Patent Application
20070273269
1. Field of the Invention
The present invention relates to a flat-panel image display using electron emission into a vacuum formed between a front substrate and a rear substrate, and particularly to an image display in which a display panel formed of a front substrate and a rear substrate with a frame therebetween has an evacuation structure.
2. Description of the Related Art
As a display device that excels in luminance and resolution, a color cathode ray tube has been widely known. However, as high-resolution image processing apparatus and television broadcasting have been recently introduced, there is an increasing need for a lightweight, compact flat panel display (FPD) characterized by high luminance and high resolution.
As typical examples of the above-mentioned image display, liquid crystal displays and plasma displays have been commercialized. Particularly, there have been various types of commercialized flat-panel image displays, such as so-called electron emission image displays or field emission image displays as high-luminance, self-luminous displays using electron emission from electron sources to a vacuum space as well as organic electroluminescent displays characterized by low power consumption.
Among the flat-panel image displays, there have been known self-luminous flat panel displays configured in such a way that electron sources are arranged in a matrix. One of known such displays is the above-mentioned electron emission image display using miniaturized, integrated cold cathodes.
Examples of the cold cathodes used in self-luminous flat panel displays (FPDs) are thin film electron sources, such as the Spindt type, surface conduction type, carbon nanotube type, MIM (Metal-Insulator-Metal) type in which metal, insulator and metal are laminated, MIS (Metal-Insulator-Semiconductor) type in which metal, insulator and semiconductor are laminated, and metal-insulator-semiconductor-metal type.
There is a known structure of the MIM-type electron source disclosed in JP-A-8-180819. A known example of the Metal-Insulator-Semiconductor-type electron source is a MOS type electron source, and known examples of the Metal-Insulator-Semiconductor-Metal-type electron source are a HEED-type electron source, an electroluminescence-type electron source and a porous silicon-type electron source.
A known self-luminous flat panel display (FPD) has a display panel configured such that a rear substrate having any of the above-mentioned electron sources faces a front substrate having a phosphor layer and an anode that forms an accelerating voltage for directing electrons emitted from the electron sources to the phosphor layer, and an encapsulation frame encapsulates the inner space between the substrates facing each other and maintains the inner space in a predetermined vacuum state. Drive circuits are combined with the display panel for operation.
In an image display having MIM electron sources, the rear substrate is made of insulating material. On the substrate are formed a plurality of scan signal electrodes that extend in one direction and are juxtaposed in another direction perpendicular to the one direction, and scan signals are successively applied to the plurality of scan signal electrodes in the other direction. On the substrate are also formed a plurality of image signal electrodes that extend in the other direction and are juxtaposed in the one direction such that the image signal electrodes cross the scan signal electrodes. The electron sources are provided at intersections of the scan signal electrodes and the image signal electrodes. Both the electrodes are connected to the electron sources via feeding electrodes and current is supplied to each of the electron sources.
Each of the electron sources makes a pair with the corresponding phosphor layer to form a unit pixel. Three color unit pixels of red (R), green (G) and blue (B) typically form one pixel (color pixel). In a color pixel, unit pixels that form each color are also called sub-pixels.
In the thus configured flat panel image display (hereinafter also referred to as FPD), in general, a plurality of gap retention members (hereinafter also referred to as spacers) are disposed in a fixed manner in the airtight space surrounded by the rear substrate, the front substrate and the frame (also referred to as a support) so as to retain a predetermined gap between both substrates in cooperation with the frame. The frame is generally formed of a plate-like member or a formed member made of insulating material, such as glass and ceramic, and disposed at the periphery outside the display area of the display panel.
In the thus configured FPD, the inside of the airtight container (vacuum container) formed of the surrounding rear substrate, front substrate and frame is maintained at a predetermined high vacuum level. As evacuation means for evacuating the airtight container, for example, JP-A-8-180819 discloses an image display having evacuation ducts provided across at least one side surface of the frame.
In another FPD, the display panel is formed by drilling a pair of through holes at diagonal corners of the rear substrate that forms the enclosure, joining the through holes with evacuation ducts in an airtight manner such that the through holes communicate with the evacuation ducts, evacuating the gas in the enclosure and chipping off the tips of the evacuation ducts.
In conventional displays, although the time required for evacuation can be reduced, no consideration has been made to how to seal the evacuation ducts and the shape of the sealed portion. Only fixing and sealing the evacuation ducts on the side surface of one side of the panel may leave a possibility of deformation of the panel due to the external pressure because no frame is present at the side where the evacuation ducts are disposed.
In an FPD of this type, since the gap between the substrates are set to as small as about 3 mm, evacuation of the gas discharged from a bonding member for fixing the spacers will likely be insufficient. This is one of the factors that cause difficulty in retaining a high vacuum level. The residual gas disadvantageously prevents increase in lifetime of the panel.
In an FPD of this type, during heating, depressurizing and sealing in the sealing process, or during evacuation in the evacuation process, the evacuation of the display panel will be insufficient, so that the display panel cannot be uniformly evacuated to a high vacuum level. To eliminate this problem, the number of the evacuation ducts is increased to improve the entire vacuum level. Furthermore, insufficient evacuation of the display panel disadvantageously causes degradation of the electron emission characteristic of the electron source due to gas contamination. In particular, the gas remaining between the spacers in the display panel unlikely flows out of the display panel, so that the vacuum level is high only around the evacuation ports.
In the configuration in which a plurality of evacuation ducts are disposed on the rear side of the rear substrate, thermal expansion caused when the vacuum container is heated generates relative positional shifts among the plurality of evacuation ducts (shift of about 5 mm for a 32-inch panel). Such positional shifts are difficult to be handled by the evacuation head of the evacuation chamber connected to the tips of the evacuation ducts, resulting in a cause of failure, such as cracks in the evacuation ducts. Furthermore, part of the evacuation ducts remains as projections after the tips of the evacuation ducts are chipped off, which disadvantageously prevents reduction in thickness of the display panel.
Moreover, evacuation ports connected to the plurality of evacuation ducts present on the rear substrate pose a problem that, for example, water splash generated by cleaning water removal in a photo-etching process for forming various electrode wiring lines on the rear substrate likely causes electrode film failure.
Therefore, the invention has been made to solve the above-described conventional problems. According to the invention, evacuation efficiency in the airtight container can be improved and the vacuum level can be improved in a short period or time. Another object of the invention is to provide an image display capable of providing high-quality, reliable image display by stabilizing the electron emission characteristics and increasing the lifetime thereof.
The image display according to the invention has an opening at least one side of a frame, the size of the opening increasing toward the outside of the display panel, and a frame member whose size is reduced toward the inside of the display panel is fit into the opening. Therefore, the display panel can be easily and uniformly evacuated to a high vacuum level and hence the problems described in the background section can be solved.
The invention provides advantages of providing an opening having a large cross-sectional area, increased conductance of the evacuation system, smooth flow of the inner gas in the display panel without remaining inside, significant improvement in vacuum level in the display panel and the like. Since the frame member is fit into the opening in an airtight manner to form a sealing structure, the assembly tolerance can be relaxed, allowing easy assembly of the display panel. Furthermore, since projections are completely eliminated from the sealed display panel, allowing a thinner display panel, removal of damage potential and an increased degree of freedom of design of the end product. Moreover, reduction in thickness of the display panel provides significantly excellent advantages, such as an increased loading amount of the display panel onto an evacuation cart.
The invention is not limited to the configuration described above and the configurations of examples described below, but various changes can be made thereto without departing from the technical spirit of the invention.
Specific embodiments of the invention will be described below in detail with reference to the drawings of examples.
A representative configuration of the image display of the invention includes an enclosure including a first substrate having electron emission elements formed thereon, a second substrate having a phosphor surface formed thereon and a frame that connects the first substrate to the second substrate such that the substrates face each other and maintain a predetermined height therebetween. At least one of the surface of the frame that faces the first substrate and the surface of the frame that faces the second substrate inclines to the outer surface of the first substrate or the outer surface of the second substrate. The height of the surface of the frame outside the enclosure is higher than the height of the surface of the frame inside the enclosure.
Reference character 3 denotes a frame obtained by cutting formed material, such as frit glass material and ceramic material, combining and bonding the cut portions into a fixed frame-like structure. The frame 3 is disposed between and at the periphery of the front substrate 1 and the rear substrate 2 using sealing material 4, such as frit glass, to bond and fix the frame 3 between the substrates. The front substrate 1 and the rear substrate 2 are thus held with a gap therebetween having a predetermined dimension, for example, about 3 mm, so as to form a display panel PNL.
In
On the other hand, the ends of the inner surfaces of the front substrate 1 and the rear substrate 2 that come into contact with the frame member 3b are configured to be inclined surfaces 11 and 21. The inclined surfaces 11 and 21 are configured such that the opening area of the display panel becomes larger toward the periphery of the display panel.
In the frame 3 that has been assembled into a frame shape, the substantially U-shaped frame body 3a having surrounding three sides has the other open side, which forms an opening as an evacuation port, as shown in
Thus, the opening 5 is formed by combining the inclined surface 11 of the front substrate 1, the inclined surface 21 of the rear substrate and the inclined surfaces 31 and 32 of the frame body 3a, so that the opening area becomes gradually larger in the direction toward the outside of the opening 5. The opening 5 is formed at a side having no terminal of each electrode wiring line formed on the rear substrate 2, which will be described later.
The frame member 3b has inclined surfaces 33, 34 and inclined surfaces 35, 36 configured such that the opening area of the opening 5 becomes smaller toward the inside of the opening 5. On the inclined surfaces 33, 34, 35 and 36 of the frame member 3b, the sealing material 4, such as frit glass, is applied, dried and calcined for deposition.
The thus formed frame body 3a and the frame member 3b are placed in a predetermined fixture in a heating furnace and heated at about 350° C. to 400° C. During this process, the display panel is evacuated and the frame member 3b is moved into the opening 5 of the frame body 3a in the direction indicated by the arrow A. Then, the sealing material 4 is melted for fitting the frame member 3b into the opening 5 of the frame body 3a. Thus, each pair of corresponding inclined surfaces is sealed in an airtight manner to form the annular frame 3.
Reference character 6 shown in
The FPD includes the two substrates, the frame that is responsible for maintaining the gap between the substrates and the plurality of spacers disposed in the display area surrounded by the frame. In an FED panel, since it is necessary to maintain a high vacuum level in the display panel, a plurality of spacers that should withstand a predetermined pressure resulting from the vacuum are required between the substrates (having a gap of about 3 mm). In a display panel of about 32 inch-size, about three spacers of about 100 mm to 110 mm in length are disposed parallel to the longer sides and about six to thirteen columns of the spacers are disposed parallel to the shorter sides. The spacers are disposed and fixed with an interposed gap of about 30 mm in the shorter axis direction.
Reference character 7 denotes a group of electron emission elements. The group of electron emission elements 7 includes a plurality of electron emission sources. Each of the electron emission sources includes a cathode and a control electrode, and a large number of electron emission sources are disposed on the rear substrate 2 at a predetermined interval. The cathode is connected to a cathode wiring line. A plurality of the cathode wiring lines extend on the inner surface of the rear substrate 2 in one direction (Y direction) and are juxtaposed in the other direction (X direction). One end of the cathode wiring line is extended to one side of the rear substrate 2 outside the airtight sealed portion as a cathode wiring extension line 71.
The cathode wiring lines (image data wiring lines) are formed, for example, by using deposition or the like or by printing silver paste obtained by mixing conductive silver particles of about 1 to 5 μm in diameter with low-melting glass that exhibits an insulating property so as to form a thick film, followed by baking, for example, at about 600° C.
The control electrode is connected to a scan wiring line, which is disposed above the cathode wiring line such that the scan wiring line is electrically insulated from the cathode wiring line. One end of the scan wiring line is extended to another side of the rear substrate 2 outside the airtight sealed portion as a scan wiring extension line 72.
The group of electron emission elements 7 disposed on the rear substrate 2 at a predetermined interval are formed of Metal-Insulator-Metal (MIM) electron emission elements, surface conduction electron sources, a diamond film or a graphite film, carbon nanotubes or the like.
Reference character 8 denotes an image forming member. The image forming member 8 includes a phosphor film, a metal-back film deposited on the phosphor film and a black matrix (BM) film. The image forming member 8 is disposed on the inner surface of the front substrate 1 such that the image forming member 8 faces the group of electron emission elements 7 on the rear substrate 2.
While the evacuation port of an conventional panel is formed at the periphery (the area that does not contribute to image display) that surrounds the area where the electron sources are formed, the evacuation port of the panel according to the invention is disposed on a side surface of the panel, allowing an increased image display area without increasing the size of the panel itself. Furthermore, while the conventional evacuation port formed at the periphery of the rear substrate does not allow the size of the evacuation port to be increased, the evacuation port of the panel according to the invention disposed on the side surface of the panel allows the size of the evacuation port to be increased. Therefore, unnecessary gas in the panel can be evacuated in a short period of time.
A method for manufacturing the image display of the invention will now be described.
Firstly, the front substrate and the rear substrate are bonded with the first frame body 3a therebetween so as to form a panel having only one open side that is provided with the inclined surfaces. Then, the side provided with the inclined surfaces is brought into contact with an evacuation duct to evacuate the gas inside the panel from that side.
Next, a method for sealing the frame 3 will be described with reference to
Then, as shown in
Then, as shown in
The opening 5 formed of the front substrate 1, the rear substrate 2 and the frame body 3a has the inclined surfaces 11, 21 and the inclined surfaces 31, 32 inside the display panel PNL, and the cross-sectional area of the opening 5 increases toward the outside of the display panel PNL. On the other hand, the frame member 3b has the inclined surfaces 33, 34, 35 and 36, and the cross-sectional area of the frame member 3b decreases toward the inside of the opening 5. In this structure, it is extremely easy to compensate for errors associated with the alignment and fitting of the frame member 3b with the opening 5. Therefore, the assembly tolerance of the display panel PNL is relaxed, allowing the evacuation and sealing of the display panel PNL to be extremely easily performed.
The panel according to the invention will not leave any evacuation ducts. Thus, there is no projection (no evacuation duct left on the panel), so that the panel is easily handled and assembled in a monitor set or a television set. Furthermore, the panel according to the invention eliminates the need to chip off the evacuation ducts and hence is easily manufactured.
According to the image display of the invention, since the area of the evacuation port can be increased, the time required for evacuating the panel can be reduced. The panel can be fabricated without providing any evacuation duct on the rear substrate. Furthermore, the inclined upper or lower surface of the frame allows the panel to be easily assembled. Moreover, since the panel can be surrounded by the frame, the gap between the rear substrate and the front substrate can be maintained in a satisfactory manner.
In this example, the first and second substrates have inclined surfaces that face each other, and the second frame has inclined surfaces that face both the first and second substrates. Alternatively, an inclined surface may be formed on one of the first and second substrates and the second frame may have only one inclined surface that faces the inclined surface formed on one of the first and second substrates.
The frame 3B shown in
One end of each of the scan lines SL is connected to a scan driver SD. On the other hand, one end of each of the data lines DL is connected to a data driver DD. The front substrate is disposed along the broken line in the figure and faces the rear substrate. The front substrate 1 and the rear substrate 2 are bonded to each other along the periphery of the area where these substrates face each other and sealed after inner gas is evacuated. The spacers described above are disposed on the scan lines SL.
In
In the example described above, although the description has been made of the image display that uses the front substrate including the phosphor film and the black matrix film on the inner surface as well as the metal-back film (anode electrode) on the rear side of the phosphor film and the metal-back film, the invention is not limited thereto.
The principal plane of the first substrate 2 has a plurality of scan wiring lines SL that extend in a first direction (X direction) and are juxtaposed in a second direction (Y-direction) that crosses the first direction as well as a plurality of cathode wiring lines (also referred to as image data wiring lines) DL that extend in the second direction (Y direction) and are juxtaposed in the first direction (X direction) that crosses the second direction. The electron emission elements, which become the electron sources, are formed at the intersections of these lines arranged in a matrix or in the regions surrounded by these wiring lines. The electron emission elements are connected to the respective scan wiring lines SL and image data wiring lines DL. A plurality of electron emission elements are formed in an electron emission area 13.
The scan wiring lines SL are connected to the scan line drive circuit SD and the data wiring lines DL are connected to the data line drive circuit DD. Each of the wiring lines receive data required for image display from each of the drive circuits.
In the image display according to the invention, the first substrate 2 on which the electron sources are formed faces the second substrate on which the phosphor layers are formed. Electrons emitted from the electron sources formed on the first substrate 2 impinge on the phosphor layers formed on the second substrate to cause the phosphors to emit light so as to display an image on the second substrate. Thus, the first substrate 2 does not need to transmit light and hence glass or ceramic material is used for the first substrate 2. Since the second substrate is disposed on the front side of the image display, the second substrate is also referred to as the front substrate, while the first substrate 2 is also referred to as the rear substrate.
The rear substrate 2 has a substantially rectangular outer shape and has the inclined surface 21 along one side thereof. There is an area where no electron emission element is formed around the electron emission area 13. The inclined surface 21 is formed in an area where no electron emission element is formed and along a side where no wiring line is disposed. The evacuation of the panel is carried out from the portion where the inclined surface is formed. Since the evacuation can be carried out from a large area of the side surface of the panel, the evacuation can be completed in a short period of time and the vacuum level can be increased.
The frame 3 includes the first frame 3a that is fixed onto a surface parallel to the inner surface of the front substrate 1 or the rear substrate 2 (the surface on which the phosphor layers are formed or the surface on which data wiring lines and the like are formed) and the second frame 3b that is fixed onto an inclined surface of the substrate. The second frame 3b is disposed on the inclined surface. The second frame 3b is fixed onto the first frame 3a, the front substrate 1 and the rear substrate 2 using frit, which is bonding material. The evacuation is carried out from the portion where the inclined surface is formed.
In the panel shown in
In the panel shown in
The panel may be configured such that an inclined surface is formed on the portion of the front substrate 1 that faces the inclined surface 21 formed on the rear substrate 2. Inclined surfaces formed on both the front substrate 1 and the rear substrate 2 allow the second frame 3b to be easily inserted, so that the panel is easily manufactured.
The second frame 3b shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-075086 | Mar 2006 | JP | national |
