TECHNICAL FIELD

The invention relates to a photochromic plastic laminate comprising a self-supporting photochromic polymer film and at least one optically transparent plastic sheet, wherein the self-supporting photochromic polymer film comprises a thermoplastic polymer and at least one organic photochromic molecule comprising a chromophore. The self-supporting photochromic polymer film can comprise a ketone. The organic photochromic molecule comprising a chromophore is preferably of the T-type. A typical photochromic plastic laminate of the invention is a self-supporting and freestanding photochromic aliphatic thermoplastic polyurethane film imbibed with a ketone, such as acetone and cyclohexanone, further comprising one or more of a spiropyran, a spirooxazine and a naphtopyran, which is laminated with a single sheet of optically transparent polymer material or which is laminated between two sheets of optically transparent material of which at least one sheet is an optical grade polycarbonate. The invention also relates to a method for the manufacturing of such a photochromic plastic laminate, and to the use of such a photochromic plastic laminate in the manufacturing of an article. Furthermore, the invention relates to an article comprising the photochromic plastic laminate, such as a window and a visor.

BACKGROUND

Photochromism is a physical phenomenon which has been well-established since the first half of the 20th century. It is the ability of a photochromic molecule to (reversibly) change from an inactivated state, at which the molecule has a relative lighter colour (high L value according to CIELAB measurement), to an activated state, at which the molecule has a relative darker colour (lower L value according to CIELAB measurement), through exposure to electromagnetic radiation, such as UV light. Basically, when exposed to UV light, in the photochromic molecules a chemical bond breaks causing molecular rearrangement into an entity that absorbs light at longer wavelengths in the visible region. This molecular rearrangement in turn causes the material in which the photochromic molecule is embedded to darken.

Photochromic molecules are separated into two categories: inorganic and organic photochromic molecules.

The first industrial application of a photochromic material was the introduction of photochromic ophthalmic lenses in the 1960s by the company Corning. US patent 3,208,860 filed in July 1962 by Corning is mentioned as the first patent describing photochromic glass and an article made thereof. Coming’s Photogray® ophthalmic lenses were the commercial result of this patent. These photochromic ophthalmic lenses turn grey upon stimulus by UV light, shading their wearers’ eyes from the sun. This first industrial application of photochromism used inorganic photochromic molecules, i.e. silver halides.

Nowadays, it is well-known that these inorganic photochromic molecules are not favourable to use when compared to organic photochromic molecules. In general, organic photochromic molecules respond faster to light stimulus. Secondly, organic photochromic molecules are in general relatively less expensive to produce. Thirdly, even though lenses comprising an inorganic photochromic molecule have a longer lifetime than plastic lenses containing organic photochromic molecules, the photochromic reaction of inorganic photochromic molecules gets stronger over time up to the point that materials containing inorganic photochromic molecules, such as silver halides, remain in their darkened state even without light stimulus, therewith rendering such lenses useless. Furthermore, silver halides cannot be used in plastic lenses, unlike organic photochromic molecules, and therefore have become less popular, since the use of glass lenses has decreased significantly, while the use of plastic lenses is now becoming the standard.

Therefore, research and product development now mainly focuses on use and application of organic photochromic molecules. Organic photochromic molecules are most commonly incorporated in dyes, which contain at least one organic photochromic molecule or compositions comprising several types of organic photochromic molecules. Commonly used organic photochromic molecules include spirooxazines, naphthopyrans, and diarylethenes. The majority of the organic photochromic molecules change colour in response to exposure to UV radiation or visible light and revert back to their original colour when the light source is removed; this is known as T-type photochromism since the back reaction is driven thermally. That is to say, the back reaction is temperature-dependent. The higher the temperature the less dark the photochromic film will be in its activated state, and in addition the faster it will return to its inactivated state. The lower the temperature, the longer a film comprising an organic photochromic molecule will take to return to its inactivated state, and in addition the darker the film will be in its activated state. Typical photochromic dyes of the T-type are spirooxazines, naphthopyrans, spiropyrans.

Available photochromic molecules are designed such that they cover a range of colour spectra, e.g. reds, blues, yellows etc., and so could have industrial applications in many market segments. Applications include, but are not limited to, use in articles such as automotive windows and aircraft windows, helmet visors, ophthalmic lenses, self-shading sunglasses, and windowpanes for buildings. All these articles are for example made from plastic and/or glass.

One method of incorporating a photochromic element such as a film comprising an organic photochromic molecule, into a product, i.e. an article, is by laminating a photochromic film onto at least one sheet. This method has been explored in many patents and patent applications, such as US 2004/0126587 A1 , US 7,036,932 B2 and US 2005/0233153 A1. Commercially available photochromic laminates made of plastic, are for example the Transitions® ophthalmic lenses and inserts for a motor visor.

However, currently available photochromic plastic laminates have several limitations that prevent them from being widely industrial applicable in many market segments. The biggest problem and concern encountered in industry is light fatigue. This light fatigue refers to the irreversible deterioration of the photochromic reaction after repeated exposure to UV radiation or to visible light. Photochromic plastic laminates may already lose photochromic activity after only 100 hours of light exposure, while they completely lose all photochromic activity after only 500 hours of light exposure. This loss of photochromic activity makes these laminates industrially inapplicable in many market segments due to high costs relating to replacement of worn laminates and with regard to unacceptable high use of raw materials related to the short turn-over time. Another problem that is preventing photochromic plastic laminates from being beneficially commercially applicable is that the photochromic reaction is too slow for various applications such as incorporation in articles such as automotive windows or aircraft windows and helmet visors, for which a relatively fast colour (intensity) switch from dark to light state, or vice versa, in the order of milliseconds to seconds is needed when for instance a car driver or a motorcyclist enters or exits a tunnel. Generally, currently available photochromic laminates cut off about 50% of light within the first minute and about 80% within 15 minutes, but the back reaction is in general much slower. Most laminates will have returned for only 60% back to the clear, non-darkened / non-coloured state after 5 minutes, and such a laminate may need up to an hour to clear completely.

Finally, another limitation of these current photochromic plastic laminates is that they cannot be produced cost-effectively to be durable at a large size. So far, no photochromic plastic laminates are commercially available for applications such as in windows in buildings, cars or aircrafts. Currently, the only solution for providing a laminate with a relatively larger surface in the order of 0,5-1 square meter, has been to add an electrochromic element to the laminate. However, such a laminate is dependent on electricity which is costly over time. Additionally, the electrochromic laminates are not reliable enough for certain applications in which failure to supply the electrochromic film with the electric current it requires to (de)activate, could have potentially catastrophic consequences. That is to say, when such an electrochromic glass laminate is applied in an article such as a helmet visor, failure to provide the electrochromic element with sufficient power, may result in a visor that remains in its dark state as a consequence of the absence of the decolouring effect.

SUMMARY

The present invention will be described with respect to particular embodiments but the invention is not limited thereto but only by the claims.

The embodiments of the invention described herein can operate in combination and cooperation, unless specified otherwise.

It is a first goal of the invention to provide an improved photochromic plastic laminate with an increased lifetime and/or with an improved velocity of discolouring once exposure of the film to UV radiation is terminated and/or which can be manufactured to have a large surface area, of e.g. 10 cm ² - 10 m ² , such as 25 cm ² -3 m ² , and/or which are more durable, and/or with allow for faster switching between light state and dark state and/or can be cost-effectively produced at a size having a relatively large surface area, e.g. 40 cm ² -1 ,5 m ² , A4 size (210 x 297 mm).

It is an objective of the current invention to provide a photochromic plastic laminate that has a high optical transparency, has good resistance to wear in terms of loss of photochromic activity over time, and can be manufactured to cover large surface areas, e.g. 300 cm ² -1 m ² .

At least one of the above objectives is achieved by providing a photochromic plastic laminate comprising a self-supporting photochromic aliphatic thermoplastic polyurethane film imbibed with a ketone and further comprising at least one organic photochromic molecule comprising a chromophore which is/are dissolvable in said ketone, bonded to at least one sheet of optically transparent polycarbonate. A first aspect of the invention relates to a photochromic laminate comprising a first sheet of optically transparent material and a self-supporting photochromic polymer film which is bonded at least partially to a surface of the first sheet of optically transparent material, wherein the self-supporting photochromic polymer film comprises:

(a) a thermoplastic polymer;

(b) between 0,0% and 14% by weight of a ketone based on the total weight of the self-supporting photochromic polymer film; and

(c) at least one organic photochromic molecule comprising a chromophore, wherein said organic photochromic molecule comprising a chromophore is soluble in said ketone of (b) at a concentration of at least 0,1 % based on the weight of a solution of the ketone containing the dissolved organic photochromic molecule comprising a chromophore at a temperature of between 15°C and 30°C,

wherein the thermoplastic polymer of (a) is thermoplastic polymer that is previously treated with the solution of the ketone containing the dissolved organic photochromic molecule comprising a chromophore of (c) and then dried such that remaining ketone after said treatment and subsequent drying is imbibed in said thermoplastic polymer.

The inventors found that surprisingly stable photochromic activity is achieved with these photochromic laminates. It is preferred that the organic photochromic dye(s) are evenly (and homogenously) distributed in the thickness of the free-standing photochromic polymer film. The polymer in the free-standing photochromic polymer film is preferably an aliphatic thermoplastic polyurethane, preferably a polyester-based aliphatic thermoplastic polyurethane or a polyether-based aliphatic thermoplastic polyurethane.

Embodiments are the photochromic laminate wherein a second sheet of optically transparent material is bonded at least partially to a free surface of the self-supporting photochromic polymer film. It is preferred that the first sheet of optically transparent film is a polycarbonate. It is also preferred that the second sheet of optically transparent film is a polycarbonate. The at least one organic photochromic molecule comprising a chromophore comprised by the self-supporting photochromic polymer film is preferably an organic T-type photochromic dye. Preferred are organic T-type photochromic molecules comprising a chromophore which are polydialkylsiloxane-substituted naphtopyrans comprising two identical chromophores.

Particularly preferred are photochromic laminates comprising the self-supporting photochromic polymer film which is containing between 0,1 % and 10% by weight ketone, preferably cyclohexanone, based on the weight of the film.

A second aspect of the invention relates to a method for producing a photochromic laminate comprising the steps of:

a) providing a self-supporting photochromic polymer film of the invention;

b) bonding a first sheet of optically transparent material at least partially to a surface of the self-supporting photochromic polymer film of step a);

c) optionally bonding a second sheet of optically transparent material at least partially to a free surface of the two-layer laminate of step b); and d) optionally laminating a third sheet of optically transparent material at least partially to a free surface of the three-layer laminate of step c).

Preferred is the method, wherein in step c) or in step d) the second sheet of optically transparent material or the third sheet of optically transparent material is bonded to the free surface of the self- supporting photochromic polymer film of the two-layer laminate provided in step b). It is preferred that the first sheet of optically transparent material is a polycarbonate and it is preferred that the second sheet of optically transparent material is a polycarbonate. It is preferred that said optional third sheet of transparent material is an anti-fog foil or an anti-scratch protective foil.

Yet a further aspect of the invention relates to the use of the photochromic laminate or use of the photochromic laminate obtainable by the method or obtained with the method in the manufacturing of an article.

Another aspect of the invention relates to an article comprising the photochromic laminate or the photochromic laminate obtainable by the method (or obtained with the method).

Preferred articles comprising the photochromic laminate or the photochromic laminate obtainable by the method are any of an optic article, preferably an optic article selected from, but not limited, to visors, goggles, ophthalmic lenses, sunglasses, face-shields, a window pane, a roof top for a car, architectural windows, automotive windows, and aeronautic windows, to name a few.

DEFINITIONS

Unless defined otherwise, all technical terms and scientific terms used herein have the same meaning as commonly understood by the relevant skilled person.

The present invention will be described with respect to particular embodiments, but the invention is not limited thereto, unless so described in the claims.

Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. The terms are interchangeable under appropriate circumstances and the embodiments of the invention can operate in other sequences than described or illustrated herein.

Moreover, the terms top, bottom, over, under and the like in the description and the claims are used for descriptive purposes and not necessarily for describing relative positions. The terms so used are interchangeable under appropriate circumstances and the embodiments of the invention described herein can operate in other orientations than described or illustrated herein.

The embodiments of the invention described herein can operate in combination and cooperation, unless specified otherwise.

Furthermore, the various embodiments, although referred to as“preferred” or“e.g.” or “for example” or“in particular” or“particularly preferred” are to be construed as exemplary manners in which the invention may be implemented rather than as limiting the scope of the invention.

The term“comprising”, used in the claims, should not be interpreted as being restricted to the elements or steps listed thereafter; it does not exclude other elements or steps or features. It needs to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of for example the expression“a photochromic polycarbonate laminate comprising A and B” should not be limited to photochromic polycarbonate laminates consisting only of components A and B, rather with respect to the present invention, the only enumerated components of the photochromic polycarbonate laminates are A and B, and further the claim should be interpreted as including equivalents of those components.

In addition, reference to an element by the indefinite article "a" or "an" does not exclude the possibility that more than one of the element are present, unless the context clearly requires that there is one and only one of the elements. The indefinite article "a" or "an" thus usually means "at least one".

The term“chromophore” has its regular scientific meaning throughout the text, and here refers to the part of a molecule that defines the colour of said molecule.

The term“photochromic” has its regular scientific meaning throughout the text, and here refers to a molecule being capable of darkening or changing colour when exposed to light.

The term“photochromism” has its regular scientific meaning throughout the text, and here refers to the reversible transformation of a chemical entity between two molecular forms having different absorption spectra induced in one or both directions by photo-irradiation, such that a reversible change of colour occurs upon exposure to light.

The term“film” has its regular scientific meaning throughout the text, and here refers to a thin sheet of material that can be flexible and can be bonded to another material such as a sheet of material.

The term“bonded” has its regular scientific meaning throughout the text, and here refers to one sheet of material being bound to another sheet or film or layer of material by any binding means indicated.

The term“laminate” has its regular scientific meaning throughout the text, and here refers to an article that comprises a first sheet or film or layer or foil of material that is bonded with at least a portion of its first major surface to at least a portion of a first major surface of a second sheet or film or layer or foil of material. Optionally, at least a portion of a first major surface of a third sheet or layer or film or foil of material is bonded to at least a portion of a second major surface of the first sheet or layer or film or foil of material and/or at least a portion of a second major surface of the second sheet or film or layer or foil of material. Optionally, further one or more layers, sheets or films or foils of material are bonded to any of the first, second and/or third foil, film, layer or sheet of material.

The term“optical grade” such as for example used in“optical grade plastic” has its regular scientific meaning throughout the text, and here refers to a material such as a plastic that is suitable for the manufacturing of optic articles, such as the optic articles defined herein.

The term“polycarbonate based on the precursor monomer bisphenol A” has its regular scientific meaning known in the art throughout the text, and here refers to the polycarbonate material obtained through the reaction of bisphenol A with phosgene.

The term“thermoplastic polyurethane film” or“TPU film” as used herein, should be understood as“ketone-treated thermoplastic polyurethane film”, which refers to the process of soaking or immersing the TPU film in a ketone solvent as hereunder defined, unless specified otherwise. In brief, an example of a process of treating the TPU film in a ketone solvent comprises the steps of:

(a) providing a non-treated TPU film with regard to ketone treatment; (b) contacting the TPU film with the ketone by for example imbibing or soaking the non- treated TPU film in ketone solvent and at least one photochromic dye dissolved in said solvent by immersion of the film in the solution of ketone with photochromic dye(s) dissolved therein;

(c) optionally discarding excess ketone solvent that is not impregnated in the TPU film or adhered to the TPU film;

(d) drying the TPU film (for example in a hot air circulating oven), for a period of time such that the TPU film comprises between for example 0% and 12% by weight residual ketone based on the weight of the imbibed TPU film.

Preferably, the TPU film comprises between 0% and 14% ketone, more preferably between 0% and 5%, most preferably between 0% and 3% based on the weight of the TPU film, preferably 0%, about 0,1 %, 1 %, 2%, or 3% or between 0,1 % and 10%, such as about 3% or 8% by weight based on the weight of the imbibed TPU film. Also preferred is the treated TPU film comprising 0,0%-12% ketone after the drying step (d), or 0,1 %-12% ketone, or less than 0,1 % ketone.

The term“optic glass” has its regular scientific meaning throughout the text, and here refers to a glass that is suitable for the manufacturing of optic articles, such as the optic articles defined herein.

The term“float glass” has its regular scientific meaning throughout the text, and here refers to a sheet of glass made by floating molten glass on a bed of molten metal, giving the float glass sheet uniform thickness and two flat major surfaces.

The term“glass plies” has its regular scientific meaning throughout the text, and here refers to a single sheet of glass.

The term“sheet of optically transparent material” as used herein refers to a material that is optically transparent and has a total transmittance of at least 50%.

The term“total transmittance” has its regular scientific meaning throughout the text, and here refers to the percentage of solar radiation that can pass through an optic article such as a laminate of polymer sheets or a sheet of glass by any means.

The term“UV protective film” has its regular scientific meaning throughout the text, and here refers to a film that can block transmittance of at least one wavelength of light within the UV spectrum.

The term“foil” has its regular scientific meaning throughout the text, and here refers to a freestanding self-supporting flexible sheet of material that can be bonded to the surface of another material, for example for the purpose of preventing or promoting a certain feature, i.e. preventing scratches, preventing light transmittance.

The term“coating” as used herein has its regular scientific meaning throughout the text, and here refers to a covering that is applied to the surface of an object, such as an article, wherein the coating is for example decorative, functional or both, e.g. a coating providing corrosion resistance to the coated object, a coating providing wear resistance to a coated article. Such a coating is not a frees- standing self-supporting layer and requires a support or substrate.

The term“L a b values” has its regular scientific meaning throughout the text, and here refers to the CIELAB measurement that measures colour differences, wherein “L” indicates lightness, “a” indicates the red/green coordinate and“b” indicates the yellow/blue coordinate. The term“decay half time”, expressed as T1/2 in seconds, as used herein refers to the time it takes for a photochromic material to reach the point where it is halfway to returning from its activated state to its original ground state before being activated.

The term“press lamination process” has its regular scientific meaning throughout the text, and here refers to a lamination process using for example a press laminator for laminating for example two or more of any of for example films, sheets, foils, layers of certain materials.

The term“autoclave process” has its regular scientific meaning throughout the text, and here refers to a lamination process by autoclaving for laminating for example two or more of any of for example films, sheets, foils and layers of certain materials.

The term“optic article” has its regular scientific meaning throughout the text, and here refers to an article with sufficient optical transparency and sufficiently high uniformness so that it is suitable for use in optic applications such as ophthalmic lenses, car windshields, helmet visors, etc.

The term“article” has its regular scientific meaning throughout the text, and here refers to an item that can be manufactured.

The term“self-supporting”, or“free-standing”, has its regular scientific meaning throughout the text, and in the context of a thermoplastic film refers to a coherent and consistent film while not being supported, by for example a carrier or a substrate.

ABBREVIATIONS USED

The abbreviation“CIELAB” has it regular scientific meaning throughout the text, and here refers to “Commission Internationale de I’Eclairage L*a*b color space”.

The abbreviation“TPU” has its regular scientific meaning throughout the text, and here refers to“thermoplastic polyurethane”.

DPC: diphenylcarbonate; PC: polycarbonate; PU: polyurethane.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 displays a photochromic laminate 1 , 2 and 3, comprising a self-supporting photochromic polymer film 10 or 100. Figure 1A. Photochromic laminate 1. A self-supporting photochromic polymer film 10 has a first major surface 20a and a second major surface 20b at the opposite site of the film. The major surface 20a of the self-supporting photochromic polymer film is bonded to the first major surface 21a of a sheet of optically transparent material 11 , e.g. a sheet of polycarbonate, providing a two-layer photochromic laminate 1. The sheet of optically transparent material has an exposed major surface 21 b. Figure 1B. Photochromic laminate 2. Similar to the two-sheet photochromic laminate of Figure 1A., a first major surface of the self-supporting photochromic polymer film 10 is bonded to a first major surface of a sheet of optically transparent material 11. In addition, the second major surface 20b of the self- supporting photochromic polymer film 10 is bonded to a first major surface 22a of a second sheet of optically transparent material 12, providing a three-layer photochromic laminate 2. The second major surfaces 21 b and 22b of the sheets of optically transparent material 11 and 12, respectively, are exposed in the laminate 2. Figure 1C. Photochromic laminate 3. A first surface of a self-supporting photochromic polymer film 100 is bonded to a first major surface of a sheet of optically transparent material 1 10 and the second surface of a self-supporting photochromic polymer film 100 is bonded to a first major surface of a sheet of optically transparent material 120. The second surface 21 b of the sheet of optically transparent material 110 is bonded to the first major surface 24a of a further sheet of optically transparent material 140, with the second surface 24b of said further sheet 140 exposed. The second surface 22b of the sheet of optically transparent material 120 is bonded to the first major surface 23a of yet a further sheet of optically transparent material 130, with the second surface 23b of said yet further sheet 130 exposed.

DETAILED DESCRIPTION

The present invention will be described with respect to particular embodiments but the invention is not limited thereto but only by the claims. The embodiments of the invention described herein can operate in combination and cooperation, unless specified otherwise.

A first aspect of the invention relates to a photochromic laminate comprising a first sheet of optically transparent material and a self-supporting photochromic polymer film which is bonded at least partially to a surface of the first sheet of optically transparent material, wherein the self-supporting photochromic polymer film comprises:

(a) a thermoplastic polymer;

(b) between 0,0% and 14% by weight of a ketone based on the total weight of the self-supporting photochromic polymer film; and

(c) at least one organic photochromic molecule comprising a chromophore, wherein said organic photochromic molecule comprising a chromophore is soluble in said ketone of (b) at a concentration of at least 0,1 % based on the weight of a solution of the ketone containing the dissolved organic photochromic molecule comprising a chromophore at a temperature of between 15°C and 30°C, wherein the thermoplastic polymer of (a) is thermoplastic polymer that is previously treated with the solution of the ketone containing the dissolved organic photochromic molecule comprising a chromophore of (c) and then dried such that remaining ketone, if any, after said treatment and subsequent drying is imbibed in said thermoplastic polymer.

A further aspect of the invention relates to a photochromic laminate comprising a first sheet of optically transparent material and a self-supporting photochromic polymer film which is bonded at least partially to a surface of the first sheet of optically transparent material, wherein the self-supporting photochromic polymer film comprises:

(a) a thermoplastic polymer;

(b) between 0,0% and 14% by weight of a ketone based on the total weight of the self-supporting photochromic polymer film; and

(c) at least one organic photochromic molecule comprising a chromophore, wherein said organic photochromic molecule comprising a chromophore is soluble in said ketone of (b) at a concentration of at least 0,1 % based on the weight of a solution of the ketone containing the dissolved organic photochromic molecule comprising a chromophore at a temperature of between 15°C and 30°C, wherein the one or more organic photochromic molecule comprising a chromophore, and the solvent if present, are distributed across the thickness of the self-supporting photochromic polymer film. The solvent is the ketone of (b) and (c).

The at least one organic photochromic molecule comprising a chromophore preferably is an organic T-type photochromic compound. An example of a photochromic laminate is provided in Figure 1A.

Treating of the thermoplastic polymer with the solution of ketone with photochromic dyes dissolved therein is for example achieved by contacting, i.e. immersion of the thermoplastic film in the solution of the ketone containing the dissolved photochromic molecule(s) comprising a chromophore. The thermoplastic polymer is thus thermoplastic polymer that is pretreated with the solution of the ketone containing the dissolved photochromic molecule(s) comprising a chromophore. By treating the thermoplastic polymer film with ketone, the ketone is imbibed in the thermoplastic polymer and the dissolved photochromic dye(s) is/are impregnated in the thickness of the thermoplastic polymer film, preferably the photochromic dye(s) are evenly and homogenously distributed in said thickness of the thermoplastic polymer film.

A further aspect of the invention relates to a photochromic laminate comprising a first sheet of optically transparent material and a self-supporting photochromic polymer film which is bonded at least partially to a surface of the first sheet of optically transparent material, wherein the self-supporting photochromic polymer film comprises:

(a) a thermoplastic polymer;

(b) between 0,1 % and 12% by weight of a ketone based on the total weight of the self-supporting photochromic polymer film; and

(c) at least one organic photochromic molecule comprising a chromophore, wherein said organic photochromic molecule comprising a chromophore is soluble in said ketone of (b) at a concentration of at least 0,1 % based on the weight of a solution of the ketone containing the dissolved organic photochromic molecule comprising a chromophore at a temperature of between 15°C and 30°C.

The at least one organic photochromic molecule comprising a chromophore, i.e. a‘photochromic dye’ or a‘photochromic molecule’ is preferably a T-type photochromic dye. Preferred is a photochromic laminate, wherein the self-supporting photochromic polymer film comprises less than 0,1 % by weight of the ketone based on the total weight of the self-supporting photochromic polymer film. It is to be understood that the photochromic laminate may also comprise more than 12% by weight of the ketone based on the total weight of the self-supporting photochromic polymer film, such as less than 20% by weight, 15%, 16% or 18% by weight. The inventors found that a lower weight percentage of residual cyclohexanone, e.g. less than 1 wt%, in the TPU film is preferable for certain embodiments where blistering may occur or when the risk of occurring said blistering is expected in the TPU film upon the manufacturing of the end product, i.e. the photochromic laminate. Similarly, the photochromic laminate can comprise an amount of ketone of for example 0,01 % by weight, 0,025, 0,050, 0,075 or 0,15% by weight, based on the total weight of the self-supporting photochromic polymer film.

The inventors surprisingly found that when a sheet, foil, layer or film of a thermoplastic polymer comprises imbibed ketone to a certain weight percentage based on the mass of the thermoplastic polymer, such as between about 0,1 wt% and 13wt% ketone, or less than 0,1 % by weight, such as between 0% and 0,05% by weight, or even no residual ketone at all after contacting (immersing) the thermoplastic polymer with the solution of the ketone containing the dissolved organic photochromic molecule(s) comprising a chromophore and a subsequent drying step, the sheet, foil, layer or film becomes more flexible, due to enhanced plasticizing of the thermoplastic polymer. The effect of improved flexibility, i.e. decreased stiffness of the film or foil due to decreased Young’s modulus, is also established when the thermoplastic polymer is first immersed or soaked in the ketone followed by completely drying the thermoplastic polymer from the ketone, although to a lower extent. Further surprisingly, the inventors thus also found that when the film of thermoplastic polymer, such as TPU, was immersed with ketone and subsequently completely dried again, the similar effect with regard to the improved flexibility, i.e. decreased stiffness of the film or foil due to decreased Young’s modulus, was achieved when compared with a film immersed with ketone which still comprises imbibed ketone to a certain extent, e.g. between 3% and 8% by weight ketone based on the total weight of the self- supporting polymer film, according to the invention.

The inventors found that for the self-supporting polymer film comprised by the photochromic laminate the glass transition temperature Tg (Tan Delta) is decreased to a surprisingly large extent, e.g. from Tg (Tan Delta) = 12°C for the thermoplastic polymer which is not treated (immersed, contacted) with a ketone, and which does not comprise imbibed ketone, to for example 7°C or even as low as -1°C, after e.g. immersion of the very same thermoplastic polymer in e.g. cyclohexanone or acetone. This decrease in softening temperature is accompanied with a decreased storage modulus for the self- supporting polymer film, further demonstrating the reduced stiffness of the self-supporting polymer film with imbibed ketone when compared to the stiffness of the thermoplastic polymer before immersion with a ketone. Thus, the self-supporting polymer film comprised by the photochromic laminate, comprising imbibed ketone has a Tg which is at least 1°C lower than the Tg for a similar film made of the thermoplastic polymer comprised by the film of the invention, though not comprising the imbibed ketone, preferably the Tg is at least 2°C lower, such as 4°C lower, 6°C lower, 8°C lower, 10°C lower, 12°C lower, 14°C lower or 16°C lower. It is preferred that the Tg (Tan Delta) for the self-supporting polymer film comprised by the photochromic laminate, is for example between 2°C and 30°C lower than the Tg (Tan Delta) of the thermoplastic polymer comprised by the film, though lacking the imbibed ketone, such as about 13°C lower, although even a larger difference in Tg (Tan Delta) is also applicable. The Tg for the self-supporting polymer film not comprising ketone anymore after immersion of thermoplastic polymer with ketone followed by complete drying such that the film does not comprise remaining ketone, is for example 16°C for an S123 TPU film with a thickness of 0,68 mm (PPG Aerospace).

Another surprising effect of this imbibed ketone in the photochromic TPU film, was that due to the plasticizing of the thermoplastic polymer, curing was no longer necessary to adhere the film to transparent materials known in the field of applying photochromic laminates. Current photochromic films known in the art commonly have the drawback that a step of curing such films is required, before such films are applicable for laminating in between layers of further sheets of material applied in the field of applying photochromism. Also surprisingly, the inventors found that at least part of the beneficial effects of the immersion of polymer film, e.g. TPU, in a ketone remained also when the ketone was completely removed from the TPU film by drying. For example, the photochromic laminate comprising the self- supporting polymer film that was previously imbibed in ketone and then fully dried, proved to be highly stable in the tests outlined here below in Example 4 and Example 5, the tests showing for example that the exposure of the photochromic laminate to 1000 hours of xenon light did not reduce the photochromic response of the laminate when irradiated with direct sunlight and for example that the loss of photochromic activity under influence of an exposure to xenon light for 100 hours is 0%-9%, such as 0% and 9%.

It is now thus established that the self-supporting photochromic polymer film comprised by the photochromic laminate of the invention has an increased loss modulus under influence of the imbibed ketone in the thermoplastic polymer, when compared to the loss modulus determined for the thermoplastic polymer lacking the ketone, i.e. thermoplastic polymer which has not been imbibed with the solvent at all. Thus, presence of the ketone in the self-supporting photochromic polymer film comprised by the photochromic laminate results in increased flexibility of the polymer molecules in the film, which increased flexibility is beneficial for the decay half time of the one or more organic photochromic molecules comprising a chromophore comprised by the film, i.e. the decay half time of such photochromic molecule is shortened when the photochromic molecule is impregnated in a film comprised by the photochromic laminate, compared to a similar film though lacking the imbibed ketone.

The self-supporting photochromic polymer film comprised by the photochromic laminate is provided by treating, such as by immersing, the thermoplastic polymer of step (a) in a solution consisting of the ketone of step (b) wherein the at least one organic photochromic molecule comprising a chromophore of step (c) is dissolved. Typically, the ketone is acetone or cyclohexanone, preferably cyclohexanone. Typically, the thermoplastic polymer is imbibed with the solution of the ketone containing the dissolved organic photochromic molecule comprising a chromophore, typically at room temperature, the concentration of the photochromic molecule(s) typically being at least 0,1 % by weight based on the weight of the solution. Typically, the thermoplastic polymer is immersed in the solution at room temperature. Further details on suitable steps for providing the self-supporting photochromic polymer film comprised by the photochromic laminate are provided in the Examples section, here below. For example, the self-supporting photochromic polymer film comprised by the photochromic laminate can be provided by following the steps of:

providing an aliphatic thermoplastic polyurethane film, the film typically having a surface area with a size of between about 5 cm ² and about 1 square meter, such as the size of A4 (210 mm x 297 mm) and typically having a thickness of about 0,1 mm, 0,2 mm, 0,38 mm, 0,63 mm or 0,68 mm;

dissolving at least one organic photochromic molecule comprising a chromophore in a ketone such as acetone or cyclohexanone, preferably cyclohexanone, to provide a solution of the ketone comprising between 0,1 % and 5% by weight of the at least one organic photochromic molecule comprising a chromophore based on the weight of the solution, typically 0,5% by weight of each of two organic photochromic molecules comprising a chromophore, based on the weight of the solution, that is dissolved in the ketone; immersion of the about 1 square meter of aliphatic thermoplastic polyurethane film at room temperature with about 200 ml to 900 ml, typically about 400-450 ml of the solution of ketone comprising the at least one dissolved organic photochromic molecule comprising a chromophore, typically at a temperature of between 17°C and 24°C, such as about 18°C, 19°C, 20°C, 21 °C or 22°C, typically for about 40 seconds to 100 seconds, such as about 60 seconds, such that the film is imbibed with the ketone and such that the at least one organic photochromic molecule comprising a chromophore is evenly distributed in the aliphatic thermoplastic polyurethane film;

after immersing the aliphatic thermoplastic polyurethane film with organic photochromic molecule comprising a chromophore in ketone, the immersed film is dried for about 90 minutes in a hot-air oven set at a temperature of about 60°C,

such that self-supporting polymer films are provided.

The self-supporting photochromic polymer film typically can have a size of e.g. 10 cm ² - 10 m ² , such as 25 cm ² -3 m ² , e.g. 40 cm ² -1 ,5 m ² , A4 size (210 x 297 mm).

Homogeneous and even distribution of the organic photochromic molecule comprising a chromophore in the thickness of the thermoplastic polymer, such as a TPU film, preferably an aliphatic TPU film, is typically established and confirmed by visualizing the photochromic effect which is apparent equally and evenly distributed throughout the whole volume of the TPU film. Thus, the thickness of the film contains evenly and homogenously impregnated photochromic dye(s).

Immersion of the thermoplastic polymer film in the solution comprising the ketone results in ketone-treated film wherein the ketone is imbibed in the whole volume of the thermoplastic polymer, which enables homogeneous distribution of the organic photochromic molecule comprising a chromophore in said volume of the thermoplastic polymer. Current approaches for providing a self- supporting polymer film comprising an organic photochromic molecule comprising a chromophore comprises the provision of a sheet of thermoplastic polymer onto which a film or a coating is provided, which film or coating is for example a thin layer or foil comprising said organic photochromic molecule comprising a chromophore. In said multilayer laminate known in the art the organic photochromic molecule comprising a chromophore is thus not present in the thickness of the thermoplastic polymer. Providing such a multilayer laminate known in the art is a multistep process and amongst other steps requires priming of the thermoplastic surface before the foil is adhered to the thermoplastic polymer. Efficient adhering the foil to the thermoplastic polymer may cause difficulties, e.g. such as those related to avoiding inclusion of air bubbles between layers, and to the foil and the thermoplastic polymer staying (fully) adhered to each other.

An embodiment is the photochromic laminate, wherein the at least one organic photochromic molecule comprising a chromophore is evenly distributed in the self-supporting photochromic polymer film. Preferred is the photochromic laminate wherein the at least one organic photochromic molecule comprising a chromophore is evenly and homogeneously distributed in the volume (the thickness) of the self-supporting photochromic polymer film. It has been established that immersion of the self- supporting polymer film in a solution of the ketone comprising photochromic dyes is efficient and sufficient for establishing such an even and homogenous distribution of the photochromic molecules in the polymer film. The immersion is preferably at room temperature, therewith avoiding subjecting the photochromic dyes to higher temperatures and thus avoiding the negatively influence of such higher temperature on the dyes (e.g. breakdown, decay, loss of photochromic activity).

Preferably, in the photochromic laminate, the thermoplastic polymer is an aliphatic thermoplastic polyurethane, preferably a polyester-based aliphatic thermoplastic polyurethane or a polyether-based aliphatic thermoplastic polyurethane.

Preferably, the self-supporting photochromic polymer film comprised by the photochromic laminate has a thickness of between 0,05 mm and 7,50 mm, preferably between 0,10 mm and 2,60 mm, more preferably between 0,20 mm and 1 ,0 mm, most preferably between 0,38 mm and 0,68 mm, such as about 0,63 mm, about 0,38 mm, about 0,68 mm, about 0,73 mm. Typically, the free-standing polymer film comprised by the photochromic laminate has a thickness of about 100 micrometer, about 200 micrometer, about 0,38 mm or about 0,76 mm. The inventors established that the self-supporting polymer film comprised by the photochromic laminate is efficaciously impregnated evenly with photochromic dye, when films are applied which have a thickness in the above mentioned range, e.g. between 0,1 mm and 1 ,2 mm, such as between 0,35 mm and 0,75 mm. In addition, the inventors established that such a film comprised by the photochromic laminate, having a thickness in the above mentioned range is endowed with increased flexibility due to the presence of the imbibed ketone, as expressed in for example an increased Tg and/or an increased value for the storage modulus, when compared to flexibility of a similar film of the thermoplastic polymer comprised by the self-supporting polymer film, though lacking the imbibed solvent or not being imbibed with a ketone at all. Further, it is preferred that the photochromic laminate of the invention has a thickness of between 0,50 mm and 8,00 mm, preferably between 0,60 mm and 7,50 mm, such as for example about 0,65 mm, 0,80 mm, 1 ,10 mm, 1 ,50 mm. The total thickness of the photochromic laminate can also be less than 0,50 mm, such as about 450 micrometer.

Immersion of a sheet or film of thermoplastic polymer, preferably an aliphatic TPU, with an aforementioned ketone such as acetone or cyclohexanone, with the least one organic photochromic molecule comprising a chromophore, preferably two of such organic photochromic molecules comprising a chromophore of a different kind, dissolved therein, is very efficient when the thickness of the film is 6,50 mm or less, such as 1 ,0 mm or less, for example about 0,7 mm or about 0,4 mm or about 0,20 mm or about 0,10 mm, with regard to the even distribution of the dye throughout the complete volume of the polymer film and with regard to the establishment of the induction of decreased Tg (Tan Delta) and/or increased flexibility of the thermoplastic polymer. Furthermore, incubating thermoplastic films, e.g. aliphatic TPU films with a thickness of e.g. smaller than 2 mm results in self-supporting polymer film having a surprisingly smooth surface.

For example, an aliphatic TPU based on a polyester and an aliphatic diisocyanate regularly has a relatively opaque and rough surface comprising recesses and protrusions to some extent. Upon exposure to a ketone, that is to say, for example the aliphatic TPU comprising a ketone imbibed in the polymer sheet at an amount of e.g. 1-10wt% based on the weight of the self-supporting polymer film, having e.g. a thickness of about 0,35 m or about 0,65 mm, is relatively smooth. In particular the photochromic laminate has a length and a width of between 2 cm and 300 cm, preferably between 3 cm and 200 cm. It is one of the many benefits of the current invention that now a photochromic laminate is provided with a surface area that exceeds the surface area of photochromic laminates known in the art, which opens the application of photochromic laminate in new technological areas and provides the opportunity to improve on current applications of photochromic laminates.

One embodiment is the photochromic laminate, wherein the aliphatic thermoplastic polyurethane is based on an aliphatic diisocyanate selected from 1 ,4-tetramethylene diisocyanate, 2,2,4-trimethyl-1 ,6-hexamethylene diisocyanate, 1 ,12-dodecamethylene diisocyanate, cyclohexane- 1 , 3-diisocyanate, cyclohexane-1 , 4-diisocyanate, 1-isocyanato-2-isocyanatomethyl cyclopentane, isophorone diisocyanate, 5-isocyanato-1-(isocyanatomethyl)-1 ,3,3-trimethylcyclohexane, bis-(4- isocyanatocyclohexyl)-methane, 2,4’-dicyclohexylmethane diisocyanate, 1 ,3-bis(isocyanatometyl)- cyclohexane, 1 ,4-bis(isocyanatometyl)-cyclohexane, bis-(4-isocyanato-3-methylcyclohexyl)-methane, a,a,a’,a’-tetramethyl-1 ,3-xylylen diisocyanate, a,a,a’,a’-tetramethyl-1 ,4-xylylen diisocyanate, 1- isocyanato-1-methyl-4(3)-isocyanatomethyl cyclohexane, 2,4-hexahydrotoluylene diisocyanate, 2,6- hexahydrotoluylene diisocyanate, 4,4’-methylene dicyclohexyl diisocyanate, hexamethylene diisocyanate, or mixtures thereof, preferably selected from 4,4’-methylene dicyclohexyl diisocyanate, hexamethylene diisocyanate and isophorone diisocyanate, or mixtures thereof. As said, the TPU is preferably an aliphatic TPU, more preferably an aliphatic TPU based on either polyester or polyether.

Part of the invention is the photochromic laminate, wherein a second sheet of optically transparent material is bonded at least partially to a free surface of the self-supporting photochromic polymer film. An example of such a photochromic laminate is provided in Figure 1 B.

Preferably, the photochromic laminate comprises a second sheet of optically transparent material that is bonded at least partially to a free surface of the self-supporting photochromic polymer film.

In particular, the photochromic laminate is provided, wherein the first sheet of transparent material is made of a polymer, preferably a polymer selected from any of an optical grade plastic, an optical grade polycarbonate, and an optical grade polycarbonate based on the precursor monomer bisphenol A or based on the precursor monomer diphenylcarbonate. Preferred are polycarbonate sheets or films such as UNC PC film, TCF, AF PC film and AS PC film.

In an embodiment, the photochromic laminate comprising a photochromic self-supporting polymer film and a first sheet of material, additionally comprises a second sheet of material, wherein at least a portion of a second major surface of the self-supporting polymer film is bonded to at least a portion of a first major surface of the second sheet of material, wherein the second sheet of optically transparent material is made of a polymer material such as a plastic or is made of a glass, preferably selected from any of an optical grade plastic, an optic glass, an optical grade polycarbonate, a float glass, an optical grade polycarbonate based on the precursor monomer bisphenol A or based on the precursor monomer diphenylcarbonate, and a soda-lime glass, more preferably selected from any of an optical grade plastic, an optical grade polycarbonate, and an optical grade polycarbonate based on the precursor monomer bisphenol A or based on the precursor monomer diphenylcarbonate. For example the polycarbonate sheet or film is UNC PC film, TCF PC, AF PC film and AS PC film. Preferably, the first sheet of optically transparent material is made of an optically transparent polycarbonate.

In a preferred embodiment, the second sheet of material in the photochromic laminate is made of a polymer, preferably a polymer selected from any of an optical grade plastic, an optical grade polycarbonate, and an optical grade polycarbonate based on the precursor monomer bisphenol A or based on the precursor monomer diphenylcarbonate.

In particular, the photochromic laminate comprises a free-standing thermoplastic polymer film, preferably self-supporting TPU film, sandwiched in between a layer of a polycarbonate adhered to the two surfaces of the free-standing thermoplastic polymer film.

The free-standing aliphatic TPU film preferably comprised by the self-supporting photochromic polymer film in the photochromic laminate, such as a polyester-based PU or a polyether-based PU, is manufactured according to procedures known in the art, which manufacturing is not part of the current inventive step.

In preferred embodiments the sheet of material or the sheets of material, i.e. the first, second and third sheet of transparent material, has/have a total transmittance at least 50%, preferably at least 65%, more preferably at least 75%, most preferably at least 80%. Preferably the sheet of material or sheets of material is/are made of a material selected from an optically transparent polycarbonate. Also preferred is the photochromic laminate, wherein the first, second and third sheet of transparent material have a total transmittance of more than 80% such as at least 85%, between 85% and 100%, such as 90-95%, about 98% or 98-99,5%. The transmittance relate to the portion of the electromagnetic spectrum that is visible to the human eye. Here,‘transparent’ is to be understood as transmission of visible light of at least 80%, such as at least 84%, and as haze of lower than 1 % (measured according to ASTM standard D1003:2013), according to the invention.

In an embodiment, the photochromic laminate comprising a photochromic self-supporting polymer film and a first sheet of material and/or a second sheet of material, additionally comprises a third sheet of material, wherein at least a portion of a first major surface of the third sheet of material is bonded to at least a portion of a second major surface of the first sheet of material and/or at least a portion of a second major surface of the second sheet of material. Thus, it is preferred that the photochromic laminate comprises a third sheet of material which is bonded at least partially to a free surface of the first sheet of optically transparent material and/or to a free surface of the second sheet of optically transparent material, wherein the third sheet of material is selected from any one of a glass, a polymer film, a UV protective film, a foil and a coating. Also, the photochromic laminate can comprise a third sheet of material that is bonded at least partially to a free surface of the first sheet of optically transparent material and/or can comprise a fourth sheet of material that is bonded at least partially to a free surface of the second sheet of optically transparent material, wherein the third sheet and/or the fourth sheet of material is/are selected from any one of a glass, a polymer film, a UV protective film, a foil and a coating. An example of such a photochromic laminate comprising a first, a second and a third sheet of transparent material is displayed in Figure 1C. Preferred is the photochromic laminate, wherein a third sheet of material is bonded at least partially to a free surface of the first sheet of transparent material and/or to a free surface of the second sheet of transparent material, wherein the third sheet of material is selected from any one of a glass, a polymer film, a UV protective film, an IR reflective film or coating, a foil and a coating. Preferably, the third sheet of material is made of a material selected from the list of materials comprising a polymer film, a UV protective film, a foil and a coating. It is preferred that said third sheet of transparent material is an anti-fog foil or an anti-scratch protective foil. Preferred is the photochromic laminate wherein the first sheet of transparent material is bonded to a first major surface of the photochromic self-supporting polymer film and the second or third sheet of transparent material is bonded to the second major surface of the photochromic self-supporting polymer film, such that the photochromic self-supporting polymer film is embedded or sandwiched in between two layers of transparent material. Preferably, said first and second/third sheet of transparent material is a sheet of optically transparent polycarbonate, such that the photochromic self-supporting polymer film is provided in between layers of polycarbonate in the laminate. Of course, the second or third layer of transparent material can also be a glass such as float glass and soda lime glass.

In an embodiment, the photochromic laminate comprises the self-supporting photochromic polymer film comprising the thermoplastic polymer, wherein said thermoplastic polymer is immersed in the solution comprising the ketone, the ketone in the solution selected from any one or more of a straight- chain ketone, a branched ketone, an unsubstituted cyclic ketone and a cyclic ketone substituted with at least one alkyl group, or a combination thereof, preferably selected from a straight-chain ketone and an unsubstituted cyclic ketone. In particular, the solvent is selected from a ketone, wherein the number of carbon atoms is between three and ten for the straight-chain ketone, between five and ten for the branched ketone, and between four and ten for the cyclic ketone substituted with at least one alkyl group. Preferably, the solvent is selected from any one of propan-2-one, butan-2-one, 3-methylbutan-2- one, pentan-2-one, pentan-3-one, cyclopentanone, 2-methylpentan-3-one, 3-methylpentan-2-one, 4- methylpentan-10 2-one, 4-m ethyl pent-3-en-2-one, pentane-2, 4-dione, hexan-2-one, 3,5,5-trimethyl-2- cyclohexene-1-one, 5-methylhexan-2-one, 1-cyclohexylpropan-1-one, 1-cyclohexylethanone, cyclohexanone, heptan-2-one, heptan-4-one, 2,6-dimethyl-4-heptanon, octan-3-one, octan-2-one, octan-4-one, or a mixture thereof, preferably the solvent is selected from propan-2-one and cyclohexanone, more preferably the solvent is cyclohexanone. It will be appreciated that any ketone is applicable within the scope of the current invention, as long as a selected dye dissolves in said ketone to a suitable extent, e.g. about 0,5wt% or at least 0,1 wt% of photochromic dye at 15°C-30°C, e.g. at ambient temperature or room temperature, such as between 8°C and 30°C, preferably between 15°C and 25°C, and as long as said ketone is imbibed in the thermoplastic polymer and induces enhanced plasticizing of the thermoplastic polymer. The ketone thus serves at least two purposes: as a carrier for dividing the dissolved dye throughout the whole volume of the sheet or film or foil or layer of thermoplastic polymer, e.g. TPU, and as a plasticizer capable of increasing the plasticity and flexibility of the photochromic self-supporting polymer film, e.g. freestanding TPU based on polyester or polyether. Of course, it is also part of the invention that the ketone first imbibed in the self-supporting photochromic polymer film is subsequently fully removed or discarded from said film by for example drying. Thus, the self-supporting photochromic polymer film comprised by the photochromic laminate comprises solvent, e.g. a ketone, upon previous immersion of the thermoplastic polymer in the solvent, or does not comprise the solvent anymore as a result of drying after said immersion. The selected ketone is thus a solvent for the at least one organic photochromic molecule comprising a chromophore, wherein the organic photochromic molecule comprising a chromophore is soluble in said solvent at a concentration of at least 0,1 % based on the weight of a solution of the solvent containing the dissolved organic photochromic molecule comprising a chromophore at a temperature of between 15°C and 30°C. Preferably, the at least one organic photochromic molecule comprising a chromophore is soluble in said selected ketone at a concentration of at least 0,3% based on the weight of a solution of the solvent containing the dissolved organic photochromic molecule comprising a chromophore, more preferably at least 0,5%, at a temperature of between 15°C and 30°C, preferably 18°C-25°C, such as room temperature or ambient temperature, e.g. about 20°C or about 22°C. For example, the solvent is cyclohexanone.

As said, the ketone in which the freestanding thermoplastic polymer comprised by the self- supporting polymer film of the photochromic laminate is immersed, serves at least two purposes: as a carrier for dividing the dissolved photochromic dye throughout the whole volume of the sheet or film of thermoplastic polymer, and as a plasticizer capable of increasing the plasticity and flexibility of the self- supporting polymer film. Surprisingly, these purposes are also achieved when the ketone is fully removed out of the thermoplastic polymer after immersion of said polymer with a solution containing ketone with dissolved organic photochromic molecule comprising a chromophore. Then, for example for a selected TPU (S123, PPG Aerospace), Tg was 16°C for a self-supporting polymer film immersed in ketone followed by completely discarding the ketone, compared to a Tg of 12°C for the same TPU film that was not immersed in ketone, whereas the TPU film treated with ketone became more flexible than the untreated film and stayed transparent upon ketone immersion followed by drying. The inventors found for example that a self-supporting polymer film comprised by the photochromic laminate, comprising 2-4wt% ketone based on the total weight of the self-supporting polymer film, or for example 7-11wt%, has significantly improved Tg, that is to say a decreased Tg (Tan Delta) when compared to a similar film of the thermoplastic material which has not been immersed with a ketone.

Yet another aspect of the invention relates to the self-supporting polymer film of the photochromic laminate, which comprises at least one organic photochromic molecule comprising a chromophore selected from one or more of a spiropyran, a spirooxazine and a naphtopyran, or a combination thereof, preferably the self-supporting polymer film comprises at least two organic photochromic molecules comprising a chromophore. Preferred is the photochromic laminate comprising the self-supporting polymer film, wherein the at least one organic photochromic molecule comprising a chromophore is selected from naphtopyrans or modified naphthopyrans. Preferred are spiropyrans, spirooxazines and naphthopyrans which are T-type photochromic dyes.

In a preferred embodiment, the self-supporting polymer film comprises at least one organic photochromic molecule comprising a chromophore selected from polydialkylsiloxane-substituted naphtopyrans, preferably a polydialkylsiloxane-substituted naphtopyran capable of taking on a blue color or a green color when irradiated with ultraviolet radiation, and/or selected from 1-[2,4-dimethyl-5- (4-methylphenyl)-3-thienyl]-2-[2-methyl-5-(4-methylphenyl)-3 -thienyl]-3,3,4,4,5,5- hexafluorocyclopentene and 1 ,2-bis(2-methoxy-5-phenyl-3-thienyl)perfluorocyclopentene, preferably the self-supporting polymer film comprises at least two selected organic photochromic molecules comprising a chromophore. The polydialkylsiloxane-substituted naphtopyran is typically an organic photochromic molecule comprising a chromophore comprising two chromophore moieties of the same type, although this not required. The photochromic dyes are typically T-type photochromic dyes.

Such a mixture of at least two organic photochromic molecules comprising a chromophore provides the self-supporting polymer film with the ability to turn from essentially colorless to a color which is a mixture of the colors of the at least two organic photochromic molecules comprising a chromophore upon exposure of these chromophores to e.g. ultraviolet radiation. Preferably, the obtained color for the self-supporting polymer film comprising at least two organic photochromic molecules comprising a chromophore is for example a brown color, a dark blue color, a dark green color and/or a color between light gray and black. It will be appreciated by the skilled person that dyes other than organic photochromic molecules comprising a chromophore selected from a spiropyran, a spirooxazine and a naphtopyran, are equally applicable, if a ketone is selected in which the alternative T-type photochromic dye or dyes dissolves/dissolve to a sufficient extent, e.g. 0,1 -1 ,5 wt% based on the weight of the solution, and if the very same ketone is suitable for inducing the increased flexibility and reduced rigidity, amongst others expressed as a decreased value for Tg (Tan Delta), when a thermoplastic polymer, preferably an aliphatic TPU such as an aliphatic TPU based on a polyester or based on a polyether and based on an aliphatic diisocyanate, is immersed with the solution comprising the ketone and the photochromic dye(s), such that at least e.g. 2wt% of the ketone is imbibed in the polymer film after drying based on the weight of the polymer film, and such that the T-type photochromic dye(s) are evenly distributed in the polymer film.

It is part of the invention that the photochromic laminate of the invention comprises the self- supporting photochromic polymer film, wherein said film comprises at least one organic photochromic molecule comprising a chromophore selected from one or more of a diarylethene, a spirooxazine and a naphtopyran, or a combination thereof, preferably the self-supporting photochromic polymer film comprises at least two organic photochromic molecules comprising a chromophore. Such a mixture of at least two organic photochromic molecules comprising a chromophore provides the self-supporting polymer film with the ability to turn from essentially colorless to a color which is a mixture of the colors of the at least two organic photochromic molecules comprising a chromophore upon exposure of these chromophores to e.g. ultraviolet radiation. Preferably, the obtained color for the self-supporting polymer film comprising at least two organic photochromic molecules comprising a chromophore is for example a brown color, a dark blue color, a dark green color and/or a color between light gray and black. The chromophores are identical, or the chromophores are different moieties in the photochromic molecules. Equally preferred in the self-supporting photochromic polymer film are photochromic molecules selected from benzopyrans, naphthopyrans, spirobenzopyrans, spironaphthopyrans, spirobenzoxzines, spironaphthoxazines, fulgides and fulgimides, as long as such photochromic molecules are soluble in the selected ketone to a sufficient extent, i.e. at least soluble to 0,1 wt% dye in the ketone, based on the weight of the provided solution. Preferred are T-type photochromic dyes.

The photochromic laminate according to the invention comprises in preferred embodiments the self-supporting photochromic polymer film, wherein said film comprises at least one organic photochromic molecule comprising a chromophore selected from polydialkylsiloxane-substituted naphtopyrans, preferably a polydialkylsiloxane-substituted naphtopyran preferably capable of taking on a blue color or a green color when irradiated with ultraviolet radiation, and/or selected from 1-[2,4- dimethyl-5-(4-methylphenyl)-3-thienyl]-2-[2-methyl-5-(4-meth ylphenyl)-3-thienyl]-3,3,4,4,5,5- hexafluorocyclopentene and 1 ,2-bis(2-methoxy-5-phenyl-3-thienyl)perfluorocyclopentene, preferably the self-supporting photochromic polymer film comprises at least two selected organic photochromic molecules comprising a chromophore. Typically preferred organic photochromic molecules comprising a chromophore in the self-supporting polymer film are those polydialkylsiloxane-substituted naphtopyrans described in US patent 8,865,029B2, i.e. the photochromic molecules outlined in Example 3, column 46, line 42 to column 50, line 2, Example 4, column 50, line 4 to column 51 line 4, Example 6, column 62, line 50 to column 53, line 30, Example 7, column 53, line 32 to column 54, line 20, and Example 9, column 57, line 50 to column 63, line 20, of US patent 8,865,029B2. Such polydialkylsiloxane-substituted naphtopyrans comprise two identical photochromic units per photochromic molecule. Particularly preferred is a self-supporting polymer film comprised by the photochromic laminate comprising cyclohexanone and one or more polydialkylsiloxane-substituted naphtopyrans. Suitable polydialkylsiloxane-substituted naphtopyrans, sufficiently soluble in e.g. cyclohexanone at e.g. room temperature, are for example Reversacol Pennine Green and Reversacol Humber Blue (Vivimed Labs Ltd). Also applicable and preferred is impregnating the thermoplastic polymer film such as an aliphatic TPU film, with Reversacol Sea Green (Vivimed Labs Ltd) by immersion of said film with the ketone, preferably cyclohexanone, wherein the photochromic molecule is dissolved.

It is preferred that the first sheet of optically transparent material to which the self-supporting, or free-standing photochromic polymer film is bonded, is made of a polymer, preferably a polymer selected from any of an optical grade plastic, an optical grade polycarbonate, and an optical grade polycarbonate based on the precursor monomer bisphenol A or based on the precursor monomer diphenylcarbonate.

The self-supporting polymer film comprised by the photochromic laminate, comprising e.g. aliphatic TPU provides, amongst others, the benefit of improved suitability for application in laminates, such as a composite laminate assembly, wherein the film is sandwiched in between sheets or layers or films of a first transparent material or in between a sheet of a first transparent material at a first side of the film surface and a sheet of a second transparent material at a second side of the film surface, dependent on the purpose of use of the sandwiched film. The self-supporting polymer film does not require any pre-preparation before being applicable for adhering to the common transparent materials applied in, for example, construction, visors, glasses, lenses, car windows, etc. That is to say, the film generally adheres to sheets or foils or films of materials for applying photochromism, e.g. glass panes, sheets of glass, polymer film such as a layer or sheet of polycarbonate. The film comprising the thermoplastic polymer such as TPU that is immersed with ketone such as cyclohexanone and then dried, exposes a tacky surface suitable for adhering the film to further layers, the immersed and dried film thus being provided with a surface acting reminiscent to surface mount glue known in the art. Furthermore, the self-supporting polymer film provides the benefit that such film absorbs water to a lesser extent, if at all, compared to commonly applied foil made of EVA (a commonly used film material) in photochromism applications. One of the drawbacks of a photochromic film made of EVA is the tendency to absorb water to an unacceptable extent. For example, the self-supporting polymer film of the invention comprising aliphatic TPU does not suffer from this drawback, i.e. absorbing water to an unacceptable extent therewith interfering with integrity of the laminate and/or interfering with transparency of the laminate and/or disrupting the adherence of layers in the laminate. This beneficial effect of the application of the aliphatic TPU in the laminate of the invention results from the lower hygroscopic activity of the aliphatic TPU when compared to EVA.

The self-supporting photochromic film comprised by the photochromic laminate is suitable for being sandwiched in between layers of the common materials, i.e. optically transparent materials used in construction, windows, car glass, visors, goggles, etc., since the film is compatible with the materials in the sense that the film does not induce softening of the polymers applied in several of those transparent materials. The photochromic molecules used for such applications degrade at high temperatures. As such, these dyes commonly cannot be incorporated in standard plastic articles, such as those made of polycarbonates, which are, for example, produced by injection moulding or extrusion. The high temperatures of these manufacturing processes would destroy the photochromic properties of the material.

The inventors found that in tests for assessing the decay half time of the switch in color when irradiation of a photochromic laminate comprising the self-supporting photochromic polymer film with ultraviolet radiation is disrupted, back to the colour of the self-supporting photochromic polymer film before being exposed to ultraviolet radiation, the decay half time is surprisingly short compared to the decay half time of photochromic laminates comprising photochromic coating currently in use. That is to say, the decay half time of the self-supporting photochromic polymer film comprised by the photochromic laminate is typically 30 seconds or less, such as for example 20 second or less, 15 seconds or less, 10 seconds or less, or even 5 seconds or less, such as 2-10 seconds or 5-20 seconds. Moreover, many of the self-supporting photochromic polymer films comprised by the photochromic laminates have a decay half time of even about 1 second or even less, as assessed with spectroscopic measurements determining values for L, a and b according to methods known in the art. Such decay half time of 10 seconds, 5 seconds, or even 4, 3, 2 or 1 second(s) are much shorter than what is common for photochromic films nowadays in use for applications such as ski goggles, sunglasses, glazing for buildings, car glass, etc., or in glass or polymers used in aerospace industry. With such short decay half time of the self-supporting photochromic polymer film comprised by the photochromic laminate, due to improved Tg and storage modulus and loss modulus, i.e. lowered values for Tg (Tan Delta) and the storage modules and increased values for the loss modulus, application of the photochromic laminate comprising the self-supporting photochromic polymer film is suitable in articles requiring a fast reaction time with regard to coloring from a relatively dark color upon irradiation with ultraviolet radiation, to a relatively light color or even a colorless state when the source of ultraviolet radiation is absent. That is to say, applying the photochromic laminate comprising the self-supporting photochromic polymer film in for example laminate type of articles for, for example, use in construction, glasses, visors for helmets, etc., now allows for the provision of articles having a relative short response time when the intensity of ultraviolet radiation to which the article is exposed, decreases.

Thus, the photochromic self-supporting polymer film comprised by the photochromic laminate of the invention provides for a more universally applicable film for the purpose of combining such film with layers of materials applied in the field of application of the photochromic effect. Herewith, a broad scope of photochromic laminates of the invention is provided, encompassing these many beneficial features of the photochromic self-supporting polymer film.

It is preferred that in the self-supporting photochromic polymer film comprised by the photochromic laminate of the invention, the at least one organic photochromic molecule comprising a chromophore is evenly distributed in the self-supporting polymer film. It was found by the inventors that imbibing the self-supporting photochromic polymer film with a ketone in which the organic photochromic molecule comprising a chromophore is dissolved, results in particularly good and even distribution of said photochromic molecule(s) in the ketone-imbibed film. Such highly even distribution of the photochromic molecule(s) in the ketone-imbibed film is beneficial to the photochromic effect and activity of said photochromic molecule(s), and thus of the photochromic laminate as a whole.

It is preferred that the thermoplastic polymer comprised by the photochromic self-supporting polymer film is an aliphatic thermoplastic polyurethane (TPU) based on a polyester known in the art or based on a polyether known in the art, and based on a here above listed aliphatic diisocyanate. Aliphatic TPUs based on polyester or on polyether and an aliphatic diisocyanate are known in the art. For manufacturing such an aliphatic TPU based on polyester or polyether and an aliphatic diisocyanate, the appropriate polyester or polyether and the appropriate aliphatic diisocyanate are selected and subjected to a poly-addition reaction for producing TPU known to the skilled person. Suitable aliphatic TPU for application in the self-supporting polymer film comprised by the photochromic laminate are for example the aliphatic TPU sold as“S-123” or as“S123” by PPG Aerospace - Sierracin/Sylmar Corp. (CA, USA), and the TPU“S-158” or“S158” sold by the same company, and for example“Krystalflex PE 399” aliphatic TPU foil sold by company Huntsman (Ml, USA). For example, the S-123 aliphatic TPU is available as a film and is for application in laminates, according to the manufacturer. Krystalflex PE 399 is an aliphatic polyester based TPU. It will be appreciated that aliphatic TPUs falling under the scope of the invention are those aliphatic TPUs suitable for forming flexible foil, sheet and film, i.e. free-standing self-supporting film. Aliphatic TPUs based on polyester, polyether or polycaprolactone are known in the art and are suitable for incorporation in the flexible photochromic self-supporting polymer film comprised by the photochromic laminate. Application of aliphatic TPU based on polyester or polyether is preferred. A suitable aliphatic TPU film based on polyether and aliphatic diisocyanate for application as thermoplastic polymer in the photochromic laminate is NovoGlass SF 1959, an aliphatic polyether TPU, made of combinations of diisocyanates, polyols and short length diols (NovoGenio).

It is one of the several benefits provided by the photochromic laminate comprising the self- supporting photochromic polymer film that such a film is presented as an optically transparent film at least after being subjected to heat and pressure according to methods commonly applied in the art. That is to say, when the self-supporting photochromic polymer film is for example subjected to a pressure of between 6 bar and 20 bar, such as about 8 bar, 12 bar or 15 bar, at a temperature of e.g. between 120°C and 165°C for a time period of between for example 1 second and 1 hour, such as for about 1 second, 30 seconds, 4 minutes, 10 minutes or 20 minutes, the direction of the pressure being essentially at both sides of the extended surface area perpendicular to the extended surface, a transparent film is obtained. Here,‘transparent’ is to be understood as optically transparent: transmission of visible light of at least 80%, such as at least 84%, and as haze of lower than 1 % as established according to ASTM standard D1003:2013. For example, such a transparent self-supporting photochromic polymer film comprised by the photochromic laminate is obtainable by adhering the film at both sides of the film surface to a transparent material, i.e. sandwiched in between two sheets of such optically transparent material. Such material is known in the art and commonly applied when the effect of photochromism is desired when such a sandwiched film is used for the purpose of shielding for light and/or radiation heat. Here, the optically transparent material is the first sheet of optically transparent material of the photochromic laminate such as a polycarbonate sheet or an optically transparent material made of a polymer, preferably a polymer selected from any of an optical grade plastic, an optical grade polycarbonate, and an optical grade polycarbonate based on the precursor monomer bisphenol A or the precursor monomer diphenylcarbonate, and is the second sheet of optically transparent material made for example of a polymer material such as a plastic or made of a glass, preferably selected from any of an optical grade plastic, an optic glass, an optical grade polycarbonate, a float glass, an optical grade polycarbonate based on the precursor monomer bisphenol A or the precursor monomer diphenylcarbonate, and a soda-lime glass, more preferably any of an optical grade plastic, an optical grade polycarbonate, and an optical grade polycarbonate based on the precursor monomer bisphenol A. Particularly, the first sheet and the second sheet are an optically transparent polycarbonate sheet.

Particularly, in the photochromic laminate, the first sheet of transparent material and/or the second sheet of transparent material, if comprised by the photochromic laminate, has/have a total transmittance of at least 50%, preferably at least 65%, more preferably at least 75%, most preferably at least 80% and/or has/have haze of lower than 1 % (measured according to ASTM standard D1003:2013). That is to say, the photochromic laminate has many applications, and amongst them applications relating to the use of the photochromic laminate in for example car glass, window panes, goggles, visors, wind shields, lenses, etc., are preferred. Therefore, the total transmittance of the photochromic laminate is sufficiently high for application in any application for which transparency or at least partial transparency is preferred or even a requirement.

Since the photochromic laminate of the invention is applicable and useful for many applications and as part of numerous articles, which are used under circumstances that for example may cause wear or even accelerated wear, and/or under circumstances that benefit from or even require shielding of subjects such as humans from direct UV light, the photochromic laminate may be provided with at least one further sheet of material, i.e. a third, fourth, etc., sheet of material. That is to say, the photochromic laminate may comprise at least a third sheet of material, wherein said third sheet of material is bonded at least partially to a free surface of the first sheet of transparent material and/or to a free surface of the second sheet of transparent material, wherein the third sheet of material is selected from any of a polymer film, a UV protective film, a foil and a coating. Such a third sheet, and such further sheets, may serve a purpose as mentioned here and/or may add a further functionality to the photochromic laminate, known to those skilled in the art of transparent laminates. For example, a coating is provided as a third or further layer of the photochromic laminate, wherein the coating serves as a layer protecting the laminate from wear, scratches, etc., and/or the third sheet of material provides the photochromic laminate with (further) strength, rigidity, etc. As said, the self-supporting photochromic polymer film comprised by the photochromic laminate, comprises between 0,0% and 9% ketone, preferably acetone or cyclohexanone, more preferably cyclohexanone, such as 0,1-9% by weight, based on the weight of the self-supporting photochromic polymer film, preferably between 0,5% and 3%, such as about 0,5% or about 3%. In one embodiment, the self-supporting photochromic polymer film comprised by the photochromic laminate, comprises between 1 % and 10% ketone based on the weight of the self-supporting polymer film, preferably between 1 ,5% and 8%, more preferably between 2% and 6%, most preferably about 3% ketone based on the weight of the self-supporting photochromic polymer film. For example, the self-supporting photochromic polymer film comprises 1 %, 2%, 3%, 4%, 5%, 6%, 8%, 9% or 10% of the ketone based on the weight of the self-supporting polymer film, the ketone, if present after the drying step, imbibed in the thermoplastic polymer, or any weight percentage in between these listed values. Presence of imbibed ketone in the self-supporting photochromic polymer film in these ranges ensures the establishment of the plasticizer effect of the ketone towards the thermoplastic polymer comprised by the film, e.g. aliphatic TPU, for example based on a polyester and an aliphatic diisocyanate or based on a polyether and an aliphatic diisocyanate. Presence of the imbibed ketone in the photochromic film as the plasticizer makes inclusion of a further plasticizer known in the art superfluous. Preferred is a self- supporting photochromic polymer film comprising at least 3wt% ketone such as cyclohexanone based on the weight of the self-supporting photochromic polymer film, such as 4wt%-11wt%, in particular 5wt%, 8wt%. Also preferred is a self-supporting photochromic polymer film comprising at least 0,2wt% ketone such as cyclohexanone based on the weight of the self-supporting polymer film, such as about 0,5%. However, photochromic laminate comprising the self-supporting photochromic polymer film wherein said film does not comprise ketone, anymore after previously being imbibed with said ketone and then subsequently dried, is also part of the invention. Such a photochromic laminate is obtained by applying self-supporting photochromic polymer film which has been imbibed previously with the ketone and subsequently has been dried such that all ketone evaporated.

A further aspect of the invention relates to a method for producing a photochromic laminate comprising the steps of:

a) providing a self-supporting photochromic polymer film according to any one of the embodiments here above described;

b) bonding a first sheet of optically transparent material at least partially to a surface of the self- supporting photochromic polymer film of step a);

c) optionally bonding a second sheet of optically transparent material at least partially to a free surface of the two-layer laminate of step b); and

d) optionally laminating a third sheet of optically transparent material at least partially to a free surface of the three-layer laminate of step c).

Preferred is the method, wherein the photochromic laminate has a length and a width of between 10 cm and 200 cm and/or wherein the self-supporting photochromic polymer film has a thickness of between 0,05 mm and 6,50 mm, preferably between 0,10 mm and 2,60 mm, more preferably between 0,2 mm and 1 ,0 mm, most preferably between 0,3 mm and 0,8 mm. Typically, the photochromic laminate has a thickness of between 0,30 mm and 7,00 mm, such as for example about 0,40 mm, 0,60 mm, 0,80 mm, 1 ,00 mm, 1 ,20 mm, 1 ,30 mm, 1 ,50 mm, 1 ,80 mm, 2,00 mm, or any thickness therein between. Typically, the thermoplastic polymer film comprised by the self-supporting photochromic film is about 100 micrometer, or about 200 micrometer, or about 0,38-0,76 mm, such as about 0,68 mm. For example, the method provides a photochromic laminate having a surface area of about 1 m ² , such as about 80 cm x 120 cm, or about the size of A4 (210 mm x 297 mm).

Preferred is the method for producing photochromic laminate wherein the self-supporting photochromic polymer film is bonded at both sides to a layer of an optically transparent polymer such as a polycarbonate. Therefore, an embodiment is the method for producing the photochromic laminate, wherein in step c) or in step d) the second sheet of optically transparent material or the third sheet of optically transparent material is bonded to the free surface of the self-supporting photochromic polymer film of the two-layer laminate provided in step b).

An embodiment is the method for producing a photochromic laminate,

wherein in step b) the bonding of the first sheet of optically transparent material to a surface of the self- supporting photochromic polymer film of step a) is by press-laminating at a temperature of between 90°C and 135°C at a pressure of between 10 and 25 bar during a time period of at least 1 minute, wherein optionally said first sheet of optically transparent material is made of a polymer selected from an optical grade plastic, an optical grade polycarbonate and an optical grade polycarbonate based on the precursor monomer bisphenol A or based on the precursor monomer diphenylcarbonate; and/or wherein in step c) the bonding of the second sheet of optically transparent material at least partially to a free surface of the two-layer laminate of step b) is by press-laminating at a temperature of between 90°C and 135°C at a pressure of between 10 and 25 bar during a time period of at least 1 minute or by autoclaving at a temperature of between 90°C and 130°C and at a pressure of between 8 bar and 15 bar, for a time period of at least 60 minutes, wherein the second sheet of transparent material is optionally made of a polymer material such as a plastic or is optionally made of a glass, preferably selected from any of an optical grade plastic, an optic glass, an optical grade polycarbonate, a float glass, an optical grade polycarbonate based on the precursor monomer bisphenol A or based on the precursor monomer diphenylcarbonate and a soda-lime glass, preferably any of a polymer selected from an optical grade plastic, an optical grade polycarbonate, and an optical grade polycarbonate based on the precursor monomer bisphenol A or based on the precursor monomer diphenylcarbonate, therewith providing a three-layer photochromic laminate; and/or wherein in step d) the third sheet of optically transparent material is selected from a polymer film, a UV protective film, an IR reflecting layer, a foil and a coating.

Current photochromic laminates cannot cost-effectively be produced with the method at a large scale. The photochromic laminate according to the invention is producible to cover large surface areas and so can be used in market segments that were previously unable to exploit the properties of a photochromic material, such as building glazing and vehicle windows and aircraft windows. Moreover, the method is applicable in roll-to-roll processes for manufacturing of the photochromic laminate. This is beneficial for producing laminate at large scale in large batches, continuously or semi-continuously, and/or with extended length (several meters, at least) and/or at high speed, e.g. 1-100m/hr or more. In preferred embodiments in the method, the sheet of optically transparent material or the sheets of optically transparent material has/have a total transmittance at least 50%, preferably at least 65%, more preferably at least 75%, most preferably at least 80%, wherein preferably the sheet of transparent material or sheets of transparent material is/are made of a transparent material selected from a polycarbonate film. It is one of the several benefits provided by the self-supporting photochromic polymer film comprised by the photochromic laminate provided by the method that such a film is presented as a transparent film after being subjected to heat and pressure. For example, the self-supporting photochromic polymer film applied in the method can be subjected to a pressure of between 6 bar and 20 bar, such as about 8 bar, 12 bar or 15 bar, at a temperature of e.g. between 120°C and 165°C for a time period of between for example 1 second and 1 hour, such as for about 1 second, 30 seconds, 4 minutes, 10 minutes or 20 minutes, with the direction of the pressure being essentially at both sides of the extended surface area perpendicular to the extended surface of the film, and an optically transparent laminate comprising the film is subsequently obtained. Here, transparent is to be understood as transmission of visible light of at least 80%, such as at least 84%. Preferred is a transmission of visible light of between 80% and 99% such as between 90% and 95%. For example, such an optically transparent self-supporting photochromic polymer film is obtainable by adhering the film at both sides of the film surface to a transparent material, i.e. sandwiched in between two sheets of such material. Preferably, at least one sheet of transparent material is a ply of polycarbonate, preferably the photochromic laminate encompasses the self-supporting photochromic polymer film wherein said film is bonded at both major surfaces to a sheet of polycarbonate.

It is preferred that the optional third sheet of transparent material is an anti-fog foil or an anti-scratch protective foil. See for example Figure 1C.

The invention also provides a method for producing the self-supporting photochromic polymer film comprised by the photochromic laminate, comprising between 0,0% and 12% by weight of a ketone based on the total weight of the self-supporting photochromic polymer film and further comprising at least one organic photochromic molecule comprising a chromophore, comprising the steps of:

(i) providing an aliphatic thermoplastic polyurethane film wherein the polyurethane is based on an aliphatic diisocyanate selected from the aliphatic diisocyanates 1 ,4-tetramethylene diisocyanate, 2,2,4-trimethyl-1 ,6-hexamethylene diisocyanate, 1 ,12-dodecamethylene diisocyanate, cyclohexane- 1 , 3-diisocyanate, cyclohexane-1 , 4-diisocyanate, 1-isocyanato-2-isocyanatomethyl cyclopentane, IPDI, 5-isocyanato-1-(isocyanatomethyl)-1 ,3,3-trimethylcyclohexane, bis-(4-isocyanatocyclohexyl)-methane, 2,4’-dicyclohexylmethane diisocyanate, 1 ,3-bis(isocyanatometyl)-cyclohexane, 1 ,4- bis(isocyanatometyl)-cyclohexane, bis-(4-isocyanato-3-methylcyclohexyl)-methane, a,a,a',a’- tetramethyl-1 ,3-xylylen diisocyanate, a,a,a’,a’-tetramethyl-1 ,4-xylylen diisocyanate, 1-isocyanato-1- methyl-4(3)-isocyanatomethyl cyclohexane, 2,4-hexahydrotoluylene diisocyanate, 2,6- hexahydrotoluylene diisocyanate, H12 MDI, HDI, or mixtures thereof, preferably selected from H12 MDI, HDI and IPDI, or mixtures thereof; providing a ketone selected from the ketones propan-2-one, butan- 2-one, 3-methylbutan-2-one, pentan-2-one, pentan-3-one, cyclopentanone, 2-methylpentan-3-one, 3- methylpentan-2-one, 4-methylpentan-2-one, 4-methylpent-3-en-2-one, pentane-2, 4-dione, hexan-2- one, 3,5,5-trimethyl-2-cyclohexene-1-one, 5-methylhexan-2-one, 1-cyclohexylpropan-1-one, 1- cyclohexylethanone, cyclohexanone, heptan-2-one, heptan-4-one, 2,6-dimethyl-4-heptanon, octan-3- one, octan-2-one, octan-4-one, or a mixture thereof; and providing at least one organic photochromic molecule comprising a chromophore selected from a diarylethene, a spirooxazine and a naphtopyran, or a combination thereof;

(ii) dissolving the at least one organic photochromic molecule comprising a chromophore of step

(i) in the ketone of step (i) therewith providing a solution with a final concentration of the at least one organic photochromic molecule comprising a chromophore in the ketone of between 0,1 % and 2,5% based on the weight of the solution;

(iii) immersing the aliphatic thermoplastic polyurethane film of step (i) with the solution of step

(ii), at a temperature of between 15°C and 30°C, for a time period of at least 5 seconds; and

(iv) drying the immersed aliphatic thermoplastic polyurethane film obtained with step (iii) for a time period of between 1 minute and 16 hours, at a temperature of between 45°C and 75°C, such that the self-supporting photochromic polymer film is obtained.

Preferably, in this method for providing the self-supporting photochromic polymer film comprised by the photochromic laminate, the at least one organic photochromic molecule comprising a chromophore of step (i) is a chromophore selected from polydialkylsiloxane-substituted naphtopyrans, preferably a polydialkylsiloxane-substituted naphtopyran capable of taking on a blue color or a green color when irradiated with ultraviolet radiation, and/or selected from 1-[2,4-dimethyl-5-(4-methylphenyl)- 3-thienyl]-2-[2-methyl-5-(4-methylphenyl)-3-thienyl]-3,3,4,4 ,5,5-hexafluorocyclopentene and 1 ,2-bis(2- methoxy-5-phenyl-3-thienyl)perfluorocyclopentene, preferably in step (i) at least two organic photochromic molecules comprising a chromophore are provided. Any single chromophore or any combination of a spiropyran, a spirooxazine and a naphtopyran can be selected for use in this method for providing the self-supporting photochromic polymer film comprised by the photochromic laminate, if the requirement is fulfilled that the organic photochromic molecule(s) comprising a chromophore is/are soluble in the selected ketone(s) at a concentration of at least 0,1 % based on the weight of a solution of the ketone(s) containing the dissolved organic photochromic molecule(s) comprising a chromophore at a temperature of between 15°C and 30°C. T-type photochromic dyes are preferred. The chromophores may be the same or may be different chromophores in the at least one photochromic molecule(s). Preferred photochromic molecules comprised by the self-supporting polymer film are photochromic molecules or a combination of photochromic molecules that are typically activated upon exposure to radiation having a wavelength of between 360 nm and 450 nm, preferably 360-400 nm, such as about 380 nm or between 370 nm and 390 nm, or 360-380 nm.

In particular, this method for providing the self-supporting polymer film comprised by the photochromic laminate, provides the self-supporting photochromic polymer film, wherein said self- supporting photochromic polymer film comprises between 0,1 % and 12% by weight of the ketone based on the total weight of the self-supporting photochromic polymer film, preferably between 3% and 8% by weight, or wherein the self-supporting polymer film comprises less than 0,1 % by weight of the ketone based on the total weight of the self-supporting polymer film. It is preferred that this method for providing the self-supporting polymer film comprised by the photochromic laminate, provides the self-supporting polymer film, wherein said self-supporting polymer film comprises less than 0,1 % by weight of the ketone based on the total weight of the self-supporting polymer film, such as about 0%.

In one embodiment, the ketone provided in step (i) is selected from propan-2-one and cyclohexanone, preferably, the ketone is cyclohexanone, and/or the aliphatic thermoplastic polyurethane film of step (i) is based on an aliphatic diisocyanate selected from H12 MDI, HDI and IPDI, or mixtures thereof, and/or the aliphatic thermoplastic polyurethane film of step (i) is based on a polyester or on a polyether. It is preferred that the selected ketone is cyclohexanone and the aliphatic thermoplastic polyurethane film of step (i) is based on an aliphatic diisocyanate selected from H12 MDI, HDI and IPDI and is based on a polyester or is based on a polyether. Thus, for example, the aliphatic thermoplastic polyurethane film of step (i) is based on the aliphatic diisocyanate H12 MDI and a polyester, on HDI and a polyester, on IPDI and a polyester, on H12 MDI and a polyether, on HDI and a polyether, and on IPDI and a polyether.

One of the benefits of this method for providing the self-supporting photochromic polymer film comprised by the photochromic laminate is the omission of a curing step after impregnating the thermoplastic polymer film with a solution of photochromic dye and ketone. Current methods for producing photochromic films require such a cumbersome i.e., time- and material consuming additional curing step for the provision of photochromic film or coating suitable for inclusion in laminate articles.

Typically, in the method for providing the self-supporting photochromic polymer film about one square meter of the aliphatic TPU is immersed with at least 300 ml of the solution comprising the ketone and the dye, preferably at least two different dyes, more preferably two different dyes. Preferably, the one square meter of the thermoplastic polymer film having a thickness of between 0,1 mm and 6,5 mm, typically between 0,3 mm and 1 ,0 mm such as about 0,38 mm or about 0,63 mm or about 0,68 mm for an aliphatic TPU, such as an aliphatic TPU based on a polyester or on a polyether and based on an aliphatic diisocyanate, is immersed with between 350 ml and 1000 ml ketone solution, such as between 400 ml and 450 ml. Applying such volume of ketone with photochromic dye dissolved therein ensures an equal distribution of the photochromic dye(s) throughout the thickness of the polymer film, e.g. TPU, and ensures a self-supporting aliphatic TPU film that is evenly imbibed with e.g. 1-11wt% ketone(s) based on the weight of the self-supporting film, preferably about 2-6wt%, such as about 3,5wt% or 3,0wt%. Equally preferred is a self-supporting photochromic polymer film comprised by the photochromic laminate, comprising two dyes and with about 6-12wt% of imbibed ketone or ketones based on the weight of the film. Also preferred is a self-supporting photochromic polymer film comprised by the photochromic laminate, comprising two dyes and with less than 0,1 wt% of imbibed ketone or ketones based on the weight of the film, such as 0wt% ketone (i.e. all ketone is removed after immersion of thermoplastic polymer with ketone, such as removed by drying in a hot-air oven).

Currently available photochromic laminates also suffer from unacceptable wear and decay during relative short period of use, i.e. often within 100-500 hours of use the current photochromic films or laminates are not applicable anymore for shielding against radiation such as ultraviolet radiation and/or for radiation heat, since the photochromic effect diminished in this time frame. Such low lifetimes incurs high costs with regard to replacement of worn laminates and use of raw materials. The self- supporting photochromic polymer films comprised by the photochromic laminate of the invention, however, have an extended life time with regard to the time period in which the photochromic film adequately changes color upon irradiation with ultraviolet radiation. That is to say, the self-supporting polymer film comprised by the photochromic laminate, such as a film comprising 2-11 % by weight or less than 0,1 % by weight cyclohexanone based on the weight of the film, and comprising aliphatic TPU based on polyester or aliphatic TPU based on polyether, has an extended life time of at least 2000 hours, as assessed in photo-stability tests known in the art. Surprisingly, the inventors established that the increased resistance against wear and decay of the photochromic effect of the film comprised by the photochromic laminate is accompanied by a relatively low value for the established decay half time. For the self-supporting polymer film comprised by the photochromic laminate, the decay half time is commonly 15 seconds or less, such as between 1 and 5 seconds, whereas the loss of photochromic activity upon exposure to ultraviolet light is surprisingly low in time. See also Example 4 and Example 5 and Example 9, here below. Thus, improved stability of the photochromic self-supporting polymer film comprised by the photochromic laminate is accompanied by yet a relatively high response speed when irradiating the film with ultraviolet radiation is stopped. Commonly, increasing photochromic film stability is hampered by occurrence of an accompanying increase in response time to changes in exposure to ultraviolet radiation, when photochromic films known in the art are assessed. These photochromic films known in the art typically suffer from the disadvantage that they can take relatively long to switch between light and dark states for various applications (like automotive or aircraft windows). Thus, the current self-supporting photochromic polymer film comprised by the photochromic laminate according to the invention both improves lifetime and allows switching between light and dark states quickly.

As said, for the photochromic laminates containing the self-supporting photochromic polymer film, the polymer being TPU, the loss of photochromic activity when irradiated with e.g. direct sunlight, under influence of exposure to ultraviolet light for 100-1000 hours, is surprisingly low. Referring to examples 5 and 9, here below in the Examples section, wear when referring to loss of photochromic activity is 0%-40%, the extent of the wear relating to the amount of residual ketone remaining in the TPU film after treating the TPU film with the ketone (e.g. imbibement, immersion), followed by drying the imbibed TPU film. The polycarbonate laminate comprising photochromic self-supporting TPU film in between two layers of polycarbonate, the TPU film containing 0% of residual cyclohexanone, does not exhibit loss of photochromic activity at all after irradiating the laminate with UV light for over 100 hours, such as 100-1000 hours, such as 100 hours, 150 hours, 1000 hours, or such laminate shows loss of photochromic activity of above 0%, such as less than 10%, such as 0%-9%. Similarly, the polycarbonate laminate comprising photochromic self-supporting TPU film in between two layers of polycarbonate, the TPU film containing 3% of residual cyclohexanone, does not exhibit loss of photochromic activity at all after irradiating the laminate with UV light for over 100 hours, such as 100-1000 hours, such as 100 hours, 150 hours, 1000 hours, or such laminate shows loss of photochromic activity of above 0%, such as less than 20%, such as 0%-15%. The polycarbonate laminate comprising photochromic self- supporting TPU film in between two layers of polycarbonate, the TPU film containing 8% of residual cyclohexanone, does exhibit loss of photochromic activity after irradiating the laminate with UV light for over 100 hours, such as 100-1000 hours, such as 100 hours, 150 hours, 1000 hours, wherein the loss of photochromic activity is 15%-50%, such as above 20%, above 25%, above 30%, about 30%, about 40%, or between 25% and 45%. The thickness of the self-supporting photochromic TPU film is 0,1 mm - 3 mm, preferably 0,1 mm - 0,8 mm, such as 0,1 mm - 0,76 mm, 0,1 mm - 0,68 mm, 0,34 mm - 0, 64 mm, or about 0,38 mm, 0,63 mm. The thickness of the optically transparent polycarbonate in the laminate is 0,1 mm - 2,5 mm, such as about 0,175 mm and about 2 mm. The content of at least one photochromic dye, preferably two dyes, preferably T-type organic photochromic molecules including spiropyrans, spirooxazines and naphthopyrans, is for example 0,5% - 1 ,5% by weight of the TPU film for the at least one or more dyes together, for example about 1 % by weight.

As said, the self-supporting photochromic polymer film comprised by the photochromic laminate does not have to be subjected to a curing step in the method in order to be suitable for adhering to transparent materials known in the field of applying photochromic laminates. Current photochromic films known in the art commonly have the drawback that a step of curing such films is required, before such films are applicable for laminating in between layers of further sheets of material applied in the field of applying photochromism.

Known photochromic laminates cannot cost-effectively be produced at a large scale. In contrast, the photochromic laminate established by the inventor is however producible to cover large surface areas and so can be used in market segments that were previously unable to exploit the properties of a photochromic material, such as building glazing and vehicle windows and aircraft windows. Typically, at least the size of an A4 (210 mm x 297 mm) can be achieved for the photochromic laminate, or even about 1 m ² or larger, when applying the method of the invention.

A further aspect of the invention relates to use of the photochromic laminate or use of the photochromic laminate obtainable by the method of the invention or obtained with the method of the invention in the manufacturing of an article.

It was found by the inventors that the method for providing the photochromic laminate provides a photochromic laminate comprising the self-supporting photochromic polymer film, wherein said film does not turn yellow upon exposure to e.g. ultraviolet light and xenon light. Thus, the self-supporting polymer film comprised by the photochromic laminate retains its transparency upon exposure to light, which is beneficial to the life time of the film when applied for its photochromic activity. The use of the photochromic laminate or the use of the photochromic laminate obtainable by the method, for example, relates to the manufacturing of car glass, glass cover for lights such as car lights, glass-based goggles, polymer-based goggles, glass- or polymer-based lenses for a glasses, glass- or polymer-based visors, window glass, construction material for buildings, etc. The inventors found that the photochromic self- supporting polymer film comprised by the photochromic laminate is particularly suitable as a host layer bonded between two transparent sheets of material commonly applied in the field of application of photochromic articles, such as sheets of glass and/or sheets of optically transparent polycarbonate. As said before, the photochromic self-supporting polymer film, in particular aliphatic polyester-based TPU or aliphatic polyether-based TPU imbibed with either acetone or cyclohexanone, is suitable for adherence to such transparent sheets of material used in the manufacturing of articles applied for the photochromic activity of included photochromic film, e.g. car windows, glazing for construction, glasses, lenses, etc. Preferred is the photochromic laminate comprising aliphatic polyether-based TPU imbibed with cyclohexanone, wherein the self-supporting photochromic polymer film comprises 0-12% by weight cyclohexanone based on the total weight of said film. Also preferred is the photochromic laminate comprising aliphatic polyester-based TPU imbibed with cyclohexanone, wherein the self-supporting photochromic polymer film comprises 0-12% by weight cyclohexanone based on the total weight of said film. Thus, particularly suitable articles comprising photochromic self-supporting polymer film of the invention are laminates made of transparent material, wherein the film is sandwiched in between such layers of transparent material. Typically, the transparent material are sheets or film of optically transparent polycarbonate.

Another aspect of the invention relates to an article comprising the photochromic laminate of the invention or the photochromic laminate obtainable by the method of the invention or obtained with the method of the invention. Figure 1 displays various embodiments of such photochromic laminates applicable to be comprised by such an article.

In a preferred embodiment, the article is an optic article, preferably an optic article selected from visors, goggles, sunglasses, sun screen, face-shields, architectural windows, automotive windows, ophthalmic lenses, and aeronautic windows. The optic article can also be ophthalmic lenses.

EXAMPLES

Examples are described below that illustrate certain embodiments of the invention. They are not intended in any way to limit the scope of the invention. It should be understood that in the exemplifying embodiments the term “thermoplastic polyurethane film” or “TPU film” should be read as “cyclohexanone-treated thermoplastic polyurethane film”, unless specified otherwise. As said before, the residual amount of ketone in the imbibed TPU film is between 0% and 12%, preferably between 0,1 % and 12%, such as about 0%, 0,1 %, 3% or 8%, based on the weight of the TPU film after the drying step of the process applied for imbibing TPU film with a ketone compared to the original weight of the untreated TPU film. Treating a film with a ketone is for example the immersion of said film in the ketone, therewith contacting the whole film with the ketone, such that the ketone becomes impregnated in the full thickness of the polymer film, such as an aliphatic polyether-based TPU or an aliphatic polyester- based TPU imbibed with either acetone or cyclohexanone, preferably cyclohexanone.

Example 1

A photochromic Lexan™(Sabic Innovative Plastics BV, Bergen op Zoom, Netherlands) polycarbonate (PC) film laminate (“PC laminate”) was prepared according to METHOD I, in two steps:

METHOD I

(1 ) A photochromic TPU film is provided by immersing at room temperature an untreated S123 TPU film (that is to say, a TPU film that was not treated by imbibing with a ketone) with a thickness of 0,68 mm and a length and a width of 10 cm times 20 cm, respectively, purchased from PPG-Sierracin/Sylmar Corp. (Sylmar, USA), in a bath of about 200 ml to 900 ml, typically about 400-450 ml, of cyclohexanone containing 0,5% Reversacol Penine Green (P.G.) and 0,5% Reversacol Humber Blue (H.B.), supplied by Vivimed Labs Europe Ltd (Yorkshire, England), both based on the weight of the cyclohexanone solution. After about 40 seconds to 100 seconds, typically about 60 seconds, the films are removed from the bath and left to dry in a hot air circulating oven, set at a temperature of 60°C, for about 90 minutes. After the drying time, the weight is determined and compared to the original weight. The percentage of remaining cyclohexanone is determined. Samples were obtained that contained 0%, 3% or 8% by weight of residual cyclohexanone, based on the weight difference of the film before and after imbibing it with cyclohexanone. Samples have been coded with the corresponding weight percentage ketone in the film, accordingly.

(2) Laminating the TPU/cyclohexanone films obtained in step 1. between a 0,175 mm Lexan™ HP92W PC film (SABIC, Netherlands) and a 0,175 mm Lexan™ 8010MC PC film (SABIC, Netherlands) using an Oasys card press laminator (Oasys Technologies Ltd, Bedfordshire, UK) at a temperature of 135°C, at a pressure of 10 bar, during a period of 120 seconds. These Lexan™ polycarbonate films are optical grade polycarbonate films coated with a UV-protective coating that absorbs all UV-light.

Note: UV protected PC foil Lexan HP92W is a coated Lexan polycarbonate foil, which blocks all UV light. UV stabilized PC foil Lexan 8010MC is not coated with such a UV light blocking foil, and is instead provided with UV absorber in the PC foil.

Homogeneous and even distribution of the organic photochromic molecule comprising a chromophore in the thermoplastic polymer, here a TPU film, was established by visualizing the photochromic effect which was apparent equally distributed throughout the whole volume of the TPU film. The organic photochromic molecules comprising a chromophore, i.e. the T-type photochromic dyes Reversacol Penine Green (P.G.) and Reversacol Humber Blue (H.B.) are evenly distributed throughout the thickness of the self-supporting polymer film provided by applying the Method I (see also example 8, here below).

The aliphatic thermoplastic polyurethane sheets referred to as “S123” have the following characteristics, as determined by the manufacturer. Specific gravity (g/cc; test method ASTM D- 792:2013, version in force in 2017 and 2018)) of 1 ,08; shore hardness of 80 A (test method ASTM D- 2240:2015, version in force in 2017 and 2018); tensile strength at 25°C of 6200 psi (42,75 MPa) (test method ASTM D-412 type C:2016, version in force in 2017 and 2018); modulus at 100% elongation at 25°C of 530 psi (3,54 MPa) (test method ASTM D-412 type C:2016); modulus at 300% elongation at 25°C of 1700 psi (11 ,72 MPa) (test method ASTM D-412 type C:2016); ultimate elongation at 25°C of 620% (test method ASTM D-412 type C:2016); tear strength at 25°C of 320 pli (kN/m) (test method ASTM D-624 C:2016), for S123 (all values are nominal values). Transmission of ultraviolet radiation is 10% and transmission of visible light is 85%.

Initial colouring of the PC laminate obtained using the two-step method I outlined here above was measured using a spectrophotometer, when the sample had not yet been exposed to light. After the initial spectrophotometer measurement, the decay half time (T1/2 in seconds) was measured when the sample had been exposed to light. This was done using the following method, according to the steps:

1. An initial measurement is done in a spectrophotometer before the sample is exposed to light to get initial Lab values. 2. After measurement of step 1 the spectrophotometer is set up to be ready to measure the colour of the sample again as soon as the sample has been exposed to light;

3. The sample is exposed to light for 1 minute using a Heraeus Suntest CPS (Heraeus Holding GmbH, Hanau, Germany), or comparable suntest equipment, using a 1500 W air-cooled xenon lamp irradiating the sample at a wavelength of between 400-750 nm;

4. After 1 minute has passed in step 3, the sample is removed from the suntester and immediately placed in the spectrophotometer (t=0 sec); this measurement gives the activated Lab values of the sample;

5. The colour of the sample is measured at an interval of every 5 seconds till t=120 sec is reached, these measurements will determine the decay half time; and

6. Once t=120 sec the final measurement at t=240 sec is performed.

Results of these measurements are shown below in Table 1. Control reference samples were used that are commonly used photochromic laminates in ophthalmic lenses that are commercially available. These controls acted as comparative materials for the current experimental PC laminates that were obtained using the production steps 1 and 2 of Method I that were described here above. Control 1 is a commercially available insert for motor visor and control 2 is a Transitions® ophthalmic lens (Transitions Optical Inc., Florida, USA).

The initial L value of all samples was relatively high, indicating that the laminates of samples 1- 3 and controls 1-2 all had a light colour, as defined by CIELAB. Based on their initial a values the experimental samples 1 , 2 and 3 were more red than green, while the control samples 1 and 2 both were more green than red. Based on their initial b values experimental sample 1 and the Transitions® control sample (control 2) were more yellow than blue, while experimental samples 2 and 3 and the commercially available insert for motor visor control sample (control 1 ) were more blue than yellow.

Table 1

The activated L values after exposure of the laminates to light were all lower than the initial L values. This indicates that in all five samples tested a photochromic reaction occurred. All experimental samples 1-3 had a lower L value than the insert for motor visor control sample (control 1 ), but a slightly higher L value than Transitions® control sample (control 2). The activated a values show that experimental samples 1 , 2 and 3 as well as the Transitions® control sample became more red, while the insert for motor visor control sample became more green. The activated b values show that experimental samples 1 , 2 and 3 as well as the commercially available insert for motor visor control sample became more blue, while the Transitions® control sample became more yellow.

The decay half time of all experimental samples 1-3 was shorter than the decay half time of both the insert for motor visor control sample and the Transitions® control sample. The sample with the strongest photochromic reaction was the Transitions® control sample followed by experimental sample 2, experimental sample 1 , experimental sample 3 and finally the sample with the weakest photochromic reaction was the insert for motor visor control sample. From this data it is concluded that the decay half time is significantly improved for all experimental samples 1-3, that is to say the decay half time is shorter for the PC laminates of the experimental samples 1-3 when compared to the two control reference laminates known in the art. This feature of the exemplifying photochromic laminates embodied by experimental samples 1-3 make said sample laminates candidates for use in commercial applications for which the Transitions® lenses (control 2) do not clear fast enough.

Out of the three experimental samples 1 , 2 and 3 the experimental PC photochromic laminate containing the TPU/cyclohexanone film with a final content of cyclohexanone of 3% (sample 2), gives the strongest photochromic response. The three experimental samples 1-3 are suitable candidates for commercial application.

Example 2

A photochromic Lexan™ polycarbonate film laminate (“PC laminate”) was prepared according to METHOD II in two steps similar to METHOD I, outlined here above for Example 1 :

METHOD II

Step 1 : A photochromic TPU film is provided by immersing at room temperature an untreated S123 TPU film (thickness is 0,38 mm, length times width is 10 cm X 10 cm) in a bath of about 200 ml to 900 ml, typically about 400-450 ml, of cyclohexanone containing 0,5% Reversacol Penine Green (P.G.) and 0,5% Reversacol Humber Blue (H.B.), both based on the weight of the cyclohexanone solution comprising the photochromic dyes. Step 2: The photochromic TPU film obtained in Step 1. was laminated between a 0,175 mm Lexan™ HP92W PC film and a 0,175 mm Lexan™ 8010MC PC film using an Oasys card press laminator at a temperature of 135°C, at a pressure of 10 bar, during a period of 120 seconds.

The thickness of the photochromic laminate provided by the method II was 0,80 mm.

The organic photochromic molecules comprising a chromophore, i.e. the Reversacol Penine Green and the Reversacol Humber Blue are evenly distributed in the self-supporting polymer film provided by applying the Method II.

Initial colouring of the PC laminate obtained using the two-step Method II outlined here above was measured using a spectrophotometer, when the sample had not yet been exposed to light. After the initial spectrophotometer measurement, the decay half time was measured when the sample had been exposed to light. This was done using the method described in Example 1.

Results of these measurements are shown below in Table 2. Control reference samples were used that are commonly used photochromic laminates in ophthalmic lenses that are commercially available. These controls acted as comparative materials for the experimental PC laminates that were made using the production steps 1 and 2 of Method II. Control 1 is a commercially available insert for motor visor, which is a laminate, and control 2 is a Transitions® ophthalmic lens (thickness is 0,75 mm). These reference samples were also applied in Example 1. Table 2

The initial L value of all samples was high, indicating that they all had a light colour, as defined by CIELAB. Based on their initial a values the experimental samples 1 , 2 and 3 were more red than green, while the control samples 1 and 2 both were more green than red. Based on their initial b values experimental sample 1 and the Transitions® control sample (control 2) were more yellow than blue, while experimental samples 2 and 3 and the insert for motor visor control sample (control 1 ) were more blue than yellow.

The activated L values were all lower than the initial L values. This indicates that in all samples a photochromic reaction took place. All experimental samples had a lower L value than the insert for motor visor control sample, but a higher L value than the Transitions® control sample. The activated a values show that experimental samples 1 , 2 and 3 as well as the Transitions® control sample became more red, while the insert for motor visor control became more green. The activated b values show that experimental samples 1 , 2 and 3 as well as the commercially available insert for motor visor control sample became more blue, while the Transitions® control sample became more yellow.

The decay half time of all experimental samples was shorter than the decay half time of both the insert for motor visor control sample and the Transitions® control sample. The sample with the strongest photochromic reaction was the Transitions® control sample followed by experimental sample 1 , experimental sample 2, experimental sample 3 and finally the sample with the weakest photochromic reaction was the insert for motor visor control sample.

From this data it is concluded that the decay half time is significantly improved for all experimental samples, that is to say the decay half time is shorter for the experimental samples 1-3 when compared to the two laminates known in the art. This feature of the experimental samples 1-3 make said sample laminates candidates for use in commercial applications for example for which the Transitions® lenses (control 2) do not clear fast enough.

Out of the three experimental samples 1 , 2 and 3 the experimental laminate containing the TPU/cyclohexanone film with a final weight content of cyclohexanone of 8% (sample 1 ), gives the strongest photochromic response.

Example 3

A photochromic Lexan™ polycarbonate film laminate (“PC laminate”) was prepared according to a Method III in two steps, similar to the Method I described in Example 1.

METHOD III

Step 1 : A photochromic TPU film is provided by immersing at room temperature an untreated S158 TPU film (dimensions: thickness times length times width is 0,68 mm X 10 cm X 10 cm) in a bath of about 200 ml to 900 ml, typically about 400-450 ml, of cyclohexanone containing 0,5% Reversacol Penine Green (P.G.) and 0,5% Reversacol Humber Blue (H.B.), both based on the weight of the cyclohexanone solution comprising the photochromic dyes. Step 2: The photochromic TPU film obtained in Step 1. is laminated between a 0,175 mm Lexan™ HP92W PC film and a 0,175 mm Lexan™ 8010MC PC film using an Oasys card press laminator at a temperature of 135°C, at a pressure of 10 bar, during a period of 120 seconds.

The organic photochromic molecules comprising a chromophore, i.e. the Reversacol Penine Green and the Reversacol Humber Blue are evenly distributed in the self-supporting polymer film provided by applying the Method III.

The aliphatic thermoplastic polyurethane sheets referred to as “S158” has the following characteristics, as determined by the manufacturer. Specific gravity (g/cc; test method ASTM D- 792:2013, version in force in 2017 and 2018)) of 1 ,08; shore hardness of 64 A (test method ASTM D- 2240:2015, version in force in 2017 and 2018); tensile strength at 25°C of 3400 psi (23,44 MPa) (test method ASTM D-412 type C:2016, version in force in 2017 and 2018); modulus at 100% elongation at 25°C of 370 psi (2,55 MPa) (test method ASTM D-412 type C:2016); modulus at 300% elongation at 25°C of 740 psi (5,10 MPa) (test method ASTM D-412 type C:2016); ultimate elongation at 25°C of 860% (test method ASTM D-412 type C:2016); tear strength at 25°C of 260 pli (test method ASTM D- 624 type C:2016), for S158 (all values are nominal values). Transmission of ultraviolet radiation is 10% and transmission of visible light is 85%.

Initial colouring of the PC laminate obtained using the two-step Method III outlined here above was measured using a spectrophotometer, when the sample had not yet been exposed to light. After the initial spectrophotometer measurement, the decay half time was measured when the sample had been exposed to light. This was done using the method described in Example 1 and Example 2.

Results of these measurements are shown below in Table 3. Control samples were the same reference laminates applied in Example 1 and 2.

Table 3

The initial L value of all samples was high, indicating that they all had a light colour, as defined by CIELAB. Based on their initial a values the experimental samples 1 , 2 and 3 were more red than green, while the control samples 1 and 2 both were more green than red. Based on their initial b values the Transitions® control sample (control 2) was more yellow than blue, while experimental samples 1 , 2 and 3 and the insert for motor visor control (control 1 ) were more blue than yellow.

The activated L values were all lower than the initial L values. This indicates that in all samples a photochromic reaction took place. All experimental samples had a lower L value than the insert for motor visor control sample (control 1 ), but a higher L value than the Transitions® control sample (control 2). The activated a values show that experimental samples 1 , 2 and 3 as well as the Transitions® control sample became more red, while the commercially available insert for motor visor control became more green. The activated b values show that experimental samples 1 , 2 and 3 as well as the insert for motor visor control sample became more blue, while the Transitions® control sample became more yellow.

The decay half time of all experimental samples was shorter than the decay half time of both the insert for motor visor control sample and the Transitions® control sample. The sample with the strongest photochromic reaction was the Transitions® control sample followed by experimental sample 2, experimental sample 1 , experimental sample 3 and finally the sample with the weakest photochromic reaction was the insert for motor visor control sample.

From this data it is concluded that the decay half time is significantly improved for all experimental samples, that is to say the decay half time is shorter for the experimental samples 1-3 when compared to the laminates known in the art. This feature of the experimental samples 1-3 make said sample laminates candidates for use in commercial applications for which the Transitions® lenses (control 2) do not clear fast enough.

Out of the three experimental samples 1 , 2 and 3 the experimental PC laminate containing the TPU/cyclohexanone film with a final content of cyclohexanone of 3% (sample 2), gives the strongest photochromic response.

Example 4

A photochromic Makrolon® UV (Covestro, Germany) polycarbonate film laminate (“PC laminate”) was prepared in two steps of Method IV, similar to Method I, II, III, described in Examples 1-3.

Method IV

Step 1 : A photochromic TPU film was provided by immersing at room temperature an untreated 0,68 mm S158 TPU film (Ixb = 10 cm x 20 cm) in a bath of about 200 ml to 900 ml, typically about 400-450 ml, of cyclohexanone containing 0,5% Reversacol Penine Green (P.G.) and 0,5% Reversacol Humber Blue (H.B.), both based on the weight of the cyclohexanone solution comprising the two photochromic dyes. The self-supporting photochromic TPU film was dried after the immersion step to an extent that all cyclohexanone imbibed in the TPU was evaporated again: the residual amount of cyclohexanone in the TPU was 0% based on the weight of the TPU film. Step 2: The photochromic TPU film was laminated between two sheets of 2 mm Makrolon® UV using an Oasys card press laminator at a temperature of 135°C, at a pressure of 10 bar, during a period of 120 seconds. Makrolon® UV is a polycarbonate sheet on which a co-extrusion layer of polycarbonate is present. This co-extrusion layer contains UV- absorbers at a level where all the UV light in the UV spectrum is absorbed.

The organic photochromic molecules comprising a chromophore, i.e. the Reversacol Penine Green and the Reversacol Humber Blue are evenly distributed in the self-supporting polymer film provided by applying the Method IV.

Initial colouring of the PC laminate obtained using the two-step method IV outlined here above was measured using a spectrophotometer, when the sample had not yet been exposed to light. After the initial spectrophotometer measurement, the decay half time was measured when the sample had been exposed to light. This was done using the method described for Examples 1-3. Results of these measurements are shown below in Table 4. Control samples were the same two references laminates that were applied in Examples 1-3.

Table 4

The initial L value of all samples was high, indicating that they all had a light colour, as defined by CIELAB. Based on their initial a values the experimental sample was more red than green, while the control samples 1 and 2 both were more green than red. Based on their initial b values the experimental sample and the Transitions® control sample (control 2) were more yellow than blue, while the insert for motor visor control sample (control 1 ) was more blue.

The activated L values were all lower than the initial L values. This indicates that in all samples a photochromic reaction took place. The experimental sample had the highest L value out of all three samples. The activated a values show that experimental sample as well as the Transitions® control sample (control 1 ) became more red, while the insert for motor visor control became more green. The activated b values show that experimental sample as well as the insert for motor visor control sample became more blue, while the Transitions® control sample became more yellow.

The decay half time of the experimental sample was shorter than the decay half time of the insert for motor visor control sample, but slightly longer than that of the Transitions® control sample. The sample with the strongest photochromic reaction was the Transitions® control sample followed by the insert for motor visor control sample, while the experimental sample had the lowest photochromic reaction.

Makrolon® UV is a special type of polycarbonate that has a UV protective layer on both sides of the polycarbonate sheet that blocks all UV radiation. This experiment has shown that a photochromic reaction can still be achieved when UV light is blocked from the photochromic film. The decay half time is still within an acceptable range, from a commercial application perspective.

The laminate‘2x 2 mm Makrolon® UV with 0,68 mm S123 0,5% Reversacol P.G + 0,5% H.B.’ (See Table 4) was subjected to a wear test by determining the extent of darkening under influence of exposure to direct sunlight of the photochromic TPU film before and after ageing the laminate upon irradiating the laminate for 1000 hours with Xenon light (IS013411 ). Darkening was assessed with laminate that was not irradiated with Xenon light and with a portion of the same laminate that was irradiated with the Xenon light. No difference in darkening of the laminate in response to exposure to direct sunlight was measured. In conclusion, the PC laminate enclosing photochromic TPU film, which film is free of residual cyclohexanone after immersing and drying the film, is resistant to wear when the extent of darkening upon exposure to direct sunlight is assessed for laminates exposed to Xenon light for 1000 hours. Example 5

The control samples (control 1 and control 2) according to the previous Examples 1-4 and the experimental photochromic polycarbonate laminates according to Example 1 , 2, 3, and 4 were all subjected to a 100 hour Xenon exposure test according to IS011341 : 2004 (version in force in 2017) after which Lab values and decay half time were measured using the same method as in the previous Examples 1-4, in order to assess if any photochromic activity had been lost. The initial Lab values are the same as measured in the previous Examples 1-4. The results of these measurements are shown below in Table 5.

Table 5

From this data it is concluded that the experimental samples from all Examples 1-4 have a longer useful life than the current commercially available laminates like the insert for motor visor laminate and Transitions® ophthalmic lens. The experimental free-standing TPU film samples lost only up to 40% of their photochromic activity after 100 hours of exposure to xenon light, while the control samples did not fare as well (turned yellow, discolored to an unacceptable extent). Both the commercially available insert for motor visor reference sample and the Transitions® reference sample were discolored after only 100 hours of exposure to xenon light. The insert for motor visor laminate was so highly discolored that the material had turned completely yellow indicating severe decay or break down of the photochromic film and/or the polycarbonate material around it, which made it unusable after only 100 hours of xenon exposure. The Transitions® control sample was slightly discolored, but also lost 42% of its photochromic activity in addition to its discoloration.

Some of the experimental samples did not lose any of their photochromic activity after 100 hours of exposure to xenon light, which is a measure for a long useful life with these experimental PC laminates, which useful life is extended compared to the useful life of the control reference samples. The samples that did not lose any photochromic activity in the 100 hours xenon light exposure test, are: - Sample 3 from Example 2: 0,38 mm S123 photochromic TPU film containing Reversacol Penine Green and Humber Blue and no residual cyclohexanone (0%) laminated between a sheet of 0,175 mm Lexan™ HP92W and a sheet of 0,175 mm Lexan™ 8010 MC.

- Sample 2 from Example 3: 0,68 mm S158 photochromic TPU/cyclohexanone film containing Reversacol Penine Green and Humber Blue with 3% residual cyclohexanone weight content laminated between a sheet of 0,175 mm Lexan™ HP92W and a sheet of 0,175 mm Lexan™ 8010MC.

- Sample 3 from Example 3: 0,68 mm S158 photochromic TPU film containing Reversacol Penine Green and Humber Blue with no residual cyclohexanone (0%) laminated between a sheet of 0,175 mm Lexan™ HP92W and a sheet of 0,175 mm Lexan™ 8010MC.

Experimental sample from Example 4: 0,68 mm S123 photochromic TPU/cyclohexanone film containing Reversacol Penine Green and Humber Blue with 3% residual cyclohexanone weight content laminated between two 2 mm Makrolon® UV sheets.

The decay halftime of the experimental free-standing photochromic TPU samples of Examples 2 and 3 increased slightly, and the decay halftime is still the same or shorter than that of the control reference samples and therefore the quality of the photochromic TPU films of Example 2 and Example 3 is still improved compared to the used reference controls, and the T1/2 values are still within an acceptable short range of decay halftime after the test.

The experimental TPU film samples obtained from all of the previous Examples 1-4 are suitable candidates for use in commercial applications whereas the current commercially available laminates do not have high enough resistance to loss of photochromic activity and/or have a decay halftime which is longer than the decay halftime obtained with the photochromic laminates of the invention.

Example 6

A certified and independent research institute (NSL Analytics, Inc., Cleveland, USA) performed comparative tests with a separately prepared batch of experimental PC laminates prepared according to Method I and II as described in Example 1 and 2, providing the exemplifying photochromic laminate of Example 2, and the Transitions® control reference laminate as described in all the previous Examples 1-5. The weight percentage of cyclohexanone in the self-supporting photochromic TPU film was 0,5% based on the weight of the TPU film.

Tests were performed that analyzed the activation rate as well as the deactivation rate of the experimental PC laminate and the control reference laminate. These tests were conducted at two different temperatures, i.e. at 23°C or at 30°C. Sixteen samples of the experimental PC laminate and control laminate each were tested of which four were used per separate test. In total four tests were conducted: activation rate at 23°C, deactivation rate at 23°C, activation rate at 30°C, and deactivation rate at 30°C.

Results of the activation rate test at 23°C of the experimental PC laminate samples and control samples are shown below in Table 6. Table 6

From this data it is concluded that both the experimental sample and the control sample cut down transmittance by 50% within one minute and so the performance of these laminates is comparable.

Results of the deactivation rate test at 23°C of the experimental samples and control samples are shown below in Table 7.

Table 7

From this data it is concluded that both the experimental samples and the control samples regain over 50% of their transmittance within 1 minute and so the performance of these laminates is comparable.

Results of the activation rate test at 30°C of the experimental samples and control samples are shown below in table 8.

Table 8

From this data it is seen that higher temperature has a negative effect on the photochromic reaction of both the experimental samples and the control samples. All samples did not get as dark as when exposed to light at 23°C, nor did the reaction go as quickly. All samples still showed to cut off around 50% of transmittance in 1 minute, but the reaction slowed significantly after that. Performance of the experimental laminates and control laminates is again comparable.

Results of the deactivation rate test at 30°C of the experimental samples and control samples are shown below in table 9.

Table 9

From this data it is concluded that both the experimental laminates and the control laminates deactivate quicker when exposed to a higher temperature. All laminates regained more than 50% of their transmittance within 30 seconds.

Overall, the performance of the experimental laminates and the control laminates is comparable.

In addition to these experiments the experimental laminates and control laminates were also subjected to a 100 hour xenon exposure test, comparable to the test outlined in Example 5, here above. The results were also comparable to what was seen in Example 5. The Transitions® control reference laminates had an area of yellow discoloration that would no longer become activated and thus would no longer darken upon light stimulus after already only 100 hours of xenon exposure, while the experimental photochromic TPU film-comprising PC laminates did not lose any photochromic activity at all.

Therefore, based on this independently acquired data, it is concluded that the experimental PC laminates comprising photochromic TPU film and residual cyclohexanone at an extent of 0-10% by weight based on the weight of the TPU film, perform better than commercially available laminates, such as the insert for motor visor used as a control reference sample in for example Examples 1-3, here above, since amongst others and for example the photochromic laminate of the invention has an improved resistance to loss of photochromic activity, therewith showing that the stability of the PC laminates comprising the self-supporting photochromic TPU film containing 0-10% by weight ketone based on the weight of the TPU film, is improved when compared to currently available laminates. Example 7

The inventors found that the photochromic plastic laminate comprising a self-supporting photochromic polymer film suitably can comprise a plate or sheet of PC based on the precursor monomer diphenylcarbonate as the first sheet of transparent material in the PC laminates comprising free-standing photochromic TPU film comprising 0-10% residual ketone based on the weight of the TPU film, and suitably can comprise a first plate or sheet of PC based on the precursor monomer diphenylcarbonate as the first sheet of transparent material and a second sheet of PC based on the precursor monomer diphenylcarbonate as the second sheet of transparent material in the PC laminates comprising freestanding photochromic TPU film comprising 0-10% residual ketone based on the weight of the TPU film.

Example 8

Photochromic molecules are homogenously and evenly distributed in photochromic TPU film after immersion of said film in a solvent comprising cyclohexanone and the photochromic molecules

A first free-standing TPU film with a thickness of 0,38 mm (PPG Aerospace - Argotec) was sprayed at room temperature with a solution consisting of cyclohexanone with 0,5% w/w of Reversacol Humber Blue and 0,5% w/w Reversacol Pennine Green based on the total weight of the solution. Subsequently, the sprayed photochromic TPU film was dried:“TPU-SPRAY”.

A second free-standing TPU film with a thickness of 0,38 mm (PPG Aerospace - Argotec) was immersed at room temperature in a solution consisting of cyclohexanone with 0,5% w/w of Reversacol Humber Blue and 0,5% w/w Reversacol Pennine Green based on the total weight of the solution. Subsequently, the TPU film imbibed with cyclohexanone and photochromic dyes was dried:“TPU- IMBIBED”.

The TPU-SPRAY and TPU-IMBIBED samples were subjected to exposure to UV light. It was observed that only the major surface of TPU-SPRAY onto which the photochromic dyes were sprayed, showed a colour change from colourless to dark purple, and not the thickness of said TPU-SPRAY film. Further, it was observed that TPU-IMBIBED was presented as a homogenously dark purple coloured film after exposure to UV light, indicative for evenly distributed photochromic dyes throughout the whole film in three dimensions. Optical micrographs were obtained in reflection using a Motic STEREO SMZ- 168T-LED microscope, equipped with a MOTICAM 580 camera and LED top light. Further, it was observed that both the colouring of the TPU-IMBIBED film upon exposure to light and the subsequent discolouring occurred evenly throughout the whole volume of the film, further showing that the photochromic molecules were homogenously and evenly distributed in the TPU film upon immersion of the film in cyclohexanone with the photochromic dyes dissolved therein.

Example 9

Exemplifying self-supporting polymer films coded RR, SS and TT were provided following the step 1 of Method I, outlined here above. Details are provided in Table 10. The two photochromic dyes in the cyclohexanone were applied at a final concentration of 0,5% by weight based on the total weight of the solution.

The examples RR, SS and TT were subjected to standardized Dynamic Mechanical Analysis (DMA) according to a set-up and procedures known in the art (ISO 6721 [6721-1 :2011 ; 6721-2:2008; 6721- 3:1994; 6721-4:2008; 6721-5:1996; 6721-6:1996; 6721-7:1996; 6721-8:1997; 6721-9:1997; 6721- 10:2015; 6721-11 :2012; 6721-12:2009], version in force in 2017 and 2018; Dynamic Mechanical Thermal Analysis, DMTA). For these three examples and for a reference S123 aliphatic thermoplastic polyurethane film that was not subjected to immersion in ketone (reference measurement for obtaining a reference value), the storage modulus between -80°C and 100°C was determined in MPa, the loss modulus in the same temperature range was determined as well as the Tan Delta (Tg) value, for determining the glass-transition temperature, Tg (temperature was ramped at 3 Kelvin/minute, the set frequency was 1 Hz, the amplitude was 10 micrometer, the preload was 0,01 N). Samples of the four films subjected to the DMA were analyzed in tensile mode. These samples of the exemplifying films and the control reference film had a size of about 3 cm times about 4 cm at minimum.

For the reference sample of the S123 polymer sheet, the Tg was 12°C (Tan Delta). For examples RR, SS, TT, the values for Tg were 16°C, 7°C and -1°C, respectively. In similar analyses with polyurethane films obtained after immersion in cyclohexanone such that about 8% by weight cyclohexanone was imbibed in the polymer sheet, based on the weight of the self-supporting polymer film, the Tg was comparable with the value obtained for example TT, comprising 10% by weight cyclohexanone based on the total weight of the self-supporting TPU film.

From these measurements and from further performed analyses with further examples of self- supporting polymer films, it is seen that the presence of imbibed ketone in the polymer film lowers the Tg, therewith inducing a softening of the aliphatic thermoplastic polyurethane film applied in the method. The ketone, e.g. the cyclohexanone or the acetone, thus beneficially serves as a plasticizer. The plasticizer effect of the imbibed ketone is further demonstrated by assessing the storage modulus for examples RR, SS, TT and the reference starting material S123, before immersion in solvent, here cyclohexanone. With increasing weight percentage of imbibed ketone in the polyurethane film, the storage modulus in MPa decreases between -80°C and 20°C and is 0 MPa for all samples tested at temperatures above about 20°C. For example, for example RR (0 wt% cyclohexanone in the film), the storage modulus is about 1400 MPa at -40°C, whereas the storage modulus at -40°C is about 800 MPa for example TT (10 wt% cyclohexanone in the film).

In the DMA, a peak value for the loss modulus in MPa was measured for all examples RR, SS and TT and the reference S123 polymer sheet, at a temperature of about -43°C. It was observed that the loss modulus was similar for the example RR compared to the reference starting material of thermoplastic polyurethane film S123 before immersion in cyclohexanone solution, i.e. about 1800 MPa at about -43°C. However, the examples SS and TT, with 3 wt% and 10 wt% cyclohexanone imbibed in the polyurethane film, respectively after immersion and drying, showed an increased loss modulus up to about 2200 MPa and 2300 MPa, respectively, at about -43°C. These data further show that immersion of the aliphatic thermoplastic polyurethane film with a ketone induces an increase in the flexibility of the polymer material, thus the ketone acting as a plasticizer.

Example 10

Films of poly-ester based PU with a thickness of 0,38 mm or with a thickness of 0,76 mm were impregnated with photochromic dye by immersion at room temperature of the film in a solution consisting of cyclohexanone and 1 % by weight Reversacol Sea Green (Vivimed Labs Ltd) based on the weight of the solution. The Reversacol Sea Green contains a single photochromic group (non-modified spirooxazine) and is an organic T-type photochromic dye. After immersion of the films, these films were dried as described for Examples 1-4, here above. The residual amount of cyclohexanone imbibed in the films was 0%, 3% or 8% by weight, based on the total weight of the photochromic TPU films obtained after drying. Subsequently, the films were laminated in between two films of polycarbonate, the films having a thickness of 0,175 mm. No adhesive was required for the lamination. The lamination was performed according to the method outlined in Example 1 as Method I.

Stability and photochromic performance of the PC laminates comprising the photochromic TPU films was assessed, according to the method outlined here above in Example 5, except that the PC laminates are now exposed for 125 hours to Xenon light (IS01 1341 : 2004, version in force in 2017). Photochromic activity after this ageing step was compared with the initial photochromic activity, and is expressed as a percentage loss of photochromic activity after exposure to Xenon light (ageing). Independent on the thickness of the TPU film (0,38 mm or 0,76 mm), for PC laminates comprising photochromic TPU film comprising 0%, 3% or 8% cyclohexanone based on the weight of said film, the measured loss of photochromic activity was about 0-9%, about 12-15% and about 30-40%, respectively.