The present invention relates to a method for providing photoluminescent products; the invention also relates to photoluminescent products per se, be they obtained by means of the method cited above or not.

In the scientific field, the set of processes by means of which some substances are capable of absorbing light radiation to then re-emit it in all directions is referenced with the term "photoluminescence", with which the effect of these processes also is defined.

It is therefore possible to utilize these properties in products of various types: by resorting to photoluminescent pigments (based on strontium aluminate or zinc sulfide, for example), these products, struck by the light radiation emitted by a source, are capable of accumulating it and progressively returning it over time, even after the interruption of the emission of the radiation on the part of the source.

The possibility to accumulate and then return light can thus be used in various manners, for example to indicate the very presence of the photoluminescent object in the dark and therefore facilitate its location (consider for example the remote control of the TV set, the mobile telephone, key rings, etc.).

In industrial contexts, the pigments can be integrated in signs and boards hung on walls, so as to allow their visibility even in case of power outage or other emergency situations and allow for example the immediate identification of the escape routes and/or of emergency exits.

It is obviously possible to identify various other applications in which photoluminescent products are used, and in which the substantial lack of associated energy consumption is appreciated, but what all uses have in common and prevents further uses is the awareness of the existence of several drawbacks which limit their appeal.

In all commercially available products the luminescent effect is in fact first of all scarcely visible and excessively limited in duration. Evidently, problems like the ones indicated above are highly unwelcome, since they render the photolummescent products unreliable and limit their field of application.

In addition to this, there are many other drawbacks which in each instance can occur and are more or less felt as a function of the specific context in which they are detected. Among them, it is possible to mention poor strengths, poor outdoor resistance (and/or resistance to atmospheric agents), early yellowing, early opacification, poor chemical-mechanical strength, poor heat resistance, poor dimensional stability, poor transparency, poor compatibility with other materials (which becomes evident in processes and couplings), the inability to support sublimation treatments (for printing), and others.

The aim of the present invention is to solve the problems described above, proposing a method that allows to provide effective photoluminescent products capable of ensuring high performance.

Within this aim, an object of the invention is to provide effective photoluminescent products capable of ensuring high performance.

Another object of the invention is to propose a method that allows to provide photoluminescent products in which the photoluminescence effect has a high intensity and/or lasts a long time.

Another object of the invention is to provide a photoluminescent product in which the photoluminescent effect has a high intensity and/or lasts a long time.

Another object of the invention is to offer on the market photoluminescent products which lack the many drawbacks that can be observed in known solutions.

Another object of the invention is to offer on the market photoluminescent products which ensure high reliability in operation.

Another object of the invention is to propose a method that adopts a technical and structural architecture that is alternative with respect to those of the methods of the known type.

Another object of the invention is to propose a method that can be performed easily starting from commonly commercially available elements and materials.

A still further object of the invention is to propose a product and a method that can be easily industrialized and embodied in a simple manner and with modest costs.

This aim and these and other objects which will become better apparent hereinafter are achieved by a method according to claim 1 and by a photoluminescent product according to claim 12.

Further characteristics and advantages of the invention will become better apparent from the description of some preferred but not exclusive embodiments of the method and of the product according to the invention, with the product shown by way of nonlimiting example in the accompanying drawings, wherein:

Figure 1 is a schematic perspective view of the product according to the invention in a first embodiment;

Figure 2 is a schematic perspective view of the product according to the invention in a second embodiment;

Figure 3 is a schematic perspective view of the product according to the invention in a third embodiment;

Figure 4 is a schematic perspective view of the product according to the invention in a fourth embodiment.

With particular reference to the cited figures, the reference numeral 1 generally designates a photoluminescent product, which is the subject matter of the present description together with a method that allows to provide photoluminescent products 1.

It is useful to specify right now that the photoluminescent product 1 can find application in any sector in which photoluminescent products are already commonly used, and likewise the product 1 is intended to be assigned also to new sectors, in particular in all fields in which, until now, the limitations of photoluminescent products of the known type, solved as will become apparent by the invention, have prevented their diffusion.

According to the invention, the method first of all entails providing, in a step a., a first layer 10 which comprises clear polyester; said first layer 10 is treated, at at least one first face thereof, with trichloroacetic acid.

It should be noted that in the art trichloroacetic acid is sometimes referenced by the acronym "TCA", which will therefore be used several times also in the continuation of the present description for the sake of simplicity.

Preferably, but not exclusively, the first layer 10 comprises glossy and clear polyester.

In practice, step a. is performed by resorting to an apparatus provided with a spool around which a film of polyester, already treated with TCA, intended to undergo the subsequent processes after its unwinding from said spool, is wound.

Step a. then provides, in an embodiment of considerable practical interest, which in any case does not limit the embodiment of the invention, for unwinding the film and making it continuously available to the subsequent processing stages, in order to allow the execution of the other provided steps.

In this regard, the method according to the invention provides, in a step b., for applying at least to the first face of the first layer 10 a second layer 20, which comprises a clear bonding agent. Then, in a step c, the method according to the invention provides for applying, on the second layer 20, a third layer 30 (obviously on the opposite side with respect to the first layer 10). The third layer 30 comprises clear polyvinyl chloride (PVC) and a photoluminescent additive.

Resorting to PVC allows to add particularly large quantities of photoluminescent additive (by choosing the corresponding thickness of the third layer 30 adequately high), being able in any case to count on the first layer 10 for stable support and mechanical strength. Therefore, the obtainable photoluminescent effect is obviously increased significantly with respect to known solutions.

The photoluminescent additive (preferably but not necessarily in powder form) can be chosen of a synthetic type or not, with any particle size and color, and can also be of a known type. Therefore, it is possible to adopt strontium aluminate or zinc sulfide or others as photoluminescent additive comprised in the third layer 30.

In an embodiment of considerable practical interest, mentioned by way of nonlimiting example of the invention, the photoluminescent additive is a strontium aluminate powder, which has a particle size comprised between 80 microns and 120 microns.

It is useful to note right now that the first layer 10 acts as backing for the subsequent materials and the use of TCA in this regard is of extreme practical interest. TCA in fact allows stable adhesion of the second layer 20 and of the third layer 30, obviating the incompatibility that polyester normally has.

Differently from known solutions, which resort to backings constituted by paper sheets (of the so-called "kraft" or "release" type), which must be discarded prior to marketing, since at the end of the production process they are merely waste, TCA allows to propose a method in which the backing (the first layer 10), on which the second layer 20 and then the subsequent ones are deposited, is maintained inside the final photoluminescent product 1. Therefore, in addition to eliminating the waste of raw material (paper), by virtue of TCA it is possible to give the photoluminescent product 1 the strength of the polyester that is present (at least) in its first layer 10.

Moreover, the polyester comprised in the first layer 10 gives (in addition to the other properties) a pleasant depth effect, by virtue of its thickness (which is chosen large at will) and its transparency.

The second layer 20, as mentioned, comprises a bonding agent; this is done to facilitate the coupling between the first layer 10 (the polyester treated with TCA) and the third layer 30, which contains the photoluminescent additive and is therefore responsible for the photoluminescent effect of the product 1 that can be obtained at the end of the method according to the invention.

In relation to the second layer 20, although it is specified that the protection claimed herein must be understood as being extended to any substance or compound indeed capable of behaving as a bonding agent (between the first layer 10 and the third layer 30), in the preferred application of the invention said bonding agent is polyurethane.

After step c, the method provides, in a step d., for applying on the third layer 30 (and obviously on the opposite side with respect to the second layer 20) a fourth layer 40, which comprises polyvinyl chloride and a white coloring agent.

As regards this last item, it is useful to specify that the protection is extended to any substance or compound that can indeed perform the function of white coloring agent: for example, a white paste or an optical whitening agent (sometimes termed "optical bleach") may be used. For example, in a solution of considerable practical interest (but which, it is useful to state once more, should not be understood in any way as limiting the application of the invention and the protective scope claimed herein), said white coloring agent is constituted by titanium oxide.

As is known, optical whitening agents (also known in English as

"optical brighteners" or "optical brightening agents"), are chemical compounds which by fluorescence (a physical phenomenon of short duration, differently from photoluminescence) absorb light in the ultraviolet range and re-emit it in the blue region, typically at 420-470 nm. This allows it to indeed perform a "brightening" function, modifying (towards white) the chromatic perception of the observer.

The fourth layer 40 therefore performs a role of absolute interest, since it imparts a powerful rebound to the light radiation, facilitating the unidirectionality of reflected radiation and a considerable increase in the accumulation of said radiation.

The intensity of the photoluminescent effect produced by the third layer 30 is thus significantly enhanced and increased by the fourth layer 40.

The photoluminescent product 1, obtained by means of the method according to the invention, is therefore composed at least of the first layer 10, the second layer 20, the third layer 30 and the fourth layer 40 (and in this first embodiment is shown schematically in Figure 1).

In this embodiment, the light is emitted by the third layer 30 (with the coloring agent in the fourth layer 40 enhancing the effect) and, by crossing the second layer 20, is emitted outward by the first layer 10.

It is useful to specify that preferably steps b., c. and d. occur at successive stations of an apparatus provided for this purpose and crossed by the film which, as shown, constitutes the first layer 10. The second layer 20, the third layer 30 and the fourth layer 40 are therefore deposited progressively thereon.

The apparatus can be of the type with autonomous modules with multiple stages, like the ones provided for the production of synthetic hides, which manage heat in a differentiated manner for each module, as a function of the material being treated and of its properties and/or requirements, applying (in that case spreading) said material with very high precision.

Both by resorting to these apparatuses and by resorting to others, the method according to the invention in any case provides for giving a considerable thickness to the first layer 10 and/or to the second layer 20 and/or to the third layer 30 and/or to the fourth layer 40, ensuring quality and performance levels of extreme interest, far higher than those obtainable with known solutions. At the end of the method the product 1 therefore is provided, preferably but not exclusively, in sheets, spools or multilayer panels, which can be cut and shaped (and packaged) according to the requirements and the specific field of application for which they are intended.

The sheet can in fact be easily die-cut, etched, glued and processed in various manners (for example it can be printed by thermal sublimation or with printing of another type, as will become apparent in the pages that follow), indeed as a function of the specific requirements.

Usefully, the method also provides for a step e., which follows step d., of application of a fifth layer 50 on the fourth layer 40, obviously on the opposite side with respect to the third layer 30; the fifth layer 50 comprises an adhesive, preferably of the type of a polyurethane-based heat-activated adhesive. The product 1 obtained by performing step e. as well is therefore shown schematically in Figure 2.

The presence of the fifth layer 50 allows the adhesion of additional backings, as a function of the specific application: for example, by virtue of the fifth layer 50 it is possible to make the product 1 adhere to fabrics or clothing (or others).

Furthermore, in an interesting embodiment of the method according to the invention, it is possible to make a coating of silicone material adhere (at least temporarily) to the fifth layer 50 by heating (obviously on the opposite side with respect to the fourth layer 40).

This treatment allows to eliminate any irregularities of the fifth layer 50, rendering it substantially smooth: thus (taking care to remove the coating) the product 1 can be made to adhere by suction effect to backings of various kinds (walls of pieces of furniture, glass panes and windows, car windscreens, etc.) in a stable but (easily) removable manner and without leaving adhesive residues of any kind on said backings.

Thus, the product 1 can be applied and removed from different backings even a few days later, offering a further appealing method of use to users.

One or more of the mentioned steps b., c, d., and e. of application can be performed by means of a method chosen among spreading, doctoring, laying, facing (indeed performed by the corresponding station of the apparatus), and the like.

Furthermore, one or more of the mentioned steps b., c, d., and e. of application provide for dispensing the corresponding layer 20, 30, 40, 50 on the layer 10, 20, 30, 40 that lies below the (at least partially) liquid layer, and subjecting it to subsequent drying.

Conveniently, the first layer 10 can be subjected to at least one additional treatment, chosen from a thermal stabilization treatment (which provides dimensional stability), a treatment to provide hydrophilicity (to the first layer 10), a treatment to increase mechanical strength (of said first layer 10 and therefore also of the final product 1), and the like.

This additional treatment can be performed at any moment of the method as a function of the specific requirements, without thereby abandoning the protective scope claimed herein, and preferably is performed upstream of step a., since polyester films wound on spools, already treated with TCA (as already shown) and already subjected to the desired additional treatment/treatments) are intended to be provided.

Usefully, a variation of the method according to the invention of considerable practical interest provides, in a step f. which precedes step b., for printing at least one image on the first face, treated with TCA, of the first layer 10. In this manner, following the application of the second layer 20 (and of the subsequent ones), the image (which is visible from outside through the first layer 10) remains protected against atmospheric agents and in general against any deteriorating effect, remaining in any case visible.

Step f. can be performed in various manners, which are in any case within the protective scope claimed herein, and for example by sublimation.

In an embodiment of considerable practical interest, the method provides, in a step g., for applying on the fourth layer 40 a sixth layer 60 (obviously on the opposite side with respect to the third layer 30) which comprises clear polyvinyl chloride and a photoluminescent additive (for example therefore of the type of the third layer 30).

Furthermore, this embodiment provides, in a step h., for applying on the sixth layer 60 (obviously on the opposite side with respect to the fourth layer 40) a seventh layer 70 which comprises a clear bonding agent (for example therefore of the type of the second layer 20).

Then, said embodiment provides, in a step i., for applying on the seventh layer 70 (obviously on the opposite side with respect to the sixth layer 60) an eighth layer 80 which comprises, at at least one first face treated with trichloroacetic acid, clear polyester (for example therefore of the type of the first layer 10).

Indeed this last embodiment option is shown schematically in Figure 3.

In practice, it should be noted that the photoluminescent product 1 that can be obtained according to what has been described above (and therefore comprising at least the first layer 10, the second layer 20, the third layer 30, the fourth layer 40, the sixth layer 60, the seventh layer 70 and the eighth layer 80) has a fourth layer 40 which is interposed between two sequences of superimposed laminar elements which are in practice mirror- symmetrical (if one refers to the respective materials that compose them).

Such a product 1 is favorably capable of ensuring photoluminescent effects at each of the two outermost surfaces, effects generated by the third layer 30 and by the sixth layer 60 (both of which contain a photoluminescent additive, of the same type or even different) and enhanced by the white coloring agent (be it titanium oxide or others) contained in the (intermediate) fourth layer 40.

Although embodiments are provided in which only a first face of the first layer 10 is treated with TCA, usefully at least the first layer 10 (and optionally also the eight layer 80) is treated with TCA at the first face and at the second face, and this allows to provide products 1 in which, on the opposite side with respect to the second layer 20, it is possible to make other backings or laminar elements adhere to the product 1 (to the first layer 10).

It is stated once again that the treatment with TCA on both faces can also be provided (for the same reasons) also for the eighth layer 80 (which in terms of composition and purpose is substantially identical to the first layer 10), where provided.

Advantageously, the method can provide for applying one or more auxiliary external layers which comprise polyester and are treated, at at least one first face, with trichloroacetic acid, in order to increase the strength (and also the resistance) of the photoluminescent product 1 and/or to allow coupling (by virtue of the properties of TCA), with additional laminar elements, be they laminated, pressed, or others.

It is useful to specify that the outer layers can be applied to one or both of the outermost surfaces of the product 1 (in any one of the possible embodiments), as a function of the specific requirements.

It should be noted that the sixth layer 60, the seventh layer 70, the eighth layer 80 and the additional outer layers also can be applied by spreading, doctoring, laying, facing, and the like, and optionally with a preliminary dispensing in the liquid state and subsequent drying.

It is not excluded, in any case, to resort for any one of the steps of the process to additional methods (and to the respective apparatuses), such as for example rolling, calendering, planar pressing (static or rotary and continuous).

Usefully, and with reference to any one of the numerous variations introduced so far (as well as to any other one in any case comprised within the protective scope outlined so far), the method according to the invention also provides for applying at least one external covering made of glass.

This choice allows to give greater elegance and pleasantness to the product 1 , allowing the public offering of constructive solutions of higher prestige (as well as of higher strength, indeed provided by the glass).

The external glass covering can be provided in any manner, according to the specific requirements, for any one of the possible embodiments of the product 1. In the embodiment shown in Figure 4 merely by way of non- limiting example, the covering comprises a film 90 of polyvinyl butyral (PVB) and/or ethylene vinyl acetate (EVA), on which a glass lamina 100 is applied externally.

It should be noted that optimum adhesion of the subsequent covering, and in particular of the film 90, is ensured when the latter is deposited on the first layer 10 or on the eighth layer 80 (with treatment with TCA on both faces) or on an auxiliary layer (with treatment with TCA on both faces).

Figure 4 indeed shows a possible embodiment of what has just been described, in which the external covering is applied to the product 1 of the "mirror symmetrical" type, described in the preceding pages and shown in Figure 3. In this case, the first layer 10 and the eighth layer 80 both comprise polyester treated with TCA on both faces.

In a further embodiment which is revealed to be of high practical interest, and which utilizes the possibility to adopt external layers comprising polyester, the method according to the invention provides, in a post-processing step j., for performing on the outer layer printing (which is covering or not, in order to obtain various light effects). The printing (which can be of the digital type or not) is provided by means of a method chosen among inkjet, thermal sublimation and the like.

Thermal sublimation in particular, which is indeed rendered possible by the external layer made of polyester, leads to an element of assured practical interest, since it allows customizations even during retail sale, which are chosen freely by the individual buyer directly at the time of purchase.

Furthermore, an additional favorable factor of thermal sublimation printing is certainly identifiable in the fact that it is does not interfere with optimum diffusion of light, which can pass freely through the images provided with this method.

As anticipated, the present description also relates to a photoluminescent product 1.

More particularly, the photoluminescent product 1 according to the invention comprises at least one first layer 10, which in turn comprises clear polyester treated, at at least one first face, with TCA. Furthermore, the product 1 comprises a second layer 20, which is applied to the first face of the first layer 10 and comprises a clear bonding agent (for example polyur ethane). A third layer 30 is then applied on the second layer 20 and comprises clear polyvinyl chloride and a photoluminescent additive. Finally, the product 1 according to the invention comprises a fourth layer 40, which is applied to the third layer 30 and comprises polyvinyl chloride and a white coloring agent (for example titanium oxide, although other options are not excluded, as shown).

The product 1 according to the invention can therefore first of all be obtained by means of the method according to the invention, and thus comprises all the particularities and the further specifications described in the preceding pages in relation to the numerous constructive variations that have been proposed or in any case can be deduced from the present description.

Moreover, it is appropriate to specify that the protection claimed herein is to be understood as extended to any photoluminescent product which comprises at least the first layer 10, the second layer 20, the third layer 30 and the fourth layer 40 (optionally with the further specifications described in the preceding pages), independently of the specific methods of embodiment.

The execution of the method according to the invention is therefore evident from what has been described so far, and the structure of the photoluminescent product 1, whether or not provided by means of the method according to the invention, is also evident.

As already anticipated, the product 1 can have a valid application in all contexts in which photoluminescence effects (with considerably improved performance with respect to known solutions) turn out to be of interest. Merely by way of example, mention is made therefore of the possibility that the product 1 is adopted in the field of furniture, building, safety, energy saving, consumption reduction, environmental protection, clothing, gadgets, objects, accessories, design of furnishing or personal accessories, shoes, coverings for floors, electrical household appliances, decorations, emergency management, and in the funeral, public, care, hospital, accident prevention, naval, aeronautical, aerospace sectors and others.

An application of assured practical interest, mentioned merely by way of nonlimiting example, provide for manufacturing with the product 1 panels to be hung on the walls of homes (or other buildings). In this manner, the panels can ensure brightness even in the absence of other light sources and without any energy consumption. Thus, the panel allows for example the people who are present to move at night, without having to turn on the lights and therefore without having to disturb the sleep of other people, in a practical manner (and with an evident energy saving).

Whatever the field of application, it is therefore useful to state once again that the method and the product 1 according to the invention achieve the intended aim since the large quantity of photoluminescent additive that can be mixed with the PVC in the third layer 30 ensures a photoluminescent effective of considerable intensity and long duration, and this effect is enhanced maximally by resorting (in the fourth layer 40) to a white coloring agent (be it titanium oxide or others).

Moreover, these results are obtained with a solution that is simple, economical and easy to industrialize. The invention therefore allows to obtain photoluminescent products 1 that are effective and capable of ensuring high performance.

Furthermore, the considerable thickness and the numerous variations described give additional properties to the product 1, which is therefore capable of overcoming the many drawbacks that can be observed in known solutions (poor intensity and poor duration of the luminous effect, poor strength, poor outdoor resistance and/or resistance to atmospheric agents, early yellowing, early opacification, poor chemical-mechanical resistance, poor thermal resistance, poor dimensional stability, poor transparency, poor compatibility with other materials, inability to support sublimation treatments, etc.).

It should be noted that the invention emits bright light for a long time at zero cost (since it simply returns effectively the light stored previously): this is of even greater practical interest, in view of the increasing attention to clean and renewable energy sources.

The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims; all the details may further be replaced with other technically equivalent elements. It is also useful to specify that the first layer 10 can constitute a valid backing (as a replacement of paper or other materials of a known type) also in relation to non-photoluminescent products, ensuring in any case a performance that is higher than known ones.

The great thickness of the first layer 10, and the mechanical strength provided by the polyester, on which it is possible to make other laminar elements adhere by virtue of the treatment with TCA (optionally with the second layer 20), in fact can be appreciated in various additional fields of application, indeed even without a third layer 30 provided with a photoluminescent additive and/or other photoluminescent materials.

Moreover, the possibility of printing by thermal submission described in the preceding pages is a particular innovation of assured appeal on the public, even in the absence of photoluminescent effects.

In the examples of embodiment shown, individual characteristics, given in relation to specific examples, may actually be interchanged with other different characteristics that exist in other examples of embodiment.

In practice, the materials used, as well as the dimensions, may be any according to the requirements and the state of the art.

The disclosures in Italian Patent Application no. 102016000094050 (UA2016A006657), from which this application claims priority, are incorporated herein by reference.

Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.