Patent Publication Number: US-2005127563-A1

Title: Method of manufacturing spacer assembly, filling method for spacer forming material, filling device for spacer forming material, molding tool, and vacuum vessel

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This is a Continuation Application of PCT Application No. PCT/JP03/08498, filed Jul. 3, 2003, which was published under PCT Article 21(2) in Japanese. 
    
    
      This application is based upon and claims the benefit of priority from prior Japanese Patent Applications No. 2002-215443, filed Jul. 24, 2002; No. 2002-352750, filed Dec. 4, 2002; and No. 2003-049051, filed Feb. 26, 2003, the entire contents of all of which are incorporated herein by reference.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      This invention relates to a method of manufacturing a spacer assembly used in an image display device such as a flat display device, a filling method for a spacer forming material used in the manufacture of the spacer assembly, a filling device for the spacer forming material, a molding tool, and a vacuum vessel.  
      2. Description of the Related Art  
      In recent years, various image flat display devices have been watched as a next generation of lightweight, thin display devices to replace cathode-ray tubes (hereinafter referred to as CRTs). For example, a surface-conduction electron emission display (hereinafter referred to as an SED) has been developed as a kind of a field emission display (hereinafter referred to as an FED) that functions as a flat display device.  
      The SED comprises a front substrate and a rear substrate that are opposed to each other with a given gap between them. These substrates have their respective peripheral portions joined together by means of a rectangular sidewall, thereby constituting a vacuum envelope. Phosphor layers of three colors are formed on the inner surface of the front substrate, and a large number of electron emitting elements corresponding to individual pixels are arranged on the inner surface of the rear substrate and serve as electron emitting sources that excite the phosphors to luminescence. Each electron emitting element is formed of an electron emitting portion (not shown), a pair of electrodes that apply voltage to the electron emitting portion, etc.  
      In the SED described above, it is important to keep the space between the front substrate and the rear substrate, that is, the interior of the vacuum envelope, at a high degree of vacuum. If the degree of vacuum is low, the life of the electron emitting elements, and therefore, the life of the device, will inevitably shorten. Since a vacuum is kept between the front substrate and the rear substrate, moreover, the atmospheric pressure acts on the front and rear substrates. In order to support the atmospheric pressure load that acts on these substrates and maintain the gap between the substrates, therefore, a large number of plate-like or columnar spacers are arranged between the two substrates.  
      In order to arrange the spacers over the whole surfaces of the front substrate and the rear substrate, very thin plate-like or columnar spacers are required lest they touch the phosphors on the front substrate and the electron emitting elements on the rear substrate. Since these spacers must inevitably be set very close to the electron emitting elements, moreover, an insulator material must be used for the spacers. At the same time, the reduction in thickness of the front substrate and the rear substrate requires an increased number of spacers, so that manufacture becomes more difficult.  
      The spacers may possibly be aligned with regions between the front substrate and the phosphors and between the rear substrate and the electron emitting elements by the following alternative methods. In one method, the spacers are attached directly to the regions between the phosphors or between the electron emitting elements. In the other method, a large number of spacers are formed with high positional accuracy on both surfaces of a metal plate previously formed having holes through which electrons pass, and the spacers on the metal plate are aligned with the front substrate or the rear substrate.  
      As an example of the latter method, a manufacturing method is described in Jpn. Pat. Appln. ROKAI Publication No. 2001-272926 or 2001-272927. According to this method, two molding tools in which a large number of holes corresponding individually to spacer shapes are adhered to the obverse and reverse surfaces of a metal plate, and through holes for spacer formation are defined by the metal plate and the two molding tools. In this state, a pasty photo-setting or thermosetting spacer forming material is filed into the through holes. After the filled spacer forming material is then cured optically or thermally in the dies, the two dies are removed from the metal plate, and moreover, the spacer forming material is vitrified. By doing this, the columnar spacers that are formed integrally on the metal plate are supposed to be obtained.  
      In the case where the spacer forming material is cured by the method described above, influences of heat can be removed to provide advantages in accuracy and manufacturing cost if it is irradiated with ultraviolet rays only. However, spacer forming holes in the molding tools are narrow and deep. If the molding tools used are formed of a metallic material, therefore, it is hard to allow sufficient ultraviolet rays for curing the spacer forming material to reach the depth of the molding tools. Thus, the spacer forming material used is a thermosetting material or a material that has a subsidiary thermosetting property as well as an ultraviolet-curing property.  
      When the spacer forming material is thermally cured, moreover, a difference in temperature distribution is caused between the grid and the molding tools by heating and cooling, so that dislocation occurs on an interface between the grid and the molding tools. This dislocation is liable to cause breakage of the spacers.  
      If the respective thermal expansion coefficients and temperatures of the materials of the grid and the molding tools are strictly controlled, quick heating and cooling are very difficult, so that it is hard to increase the productivity To cope with this, the molding tools may possibly be formed of a UV transmitting material. Since glass or resin is a general UV transmitting material, however, its mechanical stiffness and abrasion resistance are too low to be used for molding tools. Possibly, therefore, breakage of the molding tools, accuracy failure, and other problems may be caused.  
      In the manufacturing method described above, the spacer forming material can be filled relatively easily into the spacer forming holes of the molding tools if the spacer forming holes are through holes. If the spacer forming holes are through holes, however, the height accuracy of the finally formed spacers is not stable, owing to variation in the amount of fill. Since the thickness of the molding tools must be made equal to the spacer height, moreover, it is hard to improve the mechanical strength by thickening the molding tools. At the same time, the material used for the molding tools is subjected to restrictions.  
      If the spacer forming holes of the molding tools are bottomed holes having a fine shape, there is no way of escape for air in the holes, so that it is very hard to fill the spacer forming material. Possibly, the spacer forming holes may be evacuated in advance. This method is not very favorable, however, since a solvent mixed in the spacer forming material inevitably evaporates.  
      Unless the metal plate and the molding tools are fully intimately in contact with one another when the spacer forming material is filled into the molding tools, the spacer forming material unfavorably penetrates between the metal plate and the molding tools. In this case, spacers of normal shapes cannot be formed, and besides, beam apertures that are previously formed in the metal plate may possibly be blocked. Since overruns of the spacer forming material act as an adhesive, moreover, a problem arises that separation of the metal plate and the molding tools is very difficult.  
      Since the metal plate and the molding tools are in the form of a thin plate each, furthermore, it is hard for them to obtain satisfactory flatness for intimate contact in advance. In filling the spacer forming material into the molding tools, therefore, the molding tools and the grid must be held in a large number of positions, to be kept intimately in contact with one another. In this case, a large number of holding members must be provided, and they require high holding pressure and hence, use of a large, complicated manufacturing apparatus. If ultraviolet curing is selected as a spacer forming material curing process or the next stage, moreover, the holding members inevitably hinder ultraviolet irradiation.  
     BRIEF SUMMARY OF THE INVENTION  
      This invention has been made in consideration of these circumstances, and its object is to provide a method of manufacturing a spacer assembly capable of manufacturing spacers with high accuracy, a filling method for a spacer forming material used in the manufacture of the spacer assembly, a filling device for the spacer forming material, a molding tool, and a vacuum vessel.  
      In order to achieve the above object, according to an aspect of the invention, there is provided a method of manufacturing a spacer assembly, which comprises a plate-like grid having a plurality of beam apertures and a plurality of columnar spacers set up integrally on a surface of the grid and is used in an image display device, the method comprising: preparing the plate-like grid having a plurality of beam apertures; preparing a plate-like molding tool having a plurality of spacer forming holes and a plurality of hole forming portions situated individually around the spacer forming holes to define the spacer forming holes and formed of a UV transmitting material; contacting the molding tool to the surface of the grid, thereby forming an assembly composed of the molding tool and the grid; filling an ultraviolet-curing spacer forming material into the spacer forming holes of the molding tool before or after the formation of the assembly; applying ultraviolet rays to the filled spacer forming material directly or through the hole forming portions, thereby curing the spacer forming material; and separating the molding tool from the grid with the cured spacer forming material left on the grid.  
      According to another aspect of the invention, there is provided a method of manufacturing a spacer assembly, which comprises a plate-like grid having a plurality of beam apertures and a plurality of columnar spacers set up integrally on a surface of the grid and is used in an image display device, the method comprising: preparing the plate-like grid having the plurality of beam apertures; preparing a plate-like molding tool having a plurality of spacer forming holes and a plurality of hole forming portions situated individually around the spacer forming holes to define the spacer forming holes and formed of an elastic material; contacting the molding tool to the surface of the grid, thereby forming an assembly composed of the molding tool and the grid; filling a thermosetting spacer forming material into the spacer forming holes of the molding tool before or after the formation of the assembly; curing the filled spacer forming material in the assembly by heating; and separating the molding tool from the grid with the cured spacer forming material left on the grid.  
      According to another aspect of the invention, there is provided a molding tool used in the method of manufacturing a spacer assembly, the molding tool comprising: a plate-like die body; and a plurality of hole forming portions each formed of a UV transmitting material, defining the spacer forming holes, and provided integrally with the die body.  
      According to the method of manufacturing a spacer assembly and the molding tool arranged in this manner, the UV transmitting material is used for peripheral portions around the spacer forming holes, so that the spacer forming material that can be cured by ultraviolet rays only can be used. Further, a material with high mechanical strength, such as metal, can be used for the part other than the regions around the spacer forming holes, so that necessary mechanical strength for the molding tool can be fully secured. By using the elastic material for the peripheral portions around the respective opening portions of the spacer forming holes, moreover, breakage of the spacers attributable to dislocation between the grid and the molding tool can be prevented, and quick heating and cooling can be effected for thermal curing.  
      Thus, a spacer assembly manufacturing method and a molding tool can be obtained that can manufacture spacers with high accuracy without breaking the spacers. In the manufacture of the spacer assembly, moreover, the process for thermal curing may be omitted or time for the thermal curing process may be shortened to improve the productivity.  
      According to still another aspect of the invention, there is provided a filling method for a spacer forming material for filling the spacer forming material into a plurality of bottomed spacer forming holes of a molding tool which has a contact surface and the spacer forming holes opening in the contact surface, the filling method comprising: supplying a pasty spacer forming material to spacer forming hole portions of the molding tool; and rotating the molding tool supplied with the spacer forming material around a rotation axis situated off the molding tool so that air in the spacer forming holes is replaced with the spacer forming material by a centrifugal force, thereby filling the spacer forming holes with the spacer forming material.  
      According to another aspect of the invention, there is provided a method of manufacturing a spacer assembly, which comprises a plate-like member and a plurality of columnar spacers set up integrally on a surface of the plate-like member and is used in an image display device, the method comprising: preparing a molding tool having a contact surface and a plurality of bottomed spacer forming holes opening in the contact surface; supplying a pasty spacer forming material to spacer forming hole portions of the molding tool; rotating the molding tool supplied with the spacer forming material around a rotation axis situated off the molding tool so that air in the spacer forming holes is replaced with the spacer forming material by centrifugal force, thereby filling the spacer forming holes with the spacer forming material; holding the molding tool with the spacer forming holes filled with the spacer forming material in a manner such that the contact surface is intimately in contact with the surface of the plate-like member; and curing the spacer forming material with the molding tool and the plate-like member intimately in contact with each other, thereby forming a plurality of spacers on the surface of the plate-like member.  
      According to another aspect of the invention, there is provided a filling device for a spacer forming material, which fills the spacer forming material into a plurality of bottomed spacer forming holes of a molding tool which has a contact surface and the spacer forming holes opening in the contact surface, comprising: a rotor provided for rotation around a central axis; a rotating mechanism which rotates the rotor around the rotation axis; a support member which is provided on the roller and supports the molding tool so that the contact surface of the molding tool faces the rotation axis and that the molding tool is situated off the rotation axis.  
      According to the spacer forming material filling method, spacer assembly manufacturing method, and filling device arranged in this manner, the molding tool is rotated after the spacer forming material is attached to the outside of the spacer forming holes of the molding tool, and air in the spacer forming holes is replaced with the spacer forming material by a centrifugal force. By doing this, the fine spacer forming holes can be securely filled with the spacer forming material.  
      According to another aspect of the invention, there is provided a method of manufacturing a spacer assembly, which comprises a plate-like grid having a plurality of beam apertures and a plurality of columnar spacers set up on a surface of the grid and is used in an image display device, the method comprising: preparing the plate-like grid having the plurality of beam apertures; preparing a plate-like molding tool having a plurality of spacer forming holes situated in positions corresponding to regions between the beam apertures of the grid; filling a spacer forming material into the spacer forming holes of the molding tool; contacting the molding tool filled with the spacer forming material to the surface of the grid in a manner such that the spacer forming holes face the regions between the beam apertures of the grid, thereby forming an assembly composed of the molding tool and the grid; locating the assembly in an elastically deformable, flat vacuum vessel; and evacuating the vacuum vessel so that the molding tool and the grid are kept intimately in contact with each other under the atmospheric pressure.  
      According to another aspect of the invention, there is provided a vacuum vessel used in the method of manufacturing a spacer assembly, comprising: a first main wall and a second main wall each in the form of a plate arranged adjacent and opposite to the assembly, the first and second main walls being formed of an elastic material which can be elastically deformed along the assembly to adhere to the assembly when the vacuum vessel is evacuated.  
      According to the spacer assembly manufacturing method and the vacuum vessel arranged in this manner, the assembly is formed by adhering the molding tool to the surface of the grid, the assembly is located in the elastically deformable, flat vacuum vessel, and the vacuum vessel is evacuated. Then, the vacuum vessel is pressed against the assembly to be elastically deformed under the atmospheric pressure that acts on the vacuum vessel, whereby a pressure that brings the grid and the molding tool intimately into contact with each other is generated. Thus, the grid and the molding tool can be kept in an extremely intimate contact state, so that the spacer forming material that is filled in the molding tool can be securely prevented from leaking out between the molding tool and the grid. Further, it is unnecessary to arrange a large number of holding members and apply a high holding pressure to each holding member, so that manufacturing processes can be simplified, and the vacuum vessel can be miniaturized and simplified.  
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       FIG. 1  is a perspective view showing an SED provided with a spacer assembly according to an embodiment of this invention;  
       FIG. 2  is a perspective view of the SED, partially in section along line II-II of  FIG. 1 ;  
       FIG. 3  is a sectional view enlargedly showing the SED;  
       FIG. 4  is a perspective view showing the spacer assembly;  
       FIG. 5  is a sectional view showing a manufacturing process for the spacer assembly;  
       FIG. 6  is a sectional view enlargedly showing a part of the manufacturing process;  
       FIGS. 7A  to  7 E are sectional views showing manufacturing processes for a molding tool used in the manufacture of the spacer assembly;  
       FIG. 8  is a sectional view showing a process for applying ultraviolet rays to an assembly, out of the aforesaid spacer assembly manufacturing processes;  
       FIG. 9  is a sectional view showing a process for releasing the molding tool, out of the aforesaid spacer assembly manufacturing processes;  
       FIG. 10  is a sectional view showing an SED manufactured by a manufacturing method according to a second embodiment of this invention;  
       FIG. 11  is a sectional view showing a manufacturing process for a spacer assembly according to the second embodiment;  
       FIG. 12  is a perspective view showing a molding tool used in the manufacture of the spacer assembly;  
       FIG. 13  is an exploded perspective view showing a divided piece of the molding tool and a partition plate;  
       FIG. 14  is a perspective view showing the divided piece fitted with the partition plate;  
       FIG. 15  is a perspective view showing a filling device for filling a spacer forming material into the molding tool;  
       FIG. 16  is a sectional view taken along line XVI-XVI of  FIG. 15 ;  
       FIG. 17  is a sectional view corresponding to  FIG. 16  and showing the molding tool filled with the spacer forming material;  
       FIG. 18  is a sectional view showing a process for scraping off the spacer forming material with a squeegee;  
       FIG. 19  is a sectional view showing an assembly formed by adhering the molding tool and a grid to each other;  
      FIG,  20  is a sectional view showing a vacuum vessel and a manufacturing process for the spacer assembly;  
       FIG. 21  is a sectional view showing a released state of the molding tool; and  
       FIG. 22  is a perspective view showing a filling device according to a third embodiment of this invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      A manufacturing method for a spacer assembly and a molding tool according to embodiments of this invention will now be described in detail with reference to the drawings. First, an SED will be described as an example of an image display device provided with a spacer assembly that is manufactured by using the manufacturing method and the molding tool.  
      As shown in FIGS.  1  to  3 , the SED comprises a front substrate  10  and a rear substrate  12 , which are formed of a rectangular glass each. These substrates are opposed to each other with a gap of about 1.0 to 2.0 mm between them. The front substrate  10  and the rear substrate  12  have their respective peripheral edge portions joined together by a rectangular sidewall  14  of glass, and constitute a flat vacuum envelope  15  in which a vacuum is kept.  
      A phosphor screen  16  that serves as an image display surface is formed on the inner surface of the front substrate  10 . The phosphor screen  16  is formed by arranging phosphor layers R, G and  8  and a black light shielding layer  11 . These phosphor layers are in the form of stripes or dots. A metal back  17  of aluminum or the like is formed on the phosphor screen  16 .  
      A large number of surface-conduction electron emitting elements  18  are provided on the inner surface of the rear substrate  12 . They individually emit electron beams as electron sources that excite the phosphor layers of the phosphor screen  16 . These electron emitting elements  18  are arranged in a plurality of columns and a plurality of rows corresponding to individual pixels. Each electron emitting element  18  is formed of an electron emitting portion (not shown), a pair of element electrodes that apply voltage to the electron emitting portion, etc. A large number of wires  21  that supply potential to the electron emitting elements  18  are formed in a matrix on the inner surface of the rear substrate  12 , and their respective end portions are drawn oat of the vacuum envelope  15 .  
      The sidewall  14  that serves as a joining member is sealed to the respective peripheral edge portions of the front substrate  10  and the rear substrate  12  with a sealant  20  of, for example, low-melting glass or low-melting metal, and joins these substrates together.  
      As shown in FIGS.  2  to  4 , the SED comprises a spacer assembly  22  that is located between the front substrate  10  and the rear substrate  12 . In the present embodiment, the spacer assembly  22  is composed of a grid  24  in the form of a rectangular metal plate and a large number of columnar spacers that are set up integrally on the opposite sides of the grid.  
      More specifically, the grid  24  has a first surface  24   a  opposed to the inner surface of the front substrate  10  and a second surface  24   b  opposed to the inner surface of the rear substrate  12 , and is located extending parallel to these substrates. A large number of electron beam apertures  26  and a plurality of spacer openings  28  are formed in the grid  24  by etching or the like, The electron beam apertures  26  are arranged opposite the electron emitting elements  18 , individually, and transmit the electron beams emitted from the electron emitting elements. The spacer openings  28  are situated individually between the electron beam apertures  26  and arranged at a given pitch. Each spacer opening  28  is in the form of a circle having a diameter of about 0.2 to 0.5 mm, for example.  
      The grid  24  is formed of a plate of iron-nickel metal with a thickness of 0.1 to 0.25 mm, for example. An oxide film of the elements that constitutes the metal plate, e.g., Fe 3 O 4  and NiFe 3 O 4 , is formed on the surface of the grid.  
      First spacers  30   a  are set up integrally on the first surface  24   a  of the grid  24  so as to overlap the spacer openings  28 , individually. Their respective extended ends abut against the inner surface of the front substrate  10  with the interposition of the metal back  17  and the light shielding layer  11  of the phosphor screen  16 . Second spacers  30   b  are set up integrally on the second surface  24   b  of the grid  24  so as to overlap the spacer openings  28 , individually. Their respective extended ends abut against the inner surface of the rear substrate  12 . The extended ends of the second spacers  30   b  are situated individually on the wires  21  that are arranged on the inner surface of the rear substrate  12 .  
      Each of the first and second spacers  30   a  and  30   b  is tapered so that its diameter is reduced from the side of the grid  24  toward its extended end. For example, the diameter of the proximal end of each first spacer  30   a  that is situated on the side of the grid  24  is about 0.4 mm, the diameter of its extended end is about 0.3 mm, and its height is about 0.6 mm. Further, the diameter of the proximal end of each second spacer  30   b  that is situated on the side of the grid  24  is about 0.4 mm, the diameter of its extended end is about 0.25 mm, and its height is about 0.8 mm. Thus, both the diameters of the respective proximal ends of the first and second spacers  30   a  are set to be greater than the diameter of each spacer opening  28 .  
      The first and second spacers  30   a  and  30   b  are arranged individually at given spaces so as to cover the whole area of each surface of the grid  24 . The spacer openings  28  and the first and second spacers  30   a  and  30   b  are situated in alignment with one another, and the first and second spacers are coupled integrally to one another through the spacer openings  28 . Thus, the first and second spacers  30   a  and  30   b  are formed integrally with the grid  24  so as to hold the grid  24  between them from both sides.  
      The spacer assembly  22  constructed in this manner is located between the front substrate  10  and the rear substrate  12 . The first and second spacers  30   a  and  30   b  abut against the respective inner surfaces of the front substrate  10  and the rear substrate  12 , thereby supporting the atmospheric load that acts on these substrates and keeping the distance between the substrates at a given value.  
      The SED is provided with a voltage supply unit (not shown) that applies voltages to the grid  24  and the metal back  17  of the front substrate  10 . For example, voltages of 12 kV and 10 kV are applied to the grid  24  and the metal back  17 , respectively.  
      In displaying an image on the SED described above, the electron emitting elements  18  are actuated through the wires  21  so that electron beams are emitted from any of the electron emitting elements, and an anode voltage is applied to the phosphor screen  16  and the metal back  17 . The electron beams emitted from the electron emitting elements  18  are accelerated by the anode voltage. After passing through the electron beam apertures  26  of the grid  24 , they hit the phosphor screen  16 . Thereupon, the phosphor layers of the phosphor screen  16  are excited to glow, and the image is displayed.  
      The following is a description of a manufacturing method for the SED constructed in this manner. The molding tool and a manufacturing method for manufacturing the spacer assembly  22  will be described first.  
      As shown in  FIGS. 5 and 6 , the grid  24  of a given size and upper and lower dies  36   a  and  36   b , each in the form of a rectangular plate having substantially the same size as the grid, are prepared first. After a metal plate of Fe-50% Ni with a thickness of 0.12 nun is degreased, washed, and dried, the electron beam apertures  26  and the spacer openings  28  are formed by etching to prepare the grid  24 . After the whole grid  24  is oxidation-treated, thereafter, an insulating film is formed on the grid surface including the respective inner surfaces of the electron beam apertures  26  and the spacer openings  28 .  
      The upper die  36   a  has a large number of spacer forming holes  40   a  for molding the first spacers  30   a . These spacer forming holes  40   a  are arranged corresponding individually to the spacer openings  28  of the grid  24 . The lower die  36   b  has a large number of spacer forming holes  40   b  for molding the second spacers  30   b . These spacer forming holes  40   b  are arranged corresponding individually to the spacer openings  28  of the grid  24 .  
      The following is a detailed description of the respective configurations of the upper die  36   a  and the lower die  36   b  and a manufacturing method therefor, taking the upper die  36   a  as a representative.  
      As shown in  FIG. 6 , the upper die  36   a  for use as a molding tool is provided with a die body  52   a  that is formed of a rectangular plate of stainless steel or polyethylene terephthalate. The die body  52   a  is formed having a large number of through holes  54   a  corresponding individually to the spacer openings  28  of the grid  24 . Each through hole  54   a  has a diameter larger than that of each spacer forming hole. Each through hole  54   a  has therein a hole forming portion  56   a  of, for example, silicone, which serves both as a UV transmitting material and as an elastic material. This hole forming portion  56   a  is formed having the spacer forming hole  40   a  of the shape corresponding to each first spacer  30   a . Thus, the spacer forming hole  40   a  is surrounded by silicone.  
      In manufacturing the upper die  36   a , a master female die  60  that is formed having a large number of spacer forming holes with high accuracy is prepared first, as shown in  FIG. 7A . The master female die  60  is formed by laminating a plurality of metal plates, e.g., three in number, to one another. Through holes that constitute the spacer forming holes are formed in each metal plate with high accuracy by laser etching or the like. Subsequently, a spacer forming material such as silicone is filled into the master female die  60  through the large-diameter side of the spacer forming holes to form a master male die  62  that has a large number of protrusions  63  corresponding to the spacer forming holes, individually, as shown in  FIGS. 7A and 7B .  
      Then, the die body  52   a  that is formed having the large number of through holes  54   a  is prepared, as shown in  FIG. 7C . The master male die  62  is attached to the die body  52   a  and aligned with it so that the protrusions  63  of the master male die are arranged substantially coaxially with the through holes  54   a , individually, of the die body.  
      In this state, silicone is filled into the individual through holes  54   a  of the die body  52   a , as shown in  FIG. 7D . After the silicone is cured, the master male die  62  is released. Thereupon, the upper die  36   a  can be obtained integrally having the hole forming portions  56   a  that define the spacer forming holes  40   a , as shown in  FIG. 7E .  
      The lower die  36   b , which is constructed in the same manner as the upper die  36   a , is also provided with a die body  52   b  that is formed having a large number of through holes  54   b , hole forming portions  56   b  that are formed of silicone and located individually in the through holes, and spacer forming holes  40   b  formed in the hole forming portions, individually. The lower die  36   b  is manufactured in the same manner as aforesaid.  
      In manufacturing the spacer assembly  22  by using the upper die  36   a  and the lower die  36   b  fabricated in the aforesaid manner, the upper die  36   a  is positioned so that the spacer forming holes  40   a  are aligned individually with the spacer openings  28  of the grid  24 , and is adhered to the first surface  24   a  of the grid, as shown in  FIGS. 5 and 6 . Likewise, the lower die  36   b  is positioned so that the spacer forming holes  40   b  are aligned individually with the spacer openings  28  of the grid  24 , and is adhered to the second surface  24   b  of the grid. The upper die  36   a , grid  24 , and lower die  36   b  are kept intimately in contact with one another by a clamp mechanism (not shown) or the like. Thus, an assembly  42  is constructed consisting of the grid  24 , upper die  36   a , and lower die  36   b . This assembly is formed having a large number of through holes  44 , each of which is composed of the spacer forming hole  40   a , spacer opening  28 , and spacer forming hole  40   b.    
      Subsequently, the assembly  42  is kept substantially level with the lower die  36   b  situated below, and is set so that the respective central axes of the through holes  44  extend in a substantially vertical direction. In this state, a pasty spacer forming material  46  is supplied from the obverse side of the lower die  36   b  or from the underside of the assembly  42  by using a filling head, for example. The spacer forming material is filled into the through holes  44  from bottom to top under a fixed pressure.  
      A glass paste that contains at least an ultraviolet-curing binder (organic component) and a glass filler is used as the spacer forming material  46 . The viscosity of the spacer forming material  46  is adjusted to, for example, 6,000 cP to 20,000 cP. As filling conditions, the filling rate and filling pressure of the spacer forming material  46  are set at 10 mm/s to 200 mm/s and 0.1 MPa, respectively.  
      As the spacer forming material  46  is filled into the through holes  44 , a surplus of the spacer forming material runs out onto the topside of the assembly  42 , that is, the topside of the upper die  36   a , through the through holes  44 . Therefore, the upper surface of the assembly  42  is scraped with a squeegee to remove a bulging portion  47  of the spacer forming material  46 .  
      Subsequently, as shown in  FIG. 8 , ultraviolet (UV) rays are applied to the filled spacer forming material  46  from the outer surface side of the upper die  36   a  and the lower die  36   b , for example, whereby the spacer forming material is UV-cured. When this is done, regions around the spacer forming holes  40   a  and  40   b  that are filled with the spacer forming material  46  are surrounded by the hole forming portions  56   a  and  56   b  that are formed of silicone as a UV transmitting material. Accordingly, ultraviolet rays are applied to the spacer forming material  46  directly and through the hole forming portions  56   a  and  56   b . Thus, the filled spacer forming material  46  can be securely cured to its inner part.  
      Thereafter, the upper die  36   a  and the lower die  36   b  are separated from the grid  24  in a manner such that the cured spacer forming material  46  remains on the grid  24 , as shown in  FIG. 9 . Then, the grid  24  that is filled with the spacer forming material  46  is heat-treated in a heating furnace, whereby the binder is removed from the spacer forming material. Thereafter, the spacer forming material is regularly fired at about 500 to 550° C. for 30 minutes to one hour. Thereupon, the spacer assembly  22  is obtained having the first and second built-in spacers  30   a  and  30   b  on the grid  24 .  
      In manufacturing the SED, the front substrate  10 , which is provided with the frame  16  and the metal back  17 , and the rear substrate  12 , which is provided with the electron emitting elements  18  and the wires  21  and joined to the sidewall  14 , are prepared in advance.  
      Subsequently, the spacer assembly  22  obtained in this manner is positioned on the rear substrate  12 . In this state, the front substrate  10 , rear substrate  12 , and spacer assembly  22  are located in a vacuum chamber. After the vacuum chamber is evacuated, the front substrate is joined to the rear substrate by means of the sidewall  14 . Thus, the SED provided with the spacer assembly  22  is manufactured.  
      According to the molding tool and the manufacturing method for the spacer assembly constructed in this manner, the regions around the spacer forming holes  40   a  and  40   b  are surrounded by the hole forming portions  56   a  and  56   b  that are formed of silicone as a UV transmitting material. In curing the spacer forming material, therefore, the applied ultraviolet rays are transmitted through the hole forming portions  56   a  and  56   b , and reach a deep part of the spacer forming material  46 , whereby the filled spacer forming material  46  can be securely cured to its inner part. Thus, the spacers can be formed into a desired shape, and the spacers having satisfactory strength can be obtained.  
      The spacer forming material can be cured with ultraviolet irradiation only, without utilizing heat curing. In curing the spacer forming material, therefore, production of a difference in temperature distribution between the grid and the molding tool, dislocation between the grid and a molding tool interface, etc., by heating and cooling can be prevented. Thus, the spacer assembly can be manufactured with high accuracy without breaking the spacers, and the manufacturing cost can be lowered. At the same time, the respective thermal expansion coefficients and temperatures of a grid material and a molding tool material need not be strictly controlled, so that the efficiency of production of the spacer assembly can be improved.  
      On the other hand, a method may be proposed in which the upper die  36   a  and the lower die  36   b  are manufactured using resin, glass, etc. In consideration of the manufacturing cost, however, there is the premise that the upper and lower dies can be used repeatedly, so that their mechanical strength is naturally expected to be high.  
      The vacuum envelope of the SED is constructed so that the first and second spacers  30   a  and  30   b  support the atmospheric pressure, and therefore, the accuracy of the respective heights of these spacers is essential. Accordingly, abrasion of the surfaces of the upper die  36   a  and the lower die  36   b , which results in lowering of the spacer height accuracy, must be restricted. Thus, it is hard to form the upper die  36   a  and the lower die  36   b  entirely from resin or glass.  
      According to the embodiment described above, on the other hand, only minimum ranges of the molding tool around the spacer forming holes are formed of the UV transmitting material, and metal or other material that has high mechanical strength can be used for most of other parts. Thus, the mechanical rigidity and abrasion resistance can be improved considerably.  
      Although the ultraviolet-curing material is used as the spacer forming material according to the embodiment described above, a thermosetting spacer forming material may be used instead. Thus, a glass paste that contains a thermosetting binder and a glass filler may be used as the spacer forming material  46 .  
      In this case, the assembly  42  is formed by using the same grid  24 , upper die  36   a , and lower die  36   b  according to the foregoing embodiment, and the spacer forming material  46  is filled into the through holes  44 . After the assembly  42  is then heated to thermally cure the spacer forming material, the upper die  36   a  and the lower die  36   b  are separated from the grid  24 .  
      Then, the grid  24  that is filled with the spacer forming material  46  is heat-treated in the heating furnace, whereby the binder is removed from the spacer forming material. Thereafter, the spacer forming material is regularly fired at about 500 to 550° C. for 30 minutes to one hour. Thereupon, the spacer assembly  22  is obtained having the first and second built-in spacers  30   a  and  30   b  on the grid  24 .  
      In thermally curing the spacer forming material  46 , in the case of this system, a surface-direction dislocation is liable to be caused on an interface between the grid surface and the upper die and lower surfaces, owing to differences in temperature distribution and thermal expansion coefficient between the grid  24 , upper die  36   a , and lower die  36   b . According to the present embodiment, however, the hole forming portions  56   a  and  56   b  that are arranged around the spacer forming holes  40   a  and  40   b  in the upper die  36   a  and the lower die  36   b  are formed of silicone for use as an elastic material. If a surface-direction dislocation is caused between the grid and the molding tool, therefore, a load that acts on the thermally cured spacer forming material  46  can be absorbed by elastic deformation of the hole forming portions  56   a  and  56   b . Thus, breakage of the spacers that is attributable to the aforesaid dislocation can be prevented. In consequence, the spacer forming material that is thermally cured can be quickly heated and cooled, so that the manufacturing efficiency can be improved.  
      In the embodiment described above, the spacer forming material is filled into the spacer forming holes of the molding tool after the assembly is formed by adhering the molding tool to the grid. Alternatively, however, the assembly may be formed by adhering the molding tool to the grid after filling the spacer forming material into the spacer forming holes of the molding tool.  
      The diameter and height of the spacers and the dimensions and materials of the other components are not limited to those of the foregoing embodiment, and may be suitably selected as required. Likewise, the spacer forming material and the filling conditions may be variously selected as required. The UV transmitting material that is used for the hole forming portions of the molding tool is not limited to silicone, and may alternatively be polycarbonate, acrylic resin, etc.  
      In the spacer assembly, the grid may be constructed having no spacer openings. Further, the first and second spacers need not be located coaxially with one another, and may be deviated in position from one another in the surface direction of the grid. In the spacer assembly, moreover, the spacers may be provided only on one surface of the grid. In this case, the molding tool should be used only for one side of the grid, and the assembly is formed by adhering the molding tool to the grid.  
      The following is a description of a manufacturing method and a manufacturing apparatus for a spacer assembly according to a second embodiment of this invention. An SED provided with a spacer assembly that is manufactured by using the present manufacturing method is constructed in the same manner as the foregoing embodiment. As shown in  FIG. 10 , however, a grid  24  of a spacer assembly  22  has no spacer openings, and first and second spacers  30   a  and  30   b  are set up integrally on a surface of the grid between electron beam apertures  26 . This embodiment shares other configurations of the SED with the foregoing embodiment, so that like reference numerals are used to designate like portions, and a detailed embodiment of those portions is omitted.  
      In the manufacturing method according to the second embodiment, as shown in  FIG. 11 , the grid  24  of a given size and upper and lower dies  36   a  and  36   b , each in the form of a rectangular plate having substantially the same size as the grid, are prepared first. After a metal plate of Fe-50% Ni with a thickness of 0.12 mm is degreased, washed, and dried, in this case, the electron beam apertures  26  are formed by etching to prepare the grid  24 . After the whole grid  24  is oxidation-treated, an insulating film containing glass or the like is formed on the grid surface including the respective inner surfaces of the electron beam apertures  26 .  
      As shown in  FIGS. 11 and 12 , the upper die  36   a  and the lower die  36   b  that serve as a molding tool are each formed as a flat plate of a transparent material, such as transparent silicone or transparent polyethylene terephthalate, which transmits ultraviolet rays, The upper die  36   a  has a flat contact surface  41   a  that engages the grid  24  and a large number of bottomed spacer forming holes  40   a  for molding the first spacers  30   a . The spacer forming holes  40   a  separately open in the contact surface  41   a  and are arranged at given spaces.  
      In the present embodiment, the upper die  36   a  is composed of, for example, four divided pieces  37   a  that are divided in the longitudinal direction, and these divided pieces are formed so that they can be separated from and joined to one another. Each divided piece  37   a  is in the form of an elongated rectangular plate, and the spacer forming holes  40   a  form a plurality of columns that extend individually in the longitudinal direction of the divided pieces  37   a.    
      The lower die  36   b  has a flat contact surface  41   b  and a large number of bottomed spacer forming holes  40   b  for molding the second spacers  30   b . The spacer forming holes  40   b  separately open in the contact surface  41   b  and are arranged at given spaces. The lower die  36   b  is formed by connecting four divided pieces (not shown).  
      Subsequently, as shown in  FIGS. 7 and 8 , a partition plate  70  is prepared having the form of an elongated rectangular plate that is substantially equal in size to each of the divided pieces  37   a  of the upper die  36   a  and the lower die  36   b . The partition plate  70  is formed having a plurality of slits  72 , which individually extend in the longitudinal direction of the partition plate. Each slit  72  has a width a little greater than the bore diameter of each spacer forming hole  40   a  in each divided piece  37   a . The pitch of the slits  72  in the width direction of the divided pieces  37   a  is substantially the same as the pitch of the spacer forming holes in the width direction of the divided pieces.  
      The partition plate  70  is placed on the contact surface  41   a  of the divided piece  37   a  and adhered to the contact surface. In doing this, the partition plate  70  is positioned and set so that the slits  72  of the partition plate  70  face the spacer forming holes  40   a  of the divided piece  37   a . Thereupon, partition walls that are defined by the partition plate  70  are arranged on the opposite sides of each spacer forming hole  40   a  in the width direction of the divided piece  37   a . The partition plate  70  is set in like manner for each divided piece of the lower die  36   b.    
      As shown in  FIGS. 15 and 16 , the spacer forming material  46  is filled into the slits  72  of the partition plate  70  that is attached to the divided piece  37   a , and fed to regions near the respective opening portions of the spacer forming holes  40   a . A glass paste that contains at least an ultraviolet-curing binder (organic component) and a glass filler is used as the spacer forming material  46 . The specific gravity and viscosity of the glass paste are suitably selected.  
      Then, a plurality of sets, e.g., two sets, of divided pieces  37   a  and partition plates  70  that are supplied with the spacer forming material  46  are prepared and set on a filling device  80 . The filling device  80  comprises a rotor  82  and a rotating mechanism  84 . The rotor  82  is in the form of a rectangular plate that extends substantially horizontally. The rotating mechanism  84  supports the central part of the rotor with respect to the longitudinal direction and rotates the rotor around a rotation axis D that extends vertically. Plate-like support brackets  86  that serve as support members are fixed individually to the longitudinally opposite end portions of the rotor  82 . The support brackets  86  individually extend vertically and face to each other in a parallel relationship with the rotation axis D between them. The distance between each support bracket  86  and the rotation axis D is set to about 500 mm, for example. The inner surface of each support bracket  86  forms a flat support surface  86   a  that serves as a support portion.  
      The two sets of divided pieces  37   a  and partition plates  70  are mounted individually on the support brackets  86  by using a damper (not shown) or the like so that the back side of the divided pieces is intimately in contact with the support surfaces  86   a  of the support brackets  86 . Thereupon, the contact surface  41   a  of each divided piece  37   a  and the partition plate  70  extend parallel to the rotation axis D and face the rotation axis side. Further, the divided piece  37   a  and the partition plate  70  are attached to the support bracket  86  so that the slits  72  of the partition plate  70  are situated parallel to the rotation axis D. Thus, the contact surface  41   a  of the divided piece  37   a  extends in a direction tangent to a circle around the rotation axis D, as is well seen from  FIG. 16 . At the same time, the partition walls that are defined on the contact surface  41   a  by the partition plate  70  are arranged with gaps in the aforesaid tangential direction and situated on the opposite sides of the spacer forming holes  40   a.    
      Subsequently, the rotor  82  is rotated at a given rotational speed of, e.g., 700 to 800 rpm for about one to five minutes by the rotating mechanism  84 . Thereupon, centrifugal force is produced in the spacer forming material  46 , as shown in  FIGS. 16 and 17 . At the same time, this centrifugal force generates a defoaming action that forces out air in the spacer forming holes  40   a  that are formed in the divided pieces  37   a . Thus, air in the spacer forming holes  40   a  is replaced with the spacer forming material  46 , so that the spacer forming holes  40   a  are filled with the spacer forming material  46 .  
      As shown in  FIG. 16 , moreover, each divided piece  37   a  of the molding tool is in the form of a flat plate. While it is rotating, therefore, the spacer forming material  46  that is fed to regions near other spacer forming holes than the spacer forming hole  40   a  situated in the direction normal to the rotation axis D is subjected to forces not in the normal direction, that is, forces in directions such that the material flows out from the divided piece  37   a . In the present embodiment, however, the partition walls are defined on the opposite sides of each spacer forming hole  40   a  by the partition plate  70  so that the spacer forming material  46  can be restrained from flowing out as the divided piece  37   a  is rotated. With use of centrifugal force, furthermore, air components having previously been trapped in the spacer forming material  46  can be removed, so that the spacer forming holes  40   a  of the divided piece  37   a  can be filled with the spacer forming material that involves no air bubbles.  
      In the processes described above, the spacer forming material  46  is filled at a time into the spacer forming holes  40   a  of the two divided pieces  37   a . After the filling, the divided pieces  37   a  are disengaged from the support brackets  86  of the filling device  80 , and moreover, the partition plates  70  are removed from the divided pieces. As shown in  FIG. 82 , thereafter, the contact surface  41   a  of each divided piece  37   a  is rubbed with a squeegee to scrape off a surplus of the spacer forming material  46  that overflows the spacer forming holes  40   a.    
      After the spacer forming holes  40   a  of the four divided pieces  37   a  are filled with the spacer forming material  46  by repeating the same processes as aforesaid, the divided pieces are joined together to form the one upper die  36   a . In the same processes as aforesaid, the lower die  36   b  is prepared in which the spacer forming holes  40   b  are filled with the spacer forming material  46 .  
      Subsequently, as shown in  FIG. 19 , the upper die  36   a  and the lower die  36   b  that are filled with the spacer forming material  46  are adhered to the grid  24  to form the assembly  42 . In this case, the upper die  36   a  is positioned so that the spacer forming holes  40   a  are situated between the electron beam apertures  26  of the grid  24 , and the contact surface  41   a  is adhered to the first surface  24   a  of the grid  24 . Likewise, the lower die  36   b  is positioned so that the spacer forming holes  40   b  are situated between the electron beam apertures  26 , and the contact surface  41   b  is adhered to the second surface  24   b  of the grid  24 . In this manner, the assembly  42  is formed consisting of the grid  24 , upper die  36   a , and lower die  36   b . In the assembly  42 , the spacer forming holes  40   a  of the upper die  36   a  and the spacer forming holes  40   b  of the lower die  36   b  are arranged opposite one another with the grid  24  between them.  
      As shown in  FIG. 20 , thereafter, the assembly  42  is placed in a flat vacuum vessel  50 , and the upper die  36   a  and the lower die  36   b  are adhered to the grid  24  by utilizing the atmospheric pressure. The vacuum vessel  50  will now be described in detail.  
      The vacuum vessel  50  has a first main wall  52  and a second main wall  54  in the form of a rectangular plate each. The first and second main walls are arranged opposite each other with a gap between them. A sidewall  55  in the form of a rectangular frame is provided between the respective peripheral edge portions of the first and second main walls  52  and  54 . The sidewall  55  is airtightly fixed to the peripheral edge portion of the inner surface of the first main wall  52 , and is set substantially upright on the first main wall. A free end of the sidewall  55 , its upper end in this case, airtightly engages the peripheral edge portion of the inner surface of the second main wall  54  with the aid of an O-ring  56 . The interior of the vacuum vessel  50  is connected to a vacuum pump  58  through an exhaust valve  57  that is attached to the peripheral edge portion of the second main wall  54 .  
      The first and second main walls  52  and  54  are formed having a plane size larger than that of the grid  24 . Further, the first and second main walls  52  and  54  are formed of transparent silicone, transparent polyethylene terephthalate, glass, or other material that is elastically deformable and can transmit ultraviolet rays. As mentioned later, indentations are formed substantially covering the whole inner surfaces of the first and second main walls  52  and  54  so that the entire assembly  42  can be pressurized uniformly.  
      In holding the assembly  42  by means of the vacuum vessel  50  constructed in this manner, a pressure diffuser plate  60   a  is laid on the inner surface of the first main wall  52  with the second main wall  54  off, The assembly  42  is placed on the pressure diffuser plate  60   a , and the lower die  36   b  is opposed to the first main wall  52 , for example.  
      Then, a pressure diffuser plate  60   b  is placed on the assembly  42 , and the second main wall  54  is further located overlapping them and opposed to the upper die  36   a  of the assembly  42  so that its peripheral edge portion overlaps the O-ring  56 , The pressure diffuser plates  60   a  and  60   b  are formed of a UV transmitting material.  
      After the vacuum pump  58  for use as exhaust means is actuated to exhaust the interior of the vacuum vessel  50  to a given degree of vacuum in this state, the exhaust valve  57  is closed to maintain a vacuum in the vacuum vessel. If the vacuum vessel  50  is evacuated, the atmospheric pressure acts on the first and second main walls  52  and  54  of the vacuum vessel. Thus, the first and second main walls  52  and  54  press from both sides the assembly  42  that is located inside them, thereby adhering the upper die  36   a  and the lower die  36   b  to the grid  24 .  
      Since the first and second main walls  52  and  54  of the vacuum vessel  50  are formed of an elastically deformable material, as mentioned before, they are elastically deformed along the assembly  42  and adhere to the upper die  36   a  and the lower die  36   b . The respective inner surfaces of the first and second main walls  52  and  54  are ragged. Therefore, the atmospheric pressure evenly acts on the whole surfaces of the upper die  36   a  and the lower die  36   b  through the pressure diffuser plates  60   a  and  60   b , respectively. Thus, the grid  24 , upper die  36   a , and lower die  36   b  can be kept in a very good intimate contact state.  
      With the grid  24 , upper die  36   a , and lower die  36   b  kept intimately in contact with one another by utilizing the atmospheric pressure in the aforesaid manner, ultraviolet rays (UV) from ultraviolet lamps  62   a  and  62   b  outside the vacuum vessel  50  are applied toward the first and second main walls  52  and  54 , The first and second main walls  52  and  54  of the vacuum vessel  50 , pressure diffuser plates  60   a  and  60   b , upper die  36   a , and lower die  36   b  are formed of a UV transmitting material each. Therefore, the ultraviolet rays emitted from the ultraviolet lamps  62   a  and  62   b  are transmitted through the first and second main walls  52  and  54  of the vacuum vessel  50 , pressure diffuser plates  60   a  and  60   b , upper die  36   a , and lower die  36   b  are applied to the filled spacer forming material  46 . Thus, the spacer forming material  46  can be UV-cured with the assembly  42  kept in a very good intimate contact state.  
      Subsequently, the vacuum in the vacuum vessel  50  is removed, and the assembly  42  is taken out of the vacuum vessel. Since the second main wall  54  is only in contact with the O-ring  56  as this is done, the vacuum vessel can be easily opened by removing the vacuum. Thereafter, the upper die  36   a  and the lower die  36   b  are separated from the grid  24  in a manner such that the cured spacer forming material  46  remains on the grid  24 , as shown in  FIG. 21 . Then, the grid  24  that is provided with the spacer forming material  46  is heat-treated in the heating furnace, whereby the binder is removed from the spacer forming material. Thereafter, the spacer forming material is regularly fired at about 500 to 550° C. for 30 minutes to one hour. Thereupon, the spacer assembly  22  is obtained having the first and second built-in spacers  30   a  and  30   b  on the grid  24 .  
      In manufacturing the SED, on the other hand, a front substrate  10 , which is provided with a frame  16  and a metal back  17 , and a rear substrate  12 , which is provided with electron emitting elements  18  and wires  21  and joined to a sidewall  14 , are prepared in advance.  
      Subsequently, the spacer assembly  22  obtained in this manner is positioned on the rear substrate  12 . In this state, the front substrate  10 , rear substrate  12 , and spacer assembly  22  are located in the vacuum chamber. After the vacuum chamber is evacuated, the front substrate is joined to the rear substrate by means of the sidewall  14 . Thus, the SED provided with the spacer assembly  22  is manufactured.  
      According to the filling device, the vacuum vessel and the manufacturing method for the spacer assembly constructed in this manner, the molding tool is rotated after the spacer forming material is stuck to the outside of the spacer forming holes of the molding tool, and air in the spacer forming holes is replaced with the spacer forming material by utilizing centrifugal force. By doing this, the spacer forming material can be securely filled into the fine spacer forming holes. Thus, spacers having a desired shape and desired height can be formed with high accuracy. With use of centrifugal force, moreover, air components trapped in the spacer forming material daring filling operation can be removed, so that the high-quality spacers can be formed without involving any air bubbles.  
      Further, the upper and lower dies  36   a  and  36   b  are adhered individually to the opposite surfaces of the grid  24  to form the assembly  42 , this assembly is located in the elastically deformable, flat vacuum vessel  50 , and the vacuum vessel is evacuated. Then, the first and second main walls  52  and  54  of the vacuum vessel  50  are pressed against the assembly  42  to be elastically deformed by the atmospheric pressure that acts on the vacuum vessel, whereby a pressure is generated that causes the grid  24  and the upper and lower dies  36   a  and  36   b  to adhere to one another. Thus, the grid  24  and the upper and lower dies  36   a  and  36   b  can be kept in an extremely intimate contact state. Thus, the spacer forming material  46  that is filled in the upper and lower dies  36   a  and  36   b  can be securely prevented from leaking out between the dies and the grid  24 , and spacers having a desired shape and desired height can be formed with high accuracy.  
      Further, it is unnecessary to arrange a large number of holding members and apply a high holding pressure to each holding member in order to adhere the grid and the dies to one another. Thus, manufacturing processes can be simplified, and the vacuum vessel can be miniaturized and simplified.  
      A material that contains an ultraviolet-curing component is used as the spacer forming material, and the first and second main walls of the vacuum vessel  50  and the upper and lower dies are formed of a UV transmitting material. By doing this, ultraviolet rays can be applied to the spacer forming material  46  to UV-cure it without failing to keep the assembly  42  in an extremely intimate contact state. Thus, a spacer assembly that has spacers of a desired shape can be manufactured with high accuracy and more efficiently than in the conventional case.  
      In the second embodiment, the diameter and height of the spacers, the sizes and materials of the other components, etc., are not limited to the particulars or the foregoing embodiment, and may be suitably selected as required. Likewise, the spacer forming material may be variously selected as required.  
      The UV transmitting material that is used for the vacuum vessel and the molding tool is not limited to silicone, polyethylene terephthalate, glass, etc., and may alternatively be polycarbonate, acrylic resin, etc. Further, acrylic resin, nylon, ABS resin, Teflon (trademark) etc. may be used as the molding tool forming material.  
      In the spacer assembly, the first and second spacers need not be aligned coaxially with one another, and may be deviated in position from one another in the surface direction of the grid. Further, the spacer assembly is not limited to an SED and may be also applied to any other image display devices.  
      Although the molding tool is composed of the four divided pieces in the second embodiment, the number of division may be increased or reduced as required. Alternatively, a single molding tool may be used without being divided. The molding tool is not limited to the shape of a plate and may be given any ocher shape, if necessary.  
      In the embodiment described above, moreover, the filling device has the rotation axis D that extends vertically. Alternatively, however, it may be configured to have a rotation axis D that extends horizontally. According to a third embodiment shown in  FIG. 22 , a filling device  80  comprises a rotor  82  and a rotating mechanism  84 . The rotor  82  is rotatable around the horizontal rotation axis D. The rotating mechanism  84  supports the rotor and rotates the rotor around the rotation axis  0 . The rotor  82  has a pair of rotating arms  90 , each in the form of a rectangular plate that extends substantially vertically, and a pair of plate-like support brackets  86 . The support brackets  86  are fixed individually between the longitudinally opposite end portions of the pair of rotating arms  90 , individually extend horizontally, and face each other in a parallel relationship with the rotation axis D between them. The distance between each support bracket  86  and the rotation axis D is set to about 500 mm, for example.  
      The rotating mechanism  84  comprises rotating rods  92  that are coupled individually to the respective centers of the rotating arms  90 . The rotating rods  92  extend outward front the rotating arms  90  so as to be coaxial with the rotation axis D and are rotatably supported by their corresponding support posts  94 . Each support post  94  is provided with a drive mechanism (not shown) for rotating its corresponding rotating rod  92 . The rotor  82  can be rotated at a given rotational speed by rotating the rotating rods  92 .  
      When filling the spacer forming material  46  into the spacer forming holes of the molding tool by using the filling device  80 , two sets of divided pieces  37   a  and partition plates  70  that are supplied with the spacer forming material  46  are mounted on the support brackets  86  by using a clamper (not shown) or the like, as in the foregoing embodiment. As this is done, the back side of each divided piece  37   a  is adhered to a support surface  86   a  of each support bracket  86 . Thereupon, a contact surface  41   a  of each divided piece  37   a  and the partition plate  70  extend parallel to the rotation axis D and face the rotation axis side as they are attached to the support bracket  86 . Further, the divided piece  37   a  and the partition plate  70  are attached to the support bracket  86  so that slits  72  of the partition plate  70  are situated parallel to the rotation axis D.  
      In this state, the rotor  82  is rotated at the given rotational speed, e.g., 700 to 800 rpm for about one to five minutes. Thereupon, centrifugal force is produced in the spacer forming material  46 , and the spacer forming material is filled into spacer forming holes  40   a  that are formed in the divided pieces  37   a . This embodiment shares other configurations with the foregoing second embodiment, so that like reference numerals are used to designate like portions, and a detailed embodiment of those portions is omitted.  
      Also with use of the filling device  80  constructed in this manner, the same functions and effects of the foregoing second embodiment can be obtained.  
      In the second and third embodiments described above, the spacer forming material is filled at a time into two molding tools that are attached to the filling device. Alternatively, however, the spacer forming material may be filled into one or three or more molding tools that are attached to the filling device. If a plurality of support members are used for the filling device, moreover, these support members are arranged around the rotation axis. Alternatively, a plurality of molding tools may be attached to one ring-shaped support member that is provided coaxially with the rotation axis. Farther, the partition plates may be omitted if the width of the divided pieces of the main walls, that is, the width along a direction tangent to the direction of rotation, is short.  
      In the embodiment described above, the grid is used as a plate-like member, and the spacer assembly has the spacers arranged on individually on the opposite surfaces of the grid. However, the plate-like member is not limited to a grid, and any other plate material, such as a glass plate, may be used instead. Further, a spacer may be provided on only one surface of the plate-like member instead of being provided on each surface. In this case, it is necessary that only one molding tool be used and that the assembly be formed by adhering the molding tool to one surface of the grid. Another manufacturing process may be carried out in the same manner as in the foregoing second embodiment.