JP2623738B2 - Image display device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a thin image display device using a cold cathode.

2. Description of the Related Art There have conventionally been reported many thin display devices in which cold cathodes are two-dimensionally arranged and controlled by using XY matrix electrodes to display images. Among them, a thin display device using a thin film field emission type cold cathode attracts attention. This thin display device uses a micron-sized thin-film field emission cold cathode formed at a high density of 10 ⁶ to 10 ⁷ / cm ² on the substrate surface as shown in FIG.

This cold cathode forms one X electrode 22 of a matrix electrode on the surface of a substrate 21 as shown in the figure, and an insulating layer
23 and the other Y electrode 24 are formed. The Y electrode at each intersection of the X-Y electrodes is provided with 1,000 or more minute holes 25 of 1.5 to 2 μm by a photo-etching technique, and the insulating layer 23 is further etched. . The conical cold cathode chip 26 is formed by obliquely depositing high-separation point metals such as tungsten and molybdenum while rotating the substrate thus formed. After cold cathode formation,
By removing the unnecessary metal layer on the surface, a thin film field emission cold cathode electron source is produced. The XY matrix electron source and the face plate coated with the phosphor are opposed to each other to constitute an image display device. This image display device has 1000 pixels for each pixel.
Because it has more than one microelectron source, even if there are variations in the characteristics of each microelectron source, the characteristics will be averaged as a whole, and a relatively uniform brightness can be obtained over the entire screen. have.

Problems to be Solved by the Invention The image display device described above has not yet been put to practical use despite having the good features as described above. One of the reasons is that the manufacturing process is complicated and the cost is high, and that a field emission cold cathode having a uniform area required for a display device cannot be produced. Another reason is that the residual gas is ionized by the electron beam, and high-energy ions accelerated by the anode voltage applied between the cathode and the phosphor surface collide with the conical cold cathode and sputter, resulting in a short life. ,
The operation becomes unstable.

Means for Solving the Problems In an image display device in which an insulating back plate provided with an electron source controlled by an XY matrix electrode and a face plate coated with a phosphor are opposed to each other, each intersection of the XY matrix electrodes The electron source provided in the first embodiment is composed of an electrode connected to the X array electrode (hereinafter referred to as a cold cathode), and a Y array electrode (hereinafter, a portion facing the cold cathode is referred to as a gate electrode) opposing the X array electrode. I do.

Action The cold cathodes (X
When a voltage is applied between the array electrode) and the gate electrode (Y array electrode), a high electric field is generated between the cold cathode and the gate electrode, and electron emission occurs. Some of the emitted electrons collide with the opposing gate electrode, but generate secondary electrons on the surface of the gate electrode. The generated secondary electrons are accelerated by a positive voltage (hereinafter, referred to as an anode voltage) applied to the phosphor screen of the facing face plate and collide with the phosphor, causing the phosphor to emit light.

When the cold cathode and the gate electrode are formed on the same plane as in the above configuration, the distance between the cold cathode and the gate electrode is about 1 μm, and the amount of ions that are ionized by the residual gas and collide with the tip of the cathode during this interval Is several hundred times smaller than that of the conventional configuration, and the amount of sputter due to ion collision at the cathode tip is remarkably reduced, resulting in a longer life.

Example 1 FIG. 1 shows a part of a cross section of an image display device of the present invention.
A glass substrate 1 provided with a field emission electron source at each intersection of an XY matrix electrode of an image display device and a face plate 2 coated with a phosphor are opposed to each other. The field emission electron source is composed of a cold cathode 7 and a gate electrode 5 facing each other on the surface of an insulating layer 4 covering the surface of the X electrode 3. The cold cathode 7 is connected to the X electrode 3 through a through hole 6 provided in the insulating layer 4. FIG. 2 shows a simplified configuration of electrodes when the electron source is viewed from above.
A large number of convex portions 12 are formed on the end face of the cold cathode 7 facing the gate electrode 5. The distance between the tip of the convex portion provided on the cold cathode 7 and the gate electrode 5 is 0.5 to 2 μm. On the other hand, the face plate 2 is a transparent glass substrate, on the surface of which a transparent electrode 8, for example, an ITO film (indium oxide / tin film or SnO ₂ film) is provided, and on the surface thereof, a phosphor for low-speed electron beams, for example, ZnO: Zn Is applied.

When a voltage of 100 V to 150 V is applied between the X electrode (cold cathode) and the Y electrode (gate electrode) thus configured, a strong electric field of ~ 10 ⁷ V / cm is generated at the tip of the convex portion of the cold cathode. Then, electron emission occurs from the tip. These electrons are accelerated to 100 to 150 eV and collide with the gate electrode to emit secondary electrons 10. The generated secondary electrons are accelerated by the anode voltage (0.2 to 1 KV) applied to the transparent electrode 8 of the facing face plate, and collide with the phosphor to cause the phosphor to emit light. At this time, the convex part 12 of the cold cathode
When a part or the entirety of the insulating layer 11 below the tip portion is removed, a strong electric field is generated at the tip portion, so that electron emission is likely to occur, which has the effect of lowering the driving voltage.

Further, a perspective view of a more specific electrode configuration that was implemented is shown in FIG.
Shown in the figure. The cold cathode 7 and the gate electrode 5 are formed in a comb-teeth shape, and are formed in a state where they are engaged with each other. This is in order to increase the electron emission current by increasing the convex portions 12 provided on the cold cathode as much as possible and to reduce the variation between pixels due to the variation in emission current from each cold cathode tip due to an etching error. . Further, the opposed surface of the cold cathode and the gate electrode was configured to be perpendicular to the longitudinal direction of the Y electrode (the longitudinal direction of the X electrode). This is because some of the electrons emitted from the tip of the cold cathode collide with the gate electrode to generate secondary electrons,
Some of the electrons diverge to the next pixel without colliding with the gate electrode, but the divergence diverges in the vertical direction (Y-array direction) shown in FIG. Therefore, if the crosstalk in the Y array direction is suppressed, the crosstalk with an adjacent pixel can be suppressed. If the comb-shaped electrode in FIG. 3 is rotated by 90 °, the next pixel where electrons easily fly becomes a pixel of a different Y array, for example, a voltage is applied only to the gate electrode of the next pixel. In this case, crosstalk is likely to occur. Further, FIG. 4 shows the trajectory of the electron beam in a cross section cut along the longitudinal direction of the Y electrode (along the line AA ') since the electrodes are formed in a comb-like shape. As can be seen from FIG. 4, the electron beam that does not collide with the gate electrode is decelerated by the deceleration electric field generated by the next cold cathode, accelerated by the anode voltage, bent toward the phosphor surface, and does not diverge to the adjacent pixels. Therefore, electrons emitted from the electron source corresponding to one pixel collide with the phosphor in one pixel, and crosstalk can be prevented.

The rate of deterioration of the cold cathode due to ion sputtering is proportional to the product Pd of the residual gas pressure P in the panel and the electrode interval d (the amount of generated ions is proportional to Pd). For a conventional cold cathode, d
Denotes a cold cathode and an anode, which are approximately 200 to 300 μm. On the other hand, in the case of the present invention, the interval between the cold cathode and the gate electrode is 0.5 to 1.
Since it can be set to μm, the amount of ions generated during this period is 1/200 to 1/600 as compared with the conventional example, and the life of the cathode is 200 to 300 times longer at the same residual gas pressure.

Second Embodiment FIG. 5 shows a main part of an electrode configuration of a second embodiment. X-array electrodes _{X 1, X 2, X 3} ...... X n and Y-array electrodes _{Y 1, Y 2, Y 3} ...... Y m
A matrix electrode is formed, and an interdigitated electronic part 15 of the comb-shaped cold cathode connected to the X array electrode and the comb-shaped gate electrode connected to the Y array electrode is formed on the substrate surface surrounded by the X array electrode and the Y array electrode. did.

That is, the electrodes of the secondary electron emitting portion are the X array electrode and the Y electrode.
It was configured not to overlap on the surface of the array electrode. This has the effect of eliminating the occurrence of a short circuit between the two electrodes due to the pinholes generated in the insulating layer and reducing the electric capacitance between the X and Y array electrodes. When the X array electrode width is 50 μm, the Y array electrode width is 20 μm, and the pixel size is 300 × 300 μm, both the pinhole generation rate and the electric capacity are 1/20.
It could be reduced to ~ 1/50.

Next, a method of manufacturing the cold cathode will be described. A metal, for example, nickel for forming an X array electrode on the surface of a glass substrate is vapor-deposited on the entire surface with a thickness of 0.2 μm and separated into stripes by a photo-etching technique. Electrode width is 0.3m
m. Next, an SiO ₂ film was formed as an insulating layer to a thickness of 1 μm by a CVD method, and a through hole was formed in a part of the X array electrode by photoetching. Further, a tungsten metal film having a thickness of 0.2 μm is deposited thereon, and a gate electrode (Y array electrode) 5 is formed by the same photo-etching technique.
And the cold cathode 7 were formed at the same time.

Approximately 500 convex portions of the cold cathode were formed per pixel, and the distance from the gate electrode was 1 μm. Next, the entire substrate thus manufactured was immersed in an SiO ₂ film etching solution to form a concave portion 11 at the tip of the cold cathode shown in FIG.

The metal forming the X array electrode is not limited to nickel, but a metal having good adhesion to a glass substrate and low specific resistance, such as aluminum, titanium, and gold-chromium alloy, is desirable. The insulating layer is not limited to the SiO ₂ film, but is
Any material having good insulating properties such as N, BN, and SiO may be used. As cold cathode materials, besides tungsten, molybdenum, tantalum,
High-separation metals such as titanium are desirable.

In this way, the glass substrate on which the 480 × 660 matrix electron sources were formed and the face plate on which ITO having a thickness of 0.2 μm was vapor-deposited and coated with ZnO: Zn phosphor were opposed at a distance of 0.3 mm, The periphery was sealed with a low-melting glass frit and evacuated to produce an image display device with a screen size of 10 inches.

When the cold cathode (vertical scanning electrode) was set to the ground potential and 150 V was applied to the gate electrode (video signal modulation electrode), an electron emission current of about 10 μA per pixel was obtained. When applying 500 V to the phosphor surface and performing line-sequential driving at a field frequency of 60 Hz, about 50
The surface luminance of fL was obtained. The electron emission of the field emission cold cathode changes exponentially with respect to the gate voltage. 10 for gate electrode
Even when 0 V is applied, almost no electron emission occurs and the device is in a cutoff state. Therefore, a bias voltage of about 100 V was applied to the gate electrode, and the video modulation signal voltage was set to 50 V. Further, the electron emission characteristics are sensitive to the signal voltage, so that pulse width modulation is preferable to pulse wave height modulation, and pulse width modulation of 128 gradations was performed.

In this embodiment, a ZnO: Zn phosphor is used, but it goes without saying that color display can be achieved by applying three primary colors of red, green and blue in a stripe shape.

Effect of the Invention According to the present invention, a large number of cold cathodes and gate electrodes can be simultaneously formed by etching a refractory metal thin film deposited on the surface of an insulating layer coated on the surface of an X array electrode, so that uniformity is good and the manufacturing cost is low it can.

Cross talk can be prevented by arranging the opposing surfaces of the cold cathode and the gate electrode perpendicular to the longitudinal direction of the gate array electrode.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view of an image display device according to an embodiment of the present invention, FIG. 2 is a plan view of a main part of an electron source unit in the embodiment of FIG. 1, and FIG. FIG. 4 is a sectional view taken along the line AA 'of FIG. 3, and FIG.
FIG. 6 is a plan view showing the concept of electrode arrangement in another embodiment of the present invention. FIGS. 6A and 6B are a perspective view and a main part enlarged perspective view of a conventional field emission type matrix display device, respectively. DESCRIPTION OF SYMBOLS 1 ... Insulating substrate, 2 ... Face plate, 3 ... X array electrode, 4 ... Insulating layer, 5 ... Y array electrode (gate electrode), 6 ... Through hole, 7 ... Cold cathode, 8 ... ... Transparent electrode, 9 ... Phosphor, 10 ... Secondary electron, 11 ... Insulating layer removal part.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kinzo Nonomura 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-59-105252 (JP, A) JP-A-62- 261153 (JP, A) JP-A-51-50648 (JP, A) JP-A-63-274047 (JP, A) JP-A-56-167456 (JP, U) JP-B-46-20944 (JP, B1) JP-B-46-20949 (JP, B1) JP-B-54-17551 (JP, B2)

Claims (4)

(57) [Claims] 1. An image display apparatus comprising: an insulating back plate provided with a two-dimensional electron source controlled by an XY matrix electrode;
An electron source formed at each intersection of the XY matrix electrodes is formed in the shape of a comb tooth on the same plane, and the comb teeth are meshed with each other. Wherein the other corresponds to a gate electrode. 2. The comb teeth on the cold cathode side are provided with a large number of convex portions with respect to the comb teeth on the gate electrode side facing each other. The image display device as described in the above. 3. The image display device according to claim 1, wherein the teeth of the comb on the cold cathode side are surrounded by a Y array electrode serving as a gate electrode. 4. The image display device according to claim 1, wherein the opposing surfaces of the cold cathode and the gate electrode are perpendicular to the longitudinal direction of the Y array electrode (the longitudinal direction of the X array electrode).