US3505974A - Vacuum deposition apparatus - Google Patents

Description

April 14, 1970 D. w. BARKER 3,505,974

VACUUM DEPOSITION APPARATUS Filed NOV. 12, 1968 h/ Bm KcR,

INVENTOR ATTORNEY United States Patent 3,505,974 VACUUM DEPOSITION APPARATUS Dennis Walter Barker, Crawley, England, assignor to Edwards High Vacuum International Limited, Crawley, England, a British company Filed Nov. 12, 1968, Ser. No. 775,054 Claims priority, application Great Britain, Nov. 14, 1967, 51,692/ 67 Int. Cl. C23e 11/00 US. Cl. 11848 7 Claims ABSTRACT OF THE DISCLOSURE Vacuum deposition apparatus in which the material to be processed passes from an inner vacuum chamber to an outer vacuum chamber in which processing takes place. Said inner vacuum chamber is maintained at a lower pressure than said outer vacuum chamber and an aperture between said chambers through which the material passes maintains during use the pressure difierential between said two chambers. Said material may pass from rollers in said outer chamber presenting each side to an evaporation source.

This invention relates to vacuum processing apparatus and has particular, although not exclusive, reference to roll coating plant.

In its simplest form roll coating is carried out in a single evacuated chamber, a sheet material to be coated unwinding from an initial roller, passing around a series of intermediate rollers during which time it passes over one or more evaporation sources, and being rewound onto a take-up roller. This arrangement, however, suffers from an important defect which makes it virtually impossible accurately to control and maintain any desired coating quality. When the chamber is initially evacuated practically all of the process sheet material is wound on the initial roller and large quantities of air and water vapour (that is to say, large quantities as far as a typical desired working pressure of, say, torr is concerned) are trapped between the initial roller and the material and between the turns of the material. A certain amount of outgassing-particularly water vapour-also occurs from the material itself. Even though the chamber may have been pumped to a fairly stable desired pressure prior to beginning the process, the stability is lost as soon as the material starts to unwind from the initial roller releasing pockets of air and vapour. The consequential pressure fluctuations, which will vary from one roll of material to the next, will consequently affect the quality of the coating.

This disadvantage can to a large extent be overcome by the known method of using a plurality of vacuum chambers, say three. In such a case the first chamber contains the initial roller and a number of other rollers to give the unwinding material a long path within the chamber, the second chamber has more intermediate rollers and the final chamber leads the material over the evaporation sources to the take-up roller. The three chambers are pumped to, say 1 torr, 10- torr and 10* torr respectively and are separate units side by side, the material passing through narrow slots from one chamber to the next. Clearly each separate chamber has to withstand atmospheric pressure and such a plant virtually trebles the cost of the simple plant already described.

It is an object of the present invention to provide apparatus which may be constructed so that its cost compares more nearly with that of the simple plant but provides improved coating conditions.

According to the present invention there is provided Patented Apr. 14, 1970 vacuum processing apparatus including a first evacuable chamber, a second evacuable chamber housed within the first chamber and communicating means between the interiors of the two chambers for the passage of work to be processed whilst inhibiting free passage of gases or vapours.

Such apparatus is preferably vacuum roll coating apparatus also provided with a plurality of parallel rollers over which a flexible sheet of material may pass, one of the rollers being an initial roller situated within the second chamber whilst the other rollers are situated within the first chamber and comprise a take-up roller and a series of intermediate rollers over which the material may pass in its passage from the initial roller via the communicating means to the take-up roller, and which apparatus further includes processing means within the first but outside the second chamber.

The sheet material may be the material to be processed and this might be, for instance, a polyester sheet or fabric. The processing means may suitably be two evaporation sources of, say, aluminum which are situated at positions below the material as it passes over the said series of rollers, opposite sides of the material being presented to the two sources.

The second chamber is preferably generally cylindrical and the communicating means may then be in the form of a slot through the wall of the second chamber along the length thereof. The communicating means may further include a pair of milled metal plates each of which is lined with a member of material having a low coefficient of friction, the slot being formed between the said members and the metal plates being fitted into an aperture in the Wall of the second chamber along the length thereof.

The invention will now be described in greater detail by way of example, with reference to the accompanying drawing which shows a diagrammatic open-end view of the coating chamber of a roll coating plant.

Referring now to the drawing, an outer evacuable chamber 1 capable of withstanding atmospheric pressure when pumped down to process pressures in the region of l0- torr is generally cylindrical having one end closed and provided at the other end with a removable door (not shown). The door, sealed at 2, which is mounted rollers 13 and 14 and which it itself on a jig supporting rollers 39 inclusive which are accurately aligned parallel to each other. The jig also supports an inner chamber 10 bolted to the door. The roller bearings and the chamber 10 at the end remote from the door are all supported on a metal blank 11 (shown in dotted line) which is itself supported on a rail 12 running along the base of chamber 1. The blank 11 also supports two evaporation sources 15 and 16 provided with evaporation cut- off shutters 17 and 18.

The end of chamber 10 remote from the door is itself provided with an end closure (not shown) on which are mounted rollers 13 and 14 and which is itself on a trolley (not shown) which can be run out of chamber 10. In the wall of the chamber 10 and along its length is provided a slot 19 which may be lined with a material, such as polytetrafluoroethylene, having a low coefficient of friction.

Each chamber 1 and 10 is provided with a pumping port (not shown) which is attached to a pumping unit. The chamber 1 is pumped to a process pressure, typically 10- torr, using for instance a series combination of a vapour diffusion pump, a vapour booster pump and a rotary pump. Chamber 10 is also pumped to a low pressure, although in excess of that maintained in chamber 1, using for instance a vapour dilfusion pump and a 1'0- tary pump in series.

In operation of the apparatus an evaporation material say, aluminium, is evaporated from sources and 16 with the shutters open whilst a sheet material initially wound on roller 13 passes over rollers 14, 3, 4, 5, 6, 7 and 8 to be taken up on the take-up roller 9. As the material passes over the two sources, both sides of the sheet are coated, the sheet moving at a speed in the region of 600 feet per minute.

During this time both chambers 1 and 10 are being continuously pumped, pumping of the inner chamber removing most of the air and water vapour which is evolved and is released during unwinding of the material. The pressure difference between the two chambers will tend to cause leakage through slot 19 but this can be reduced to a minimum by keeping it as narrow as possible. With a lining of PTFE the material 20 can be made to contact the lining on both sides as it passes through, the PTFE not damaging the material due to its low friction characteristics, and leakage may thus be maintained relatively low. Leakage :may further be reduced by increasing the depth of the slot. The slot may be formed by milling two metal plates and, attaching them together so that there is a slot of about /2" width. This is then permanently fitted in a vacuum tight manner into the aperture out along the wall of chamber 10. Into the slot may now be slipped a pair of preformed lining parts (PTFE) between which is the slot 19. By changing only the lining parts, materials 20 of difierent thicknesses may be used. Clearly the depth of slot 19 will only depend on the depth of the metal plates and the lining parts, and can be independent of the wall thickness of chamber 10. Thus the slot depth is really only limited by the space available. A ten inch deep slot of 10 thou. width or less may be suitable for a material having a thickness of 2 thou.

It will be seen from the above description that, by providing one vacuum chamber within the other, there is no question of the inner chamber having to withstand full atmospheric pressure. This allows for a relatively cheap two chamber plant.

The present invention as illustrated with reference to the accompanying drawing is not limited to such an arrangement or construction. Many alternatives might be considered. If there is sufiicient space, there is -not any reason why there should not be a further chamber surrounding the inner chamber, the further chamber being separately pumped. Again the material 20 might merely form a carrier on which small workpieces are mounted. In this case, as long as two workpieces are at least partially within the slot 19 at any one time, the sealing problem between the two chambers could be solved.

What is claimed is:

1. Vacuum deposition apparatus for coating a moving substrate and comprising:

a first vacuum chamber;

a second vacuum chamber housed Within said first chamber and communicating therewith through sealing means defined by a pair of blade elements incorporated in the wall structure of said second cham- 4 ber and operatively associated with said substrate passing therebetween;

said second chamber housing a supply of said substrate to be coated;

vacuum deposition means located in said first chamber;

roller means to guide said moving substrate past said deposition means in a position 'whereby said substrate is coated;

Windup means disposed in said first chamber whereby to store the coated substrate.

2. Apparatus according to claim 1 wherein said vacuum deposition means include first and second evaporation sources and said roller guide means are located so that each substrate surface is coated by a respective one of said sources.

3. Apparatus according to claim 1, in which said communicating means further includes a pair of complementary milled metal plates each of which said plates is lined with a member of material having a low coefiicient of friction, said wall of said second chamber having an aperture along the length thereof and said pair of plates fitting into said aperture defining said slot between said low coeflicient of friction lining members.

4. Apparatus according to claim 3, in which said metal plates extend in a radial direction with respect to said second chamber by an amount in excess of the thickness of said wall.

5. Apparatus according to claim 3, in which said lining members comprise polytetrafluoroethylene.

6. Apparatus according to claim 3, in which said lining members are removable and interchangeable with other lining members to give diiferent slot widths.

7. Apparatus according to claim 1, in which said first chamber is generally cylindrical having a first closed end and a second end closed by a door, said door being removable axially away from said first chamber and carrying said second chamber and said roller means.

References Cited UNITED STATES PATENTS 1,551,850 9/1925 Schmidmer et a1. 11849 X 1,819,109 8/1931 Miller 118-50 2,384,500 9/1945 Stoll 1l8-49.l X 2,622,041 12/1952 Godley 118-49 X 2,657,457 11/1953 Toulmin 11849 X 2,768,098 10/1956 Hoppe 1l849.1 X 2,971,862 2/1961 Baer et al. 1l849 X 3,043,728 7/1962 Staufler 118-49 X 3,158,507 11/1964 Alexander 118-49 3,220,378 11/1965 Lefevre et al. 1189 3,397,672 8/1968 Dykeman et al. 1l849.5 X

FOREIGN PATENTS 1,051,247 9/ 1953 France.

926,069 5/ 1963 Great Britain.

MORRIS KAPLAN, Primary Examiner

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