EP1047962A1

EP1047962A1 - Neutral-colored gray photochromic plastic object

Info

Publication number: EP1047962A1
Application number: EP99959280A
Authority: EP
Inventors: Claudia Mann; Manfred Melzig; Udo Weigand
Original assignee: Rodenstock GmbH; Optische Werke G Rodenstock
Current assignee: Rodenstock GmbH
Priority date: 1998-11-16
Filing date: 1999-11-16
Publication date: 2000-11-02
Also published as: AU1651900A; JP2002530686A; US6373615B1; CA2318239A1; CA2318239C; AU750198B2; WO2000029877A1

Abstract

The present invention relates to a neutral-colored gray photochromic plastic object that remains neutral-colored or gray during lightening or darkening of luminosity. The inventive plastic object can be used more particularly as a neutral-colored photochromic spectacle glass.

Description

'Neutral colored gray photochromic plastic object "

description

The present invention relates to a neutral-colored gray photochromic plastic object which remains almost completely neutral or gray both during the darkening and during the lightening. The plastic object according to the invention can be used in particular as a neutral-colored gray photochromic spectacle lens.

Photochromic plastic products, especially eyeglass lenses, have been on the market since the 1980s. The first glasses that became more widespread, e.g. B. Rodenstock Perfalit Colormatic (since 1 986) or that of Transitions Optical Inc. (since 1 990) colored transitions offered by several glass manufacturers

Glass contained only spirooxazines as photochromic dyes, which darkened in blue tones. With medium excitation, this together with the brownish pre-coloring of the glass resulted in an almost gray color. Later products, such as the "gray" Transitions Plus glass (since 1 992), or the brown glasses Transitions Eurobraun and Hoya Sunbrown (since 1 994) or the Rodenstock-

Glass Perfalit Colormatic new (since 1 995) already contained pyrans in addition to spiro-oxazines and / or fulgides. The products currently commercially available, such as glass Transitions III, preferably use pyrans, especially naphthopyrans and larger ring systems derived from them. The Transitions II I products with the refractive index 1, 56 are based on US 5,753, 1 46.

Various color systems were developed and defined for the objective characterization of color. The most widespread and most suitable color system for eyeglass lenses is the l_ * a * b * or CIELAB color system (1 976), in which the brightness (L *) and the color (a *, b *) are indicated by a point within one Sphere can be represented. A photochromic glass can be darkened and brightened by a continuous set of points, i.e. a curve in three-dimensional space. For the evaluation of the trans mission color of a lens, the projection of this curve onto the central plane is decisive, ie only the a * and b * values. The system is equally spaced, ie the same color differences in the system also correspond to the same visual color differences.

In this color space, a glass that is in the zero point during the darkening and brightening cycle with respect to a * and b *, and which therefore only moves along the L * axis, represents the ideal case of a neutral-colored glass. It theoretically runs through white (= colorless, since a lens, especially an eyeglass lens, is viewed in transmission and not in reflection) all grayscale up to black, ie up to complete impermeability. In all cases it is a colorless or gray glass. This mathematical target value - like the end points - is not absolutely achievable in reality, i.e. small deviations from the zero point in the a * b * plane are unavoidable.

US 5,753,146 relates to compositions comprising at least two photochromic naphthopyran compounds which are free of amino-substituted aryl groups on the carbon atom which is adjacent to the oxygen atom of the pyran ring. When activated in a suitable carrier and exposed to ultraviolet solar radiation, these compositions are said to have a gray or brown neutral color when activated, which in the a * and b * ranges from + 10 to -10 of the CIELAB- Color system is included. Measurements of the glasses described as prior art in US Pat. No. 5,753,146 have shown that their color position in the darkened state is a * ~ + 8undb * ~ +4. In the brightening phase, even

Values of a * ~ + 12 and b * = + 14 reached. For the colourfulness C *, which is defined as the root of the sum of the squares of a * and b * and characterizes the deviation from the ideal gray point, values of C * ~ 9.0 result in the darkened state, in extreme cases up to C * ~ 18.8. In this respect, it is no longer possible to speak of a color-neutral glass, but rather the strong one

Color shift during darkening and brightening to an effect called "chameleon effect". The photochromic "gray" glasses described in US Pat. No. 5,753,146 and also others in the prior art Glasses available in technology move in the darkening and brightening far away from the zero point. The color location of corresponding glasses could be restricted to smaller values by the measures described in US Pat. No. 5,753,146. The C * value was halved at 9, 26, but almost the entire color gradient takes place in the green-blue color quadrant. In this respect, the still high level of colourfulness and the blue-dominated color gradient are still far from the ideal case of a neutral-colored gray glass. A strong color gradient during darkening and brightening is therefore characteristic of the glasses known in the prior art, in particular also for the glasses described in US Pat. No. 753,146.

The present invention is therefore based on the object of providing a color-neutral gray photochromic plastic object which is almost completely color-neutral, i.e. during the darkening and during the lightening. remains gray.

This object is achieved by the embodiments characterized in the claims. In particular, a color-neutral or gray photochromic plastic object is provided which, when introduced, comprises at least two different photochromic color centers from the class of benzopyrans and higher, fused ring systems derived therefrom, the object being distinguished by the fact that it lasts for 15 minutes Exposure with 50 klux at 23 ° C according to prEN 8980 and a 1 5-minute lightening in the dark only goes through color locations whose chroma is C * <8, preferably C * <6, more preferably C * <5.

In a particularly preferred embodiment of the present invention, after a 15-minute exposure to 50 klux at 23 ° C. according to prEN 8980, the color locus of the plastic object has a C * value <5, preferably C * <4, more preferably C * <3 , on.

In a further embodiment of the present invention, the spectral transmission of the object according to the invention is in the range from 400 to 650 nm in the darkened state after exposure for 1 5 minutes with 50 klux at 23 ° C. according to prEN 8980, preferably below 25%, more preferably below 20%. The spectral transmission of the object according to the invention at 700 nm in the darkened state after exposure for 15 minutes with 50 klux at 23 ° C. according to prEN 8980 is preferably below 50%.

It is important that the transmission is as constant as possible in the central area of the visible. For example, the spectral transmission difference in the range from 41 5 to 640 nm in the darkened state after 15 minutes of exposure to 50 klux at 23 ° C. according to prEN 8980 should be, for example, less than 10%, more preferably less than 8%.

In a further embodiment, the spectral transmission according to V ^ in the completely deactivated state is preferably over 80% with a material thickness of 2 mm without antireflection coating. Photochromic glasses are all-round glasses, ideally they should replace both a colorless glass and a sun protection glass. This results in the requirement for the highest possible transmission without light excitation, e.g. at night. With anti-reflective coating, the aforementioned value enables transmission values close to or around 90%.

The plastic object according to the invention can be used as an optical element, such as a lens, whose refractive index, measured with the Na-d line, is between 1.49 and 1.76. In particular, the plastic object according to the invention is used as a spectacle lens.

Fig. 1 shows the absorption in the visible spectral range of a typical example according to the invention after 15 minutes of darkening with 50 klux at 23 ° C. according to the measurement method described in prEN 8980.

Fig. 2 shows the color locus in the a * -b * color space of the CIELAB system for a typical example according to the invention in comparison with the color locus in example 4 of US Pat. No. 5,753,146 (corresponds to the glass transition gray 1, 56) during a 1st 5-minute exposure with 50 klux according to prEN 8980 and a 1 5 minutes of lightening in the dark at 23 ° C.

According to the present invention, a photochromic plastic article is provided for the first time, which is almost completely color-neutral, i.e. during the darkening and during the lightening. actually stays gray throughout. The present invention is based on the consideration of specific selection parameters with regard to the photochromic dyes to be used in a photochromic plastic glass.

A neutral-colored gray photochromic plastic object according to the invention has, for example, the one shown in FIG. 1 reproduced spectral absorption in the visible spectral range after 1 5-minute darkening with 50 klux at 23 ° C according to the measurement method described in prEN 8980. In the range from 420 to 620 nm the spectral transmission difference is less than 1 0%, this condition is also with a tolerance of the limits of ± 1 0 nm during the

Darkening and the first 1 5 minutes of brightening are observed. If a lower absorption in the red spectral range is desired or accepted, the neutral-colored impression can also be achieved, for example, with a range reduced to 600 nm.

The color location of a photochromic plastic glass that contains more than one photochromic dye also depends on the spectral composition of the excitation light. This applies not only in the excitation phase (direct sunlight or scattered light), but also in the brightening phase for the residual light. In the context of the present invention, a standard is used below which is independent of all eventualities at the measurement location, such as the time of year and day, latitude, altitude, weather and climate conditions etc. With the sun simulator described in prEN 8980, exposure close to natural conditions is possible at different temperatures and exposure levels. The analysis of the transmission light using a diode array and EDP - as described in more detail in the technical section of prEN 8980 - allows the transmission and the color location to be determined every 3 seconds. In the context of the present invention, the color gradient Darkening over 50 minutes with 50 klux followed by 15 minutes of lightening in the dark at a standard temperature of 23 ° C.

According to the present invention, a color-neutral gray photochromic plastic object is one whose color location is constantly close to the zero point during the darkening and brightening described. All 4 quadrants of the CIELAB color system are preferably run through here. This can be done clockwise or counterclockwise or in a loop movement (shape of an eight). Since the starting point is usually only reached again by special measures (eg baking out) and not lightened within 15 minutes at 23 ° C, the color locus is usually not closed. The ideal case of a circle concentric around the zero point is not attainable, rather the shape of the color locus movement is mostly ellipsoid, square or diamond-shaped. The C * value is important for the neutral gray color. The color neutral gray photochromic plastic object according to the present

The invention has a C * value that does not exceed 8 at any point in the cycle described. The color-neutral gray photochromic plastic object according to the present invention preferably has a C * value of C * <6, more preferably C * <5.

Of particular importance for the wearer of the glasses is the color location in the fully darkened state after 15 minutes of exposure. Unlike the color loci, this becomes quasi-stationary during darkening and brightening, i.e. over a longer period of time. According to the present invention, the color-neutral gray photochromic plastic object has a color location after a 15-minute period

Exposure with 50 klux at 23 ° C according to prEN 8980 with a C * value <5, preferably with C * <4, particularly preferably with C * <3.

It is generally known that a neutral hue in additive mixing results from the mixing of at least two colors. If there are only two colors, these should be approximately complementary, i.e. the absorptions of the photochromic dyes or their maxima in the visible spectral range must be shown in the UCS color table of CIE 1 976 for 2 ° normal observers by a the "Weissfeld" straight line can be connected. With only two dyes, this means that the absorption maximum of one dye should be below approximately 495 nm, that of the other should be above approximately 570 nm. The difference between the absorption maxima of possible combinations results in values of approx. 1 00 to 1 30 nm.

Decisive for the true color locus of color-neutral gray glasses is not only the position of the absorption maximum, but the band shape of the absorption in the visible spectral range. In contrast to oxazines, pyrans have a very broad “soft” structure-free absorption band in the visible spectral range. In addition, various pyrans, for example those described in WO 98/28289, have two absorption bands in the visible spectral range, the shorter-wave ones having almost the same intensity as the longer-wave ones. These compounds are preferably used when the second dye is to have a clear absorption even in the very long-wave visible spectral range around 700 nm. If such a broad absorption is desired, three or more photochromic compounds are preferably used.

In order to prevent photochromic plastic glasses from being exposed to different exposure conditions, e.g. early in the morning or late in the afternoon compared to the midday sun, showing different colors, UV absorption is of crucial importance. UV does not only mean the pure UV range up to 380 nm, but also the very short-wave visible light up to about 400 nm. The location of the UV maximum is less so than

The shape of the UV absorption bands is crucial. The absorption and concentration of the dyes must be selected in such a way that no dye alone takes up more than 60% of the intensity of the excitation light above 380 nm.

If a dye has several almost equally intense absorption bands in the visible range that reliably cover the wavelength range from 420 to 580 nm, a photochromic dye is already a neutral-colored glass possible. This has the additional advantage that all factors that impair a neutral color during the darkening and brightening, such as different darkening and brightening speeds, are excluded. In this case, the color is not influenced by the temperature (no different temperature dependency) or the spectral composition of the excitation light (no different excitation spectra).

In principle, photochromic plastic glasses can be manufactured in three different ways. On the one hand, the photochromic dyes can be distributed homogeneously in the mass of the plastic glass. Alternatively, they can (usually only on the convex side) be introduced into the surface of the plastic glass using heat by diffusion. Furthermore, they can be applied in a layer on the plastic glass. Concentrations can be determined for the former and the latter type of production according to the individual data of the individual photochromic dyes, for diffusion-colored ones

Additional key figures are necessary for glasses. In addition to the dyes, the specially used plastic matrix, the rate of diffusion and the depth of penetration of the dyes are also decisive here. Furthermore, the dyeing time, dyeing temperature, the type of intermediate support (lacquer) used, and even the polymerization conditions of the plastic glass are important.

As already described above, the ideal solution for providing a neutral-colored gray photochromic plastic object would be a single photochromic dye with the corresponding absorption properties. In addition to the advantages mentioned above, all the problems mentioned below would also be

Measures to match the dyes no longer apply. At the moment, however, no single photochromic dye with only one color center is known that even approximates this property. In this respect, at least two photochromic color centers are currently always required. In the context of the present invention, however, it is considered that the at least two color centers can be present in a single molecule in which these color centers are covalently linked to one another, for example via spacer groups, such as alkyl chains, as described, for example, in DE 44 20 378 . According to the teaching in US Pat. No. 5,753,146, a glass is colored with two pyrans, which have similar absorption maxima in the UV range, saturation absorptions, darkening and brightening rates and their long-wave absorption maximum at 425 nm and 540 in the visible spectral range nm, a particularly preferred example. As already mentioned, such a glass is never gray or brown, but red to red-violet. It is completely ignored in US Pat. No. 5,753,146 that pyrans in particular with Λ _max > 525 nm are often distinguished by two or more absorption maxima in the visible spectral range. These must be taken into account if their intensity is more than approx. 50% of the main band. Furthermore, not only the position, but also the shape or width of the absorption band (s) is of eminent importance. In US Pat. No. 5,753,146, the individual dyes and the mixtures are introduced into different plastics and according to different dyeing processes. This makes little sense, since photochromic dyes, especially in the polar open form, show solvatochrome effects. This means that / i _{max is} used

Depending on the plastic matrix. This also applies to sensitivity to light and saturation absorption, but above all to the speed of lightening.

Therefore, to produce the plastic object according to the invention, the individual dyes to be used must be tested in the plastic in which the

Mixture should be used. In the case of diffusion, the procedure is such that all the coloring parameters also correspond to the process used later in the production. First, with regard to the individual dyes to be used, full UV-VIS spectra in the range from 300 to 780 nm have to be recorded in absorption (extinction), both in the unexposed and in the exposed state after exposure for 15 minutes at 23 ° C. The difference can result from this spectral ΔOD curve are created (OD = optical density). The concentration of the dyes in the test specimens can then be adjusted such that approximately equal values are achieved in AOD-l_- _ax VIS.

To produce a plastic object according to the invention, the selection must then be made according to the spectral absorption behavior in the UV range. Here, as already mentioned, is not only / i _max UV, but the total UV absorption is crucial. First, the absorption (extinction) in the unexposed state is assessed. Since some of the photochromic dyes in question still absorb well beyond the UV limit, which is generally applied at 380 nm, the UV range here means the wavelength range <41 0 nm, in which the spectral sensitivity to light of the average human eye is still below about 0.1% of the maximum value. Then the absorption function is folded with the spectral distribution of the solar radiation E _sA (Λ) if the use of the photochromic plastic _object under natural sunlight is the main application. You can do this from the values

"proposed standard solar-radioation curves for engineering use", J. Franklin Inst. 230 (1 940). The spectral distribution of the radiation from the respective excitation light source is to be used for other purposes. Only those dyes are selected for common use whose absorption integrals assessed in this way differ from one another by no more than a factor of 2. This is then repeated in the same way for UV absorption (extinction) in the exposed state.

The absorption behavior in the visible spectral range is then used to produce a plastic object according to the invention. For each

Dye the absorption range can be determined, in which the absorption ΔOD min. 80% of the / l _max VIS value. To produce a plastic article according to the invention, the dyes are selected such that the absorption ranges cover the spectral range from 420 to 600 nm in such a way that the differences and / or overlaps at the limits are <10 nm. Insofar as two or more dyes are used, absorption envelopes are to be calculated for dyes whose Λ _ma) NIS difference is <50 nm. These can be treated like the absorption curves of the individual dyes.

For the production of a plastic article according to the invention, the saturation absorption is not of the importance as described in US Pat Mix can be adjusted. It is also a function of the lightening speed, i.e. slower brightening photochromic dyes always have higher ΔOD values in saturation than faster brightening dyes of a related structure. Since inefficient photochromic dyes cannot be used economically, commercially available dyes in ΔOD _Sätt only differ by a maximum of about a factor of 2, as is also shown in Table 1 in US Pat. No. 5,753,146. Since the absorption is an exponential function for concentration according to the Lambert-Beer law, this can be achieved with small concentration variations (at least as long as you are still in the approximately linear range).

This allows the conditions of the neutral color impression to be fulfilled in the fully darkened state, which - as mentioned above - is of particular importance for the wearer of the glasses, since he is quasi-stationary, i.e. over a longer period of time. For the neutrality of the color locus during the entire darkening and lightening process, further parameters have to be taken into account in the production of a plastic object according to the invention, such as in particular the reaction rate of the dyes during darkening. Darkening over time is not a linear function. Photochromic plastic lenses currently available reach among these

Measurement conditions at 23 ° C after 1 minute about 60 to 76% of the maximum darkening after 1 5 minutes exposure (calculated in ΔOD). The 50% value is reached after 1 7 to 40 s. However, an assessment of the absorption after 5 s and an extrapolation to the value for one minute, as proposed in US Pat. No. 5,753,146, gives an incorrect picture in this regard. After this time, only 1 5 to 25% of the final value is reached. "High flyers" among the dyes that are overtaken by the rest after 10 seconds and therefore cannot have a dominant influence on the color impression are thus overrated. Absolute values are not very useful even with this parameter, rather the mutual relationship is important. To produce a plastic article according to the invention, the procedure can be such that the time in which the photochromic dye in question reaches 50% of the final value is evaluated. The faster (fastest) darkening Dye should not undercut the slower (slowest) darkening dye by more than about 30%.

For the production of a plastic object according to the invention, the coincidence of the lightening times is extremely important. The lightening or half-life is the time that the dye in the plastic article needs at 23 ° C to reach half the absorption difference between the unexposed state and the state after 15 minutes of exposure. In order to obtain the neutral color impression over a 1 5-minute lightening phase, the relative difference should not exceed 25%. In contrast to the teaching in US Pat. No. 5,753,146, the absolute value or the absolute difference is meaningless for the neutrality of the color, rather the intended use of the plastic object determines the framework for the absolute value of the brightening rate.

Since the expert does not have an unlimited selection of photochromic dyes

Is available, is the ideal case described at the beginning in the prior art, i.e. an absolutely neutral glass, the color location of which is always at the zero point during the darkening and brightening cycle with respect to a * and b * and only moves along the L * axis, can only be achieved theoretically, however the procedure described here leads to the production of a Plastic article according to the present invention, which for the first time approaches this ideal case largely, i.e. to an actually neutral colored gray plastic object or plastic glass.

It is possible to place the color location in the fully darkened state in the zero point of the a * b * coordinate system, but a deviation cannot be avoided for the other color locations. However, such deviations are harmless or are no longer perceived as color deviations even by the color-trained spectacle wearer if the chromaticity C * or chromaticity difference ΔC * is approximately 1 or less. This is understandable in that the color states are seen one after the other and not next to each other.

In Fig. 2 is the color locus in the a * -b * color space of the CIELAB system for a typical example according to the invention (mass-colored in the plastic material TS-1 50 from Tokuyama) and for example 4 from US Pat. No. 5,753, 1 46 as a representative comparative example (surface-colored in CR-407 from PPG) during a 1-minute exposure to 50 klux according to prEN 8980 and a 1 5-minute lightening in the dark at 23 ° C.

The color C * of the comparative example is 1 0.5 in the fully darkened state, whereas the value of the example according to the invention is C * <3. Furthermore, a C * value of 5 is never exceeded during darkening and brightening.

The procedure for producing a neutral-colored gray photochromic plastic object according to the invention is explained in more detail below.

With regard to the production of the samples and the measuring apparatus, reference is made to PCT-DE 98/02820.

The plastic object according to the invention contains one or more plastic materials as a carrier or matrix for the photochromic dyes to be used or used. The plastic materials used can be the plastics which can usually be used in the prior art, in particular for ophthalmic purposes. For example, the plastic material made of poly (C ₁ -C ₁₂ alkyl) methacrylates, polyoxyalkylene methacrylates, polyalkoxyphenol methacrylates, cellulose acetate, cellulose triacetate, cellulose acetate propionate,

Cellulose acetate butyrate, polyvinyl acetate, polyvinyl alcohol, polyvinyl chloride, polyvinylidene chloride, polycarbonates, polyesters, polyurethanes, polyethylene terephthalate, polystyrene, poly-σ-methylstyrene, polyvinyl butyrate, copolyfstyrene-methyl methacrylate), copoly (styrene-acrylonitrile) and polymers consisting of constituents of the group consisting of poly, the group consisting of polyesters allyl carbonate) monomeric, polyfunctional acrylic, methacrylate or diethylene glycol dimethacrylate monomers, ethoxylated bisphenol-A dimethacrylate monomers, diisopropenylbenzene monomers, ethylene glycol bis methacrylate monomers, poly (ethylene glycol) bis methacrylate monomers, ethoxylated phenol methacrylate monomers, alkoxylated polyalcohol acrylates and diallylidene pentaerythritol monomers or mixtures thereof.

First of all, all the characteristic values of the photochromic compounds in question must be in the material for the neutral gray according to the invention

Plastic object is provided to be measured. Depending on the method with which the photochromic staining is to be carried out, the test specimens for the characteristic values can be produced in different ways. In the case of bulk coloring, i.e. the addition of the photochromic dyes before the polymerization, the following method has proven to be particularly advantageous. The dyes are the finished cast resin batch (monomers, initiator, possibly additives such as antioxidants, UV absorbers) in a concentration of 0.01 to 0.1 wt .-%, preferably 0.03 to 0.06 wt .-%, admitted. The polymerization of these test specimens takes place in the same polymerization program that is intended for the final plastic object. To determine the excitation maximum in the UV or short-wave visible spectral range, the dyes must be mixed in the same way in a cast resin batch without additives. In the case of photochromic coloring of the plastic object by means of a coating, the concentration depends on the thickness of the coating. For example, 2 wt.

%, for 40 .m 1 wt .-% proved to be suitable. The product of the concentration of the dye in the fully cured layer in% of the layer weight and the layer thickness should preferably have the value 4 x 10 ^"7 m. If photochromic surface coloring by thermal diffusion is provided for the plastic object, the concentration is only directly with enormous effort to determine, for example by quantitative analysis or by UV absorption of concentration series, but it has proven to be sufficient to adjust the dyeing conditions (temperature program) for a dye whose absorption maximum is in the visible spectral range at about 550 nm so that the test specimen before and after standard exposure one

Absorbance difference of 0.7 has - evaluated in ΔOD according to V ^, the spectral sensitivity of the human eye. All other samples are then exactly the same staining parameters with the other photo- chrome dyes

The test specimens are measured, as described in the experimental part of prEN 8980, in a kinetic bench. The measuring light passing through the test specimen should be able to be analyzed in quick succession for transmission and color location, e.g. using a diode array spectrometer. The result of this measurement is the color location of the test specimen before the exposure and at any time during the exposure and the brightening phase. This usually takes place in the dark. Depending on the application of the plastic object, this can also be done under standard type A (incandescent lamps) or under weakened exposure (shadow condition) A spectral analysis is carried out at least before the exposure, at the end of the exposure and at the end of the measurement, that is to say an absorption spectrum in the range from about 350 to 800 nm is recorded. The conditions for simulating natural lighting by sunlight, such as

Intensity and spectral distribution of the excitation light are recorded in prEN 8980. For glasses, a measuring temperature of 23 ° C and an exposure intensity of 50 klux have proven to be useful. However, other temperatures or exposures are also possible - according to the later main application of the plastic object. If the photochromic

If the object is to be used in a further temperature range, the temperature dependence of the photochromic effect is generally also important. In this case, the samples are measured at two temperatures that at least cover the later control range. Include 80%. In the case of spectacle lenses for European markets, these are, for example, 10 ° C. and 35 ° C. If the fatigue of the photochromic reaction due to aging is important for the object according to the invention, the samples are subjected to artificial aging (for example 50 hours in a Suntest device from Fa . Heraeus) measured again.

The following data are then taken from the spectral measurements - the longest wave excitation _maximum in the UV (UV _max ) from the spectrum in the unexposed state and the longest wave absorption value from the last spectrum at the end of the exposure, which generally corresponds to the fully activated state. maximum in the visible spectral range (VIS _may ) The difference in optical density (ΔOD) measured at VIS _max with regard to the fully activated state compared to the unnoticed state is referred to as L _max . The difference after 15 s exposure to the unexposed state is referred to as L _e . The quotient of L _e through L _max is V _e. In the brightening, the time Z _a which the test body needs to lighten in VIS _max from the fully darkened state in the optical density by the value L _max / 2 is the decisive parameter The value Z _a is given in seconds

If the temperature dependency is also required, the absolute one delivers

Difference of the L _max values for both limit values, divided by the average value of both L _max values, the corresponding characteristic value T _a This is all the more large, the high is the temperature dependence of the sample patterns, the quotient of L _max - values of the samples after and before aging is called aging value A.

The photochromic dyes are then arranged in a table in a first column according to their VIS _max value. The corresponding Z _a values are entered in a second column and the V _e values in a third column. The UV _max values are listed in a fourth column. The temperature dependence T _a can be entered in a fifth column and the aging value A can be entered in a sixth column

For a neutral gray object according to the invention, photochromic dyes are used as the basic dye, the VIS _max value of which is above 550 nm, ie. one or more substantially blue naphthopyran dyes as set forth below. Since the spectral perception of light of the human eye is greatest at this wavelength and its product with the standard illuminant D 65 at 620 nm essentially corresponds to that at 500 nm, the subjective impression of the photochromic reaction, i.e. Intensity of darkening, speed of darkening and brightening, etc., mainly characterized by these dyes. These and the remaining dyes are therefore divided into two groups. The selection of one (or more) photochromic dyes from this group of long-wave dyes forms as follows cited, the basis of the neutral gray plastic object according to the invention. The selection is made according to the requirements regarding the reaction speed of the darkening and lightening, the temperature dependency and the aging resistance. VIS _max values around 590 nm have proven to be particularly preferred. Will only be a photochromic

If dye is selected from the group above 550 nm, VIS _max values above 620 nm and below 570 nm have proven to be unfavorable. In both cases the color correction is difficult, in the second case the permeability in the red spectral range is usually so high that color distortion occurs in extreme darkness, for example when skiing. Become two or more

If dyes are selected from this group, the mean values of their characteristic values (Z _a , V _e , T _a , A) can be treated like the characteristic values of a single dye, provided their relative values do not differ by more than 15%. Otherwise, the further dyes to be added must be selected for each individual, appropriately selected basic dye, as shown below.

Different criteria are not valid for a neutral gray plastic object according to the invention - in contrast to the information given in US Pat. No. 5,753,146, others, however, are more restricted. Above all, it is not the absolute but the relative deviations of the dyes that are important. L _max , the maximum darkening performance of the dyes, is of no importance. For the examples selected in US Pat. No. 5,753,146, ΔL _{max is} 0.01. According to the invention, those with ΔL _max > 0.2 (or rel. 30%) can also be selected. All other photochromic dyes whose V _e and Z _a values are more than 30% of those of the reference dye, i.e. the basic dye. A deviation from rel. up to 50%, as in the examples of US Pat. No. 5,753, 1,46, prevents the gray color from being maintained during the darkening and lightening. The absolute size, however, is irrelevant for maintaining a neutral gray color.

If the temperature dependency is important, the remaining, available photochromic dyes all those whose T _a value deviates by more than 30% from that of the reference dye are deleted. If the resistance to aging is important, all those are deleted from the remaining ones whose A value deviates by more than 20% from that of the reference dye. When using the photochromic according to the invention

Object under greatly varying illumination conditions, especially with very different spectral relative intensities in the UV and short-wave range, such as in spectacle lenses, is also the UV_- _ax value critical. The ratio of the intensity of the shortwave radiation at 360 nm and 390 nm ₍₃₆₀ l / l ₃₉ o) ^'st example, in Großstadtsmog much smaller than in the

High mountains. If the neutral gray color according to the invention is to be maintained not only under normal light, but also under these opposing conditions, the UV _max values may not deviate from that of the reference dye by more than 15 nm.

Starting from, for example, 1 00 photochromic dyes from the group of benzopyrans and higher fused ring systems derived therefrom, such as e.g. Naphthopyran dyes, which are readily available to a person skilled in the art, are reduced according to the preceding criteria - depending on the selected reference dye or base dye - the number of

Production of the neutral-colored, gray plastic object according to the invention further photochromic dyes to be mixed regularly to less than a dozen. The absorption spectrum of the reference dye in the fully activated state is then used to further narrow down the further photochromic dyes required to achieve a photochromic plastic object according to the invention. From a physical point of view, an ideal gray glass has a constant absorption over the entire visible spectral range from 380 to 780 nm. However, due to the spectral sensitivity of the human eye to light, this is not necessary from a physiological point of view. The areas below 430 nm and above all above 680 nm are of minor importance. First, the wavelengths are determined in which there is a relative absorption minimum. Then the dyes with the corresponding VIS _max - Values selected that are suitable to close this absorption gap. If, according to the previous restrictions, the selection is too small to find an exactly matching dye, an appropriate dye mixture is used to fill such an absorption gap. The total concentration used is about 25 to 40% by weight of the reference dye. For most applications, e.g. B. for use as sun protection glasses in glasses, the concentration of the reference dye necessary for sufficient darkening is outside the scope of Lambert-Beer law.

The photochromic compounds which can be used for the present invention all belong to the class of benzopyrans and higher, fused ring systems derived therefrom, such as, for. As naphthopyrans or fluorenopyrans. For the upper wavelength range there are mainly [2H] -naphtho (1, 2-b) -pyrans which are aromatic or heteroaromatic substituted in the 2,2-position, for the lower one

Wavelength range in the 3.3 position correspondingly substituted [3H] -naphtho (2, 1-b) pyrans. Long-wave absorbing dyes which function as reference dye or basic dye (Λ _max > 550 nm) can be, for example, the naphthopyrans described in PCT-DE 98/02820 and the lndeno [2, 1-f] naphtho described in PCT / EP 99/05258 [1, 2-b] pyran derivatives and / or spiro-9-fluoro-no [1, 2-b] pyane derivatives. As preferred examples of this can be

3, 1 3-diphenyl-3- (4-diphenylaminophenyl) -1 3-hydroxy-6-methoxy-indeno [2, 1-f] - naphtho [1, 2-b] pyran, 1 3- (2.5 -Dimethylphenyl) -3- (4-diphenylaminophenyl) -1 3-hydroxy-6-methoxy-

3-phenyl-indeno [2, 1-f] -naphtho [1, 2-b] pyran,

1 3- (2,5-Dimethylphenyl) -3- (4-diphenylaminophenyl) - 1 3-hydroxy-3-phenyl-inde- [2, 1-f] -naphtho [1, 2-b] pyran, spiro -9-fluoren- 1 3 '- [3- (4-dimethylaminophenyi) -6-methoxy-3-phenyl-indeno [2, 1 - f] naphtho [1, 2-b] pyran],

Spiro-9-fluoren-1 3 '- [3- (4-dimethylaminophenyl) -3-phenyl-indeno [2, 1 -f.naphtho-

[1, 2-b] pyran],

Spiro-9-fluorene-1 3 '- [3- (4-diphenylaminophenyl) -6-methoxy-3-phenyl-indeno [2, 1 - f] naphtho [1, 2-b] pyran],

Spiro-9-fluoren-1 3 '- [3- (4-diphenylaminophenyl) -3-phenyl-indeno [2, 1-fnaphtho- [1, 2-b] pyran],

Spiro-9-fluoren-1 3 '- {3- [4- (N-morpholinyl) phenyi] -6-methoxy-3-phenyi-indeno [2, 1 - f] naphtho [1, 2-b] pyran} ,

Spiro-9-fluoren-1 3 '- {3- [4- (N-morpholinyl) phenyl] -3-phenyl-indeno [2, 1-fnaphtho- [1, 2-b] pyran},

Spiro-9-fluoren-1 3 '- {6-methoxy-3-phenyl-3- [4- (N-piperidinyl) phenyl] -indeno [2, 1 - f] naphtho [1, 2-b] pyran} and spiro-9-fiuoren- 1 3 '- {3-phenyl-3- [4- (N-piperidinyl) phenyl] -indeno [2, 1 -fnaphtho-

[1, 2-b] pyran} can be mentioned.

The shorter-wave absorbing photochromic dyes that can be combined with the base dye are, for example, 3- (4-diphenylaminophenyl) -3- (2-fluorophenyl) -3H-naphtho [2, 1-bpyran,

3- (4-Dimethylaminophenyl) -3- (2-fluorophenyl) -3H-naphtho [2, 1 -b] pyran, 3- (2-fluorophenyl) -3- [4- (N-morpholinyi) phenyl] -3H -naphtho [2, 1 -pyran, 3- (2-fluorophenyl) -3- [4- (N-piperidinyl) phenyl] -3H-naphtho [2, 1 -pyran, 3- (4-dimethylaminophenyl) -6- (N-morpholinyl) -3-pheny! -3H-naphtho [2, 1-bjpyran, 6- (N-morpholinyl) -3- [4- (N-morpholinyl) phenyl] -3-phenyl-3H-naphtho [ 2, 1 -bjpyran,

6- (N-morpholinyl) -3-phenyl-3- [4- (N-piperidinyl) phenyl] -3H-naphtho [2, 1-bjpyran 6- (N-morpholinyl) -3-phenyl-3- [4 - (N-pyrrolidinyl) phenyl] -3H-naphtho [2, 1-bjpyran, 3-phenyl-3- (2-fluorophenyl) -3H-naphtho [2, 1 -bjpyran, 6- (N-morpholinyl) -3 , 3-diphenyl-3H-naphtho [2, 1-bjpyran and

6- (N-Morpholinyl) -3- (4-methoxyphenyl) -3-phenyl-3H-naphtho [2, 1-bpyran.

However, the pyrans described in US 5,753, 1 46 and EP-A-0 562 91 5 can also be used. It is for someone working in this field

Those skilled in the art are familiar with adding or mixing in small amounts of photochromic dyes of other classes, for example oxazines or fulgides, such as, for example, the oxazines described in US Pat. No. 5,753,146, without the Leave the essence of the present invention. Further usable Oxazine M _max > 600 nm) are sold by HCH James Robinson. For purposes in which there is no long-term long-term exposure or this only plays a subordinate role, small amounts of fulgides can be added, for example from the company Tokuyama are offered, their /. _max value should exceed 570 nm.

While the information or measures described in the prior art for providing a gray plastic glass were inadequate or even misleading, the above-described procedure leads to the object according to the invention, an actually neutral-colored gray photochromic plastic object, which both during darkening and during the brightening remains almost completely neutral in color or gray. Any minor corrections are in the specialist knowledge of an average specialist.

Claims

"Neutral colored gray photochromic plastic object" claims

1 . Neutral-colored, gray, photochromic plastic object which, when incorporated therein, comprises at least two different photochromic color centers from the class of benzopyrans and higher, fused ring systems derived therefrom, the object being exposed to 50 klux at 23 ° C. for 15 minutes in accordance with prEN 8980 and a first 5-minute lightening in the dark only goes through color locations whose chroma is C * <8.

2. Plastic object according to claim 1, wherein the chromaticity of the color loci is C * <5.

3. Plastic object according to claim 1 or 2, wherein the color locus of the

Object after a 1 5-minute exposure to 50 klux at 23 ° C according to prEN 8980 has a C * value <5.

4. Plastic object according to claim 3, wherein the color locus has a C * value <3.

5. Plastic object according to one of claims 1 to 4, wherein its spectral transmission in the range from 400 to 650 nm in the darkened state after 15 minutes exposure to 50 klux at 23 ° C according to prEN 8980 is below 25%.

6. Plastic object according to one of claims 1 to 5, wherein its spectral transmission at 700 nm in the darkened state after 1 5 minutes of exposure to 50 klux at 23 ° C according to prEN 8980 is less than 50%.

7. Plastic object according to one of claims 1 to 6, wherein its spectral transmission according to V ^ in the deactivated state at 2 mm material thickness without anti-reflection is over 80%.

8. Plastic article according to one of claims 1 to 7, which is a spectacle lens.