WO2002073579A2

WO2002073579A2 - Three plate structure vacuum flat panel display

Info

Publication number: WO2002073579A2
Application number: PCT/US2002/008353
Authority: WO
Inventors: Jessica Stevens; Victoria Kolakowski
Original assignee: Telegen Corporation
Priority date: 2001-03-14
Filing date: 2002-03-14
Publication date: 2002-09-19
Also published as: WO2002073579A3; AU2002252403A1

Abstract

A display panel includes a top plate (42), a middle plate (44), and a bottom plate (46) forming a sealing system having an offset V-groove sealing structure (48, 50).

Description

THREE PLATE STRUCTURE VACUUM FLAT PANEL DISPLAY

FIELD OF THE INVENTION

This invention relates to sealing flat panel video screen technology, more specifically, to sealing multiple plates of flat panel displays.

BACKGROUND OF THE INVENTION

A considerably difficult engineering problem exists with regards to sealing flat panel video displays. The need to join elements of different mass, geometry or material creates construction problems unaddressed by current manufacturing processes. The present state of the art is highly economically inefficient due to material constraints and structural design requirements.

Current flat panel displays consist of a top plate connected to side plates that are, in turn, connected to a middle plate and a bottom plate. Alternatively, a molded top plate may be used, either with or without the side plates. In either embodiment, a frit material is placed between the various pieces at the contact points to server as the sealing means once a heating process is applied.

The use of a frit material for sealing glass is commonly known. However, a critical feature under current design practices is that the frit must be applied very evenly across the contact surfaces bringing rise to one of the major challenges of the current display panel structure - proper alignment of the plates. The frit, in order to be effective, must be aligned properly with the pieces to be fused together, and the pieces must be properly located on the display if the manufacture is to be proper. Under current design practices, the relative contact surfaces are flat and are prone to shifting during the manufacturing process. Any shifting or misalignment of the parts will yield a substandard or ineffective display panel that is prone to premature failure.

An additional problem with the current flat panel display design employing frit sealing is that the entire panel must be constructed, heated and cooled to seal the frit before the panel can be operationally tested. This drastically increases cost of failed parts.

A further problem with current flat panel designs involves the adverse effect the relatively large number of information transfer wires or grids. Many of the newer active matrix panels used today have in excess of 2400 information lines passing through the system, all of which must somehow pass through the sealing means to access the outside environment. Typically, the lines are embedded in the frit during sealing. This common practice causes a problem in proper sealing of the display due to the relative thermal coefficients of expansion of the frit, panels and wires. Another significant problem with the current state of the art is the surface conditions of the respective plates. Any defect on the contact surfaces of the pieces is a potential pressure balancing, or moisture admitting port. In either case, the display . may again be rendered inoperable or otherwise defective. Still further, the relative flatness of the connecting surfaces is critical to proper sealing of the display. Should either surface be inclined relative to the other the result is a drastic reduction in the sealing contact surface. This, of course, increases the odds of seal failure by the decrease in the effective seal surface area. Also, similar to leaning a chair back from its normal up-right position, the inclination may result in unwanted relative movement between the contact surfaces.

Another significant problem with the existing display panels is the creation of excessive residual internal stresses caused in part by the vacuum. More specifically, when different materials or materials of varying mass are connected together, heated and then cooled, the differing rates of expansion create internal stresses. This especially occurs when the grid or wire associated with the internal active matrix, passes through the frit sealing to the outside environment. The grid or wire, generally metallic in nature, conducts heat quickly, thereby expands and contracts faster than the surrounding material, leaving space around the wire port. The space prevents the display panel from having a vacuum in the inner space and allows circuitry-damaging pollutants into the display.

Another limitation of the present state of the art is the material choices - chiefly, the type of glass that may be used in the displays. Currently, due to design limitations, only soda lime glass is used. The use of soda lime glass tends to increase the overall weight of the display, which is undesirable. Also, the larger mass of the soda lime glass required to produce the display requires more time to heat and cool, resulting in increased cost of manufacture. SUMMARY OF THE INVENTION

A display panel, comprising a top panel, a middle panel that supports display components, a bottom panel and a mated sealing system for forming a vacuum chamber, wherein the sealing system includes offset V-grooves.

In accordance with other aspects of the invention, circuit components are embedded within the middle plate between the offset V- grooves. In accordance with further aspects of the invention, the top and bottom panels are molded or arched.

In accordance with still further aspects of the invention, the sealing system further comprises one or more of a plating, a washer, or a metallic drop. In accordance with yet other aspects of the invention, the circuit components include one or more of a fillet or prefabricated layers of conductive material for allowing internal circuit components connections to external display circuit components.

It will be readily appreciated from the foregoing summary, the invention provides a new and improved system for aligning and sealing three panel displays.

BRIEF DESCRIPTION OF THE DRAWINGS

The preferred embodiment of the present invention is described in detail below with reference to the following drawings: FIGURE 1 is a cross-sectional side view of an embodiment of the prior art;

FIGURE 2 is a front view of the display of FIGURE 1 ;

FIGURE 3 is cross-sectional side view of an embodiment of the instant invention;

FIGURE 4 is a front view of the display of FIGURE 3;

FIGURE 5 is a cross-sectional side view of another embodiment of the instant invention;

FIGURE 6 is a front view of the display of FIGURE 5; FIGURE 7 is a cross-sectional side view of the sealing structure and circuit assembly of an embodiment of the instant invention;

FIGURE 8 is a cross-sectional side view of the sealing structure and circuit assembly of another embodiment of the instant invention; and FIGURE 9 is a cross-sectional side view of the sealing structure of an embodiment of the instant invention.

DETAILED DESCRIPTION OF THE INVENTION

FIGURES 1 and 2 illustrate an embodiment of the prior art. More specifically, FIGURES 1 and 2 illustrate a cross-sectional and front view, respectively, of current, three panel display construction.

The prior art flat panel construction, such as display 20, typically uses a top panel 22, a bottom panel 26 and a plurality of side panel pieces

24. The side panel pieces 24 are arranged around the periphery and placed between the top panel 22 and the bottom panel 26, thereby creating an inner space 32. The side panel pieces 24 are typically rectangular in shape and are cut in length to extend substantially entirely around the periphery of the display 20.

The top panel 22, side panel 24 and bottom panels 26 are typically fused together by frit 28 - a glassy material that goes into solution at a relatively low temperature. Care must be taken to apply the frit 28 to all contact surfaces on the panels. When heated, the frit "wets" the contact surfaces of the glass pieces that form an airtight seal around the inner space 32 that is a vacuum. FIGURES 3 and 4 illustrate a cross-sectional and front view, respectively, of a three plate display 40. In this embodiment sealing devices are located on the contact surfaces of the three plates of the display 40. Located on the contact surfaces of the V-groove top plate 42 and the V-groove bottom plate 46, respectively, are V-groove projections 48 and V-groove recesses 50. The respective projections 48 and recesses 50 are generally centrally located on the flange portion 58 of the top plate 42 and bottom plate 46. Further, the relationship between the size of the flange portion 58 relative to the geometry of projections 48 and recesses if a function of material choice and sealing requirements. The projections 48 and recesses 50 cooperatively work to solve the above mentioned problems. More specifically, the V-groove sealing arrangement provides alignment, compensation of irregular surface conditions, flatness of contact points and reduces stresses of the display. The recesses may also be located in the top or bottom plate 42, 46. The above mentioned alignment problems are overcome by the inter-relation of the V-groove projections 48 and recesses 50. When the three plates of the display 40 are combined, the top plate 42 and the V- groove bottom plate 46 are positioned in constant relation with one another. Consequently, regardless of the specific manufacturing process used, the relation between the top plate 42 and the bottom plate 46 is a constant. This constant relation between the plates, unlike the prior art, prevents improper application of additional sealing means such as misaligned frit 28, or other additional sealing means described in more detail below.

One of the primary benefits of the three plate display 40 is the allowance of a thinner, or generally smaller, middle plate 44, than in prior art embodiments. Thus, a thinner middle plate generates a less cumbersome display that requires less time to manufacture because the heating times are reduced due to the reduced size.

A further benefit of the three plate display 40 is that the top plate 42 and bottom plate 46 is no longer related to the construction of the image. The top plate 42 and bottom plate 46 only serve to create an area for and maintain a vacuum in the inner space 32. Thus, as long as the middle plate 44 is properly situated, and an air-tight seal is maintained between the plates, critical alignment between the top plate 42 and the bottom plate 46 is not necessary. Also, the limited roll the top plate 42 and bottom plate 46 play in the function of the display 40 - creating a vacuum space -permits pre-assembly and testing of the electronics attached to the middle plate. An additional benefit of the unique sealing of V-groove three panel display is that the V-groove compensates for any irregular surface conditions. More specifically, it may be desirable to design the V-groove projection 48 and the V-groove recession 50 such that the majority of the connecting loading bares on the tip region of the V, thereby locating the bulk of the sealing properties deep within the V-groove recession 50. As such, the irregular surface conditions are largely rendered moot.

Another problem, similar to surface condition, regards the relative flatness of the connecting surfaces. As discussed above, when the relative plates are brought together, considerable atmospheric pressure related forces are acting on the plates. Due to the hollow inner space 32, and the contact surfaces being located around the periphery of the display 40, a deflection occurs around the base of the contact surfaces, thereby weakening the sealed joint. The present invention eliminates this problem in the same way the surface condition problem is eliminated. The present invention can be constructed to perform most of the sealing deep in the V- groove recess 50. Therefore, deflections at the contact surfaces are largely inconsequential.

Finally, the V-groove design eliminates the resultant build-up of internal stresses in the three plate display - a common problem in the prior art designs. As discussed above, the use of materials having different Coefficients of Thermal Expansion (CTE), or materials of substantially different masses yields different heating and cooling rates or times, which in turn generates stresses in the display. However, the present invention reduces the effective area of the contact area, and thereby eliminates the problem of excessive internal stresses. Thus, the present invention permits the use of various materials or masses, as long as the mass and material at the contact surfaces are within an allowable CTE range from one another. As shown in FIGURES 5 and 6, an alternative embodiment of the three plate display 70 is presented that employs an arched top plate 72 and an arched bottom plate 76. Another advantage of the present invention is the flexibility of design choice for the middle plate 44. As shown in FIGURE 7, the middle plate 44 is similar in design to the previous embodiment, however, it is permissible to use other middle plate 44 designs. The only critical relationship related between the three plates is that the flange portion 58 or contact area interface of the respective plates be compatible in size and CTE. The present invention does not limit the shape of the display panel. Rather, the simplicity and reliability of the present invention permits greater flexibility in the design of the display panel. As the critical sealing features are limited to the V-groove area a designer is free to shape the panel as they choose.

FIGURE 7 is an isolated illustration of an embodiment of the V- groove seal as depicted in FIGURES 3-6. As seen in FIGURE 7, a generic V-groove top plate 92 is combined with a generic V-groove bottom plate 94. Generic, in this disclosure is intended to mean a plate of any embodiment of this disclosure. The wires or conductive circuit connections 56 associated with the control of the internal components of the display are passed through the middle plate 44. More specifically, the wires 56 are passed through fillets 96a, wherein the wires are embedded within the middle plate 44 until they exit the plate 44 via exit fillets 96b near the end of the plate 44. As shown, the wires may exit the middle panel on its top or bottom surface. Any number of input/output circuit lines can be used without the wires 56 affecting the sealing integrity of the plates. Also, evident in this illustration is the offset nature of the relative

V-groove projections 48. The offset feature allows the positive sealing benefits of the V-groove system without inherently weakening the middle plate 44 by the close association of the V-groove recesses 50.

FIGURE 8 shows another embodiment with wires or other electrical contact devices 96 that are embedded in a middle plate 100 in a multi-layer display 90. This embodiment allows a high number of wires to pass from the internal portion of the display to an external portion without significantly affecting the integrity of the vacuum seal.

FIGURE 9 shows various embodiments of the V-groove seal as depicted in FIGURES 3-8. As can be seen from this illustration, an ordinary frit seal may be used with this sealing geometry. Further, the V- groove projection 48 and the V-groove recess 50 may be plated 108 with a number of materials, such as nickel, silver, or other such material having similar properties. Also shown in FIGURE 9 is a metallic drop 104, which may be used separately or in combination with the plating 108. The metallic drop 104 is generally a piece of malleable metal, such as gold, aluminum, or the like, placed in the bottom of the V-groove recess 50. The pressure exerted on the respective plates is transferred to the metallic drop 104, thereby deforming the metallic drop 104 and forming a positive seal in the V- groove. One possible combination is silver plating 108 coupled with a gold metallic drop 104, as these two metals work well together. However, any other metallic combination having similar properties may be used for plating 108 or the metallic drop 104 without exceeding the scope of this invention.

In an alternative embodiment, a washer 106 is used in place of the metallic drop 104. Because the V-groove focuses the contact pressure on the point of the V, very high deformation forces are created at that point, and deformation of the washer to fill the groove is achieved. As with the metallic drop 104, the washer 106 must have certain physical properties in order for it to function properly as a sealing device. More specifically, the washer 106 must be significantly tough enough to withstand the pressure exerted and the geometric deformation it will undergo. As well, the washer 106 must be pliable or malleable enough to form an adequate seal along the entire seam. The washer 106 is constructed from either a conducting or non-conducting material that is not of an organic nature. An example washer 106 is an indium washer. And like the metallic drop 106, the washer may be used in conjunction with plating 108 of the V-groove projections 48 and recesses 50. It is further recognized that a variety of materials may be used in the construction of the display panels. Since the geometry and construction of the sealing area permits the use of a low temperature frit, soda lime glass is no longer the only material choice. For example, a boro silicate, tempered or complex glass may be used. Also, as long as the CTE's of the materials at the critical surfaces are within tolerable ranges of one another (approximately 5%). It is conceivable that materials such as ceramics and steels may be used in the manufacture of the display panels.

While the preferred embodiment of the invention has been illustrated and described, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiment. Instead, the invention should be determined entirely by reference to the claims that follow.

Claims

1. A display panel, comprising: a top panel; a middle panel supporting display components; a bottom panel; and a mated sealing system for aligning the panels, thereby forming a vacuum chamber between the top panel and the bottom panel, the mated sealing system comprising an offset V-groove sealing structure.

2. The display panel of Claim 1, wherein a circuit arrangement is embedded within the middle plate, running between the offset V-groove sealing structure.

3. The display panel of Claim 2, wherein the top and bottom panels are molded.

4. The display panel of Claim 3, wherein the sealing system further comprises one or more of a plating, a washer, or a metallic drop.

5. The display panel of Claim 2, wherein the top and bottom panels are arched.

6. The display panel of Claim 5, wherein the sealing structure further comprises one or more of a plating, a washer, or a metallic drop.

7. The display panel of Claim 2, wherein the circuit arrangement includes one or more of a fillet or a layering for supporting the circuit arrangement within the middle plate.