Method of reducing the reflectance of a transparent viewing screen and viewing screen with reduced reflectance
AssigneeU.S. Philips Corporation
InventorsJan Haisma, Johannes M. M. Pasmans, Pieter van der Werf, Albertus J. M. Rombouts
Life of this patent
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Abstract
A viewing screen is described, in particular the screen of a display tube, which has excellent anti-reflective properties and a method of making this screen anti-reflective. In this method the outer surface of the screen is mechanically roughened in conformity with specific requirements and subsequently an anti-reflective coating of constant thickness is applied to the roughened surface.
Claims17
A method of reducing the reflectance of a transparent viewing screen comprising first mechanically roughening the outer surface of the screen until the roughness parameters of the resultant roughened outer surface satisfies the following requirements
- 25 nm<R.sub.a <200 nm
- 50 nm<R.sub.q <250 nm
- 25 nm<R.sub.tm <1500 nm
- 25 .mu.m<S.sub.m <100 .mu.m
- wherein
- R.sub.a is the arithmetic average of the absolute difference between the surface profile and the average surface level measured along a line,
- R.sub.q is the square root of the average difference squared between the surface profile and the average surface level measured along a line,
- R.sub.tm is the peak-to-valley height difference of the surface profile averaged over a number of line intervals, and
- S.sub.m is the average distance between positive crossings of the surface profile and the average surface level measured along a line and
- then providing an anti-reflective coating on the roughened outer surface in such a manner that the thickness of the resultant coating is constant.
A viewing screen whose outer surface is provided with an anti-reflective coating, characterized in that at least the outer surface of the viewing screen is mechanically roughened, the roughness parameters satisfying the following requirements:
- 25 nm>R.sub.a >200 nm
- 50 nm<R.sub.q <250 nm
- 250 nm<R.sub.tm <1500 nm
- 25 .mu.m<S.sub.m <100 .mu.m
- wherein
- R.sub.a is the arithmetic average of the absolute difference between the surface profile and the average surface level measured along a line,
- R.sub.q is the square root of the average difference squared between the surface profile and the average surface level measured along a line,
- R.sub.tm is the peak-to-valley height difference of the surface profile averaged over a number of line intervals, and
- S.sub.m is the average distance between positive crossings of the surface profile and the average surface level measured along a line
- the anti-reflective coating on the roughened outer surface having a constant thickness and following the surface profile after roughening.
Dependencies are inferred from the claim text.