JPH03187139A - Image display device - Google Patents

Abstract

PURPOSE:To suppress the deterioration of image quality due to the damage to a cathode point, and to achieve longevity of an image display device by providing plurality of cathode points in one electrode hole. CONSTITUTION:Cavities 24a and electrode holes 25a are provided on an insulating film 24 and on a gate electrode 25, while plurality of cathode points 26 are arranged in each cavity 24a (or electrode hole 25a) on a base electrode 23. In case one cathode point 26 is broken, the display can be carried out on the electrode hole 25a by the irradiation electron flow from the holder cathode points 26, and a bad effect to an image quality due to the damage given to the cathode point can be suppressed to a lower degree. Since the cathode point 26 can be provided in the position decentered in the gate electrode hole 25a, the voltage decrease caused by the current running in the gate electrode 25 can be suppressed to a lower level. Thereby the working life of the device can be expected to be longer, and the quality of display can be improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an image display device that irradiates a phosphor with a stream of radiated electrons emitted from a cold cathode and displays an image using the light from the phosphor. It is.

[Conventional technology]

Figure 2 shows IEEE Transactions of Electron Devices.
actions of Electron Devi
ces, 36 [1] (1989-1), C,A,
5pindt, “Field-Eriitter
Arrays＾pplied to Vacuul FI
uorescentDisplay” P, 225-2
27 is a diagram showing a conventional image display device described in 27.

In the conventional device shown in FIG. 2, a base electrode f#l (cathode) 3 is formed on an SL substrate 1 covered with an oxide film 2, and a gate electrode 5 is formed on it via an insulating film 4. Several tens to hundreds of electrode holes 6 are formed in the gate electrode 5, and a cathode tip (not shown) formed in the shape of a conical projection is formed within the electrode hole 6. ing.

On the other hand, a transparent front substrate 8 placed opposite to the substrate 1 with a spacer 7 in between has an IT
It has a transparent conductive Wi, (anode) made of O or the like, and three types of phosphor layers 10 having different fluorescent colors are formed thereon.

Here, Figure 3 is from the Journal of Applied Physics.
l+ysics, 47 [12] (1976-12
) (USA), Anerican In5tituteo
f Physics, C, ^, 5pindt, ”P
physical properties of thin
-fillfield eission cath
odes with molybdenun+ cone
s", P, 5248-5263). The cathode tip shown here is applied to a portion 6 whose details are not shown in FIG. 2. As shown in FIG.
Insulation consisting of i 02) IG! 12 is formed, and one cathode tip 13 in the shape of a conical projection is formed in the center of the cavity 12a of the insulating film 12. Further, on the insulating film 12, there is a gate salt [! 14 are provided.

Then, in order to emit electrons from the cathode tip 13, 10
A strong electric field of about 7 V/(2) is applied to emit a current of electrons from the cathode tip 13, and this radiated electron current is accelerated and aggregated by a transparent conductor @M (reference numeral 9 in FIG. 2) to form a phosphor layer ( The image is displayed by irradiating the area 10) in FIG.

[Problem to be solved by the invention]

However, in the conventional example shown in FIGS. 2 and 3, since only one cathode tip is provided in one electrode hole, one cathode tip may be damaged by the impact of residual gas ions.
If the function of each cathode tip is impaired and electron flow cannot be emitted, the gate electrode hole portion (reference numeral 6 in Figure 2) will no longer be able to operate. However, since the display quality is adversely affected, there is a problem that the operating life of the device is short.

Furthermore, conventionally, in order to obtain a strong electric field, the cathode tip and the edge of the gate electrode hole are brought extremely close to each other, but in this case, the component of the emitted electron flow that flows into the gate electrode increases. , losses such as voltage drop occur on long striped gate electrodes, resulting in a decrease in display brightness toward the tip of the electrode stripe, and an increased burden on the drive circuit for gate voltage control based on image signals. , there was a problem of deteriorating display quality.

Therefore, the present invention has been made to solve the problems of the prior art described above, and its purpose is to display an image that has a long operating life, improves display quality, and improves reliability. The goal is to provide equipment.

[Means to solve the problem]

An image display device according to the present invention includes an insulating substrate, a cathode provided on the insulating substrate, a cathode tip formed in the shape of a protrusion having a sharp tip portion on the cathode, and a cathode tip provided on the cathode in the form of a protrusion, and an insulating film formed to have a cavity surrounding the cathode tip, a gate electrode formed on the insulating film to have an electrode hole surrounding the cathode tip, and a predetermined distance from the insulating substrate. a transparent substrate disposed to face each other; an anode provided on a surface facing the cathode tip; In the image display device having a phosphor layer, a plurality of the cathode tips are provided inside the same electrode hole of the gate electrode.

[For production]

In the present invention, by providing a plurality of cathode tips in one electrode hole, even if one cathode tip is damaged and its function is impaired, the radiation electron flow from other cathode tips can prevent
Display is performed at the electrode hole portion. Therefore, the adverse effect on image quality due to damage to the cathode tip can be suppressed to a low level. Furthermore, since a plurality of cathode tips are provided in one electrode hole, the cathode tips are provided at eccentric positions inside the gate electrode hole. When the cathode tip is provided at an eccentric position in this way, the component of the emitted electron flow that flows into the gate electrode is reduced compared to when the cathode tip is placed at the center of the electrode hole (this principle will be explained in the (Explained in Figure 6). Therefore, the voltage drop due to the current flowing through the gate electrode can be suppressed to a low level, and the burden on the circuit for controlling the gate voltage based on the image signal is reduced.

〔Example〕

The present invention will be explained below based on illustrated embodiments.

FIG. 1 is a configuration diagram showing an embodiment of an image display device according to the present invention. As shown in the figure, in this embodiment, the thickness of the Si substrate 21, which is the rear substrate, is 0.
．． The upper surface of the insulating film 22 having a thickness of about 5 to 1.0 μm is coated with a thickness of 0.0 μm.
A striped base electrode (cathode) 23 with a thickness of about 5 μm is provided, on which an insulating WA 24 with a thickness of about 0.5 to 1.5 μm and a striped base electrode made of Mo with a thickness of about 0.2 to 0.5 μm are provided. gate electrodes 25 are provided in sequence. Further, the insulation ff124 and the gate electrode 25 have a cavity 24a and an NM hole 25a each having a diameter of about 3 to 30 μm.
There are several to hundreds of .

In this embodiment, a cathode tip 26 made of Mo with a radius of curvature of about 0.05 to 0.2 μm at the tip is placed in each cavity 24a (electrode hole 25a) on the base electrode 23. Multiple pieces are placed.

Here, FIG. 4 is a plan view showing the arrangement of the cavity 24a and the electrode hole 25a, as well as the arrangement of the cathode tips 26 in this embodiment, and shows a case where a plurality of cathode tips 26 are arranged randomly. There is. In addition, FIGS. 5(a) and (b) are 1
A plurality of cathode tips 26 arranged in the cavities 24a
Figure (a) is a vertical cross-sectional view, Figure (b) is a vertical cross-sectional view.
is a plan view.

Furthermore, as shown in FIG. 1, in this embodiment, a front substrate 27 made of transparent glass is provided opposite to the SL substrate 21.
is arranged, and the cathode tip 2 of this front substrate 27
6fP! A transparent conductive Jlli 28 as an anode is provided on the surface of the electrode. Further, on the transparent conductive film 28, a striped phosphor layer 29 is provided which emits R (red), G (green), and B (blue) color light by fluorescence.

In this embodiment, the gate voltage ′! By applying a gate voltage to f125, electrons are emitted from the cathode tip 26, the electrons are accelerated by the transparent conductive film 28, and an image is displayed using R, G, and B color light obtained by irradiating the electrons to the phosphor 29. are doing.

The reason why a plurality of cathode tips 26 are provided in one electrode hole 25a in this embodiment as described above is due to the following two reasons.

First, if the discharge current emitted from the cathode tip is I, and the electric field at the tip of the cathode tip is E, then the current ■ is expressed by the following equation (1
).

r=BEexp(-β/E)・(1)
Here, B and β are constants determined by the work function of the cathode material.

Furthermore, the electric field E at the cathode tip has a radius of curvature of the tip portion r. (inner sphere radius), and the distance from the cathode tip to the edge of the gate electrode is ra (equivalent outer sphere radius). If the gate El & voltage are Va, then the following equation (
2> is approximately expressed.

1 E = (Va / ' o ) < 1 r o /
r a )...(2) Here, the equivalent outer sphere radius ra is the inner sphere radius r. If it is sufficiently larger than , equation (2) can be expressed as the following equation (3).

E~ Va/ro...(3) Equation (3) shows that the electric field E at the cathode tip is the radius of curvature r of the cathode tip.
, but is independent of the distance from the cathode tip to the edge of the electrode hole. From this, the cathode tip does not necessarily need to be close to the edge of the electrode hole, and even if the diameter of the electrode hole is enlarged or the cathode tip is placed unevenly within the electrode hole, it will not necessarily respond to the electric field E. It can be seen that the effect on the magnitude of the radiation electron flow is very small. Further, if the thickness of the tip portion of the cathode tip is about 1 μm, it is possible to arrange a plurality of cathode tips in one electrode hole. The first reason for providing multiple cathode tips in one electrode hole is that even if the diameter of the electrode hole is enlarged or the cathode tips are arranged unevenly within the electrode hole, This is because it does not affect the magnitude of the radiation electron flow.

In addition, Figures 6 (a) to (C) are for explaining the influence of the position of the cathode tip and the diameter of the electrode hole on the gate current. The case where the gate electrode is located at the center and the equivalent gate electrode radius is ral (case 1) is shown.
Figure (b) shows the case where the cathode tip is located at the center of the electrode hole and the equivalent gate electrode radius is ra2 larger than 'at (case 2).
), and FIG. 6(c) shows a case (case 3) in which the cathode tip shown in FIG. 4(b) is placed at a biased position within the electrode hole.

By the way, although the gate current is non-directional in the above spherical model, it actually has a finite radiation angle (for example, 30 to 40 degrees) and only flows into the edge of the gate electrode within a specific range. , Therefore, when comparing Cases 1 to 3 regarding the gate electron flow, Case 1 has a smaller diameter electrode hole.
case (when the equivalent gate electrode radius is small) is the largest, and case 2, where the electrode hole diameter is large (when the equivalent gate electrode radius is large), is the next largest; Case 3, which has the same size but has the cathode tip located at a position offset from the center of the hole, has the smallest amount. That is, the gate current is reduced when the cathode tip is provided at an eccentric position.

Furthermore, when a plurality of cathode tips are provided inside one gate electrode hole, the radiated electron current is given by the superposition of currents from the individual cathode tips, but as mentioned above, the effective current is Since it hardly changes due to enlargement or eccentricity, it is given by the sum of the effective currents of the individual cathode tips in one gate electrode hole, and the radiated electron flow can be effectively increased. The second reason why multiple cathode tips are provided in one electrode hole is that if the gate electrode hole has the same diameter, the gate current from the eccentrically placed cathode tip is smaller and more effective. This is because the current of radiation electrons can be increased.

As explained above, according to this embodiment, by providing a plurality of cathode tips in one electrode hole, even if one cathode tip is damaged and its function is impaired, it will not be affected by other cathode tips. Display at the electrode hole portion is performed by a flow of radiated electrons. Therefore, the adverse effect on image quality due to damage to the cathode tip can be suppressed to a low level, and as a result, the operating life of the device can be extended.

Further, since a plurality of cathode tips are provided in one electrode hole, the cathode tips are provided at an eccentric position inside the gate Th electrode hole. In this way, the cathode tip is placed at an eccentric position.
When the cathode tip is placed at the center of the electrode hole, the component of the emitted electron flow that flows into the gate electrode is reduced, so the voltage drop due to the current flowing through the gate electrode can be suppressed. The burden on the drive circuit for controlling the gate voltage based on the image signal can be reduced. Therefore, it is possible to prevent deterioration in image quality due to voltage effects and deterioration in reliability due to increased load on the drive circuit.

In the above embodiment, the cathode tips are arranged randomly, but the present invention is not limited thereto. FIG. 7 is a plan view showing another example of the arrangement of the cathode tips. As shown in the figure, the gate electrode hole 25
A predetermined number of IF within a! The pole cusps f@26 may be provided in a determined arrangement.

FIG. 8 is a configuration diagram showing an example to which the image display device of this embodiment is applied. In this figure, the same components as in FIG. 1 are designated by the same reference numerals.This example differs from the embodiment in FIG. 1 only in that an electron multiplier function board 30 is incorporated. Here, the electron multiplier function board 30 is provided with a large number of through holes 31, and an input side electrode 33 and an output side electrode 3 for forming an accelerating electric field for the electron flow passing through the through holes 31.
4 are provided on both sides of the electron multiplier function board 30.

The opening portion of the through hole 31 is set to collect the electron flows of the plurality of gate electrode holes 25a, and the opening portion of the through hole 3
1 (equal to the thickness of the electron multiplier function board 30) is set to be several times to several hundred times the equivalent diameter of the through hole 31. By doing so, it is possible to achieve a multiplication gain of several tens to hundreds of times the electron flow.

Therefore, according to the example shown in Fig. 8, it is possible to reduce the electric field at the cathode tip and increase the radius of curvature of the cathode tip, which reduces problems in microstructure processing and allows the application of simple manufacturing methods. becomes possible.

〔Effect of the invention〕

As explained above, according to the present invention, by providing a plurality of cathode tips in one electrode hole, it is possible to suppress the negative effect on image quality due to damage to the camellia tip, and as a result, the device is improved. The operating life can be extended.

In addition, since multiple cathode tips are provided in one electrode hole, it is possible to reduce the component of the emitted electron flow that flows into the gate electrode, thereby keeping the voltage drop caused by the current flowing through the gate to a low level. be able to. Therefore, it is possible to reduce the load on the drive circuit for controlling the gate voltage based on the image signal, and it is possible to prevent a decrease in image quality due to this voltage drop and a decrease in reliability due to an increase in the load on the drive circuit.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of an image display device according to the present invention, Fig. 2 is a block diagram showing a conventional image display device, and Fig. 3 is a cross section showing a cathode tip portion of a conventional image display device. Figure 4 is a plan view showing the arrangement of the cavity and electrode holes and the arrangement of the cathode tip 26 in this embodiment, and Figures 5(a) and 5(b) show a plurality of electrode holes arranged in one cavity. 6(a) to (c) are explanatory diagrams for explaining the influence of the position of the cathode tip and the diameter of the electrode hole on the gate electrode hole; FIG. 7 8 is a plan view showing another example of the arrangement of cathode tips, and FIG. 8 is a configuration diagram showing an example to which the image display device of this embodiment is applied. 21... St substrate 22... Insulating film 23... Base electrode (cathode) 24... Insulating film 24a... Cavity part 25... Gate electrode 25a... Gate electrode hole 26... Cathode tip 27...front substrate 28...transparent conductive film 29...phosphor layer (anode)

Claims (1)

[Scope of Claims] An insulating substrate, a cathode provided on the insulating substrate, a cathode tip formed in the shape of a protrusion having a sharp tip portion on the cathode, and a cathode tip provided on the cathode. an insulating film formed to have a cavity surrounding it; a gate electrode formed on the insulating film to have an electrode hole surrounding the cathode tip; and facing the insulating substrate at a predetermined distance. an anode provided on a surface of the transparent substrate opposite to the cathode tip; An image display device comprising a phosphor layer that emits light, wherein a plurality of the cathode tips are provided inside the same electrode hole of the gate electrode.