JPH0817343A - Manufacture of cover glass for fluorescent character display tube - Google Patents

Abstract

PURPOSE:To provide a fluorescent character display tube cover glass at low cost, while enhancing reliability in keeping a vacuum seal, and facilitating the mechanization of its fabrication process. CONSTITUTION:A glass plate 50 is inserted between a first forming die 40 in which a recess 41 slightly greater than the outside dimension of a cover glass 20 is formed and a second forming die 30 having a projection 31 slightly greater than the inside dimension of the cover glass 20, and the first and second forming dies 30, 40 with the glass plate 50 sandwiched between them are passed through a forming furnace heated to the softening point of glass. A fluorescent character display tube cover glass 20 with a front 21 and a frame body 22 integrally formed from one glass plate 50 is thus formed, with no air tight sealing adhesive portion of frit glass present on the cover glass.

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 method of manufacturing a cover glass applied to a fluorescent display tube that is airtightly maintained in a vacuum, and particularly to a method of manufacturing a cover glass for a fluorescent display tube that is highly reliable and inexpensive to maintain vacuum airtightness.

[0002]

2. Description of the Related Art FIG. 8 is an exploded perspective view showing a structure of a cover glass used in a conventional fluorescent display tube. FIG.
In the above, reference numeral 81 is a windshield part which is a frit glass layer 82 applied by a thick film printing method or a dispenser method and serves as a display observation part of the fluorescent display tube. Also, 83 is a cutout portion 8 for attaching the exhaust pipe 86.
4 and a frame made of a combination of glass strips having a predetermined height for forming a dish-shaped space, which is provided with an end surface 85 to which a frit glass (not shown) for airtightly adhering to the anode substrate of the fluorescent display tube is applied. The body portion 86 is a glass exhaust pipe for exhausting the space covered with the cover glass.

The aforementioned windshield portion 81 and frame portion 8
The cover glass including 3 and the exhaust pipe 86 as main components includes a windshield 81 that has been subjected to the calcination process after the frit glass 82 is applied and formed, and a calcination process after the frit glass is applied to the end face 85. And the frame body 83
Exhaust pipe 8 with frit glass applied around one end
6 and 6 are combined on a predetermined assembling jig and passed through a firing furnace to be bonded and fixed with frit glass to obtain a cover glass finished product.

On the other hand, in a separate process, the end surface 8 is obtained by stacking the above-mentioned finished cover glass product on an anode substrate on which a phosphor anode, a control electrode, a thermionic cathode, etc. are assembled.
Fluorescent display is performed through a sealing process of sealing the anode substrate and the cover glass with the frit glass applied to No. 5 and an exhaust process of evacuating the space formed by the anode substrate and the cover glass through the exhaust pipe 86. It is considered to be a finished tube product.

The frame body 83 is a method of cutting a cylindrical glass body made of a combination of glass plates described in Japanese Patent Publication No. 7138/1990 into a frame body 83 by cutting with a diamond cutter. A thin strip piece obtained by cutting a glass plate described in Japanese Patent Publication No. 63-11287 is burner-heated and bent at three to four places at right angles to form a frame 83, or other small pieces of glass strip 4 ~ 5
It was produced by a method in which the individual pieces were inserted into a molding die, and the abutted portions of the glass pieces were welded while being heat-molded.

[0006]

However, the conventional cover glass for a fluorescent display tube having the above-mentioned structure has the following problems. Since the windshield 81 and the frame body 83 are adhered to each other by the frit glass, the airtightness of the adhered portion, especially when a flammable foreign substance is mixed in the frit glass, the portion becomes a leak path, and the fluorescent display tube. Cannot maintain the vacuum tightness of. In particular, it causes a super slow leak, and it is extremely difficult to pursue the cause of the leak path, which may deteriorate the reliability of the product. The windshield 81 and the frame body 83 are produced in separate steps, respectively, but unless the two are prepared in pairs, the assembly step cannot proceed to the next step, which complicates the step management. The frame 83 is manufactured by the various methods described above, and any of the methods manufactured by the method has a large dimensional variation in the height direction or twisting, which is a subsequent step of applying frit glass. Mechanization of the process is difficult, and since the frame body 83 is a glass piece, it is difficult to mechanize the assembling process.

Therefore, the present invention has been made to solve the above-mentioned conventional problems, and an object thereof is to provide a highly reliable vacuum airtightness, facilitate the mechanization of its manufacturing process, and provide an inexpensive cover. An object of the present invention is to provide a method for producing a cover glass for a fluorescent display tube, which is capable of obtaining glass.

[0008]

In order to achieve such an object, the present invention provides a first mold having a concave portion having a dimension slightly larger than the outer dimension of the cover glass, and an inner dimension of the cover glass. One glass plate is inserted between a second molding die having a slightly large protrusion, and the first molding die and the second molding die sandwiching the glass plate are overlapped with each other. The cover glass for a fluorescent display tube is manufactured by passing through a forming furnace heated to the softening flow temperature of glass in this state.

According to another aspect of the invention, a flat protruding portion smaller than the outer dimension of the cover glass molded body is formed in the main portion, and a recessed portion slightly larger than the outer dimension of the cover glass molded body is formed. One glass plate was inserted between the first molding die and a second molding die having a flat portion slightly larger than the inner dimension of the cover glass, and the first glass plate sandwiched between the glass plates was inserted. A cover glass for a fluorescent display tube is manufactured by passing a mold and a second mold together in a molding furnace heated to a softening flow temperature of glass in a state of being superposed on each other.

[0010]

In the cover glass of the present invention, the windshield portion and the frame portion are integrally formed from a single glass plate, so that a cover glass for a fluorescent display tube having no airtight adhesion portion due to the frit glass can be obtained. .

[0011]

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 formed by the method for manufacturing a cover glass for a fluorescent display tube according to the present invention. In FIG.
In this fluorescent display tube, a wiring pattern (not shown), an insulating layer, and a phosphor electrode for light emission display are formed on a glass plate 1a by a thick film printing method, etc., a grid electrode as a control electrode, a cathode for thermionic 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 of the electrodes is mounted, and a cover glass 3 in which a dish-shaped internal space is formed is an anode made of frit glass. A vacuum container is formed by airtightly adhering to the substrate 1, the end of the exhaust pipe 4 is connected to a vacuum exhaust device to exhaust the above-mentioned vacuum space, and then the vicinity of the fixed portion of the exhaust pipe 4 with the cover glass 3 is closed by a gas burner. A finished product of a fluorescent display tube whose internal space is hermetically maintained in a vacuum is obtained by sealing and cutting.

FIG. 2 is a perspective view showing the structure of the cover glass 3 described above. In FIG. 2, the cover glass 20
Includes a front portion 21, which is a translucent light emitting display surface, a frame portion 22, and an exhaust pipe mounting groove 23, which are integrally formed seamlessly. Here, the dimensions a1, b1, and d1 indicate the outer dimensions of the long side, short side, and height of the cover glass 20, and the dimensions a2, b2, and d2 are the cover glass 20.
The internal dimensions of the long side, short side, and depth are shown.

FIG. 3 is a perspective view showing the structure of the second molding die 30 for forming the space inside the cover glass 20 described above. In FIG. 3, this second mold 30
Is a protruding portion 31 having a smooth surface that contacts the front portion 21 of the cover glass 20, and an exhaust pipe mounting groove 23.
And a flange portion 33 for restricting the depth to which the molding die sinks. Here, a0, b0, d0 are internal dimensions a of the cover glass 20.
The dimensions are 2, b2 and d2.

FIG. 4 is a perspective view showing the structure of the first molding die 40 for forming the outer shape of the cover glass 20 described above. In FIG. 4, the first molding die 40 includes a recess 41 formed in a, b, and d dimensions corresponding to the outer dimensions a1, b1, and d1 of the cover glass 20, and the first molding die 30. And a frame portion 42 corresponding to the collar portion 33.

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. In FIG. 5, the glass plate 50 is formed by cutting it into a rectangular shape having a dimension A on the long side, a dimension B on the short side, and a dimension D on the thickness side.

(Embodiment 1) FIG. 6 is a view for explaining a first embodiment of the method for manufacturing a cover glass for a fluorescent display tube according to the present invention, and FIGS. 6 (a), 6 (b) and 6 (c) are FIG. 4 is a cross-sectional view of each step showing the order of forming the glass plate 50 on the cover glass 20 using the first forming die 40 and the second forming die 30. In FIG. 6, first, FIG.
As shown in, a first molding die 40, a second molding die 30, and a rectangular glass plate 50 are prepared. Next, as shown in FIG. 6B, the rectangular glass plate 50 is inserted into the concave portion 41 formed in the first molding die 40, and the protruding portion 31 of the second molding die 30 is placed on the rectangular glass plate 50. Is placed so as to contact the upper surface of the rectangular glass plate 50. Next, in the state of FIG. 6B, the glass plate 50 is passed through a molding furnace (not shown) heated to a temperature at which the glass plate 50 softens and flows.

Next, when passing through the forming furnace, as shown in FIG. 6 (c), the glass plate 50 causes the flange portion 33 of the second forming die 30 to move to the first forming die due to the weight of the second forming die 30. It sinks until it contacts the frame 42 of 40. As a result, the plate thickness D of the rectangular glass plate 50 becomes thin to the size of the front portion 21 of the cover glass 20, and the glass corresponding to the volume of the thin glass plate forms the frame portion 22.

In such a structure, the first molding die 4
0 and the characteristics required for the material used for the second molding die 30 are materials that are less likely to wet with glass and have good mold releasability, and materials having a smaller coefficient of thermal expansion than glass for the reasons described below. Is. The cover glass of the fluorescent display tube is
Usually, soda glass (coefficient of thermal expansion α = 90 × 10 ⁻⁷ ) used as a window glass for a building material that is inexpensive and easily available is used. Although the softening point of soda glass is about 740 ° C., it has been experimentally confirmed that the flow viscosity of the glass for which the above-described molding shown in FIG. 6 is favorably performed is 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 since the glass is in a flowing state, 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, in the present invention, graphite (coefficient of thermal expansion α = about 45 × 10 ⁻⁷ ) is used as the mold material for the first mold 40 and the second mold 30. Graphite has a thermal expansion coefficient smaller than that of soda glass and satisfies the above-mentioned conditions,
As such, it does not get wet with the glass itself, and the mold releasability is good, and in particular, troublesome work such as applying a mold release agent to the mold becomes unnecessary. Further, since the difference in the coefficient of thermal expansion from the soda glass is large, in FIG. 6 (c), when the molded cover glass 20 is extracted from the first molding die 40, an appropriate gap is formed, and a vacuum chuck or the like is formed. It was easy to pull out with a machine.

The internal dimensions a, b, d of the recess 41 of the first mold 40 are a> a1, b> b1 with respect to the outer dimensions a1, b1, d1 of the completed cover glass 20. ，
The dimensions a0, b0, d0 of the protrusion 31 of the second molding die 30 are made to be d = d1, and the dimensions a0> a2, a2> b2, and d2 of the finished cover glass 20.
b0> b2 and d0 = d2. Here, the difference in each of the dimensions a and a1, b and b1, a0 and a2, b0 and b2 is set to a value close to the dimensional difference caused by thermal expansion at the glass forming temperature. You can obtain the product according to the dimensions in the drawing.

In this case, the concave portion 41 of the first molding die 40
Since the dimensions of a0> a2 and b0> b2 are set, it is feared that the cover glass 20 will not come off from the first molding die 40, but an inclined portion is formed on the end surface of the protrusion 31 of the second molding die 30. Since it is formed, the first molding die 30 is automatically lifted during cooling and the cover glass 20 is in a state of being detached from the first molding die 30, so that such a concern does not occur at all.

In a normal fluorescent display tube, the dimension d1,
Since d2 is 10 mm or less, dimensions d = d1, d0 = d2
As a result, the thermal expansion in the depth direction is ignored, and the product dimensions do not cause any problems.

Further, in FIG. 5, the outer dimensions A and B of the glass plate 50 are cut by 0.5 to 5.0 mm smaller than the inner dimensions a and b of the recess 41 of the second molding die 40. Is desirable. Here, the weight of the glass plate 50 must be cut so that it becomes the weight of the completed cover glass 20, but the thickness D of the glass plate 50 is, for example, 1.8 or 2 defined by the JIS standard. .8, 3.4, 3.
It is necessary to select from 8, 4.8, ... mm.

Therefore, the weight is adjusted for the selected glass plate thickness D by adjusting the dimension A or B. Further, if the above-mentioned dimensional difference is smaller than 0.5 mm,
A device with high positioning accuracy is required to insert the glass plate 50 into the recess 41 of the first molding die 40 with a vacuum chuck or the like. If the dimensional difference is larger than 5 mm, the softening flow distance of the glass plate 50 becomes large. As a result, bubbles may be generated on the cover glass 20 or streaks may remain, which lowers the commercial value.

Further, in the state shown in FIG. 6 (b), the temperature when passing through the forming furnace is preferably 900 to 1000 ° C., which is about 200 ° C. higher than the softening point of soda glass which is the material of the cover glass 20 is about 740 ° C. Met. This temperature is about 9
If the temperature is lower than 00 ° C., the glass does not sufficiently flow into the corners of the first molding die 40 and the second molding die 30, and the cover glass 20 has a large roundness, and in extreme cases, the frame portion. 22 was not formed and could not be used as a product. Next, when the molding temperature exceeds about 1000 ° C., glass coloring occurs, which is expected that either part of the molding material component diffuses into the material glass or part of the glass component dissipates. The cover glass 20 has a low transmittance of fluorescent display light, which reduces the commercial value.

At the above-mentioned molding temperature, various weights were mounted on the second molding die 30 to prepare the cover glass 20, and the molding state was observed. The conditions for producing the cover glass 20 in a good molded state are the glass plate 5
2.5 to 25 g / cm ² per area of 0. When the load per area is 2.5 g / cm ² or less, the cover glass 20 does not have the frame portion 22 formed. To prevent this, the molding temperature is set to about 1000 ° C.
I needed to do more. Also, the load per area is 2
In the case of 5 g / cm ² or more, the glass flows before the glass plate 50 reaches the softening and flowing viscosity, so that the formed glass glass 20 has streaks, bubble bites, wrinkles, and the like, which reduces the commercial value. Reduce.

(Embodiment 2) FIG. 7 is a view for explaining a second embodiment of the method for manufacturing a cover glass for a fluorescent display tube according to the present invention, and FIGS. 7 (a), 7 (b) and 7 (c) are FIG. 7 is a cross-sectional view of each step showing the order of forming the glass plate 50 into the cover glass 20 using the third forming die 60, the fourth forming die 65, and the fifth forming die 70. In FIG. 7, first, as shown in FIG.
A frame-shaped fourth molding die 65 combined with the peripheral portion of the third molding die 60, and a flat plate-shaped fifth molding die 70.
And the rectangular glass plate 50 are prepared. In this case, the frame-shaped fourth molding die 65 is combined with the peripheral portion of the third molding die 60 to form the recessed portion 62 having the protrusion 61 in the central portion.

Next, as shown in FIG. 7B, a rectangular glass plate 50 is inserted into a concave portion 62 formed by combining the third molding die 60 with the fourth molding die 65, and the rectangular glass plate 50 is inserted. The flat plate-shaped fifth mold 70 is placed on the plate 50 so that the flat surface portion thereof contacts the upper surface of the rectangular glass plate 50. Next in FIG.
In the state of (b), the glass plate 50 is passed through a molding furnace (not shown) heated to a temperature at which it softens and flows.

Next, when it passes through the forming furnace, as shown in FIG. 7C, the glass plate 50 has a flat surface of the fifth forming die 70 due to the weight of the fifth forming die 70 and a fourth forming die 65. Sink until it touches the open end of. As a result, the plate thickness D of the rectangular glass plate 50 is set to the front portion 2 of the cover glass 20.
The glass corresponding to the volume reduced to the size of 1 and the glass plate thickness reduced forms the frame portion 22.

Also in such a structure, the materials used for the third molding die 60, the fourth molding die 65 and the fifth molding die 70 are the first molding die 40 and the second molding die 40 of the first embodiment described above. Like the molding die 30 of No. 1, it is difficult to get wet with glass,
A carbon material having a thermal expansion coefficient smaller than that of glass having good releasability is used. Further, the molding conditions such as the size of each molding die and the molding temperature are exactly the same as those in the first embodiment.

Now, comparing the method described in the first embodiment with the method described in the second embodiment, the frame body 22 according to the first embodiment needs to lift the melt-softened glass by a load. On the other hand, in the method of the second embodiment, the frame body portion 22 is formed by the melted and softened glass hanging down. Therefore, in the method of Example 2, the load applied to the mold is small, and as a result, the total weight of the mold including the weight is reduced. As a result, the amount of heat taken out by the mold material is reduced, so that the thermal efficiency of the molding furnace is improved, and the driving system required to pass through the molding furnace can operate with a small driving force.

The portion of the cover glass 20 of the molding die which comes into contact with the front portion 21 which is the display surface must be finished with high surface accuracy. However, in the mold 40 of FIG. 6, since the concave portion is in the shape of a bag, it is difficult to perform the surface finishing mechanical work. On the other hand, the surfaces of the fifth molding die 70 and the third molding die 60 of FIG. 7 that are in contact with the front portion 21 of the cover glass 20 can be machine-finished to obtain surface accuracy.

In the second embodiment described above, the third molding die 60 and the fourth molding die 65 are separately formed, and the third molding die 60 and the fourth molding die 65 are formed at the time of molding. The case where the molding die is configured by combining and integrating the above has been described. However, the third molding die 60 and the fourth molding die 65 are previously formed.
It is needless to say that the cover glass 20 can be molded even when a molding die configured as an integral type is used.

[0035]

As described above, according to the present invention,
Since cover glass can be produced by molding from glass plate, cover glass with high reliability of vacuum airtight without adhesive part by frit glass uses glass plate as a material, so compared to using molten glass as a material It is easy to control the weight of the glass, and it is easy to mechanize the insertion of the material into the mold and the take-out of the product. To be

[Brief description of drawings]

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

FIG. 3 is a perspective view showing a configuration of a second mold used in the method for manufacturing a cover glass for a fluorescent display tube according to the present invention.

FIG. 4 is a perspective view showing the configuration of a first mold used in the method for manufacturing a cover glass for a fluorescent display tube according to the present invention.

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

FIG. 6 is a sectional view of each step showing the first embodiment of the method of manufacturing a cover glass for a fluorescent display tube according to the present invention.

FIG. 7 is a sectional view of each step showing the second embodiment of the method for manufacturing a 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 ...
Front part, 22 ... Frame part, 23 ... Exhaust pipe mounting groove,
30 ... 2nd shaping | molding die, 31 ... protrusion part, 32 ... protrusion part, 3
3 ... Collar part, 40 ... 1st shaping | molding die, 41 ... Recessed part, 42 ...
Frame part, 50 ... Material glass plate, 60 ... Third molding die, 61
... Projection part, 62 ... Recessed part, 65 ... Fourth mold, 70 ...
Fifth mold.

Claims (8)

[Claims] 1. A molding die made of a mold material having a thermal expansion coefficient smaller than that of glass used as a material of a cover glass for a fluorescent display is used, and the molding die is a recess slightly larger than the outer dimension of the molded body of the cover glass. And a second molding die having a protrusion slightly larger than the inner shape dimension of the cover glass molding, and the inner shape dimension of the recessed portion of the first molding die. A first step of preparing a rectangular glass plate having a slightly smaller outer dimension and a plate thickness selected so as to have substantially the same weight as that of the cover glass molded body; A second step of inserting the rectangular glass plate; and a step of sandwiching the rectangular glass plate so that the protrusion of the second molding die corresponds to the first molding die and the first molding die and the second molding die. Third process of overlapping the mold And a fourth step of passing a furnace having a temperature higher than the softening point of the glass in a state where the first molding die and the second molding die sandwiching the rectangular glass plate are overlapped with each other. A method of manufacturing a cover glass for a fluorescent display tube, which comprises: 2. A molding die made of a mold material having a thermal expansion coefficient smaller than that of glass used as a material of a cover glass for a fluorescent display tube is used, and the molding die has a flat protrusion smaller than an outer dimension of a molded body of the cover glass. A first mold having a concave portion slightly larger than the outer dimension of the cover glass molding, and a flat portion slightly larger than the outer dimension of the cover glass molding. A rectangular shape having a plate thickness selected so that the outer shape dimension is slightly smaller than the inner shape dimension of the concave portion of the first molding die and the weight is substantially the same as that of the cover glass molded body. A first step of preparing a glass plate; a second step of inserting the rectangular glass plate into a concave portion of the first molding die; and a flat portion of the second molding die having the first molding die. To correspond to A third step of sandwiching the rectangular glass plate and superimposing the first molding die and the second molding die, and superimposing the first molding die and the second molding die sandwiching the rectangular glass plate. A fourth step of passing the combined glass through a furnace having a temperature higher than the softening point of the glass, the method for manufacturing a cover glass for a fluorescent display tube. 3. The first mold and the second mold according to claim 1, wherein the first mold has a coefficient of thermal expansion smaller than that of the glass.
The method for manufacturing a cover glass for a fluorescent display tube, wherein the mold is made of graphite. 4. The inner size of the recess of the first mold and the size of the protrusion of the second mold according to claim 1, wherein the difference in thermal expansion coefficient between the glass and the mold causes 4. A method of manufacturing a cover glass for a fluorescent display tube, which is formed to have a size larger than a size of a cover glass molded body by a size close to a size difference caused by a temperature applied in step 4. 5. The dimension according to claim 2, wherein the inner dimension of the recessed portion of the first molding die is generated at the temperature applied in the fourth step due to the difference in thermal expansion coefficient between the glass and the molding die. A method of manufacturing a cover glass for a fluorescent display, comprising forming a cover glass molded body having a size close to the difference, which is larger than the cover glass molded body size. 6. The outer dimension of the rectangular glass plate prepared in the first step according to claim 1 or 2, which is 0.5 to 5.0 mm larger than the inner dimension of the concave portion of the first mold.
A method for manufacturing a cover glass for a fluorescent display tube, which is small. 7. The cover glass for a fluorescent display according to claim 1 or 2, wherein the temperature of the furnace in the fourth step is a temperature at which the glass softens and flows above the softening point of the glass. Manufacturing method. 8. The method according to claim 1 or 2, wherein the second mold has 2.5 to 25 g / c on the rectangular glass plate.
A method of manufacturing a cover glass for a fluorescent display tube, characterized in that the weight is a load of m ² .