JPS62225Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a display device such as a fluorescent display device formed by thick film circuit technology, particularly the structure of the sealing part of the envelope of the display device, and more specifically, An insulating material containing an alkaline component is used as the substrate, and a front bulb made of an insulating material containing an alkaline component, such as glass, is hermetically sealed around the periphery of the substrate with a sealing cement made of lead glass. A wiring conductor is formed on the substrate in the envelope according to a predetermined circuit pattern, and the wiring conductor is covered with a second insulating layer made of glass. The upper surface of the second insulating layer is electrically connected to and driven by the wiring conductor through a through hole provided in the second insulating layer. This relates to the structure of a sealed portion of an envelope of a display device in which a display portion is formed, and the external connection terminal portion of the wiring conductor hermetically penetrates the sealed portion of the envelope and is drawn out to the outside. It is.

In display devices formed using thick film circuit technology,
A conductive material that will become a wiring conductor is printed on a substrate made of an insulating material using a screen printing method, and then baked.
Furthermore, in order to increase the circuit packaging density as needed, an insulating layer (hereinafter referred to as a cross-over) that performs interlayer insulation is printed and fired on the wiring conductor to create a multilayer structure, so that an electric circuit can be printed on a single board. We are trying to form a

In this way, an electric circuit can be formed in the device by repeating the printing and firing process, which simplifies the manufacturing process, and by increasing the density of the circuit portion, the device in which this electric circuit is incorporated can be made smaller. For this reason, it has come to be used as a means for forming circuits in many electronic devices.

For example, thermionic electrons emitted from a heated filament cathode are made to collide with an anode having a phosphor layer coated on its upper surface to produce a fluorescent display tube that displays numbers, letters, figures, etc. In recent years, the introduction of thick film circuit technology has made it easier to flatten the display and increase the number of display digits.

That is, to illustrate an example of the substrate portion of a fluorescent display tube, as shown in the perspective view and enlarged sectional view of the main part in FIGS. A wiring conductor 2 for applying a drive signal to an electrode or the like is printed in a predetermined pattern using a screen printing method and fired, and then a crossover 3 is formed with a through hole communicating with the wiring conductor 2 at a predetermined position. Print and fire. Further, an anode 4 is formed on the crossover 3, which is electrically connected to a predetermined wiring conductor 2 through the through hole, and has a phosphor layer deposited on its upper surface, and is driven from the outside. It has a structure in which an external connection terminal 5 for giving a signal is connected to the end of the wiring conductor 2, and the use of thick film circuit technology greatly simplifies its manufacture, and also allows for flattening and display. Multi-digitization is becoming easier.

By the way, so-called porcelain ceramics such as alumina porcelain have traditionally been used as substrates for this type of device.
Since such ceramics are expensive in themselves, plate glass, which is much cheaper than ceramics, is being used as the substrate 1, for example, in the above-mentioned fluorescent display tubes.

However, as this type of device has come to be used as a variety of display devices in a variety of environments, the wiring of the above-mentioned display device using glass as a substrate may deteriorate if used for a long time under high temperatures. It was found that there was a problem in that the insulation between conductors deteriorated.

Regarding the cause of this insulation deterioration, the inventors of the present invention
As a result of various experiments, they discovered the following.

In general, plain glass is often used as a substrate for this type of display device because it is inexpensive and easy to process.
This plate glass is soda lime glass,
In addition to SiO ₂ , it contains Na ₂ O as the main alkaline component. On the other hand, for a crossover that performs interlayer insulation, it is necessary that the firing temperature is lower than the softening temperature of the plate glass used as the substrate, and that its coefficient of thermal expansion is close to that of the substrate made of the plate glass.
Generally, an insulating material made of lead-borate glass containing PbO as a main component is selected and printed and fired on the substrate.

However, in this case, as shown in the enlarged cross-sectional view of the main part in FIG.
Na ⁺ ions released from the network bonds of the plate glass diffuse in the three directions of the crossover.

When a potential difference is applied between the wiring conductors 2 in such a state containing Na ⁺ , the Na ⁺ ions move to a portion of the wiring conductor 2 having a negative potential, where they are discharged and Na is generated. Since this Na is active, it reduces PbO in crossover 3. That is, lead (Pb) is precipitated by the reaction 2Na + PbO → Pb + Na ₂ O of the following formula.

This precipitated Pb extends like a tree from the wiring conductor 2 to which a negative potential has been applied, as shown in A shown in FIG. 2, and reduces the insulation resistance between the wiring conductors 2.
This will cause insulation failure.

Moreover, the movement of the Na ⁺ ions becomes more active at higher temperatures, so if this type of display device is left at high temperatures for a long time with voltage applied, it will cause insulation failure and shorten its lifespan. It is conceivable.

Furthermore, in the case of the above-mentioned fluorescent display tube, in order to maintain the electrode portion in a high vacuum state, the above-mentioned substrate portion on which each electrode is formed is sealed in a vacuum envelope. That is, in the case of a flat fluorescent display tube, a front bulb made of glass or the like is hermetically sealed around the periphery of the substrate, and the front bulb and the substrate form a vacuum envelope. In this case, the external connection terminal section that applies a drive signal to each electrode section is adapted to be drawn out to the outside by hermetically passing through the sealed section between the front valve and the substrate, and the sealed section is It is sealed with a sealing cement such as fritted glass containing PbO. Therefore, when a potential difference is applied between the external connection terminals at high temperatures, Na ⁺ ions that have diffused from the substrate or front valve into the sealing cement part become metallic Na, reduce PbO, and precipitate metallic lead. This causes the insulation between external connection terminals to deteriorate.

The present invention has been developed in view of the above-mentioned circumstances, and it prevents the precipitation of lead due to electrolytic phenomena at the external connection terminals, especially in the sealed part of the envelope of this type of display device, and prevents the occurrence of lead precipitation due to electrolytic phenomena, for example, when left at high temperatures. It is an object of the present invention to provide a display device of this type that can extend its life without causing insulation deterioration between external connection terminal portions even at the bottom, and can always maintain stable and normal circuit operation.

In order to achieve the above object, the display device of the present invention includes at least the external connection terminal section 15 as shown in FIGS. 3 and 4 corresponding to the embodiment.
A first crossover 12 made of alkali-free glass is formed on the upper surface of the substrate 11 where the external connection terminal portion 15 is formed on the upper surface of the first crossover 12. and a front bulb-side insulating layer 17 made of alkali-free glass is formed on at least a portion of the sealed portion on the lower surface of the front bulb 16 through which the external connection terminal portion 15 penetrates. There is.

Due to this structure, the present invention prevents Na + ions from entering the sealing cement made of lead-borate glass that covers the external connection terminal part, thereby preventing the entry of Na ⁺ ions from the board and front valve. The movement of the diffused alkali metal ions is prevented by the first crossover and the front valve side insulating layer, so that precipitation of lead due to electrolytic phenomenon does not occur at the external connection terminal portion.

Hereinafter, an embodiment of the display device according to the present invention will be described with reference to FIGS. 3 and 4.

FIGS. 3a and 3b are a perspective view and an enlarged sectional view of a main part, partially broken away, showing a substrate side portion constituting a display device as a fluorescent display tube according to the present invention.

Here, 11 is a substrate formed by cutting a plate glass, for example, soda lime glass, into a predetermined shape, containing an oxide of an alkali metal such as Na ₂ O;
For example, 100 ml of alkali-free fritted glass is used as a material on at least a portion of the substrate 11 where multilayering is required by screen printing or the like.
The first crossover was printed to a thickness of ~50 μm and fired at the firing temperature of 550°C.

The alkali-free glass that forms this first crossover 12 is a glass that does not contain an alkali metal as a main component, apart from a small amount of alkali metal contained as an impurity in the constituent components itself. %, _B2O3 10-20% _,
It has a composition containing 10 to 20% SiO ₂ and other materials such as Al ₂ O ₃ and ZnO, and its softening temperature is higher than that of the support 11.
A frit glass whose softening temperature is lower than that of the substrate 11 and whose coefficient of thermal expansion matches that of the substrate 11 is used as a material, and a binder and flux are mixed with the frit glass to form a paste, which is then printed and fired on the substrate 11.

Further, 13 is a wiring conductor formed on the first crossover 12 according to a predetermined circuit pattern, and this wiring conductor 13 is made of an insulating material constituting the first crossover 12, for example. It is covered by a second crossover 14 made of glass of the same composition.

According to the structure on the substrate side shown in FIGS. 3a and 3b, Na ⁺ in the substrate 11 is caused by heating during firing.
The ions diffuse into the substrate 11 as shown in FIG. 3b.
Even if the Na + ions penetrate into the first crossover 12 through the annular interface between the first crossover 12 and the first crossover 12, the penetration depth of the Na ⁺ ions into the first crossover 12 is about 10 μm at most. Therefore, as mentioned above, if the first crossover 12 is formed to have a thickness of at least 10 μm, preferably 20 μm or more, the movement of Na ⁺ ions toward the wiring conductor 13 can be prevented. Become. Therefore,
For example, even if a potential difference is applied between arbitrary wiring conductors 13, an electrolysis phenomenon of Na ⁺ ions does not occur, and lead precipitation in the second crossover 14 is prevented.

FIGS. 4A and 4B show the main parts of the display device according to the present invention as a fluorescent display tube, which has a front bulb sealed around the upper surface of the substrate as explained in FIGS. 3A and 3B above. It is an exploded cross-sectional view of a vertical cross-sectional view.

Here, a first crossover 12 is printed and fired on the upper surface of the portion of the substrate 11 where at least the wiring conductor 13 and its external connection terminal portion 15 are formed, and on the other hand, at least the external connection terminal portion of the front valve 16 is printed and fired. A front bulb-side insulating layer 17 is formed in advance from the same material as the first crossover in the sealed portion through which the wire 15 is led out, and then the substrate 11 and the front bulb 16 are made of lead glass such as fritted glass. It is sealed with a sealing cement 18 to form a vacuum envelope 19 of the fluorescent display tube.

With such a configuration, the substrate 11,
Alternatively, Na ⁺ ions diffusing from the front valve 16 to the sealed portion are prevented from moving by the crossover 12 and the insulating layer 17, and insulation deterioration between the external connection terminals 15 is prevented. It will become.

That is, the board 11 or the front valve 1
The precipitation of lead due to the electrolytic phenomenon of Na ⁺ ions moving from the conductor 6 is completely prevented, and sufficient insulation is maintained between the wiring conductors 13 or their external connection terminals 15 even when left at high temperatures. In addition to maintaining normal and stable circuit operation,
Moreover, the lifespan can be extended.

In addition, in FIG. 4 above, the external connection terminal section 15
Although an example is shown in which the external connection terminal portion is formed using a metal lead wire, it is of course possible to extend and form the external connection terminal portion integrally with the above-mentioned wiring conductor using a printing method.

As explained above, the structure of the sealed portion of the display device envelope according to the present invention prevents the movement of, for example, Na ⁺ ions from the substrate 11 and front bulb 16 toward the external connection terminal portion 15 due to heating or the like. , is prevented by the presence of the first crossover 12 (insulating layer) and the front valve side insulating layer 17, and Na ⁺
Electrolysis of ions, sealing with Na in cement 18
The phenomenon of reduction of PbO and precipitation of Pb hardly occurs, and insulation deterioration between the external connection terminals 15 is prevented, and a long life with stable quality can be expected.
This provides an extremely excellent effect in that normal circuit operation can be expected for a long period of time even when left at high temperatures.

Further, the display device according to the present invention is inexpensive and easily available as a substrate and a front bulb. In addition, since plate glass with good workability can be used, the effects obtained from the viewpoint of manufacturing and cost reduction are extremely large.

[Brief explanation of the drawing]

Figures 1a and 1b are perspective views and cross-sectional views of essential parts showing the structure of the substrate portion of a conventional fluorescent display tube formed using thick film circuit technology, and Figure 2 is a conventional fluorescent display tube. FIGS. 3a and 3b are diagrams for explaining problems with the tube, and FIGS.
Figures a and b are a sectional view and an exploded view of a main part showing an embodiment of a display device according to the present invention. 11...Substrate, 12...First insulating layer, 13...
... Wiring conductor, 14 ... Second insulating layer (crossover), 15 ... External connection terminal section, 16 ... Front valve, 17 ... Front valve side insulating layer, 1
8...Sealing cement, 19...Envelope.

Claims (1)

[Claims for Utility Model Registration] 1. An insulating material containing an alkaline component such as plate glass is used as the substrate 11, and the peripheral portion of the substrate 11 is formed of an insulating material containing an alkaline component such as glass. front valve 1
6 has an envelope 19 hermetically sealed with a sealing cement 18 made of lead glass, and on the substrate 11 in this envelope 19, wiring conductors 13 are arranged according to a predetermined circuit pattern. The wiring conductor 13 is formed so as to be covered with a second insulating layer 14 made of glass, and the second insulating layer 14 is formed on the upper surface of the second insulating layer 14. A display section is formed which is electrically connected to the wiring conductor 3 through the through hole provided in the wiring conductor 14 to be driven. In a display device that is airtightly penetrated and drawn out to the outside, a first insulating layer 12 made of non-alkali glass is coated at least on the top surface of the substrate 11 where the external connection terminal portion 15 is formed. The external connection terminal portion 15
is formed on the upper surface of the first insulating layer 12, and at least the external connection terminal portion 1 in the sealing portion on the lower surface of the front valve 16.
5. A display device characterized in that a front bulb-side insulating layer 17 made of non-alkali glass is adhered to the portion through which the reference numeral 5 penetrates. 2. The display device according to claim 1, wherein the external connection terminal portion 15 is formed integrally with the wiring conductor 13 by being attached thereto.