has an electron emission layer formed thereon, and at least one of the phosphor layers of the anode that emits light due to the impact of electrons emitted from the cathode. A fluorescent display tube in which a portion of the getter film is provided with a sulfide-based phosphor, wherein a portion of the getter film contains at least one element selected from Mg, Ca, and Mn. . (2) the getter material forming the getter film is Mg;
The fluorescent display tube according to claim 1, which is a silicon compound of Ca and Mn.