Photochromic Film

The invention relates to a photochromic film, the preparation and use of such a film, objects covered by such a photochromic film, such as window panes, and devices comprising objects covered by such a photochromic film, such as windows.

Background of the Invention

Photochromic materials in which a color change is induced by light are known from a number of applications, wherein said color change is caused by inorganic as well as organic pigments or dyes. In particular, such materials have been known from glasses that grow increasingly dark as the solar irradiation increases. For this purpose, the glass was first colored with inorganic pigments which were thereby embedded and protected from environmental influences and had a long life. In consequence of the need for light-weight comfortable glasses, organic photochromic lenses were also developed. Such lenses usually contain organic photochromic compounds which may also be used in other systems, such as optical switches or memories. A survey of organic photochromicity and compounds suitable therefor can be found, for example, in Heinz Dϋrr, Angew. Chem. 2004, 116, p. 3404-3418. It is also known therefrom that organic photochromic dyes fatigue and are destroyed by oxidation, in particular. An important characteristic used to characterize photochromic compounds is the number of cycles. Thus, the C ₅ o indicates after how many coloring/decoloring cycles the initial absorption value is reduced to half.

To improve the stability and number of cycles of photochromic systems, a wide variety of works have been performed, in which it was tried, in particular, to find advantageous organic photochromic dyes, as described, for example, in US 2004/0267013, US 6,686,468, US 6,683,709 and EP-A-945451. Further experiments were directed to adjusting the matrix in which the photochromic dye is embedded, as described, for example, in WO 99/15518, US 2004/0138382, EP-A- 1099743 and US 6,171,525. Further, photochromic dyes can be introduced in inorganic-organic hybrid polymers, so-called ORMOCERs. Such photochromic layers prepared by sol-gel coating are described in U. Posset et. al. in Materials Science (2002), 20(1), 95-104, and H. Schmidt et. al in Materials Research Soc. Symp. Proceedings (1999) 576, p. 409-414, and WO 01/90268. As the preferred embedding method, it states bulk coloring, for example, the introduction of the dye in the whole bulk of a plastic lens, for example, but the dye may also be applied thereto

as a thin coating. WO 05/014739 mentions a further layer for improving the scratch resistance over said photochromic layer. According to US 2005/0026072, certain phototropic compositions can be cast by various methods upon support materials which may consist, for example, of glass, steel, ceramics or plastic materials and which can be subsequently employed on any surfaces, such as windows or sunroofs, directly in this composite or after detaching the phototropic layer. A film material containing a photochromic layer is also known from WO 04/106662, wherein its surface has such a shape that it absorbs the noise of falling rain when applied to roofs. For further improving the stability, EP-A-1099743 discloses that the dye is surrounded by a supramolecular protection coat, and from US 5,498,686 it is known to add antioxidants or singlet oxygen quenchers to a photochromically colored lens or to coat it by vapor-deposition with comparably gas-tight inorganic layers, such as quartz. An oxygen barrier layer for photochromic plastic articles which is prepared by plasma polymerization and is supposed to be superior to the previously mentioned quartz is described in DE-A-4220251.

From DE-A-4024330, films colored with photochromic substances are known which are suitable, in particular, as intermediate films for laminated safety glass panes. Similar systems are described in US 4,962,013. The known phototropic materials are still unsatisfactory in terms of their weather resistance, especially light resistance, especially if they are to be employed as high quality window films for automatic shading adapted to solar irradiation. Since the application of such window films requires a high manual expenditure, it is expected that their stability should be very high and the films can be exposed to environ- mental influences at the window for several years without considerably losing their function. However, this is not satisfactorily ensured by the photochromic films of the prior art since the photochromic substances in such films are decomposed too quickly.

One particular problem is the fact that the user desires a window film that con- stantly darkens to neutrally gray. However, with usual dyes, coloring to gray is only possible by mixing several dyes. Since the different dyes are destroyed to a different extent in the course of time, there is selective bleaching, and the film obtains an increasingly growing color fault that strongly limits its useful life.

Laminate glass materials having glass on both sides of the phototropic layer show a good stability. However, such systems are not suitable for the later reversible application to transparent materials and additionally require complicated production processes. The known protection layers can improve the stability of photochromic materials with rigid supports, but require a complicated production process which entails correspondingly high production cost. In addition, the stability improvement which can be achieved thereby is unsatisfactory for high demands on weather and scratch resistance. Thus, it is the object of the present invention to avoid the above mentioned drawbacks.

Summary of the Invention

It was now found that a photochromic material comprising a flexible support and a layer which has a low oxygen permeability and/or which has an oxygen absorption property provides for a suitable photochromic protection layer. Thus, the invention relates to

(1) a photochromic material comprising a support, a photochromic composition and at least one oxygen reducing compound, wherein said photochromic composition is contained in the support (C) and/or in at least one separate layer (B) applied thereto, and the oxygen reducing compound is present in the sup- port, and/or in at least one separate layer (A), and/or in said at least one separate layer (B) with the photochromic composition;

(2) a process for preparing a photochromic material as defined in (1) above, which comprises applying at least one layer to the support by a continuous casting process; (3) the use of a photochromic material as defined in (1) above or of a photochromic material prepared by the method as defined in (2) above as a window film thereof;

(4) an object coated with a photochromic material as defined in (1) above or of a photochromic material prepared by the method as defined in (2) above; and (5) a device containing an object defined in (4) above.

Detailed Description of the Invention

Photochrome materials according to the present invention include at least one flexible support and contain at least one photochrome composition, wherein said photochro- mic composition may be directly contained in the support. However, the photochromic composition may also or exclusively be contained in one or more layers applied to the support. According to the present invention, a layer having a low oxygen permeability and/or having an oxygen absorption property is applied above the layer in which the photochromic composition is contained.

In the simplest case, a photochromic material according to the present invention therefore consists of a flexible support containing a photochromic composition, and a layer having a low oxygen permeability and/or having an oxygen absorption property.

In another embodiment of the present invention, the photochromic material consists, in the order given, of a flexible support which may contain a photochromic composition, at least one layer applied to said support which contains a photochromic composition, and at least one layer having a low oxygen permeability and/or having an oxygen absorption property, wherein one or more further layers may be arranged respectively between said support and said layer containing the photochromic composition, and/or between said layer containing the photochromic composition and said layer having a low oxygen permeability and/or having an oxygen absorption property, as well as on top thereof. In the following, a low oxygen permeability is also referred to as a barrier effect, and the absorption of oxygen is also referred to as absorption effect. Within the scope of the present invention, "absorption effect" means any physical or chemical binding of oxygen whereby the content of free oxygen in the respective layer is reduced.

For the layer structure of a material according to the present invention, the following abbreviations are also used in the following : (SU) support with or without a photochromic composition; (SUP) support with a photochromic composition;

(PL) photochromic layer; (BL) layer having a low oxygen permeability (barrier layer); (AL) oxygen-absorbing layer (absorber layer)

A barrier layer may additionally have an absorption effect, and an absorber layer may additionally have a barrier effect.

Thus, in the simplest case, a material according to the present invention has the following layer structure: (SUP)-(BL), (SUP-AL), (SU-PL-BL) or (SU-PL-AL). Here as well as in the layer structures stated below, this is to be understood in such terms

that the material may contain one or more further layers of any kind at any position or positions in addition to the layers mentioned. Thus, for example, the structure (SU- PL-AL) means that the material contains the three layers in the stated order and that further layers of any kind may be arranged on the free side of (SU), between (SU) and (PL), between (PL) and (AL), and on the free side of (AL).

According to the present invention, it was found that such photochromic materials meet even high demands on weather and light stability and are at least comparable to the materials onto which an oxygen barrier layer was deposited by a complicated process, and are often even superior in terms of stability. The individual layers of the photochromic material according to the invention can be applied by usual methods, such as laminating or casting methods. Preferably, at least one layer having a barrier and/or absorption effect is not applied by a vapor deposition technique, and more preferably none of the barrier and/or absorption layers is applied by a vapor deposition technique, and even more preferably, no layer is applied by a vapor deposition technique.

Suitable casting methods include all known methods for the liquid coating of materials, for example, knife casting. However, it has been found particularly preferred to use as the support a flexible film which is sufficiently stable for the casting method and to subject it to continuous casting, for which, especially when more than one layer is present, a multiple casting system, especially a cascade or curtain casting machine is preferred with which the multilayered material is produced, especially in one machine run (multiple casting). Surprisingly, the stability of the photochromic material prepared by continuous casting towards the usual simple application methods, such as knife coating or brushing, is significantly improved. In multilayered materials, a further significant improvement is to be observed by the simultaneous application of several layers (multiple casting) as compared to several successive individual castings. Without knowing the underlying mechanism, this could be due to the uniformity of the layers which is possible with such casting methods, whereby there are no weak points in the barrier and/or absorber effect. What also speaks in favor of this theory is the fact that the stability of the photochromic materials could be further improved within the scope of the present invention by the known measures for improving the casting quality, such as optimization of the rheological properties of the casting solutions and/or the careful degassing thereof.

Each of the layers mentioned may be single layers or multiple layers as long as the photochromic layer remotest from the support is covered by at least one barrier and/or absorber layer which is even remoter from the support.

Although the advantages of the present invention are achieved already if only a barrier layer or only an absorber layer is present, better results are achieved if a layer having both barrier and absorber effects is present, and especially if several such layers are present.

Surprisingly, it has been found that the stability improvement can be enhanced even further if two layers are applied instead of such a combination layer, wherein one is essentially a barrier layer, and the other is essentially an absorber layer, and wherein it is particularly preferred if the barrier layer is remoter from the support than the absorber layer. In the following, such a double layer is also referred to as a "barrier layer/absorber layer pair" or simply "pair". Thus, a particularly preferred material according to the present invention has the following structure, for example: first the support, thereon the photochromic layer, on top thereof the absorber layer and finally the barrier layer, or briefly: (SU-PL-AL-BL), or if (only) the support contains a photochromic composition : (SUP-AL-BL).

The material according to the present invention may be one-sided or two-sided, wherein the coating of the support on the two sides may be different in the two-sided case. For example, the material may contain at least one photochromic layer only on one side of the support or on either side thereof. For example, a two-sided material could have the following structure: (BL-PL-SU-PL-BL). Despite the higher production expenditure, such a structure could offer itself if a very good flatness is required, because the tensile forces from the coating on the support are compensated by the symmetrical structure.

If the support has a relatively high oxygen permeability, it is preferred if it contains at least one barrier and/or absorber layer on the backside. This is all the more true since the support itself contains a photochromic composition. Therefore, a further preferred embodiment of the photochromic material according to the present invention has the following layer structure, for example: (BL-SU-PL-BL).

In addition, in the case of a support having a relatively high oxygen permeability, it has been found advantageous if the support does not contain a photochromic composition, and a barrier and/or absorber layer is arranged between the support and

the photochrome layer, for example, according to the following layer structures: (SU- AL-PL-BL) or (SU-BL-PL-BL). This has been found preferred even if the side of the support lacking a photochromic layer is otherwise rendered impervious to oxygen, for example, by adhering the support onto a glass plate. The mechanism thereof is not known either, but afterwards, it is assumed that oxygen may diffuse in laterally through free cutting edges of the support, migrate through the support and then enter the photochromic layer if it is applied directly to the support.

Within the scope of the present invention, a "barrier layer" preferably means a layer that has a permeability coefficient, P, of smaller than 0.1, preferably smaller than 0.01. A definition of the permeability coefficient P and its values for numerous polymers can be found in the Polymer Handbook, 4 ^th edition, J. Brandrup, E. H . Immergut and E. A. Grulke, John Wiley & Sons, Inc. New York, pages VI/543 ff. Suitable examples are stated in Table 1, and the permeability coefficient as mentioned therein is in units of cm ³ (273.15 K; 1.013 • 10 ⁵ Pa) • cm / (cm ² • s • Pa).

Table 1

The barrier layers are preferably cast from a solution, especially aqueous solution, or applied in the form of dispersions. The barrier polymers may contain additives such as plasticizers, wetting agents and/or anti-ageing agents. Suitable plasticizers include, for example, tricresyl phosphate, dibutyl phthalate, tributyl citrate or sebacic ester alone or as a mixture.

As barrier polymers, those polyvinyl alcohols which have a medium molecular weight and a degree of hydrolysis of about 99% are particularly preferred.

Within the scope of the present invention, an "absorber or absorption layer" preferably means a layer which is capable of permanently binding molecular oxygen and thus reducing the oxygen partial pressure in the layer. Thus, oxygen present in the layer or diffusing into the layer is trapped within the layer as completely as possible. Said trapping of the oxygen may be effected either physically, for example, by adsorption, or chemically, for example, by chemisorption or reduction. Within the scope of the present invention, all means with which oxygen is trapped are referred to as oxygen scavengers in the following.

When oxygen scavengers are used that are insoluble in the respective casting solution, they are introduced in the form of dispersions. For preparing the dispersions, the oxygen scavengers is dispersed in an aqueous polymer solution in a known manner by means of a dispersing device using wetting agents or dispersing agents.

This method is advantageous in particular to enable aqueous casting solutions, which are preferred for all layers according to the present invention that are applied by a casting method because they place less of a load on the environment as compared to organic solutions and do not require any explosion protection measures. When organic soluble oxygen scavengers are used, the compounds are dissolved, for example, in a high-boiling solvent (oil former, permanent solvent), and the solution is emulsified into an aqueous polymer solution using an emulsifying device. Conveniently, emulsification aids, such as emulsifiers, or low-boiling water-insoluble solvents which are evaporated off during the emulsification process are used. Examples of water-soluble polymers include polyvinyl alcohol, gelatin, polyacrylamides, polyvinylpyrrolidone, polyvinylimidazole, hydroxyethylcellulose, cellulose, polyoxazoli- nones, polyallylamine, polyacrylic acids or copolymers or mixtures of such polymers. Examples of high-boiling solvents include tricresyl phosphate, tritoluyl phosphate, dibutyl phthalate, N,N-diethyldodecanamide, N,N-dibutyldodecanamide, tris(2-ethylhexyl) phosphate, acetyltributyl citrate, 2,4-di-tert-pentylphenol, 2-(2- butoxyethoxy)ethyl acetate and l,4-cyclohexyldimethylenebis(2-ethylhexanoate). As examples of auxiliary solvents, ethyl acetate or diethyl carbonate may be mentioned.

Another possibility of introduction when water-soluble polymers are used is to use the water-insoluble oxygen scavenger together with a polymer dispersion or a polymer latex in a finely dispersed form. This technique is known under the designation of "charging of latexes" and is described, for example, in DE 25 41 274, US 4 199 363, DE 25 41 230, US 4 247 625 and EP 049 399.

When water-soluble oxygen scavengers are used, they are dissolved in water together with an aqueous binder solution or binder dispersion, followed by casting into a layer and drying. As binders, there may be used, for example, PVA, gelatin, polyvinylimidazole, polyvinylpyrrolidone, substituted celluloses, polyacrylic acids, polyacrylamide and mixtures thereof.

Prior to casting, the thus obtained dispersions, emulsions or solutions can be admixed in the known manner with wetting agents for casting, biocides, thickening agents or other additives in order to improve the casting quality and stability.

As oxygen scavengers, any compounds are suitable which are capable of binding or converting molecular oxygen, especially adsorbents and reducing agents. The

oxygen scavengers may be introduced directly in their reactive form, but activat- able oxygen scavengers are more preferred. By the activation, it can be avoided that the oxygen scavenger is already partially consumed in the preparation process of the photochromic material. Suitable activation reactions can be triggered by, for example, light, heat or chemical additives. Any reactions can be applied that are suitable for releasing a compound acting as an oxygen scavenger, especially the cleavage of camouflaged oxygen scavengers.

Suitable oxygen scavengers are, for example, the compounds stated in US 5 350 622, US 5 211 875, US 6 287 481, WO 94/12590 and especially in US 6 942 821, columns 7 to 10. For the present invention, it is preferred to select those oxygen scavengers that cause only a little turbidity visible to the eye in the amount employed, especially those that do not cause any turbidity visible to the eye at all. In addition, it is preferred if the oxygen scavengers do not exhibit an absorption for visible light, or at most appear as neutral in color (gray) as possible. Examples of oxygen scavengers according to the present invention include, alone or in a mixture, organic oxygen scavengers, for example, unsaturated hydrocarbons, both high and low molecular weight, in combination with transition metal compounds, ascorbic acid, ascorbates, isoascorbic acid, isoascorbates, ascorbyl palmitate, gallic acid and its salts, tocopherol, hydroquinone, catechol, resorcinols, dibutylhydroxy- toluene, dibutylhydroxyanisole, pyrogallol, rongalite, sorbose, glucose, lignins, sulfites, tannin, ascorbates in combination with transition metal catalysts, thiosulfite, mercaptopropionic acid, thiosulfate, bisulfite, hydrogensulfite, dithionate, dithionite, hyposulfite, sulfide, tin compounds, hydroxylamine, hydrazine, phosphine compounds, iron-based oxygen scavengers, such as iron powder, activated iron, iron oxide or iron salts, polymeric oxygen scavengers, such as oxidation-reduction resins and polymeric metal complexes, oxygen adsorbers, such as zeolites and active charcoal, or mixtures of the mentioned oxygen scavengers. Preferred phosphine compounds include triphenylphosphine, tri-p-tolylphosphine, diphenylmethyl- phosphine, diphenylethylphosphine, diphenylpropylphosphine, dimethylphenyl- phosphines, diethylphenylphosphine, dipropylphenylphosphine, divinylphenyl- phosphine, divinyl-p-methoxyphenylphosphine, divinyl-p-bromophenylphosphine, divinyl-p-tolylphosphine, diallylphenylphosphine, diallyl-p-methoxyphenylphos- phine, diallyl-p-bromophenylphosphine and diallyl-p-tolylphosphine. Triphenylphos-

phine is particularly preferred. Preferred ascorbates and phenolic oxygen scavengers are described, for example, in US 5,977,212, column 5, lines 15-67.

In a preferred embodiment of the present invention, the photochromic material contains oxygen quenchers and especially singlet oxygen quenchers. The men- tioned quenchers may be contained in any layer of the material and also in several layers. Preferably, they are present in the absorber layer and/or in a layer that contains at least one photochromic dye, or in the support if it contains a photo- chromic dye. It is particularly preferred for the quenchers and especially the singlet oxygen quenchers to be present in a layer or in the support that contains at least one photochromic dye.

Suitable singlet oxygen quenchers are known, for example, from JP-A Nos. 58- 175693, 59-81194, 60-18387, 60-19586, 60-19587, 60-35054, 60-36190, 60- 36191, 60-44554, 60-44555, 60-44389, 60-44390, 60-54892, 60-47069, 63- 209995 and 4-25492, JP-B Nos. 1-38680 and 6-26028, DE-A-350399 and Journal of the Chemical Society of Japan, October 1992, p. 1141. NQ-13 from Hayashibara Biochemical Laboratory, Inc. is an example of a commercially available singlet oxygen quencher.

In a preferred embodiment of the present invention, conjugated polyenes, transition metal complexes, amines including hindered amines (HALS compounds), aminium salts, iminium salts and/or the oxygen quenchers stated in EP-B-O 486 216, especially the substances referred to as compounds of formula II-a-2 and R therein, are used as singlet oxygen quenchers. Particularly preferred transition metal complexes correspond to the general formula Q-I or Q-II:

Q-I

wherein the phenyl rings may be unsubstituted or substituted. Suitable substituents include, in particular, electron-withdrawing substituents, such as halogen atoms or ether groups.

Examples of suitable quenchers are shown below:

i - — H ₉ N C ^' ₄ 4H' ' _Q 9-n Q-3

In the photochromic material, said oxygen scavengers or singlet oxygen scavengers are usually employed in an amount of from 0.1 to 500% by weight, preferably from 0.5 to 100% by weight, especially from 3 to 40% by weight and more preferably from 5 to 25% by weight, based on the total amount of photochromic dye or dyes in said material. A single quencher compound or a mixture of such compounds, also from different chemical classes, may be employed.

Within the scope of the present invention, "photochromic layer" means a layer that contains at least one photochromically reacting pigment or photochromically reacting dye. Preferably, it is an organic photochromic dye, also briefly referred to as "photochromic dye" in the following, or a mixture of two, three, four or more different photochromic dyes. Photochromic dyes are characterized, in particular, by their absorption spectrum in the switched state and in the basic state, it being preferred for the present invention if said photochromic dye will absorb only a little to not at all in the visible light region in its basic state, but in its switched state will absorb as strongly as possible in the visible light region. The switching, i.e., the excitation into the (more strongly) colored state, is preferably effected with radiation having a short wavelength, such as blue or ultraviolet light, for example, light of from 200 to 500 nm, preferably light of from 250 to 450 nm, more preferably light of from 300 to 420 nm, especially from 350 to 420 nm. Preferably, the photochromic dyes according to the present invention are not introduced into inorganic-organic hybrid polymers, so-

called ORMOCERs, and preferably are not surrounded by a supramolecular protective coat either.

In a preferred embodiment of the present invention, the coloring with said photo- chromic dye or said mixture of dyes is substantially neutral gray. As a criterion for this, the subjective color sensation of a statistically relevant group of persons is used who evaluate a colored film with the desired coloration in the switched state that covers only half of the window area of a room. The better the color neutrality of the film is evaluated, the more suitable for the present invention is the dye or mixture of dyes contained therein. Only half of the window area is covered in order to prevent color adaptation by the human eye, which corresponds, for example, the state when windows are partially open. It is particularly preferred to select those photochromic dyes which ensure an acceptable neutrality in the test already as a single dye. Such dyes exhibit a higher long-term stability of gray neutrality, whereas discoloration is often to be observed in the course of time for gray-neutral mixtures of dyes.

The photochromic compounds which may be used for the present invention are not specifically limited. Preferably, they can be selected from the class of benzopyrans, spirobenzopyrans, spirobenzoxazines and higher annelated ring systems derived therefrom, in particular, naphthopyrans, spironaphthopyrans, spironaphthoxazines or fluorenopyrans, as well as fulgides and fulgimides. Thus, for example, (2H)- naphtho[l,2-b]pyrans aromatically or heteroaromatically substituted in 2,2- position, but also (3H)-naphtho[2,l-b]pyrans correspondingly substituted in 3,3- position, such as the naphthopyrans described in PCT/DE 98/02820 and the indeno[2,l-f]naphtho[l,2-b]pyran derivatives and/or spiro-9-fluoreno[l,2-b]pyran derivatives described in WO 00/05602, can be used.

Examples of photochromic dyes according to the present invention include: 3,13- diphenyl-3-(4-diphenylaminophenyl)-13-hydroxy-6-methoxy-inde no[2,l-f]naphtha- [l,2-b]pyran; 13-(2,5-dimethylphenyl)-3-(4-diphenylaminophenyl)-13-hydroxy -6- methoxy-3-phenylindeno[2,l-f]naphtho[l,2-b]pyran; 13-(2,5-dimethylphenyl)-3- (4-diphenylaminophenyl)-13-hydroxy-3-phenylindeno[2,l-f]naph tho[l,2-b]pyran; spiro-9-fluoreno-13'-[3-(4-dimethylaminophenyl)-6-methoxy-3- phenylindeno[2,l- f]naphtho[l,2-b]pyran]; spiro-9-fluoreno-13'-[3-(4-dimethylaminophenyl)-3- phenylindeno[2,l-f]naphtho[l,2-b]pyran]; spiro-9-fluoreno-13'-[3-(4-diphenyl- aminophenyl)-6-methoxy-3-phenylindeno[2,l-f]naphtho[l,2-b]py ran]; spiro-9-

fluoreno-13'-[3-(4-diphenylaminophenyl)-3-phenyl-indeno[2 ,l-f]naphtho[l,2-b]- pyran]; spiro-9-fluoreno-13'-{3-[4-(N-morpholinyl)phenyl]-6-methoxy- 3-phenyl- indeno[2,l-f]naphtho[l,2-b]pyran}; spiro-9-fluoreno-13'-{3-[4-(N-morpholinyl)- phenyl]-3-phenyl-indeno[2,l-f]naphtho[l,2-b]pyran}; spiro-9-fluoreno-13'-{6- methoxy-3-phenyl-3-[4-(N-piperidinyl)phenyl]indeno[2,l-f]nap htho[l,2-b]pyran}; spiro-9-fluoreno-13'-{3-phenyl-3-[4-(N-piperidinyl)phenyl]-i ndeno[2,l-f]naphtho- [l,2-b]pyran}; 3-(4-diphenylaminophenyl)-3-(2-fluorophenyl)-3H-naphtho[2,l- b]- pyran; 3-(4-dimethylaminophenyl)-3-(2-fluorophenyl)-3H-naphtho[2,l- b]pyran; 3- (2-fluorophenyl)-3-[4-(N-morpholinyl)phenyl]-3H-naphtho[2,l- b]pyran; 3-(2-flu- orophenyl)-3-[4-(N-piperidinyl)phenyl]-3H-naphtho[2,l-b]pyra n; 3-(4-dimethyl- aminophenyl)-6-(N-morpholinyl)-3-phenyl-3H-naphtho[2,l-b]pyr an; 6-(N-morpho- linyl)-3-[4-(N-morpholinyl)phenyl]-3-phenyl-3H-naphtho[2,l-b ]pyran; 6-(N- morpholinyl)-3-phenyl-3-[4-(N-piperidinyl)phenyl]-3H-naphtho [2,l-b]pyran; 6-(N- morpholinyl)-3-phenyl-3-[4-(N-pyrrolidinyl)phenyl]-3H-naphth o[2,l-b]pyran; 3- phenyl-3-(2-fluorophenyl)-3H-naphtho[2,l-b]pyran; 6-(N-morpholinyl)-3,3-diphen- yl-3H-naphtho[2,l-b]pyran; and 6-(N-morpholinyl)-3-(4-methoxyphenyl)-3- phenyl-3H-naphtho[2,l-b]pyran.

However, the pyrans described in US 5,753,146 and EP-A-O 562 915 as well as photochrome dyes of other classes, for example, oxazines, such as the oxazines described in US 5,753,146, or fulgides may also be used.

In a preferred embodiment of the present invention, spirofluorenopyrans of formula (PF-I) are employed as photochromic dyes:

wherein R ¹ is a substituent selected from group A consisting of (Ci to C ₆ ) alkyl, (Ci to C ₆ ) alkoxy, phenyl, bromo, chloro and fluoro;

R ² , R ³ , R ⁴ are independently the same or different and represent a substituent selected from group A' consisting of hydrogen and the substituents of

group A, or (R ¹ together with R ² ) and/or (R ³ together with R ⁴ ) independently represent an unsubstituted, mono- or disubstituted benzo or pyrido ring whose substituents are selected from group A;

G counting in the spiro carbon atom, represents a 5- to 8-membered ring to which at least one aromatic or heteroaromatic ring system is anne- lated, wherein said ring system or systems are selected from group E consisting of benzene, naphthalene, phenanthrene, pyridine, quinoline, furan, thiophene, pyrrole, benzofuran, benzothiophene, indene and car- bazol, which in turn may have one or two substituents selected from group A; and

B, B' are independently selected from the following groups a), b), c) or d), with a) phenyl or naphthyl which are unsubstituted, mono-, di- or trisubsti- tuted; or b) the heterocycles pyridyl, furanyl, benzofuranyl, thienyl, benzothienyl and julolidinyl which are unsubstituted, mono- or disubstituted; wherein said substituent or substituents of the aryl or heteroaryl groups in a) and b) are selected from group F consisting of hydroxy, amino, mono(Ci to C ₆ )alkylamino, di(Ci to C ₆ )alkylamino, mono- and diphenyl- amino unsubstituted, mono- or disubstituted at the phenyl ring, piperid- inyl, N-substituted piperazinyl, pyrrolidinyl, imidazolidinyl, pyrazolidinyl, indolinyl, morpholinyl, carbazolyl, unsubstituted, mono- and disubstituted pyrryl, (Ci to C ₆ ) alkyl, (Ci to C ₆ ) alkoxy, bromo, chloro and fluoro, wherein said substituent or substituents at the aromatics and heteroaromatics are selected from the group consisting of (Ci to C ₆ ) alkyl, (Ci to C ₆ ) alkoxy, bromo, chloro and fluoro; or c) the groups having the following structures:

wherein Y and Z are independently selected from the group O, S, CH, CH ₂ , NR ^N , and the nitrogen substituents R ^N are selected from the group consisting of (Ci to C ₆ ) alkyl, (Ci to C ₆ ) acyl, phenyl and hydrogen, and

the substituents R ⁵ are selected from group A and hydroxy, wherein m = 0, 1 or 2, and R ⁶ and R ⁷ are independently hydrogen and/or (Ci to C ₆ ) alkyl; or d) B and B' together form an unsaturated, mono- or disubstituted fluoren-9-ylidene or a saturated hydrocarbon which is C ₃ to Ci ₂ spiro- monocyclic, C ₇ to Ci ₂ spirobicyclic and/or C ₇ to Ci ₂ spirotricyclic, wherein the fluorene substituents are selected from group A.

Accordingly, the ring system G including the spiro carbon atom is a 5- to 8-membered ring. To this ring, at least one aromatic or heteroaromatic ring system is annelated. According to the invention, said annelated ring system or systems may be independently selected from the group consisting of benzene, naphthalene, phenanthrene, pyridine, quinoline, furan, thiophene, pyrrole, benzofuran, benzothiophene, indene and carbazol. Of course, the ring systems may be unsubstituted as well as mono- or disubstituted, wherein said substituent or substituents are selected from group A as defined above.

In the present invention, "C ₃ to Ci ₂ spiromonocyclic" is intended to mean a 3- to 12-membered ring as known to the skilled person. C ₇ to Ci ₂ spirobicyclic systems, which may be present according to the invention, also belong to the skilled person's knowledge. For example, there may be mentioned norbornane, norbornene, 2,5- norbornadiene, norcarane and pinane. A known spirotricyclic system that can be used in the invention is adamantane, for example.

In another preferred embodiment of the present invention, spirofluorenopyrans of formula (PF-II) are employed as said photochromic dyes:

wherein

R ¹ to R ⁴ , B and B' are as defined above;

X is either a single bond or is selected from the group consisting of -O-,

-S-, - (CRz) _n -, -D=D'- or -L-L'-, n is 1, 2 or 3,

D, D' are N or CR,

L, L' are O, S, NR, CHR or CR ₂ , and R is H, (Ci to C ₆ ) alkyl or phenyl; and wherein L and L' are not both O or S; and C and C are independently selected from group E as defined above and may each have one or two substituents selected from group A.

When X is referred to as a "single bond" in the description of the present invention, this means that there is a direct link between the ring systems C and C to be linked, for example, i.e., no other atom is to serve as a bridge.

According to another preferred embodiment of the invention, X represents a single bond, wherein the two existing ring systems C and C are bridged by another link in ortho,ortho' position to the first link. Such a bridge includes any possibility known to the skilled person to join the two ring systems C and C, such as through heteroa- toms, such as oxygen or sulfur, saturated or unsaturated C ₂ to C ₅ carbon chains or the like. For example, said further link in ortho,ortho' position may result in a 4,5- phenanthryl spiro compound, wherein the spiro compounds according to the invention may then have the following general structure (PF-III):

It may also be advantageous if B and B' in the spiro compounds according to the invention are independently selected from the group a) or d). More preferably, B and B' independently represent unsubstituted or monosubstituted phenyl or naphthyl, wherein said substituent is respectively selected from group F as defined above. In the photochromic spiro compounds according to the invention, B and B' may also be the same substituents.

According to another preferred embodiment of the invention, C and C are independently unsubstituted or monosubstituted phenyl or naphthyl, wherein said substituent is respectively selected from group A. Also, C and C may represent the same substituents. The following photochromic spirofluorenopyrans have advantageous properties:

1) Spiro-9-fluoren-13'-[3,3-diphenyl-6-methoxyindeno[2,l-f]naph tho[l,2-b]- pyran];

2) Spiro-9-fluoren-13'-[6-methoxy-3-(4-methoxyphenyl)-3-phenyli ndeno[2,l- f]naphtho[l,2-b]pyran]; 3) Spiro-9-xanthen-13'-[6-methoxy-3-(4-methoxyphenyl)-3-phenyli ndeno[2,l- f]naphtho[l,2-b]pyran];

4) Spiro-9-fluoren-13'-[3,3-bis(4-methoxyphenyl)-6-methoxyinden o[2,l-f]naph- tho[l,2-b]pyran];

5) Spiro-9-xanthen-13'-[3,3-bis(4-methoxyphenyl)-6-methoxyinden o[2,l-f]- naphtho[l,2-b]pyran];

6) Spiro-9-(9,10-dihydroanthracene)-13'-[3,3-bis(4-methoxypheny l)-6- methoxyindeno[2,l-f]naphtho[l,2-b]pyran];

7) Spiro-9-fluoren-13'-{6-methoxy-3-[4-(N-morpholinyl)phenyl]-3 -phenyl- indeno[2,l-f]naphtho[l,2-b]pyran}; 8) Spiro-9-fluoren-13'-[3-(4-dimethylaminophenyl)-6-methoxy-3-p henylindeno-

[2,l-f]naphtho[l,2-b]pyran];

9) Spiro-9-fluoren-13'-[3-(4-diphenylaminophenyl)-6-methoxy-3-p henylindeno- [2,l-f]naphtho[l,2-b]pyran];

10) Spiro-9-fluoren-13'-[3,3-bis(4-methoxyphenyl)indeno[2,l-f]na phtho[l,2-b]- pyran];

11) Spiro-9-fluoren-13'-{3-[4-(N-morpholinyl)phenyl]-3-phenylind eno[2,l-f]- naphtho[l,2-b]pyran};

12) Spiro-9-fluoren-ll'-[3,3-bis(4-methoxyphenyl)-5-bromofluoren o[2,l-b]pyran]; or 13) Spiro-9-fluoren-13'-[3,3-bis(4-methoxyphenyl)-5-bromobenzo[l ]fluoreno[2,l- b]pyran].

Examples of particularly advantageous photochromic dyes within the scope of the present invention include the below mentioned dyes of formula (PF-IV) and especially the below mentioned dyes of formula (PF-V):

The photochromic dyes can be introduced into layers consisting of organic soluble or water-soluble (co)polymers.

For polymers soluble in organic solvents, the photochromic dye is dissolved in an organic solvent together with the polymer, cast and dried. As organic solvents, there may be used, for example, acetone, ethanol, ethyl acetate, tetrahydrofuran, methylene chloride, methanol, dioxan, butyl acetate, isopropanol, toluene or mixtures of such solvents.

As (co)polymers, there may be used, for example, poly(methyl methacrylate), co- poly(butyl acrylate-styrene 45: 55), polycarbonate, cellulose triacetate, polybutyl methacrylate, polyester, polyurethane, polyamides, copolymers of vinylidene chloride and acrylic acid esters as well as acrylonitrile copolymers.

In a particular embodiment, mixtures of (meth)acryl-modified polymers with reactive solvents, such as hexanediol diacrylate or trimethylolpropane triacrylate, may also be used. These solutions are applied and subsequently cured thermally or by means of ultraviolet light or electron beams. Depending on the kind of curing, such solutions contain thermally activatable curing agents, such as peroxides or azo compounds, or ultraviolet-activatable curing agents, such as Darocure ^® or Irgacure ^® compounds. For curing with electron beams, curing agents are not necessarily required.

For improving the stability of the photochromic dyes enclosed in the polymer matrix, further monomers, such as acrylamides, vinylpyridine or vinylimidazole, may be added to the reactive polymers.

For water-soluble copolymers, the water-insoluble photochromic dyes are introduced in the form of dispersions, emulsions or loaded polymer latexes.

For the preparation of dispersions, the dye is dispersed into the aqueous polymer solutions in a known way with a dispersing device by means of wetting agents or dispersing agents.

For the preparation of emulsions, the dye is dissolved, for example, in a high-boiling solvent, and the solution is emulsified into the aqueous polymer solution using an emulsifying device. Conveniently, emulsification aids, such as emulsifiers, or low- boiling water-insoluble solvents which are evaporated off during the emulsification process are used. Examples of water-soluble polymers include polyvinyl alcohol, gelatin, polyacrylamides, polyvinylpyrrolidone, polyvinylimidazole, hydroxyethylcel- lulose, cellulose, polyoxazolinones, polyallylamine, polyacrylic acids or copolymers or mixtures of such polymers. For examples of high-boiling solvents, see above. As examples of auxiliary solvents, ethyl acetate or diethyl carbonate may be men- tioned.

Another possibility of introduction when water-soluble polymers are used is to use the water-insoluble dye together with a polymer dispersion or a polymer latex in a finely dispersed form. This technique is known under the designation of "loading of latexes" and has been described above as a possible introduction method for oxygen scavengers.

In a preferred embodiment of the present invention, dispersions of particles of an ionically modified polymer are loaded with photochromic dyes. This is possible without the occurrence of crystallization or precipitations of the dye. The ionically modified polymers are preferably ionomeric polyaddition or polycondensation products.

The ionomeric polyaddition or polycondensation products used according to the invention contain, per 100 g of product, from 4 to 180 milliequivalents, preferably from 4 to 100 milliequivalents, of ionic groups or groups that con be converted to ionic groups, and optionally from 1 to 20% by weight of alkylene oxide units of formula -CH ₂ -CH ₂ -O- incorporated within a polyether chain, wherein said polyether chain can be pendant or contained in the main chain.

The ionomeric polyaddition or polycondensation products which may be used according to the invention, which will be referred to as "ionomeric products" in the

following, include polyurethanes, polyesters, polyamides, polyureas, polycarbonates, polyacetals or polyethers and, in addition, further ionomeric products which simultaneously belong to 2 or more polymer types, such as polyester polyurethanes, polyether polyurethanes or polyester polyureas. Ionomeric products as used according to the invention are per se known and are described, for example, in Angewandte Makromolekulare Chemie 26 (1972), pages 45 to 106; Angewandte Makromolekulare Chemie 82 (1979), pages 53 ff; J. Oil. CoI. Chem. Assoc. 53 (1970), pages 363. Further descriptions of suitable ionomeric products are found in the German Laid-Open Publication Nos. (DE-A-) 26 37 690, 26 42 973, 26 51 505, 26 51 506, 26 59 617, 27 29 245, 27 30 514, 27 32 131, 27 34 576 and 28 11 148.

Ionomeric products having anionic groups are preferred. Ionomeric products that are particularly suitable for the process according to the present invention are described in DE-B2-1 472 746. These ionomeric products are based on polyurethanes obtained from compounds with several reactive hydrogens having a molecular weight of from 300 to 10,000, polyisocyanates and optionally chain extenders with reactive hydrogens. During the preparation of these polyurethanes or subsequently, any isocyanate groups still present therein are reacted with a compound having at least one active hydrogen atom and at least one salt-like group or group capable of salt formation. When compounds having groups capable of salt formation are used, , the resulting anionic polyurethanes are subsequently converted at least partially to the salt form in a per se known manner. The term "salt-like group" preferably means -SO ₃ ^" and -COO ^" groups.

As starting components for the preparation of the anionic polyurethanes, the com- pounds described in the following are suitable, for example:

I. Compounds with active hydrogens: These compounds are essentially linear and have a molecular weight of about 300 to 10,000, preferably from 500 to 4000. The per se known compounds have terminal hydroxy and/or amino groups. Preferred are polyhydroxy compounds, such as polyesters, polyacetals, polyethers, polyamides and polyesteramides. The hydroxyl number of these compounds is about 370 to 10, especially 225 to 28.

As polyethers, there may be mentioned, for example, the polymerization products of ethylene oxide, propylene oxide, tetrahydrofuran, butylene oxide as well as their

mixed and graft polymerization products as well as condensates obtained by the condensation of polyhydric alcohols or mixtures thereof, and the products obtained by the alkoxylation of polyhydric alcohols. As polyacetals, there may be used, for example, the compounds that can be prepared from hexanediol and formaldehyde. As polyesters, polyesteramides and polyamides, the predominantly linear condensates obtained from polyhydric saturated carboxylic acids and polyhydric saturated alcohols, aminoalcohols, diamines and mixtures thereof are suitable.

Polyhydroxy compounds that already contain urethane or urea groups as well as optionally modified natural polyols, such as castor oil or hydrocarbons, can also be used.

For varying the lyophilicity or hydrophobicity and the mechanical properties of the process products, mixtures of different polyhydroxy compounds may also be employed.

II. Polvisocvanates: As polyisocyanates, all aromatic and aliphatic diisocyanates are suitable, such as 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate,

4,4'-diphenyldimethylmethane diisocyanate, di- and tetraalkyldiphenylmethane diisocyanate, 4,4'-dibenzyl diisocyanate, 1,3-phenylene diisocyanate, 1,4- phenylene diisocyanate, the isomers of toluylene diisocyanate, optionally as a mixture, preferably the aliphatic diisocyanates, butane-1,4 diisocyanate, hexane- 1,6 diisocyanate, dicyclohexylmethane diisocyanate, cyclohexane-1,4 diisocyanates as well as isophorone diisocyanate.

III. Chain extenders: The chain extenders having reactive hydrogens include:

1. the usual glycols, such as ethylene glycol or condensates of ethylene glycol, butanediol, propanediol-1,2, propanediol-1,3, neopentyl glycol, hexane diol, bishydroxymethylcyclohexane;

2. the aliphatic, cycloaliphatic and aromatic diamines, such as ethylenediamine, hexamethylenediamine, 1,4-cyclohexyldiamine, benzidine, diaminodiphenyl- methane, the isomers of phenylenediamine, hydrazine, ammonia;

3. aminoalcohols, such as ethanolamine, propanolamine, butanolamine; 4. polyfunctional amines or hydroxy compounds, such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, hex- aethyleneheptamine, glycerol, pentaerythritol, 1,3-diaminoisopropanol, 1,2- diaminopropanol, the monooxalkylated polyamines, such as N-

oxethylethylenediamine, N-oxethyl hydrazine, N-oxethylhexamethylene- diamine; 5. water.

IV. Compounds capable of salt formation: 1. Compounds with a ready formed acidic group. a) hydroxy acids, such as glycerolic acid, lactic acid, trichlorolactic acid, malic acid, dioxymaleic acid, dioxyfumaric acid, tartaric acid, dioxy- tartaric acid, citric acid, dimethylolpropionic acid and dimethylolbutyric acid, the aliphatic, cycloaliphatic, aromatic and heterocyclic mono- and diaminocarboxylic acids, such as glycine, α- and β-alanine, 6- aminocapronic acid, 4-aminobutyric acid, the isomeric mono- and dia- minobenzoic acids, the isomeric mono- and diaminonaphthoic acids; b) hydroxy- and carboxysulfonic acids; 2-hydroxyethanesulfonic acid, phenolsulfonic acid-(2), phenolsulfonic acid-(3), phenolsulfonic acid- (4), phenolsulfonic acid-(2,4), sulfoacetic acid, m-sulfobenzoic acid, p- sulfobenzoic acid, benzoic acid-(l)-disulfonic acid-(3,5), 2- chlorobenzoic acid(l)-sulfonic acid-(4), 2-hydroxybenzoic acid-(l)- sulfonic acid-(5), naphthol-(l)-sulfonic acid, naphthol-(l)-disulfonic acid, 8-chloronaphthol-(l)-disulfonic acid, naphthol-(l)-trisulfonic acid, naphthol-(2)-sulfonic acid-(l) and Naphthol-(2)-trisulfonic acid; c) aminosulfonic acids; amidosulfonic acid, hydroxylaminemonosulfonic acid, hydrazinedisulfonic acid, sulfanilic acid, N-phenylamino- methanesulfonic acid, 4,6-dichloroanilinesulfonic acid-(2), phenyl- enediamine-(l,3)-disulfonic acid-(4,6), naphthyleneamine-(l)-sulfonic acid, naphthylamine-(2)-sulfonic acid, naphthylaminedisulfonic acid, naphthylaminetrisulfonic acid, 4,4'-di(p-aminobenzoylamino)- diphenylureadisulfonic acid-(3,3'), phenylhydrazinedisulfonic acid- (2,5), taurine, methyltaurine, butyltaurine, 3-aminobenzoic acid-(l)- sulfonic acid-(5), 3-aminotoluene-N-methanesulfonic acid, 4,6- diaminobenzenedisulfonic acid-(l,3), 2,4-diaminotoluenesulfonic acid-

(5), 4,4'-diaminodiphenyldisulfonic acid-(2,2'), 2-aminophenolsulfonic acid-(4), 4,4'-diaminodiphenyl ethersulfonic acid-(2), 2-aminoanisol-N- methanesulfonic acid, 2-aminodiphenylaminesulfonic acid, ethylene-

glycolsulfonic acid, 2,4-diaminobenzenesulfonic acid, N- sulfonatoethylethyleneamine; d) further, said hydroxy- and aminocarboxylic acids and -sulfonic acids, polycarboxylic and polysulfonic acids include the (optionally saponified) addition products of unsaturated acids, such as acrylic acid, methacrylic acid, vinylsulfonic acid, styrenesulfonic acid, and unsaturated nitriles, such as acrylonitrile, of cyclic dicarboxylic acid anhydrides, such as maleic acid, phthalic acid, succinic acid anhydride, of sulfocarboxylic acid anhydrides, such as sulfoacetic acid, o- sulfobenzoic acid anhydride, of lactones, such as β-propiolactone, γ- butyrolactone, the addition products of the reaction products of olefins with sulfur trioxide, such as carbyl sulfate, of epoxycarboxylic and - sulfonic acids, such as glycidic acid, 2,3-epoxypropanesulfonic acid, of sultones, such as 1,3-propanesultone, 1,4-butanesultone, 1,8- naphthylsultone, of cyclic sulfates, such as glycol sulfate, of disulfonic acid anhydrides, such as benzenedisulfonic acid-(l,2)-anhydride, to aliphatic and aromatic amines, such as 1,2-ethylenediamine, 1,6- hexamethylenediamine, the isomeric phenylenediamines, diethyl- enetriamine, triethylenetetramine, tetraethylenepentamine, further the addition products of sodium hydrogensulfite to olefinically unsaturated compounds, such as allyl alcohol, maleic acid, maleic acid bisethylene and bispropylene glycol ester; e) hydrazinecarboxylic acids.

2. Reactive compounds with 3 to 7 ring members having salt-like groups or groups capable of salt formation upon ring opening : a) dicarboxylic acid anhydrides, such as succinic acid anhydride, maleic acid anhydride, optionally hydrogenated phthalic acid anhydride; b) tetracarboxylic acid dianhydrides, such as 1,2,4,5-benzenetetra- carboxylic acid anhydride; c) disulfonic acid anhydride, such as benzenedisulfonic acid(l,2)-an- hydride; d) sulfocarboxylic acid anhydrides, such as sulfoacetic acid anhydride, o- sulfobenzoic acid anhydride; e) sultones, such as 1,3-propanesultone, 1,4-butanesultone, 1,8- naphthsultone;

f) lactones, such as β-propiolactone, γ-butyrolactone; g) epoxycarboxylic acids, such as glycidic acids, optionally in the form of their alkali salts; h) epoxysulfonic acids, such as 2,3-epoxypropanesulfonic acid-1, option- ally in the form of their alkali salts, as well as the adducts of epoxy aldehydes and alkali hydrogensulfites, such as the bisulfite compound of glycid aldehyde.

The above acidic groups can be converted in a usual way to the salt form by reacting them with the compounds mentioned in the following : inorganic bases, basic or base- cleaving compounds, such as monovalent metal hydroxides, carbonates and oxides, such as sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogencarbonate. Further, organic bases, such as tertiary amines, for example, trimethylamine, triethylamine, dimethylaminoethanol, dimethyl- aminopropanol, ammonia and the like. Suitable constituents further include, for example, mono- or dihydric alcohols having ethylene oxide units and being incorporated within polyether chains.

When such monofunctional non-ionic hydrophilic polyethers are included, it may often be advantageous to prevent premature chain termination by including higher than difunctional constituents. The monofunctional polyethers of the last mentioned general formula are prepared by per se known methods such as those described, for example, in U.S. Patents 3,905,929, 4,190,566 or 4,237,264.

Such constituents confer additional punctual hydrophilization, electrolyte stability, freezing stability and improved sliding properties to the polyurethanes to be used according to the invention. Preferably, the amount of polyisocyanates is selected in such a way that all the groups reactive towards isocyanate groups will react.

The reaction is optionally performed with including solvents, wherein low-boiling solvents having a boiling point of lower than 120 ⁰ C, such as acetone, methyl ethyl ketone, acetonitrile, tetrahydrofuran, dioxan, which may optionally contain a proportion of water, are preferably suitable. As the solvent for inorganic bases and compounds having at least one hydrogen reactive towards isocyanate groups and at least one salt-like group or group capable of salt formation, water may be used, optionally without the addition of organic solvents.

The predominantly linear, high molecular weight anionic polyurethanes are generally obtained as clear to slightly opalescent solutions in the polar solvents mentioned. Their solids content is about 5 to 50% by weight of ionic polyurethane. Preferably, polyester or polyether polyurethanes are used. The production process of the ionomeric products used according to the invention shall be illustrated by the following Examples.

Polymer P-I : From 800 g (0.356 mol) of a polyester of adipic acid and 1,4- butanediol (dehydrated) and 95 g (0.546 mol) of 2,4-toluylenediisocyanate, an NCO prepolymer is prepared at 75 to 85 ⁰ C in 1.5 h (1.78% NCO). It is dissolved while still hot in 1060 g of tetrahydrofuran, and at 50 ⁰ C, a solution of 53 g (0.13 mol) of an aqueous solution of the sodium salt of N-sulfonateethyl-ethylenediamine in 100 ml of water is added. After 5 min, another 500 g of tetrahydrofuran is added because of the strong increase in viscosity. A clear polyurethane polyurea solution with the following characteristic data is obtained : Solids content: 35.3% by weight; viscosity (24 ⁰ C) : 1000 mPa-s; viscosity (24 ⁰ C) of a sample of the solution adjusted to 30% with tetrahydrofuran : 400 mPa-s; content of sulfonate groups: 14.1 milliequivalents/100 g.

Polymer P-2: From 550 g (1.0 mol) of a polyether based on bisphenol A and propylene oxide and 140 g (0.08 mol) of a polyester of phthalic acid, adipic acid and ethylene glycol (all dehydrated) as well as 145 g (0.239 mol) of a 70% solution of a propoxylated adduct of butenediol and sodium bisulfite in toluene and 315 g (1.875 mol) of 1,6-diisocyanatohexane, an NCO prepolymer is prepared at 100 ⁰ C in 6.5 h (4.11% NCO). It is admixed with 77 g (1.283 mol) of urea, briefly heated at 135 ⁰ C and stirred at 130 ⁰ C until no more NCO can be detected in the IR spectrum. Now, with cooling, 290 ml of water at first and then 290 ml of water and then 1582 g of acetone are added. A clear, slightly yellow solution of a polyurethane polyurea with the following characteristic data is obtained :

Solids content: 40% by weight; viscosity (23 ⁰ C) : 60 mPa-s; content of sulfonate groups: 19 milliequivalents/100 g. Polymer P-3: 407.4 g (0.2396 mol) of hexanediol/neopentyl glycol polyadipate is dehydrated at 120 ⁰ C in a water-jet vacuum. At 70-80 ⁰ C, 77.7 g (0.4625 mol) of 1,6-diisocyanatohexane is added, and the mixture is stirred at 100 ⁰ C for another 1.5 h. The prepolymer has an NCO content of 3.4%. After 33% dissolving in

acetone, 75.0 g (0.1924 mol) of 2-aminoethyl-β-aminopropionic acid Na salt (39.5% in water) is added at 50 ⁰ C, and after 7 min, the mixture is dispersed with 1160 ml of fully desalted water. After distilling off the acetone in a water-jet vacuum, a very finely divided dispersion with the following characteristic data is obtained :

Content of carboxy groups: 16 milliequivalents/100 g; solids content: 30% by weight; pH : 7.6; particle size: 60 nm.

For preparing the dispersions of particles containing the photochromic dyes (dye latexes) as used according to the invention, water is allowed to flow into a solution of the water-insoluble photochromic dyes and the ionomeric product in a water-miscible low-boiling solvent or solvent/water mixture with stirring.

From the dispersion formed, the solvent is separated by distillation or by other suitable separation processes, such as dialysis or ultrafiltration.

According to another embodiment, the solution of the water-insoluble photochromic dyes in a water-miscible low-boiling solvent can be combined with the solution of a urethane prepolymer which still contains NCO groups, whereupon the polyaddition is completed in the presence of the dyes. This embodiment can be used to advantage especially when the dyes do not contain any groups reactive towards isocyanate.

As water-miscible organic solvents for the preparation of the dispersion, those are suitable that are able to dissolve both the ionomeric products and the photochromic dyes. Examples of such solvents include acetone, tetrahydrofuran, dioxan, isopropa- nol, methanol, ethanol, methyl ethyl ketone, acetonitrile.

The amount of photochromic dye used for the preparation of the dispersion is generally from 2 to 200% by weight, based on ionically modified polymer. Weight ratios of dye to polymer of from 1 : 200 to 1 : 10 are preferred.

This procedure allows to prepare dispersions of dyes having a particle size of below 150 nm. Preferably, the average particle size (diameter) is within a range of from 10 to 100 nm. In contrast, the particles of dispersions prepared with the use of usual oil formers are significantly larger. In addition to the dye, the latexes may also be loaded with suitable light stabilizers and/or antioxidants, which increases the stability of the photochromic dye.

The dye latexes may further be admixed with surface-active compounds.

In addition to natural surface-active compounds, such as saponine, synthetic surface-active compounds (surfactants) are mainly used : non-ionic surfactants, for example, alkylene oxide compounds, glycerol compounds or glycidol compounds, cationic surfactants, for example, higher alkylamines, quaternary ammonium salts, pyridine compounds and other heterocyclic compounds, sulfonium compounds or phosphonium compounds, anionic surfactants containing an acid group, for example, carboxylic acid, sulfonic acid, phosphoric acid, sulfuric acid ester or phosphoric acid ester group, ampholytic surfactants, for example, amino acid and aminosulfo- nic acid compounds, as well as sulfuric or phosphoric acid esters of an aminoalco- hoi.

Further surface-active compounds are described in RD 308 119 (1989) and in EP-A- 314 425, 362 990, 549 496, US Patents 4,839,262, 4,847,186, 4,916,054, 5,221,603, WO 90/12782 and WO 92/15554.

Preferably, anionic and non-ionic surface-active compounds, more preferably non- ionic compounds, are employed.

The dye-polymer dispersions prepared by the loading process have particle sizes of from 10 to 2000 nm, preferably from 30 to 300 nm.

Preparation of a photochromic dye latex

Dye latex FL: 72.7 g of polymer P- 3 was admixed with 550 g of acetone, heated at 50 ⁰ C and admixed with a solution of 1.09 g of photochromic dye (FS-I) dissolved in

80 g of acetone. After 15 minutes, 220 g of water was added dropwise, and the acetone was distilled off under vacuum. Subsequently, the loaded latex is purified by ultrafiltration and concentrated to the stated solids content. A dye latex with the following characteristic data was obtained : Solids content: 20% by weight; mean particle size: 82 nm; amount of dye, based on the ionomer: 5% by weight; pH : 7.0.

Preferably, the photochromic layers according to the present invention also contain dye stabilizers. Particularly suitable dye stabilizers are shown below.

-o-c ₁₃ H ₂₇ -I ST-3

Benzofuranone ST- 8

The dye stabilizer ST-IO is commercially available under the trade name Lowinox 22CP46.

In addition, thiomorpholine dioxide stabilizers (singlet oxygen quenchers) as described, for example, in US 5,491,054 and US 5,484,696 as well as silicon- bridged bisphenols as described, for example, in EP 1 191 398 have proven advantageous within the scope of the present invention. Further, the known antioxidants are preferred as dye stabilizers. These include, in particular, the following classes of substances, wherein the trade names are given respectively for some typical representatives thereof:

Phenols, especially sterically hindered phenols: Irganox 1135, Konica A 13, Irganox

259, Irganox 1010, Alvinox 100, Irganox 245 and Konica A35; o-bisphenols, especially sterically hindered o-bisphenols: Lowinox 22 IB 46,

Vulkanox ZKF, Vulkanox BKF and Irganox 3052; p-bisphenols, especially sterically hindered p-bisphenols: Lowinox 44 B 25, Lowinox

CA 22 and Hostanox 03; sterically hindered amines (HALS compounds, Hindered Amine Light Stabilizers) : Tinuvin 292, CG L-123 and Tinuvin 440; sulfides: Lowinox DSTDP and Vulkanol 88; phosphites: Naugard 524 and Naugard TNPP; mixtures of phenols, especially sterically hindered phenols, and HALS compounds:

Irgaperm 1994;

mixtures of phenols, especially sterically hindered phenols, and sulfides: CG 25- 650, Irganox 1035 and Irganox 1520; mixtures of o-bisphenols, especially sterically hindered o-bisphenols, and sulfides: Irganox 1081; and mixtures of p-bisphenols, especially sterically hindered p-bisphenols, and sulfides: Lowinox 44 S 36.

Within the scope of the present invention, it has been found that particularly high stabilities can be achieved with an oxygen-impermeable support, which holds for, for example, metals and glass, both of which are also available as a flexible film material and can be cast upon.

In an advantageous embodiment of the present invention, the photochromic material according to the present invention comprises further layers, such as intermediate layers, functional and protective layers, with which the stability can be further improved and with which the material can be adapted to the desired application.

For light stability, it has been found preferred for the material to contain at least one UV absorber. Although the UV absorber leads to stability benefits in any layer, i.e., for example, also in the photochromic, barrier and/or absorber layers as well as in the support, the effect is the more pronounced, the closer it is to the side of the material which is directly exposed to the light, and it is particularly pronounced if it is contained in a separate layer UL which, as the uppermost layer, is directly exposed to the light. Such a structure is, for example:

SU - PL - AL - BL - UL or UL - SU - BL - AL - PL, depending on the arrangement of the material.

As the UV absorbers, any substances which absorb ultraviolet radiation may be used alone or in admixture. However, when the UV absorber and its amount to be employed are selected, not only must the stability gain be considered, but it is to be taken care that, in spite of the UV absorption, the photochromic dye obtains enough UV light to switch as desired. UV absorbers suitable therefor and their amounts to be employed can be found out by a person skilled in the art by usual experimentation. Preferably suitable are organic substances, such as triazines (e.g., according to EP-A- 531258), hydroxyphenylbenzothiazoles (e.g., according to EP-A-451813, EP-A-

190003 and EP-A-577122), polymeric UV absorbers (e.g ., according to DE-A- 19500441) and inorganic compounds, such as ZnO nanoparticles (e.g ., according to DE-A-19832937 and US 6,015,655), as well as the classes of substances as described in DE-A-19746513.

The following UV absorbers are preferred : a) Benzotriazole derivatives:

wherein

R, X are the same or different and represent H or alkyl or alkylaryl; b) dimeric benzotriazole derivatives:

wherein

R ¹ , R ² are the same or different and represent H, halogen, Ci to Ci ₀ alkyl, C ₅ to

Cio cycloalkyl, C ₇ to Ci ₃ aralkyl, C ₆ to Ci ₄ aryl, -OR ⁵ or -(CO)-OR ⁵ ; R ³ , R ⁴ are the same or different and represent H, Ci to C ₄ alkyl, C ₅ to C ₆ cycloalkyl, benzyl or C ₆ to C _i4 aryl;

R ⁵ represents H or Ci to C ₄ alkyl; m is 1, 2 or 3; and n is 1, 2, 3 or 4;

wherein

L ¹ represents the bridge -(CHR ³ ) _p -C(=O)-O-(Y-O) _q -C-(CHR ⁴ ) _p -; p is an integer of from 0 to 3; q is an integer of from 1 to 10;

Y represents -CH ₂ -CH ₂ -, -(CHz) ₃ -, -(CHz) ₄ -, -(CHz) ₅ -, -(CHz) ₆ - or CH(CH ₃ )-

CH ₂ -; and

R ¹ , R ² , R ³ , R ⁴ , m and n have the meanings as stated for formula (UV-III); c) triazine derivatives

wherein

R ¹ , R ² , R ³ , R ⁴ independently represent H, alkyl, CN or halogen; and

X represents alkyl; d) triazine derivatives as described in EP1033243; e) dimeric triazine derivatives

wherein

R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ independently represent H, alkyl, CN or halogen; and X represents alkyl or -(CH ₂ CH ₂ -O-) _n -C(=O)-; f) diarylcyanoacrylates

wherein

R represents C ₂ alkyl to Ci ₀ alkyl or aryl; and of which Uvinul 3035 with R = -C ₂ H ₅ and Uvinul 3039 with R -CH ₂ CH(C ₂ H ₅ )C ₄ H ₉ are preferred; h) hydroxybenzophenone derivatives

wherein

A represents H or OH; and

R represents H, alkyl, acyl, -(CH ₂ ) _n -O-(CH ₂ ) _n -CH ₃ , -(CH ₂ ) _n -O-C(=O)-(CH ₂ ) _n -

CH ₃ ; and n is an integer of from 1 to 20; i) resorcinol derivatives

Ar represents phenyl, naphthyl, alkylphenyl or alkoxyphenyl; and R represents H, alkyl, isoalkyl, cycloalkyl, acyl, -(CH ₂ )n-O-(CH ₂ )n-CH3, -(CH ₂ ) _n -O-C(=O)-(CH ₂ ) _n -CH ₃ , -C(=O)-(CH ₂ ) _n -CH ₃ or -C(=0)-Ar; und n is an integer of from 1 to 20;

Particularly suitable UV absorbers among the above mentioned classes of substances include, for example, Tinuvin 234, Tinuvin 360, Tinuvin 1577, Uvinul 3030, Chinaas- sorb 81, Tinuvin 329, Tinuvin 350, Uvinul 3035 and Uvinul 3039.

Surprisingly, in the material according to the present invention, it is also possible to apply an anti-scratch layer without deteriorating the light stability of the material. Rather, this coating, which is preferably applied as an outer layer, can even improve the light stability. In particular, an anti-scratch layer has proven beneficial also in terms of the weather resistance of the material. As an anti-scratch layer, for example, UV-curable acrylate paints are suitable which are obtainable, inter alia, from Bayer and Cytec and preferably contain nanoparticles, for example, from Clariant or Byk.

If the material according to the present invention is a film coated on one side thereof with a photochromic material and intended for being applied to another object, such as a window surface, the adhesion between the object and the film can be sufficient to enable the bonding in favorable cases.

The mentioned object to be coated is preferably transparent and more preferably consists of glass or composite glass which may have further coatings.

In the case of composite materials, the photochromic film according to the present invention may also be within the composite material.

For a more secure application, it is preferred to provide the photochromic film according to the present invention with an adhesive layer (AL) on the desired side, which advantageously in turn has a covering film. The adhesive layer and film are preferably applied in one step after the casting of the photochromic material, espe-

daily by lamination, but may also be cast directly upon a film already provided with the adhesive layer and the cover layer. It is also possible to use the cover film provided with the adhesive layer itself as a support according to the present invention and to cover it by casting if the thus obtained layer composite including the adhesive layer has sufficient mechanical strength to peel it off from the cover film.

In the case of a window film, after the cover film has been peeled off and the film has been applied to the window pane, the material has the following structure in the order given, for example: glass pane - adhesive - photochromic layer - barrier and/or absorber layer(s) - support - anti-scratch layer - air. When applied as a window film, the photochromic coating can successfully reduce the light entering a room automatically with increasing outdoor brightness. When the solar irradiation is high, the blinding effect is thus reduced, and the heating of the room caused by conversion of visible light to heat is reduced.

However, it may be that the room nevertheless heats up too much when the solar irradiation is high, depending on requirements. In order to avoid this, the photochromic material according to the present invention can be designed in such a way that it additionally absorbs and/or reflects light in the infrared region, especially in the near infrared region, i.e., with wavelengths of larger than 700 nm, preferably between 700 nm and 2000 nm, especially between 700 nm and 1500 nm. Such absorption and/or reflection may also increase with increasing radiation (thermochromicity), but may also be permanent because it does not cause any visible deterioration when the solar irradiation is low. The absorption or reflection can be achieved by appropriate dyes in the support material or in a layer of the photochromic material (IR or NIR filter), but also, for example, by interference or refraction effects, such as several thin layers having the appropriate layer thickness and different refractive indices.

All the above mentioned layers may not only be applied on one side of the support, but alone or in combination also on the other side of the support, for example, in order to obtain particularly light-stable films.

In particular, thin films and sheets having a thickness of from 10 to 300 μm, espe- daily from 50 to 150 μm, are suitable as the support. A survey of support materials and auxiliary layers applied to their front and back sides is set forth in Research Disclosure 37254, Part 1 (1995), p. 285, and in Research Disclosure 38957, Part XV (1996), p. 627. Support materials which are particularly suitable for the present

invention include cellulose triacetate, polycarbonate, polystyrene, poly(vinyl chloride) and polyesters, such as polyethylene terephthalate (PET) or polyesters of ethylene glycol and naphthalene dicarboxylic acid (PEN).

Information about binders suitable for the layers according to the present invention may be found in Research Disclosure 37254, Part 2 (1995), p. 286, and Research Disclosure 38957, Part ILA (1996), p. 598.

Hydrophobic components of the layers, such as UV absorbers, stabilizers, oxygen scavengers etc., are preferably dissolved or dispersed in high-boiling organic solvents or introduced using loadable latexes, as described above for oxygen scavengers, for example.

The photochromic material may further contain filter dyes, plasticizers (latexes), biocides, additives for reducing the yellowing and others. Suitable compounds may be found, for example, in Research Disclosure 37254, Part 8 (1995), p. 292, Research Disclosure 37038, Parts IV, V, VI, VII, X, XI and XIII (1995), p. 84ff, and Research Disclosure 38957, Parts VI, VIII, IX and X (1996), p. 607 and 610 ff.

The layers of photochromic materials can be cured, i.e., the binder employed, for example, gelatin or PVA, is cross-linked by suitable chemical processes.

Suitable curing agents may be found, for example, in Research Disclosure 37254, Part 9 (1995), p. 294, Research Disclosure 37038, Part XII (1995), page 86, and Research Disclosure 38957, Part II. B (1996), p. 599.

The invention is described more closely in the following examples which are, however, not to be construed as limiting the invention.

Examples

Example 1 : Layer Structures Layer structure 101 (structure: SU-PL) : The photochromic material 101 was prepared by applying a layer having the following composition at first to a triacetate film having a thickness of 120 μm by means of a continuously operating casting machine: Layer 1 (photochromic layer, PL), dry application 10 μm

99.97% by weight of acrylate paint (30% by weight solids) with a solvent mixture of ethyl and butyl acetates of 1 : 1; and

0.03% by weight of dye according to Table 1.

Thus, the dye was dissolved in toluene at a concentration of 30 g/l each. In this layer and in the layers mentioned below, the stated weights are respectively based on the

dry mass of the stated additives, i.e., without the substances which are volatile upon drying, such as volatile solvents.

Layer structure 201 (structure: SU-PL-BD : Subsequently, the material was dried at room temperature in air. The photochromic material 201 was first prepared as described for 101, and thereafter, another layer having the following composition was applied : Layer 2 barrier layer BL), dry application 10 μm

100.00% by weight of polyvinyl alcohol Elvanol T-66 from Dupont (10% by weight), aqueous solution. The material obtained was again dried at room temperature in air. The photochromic materials were irradiated with the light of a 100 kLx xenon lamp normalized to daylight, and the percent density reduction of the dye in the switched state was measured. Low percent density reductions correlate with a high stability of the dye in the photochromic layer. A sample exposed until the maximum absorption was reached respectively served as a 100% sample. As a measure of the useful life, the irradiation time after which the optical density in the switched state was reduced to 1/lOth of the initial value was determined. The values of the relative useful life are stated in Table 2 as percent values, wherein the value for layer structure 101 was arbitrarily set at 100%. Table 2

As can be seen from Table 2, a barrier layer according to the present invention significantly improves the useful life of the photochromic layer.

Example 2: Dye Stabilization For a stability test, phototropic dye was dissolved in toluene in six different concentrations from 0.6 to 10 g/l, and the stabilizer to be tested was respectively added to these solutions at the same concentration as the dye. In a quartz cuvette of 1 mm thickness, the solutions were exposed for 24 h to the radiation of a 100 kLx xenon lamp normalized to daylight. The total dose was 4-10 ⁶ Lxh. Subsequently, the

maximum reachable coloration of the solution was measured in comparison with the coloration prior to irradiation.

The penetration depth for UV is limited by the absorbing dye. It depends on the concentration of the dye and generally is significantly smaller than the cuvette thickness of 1 mm. The dye is destroyed layer by layer. As long as a layer that is larger than the penetration depth of the UV remains undestroyed, the maximum reachable coloration is not affected. Only after the destruction of the last layer, the coloration is drastically reduced. A measure of the action of the stabilizer is the concentration of the dye at which the remaining maximum coloration is lowered to half after 24 h. These values are summarized in Table 3 as K _FS 5o- From this value, the relative percent useful life of the dye can be calculated; it is stated in Table 2 as LDFS5O- Thus, the dye useful life L _DFS5 o in solution 2-1 was arbitrarily set to 100%, and the values for the other respective solutions were obtained according to the formula: K _F s5o in solution 2-1 divided by K _FS5 o in the respective solution. Table 3

As can be clearly seen from Table 3, the dye useful life can be significantly extended by suitable stabilizers. The stability test shown in this Example has proven to be a good preselection for photochromic compositions for which comparable tendencies are found in layer structures such as those according to Example 1.

Example 3: Self-supporting photochromic sheets based on cellulose esters 75 solutions of a cellulose ester in dichloromethane/methanol 9: 1 with the additives summarized in Table 3 below were prepared, coated with a doctor knife onto a polished chrome-nickel steel plate, partially dried, peeled off the plate and dried

with the air temperature increasing up to 100 ⁰ C to form clear photochromic layers having a dry layer thickness of about 45-60 μm. The variations in the layer thickness were reflected in the achievable maximum densities. The folloing cellulose ester (Matrix) were employed : Cellulose triacetate (TAC), cellulose acetate propion- ate (CAP) and cellulose acetate butyrate (CAB). The basic formulation contained 50 g of cellulose triacetate (Eastman), 274 g of dichloromethane and 19.5 g of methanol.

The following compounds were employed as plasticizers: Triphenyl phosphate (TPP), Tricresyl phosphate (TCP), Diphenyl 2-ethylhexyl phosphate (DOP), Tris(2- ethylhexyl) phosphate (TOP), Triacetin (TRI), N-Octylpyrrolidone (NOP), Triton XlOO (TXlOO), N,N-Dibutylformamide (DBF) and a polyglycol ether (PEGE). The following compounds were employed as photostabilizers (quenchers): UV 1084 (commercial product supplied by Dayang Chemical Co., corresponds to Cyasorb UV 1084 (Cytec), UV 2002, (corresponds to Irgastab 2002 (Ciba).) 3-Amino-l,2,4-triazole, Ni di-n-butyldithiocarbamate, Uvinul 5050H (sterically hindered amine, so-called HALS compound, BASF).

BHA is butylated 4-hydroxyanisole, a known antioxidant. PEGE is a commercially available polyethylene glycol methyl ether. For information about the prior art, reference is made to the review ,,Photostabilization of Polymers" by J.F.Rabek, Elsevier 1990, and the primary literature referenced therein.

The following compounds were employed and tested as UV absorbers: Uvinul 3030, Uvinul 3033, 199 02 771 Al.

The photochromic compound (hereinafter: ,,dye") was Spiro-7 of DE 19902771. The amount employed is stated in percent by weight (%), based on the cellulose ester, and further additives vary according to the individual experiments and are stated in the Tables in %.

The measurement of the density drop after the irradiation had been switched off (from D _max to D _mιn ) was effected on the dried sample after 24 hours and - after 6 days of storage in air.

The air temperature in the measuring space was kept substantially constant at 25° ± 3°.

The finished layers were irradiated in a capsulated irradiation plant under an ultraviolet lamp for 20 s, exported and measured under a transmission photometer with a delay of 100 +/- 10 ms (The maximum density D _max and the decaying dark

color of the samples were recorded over 2 min. From the density versus time profile, the half-life τ/2 for the decay is calculated to 50% of the maximum value

0.5 x (Dmax minus D _mιn ). The change of the maximum density D _max (loss of color) and the minimum density D _mιn (decrease of capability of being decolored) are stated in percent.

The testing of the layers for photostability of the photochromic system was effected in an irradiation device Atlas Xenon Weather-O- Meter CI 3000+ over 12 h with an irradiation density of 1 W/m ² . The setting of the chamber conditions was: Chamber temperature 35°C, relative humidity: 70%

The change in density as a consequence of irradiation is stated in percent (%), based on the maximum density.

Table 4