Cleaning and liquid contact with solids – Apparatus – Sequential work treating receptacles or stations with means...
Reexamination Certificate
1997-12-17
2001-08-14
Stinson, Frankie L. (Department: 1743)
Cleaning and liquid contact with solids
Apparatus
Sequential work treating receptacles or stations with means...
C134S078000, C134S12200P, C134S073000, C198S780000
Reexamination Certificate
active
06273105
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to methods and apparatus for cleaning thin, sensitive substrates such as glass plates used for liquid crystal displays and solar panels.
BACKGROUND
In the art of processing articles sensitive to contamination, such as glass plates for Liquid Crystal Displays (LCD's), solar panels, etc. (hereinafter referred to as “substrates”), it is desirable to have a process that has both an efficient cleaning capability and high throughput rate.
The present art includes primarily conveyorized processing and batch processing apparatuses. Conveyorized processing has the advantage of continuous processing and a potentially high throughput rate. Present systems convey the substrate with the substrate in horizontal and/or vertical orientations. The present art includes systems with brushes or other mechanical scrubbing devices which are used to remove undesired stains and particulates from the substrate surface. Because of the forces exerted by these scrubbing devices, grippers that contact an undesirable amount of substrate surface area are employed to hold and/or convey the substrate. This contact can leave microscopic particulates on the substrate surface, which are undesirable. Also, mechanical contact is employed to remove liquid from the surface of the substrate to reduce the amount of liquid carried on the substrate to previous or subsequent processes, a phenomenon known as “dragout.” Dragout is undesirable from both the standpoint of cleaning efficiency and chemical waste treatment efficiency. In the cases where a gaseous barrier is used in place of mechanical contact, the consequence of drying the liquid prematurely on the substrate surface and depositing undesirable residues can result. Mechanical contact is also employed on the bottom surface of horizontally conveyed substrates to support the substrate from sagging or by a clamp or wheels or cylinders for vertically conveying substrates, both of which can leave unwanted microscopic debris on the substrate surfaces. As a result of these disadvantages, substrates processed with conveyorized equipment are typically only used for applications with relatively relaxed cleanliness requirements (such as glass for twisted-pneumatic(TN) LCD's), or significant portions of the substrate are not used, such as areas where wheels or clamps come into contact with the substrate.
Batch processing can overcome many of the disadvantages above regarding cleaning efficiency. For example, carrier racks or baskets can be constructed which contact the substrates primarily on the edges along the perimeter of the substrate rather than on the surfaces. In dip-tank processing, multiple immersion processes are used to treat, clean, rinse and dry the substrate. The carrier rack or basket is placed vertically into and from each process tank. The disadvantages of using this type of method are both the additional handling needed to load and unload the substrate from the carrier and also the relatively long length of time the basket or rack must be drained after each step to minimize dragout. Additionally, carriers or racks must be adjusted or re-fabricated for processing substrates of different sizes. Other batch processors sequentially perform several steps in one chamber, such as scrubbing, rinsing and drying, and as a result are relatively low in throughput. Overall, the batch-type processors typically perform with lower throughput than would be desired and/or require additional handling steps, both of which increase the cost of processing the substrates.
Therefore, there is a need for a relatively simple and cost effective method and apparatus for cleaning thin, sensitive substrates which has a high throughput rate which does not impart microscopic debris on the substrate surface and which allows minimum dragout.
SUMMARY
The invention is an apparatus and a method for using the apparatus for the fine cleaning of a thin substrate. The apparatus comprises a transporter having one or more edge contactors which move the substrate along a transport path at a uniform transport velocity by non-fluid contact with the edges of the substrate alone. One or more washing delivery fluid ejectors is disposed along the transport path for delivering washing fluids to substrates transported along the transport path. One or more supporting fluid delivery ejectors capable of delivering a supporting fluid to a substrate transported along the transport path is also provided.
In a preferred embodiment, the transporter can comprise a plurality of centrally-tapered rollers which contact the substrate along the substrate edges only. Alternatively, the transporter can comprise a plurality of movable wheels or one or more conveying belts.
Typically, the washing fluid ejectors are jet nozzles which emit a liquid washing fluid. Alternatively, spray nozzles can be used.
Typically, the support fluid is a clean gaseous material. Alternatively, liquids can be used. In one embodiment, the washing fluid and the support fluid are one and the same.
In a preferred embodiment, the invention further comprises an anti-dragout device disposed after the washing fluid ejectors along the transport path. The anti-dragout device comprises a plurality of anti-dragout ejectors disposed at an angle between about 10° and about 80° with respect to the transport path. The anti-dragout ejectors are capable of delivering a countercurrent fluid stream to the transport path such that liquid flowing past the anti-dragout ejectors is less than about 10 milliliters per square foot of substrate surface.
In another preferred embodiment, the invention further comprises a drying device comprising a first row of fluid ejectors disposed transverse to the transport path. Each fluid ejector is inclined with respect to the transport path at an angle of between about 0° and about 45°. The ratio of the center-to-center spacing to the average diameter of the fluid ejectors is between about 1.25 and about 5.
With the present invention, contact on the surface of substrates is minimized while cleaning or treating, rinsing and drying the substrate, and liquid dragout is minimized without long drain times or mechanical or gaseous contact. An efficient fluid-delivery system replaces mechanical scrubbing for debris and film removal. As a result, substrates can be processed both with efficient cleaning capability and a relatively high rate of throughput.
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Akin Gump Strauss Hauer & Feld L.L.P.
McDonald Eamon P.
Stinson Frankie L.
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