Chemistry: electrical and wave energy – Processes and products – Coating – forming or etching by sputtering
Patent
1995-09-29
2000-11-07
McDonald, Rodney
Chemistry: electrical and wave energy
Processes and products
Coating, forming or etching by sputtering
20419212, 20419216, 20429811, 20429815, 20429819, 20429826, 118500, 118504, 118505, 118721, 118728, C23C 1435, C23C 1450
Patent
active
061431435
DESCRIPTION:
BRIEF SUMMARY
The invention relates to the provision of masking means for certain surfaces of substrates when other surfaces of the said substrates are coated by a Physical Vapour Deposition system (PVD) wherein the deposition of material is applied by sputtering of the material onto the surfaces to be coated.
In particular the invention relates to improvements in the application of coatings to substrates such as optical lenses and other articles of similar dimensions. The lenses can be used for many purposes, including use in spectacle frames, and may be formed from glass or a plastics material.
In any sputtering process there is a prevalence of material moving onto and around the surface of the substrate which is being coated. Although, as in the coating process described in our clients co-pending application PCT/GB92/00071, considerable control of the sputtering process can be achieved to obtain the best possible coating finish on the coated surface it has been found that it is not possible to completely control the path of the sputtered material.
To briefly describe a sputtering coating process and with reference to the applicants' machine and apparatus described in their co-pending application, there is typically provided a plurality of substrates, in this case lenses, mounted in lens holders and received in a disc holder which in this embodiment is held in a horizontal plane in a chamber. In proximity to the disc there is provided at least one magnetron and target, the target containing the material which it is desired be sputtered onto the lens, typically as an oxide, and the magnetron induces sputtering of the material when the chamber is in vacuum. Typically the machine is preprogrammed such that after the lens holders have been placed on the disc the machine is operable to apply a first "adhesion" layer of material and then at least one coating of the desired material oxide onto a surface of each of the lenses by activating sputtering of the target as the disc holder is rotated. The sputtering of the material is then followed by rotating the disc and substrates through a reactive plasma from an unbalanced magnetron which encourages a chemical reaction such as oxidation to occur in the material to arrive at the desired coating on the surface. In the case of the applicant's machine and other, similar machines, there is provided means for coating both optical surfaces of the lens wherein when the first surface of the lens is coated, the lens is turned over and the second surface is coated.
While this and sputter deposition machines in general have been found to be of commercial value it has been found that problems exist with the occurence of sputtered material landing on the second surface of the lens during sputter coating of the first surface of the lens, and vice versa. This is known as back-scattering and can cause problems once the first surface has been coated and, if required, the lens is turned over to perform the coating of the second surface of the lens. In the event of the second surface being required to be coated an adhesion layer is applied thereto and this layer will, in some instances, not adhere to the surface due to the irregularities caused by the backscattered material which has been applied therein during the coating of the first surface.
Furthermore, it has been found that the lenses which are affected by the backscattering problem can subsequently be rejected after a period of time due to inferior optical quality. The reduction in optical quality occurs over a period of time after substantial use of the lens as part of, for example, to spectacles where loss of the coating can occur and accelerated lifetime tests have shown that coating loss and poor optical quality occur on the second surface which has been subjected to back-scattering.
While the problem can exist with the coating of any lens it has been found to be particularly prevalent when lenses are mounted in position in the apparatus for coating of the surfaces and a gap exists between the second surface of the lens and the lens hol
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Spencer Alaric Graham
Walls John Michael
Waugh Alan Robert
White Norman Henry
Applied Vision Limited
McDonald Rodney
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