JP4916221B2 - Method for manufacturing cold cathode and method for manufacturing apparatus equipped with cold cathode - Google Patents

Description

  The present invention relates to a method for manufacturing a field emission cold cathode.

  A field emission type cold cathode has a minute projection-like cathode and has a structure in which an electric field generated by a potential applied to a projection is concentrated on a minute tip having a nano-order diameter. As a result, electrons pass through the work function barrier on the surface of the protrusion due to a tunnel phenomenon, so that the electrons can be emitted into a vacuum even at room temperature. Such a field emission cold cathode can be used for a field emission display (FED), a radiation source, a lighting device, and the like.

  As a method for forming a microprojection of a field emission type cold cathode, a method of forming a conical microprojection by depositing an electrode material inside a small circular opening formed by a thin film processing technique is known. Also. In Patent Document 1, a large number of carbon nanotubes (microprojections) are prepared by dispersing carbon nanotubes formed in advance by an arc method or the like in a binder solution, applying the solution onto an electrode, and then fixing by heating. Disclosed is a method of manufacturing a cathode. At this time, in Patent Document 1, the adhesion between the carbon nanotube to be applied and the electrode is improved by fixing the silica gel layer on the surface of the carbon nanotube before the application.

Patent Document 2 discloses a method of manufacturing a field emission cold cathode using a graphite substrate having a mirror-like surface exposed to plasma to form minute irregularities on the surface and using the convex portions as minute projections. Yes.
JP 2005-71863 A Japanese Patent Laid-Open No. 2005-32638

  The cold cathode manufactured by the method described in Patent Document 1 is a separate member from the carbon nanotubes that form minute protrusions and the electrode to which the carbon nanotubes are fixed. The electrical resistance at the interface causes a voltage drop, and current saturation occurs. Cause.

  On the other hand, as described in Patent Document 2, the method for forming minute irregularities on the surface of the graphite substrate is that the formed protrusion is originally a part of the substrate, so that the adhesion and conductivity between the substrate and the protrusion are improved. An excellent cold cathode can be produced.

  The manufacturing method described in Patent Document 2 needs to expose the graphite substrate to plasma, but there are various methods for generating plasma. For example, when microwave plasma is used, the quartz tube 103 is arranged so as to intersect the waveguide 101 of the microwave 105 as shown in FIG. A holder 107 in which a graphite member (graphite rod) 102 to be processed is placed is inserted into the quartz tube 103. A predetermined gas 106 such as hydrogen is supplied to the inside of the quartz tube 103. In this state, when the microwave tube 105 is irradiated with the microwave 105, a surface wave is generated in the space inside the tube at the microwave irradiation site (irradiation window) of the quartz tube 103, and the electrons are accelerated by the electric field, thereby generating the plasma 104. appear.

  Since the plasma 104 is generated along the traveling direction of the surface wave, depending on the positional relationship between the microwave irradiation window of the quartz tube 103 and the plurality of graphite members 102 in the tube, the influence of the other members 102 on the plasma is affected. The member 102 to be formed is generated, and the generation of the fine structure (unevenness) may be uneven. Moreover, since the apparatus which produces | generates a microwave plasma is expensive, the method of manufacturing a cold cathode cheaply using plasma is desired.

  As apparatuses capable of generating plasma, film forming apparatuses using plasma, particularly sputtering apparatuses, are widely used. However, since the sputtering apparatus has a configuration in which the cathode is sputtered by positive ions in the plasma, the protruding cathode material may adhere to the graphite member. For this reason, there is a high possibility of affecting the electron emission characteristics of the formed cold cathode.

  An object of the present invention is to provide a method for producing a cold cathode having excellent electron emission characteristics using a simple plasma generator.

  In order to achieve the above object, according to a first aspect of the present invention, there is provided an upper surface of a sputtering apparatus comprising a cathode having a coating layer made of the same element as the material serving as an electron emission source disposed on the upper surface. In addition, a cold cathode member made of a material serving as an electron emission source is disposed, a plasma is generated between the cathode and the anode, and the cold cathode member is exposed to the plasma, whereby the surface of the cold cathode member is exposed. Form microprojections. Thereby, while using a simple sputtering apparatus, mixing of impurities due to sputtering of the cathode can be prevented, and a cold cathode excellent in electron emission characteristics can be manufactured.

  Further, in the second aspect of the present invention, an electron is disposed between a cathode disposed on the upper surface of a coating layer made of the same element as the material serving as an electron emission source and an anode disposed so as to face the cathode. A cold cathode member is formed by disposing a cold cathode member made of a material to be an emission source, generating a plasma by applying a voltage between the cathode and the anode, and exposing the cold cathode member to the plasma. Microprotrusions are formed on the surface. As a result, a cold cathode having excellent electron emission characteristics can be produced while preventing contamination by the plasma generated with a simple configuration of the counter electrode.

  In the cold cathode manufacturing methods of the first and second embodiments, it is possible to previously arrange a magnet under the cathode and generate plasma near the cathode. Thereby, the magnetron plasma which raised the plasma density using the drift of the electron by an electric field and a magnetic field is produced, and a microprotrusion can be efficiently created by installing the member for cold cathodes in it. The cold cathode member can be made of graphite, and the coating layer can be made of carbon. By forming a predetermined groove in the cold cathode member in a region where electrons should be emitted, it is possible to improve the aspect ratio and density of the fine protrusions to be formed.

A method for manufacturing a cold cathode according to an embodiment of the present invention will be described with reference to the drawings.
(First embodiment)
As a first embodiment, a method of manufacturing a cold cathode using a magnetron sputtering apparatus will be described with reference to FIGS.

  First, a member 20 made of a material that becomes an electron emission source and having a desired cold cathode shape is prepared. The member 20 can have various shapes depending on the device in which the cold cathode is used. However, the region of the member 20 serving as an electron emission portion is large enough to enter the plasma formed by the magnetron sputtering device. It is desirable that

  For example, in the case of a cold cathode used for illumination or a radiation source, a rod-shaped graphite member having a diameter of about 0.05 to 2 mm and a length of 1 to 100 mm can be used.

  In the present embodiment, an example using a graphite member 20 formed in a rod shape (columnar shape) in advance will be described. The portion where the minute protrusions are formed is the tip surface (upper surface) of the rod.

  In addition to graphite, carbon, boron nitride, zinc oxide, molybdenum, or the like can be used as a material that becomes an electron emission source constituting the member 20.

  A magnetron sputtering apparatus generally has a structure shown in FIG. In other words, the cathode 11 and the anode 12 arranged opposite to each other, and the magnet 13 arranged on the back surface side of the cathode 13 are provided. As shown in FIG. 1, the magnet 13 has one pole (S pole in FIG. 1) at the center and the other pole (N pole in FIG. 1) along the periphery of the cathode. Here, as an example, the cathode 11 and the anode 12 are disk-shaped, the N poles of the magnet 13 are arranged in a ring shape, and an annular (doughnut-shaped) plasma 17 is generated in the space near the surface of the cathode 11. Although an example will be described, a device in which the cathode 11 and the anode 12 are not disk-shaped may be used. The cathode 11 and the anode 12 are disposed in a vacuum vessel (not shown), and at least a space between the cathode 11 and the anode 12 is reduced to a predetermined pressure. A predetermined gas is supplied to the space between the cathode and the anode 12 by a gas supply pipe (not shown).

When a chemical etching action by plasma is mainly used to form microprotrusions at the tip of the graphite member 20, hydrogen, oxygen, CH ₄ , CF ₄ or the like is used as a gas to be supplied. On the other hand, when a physical sputtering phenomenon is used, an inert gas such as Ar or nitrogen is used. The gas pressure is desirably set in the range of 0.1 to 100 Pa.

  A direct current or high frequency voltage is applied from the power source 14 between the cathode 11 and the anode 12. The output of the power supply 14 is desirably set to about 10 to 800 W. By applying a voltage, electrons in the space between the cathode 11 and the anode 12 drift due to the magnetic field lines of the magnetic field 17 of the magnet 13 and the electric field between the anode 12 and the cathode 11 perpendicular to the magnetic field 17. A high magnetron plasma 15 is generated. At this time, the place where the magnetic field formed by the magnet 13 and the electric field between the anode 12 and the cathode 11 are orthogonal is a donut shape in the space near the cathode 11, so that the plasma 15 is also generated in a donut shape. Here, as an example, the diameter of the cathode 11 is set to about 7.2 cm, the distance between the cathode 11 and the anode 12 is set to about 2.5 cm, the gas pressure is 4 Pa, and the applied power is 100 W. The donut-shaped plasma 15 is generated on the cathode 11, and the density thereof is uniform along the circumferential direction.

  When film formation, which is a normal method of using a magnetron sputtering apparatus, is performed, a target 16 that is a thin film material is disposed on the surface of the cathode 16. In this embodiment, a donut-shaped plasma 15 is used to form a graphite member. As shown in FIG. 2, the target 16 is not disposed, and the graphite member 20 is placed vertically along the circumferential direction in the region where the donut-shaped plasma 15 is formed on the cathode 11 as shown in FIG. Deploy. For example, the graphite member 20 can be vertically arranged by inserting the lower end of the graphite member 20 into a recess provided in advance on the surface of the cathode 11. Since the tip of the graphite member 20 where the microprojections are to be formed cannot be efficiently processed unless it is arranged at a position where the donut-shaped plasma 15 is generated, the graphite member 20 shorter than the height of the generated plasma 15 is used. There is a need. In this embodiment, since the distance between the cathode 11 and the anode 12 is 2.5 cm, the graphite member 20 protruding on the cathode 11 has a length of 2.5 cm or less, and the graphite member 20 is used. Is arranged at a position where the plasma 15 is generated.

  Further, since the donut-shaped plasma 15 is uniform along the circumferential direction, a plurality of graphite members 20 can be arranged along the circumferential direction as shown in FIG. 2 and processed at a time.

  As described above, by exposing the graphite member 20 to the magnetron plasma 15, a portion in contact with the plasma 15 on the surface of the graphite member 20 by a chemical etching action, a physical sputtering action, or an action in which both are mixed. Unevenness is formed on all. Thereby, fine unevenness | corrugation can be formed in the front end surface (cylinder upper surface) of the graphite member 20. FIG. Therefore, the graphite member 20 (cold cathode) provided with a large number of minute protrusions (convex portions) capable of emitting electrons can be manufactured.

  At this time, since the chemical etching action and the physical sputtering action by the plasma 15 also occur in the cathode 11 itself of the sputtering apparatus, the material constituting the cathode 11 is sputtered and adheres to the tip of the graphite member 20. Therefore, depending on the material constituting the cathode 11, the electron emission characteristics of the fine protrusions at the tip of the graphite member 20 may be adversely affected.

  Therefore, in the present embodiment, the coating layer 21 made of the same element as the material constituting the member 20 is disposed on at least the upper surface of the metal cathode 11. Thereby, the material which jumps out when the coating layer 21 on the upper surface of the cathode 11 is sputtered by the plasma 15 is made of the same element as the electron emission source material. Therefore, even if it adheres to the tip of the graphite member 20, the electron emission characteristics are not adversely affected.

  The material constituting the coating layer 21 is preferably the same electron emission source material as that of the member 20, but the crystal structure does not have to be the same as that of the member 20, and is a material composed of the same elements as the constituent elements of the member 20. I just need it. Therefore, the crystal structure of the member 20 may be amorphous. For example, when the member 20 is made of graphite, the coating layer 21 may be made of a material (allotropic body) made of carbon, and may be made of amorphous carbon. However, when the member 20 is made of a compound such as boron nitride or zinc oxide or molybdenum, it is desirable that the coating layer 21 is also formed of the same compound or molybdenum such as boron nitride or zinc oxide as the member 20.

  Thus, according to the first embodiment, it is possible to form minute protrusions on the tip surface of the member 20 using the magnetron sputtering apparatus. Therefore, it is not necessary to use an expensive microwave generator as in the case of using microwave plasma, and the plasma 15 can be generated by the high-voltage power supply 14 satisfying predetermined characteristics, so that a cold cathode can be manufactured at low cost.

  Since the magnetron plasma has a higher density than the plasma generated without applying a magnetic field, microprojections can be efficiently formed. Further, since the ring-shaped plasma 15 using the magnetron effect is uniform in the circumferential direction, the difference caused by the installation location is small in the microstructure formed by installing the member 20 in the circumferential direction. Therefore, a fine structure without unevenness can be formed on the plurality of graphite members 20 at a time.

  In addition, since the cathode 11 is covered with the electron emission material coating layer 21, the cold cathode made of the manufactured member 20 does not adhere impurities to the minute protrusions and can exhibit good electron emission characteristics.

(Second Embodiment)
In the second embodiment, a method for manufacturing a cold cathode having minute protrusions using a DC (direct current) or RF (high frequency) sputtering apparatus will be described. Also in the second embodiment, as in the first embodiment, a case where a large number of minute protrusions are formed on the tip (upper surface) of a bar-shaped (columnar) graphite member 20 will be described as an example.

  As shown in FIG. 3, the DC or RF sputtering apparatus has a cathode 11 and an anode 12 arranged opposite to each other as in the magnetron sputtering apparatus, but does not include a magnet 13. Further, the DC or RF sputtering apparatus includes a gas supply pipe (not shown) for supplying a predetermined gas to the space between the cathode 11 and the anode 12 and a power source 14. The gas pressure is desirably set in the range of 0.1 to 100 Pa.

  A direct current or a high frequency voltage is applied from the power source 14 between the cathode 11 and the anode 12. The output of the power supply 14 is desirably set to about 10 to 800 W. A plasma 31 is generated between the cathode 11 and the anode 12 by applying a voltage. The plasma 31 does not have a donut shape, but is generated substantially uniformly in the radial direction of the cathode 11. Here, as an example, the diameter of the cathode 11 is about 7.2 cm, the distance between the cathode 11 and the anode 12 is about 2.5 cm, the gas pressure is 4 Pa, and the applied power is 100 W (DC voltage). As a result, the plasma generated between the cathode 11 and the anode 12 is substantially uniform both in the radial direction and in the circumferential direction.

  When a thin film is formed as in a general method of using a sputtering apparatus, the target 16 is disposed on the upper surface of the cathode 11 as shown in FIG. 3, but in this embodiment, fine irregularities are formed as shown in FIG. The graphite member 20 to be placed is placed upright on the upper surface of the cathode 11. Moreover, the several member 20 can be arrange | positioned at once like FIG.

  At this time, the upper surface of the cathode 11 is covered with the coating layer 21 as in the first embodiment. The covering layer 21 is formed of a material made of an element constituting the electron emission source material of the member 20. For example, it covers with the coating layer 21 which consists of carbon. Thereby, even if the material sputtered out from the cathode 11 adheres to the graphite member 20, it does not become an impurity and hardly affects the electron emission characteristics of the graphite member. About the crystal structure of the material which comprises the coating layer 21, it is the same as that of the coating layer 21 of 1st Embodiment.

  In the second embodiment, since the tip surface of the graphite member 20 can be exposed to the plasma generated between the cathode 11 and the anode 12 by a DC or RF sputtering apparatus, fine tips are formed on the tip surface. Can be formed. Therefore, the graphite member 20 (cold cathode) provided with a large number of minute protrusions (convex portions) at the tip can be manufactured.

  As described above, in the second embodiment, a cold cathode having minute protrusions can be manufactured without being affected by impurities while using a widely used apparatus such as a DC or RF sputtering apparatus.

  When manufacturing a wire-shaped cold cathode, a wire-shaped member 51 made of an electron emission source material is disposed on the covering layer 21 as shown in FIG. The surface facing the anode 21 can be exposed to plasma, and minute protrusions can be formed.

  Similarly, when manufacturing a surface cold cathode having a large diameter, a wide upper surface such as a plate-shaped member made of a material serving as an electron emission source or a columnar member 62 as shown in FIG. The member having the same is disposed on the coating layer 21 so as to face the anode 12 as in FIG. Thereby, microprotrusions can be formed on the surface facing the anode 12.

(Third embodiment)
In the first and second embodiments, the method of forming the microprojections by exposing the flat upper surface of the member 20 to plasma has been described. However, the third embodiment is as shown in FIG. Next, a method of manufacturing a cold cathode having microprojections having a large aspect ratio and a high density by forming grooves 63 in advance on the upper surface of the member 62 will be described.

  The groove 63 formed on the upper surface of the member 62 preferably has a rectangular or U-shaped cross section. The arrangement of the grooves 63 may be any arrangement, and may be any of a lattice, a parallel arrangement, and a radial arrangement.

  The shape of the member 62 may be any shape. For example, in the case of a cold cathode used in a lighting device having the structure shown in FIG. 8 described later, the diameter is about 0.1 to 2 mm and the length is 1 A bar-shaped graphite member having a diameter of 10 mm or a disk-shaped member having a diameter of 1 to 10 mm and a thickness of about 1 mm can be used.

  As in the first and second embodiments, the member 62 with the groove formed in this way is placed on the cathode 11 provided with the coating 21 and exposed to plasma. As a result, minute protrusions can be formed in the groove 63 as well as in the flat portion 64 between the groove 63 and the groove 63.

  Compared with the case where no groove is formed, the fine protrusions formed inside the groove 63 have a large aspect ratio (the height of the protrusion / the diameter of the base of the protrusion) and can be formed with a high density. Further, in the flat portion 64, the density of the formed protrusions is higher than that in the case where the groove 63 is not formed. In particular, as shown in FIG. 7, the flat portion 64 of the peripheral region 71 on the upper surface where the groove 63 is formed has higher density of fine protrusions than the flat portion of the peripheral region 71 on the upper surface when the groove is not formed. Is done.

  The microprotrusions formed according to the third embodiment are more likely to emit electrons as the aspect ratio is larger, and the number of microprotrusions in the cold cathode increases as the density of the protrusions increases. Large amount of electrons. Therefore, by using the manufacturing method of the third embodiment, a cold cathode having excellent electron emission characteristics can be manufactured.

(Fourth embodiment)
Next, as a fourth embodiment, an illumination device using the cold cathode manufactured in the first to third embodiments will be described.

FIG. 8 shows a cross-sectional view of the lighting apparatus of the present embodiment. A face glass 811 is bonded with a low melting point frit glass to an open end of a cylindrical glass bulb 810 having one end closed and the other end open to form an outer wall. The space inside the outer wall is evacuated so that the pressure is 1.33 × 10 ⁻³ Pa (1 × 10 ⁻⁵ Torr) or less. In the glass bulb 810, a cold cathode 812, a grid (electron extraction electrode) 813, and an anode 814 are sequentially arranged from the closed end toward the face glass 811.

  As the cold cathode 812, any of the graphite members 20, 51, 62 produced by the manufacturing methods of the first to third embodiments can be used. When the rod-like (columnar) graphite members 20 and 62 are used, if the length is too long, they can be cut and used. The graphite members 20, 51 and 62 are fixed by directly adhering to the cathode wiring (lead pin 817 described later) or by fixing to a separately prepared metal cup and then attaching to the cathode wiring (lead pin 817).

  The graphite member 20, 51, 62 faces the face glass 811 on the surface that has been roughened by the plasma treatment. A grid 813 is disposed so as to face the surface of the cold cathode 12 where the irregularities are formed. The grid 813 may have a shape along a plane, or may have a shape along a spherical surface that swells away from the cold cathode 812. When a voltage is applied to the cold cathode 812 and the grid 813, an electrostatic force is generated in the direction in which both approach. By making the grid 813 into a shape along the spherical surface, the contact between the grid 813 and the cold cathode 812 can be made difficult to occur.

The anode 814 is composed of an annular conductor. Note that the anode 814 may have a mesh shape. A phosphor layer 816 having a thickness of 20 μm is disposed on the inner surface of the face glass 811, and a metal back film 815 having a thickness of 100 to 200 nm made of aluminum is formed on the surface. For example, when producing a white lamp, a white phosphor, for example, a phosphor in which Y ₂ O ₃ S: Tb and Y ₂ O ₃ : Eu are mixed, is dissolved in a solvent and applied to the inner surface of the face glass 811; The phosphor layer 816 is formed by drying.

  The cold cathode 812, the grid 813, and the anode 814 are supported in the glass bulb 810 by lead pins 817, 818, and 819, respectively. The lead pins 817, 818, and 819 are led out through the closed end of the glass bulb 810. The tip of the lead pin 819 in the glass bulb 810 is electrically connected to the metal back film 815 via the contact piece 820. A predetermined voltage is applied to the cold cathode 812 via the lead pin 817, a predetermined voltage is applied to the grid 813 via the lead pin 818, and a predetermined voltage is applied to the anode 814 via the lead pin 819. Further, the same voltage as that applied to the anode 814 is applied to the metal back film 815 via the connection piece 820.

  A getter material such as barium (Ba) or titanium (Ti) is fixed to a part of a portion of the lead wire 819 in the glass bulb 810 by welding or the like. The getter material plays a role of keeping the inside of the glass bulb 810 at a high vacuum.

  A voltage large enough for electrons to be emitted from the cold cathode 812 is applied between the cold cathode 812 and the grid 813. A voltage higher than the voltage applied to the grid 813 is applied to the anode 814. Electrons emitted from the cold cathode 812 pass through the grid 813, are accelerated by the voltage applied to the anode 814, and enter the metal back film 815. The electrons incident on the metal back film 815 pass through the metal back film 815 and reach the phosphor layer 816. Thereby, fluorescence is generated from the phosphor layer 816 and is transmitted through the face glass 811 and emitted to the outside. By giving the face glass 811 the function of a convex lens, emitted fluorescence can be collected.

For example, when the distance between the grid 813 and the cold cathode 812 is 0.5 mm, a current of 1 mA / cm ² can be obtained by grounding the grid 813 and applying a voltage of −10 kV to the cold cathode 812. it can. A positive voltage of about 30 kV is applied to the anode 814. As a result, electrons with an energy of 10 to 30 keV collide with the metal back film 815, and the white phosphor can efficiently emit light.

  Thus, according to the fourth embodiment, an apparatus can be provided using the cold cathode obtained in the first to third embodiments. Although a tubular lighting device (field emission lamp) has been described as an example here, a spherical or planar lamp can be configured. A radiation source such as an X-ray source can also be configured using the cold cathodes obtained in the first to third embodiments. It is also possible to configure other cold cathode devices such as a field emission display.

Example 1
As a first example, a cold cathode was manufactured using a magnetron sputtering apparatus by the manufacturing method of the first embodiment. The configuration and manufacturing procedure of the magnetron sputtering apparatus used are the same as in the first embodiment. In the magnetron sputtering apparatus, the diameter of the cathode 11 and the anode 12 was about 7.2 cm, and the distance between the cathode 11 and the anode 12 was about 2.5 cm. Ar was used as the introduced gas. The covering layer 21 of the cathode 11 is a graphite layer.

  A rod-like graphite member having a diameter of 0.9 mm and a length of 11 mm was used as the member 20 that is a target for forming the minute protrusions.

  This graphite member 20 was inserted into a recess provided in advance on the cathode 11 of the magnetron sputtering apparatus, and was placed upright as shown in FIG. On the cathode 11, the graphite member 20 protruded by about 5 mm. Plasma treatment was performed at an applied power of 100 W and a gas pressure of 4 Pa for 60 minutes to form irregularities on the tip surface.

  The photograph which image | photographed the front end surface in which the unevenness | corrugation of the graphite member 20 after a process was formed with the scanning electron microscope is shown in FIG. 9 and FIG. 9 is a photograph of the central region 72 (see FIG. 7) of the tip surface of the graphite member 20, and FIG. 10 is a photograph of the peripheral region 71 (see FIG. 7) of the tip surface of the member 20. 9 and 10, it can be seen that a number of minute protrusions are formed on the tip surface of the graphite member 20 by the plasma treatment of this embodiment.

  Even on the tip surface of the same graphite member 20, the shape of the minute protrusion formed in the central region 72 and the shape of the minute protrusion formed in the peripheral region 71 were different. The microprotrusions formed in the center region 72 of the distal end surface have a shape as shown in FIG. 9 and have a root diameter of about 200 to 1500 nm and a height of about 500 to 700 nm. On the other hand, the microprotrusions formed in the peripheral region 71 have a shape as shown in FIG. 10 and have a root diameter of about 300 to 1000 nm and a height of about 200 to 1000 nm. Therefore, the minute protrusion formed in the center region 72 of the tip surface has a larger aspect ratio and sharper than the minute protrusion formed in the peripheral region 71 of the tip surface.

  The electron emission characteristics of the graphite member 20 (cold cathode) plasma-treated by the method of Example 1 were measured. The result is shown in FIG. The horizontal axis in FIG. 11 represents the electric field magnitude (V / μm) on the surface of the cold cathode, and the vertical axis represents the current value (A) due to the emitted electrons. From FIG. 11, the current value of the cold cathode of Example 1 rose steeply from an electric field of 8 V / μm. From this, it was confirmed that the cold cathode of this example had low resistance and excellent electron emission characteristics.

  Thus, by using the manufacturing method of Example 1, it was possible to manufacture a cold cathode having excellent electron emission characteristics using a magnetron sputtering apparatus. The magnetron sputtering apparatus has a simpler configuration than the microwave plasma generation apparatus, and the generated plasma is high density and uniform, so that a plurality of cold cathodes can be efficiently plasma processed at one time. Therefore, by using the manufacturing method of Example 1, it is possible to mass-produce cold cathodes having excellent electron emission characteristics at low cost.

(Example 2)
Next, as a second example, a cold cathode was manufactured by forming minute protrusions on a member 62 in which a groove 63 was previously formed by using a magnetron sputtering apparatus by the manufacturing method of the third embodiment. . The configuration of the magnetron sputtering apparatus used and the conditions for the plasma treatment are the same as in Example 1.

  The member 62 which is a target for forming the minute protrusions is a bar-shaped graphite member having the same size as the member 20 of Example 1, and a groove 63 is formed in advance on the tip surface. The shape of the groove 63 was rectangular in cross section. The arrangement of the grooves 63 is radial.

  As shown in FIG. 2, the member 62 having the groove formed thereon is arranged on the cathode 11 having the coating 21, and plasma treatment is performed at an applied power of 100 W and a gas pressure of 4 Pa for 60 minutes to form irregularities on the tip surface. did.

  The photograph which image | photographed the front end surface in which the unevenness | corrugation of the graphite member 62 after a process was formed with the scanning electron microscope is shown in FIG. 12 and FIG. A cross-sectional view of the groove 63 is shown in FIG. 12 is a photograph of the center region 72 (see FIG. 7) of the tip surface of the graphite member 62, and FIG. 13 is a photograph of the peripheral region 71 (see FIG. 7) of the tip surface of the member 62. 12 and 13, it can be seen that a number of minute protrusions are formed on the tip surface of the graphite member 62 by the plasma treatment of this embodiment. The microprotrusions (FIG. 12) formed in the central region 72 have a larger aspect ratio and are sharper than the microprotrusions (FIG. 13) formed in the peripheral region 71. Same as 1.

  Specifically, the microprotrusions formed in the central region of the distal end surface have a shape as shown in FIG. 12, and have a root diameter of about 200 to 1000 nm and a height of about 7 to 30 μm. The microprotrusions formed in the peripheral region had a shape as shown in FIG. 13 and had a root diameter of about 300 to 900 nm and a height of about 400 to 1800 nm. As a result, both the central region 72 and the peripheral region 71 have an aspect ratio of the microprojections and the microprojections (FIGS. 9 and 10) of the central region 72 and the peripheral region 71 of the first embodiment in which the groove 63 is not formed. It was confirmed that the density was increased.

  Further, as shown in FIG. 14, the protrusion inside the groove 63 is formed with a fine protrusion having a higher aspect ratio than the flat portion 64 (see FIG. 6B) between the groove 63 and the groove 63. I understand.

  As described above, it was confirmed that a projection having a high aspect ratio can be formed by performing plasma treatment on a member in which the groove 63 is formed in advance. In particular, by cutting the groove 63 in a portion where electron emission is desired, a projection with a high aspect ratio that causes electron emission from the inside of the groove 63 can be produced.

  The electron emission characteristics of the graphite member 62 (cold cathode) plasma-treated by the method of Example 2 were measured. The result is shown in FIG. From FIG. 11, the current value of the cold cathode of Example 2 rose steeply from an electric field of 6 V / μm. From this, it was confirmed that the cold cathode of Example 2 had a smaller resistance than the cold cathode of Example 1 and was excellent in electron emission characteristics.

  By forming grooves in the processing target member in advance as in the manufacturing method of Example 2, a cold cathode having excellent electron emission characteristics could be manufactured using a magnetron sputtering apparatus. The magnetron sputtering apparatus has a simpler configuration than the microwave plasma generator, and the generated plasma is high density and uniform, so that a plurality of cold cathodes can be plasma-treated at once. Therefore, by using the manufacturing method of Example 2, it is possible to mass-produce cold cathodes having better electron emission characteristics than the cold cathode of Example 1 at a low cost.

Explanatory drawing which shows the structure of the magnetron sputtering apparatus used by 1st Embodiment. The perspective view which shows the state which has arrange | positioned the member 20 on the cathode 11 of the magnetron sputtering apparatus of FIG. Explanatory drawing which shows the structure of the DC or RF sputtering device used in 2nd Embodiment. The perspective view which shows the state which has arrange | positioned the member 20 on the cathode 11 of the DC or RF sputtering device of FIG. The perspective view which shows the state which has arrange | positioned the wire-shaped member 51 on the cathode 11 of the DC or RF sputtering apparatus of FIG. (A) The perspective view which shows the cylindrical member with a flat upper surface, (b) The perspective view which shows the cylindrical member which formed the groove | channel in the upper surface used in 3rd Embodiment. The perspective view which shows the peripheral area | region 71 and the center area | region 72 in the upper surface of the cylindrical members 20 and 62. FIG. Sectional drawing which shows the structure of the illuminating device of 4th Embodiment. The scanning electron micrograph which shows the unevenness | corrugation of the center area | region of the member 20 upper surface formed by the plasma processing of Example 1. FIG. The scanning electron micrograph which shows the unevenness | corrugation of the peripheral area | region of the member 20 upper surface formed by the plasma processing of Example 1. FIG. 3 is a graph showing electron emission characteristics of cold cathodes manufactured in Example 1 and Example 2. FIG. The scanning electron micrograph which shows the unevenness | corrugation of the center area | region of the member 62 upper surface formed by the plasma processing of Example 2. FIG. 6 is a scanning electron micrograph showing the irregularities in the peripheral region on the upper surface of the member 62 formed by the plasma treatment of Example 2. FIG. The scanning electron micrograph about the cross section of the groove part of the member 62 formed by the plasma processing of Example 2. FIG. Explanatory drawing which shows the apparatus structure in the case of carrying out plasma processing of the graphite rod using a microwave plasma generator.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Cathode, 12 ... Anode, 13 ... Magnet, 14 ... Power supply, 15 ... Donut-shaped plasma, 16 ... Target, 17 ... Electric field, 20 ... Member of process object, 21 ... Covering layer, 31 ... Plasma, 62 ... Process object Member, 71 ... peripheral region, 72 ... central region.

Claims (7)

A member for cold cathode, comprising a cathode having a coating layer made of the same element as the material to be an electron emission source and having a cathode disposed on the upper surface, the cold cathode member being made of the material to be an electron emission source on the coating layer And place
A cold projection having a microprojection is characterized by forming a microprotrusion on the surface of the cold cathode member by generating a plasma between the cathode and the anode and exposing the cold cathode member to the plasma. Manufacturing method of cathode. A cold cathode composed of a material serving as an electron emission source between a cathode disposed on the upper surface of a coating layer composed of the same element as the material serving as an electron emission source and an anode disposed so as to face the cathode Place the material for
Plasma is generated by applying a voltage between the cathode and the anode, and the cold cathode member is exposed to the plasma, thereby forming minute protrusions on the surface of the cold cathode member. A method for producing a cold cathode provided with fine protrusions.   3. The method of manufacturing a cold cathode according to claim 1 or 2, wherein a magnet is previously disposed under the cathode and plasma is generated in the vicinity of the cathode.   4. The method of manufacturing a cold cathode according to claim 1, wherein the cold cathode member is graphite, and the coating layer is made of carbon. 5.   5. The method of manufacturing a cold cathode according to claim 1, wherein a predetermined groove is formed in the cold cathode member in a region where electrons are to be emitted in advance. A method for producing a cold cathode. A method of manufacturing a device provided with a field emission cold cathode,
The step of manufacturing the field emission cold cathode comprises:
A member for cold cathode, comprising a cathode having a coating layer made of the same element as the material to be an electron emission source and having a cathode disposed on the upper surface, the cold cathode member being made of the material to be an electron emission source on the coating layer A step of arranging
And a step of forming microprojections on the surface of the cold cathode member by a method of generating plasma between the cathode and the anode and exposing the cold cathode member to the plasma. A method for manufacturing a device having a cold cathode. A method of manufacturing a device provided with a field emission cold cathode,
The step of manufacturing the field emission cold cathode comprises:
A cold cathode composed of a material serving as an electron emission source between a cathode disposed on the upper surface of a coating layer composed of the same element as the material serving as an electron emission source and an anode disposed so as to face the cathode Place the material for
Generating a plasma by applying a voltage between the cathode and the anode, and exposing the cold cathode member to the plasma to form microprotrusions on the surface of the cold cathode member. A method of manufacturing a device comprising a field emission cold cathode.