JPS5924486B2 - multi-digit fluorescent display tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a diode structure which operates with one drive circuit using a static drive system (hereinafter referred to as static drive circuit) and has no control electrode (so-called grid) for controlling the anode current. In addition, it is a multi-digit display that can uniformly display multi-digit characters, numbers, symbols, etc. (hereinafter referred to as letters), and is suitable for use in various small electronic devices, such as electronic watches with digital displays. This invention relates to a fluorescent display tube.

Fluorescent display tubes generally use a phosphor that is excited to emit light by the bombardment of electrons from a cathode, and because they provide an extremely easy-to-read display, they are often used in small electronic desktop calculators or digital electronic clocks (hereinafter referred to as digital clocks). ) and are widely used for digital displays in various electronic devices.

Also, recently, so-called multi-digit fluorescent display tubes (hereinafter simply referred to as fluorescent display tubes) are equipped with multiple digit pattern display sections that can display characters, etc. in one vacuum-tight envelope. A structure called `` is often used.

In addition, such a phosphorescent display tube includes a multi-digit pattern display area composed of a group of segmented anodes each having a phosphor layer, and a filament-shaped display area that emits electrons toward the pattern display area. It has a structure that includes a directly heated cathode (hereinafter referred to as a cathode) and a control electrode that accelerates and controls electrons emitted from the cathode, located between each of these pattern display areas and the cathode. Usually by dynamic drive method.

It is operated by a drive circuit. However, in the drive circuit using such a dynamic drive method, when operating the fluorescent display tube, there is a
Since a pulse current that is a noise source is passed through the drive circuit, it is applicable to digital displays such as electronic clocks that are built into electronic equipment that dislikes noise sources such as audio such as radios or images such as televisions. could not.

Therefore, for fluorescent display tubes that are used in electronic devices that are sensitive to the noise sources mentioned above, it is desirable that they be able to be used with so-called static drive circuits that do not use a pulsed power source, which is a source of noise. be.

In the case of a static 1 drive circuit, a direct current is passed between the anode and cathode of the segment of the digit selected according to the character to be displayed by emitting light, so there is no need for a control electrode for digit selection. A fluorescent display tube is used which functions as a diode structure.

However, in a fluorescent display tube with a so-called normal bipolar structure in which a control electrode is not disposed between a cathode and an anode, there is a structure on the inner wall surface of the envelope above the display part to reduce the electric field from the outside. A transparent conductive film electrically connected to the cathode is disposed, but the upper surface of the periphery near each segment anode on the substrate is unevenly exposed to negative (-) by electrons flying from the cathode. ) is easily charged, and once charged, the normal electric field and electron flow between the cathode and anode, which is the path of electron flow from the cathode to each segment anode, is disturbed. In this case, the luminescence of the phosphor layer on the segment anode becomes uneven or uneven, and in severe cases, the segment anode that should emit light may not emit sufficient light.

For this reason, conventionally, fluorescent display tubes used in static drive circuits have a structure in which a mesh-like auxiliary control electrode is disposed between the cathode and the plurality of pattern display sections. This auxiliary control electrode has a positive (
By applying the direct current potential of 1), consideration has been made so that a normal electric field and electron flow that are not affected by the charging around the anode and the external electric field as described above can be obtained between the cathode and the anode.

However, when a mesh-like auxiliary control electrode having the above-mentioned function is provided, the auxiliary control electrode is placed very close to the pattern display section formed by the group of segment anodes (usually about 0.5 mm). (within 3 mm).

Moreover, this auxiliary control electrode is made of a mesh made of an extremely thin metal plate (approximately 0.05 mm thick) with an extremely fine mesh formed thereon so that the light emitting display of the pattern display section can be viewed from above without any hindrance. .

Therefore, the distance between this mesh-like auxiliary control electrode and the pattern display section is 0.0000000000000000000000000000000000000000000000000000000000.0.0.0.0.0.
At a distance of 3 m, the problem arises that charging in the vicinity of each segment anode on the substrate affects it, making it impossible to obtain a sufficient luminescent display.

Furthermore, since this auxiliary control electrode is a mesh formed from an extremely thin thin metal plate, the size of the mesh-like auxiliary control electrode becomes large in a fluorescent display tube with a pattern display section that displays large characters. Even during the manufacturing process of fluorescent display tubes or after completion, they are easily deformed due to expansion and contraction due to ambient temperature, etc., making it impossible to maintain the distance between adjacent segment anodes, and in extreme cases, causing large damage such as contact with segment anodes. There was a problem.

For this reason, the conventional fluorescent display tube, which has a mesh-like auxiliary control electrode close to the pattern display section as described above, can be applied to large digital clocks that display large characters. This was extremely difficult.

An object of the present invention is to provide a multi-digit fluorescent display tube having a static drive circuit type diode structure without mesh-like auxiliary control electrodes, which solves the conventional problems as described above.
The goal is to significantly improve its light emitting function.

That is, in the present invention, letters and letters are formed by a plurality of segment anodes having a phosphor layer at least on the upper surface of the substrate in an envelope formed by sealing a substrate and an upper surface plate.
A multi-digit pattern display section that displays numbers, symbols, etc.;
In a multi-digit fluorescent display tube having a diode structure for a static drive circuit and having a cathode stretched in a position facing the pattern display section, charging is prevented in a peripheral portion of the substrate near the segment anode. An antistatic layer having the function of
During operation, the configuration includes a diffusion electrode that applies a positive potential to the cathode and makes the density of electron flow uniform from the cathode to each segment anode, and the antistatic layer is Each part provided corresponding to the pattern display section of each digit is electrically connected together, and each part of the diffusion electrode provided corresponding to each digit pattern display section is electrically connected together. Further, the antistatic layer and the diffusion electrode are configured to be provided with a constant + (plus) potential at least during the operation of the multi-digit fluorescent display tube via the external terminal lead-in wire. It is located on a multi-digit fluorescent display tube.

Hereinafter, a fluorescent display tube according to the present invention will be explained in detail with reference to the drawings.

FIGS. 1A and 1B are a cutaway plan view and an enlarged sectional view of a main part showing an embodiment of a fluorescent display tube according to the present invention.

In the figure, 11 is a substrate made of an insulating material such as glass or ceramics, and 12 is a top plate made of a transparent glass plate. The envelope 13 is sealed in a vacuum-tight manner using a sealing material such as low melting point frit glass.

Further, 14 is a sealing portion thereof.

A plurality of wiring films 15 and an insulating film 16 are laminated and adhered to the upper surface of the substrate 11 in this envelope 13, and furthermore, a plurality of digit patterns are formed on the upper surface of this insulating film 16. The display parts 17 are arranged and attached in parallel.

Each pattern display section 17 has a plurality of segment anodes 1 so as to selectively display a plurality of characters, etc.
In the illustrated example, seven segment anodes 18a, 18b...18g are arranged in a Japanese character shape.
Each pattern display section 17 is configured to selectively display 10 numbers from 0 to 9.

On the upper surface of each segment anode 18 (18a to 18g) is a phosphor layer 19 that is excited to emit light by the impact of electrons.
is formed by adhesion.

Each of the segment anodes 18 has a plurality of connecting portions 20 (
20a), and are electrically connected to external terminal lead-in wires 21a for each segment anode.

22 is a cathode formed by coating the surface of a filament-like thin wire usually made of a high-melting point metal such as tungsten with a coating material having good thermionic emission efficiency.

This cathode 22'' is composed of one or more cathodes, and is stretched and held in parallel by a filament support 23 at a position facing the pattern display section 17 arranged in parallel. It is connected to the terminal introduction line 21b.

Here, a plurality of segment anodes 18 (18a...
・A cathode 22 is placed around the cathode 22 on the same plane near the
A plurality of antistatic layers 24 are deposited to prevent charging due to electrons flying from the substrate and are electrically connected together.

This antistatic layer 24 is electrically connected through a connecting portion 20 (20b) provided in an opening provided in the insulating coating 16, and further connected to an external terminal lead-in wire 21c through the wiring coating 15.

Therefore, a constant + (plus) potential is always applied from this external terminal lead-in line 21c at least during the operation of the multi-digit fluorescent display tube.

Reference numeral 28 denotes a mesh-like diffusion electrode disposed close to the inner wall surface 29 of the top plate 12 facing the pattern display section 11 and the cathode 22.

That is, the diffusion electrode 28 is made of a coarse mesh formed in a lattice or honeycomb shape with extremely thin lines so as not to obstruct the visual observation of the light emitting display of the pattern display section 17 from above. Using an adhesive such as melting point crystalline frit glass, it is adhered and held at a plurality of arbitrary locations on the inner wall surface 29 that do not interfere with display.

Further, this diffusion electrode 28 is electrically connected to the charged waterproof layer 24 disposed on the substrate 11 by a strip-shaped connecting piece 30 connected at an arbitrary position.

The diffusion electrode 28 arranged in this manner is operated by applying a positive potential to the cathode 22 together with the antistatic layer 24, so that the diffusion electrode 28 is connected from the cathode 22 to each segment anode 18 of the plurality of pattern display sections 17. It has the function of creating an electric field that diffuses the flowing electron flow and averages out the electron density.

As described above, a plurality of pattern display parts 17 are formed of a group of segment anodes 18 having a wiring film 15, an insulating film 16, and a phosphor layer 19, which are laminated on the upper surface of the substrate 11. and a cathode 2 stretched across the antistatic layer 24 and the plurality of pattern display sections 17.
2 and the diffusion electrode 28 and the like disposed close to the inner wall surface 29 of the top plate 12 are formed by being airtightly sealed by the substrate 11 and the top plate 12 at the sealing part 14 at the periphery thereof. It is housed in a vacuum atmosphere inside an envelope 13.

In addition, each segment anode 18, cathode 22, antistatic layer 24, diffusion electrode 28, etc. in this envelope 13 has respective external terminal lead-in wires 2 which are sealed through the sealing part 14.
Electricity is supplied from the outside through 1a, 21b, and 21c.

The fluorescent display tube according to the embodiment of the present invention having the above-described structure is suitable for use in a static drive circuit.
When driving this, a bias potential that is at least more positive (1) than the potential of the cathode 22 is applied to the antistatic layer 24 and the diffusion electrode 28 through a common external terminal lead-in line 21c, preferably between the cathode and the anode. A bias potential of plus (1), which is closer to the anode potential than the intermediate potential of , is applied to at least the operating center of the fluorescent display tube with a large number of digits, and the bias potential is applied to the cathode 22 and the digit characters, etc. to be displayed. Selected segment anode 18 (18a).

18b, 18g), which is a so-called static drive method in which a direct current is sequentially applied and energized, and the device is operated, and by this, a fluorescent display of any character, etc. of any desired digit can be made. You can get it.

In this case, the potential distribution diagram between the cathode and anode in this fluorescent display tube is as shown in FIG.

That is, in a fluorescent display tube with a conventional structure, the density of electrons striking the portion near the segment anode 3 close to the cathode 1 is high, causing uneven luminance of light emission. According to the present invention, the same positive (1) potential as the segment anode 18 is always applied to the cathode 22 to the diffusion electrode 28 and the antistatic layer 24 disposed close to the inner wall surface 29 of the top plate 12. Since the electric field is operated by the electric field, the density of the electron flow from the cathode 22 to the segment anode 18 is diffused and averaged as shown in FIG. It has a diode structure with no control electrode disposed between the cathode and anode, and has the excellent feature of providing a uniform light-emitting display without uneven brightness.

Furthermore, in the fluorescent display tube according to the present invention, the potential distribution between the cathode 22 and the group of segment anodes 18 has a uniform potential gradient, particularly in the vicinity of the cathode 22 that emits electrons, as shown in FIG. Therefore, segment anode 18
It has the feature that the amount of electrons that strike the device becomes a dog, and a light emitting display with brighter brightness than that of conventional devices can be obtained.

That is, according to various comparative experiments conducted by the inventors,
When the same voltage was applied between the cathode and the anode, the device according to the present invention shown in FIG. 2 produced a bright luminescent display with a brightness approximately 50% higher than that of the conventional device of this type.

Further, in the fluorescent display tube according to the present invention, the substrate 11
has an antistatic layer 24 on the top surface of each segment anode 18 in close proximity to each segment anode 18, so that during operation, each segment anode 18
This prevents the electrons flying from the cathode 22 from being charged in the vicinity of the gap, and further prevents the electric field from various electronic devices approaching from below the substrate 11 from entering the area where the electrons flow between the cathode and the anode. Because it is so easy to use, it eliminates the problems of so-called diode structures in which the control electrode is not placed in the middle, such as display fading due to charging and the influence of external electric fields. Since there is no control electrode that would reduce brightness, it also has the excellent feature of providing an extremely clear luminescent display.

Further, as described above, the diffusion electrode 28 disposed close to the inner wall surface 29 of the top plate 12 is for applying an electric field to diffuse the electron flow from the cathode 22 to the segment anode 18. The conventional control electrode (grid) placed between the cathode and anode does not require dimensional accuracy, and can be easily attached to the top plate, resulting in high productivity.

Furthermore, when the diffusion electrode 28 is formed of a mesh, the mesh is much coarser than that of a conventional control electrode, and is formed of a grid or honeycomb-like structure of extremely thin lines.

That is, while the porosity of the control electrode mesh that is commonly used is about 80%, the porosity of the diffusion electrode that forms the mesh may be about 90 to 95 inches.

Therefore, this diffusion electrode is not a scale with good workability, and it does not interfere at all with viewing the light emitting display of the pattern display section 17 from above. be.

Here, in the above-described embodiment, the diffusion electrode of the fluorescent display tube according to the present invention is formed by a mesh disposed close to the inner wall surface 29 of the top plate 12, but is not limited to this. On the inner wall surface 29 of the top plate 12 facing the display section 17, a mesh-like conductive film such as a thin mesh or stripes is formed by printing or the like, or a tin oxide film called Nesa, for example, is formed. A diffusion electrode can be formed by depositing a transparent conductive film such as, or by depositing both a mesh-like conductive film formed by printing as described above and a transparent conductive film made by Nesa or the like. Of course you can.

If a diffusion electrode is formed using a transparent conductive film or the like that adheres to the inner wall surface 29, the pattern display section 17 can be exposed from above.
Since there is no mesh in the middle that would obstruct visual viewing of the light emitting display, an excellent effect is obtained in that an extremely bright display can be obtained.

However, when disposing only a transparent conductive film as a diffusion electrode, the conductivity should be at least about 100 Ω/min or less, and more preferably several Ω to several + Ω/min. desirable.

Further, the diffusion electrode is constituted by a transparent conductive film deposited on a portion of the inner wall surface 29 of the top plate 12 facing the pattern display portion, and a mesh disposed close to the surface of the transparent conductive film. Of course, you can do it like this.

In this way, the transparent conductive film may be one having a low conductivity over a wide range, such as the commonly used so-called NESA film, that is, from about several hundred Ω/C-rrL to approximately M
The mesh may have a conductivity of Ω/cm or so, and the mesh may have a coarse mesh that has better light transmittance than a mesh used as a diffusion electrode and does not interfere with visual viewing of the luminescent display. Since the material may have a porosity of about 95% or more, the workability is further improved, the inner wall surface 29 of the top plate 12 is less likely to be charged, and its function as a diffusion electrode is improved.

According to the present invention, the electron flow is controlled by the diffusion electrode 28 to which a constant potential of 10 is always applied to each digit, regardless of whether each digit or segment anode is lit or not, as explained with reference to FIG. , diffusion to the pattern display area is performed,
Therefore, sufficient electrons can reach the segment anodes 18 near the boundaries of each pattern display area, and the amount of electrons hitting the segment anodes 18 increases, resulting in a clear display.

In addition, the antistatic layer 24, which is common to each digit and is always applied with a constant potential of 10, prevents the accumulation of electricity around each segment anode 18, and there is no risk of display failure.

In this manner, the electrically integrated diffusion electrode 28 and the antistatic layer 24 work together to greatly improve the light emitting function of a multi-digit fluorescent display tube using a static drive circuit system without a mesh-like control electrode. There is an effect that can be done.

Next, according to the present invention, the antistatic layer and the diffusion electrode are commonly electrically connected to the multi-digit pattern display area, so the structure, especially the external lead structure, is simple and easy to manufacture. It has the effect of making it easier.

Further, in the fluorescent display tube according to the present invention, a constant + (plus) potential is always applied to the antistatic layer and the diffusion electrode through the external terminal lead-in wire at least during operation of the fluorescent display tube. Therefore, the antistatic function, electron flow averaging function, and external electric field shielding function are working during the operation of the fluorescent display tube, and the above functions are permanent and extremely reliable. can get.

[Brief explanation of the drawing]

1A and 1B are a cutaway plan view and an enlarged sectional view of essential parts showing an embodiment of the multi-digit fluorescent display tube of the present invention, and FIG. 2 is a potential of the multi-digit fluorescent display tube of the present invention. It is a distribution map. 11...Substrate, 12...Top plate, 13
... Envelope, 17 ... Pattern display section, 18 (18a, 18b, 18g) ... Segment anode, 19.
...phosphor layer, 21a, 21b, 21c...
...External terminal lead-in wire, 22...Cathode, 24
. . . Antistatic layer, 28 . . . Diffusion electrode.

Claims (1)

[Claims] 1. In an envelope formed by sealing a substrate and a top plate, at least a plurality of digits displaying letters, numbers, symbols, etc. on the top surface of the substrate by a plurality of segment anodes having a phosphor layer are provided. In a multi-digit fluorescent display tube having a diode structure for a static 1 drive circuit, the display tube has a pattern display section, and a cathode stretched at a position opposite to the pattern display section. An antistatic layer having a function of preventing static electricity is provided in the peripheral area, and an antistatic layer is provided on the inner wall surface of the top plate facing the pattern display section or a portion close to this inner wall surface against the cathode during operation. The structure includes a diffusion electrode that has the function of applying a positive potential and uniformizing the density of electron flow from the cathode to the anode of each segment, and the antistatic layer corresponds to the pattern display area of each digit. The respective portions of the diffusion electrode provided corresponding to the pattern display portions of each digit are electrically connected together, and the antistatic layer A multi-digit fluorescent display tube characterized in that a constant + (plus) potential is applied to at least the operating center of the multi-digit fluorescent display tube through the external terminal lead-in wire to the diffuser electrode and the diffusion electrode. .