Image display apparatus

Abstract: An image display apparatus comprises a display panel formed by arranging in juxtaposition a face plate carrying thereon a phosphor and a rear plate carrying thereon electron-emitting devices within a housing. The phosphor is so arranged as to be irradiated with electrons emitted from the electron-emitting devices to display images. The image display apparatus further comprises an air blowing means for causing air to flow between the display panel and the housing.

Description: This invention relates to a flat panel image display apparatus comprising electron emitting devices. In recent years, lightweight and slim so-called flat panel image display apparatuses are drawing attention and expected to rapidly replace conventional heavy and bulky display apparatuses that comprise a cathode ray tube. While tremendous research efforts have been paid in the technological development of liquid crystal displays in order to realize a slim and flat profile, they are accompanied by the problem of a rather dark view screen and a limited viewing angle along with other problems. An emission type flat type display apparatus comprising an electron source for emitting electron beams and a phosphor that produces visible images when irradiated with electron beams is advantageous in that it has a bright screen and a wide viewing angle and therefore can adapt itself to a large screen arrangement and highly defined images if compared with a liquid crystal display. The demand for emission type flat panel display apparatuses is remarkably increasing because of these and other advantages. An emission type flat panel image display apparatus that utilizes electron beams for producing images typically comprises a number of electron-emitting devices arranged in the form of a matrix between a face plate and a rear plate. A number of flat panel image display apparatuses comprising surface conduction electron-emitting devices for emitting electron beams and a phosphor for displaying images when irradiated by accelerated electron beams have already been disclosed and applied for patent, including those invented by the applicant of the present patent application. (See inter alia Japanese Patent Publication No. 3-261024.) Fig. 6 of the accompanying drawings is a simplified schematic sectional view of a typical flat type image display apparatus comprising surface conduction electron-emitting devices as mentioned above. Referring to Fig. 6, the image display apparatus comprises a substrate 1001 made of an insulating material such as soda lime glass, a number of surface conduction electron-emitting devices 1002 arranged on the substrate 1001, an insulation layer 1003 formed on the substrate 1001 and grids 1004, each having a hole for allowing electron beams to pass therethrough and operating as a modulation electrode. The apparatus further comprises a face plate 1005 made of soda lime glass and provided on the inside with a phosphor 1006 covered by a metal back 1007 of aluminum thin film and a lateral frame 1009 disposed between and bonded to said substrate 1001 and said face plate 1005 by means of frit glass 1008 to form a sealed envelope. The surface conduction electron-emitting devices 1002 and the grids 1003 are electrically connected to an external drive circuit (not shown), while the metal back 1007 is electrically connected to a high voltage power source 1013 by way of a high voltage power cable 1014. Fig. 7 is a perspective view of a surface conduction electron-emitting device 1002, showing its configuration in detail. Referring to Fig. 7, it comprises a pair of device electrodes 1102 and 1103 separated from each other by a predetermined distance L and a thin film 1104 prepared by applying an organic palladium compound (e.g., ccp-4230: available from Okuno Pharmaceutical Co., Ltd.) onto the device and having an electron-emitting region 1105 produced in the thin film by subjecting the latter to an electrically energizing process called "forming". "Forming" is a process in which a voltage is applied between the device electrodes 1102 and 1103 to partly destruct, deform or modify the composition of the thin film 1104 and to produce an electron-emitting region 1105 which is electrically highly resistant. The electron-emitting region 1105 may be an area of the thin film 1104 having fissures. If such is the case, electrons are emitted from and near the fissures. Proposed materials that can suitably be used for the thin film of a surface conduction electron-emitting device include SnO 2 , Au [G. Dittmer: "Thin Solid Films", 9, 317 (1972)], In 2 O 3 /SnO 2 [M. Hartwell and C. G. Fonstad: "IEEE Trans. ED Conf.", 519 (1975)] and carbon [H. Araki et al.: "Vacuum", Vol. 26, No. 1, p. 22 (1983)]. When the internal pressure of the above described image display apparatus is held to about 10 -4 Pa (10 -6 Torr) and a drive pulse voltage is applied to the device electrodes 1102 and 1103 of the surface conduction electron-emitting device having a configuration as shown in Fig. 7 by the external drive circuit, the device emits an electron beam. The electron beam then passes through the corresponding grid 1104 and is accelerated by the positive voltage being applied to the phosphor 1006 and the metal back 1007 by the high voltage power source 1013 to eventually collide with the phosphor 1006 and make it emit light. The speed at which the electron beam travels can be controlled by the voltage applied to the grid 1006 by the drive circuit (not shown) so that consequently the fluorescent body may emit light in a controlled manner to produce an intended image on the screen. Electron-emitting devices other than those of the surface conduction type include those utilizing thermoelectron sources, field emission electron-emitting devices [W. P. Dyke & W. W. Dolan, "Field emission", Advances in Electron Physics, 8, 89 (1956) and C. A. Spindt, "Physical properties of thin-film field emission cathodes with molybdenum cones", J. Appl. Phys., 47, 5248 (1976)] and metal/insulation layer/metal electron-emitting devices [C. A. Mead, "The tunnel-emission amplifier", J. Appl. Phys., 32, 646 (1961)]. In any of the above mentioned image display apparatuses, heat is inevitably generated therein when electrons are made to collide with a phosphor for emission of light, when electron-emitting devices are electrically energized to emit electrons and/or when electron-emitting devices arranged on a plane are sequentially driven to operate by way of wires. As heat is generated, the substrate 1001 and the face plate 1005 of the apparatus are heated to show a temperature difference between them and/or an uneven thermal distribution within the apparatus, which can in turn result in a differentiated thermal expansion that may give rise to a distorted display screen, a colour breakup and/or other problems. These problems will be serious when the image display apparatus has a large display screen. It is therefore an object of the present invention to provide an image display apparatus in which the above identified technological problems are at least alleviated. Another object of the invention is to provide an image display apparatus that hardly, if at all, gives rise to a differentiated thermal expansion in the rear plate and the face plate of the display panel of the apparatus. Still another object of the invention is to provide an image display apparatus that can stably display high quality images and is free from distortions and, in the case of a colour image display apparatus, free from the phenomenon of colour breakup. Patent Abstracts of Japan, vol. 9, No. 150 (E-324) 25 June 1995 and JP-A-60032239 discloses a flat panel image display apparatus having those features recited in the preamble of claim 1 attached. This addresses the problem of faceplate overheating and provides a liquid coolant heat exchanger in contact with the faceplate on the surface opposite to the phosphor. No additional provision is made to equilibrate the temperatures of the faceplate and the new plate. The flat panel image display apparatus in accordance with the present invention is characterised by: air blowing means which is fitted to the housing and is arranged to force cooling air to flow between the housing and the display panel so that the cooling air exchanges heat with the rear plate; a thermally conductive member, arranged on the surface of the rear plate opposite to the surface carrying thereon the electron-emitting devices; a transparent and thermally conductive member, arranged on the surface of the face plate opposite to the surface carrying thereon the phosphor; and thermally conductive material, connecting the thermally conductive members. While air cooling is used in the apparatus of this invention, it is acknowledged that air cooling has been considered in relation to other kinds of flat panel image display, for example liquid crystal flat panel displays. US-A-4952925 describes an arrangement in which air is drawn from one end of a chamber and forced along parallel flow paths, respectively, above and below the flat panel display, by means of an extractor fan at the other end of the chamber. In the present invention the heat discharging effect of the rear plate is enhanced to improve the thermal distribution pattern of the display panel by arranging a thermally conductive member having a high thermal conductivity on the rear plate. The thermal distribution pattern of the display panel is also improved by covering the face plate with a transparent thermally conductive member and physically connecting the thermally conductive members on the face plate and the rear plate by means of a thermally conductive material. With such an arrangement, reflection of ambient light also can be reduced and particles of dirt can be prevented from being absorbed by the display panel. The face plate and the rear plate exchange heat to reduce the difference of temperature existing therebetween. Additionally, since both the face plate and the rear plate show an even thermal distribution, any differentiated thermal expansion that may exist in the rear plate and the face plate of the display panel of the apparatus can be minimised. Thus, an image display apparatus according to the invention can stably display high quality images and remains free from distortions. Also, in the case of a colour image display apparatus, the phenomenon of colour breakup is avoided. Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a schematic cross-sectional side view of a first embodiment of image display apparatus according to the invention (thermally conductive members are not shown); Fig. 2 is a schematic cross-sectional side view of the display panel 100 of Fig. 1; Figs. 3A and 3B are respectively a schematic plan view and a schematic front view of an electron-emitting device that can be used for an image display apparatus according to an embodiment of the invention; Fig. 4 is a schematic cross-sectional side view of a second embodiment of image display apparatus according to the invention and comprising fins; Fig. 5 is a schematic perspective view of the embodiment of fig. 4, showing in particular the arrangement of the fins; Fig. 6 is a schematic cross-sectional side view of a known image display apparatus comprising surface conduction electron-emitting devices; and Fig. 7 is a schematic perspective view of a known surface conduction electron-emitting device. Now, the present invention will be described in greater detail by referring to the accompanying drawings that illustrate preferred embodiments of the invention. First Embodiment A first embodiment of image display apparatus will be described by referring to Fig. 1, which schematically shows a side view of the embodiment in cross-section. The image display apparatus of Fig. 1 comprises a display panel 100 enclosed in a housing 115. The display panel 100 is prepared by arranging in juxtaposition a face plate 205 carrying thereon a phosphor 206 and a rear plate 201 carrying thereon a number of electron-emitting devices 202. The embodiment additionally comprises a fan (air blowing means) 117 for causing air to flow between the display panel 100 and the housing 115. Said fan 117 draws air from the outside and causes it to flow along arrow 116 as cooling air. The heat discharging effect of the rear plate is enhanced to improve the thermal distribution pattern of the display panel by arranging a thermally conductive member (not shown) having a high thermal conductivity on the rear plate. The thermal distribution pattern of the display panel is also improved by covering the face plate with a transparent thermally conductive member (not shown) and physically connecting the thermally conductive members on the face plate and the rear plate by means of a thermally conductive material. With such an arrangement, advantageously, reflection of ambient light can be reduced and particles of dirt can be prevented from being adsorbed by the display panel. The thermally conductive member to be arranged on the rear plate is preferably made of a metal having a high thermal conductivity such as Cu or Al, of which Cu is particularly preferable. On the other hand, the thermally conductive member to be arranged on the face plate is preferably made of ITO or SnO 2 . While an image display apparatus according to the invention comprises the above components as principal parts thereof, the embodiment of Fig. 1 additionally has a high voltage power source 113, a high voltage cable 114 for feeding the phosphor of the display panel 100 with a high voltage and a filter 118 for removing dirt out of the air drawn into the housing from the outside. The above embodiment operates to cool the display panel 100 in a manner as described below. Cooling air is drawn in from the outside by means of the fan 117 fitted to the housing 115 that encloses the display panel 100. The cooling air is then made to pass through the filter 118 to get rid of dirt and flows along the arrowed lines 116 to cool the substrate 201 of the display panel 100 and raise the temperature of itself. Thereafter, the cooling air turns around the face plate 205 of the display panel 100 and exchanges heat with it until the face plate 205 is cooled down close to the temperature of the cooling air. As a result, the rear plate or the substrate 201 of the display panel 100 and the face plate 205 do not practically show any temperature difference and an even thermal distribution throughout the display panel 100 including the face plate 205 and the substrate 201 is realised so that no difference may be observed between the thermal expansion of the face plate 205 and that of the substrate 201 to minimise their thermal distortions and the phenomenon of distorted image and colour breakup. Note that the flow route of cooling air may be reversed and cooling air may be introduced from the side of the face plate 205 and then fed to the substrate 201. While the position where the air blowing means is fitted to the housing 115 is not particularly specified, a screen cover may preferably be used to cover the opening of the face plate 205 to enhance the efficiency with which it exchanges heat with the cooling air because the cooling air flowing along the face plate 205 is not brought into direct contact with the ambient air. While an image display apparatus is required to be provided with a drive circuit comprising ICs in order to display images on the display panel, it is also preferable that the drive circuit is cooled at the same time. This can be done without increasing the dimensions of the image display apparatus by arranging the drive circuit somewhere in the flow path of cooling air in such a manner that it does not particularly block the air flow. The display panel 100 of the above described embodiment is driven to operate by a drive circuit (not shown) that generates a drive signal in response to an image display signal applied to it. Now, the display panel 100 will be described by referring to Figs. 2, 3A and 3B. Fig. 2 is a cross-sectional view of the display panel 100. Figs. 3A and 3B are respectively a schematic plan view and a schematic front view of one of the surface conduction electron-emitting device contained in the embodiment. Note that the number of electron-emitting devices 202 is not necessarily limited to that of Fig. 2. Referring to Fig. 2, the display panel 100 comprises a substrate 201 or a rear plate made of an insulating material such as glass and a number of surface conduction electron-emitting devices 202 as well as insulation layer 203 formed on the substrate 201 and grids 204 formed on the insulation layer 203 and provided with respective holes for allowing electron beams to pass therethrough, each of said grids 204 operating as a modulation electrode. The display panel 100 further comprises a face plate 205 provided with a phosphor 206 on the inner surface thereof which is by turn covered by a metal back made of an Al thin film, said face plate 205 and said substrate 201 being bonded together by means of frit glass 208 with a lateral frame 209 disposed therebetween to produce a vacuum envelope. The device electrodes 207, the grids 204 and the fluorescent body 206 are electrically extended to the outside of the envelope by wires (not shown) for electric connection. An electron-emitting device 202 that can be used for the purpose of the invention will now be described in detail by referring to Figs. 3A and 3B. As shown in Figs. 3A and 3B, the electron-emitting device comprises a pair of device electrodes 302, 303 separated by a predetermined distance and an electron-emitting region-containing thin film 304 and an electron-emitting region 305. The electron-emitting region 305 of the electron-emitting region-containing thin film 304 is constituted by electroconductive fine particles having a diameter of tens of several Å (1Å=0.1 nm), whereas the electron-emitting region-containing thin film 304 other than the electron-emitting region 305 is a fine particle film. The term "a fine particle film" as used herein refers to a thin film constituted of a large number of fine particles that may be loosely dispersed, tightly arranged or mutually and randomly overlapping (to form an island structure under certain conditions). The electron-emitting region-containing thin film 304 may be a carbon thin film that contains dispersed electroconductive particles. Now, the method of manufacturing the above embodiment of image display apparatus will be described. Firstly, how each of the surface conduction electron-emitting devices 202 is prepared will be described. After thoroughly cleaning a substrate 301, a pair of device electrodes 302, 303 typically of nickel are formed on the substrate 301 by vacuum deposition or photolithography (including techniques such as etching and lift-off) in such a way that they are separated by distance L=2µm and have a length W=300µm and a thickness d= 100nm (1,000Å). Alternatively, the device electrodes may be made of a metal other then nickel or a semiconductor material. Then, an organic metal thin film is formed between the device electrodes 302 and 303 by applying an organic metal solution. The term "an organic metal solution" as used herein refers to a solution of an organic compound containing as a principal component thereof a metal selected from Pd, Ru, Ag, Au, Ti, In, Cu, Cr, Fe, Zn, Sn, Ta, W, Pb and so on. Thereafter, the organic metal thin film is heated, baked and subjected to a patterning operation by using a technique such as lift-off or etching to produce a thin film 304 having a profile as shown in Figs. 3A and 3B. Materials that can be used for the thin film 304 are not limited to those listed above and may include metals such as Pd, Ru, Ag, Au, Ti, In, Cu, Cr, Fe, Zn, Sn, Ta, W, Pb and so on, oxides such as PdO, SnO 2 , In 2 O 3 , PbO, Sb 2 O 3 , borides such as HfB 2 , ZrB 2 , LaB 6 , CeB 6 , YB 4 , GdB 4 and so on, carbides such as TiC, ZrC, HfC, TaC, SiC, WC and so on, nitrides such as TiN, ZrN, HfN and so on, semiconductor materials such as Si, Ge and so on, carbon, AgMg, NiCu, Pb and Sn. Techniques that can be used for preparing an electron-emitting region-containing thin film 304 include vacuum deposition, sputtering, chemical vapour phase deposition, dispersive application, dipping, spinning and other techniques that can appropriately be used for forming a thin film. For the purpose of the present invention, thermion sources comprising a hot cathode, field emission electron-emitting devices and other electron sources that can emit electrons may also be used in place of the surface conduction electron-emitting devices described above. Thereafter, wires (not shown) for feeding the semiconductor electron-emitting devices 202 with power are arranged. For this, a film of a metal such as Au, Cu or Al is formed to a thickness of several µm by vapour deposition or sputtering and wires are arranged by photolithography (including techniques such as etching and lift-off) in such a way that they are partly laid on the respective device electrodes 303, 304. The distal ends of the wires are extended to the outside of the envelope for external electric connection. Note that the wires may be arranged by any appropriate technique other than photolithography such as plating or printing using electroconductive paste. Then, grids 204 and an insulation layer 203 are prepared. For this, an SiO 2 film is formed to a thickness of 1 to 5µm by sputtering and then an Au, Cu or some other metal film is formed to a thickness of 0.5 to 1µm by vapour deposition or sputtering. Thereafter, holes larger than the electron-emitting region 305 of the surface conduction electron-emitting device 202 are made by photolithography (including techniques such as etching and lift-off) to allow electrons to pass therethrough and the oxide film that operates as an insulation layer is etched by using the metal film as a mask to produce similar holes. Finally, grids are produced out of the metal layer as it is processed by photolithography (including techniques such as etching and lift-off), said grids having wires that extend out of the envelope for external electric connection. Subsequently, a face plate 205 prepared by applying a fluorescent material to produce a phosphor 206 and arranging a metal back of aluminium on the phosphor 206 and a substrate 201 carrying thereon a number of surface conduction electron-emitting devices are bonded together with a lateral frame 209 arranged therebetween to produce a display panel by means of frit glass 208, which is heated to a temperature appropriate for the frit glass to hermetically seal the display panel (e.g., 450°C for LS-0206: available from Nippon Electric Glass Co., Ltd.) for a predetermined period of time (10 minutes for LS-0206). If a colour phosphor is used, the pixels of the phosphor 206 have to be aligned with the respective electron-emitting devices on the substrate. Then, the internal pressure of the display panel 100 is reduced to about 10 -4 Pa (about 10 -6 Torr) by way of an exhaust pipe (not shown) to produce a quasi-vacuum condition and the electron-emitting devices are subjected to an electric forming operation, where the device electrodes 302, 303 are electrically energised. Thereafter, the entire display panel 100 is heated and degassed by flushing it with a getter (not shown), and the exhaust pipe is sealed off. Thereafter, the aforementioned thermally conductive members and connective thermally conductive material are provided and the display panel 100 is placed within a housing 115. Second Embodiment In this second embodiment, the entire surface of a display panel comprising a face plate, a lateral frame and a rear plate was coated with a thermally conductive transparent film and a metal plate and (flat) fins having a thermal conductivity greater than that of the material of the rear plate (soda lime glass) were arranged on the rear plate in a manner as illustrated in Fig. 4. Referring to Fig. 4, reference numeral 830 denotes a thermally conductive transparent film formed on the entire surface of the display panel in order to achieve a flat and even temperature profile and avoid adhesion of electrically charged dirt particles. The extended electrode section was also coated with the transparent film 830 after it was covered by an insulation film (not shown) made of glass. The apparatus additionally comprised a side flow fan 817 having a blowing capacity of 5m 3 /minute and a thermally conductive aluminium plate 826 arranged on the rear plate and a number of aluminium fins 827 arranged on the metal plate 826. The fins 827 were longitudinally aligned with the direction of the air flow in the apparatus. Fig. 5 shows a schematic perspective view of the aluminium plate 826 and the aluminium fins 817. The display panel 100 comprising a face plate, a lateral frame and a rear plate was prepared as follows. The substrate 201 of the display panel 100 had dimensions of 240mm x 320mm, whereas the face plate was 190mm x 270mm large. Each of the surface conduction electron-emitting devices 202 had a configuration as illustrated in Figs. 3A and 3B and was prepared by arranginga pair of 100nm (1,000Å) thick gold device electrodes 302, 303 having a length W=150µm in juxtaposition and separating them with a distance L=2µm. Then, a solution containing organic palladium compound (ccp-4230: available from Okuno Pharmaceutical Co., Ltd.) was applied onto the device to produce a thin film 304, which was then heated at 300°C for 10 minutes to make it a film of fine particles containing palladium as a principal ingredient. Then, Cu wires (not shown) for feeding the surface conduction electron-emitting device 202 and having a thickness of 2µm and a width of 150µm were arranged and grids 204 of gold having a thickness of 1µm and a width of 800µm and provided with respective holes of 500µm x 100µm were formed. SiO 2 was used for the insulation layer 203. Of the above members, the metal film and the SiO 2 film were prepared by sputtering and then processed by photolithography (including techniques such as etching and lift-off). The face plate 205 carried a colour phosphor 206 of red, green and blue thereon and each of the pixels for one colour was 800µm x 250µm large. Thereafter, the substrate 201 and the face plate 205 were aligned with each other and bonded together with a lateral frame 209 arranged therebetween to produce a sealed display panel by using LS-0206 available from Nippon Electric Glass Co., Ltd. and heating them at 450°C for 10 minutes. Thereafter, the display panel was evacuated by way of an exhaust pipe (not shown) to realise a quasi-vacuum condition of 10 -4 Pa (10 -6 Torr). An electric forming operation was carried out on each of the electron-emitting devices to produce an electron-emitting region 305 thereby applying a triangular voltage pulse (having a bottom of 1 millisecond, a period of 10 milliseconds and a wave height of 5V)for 60 seconds. Subsequently, the entire display panel 100 was heated at 130°C for 24 hours for degassing, flushed with a getter (not shown) and then the exhaust pipe was sealed off to produce a panel section for an image display apparatus. The transparent film 830 on the entire surface of the display panel was formed by vacuum deposition and by applying ITO/SnO 2 . As for the aluminium plate 826 and the fins 827 arranged on the aluminium plate 826, the former had a thickness of 3mm whereas each of the fins 827 had a height, a width and a length of 3mm, 2mm and 10mm respectively. Since the metal plate 826 had a thermal conductivity of about 190W/mK which was by far greater than that of the rear plate (1.1W/mK) of soda lime glass, heat was transmitted through the metal plate 826 to realize a flat and even temperature profile for the rear plate. Note that the metal plate 826 may be arranged not only on the back side of the rear plate but also the lateral frame and the face plate 205 except the area for displaying images and that it is recommendable to arrange a large metal plate 826 unless it disadvantageously increases the total weight of the apparatus. It was proved that the anti-dirt film 830 on the face plate could effectively prevent particles of dirt from adhering thereto and the temperature profile of the face plate was improved if compared with an apparatus having no such film. It was also proved that the heat generated in the display panel 100 could be effectively transmitted through the fins 827 on the metal film 826 and dispersed into the cooling air coming from the side flow fan 817 and that the ICs in the drive circuits 820 were also effectively cooled. Since the fins 827 of the apparatus of this example were longitudinally aligned with the direction of the air flow in the apparatus, the heat dispersing effect of the apparatus was further improved. The arrangement of this example operates for cooling in a manner as described below. The external air drawn into the apparatus by means of the side blow fan 817 is cleaned by a filter 818 to get rid of dirt and the cleaned air is made to flow along the arrowed lines 816. Consequently, the cooling air cools the metal film 826 and the fins 827 on the back side of the substrate 201 of the display panel 100 while it raises its own temperature. As the cooling air exchanges heat with the metal plate 826 and the fins 827 to a sufficient extent, heat flows mainly through the thermal conductive transparent film 830 arranged on the display panel as a function of the temperature gradient existing there until the display panel shows a very flat and even temperature profile. After operating the apparatus for a long time, no colour breakup was observed in the peripheral areas of the screen and the apparatus was completely free from damage. Since the drive circuit 820 of this embodiment was enclosed in the housing 815 of the apparatus the apparatus offered an improved convenience of handling because it operated simply by feeding it with image display signals. The ITO/SnO 2 transparent film 830 may be formed by a method other than vacuum deposition as described above such as printing or spraying. Note that the face plate may be covered with an opaque film except the area where images are actually displayed. Note also that the lateral frame and back side of the rear plate may be covered by an Ag film. The fins 827 may have a profile more complicated than the above described one. Additionally, fins may be formed on the existing fins in order to increase the surface area to be exposed to the cooling air, although the pressure loss on the part of the fan increases with the increase in the surface area to reduce the air flow rate. So, the profile of the fins and the surface area to be exposed to the cooling air have to be appropriately selected, taking the contour of the air flow paths into consideration.

Claims: A flat panel image display apparatus comprising: a housing (115;815); a display panel (100), to display images, arranged within said housing, said display panel having a face plate (205) carrying thereon a phosphor (206) and a rear plate (201) carrying thereon electron-emitting devices (202), said phosphor being arranged so as to be irradiated with electrons emitted from said electron-emitting devices to display the images; characterised by: air blowing means (117;817) which is fitted to said housing and is arranged to force cooling air to flow across said rear plate so that said cooling air exchanges heat with said rear plate; a thermally conductive member (826), arranged on the surface of said rear plate opposite to the surface carrying thereon said electron-emitting devices; a transparent and thermally conductive member (830), arranged on the surface of said face plate opposite to the surface carrying thereon said phosphor; and thermally conductive material (830), connecting said thermally conductive members. Apparatus according to claim 1 wherein said air blowing means (117) is arranged at the centre of said housing facing said rear plate. Apparatus according to claim 1 wherein said air blowing means (817) is arranged at a lateral proximity of said display panel. Apparatus according to claim 3 having a plurality of flat projections (827) arranged on said rear plate. Apparatus according to claim 4 wherein the longitudinal axes of said plurality of flat projections are arranged in parallel with the direction of air flow (816) produced by said air blowing means. Apparatus according to any preceding claim wherein said transparent and conductive member is composed of indium tin oxide (ITO) or tin oxide (SnO 2 ). Apparatus according to any preceding claim, wherein a drive circuit (820) for driving said display panel is arranged within said housing. Apparatus according to any preceding claim, wherein said electron-emitting devices (202) are surface conduction electron-emitting devices (302-305). Apparatus according to any of claims 1 to 7, wherein said electron-emitting devices (202) are thermion sources (502-504). Apparatus according to any of claims 1 to 7, wherein said electron-emitting devices (202) are field emission electron-emitting devices.

Inventors: AZUMA HISANOBU, KAWATE SHINICHI, SATO YASUE, AZUMA, HISANOBU, KAWATE,SHINICHI, SATO, YASUE, Azuma, Hisanobu, c/o Canon K.K., Kawate,Shinichi , c/o Canon K.K., Sato, Yasue, c/o Canon K.K.
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1995
Main classification: H01J29
IPC codes: H01J7, G09F9, H01J29, H01J31