JP2006156111A - Electron emission electrode, its manufacturing method, and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electron emitting electrode which enables a highly clear display, and a display device using it. <P>SOLUTION: This is the electron emitting electrode which has a protrusion 6 erected and installed on a conductive substrate 7 and in which the protrusion is a composite of a metal 11 and a conductive fiber 12 arranged in the longitudinal direction of its protrusion 6. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electron emission electrode that emits electrons from a tip by applying an electric field, a manufacturing method thereof, and a display device.

  A field emission display (FED) is attracting attention as a candidate for a next-generation display that replaces a liquid crystal display (LCD). Field emission refers to a phenomenon in which when a strong electric field is applied to a solid surface, the potential barrier of the solid surface confining electrons is lowered and electrons are emitted from the solid surface. As a field emission display element utilizing such a phenomenon, a microemitter such as silicon or molybdenum having a sharp tip is conventionally known. However, carbon nanotubes (Carbon Nano-Tube: CNT), which are conductive fibers, have a nano-level diameter, high aspect ratio, high current density, high toughness, high heat resistance and high resistance due to the developed graphite structure. Since it has chemical stability, it is expected to be a field emission display device superior to the aforementioned metallic microemitter.

  In order to use CNTs for FED, it is preferable to orient CNTs so that they are as perpendicular to the display as possible. As a method for orienting CNTs vertically, for example, a method is known in which a mixture of CNTs, magnetic particles, and a binder is applied on a circuit board and then a magnetic field is applied to stand vertically on the circuit board ( (See Patent Document 1). There is also known a method in which a suspension containing CNTs is solidified with a resin through a filter and stands on a circuit board.

JP-A-2004-234865 (Claims)

  However, the above-mentioned conventionally known production method and the result thereof have the following problems. In a method in which a magnetic field is applied after a mixture of CNT, magnetic particles, and a binder (resin) is applied to a circuit board, a binder component is present in the film containing CNTs. For this reason, when an electric field is applied, there is a risk that the binder will volatilize and display defects will occur. In addition, since the CNTs are only dispersed on the circuit board, there is a problem that the CNTs cannot be uniformly dispersed and a high-definition display cannot be realized. Further, in the method in which the CNTs are vertically aligned in the resin through a filter, the resin is left on the circuit board. Therefore, when the electric field is applied, the resin volatilizes and there is a risk of causing a display defect.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an electron-emitting electrode that enables high-definition display, a manufacturing method thereof, and a display device using the electron-emitting electrode. .

  In order to achieve the above object, the present invention has a protrusion standing on a conductive substrate, and the protrusion is a composite of a metal and a conductive fiber oriented in the length direction of the protrusion. Electron emission electrode. As described above, since the protrusions made of the composite of the metal and the conductive fiber are erected, the volatilization of a substance (for example, a resin) having a melting point lower than that of the composite when using as an electron emission electrode. There is no. In addition, since the conductive fiber is exposed from the tip of the protrusion, the fiber can be uniformly dispersed by arranging the protrusions uniformly on the electron emission electrode. For this reason, high-definition display is possible.

  Another aspect of the present invention is an electron emission electrode in which the conductive fiber in the previous invention is oriented substantially perpendicular to the conductive substrate. For this reason, clearer display is possible.

  In another aspect of the present invention, an electron emission electrode in which the conductive fiber in the previous invention is a carbon nanotube is used. For this reason, it becomes easier to cause field emission at a lower voltage.

  The present invention also includes a step of forming a resist film on a conductive substrate, a step of forming a hole exposing the conductive substrate in the resist film, and a step of forming a composite plating made of a metal and a conductive fiber in the hole. And an electron emission electrode manufacturing method including a step of removing the resist film after formation of the composite plating. By using such a manufacturing method, an electron-emitting electrode that enables clear display can be obtained. In addition, by controlling the diameter of the hole in the hole forming step, the number and size of the protrusions can be controlled, and the number of conductive fibers exposed at the tip can also be controlled. For example, if the diameter of the hole is small and many are formed, the diameter of the protrusion formed by the transfer is small and the number is large. As a result, the number of conductive fibers contained in the protrusion is reduced, and it becomes easy to orient perpendicularly to the conductive substrate.

  Another aspect of the present invention is an electron emission electrode manufacturing method in which at least one of the conductive fibers in the previous invention is longer than the longest distance in the opening surface of the hole. For this reason, at least one conductive fiber is not horizontal to the conductive substrate. Therefore, the at least one conductive fiber is oriented in the plating growth direction. When the conductive fiber does not protrude from the plated object, the metal in the plated object can be melted using an acid or the like so that the conductive fiber protrudes from the plated object. In addition, by forming a conical or angularly shaped hole with a narrow inlet and expanding the inside, the at least one conductive fiber is made substantially vertical at the hole inlet and is contained in the plated product as it is. It can also be made.

  Another invention of the present invention is a method for manufacturing an electron-emitting electrode, wherein the resist film in the previous invention is a photoresist, and the step of forming holes is a step by light irradiation. This makes it easier to form fine and uniformly dispersed holes.

  Another aspect of the present invention is a method for manufacturing an electron emission electrode in which the conductive fiber in the previous invention is a carbon nanotube. For this reason, it becomes easier to cause field emission at a lower voltage.

  In addition, the present invention is a display device that performs display on a display opposite to the electron emission electrode described above. For this reason, it can be applied to a next-generation thin TV having a high-definition display capability.

  The conductive substrate may be a metal, a conductive resin substrate, or a ceramic or the like coated with a thin film of metal or conductive resin as long as it is a conductive substrate that can be subjected to electrolytic plating. Moreover, the metal used as the matrix in the composite material is not limited to copper, nickel, iron, cobalt, gold, silver, or the like, and may be of any kind. The metal may be an alloy composed of a plurality of elements as well as a single element. A preferable form of the metal is gold, copper, nickel, or an alloy containing any of these.

  The conductive fiber refers to a material having conductivity and an aspect ratio (length / diameter) larger than 1. The term “conductivity” as used herein is interpreted to exclude insulation, and the semiconductor and the conductor are also interpreted as having conductivity. CNT which is one form of the conductive fiber is a cylindrical carbon fiber, and the diameter and length of the cylinder are not particularly limited, but preferably the diameter is 200 nm or less and the aspect ratio (length / diameter) is 10 or more. Is good. As the conductive fiber, non-cylindrical carbon fiber may be adopted instead of CNT.

  The resist film is mainly a photosensitive resin, regardless of whether it is a positive type or a negative type. Examples of the positive resist include those obtained by esterifying ortho-naphthoquinone diazide sulfonic acid with a novolak resin, and those obtained by esterifying trihydroxybenzophenone or tetrahydroxybenzophenone with a meta-cresol type novolak resin. Examples of the negative resist include polyvinyl cinnamate, rubber resist, and novolac resin-azide resist. Further, the resist film may be a non-photosensitive resin. In that case, as a method of forming a hole in a specific place, processing using a laser or the like can be used instead of using crosslinking or decomposition by light irradiation.

  The hole is a concept including a substantially cylindrical shape or a polygonal column shape, or a substantially conical or angularly shaped hole, or any other shape. Here, the substantially cylindrical shape includes not only an accurate cylindrical shape but also a column shape having an elliptical surface. Further, the substantially polygonal column shape means a column shape having a triangular, quadrangular, or more-shaped surface, and it does not matter whether it is a regular polygon such as a regular triangle. The substantially conical shape includes not only an accurate conical shape but also an elliptical shape. Furthermore, the substantially angular guess shape means a guess shape having a bottom surface of a triangle, a quadrangle, or a shape having more than that, regardless of whether the bottom surface is a regular polygon such as a regular triangle. . It does not matter whether the bottom surface of the hole is flat or curved.

  Orientation means other than the state in which the conductive fibers are dispersed in a random direction. Not only is the state in which all the conductive fibers are oriented exactly in one direction, but the dispersion is clearly biased in either direction. It shall be interpreted in a broad sense that encompasses the state of being.

  When the diameter of the opening surface of the hole or the longest diagonal line is long with respect to the length of the conductive fiber, the conductive fiber is freely dispersed. On the other hand, when the diameter of the opening surface or the longest diagonal line is shorter than the length of the conductive fiber, the conductive fiber is not dispersed horizontally with respect to the conductive substrate, but is oriented and dispersed in the length direction of the hole. To do. If at least one conductive fiber is longer than the diameter of the aperture or the longest diagonal, the at least one conductive fiber will be oriented in the length direction of the hole. In addition, when a conical hole having a narrow entrance is formed, when the conductive fiber enters the hole, it is oriented almost perpendicularly to the conductive electrode and is easily included in the plated product as it is. Therefore, when used as an electron emission electrode, electrons are easily emitted in one direction.

  According to the present invention, clear display can be realized in the FED.

  Embodiments of an electron emission electrode, a manufacturing method thereof, and a display device according to the present invention will be described below with reference to the drawings. In the following embodiment, CNT which is one form thereof is used as the conductive fiber.

  FIG. 1 is a schematic view of a display device having an electron emission electrode according to an embodiment of the present invention.

  The display device shown in FIG. 1 (herein described as “FED”) has a configuration in which a cathode glass sheet 1 and an anode glass sheet 2 are arranged to face each other in a vacuum. On the surface of the anode glass sheet 2 on the vacuum region side, an electrode 4 on which a phosphor 3 is arranged is provided. On the other hand, the cathode glass sheet 1 is provided with a substrate 8 to which a gate electrode 5 and a reference wiring (conductive substrate) 7 having a metal-CNT composite plating product (field emission display element) 6 are attached. The electron emission electrode includes one or a plurality of metal-CNT composite plated articles (field emission display elements) 6 and a reference wiring 7 connected thereto as structural units. Here, the reference wiring 7 is formed by a method of dissolving unnecessary portions after electroless plating. However, the reference wiring 7 may be formed by a chemical vapor deposition (CVD) method or a physical vapor deposition (PVD) method.

  In such an FED, when a voltage is applied between the reference wiring 7 and the gate electrode 5, electrons are emitted from the CNT protruding from the tip of the metal-CNT composite plating 6 into the vacuum. The electrons travel toward the anode glass sheet 2 by the voltage applied between the electrode 4 and the substrate 8 and collide with the phosphor 3 to emit light. Since the CNT protrudes from the metal-CNT composite plated product 6 and is oriented in the length direction of the metal-CNT composite plated product 6, electrons can be emitted almost vertically toward the phosphor 3.

  FIG. 2 is a flowchart showing a part of the manufacturing process of the field emission display having the electron emission electrode according to the embodiment of the present invention. FIG. 3 shows a state in which a field emission display having an electron emission electrode is formed by each step of FIG. However, in FIG. 3, the gate electrode 5 is omitted. In addition, hereinafter, there are symbols that indicate only some of the objects in the figure, but all the objects of the same type are instructed.

  In order to manufacture a field emission display including an electron emission electrode according to an embodiment of the present invention, first, the reference wiring 7 is attached to the substrate 8 in a stripe shape (step S1). The gate electrode 5 can be attached before or after step S1 or simultaneously with step S1. Next, a negative resist film 9 which is one form of a resist film is formed on the reference wiring 7 (step S2). Next, a negative mask is placed on the negative resist film 9 and exposed. Development is performed following exposure, and holes 10 are formed according to the pattern of the negative mask (step S3). When a negative resist is used, the exposed part is insolubilized. For this reason, only the non-exposed part is removed and the hole 10 is formed. In this embodiment, the non-exposed portions are a plurality of small circles having a diameter on the order of microns arranged regularly. Therefore, after the development, many negative holes 10 exposing the reference wiring 7 are formed in the negative resist film 9. Instead of the negative resist film 9, a positive resist film may be adopted.

  Next, electrolytic plating is performed using the reference wiring 7 provided with the perforated negative resist film 9 as one electrode. A plating bath contains the ion (nickel ion) of nickel 11 which is one form of metal, and CNT12. By performing electrolytic plating in such a plating bath, the metal-CNT composite plated product 6 composed of nickel 11 and CNTs 12 is formed in the cylindrical hole 10 (step S4). In this composite plating step (step S4), the CNTs 12 are taken into the cylindrical holes 10 when nickel ions are attracted and moved by the reference wiring 7, and are contained in the plating. In addition, you may make it be attracted | sucked to the reference | standard wiring 7 with nickel ion by attaching a charged particle to CNT12 itself and making it charge positively. Further, an adhesive material may be attached to the CNT 12 itself so that it can be easily fixed in the hole 10. After step S4, the remaining negative resist film 9 is removed (step S5). Next, an extraction electrode in a direction perpendicular to the reference wiring 7 is attached (step S6).

  FIG. 4 is a diagram schematically showing the composite plating step (step S4 in FIG. 2).

  A substrate 8 provided with a perforated negative resist film 9 and another electrode 15 are inserted into a plating bath 14 placed in a container 13, and the reference wiring 7 on the substrate 8 is a negative electrode, and the other electrode 15 is a positive electrode. Thus, the reference wiring 7 on the substrate 8 and another electrode 15 are connected to the DC power source 16. The plating bath 14 is a mixture of CNTs 12 in a nickel bath containing nickel ions 11a. When a voltage is applied between the reference wiring 7 and another electrode 15, the nickel ions 11 a in the plating bath 14 are attracted to the hole 10 side and are deposited as nickel 11 as shown by the arrows in the figure. At this time, the CNT 12 is taken into the precipitated nickel 11. In this way, the metal-CNT composite plated product 6 is formed in the hole 10. The power source is not limited to the DC power source 16 alone, and superposition with an AC power source may be employed. In this way, the metal-CNT composite plated product 6 that is a projection is formed by plating, so that a large surface field emission display can be easily achieved by enlarging the container 13 containing the plating bath 14. Can be produced.

  FIG. 5 shows a part of a field emission display body which is an assembly of electron emission electrodes in which a metal-CNT composite plating product 6 is erected on a reference wiring 7 and one metal constituting the electron emission electrode. -It is a figure which shows the enlarged view of the CNT composite plated article 6. FIG.

  The electron emission display has a form like a so-called Kenzan. In the electron emission electrode constituting this, the CNTs 12 in the metal-CNT composite plated product 6 are present in a state of being oriented in the tip direction of the metal-CNT composite plated product 6. At the tip of the metal-CNT composite plating product 6, a part of the tip of the CNT 12 protrudes and is embedded. This portion is a portion that emits electrons. When the CNT 12 longer than the diameter of the hole 10 or the longest diagonal does not protrude from the metal-CNT composite plated product 6, the CNT 12 may be protruded by dissolving the metal 11 portion by acid treatment or the like. .

  FIG. 6 is a diagram schematically showing how the CNTs 12 move into the holes 10 formed in the negative resist film 9 when the metal-CNT composite plated product 6 is formed. FIG. 7 is a diagram schematically showing how the CNT 12 having a length √2 times the diameter D of the hole 10 enters the hole 10.

  As shown in FIG. 6, when the length L of the CNT 12 is equal to or smaller than the diameter D of the hole 10, the CNT 12 is dispersed in the nickel 11 in a random direction. On the other hand, when a CNT 12 longer than the diameter D exists, the long CNT 12 does not exist in a state parallel to the reference wiring 7. As shown in FIG. 7, if only the CNT 12 having a length of √2 times the diameter D or more is used, the CNT 12 is 45 ° with respect to the direction perpendicular to the reference wiring 7 even when it is horizontal. It can only be in an angled state. Therefore, the orientation can be adjusted by controlling the relationship between the diameter D of the hole 10 and the length of the CNT 12. When at least one of all the CNTs 12 is longer than the diameter D of the hole 10, the CNTs 12 can be oriented in the length direction of the metal-CNT composite plated product 6. The more CNTs 12 that are longer than the diameter D are present, the higher the probability that the CNTs 12 are oriented in the direction perpendicular to the reference wiring 7.

  FIG. 8 is a scanning electron microscope (SEM) photograph of a product obtained when the electroplating process is performed under the condition that the diameter D of the hole 10 is sufficiently larger than the length of the CNT 12. In these photographs, the magnification increases in the order of upper left (25 times), upper right (100 times), lower left (700 times), and lower right (10,000 times).

The diameter of the cylindrical hole 10 formed by removing the negative resist film 9 is about 50 microns. The used CNT 12 is VGCF (manufactured by Showa Denko KK) having an average diameter of 100 to 150 nm, a length of 10 to 20 μm, and a true density of 2.0 g / cm ³ . In these photographs, a metal-CNT composite plated product 6 is formed in a small circle portion. When the metal-CNT composite plated product 6 is enlarged, it can be seen that the CNT 12 is embedded in the metal-CNT composite plated product 6 with the surface exposed. When the diameter D of these holes 10 is smaller than 10 microns, the CNTs 12 are easily oriented in the vertical direction.

  FIG. 9 is a diagram illustrating holes 10 in the negative resist film 9 and illustrating polygonal holes 10.

  The shape of the hole 10 may be a hexagonal shape or a quadrangular shape as shown in FIG. When these shapes of holes 10 are employed, the length D of the diagonal line is the largest among the linear distances in the plane of the holes 10. Therefore, when the hole 10 is formed so that the length D is smaller than the length of the CNT 12, the CNT 12 is easily remarkably oriented in a direction perpendicular to the surface of the reference wiring 7. In addition, when the shape of the hole 10 is a triangle, if the size of the hole 10 is determined so that the longest side of the triangle is shorter than the length of the CNT 12, the orientation is similarly facilitated.

  FIG. 10 is a view showing a modified example of the present invention different from the above-described embodiment, and schematically showing how the CNT 12 enters the substantially conical hole 10.

  As shown in FIG. 10, when the length of at least one CNT 12 is longer than the diameter D of the conical hole 10, the CNT 12 faces the hole 10 in a state of being perpendicular to the reference wiring 7. Therefore, the CNTs 12 are oriented in the direction perpendicular to the reference wiring 7 and are easily taken into the plated product. Thus, the shape of the hole 10 is not limited to the columnar shape, and may be a shape such as circular thrust. Further, the hole 10 in FIG. 10 may be a pyramid shape instead of a conical shape. In this case, the length indicated by D is the longest distance of the opening surface.

  The present invention is applicable to industries that manufacture or use FEDs.

It is a schematic diagram of the display apparatus which has the electron emission electrode concerning embodiment of this invention. It is a flowchart which shows the manufacturing process of the field emission display body provided with the electron emission electrode concerning embodiment of this invention. FIG. 3 illustrates how a field emission display including an electron emission electrode is formed by each step of FIG. 2. It is a figure which shows typically step 4 (process of composite plating) of FIG. A part of a field emission display which is an assembly of electron emission electrodes on which a metal-CNT composite plating product is erected, and an enlarged view of one metal-CNT composite plating product constituting the electron emission electrode; FIG. It is a figure which shows typically a mode that CNT moves to the hole opened in the negative resist film at the time of formation of metal-CNT composite plating. It is a figure which shows typically a mode that CNT which has a length of 2 times the diameter D of a hole enters a hole. It is a scanning electron microscope (SEM) photograph of the product at the stage when the diameter D of the hole was subjected to the electrolytic plating process under a condition sufficiently larger than the length of the CNT. In these photographs, the upper left (A) is 25 times, the upper right (B) is 100 times, the lower left (C) is 700 times, and the lower right (D) is 10,000 times. It is a figure which is a hole in a negative resist film, Comprising: It is a figure which illustrates a polygonal hole. It is a figure which shows the modification of this invention, Comprising: It is a figure which shows typically a mode that CNT enters into a substantially cone-shaped hole.

Explanation of symbols

6 Metal-CNT composite plating (projection)
7 Reference wiring (conducting substrate)
9 Negative resist film (resist film)
10 holes 11 nickel (metal)
11a Nickel ion (metal ion)
12 CNT (conductive fiber)

Claims (8)

Having protrusions standing on the conductive substrate,
The projection is a composite of a metal and a conductive fiber oriented in the length direction of the projection.   The electron-emitting electrode according to claim 1, wherein the conductive fiber is oriented substantially perpendicular to the conductive substrate.   The electron-emitting electrode according to claim 1, wherein the conductive fiber is a carbon nanotube. Forming a resist film on the conductive substrate;
Forming a hole exposing the conductive substrate in the resist film;
Forming a composite plating made of a metal and a conductive fiber in the hole;
A step of removing the resist film after the formation of the composite plating;
A method for producing an electron-emitting electrode, comprising:   The method of manufacturing an electron-emitting electrode according to claim 4, wherein at least one of the conductive fibers is longer than a longest distance in an opening surface of the hole.   6. The method of manufacturing an electron-emitting electrode according to claim 4, wherein the step of forming the hole using the resist film as a photoresist is a step of irradiating light.   The method of manufacturing an electron-emitting electrode according to claim 4, wherein the conductive fiber is a carbon nanotube.   A display device for performing display on a display opposite to the electron emission electrode according to claim 1, 2 or 3.