WO2013054367A1

WO2013054367A1 - Electrochromic device

Info

Publication number: WO2013054367A1
Application number: PCT/IT2012/000309
Authority: WO
Inventors: Marco CASTRIOTA; Enzo CAZZANELLI; Giuseppe De Santo; Massimo LA DEDA; Roberto TERMINE
Original assignee: Università Della Calabria
Priority date: 2011-10-10
Filing date: 2012-10-08
Publication date: 2013-04-18
Also published as: WO2013054367A4; ITRM20110536A1

Abstract

This invention relates to an electrochromic device comprising a plurality of layers that comprise a rear (12a; 22a) transparent substrate adjacent to a rear layer (13a; 23a) of a transparent electronic conductor adjacent to and electrochromic set of one or more electrochromic layers (14, 15, 16; 24) adjacent to a front layer (13; 23) of a transparent electronic conductor adjacent to a front transparent substrate (12; 22), said electrochromic set being capable of developing an electrochromic process through which at least a portion of said electrochromic set commutes between a transparent state and a coloured state, said device being characterized in that it comprises also one or more thin batteries (17; 25) interposed between two layers of said plurality of layers, and thin layer electronic means (18, 19; 26, 27) for switching control, said electronic means comprising one or more electronic components each one of the same being interposed between two layers of said plurality of layers, said thin layer control means (18, 19; 26, 27) being electrically connected to said one or more thin batteries (17; 25) as well as to the rear (13a; 23a) and front (13; 23) transparent electronic conductors so that said control means are capable of controlling an electrical connection between said one or more thin batteries (17; 25) and the rear (13a; 23a) and front (13; 23) transparent electronic conductors to enable and/or disable said electrochromic process.

Description

ELECTROCHROMIC DEVICE

This invention relates to an electrochromic device that allows wide surfaces like building windows to be covered for applications of energy saving. Moreover, the electrochromic device according to this invention can be employed as an additional and non-structural element in many industrial applications, like vehicle internal rear-view mirrors, upper parts of vehicle windshields, vehicle sunshade roofs, vehicle windows (cars, buses, trains, ships, aircraft, etc.), privacy applications, decorative applications, traffic signalling devices, optical memories, and monitors or displays.

In the latest twenty years, the electrochromic device technology has been in continuous development, as the remarkable numbers of patent applications filed concerning them confirms. An electrochromic device can be classified according to various typologies on the basis of the materials employed for manufacturing the same. In particular, there are at least three types of configurations of electrochromic devices: a first type, that in the following will be pointed out as the 'type 1', in which the electrochromic materials are always in solution; a second type, that in the following will be pointed out also as the 'type 2', in which the electrochromic materials are initially in solution and colourless and, as a result of an electronic transfer reaction, they form a solid membrane or film on the surface of an electrode; and a third type, that in the following will be pointed out also as the 'type 3', in which the electrochromic materials are deposited on the electrodes in the form of thin films.

The two first types are the so-called 'self-erasing' electrochromic devices (i.e. devices featuring self-erasure), because the electrochromic species are dissolved in a liquid electrolyte or in the form of a gel, so that they can easily diffuse; they do not feature any open circuit memory, i.e. any optical memory. Electrochromic materials are placed between two glass (or plastic) supports which are covered with a transparent electronic conductor, as for instance Indium-Tin-Oxide which is also known as the ITO (indium tin oxide). In the case of type 3 devices, a substrate is covered with the active electrochromic materiaL(the working electrode), whereas a material that works as an ion reservoir is deposited on the other substrate (the counter-electrode), that can even be a complementary electrochromic material. Said working electrode and the counter-electrode are separated by an ionic conductor (a layer) that can be: a liquid, a polymer or a gel layer (i.e. a polymer with a fraction of a solvent and a salt). The technological properties of an electrochromic device depend both by the electrochromic materials and by the type of ionic conductor. The configuration of type 3 can be employed for obtaining electrochromic devices with open circuit extended memories (optical memories).

The electrochemistry that is involved in electrochromic processes is substantially a reversible redox reaction in which two species red_1 and ox_2 initially in the transparent state, after the application of a suitable voltage to the electrodes, become ox_1 and red_2, so going to the coloured state; in the case of devices featuring a type 1 and 2 configuration, the inverse reaction occurs spontaneously after removal of the applied voltage ('self-erasing' configuration). In the case of type 3 devices, an inverse voltage is to be applied in order to make the inversed sense reaction from the coloured state into the colourless state to occur.

The electrochromic materials are classified as anodic or cathodic according to their passage from the colourless state into the coloured state during the oxidation or during the reduction respectively. In particular, the electrochromic devices are made up of a sandwich-type structure in which the electrochromic species are placed between two transparent electrodes connected to the voltage supply. Figure 1 shows a schematic exploded view of a typical electrochromic device of type 3, that includes two outside transparent substrate 1 , which are adjacent to two respective layers 2 of a transparent electronic conductor, an active electrochromic layer 3 (the working electrode) which is adjacent to the rear layer 2 of a transparent electronic conductor, an ionic conductor 4 which is adjacent to the active electrochromic layer 3, and a layer 5 that makes up the ionic reservoir (the counter-electrode), which is interposed between the ionic conductor 4 and the front layer 2 of a transparent electronic conductor; the device of Figure 1 also includes a voltage supply 6. The layers of the device shown in Figure 1 are coupled to one another. The transparent substrates 1 can consist of glass plates that are covered with a transparent thin film of electronic conductors 2, as for instance is described in the U.S. Patent 6,587,250 B2: ITO, thin oxide or fluorine and tin. As is described in the US Patent No. 4,194,812, the active electrochromic layer 3 (the working electrode) and the layer 5 featuring a ionic reservoir properties (the counter-electrode) are preferably obtained from heavy metal oxides, as for instance the tungsten trioxide WO3, which is a cathodic electrochromic material employed as the working electrode 3, and the vanadium pentoxide V2O5, an anodic electrochromic material employed as the counter-electrode 5. The ionic conductor layer 4 can be realized in various ways; as is described in the US Application 2009/0078917 A1 , it can be made of polymer electrolytes as for instance polyethylene oxide containing lithium salts (e.g. lithium triflate). As is described in the journals J. Chem. Phys. (2002), 117, 7373, J. Phys. Chem. A (2005), 109, 92, Ionics (2005), 11 , 220 and Solid State Ionics (2006), 177, 581 , in order to improve the compression and bending stress resistance as well as the conductivity of polymer electrolytes (and hence the performance of the electrochromic device), various possibilities have been investigated, as for instance: mixtures of polymer electrolytes with thermoplastic or elastomeric polymers, the nano-confinement of electrolytic polymers, the addition of ionic liquids to polymer electrolytes, as for instance (N-methyl-N-propylpirrolidinium, bis(trifluoromethansulfonyl) imide.

In the latest year, electrochromic devices like that shown in Figure 1 have been realized employing conductor and electroactive organic polymers as the working electrodes. As is described in the US Application 2003/0174377 A1 , the employment of conductor organic polymers allows electrochromic devices to be manufactured featuring a 'coloured' state that can be selected non only within the range of visible light, but also within the range of microwaves and the infrared light (US 0174377 A1), so remarkably increasing the number and the segments of the industrial applications as relative.

Figure 2 shows an exploded schematic view of a type 1 electrochromic device, that comprises a lower number of layers than the type 3 device (shown in Figure 1), and precisely five layers: two external transparent substrates 7, which are adjacent to two respective layers 8 of a transparent electronic conductor, between which a solvent or a transparent polymer 9 is interposed in which the materials necessary to the redox reaction are dispersed; said device also comprising a voltage generator 10. The electrochromic process involves at least a single electrochromic species, that goes from the transparent into the coloured state as a result of a reduction or oxidation reaction that occurs with the help of another material which is capable of donating or accepting, respectively, in a reversible way the electrons involved in the electrochromic redox process. In particular, the viologens (salts of 1 ,1'- disubstituted-4,4'-bipiridinium) are the most used cathodic materials for type electrochromic devices. Said viologens have the following redox states which are illustrated in the following scheme: a dicationic form (shown in the upper portion); a cationic radical (shown at the middle); and a neuter reduced form (shown in the lower part.

If the dicationic form of viologens is the pure one, it is the most stable and colourless (unless charge transfers occur that involve the counter-anion). Various anions can be coupled to the dicationic form of viologens, as for instance those described in the US Patent No. 6,045,724: tetrafluoborate (BF₄ ^"), perchlorate (CIO4^"), trifluoromethan sulfonate (CF3SO3 ) and hexafluophosphate (PF₆ ^"), the last one among those mentioned seems to be the anion that best improves the viologens solubility.

The dicationic form of viologens can acquire one only electron for becoming a cationic radical: cationic radical viologens are intensely coloured, with a high molar absorption coefficient. The stability of the cationic radicals is due to the derealization of the unpaired electrons of the aromatic rings of pyridine. The addition one more electron to the cationic radical form of viologens causes the formation of the neutral reduced form, that generally shows various colours as a function of the nature of the R groups linked to the bipyridinium structure. The intense colour of the cationic radical with respect to its neutral form is the result of an intramolecular charge transfer in the radical form. Viologens having different R, R' groups show neutral forms of different colours that are present in any part of the visible region of the electromagnetic spectrum. For example, as is described by M. Castriota in his PhD Thesis 'Development and Spectroscopic Characterization of Materials for Applications in Electrochromic Devices and Novel Liquid Crystalline Cells' 2004, University of Calabria, Italy, if the groups R, R' are simple alkyl chains with low number of carbon atoms, the colour of the neutral form of viologens is blue/violet, whereas if the groups R, R' comprise aryl rings, as for instance 4-cyanophenyl's then the colour of the neutral form is green and so on.

The electrons necessary to the reduction of the dicationic form of viologens, first to the radical cationic form and then to the neutral form are supplied by another material that is to be present in the reaction environment. In particular, as viologens are cathodic materials (they go from the transparent to the coloured state during the reduction semi- reaction), within the reaction environment anodic materials are to be present in order to balance the whole electrochromic redox reaction. The anodic material coupled with viologens can be in its turn electrochromic or not: if during the oxidation semi-reaction such material changes from the transparent to the coloured state, it is an electrochromic material, if on the contrary it changes from the transparent state into another transparent state it is not an electrochromic material. However, if the anodic material is an electrochromic material, then it should be chosen by taking into account that its oxidized form shows a colour different from the colour of the reduced form of the cathodic material, otherwise the electrochromic device would not show any change in colour during the electrochromic process. In Table 1 the most employed anodic materials are listedjhatare to be coupled with the viologens (cathodic materials) in order to realize the type 1 electrochromic devices.

Regardless of the configuration type (i.e. type 1 , type 2 or type 3), the electrochromic devices can be employed in various industrial applications, as for instance: smart windows, rear-view mirrors, sunshade roofs, thermal exposure indicators (for frozen food), glasses, sunglasses, and, in order to increase the power efficiency of vehicles, aircraft, ships or space vehicles, for the thermal control of orbiting satellites, for display, in the development of electrochromic writing paper, in which an electrochromic image is generated on the sheet as result of its contact with a pen-shaped electrode.

Electrochromic windows can be useful for the control of heat and light flow from the inside to outside of buildings, and vice versa by means of the modulation of the transmission properties of the electrochromic materials employed for realizing the windows themselves. As is described by C. M. Lampert IN 'Smart Windows for Energy Efficiency', New Glass Forum, Tokyo. October 16 (1995) and by the same C. M. Lampert in 'Solar Energy Materials & Solar Cells' (1998), 52, 207, the employment of electrochromic glasses can improve the total thermal yield of buildings with respect to the static thermal control which is employed at the present time. The power saving coming from the employment of electrochromic windows reaches up to 30 % of the power actually consumed because their employment during the summer months allows the heating due to the sun irradiation to be reduced and, consequently, the use of conditioning apparatus to be reduced, whereas during the winter months their employment allows the heat flow from the inside to the outside of the buildings to be reduced and consequently the use of the heating systems to be reduced.

However, in spite of the important and widespread activity carried out by many teams of researchers in public or private laboratories all over the world and the potential earnings stemming from the very numerous industrial applications, the products based on the electrochromic technology are diffusely employed just as rear-view mirrors in some luxury cars. As an example, electrochromic windows did not enjoy a widespread commercial employment, in particular as an effect of the high costs and of the short warranted duration with respect to the standards concerning structural members of buildings. Indeed, electrochromic windows are costly because both the material costs and the complex manufacturing processes make the industrial production of a large number of pieces expensive, and their duration is quite short with respect to the traditional windows. In particular, electrochromic windows cannot be warranted for twenty years, as is required for the structural products in the building industry: at the present time, electrochromic technology knowledge does not allow a so long duration to be warranted for electrochromic.

Moreover, a further trouble is due to the complexity of obtaining the so-called scaling-up of electrochromic technology, i.e. the difficulty of building electrochromic devices featuring large surfaces. Indeed, it is quite simple to realize an electrochromic device of limited sizes, for instance 10 cm x 10 cm, because transparent electronic conductors (for instance ITO) supply a homogeneous voltage on the surface up to the maximum distance of 5 cm which is the distance between the centre and the edge of the electrode where the electrical cables connected to the voltage generator are welded; however, when the sizes of the electrochromic device increase, the distance between the centre and the edge of the electrode (where the cable connections are present) also increases, and the transparent electronic conductors become increasingly less capable of supplying a homogeneous surface voltage, because of the voltage drop which is proper for the conductor.

Moreover, the commercial diffusion of electrochromic windows is much conditioned by the need for modifying the new and the old buildings so as to have the possibility of assembling electrochromic windows. Indeed, as the voltage necessary for the operation of electrochromic windows is supplied by the home electric network, it is necessary to equip all windows with 'sockets' by passing the electrical cables inside the walls of the building. This last pre-requisite needed for buildings, or the need for infrastructural changes in the building, cause the costs for the first assembly of the electrochromic windows to grow, and as a consequence discourages the consumers and thus stops the spread of electrochromic windows technology.

Accordingly, it is the object of this invention to supply the possibility in a reliable, versatile, efficient and economic way of solving the problems mentioned above concerning the conventional electrochromic devices, by reducing their costs and by increasing their lifetimes so as to allow the use of such windows in a large number of industrial applications.

It is a further object of this invention the possibility of realizing the scaling-up of electrochromic technology.

It is a further object of this invention that of making the application of the electrochromic devices easier also in the case of already existing structures, as for instance windows of buildings that already exist.

It is a further specific object of this invention an electrochromic device comprising a plurality of layers, said layers including a rear transparent substrate which is adjacent to a rear layer made up of a transparent electronic conductor which is adjacent to an electrochromic set consisting of one or more electrochromic layers, said electrochromic set being adjacent to a front layer of a transparent electronic conductor which is adjacent to a front transparent substrate, said electrochromic set being capable to develop an electrochromic process so that at least a portion of said electrochromic set commutes between a transparent and a coloured state, said device being characterized in that it comprises also one or more thin batteries which are interposed between two layers of said plurality of layers, and thin layer electronic means for commutation control that comprise one or more electronic components, each one of them being interposed between two layers of said plurality of layers, said thin layer control means being electrically connected to said one or more thin batteries and to rear and front transparent electronic conductors in such a way as to be able to control an electrical connection between said one or more thin batteries and the rear and front transparent electronic conductors in order to enable and/or disable said electrochromic process.

Again according to this invention, said thin layer control means can include commutation means, preferably comprising at least a switch and/or a multiplexer.

Again according to this invention, said thin layer control means can include receiving antenna means fit for receiving control signals from at least a remote control switch, on whose basis said thin layer control means control the electrical connection between said one or more thin batteries and the rear and front transparent electronic conductors.

Further according to this invention, said thin layer control means can comprise at least a brightness sensor, preferably a photodiode, which is suitable to detect a brightness on whose basis said thin layer control means control the electrical connection between said one or more thin batteries and the rear and front transparent electronic conductors.

Again according to this invention, said one or more electronic components of said thin layer electronic means for commutation control can be embedded in chips.

Again according to this invention, said one or more thin batteries and said one or more electronic components of said thin layer electronic means can all be interposed between the two same layers of said plurality of layers. Further according to this invention, at least a portion of at least one of the rear layer of transparent electronic conductor and the front layer of transparent electronic conductor can be shaped according to a two-dimensional matrix comprising a plurality of pixels, said pixels being connected to said thin layer control means through a plurality of sub- micrometer tracks, said thin layer control means performing the control of the electrical connections between said one or more thin batteries and the rear and front transparent electronic conductors so as to cause at least a portion of the electrochromic device to work as a display.

Again according to this invention, at least a portion of at least one of the rear layer of transparent electronic conductor and the front layer of the transparent electronic conductor can be shaped according at least a shape, said at least one shape being connected to said thin layer control means through one or more sub-micrometer tracks.

Again according to this invention, the electrochromic device can include also planar fastening means adjacent to the rear transparent substrate, said planar fastening means including or consisting preferably of a transparent adhesive layer, said planar fastening means being a part of said plurality of layers, so that the electrochromic device can be coupled through said planar fastening means to a structure selected from the group comprising a glass and a mirror.

Further according to this invention, the electrochromic device can also include a housing frame of an outside structure, preferably comprising a reflecting surface, and more preferably a rear-view mirror, so that the electrochromic device can be assembled on said outside structure. Again according to this invention, said electrochromic group can include three electrochromic layers which are adjacent to each other in the following order:

- an active electrochromic layer with the function of the working electrode;

- an ionic conductor layer, and

- an ionic reservoir layer working as the counter-lectrode.

Again according to this invention, at least a portion of at least one of three such electrochromic layers of said electrochromic group can be shaped as a two-dimensional matrix comprising a plurality of pixels and/or according to at least a shape.

Further according to this invention, said electrochromic group can comprise or consist of an electrochromic layer that contains electrochromic materials dissolved in a solvent or in a polymeric matrix.

The advantages offered by the electrochromic device according to this invention area numerous.

Such device is an adhesive, flexible, energetically self- sufficient device which possibly can be controlled by means of the wireless technology, said device being suitable for all industrial applications that are mentioned above, even as an additional and non structural electrochromic member. Indeed, the electrochromic device according to this invention can be applied (for instance glued) to already existing windowpanes in buildings, and it allows large surfaces to be covered so overcoming the scaling-up problem which is inherent to electrochromic technology.

Moreover, a plurality of electrochromic devices according to this invention, synchronized and simultaneously controlled can be employed for covering large windows, so transforming the traditional windows into electrochromic windows, with energy and money savings with no one of the problems concerning the employment of conventional electrochromic windows. In case of the need for changing one or more of the devices according to this invention, this operation can be performed directly by the users without any action on the structural properties of the building, that depend on the already existing windowpanes that would not be affected as to their mechanical properties by the presence or the absence of the electrochromic devices according to this invention.

Other applications of the electrochromic devices according to this invention can be for instance: internal rear-view mirrors, upper arts of windshields, sunshade roofs for vehicles, panes of windows of vehicles (cars, buses, trains, ships, aircraft and so on), for privacy, for decorative applications, road signs, warning signs, optical memories and various industrial applications in the field of displays.

Further, the electrochromic device according to this invention is light and not cumbersome.

An interesting example of application of the electrochromic device according to this invention in a field different from that of energy saving is its application as an additional, non-structural electrochromic member to rear-view mirrors. In that case, the electrochromic process is activated by the light of the main headlights of vehicles that travel behind the vehicle equipped with the rear-view mirror fitted with the electrochromic device according to this invention, and it goes back spontaneously from the coloured to the transparent state when the light is removed. In such way, the traditional rear-view mirrors can become electrochromic rear-view mirrors without modifying in any way a car and so without any costs, as it is necessary on the contrary when the traditional electrochromic technology is employed. The electrochromic process of the device according to this invention can occur automatically, for instance as an answer to a dazzling action, or it can be controlled by a user.

This invention will be now described, just for illustration and not limitative purposes, according to its preferred forms of embodiment, with particular reference to the figures shown in the enclosed drawings, in which:

Figure 1 shows schematically an exploded perspective view of a first electrochromic device according to the prior art.

Figure 2 shows schematically an exploded perspective view of a second electrochromic device according to the prior art;

Figure 3 shows schematically an exploded perspective view (Figure 3A), a rear perspective view (Figure 3B) and front perspective view (Figure 3C) of a first form of embodiment of the electrochromic device according to this invention;

Figure 4 shows schematically an exploded perspective view (Figure 4A), a rear perspective view (Figure 4B) and front perspective view (Figure 4C) of a second form of embodiment of the electrochromic device according to this invention;

Figure 5 shows schematically a front view of some of the disassembled members (Figure 5A) and of an assembled device as relative (Figure 5B) for a first application as an example of the electrochromic device according to this invention;

Figure 6 shows schematically a front view of some of the disassembled members (Figure 6A) and of an assembled device as relative (Figure 6B) for a second application as an example of the electrochromic device according to this invention; Figure 7 shows schematically a front view of some of the disassembled members (Figure 7A) and of an assembled device as relative (Figure 7B) for a third application as an example of the electrochromic device according to this invention;

Figure 8 shows schematically a front view of two alternative versions of a fourth application as an example of the electrochromic device according to this invention (Figure 8A), a front view of two such alternative versions when the electrochromic process is disabled (Figure 8B) and a front view of two such alternative versions when the electrochromic process is enabled (Figure 8C);

Figure 9 shows schematically a front view of two alternative versions of a fifth application as an example of the electrochromic device according to this invention (Figure 9A), a front view of two such alternative versions when the electrochromic process is disabled (Figure 9B) and a front view of two such alternative versions when the electrochromic process is enabled (Figure 9C);

Figure 10 shows schematically a front view of two alternative versions of a sixth application as an example of the electrochromic device according to this invention (Figure 10A), a front view of two such alternative versions when the electrochromic process is disabled (Figure 10B) and a front view of two such alternative versions when the electrochromic process is enabled (Figure 10C); and

Figure 11 shows schematically a front view of a rear-view mirror, and of a third form of embodiment of the electrochromic device according to this invention which can be applied to said rear-view mirror (Figure 11A), a perspective view, with some hidden elements made visible, of the third form of embodiment of the electrochromic device according to this invention, and a front view of the rear-view mirror to which the third form of embodiment of the electrochromic device according to this invention is applied when the electrochromic process is disabled and when the electrochromic is enabled (Figure 11 C).

In the figures, equal reference numbers will be employed for analogous members.

The electrochromic device according to this invention can be realized in anyone of the three configurations of electrochromic device mentioned above (i.e. type 1 , type 2 and type 3).

Figure 3 shows a first form of embodiment of the electrochromic device according to this invention, realized according to the type 3 sandwich configuration, which has a substantially asymmetric structure. The face of the rear transparent substrate 12a which is exposed to the outside is covered and coupled with a transparent adhesive layer 11 , so that the electrochromic device according to this invention can be attached to a glass sheet, for instance to a window's pane. The other face of said rear substrate 12a is coupled to the transparent electronic conductor 13a which is coupled in its turn to the active electrochromic layer 14 (i.e. the working electrode). The latter is coupled to the ionic conductor 15 which in its turn is coupled to the layer 16 that works as an ionic reservoir (the counter-electrode), the same being spread on the front layer 3 of the transparent electronic conductor realized through the front transparent substrate 12.

The device of Figure 3 comprises one or more thin accumulators/batteries 17, whose number depends on the electrochromic materials employed for preparing the device as well as on its final application. Said accumulators 17 supply the power necessary for allowing the electrochromic device according to this invention to work, that is in order to make it possible the electrochemical reaction (i.e. the electrochromic process) to occur, said reaction allowing the change from the transparent into the coloured state in a reversible way. The accumulators 17 are connected to the electrodes 12a and 13 by means of a switch 18 that switches on (or switches off) the electrochromic process. The switch 18 is connected to a thin layer antenna 19 which can receive the signals transmitted by a remote control device 20 which is acted upon by a user, and said signals control the switch 18 so switching on or switching off the electrochromic device according to this invention from a far point. Preferably, the switch off and said antenna 19 are embedded in a electronic chip, which possibly is supplied with processing and control units (as well as with a memory unit) for the management of the operation of said device, and in particular of the switch 18 and the antenna 19. In the form of embodiment which is shown in Figure 3, the electronic components, i.e. the accumulators 17, the switch 18 and the antenna 19 are interposed between the counter-electrode 16 and the front transparent electronic conductor 13; however, it is to be taken into account that such electronic components can be positioned between any two layers of those shown in Figure 3, and each one can also be positioned between two layers that differ from those between which the other ones are positioned, so again allowing the electrochromic device according to this invention to work.

Other forms of embodiment of the electrochromic device according to this invention can be realized according to the type 1 configuration, in which configuration a lower number of layers is needed and the electrochromic materials involved in the electrochromic redox reaction are dissolved in a solvent or in a transparent polymeric matrix. Figure 4 shows a second form of embodiment of the electrochromic device according to this invention which is realized according to a type 1 configuration, that also features an asymmetric structure. The device of Figure 4 comprises a rear transparent substrate 22a, whose face which is exposed to the outside is covered and coupled with a transparent adhesive layer 21 , whereas the other face is coupled to a rear layer 23a of a transparent electronic conductor. The front transparent substrate 22 is coupled to a front layer 23a of a transparent electronic conductor which is adjacent to the electrochromic layer 24 that contains the electrochromic materials dissolved in a solvent or in a polymeric matrix; preferably, the electrochromic layer 24 is realized by means of a transparent polymeric matrix that allows the development of the electrochemical reaction (the electrochromic process). Also the device shown in Figure 4 comprises one or more thin accumulators/batteries 25, whose number depends on the electrochromic materials employed and on the final application, said accumulators/batteries being connected to the electrodes 22a and 23 by means of a switch 26, that switches on (or switches off) the electrochromic process, and is in its turn connected to a thin layer antenna 27 capable of receiving the signals transmitted by a remote control device 28 which can control the electrochromic process from a far place. Again also in this case, said switch 18 and antenna 19 are embedded in an electronic chip, which is possibly provided with processing and memory units for the management of the operation of said device. In the form of embodiment shown in Figure 4, the electronic components, i.e. the accumulators 25, the switch 26 and the antenna 27 are interposed between the electrochromic layer 24 and the front transparent electronic conductor 23; however it is to be taken into account that such electronic components can be placed between any two layers of those shown in Figure 4, and each one can also be placed between two layers that differ from those between which the other ones are placed. In order to better understand this invention, some applications and the working ways as relative of the electrochromic device are described just for exemplification and not for limitative purposes.

A first example concerns the application of the electrochromic device according to this invention for covering the window's panes of buildings in order to get energy savings up to 30 %. Figure 5A shows schematically a window having a frame 29 and a pane 30, and an electrochromic device 31 according to this invention (that can indifferently be that of Figure 3 or that of Figure 4), said device being shown frontally, with a rectangular shape. The device 31 , that can be applied for covering the panes 30 of the window, comprises one or more thin accumulators/batteries 32, the switch 33 and the thin layer antenna 34. Moreover, Figure 5A shows the remote control device 35. Figure 5B shows schematically four electrochromic devices 31 employed for covering the left half of the pane 30, so that the electronic components are arranged in correspondence with the frame 29. In that way, the problem of sizes which is typical for the electrochromic technology, is overcome by means of the employment of a plurality of electrochromic devices 31 in a number which is sufficient to cover the panes 30 of the window, in a way independent of its size. In particular, the electrochromic devices 31 are attached to the pane 30 of the window by means of the transparent adhesive layer (11 or 21) which is present on the face of the rear transparent substrate (12a or 22a) of the electrochromic device 31 which is exposed to the outside. The application of the electrochromic device according to this invention to the pane 30 of the window can be carried out by the user without any need for involvement of skilled personnel.

The various electrochromic devices 31 of the plurality which is employed for covering a same pane 30 are synchronised and controlled through the same remote control device 35. In that way, when the user switches on by means of said remote control device 35 the electrochromic devices 31 , all such devices 31 simultaneously change their states from the transparent to the coloured state, so working just as one single electrochromic device. Synchronisation occurs preferably the first time that the electrochromic device according to this invention are switched on when the respective chips (that embed switches and antennas) at about the same distance from the remote control device 35 store in the memory unit the same first signal transmitted by the same remote control device. In that way, the electrochromic devices according to this invention, applied to the same pane 30, are controlled just through the proper remote control device 35.

In the case in which the electrochromic devices according to this invention are those of type 3 of Figure 3, the pane 30 to which they are applied becomes coloured when the voltage of the accumulators is applied to the electrodes, and such pane keeps in that state even though the voltage is removed, until a voltage of opposite sign is applied, that causes the pane to go back to the transparent state; in that case, the remote control device can have a number of buttons more than the two buttons which are shown as an example in Figure 5, and the switch through which the accumulators are connected to the electrodes can consists of a switch capable of inverting the polarities of the voltage applied to the electrodes. In a different way, in case the electrochromic devices according to this invention are those of type 1 of Figure 4, the pane 30 to which they are applied becomes coloured when the accumulator voltage is applied to the electrodes, and goes back to transparent state spontaneously immediately when the voltage Js removed. Alternatively or in addition to the control carried out by means of a remote control device, the chips of the devices 31 could even embed some brightness sensors capable of detecting the outside brightness of the sun which hits the pane 30, so that a processing and control unit activates automatically the electrochromic process so causing the devices to go from the transparent into the coloured state, in case the brightness detected by the sensors is higher than a maximum threshold value.

In the application shown in Figure 5, the single electrochromic devices according to this invention can be removed without compromising or affecting the features of the window as a structural member of the building. In a similar way, as such devices are not structural members of the building, their installation does not require any previous arrangement of the building for such electrochromic devices according to this invention. Moreover, the electrochromic devices according to this invention as is described in the example of Figure 5, can be employed also in applications concerning the privacy, where it is necessary to have walls featuring a variable transparency, as for instance in the case of open-space offices and shower boxes.

As is shown in Figure 6, a second example of application of the electrochromic device according to this invention concerns its application in the upper part of windscreens of cars, of buses, of trains and other vehicles in order to prevent to sun light from dazzling drivers as well as other passengers. The first advantage consists in the possibility of the user his/herself of choosing whether the electrochromic device according to this invention is to be coloured or not (according to the particular needs: in sunny weather, in cloudy weather, by night, within tunnels etc.) in a way opposite to what occurs in the case of windscreens realized with their upper part permanently coloured. Figure 6A shows schematically a windscreen, as viewed from the inside of the vehicle, said windscreen comprising a frame 36 and a glass plate 37, and also the inner rear-view mirror comprising the frame 38 and the mirror 39. Moreover, four electrochromic devices 40-43 according to this invention are shown (that can be used indifferently like that of Figure 3 or of figure 4) each one comprising one or more thin accumulators/batteries 44, the switch 45 and the thin layer antenna 46, all embedded within the multilayer structure of the electrochromic devices according to this invention. Each one of said devices 40-43 is controlled through a single remote control device 47. With reference to Figure 6B it can be remarked that the windscreen can be equipped in its upper part with the four shaped devices 40-43 of Figure 6A. In particular, said devices 40-43 are attached to the glass sheet 37 of the windscreen by means of the respective transparent adhesive layers in such a way that the respective electronic components are in the position that matches the windscreen frame 36. In a way analogous to the application example shown in Figure 5, all the electrochromic device 40-43 applied on the windscreen are synchronized and simultaneously controlled by the same remote control device 47, so that they behave as a single electrochromic component; their working ways are similar to those illustrated with reference to Figure 5. In particular, the devices 40-43 can be switched on by means of said remote control device 47, so that they can go from the transparent to the coloured state in order to protect both the driver and the passengers from sunrays; rapidly, by disabling the voltage applied to the devices 40-43 if they are of type 1 , or by applying an opposite voltage if the devices are of type 3, and the upper part of the windscreen becomes again transparent.

Alternatively, or in addition to the control carried out by means of a remote control device, the chips of said devices 40-43 would also embody embed some sensors of brightness that are able of detecting the brightness of the sun (or the brightness of dazzling beam that hits the windscreen) so that a processing and control unit activates automatically the electrochromic process, so causing the devices to go from the transparent to the coloured state, in case the brightness detected by sensors is higher than a maximum threshold value.

As is shown in Figure 7, a third example of application of the electrochromic device according to this invention concerns its application as an element for darkening also the other window panes present on the vehicles ad for instance the panes of the rear door, the car tops and so on. Figure 7A shows a general window of a rear door of a car, with a frame 48 and a pane 49 (preferably with a position adjustable in the vertical direction), and four electrochromic devices 50-53 according to this invention of a different shape, each one equipped with one or more thins accumulators/batteries 54, the switch 55 and the thin layer antenna 56.

As is shown in Figure 7B, the whole pane 49 is covered with seven electrochromic devices according to this invention, which are attached to the pane 49 by means of their respective transparent adhesive layers: four with a rectangular shape 50, and one of each one of the other three devices 51-53. All devices covering the pane 49 can be controlled from a far position by means of the remote control device 57 in a way similar to what has been discussed for the application shown in Figure 6; also in that case, the devices can be controlled, alternatively or in addition to the remote control device 57, on the basis of the brightness detection which is performed by suitable sensors.

As shown in Figure 8, a forth example of application of the electrochromic device according to this invention relates to its application for decoration purposes. In that case, it is sufficient to draw the desired decorative image on the transparent electronic conductor which is present on (at least) one of the two transparent electronic conductors that realize the electrodes of the electrochromic device according to this invention (that can be indifferently that of Figure 3 or that of Figure 4). In the case of the forms of embodiment of the electrochromic devices according to this invention which are built according to the configuration of type 3 electrochromic devices, the same result is attained if the electrochromic layer is built by realizing the desired drawings. In Figure 8, a form of embodiment is shown in which the desired image is realized on one of the two electrodes of the electrochromic device according to this invention; in particular, different methods can be employed for removing the transparent electronic conductor in a precise way in order to draw an image on the same, as for instance a selective chemical etching and/or an electron beam lithography.

Figure 8A shows two forms of embodiment of the electrochromic device according to this invention in which the same images (a smile, a star, and a heart) are realized in two different ways on the front transparent electrode: while in the case of the front electrode 59 of the device 58A the material of the front transparent electronic conductor has been removed from the inside of the images themselves, in the case of the front electrode 59 of the device 58b the material of the front transparent electronic conductor has been removed from the outside of the images themselves. In the first case, the material of the transparent electronic conductor 59 is outside the images, whereas in the second case it is inside the images. In both cases, the material of the front transparent electronic conductor 59 is connected to the electronic components of the electrochromic device according to this invention (one or more thin accumulators/batteries 60, the switch 61 , the thin layer antenna 62) so as to allow the application of the voltage needed in order the electrochromic process to occur when the remote control device 63 is acted upon by the user for switching the device on, be it the 58A or the 58B device. In the case of the device 58B, the material of the front transparent electronic conductor 59, which has been shaped according to the decorative images, is connected to the electronic components through sub-micrometre tracks of a transparent electronic conductor material, preferably of width lower than 0,5 pm so that they are not visible to the human eye; possibly, each portion of front transparent electronic conductor 59 can be connected to the other ones and/or to the electronic components by means of a plurality of sub-micrometres tracks, in order to ensure an efficient connection.

Figure 8B shows the fact that when the electrochromic devices 58A and 58B are switched off (i.e. when the electrochromic process is inactive) they do not show any appreciable difference to the final user. On the contrary, Figure 8C shows the electrochromic devices 58A and 58B when they have been switched on by means of the remote control device 63, and in the first one of said devices the images are transparent on a coloured background, whereas in the second of the mentioned devices the images are coloured on a transparent background.

As shown in Figure 9, a fifth example of application of the electrochromic device according to this invention relates to its application as a road sign, as a temporary signal, or as a warning board. The indication is obtained by means of a image produced in a way similar to what has been illustrated as to the images of Figure 8, or by shaping (at least) one of the two electrodes of the electrochromic device according to this invention (that can be indifferently that of Figure 3 or that of Figure 4) or, in the case of electrochromic devices of type 3, by realizing the desired drawings on the electrochromic layer. As is shown in Figure 10, a sixth example of application of the electrochromic device according to this invention relates to its application as a monitor or a display. For this application, a two- dimensional matrix is to be realized on (at east) one of the two transparent electronic conductors that realize the electrodes of the electrochromic device according to this invention (that can be indifferently that of Figure 3 or that of Figure 4): a pixel corresponds to each one of the intersections. The minimum distance between two pixels corresponds to the resolution of the screen. In the case of the electrochromic device according to this invention of type 3 configuration, this can be obtained even though said matrix is realized in the electrochromic layer. Many methods can be employed for removing in a precise way the transparent conductive materials from the electrode, so as to draw a two-dimensional grid of pixels, for instance by etching and/or by mean of electron beam lithography. Figure 10 shows two forms of embodiment of the electrochromic device according this invention, respectively 70A and 70B, whose conductive transparent layers have been processed for obtaining a grid of pixels (the scale of the drawing of Figure 10 has been enlarged for a better understanding of the figures), each pixel being represented by a circle: in the device 70A, the transparent electronic conductive material 71 has been removed around the pixel (the circle); in the device 70B, the transparent electronic conductive material has been removed from the pixel inside (from the circle inside). Accordingly, pixels in the device 70A are the active electrochromic part of the display, whereas in the case of the device 70B the electrochromic reaction occurs within the areas around the pixels (the circles). In that way, in order to switch on a pixel in the device 70 ^ i^is jiecessary to supply a voltage just jto the_ pixel area, whereas in the device 70B it is necessary to supply a voltage simultaneously to the four areas around the pixel.

In both cases, the transparent conductive material is connected to the electronic components (the batteries 72, the switch 73, the thin layer antenna 74) of the electrochromic device 70A or 70B, by means of submicrometre lines of material of a transparent electronic conductor which allows the voltage needed to support the electrochromic process to be supplied. Each pixel in case of the device 70A and each set of four areas around the pixel in the device 70B are controlled one by one by the chip that embeds the respective switch 73 and the respective thin layer antenna 74; in particular, the control of the single pixels occurs in a way similar to that of conventional displays, and the switch 73 is preferably substituted with one or more multiplexers. Preferably, the control of each active area is performed by a computer 75 that communicates with said display by means of a wireless technology.

Figure 10B shows that the electrochromic devices 70A and 70B, do not show any appreciable difference by the final users when they are switched off (i.e. when is the electrochromic process is inactive). On the contrary, Figure 10C shows the electrochromic devices 70A and 70B activated to visualize, just for exemplification purposes some letters; it is to be understood that said electrochromic devices 70A and 70B can be employed according to their resolution power as normal liquid crystal monitors. In case the devices 70A and 70B are of type 3, once they have been put in the coloured state, they keep in that state, so showing an optical memory, until an opposite voltage is applied. On the contrary, in case the devices 70A and 70B are of type 1 , once the switch on voltage which necessary for their transition from the transparent to the coloured state has been removed, they go back spontaneously to the transparent state.

The employment of the electrochromic device according to this invention in the field of displays is particularly advantageous because it does not require a back-lighting but it employs just the outside light.

As is shown in Figure 11 , a seventh example of application of the electrochromic device according to this invention relates to its application to rear-view mirrors of vehicles as an additional, non-structural member. The electrochromic process is activated by the dazzling light beam from the vehicle that travels behind the vehicle endowed with the electrochromic device according to this invention, and it is inverted spontaneously when the dazzling beam is lowered.

The control means of the electrochromic device 78 of Figure 11 comprise a brightness sensor 81 (for instance a photodiode which is sensitive to the possible dazzling beam from the vehicle that travels behind. The electrochromic device of Figure 11 comprises an empty frame 77 which is preferably made up of a plastic material and is capable of fitting the rear-view mirror 76 on which it is to be assembled perfectly. Inside said frame 77, in the empty part (the hollow) the electronic components of the devices are inserted: one or more thin accumulators/batteries 79, the switch 80 and the brightness sensor 81. The material (preferably a plastic material) that covers the brightness sensor 81 is pierced so that light can hit the sensor 81. The part of the device 78 which is intended for covering the reflecting zone of the rear- view mirror 76 is realized as is described previously with reference to Figure 3 or to Figure 4 and it is perfectly adherent to the rear-view mirror 76 of the vehicle. Figure 11A shows a general example of rear-view mirror 76, the empty frame 77 wherein the electronic components are housed, and the electrochromic device 78. Figure 11 B shows the empty frame 77 which is endowed with hooks (not shown) for fastening it to the rear-view mirror 76, and a perspective view in which the housing of the electronic components in the empty frame 77 and of the electrochromic device 78 can be viewed.

Figure 11C shows the device assembled on the rear-view mirror 76 in the switched off state (in the upper part) in which state it is transparent, and in the switched on state (in the lower part) as the effect of a dazzling light beam from the vehicle that travels behind; in the latter case, the use of the electrochromic device according to this invention does not allow the rear-view mirror to reflect the light beam that dazzles the driver and possibly the passengers present in the vehicle equipped with said device, so improving the driving safety. When the dazzling light beam from the vehicle that travels behind is removed, the electrochromic device 78 goes back spontaneously to the switched off state, so becoming again transparent.

The preferred forms of embodiment of this invention have been disclosed above and some variants of them have been suggested, but it is to be understood that those who are skilled in technical field can carry out modifications and changes without going out of the protection scope as relative which is set forth by the enclosed claims.

Claims

1. An electrochromic device comprising a plurality of layers that comprise a rear transparent substrate (12a; 22a), which is adjacent to a rear layer (13a; 23a) of a transparent electronic conductor adjacent to an electrochromic set made up of one or more electrochromic layers (14, 15, 16; 24), that is adjacent to a front layer (13; 23) of a transparent electronic conductor (12; 22), said electrochromic set being capable of developing an electrochromic process through which at least a portion of said electrochromic set commutes between a transparent and a coloured state, the device being characterized in that it also comprises one or more thin batteries (17; 25), which are interposed between two layers of said plurality of layers, and thin layer electronic means (18, 19; 26, 27) for switching control, said electronic means comprising one or more electronic components each one of them being interposed between two layers of said plurality of layers, said thin layer control means (18, 19; 26, 27) being electrically connected to said one or more thin batteries (17; 25) and two said rear (13a; 23a) and front (13; 23) transparent electronic conductors so that they are capable of controlling an electrical connection between said one or more thin batteries (17; 25) and the rear (13a; 23a) and front (13; 23) transparent electronic conductors for enabling and/or disabling sais electrochromic process.

2. An electrochromic device according to claim 1 , characterized in that said thin layer control means comprise switching means ( 8; 26), preferably comprising at least a switch and/or at least a multiplexer.

3. An electrochromic device according to claims 1 pj^2, characterized in that said thin layer control means comprise receiver antenna means (19; 27) which are capable to receive control signals from at least one remote control operated switch (20; 28) on whose basis said thin layer control means control the electrical connection between said one o more thin batteries (17; 25) and the rear (13a; 23a) and front (13; 23) transparent electronic conductors.

4. An electrochromic device according to anyone of the preceding claims, characterized in that said thin layer control means comprise at least a brightness sensor (81), preferably a photodiode, which is capable of detecting a brightness on whose basis said thin layer control means control the electrical connection between said one or more thin batteries (17; 25) and the rear (13a; 23a) and front (13; 23) transparent electronic conductors.

5. An electrochromic device according to anyone of the preceding claims, characterized in that said one or more electronic components of said thin layer electronic means (18, 19; 26, 27) for switching control are embedded in a chip.

6. An electrochromic device according to anyone of the preceding claims, characterized in that said one or more thin batteries (17; 25) and said one or more electronic components of said thin layer electronic means ( 8, 19; 26, 27) are all interposed between the two same layers of said plurality of layers.

7. An electrochromic device according to anyone of the preceding claims, characterized in that at least a portion of at least one of the rear layer (13a; 23a) of transparent electronic conductor and the front layer (13; 23) of transparent electronic conductor is shaped according to a two-dimensional matrix comprising a plurality of pixels, said pixels being connected to said thin layer control means (18, 19; 26, 27) by means of a plurality of sub-micrometer tracks, said thin layer control means (18, 19; 26, 27) controlling the electrical connection between said one or more thin batteries (17; 25) and the rear (13a; 23a) and front (13; 23) transparent electronic conductors in such a way as to cause at least a portion of the electrochromic device to work as a display.

8. An electrochromic device according to anyone of the preceding claims, characterized in that at least a portion of at least one of the rear layer (13a; 23a) of transparent electronic conductor and the front layer (13; 23) of transparent electronic conductor is shaped according to at least one drawing, said at least one drawing being connected to said thin layer control means (18, 19; 26, 27) by means of one or more sub- micrometer tracks.

9. An electrochromic device according to anyone of the preceding claims, characterized in that it also comprises planar fastening means (11 ; 21) which are adjacent to the rear transparent substrate (12a; 22a), said planar fastening means comprising preferably or consisting preferably of a transparent adhesive layer (11 ; 21), said planar fastening means (11 ; 21) making part of said plurality of layers, so that the electrochromic device can be coupled by means of said planar fastening means (11 ; 21) to a structure selected from the group comprising a glass sheet or pane (30; 37; 49) and a mirror (76).

10. An electrochromic device according to anyone of the preceding claims, characterized in that it also comprises a frame (77) for housing an outside structure, that preferably comprises a reflecting surface, more preferably a rear-view mirror (76) so that said electrochromic device can be assembled on said outside structure.

11. An electrochromic device according to anyone of the preceding claims, characterized in that said electrochromic set comprises three electrochromic layer which are adjacent to one another in the following order:

- an active electrochromic layer (14) that functions as a working electrode,

- a layer of an ionic conductor (15), and

- a layer (16) consisting of a ionic reservoir that functions as the counter-electrode.

12. An electrochromic device according to claim 11 , characterized in that at least a portion of at least one of the three electrochromic layers of said electrochromic set is shaped according to atwo-dimensional matrix comprising a plurality of pixels and/or according at least a drawing.

13. An electrochromic device according to anyone of the claims 1-10, characterized in that said electrochromic set comprised or consists of an electrochromic layer 24 that contains the electrochromic materials dissolved in a solvent or in polymer.