JPH0589806A - Image display device - Google Patents

Abstract

PURPOSE:To manufacture a thin type image display device with a simple process at a low cost and achieve a stable operation. CONSTITUTION:An image display device includes a clear face plate 30 located on the displaying side, a clear electroconductive film layer 31 functioning as anode electrode, a fluorescent substance layer 32, an electric insulating layer 33 presenting the tunnel effect, a cold cathode array 34 having electron source, an electric insulating layer 35 working as core, a cold cathode array electrode 21 functioning as cathode electrode, and a back supporting plate 20. When an voltage is impressed between the cold cathode array electrode 21 on the back supporting plate 20 side and the clear electroconductive film layer 31 on the face plate 30 side, a strong electric field is induced at the tip contacting the insulating layer 33 in the electron source of the cold cathode array 34. and electrons pass due to the tunnel phenomenon through a potential barrier between the tip of the array 34 and the insulating layer 33 and are cast incident to the fluorescent substance layer 32 to cause it to emit light.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin image display device,
That is, it relates to a flat panel display.

[0002]

2. Description of the Related Art In recent years, many information devices and OA devices have been developed in response to information technology. As an image display device, a cathode ray tube having good performance in terms of color, brightness, contrast and resolution is usually used, but in recent years there has been an increase in the amount of information, personalization, and a market need for light, thin, short and small markets. The development of various thin panel displays is rapidly expanding in order to meet the requirements.

As a thin panel display, a flat panel display in which field emission type cold cathode microguns are arranged in a matrix has attracted attention.
Heyer et al.'S "Microtips Fluorescent Display" is "Ja
pan Display 1986 ”conference. This type of microgun is composed of a plurality of chips of molybdenum, an electric field is applied to the chip from a gate located above the chip, and electrons are extracted from the top of the chip by the electric field effect. The anode is formed of a luminophore material and is formed at a distance of about 100 μm from the gate surface.

[0004]

However, the conventional flat panel display using this type of microgun is thin and has a display performance superior to that of an ordinary CRT, but it is put to practical use for the following three reasons. Not not. That is, first, since a vacuum state must be maintained between the cold cathode and the anode luminophore material, the manufacturing process is complicated and the cost is high. Next, even if a small amount of foreign atoms are adsorbed on the surface of the electron emitting portion of the cold cathode, the work function of the electron emitting portion of the cold cathode changes significantly, so that stable electron emitting characteristics cannot be realized. Finally, the residual gas ionized by the electron beam is accelerated by the anode voltage applied between the cold cathode and the anode luminophore material, and collides with the convex cold cathode with high energy and spatters. Therefore, the life is short and the operation becomes unstable.

The present invention has been made in view of the above-mentioned conventional problems, and it is an object of the present invention to provide an image display device which can be manufactured at a low cost by a simple process and can realize a stable operation. To do.

[0006]

In order to achieve the above-mentioned object, an image display device of the present invention is provided with a substrate, an XY matrix electrode arranged on the substrate, and an XY matrix electrode. The X-Y matrix electrode controls X
An electron emission layer which selectively emits electrons from a position corresponding to the Y matrix, an anode layer which is arranged so as to face the electron emission layer, and an electron emission layer which is arranged between the electron emission layer and the anode layer. An insulating layer through which electrons emitted from the layer toward the anode layer pass due to a tunnel effect, and a phosphor layer which is disposed between the insulating layer and the anode layer and emits light by electrons incident through the insulating layer. It is characterized by having.

[0007]

In the image display device of the present invention, when the electron emission layer emits electrons under the control of the XY matrix electrode, the emitted electrons pass through the insulating layer toward the anode layer due to the tunnel effect. .. Here, in general, when an electron having an energy equal to or higher than a certain threshold is incident on the phosphor, an electron-hole pair is generated in the phosphor, and the phosphor emits light by the transition of the electrons. Therefore, in the present invention, when a voltage equal to or higher than a certain threshold is applied between the cathode layer and the anode layer, the phosphor layer emits light by the electrons incident through the insulating layer. Therefore, if such a light emitting operation is controlled by the XY matrix electrode, a desired image display can be obtained on the phosphor layer.

According to the above-mentioned structure of the image display device of the present invention, the insulating layer is arranged between the electron emission layer and the phosphor layer, and it is necessary to provide the vacuum layer as in the conventional example. Therefore, it can be manufactured at a low cost by a simple process. Further, since the electron emitting portion of the electron emitting layer is protected by the insulating layer disposed between the electron emitting layer and the phosphor layer, stable electron emitting characteristics can be realized and the life can be extended. It is possible to stabilize the operation.

The action of the present invention will be more apparent from the following examples of the present invention, and other actions of the present invention will be further clarified.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a fragmentary perspective view showing an embodiment of an image display device according to the present invention, FIG. 2 is an enlarged cross-sectional view of an essential part showing a portion indicated by a dotted line in FIG. 1, and FIG. 1 and 2 are perspective views showing the overall appearance of the image display device shown in FIGS.
FIG. 4 is an explanatory diagram showing a method of manufacturing the image display device shown in FIGS. 1 to 3.

In FIG. 1 and FIG. 2, the image display device is
A transparent face plate 30 located on the display side and an
An electron having a transparent conductive film layer 31 as an example of an anode layer functioning as a cathode electrode, a phosphor layer 32, an electric insulating layer 33 having a tunnel effect, and an electron emission source 34a constituting an example of a conical emission portion. A cold cathode array 34 as an example of an emission layer, an electrical insulating layer 35 as a core, a cold cathode array electrode 21 as an example of an XY matrix electrode functioning as a cathode electrode, and an example of a substrate. And a back support plate 20. In FIG. 2, the layer B on the face plate 30 side is
And layer A on the back support plate 20 side are shown spaced apart, but are actually integrated.

A plurality of electron-emitting sources 34a having a polygonal pyramidal shape or a conical convex shape correspond to one pixel. The electron emitting source 34a has a sharp tip, which is an electron emitting portion,
The bottoms are integrated to form a cold cathode array 34. The cold cathode array 34 is electrically surface-connected to the cold cathode array electrode 21. Like the cold cathode array electrode 21, the cold cathode array 34 is partitioned into an XY matrix, covered with the core of the insulating layer 35 and electrically insulated from each other, and the tips have a tunnel effect. It is in contact with the electrically insulating layer 33. A transparent conductive film layer 31 serving as an anode electrode and a phosphor layer 32 are sequentially formed on the face plate 30, and the phosphor layer 32 is formed on the cold cathode array 34 via an electric insulating layer 33. Opposite the tip.

The cold cathode array electrode (cathode electrode) 21 is
In order to address each pixel of the phosphor layer 32 coated on the face plate 30, as shown in FIG. 1, the area defined by the scanning lines 23 and the signal lines 24 intersecting with each other is provided. The XY matrix electrode is formed so as to be electrically insulated from the formed cathode electrode in the adjacent region. That is, the flat panel display of the present embodiment employs a driving principle that is substantially the same as the XY matrix method in which scanning lines and signal lines intersect, which is used in liquid crystal displays.

In the area where the scanning line 23 and the signal line 24 intersect,
A thin film transistor (TFT) 25 of amorphous silicon (a-Si) is formed, and a cold cathode array 34 and a face plate coated with a phosphor layer 32 are formed by the TFT 25.
The applied voltage corresponding to any pixel between the eleven transparent conductive film layers 31 can be controlled. The TFT 25 of this embodiment is
It is formed by a known inverted stagger structure, the gate wiring serves as a scanning line, and the signal line also serves as a source electrode and a drain electrode. Further, although the TFT 25 has a three-dimensional structure, it is practically flattened according to the transparent conductive film layer 31.

In such a structure, as shown in FIG. 3, the cathode electrode (cold cathode array electrode 21) on the back support plate 20 side and the anode electrode on the face plate 30 side ( When a voltage is applied between the transparent conductive film layer 31) by the phosphor voltage circuit 11 and the substrate driving circuit 12, in the electron emission source 34a of the cold cathode array 34, especially at the tip portion in contact with the electric insulating layer 33. A strong electric field is induced and electrons are generated in the cold cathode array 34.
Tunnels through the potential barrier between the tip of the and the electric insulating layer 33 to enter the phosphor layer 32.

Here, the emitted light is caused by incident electrons by the phosphor layer.
It is considered that an electron-hole pair is generated in 32, and light is emitted by the transition of this electron. In order for an incident electron to contribute to light emission, it is necessary to have energy higher than the energy generated by the electron-hole pair. There is. That is, a voltage is applied between the cold cathode array electrode 21 and the transparent conductive film layer 31 so that the incident electrons have energy equal to or higher than the energy generated by the electron-hole pair.

Next, a method of manufacturing this image display device will be described with reference to FIGS. Here, as described above, the layer A on the backside support plate 20 side shown in FIG. 2 is almost the same as the active matrix type electrode of the known liquid crystal display, and therefore its description is omitted. In the semiconductor layer of the TFT 25, inexpensive glass can be used as the substrate, and a-Si is used because the screen can be easily enlarged.

Next, the structure of the layer B on the side of the face plate 30 shown in FIG. 2 will be described in detail. First, as shown in FIG. 4, the transparent conductive film is sequentially formed on the face plate 30. Layer 31,
The phosphor layer 32 and the electric insulating layer 33, that is, the tunnel layer are formed.
In this embodiment, first, a transparent glass substrate having a thickness of 1.1 mm is used as a material for the face plate 30, and then In-Sn-O is used as a material for the transparent conductive film layer 31 on the glass substrate.
(ITO) or Sn O ₂ is mainly used, and the film thickness is about 0.2
It was formed to have a thickness of μm. The formation method is a sputtering method in which an oxide can be used as a target, or I
A reactive sputtering method using an n-Sn alloy or Sn metal target was used.

As a material for the phosphor layer 32, ZnO: Zn (10 [lm /
W]) was used. The film thickness of the phosphor layer 32 was prototyped in the range of 0.08 to 1.2 μm, and was 0.3 μm in the embodiment.
The formation method is an electron beam evaporation method, and the base temperature is 200
After film formation at ° C, heat treatment was performed at 550 ° C for 1 hour in vacuum (about 10 ^-4 Pa). Incidentally, ZnO and Zn are used as vapor deposition sources.
Zn sintered body was used to set the Zn concentration to an appropriate value.

Here, the energy gap of the phosphor layer 32 is about 3.26 eV, and the Fermi level is about 0.04 e under the conduction band.
V can be estimated. Since the threshold value of the generated energy of electron-hole pairs is about 7.9 eV, in order to cause the phosphor layer 32 to emit light, an electric field of at least 4.68 eV is applied to the electron emitting portion of the cold cathode array 34. There is a need.

The electrically insulating layer 33, that is, the tunnel layer is formed on the planarized phosphor layer 32. This electrical insulation layer 33
Is a layer that strongly affects the electron tunneling probability,
In the embodiment, it is formed by the plasma CVD method using Si Nx. Generally, SiH ₄ , NH ₃ , and N ₂ are used as the source gas, but in this embodiment, H ₂ was added so that the internal stress could be arbitrarily controlled from tensile to compression. The composition ratio of the electrical insulating layer 33 is slightly N-rich (X> 1.33) as compared with the stoichiometric composition, and the film thickness is 2
Formed at ~ 3 nm.

Next, as shown in FIG. 5, S is used as an electric insulating layer (core layer) 35 which becomes the core of the convex cathode array 34.
_{i O 2, Si C, Si} N x, although _{Ta 2 O 5, Al 2 O} 3 is used, in the present embodiment, the same as the electrically insulating layer 33 S
Using iNx, a 1 μm thick layer was formed in the same manner. That is, in this embodiment, the electric insulating layer 33 and the electric insulating layer 35 are
Can be continuously formed.

Next, a plurality of V-grooves 35a as shown in FIGS. 6 and 7 were formed in parallel using a focused ion beam processing apparatus used for fine processing of LSI. In this case, an Au-Si-Be liquid metal ion source is used as the ion source of the focused ion beam, and the acceleration energy is 40 to 300 kV.
The V groove 35a is formed so as to reach a distance half the distance to the electric insulating layer 33. The beam has a Gaussian shape and a beam diameter of about 0.1 μm.
Those with m are preferred.

Further, as shown in FIG. 8 to FIG.
A plurality of V grooves 35b are formed in parallel so as to be orthogonal to 35a. At this time, the processing depth was controlled so that the tip of the pyramidal recess 35c formed at the intersection with the V groove 35a accurately reaches the electric insulating layer 33. Incidentally, FIG. 8 shows a side cross-section in this case, and FIG.
FIG. 10 is a perspective view of FIG. That is, as shown in FIG. 9, since the V-grooves are formed twice, the points where the vertices of the V-grooves intersect are the deepest (numerical value “2” in the figure), and the intersections reach the electric insulating layer 33.

Next, as shown in FIG. 11, a metal, which is the material of the convex cathode array 34, is deposited by a sputtering method, a vapor deposition method or the like so as to fill the concave portions 35a to 35c of the electric insulating layer 35, and the surface is By flattening, a cathode array 34 having a pyramidal electron emission source 34a corresponding to the recess 35c was formed. In this embodiment, the material of the cathode array 34 is Al
Was used. The layer B on the side of the face plate 30 and the layer A on the side of the back support plate 20 thus formed are connected to the cathode array 34.
When the cold cathode array electrode 21 and the cold cathode array electrode 21 are closely contacted and electrically connected to each other, a flat panel display as shown in FIGS. 1 to 3 is completed.

Here, the screen size of this flat panel display is 110 × 90 mm ² (equivalent to 6 inches) and the number of pixels is 25.
6 × 256, the number of convex portions of the electron emission source 34a is 1 per pixel
When formed as 815 (= 33 × 55) pieces, the operating characteristics are
The screen brightness was about 100 cd / m ² when the cathode-anode voltage was about 10V. Therefore, in the conventional device, a voltage of several hundreds of V is required, but in the structure of the present invention, a voltage of several tens of V is sufficient, and therefore it can be put to practical use.

As a means for improving the luminous efficiency, it is desirable to use a thin film of good quality that reduces the scattering of tunnel electrons in the electric insulating layer 33 that will be the tunnel layer. Although an SiNx amorphous film is used in the embodiment, a single crystal film of the electric insulating layer 33 may be formed by using MBE (Molecular Beam Epitaxy) technology or atomic layer epitaxy technology. Increasing the capacitance of layer 33 is effective. Further, in this embodiment, the V grooves 35a and 35b are formed by the focused ion beam processing apparatus, but they may be formed by electron beam exposure and hot molecular beam dry etching. Further, although ZnO: Zn is used as the material of the phosphor layer 32, a color image can be displayed by using phosphors of three primary colors of red, blue and green instead.

[0028]

As described in detail above, according to the image display device of the present invention, the electron emission layer controlled by the XY matrix electrodes to emit electrons and the electron emission layer are arranged so as to face each other. Between the insulating layer and the anode layer, and an insulating layer that is disposed between the electron emitting layer and the anode layer and through which electrons emitted from the electron emitting layer toward the anode layer pass by the tunnel effect. It is equipped with a phosphor layer that is placed in, and emits light by electrons that pass through the insulating layer, so it can be manufactured at a low cost through a simple process, and stable electron emission characteristics are realized to achieve a long service life. Can be lengthened and the operation can be stabilized.

As a result of the above, according to the present invention, it is possible to realize a thin image display device which is inexpensive and excellent in reliability and stability.

[Brief description of drawings]

FIG. 1 is a fragmentary perspective view showing an embodiment of an image display device according to the present invention.

FIG. 2 is an enlarged sectional view of an essential part showing a portion indicated by a dotted line in FIG.

FIG. 3 is a perspective view showing an overall appearance of the image display device shown in FIGS. 1 and 2.

FIG. 4 is an explanatory diagram showing a method of manufacturing the image display device shown in FIGS. 1 to 3.

FIG. 5 is an explanatory diagram showing a method of manufacturing the image display device shown in FIGS.

FIG. 6 is an explanatory diagram showing a method of manufacturing the image display device shown in FIGS. 1 to 3.

FIG. 7 is an explanatory diagram showing a method of manufacturing the image display device shown in FIGS. 1 to 3.

FIG. 8 is an explanatory diagram showing a method of manufacturing the image display device shown in FIGS. 1 to 3.

9 is an explanatory diagram showing a method of manufacturing the image display device shown in FIGS. 1 to 3. FIG.

10 is an explanatory diagram showing a method of manufacturing the image display device shown in FIGS. 1 to 3. FIG.

FIG. 11 is an explanatory diagram showing a method of manufacturing the image display device shown in FIGS. 1 to 3.

[Explanation of symbols]

 20 Back Support Plate 21 Cold Cathode Array Electrode 31 Transparent Conductive Layer 32 Phosphor Layer 33 Insulating Layer (Tunnel Layer) 34 Cold Cathode Array 34a Electron Emission Source 35 Insulating Layer (Core Layer)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yu Akagi 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka

Claims (2)

[Claims] 1. A substrate, an XY matrix electrode arranged on the substrate, and arranged on the XY matrix electrode and controlled by the XY matrix electrode to correspond to an XY matrix. The electron-emitting layer that selectively emits electrons from the above-mentioned position, the anode layer that faces the electron-emitting layer, and the electron-emitting layer that is disposed between the electron-emitting layer and the anode layer. An insulating layer through which electrons emitted from the anode layer pass due to a tunnel effect, and a fluorescent light which is arranged between the insulating layer and the anode layer and emits light by an electron incident through the insulating layer. An image display device comprising: a body layer. 2. The electron emission layer has a plurality of pyramidal emission portions each protruding toward the insulating layer at a position corresponding to the XY matrix and emitting electrons from a tip thereof. The image display device according to claim 1.