JP2002509337A - Field emission device with synthetic spacer - Google Patents

Abstract

(57) Abstract: A field emission display (100) comprises a cathode (102) having a plurality of electron emitters (124), an anode (104) opposite the cathode (102), an anode (104) and a cathode. (102) and a synthetic spacer (108) extending therebetween. The composite spacer (108) is composed of a first layer (107) made of a dielectric material or a bulk resistance material, and a conductive layer (109) bonded to the first layer (107) and made of a metal, a metal alloy or a ceramic-metal composite material. And The height of the composite spacer (108) is greater than 500 micrometers.

Description

DETAILED DESCRIPTION OF THE INVENTION

RELATED APPLICATION A related subject is U.S. Patent Application "Method for Fabricating a F. No. FD97091, filed on the same date as the present application and assigned to the same assignee.
ield Emission Device Having a Composite Spacer ".

The present invention relates to the field of field emission devices, and more particularly, to a field emission display.

[0002] The use of a spacer structure between a cathode plate and an anode plate of a field emission display is known in the art. The spacer structure maintains the separation between the cathode and the anode. Also, the spacer structure must withstand the potential difference between the cathode and the anode.

However, the spacer may adversely affect the flow of electrons toward the anode in the vicinity of the spacer. Some of the electrons emitted from the cathode may electrostatically charge the surface of the spacer, changing the voltage distribution near the spacer from the desired voltage distribution. Changes in the voltage distribution near the spacers may result in distortion of the electron flow. Also, as a result, as between the spacer and the cathode, an electric arc (elect.
rical arching) may occur.

In a field emission display, an image displayed by the display may be distorted due to distortion of the electron flow near the spacer.
In particular, this distortion makes the spacers "visible" by creating dark areas in the image at each spacer location.

[0005] Some conventional spacers attempt to overcome the problems associated with spacer charging. For example, a spacer with a surface having a sheet resistance that is low enough to eliminate impinging electrons by conduction, but high enough to improve power loss due to anode-to-cathode current. It is known in the art to provide This resistive surface can be achieved by coating the spacer with a film having the desired resistance. However, these membranes
Susceptible to physical damage and / or changes, such as would occur during handling of the spacer. Also, these films may cause, for example, chemical incompatibility with the cathode. Chemical inconsistencies can adversely affect the emission characteristics of the electron emitter on the cathode. Also, coated membranes can be difficult to manufacture.

It is also known in the art to provide additional independently controlled electrodes along the height of the spacer to control the voltage distribution near the spacer. However, this conventional method includes an extra step for forming a spacer electrode, and this spacer electrode is also susceptible to physical damage. In addition, this conventional method utilizes an extra voltage source for applying a potential to the spacer electrode, which may increase the power requirements of the device.

[0007] Accordingly, there is a need for an improved field emission device having spacers that reduce distortion of the electron flow and do not cause excessive power dissipation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS It should be understood that for simplicity and clarity of illustration, the elements shown in the figures are not necessarily to scale. For example, the dimensions of some elements are exaggerated with respect to one another.

[0009] The present invention is directed to a field emission device having composite spacers. Each composite spacer has a first layer, which can be made from a dielectric material or a bulk resistive material, and a conductive layer adhered to the first layer. The conductive layer is adjacent to the cathode, and the first layer is adjacent to the anode. The conductive layer causes the electrons to move away from the composite spacer, so that the charging of the spacer surface is controlled. This controlled charging has the effect of reducing the distortion of the trajectory of electrons due to the presence of the spacer. Also, the composite spacer has a height greater than 500 micrometers, which makes the composite spacer of the present invention useful in high voltage field emission devices operating with cathode-anode potentials greater than about 2500 volts. .
In one embodiment of the present invention, the field emission device is a field emission display having a composite spacer that is invisible to a user of the field emission display.

FIG. 1 shows a field emission display (FED: fi) according to the present invention.
FIG. 3 is a cross-sectional view of an eld emission display. FED 100 has cathode 102 opposite anode 104. A vacuum region 106 exists between the cathode 102 and the anode 104. The pressure in the vacuum region 106 is less than about 10 ^-6 UU Torr. Synthetic spacer 108 extends between cathode 102 and anode 104. The composite spacer 108 provides a physical support for maintaining the separation between the cathode 102 and the anode 104. In addition, the synthetic spacer 108
The composite spacer 108 has a feature of improving electrostatic charging. By controlling the electrostatic charging of the composite spacer 108, the distortion of the trajectory of the electron current 132 in the FED 100 is also controlled. In the embodiment of FIG.
It has the feature of making it invisible to the user of 00.

The cathode 102 includes a substrate 116 that can be made from glass, silicon, or the like.
Provided on the substrate 116 is a cathode conductor 118, which may include a thin layer of molybdenum. Dielectric layer 120
Is formed on the cathode conductor 118. The dielectric layer 120 can be made of, for example, silicon dioxide. The dielectric layer 120 defines a plurality of emitter wells 122, each having a plurality of electron emitters 1 in each of the wells 122.
24 are provided. In the embodiment of FIG. 1, the electron emitter 124 is a Spindt chip
(Spindt tips).

However, the field emission device according to the present invention is not limited to a Spindt chip electronic source. For example, an emissive carbon film may be used as the cathode electron source.

The cathode 102 further includes a plurality of gate extraction electrodes. FIG. 1 shows a first gate extraction electrode 126 and a second gate extraction electrode 128. Generally, a gate extraction electrode is used to selectively address an electron emitter.

The anode 104 includes a transparent substrate 110, on which an anode conductor 112 is provided, the anode conductor 112 being transparent and may include a thin layer of indium tin oxide. A plurality of phosphors 114 are provided on the anode conductor 112. Phosphor 114 is opposed to electron emitter 124.

The first voltage source 136 is connected to the anode conductor 112. The second voltage source 138 is connected to the second gate extraction electrode 128. The third voltage source 140 is connected to the first gate extraction electrode 126, and the fourth voltage source 142 is connected to the cathode conductor 118.

The synthetic spacer 108 extends between the cathode 102 and the anode 104,
Provides physical support. The height of the composite spacer 108 is sufficient to help prevent electrical arcing between the anode 104 and the cathode 102. For example, if the potential difference between the anode 104 and the cathode 102 is greater than about 2500, the height of the composite spacer 108 is greater than about 500 micrometers, preferably in the range of 700-1200 micrometers. One end of the synthetic spacer 108 contacts the anode 104 on the side not covered by the phosphor 114, and the other end of the synthetic spacer 108 contacts the cathode 102 at a portion that does not define the emitter well 122.

In accordance with the present invention, the composite spacer 108 includes a first layer 107 that extends toward the anode 104 from a point halfway between the ends of the composite spacer 108. First layer 10
7 has a height H. The composite spacer 108 also includes a conductive layer 109 connected to the first layer 107 and extending toward the cathode 102. The conductive layer 109 has a conductive surface 111 provided in the vacuum region 106. The conductive layer 109 has a height h.

The first layer 107 includes a dielectric material or a bulk resistance material. The material of the first layer 107 is selected to withstand the applied potential. The material of the first layer 107 is preferably
It has a high work function to improve spurious electron emissions from the first layer 107. Also, the first layer 107 preferably has a very smooth surface to reduce charge storage and spurious emissions. Dielectric materials useful as first layer 107 include ceramic, glass, sapphire, quartz, and the like.
Bulk resistance materials useful as first layer 107 include iron-containing glass ceramics, tin oxide, nickel oxide, silicon nitride, neodymium titanate, zirconium oxide, and the like. Generally, bulk resistive materials have a resistance in the range of 10 ⁵ to 10 ¹³ Ω · cm.

The conductive layer 109 contains a conductive material. Preferably, conductive layer 109 is made of a metal such as aluminum, gold, or copper. Moreover, it can be manufactured from a metal alloy. In another embodiment of the present invention, conductive layer 109 comprises a ceramic-metal composite. Conductive layer 109
Is necessary to effect electron deflection or focusing as described above.

The material making up the conductive layer 109 can be selected to provide additional benefits. For example, a ductile metal reduces the risk of breakage to cathode 102 during assembly of FED 100. The material of the conductive layer 109 can have a high work function to control spurious electron emissions from the conductive layer 109. Also, the conductive layer 1
The material selected as 09 must be very inert with respect to the material of the cathode 102 to prevent the formation of intermetallics and other undesirable chemical reactions.

The height h of the conductive layer 109 is selected to improve the electrostatic charging of the composite spacer 108 and to deflect the electron current 132 sufficiently to direct the electron current 132 to the appropriate phosphor. You. That is, the height h is selected so that the electrons hit the phosphor opposite the electron emitter. By deflecting the electrons, the conductive layer 109 prevents excessive electrostatic charging of the composite spacer 108, or otherwise, due to this electrostatic charging,
Undesirable results such as excessive distortion of the trajectory of the electron current 130, visible spacers, and electric arcs may occur.

In a preferred embodiment of the present invention, conductive layer 109 is connected to a potential, which is
It is useful to remove the electrostatic charge generated on the composite spacer 108 during the 00 operation. In the embodiment of FIG. 1, the discharge potential is provided at the second conductive layer 130. The second conductive layer 130 is provided on the dielectric layer 120 and includes a thin layer of a conductive metal such as molybdenum and aluminum.

The potential of the second conductive layer 130 can be independently controlled. Most preferably, the second conductive layer 130 is connected to an electrical ground. Connecting to an electrical ground improves electron deflection and does not require extra power. However, it can also be connected to a fifth potential source (not shown) for applying a selected potential to provide the desired degree of electron deflection and / or charge dissipation characteristics of the composite spacer 108. Alternatively, the second conductive layer 130 may be connected to, or be a part of, one of the gate extraction electrodes of the FED 100, in which case no additional potential source is required.

In the embodiment of FIG. 1, the electron current 132 causes the composite spacer 108 to be FED during operation.
It is controlled to a degree sufficient to make it invisible to 100 users. Specifically, conductive layer 109 is needed to create an electric field near composite spacer 108. In order to provide the electric field forming function, it is important that the conductive material of the conductive layer 109 is exposed to the vacuum region 106.

Here, a configuration as an example of the field emission device according to the present invention will be described with reference to FIG. It should be understood that the field emission device embodying the present invention is not limited to the geometry described with reference to FIG. This configuration is useful in the operation of FED 100 when the potential difference between cathode 102 and anode 104 is greater than about 300 volts, and preferably within the range of about 2500 to 10,000 volts. This configuration also includes a VGA configuration. However, the field emission that embodies the present invention
It should be understood that the display is not limited to a VGA configuration.

In the embodiment of FIG. 1, each of the transparent substrate 110 and the substrate 116 has about 1
It has a thickness of millimeters. The synthetic spacer 108 is a rectangular plate.
latelet), which is about 5 millimeters long (enters the page), about 1 millimeter tall (extending between cathode 102 and anode 104), and about 0 millimeters.
. And a thickness t of 07 millimeters. The distance from the center to the center between the first gate extraction electrode 126 and the second gate extraction electrode 128 is about 0.3 mm. The FED 100 can operate with a potential difference between the anode conductor 112 and the first and second gate extraction electrodes 126, 128 in the range of about 2500-10,000 volts. In this voltage range, it is essential that the distance between anode 104 and cathode 102 be greater than 500 micrometers in order to reduce the risk of an electric arc between anode 104 and cathode 102.

During the operation of the FED 100, the potential is changed to the first and second gate extraction electrodes 126, 1.
28, the cathode conductor 118 and the cathode conductor 112 to cause selected electron emissions at the electron emitter 124 to transfer electrons to the vacuum region 106.
Through to the phosphor 114. The phosphor 114 is caused to emit light by the colliding electrons.

The conductive layer 109 creates an electric field near the composite spacer 108 so that electrons emitted near the composite spacer 108 are directed to the phosphor 114 and do not collide with the composite spacer 108. In the exemplary configuration described with reference to FIG. 1, if the potential difference between the anode conductor 112 and the first and second gate extraction electrodes 126 and 128 is in the range of 2500 to 10,000 volts, the conductive layer 109 Is preferably in the range of about 75-150 micrometers.

The synthetic spacer according to the invention can be produced using a very economical and simple method. The synthetic spacer of the present invention does not require a photolithography step, expensive X-ray lithography, or a highly directional etching / deposition method. Also, there is no need for a step of coating the electron emitter, which can compromise the integrity of the electron emitter.

The composite spacer 108 is made by first providing a sheet of dielectric or bulk resistive material. Such sheets are generally available. silk·
The metal layer is formed on a dielectric or bulk resistive sheet by one of a number of conventional methods, such as screening, brazing of metal foil, electrolytic plating, electroless plating, and acoustophoresis. Next, the composite sheet with the metal layer adhered to the dielectric or bulk resistive layer is cut into individual spacers, such as with a wire saw or dicing saw. Preferably, the cutting step is initiated at the surface of the dielectric or bulk resistive material to avoid coating the surface of the first layer 107 with a conductive material.

In order to produce an embodiment in which the conductive layer 109 is made of a ceramic-metal composite material, the ceramic-metal composite material is first produced by dispersing an insulating ceramic phase in a metal powder. The mixture is tape castin
g) Formed into thin sheets via standard ceramic forming methods such as dry pressing, slip casting, etc. From this forming process, a monolith is cut out. The monolith is laminated to a layer of a selected dielectric or bulk resistive material. This laminating step is performed by applying pressure to the bonding interface at a temperature below about 200 ° C. Alternatively, bonding can be performed by heat treatment at a temperature of about 200 ° C. or more in a reducing atmosphere to prevent oxidation of the metal component. By changing the composition of the metal and the ceramic, the mechanical and thermal properties can be adjusted to achieve desired properties such as a desired coefficient of thermal expansion of the conductive layer 109. This embodiment is useful, for example, when a larger mechanical strength is desired in the conductive layer 109 instead of compliance.

[0032] Methods of forming anode 104 and cathode 102 are well known to those skilled in the art. After the anode 104 and the cathode 102 have been made, the composite spacer 108 may be bonded, for example, by thermocompression, to maintain a vertical configuration with respect to the cathode 102.
It is bonded to the second conductive layer 130. Next, the anode 104 is
And the package is sealed in a vacuum environment.

As described above, the present invention relates to a field emission device having a synthetic spacer. The field emission device of the present invention can operate at an anode-cathode potential above 300 volts, and preferably in the range of about 2500-10,000 volts. Field emission displays according to the present invention have "invisible spacers" which are invisible to the user of the display. The synthetic spacer of the present invention can be made using a simple and economical method.

While specific embodiments of the present invention have been illustrated, further modifications and improvements will occur to those skilled in the art. Therefore, it is not intended that the invention be limited to the specific forms shown, and the claims will cover all modifications that do not depart from the spirit and scope of the invention.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an embodiment of a field emission device according to the present invention.

──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5C032 CC10 5C036 EE09 EF01 EF06 EF09 EG01 EG12 EH04 EH08

Claims (9)

[Claims] 1. A field emission device (100) comprising: a cathode (102) having a plurality of electron emitters (124), said plurality of electron emitters (124) providing an electron current (132). A cathode (102) intended to emit; an anode (104) provided to receive an electron current (132) emitted from the plurality of electron emitters (124); the cathode (102) and the anode (104) ), And a vacuum region (106) provided between the anode (104) and the cathode (102);
107) and a conductive layer (109), wherein the conductive layer (109) of the synthetic spacer (108) is a conductive surface (111) provided in the vacuum region (106). ) And the synthetic spacer (10)
8) is a composite spacer (1) having a height greater than 500 micrometers.
08); a field emission device comprising:
100). 2. The first layer (107) extends between the anode (104) and the conductive layer (109), and the conductive layer (109) is connected to the first layer (107).
2. The field emission device (100) according to claim 1, wherein the device extends between the cathode (102) and the cathode (102). 3. The field emission device (100) according to claim 1, wherein the conductive layer (109) of the composite spacer (108) comprises a metal. 4. The field device according to claim 1, wherein said conductive layer of said composite spacer is made of a ceramic-metal composite material.
Emission device (100). 5. The field emission device (100) of claim 1, wherein the first layer (107) of the composite spacer (108) is comprised of a bulk resistive material. 6. The field emission device (100) according to claim 1, wherein the first layer (107) of the composite spacer (108) comprises a dielectric material. 7. The conductive layer (109) of the composite spacer (108) has a sufficient electron current (132) to prevent excessive electrostatic charging of the composite spacer (108) by the electron current (132). The field emission device (100) of claim 1, having a height selected to cause the deflection of (132). 8. The cathode (102) includes a dielectric layer (120), and the cathode (102) includes a second conductive layer (13) provided on the dielectric layer (120).
0), wherein the second conductive layer (130) comprises the composite spacer (108).
The electrostatic charge generated on the composite spacer (108) during operation of the field emission device (100) is dissipated through the second conductive layer (130). A field emission device (100) according to claim 1, characterized in that:
). 9. The cathode (102) includes a plurality of gate extraction electrodes (12).
The field emission device (100) of claim 8, wherein the second conductive layer (130) is connected to one of the plurality of gate extraction electrodes. .