Patent
1987-03-19
1989-08-01
Arnold, Bruce Y.
350 16, G02B 526, G02B 523, G02B 110
Patent
active
048529745
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL BACKGROUND
The invention relates to an anti-reflection film for an optical element consisting of an organic material with photochromic properties, and in particular to a spectacle lens of this type.
STATE OF THE ART
In the past a number of proposals have become known to design optical elements consisting of an organic material and, in particular, spectacle lenses consisting of an organic material with photochromic properties. In this context "photochromic" is to be understood as the property of the colour impression and of the darkening of the optical element of changing with the amount of illumination, i.e. with the intensity of the radiation.
The photochromic properties of optical elements consisting of an organic material are, as a rule, obtained by introducing organic substances with photochromic properties, for example, spiro-oxazine compounds, into the matrix of the optical element or by applying them to the optical element.
On the other hand, at present most spectacle lenses are provided with an anti-reflection film which will usually consist of several high refractive index and low refractive index layers. Up until now, the question as to which anti-reflection film is best suited to a spectacle lens consisting of an organic material with photochromic properties has not been considered in the literature. The same anti-reflection films are applied to actually developed spectacle lenses consisting of an organic material with photochromic properties as are also used for spectacle lenses consisting of an organic material without photochromic properties.
SUMMARY OF THE INVENTION
It has now been recognised in accordance with this invention that the properties of spectacle lenses consisting of an organic material into which photochromic substances have been introduced or onto which photochromic substances have been applied, can be influenced by the suitable choice of an anti-reflection film.
For this reason, it is the object of this invention to provide an anti-reflection film on an optical element consisting of an organic material with photochromic properties.
In accordance with this invention it has been recognised that an anti-reflection film of several layers for an optical element consisting of an organic material with photochromic properties must possess the following characteristics:
1. In the wavelength range between 330 nm and 380 nm the reflection should be as low as possible to ensure a sufficient stimulation of the photochromic substance or, in the case of several substances having been introduced, of the different substances.
2. In the wavelength range below 330 nm the reflection should increase steeply as radiation in this wavelength range, which also stimulates the photochromic effect, will--as has also been recognised in accordance with the invention--reduced the life of the photochromic effect.
3. In the wavelength range below 290 nm the reflection properties of the anti-reflection film no longer play a decisive role as the absorption properties of the atmosphere prevent such radiation from stimulating and so perhaps damaging the organic substances to any noticeable extent.
This means that the anti-reflection film provided in accordance with this invention differs from the films used up to now for both spectacle lenses in plastic without photochromic properties and for such with photochromic properties in that it has defined reflection properties not only in the range of visible light from 380 nm to 780 nm but also in the range from 290 nm to 380 nm. No consideration has been given up to now to the curve behaviour below 380 nm.
The film in accordance with the invention provided on an optical element consisting of an organic material and, in particular, for a spectacle lens with photochromic properties has the following advantages:
It ensures a sufficient stimulation of the photochromic effect in dependence on the pertaining amount of illumination. As a result, when the anti-reflection film according to the invention is used, the kinetics of the photochromic effect is bette
REFERENCES:
patent: 3410625 (1968-11-01), Edwards
patent: 4320936 (1982-03-01), Sawamura
M. Blanc, "Nouveaux Filtres Interferentiels pour le Proche Ultraviolet", 6-12-79, pp. 1313-1325, Optica Acta, 1980, vol. 27, No. 9.
Effer Erhard
Melzig Manfred
Arnold Bruce Y.
Callaghan Terry S.
Optische Werke G. Rodenstock
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