JPH0817362A - Cover glass for fluorescent character display tube - Google Patents

Abstract

PURPOSE:To provide a fluorescent character display tube cover which ensures high reliability in keeping a vacuum seal, is easy to handle, emits little gas, and is fabricated by easily mechanized processes, that is, inexpensive. CONSTITUTION:A cover glass 20 comprises an inner face electrode 21 made of a thin metallic plate bonded to the glass surface, a frame 22, and an exhaust- pipe mounting groove 23, all of which are integrally and seamlessly formed. The fluorescent character display tube cover glass having no hermetic bond made of frit glass can thus be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a glass anode substrate provided with a phosphor anode, a control electrode and a thermionic emission cathode, and a space formed by covering each of these electrodes with a dish-shaped glass cover glass. The present invention relates to a cover glass applied to a fluorescent display tube which is hermetically held in a vacuum, and more particularly to a fluorescent display tube for observing the emission display of a phosphor from the anode substrate side.

[0002]

2. Description of the Related Art FIG. 8 is an exploded perspective view showing a structure of a cover glass 80 used in a conventional fluorescent display tube.
In FIG. 8, reference numeral 81 is a glass plate on which a carbon paste layer 82 formed by a thick film printing method and a frit glass layer 83 applied by a thick film printing method or a dispenser method are formed. Further, reference numeral 86 is provided with a cutout portion 84 for attaching the exhaust pipe 87 and an end face 85 of a spacer glass to which a frit glass (not shown) for airtightly adhering to the anode substrate of the fluorescent display tube is provided, and a dish-shaped space is provided. A frame portion made of a combination of glass strips having a predetermined height for forming the glass, and a glass exhaust pipe 87 for exhausting the space formed by the cover glass 80 and the anode substrate to a vacuum.

The cover glass whose main components are the glass plate 81, the frame body portion 86 and the exhaust pipe 87 described above is a glass which has been subjected to the preliminary firing process after the carbon paste layer 82 and the frit glass 82 have been applied and formed. The plate 81, the frame 86 that has been subjected to the calcination process after the frit glass has been applied to the end face 85, and the exhaust pipe 87 that has the frit glass applied to the periphery of one end are mounted on a predetermined assembly jig. By combining and passing through a firing furnace, each component is bonded and fixed with frit glass, and the cover glass 80 is completed.

On the other hand, a frit glass applied on the end face 85 in a state where the finished product of the cover glass 80 is superposed on the anode substrate on which the phosphor anode, the control electrode, the thermionic cathode and the like are assembled in a separate process. Then, the fluorescent display tube is completed as a finished product through a sealing step of sealing the anode substrate and the cover glass to each other and an exhaust step of evacuating the space formed by the anode substrate and the cover glass through the exhaust tube 87. .

The carbon paste layer 82 described above is used.
Is usually formed by the thick film printing method as described above,
Depending on the case, a film may be formed by a spray method using a pattern mask formed corresponding to the coating shape on a dish-shaped cover glass structure in which the glass plate 81 and the frame body portion 86 are bonded by the frit glass 83. There is also.

Here, the reason for providing the carbon paste layer 82 will be described. A conductive film for preventing display abnormality due to static electricity is formed on the inner surface of the container of the fluorescent display tube, and this conductive film is usually set to the same potential as the cathode and used.

In an ordinary fluorescent display tube for observing the luminescent display of the phosphor from the transparent cover glass side, a transparent conductive film such as a NES film or an ITO film is used as the above-mentioned conductive film. However, in the fluorescent display tube for observing the display from the side of the anode substrate which is the object of the present application, a black conductive film is used in order to improve the contrast of light emission and prevent external light from entering the display portion from the outside of the cover glass. I need.

The above-mentioned conductive film may be used not only as a countermeasure against static electricity in the case of, but also as an electrode for applying a positive side potential to the cathode to the conductive film to improve the light emission display. is there. In this case, a low resistance film is required.

[0009]

However, the conventional cover glass for a fluorescent display tube having the above-mentioned structure has the following problems. In order to form the carbon paste layer 82 by the thick film printing method, the flat portion of the cover glass 80 must be the glass plate 81. Therefore, the structure of the cover glass 80 is
As shown in FIG. 8, there is no means other than a combination of three components.

Since the cover glass 80 is formed from a combination of the above-mentioned three components, the assembling process is complicated, the manufacturing cost of the cover glass 80 becomes expensive, and considerable skill is required for its manufacture. I did. As shown in FIG. 8, frit glass 8
Since the dish-shaped container is formed by adhering and fixing at 3, the reliability of the adhering portion against a vacuum leak is slightly lowered.

When the carbon paste layer 82 is formed by a spray method, it can be formed in a dish-shaped container instead of being formed on the glass plate 81, but carbon is prevented from adhering to unnecessary portions. Therefore, a pattern mask is required. Therefore, the pattern accuracy is somewhat low, making it difficult to mechanize the process.

Carbon paste is an expensive material and requires special consideration for storage in the paste state.
Further, the formed carbon paste layer 82 has a very high hygroscopic property, and unless carefully stored, it causes gas emission after the fluorescent display tube becomes a finished product, and causes deterioration of electrical characteristics due to a decrease in vacuum degree. May cause deterioration. The carbon paste has a weak adhesion to glass and is easily peeled off or scratched.

Therefore, the present invention has been made in order to solve the above-mentioned conventional problems, and its purpose is to maintain the vacuum airtightness with high reliability, easy handling, less gas emission, and its production. An object of the present invention is to provide a cover for a fluorescent display tube that is easy to process, that is, inexpensive.

[0014]

In order to achieve such an object, the present invention provides a cover glass on an anode substrate on which an anode having a phosphor layer formed thereon, a control electrode and a thermionic emission cathode are mounted. In a cover glass for a fluorescent display tube that is hermetically sealed and observes the light emission of the phosphor layer from the anode substrate side, the cover glass is formed into a dish shape in the glass plate forming step, and a metal plate is integrally attached to the inner surface. Is configured.

[0015]

The cover glass according to the present invention is formed in a dish shape in the glass plate forming step, so that a cover glass for a fluorescent display tube having no airtight adhesion portion due to frit glass is obtained, and the cover glass has an inner surface. A cover plate for a fluorescent display tube, which has a metal plate attached thereto and can be used as a conductive film, is obtained.

[0016]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a perspective view showing a structure of a fluorescent display tube using a cover glass for a fluorescent display tube according to the present invention. In FIG. 1, this fluorescent display tube has a wiring pattern (not shown), an insulating layer, and a phosphor electrode for light emission display formed on a glass plate 1a by a thick film printing method, a grid electrode which is a control electrode, a thermoelectron emission. A lead terminal 2 for supplying an electric signal to each of the above-mentioned electrodes is led out from an anode substrate 1 on which each electrode such as a cathode is mounted.

The cover glass 3 having a dish-shaped internal space is airtightly adhered to the anode substrate 1 by frit glass to form a vacuum container, and the tip of the exhaust pipe 4 is connected to a vacuum exhaust device as described above. After exhausting the vacuum space, exhaust pipe 4
In the vicinity of the fixed portion with the cover glass 3 is sealed and cut with a gas burner or the like to obtain a finished product of the fluorescent display tube in which the internal space is hermetically maintained in vacuum. The fluorescent display tube is a fluorescent display tube having a structure for observing the emission display of the phosphor from the direction of the anode substrate 1.

FIG. 2 is a perspective view showing the structure of the cover glass 3 described above, and FIG. 3 is a sectional view taken along the line CC ′ of FIG. 2 and 3, the cover glass 20
The inner surface electrode 21 made of a thin metal plate attached to the glass surface, the frame body portion 22, and the exhaust pipe mounting groove 23 are integrally formed seamlessly.

FIG. 4 is a perspective view showing the structure of a thin metal plate 40 for forming the inner electrode 21 attached to the inner surface of the cover glass 20 described above. In FIG. 4, the metal plate 40 is made of the cover glass 2 as its material.
A 426 alloy (Ni42-Cr6), which is a metal having a coefficient of thermal expansion matching that of soda glass forming 0, was used.

The dimensions a and b of the metal plate 40 in the vertical and horizontal directions are those cut to the size required for the pattern of the inner surface electrode 21, and the plate thickness t is about 0.05 mm. There is no restriction, and a plate thickness that is easy to handle may be selected according to the size of the cover glass 20.

FIG. 5 is a perspective view showing the structure of the glass plate 50 which is the material of the cover glass 20 described above. The glass plate 50 is formed to have a rectangular shape cut into each dimension of A on the long side, B on the short side and D on the thickness side.

FIGS. 6A, 6B and 6C show the metal plate 4
6 is a cross-sectional view of each step for explaining the order of forming the glass plate 0 and the glass plate 50 on the cover glass 20 using the first mold 60 and the second mold 61. FIG. First, as shown in FIG. 6A, a first mold 60, a second mold 61, a metal plate 40, and a rectangular glass plate 50 are prepared.

Next, as shown in FIG. 6B, the rectangular glass plate 50 is placed in the recess 60a formed in the first molding die 60.
, The metal plate 40 is overlaid on the rectangular glass plate 50, and then the protrusion 61a of the second molding die 61 is attached to the metal plate 40.
Place it so that it touches. Next, in the state shown in FIG. 6B, a molding furnace (not shown) heated to a temperature at which the glass plate 50 is softened and flown by applying a load to the second molding die 61 with a weight (not shown) having a predetermined weight is used. Let it pass.

Next, when the rectangular glass plate 50 is passed through the forming furnace, the flange portion 61b of the second forming die 61 of the rectangular glass plate 50 is opened by the load of the second forming die 61. It sinks until it touches the edge. As a result, the plate thickness D of the rectangular glass plate 50 becomes thin to the size of the flat part of the cover glass 20, and the glass corresponding to the volume of the thin glass plate forms a frame part. At this time, at the same time, the metal plate 40 is attached to the inner surface of the cover glass 20 formed in the dish-shaped container to form the inner electrode 21.

In such a structure, the first molding die 6
0 and the characteristics required for the material used for the second molding die 61 are materials that are less likely to wet with glass and have good releasability, and a material having a smaller thermal expansion coefficient than glass for the reasons described below. Graphite is suitable.

As the cover glass for a fluorescent display tube, soda glass (coefficient of thermal expansion α = 90 × 10 ⁻⁷ ) used for window glass for building materials that is inexpensive and easily available is usually used. Although the softening point of soda glass is about 740 ° C., it has been confirmed by experiments that the flow viscosity of the glass that is satisfactorily molded as shown in FIG. 6 is a viscosity that can be obtained in the temperature range of 900 to 1100 ° C. .

Therefore, at the molding temperature, the mold has undergone thermal expansion corresponding to that temperature, and the glass is in a flowing state, so that it has the dimensions of the mold, and in the cooling process of the mold and the glass, both are at the same time. If the mold shrinks and the coefficient of thermal expansion of the mold is larger than that of glass, the amount of shrinkage is larger than that of glass, and the cover glass 20 is destroyed during cooling.

Therefore, the present inventors have made the first mold 60.
And graphite (coefficient of thermal expansion α =
About 45 × 10 ⁻⁷ ) was used. Graphite has a smaller coefficient of thermal expansion than soda glass, satisfies the above-mentioned conditions, does not cause wetting with glass itself, and has good mold releasability, especially when a mold release agent is applied to the mold. No need for troublesome work. Further, since the difference in the coefficient of thermal expansion from the soda glass is large, in FIG. 6C, when the molded cover glass 20 is extracted from the first molding die 60,
Since there was a proper gap, it was easy to extract it with a machine such as a vacuum chuck.

Further, in particular, by using a graphite material for the second molding die 61, the surface of the metal plate 40 that was in contact with the second molding die 61 is carburized to the metal plate 40, so that the cover glass 20 is covered. As the inner electrode 21, a black film having an extremely good color tone could be obtained.

It should be noted that gas which is considered to be released from the glass during the molding of the glass plate 50 may cause bubbles in the bonding surface between the metal plate 40 and the glass plate 50. The bubbles do not impair the function of the inner surface electrode 21 at all, nor do they impair the characteristics required for the cover glass 20.

However, this bubble may be a little unsightly in appearance, but in order to eliminate this defect, for example, as shown in a plan view in FIGS. 7A, 7B, and 7C, a metal plate is used. 40 has a rectangular slit 71, a circular hole 72, and a circular hole 72 each having a size that does not particularly deteriorate the function as an electrode.
Metal plates 41, 4 provided with parallelogram slits 73, etc.
This can be prevented by using 2,43. In addition,
The contact surface between the glass and the graphite, which is the molding material, has minute pores in the graphite, and these pores serve as gas outflow paths.
No bubbles are generated.

[0032]

As described above, according to the present invention,
By forming the cover glass into a dish shape during the glass plate forming process, it is possible to obtain a highly reliable cover glass that does not have an adhesive portion due to frit glass and that maintains vacuum tightness. Since the plate is attached, a cover glass for a fluorescent display tube that can be used as a conductive film can be obtained.

Further, according to the present invention, the cover glass is
Since the glass plate is used as the material, it is easier to control the weight of the glass compared to using molten glass as the material, and it is easy to mechanize the insertion of the material into the mold and the removal of the product. The extremely excellent effect that the cover glass can be obtained at low cost can be obtained.

Further, according to the present invention, the inner surface electrode formed on the inner surface of the cover glass can be formed simultaneously with the molding of the cover glass by using the metal plate, and has various characteristics which cannot be obtained by the conventional carbon paste. An extremely excellent effect such as the formation of electrodes can be obtained.

Further, according to the present invention, by providing a plurality of openings in the metal plate attached to the inner surface of the cover glass, the air bubbles generated on the bonding surface between the metal plate and the cover glass are removed, and the metal plate as an electrode is removed. Without degrading function
It is possible to eliminate the unsightly appearance.

[Brief description of drawings]

FIG. 1 is a perspective view showing a structure of a fluorescent display tube using a cover glass for a fluorescent display tube according to the present invention.

FIG. 2 is a perspective view showing a structure of a cover glass for a fluorescent display tube according to the present invention.

3 is a cross-sectional view taken along the line CC ′ of FIG.

FIG. 4 is a perspective view showing a metal plate used for a cover glass for a fluorescent display tube according to the present invention.

FIG. 5 is a perspective view showing a structure of a glass plate which is a material of a cover glass used for manufacturing a cover glass for a fluorescent display tube according to the present invention.

FIG. 6 is a cross-sectional view of each step illustrating a method for manufacturing a cover glass for a fluorescent display tube according to the present invention.

FIG. 7 is a plan view showing another embodiment of the metal plate integrally attached to the inner surface of the cover glass for a fluorescent display tube according to the present invention.

FIG. 8 is an exploded perspective view illustrating a configuration of a conventional cover glass for a fluorescent display tube.

[Explanation of symbols]

1 ... Anode substrate, 1a ... Glass plate, 2 ... Lead wire, 3 ... Cover glass, 4 ... Exhaust pipe, 20 ... Cover glass, 21 ...
Inner surface electrode, 22 ... Frame body portion, 23 ... Exhaust pipe mounting groove, 4
0 ... Metal plate, 41 ... Metal plate, 42 ... Metal plate, 43 ... Metal plate, 50 ... Material glass plate, 60 ... First molding die, 60a
... Recessed portion, 61 ... Second molding die, 61a ... Projection portion, 61
b ... collar part, 71 ... rectangular slit, 72 circular hole, 73 ...
Parallelogram slit.

Claims (2)

[Claims] 1. A cover glass is hermetically sealed on an anode substrate on which an anode on which a phosphor layer is formed, a control electrode and a thermionic emission cathode are mounted, and light emission of the phosphor layer is observed from the side of the anode substrate. In the cover glass for a fluorescent display tube, the cover glass is formed into a dish shape in a glass plate forming step, and a metal plate is integrally attached to an inner surface of the cover glass. 2. The cover glass for a fluorescent display tube according to claim 1, wherein the metal plate has a plurality of openings.