JP2003502798A - Field emission cathode and method of manufacturing light source including the same - Google Patents

Abstract

(57) Abstract: A method for producing a field emission cathode for a light source including at least one field emitter having a field emission surface. The method includes the step of deforming the emitting surfaces to provide an irregularly shaped portion for emitting at least one electric field on each field emitting surface. The method of the present invention differs from the conventional method in that at least one laser beam is irradiated on the radiator to form the radiator, while the radiating surface is deformed by contact with the radiating surface. The invention also relates to the field emission cathode thus produced and to a light source comprising this emission cathode.

Description

Detailed Description of the Invention

The present invention relates to a method for manufacturing a field emission cathode for a light source. The present invention also relates to a field emission cathode manufactured in this manner and a light source including the same.

[0006] WO96 / 25753 discloses a field emission lighting device that employs a cold cathode and a manufacturing method thereof. Field emission lighting devices have significant advantages over other types of lighting devices such as fluorescent lamps. The latter requires complicated external electronics for its function and contains materials that have a negative impact on the environment. The fluorescent tube employs a gas discharge for emission to a fluorescent material that emits visible light. Field emission lighting devices, on the other hand, do not use materials that are harmful to the environment and operate using simple and economical devices.

Further, in WO96 / 25753, a cold field emission cathode used for the field emission light source is provided with a geometrical structure on its surface in order to easily obtain locally high electric field intensity for electron field emission. It is disclosed that it has been done. It is further described to form a field emission cathode having an emission surface having a particular shape that promotes electron field emission. Furthermore, it is described that the field emission cathode is formed with a portion exhibiting irregularity in order to improve mechanical and electrical resistance, operating life and energy emission per surface area.

According to WO 96/25753, this is done by irradiating the radiating end of the fiber with ions of a low-working functional material in order to reduce the electronically actuating function of the radiating end. This irradiation step forms sharp irregularities at the radiating end. Then, a deformation process is performed to deform the high and sharp irregularities into a rounded shape, which improves the effect and durability of the radiating end and provides a cathode that can withstand long-term use. .

Although the above-mentioned prior art methods result in well-functioning cathodes, the manufacturing method is complicated and time-consuming and therefore expensive to manufacture.

The main object of the present invention is to provide a method for manufacturing a cold field emission cathode for a light source, which overcomes the drawbacks of the known methods. Another object of the present invention is to provide a method for producing a cold field cathode that is effective and can withstand long-term use.

For this purpose, for a light source including at least one field emitter, comprising the step of deforming the field emission surface to provide at least one irregular portion for emitting electricity on the field emission surface of the field emitter. A method of manufacturing a field emission cathode, characterized in that at least one laser beam is applied to said radiator and at the same time brought into contact with a field emission surface to modify the surface of said radiator. .

By manufacturing a cold field emission cathode for a field emission light source in this way, it is possible to manufacture it more easily and thus cheaply. Furthermore, the manufacturing time can be shortened,
It eliminates the need for complicated processes as in the past.

The treatment performed by contacting the laser beam with the electrolytic emission surface of the radiator results in a thermo-chemical treatment which is desirable for the size and distribution of the field emission elements obtained in carrying out the method of the invention. It is possible to reliably control the result. This is in contrast to the known method, which has the inherent weakness that the individual ion bundles do not form a uniform surface in the ion irradiation and deformation treatment steps described above. The reason why the treatment according to the invention gives good results is explained by a synergistic effect with the energy and length of the laser beam and a slight non-uniform structure of the material of the radiator, which has different properties in different regions. These different regions show a slightly different response to the laser treatment, which results in an irregular shape with the desired height and a rounded shape.

In terms of carbon fibers, this material is oriented in a phase state with some degree of regularity, such as the crystallites found in graphite, which provide high strength, elasticity, conductivity and chemical stability within the matrix. It has features such as a fine structure and a skin layer found in amorphous carbon. In the present invention, the laser treatment causes the crystallite and the amorphous material to react with the laser treatment to exhibit a desired local disorder.

Further, the electrical properties of the skin layer of the carbon fiber, which is inferior to the regularity phase, can be improved by laser treatment.

The fact that the radiator is surface treated and shaped at the same time offers several additional advantages. It is an efficient and economical method to cut the radiator by laser irradiation so as to cut it into a desired size and length, and at the same time, deform the irradiated surface with a laser. This laser treatment eliminates the need for mechanical cutting work, and can prevent problems due to mechanical cutting such as unwanted deformation of the radiator surface portion. Laser cutting has the advantage of reducing chips compared to mechanical cutting. It has been discovered that light sources, including emitters made by conventional methods, are inefficient and have a short operating life due to the chips produced by such mechanical cutting.

Furthermore, an illuminating device comprising a field emission cathode made according to the invention in which the emission body is laser-shaped and at the same time the emission surface is treated is more efficient. The reason is,
Because more current flows through the cathode, which causes more light to be emitted from the light source than conventional light sources that do not have a uniform surface. Therefore, a longer operating light source will be obtained. By making the emitting surface more uniform, good electron emission action is obtained. When fibers are used, the treated fibers of the present invention carry five times as much current as compared to devices made by conventional methods. This can be used to make a light source with a longer service life than before and / or a light source that emits more intense light than before. Providing a uniform emitting surface is advantageous in that it provides a more uniform and comfortable distribution of light compared to conventional light sources.

The present invention is of the type used in WO 96/25753, such as carbon foam tubes such as carbon nano tubes (CNTs), diamond-like carbons (DLCs) and reticulated vitreous carbons (RVCs). It is also applicable to different types of field emitters such as strand fibers. The material on which the method of the invention is carried out is a carbon material, but materials with other similar functions can also be used as radiators. Therefore, other materials and radiator shapes are not excluded from the present invention.

The present invention is basically a one-step process in which cutting, shaping and surface treatment are performed simultaneously.

However, in some cases laser cutting and surface treatment may require additional laser treatment to obtain a more effective emitting surface. In one aspect of the invention, this is done by further irradiating the pre-treated surface with a laser for optimal treatment, which laser is of a different type and / or intensity than the first laser irradiation for cutting. May be

The method of the present invention can also be applied to an integral porous body such as a foamable carbon material.
Such a porous body is formed by interconnecting thin structures so as to form an integral structure. For example, it can be formed by cutting or molding a flat or cylindrical radiation surface with a laser. The resulting surface is modified so as to obtain the preferred electron emitting surface as described when using fibers. The field emission cathode manufactured in this manner can be manufactured relatively easily and inexpensively.

The present invention is also applicable to woven structures made from yarns containing carbon or similar materials.

DE-A1-19653820 describes the production of field emission surfaces used in particular for flat screens. In this method, a laser is locally applied to the diamond or diamond-like carbon layer, for example by masking techniques. As a result, a protruding region, which is not preferable for the present invention, is formed on the region adjacent to the treated portion.

While the invention has further advantages, these are described in more detail below with reference to the accompanying drawings.

In the method of the present invention, the field emission cathode is made from fiber bundles commercially available as polyacrylonitrile carbon fibers. Other suitable materials, including carbon or similar materials in the range of a few microns (μm) in diameter, can be used equally. Figure 1
As shown in FIG. 3, the light source has a field emission cathode in the shape of the fiber bundle 1, and these fiber bundles are in a matrix and arranged on the conductive substrate. The modulation electrode 12 (modulato 12) is provided in the vicinity of 1/10 mm on the radiation end of the fiber bundle 1 on the same surface as the matrix.
r electrode), which has an opening around each fiber bundle. The substrate 17 and the electrodes 12 are supported on a dielectric support 18 inside a vacuum glass container having upper and lower bounding glass plates 15,16. Inside the upper boundary glass plate 15 opposite the fiber bundle 1 and the electrode, the anode layer 13 and the light emitting layer 1
4 are provided. Each of the anode layer 13, the modulation electrode 12 and the substrate 17 has terminals A, B and C for applying a voltage for guiding electrons from the fiber bundle 1 to the light emitting layer 14 connected to the anode layer 13 through the opening of the modulation electrode. Have. When electrons enter the light emitting layer 14, light is emitted avoiding the transparent anode 13 and the glass container.

[0022]   The light source may be configured as a diode that does not require a modulation electrode.

What is important here is that the matrix of fiber bundles arranged on the substrate 17 has a uniform surface and can easily repel electrons when the substrate is exposed to a potential difference. Thus, a plurality of irregular shapes are uniformly provided on the surface of each radiator. Further, it is important to make the irregular shape of the surface round so that these irregular shapes do not excessively deform during use. The deformation of the surface shortens the service life of the light source.

In the present invention, the unit composed of the substrate 17 and the fiber bundle is formed and treated by laser light, whereby the fibers are precisely cut so as to form an overall uniform surface, and laser-treated. The surface exhibits the desired rounded irregular shape. If necessary, further radiation treatment may be applied to sweep the cut surface.

FIG. 2 shows a cross section of one fiber 9 after cutting with a laser beam and surface modification treatment. This radiating end section has a height and a slightly rounded irregularity 11.

FIG. 3 shows a field emission light source 20 that employs a field emission cathode 21 made from a foamable carbon material. Reference numeral 22 indicates a modulator grid, reference numeral 23 indicates the anode layer 23, and reference numeral 24 indicates a phosphor layer. Radiation cathode 2
1, the modulation grid 22 and the anode layer 23 are provided with terminals A, B and C, respectively, so that these elements are exposed to an appropriate potential difference. The face 25 of the cathode is evenly cut by the laser so as to provide an emitting face which lies substantially in one face and is shaped to the desired dimensions. If desired, surface 25 may be further laser treated to obtain a more complete emitting surface.

As mentioned above, the method of the present invention can be used with different geometries and different field emission cathodes. Laser cutting and radiation in the case of a cylindrical cathode for radially emitting an electric field formed from a cylindrical porous structure of a fiber or expandable carbon material as disclosed in WO98 / 57344 or WO98 / 57345 The surface treatment is performed, for example, by rotating the cathode and sweeping with a laser beam.

This step is shown in FIG. A cylindrical radiator 30 having a circumferential surface provided with a material to be molded and surface-treated is axially rotated. Then, the laser 31 oscillates about the axis, and the laser sweeps the body surface by following the tangent line of the cylindrical body 30 as shown by the broken line. In this way, the body is molded and the material protruding above a certain height is removed by laser and subjected to the above-mentioned surface modification treatment.

Another mode other than this is shown in FIG. In this embodiment a flat radiator 32 is swept by a laser 33. This sweeping operation is performed by laterally displacing the laser with respect to the upper surface of the radiator to be shaped and surface-modified. As a result, the same effect as the method described with reference to FIG. 4 can be obtained.

The laser beam sweep may be performed by moving an optical device such as a mirror and a lens according to a method known per se. In this regard, what is important in the present invention is that
This means that if the surface to be treated is a curved surface, the laser is directed along the surface so that it is tangent to the surface and if the surface is a flat surface, it coincides with the direction of the surface.

An advantage of the present invention is that the purity of the resulting material can be controlled and / or the resulting material can be tailored to impart different characteristics to the emitting surface in addition to some required properties. It means that you can do it. This is done by etching. This is the composition of the atmosphere surrounding the radiating fuselage being processed, the intensity of the laser beam,
It depends on the size of the area irradiated by the laser beam and the flow characteristics of the atmosphere. Amorphous carbon can be evaporated or sublimated in an inert atmosphere. In the presence of oxygen or hydrogen, catalytic graphitization of amorphous carbon can be performed.
In an atmosphere containing nitrogen or air, surface groups with bound oxygen and / or nitrogen are formed in a gently flowing atmosphere. Hot corrosion can be performed under fast flowing atmospheric conditions.

It is also possible to add various substances to the emitting surface in a manner known per se in order to change the properties of the emitting surface.

The present invention can also be incorporated into known methods such as those described in the above mentioned prior art documents. If the carbon fibers have been treated with, for example, a polymeric material and the polymeric material needs to be removed, the material can be removed during the laser treatment or by another suitable heat treatment.

In principle, it is possible to use all kinds of lasers which have sufficient intensity and operate in or near the visible light range. The light beam may be in the form of an annular or oval section or any other suitable section. The shape of the laser beam corresponds to the material to be processed.

In all the steps of cutting, etching and surface treatment, the laser is 0.01-0.
It is supplied at a speed of 1 m / s and its intensity is selected in the range of 0.1-10 kW / mm ² . Commercially available JAG and diode lasers of about 100-1000 W may be used. The laser beam may be pulsed or non-pulsed.
The formation of the radiator is carried out by vaporizing the unwanted material and melting it locally at the emitting surface of the material to be laser treated. In this way the emitting surface can be cleaned. Small amounts of excess material and other unstable materials can be fixed or evaporated by etching. The light source obtained by this treatment is stable, and the service life can be extended.

The molding operation can be molded into any shape. For example, it may be formed flat or cylindrical. A flat emitting surface can be used to displace the laser laterally with respect to the radiator to sweep it in a straight line (see Figure 5) or to fix the laser beam source in the same way as the material to be shaped and surface treated. It can be manufactured by displacing in the direction.
A method of producing a cylindrical emitting surface other than that shown in FIG. 4 is, for example, by rotating the material to be formed and molded with respect to a fixed laser source or by sweeping the laser laterally in an annular direction with respect to the material. And the like.

[Brief description of drawings]

[Figure 1]   3 shows a field emission light source according to the present invention.

[Fig. 2]   The enlarged view of the radiation surface of a radiator.

[Figure 3]   3 shows a field emission light source according to a second aspect of the invention.

[Figure 4]   1 is a schematic representation of a first aspect of the method according to the invention.

[Figure 5]   3 is a schematic representation of a second aspect of the method according to the invention.

[Procedure for Amendment] Submission for translation of Article 34 Amendment of Patent Cooperation Treaty

[Submission date] August 30, 2001 (2001.08.30)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Contents of correction]

[Claims]

─────────────────────────────────────────────────── ─── Continued front page    (81) Designated countries EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, I T, LU, MC, NL, PT, SE), OA (BF, BJ , CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, GM, K E, LS, MW, MZ, SD, SL, SZ, TZ, UG , ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AE, AG, AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, CA, C H, CN, CR, CU, CZ, DE, DK, DM, DZ , EE, ES, FI, GB, GD, GE, GH, GM, HR, HU, ID, IL, IN, IS, JP, KE, K G, KP, KR, KZ, LC, LK, LR, LS, LT , LU, LV, MA, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, S E, SG, SI, SK, SL, TJ, TM, TR, TT , TZ, UA, UG, US, UZ, VN, YU, ZA, ZW

Claims (16)

[Claims] 1. A field emission cathode for a light source including at least one field emitter, the method comprising the step of deforming said field emission surface to provide at least one irregular portion for emitting electricity on the field emission surface of the field emitter. The method of manufacturing a method according to claim 1, wherein at least one laser beam is applied to form the radiator and at the same time contacts the field emission surface to deform the surface of the radiator. 2. Method according to claim 1, characterized in that it is carried out on at least one fibrous radiator. 3. The method of claim 2, wherein each laser beam deforms the emitting surface and simultaneously cuts each fiber. 4. The method of claim 1, wherein the method is performed on a monolithic porous radiant body. 5. The method of claim 4, wherein the radiator is made of a foamable carbon material. 6. The method of claim 1, wherein the radiator is formed from carbon nanotubes. 7. The method of claim 1, wherein the radiator is made of a fabric made of yarn containing carbon or a similar material. 8. The method according to claim 1, wherein the emitting surface is subjected to a further laser treatment. 9. The method according to claim 1, wherein the laser beam is arranged to sweep the emitting surface. 10. The method according to claim 1, wherein laser light in the visible light region or in the vicinity thereof is used. 11. The laser beam has an intensity of about 0.1 to 10 kW / mm ^2.
A method according to any one of the preceding claims, characterized in that 12. The method according to claim 1, wherein the laser beam moves at a speed of about 0.01 to 0.1 m / s during the cutting or deformation process. 13. Method according to any one of the preceding claims, characterized in that the laser treatment is carried out in the atmosphere. 14. The method according to claim 1, wherein the laser treatment is carried out in an inert atmosphere. 15. A field emission cathode made by the method of any one of claims 1-14. 16. At least one provided with a conductive layer forming a light emitting layer and an anode.
16. A light source comprising a vacuum container comprising one wall, a field emission cathode and means for generating an electric field for emitting electrons from the cathode, the light source comprising the field emission cathode according to claim 15.