Patent Publication Number: US-7722424-B2

Title: Electron emitter, method of manufacturing electron emitter, electro-optical device, and electronic apparatus

Description:
BACKGROUND 
   1. Technical Field 
   The present invention relates to an electron emitter, a method of manufacturing the electron emitter, and an electro-optical device and an electronic apparatus having the electron emitter. 
   2. Related Art 
   In the past, as electron emitters, there were known a thermal electron emission type and a cold-cathode electron emission type. As the electron emitters of the cold-cathode electron emission type, there were known a field emission type that electrons are emitted by an electric field and a surface conduction type that electrons are emitted from a conduction band of an electrode surface by allowing current to flow in the electrode. 
   As the electron emitter of the surface conduction type among them, there is known an electron emitter in which an electron emission portion is formed through an electrification forming process. Through the electrification forming process, a conductive thin film is destroyed locally to form a micro crack (narrow gap) destroyed locally. In this state, the electron emission portion is embodied by using the property that electrons with vacuum level are leaked from the micro crack when current is allowed to flow in the conductive thin film (for example, see JP A-9-213210). 
   The conductive thin film of the electron emitter according to Patent Document 1 is formed by the use of a so-called droplet jetting method (inkjet method). In this method, the conductive film is formed by applying a functional solution containing a conductive material in a pattern onto a substrate by the use of the droplet jetting method and then removing a solvent of the functional solution through the use of a dry process or the like. 
   According to this method, it is possible to relatively easily form the patterned conductive thin film, but it is difficult to control the film surface. That is, in the conductive thin film formed by the use of the droplet jetting method, the film surface can be easily disturbed after forming the conductive thin film and such a disturbance remarkably appears in the outer edge portions of the pattern. The electron emission characteristic of the electron emitter having such a conductive thin film is affected by the disturbance of the film surface of the conductive thin film, thereby causing deviation in characteristic within an element and between elements. 
   SUMMARY 
   An advantage of the present invention is to provide an electron emitter of which deviation in electron emission characteristic is small and which can be easily manufactured, a method of manufacturing the electron emitter, an electro-optical device having the electron emitter, and an electronic apparatus having the electron emitter. 
   According to an aspect of the present invention, there is provided a method of manufacturing an electron emitter in which electrons are emitted from an electron emission portion formed in a conductive film, the method comprising: forming the conductive film in a pattern on a substrate by the use of a droplet jetting method; selectively removing a part of the conductive film; and forming the electron emission portion in the conductive film. 
   In the method of manufacturing an electron emitter according to the present invention, since only a portion with a film surface excellent in flatness of the conductive film formed by the use of the droplet jetting method can be left and used, it is possible to manufacture an electron emitter of which deviation in electron emission characteristic is small. 
   In the method of manufacturing an electron emitter, the removing of a part of the conductive film may include: forming a dummy functional film in a pattern on the conductive film by the use of the droplet jetting method; and etching an exposed portion of the conductive film by using the dummy functional film as a mask. 
   According to the method of manufacturing an electron emitter, since the dummy functional film serving as an etching mask is formed by the use of the droplet jetting method, the dummy functional film can be easily formed by the use of the apparatus (droplet jetting apparatus or dry apparatus) common to the film forming process. 
   In the method of manufacturing an electron emitter, an outer edge portion of the conductive film may be removed in the removing of a part of the conductive film. 
   According to the method of manufacturing an electron emitter, since the outer edge portion which can easily cause disturbance of the film surface in the conductive film formed by the use of the droplet jetting method is removed, the flatness of the conductive film after the shaping can be improved. 
   According to another aspect of the present invention, there is provided an electron emitter comprising a conductive film formed on a substrate, in which electrons are emitted from an electron emission portion formed in the conductive film, wherein the conductive film is formed by removing a part of a conductive film formed by the use of a droplet jetting method. 
   According to the electron emitter of the present invention, since the conductive film includes only a portion with a film surface excellent in flatness of the conductive film formed by the use of the droplet jetting method, the deviation in electron emission characteristic is small. 
   According to still another aspect of the present invention, there is provided an electro-optical device comprising the electron emitter. 
   The electro-optical device according to the present invention includes electron emitters formed corresponding to the pixels of a display unit and the display is embodied, for example, by allowing the emitted electrons to collide with fluorescent substances formed on a positive electrode. Since the electron emitters of the electro-optical device include the conductive film with a film surface excellent in flatness, the deviation in electron emission characteristic within an element and between elements is small and it is thus possible to display images with high quality. 
   According to still another aspect of the present invention, there is provided an electronic apparatus comprising the electron emitter. 
   Since the electron emitters of the electronic apparatus according to the present invention include the conductive film with a film surface excellent in flatness, the deviation in electron emission characteristic is small and the electronic apparatus can thus provide excellent performance. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements and wherein: 
       FIG. 1A  is a plan view illustrating an electron emitter according to a first embodiment of the present invention and  FIG. 1B  is a cross-sectional view illustrating the electron emitter according to the first embodiment; 
       FIG. 2  is a schematic perspective view illustrating an example of a droplet jetting apparatus used for manufacturing the electron emitter; 
       FIG. 3  is a flowchart illustrating a method of manufacturing the electron emitter according to the first embodiment; 
       FIGS. 4A to 4F  are schematic cross-sectional views illustrating one step of the method of manufacturing the electron emitter according to the first embodiment, respectively; 
       FIG. 5A  is a schematic cross-sectional view illustrating a structure of an important part of an electro-optical device and  FIG. 5B  is a schematic plan view illustrating a layout of electron emitters on an element substrate; 
       FIG. 6  is schematic perspective view illustrating an example of an electronic apparatus; 
       FIG. 7  is a flowchart illustrating a method of manufacturing an electron emitter according to a second embodiment of the present invention; 
       FIGS. 8A to 8E  are schematic cross-sectional views illustrating one step of the method of manufacturing the electron emitter according to the second embodiment, respectively; and 
       FIGS. 9F to 9I  are schematic cross-sectional views illustrating one step of the method of manufacturing the electron emitter according to the second embodiment. 
   

   DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
   Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
   Since the exemplary embodiments described below are specific examples suitable for the present invention, technically exemplary limitations are attached thereto, but the scope of the present invention is not limited to the embodiments as long as particular intentions of limiting the present invention are not described in the following description. In the drawings referred to by the following description, scales or aspect ratios of layers or elements are different from the real ones, for the purpose of recognizing the layers or elements from the drawings. 
   First Embodiment 
   (Structure of Electron Emitter) 
   First, a structure of an electron emitter will be described with reference to  FIG. 1 .  FIG. 1  is a diagram illustrating an electron emitter according to a first embodiment of the present invention, wherein  FIG. 1A  is a plan view of the electron emitter and  FIG. 2A  is a cross-sectional view of the electron emitter. 
   In  FIG. 1 , the electron emitter  10  includes a conductive film  12 , a first element electrode  14 , and a second element electrode  15  on an element substrate  11 . A first signal line  16  and a second signal line  17  for applying drive signals to the element electrodes  14  and  15  are arranged on the element substrate  11  and the signal lines  16  and  17  are electrically isolated from each other by the use of an interlayer insulating film  18 . Surroundings of the electron emitter  10  are sealed in high vacuum. 
   A glass substrate or a ceramic substrate is used as the element substrate  11 . 
   The first element electrode  14  and the second element electrode  15  come in contact with both ends of the conductive film  12 , respectively, and have a thickness of several hundreds nm to several μm. Examples of a material of the element electrodes can include metals such as Au, Mo, W, Pt, Ti, Al, Cu, Pd, Ni, and Cr and alloys thereof, and a transparent conductive material such as indium tin oxide (ITO). 
   The conductive film  12  is a thin film having a thickness of about several angstroms to several thousands angstroms, which extends in the X axis direction and has an electron emission portion  13  (which is schematically shown in the figures) formed as a crack at the center portion thereof. Examples of a material of the conductive film can include metal such as Pd, Pt, Ti, Ru, In, Cu, Cr, Ag, Au, Fe, Zn, Sn, Ta, W, and Pb, oxide such as PdO, SnO 2 , In 2 O 3 , PbO, and Sb 2 O 3 , boride such as HfB 2 , ZrB 2 , LaB 6 , CeB 6 , YB 4 , and GdB 4 , carbide such as TiC, ZrC, HfC, TaC, SiC, and Wc, nitride such as TiN, ZrN, and HfN, semiconductor such as Si and Ge, carbon, and the like. 
   In the above-mentioned structure, when a voltage is applied between the element electrodes  14  and  15  through the signal lines  16  and  17 , electron conduction occurs in the conductive film  12  over the electron emission portion  13 . At this time, a part of the electrons conducted through the crack of the electron emission portion  13  are leaked to vacuum by means of a quantum mechanical effect and the leaked electrons can be used as emitted electrons. 
   (Structure of Droplet Jetting Apparatus) 
   Next, a structure of a droplet jetting apparatus used for manufacturing the electron emitter  10  will be described with reference to  FIG. 2 .  FIG. 2  is a schematic perspective view illustrating an example of a droplet jetting apparatus used for manufacturing the electron emitter. 
   As shown in  FIG. 2 , the droplet jetting apparatus  100  includes a head mechanism section  102  which has a head unit  110  jetting droplets, a substrate mechanism section  103  to be mounted with a substrate  120  as a target of droplets jetted from the head unit  110 , a functional solution supply section  104  which supplies a functional solution  133  to the head unit  110 , and a controller  105  which totally controls the mechanism sections and the supply section. 
   The head unit  110  is fitted with a droplet jetting head (not shown) having a plurality of nozzles used for an inkjet printer, is supplied with electrical signals from the controller  105 , and then jets the functional solution  133  in a droplet shape. The jetting of droplets can be controlled by the controller  105  in a unit of nozzles. 
   A glass substrate, a metal substrate, a synthetic resin substrate, or the like can be used as the substrate  120  and most substrates can be used only if they have a flat panel shape. In manufacturing the electron emitter to be described later, the element substrate  11  shown in  FIG. 1  is used as the substrate  120 . 
   As the functional solution  133 , a solution containing, for example, a filter material for a color filter, a light emitting material or a fluorescent material used for an electro-optical device, a plastic resin material used for forming a bank or a surface coating layer on a surface of a substrate, a conductive material for forming an electrode or a metal line, a resist material, and the like can be prepared corresponding to the purpose of drawing. In manufacturing the electron emitter to be described later, a conductive functional solution for forming the conductive film (see  FIG. 1 ) and the like and a resist solution are used. 
   The droplet jetting apparatus  100  includes a plurality of support legs  106  provided on a floor and a surface table  107  provided on the support legs  106 . The substrate mechanism section  103  is disposed on the surface table  107  in the longitudinal direction (X axis direction) of the surface table  107  and the head mechanism section  102  of which both ends are supported by two pillars fixed to the surface table  107  is disposed on the substrate mechanism section  103  in the direction (Y axis direction) perpendicular to the substrate mechanism section  103 . the functional solution supply section  104  which communicates with the head unit  110  of the head mechanism section  102  and serves to supply the functional solution  133  is disposed on one end of the surface table  107 . 
   The head mechanism section  102  includes the head unit  110  which jets the functional solution  133 , a carriage  111  which is mounted with the head unit  110 , a Y axis guide  113  which guides movement of the carriage  111  in the Y axis direction, a Y axis ball screw which is disposed along the Y axis guide  113 , a Y axis motor  114  which allows the Y axis ball screw  115  to positively and negatively rotate, and a carriage screw-coupling portion  112  which has a female screw portion formed under the carriage  111 , wherein the female screw portion is screw-coupled to the Y axis ball screw  115  and serves to move the carriage  111 . 
   The movement mechanism of the substrate mechanism section  103  is disposed in the X axis with almost the same structure as the head mechanism section  102 . That is, the substrate mechanism section  103  includes a platform  121  which is mounted with the substrate  120 , an X axis guide  123  which guides the movement of the platform  121 , an X axis ball screw  125  which is disposed along the X axis guide  123 , an X axis motor  124  which allows the X axis ball screw  125  to positively and negatively rotate, and a platform screw-coupling portion  122  which is screw-coupled to the X axis ball screw  125  under the platform  121  and serves to move the platform  121 . 
   The functional solution supply section  104  supplying the functional solution  133  to the head unit  110  includes a tube  131   a  forming a flow path communicating with the head unit  110 , a pump  132  feeding a liquid to the tube  131   a , a tube  131   b  (flow path) feeding the functional solution  133  to the pump  132 , and a tank  130  communicating with the tube  131   b  and storing the functional solution  133 . The functional solution supply section is disposed at one end on the surface table  107 . 
   In the above-mentioned structure, the head unit  110  can freely and relatively move in the Y axis direction with respect to the substrate  120  and can place the droplets jetted from the head unit  110  at any position on the substrate  120 . Then, by performing the position control and the jetting control in a unit of nozzles in the head unit  110  in synchronism with each other, it is possible to place (draw) the functional solution  133  in a predetermined pattern on the substrate  120 . 
   Although it has been shown in  FIG. 2  that the functional solution supply section  104  supplies a kind of functional solution to the head unit  110 , the functional solution supply section can substantially supply plural kinds of functional solutions at a time and the head unit  110  can jet the plural kinds of functional solutions at the same time. 
   (Method of Manufacturing Electron Emitter) 
   Next, a method of manufacturing an electron emitter will be described with reference to  FIG. 4  on the basis of a flowchart shown in  FIG. 3 .  FIG. 3  is a flowchart illustrating a method of manufacturing the electron emitter according to the first embodiment of the present invention.  FIGS. 4A to 4F  are schematic cross-sectional views illustrating one step of the method of manufacturing the electron emitter according to the first embodiment, respectively. 
   First, as shown in  FIG. 4A , a conductive functional solution  30  are arranged in a pattern on the element substrate  11  by the use of the droplet jetting apparatus  100  shown in  FIG. 2  (step S 1  of  FIG. 3  which constitutes a film forming process). Here, a solution in which conductive particulates are dispersed in a dispersion medium is used as the conductive functional solution  30 . 
   The conductive particulates are obtained by graining the above-mentioned material for the conductive film  12  into particulates and the surfaces thereof may be coated with an organic material for use in order to improve a dispersion property. Water, alcohols, hydrocarbon compounds, ether compounds, or the like can be used as the dispersion medium and the vapor pressure of the dispersion medium is preferably in the range of 0.1 Pa to 27 kPa, from the view point of a dry speed at the time of film formation or a storage stability when the functional solution is stored in the droplet jetting apparatus  100 . The surface tension of the conductive functional solution  30  is preferably in the range of 0.02 N/m to 0.07 N/m, from the view point of jetting stability, and may be adjusted by adding a surface active agent thereto. A resin for improving a fixing property after film formation or various additives for adjustment of viscosity and storage stability can be properly added to the conductive functional solution  30 . 
   As a pre-treatment before drawing, lyophilic and lyophobic surface treatments (for example, film formation using a plasma process or surface adsorbing molecules) may be performed or patterns may be partitioned by barrier walls referred to as banks, correspondingly to desired patterns. By performing such a pre-treatment, it is possible to place the conductive functional solution  30  in a desired pattern with higher accuracy. 
   After placing the conductive functional solution  30  in a desired pattern, as shown in  FIG. 4B , the dispersion medium of the conductive functional solution  30  is removed through a dry or baking process, thereby form the conductive film  12  (step S 2  of  FIG. 3  constituting the film forming process). At this time, the conductive film  12  is formed such that the film surface at the center portion  12   b  thereof is relatively flat and the film surface at the outer edge portion  12   a  thereof is raised to form an outer ring. As shown in  FIG. 4A , this is, it is considered, because the dry speeds at the center portion  30   b  and the outer edge portion  30   a  are different from each other due to the curved surface of the conductive functional solution  30  and thus non-uniformity in concentration of the conductive particulates are generated due to an internal convection. 
   In this way, since the conductive film  12  formed by the use of the droplet jetting method has a largely disturbed film surface specifically at the outer edge portion  12   a , it is preferable that such disturbance of the film surface is excluded through a shaping process described below. 
   The shaping process approximately includes a dummy functional film forming process and an etching process. 
   First, as shown in  FIG. 4C , a resist solution  32  is arranged in a pattern on the center portion  12   b  of the conductive film  12  by the use of the droplet jetting apparatus  100  shown in  FIG. 2  (step S 3  of  FIG. 3  which constitutes the dummy functional film forming process). Next, as shown in  FIG. 4D , a resist film  33  as a dummy functional film is formed by drying the resist solution  32  (step S 4  of  FIG. 3  which constitutes the dummy functional film forming process). The resist film  33  serves to mask the conductive film  12  and is also formed in other places on the element substrate  11  as needed (for example, when electrodes and the like are formed in advance). 
   Next, as shown in  FIG. 4E , an outer edge portion  12   a  of the conductive film  12  is etched by using the resist film  33  as a mask (step S 5  of  FIG. 3  which constitutes an etching process) and then as shown in  FIG. 4F , the resist film  33  is removed (step S 6  of  FIG. 3 ). The etching process is performed by the use of a wet etching method, a dry etching method, an electrolysis etching method, or the like. Since the resist film  33  serving as an etching mask is formed by the use of the droplet jetting method, the resist film can be easily formed by the use of the apparatus (droplet jetting apparatus  100  or dry apparatus) common to the film forming process (steps S 1  and S 2 ). 
   As described above, the conductive film  12  with a film surface excellent in flatness is formed on the element substrate  11  through the film forming process of steps S 1  and S 2  and the shaping process of steps S 3  to S 6 . 
   Finally, the element electrodes  14  and  15 , the signal lines  16  and  17 , and the interlayer insulating film  18  are formed in patterns (step S 7  of  FIG. 3 ) and the electron emission portion  13  is formed in the conductive film  12  through an electrification forming method (step S 8  of  FIG. 3  as an electron emission portion forming process), thereby completing the electron emitter  10  shown in  FIG. 1 . 
   In this way, the conductive film  12  according to the present embodiment is formed slightly larger than the completed conductive film and then the outer edge portion  12   a  having a disturbed film surface is removed. Accordingly, since the film surface of the conductive film  12  has excellent flatness, it is possible to provide an electron emitter  10  with small deviation in electron emission characteristic. 
   (Structure of Electro-optical Device) 
   Next, a structure of an electro-optical device will be described with reference to  FIG. 5 .  FIG. 5A  is a schematic cross-sectional view illustrating a structure of an important part of an electro-optical device and  FIG. 5B  is a schematic plan view illustrating a layout of electron emitters on an element substrate. 
   In  FIG. 5A , an electro-optical device  70  includes an element substrate  11  on which the electron emitters  10  are arranged and a display substrate  71  opposed to the element substrate  11 . The element substrate  11  and the display substrate  71  are apart by a constant distance from each other by external frame members not shown and the space  72  between both substrates  11  and  71  is sealed in vacuum with 10 −7  Torr. Here, in order to maintain the degree of vacuum, a gas adsorbing film not shown may be formed on the surface facing the space  72 . 
   As shown in  FIG. 5B , the element substrate  11  includes first signal lines  16  and second signal lines  17  which are arranged in a matrix shape, first element electrodes  14  and second element electrodes  15  which are formed along both signal lines  16  and  17 , and an arrangement in which the electron emitters  10  are arranged in a unit of pixels. The first signal lines  16  and the second signal lines  17  are electrically isolated from each other by an interlayer insulating film  18  made of an insulating material and are supplied with different signals, respectively. That is, the second signal lines  17  are supplied with a scan signal for driving the electron emitters  10  sequentially by one row (line in the X axis direction of the figure) and the first signal lines  16  are supplied with a gray-scale signal for controlling electron emission of the electron emitters  10  in the row selected by the scan signal, thereby controlling the electron emission in a unit of pixels. 
   In  FIG. 5A , the display substrate  71  includes a counter electrode  73 , a fluorescent film  74 , and a light-shielding film  75 . The light-shielding film  75  is formed corresponding to the arrangement of the electron emitters  10  so as to partition the pixels and serves to reduce crosstalk between the pixels or reflection of external light from the fluorescent film  74 . The light-shielding film may be made of a material having conductivity and light-shielding property such as graphite or the like. 
   The fluorescent film  74  contains fluorescent substances and serves to turn on the pixels by allowing the fluorescent substances to emit light by means of collision of the electrons emitted from the electron emitters  10  therewith. When the electro-optical device  70  is a color display type, the fluorescent film  74  is divided and formed into fluorescent substances corresponding to the three primary colors every pixel. 
   The counter electrode  73  is supplied with an acceleration voltage (for example, about 10 kV) and serves to accelerate the emitted electrons so as to give sufficient energy for exciting the fluorescent substances of the fluorescent film  74 . The counter electrode  73  may be made of a transparent conductive material such as ITO or the like. 
   In the above-mentioned structure, the scan signals supplied to the second signal lines  17  and the gray-scale signals supplied to the first signal lines  16  are controlled to emit the electrons from the electron emitters  10  and the emitted electrons accelerated by the counter electrode  73  collide with the fluorescent film  74  to turn on the pixels, thereby displaying a desired image. Since the electro-optical device  70  has the electron emitters  10  described above, the irradiation accuracy of the emitted electrons is excellent and it is thus possible to display an image with high accuracy. 
   (Electronic Apparatus) 
   Next, a specific example of an electronic apparatus will be described with reference to  FIG. 6 .  FIG. 6  is a schematic perspective view illustrating an example of an electronic apparatus. 
   A portable information processing apparatus  700  as an electronic apparatus shown in  FIG. 6  includes a keyboard  701 , an information processing apparatus body  703 , and an electro-optical device  702 . More specific examples of such a portable information processing apparatus  700  can include a word processor and a personal computer (PC). Since the portable information processing apparatus  700  includes the electro-optical device  72  having the electron emitters  10  described above, the irradiation accuracy of the emitted electrons is excellent and it is thus possible to display an image with high quality. 
   Other examples of the electronic apparatus including the electron emitters  10  can include a variety of apparatuses employing the electron emitters  10  as a coherent electron source, such as a coherent electron beam convergence apparatus, an electron beam holography apparatus, a monochromatic electron gun, an electron microscope, a multi coherent electron beam generating apparatus, an electron beam exposure apparatus, and a patterning apparatus of an electro-photograph printer. 
   Second Embodiment 
   Next, a second embodiment of the present invention will be described with reference to  FIGS. 8 and 9  on the basis of a flowchart shown in  FIG. 7 . Hereinafter, details equal to those of the above-mentioned embodiment are not described again but details different from those of the above-mentioned embodiment are mainly described. 
     FIG. 7  is a flowchart illustrating a method of manufacturing an electron emitter according to a second embodiment.  FIGS. 8A to 8E  and  FIGS. 9F to 9I  are schematic cross-sectional views illustrating one step of the method of manufacturing an electron emitter according to the second embodiment, respectively. 
   In the second embodiment, first, as shown in FIG.  8 A, a first conductive film  21  is formed in a pattern on the element substrate  11  by the use of the droplet jetting method (step S 11  of  FIG. 7  as a film forming process). Next, as shown in  FIG. 8B , an SiO 2  film  25  as a dummy functional film is formed in a pattern on the center portion  21   b  of the first conductive film  21  (step S 12  of  FIG. 7 ) and as shown in  FIG. 8C , the outer edge portion  21   a  of the first conductive film  21  is etched by using the SiO 2  film  25  as a mask (step S 13  of  FIG. 7 ), thereby shaping the first conductive film. 
   In this way, the material of the dummy functional film in the shaping process is not limited to the resist material, but any material may be used only if it can function as an etching mask in the etching process. 
   Next, the SiO 2  film  25  is once removed through the etching process with an HF solution or the like (step S 14  of  FIG. 7 ) and then as shown in  FIG. 8D , an SiO 2  film  26  is formed as a micro thin film with a thickness of about 1 nm to 50 nm to cover the whole surface of the first conductive film  21  (step S 15  of  FIG. 7 ). Then, as shown in  FIG. 8E , a second conductive film  22  is formed to overlap with the first conductive film  21  with the SiO 2  film  26  therebetween (step S 16  of  FIG. 7 ). 
   The SiO 2  film  26  formed here is not a functional film serving as a mask like the SiO 2  film  25  described above, but serves to form a narrow gap defined by the thickness of the SiO 2  film  26  between the conductive films  21  and  22 . 
   Next, as shown in  FIG. 9F , a SiO 2  film  27  as a dummy functional film is formed in a pattern on the second conductive film  22  (step S 17  of  FIG. 7 ) and a part of the outer edge portion  22   a  and the center portion  22   b  of the second conductive film  22  is etched by using the SiO 2  film  27  as a mask (step S 18  of  FIG. 7 ). In this way, as shown in  FIG. 9G , a structure that the new outer edge portion  21   c  of the first conductive film  21  and the new outer edge portion  22   c  of the second conductive film  22  are opposed to each other with the SiO 2  film  26  therebetween is obtained. Then, as shown in  FIG. 9H , by removing the SiO 2  film  26  and the SiO 2  film  27  (step S 19  of  FIG. 7 ), a narrow gap is formed at the portion corresponding to the opposed structure and serves as an electron emission portion  23 . Finally, as shown in  FIG. 9I , the electron electrodes  14  and  15  and the signal lines  16  and  17  are formed in patterns (step S 20  of  FIG. 7 ), thereby completing an electron emitter  20 . 
   In this way, the film forming process and the shaping process may be separately performed several times and the electron emission portion forming process, the film forming process, and the shaping process may be performed in an overlapping manner. 
   The present invention is not limited to the above-mentioned embodiments. For example, in the shaping process (steps S 3  to S 6  in  FIG. 3 ) of the first embodiment, the etching of the outer edge portion  12   a  of the conductive film  12  may be performed only to a part (for example, a portion where the electron emission portion  13  is formed) of the outer edge portion, not to the entire outer edge portion. 
   In the first embodiment, the electron emitter may be formed through the use of a forming process with electron beams or a local polishing process, instead of the electrification forming process. 
   In the first embodiment, the electron emission portion may be formed at the time after the film forming process and before the shaping process. 
   The elements of the respective embodiments may be combined or omitted properly, or may be combined with other elements not shown.