JPH0836977A - Cover glass for fluorescent display tube - Google Patents

Abstract

PURPOSE:To obtain an inexpensive cover glass for fluorescent display tube with its high reliability for holding a vacuum air tightness, its easy handling, its stable resistance value and the light transmission ratio of a transparent conductor film, and easy mechanization of its manufacturing process. CONSTITUTION:For a cover glass 20, an internal surface electrode 21 composed of a mesh-shaped light transparent metal thin film stretched on a glass surface, a frame body part 22, and an exhaust pipe mounting groove 23 are seamlessly formed in one body. Therefore, a cover glass for fluorescent display tube in which no air tight adhering part due to a frit glass is present can 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 a light emitting display of a phosphor from the cover glass side.

[0002]

2. Description of the Related Art FIG. 8 is an exploded perspective view illustrating the structure of a cover glass 80 used in a conventional fluorescent display tube. In FIG. 8, reference numeral 81 denotes a glass on which a transparent conductive film 82 made of a Nesa film formed by a spray method or an ITO film formed by a sputtering method and a frit glass layer 83 applied by a thick film printing method or a dispenser method are formed. It is a plate.

Further, 84 is provided with a cutout portion 86 for attaching the exhaust pipe 85 and an end face 87 of a spacer glass to which a frit glass (not shown) for airtightly adhering to the anode substrate of the fluorescent display tube is applied. Is a frame body formed of a combination of glass strips having a predetermined height for forming the space. Reference numeral 85 is a glass exhaust pipe for evacuating a space formed by the cover glass 80 and an anode substrate (not shown) to a vacuum.

In the cover glass 80 whose main components are the glass plate 81, the frame portion 84 and the exhaust pipe 85, the frit glass layer 83 is applied to the glass plate 81 on which the transparent conductive film 82 is formed. The glass plate 81 after the calcination process is finished, the frame body portion 84 after the frit glass is applied to the end face 87 and the calcination process is completed, and the exhaust pipe where the frit glass is applied around one end. By combining 85 with a predetermined assembly jig and passing through a firing furnace, each component is adhesively fixed with frit glass to complete the cover glass 80.

On the other hand, the frit glass applied to the end face 87 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. And a sealing process for sealing the anode substrate and the cover glass, and an exhaust process for evacuating the space formed by the anode substrate and the cover glass through the exhaust pipe 85 to complete a fluorescent display tube. .

The above-mentioned transparent conductive film 82 is usually
On the surface of the glass plate 81 on the inner surface side of the container of the fluorescent display tube, a Nesa film formed by a spray method or an ITO film formed by a sputtering method is used.

Here, the reason for providing the transparent conductive film 82 will be described. The transparent conductive film 82 is a film for preventing display abnormality due to static electricity generated on the inner surface side of the container of the fluorescent display tube,
The transparent conductive film 82 is usually set to the same potential as the cathode for use.

The transparent conductive film 82 is used not only as a measure against static electricity in the above case, but also when it is used as an electrode for applying a positive electrode potential to the cathode to the transparent conductive film 82 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 transparent conductive film 82 made of a NESA film or an ITO film on the surface of the glass plate, the film is attached to a flat glass plate and then cut into the size of the windshield of the cover glass 80 to form the glass plate 81. There are many. Therefore, the structure of the cover glass 80 has no means other than the combination of three components as shown in FIG.

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 it is formed into a dish-shaped container by being adhesively fixed at 3, the reliability of the adhered portion against a vacuum leak is slightly lowered.

Even if the transparent conductive film 82 is a Nesa film or an ITO film, the relationship between the normal resistance value and the film thickness is inversely proportional. Therefore, when a film having a low resistance is obtained, the film thickness becomes large and the light transmission is This will lead to lower rates. Therefore, it is necessary to pay close attention to maintain the balance between the two and stabilize the process.

Therefore, the present invention has been made to solve the above-mentioned conventional problems, and its purpose is to maintain the vacuum airtightness with high reliability and easy handling, and to obtain the resistance value and light of the transparent conductive film. It is an object of the present invention to provide a cover glass for a fluorescent display tube which has a stable transmittance and whose manufacturing process is easy to mechanize, that is, inexpensive.

[0013]

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 that is hermetically sealed and observes the light emission of the phosphor layer from the cover glass side, this cover glass is formed into a dish shape during the glass plate forming process, and has a semi-transparent mesh shape on the inner surface. A metal plate is integrally attached and configured.

[0014]

In the cover glass of the present invention, since the dish-shaped container is integrally formed in the step of forming one glass plate, a cover glass for a fluorescent display tube having no airtight adhesion portion due to frit glass is obtained. Since the mesh-shaped light-transmissive metal plate attached to the inner surface of the cover glass can be used as the transparent conductive film, a cover glass for a fluorescent display tube having stable resistance and light transmittance can be obtained.

[0015]

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 the inner surface of a glass plate 1a by a thick film printing method or the like, a grid electrode which is a control electrode, a thermal electrode. 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 for electron emission is mounted.

Further, the cover glass 3 having the 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 the 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 luminescent display of the phosphor from the direction of the cover glass 3, and for example, the luminescent display is comparatively observable from a distance of about 1 m or more. A large-sized fluorescent display tube is suitable.
However, the above-mentioned distance or display size is not limited as long as the observation of the light-emitting display is not hindered.

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
Is an inner surface electrode 21 made of a metal thin plate having a mesh shape and attached to a glass surface, and a 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 the inner electrode 21 attached to the inner surface of the cover glass 20 described above. In FIG. 4, a mesh-shaped light-transmitting metal thin plate 40 forming the inner surface electrode 21 has a mesh-shaped light-transmitting portion 41, a frame portion 42 for supporting and fixing the light-transmitting portion 41, and a potential. It has the terminal part 43 for giving, and is integrally comprised. The material for forming the thin metal plate 40 is a metal having a coefficient of thermal expansion matching that of the soda glass forming the cover glass 20, for example, 42.
6 alloy (Ni42-Cr6) was used.

Further, the dimensions a and b in the vertical and horizontal directions of the thin metal plate 40 are those cut into a 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 on the dimensions, and a plate thickness that is easy to handle may be selected according to the size of the cover glass 20.

Further, the light transmitting portion 41 of the metal thin plate 40.
Is a hexagonal mesh having a line width of about 0.05 mm and a side of about 3 mm, and is formed by etching. If the mesh size is too large, the exposed surface area of the glass surface will become large, so that it will not function as a conductive film, and if it is too small, the light transmittance will decrease, so depending on the intended use of the fluorescent display tube. Need to decide. Also with regard to the line width, if properly selected, it may hinder the display or reduce the light transmittance. Incidentally, in the fluorescent display tube for observing the light emitting display from a place separated by about 1 m as described above, no problems such as the obstruction of the display and the reduction of the light transmittance were observed with the above mesh size.

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 a mesh-shaped light-transmitting metal thin plate 40 and a glass plate 50.
FIG. 9 is a cross-sectional view of each step for explaining the order of forming the cover glass 20 using the first molding die 60 and the second molding die 61. First, as shown in FIG. 6A, a first mold 60, a second mold 61, a thin metal plate 40, and a rectangular glass plate 50 are prepared.

Next, as shown in FIG. 6 (b), the rectangular glass plate 50 is placed in the recess 60a formed in the first molding die 60.
Then, the metal thin plate 40 is superposed on the rectangular glass plate 50, and then the second molding die 61 is placed so that the protruding portion 61a of the second molding die 61 contacts the metal thin plate 40. 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 sheet 50 is opened by the load applied from 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 thin 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 ) which is used as a window glass for building materials which is inexpensive and easy to obtain 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 fluid state, so that it has the dimensions of the mold, and during 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 molding die 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.

In particular, by using a graphite material for the second molding die 61, the surface of the metal thin plate 40 which is in contact with the second molding die 61 is colored black due to the carburizing phenomenon on the metal thin plate 40. Since the metallic luster disappears and reflected light can be prevented, a fluorescent display tube having a good display contrast can be obtained.

In the above-described embodiment, the case where the light transmissive portion 41 of the metal thin plate 40 is formed of the hexagonal mesh portion has been described. For example, as shown in the plan view of FIG. 40A or a thin metal plate having a light-transmitting portion 41a formed of a rectangular mesh portion of FIG.
As shown in FIG. 3, the light-transmitting portion 4 including a diamond-shaped mesh portion
Even if the metal thin plate 40B having 1b is used, the same effect as described above can be obtained.

[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 thin 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 at the same time when the cover glass is formed by using the metal thin plate, and the inner surface electrode is more resistant than the Nesa film or the ITO film. Values and light transmittance can be stably formed, and extremely excellent effects such as the formation of electrodes having various characteristics which cannot be obtained by the conventional cover glass can be obtained.

[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 thin metal plate used for the 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 a thin 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 thin plate, 40A ... metal thin plate, 40B ... metal thin plate,
41 ... Mesh-shaped light transmissive part, 41a ... Light transmissive part composed of rectangular mesh part, 41b ... Light transmissive part composed of diamond-shaped mesh part, 42 ... Frame part, 43 ... Terminal part, 50 ... Material glass plate , 60 ... First mold, 60a ... Recessed portion, 6
1 ... 2nd shaping | molding die, 61a ... protrusion part, 61b ... collar part.

Claims (2)

[Claims] 1. A cover glass is hermetically sealed to an anode substrate on which an anode having a phosphor layer formed thereon, a control electrode, and a thermionic emission cathode are mounted, and light emission of the phosphor layer is observed from the cover glass side. In the cover glass for a fluorescent display tube, the cover glass is formed in a dish shape, and a mesh-like metal plate having semi-transparency is integrally attached to an inner surface of the cover glass. 2. The cover glass for a fluorescent display according to claim 1, wherein the mesh-shaped metal plate has a hexagonal, rectangular or rhombic lattice.