Photon and / or photoelectron driven full color reflective passive screen

Abstract

The present invention relates to a photon and / or photoelectron driven full color reflective passive screen, which preferably comprises at least three photochromic and / or photoelectrochromic materials, different photochromic materials are capable of absorbing photons of different wavelengths and changing to different colors, and by arranging a mixture of the different colors a full color screen can be formed.

Description

[Technical Field]

[0001] The present invention relates generally to the field of screens and screen systems, preferably to passive and / or reflective screens, and more particularly to photochromic and / or photoelectrochromic screens, especially photon- or photoelectron-driven screens such as multicolor or full-color screens. [Background technology]

[0002] Chromism is a process that refers to a color change in a substance, often reversible. In most cases, chromism is based on a change in the electronic state of the substance. To date, many compounds with specific chromism have been synthesized. Photochromic materials are materials that reversibly change color upon absorption of electromagnetic radiation. One of the most well-known applications of reversible photochromism is color-changing sunglasses lenses.

[0003] Recently, the possibility of developing screens that utilize the properties of photochromic materials has been investigated. The color change of photochromic materials is influenced by the wavelength, intensity, and exposure time of the incident light. In photoelectrochromic materials, another type of light-induced color-changing material, the color change is accompanied by the generation of photoelectrons, which are free charges in the photoelectrochromic material that cause the color change.

[0004] U.S. Patent No. 7,410,750 (B2) discloses a multicolor screen having a substrate with a coating of marking particles containing a mixture of two photochromic materials (a spiropyran material and a single dithienylethene). This document mentions a screen, but only an image, not the possibility of full color. Furthermore, this document does not mention driving the display.

[0005] JP 2004258474(A) discloses a photochromic screen that uses light emitted from an electrochemiluminescent layer disposed between substrates with electrodes. This light is driven by an active matrix and supplied to the photochromic layer to cause the appropriate color change. Therefore, the luminescent layer in the screen emits light, which can also pass through the transparent substrate to excite the screen and enter the viewer's eye. As a result, this type of screen is not considered a completely passive screen. Due to the complexity of the structure, including the active matrix and electrochemiluminescent layer, the manufacturing process for this device is complicated. This document also makes no mention of bleaching of the image produced by the photochromic dye.

[0006] Another technology concerns e-paper or e-ink devices, which can be considered passive displays in that they are based on light reflection and do not emit light. However, these devices also generally require an active matrix to address the image units. Generally, e-paper screens are monochrome devices. While full-color e-paper has been devised, its performance is generally poor. A drawback that applies to all active-matrix-based screens is that the display surface is generally limited to the size of the active matrix. An active matrix significantly increases the cost of the final product, especially when the device size exceeds 100 inches. Therefore, it is an object of the present invention to provide a display that can be easily and cost-effectively implemented in any desired size, including large outdoor displays.

[0007] The present invention further addresses the objective of providing a passive screen that preferably does not emit light itself. Passive screens have certain characteristics that distinguish them from other screens, such as liquid crystal screens (LCD) or organic light-emitting diode (OLED) screens. Passive screens do not emit light themselves, but instead reflect or transmit ambient light depending on the color characteristics of the materials used in the screen. Continuous use of passive screens is believed to cause less eye fatigue than luminescently illuminated screens, such as the LCD and OLED screens mentioned above. Viewing a passive screen is closer to viewing a print medium (light reflected from the environment) than using a luminescent screen. Passive screens offer several additional advantages, including a wide viewing angle, low energy consumption, and efficient light utilization. Therefore, passive screens can be considered particularly advantageous for outdoor viewing (ambient light) and screen reading (high contrast, less eye fatigue). [Prior art documents] [Patent documents]

[0008] [Patent Document 1] U.S. Patent No. 7,410,750(B2) [Patent Document 2] Patent Publication No. 2004258474(A) [Patent Document 3] International Publication No. 2013084029(A1) [Non-patent literature]

[0009] [Non-Patent Document 1] Qi Shao et al., Determining Locations of Conduction Bands and Valence Bands of Semiconductor Nanoparticles Based on Their Band Gaps, ACS Omega, May 18, 2020, pp. 10297-10300 Summary of the Invention [Problem to be solved by the invention]

[0010] In view of the above, it is an object of the present invention to provide a passive reflective full-color screen that has no internal light source and no active matrix and that can be easily provided in any desired size, including large sizes, e.g., greater than 100 inches. It is a further object to provide a solution for driving a passive full-color screen without using an active matrix.

[0011] Another objective is to provide a new structure for photo(electro)chromic screens.

[0012] The present invention addresses the problems and objectives set forth above. [Means for solving the problem]

[0013] The present inventors provide a screen system and a screen, which is noteworthy in that the screen is based on photochromic and / or photoelectrochromic materials. The screen is suitable for displaying an image when properly illuminated by an electromagnetic radiation source. The screen can be realized as a multicolor screen, preferably a full-color screen. The screen is preferably a passive reflective screen.

[0014] In one aspect, the present invention provides a screen comprising first and second substrates, a space between said substrates, and a chromic material disposed in said space, said chromic material being selected from a photoelectrochromic material, a photochromic material, and combinations thereof, said chromic material preferably having the property of changing color when activated by electromagnetic radiation or by photoelectrons generated by electromagnetic radiation.

[0015] In one embodiment, the chromic material comprises at least first and second chromic materials that have first and second colors when activated, the first color and the second color being different.

[0016] In one aspect, the present invention provides a screen comprising first and second substrates, a space between said substrates, a support material, and a chromic material, said support material being disposed in said space; said chromic material being selected from a photoelectrochromic material, a photochromic material, and combinations thereof; said chromic material preferably having the property of changing color when activated by electromagnetic radiation or by photoelectrons generated by electromagnetic radiation; said chromic material comprising at least first and second chromic materials having first and second colors when activated, said first color and said second color being different; and said at least first and second chromic materials being disposed on said support material.

[0017] In one aspect, the present invention provides a screen comprising the screen of the present invention, a light emitting device, and a driver unit.

[0018] In a preferred embodiment, the light-emitting device is configured to emit light in the direction of the screen to activate the chromic material, and the light-emitting device is further configured to emit light having at least first and second different predetermined wavelengths or wavelength ranges. Preferably, light having the first wavelength or wavelength range is suitable for activating the first chromic material or generating photoelectrons capable of activating the first chromic material, and light having the second wavelength or wavelength range is suitable for activating the second chromic material or generating photoelectrons capable of activating the second chromic material. Preferably, the first wavelength or wavelength range and the second wavelength or wavelength range are different.

[0019] In one aspect, the present invention provides a method for operating a screen system of the present invention, the method comprising the step of causing the light emitting device to emit light of the first and second wavelengths and / or wavelength ranges, and, if applicable, the second wavelength and / or wavelength range, onto one or more spots on the screen, thereby activating the first and second chromic materials, and, if applicable, the third chromic material, at the spots.

[0020] In one embodiment, the light emitting device is configured to emit light having a first wavelength or wavelength range. Preferably, the third wavelength or wavelength range is different from the first and second wavelengths or wavelength ranges. In the case of wavelength ranges, there may be overlap between the wavelength ranges. In a preferred embodiment, there is no overlap between the different wavelength ranges.

[0021] Further aspects and preferred embodiments of the present invention are defined below in the specification and in the appended claims. Additional embodiments, features, and advantages of the present invention will become apparent to those skilled in the art from the following description of the preferred embodiments. [Brief explanation of the drawings]

[0022] [Figure 1A]1 is a schematic diagram of an embodiment of a screen system according to the present invention; [Figure 1B] 1B is a schematic diagram of an alternative embodiment of the screen system according to the present invention to that of FIG. 1A; [Figure 2A] 1 is a schematic diagram of the structure of a screen device according to a preferred embodiment of the present invention; [Figure 2B] 1 is a schematic diagram of the structure of a screen device according to a preferred embodiment of the present invention; [Figure 2C] 1 is a schematic diagram of the structure of a screen device according to a preferred embodiment of the present invention; [Figure 2D] 1 is a schematic diagram of the structure of a screen device according to a preferred embodiment of the present invention; [Figure 2E] 1 is a schematic diagram of the structure of a screen device according to a preferred embodiment of the present invention; [Figure 3] 1 is a schematic diagram of nanoparticles with adsorbed chromic materials, according to one embodiment of the present invention. [Figure 4] 1A-1C are schematic diagrams of different nanoparticles with different chromic materials adsorbed thereon, according to one embodiment of the present invention. [Figure 5] 1 is a diagram of the chemical structure of a photoelectrochromic material according to an embodiment of the present invention. [Figure 6] FIG. 1 is a schematic diagram of the preparation of coated nanoparticles according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0023] In the following, preferred embodiments of the device of the present invention will be described for the purpose of illustrating the present invention, without intending to limit the scope of the invention.

[0024] In some embodiments, the present invention relates to a screen system comprising a screen functioning based on photochromic and / or photoelectrochromic materials, the screen system preferably being configured to illuminate the screen with electromagnetic radiation in order to display graphic and / or textual information or images.

[0025] In this specification, for example, the term "chromic" in the expression "chromic material" means "photochromic and / or photoelectrochromic."

[0026] A "photochromic material" is a material that can undergo a color change under the influence of electromagnetic radiation, preferably electromagnetic radiation in the infrared to ultraviolet wavelength range.

[0027] A "photoelectrochromic material" is a material that undergoes a color change when excited by electrons, preferably generated by the exposure of the material to light or the exposure of a photosensitizer material with which the photoelectrochromic material is in electrical contact.

[0028] As used herein, "black" and "white" are also considered colors. For example, a change from clear or white to black, and vice versa, is considered a "color change."

[0029] 1A shows a screen system 60 comprising a screen 10 and a light emitting device, here a projector 6, preferably a laser projector. The system further comprises a driver unit 3 controlling the projector and in particular the light 15, 16 and 17 emitted by the projector.

[0030] Screen 10 has a front side 41 and a back side 42, the front side being configured to be illuminated by projector 6. The screen includes a chromic material that is activated by light emitted by the projector or photoelectrons generated by the light. Exemplary constructions of screens that include chromic material are described in more detail elsewhere herein.

[0031] To generate a multicolor, preferably full-color, image on the screen, the projector is preferably configured to emit light of different wavelengths and / or wavelength ranges, thereby corresponding to the different chromic materials present in the screen. As shown in FIG. 1A, light beams 15, 16, and 17 are characterized by different wavelengths. The light beams preferably traverse a space separating the front side of the screen from the projector. The light beams are directed toward an area or spot 19 of the screen to cause a color change in the chromic material in that area. The projector is suitable for illuminating the entire screen, preferably simultaneously, thereby generating an image on the screen.

[0032] The driver unit is configured to control the light emitted by the light-emitting device. The driver unit 3 is preferably configured to adjust the direction of specific light of specific wavelengths emitted by the projector, and also the duration and intensity of the illumination for any specific sport, thereby contributing to the generation of information shown on the screen. The driver unit also preferably controls the wavelength of the emitted light. To adjust the direction of light emission, the projector preferably comprises a motor suitable for acting on the optics to direct the light under the control of the driver 3.

[0033] The driver unit 3 preferably comprises a data processing entity, such as a microcontroller or computer, including a CPU and memory, and preferably software and / or firmware for driving the light source.

[0034] In one embodiment, the light emitting device is suitable for producing light at at least two, preferably at least three, more preferably at least four different wavelengths or wavelength ranges, such that the system is capable of inducing color changes in different chromic materials responsive to said different wavelengths.

[0035] 1B shows a system 65 according to another embodiment of the present invention, in which the light emitting device is a light emitting panel 7 instead of a projector. The light emitting panel is provided on the back side 42 of the screen 10 and is preferably rigidly connected to the back side 42 of the screen 10. The light emitting panel preferably comprises a plurality of separate light sources. In this case, the driver 3 preferably controls one or more selected from which light sources of the panel are lit, how much light intensity is produced by the light sources, and the duration of the light emission.

[0036] In one embodiment, the light-emitting panel 7 is selected from an LED display, a liquid crystal display (LCD), and a plasma display (PDP). Similar to a projector, the panel 7 is preferably configured to emit light at different wavelengths, preferably two or more, more preferably three or more, for example up to four different wavelengths or wavelength ranges, to correspond to responsive chromic materials contained within the display. In this embodiment, the light rays preferably do not cross the space provided between the light source and the chromic material of the screen.

[0037] Figures 2A to 2E show device structures of screens according to different embodiments of the invention. These figures represent cross sections extending perpendicular to the opposing outer surfaces 41, 42 of the screen. The device 10 shown in Figure 2A comprises first and second substantially planar substrates 1, 2 spaced apart from one another to define a space 5 between the substrates. At least one of the substrates 1, 2 is transparent. The transparent substrate can be made from materials including and / or consisting essentially of glass and plastic.

[0038] The term "substrate" does not imply that both layers 1 and 2 carry a layer disposed between them. Thus, if a layer sandwiched between layers 1 and 2 is assumed to be deposited on one of the two substrates 1 or 2, at least the other can also be considered as a protective layer. It should also be noted that the substrate can comprise and / or consist essentially of a conductive material, such that the substrate can also be an electrode.

[0039] Transparent substrates ensure that light can enter the interior space and be reflected out of the screen, thereby displaying an image. In a preferred embodiment, both the first and second substrates are transparent. In one embodiment, one or both substrates are transparent to all visible light, preferably in addition to ultraviolet and infrared and / or near infrared radiation. In some embodiments, one of the substrates is not or need not be transparent.

[0040] As will become apparent, in the embodiment shown in Figure 1B, both substrates 1, 2 of the screen are preferably transparent, so that light enters through one substrate (e.g., 2) and the image produced by the screen is viewable through the other of the two substrates (e.g., 1). With respect to the screen of the system shown in Figure 1A, here, the front substrate, through which light 15-17 enters the device, is preferably transparent, while the back substrate may or may not be transparent. In the embodiment shown in Figure 1B, the displayed information is viewable on the front or first side 41 of the screen, while the light-emitting device 7 is in contact with or adjacent to the second or back side 42 of the screen.

[0041] A support material or layer 24 is provided in the space 5 between the first and second substrates. Preferably, a chromic material is provided on the support material.

[0042] Preferably, the support material comprises or consists essentially of nanoparticles, examples of which are described in more detail elsewhere herein.

[0043] In one embodiment, one or several different photochromic and / or photoelectrochromic materials are preferably coated and / or adsorbed onto the nanoparticles, the chromic materials preferably being in electrical contact with the support material and / or the nanoparticles.

[0044] As used herein, the terms "electrically connected" or "in electrical contact" mean that a steady flow of current (electrons, holes) occurs between electrically connected items under a constant potential difference. In other words, charge transport occurs by electron movement, not ionic transport.

[0045] As mentioned above, the layer 24 as shown in Figures 1A-1E can comprise several layers, for example two, three or four layers, preferably provided one on top of the other, for example in the case of RGB color mixing.

[0046] In one embodiment, the chromic material provides a monolayer, preferably a monolayer, on the surface of said support material.

[0047] FIG. 2B shows a device similar to FIG. 2A, but with conductive layers 11 and 12 provided on the inner surfaces of the first and second substrates 1 and 2, respectively. At least one of the conductive layers 11 and 12, and possibly both, is a transparent conductive layer. The conductive layers 11 and 12 can comprise and / or consist essentially of, for example, a conductive metal oxide or a conductive polymer. The transparent conductive oxide (TCO) can be selected from, for example, indium-doped tin oxide (ITO), fluorine-doped tin oxide (FTO), ZnO—GaO, ZnO—AlO, tin oxide, antimony-doped tin oxide (ATO), SrGeO, and zinc oxide, or a combination thereof. In the embodiment shown in Figure 2B, the interior space 5 is defined by the space between two surfaces provided by the conductive layers 11, 12, which face each other and face the support layer 24. The conductive layers, if present, can be understood to be part of the substrate, so that the corresponding substrate can be said to be a conductive substrate, preferably a transparent conductive substrate. The conductive layer(s) can also be referred to as an electrode layer.

[0048] In one embodiment, at least one conductive layer is transparent to all visible light, and is also transparent to infrared and / or near-infrared light in addition to ultraviolet light. Thus, one conductive layer does not have to be transparent.

[0049] In one embodiment, the first electrode 11 is a working electrode and the second electrode 12 is a counter electrode.

[0050] The device shown in Figure 2C differs from the device of Figure 1B essentially in the presence of an electrolyte 13 in the space 5 defined by the substrates 1, 2. The electrolyte is preferably provided to enable rapid switching of the chromic material, particularly the photoelectrochromic material, and / or to prevent undesired bleaching. The bleached and / or original state or color of the chromic material is preferably the state or color that the material exhibits in the absence of illumination or photon-induced excitation.

[0051] 2D shows a device further comprising a scattering layer 45. The scattering layer is preferably formed by nanoparticles or microparticles having a diameter of preferably 100 nm to 5 μm, preferably 150 to 2000 nm, more preferably 200 to 1000 nm. In the embodiment shown, the scattering layer is deposited directly on the nanoparticle support layer 24 provided with the chromic material. In another embodiment, the scattering layer 45 is deposited on the second substrate 2 or on the conductive layer 12 of the second substrate (this embodiment is not shown).

[0052] Materials for the scattering layer may preferably be selected from TiO2, Al2O3, or other and / or related metal oxide materials, for example in the form of white nanoparticles.

[0053] Figure 2E differs from the embodiment shown in Figure 2D in that a second conductive layer 12 is present on the second substrate as shown in Figure 2B, and differs from the embodiment of Figure 2C in that a scattering layer is present. An electrolyte 13 is preferably present in the embodiments shown in Figures 2C-2E, and may optionally also be present in the embodiments shown in Figures 2A and 2B (although not shown in these figures).

[0054] As shown in Figures 2A-2E, an electrolyte may, but need not, be present in the device of the present invention, in particular in the space 5 defined by substrate 1 and substrate 2, or, if applicable, the space 5 defined by the substrates with or without electrode layers 11, 12.

[0055] The electrolyte preferably comprises a charged species and a dispersion matrix. In some embodiments, the dispersion matrix is ​​selected from water and polar or non-polar organic solvents. In some embodiments, the electrolyte comprises a molten salt, a eutectic melt, and the like.

[0056] The charged species can be selected from salts, halides, alkali metal ions, metalloid ions, metal ions, and / or charged molecules, such as organic cations and organic anions. In some embodiments, the electrolyte comprises a redox material.

[0057] In other embodiments, the electrolyte is free of redox materials, but includes one or more charged species as described above.

[0058] The function of the charged species in the electrolyte is to stabilize the chromic material and / or the photosensitizing support material after electrons are injected into the chromic material. The charged species can form an electric double layer on the support material and / or around the chromic material, thereby preventing or slowing down charge recombination. For example, when electrons are injected from the support material into the chromic material, positively charged species can enter near the surface of the support material and form the layer that stabilizes charge separation.

[0059] In some embodiments, the electrolyte can include a redox-active species. If present, the redox-active species can preferably transfer electrons back to the support material (or take holes from the support material) after the support material is excited and transfers electrons to the chromic material. This also prevents charge recombination, since electrons in the chromic material cannot return to the support material.

[0060] Stabilizing the charge separation preferably stabilizes the activated, preferably colored, form of the chromic material, thereby reducing undesired bleaching of the chromic material.

[0061] Exemplary electrolytes include, for example, aqueous KCl solutions, solutions of lithium bis(trifluoromethanesulfonyl)imide dissolved in water or polar or non-polar organic solvents such as acetonitrile and gamma-butyrolactone, and solutions of tetrabutylammonium hexafluorophosphate dissolved in polar organic solvents such as propylene carbonate or toluene.

[0062] 2A-2E show a screen comprising a nanoparticle support material. According to this embodiment, the support material comprises or forms one or more selected from the group of non-smooth, surface-enhancing surfaces, particularly structured on a mesoscopic scale. According to this embodiment, the support material provides or forms a scaffold, particularly a 3D scaffold, onto which the chromic material is provided, preferably adsorbed. The 3D scaffold preferably comprises one or more selected from a mesoporous structure, a nanoporous structure, a nanopillar structure, and a nanotube structure, or a combination comprising two or more of the foregoing.

[0063] The average dimension and / or size of the nanoparticles of the support material is preferably in the range of 2 to 1500 nm, preferably 3 to 1000 nm, even more preferably 4 to 500 nm, and most preferably 5 to 200 nm. "Dimension" or "size" in reference to nanoparticles herein means the length in any direction in space, preferably the average maximum length of the nanoparticles. In the case of substantially spherical or ellipsoidal particles, the average diameter is preferably referred to. In the case of nanosheets, the indicated dimensions refer to length and thickness. The size of the nanoparticles is preferably measured, for example, by microscopy techniques.

[0064] In another embodiment, not separately shown, the support material comprises or forms one or more selected from flat, smooth, and / or uniform surfaces onto which the chromic material is provided, preferably adsorbed, and the flat, smooth, and / or uniform surfaces are preferably applied to a surface on a mesoscopic scale.

[0065] FIG. 3 shows an example of nanoparticles in nanoparticle layer 24, particularly in a multicolor screen, preferably a full-color screen. In the example shown, three different chromic materials, first, second, and third chromic materials 21, 22, and 23, are deposited on nanoparticles 31. Chromic materials 21, 22, and 23 are preferably molecules with different structures resulting in different color properties. In a preferred example, the chromic materials are attached to the nanoparticles by anchor groups that are part of the molecules. More details regarding exemplary chromic materials are disclosed elsewhere herein.

[0066] Preferably, the first chromic material 21 exhibits a first color when activated, the second chromic material 22 exhibits a second color when activated, and the third chromic material 21 exhibits a third color when activated, where the first, second, and third colors are different. In one embodiment, the first, second, and third colors are red, green, and blue (RGB color mixture). In another embodiment, the first, second, and third colors are cyan, magenta, and yellow (CMY color mixture). The present invention also includes CMYK (or CMYB) color mixtures with a fourth chromic material selected, for example, from black, dark blue, or dark brown.

[0067] The illumination of the chromic material, photosensitizer, semiconductive material, and / or metal oxide material to achieve the color change of the chromic material according to various embodiments of the present invention is preferably referred to as “activation.” Thus, when a chromic material is “activated,” it undergoes a color change.

[0068] Activation of the chromic material can occur in a variety of ways. In a preferred embodiment, activation occurs by photoelectrons generated when light strikes the chromic material or a support material, preferably the support material including a photosensitizer. In another embodiment, activation occurs, for example, by direct light impinging on the photochromic material without the generation of photoelectrons.

[0069] In a single screen containing different chromic materials, the different chromic materials may be photochromic and / or photoelectrochromic materials alone, may be photoactivated alone, or may be activated directly by light.

[0070] In a preferred embodiment, the chromic materials are activated in all the different chromic materials of the screen by photoelectrons that are generated when light strikes the chromic materials or the supporting material.

[0071] It should also be noted that the color change of the chromic material is preferably reversible. The reversal of the color change, also known as "bleaching," returns the chromic material to its original, preferably colorless, state, which may be caused independently by one or several of a variety of processes, such as those further described below.

[0072] In a preferred embodiment, the support material, in particular the nanoparticles, 3D scaffolds and / or surface area enhancing structures, comprises or consists essentially of a semiconducting material, preferably a photosensitizer material.

[0073] The photosensitizer material is preferably a material that absorbs light of a specific wavelength and generates photoelectrons when excited by that light. The support material and chromic material are arranged so that the photoelectrons are then transferred to the chromic material, preferably a photoelectrochromic material, to cause a color change. In this regard, the light emitted by the light-emitting device is suitable for activating the support material, and therefore, this light can be considered to indirectly activate the chromic material via the support material.

[0074] According to one embodiment, the light of the first and second wavelengths and / or wavelength ranges, and, if applicable, the light of the third wavelength and / or wavelength range, is suitable for activating (directly or via a corresponding support material) the first and second chromic materials, and, if applicable, the third chromic material.

[0075] Preferably, light of said first wavelength or wavelength range does not activate, or does not substantially activate, said second and / or third chromic materials (either directly or via a corresponding supporting material).

[0076] Preferably, light of said second wavelength or wavelength range does not activate, or does not substantially activate, said first and / or third chromic materials (either directly or via a corresponding supporting material).

[0077] Preferably, light of said third wavelength or wavelength range does not activate, or does not substantially activate, said first and / or second chromic materials (either directly or via a corresponding supporting material).

[0078] The above features may also be understood to mean that the first wavelength and / or wavelength range primarily activates the first chromic material, the second wavelength and / or wavelength range primarily activates the second chromic material, etc.

[0079] As used herein, "photosensitizing" materials include photoelectric and / or photovoltaic materials.

[0080] In one embodiment, the photosensitizer material absorbs ultraviolet light. An example of such a photosensitizer material is TiO2. When activated and / or irradiated with ultraviolet light, photoelectrons are generated, causing the desired chromic behavior, particularly a color change, in the chromic material.

[0081] In one embodiment, the chromic material exhibits a conduction band minimum, and the chromic material exhibits a reduction potential, the conduction band minimum being less negative than the reduction potential. The reduction potential of the electrochromic material can be determined preferably relative to a reference electrode, such as a standard hydrogen electrode or a calomel electrode. The band gap of the semiconductor material can be determined from the onset of the absorption spectrum. The conduction band and / or valence band can be determined, for example, by calculation from the band gap; see, for example, Qi Shao et al., "Determining Locations of Conduction Bands and Valence Bands of Semiconductor Nanoparticles Based on Their Band Gaps," ACS Omega, May 18, 2020, pp. 10297-10300.

[0082] When the support material includes first, second, and, if applicable, third chromic materials, the materials may exhibit first, second, and, if applicable, third conduction band minima, respectively. In this case, the first, second, and, if applicable, third chromic materials preferably exhibit first, second, and, if applicable, third reduction potentials, respectively. The first conduction band minimum is preferably less negative than the first reduction potential. The second conduction band minimum is preferably less negative than the second reduction potential. If applicable, the third conduction band minimum is preferably less negative than the third reduction potential.

[0083] According to one embodiment, the support material may be Si, SO2, TiO2, Al2O3, ZrO2, HfO2, SnO2, Fe2O3, ZnO, WO3, Nb2O5, In2O3, Bi2O3, Y2O3, Pr2O3, CeO2, and other rare earth metal oxides, CdS, ZnS, PbS, Bi2S3, CdSe, CdTe, MgTiO3, SrTiO3, BaTiO3, Al2TiO5, Bi4TiO 12, and other titanates, CaSnO3, SrSnO3, BaSnO3, Bi2Sn3O9, Zn2SnO4, ZnSnO3, and other stannates, CaZrO3, SrZrO3, BaZrO3, Bi4Zr3O 12 and other zirconates, the foregoing oxides, and combinations of two or more of the alkali metals, alkaline earth metal elements, Al, Ga, In, Si, Ge, Sn, Pb, Sb, Bi, Sc, Y, La, or any other lanthanide, Ti, Zr, Hf, Nb, Ta, Mo, W, Ni, or Cu.

[0084] In one embodiment, one or more of the photosensitizers are colored, meaning that such photosensitizers reflect light in the visible light spectrum.

[0085] In a preferred embodiment, the photosensitizer material is, for example, TiO2, SnO2, CdS, CdSe, CdTe, ZnS, Si, Fe2O 3 , PbS, Bi2S3, and organic-inorganic and purely inorganic perovskites such as Pb or Sn halide perovskites.

[0086] In preferred embodiments, the support material is selected from organic photovoltaic materials, quantum dot photovoltaic materials (such as CdS, CdTe, CdSe), perovskite photovoltaic materials, TiO2, SnO2, and combinations of the foregoing.

[0087] The aforementioned exemplary and preferred support materials may be doped or undoped.

[0088] The chromic material can be selected from organic compounds, metal oxides, particularly transition metal oxides, and organometallic compounds. The chromic material is preferably an organic compound. The organic compound is preferably selected from small molecules and polymers, as well as salts of such organic compounds. The small molecule or monomer portion of the polymer can have 5 to 150 carbon atoms and 0 to 60 heteroatoms, where the heteroatoms can be selected from, for example, B, Si, As, O, S, Se, Te, N, P, and halogens. The small molecule or monomer portion preferably has 6 to 100 carbon atoms and 1 to 50 heteroatoms, and most preferably has 7 to 50 carbon atoms and 1 to 30 heteroatoms.

[0089] In one embodiment, the chromic material comprises an anchor group and is adsorbed to the support material via the anchor group. Suitable anchor groups include, but are not limited to, —COOH, —PO3H2, —PO4H2, —P(R 1 )OH (phosphinic acid), -SO3H2, -SO4H2, -CONHOH, 1,2-hydroxybenzene, 1-hydroxy-2-carboxybenzene, acetylacetonate, deprotonated forms of the foregoing, organic and / or inorganic salts of said deprotonated forms, and chelating groups with π-conductivity. 1 may be an organic substituent containing 1 to 50 carbon atoms and 0 to 25 heteroatoms, said hydrocarbon being covalently bonded to the P atom of said phosphinic acid group by a carbon atom.

[0090] 4 shows an embodiment of the present invention in which different chromic materials 21, 22, 23 are provided on different support materials 31, 32, 33, preferably comprising different photosensitizing (or photosensitizer) and / or semiconductive support materials. Thus, a first chromic material 21 is provided in contact with (preferably adsorbed to) a first photosensitizer material 31, a second chromic material 22 is provided in contact with a second photosensitizer material 32, and optionally a third chromic material 23 is provided in contact with a third photosensitizer material 33. According to an even more preferred embodiment, a fourth chromic material is provided in contact with a fourth photosensitizer material (not shown in FIG. 4).

[0091] According to one embodiment, the first, second and third chromic materials are adapted to have the colors red, green and blue when activated, thereby enabling a full color display on the screen based on RGB additive color mixing, where there is no fourth chromic material that becomes black when activated.

[0092] According to another embodiment, the first, second and third chromic materials are suitable to have the colours blue, red and yellow when activated, thus allowing for cyan, magenta and yellow (CMY) colour mixing, and preferably the fourth chromic material is black when activated, thus allowing for CMYB colour mixing.

[0093] In embodiments such as that shown in FIG. 4, when applied to any one of the structures shown in FIGS. 2A-2E, these devices include two or more, preferably three or more, e.g., four or more, different chromic materials, preferably on different suitable photosensitizer materials.

[0094] Figure 5 shows exemplary photoelectrochromic materials 1-3. Compound 1 is 1-ethyl-1'-(2-phosphonoethyl)-[4,4'-bipyridine]-1,1'-dium cation. The chromic moiety of Compound 1 includes 1,1'-diethyl-[4,4'-bipyridine]-1,1'-dium. Compound 1 turns blue when excited by blue light, particularly light having a wavelength of about 350 to about 450 nm.

[0095] Compound 2 is a 1-phenyl-1'-(4-(2-phosphonoethyl)phenyl)-[4,4'-bipyridine]-1,1'-diium cation. The chromic moiety of Compound 2 contains 1,1'-diphenyl-[4,4'-bipyridine]-1,1'-dium as a chromic core. Compound 2 turns green when excited by green light, particularly light having a wavelength of about 500 nm to about 550 nm.

[0096] Compound 3 is a 1-ethyl-4-(4-(1-(2-phosphonoethyl)pyridin-1-ium-4-yl)phenyl)pyridin-1-ium cation and contains 4,4′-(1,4-phenylene)bis(1-ethylpyridin-1-ium) as the chromic core.

[0097] Compounds 1-3 are shown with the bromide anion, which is not required, but is present due to the synthetic route used to prepare the compounds. Compounds 1-3 can be used for coating nanoparticles, for example, according to the examples shown in Figures 3 or 4.

[0098] Several examples are disclosed herein that are based on the compounds shown in FIG. 5 when used with different nanoparticle-sensitized support materials, as shown in FIG.

[0099] In a specific embodiment, the first chromic material includes 1,1'-diethyl-[4,4'-bipyridine]-1,1'-dium as the chromic moiety. For example, compound 1 in Figure 5 is the first chromic material. The chromic material may be disposed on or in electrical contact with a CdS (cadmium sulfide) support, preferably CdS nanoparticles, which provides the first support material. This assembly can be excited by blue light having a wavelength of about 350 to about 450 nm, and the chromic material turns blue upon excitation.

[0100] In one embodiment, the second chromic material includes 1,1'-diphenyl-[4,4'-bipyridine]-1,1'-dium as a chromic moiety. For example, compound 2 in FIG. 5 is the second chromic material. The chromic material can be provided on or in electrical contact with a CsPbBr3 perovskite support, preferably a CsPbBr3 perovskite quantum dot or nanoparticle, which provides the second support material. The assembly can be excited, for example, by green light having a wavelength of about 550 nm, causing the chromic material to turn green upon excitation.

[0101] In one embodiment, the third chromic material includes 4,4'-(1,4-phenylene)bis(1-ethylpyridin-1-ium) as the chromic moiety. For example, compound 3 in Figure 5 is the third chromic material. The chromic material can be disposed on or in electrical contact with a TiO2 support, preferably TiO2 nanoparticles, which provides the third support material. This assembly can be excited by ultraviolet light, for example, at a wavelength of about 350 nm to about 400 nm, and the chromic material turns red upon excitation.

[0102] Of course, different combinations of chromic materials and photosensitizer materials may be provided, and the present invention is in no way limited to the exemplary embodiments disclosed above. For example, Compound 1 may be provided on a TiO2 photosensitizer and activated with ultraviolet light having a wavelength of about 350-450 nm, by way of example only.

[0103] As shown with reference to Figure 3, the present invention also encompasses different chromic materials (such as those listed above) being provided in contact with, for example immobilized or adsorbed on, a single photosensitizer material. According to this embodiment, there may be a single type of support material and two or more different chromic materials. In yet another embodiment, the screen may include two different support materials and three or more different chromic materials. The present invention preferably encompasses a variety of possibilities.

[0104] FIG. 6 shows an example of the preparation of a photosensitizer support material combined with a chromic material. The sensitizer support and chromic material, shown here in the form of nanoparticles, are typically mixed in a container with a solvent and, optionally, additives, and allowed to contact each other. The conditions in the container are selected to allow the chromic material to coat, adsorb, and / or immobilize the surface of the sensitizer support. This contacting step can be performed separately for each combination of photosensitizer and chromic material. For example, a first sensitizer material can be combined with a first chromic material in a first container, a second sensitizer material can be combined with a second chromic material in a second container, and so on, up to four or more combinations of sensitizer and chromic materials can be prepared. Finally, the various combinations in the containers can be mixed together, for example, before being coated onto the substrate 1 or the conductive layer 11 of the substrate (FIGS. 2A-2E). The device assembly can then be completed to obtain a screen of the present invention, for example, according to the structure shown in FIGS. 2A-2E.

[0105] We have previously described how chromic materials can be activated by illumination with a light-emitting device, either directly or via photoelectrons. As previously described, the color change of a chromic material is preferably reversible. Reversal of the color change, also known as "bleaching," is the process by which a chromic material returns to its original, preferably colorless, state. Bleaching can be induced independently by one or several different processes. For example, reversal of the color state can be achieved by applying a voltage to either one or both electrodes (see electrodes 11 and 12 in Figures 2B-2E), by illumination, or via an electrolyte (electrolyte 13 in Figures 2C-2E).

[0106] In one embodiment, bleaching occurs naturally (automatically) over time. For example, when illumination ceases, the photoelectrons naturally recombine with the support material, particularly with the positive charges or holes created in the support material as the photoelectrons were generated. Recombination is generally driven by Coulomb forces.

[0107] In one embodiment, the device includes a diffusion voltage barrier that slows or prevents the reversion of the chromic material to a bleached, non-activated state. In one embodiment, the support material includes additional layers to prevent charge recombination. Such layers may be referred to as blocking layers, insulating layers, and / or passivation layers.

[0108] In a preferred embodiment, the blocking layer is disposed on the support material, preferably between the support material and the chromic material.

[0109] When present, the blocking layer preferably has a thickness of from 0 to 0.5 nm, preferably from 0 to 0.2 nm. In one embodiment, the thickness of the blocking layer is such that electrons are still able to transfer from the photoexcited photosensitized support material to the chromic material, for example by tunneling, but electrons are difficult or impossible to transfer from the chromic material to the sensitized support material.

[0110] In one embodiment, the blocking layer has an appropriate conduction band position (E C Suitable blocking layer materials include and / or consist of suitable metal or Si oxide materials having E C Further details regarding the determination of LUMO values ​​can be found in WO2013084029A1.

[0111] While certain preferred embodiments of the present invention have been described and exemplified in detail, it is not intended that the present invention be limited to such embodiments. Various modifications may be made without departing from the scope and spirit of the present invention as defined in the following claims. Below, examples of the present invention are disclosed. These examples are for illustrative purposes only and are not intended to limit the scope of the present invention. [Example]

[0112] A full-color passive screen with the device structure shown in FIG. 2C and the photoelectrochromic material shown in FIG. 4 is prepared as follows.

[0113] material The photoelectrochromic dyes (compounds 1-3 in Figure 5) are designed and fabricated in-house. Photovoltaic quantum dots, TiO2 nanoparticles, and perovskite quantum dots are synthesized using procedures reported in the literature. FTO and other chemicals are purchased commercially. The electrolyte is prepared by dissolving 1M t-BuPF6 in propylene carbonate.

[0114] Preparation of working electrode A TiO2 dye mixture is prepared by mixing TiO2 paste (including solvent and binder) with Compound 3 (Figure 3). The paste and dye are mixed until the dye mixture is homogeneous. This mixture is then screen-printed onto FTO glass and slowly heated to remove the solvent. The TiO2 coated with dye 1 is then transferred onto a transparent electrode by screen printing.

[0115] Two other dye-coated nanoparticles, including CdS nanoparticles coated with compound 1 (Figure 3) and CsPbBr nanoparticles coated with compound 2 (Figure 3), are then screen-printed layer by layer onto the electrode.

[0116] Preparation of the counter electrode The counter electrode is prepared by electrodepositing a thin layer of PEDOT on the surface of a commercially available FTO transparent electrode.

[0117] Fabrication of PECD device The PECD devices are fabricated here by the hole-filling method in the laboratory, but can equally be prepared by widely used industrial processes, such as the one-drop-filling (ODF) method.

[0118] The working and counter electrodes are stacked together with a 10-100 µm spacer and glued around the active area, leaving two holes in either the glass or a piece of sealing adhesive. An electrolyte (see "Materials") is then filled into the cavity created by the spacer and adhesive. After filling, the two holes are sealed with adhesive, resulting in a photoelectrochromic display (PECD) device.

[0119] operation The resulting device functions as a screen and can be used to display images when illuminated by a modified laser projector equipped with three lasers emitting blue light at wavelengths of 450-500 nm, ultraviolet light at wavelengths of 350-400 nm, and green light at wavelengths of 500-550 nm, activating the chromic material on the screen and generating a projected image.

[0120] bleaching The image displayed on the screen can be bleached within 10 seconds by reverse biasing the PECD potential. The image also bleaches spontaneously after 30 minutes.

Claims

1. A screen (10) comprising first and second substrates (1, 2), a space (5) between said substrates, a support material (24), and a chromic material (21, 22), The support material is provided in the space (5), the chromic material is selected from a photoelectrochromic material, a photochromic material, and a combination thereof, and the chromic material has the property of changing color when activated by electromagnetic radiation or by photoelectrons generated by electromagnetic radiation; the chromic material is provided on the support material; the chromic material comprises at least first and second chromic materials (21, 22) having first and second colors when activated, respectively, the first color and the second color being different, and the at least first and second chromic materials are provided on the support material; the first chromic material is activated by light having a first wavelength or range of wavelengths, either directly or via photoelectrons generated by the support material; the second chromic material is independently activated, either directly or via photoelectrons generated by the support material, by light having a second wavelength or range of wavelengths; the first and second wavelengths and / or wavelength ranges are different; A screen wherein said support material comprises and / or consists essentially of a photosensitizer material.

2. 2. The screen of claim 1, wherein the support material comprises one or more selected from nanoparticles, a 3D scaffold, and a surface-enhancing structure, and the chromic material is provided on and / or in contact with the nanoparticles, the 3D scaffold, and / or the surface-enhancing structure, respectively.

3. The screen of claim 2 , wherein the chromic material is adsorbed onto the nanoparticles, 3D scaffolds, and / or surface-enhancing structures, respectively.

4. 3. A screen according to claim 1 or 2, wherein the support material comprises a semiconductive photosensitizer material.

5. 3. The screen system of claim 1, wherein the support material exhibits a conduction band minimum and the chromic material exhibits a reduction potential, the conduction band minimum being less negative than the reduction potential.

6. 3. The screen of claim 1, wherein the support material comprises a first support material and a second support material, the first support material and the second support material being different.

7. A screen as described in claim 6, wherein the first chromic material is provided on the first support material and the second chromic material is provided on the second support material.

8. A screen as described in claim 7, wherein the first support material is provided in one or more forms selected from first nanoparticles (31), a first 3D scaffold, and / or a first surface-enhancing structure, and the second support material is provided in one or more forms selected from second nanoparticles (32), a second 3D scaffold, and / or a second surface-enhancing structure.

9. 2. The screen of claim 1, wherein the chromic materials include at least a third chromic material (23), the third chromic material having a third color when activated, the third color being different from the first and second colors.

10. 8. The screen of claim 7, wherein the support material comprises a third support material different from the first and second support materials, the third support material being provided in the form of third nanoparticles (33), a third 3D scaffold, and / or a third surface-enhancing structure, respectively; the chromic material comprises at least a third chromic material (23), the third chromic material having a third color when activated, the third color being different from the first and second colors, and the third chromic material (23) being provided on the third support material.

11. 8. The screen of claim 7, wherein the first support material generates photoelectrons upon absorption of light having the first wavelength and / or wavelength range, and the second support material generates photoelectrons upon absorption of light having the second wavelength and / or wavelength range.

12. A screen as described in claim 10, wherein the first support material generates photoelectrons upon absorption of light having the first wavelength and / or wavelength range, the second support material generates photoelectrons upon absorption of light having the second wavelength and / or wavelength range, and the third support material generates photoelectrons upon absorption of light having the third wavelength and / or wavelength range.

13. 2. A screen according to claim 1, further comprising an electrode (11) provided on said first substrate (1), said electrode being in electrical contact with said support material.

14. A screen according to claim 1, a light-emitting device (6, 7), and a driver unit (3), the light-emitting device is configured by the driver unit to emit light (15, 16, 17) in the direction of the screen so as to activate the chromic material and / or the support material; the light emitting device is further configured to emit light having at least first and second different predetermined wavelengths or ranges of wavelengths; light having the first wavelength or range of wavelengths is suitable for activating the first chromic material or for generating photoelectrons capable of activating the first chromic material; a screen system, wherein light having the second wavelength or range of wavelengths is suitable for activating the second chromic material or for generating photoelectrons capable of activating the second chromic material.

15. 15. The screen system of claim 14, wherein the light emitting device is further configured to emit light having a third wavelength or range of wavelengths, the third wavelength being different from the first and second wavelengths or ranges of wavelengths, and wherein light having the third wavelength or range of wavelengths is suitable for activating the third chromic material.

16. 15. The screen system according to claim 14, wherein the driver unit is suitable for adjusting the light emitting intensity and / or the light emitting duration of the light emitting device.

17. causing the light-emitting device to emit light of the first and second wavelengths and / or wavelength ranges (15, 16) and, if applicable, the third wavelength and / or wavelength range in the direction of one or more spots (19) on the screen, thereby activating the first and second chromic materials and, if applicable, the third chromic material in the one or more spots, 15. A method for operating a screen system according to claim 14.

Images