JP2001176376A - Cold-cathode field-emission-type electron source and displayer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformize electric field on the surface of an emitter and to improve the uniformity of electrons emitted by the emitter in a plane-shaped cold-cathode field-emission-type electron source. SOLUTION: In a cold-cathode field-emission-type electron source which has a cathode electrode 4 on the substrate, it has a plane-shaped emitter 3 on the cathode electrode 4, has a gate insulation layer surrounding the emitter 3 and has gate electrodes 1 on the gate insulation layer, an emitter end 6 is intruded into the gate insulation layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cold cathode electron source which emits electrons by utilizing a field emission phenomenon called a cold cathode field emission, and more particularly to a display, a lamp, a fluorescent display tube and the like. A possible cold cathode field emission electron source.

[0002]

2. Description of the Related Art In recent years, research on a cold cathode electron source which emits electrons by utilizing a field emission phenomenon called a cold cathode field emission has been actively carried out, and a flat panel display called a field emission display (FED) has been developed. Application is expected.

[0003] The operation and manufacturing method of such a field emission electron source is described by Stanford Research Institute's CA Sp.
Journal of Applied Physics, Vol. 47, N by indt et al.
o, 12, pp. 5248-5263 (1976), and is also known from U.S. Patent No. 3,665,241 by CA Spindt et al. and U.S. Patent No. No. 4,307,507.

[0004] Each of the field emission type electron sources disclosed in these documents has a projecting electron emission portion (emitter) formed on a semiconductor substrate or a metal substrate, and an electric field for extracting electrons is provided around the emitter. Is formed. Electrons emitted from the emitter by applying a voltage to the gate travel toward the anode formed above the emitter.

Recently, as disclosed in Japanese Patent Application Laid-Open No. 5-282990, a material that emits electrons in a low electric field such as diamond is used for the emitter portion, electrons are extracted from the emitter by a voltage applied to the anode, and a gate electrode is formed. A field emission electron source used for suppressing electron emission has been proposed. In addition, Ise Electronics Uemura et al., SID 98 DIGEST, pp.1052-10
In 55, using carbon nanotubes for the emitter,
A field emission type electron source having a gate electrode in a mesh or grid shape has been proposed.

[0006]

In a field emission type electron source that emits electrons from a projecting emitter, when the electrons emitted from the emitter travel toward the anode, they move in a direction perpendicular to the traveling direction. Since it is bent in the vertical direction (outside) by receiving a force from the gate, when applied to a flat panel display, phenomena such as crosstalk and the like occur, making it difficult to use.

In the structure disclosed in Japanese Patent Application Laid-Open No. 5-282990, the microstructure of the emitter (diamond microcrystal) is sufficiently smaller than the size of the emitter opening, so that the emitter is, as shown in FIG. It can be regarded as almost flat. In FIG. 1A, electrons emitted from a planar emitter 3 by an anode voltage applied between an anode electrode (not shown) and a cathode electrode 4 travel toward the anode electrode. In the case of a display, a phosphor is coated on the anode electrode, and light is emitted when electrons emitted from the emitter 3 collide with the phosphor. Here, the current amount is controlled by applying an appropriate voltage to the gate electrode 1. When no voltage is applied to the gate electrode 1, electrons emitted from the emitter can be regarded as substantially uniform over the entire surface of the emitter.

However, when a voltage is applied to the gate electrode to control the amount of current, the electric field concentrates at the emitter end as shown by a curve a in FIG. Therefore, most of the electrons emitted from the emitter 6 are limited to the peripheral portion of the emitter 6, and the electron emission efficiency is poor, causing uneven light emission in the display. Furthermore, in order to obtain a gradation, it is necessary to control the amount of current by changing the gate voltage, but the electric field distribution on the emitter changes with the change in the gate voltage, and the phosphor applied to the anode electrode is changed. There is also an inconvenience that a good gray scale display cannot be obtained due to a change in the light emitting portion in the middle. Further, if electrons are not uniformly emitted from the entire emitter, a load is applied to only a part of the emitter, so that the life of the emitter is shortened.

When a mesh gate electrode is used as disclosed in SID 98 DIGEST, pp. 1052 to 1055, an electric field is uniformly applied to the entire surface of the emitter, but a positive voltage is applied to the gate electrode. Therefore, the ratio of electrons emitted from the emitter to be absorbed by the gate electrode increases, and the loss increases.

Therefore, the present invention has been made to solve the above problems, and has as its object to solve the problems of uneven light emission and gradation display.

[0011]

In order to achieve the above object, a cold cathode field emission type electron source according to the present invention comprises a cathode electrode on a substrate, a planar emitter on the cathode electrode, A gate insulating layer disposed around
A cold cathode field emission electron source comprising a gate electrode on the gate insulating layer, extracting electrons by applying a voltage to the anode, and suppressing the emission of electrons by the voltage applied to the gate electrode; It is characterized by being penetrated into the gate insulating layer.

With this configuration, in a cold cathode field emission type electron source in which electrons can be extracted at an anode voltage and emission of electrons can be suppressed at a gate voltage, emission of electrons from an emitter end is suppressed and the insulating layer is covered. It is possible to improve the uniformity of the electric field of the emitter region where no electrons can be emitted.

Preferably, the length of the emitter biting into the gate insulating layer is at least twice the thickness of the emitter.

Further, by using the cold cathode field emission type electron source as an electron source, it is possible to manufacture a display device having excellent in-pixel luminance uniformity.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1B is a sectional view showing a cell configuration of a cold cathode field emission electron source according to the present invention.
This cold cathode field emission type electron source has a laminated structure of a substrate 5, a gate insulating layer 2, and a gate electrode 1, and a circular, elliptical, or square hole is formed between the gate electrode 1 and the gate insulating layer 2. Penetrates, and a planar emitter 3 is formed at the bottom of the hole. The emitter end is formed so as to bite into the gate insulating layer 2. An anode (not shown) is provided above the emitter 3 and the gate electrode 1 so as to be electrically insulated from the emitter 3 and the gate electrode 1.

The metal layer 4 between the substrate 5 and the emitter 3
It is a cathode electrode for providing electrical continuity to the emitter 3 from a voltage source (not shown). Carbon nanotubes are used for the emitter 3 in order to easily emit electrons. Uemura et al. At ISE Electronics SID
As described in a research report published in 98 DIGEST, pp. 1052 to 1055, electrons can be emitted by applying an electric field of about 0.8 V / μm. Therefore, it can be driven by applying a voltage of about 1 kV at an anode-emitter distance of 1 mm. The carbon nanotube is formed by a sputtering method, a CVD method, or by applying fine particles. By arranging the gate electrode 1 and the cathode electrode 4 in a matrix, an electron source array of a field emission display (FED) is constructed.

Here, for example, a 30-inch HDTV (19
Consider application to FED (20 × 1080 pixels). FIG.
Shows the shape and size of one pixel composed of one subpixel for each of G and B. Subpixel pitch is 110μm × 3
Since the width of the gate electrode 1 is about 40 μm,
m, and the width of the cathode electrode 4 was 290 μm. The gate opening was set to 20 μm × 250 μm in consideration of the bite of the emitter 3 into the gate insulating layer 2. Here, the height from the emitter 3 to the lower end of the gate electrode 1 is 20 μm,
The distance from the anode to the emitter was 1 mm. The voltage applied to the anode was 5 kV throughout the experiment. A broken line 6 in the drawing indicates a biting end of the emitter 3 into the gate insulating layer existing below the gate electrode 1.

Here, the allowable electric field distribution width is considered.
When a disk-shaped object with a viewing angle of 4 'was presented for 0.2 seconds in a uniform background luminance in the New Color Science Handbook (June 1998, The University of Tokyo Press, p. 54), The minimum luminance difference between the distinguishable background luminance and the object (luminance difference discrimination threshold) is given. Assuming that the background luminance is 300 Cd / m ² , which is a general luminance of the display, the luminance difference discrimination threshold is 25 Cd / m ² , that is, approximately 10% of the background luminance.
This means that a luminance difference within 10% of the background luminance cannot be detected.

Therefore, assuming that the luminance of the phosphor is proportional to the electron current incident on the phosphor, the allowable current distribution width may be considered to be 10% or less. The electron source of the present application is a field emission type electron source, and the current follows the Fowler-Nordheim equation. Therefore, as a first approximation, if the electric field width is small, the allowable electric field width is の of the current width, and the allowable current is Can be estimated to be 5% or less.

<First Embodiment> First, the thickness of the gate electrode is 10 μm, the width (length) of the emitter is 20 μm, the thickness of the emitter is 1 μm, and the penetration of the emitter end into the insulating layer is 4 μm at each end. did. A curve b in FIG. 1C shows the electric field intensity distribution on the emitter surface when the gate voltage is set to 20V. Electric field strength distribution at emitter surface is ± 5
%, And the electron emission from the emitter surface is within the above-mentioned allowable range and almost uniform.

FIG. 2 shows that only the gate voltage is 20
5 shows the electric field intensity distribution on the emitter surface when V, 10 V, and 5 V are changed. The electric field intensity distribution on the emitter surface is within ± 5% in each case. It is necessary to control the amount of current by changing the gate voltage in order to obtain the gradation by the FED. However, since the electric field intensity on the emitter surface is uniform at any gate voltage, the phosphor coated on the anode electrode Good gradation display can be obtained without changing the light emitting portion in the middle.

<First Comparative Embodiment> FIG. 1A shows the configuration of the cold cathode field emission type electron source of the first embodiment except that the emitter end does not penetrate into the gate insulating layer 2. The same reference numerals are given to parts corresponding to the parts described in FIG. The curve a in FIG. 1C shows that the anode voltage is 5 kV and the structure in FIG.
The electric field intensity distribution on the emitter surface when the gate voltage is 20 V is shown. The electric field intensity distribution on the emitter surface is ± 30% or more, and the electron emission from the emitter surface is extremely non-uniform as compared with the case of the first embodiment. You can see that.

<Second Embodiment> FIG. 3 shows the emitter surface with respect to the thickness of the gate electrode 1 when a voltage of 20 V is applied to the gate of an electron source having a bite of 4 μm at the end of the emitter into the gate insulating layer 2. 4 shows the dependence of the electric field intensity distribution on the graph. Curves a, b, and c in FIG. 3 are electric field intensity distributions on the emitter surface when the thickness of the gate electrode 1 is 10 μm, 3 μm, and 1 μm, respectively. The curve a in FIG.
It is the same as the curve b in (c). When the gate electrode 1 is made thinner, the effect of shielding the electric field from the anode by the gate electric field becomes weaker, so that the electric field at the central portion of the emitter becomes stronger.

FIGS. 4 and 5 show the distribution of the electric field intensity on the emitter surface when the thickness of the gate electrode 1 is fixed to 10 μm and 1 μm, respectively, and the penetration of the emitter end into the gate insulating layer 2 is changed. Dependencies are shown. In each case, the thickness of the emitter is 1 μm. In each of FIGS. 4 and 5, curves a, b, and c indicate that the penetration of the emitter end into the gate insulating layer is 4 μm, respectively.
It is an electric field intensity distribution on the emitter surface in the case of 2 μm and 1 μm. A curve d in FIG. 4 indicates the gate insulating layer 2 at the emitter end.
4 shows an electric field intensity distribution on the emitter surface when there is no bite into the emitter.

In both FIGS. 4 and 5, when the bite amount at the emitter end is 2 μm or more, that is, twice or more the thickness of the emitter, the electric field intensity distribution on the emitter surface is within ± 5%. However, it shows that when the amount of bite at the emitter end is less than twice the thickness of the emitter, the electric field intensity distribution on the emitter surface sharply increases.

FIG. 6 shows the distribution of the emitter current density with respect to various amounts of bite at the emitter end when the thickness of the gate electrode 1 is 10 μm. Curves a, b, c
Shows distributions when the emitter ends are 4 μm, 2 μm, and 1 μm, respectively. Curve d shows the case where there is no bite at the emitter end. Emitter depth at emitter end is 2μ
At m or more, the distribution of the emitter current density is about 10%, but when the bite amount at the emitter end becomes 1 μm, the distribution of the current density becomes large.

FIG. 7 shows the current density when the thickness of the gate electrode 1 is 1 μm and the bite amount at the emitter end is 4 μm, 2 μm, and 1 μm. Although the same tendency as in FIG. 6 is shown, the distribution of the current density becomes extremely large when the bite amount is 2 μm or less.

[0028]

According to the present invention, in a cold cathode field emission type electron source in which electrons can be extracted with an anode voltage and emission of electrons can be suppressed with a gate voltage, the emitter end where the electric field concentrates is cut into the gate insulating layer to thereby reduce the electric field on the emitter surface. The strength can be made uniform.

Further, by making the amount of the bite (length) of the emitter end into the insulating layer more than twice the thickness of the emitter, uneven light emission and gradation display, which have been problems in display applications in the past, are disadvantageous. It has become possible to solve such problems.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a cold cathode field emission electron source of the related art and the present invention, and a diagram showing electric field strength.

FIG. 2 is a diagram illustrating electric field intensity dependence on a gate voltage according to the first embodiment.

FIG. 3 is a diagram illustrating the dependence of the electric field intensity on the gate thickness in the second embodiment.

FIG. 4 is a diagram showing the dependence of the electric field intensity on the bite amount of the emitter according to the second embodiment.

FIG. 5 is a diagram showing electric field intensity dependence on the amount of bite of an emitter according to the second embodiment.

FIG. 6 is a diagram showing current density dependence on the amount of bite of an emitter according to the second embodiment.

FIG. 7 is a diagram showing the current density dependence on the bite amount of the emitter according to the second embodiment.

FIG. 8 is a diagram illustrating a pixel structure of an emitter according to the first embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gate electrode 2 Gate insulating layer 3 Emitter 4 Cathode electrode 5 Substrate 6 Emitter end of emitter into gate insulating layer

Claims (3)

[Claims] An anode comprising: a cathode electrode on a substrate; a planar emitter on the cathode electrode; a gate insulating layer disposed around the emitter; and a gate electrode on the gate insulating layer. A cold cathode field emission type electron source in which electrons are drawn out by applying a voltage to the gate electrode and the emission of electrons is suppressed by a voltage applied to the gate electrode, wherein the emitter end bites into the gate insulating layer. Field emission electron source. 2. The cold cathode field emission electron source according to claim 1, wherein the length of the bite of the emitter into the gate insulating layer is at least twice the thickness of the emitter. 3. A display device using the cold cathode field emission type electron source according to claim 1 as an electron source.