Invention for Method for forming a Tetraode Field Display including a Composite Mesh El

Invented by Kuo-Rong Chen, Jin-Shou Fang, Kuei-Wen Cheng, Teco Nanotech Co Ltd

The Teco Nanotech Co Ltd invention works as follows

A tetraode-field-emission display is disclosed and a method for fabricating it. Between an anode and cathode plates, a mesh is placed. To form a sandwich structure, the mesh contains a gate layer and converging electrode layers. Each set of anode or cathode has its own aperture. The mesh has many of these apertures. To act as a spacer, a glass plate is placed between mesh and anode. To limit the range of electron beams emitted from an electron emission source, the converging electrode layer faces the anode plate. The electron beam can then impinge on the anode with greater precision.

Background for Method for forming a Tetraode Field Display including a Composite Mesh El

The present invention is generally a field emission display and a process of fabricating it, and more specifically to a method that introduces a fourth electrode (converging electro) to a traditional triode field emit display, and a glass plate to act as a spacer.

Flat panel displays like field-emission (FED), liquid Crystal Display (LCD), Plasma display Panel (PDP), and Organic Light Emitting Diode (OLED) are becoming more popular on the market. Flat panel displays are light and thin. Some of these flat panel displays are suitable for smaller display panels such as cell phones and personal data assistants (PDA), while others are suitable to display large sizes such as television and computers. Others are suitable for larger display sizes such as outdoor panels. Many displays are aiming to achieve high image quality, large display areas, low cost, and long-lasting performance.

The field-emission display technology is relatively new. This type of display is self-illuminant and does not require a backlight source like the liquid crystal. The viewing angle is wider, power consumption is lower and response time is faster. There is also a greater temperature range. While the image quality of field-emission displays is comparable to conventional cathode-ray tube (CRT), displays, the field-emission displays are smaller and lighter than the cathode-ray tube displays, it has a much better image quality. It is possible that the field emission display could replace the liquid crystal display on the market. Further, nanotechnology allows for the application of nano-material in the field emitting display. This will make it commercially viable.

FIG. “FIG. 1” shows a traditional triode field-emission display that includes an anode and cathode plates 10 and 20. To provide support and isolation, a spacer 14 is placed between the cathode plates 20 and the anode plates 10. Anode plate 10 contains an anode substrate 11 and an anode conductive layer 12. A phosphor layer 13 are also included. The cathode plat 20 contains a cathode substrate 21, an electron emission layer 23 and a dielectric layer 24. To induce electron beam emission from layer 23, a potential difference is applied to the gate layer 25, The anode conductive 12 provides enough voltage to accelerate the electron beam and induce light emission. The vacuum must be maintained below 10?5 Torr to allow electrons to move in the field-emission display. To prevent contamination or poisoning of the electron emission source or the phosphors layers, it is important to avoid. The electron emission layer 23 must be separated from the phosphors layers 13 by a predetermined distance to accelerate the electron with the required energy to produce light from the 13 phosphors layers.

The traditional electron emission layer is usually in the form a spike structure (as illustrated in FIG. 1) or a Spindt structure. This structure also includes a spike structure made by photolithography or thin-film process. A variety of Spindt-type field-emission displays have been developed and improved through further development of the thin-film process. Normally, the electron beam generated by an electric field at the spike propagates in a small radius curve. In the conventional field-emission displays, control electrodes of different configurations are used to adjust the cross section or guide the electron beam along a path that will impinge on the phosphors at their correct positions. Therefore, the conventional field-emission display requires the spike structure of the electron emission source, the electron configurations, and the process of thin-film, photolithography or micro-electro-machining. These requirements have impeded the development of field emission display since the sixties.

Iijima recently proposed a carbon nanotube. The carbon nanotube is a popular source of electron emission because it has a high aspect ratio, high machine strength and chemical resistance. The field electron emission can be achieved by applying an electric field to a material’s surface to decrease its thickness. This allows electrons to escape from the material and become free electrons according to quantum-mechanical tunneling effects. You can increase the current generated by field electron emission by decreasing the work function of the surface. The electric field generates the free electron, so a heat source does not need to be used. This is why the field electron emission apparatus may also be called a cold cathode.

The carbon nanotube is continuously improving and being applied to enhance the field-emission display’s electron emission. The carbon nanotube is currently possible to be made by thick-film processes (such as spray printing or screen printing). Chinese (Taiwanese Patent Publication No. 502495 – The carbon nanotube can be directly printed on the cathode conductor layer 22 to create the electron emission layer 23. The conventional triode field emission display isn’t limited to thin-film technology. The carbon nanotube electron emitter has a high electron emission efficiency with a current density of 10?A/cm2 at a threshold voltage 1.5 V/m and current density 10 mA/cm2 at 2.5 V/m. This creates a perfect dynamic display effect and low cost driving circuit. Each electron emission source unit is made of a plurality carbon nanotubes so that the electron beam generated within the distance between anode and cathode is identical to that produced by the spike-emission source. FIG. 26 shows that the cross section of the collected electron light beam 26 diverges as it approaches the anode. 2. The electron beam 26’s cross section is larger the farther the distance. The cross section could be larger than the luminescent surface of the phosphors 13 layer, or the diffused electron beam 26 may impinge on the phosphors 13 layer nearby to alter the image resolution or color purity.

To resolve color purity issues or image resolution, the area of electron emission source is reduced. The electron beam 26 is generated in a similar way to that of the excited phosphors layer 13. The reduction in cross-section results in a lower efficiency or reduced unit area for the corresponding phosphors layers 13, which in turn increases the distance between neighboring phosphors layers 13 and decreases the image resolution.

Another way to solve the problem is to adjust the voltage between the gate electrode 25 & the cathode conductor layer 22. The gate layer 25, in addition to controlling electron drainage, can adjust the voltage to control the cross section and electron beam. This design leads to a lower efficiency in electron generation and a more complicated circuit design. The image quality is also affected by the increased response time and lower quality.

The third way to solve the problem is to form more than one control electrode between the anode and cathode. The control gate acts as a bias voltage or converging voltage that confines the electron beam’s cross section or deflects it so that the electron beam can reach the phosphors layer 13. This type of design is not suitable for large-area display or mass production.

On the contrary, the vacuum space between cathode and anode plates 20 of the conventional triode-field-emission display is supported either by a single spacer 14 (or a rib). The spacer 14 is made of a glass ball, cross-glass plate, or other solid strips. This prevents the anode and cathode plates 20 to 10 from falling down under very low pressure vacuum conditions. The spacer 14 is attached using adhesive to the anode plates 10 and 20. A sintering process is used to secure the spacer to the cathode plates 20 and 10. The spacer 14 is approximately 50? Spacer 14 is approximately 50?m. This spacer 14 is difficult to fabricate.

1. Complex fabrication process: Because the 14-mm spacer is very thin, it is more difficult to attach and transport the equipment necessary for installation.

2. Adhesion on the spacer can easily cause contamination. Conventional spacer 14 is coated with adhesion paste. The heating process causes the adhesion paste to become a contamination source. Secondary contamination can be caused by the solvent in the adhesion paste being evaporated during the sintering process.

Also, in an electric field operation, the spacer 14’s surface is easy to accumulate charges to create an electric field around it, so that the path and impinging effect of electron beam upon the 13 phosphor layers will be affected.

The present invention provides a tetraode-field-emission display and a process for fabricating it. A tetraode structure can be formed by placing a gate layer, and a converging electro layer, between an anode or a cathode. By installing the fourth electrode (the converging electrode), the electron beam’s diverging range is effectively limited. This effectively reduces the cross section of electron beam to impinge at a predetermined spot on the phosphor, without affecting color purity, brightness, or resolution. The fabrication cost of the phosphor layer will not increase.

The present invention also includes a tetraode-field-emission display that comprises a converging electrode electrode layer made from metal conductive plates and a gate electrode. To form a sandwich structure, the converging and gate electrodes are placed on opposite sides of the metal conductor layer. You can make the mesh by yourself and then package it with the anode plates in a subsequent step. The traditional structure’s thickness and high cost are not required anymore.

The invention also provides a tetraode-field-emission display as well as a method for fabricating it.” This type of display is easy to fabricate and can be mass produced.

The invention also provides a tetraode-field-emission display and a process of fabricating it. A glass plate is placed between the mesh and anode plates to replace the multiple spacers. This ensures that no charges are accumulated around the spacers, which will prevent them from generating an unintended electric field. An electron beam can therefore impinge upon the phosphor layer precisely at a predetermined location.

The present invention provides a tetraode-field-emission display that includes a mesh between an and cathode plates. The mesh is a sandwich structure consisting of a gate layer, a converging electro player and a gate layer. It is located on the two opposite sides of an insulation layer. There are a number of apertures that run through the mesh. Each aperture corresponds to a set each of anode units and cathode units. The anode plate is facing the converging electrode layer. This restricts the range of divergent electron beams emitted from the electron emission source. To support the display, a spacing plate is placed between the anode and converging electrode layers.

Referring to FIG. “Referring to FIG. An anode unit for the cathode plates 30 has an anode-conductive layer 32 and an attached phosphor layer 33. Anode substrate 31 is used to form the anode conductive 32 layer. Cathode plates 30 include a cathode sub-41. Each cathode unit has a cathode layer 42 that is formed on the cathode sub-41 and an electron emission source layer layer 43 that is attached to the cathode layer 42. Between the cathode plates 40 and 30, a mesh 5 is placed. The mesh 5 consists of a converging electrode 51, an insulation 52, and a gate 53 that are stacked together. The converging electrode 51 faces the anodeplate 30, while the gate 53 faces the cathodeplate 40. Each gate layer 53 and converging electrode 51 are connected to a particular potential. The mesh 5 contains a number of apertures 54 that are aligned with the appropriate set of anode or cathode units. This allows electrons emitted by the electron emission source layer43 to propagate through the aperture 51 to the phosphor layer33.

FIG. “FIG. The mesh 5 contains the insulation layer 52, sandwiched between the converging electrode 51 and the gate 53. The converging electrode 51 is made from a metal-conductive plate on one side of insulation layer 52. The gate 53 is made from a conductive sheet on the opposite side of insulation layer 52. The array of apertures 54 extends through the converging layer 51, 52, and 53. The rectangular apertures 54 in this embodiment are aligned to the respective sets of anode or cathode units. 54 apertures allow electrons from the cathode unit to project to the appropriate anode units. An invalid region 55 is located at the periphery 5 of the mesh. An assortment of markings 551 may be placed on the invalid area 55 to align during the vacuum packaging process, or between the apertures 54 with the appropriate set of anode- and cathode unit.

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