display

Abstract

A display device configured to display a display item, the device comprising an anode comprising a transition group metal, a cathode comprising a transition group metal, a substrate, wherein the anode and / or the cathode are disposed on the substrate, a dielectric layer in contact with the anode, and an electrolyte layer disposed between the anode and the cathode, the electrolyte layer comprising an electrolyte.

Description

[0001] DISPLAY

[0002] BACKGROUND

[0003] Electronic display devices are well known. For example, liquid crystal display (LCD) displays are incorporated into numerous devices.

[0004] However, when incorporated into small devices, known arrangements of displays may take up a disproportionately large amount of space, thus increasing the overall size of the device. Further, such displays may be expensive to produce, especially when incorporated into disposable devices, relative to the overall cost of those devices.

[0005] Further, in known display devices it is sometimes possible to view the item which will be displayed by the device (e.g. a message, or symbol) before the device has been activated. For example, even though the device has not been activated, it may be possible to see the outline of what will be displayed when the display is eventually activated. This may be problematic in a number of situations.

[0006] For example, in a pregnancy test, the words “not” and “pregnant” may be selectively displayed, with the word “not” being activated or not depending on whether a positive test is detected. If the user of the test is able to see the message either “pregnant” or “not pregnant” before the device has been activated, this may cause the user to misinterpret the test or believe that the test has been completed when it has not been completed. Thus, it would be desirable to provide displays in which the item to be displayed is “masked” before the test is activated.

[0007] It is an aim of the present invention to at least partially address the problems set out above.

[0008] SUMMARY OF THE INVENTION

[0009] According to a first aspect, there is provided a display device configured to display a display item, the device comprising an anode comprising a transition group metal, a cathode comprising a transition group metal, a substrate, wherein the anode and / or the cathode aredisposed on the substrate, a dielectric layer in contact with the anode, and an electrolyte layer disposed between the anode and the cathode, the electrolyte layer comprising an electrolyte.

[0010] Optionally, the electrolyte layer is configured to oxidise a portion of the anode when a voltage is applied between the anode and the cathode.

[0011] Optionally, the display further comprises an electrochromic layer disposed between the electrolyte layer and the cathode, the electrochromic layer comprising an electrochromic material.

[0012] Optionally, the electrochromic material comprises one or more of WO3, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate, Prussian Blue, a doped Tungsten oxide, a viologen, a polythiophene, a polyaniline, or a combination thereof.

[0013] Optionally, the display device further comprises an ion storage layer disposed between the electrolyte layer and the anode.

[0014] Optionally, the ion storage layer includes Prussian Blue.

[0015] Optionally, the anode and the cathode are disposed on the substrate.

[0016] Optionally, the display device further comprises a second substrate, wherein the anode is disposed on the first substrate and the cathode is disposed on the second substrate.

[0017] Optionally, the first substrate and the second substrate are integrally formed.

[0018] Optionally, the display item is at least partially defined by the shape of the anode.

[0019] Optionally, the display item is at least partially defined by the shape of the dielectric layer.

[0020] Optionally, the display item is text and / or an image.Optionally, the device is configured to reversibly display the display item.

[0021] Optionally, the device is configured to irreversibly display the display item.

[0022] Optionally, the electrolyte comprises one or more inorganic salts comprising chlorine, bromine or iodine.

[0023] Optionally, the electrolyte comprises one or more inorganic salts comprising sulphur, phosphorous, arsenic, selenium or antimony.

[0024] Optionally, the electrolyte comprises one or more of potassium chloride, polyvinyl acetate, potassium hydroxide, sodium hydroxide, poly(methyl methacrylate), lithium perchlorate, and a polycarbonate.

[0025] Optionally, the electrolyte comprises one or more of a thickener, a binder, a photoinitiator and a plasticizer.

[0026] Optionally, the electrolyte comprises one or more of Acrylic Acid, Carboxymethyl Cellulose Sodium Salt, 2-Hydroxy-2-methylpropiophenone, and glycerol.

[0027] Optionally, the electrolyte is a UV curable polymer.

[0028] Optionally, the electrolyte is a pressure sensitive adhesive.

[0029] Optionally, the anode, the cathode and the electrolyte layer are disposed in a hermetically sealed compartment.

[0030] Optionally, the display device further comprises a second dielectric layer in contact with the cathode.Optionally, the anode comprises an electrically conductive mesh, preferably wherein the mesh includes openings having a width from 10pm to 1000 pm, and a length from 10pm to 1000 pm and / or filaments having a width from 25pm to 500pm.

[0031] Optionally, the anode is a solid electrode.

[0032] Optionally, the cathode comprises an electrically conductive mesh, preferably wherein the mesh includes openings having a width from 10pm to 1000 pm, and a length from 10pm to 1000 pm and / or filaments having a width from 25pm to 500pm.

[0033] Optionally, the cathode is a solid electrode.

[0034] Optionally, the mesh is configured to obscure the display item prior to the device being activated.

[0035] Optionally, the mesh further comprises a colouring agent, the colouring agent optionally comprising one or more of graphene, carbon black, hexagonal boron nitride flakes and titanium oxide particles.

[0036] Optionally, the anode and / or the cathode comprises flakes, wherein the flakes have a length of from 0.1 pm to 3 pm, a thickness of 0.8 nm to 200 nm, and an aspect ratio of from 5:1 to 3750:1, optionally wherein the flakes comprise one or more of silver, graphene, and boron nitride.

[0037] Optionally, the flakes have a length of from 0.1 pm to 1 pm, and / or a thickness of 10 nm to 100 nm, and / or an aspect ratio of from 10:1 to 300:1.

[0038] Optionally, the transition group metal of the anode and / or the cathode is silver.

[0039] Optionally, the substrate comprises a base layer and a porous layer, optionally wherein the base layer of the comprises a polymer and is transparent, and / or the porous layer comprises a nanoporous material, optionally nanosilica and / or nanoalumina.Optionally, the surface of the porous layer has a surface roughness of 500 nm or less and / or a porosity of 30% or more, optionally wherein the porous layer has: a surface roughness of 200 nm or less, and / or a porosity from 30% to 80%, and / or a porosity of 50% or more, and / or a porosity of 75% or less.

[0040] Optionally, at least one of the substrate, the anode, the cathode, the dielectric layer and the electrolyte layer are printed.

[0041] According to another aspect, there is provided a flexible article comprising a substrate, an anode comprising a transition group metal, a cathode comprising a transition group metal, a dielectric layer, and an electrolyte layer comprising an electrolyte, wherein the flexible article is configured to be folded and / or selectively joined and / or cut such that the electrolyte layer is disposed between the anode and the cathode.

[0042] According to another aspect, there is provided a method of manufacturing a display device, the method comprising providing a substrate, printing an anode comprising a transition group metal and a cathode comprising a transition group metal onto one or more substrates, printing a dielectric layer onto the anode, and printing an electrolyte layer.

[0043] Optionally, the anode and the cathode are printed onto the same substrate.

[0044] Optionally, the anode is printed onto a first substrate, and the cathode is printed into a second substrate.

[0045] Optionally, providing the substrate comprises positioning the substrate on a backing template, wherein the method further comprises folding and / or selectively joining and / or and cutting parts of the backing template such that the electrolyte layer is positioned between the anode and the cathode

[0046] According to another aspect, there is provided a method of printing a grid, the method comprising providing a printable medium, providing a substrate, and applying the printablemedium to the substrate in a grid pattern, wherein the printable medium comprises flakes and a liquid, wherein the flakes comprise silver, graphene, boron nitride, or a mixture thereof, and have a length of from 0.1 pm to 3 pm, a thickness of 0.8 nm to 200 nm, and an aspect ratio of from 5:1 to 3750:1, and wherein the printable medium has a viscosity in the range of 0.1 to 25 Pa-s, and the substrate comprises a porous receiving layer provided on a base layer, and the porous receiving layer has a surface roughness of 500 nm or less and / or a pore size which is 50% or less of the length of the flakes in the conductive layer, optionally wherein the printable medium is applied to the substrate using a printing apparatus, preferably a flexographic printing apparatus.

[0047] BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The present invention will now be described, by way of non-limitative example only, with reference to the accompanying drawings, in which:

[0049] Figure 1 shows a schematic depiction of a display device according to the present invention in cross-sectional view;

[0050] Figure 2 shows a schematic depiction of a further arrangement of display device according to the present invention in top view;

[0051] Figure 3 shows a schematic depiction of a further arrangement of display device according to the present invention in cross-sectional view;

[0052] Figure 4 shows an example arrangement of anode and cathode according to the present invention in top view;

[0053] Figure 5 shows an example arrangement of dielectric material layout according to the present invention in top view;

[0054] Figure 6 shows an example arrangement of anode and cathode according to the present invention in top view;

[0055] Figure 7 shows an example arrangement of dielectric material layout according to the present invention in top view;

[0056] Figure 8 shows a display of the present invention before and after activation;

[0057] Figure 9 shows a cross-sectional view of a display device according to the present invention;Figure 10 shows a cross-sectional view of a display device according to the present invention

[0058] Figure 11 shows a cross-sectional view of a display device according to the present invention

[0059] Figure 12 shows a cross-sectional view of a display device according to the present invention

[0060] Figure 13 shows a cross-sectional view of a display device according to the present invention; and

[0061] Figure 14 shows a cross-sectional view of a display device according to the present invention.

[0062] DETAILED DESCRIPTION

[0063] A first arrangement of display device according to the present invention is shown in figure 1. It will be understood that figure 1 (as well as figures 2 and 3, which will be described below) is merely a schematic figure intended to illustrate the principle of the invention, and that real-world implementations of the display device may differ significantly in appearance to the schematic depiction shown in figure 1.

[0064] The display device 10 shown in figure 1 includes an anode 11 and a cathode 12. The anode 11 and the cathode 12 may be collectively referred to as electrodes.

[0065] The anode 11 comprises a transition group metal. For example, the anode 11 may comprise (or be formed of) silver. The silver may be formed by printing a silver ink.

[0066] The cathode 12 comprises a transition group metal. For example, the anode 12 may comprise (or be formed of) silver. The silver may be formed by printing a silver ink.

[0067] The device further includes a first substrate 13a and a second substrate 13b. The anode 11 is disposed on the substrate 13 a, and the cathode 12 is disposed on the second substrate 13b. It will be understood that, in some arrangements, one of the substrates 13a and 13b may be omitted, such that only one of the electrodes is disposed on the (single) substrate, and theother electrode is not disposed on any substrate. However, it will be understood that in the arrangement of figure 1, the anode 11 and the cathode 12 are in different planes to each other, regardless of the specific configuration of substrates. Where a substrate is omitted, the display may be applied directly to a surface of a second device, such as a surface of a printed circuit board, or a surface of a device housing.

[0068] The device further comprises a dielectric layer 14. The dielectric layer 14 is in contact with the anode 11.

[0069] The device further comprises an electrolyte layer 15. The electrolyte layer 15 is disposed between the anode 11 and a cathode 12. The electrolyte layer 15 comprises an electrolyte.

[0070] It will be understood that the term “layer” need not imply that the layer extends over the full width of the device. For example, as explained in further detail below, in the arrangement of figure 1, the dielectric layer 14 extends only partially across the anode. That is, some parts of the anode 11 are in direct contact with the electrolyte layer 15, and other parts of the anode have the dielectric layer 14 interposed between the anode and the electrolyte layer 15. Any of the layers described herein, including the dielectric layer 14, may be patterned (i.e. split into several discontinuous parts across the width of the device).

[0071] In some arrangements, one or more of the electrodes (i.e. the anode and the cathode) may include (or take the form of) an electroconductive mesh (i.e. a grid). This may allow the user to see the display item through the mesh when the display has been activated, whilst also obscuring the display item before the display has been activated. For example, in the arrangement of figure 1, either of the anode 11 and the cathode 12 may take the form of a mesh. The electrode which takes the form of a mesh may be on the “eye side” of the device (i.e. the side from which the user looks at the display). The other electrode may also be a mesh, or may be a solid electrode. The term “solid” is used to describe an electrode which is not a mesh. However, it will be understood that a solid electrode may nonetheless be patterned, with the parts of the pattern being individually solid. In other words, a “solid” electrode may be a continuous piece of material (i.e. without the openings and solid parts of a mesh), and a mesh may be a discontinuous piece of material (i.e. with openings and solidregions therebetween). Other arrangements with various combinations of solid and mesh electrodes will be described later.

[0072] In the arrangement of figure 1 , when a voltage is applied between the anode 11 and the cathode 12, the parts of the anode 11 which are in direct contact with the electrolyte layer 15 are oxidised. This causes a colour change of these parts of the anode. In turn, this colour change may be used to cause the display device to display a display item. The dielectric layer 14 “masks” parts of the anode 11 and prevents them from becoming oxidised. This oxidation is caused by the movement of ions through the electrolyte layer. Thus, the electrolyte layer is configured to oxidise a portion of the anode when a voltage is applied between the anode and the cathode. As an example, where the anode comprises silver, and the electrolyte comprises a salt of chlorine, silver chloride may be formed.

[0073] It will be understood that, although the dielectric layer depicted in figure 1 is a rectangular block, any pattern or shape of dielectric layer may be used so as to define the item to be displayed by the display when the display is activated. This item can be considered to be a “display item”, and may be, for example, a text, an image, or a combination thereof. In the arrangement of figure 1, the display item is partially defined by the shape of the anode, and is partially defined by the shape of the dielectric layer. In other words, the combination of the shape of the anode (part of which is oxidised in order to display the display item) and the shape of the dielectric layer (which prevents part of the anode from being oxidised) defines the display item.

[0074] The display device may be configured to irreversibly or reversibly display the display item. That is, in irreversible arrangements, once the display item has been displayed, the display item cannot then be hidden again from view. On the other hand, in reversible arrangements, the display can be switched between displaying and not displaying the display item. In other words, the display may be one-time switchable, or may be bistable. As will be described in more detail below, whether the display of the display item is reversible or irreversible may at least partially depend on the composition of the electrolyte in the electrolyte layer 15.In a variation of the arrangement of figure 1 , a second dielectric layer may be provided in contact with the cathode. Such a dielectric layer may be the same as, or different to, the dielectric layer in contact with the anode.

[0075] Figure 2 schematically depicts a further arrangement of display device. Unlike figure 1 (which is a side view), the arrangement of figure 2 is a top view of the device.

[0076] In the arrangement of figure 2, both the anode 11 and the cathode 12 are mounted on a single substrate 13 (i.e. on the same substrate, and in the same plane as each other). Although not shown in figure 2, the anode 11 and the cathode 12 may be electrically isolated from each other by a small gap.

[0077] In the arrangement of figure 2, the electrolyte layer 15 is disposed between the anode 11 and the cathode 12 (bridging between the anode and the cathode), and the dielectric layer 14 is in contact with the anode 11. As in the arrangement of figure 1, the dielectric layer 14 masks (or occludes) part of the anode 11. Thus, again, when a voltage is applied between the anode and the cathode, the portion of the anode 11 which is not covered by dielectric 14 is oxidised, thus changing the colour of this portion to display a display item.

[0078] Again, although the dielectric and anode are schematically depicted in figure 2 as rectangles (which would result in a rectangular display item being displayed by the device), it will be understood that other shapes of dielectric and / or anode may be used as to display any desired display items (such as text or images). Specific examples of this will be described below.

[0079] The arrangements described above in figures 1 and 2 work on the principle of corrosion of the anode in order to cause a colour change. These displays may thus be considered to be “electrolytic” or “electrocorrosive” displays. In such arrangements, the anode material is a transition group element that on electro-oxidation undergoes a colour change. The electrolyte may be formulated to include a suitable counter ion that reacts with the oxidised metal ions to yield a stable salt. The electrode metal and electrolyte ions may be selected to as to ensure that spontaneous oxidation of the metal does not occur. Thus, the colour change only occurs when a voltage is applied between the cathode and anode.Figure 3 schematically depicts a further arrangement of display according to the present invention. Unlike the arrangement of figures 1 and 2, the arrangement of figure 3 is an electrochromic display.

[0080] Similarly to the arrangement of figure 1, the arrangement of figure 3 includes an anode 11, a cathode 12, a dielectric layer 14, an electrolyte layer 15, a first substrate 13a, and a second substrate 13b. That is, the anode 11 and the cathode 12 are not mounted on the same substrate. Unless stated otherwise, the description of the arrangement of figure 1 above applies equally to the arrangement of figure 3.

[0081] In addition to the layers described above in relation to figure 1, the display 30 of figure 3 includes an electrochromic layer 31. The electrochromic layer 31 is disposed between the electrolyte layer 15 and the cathode 12.

[0082] The electrochromic layer 31 includes an electrochromic material. The electrochromic material may include (or be) tungsten trioxide (WO3), poly(3,4-ethylenedioxythiophene) polystyrene sulfonate, Prussian Blue, a doped Tungsten oxide, a viologen, a polythiophene, a polyaniline, or a combination thereof.

[0083] The display device 30 of figure 3 further includes an ion storage layer 32. The ion storage layer 32 is disposed between the electrolyte layer 15 and the anode 11. In some arrangements, the ion storage layer 32 includes Prussian blue.

[0084] In the arrangements of electrochromic display of the present invention, such as that of figure 3, when a voltage is applied between the anode and the cathode, ions migrate from the ion storage layer 32, through the electrolyte layer 15, to the electrochromic layer 31. This causes a change in colour of the electrochromic layer 31. The change in colour may be due to oxidation of the electrochromic layer. In these arrangements, the dielectric layer 14 may serve to mask (or occlude) parts of one or more layers, such that colour change of the electrochromic layer 31 does not occur in regions corresponding to the locations where dielectric material is present (because electrons typically travel the shortest path between theanode and the cathode, and thus are blocked by the dielectric from reaching and changing the colour of the corresponding portions of the electrochromic layer 31). In the arrangement of figure 3, the dielectric material is disposed on the anode 11, although other arrangements are possible in which other layers (e.g. the cathode 12) alternatively or additionally have a dielectric layer disposed thereon.

[0085] In arrangements such as those of figure 3, in which an ion storage layer is present, the display of the display item is reversible (i.e. bistable), because the display can be reversed by reversing the potential difference across the electrodes, which in turn causes ions to migrate from the electrochromic layer 31, through the electrolyte layer 15, and to the ion storage layer 32. In this process, the electrochromic material is reduced, returning it to its original colour. It will be understood that in some arrangements, the initial colour change may instead be produced by reduction of the electrochromic layer, and the original colour returned (i.e. the colour change reversed) by oxidation of the electrochromic layer. The oxidation or reduction of the electrochromic layer and the concurrent reduction or oxidation of the ion storage layer can result in a colour change of the respective layers which may complement one another, thus enhancing the intensity of the displayed text or image.

[0086] In a further variation of the arrangement of figure 3, the ion storage layer 32 may be omitted. In these arrangements, ions from the electrolyte layer 15 migrate to the electrochromic layer 31 , and cause the electrochromic layer to change colour. In such arrangements, the display of the display item is irreversible (i.e. one time switchable).

[0087] The below description of the electrolyte sets out features which can be applied to any of the arrangements of figures 1-3, as well as (unless stated otherwise) the further arrangements of figures 4-14 described below.

[0088] The electrolyte may comprise one or more inorganic salts. The salt may preferably be a water soluble salt.

[0089] The inorganic salt (or salts) of the electrolyte may be a salt of chlorine, bromine or iodine. Salts of potassium, sodium, lithium, calcium or iron may be used. Examples of suitable saltsinclude sodium hydroxide, potassium hydroxide, sodium chloride, potassium bromide, lithium perchlorate, sodium iodide, and combinations thereof. The inorganic salts listed above may be particularly suitable for “one time switchable” arrangements.

[0090] The inorganic salt (or salts) of the electrolyte may be a salt of one or more of sulphur, phosphorous, arsenic, selenium or antimony. Potassium disulfite or sodium disulphite (also known as metabisulfite or pyrosulfate) may be used. The inorganic salts listed above may be particularly suitable for “bistable” arrangements.

[0091] Figures 4 and 5 depict an example arrangement of anode 11, cathode 12 and dielectric layer 14, which can be used in the display devices of the present invention.

[0092] The anode 11 is a solid anode (albeit does not extend over the full extent of the device). The cathode 12 is a metallic grid. The anode 11 and cathode 12 may be used in combination with other layers, such as in an arrangement similar to that shown in figure 1. The anode 11 is on a first substrate 13a, and the cathode 12 is on a second substrate 13b. As shown in figure 4, the first substrate 13a and second substrate 13b may be formed as a single piece, and folded about line L depicted in figure 4. This positions and spatially aligns the anode 11 and the cathode 12 in different planes to each other, and may effectively form two different substrates.

[0093] The anode 11 is divided into a plurality of portions, each of which can be separately activated so as to selectively display different display items. Although three portions are shown in figure 4, it will be understood that the anode may have only a single portion, or may also have a different number of portions.

[0094] The dielectric layer 14 shown in figure 5 may be used in combination with the electrodes shown in figure 4. It will be noted that the words “not” and “pregnant”, and the image of the flower, each line up with a different portion of anode 11 (and are located on those portions in the assembled device). The arrangement of figure 5 also has a dielectric layer which is in contact with the cathode 12 in the assembled device (i.e. the left hand portion in figure 5), although in some arrangements this portion may be omitted.When the electrodes of figure 4 are used in a display device, the metallic grid cathode 12 is on the eye side (i.e. nearest to the user when the user looks at the device) and the anode 11 is on the non-eye side (i.e. the side furthest from the user). The dielectric layer 14 is provided on both the anode 11 and the cathode 12, with the electrolyte therebetween. As described above, the combination of the shape of the dielectric (which shows the words “not pregnant” and an image of a flower) together with the anode, defines the display item. That is, the parts of the anode 11 (which has 3 sections corresponding to the word “not” the word “pregnant” and the image of the flower) has portions which are masked by the dielectric layer, stopping these portions from being oxidised and changing colour. As described above, each of the three sections of the anode may be separately activated by having an electric current (or voltage) applied thereto. This may allow selective activation of each section (so that, for example, the messages “pregnant” and “not pregnant” can be selectively displayed, and so that the flower can be used to indicate completion of the test).

[0095] It will be noted that in both figures 4 and 5, there is depicted a line L about which the components may be folded. This may allow the components to be produced as a single part, combined together (optionally with further components), and subsequently folded over in order to form the device. This process will be described in more detail below.

[0096] Figures 6 and 7 depict a further set of electrodes (i.e. anode and cathode) shown in figure 6 and dielectric layer shown in figure 7. The arrangement of figures 6 and 7 is of the type shown in figure 2, where the anode and the cathode are mounted on a single substrate 13 and are substantially coplanar with each other. Again, as shown in figure 6, the anode 11 is divided into multiple sections, with the cathode 12 being disposed around the anode 11, with small gaps (labelled G) therebetween, so as to provide electrical isolation between the anode and the cathode. In figure 7, the light coloured regions are the dielectric material, and the dark coloured regions represent areas where there is no dielectric material.

[0097] Again, in the arrangement of figures 6 and 7 the display item (in this case, the words “not” and “pregnant”, 3 rectangular bars, and a triangle) are defined by the combination of the shape of the anode 11 and the shape of the dielectric material. In particular, the shape of the anodedefines the outer boundaries of the various parts of the display item, and the dielectric material defines the inner boundary of the parts of the display item.

[0098] Figure 8 depicts a display incorporating an anode, cathode and dielectric layer, similar to those shown in figures 6 and 7 (albeit omitting the rectangular bars) before and after activation. It will be seen that the parts of the anode 11 where there is no dielectric material (corresponding to the black portions shown in figure 7) have darkened due to oxidation of the anode, so as to show the display item. Taking, for example, the letter “o”, the shape of the letter (formed by the anode where there is no dielectric material) has darkened, and the circle in the middle of the letter (which is part of the anode, with dielectric overlaid, as shown by figure 6 and 7) has not changed colour. It will be appreciated that by choosing the shape of anode and patterning the dielectric material appropriately, any shape of display item can be provided.

[0099] Figure 9 onwards show, in more detail, the configurations of possible display devices in cross-sectional view. It will be understood that the eye depicted in each of these figures represents the side of the device from which the viewer looks at the device.

[0100] Figure 9 shows a further arrangement of electrochromic display, with a similar configuration to that shown in figure 3. Description of the layers which are common with figure 3 will not be repeated.

[0101] The cathode 12 takes (partially) the form of an electrically conductive mesh (as depicted by the small squares which represent individual filaments of the mesh), which allows the electrochromic layer 31 (which is the part which changes colour when the display is activated) to be seen through the mesh. The left hand end portion of the cathode 12 (in the view shown in figure 9) is solid. It will be noted that dielectric layers 14 are provided in contact with both the anode and the cathode.

[0102] The electrochromic layer 31 may include tungsten trioxide, and the ion storage layer 32 may include Prussian blue. As explained above, the presence of these two layers may allow thedisplay item to be reversibly displayed, by oxidation and reduction of the electrochromic layer to change its colour, and to reverse the colour change, respectively.

[0103] The upper dielectric layer and the electrochromic layer 31 are patterned (i.e. do not extend the full width of the device) so as to define the display item. Likewise, the lower dielectric layer and the ion storage layer 32 are patterned.

[0104] In arrangements where the device is manufactured flat and subsequently folded to form the device, a hinge 91 (i.e. a score or fold line) may be provided.

[0105] Various adhesive portions may be provided in the device. A first adhesive portion 92 may be used to adhere the layers which come together when the device is folded during manufacture. Electrical contact between the layers may be provided by a conductive adhesive portion 93, which may be an anisotropic conductive adhesive (ACF) tape, or an anisotropically conductive adhesive paste. This connection may also be provided by direct contact between extended portions of the electrodes, or through a cured conductive adhesive. Further, an external adhesive portion 94 (including, for example, a pressure sensitive adhesive) may be provided, to allow the device to be secured to another component.

[0106] Figure 10 shows a further arrangement of electrochromic display, similar to that shown in figure 9. However, in the arrangement of figure 10, the ion storage layer is omitted. Thus, unlike the arrangement of figure 9, the arrangement of figure 10 is one time switchable. That is, once the display item has been displayed, the display of the display item is irreversible. Thus, once the electrochromic layer 31 has changed colour, by being oxidised, the colour change cannot be reversed by the electrochromic layer undergoing a reduction reaction. In such arrangements, the electrolyte may include sodium hydroxide or potassium hydroxide.

[0107] In some arrangements, such as that of figure 10, a top layer 95 may be provided, as the outermost layer of the device. This layer may be a CMYK-white layer. This may obscure the display item so that the user cannot see the display item prior to activation, but allow the display item to be seen through the CMYK-white layer once the device has been activated.The top layer 95 may also be removable (e.g. peelable or scratchable), or may be omitted altogether.

[0108] In some arrangements, such as that of figure 10, the substrate 13a may have a backing layer 96. This layer may be opaque, and may be white or have printing thereon. This layer may provide a solid colour for the rear side of the device, and may prevent light from shining through the device from the back side (which may help to prevent the user seeing the display prior to use). Such a layer may be applied to any of the arrangements described herein.

[0109] Figure 11 depicts a further arrangement of electrocorrosive display, similar to that depicted in figure 1. In other words, similarly to the arrangement of figure 1, the anode 11 and the cathode 12 are not in the same plane, and have the electrolyte layer 15 therebetween. This arrangement also has some common features with the arrangements of figures 9 and 10 (description of which will not be repeated, for conciseness). As described above, the dielectric layer in contact with the anode 11, together with the shape of the anode, defines the shape of the display item. Part of the cathode 12 takes the form of an electrically conductive mesh or grid, allowing the anode 11 and the dielectric layer 14 (and thus the display item, when the display is activated) to be seen through the mesh. This is depicted by viewing zone V (i.e. the area through which the display item can be seen). Part of the cathode 12 is a solid electrode (i.e. the left hand end in the view of figure 11). However, arrangements are possible in which the entirety of the cathode 12 is a mesh.

[0110] Figure 12 shows a further arrangement of electrocorrosive display, with a similar layout to that depicted in figure 2 (i.e. with the anode and the cathode in the same plane). This arrangement also has some common features with the arrangements of figures 9 and 10 (description of which will not be repeated, for conciseness). The anode 11 and the cathode 12 are both solid electrodes, mounted on the same substrate 13a. In this arrangement, the electrolyte bridges between the anode and the cathode, which are also separated by dielectric layer 14. The shape of the dielectric layer 14 (e.g. the edges thereof), together with the shape of the anode, define the display item. The arrangement of figure 12 also comprises an upper substrate 13b and an upper dielectric layer 14b, on the opposite side of the device (i.e. on the eye side) to the substrate on which the anode 11 and the cathode 12 are mounted. In order toallow the display item to be viewed, the upper substrate 13b and the upper dielectric layer 14b may be transparent.

[0111] In the arrangements of figures 11 and 12, the anode (which is the electrode which undergoes a colour change when the display is activated) is in the far side of the display to the “eye side”. That is, the anode is viewed through several other layers. However, arrangements are possible in which the anode is on the eye side of the display. In these arrangements, the anode may be a solid electrode, with a thickness such that when the anode is oxidised, substantially the entire thickness of the anode is oxidised (rather than only a surface portion being oxidised), allowing the display item to be seen. In some arrangements, the thickness of the anode may be 20pm or less, and in preferable arrangements, 2pm or less. Thus, the eye side electrode (i.e. the anode) need not be a mesh in these arrangements, because the display item is visible as a consequence of the electrode undergoing colour change at the anode substrate interface. In order to allow the colour change of the anode to be seen, the substrate on which the anode is mounted may be transparent. It will be understood that in these arrangements, the user cannot see the display item prior to the activation of the device, because the dieletric which partially defines the display item is on the opposite side of the anode to the user, and thus the user merely sees a solid (i.e. plain) electrode. In some arrangements, porous silver may be used to form such an electrode. Figures 13 and 14 are examples of such arrangements, with the anode and cathode being in different planes, and in the same plane, respectively.

[0112] Figure 13 shows an arrangement of display with a similar arrangement to that of figure 11 (i.e. with the anode and the cathode in different planes, with the electrolyte layer 15 therebetween). However, the positions of the anode and the cathode are swapped (relative to the eye side) such that the anode 11 is on the eye side. The anode 11 is a solid electrode, with a thickness which allows substantially the entire thickness of the anode to be oxidised when the display is activated. The dielectric 14 (which is patterned) is on the opposite side of the anode 11 to the eye side. The cathode 12 is a solid electrode rather than a conductive grid. When the display is activated and the portions of the anode which are not masked by the dielectric material are oxidised, the full thickness of the anode is oxidised, causing the colour change to be visible on the opposite side of the anode (i.e. the eye side). In this arrangement,the substrate 13a on which the anode 11 is mounted is transparent (in the viewing zone V at least) so as to allow the colour change of the anode to be seen.

[0113] Figure 14 shows a further arrangement of display device, which works on a similar principle to that of figure 13, but includes the anode and the cathode mounted on a single substrate 13a (i.e. in the same plane as each other, similarly to the arrangement of figure 12). The arrangement of figure 14 can therefore be considered to be a hybrid of the arrangements of figures 12 and 13. In this arrangement, both the anode 11 and the cathode 12 are on the eye side of the device, mounted on a transparent substrate 13a. As described above in relation to figures 6 and 7, the anode 11 and the cathode 12 are separated from each other by a small gap and by the dielectric material of the dielectric layer 14. When a voltage is applied between the anode 11 and the cathode 12, and the portions of the anode which are not masked by the dielectric material are oxidised, the full thickness of the anode is oxidised, causing the colour change to be visible on the opposite side of the anode (i.e. the eye side). A lower substrate 13b and a lower dielectric layer 14b may also be provided, on the opposite side to the transparent substrate 13a and the dielectric layer 14.

[0114] In all of the arrangement of figures 11-14, the display may either be one time switchable or bistable. Whether the display is one time switchable or bistable depends at least partially on the electrolyte used. In arrangements where the electrolyte contains chlorine, bromine, or iodine, the display may be one time switchable. Where the electrolyte contains sulphur, selenium, phosphorus, arsenic, or antinomy, the display may be bistable.

[0115] The below description may be applied to any of the arrangements of figures 1-14 set out above, unless stated otherwise.

[0116] The dielectric material may be chosen so as to match the colour of the unoxidized anode, or it may be sufficiently transparent that it does not alter the appearance of the anode material that is covered by the dielectric compared to the uncovered regions of the electrode. This may result in a uniform appearance to the viewer prior to activation, thus preventing the user from seeing the display item before the device is activated.The electrolyte may incorporate materials which scatters light through abrupt changes in refractive index. For arrangements where the electrolyte is positioned between the anode and the user’s eye, this may prevent the user from seeing the display item before the device is activated.

[0117] In some arrangements, the electrolyte may comprise one or more of potassium chloride, polyvinyl acetate, potassium hydroxide, sodium hydroxide, poly(methyl methacrylate), lithium perchlorate, and a polycarbonate.

[0118] In some arrangements, the electrolyte may comprise one or more of a thickener, a binder, a photoinitiator and a plasticizer. For example, the electrolyte may comprise one or more of acrylic acid, Carboxymethyl Cellulose Sodium Salt, 2-Hydroxy-2-methylpropiophenone, and glycerol. The acrylic acid and the 2-Hydroxy-2-methylpropiophenone (which may act as a photoinitiator) may form polyacrylic acid in the electrolyte. Glycerol may act as a plasticizer.

[0119] In some arrangements, the electrolyte is a UV curable polymer or a pressure sensitive adhesive. Where a pressure sensitive adhesive is used, the adhesive may both act as the electrolyte and adhere one or more of the layers of the device together.

[0120] In some arrangements, the anode, the cathode and the electrolyte layer are disposed in a hermetically sealed compartment. This may ensure that the electrolyte remains hydrated, in turn ensuring that ion migration occurs when a voltage is applied across the anode and cathode. The hermetic seal may be provided by laminating with a siliconized polypropylene film, folding and sealing by an adhesive, by heat sealing or by ultrasonic sealing. The compartment may be formed at the perimeter of the display device, or elsewhere.

[0121] In some arrangements, the anode may be a solid electrode. In other arrangements, the anode may comprise an electrically conductive mesh. The anode may be partially made up of a mesh and partially made up of a solid (i.e. non-mesh) material. That is, the anode may have a mesh portion and a solid portion. The mesh may be made up of openings and filaments (i.e. thin pieces defining the boundaries of the openings in the mesh). The size of the filaments and / or openings may be chosen depending on the dimensions of the display, and how far fromthe user the display is intended to be viewed. The openings may have a width from 10pm to 1000 pm (and preferably 10pm to 200 pm), and a length from 10pm to 1000 pm (and preferably 10pm to 200 pm). The filaments may have a width from 25pm to 500pm. The rate of display colour change may depend on the dimensions of the filaments and the size of the openings (i.e. the space) between them. The mesh may be uniform (i.e. have the same spacing of openings and / or filaments over its extent), or may be non-uniform (i.e. have differing spacing of openings and / or filaments over its extent). A non-uniform mesh may act to further obscure the display item behind, by using a “camouflage” type effect.

[0122] In some arrangements, the cathode may be a solid electrode. In other arrangements, the cathode may comprise an electrically conductive mesh. The anode may be partially made up of a mesh and partially made up of a solid (i.e. non-mesh) material. That is, the anode may have a mesh portion and a solid portion. The mesh may be made up of openings and filaments (i.e. thin pieces defining the boundaries of the openings in the mesh). The size of the filaments and / or openings may be chosen depending on the dimensions of the display, and how far from the user the display is intended to be viewed. The openings may have a width from 10pm to 1000 pm (and preferably 10pm to 200 pm), and a length from 10pm to 1000 pm (and preferably 10pm to 200 pm). The filaments may have a width from 25pm to 500pm. The rate of display colour change may depend on the dimensions of the filaments and the size of the openings (i.e. the space) between them. The mesh may be uniform (i.e. have the same spacing of openings and / or filaments over its extent), or may be non-uniform (i.e. have differing spacing of openings and / or filaments over its extent). A non-uniform mesh may act to further obscure the display item behind, by using a “camouflage” type effect.

[0123] In some arrangements, the mesh further comprises a colouring agent. The colouring agent may comprise one or more of graphene, carbon black, hexagonal boron nitride flakes and titanium oxide particles. The addition of flakes of these species may change the colour of the mesh without altering the conductivity of the mesh. This may aid in masking the display item prior to activation of the display, by altering the reflectivity of the mesh electrode.

[0124] One or both of the electrodes (i.e. the anode and / or the cathode) may be printed using an ink. Where the electrode comprises silver, the electrode may be printed using a silver-based ink.The ink may be formulated using an aqueous solvent or an organic solvent. The ink may not require thermal curing or annealing to become functionally conductive. An example of such an ink is described in PCT / GB2024 / 050522, the contents of which are incorporated herein by reference. The ink used for printing may comprise flakes. In some arrangements, the flakes may have a length of from 0.1 pm to 3 pm, a thickness of 0.8 nm to 200 nm, and an aspect ratio of from 5:1 to 3750:1. The flakes may comprise one or more of silver, graphene, and boron nitride. In some arrangements, the flakes may have a length of from 0.1 pm to 1 pm. The flakes may have a thickness of 10 nm to 100 nm. The flakes may also have an aspect ratio of from 10:1 to 300:1.

[0125] As described above, the transition group metal of the anode and / or the cathode may be silver. However, other transition group metals may be used. Further, the electrodes may comprise silver coated copper flakes, or silver coated non-conductive flakes.

[0126] The substrate (or where multiple substrates are present, at least one of the substrates) may take any suitable form. However, in some arrangements, the substrate may comprise a base layer and a porous layer. The base layer may comprise a polymer and be transparent. The porous layer may comprise a nanoporous material, such as nanosilica and / or nanoalumina. Such a nanoporous layer may aid in adhesion of silver based inks, where such inks are used.

[0127] Where a porous layer is present, the surface of the porous layer may have a surface roughness of 500 nm or less and / or a porosity of 30% or more. The porous layer may also have a surface roughness of 200 nm or less and / or a porosity from 30% to 80%, and / or a porosity of 50% or more, and / or a porosity of 75% or less.

[0128] In some arrangements, the substrate on the non-eye side may include an aluminium foil layer to achieve a low moisture vapour transmission rate. The substrate on the eye side may include a low MVTR transparent polymer film, such a Cyclic Olefin Co-polymer or clear biaxially orientated polypropylene.

[0129] The devices of the present invention may be manufactured by any suitable methods.

[0130] However, in some advantageous methods, some or all of the various components may beprinted. That is, at least one of the substrate, the anode, the cathode, the dielectric layer and the electrolyte layer may be printed. The printing may be carried out by flexographic printing.

[0131] For example, a display device may be manufactured by providing a substrate, printing an anode comprising a transition group metal and cathode comprising a transition group metal onto one or more substrates, printing a dielectric layer onto the anode, and printing an electrolyte layer. Such a method may produce a device corresponding to that shown in figure 1.

[0132] Where a second substrate is present (as in the arrangement of figure 1), the anode may be printed onto a first substrate, and the cathode may be printed into a second substrate.

[0133] Alternatively, the anode and the cathode may be printed onto the same substrate (and then brought into an opposing configuration, in different planes to each other by folding the substrate by a scored fold line). Any other layers (such as an electro chromic layer and / or an ion storage layer) may also be printed.

[0134] The step of providing the substrate in the manufacturing process may include positioning the substrate on a backing template. Parts of the backing template may be folded and / or selectively joined and / or and cut such that the various other layers (e.g. the anode, the cathode, the dielectric layer and the electrolyte layer, and any other layers present) are positioned between the first substrate and the second substrate. This may also result in the electrolyte layer being disposed between the anode and the cathode. Thus, the various layers of the device are printed onto a planar substrate, and then folded to form the device.

[0135] In order to bond various layers of the device together (e.g. the upper and lower substrates), one or more adhesive boundary layers may be printed prior to the printing of the other layers. This may be protected with a release liner during the rest of the manufacturing process. The release liner may then be removed later in the process, either before or after the folding of the device. The adhesive boundary layers may also provide the hermetic seal described above.Although the methods above have been described in general terms, the methods may be advantageously combined with a reel-to-reel manufacturing process. In particular, the various components (or combinations thereof) may be placed onto a roll, and may be brought together using a reel-to-reel process. For example, a plurality of housing templates may be produced on a first roll, and the components which are placed on the housing template may be produced on one or more different rolls. These may then be brought together using a reel-to-reel process so as to position the components on the housing template. The housing template may then be folded (or otherwise manoeuvred to produce the housing), either on the roll, or separately from the roll. This may allow a large number of devices to be manufactured quickly and accurately.

[0136] The manufacturing methods of the present invention may also be used to produce an article which is not a finished display, but is rather a flexible article which can be manipulated (e.g. folded and / or selectively joined and / or cut) so as to produce a display. The unfolded article may be produced in large numbers and shipped in bulk, before being folded.

[0137] The present invention may also provide a method of printing a grid (for use as the electrically conductive meshes described above, for example). Such a method may include providing a printable medium, providing a substrate, and applying the printable medium to the substrate in a grid pattern. The printable medium may be an ink. The printable medium may comprise flakes and a liquid. The flakes may comprise silver, graphene, boron nitride, or a mixture thereof. The flakes may have a length of from 0.1 pm to 3 pm, a thickness of 0.8 nm to 200 nm, and an aspect ratio of from 5: 1 to 3750: 1. The printable medium may have a viscosity in the range of 0.1 to 25 Pa-s. The substrate may comprise a porous receiving layer provided on a base layer. The porous receiving layer may have a surface roughness of 500 nm or less and / or a pore size which is 50% or less of the length of the flakes in the conductive layer. The printable medium may be applied to the substrate using a printing apparatus, such as a flexographic printing apparatus

[0138] It should be understood by those skilled in the art that while the present invention has been described with reference to exemplary embodiments, it is not limited to the disclosed exemplary embodiments. Various modifications, combinations, sub-combinations andalterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof. Features from any example or embodiment of the present disclosure can be combined with features from any other example or embodiment of the present disclosure.

Claims

CLAIMS1. A display device configured to display a display item, the device comprising:an anode comprising a transition group metal;a cathode comprising a transition group metal;a substrate, wherein the anode and / or the cathode are disposed on the substrate;a dielectric layer in contact with the anode; andan electrolyte layer disposed between the anode and the cathode, the electrolyte layer comprising an electrolyte.

2. The display device of claim 1, wherein the electrolyte layer is configured to oxidise a portion of the anode when a voltage is applied between the anode and the cathode.

3. The display device of claim 1, further comprising an electrochromic layer disposed between the electrolyte layer and the cathode, the electrochromic layer comprising an electrochromic material.

4. The display device of claim 3, wherein the electrochromic material comprises one or more of WO3, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate, Prussian Blue, a doped Tungsten oxide, a viologen, a polythiophene, a polyaniline, or a combination thereof.

5. The display device of claim 3 or 4, further comprising an ion storage layer disposed between the electrolyte layer and the anode.

6. The display device of claim 5, wherein the ion storage layer includes Prussian Blue.

7. The display device of any preceding claim, wherein the anode and the cathode are disposed on the substrate.

8. The display device of any of claims 1-6, further comprising a second substrate, wherein the anode is disposed on the first substrate and the cathode is disposed on the second substrate.

9. The display device of claim 8, wherein the first substrate and the second substrate are integrally formed.

10. The display device of any preceding claim, wherein the display item is at least partially defined by the shape of the anode.

11. The display device of any preceding claim, wherein the display item is at least partially defined by the shape of the dielectric layer.

12. The display device of any preceding claim, wherein the display item is text and / or an image.

13. The display device of any preceding claim, wherein the device is configured to reversibly display the display item.

14. The display device of any of claims 1-12, wherein the device is configured to irreversibly display the display item.

15. The display device of any preceding claim, wherein the electrolyte comprises one or more inorganic salts comprising chlorine, bromine or iodine.

16. The display device of any preceding claim, wherein the electrolyte comprises one or more inorganic salts comprising sulphur, phosphorous, arsenic, selenium or antimony.

17. The display device of any preceding claim, wherein the electrolyte comprises one or more of potassium chloride, polyvinyl acetate, potassium hydroxide, sodium hydroxide, poly(methyl methacrylate), lithium perchlorate, and a polycarbonate.

18. The display device, wherein the electrolyte comprises one or more of a thickener, a binder, a photoinitiator and a plasticizer.

19. The display device of any preceding claim, wherein the electrolyte comprises one or more of Acrylic Acid, Carboxymethyl Cellulose Sodium Salt, 2-Hydroxy-2-methylpropiophenone, and glycerol.

20. The display device of any preceding claim, wherein the electrolyte is a UV curable polymer.

21. The display device of any preceding claim, wherein the electrolyte is a pressure sensitive adhesive.

22. The display device of any preceding claim, wherein the anode, the cathode and the electrolyte layer are disposed in a hermetically sealed compartment.

23. The display device of any preceding claim, further comprising a second dielectric layer in contact with the cathode.

24. The display device of any preceding claim, wherein the anode comprises an electrically conductive mesh, preferably wherein the mesh includes openings having a width from 10pm to 1000 pm, and a length from 10pm to 1000 pm and / or filaments having a width from 25pm to 500pm.

25. The display device of any of claims 1-23, wherein the anode is a solid electrode.

26. The display device of any preceding claim, wherein the cathode comprises an electrically conductive mesh, preferably wherein the mesh includes openings having a width from 10pm to 1000 pm, and a length from 10pm to 1000 pm and / or filaments having a width from 25pm to 500pm.

27. The display device of any of claims 1-25, wherein the cathode is a solid electrode.

28. The display device of claim 24 or 26, wherein the mesh is configured to obscure the display item prior to the device being activated.

29. The display device of claim 24, 26 or 28, wherein the mesh further comprises a colouring agent, the colouring agent optionally comprising one or more of graphene, carbon black, hexagonal boron nitride flakes and titanium oxide particles.

30. The electrochromic display of any preceding claim, wherein the anode and / or the cathode comprises flakes, wherein the flakes have a length of from 0.1 pm to 3 pm, a thickness of 0.8 nm to 200 nm, and an aspect ratio of from 5:1 to 3750:1, optionally wherein the flakes comprise one or more of silver, graphene, and boron nitride.

31. The electrochromic display of claim 30, wherein the flakes have:a length of from 0.1 pm to 1 pm; and / ora thickness of 10 nm to 100 nm; and / oran aspect ratio of from 10:1 to 300:1.

32. The display device of any preceding claim, wherein the transition group metal of the anode and / or the cathode is silver.

33. The display device of any preceding claim, wherein the substrate comprises a base layer and a porous layer, optionally wherein:a. the base layer of the comprises a polymer and is transparent; and / orb. the porous layer comprises a nanoporous material, optionally nanosilica and / or nanoalumina.

34. The display of device of claim 33, wherein the surface of the porous layer has a surface roughness of 500 nm or less and / or a porosity of 30% or more, optionally wherein the porous layer has:a. a surface roughness of 200 nm or less; and / orb. a porosity from 30% to 80%; and / orb. a porosity of 50% or more; and / orc. a porosity of 75% or less.

35. The display of any preceding claim, where at least one of the substrate, the anode, the cathode, the dielectric layer and the electrolyte layer are printed.

36. A flexible article comprising:a substrate;an anode comprising a transition group metal;a cathode comprising a transition group metal;a dielectric layer; andan electrolyte layer comprising an electrolyte;wherein the flexible article is configured to be folded and / or selectively joined and / or cut such that the electrolyte layer is disposed between the anode and the cathode.

37. A method of manufacturing a display device, the method comprising:providing a substrate;printing an anode comprising a transition group metal and a cathode comprising a transition group metal onto one or more substrates;printing a dielectric layer onto the anode; andprinting an electrolyte layer.

38. The method of claim 37, wherein the anode and the cathode are printed onto the same substrate.

39. The method of claim 37, wherein the anode is printed onto a first substrate, and the cathode is printed into a second substrate.

40. The method of any of claims 37-39, wherein providing the substrate comprises positioning the substrate on a backing template;wherein the method further comprises folding and / or selectively joining and / or and cutting parts of the backing template such that the electrolyte layer is positioned between the anode and the cathode41. A method of printing a grid, the method comprising providing a printable medium, providing a substrate, and applying the printable medium to the substrate in a grid pattern, wherein:the printable medium comprises flakes and a liquid, wherein the flakes comprise silver, graphene, boron nitride, or a mixture thereof, and have a length of from 0.1 pm to 3 pm, a thickness of 0.8 nm to 200 nm, and an aspect ratio of from 5: 1 to 3750:1; and wherein the printable medium has a viscosity in the range of 0.1 to 25 Pa-s; andthe substrate comprises a porous receiving layer provided on a base layer, and the porous receiving layer has a surface roughness of 500 nm or less and / or a pore size which is 50% or less of the length of the flakes in the conductive layer;optionally wherein the printable medium is applied to the substrate using a printing apparatus, preferably a flexographic printing apparatus.

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