JPS63221545A - Fluorescent character display tube - Google Patents

Abstract

PURPOSE:To efficiently accelerate the thermoelectrons emitted from a hot cathode to collide with phosphors, increase the luminous brightness, and display in a bright state by forming a grid into a grid electrode with the thermoelectron passing shape and the size wholly covering the phosphors. CONSTITUTION:Many phosphors 3 with a fine dot shape and segment electrodes 2 are formed on the substrate 1 of a fluorescent character display tube in an array shape, a transparent case is fixed to this substrate 1, and a vacuum space 7 is formed with the substrate 1. A hot cathode made of a tungsten wire 6 is stretched along the array direction of the phosphors 3 facing the substrate 1 in this vacuum space 7. A grid electrode 9 made of a transparent material is arranged between the phosphors 3 and the tungsten wire 6 of this display tube, this grid electrode 9 is formed into a hexagon mesh structure with a thermoelectron passing shape to cover the whole phosphors 3. The thermoelectrons emitted from the tungsten wire 6 are efficiently accelerated and collide with the phosphors 3, and the display brightness is made bright.

Description

TECHNICAL FIELD The present invention relates to a fluorescent display tube that displays information using fluorescence emitted when thermoelectrons emitted from a hot cathode collide with a phosphor.

In a conventional fluorescent display tube, a phosphor screen made of phosphor is formed in the shape of minute dots on a number of segment electrodes arranged in one or more rows in one direction, and this is sealed in a vacuum container together with a hot cathode. Then, while generating thermionic electrons from the hot cathode,
A positive voltage is selectively applied to the segment electrodes according to the information to be displayed, and thermoelectrons are attracted to the selected segment electrodes and caused to collide with the phosphor on the segment electrodes. In this way, information is displayed by the fluorescence emitted from the phosphor screen when thermoelectrons collide with the phosphor. Such fluorescent display tubes are already well known as, for example, bar code display tubes and phosphor dot array tubes.

Here, a conventional fluorescent display tube will be schematically explained using FIGS. 5 and 6, taking the case of a phosphor dot array tube as an example. First, a long substrate 1 made of an insulating material such as glass, ceramic, or resin is provided. On this substrate 1, a series of segment electrodes 2 in the form of a large number of strips are arranged at equal intervals in the longitudinal direction with a minute pitch, and adjacent electrodes are formed so that their drawing directions are alternately different. A phosphor 3 is provided on each segment electrode 2 so as to be located on the longitudinal center line of the substrate 1. The size of each phosphor screen of these phosphors 3 is, for example, 40×40 μm2 to 50×50 μm2.
Although it is an extremely small dot on the order of μm2, it is exaggerated and shown larger in the drawing.

On both sides of the substrate 1 in the playing direction of the phosphor 3, an insulator layer 4a covers the segment electrodes 2.

4b is formed along the longitudinal direction. Grid electrodes 5a and 5b are formed on these insulator layers 4a and 4b, respectively. Furthermore, such a grid electrode 5a,
Two tungsten wires 6 serving as hot cathodes are provided above 5b and stretched in the longitudinal direction of the substrate. These tungsten wires 6 have BaO, S on their surfaces.
It is made by coating an electron radioactive substance such as rO. Furthermore.

In order to form the vacuum space 7 as described above, it is covered with a face member 8 made of a transparent material such as glass that is integrated with the substrate 1 side. That is, in a highly vacuum space 7 closed by the face member 8 and the substrate 1, the segment electrode 2, the phosphor 3, the tungsten wire 6,
Grid electrodes 5a, 5b, etc. are confined.

In such a configuration, the grid electrode 5a.

An appropriate voltage is applied to 5b. When an alternating current of about several mA is passed through the tungsten wire 6, the tungsten wire 6 is heated by Joule heat and emits thermoelectrons. In this state, when a positive voltage is applied to one of the segment electrodes 2 to make it have a positive potential, the thermoelectrons emitted from the tungsten wire 6 are attracted to the electrode portion of this segment electrode 2 that has a positive potential. In this manner, the thermoelectrons collide with the phosphor 3 when being sucked into the electrode portion, exciting the energy state of the phosphor on its surface. The excited fluorescent substance emits fluorescence when returning to the ground state. Fluorescence in such a phosphor 3 is caused by the face member 8
observed through.

Here, the grid electrodes 5a and 5b have a function of controlling the amount of thermoelectrons emitted from the tungsten wire 6 reaching the phosphor 3 side according to the applied voltage, and keep the phosphor 3 at a predetermined level. This is for emitting light with brightness. Here, the functions required of such a grid electrode are that thermionic electrons can pass therethrough, and even if it is placed between the tungsten wire 6 and the phosphor 3, it must be visible from the face member 8 side. . Therefore, conventionally,
The grid electrodes 5a, 5b are formed by etching a stainless steel material, for example, into a hexagonal mesh shape with a size of about 50 to 75 μm as shown in FIG. 5b is divided into two parts with an interval of dimension d between them.

However, with the opening-type grid electrodes 5a and 5b, which are arranged in two halves on both sides of the phosphor 3, the thermoelectrons cannot efficiently reach the surface of the phosphor 3, and there is insufficient energy. In this case, the luminance cannot be obtained. In addition, when considering the installation/assembly process, it is necessary to be very careful when installing the grid electrodes 5a and 5b so that they sandwich the phosphor 3 from both sides so as not to cover it, and normally the distance between the grid electrodes 5a and 5b is The interval d tends to be wide. This aggravates the above-mentioned inefficiency and is also a factor in deteriorating the efficiency of supplying thermoelectrons to the phosphor 3.

the purpose The present invention was made in view of these points.

The purpose of the present invention is to provide a fluorescent display tube that efficiently supplies thermoelectrons emitted from a hot cathode to a fluorescent substance, enables display with sufficient luminance, and does not impair visibility.

Structure In order to achieve the above object, the present invention provides a substrate on which a large number of microdot-shaped phosphors are formed together with segment electrodes in an array, a transparent cover fixed to this substrate to form a vacuum space, and a transparent cover that forms a vacuum space. a wire-shaped hot cathode facing the substrate and stretched along the array direction of the phosphors; It is characterized by comprising a grid electrode made of a transparent material placed between the hot cathode and the hot cathode.

Hereinafter, one embodiment of the present invention will be described based on FIGS. 1 and 2. The basic structure of the fluorescent display tube is the same as that of the conventional one, and the same parts as shown in FIGS. 5 to 7 are designated by the same reference numerals.

In this example, the grid electrode is different.

First, unlike the conventional grid electrodes 5a and 5b, the grid electrode 9 of this embodiment is made of a transparent material, such as conductive glass. Such conductive glass is produced by forming a transparent conductive film on a glass substrate using a chemical film forming method (for example,
It is formed by forming a film using a spray method) or a physical film forming method (for example, a sputtering method). Here, the transparent conductive film is generally a film that has both high conductivity and high transparency in the visible wavelength range, and also has high reflectivity in the infrared wavelength range. As transparent conductive film materials having such properties, for example, 203 and SnO are common.

Therefore, the grid electrode 9 made of such a transparent material is not separated from the part corresponding to the phosphor 3, but is connected to the phosphor 3.
The insulator layer 4 is formed to have a size that completely covers the entire surface of the substrate 1 , more specifically, the same size as the substrate 1 , and is placed on the insulator layer 4 . In other words, the arrangement position is an intermediate position between the tungsten wire 6 and the phosphor 3, as in the conventional case. By the way, such a grid electrode 9 must be able to pass the thermoelectrons emitted from the tungsten wire 6 toward the phosphor 3 side, and in this embodiment, the grid electrode 9 has a shape as shown in FIG. The hexagonal network structure is etched to ensure a thermoelectron passage area.

According to such a configuration, the thermoelectrons emitted from the tungsten wire 6 and directed toward the phosphor 3 are efficiently accelerated and controlled by the grid electrode 9 that is present over the portion corresponding to the phosphor 3. In other words, the thermoelectrons collide with the phosphor 3 on the selected segment electrode 2 while receiving sufficient acceleration control by the grid electrode 9, resulting in fluorescent display with sufficient luminance. Here, the display is visible from the face member 8 side, but since both the grid electrode 9 covering the phosphor 3 and the face member 8 are transparent, there is no problem in viewing the information. Also, the grid electrode 9
Since it is not divided into two parts and is made up of a single piece, its installation becomes easy.

Note that when using the grid electrode 9 having such a configuration,
There is a possibility that thermoelectrons may also adhere to the inner wall surface of the grid electrode 9. As a countermeasure against this, when attaching the transparent conductive film onto the glass substrate, the transparent conductive film may be formed by, for example, a spray method so that the transparent conductive film also penetrates and adheres to the inner wall surface side.

Further, the shape of the grid electrode 9 for passing thermoelectrons may be a simplified pattern shape such as a square mesh structure as shown in FIG. 3, for example.

Furthermore, as shown in FIG. 4, the grid electrode 11 may have a structure using glass fiber 10 as a base material.

That is, according to this, by arranging a plurality of glass fibers 10 at intervals, it is possible to form a grid electrode 11 through which thermoelectrons can pass. This eliminates the need for an etching patterning process. Here, the glass fiber 10 can be used up to a thickness of about several μm, and a transparent conductive film 12 is attached around the glass fiber 10 as shown in a partially enlarged view.

Effects As described above, in the present invention, the grid electrode has a thermion-passing shape and is large enough to completely cover the phosphor, so the thermionic electrons emitted from the hot cathode are efficiently accelerated and collided with the phosphor. Therefore, since the grid electrode is transparent, the visibility of information due to the fluorescence of the phosphor is not impaired, and further This also makes it easier to attach the grid electrode.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing one embodiment of the present invention, Fig. 2 is a longitudinal sectional front view thereof, Fig. 3 is a plan view showing a modification, and Fig. 4 shows a different modification including a partially enlarged view. A plan view, and FIG. 5 is an exploded perspective view showing a conventional example. FIG. 6 is a longitudinal sectional front view thereof, and FIG. 7 is a plan view thereof. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Segment electrode, 3... Fluorescent substance, 6... Tungsten wire (hot cathode), 7...
Vacuum space, 8...Face member (transparent cover), 9.
... Grid electrode, 11... For grid electrode Applicant Ricoh Co., Ltd. -U, A
Figure 3 Figure 5.3 Figure Ju, 4jZ ZjA Otsu-mi 5 Figure

Claims (1)

[Claims] a substrate on which a large number of microdot-shaped phosphors are formed in an array together with segment electrodes; a transparent cover fixed to this substrate to form a vacuum space; and an array of phosphors facing the substrate in the vacuum space. a wire-shaped hot cathode stretched along the direction; and a transparent material having a thermion-passing shape and having a size that completely covers the phosphor and disposed between the phosphor and the hot cathode. A fluorescent display tube characterized by comprising a grid electrode.