JPH07312167A - Manufacture of cold cathode for display discharge tube - Google Patents

Abstract

PURPOSE:To realize technique whereby a surface of a cold cathode base body can be coated with an emitter substance, without adsorbing Xe while excellent in sputter resistance with a small work function, by a method except high temperature heat treating and plasma flame spraying. CONSTITUTION:In a method of manufacturing a cold cathode 18 of DC-PDP1O, to a surface of a cold cathode base body 18a consisting of conductive material, paste, formed by mixing GdB6 (gadolinium hexaboride), BaAl2O4 (barium aluminate), organic metal (Al alkoxide or carboxylic salt) formed in metal oxide by burning and a solvent containing thinner, is applied and dried. By burning this paste heated to a decomposition temperature or more of the organic metal, an emitter layer 18b is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a cold cathode for a display discharge tube, and more particularly, to forming an emitter layer on the surface of a cathode substrate to reduce discharge voltage and improve spatter resistance. And a method for manufacturing a cold cathode for a display discharge tube.

[0002]

2. Description of the Related Art For direct current driven plasma display panels and display discharge tubes such as neon pilot lamps,
A cold cathode made of a conductive material such as Ni or Fe is used. Further, these conductive materials generally have problems that they have a large work function and a high discharge voltage, and that they have a low melting point and are vulnerable to ion bombardment, so that sputtering due to discharge is severe. The emitter material is deposited on the surface of the cold cathode to form an emitter layer, thereby reducing the discharge voltage and improving the sputtering resistance. Further, LaB ₆ (lanthanum hexaboride) has been used as one of the emitter materials constituting this emitter layer.

Indeed, this LaB ₆ has a melting point of about 260.
It has a relatively high temperature of 0 ° C and has little wear due to ion bombardment. However, it is hard to say that the work function of LaB ₆ is sufficiently small (about 2.7e).
V), and therefore the discharge voltage reduction, was still unsatisfactory. Further, since LaB ₆ has good conductivity, discharge can be realized only by energizing a part of the emitter layer, and negative glow due to discharge cannot be widely and uniformly generated on the cold cathode. This is a problem in that it causes uneven brightness.

Therefore, an attempt has been made to form an emitter layer from a substance obtained by mixing BaAl ₂ O ₄ with this LaB ₆ . That is, since the work function of BaAl ₂ O ₄ is remarkably smaller than that of LaB _{6 and the} function of reducing the discharge voltage is remarkable, mixing both at an appropriate ratio lowers the work function of the entire emitter material. Can be achieved. Further, since BaAl ₂ O ₄ is an oxide and lacks conductivity itself, the conductivity of the entire emitter layer is reduced as compared with the case of using LaB ₆ alone. Therefore, in order to secure the necessary amount of current, the entire surface of the emitter layer is involved in the discharge, and as a result, it becomes possible to generate the negative glow in a wide range.

[0005]

However, this L
Since the emitter material composed of a mixture of aB ₆ and BaAl ₂ O ₄ has a very high melting point, it has been very difficult to deposit it on the surface of the cold cathode. For example, in order to form the emitter layer by forming the above-mentioned emitter material into a paste using an appropriate vehicle and depositing it on the surface of the cathode substrate by thick film printing, etc. It is necessary to perform high-temperature heat treatment, and thus large-scale equipment is required. Further, in the case of a cold cathode for a plasma display panel, it is necessary to heat the entire glass substrate on which the cathode substrate is formed in advance, which may result in deformation of the glass substrate. There is also a method of depositing the above-mentioned emitter material on the surface of the cathode substrate by plasma spraying, but it is difficult to precisely control the deposition area, and therefore, in the plasma display panel, the dot pitch of the discharge cell is increased. Precision (0.31 mm or less)
However, there was a pity that it could not cope with the finer display.

Further, so-called ultraviolet light emission, in which Xe gas for ultraviolet radiation is sealed, a fluorescent substance is arranged around the cold cathode, and the fluorescent substance is excited by the ultraviolet light generated by the discharge to obtain a desired emission color. -Type display discharge tube, when the emitter layer of the cold cathode is formed of a mixed material of LaB ₆ and BaAl ₂ O ₄ , there is a problem that the brightness thereof decreases and the emission color changes with the passage of time. Occurs. As a result of various investigations to investigate the cause, the inventors have found that Xe, which is an ultraviolet radiation gas, is gradually adsorbed by LaB ₆ which constitutes the emitter material.
(X-ray microanalyzer) was used for verification. That is, since the amount of Xe decreases and the amount of ultraviolet rays generated decreases, the amount of light emitted from the phosphor itself decreases and the brightness of the display tube decreases.

The present invention has been made in view of the above-mentioned drawbacks of the conventional example, and an object thereof is to provide an emitter material which has a small work function and is excellent in spatter resistance and which does not adsorb Xe. The purpose is to realize a technique capable of depositing on the surface of the cathode substrate by a method other than high temperature heat treatment or plasma spraying.

[0008]

In order to achieve the above object, a method for producing a cold cathode for a display discharge tube according to the present invention is a method for producing a cold cathode for a display discharge tube comprising an emitter layer formed on the surface of a cathode substrate. At the surface of the cathode substrate made of a conductive material, GdB ₆ (gadolinium hexaboride) and Ba
A paste formed by mixing Al ₂ O ₄ (barium aluminate), an organic metal that becomes a metal oxide by firing, and a solvent is applied and dried, and this is heated at a temperature equal to or higher than the decomposition temperature of the organic metal. And is then fired. Examples of the organic metal include Al and Si alkoxides or carboxylates. Alternatively, a substance such as an alkaline earth metal element, an alkali metal element, an alkoxide of a rare earth element, or a carboxylate which becomes a metal oxide having emitter characteristics by firing may be selected.

[0009]

[Action] GdB ₆ belongs to the hexaboride of the same rare earth elements as LaB _6, similarly to the LaB _6, has excellent sputtering resistance. Further, since GdB ₆ does not have the property of adsorbing Xe unlike LaB ₆ , it is possible to use an emitter substance containing GdB ₆ in a UV-emission type display discharge tube in which Xe is enclosed as a UV-emission gas. , Xe does not cause deterioration of display characteristics.

Further, GdB ₆ has a work function that is not always sufficiently small, or has a conductivity that is too good, so that luminance unevenness is likely to occur in the display discharge tube.
₆ is common, but these defects are eliminated by being mixed with BaAl ₂ O ₄ .

Further, the mixed substance of GdB ₆ and BaAl ₂ O ₄ itself has a high melting point, and therefore, melting itself and depositing it on the surface of the cathode substrate is not possible with LaB ₆ and BaAl ₂ O _4.
As with the mixed material with O ₄ , it is very difficult. However, as described above, when an organic metal (for example, an alkoxide of Al) is mixed in a mixed substance of GdB ₆ and BaAl ₂ O ₄ and heated above the decomposition temperature of the organic metal,
Metal oxide (Al ₂ O ₃₎ is generated and thus the metal oxide can function as a binder to fix the particles of GdB ₆ and BaAl ₂ O _4, without melting the GdB ₆ and BaAl ₂ O ₄ itself The emitter layer can be firmly formed on the surface of the cathode substrate. Moreover, the decomposition of the organic metal is
Since it can be realized by performing the heat treatment at a relatively low temperature of about 100 ° C., it can sufficiently cope with the normal working temperature (400 ° C. to 600 ° C.) in the manufacturing process of the display discharge tube.

Further, since the paste containing the emitter material is applied to the cathode substrate and fired, the deposition area can be controlled extremely finely by using, for example, the thick film printing technique. Therefore, if the present invention is applied to the cold cathode of the plasma display panel, the dot pitch of the discharge cell can be made finer.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method of manufacturing a cold cathode for a display discharge tube according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a dot-matrix type DC drive type plasma display panel as a display discharge tube (hereinafter referred to as “DC-P”).
This is referred to as "DP"). This D
The C-PDP 10 includes a rear substrate 12 made of an insulating material such as flat glass, and a front substrate 14 made of a transparent insulating material such as flat glass, which are opposed to each other with a predetermined gap therebetween, and the peripheral edges of both substrates are made of low-melting glass. The airtight container 16 is formed by sealing with a sealing material (not shown) such as the above, and a discharge gas is sealed in the internal space of the airtight container 16. This discharge gas is composed of a mixture of Xe as an ultraviolet radiation gas and He, Ar, Ne or the like.

As shown in FIG. 2, a plurality of strip-shaped cathode base bodies 18a made of Ag / Pd paste or the like are arranged in parallel on the opposite surface of the rear substrate 12. In addition, each cathode substrate 18
The surface of a has GdB ₆ and BaA as emitter materials.
An emitter layer 18b having a structure in which particles of l ₂ O ₄ are bonded by a metal oxide as a binder is formed. This cathode substrate 18a and the emitter layer 18b covering the surface of the cathode substrate 18a form a cold cathode of the DC-PDP 10.
18 are composed.

On the opposite surface of the front substrate 14, a plurality of strip-shaped transparent anodes 20 made of a NESA film (SnO ₂ ) or an ITO film (In ₂ O ₃ .SnO ₂ ) are arranged in parallel. Also,
First partition walls 22a for partitioning the transparent anodes 20 and the transparent anodes
Lattice-shaped barrier ribs 22 having second partition walls 22b that divide 20 at predetermined intervals in the longitudinal direction are formed. The barrier rib 22 is made of an insulating material such as glass. Further, a spacer 24 made of an insulating material such as glass is formed at the intersection of the barrier rib 22 with the first partition 22a and the second partition 22b.

The cold cathode 18 and the transparent anode 20 are arranged so as to be opposed to each other with a predetermined distance therebetween, and the discharge cells surrounded by the barrier ribs 22 at each intersection.
A large number of 26 are formed in a dot matrix shape. Although not shown, each discharge cell 26 is coated with a phosphor corresponding to a desired emission color. Further, since the end surface of the spacer 24 is in contact with the facing surface of the back substrate 12, the spacer 24 is provided between each end surface of the first partition wall 22a and the second partition wall 22b and the facing surface of the back substrate 12. A gap 28 corresponding to the height is formed.

Therefore, a transparent anode is supplied from a power source (not shown).
When a DC voltage is applied between the cold cathode 20 and the cold cathode 18, the discharge cell
A discharge is generated within 26 and ultraviolet rays are generated. This ultraviolet ray excites the phosphor in the discharge cell 26, and light having a predetermined emission color is transmitted to the outside through the transparent anode 20 and the front substrate 14. By selectively executing this voltage application via a control / driving circuit (not shown), discharge light emission can be generated in a desired discharge cell 26, and arbitrary characters or figures can be displayed on the front substrate 14. . It should be noted that the flow of ions between the discharge cells 26 is ensured through the gap 28.

The cold cathode 18 is formed by the following procedure. First, an Ag / Pd-based paste is thick-film printed on the opposite surface of the rear substrate 12 to apply the base material of the cathode substrate 18a, which is dried and then sintered to form the cathode substrate 18a. Next,
A paste containing an emitter material is applied to the surface of the cathode substrate 18a by thick film printing to a thickness of about 20 μm. This paste is about 50 to 54% by weight of an emitter material prepared by mixing GdB ₆ particles and BaAl ₂ O ₄ particles in a predetermined ratio in a solvent containing a thinner for dilution, and about 2 parts of an alkoxide or carboxylate of Al. It has a certain degree of viscosity because it is added by weight%. After printing this paste, it is dried at a temperature of 150 ° C. for about 10 minutes, and then heated and baked at a temperature of 500 ° C. or higher for 10 minutes to complete the cold cathode 18. During the firing process, the Al alkoxide or carboxylate is decomposed into Al ₂ O ₃ , which is the emitter material (G
It functions as a binder for firmly binding the particles of dB ₆ and BaAl ₂ O ₄ ). Further, in the firing process, the solvent in the paste is burned. Note that Gd
The mixing ratio of the B ₆ particles and the BaAl ₂ O ₄ particles is not particularly limited, and can be appropriately set depending on the balance with various discharge conditions. However, in general, it can be said that better emitter characteristics can be realized by setting the ratio of GdB ₆ particles higher than the ratio of BaAl ₂ O ₄ particles.

In the above description, an example in which an alkoxide or carboxylate of Al is mixed in the paste for forming a binder for binding particles of the emitter material has been shown, but the present invention is not limited to this. That is, any organic metal that becomes a metal oxide by firing can be widely adopted as a material for forming a binder.
Alkaline earth metal elements, alkoxides of alkali metal elements or rare earth elements, carboxylates and the like are applicable.

For example, a mixture of barium butyrate, which is an alkoxide of Ba (barium), and strontium propionate, which is an alkoxide of Sr (strontium), is mixed as a binder-forming substance into a paste, and the decomposition temperature of these alkoxides (about When heated at 100 ° C. or higher, a binder composed of a mixed metal oxide of barium oxide and strontium oxide (BaO.SrO) is formed. Other organic metals include barium lauryl oxide (for forming BaO), barium octylate (for forming BaO), magnesium caprate (for forming MgO), a mixture of barium butyrate and lanthanum butyrate (BaO.La ₂
(For forming O ₃ ).

The metal oxides (BaO.SrO,
BaO, MgO, and BaO.La ₂ O ₃ ) have excellent emitter characteristics by themselves, and therefore, by adopting these as binders that combine GdB ₆ and BaAl ₂ O ₄ , the discharge voltage at the cold cathode 18 is reduced. And reduction of spatter can be more effectively realized.

The present invention can be applied not only to the DC-PDP 10 described above, but also to the production of cold cathodes incorporated in various display discharge tubes such as neon pilot lamps, glow lamps, and numerical display discharge tubes. For example, as shown in FIG. 3, a rod-shaped electrode base body 32a made of a conductive material such as Ni is attached to the tips of a pair of lead wires 30, 30 made of Dumet wire.
32a is connected, emitter layers 32b and 32b are formed on the surfaces of the electrode bases 32a and 32a to form discharge electrodes 32 and 32, and both discharge electrodes 32 and 32 are arranged in parallel with a predetermined discharge gap 34. Then
This can also be applied to a display discharge tube 38 of the type in which an airtight container 36 formed by fusing the upper and lower ends of a cylindrical glass tube is sealed together with a predetermined discharge gas. That is, the discharge electrode
32 is GdB ₆ and BaAl ₂ O on the surface of the electrode substrate 32a.
₄ and an organic metal that becomes a metal oxide by firing and a suitable solvent are applied and dried, and then heated at a temperature equal to or higher than the decomposition temperature of the organic metal to form the electrode base 32a. It is formed by sintering the emitter layer 32b on the surface. When the display discharge tube 38 is driven by direct current, one of the discharge electrodes 32 serves as a cold cathode, and when driven by alternating current, the cold cathode is alternately switched according to the polarity change of the power supply.
32.

[0023]

As described above, according to the present invention, an emitter layer formed by firmly bonding particles of GdB ₆ and BaAl ₂ O ₄ with a metal oxide binder by firing at a relatively low temperature is formed. , Can be formed on the surface of the cold cathode. That is, since the normal working temperature in the manufacturing process of the display discharge tube can be sufficiently coped with, it is not necessary to prepare special equipment for high temperature heat treatment, and there is no fear that the shape of the display discharge tube is thermally deformed.

Further, since the emitter layer is formed by applying a paste containing GdB ₆ and BaAl ₂ O ₄ on the cathode substrate and baking it, for example, if a thick film printing technique is used,
The formation region of the emitter layer can be controlled extremely finely. Therefore, if the present invention is applied to the formation of the cold cathode in the plasma display panel, the dot pitch of the discharge cell can be made finer.

Further, GdB ₆ contained in the emitter material
Differs from LaB ₆ in that it has no property of adsorbing Xe. Therefore, even if the present invention is applied to an ultraviolet radiation type display discharge tube in which Xe is encapsulated, the display characteristics are deteriorated due to the decrease of Xe. There is no.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of a display discharge tube including a cold cathode formed according to the present invention.

FIG. 2 is a schematic perspective view showing a cold cathode of the display discharge tube.

FIG. 3 is a schematic cross-sectional view showing another example of a display discharge tube including a cold cathode formed according to the present invention.

[Explanation of symbols]

 10 DC-PDP 12 Rear substrate 14 Front substrate 16 Airtight container 18 Cold cathode 18a Cathode base 18b Emitter layer 32 Discharge electrode 32a Electrode base 32b Emitter layer 38 Display discharge tube

Claims (4)

[Claims] 1. A method for manufacturing a cold cathode for a display discharge tube comprising an emitter layer formed on the surface of a cathode substrate, wherein GdB ₆ (gadolinium hexaboride) and BaAl ₂ are formed on the surface of the cathode substrate made of a conductive material. O ₄ (barium aluminate),
A display discharge characterized by applying a paste obtained by mixing an organic metal to be a metal oxide by firing and a solvent, drying the paste, and heating the paste at a temperature equal to or higher than the decomposition temperature of the above-mentioned organometal to be fired. Method for manufacturing cold cathode for tube. 2. The organic metal is Al (aluminum).
Alternatively, it is an alkoxide or carboxylate of Si (silicon), and the method for producing a cold cathode for a display discharge tube according to claim 1. 3. The method for producing a cold cathode for a display discharge tube according to claim 1, wherein the organic metal is a substance which becomes a metal oxide having an emitter characteristic by firing. 4. The material according to claim 3, wherein the substance that becomes a metal oxide having an emitter characteristic by the firing is an alkaline earth metal element, an alkoxide or a carboxylate of an alkaline metal element or a rare earth element. A method for producing a cold cathode for a display discharge tube as described.