Optical element with a phototropic coating.

Technical field

The invention relates to an optical element with a phototropic coating, for example a sun protection spectacle lens.

State of the art

Optical elements with phototropic coatings, ie coatings whose coloring changes in intensity and color impression in accordance with the ambient lighting, are known for example from DE-OS 29 26 255.

This document describes two ways in which a phototropic coating can be applied to an optical element. According to one method, a mixture of the phototropic substance and an optically clear plastic material, as is also used for plastic lenses, is produced and this mixture is applied to the optical element. In the other method described, the phototropic substance is first dissolved in a solvent; the optical element is then immersed in the solution for several hours.

A disadvantage of the coatings applied according to DE-OS 29 36 255 is that the coatings are either lengthy to produce, adhere poorly and / or the optical quality of the optical element is reduced.

Presentation of the invention

The invention has for its object to further develop an optical element with a phototropic coating such that the easily applied coating adheres well and does not deteriorate the optical quality of the element.

This object is achieved in that the coating consists of a lacquer in which one or more phototropic substances are introduced.

The lacquer can be applied to the front and back of the optical element or only on one side.

In particular, it is advantageous if a protective lacquer is used as the lacquer, as is usually used to protect plastic glasses against mechanical and / or other effects. This has the additional advantage that no additional operation is required to apply the phototropic coating in plastic glasses; rather, the optical element, for example a spectacle lens, receives the phototropic coating by applying the protective lacquer which is in any case necessary to protect against external influences.

Developments of the invention are specified in the subclaims.

According to claim 2, the lacquer can have several layers, the phototropic coloring of which can be different. Mixed colors and / or colored patterns can be generated in this way. In addition, one or more phototropic substances can also be introduced into the optical element.

According to the invention, it has been recognized that in order to achieve, for example, a cosmetically appealing neutral gray or brown coloration of phototropic glasses, at least two different substances are required, the physical properties of which must be coordinated with one another in such a way that no color differences become visible during the lightening or darkening phase. This adaptation of the overall system to the desired properties can - as has also been recognized according to the invention - be carried out by suitable selection and / or variation of the respective matrix in which the various phototropic substances are embedded.

The properties of phototropic compounds, such as saturation transmission, kinetics of darkening and brightening, temperature dependence and lifespan of the phototropic effect, transmission in the brightened state and also the color impression depend to a large extent on the chemical environment of the phototropic compounds, i.e. the matrix, into the phototropic substances are introduced.

In this way, it is possible according to the invention to achieve different colors and / or different kinetics of lightening and darkening by varying the phototropic substances and / or the lacquer in which the phototropic compounds are incorporated.

Surprisingly, the many phototropic substances, if they are introduced into a lacquer according to the invention, have a longer service life with regard to the phototropic effect than when they are introduced, for example, into the plastic material of the optical element.

The optical element and / or the coating can further be colored according to claim 4 additionally in a manner known per se non-phototropically. For example, if the optical element is a spectacle lens, the lens may not be optically clear, but rather be provided with a certain "initial absorption".

Of course, both the phototropic and the nonphototropic coloring can be homogeneous or partial. In the case of sun protection glasses in particular, the coloring can be gradual, for example in such a way that the coloring decreases from the top edge of the glass towards the bottom. In the case of photroper gradual coloring, the phototropic or photochromic substances can be introduced either gradually in the coating or in the optical element itself.

Various advantageous protective lacquers are specified in claim 7. The choice of different types of lacquer and the different application methods specified in claim 8 make it possible - as already mentioned - to achieve a different response and even a different color impression with the same phototropic connection.

In addition, it is possible, for example by curing the lacquer with ionizing radiation, in the presence of initiator systems or by photoinitiators and by exposure to heat or UV radiation, the matrix of the phototropic compound and thus the properties of the phototropic compound, for example with regard to the kinetics of the coloring, life To influence saturation transmission, color etc.

In particular, it is possible, according to claim 9, to add stabilizers to the phototropic lacquer which prevent photooxidative and / or photolytic aging or destruction of the phototropic compounds introduced into the lacquer and / or the optical element, for example by atmospheric oxygen and / or UV rays or at least delay it. The stabilizers can be UV absorbers of the usual type, such as benzophenone, benzotriazole acrylic acid derivatives. Furthermore, the stabilizers described in DE-OS 33 10 388 can be used, for example.

Various possible materials for the optical element are characterized in claims 10 and 11.

Of course, a wide variety of compounds can be used as phototropic or photochromic compounds or substances, as described, for example, in US Pat. Nos. 3,562,172 and 3,578,602 or in DE-OS 29 36 255. However, the phototropic compounds according to claim 12 are particularly advantageous with regard to temperature stability and service life.

Way of carrying out the invention

The invention is explained in more detail below on the basis of comparisons with optical elements, the phototropic effect of which has been generated in a conventional manner.

Comparison 1

Flat glass panes made of CR 39 with a thickness of 2 mm are once in with the phototropic substance 1,3,3, -trimethyl-8'-methoxy-6'nitro-2'H-1'bezopyran known from US Pat. No. 2,953,454 conventional dip dyeing (analogous to DE-OS 2 347 018) and once with a coating according to the invention based on polysiloxane with a layer thickness of approx.

The table below shows the change in the optical density OD (V-weighted) and the half-life HWZ of the brightening at various temperatures after a 15-minute exposure with a 150 W XBO lamp with an illuminance of 50 klux:<tables id="tabl0001" num="0001"><img file="EP0146136A2_D0001.tif" /></tables>

In spite of minor changes in the optical density of the optical element produced with conventional dip coloring, the phototropic substance in the case of the usual diffusion coloring of the CR 39 material takes over eight times as long to brighten to half the darkening than in the case of the introduction according to the invention.

Comparison 2

Flat glass panes made of CR 39 with a thickness of 2 mm are made with the phototropic substance 1,3,3, -trimethyl-spiro (indoline-2,3'naphth (2,1-6) (1 - 6)) known from US Pat. No. 3,578,602 , 4) -oxazine) once in conventional dip dyeing (analogous to US Pat. No. 3,578,602) and once with a coating according to the invention based on polysiloxane with a layer thickness of approx.

The table below shows the darkening and brightening at 5 ° C. An illuminance of 50 klux was maintained during a 15-minute exposure. The specified transmission values ​​are V-weighted.<tables id="tabl0002" num="0002"><img file="EP0146136A2_D0002.tif" /></tables><tables id="tabl0003" num="0003"><img file="EP0146136A2_D0003.tif" /></tables>

In the case of the dyeing according to the invention, in which the phototropic substance is introduced into a lacquer, over 94% of the maximum darkening is achieved in one minute, with more conventional. In contrast, dyeing technology only 56%. The brightening is also significantly faster, a brightening to 70% of the maximum transmission is achieved in 2.5 minutes instead of only in 20 minutes.

The advantage of introducing phototropic substances according to the invention is that already known phototropic compounds can be used as sun protection filters at all or even at low temperatures.