Electric lamp and discharge devices – With luminescent solid or liquid material – Vacuum-type tube
Reexamination Certificate
2003-01-27
2004-12-14
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
Vacuum-type tube
C313S022000, C313S024000, C313S035000, C313S036000, C313S025000, C445S024000
Reexamination Certificate
active
06831404
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to sealing flat panel displays, and more particularly, to cooling flat panel displays during a thermal sealing process.
BACKGROUND OF THE INVENTION
Cathode ray tube (CRT) displays are commonly used in display devices such as televisions and desktop computer screens. CRT displays operate as a result of a scanning electron beam from an electron gun striking phosphors resident on a distant screen, which in turn increase the energy level of the phosphors. When the phosphors return to their original energy level, they release photons that are transmitted through the display screen (normally glass), forming a visual image to a person looking at the screen. A colored CRT display utilizes an array of display pixels, where each individual display pixel includes a trio of color-generating phosphors. For example, each pixel is split into three colored parts, which alone or in combination create colors when activated. Exciting the appropriate colored phosphors thus create the color images.
On the other hand, flat panel displays are becoming more popular in today's market. These displays are being used more frequently, particularly to display the information of computer systems and other devices. Typically, flat panel displays are lighter and utilize less power than conventional CRT display devices.
There are different types of flat panel displays. One type of flat panel display is known as a field emission display (FED). FEDs are similar to CRT displays in that they use electrons to illuminate a cathodoluminescent screen. The electron gun is replaced with numerous (at least one per display pixel) emitter sites. When activated by a high voltage, the emitter sites release electrons, which strike the display screen's phosphor coating. As in CRT displays, the phosphor releases photons which are transmitted through the display screen (normally glass), displaying a visual image to a person looking at the screen. Each pixel can be formed by a trio of color-generating phosphors, each associated with a separate emitter.
In order to obtain proper operation of the flat panel display, it is important for an FED to maintain an evacuated cavity between the emitter sites (acting as a cathode) and the display screen (acting as a corresponding anode). The typical FED is evacuated to a reduced atmospheric pressure of about 10
−6
Torr or less to allow electron emission. In addition, since there is a high voltage differential between the screen and the emitter sites, the reduced pressure is also required to prevent particles from shorting across the electrodes.
Generally, the assembly of a flat panel display comprises a baseplate and a faceplate that are physically bonded together in forming a hermetic seal. For example, a glass powder, or frit, is placed in a continuous pattern along the outside perimeter of the display viewing area and melted at elevated temperatures to provide the desired hermetic seal. Typically, the cavity between the baseplate and faceplate is evacuated through an opening while a thermal cycle melts the frit. Once the display is sealed, it is generally important to uniformly cool the display assembly to minimize any thermal stress or shock that may result from immediate exposure to ambient temperature.
To achieve uniform cooling of the display, however, using conventional methods such as conductive cooling takes long periods of time that can not be afforded in a manufacturing environment. Accordingly, there exists a need for a more rapid cooling process during high vacuum sealing of a flat panel display assembly.
SUMMARY OF THE INVENTION
These and other needs are satisfied by several aspects of the present invention.
In accordance with one aspect of the invention, a method is provided for high vacuum sealing a flat panel display. The method includes lining the edges of a first component plate with a bonding material. A second component plate is positioned over the first component plate. The bonding material is thus sandwiched between the component plates, defining a cavity between the plates. The bonding material between the component plates is heated, followed by channeling a cooling fluid through the cavity. The cooling fluid has a lower temperature than the component plates. The cavity is thereafter evacuated.
In accordance with another aspect of the present invention, a method for manufacturing a flat panel display. The method includes forming a flat panel display assembly with an internal cavity. The assembly is thermally processed in a processing chamber. After thermal processing, a first fluid flows through the cavity, cooling inner surfaces of the assembly by convection. Simultaneously, a second fluid flows within the processing chamber, cooling outer surfaces of the assembly by convection. The cavity can then be sealed.
In accordance with another aspect of the invention, a method is provided for cooling a flat panel display assembly that includes at least two component plates. Cooling is conducted after melting a frit to bond the plates together and define a cavity between the plates. The cooling method includes simultaneously supplying heated gas to inside and outside surfaces of the flat panel display assembly while gradually cooling the gas.
In accordance with another aspect of the present invention, a vacuum-sealed flat panel display is provided. The display includes a middle plate spaced between an upper plate and a lower plate. An upper cavity is thus defined above the middle plate, while a lower cavity is defined below the middle plate. In addition, a divider block extends between the middle plate and the rear plate. The block divides the lower cavity into two compartments, each of the which communicate with the upper cavity through at least one opening in the middle plate.
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Browning Jim
Dunham Craig M.
Garcia Michael
Lee Seung-woo
Knobbe Martens Olson & Bear LLP
Patel Ashok
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