Display materials containing patterned areas of encapsulated electrophoretic medium - Patents.com

Abstract

A method for forming a patterned display comprising isolated portions of an encapsulated electrophoretic medium disposed between continuous light-transmitting electrodes. The resulting patterned electrophoretic display allows a viewer to see through the gaps between the portions of the encapsulated electrophoretic medium, thereby allowing the viewer to visualize a surface or object behind the electrophoretic display. The invention provides displays comprising patterned areas of electro-optic material. The electro-optic material is typically an encapsulated electrophoretic material, i.e., an electrophoretic medium encapsulated in a capsule, an array of sealed microcells, or dispersed in a polymer that is not miscible with the electrophoretic medium.

Description

[Technical field]

[0001] (Related Applications) This application claims priority to U.S. Provisional Application No. 63 / 330,751, filed April 13, 2022. All patents and patent applications disclosed herein are incorporated by reference in their entirety.

[0002] The present invention relates to the field of electrophoretic displays and color-changing materials made using an electrophoretic medium. [Background technology]

[0003] Historically, the electrophoretic display medium in electro-optic displays has been continuous, sandwiched between control electrodes. For example, if the control electrodes were also continuous, the resulting (optionally flexible) sheet material could result in complex designs that could be cut and electronically switched between optical states (e.g., E INK PRISM TM Alternatively, the continuous electrophoretic medium may span multiple electrodes, as in the case of active matrix electrophoretic display modules, in which a continuous encapsulating layer of electrophoretic medium is coated over an active matrix of pixel electrodes. Such assemblies are commonly incorporated into e-readers, such as the Amazon KINDLE®. Alternatively, a continuous encapsulating layer of electrophoretic medium may span multiple electrodes, as in the case of active matrix electrophoretic display modules, in which a continuous encapsulating layer of electrophoretic medium is coated over an active matrix of pixel electrodes. Such assemblies are commonly incorporated into e-readers, such as the Amazon KINDLE®. TM As in a display line module, it may be encapsulated in a sealed microcell and laminated to an active matrix backplane. Previously, it has not been disclosed to create segments that are intentionally isolated from one another by intentionally cutting portions of the electrophoretic medium and placing multiple electrophoretic segments that do not contact one another between the same continuous top and bottom electrodes, which are then formed into a display.

[0004] The present invention relates to electro-optical and related devices and methods for producing such devices. The invention is particularly, but not exclusively, intended for displays comprising an electrophoretic medium. The term "electro-optical" is used herein in its conventional sense in the imaging arts as applied to materials or displays or devices to refer to a material having first and second display states with different at least one optical property, which is changed from its first display state to its second display state by application of an electric field to the material. The optical property is typically a color perceptible to the human eye, but it can be another optical property such as optical transmittance, reflectance, luminescence, or, in the case of displays intended for machine reading, pseudocolor in the sense of a change in reflectance of electromagnetic wavelengths outside the visible range.

[0005] The term "gray state" is used herein in its conventional sense in the imaging arts to refer to a state intermediate between two extreme pixel optical states, and does not necessarily imply a black-white transition between these two extreme states. For example, some of E Ink's patents and published applications referenced below describe electrophoretic displays in which the extreme states are white and dark blue, such that an intermediate "gray state" would actually be light blue. In fact, as already mentioned, the change in optical state may not be a change in color at all. The terms "black" and "white" may be used hereinafter to refer to the two extreme optical states of the display, and should be understood to include extreme optical states that are not typically strictly black and white, such as the white and dark blue states mentioned above. The term "monochrome" may be used hereinafter to refer to a drive scheme that drives pixels to only their two extreme optical states, without any intervening gray states.

[0006] The terms "bistable" and "bistable" are used herein in their conventional meaning in the art to refer to a display comprising display elements having first and second display states differing in at least one optical property, such that after any given element is driven with an addressing pulse of finite duration to assume either its first or second display state, that state persists after the addressing pulse is terminated for at least several times, e.g., at least four times, the minimum duration of the addressing pulse required to change the state of the display element. In U.S. Pat. No. 7,170,670, it is shown that some particle-based electrophoretic displays capable of gray scale are stable not only in their extreme black and white states, but also in their intermediate gray states, and the same is true for some other types of electro-optic displays. This type of display is properly called "multistable" rather than bistable, but for convenience the term "bistable" may be used herein to cover both bistable and multistable displays.

[0007] Several types of electro-optic displays are known. One type of electro-optic display is the rotating dichroic member type, as described, for example, in U.S. Patent Nos. 5,808,783, 5,777,782, 5,760,761, 6,054,071, 6,055,091, 6,097,531, 6,128,124, 6,137,467, and 6,147,791 (this type of display is often referred to as a "rotating dichroic ball" display, but in some of the patents mentioned above, the rotating member is not spherical, so the term "rotating dichroic member" is preferred as it is more accurate). Such displays use a large number of small bodies (typically spherical or cylindrical) that have two or more sections with different optical properties and an internal dipole. These bodies are suspended within liquid-filled vesicles in a matrix, and the vesicles are filled with liquid so that the bodies are free to rotate. The appearance of the display is changed by applying an electric field to it, thus rotating the bodies to various positions and varying the section of the body that is seen through the viewing surface. This type of electro-optic medium is typically bistable.

[0008] Another type of electro-optic display that has been the subject of intensive research and development for many years is the particle-based electrophoretic display, in which a plurality of charged particles move through a fluid under the influence of an electric field. Electrophoretic displays can have attributes of good brightness and contrast, wide viewing angles, state bistability, and low power consumption when compared to liquid crystal displays. Nevertheless, problems with the long-term image quality of these displays have prevented their widespread use. For example, the particles that make up electrophoretic displays tend to settle, resulting in an inadequate usable life for these displays.

[0009] As described above, electrophoretic media require the presence of a fluid. In most prior art electrophoretic media, this fluid is a liquid, but electrophoretic media can be produced using gaseous fluids. See, for example, Kitamura, T., et al., "Electrical toner movement for electronic paper-like display", IDW Japan, 2001, Paper HCS1-1, and Yamaguchi, Y., et al., "Toner display using insulative particles charged triboelectrically", IDW Japan, 2001, Paper AMD4-4. See also U.S. Patent Publication No. 2005 / 0001810, European Patent Applications Nos. 1,462,847, 1,482,354, 1,484,635, 1,500,971, 1,501,194, 1,536,271, 1,542,067, 1,577,702, 1,577,703, and 1,598,694, and International Applications Nos. WO 2004 / 090626, WO 2004 / 079442, and WO 2004 / 001498. Such gas-based electrophoretic media are believed to be susceptible to the same types of problems due to particle settling as liquid-based electrophoretic media when the media is used in an orientation that allows for such settling, for example in a sign where the media is positioned in a vertical plane. Indeed, particle settling is believed to be a more severe problem in gas-based electrophoretic media than in liquid-based electrophoretic media due to the lower viscosity of the gaseous suspending fluid compared to the viscosity of a liquid, which allows for faster settling of the electrophoretic particles.

[0010] Numerous patents and applications assigned to or in the name of Massachusetts Institute of Technology (MIT), E Ink Corporation, E Ink California, LLC, and related companies describe various techniques used for encapsulation and microcell electrophoretic and other electro-optic media. Encapsulated electrophoretic media include a number of microcapsules, each of which itself includes an internal phase containing electrophoretically mobile particles in a fluid medium, and a capsule wall surrounding the internal phase. Typically, the microcapsules themselves are held in a polymeric binder to form a coherent layer that is positioned between two electrodes. In microcell electrophoretic displays, the charged particles and fluid are not encapsulated in microcapsules, but instead are held within a number of cavities formed in a carrier medium, typically a polymeric film. Techniques described in these patents and applications include the following: (a) Electrophoretic particles, fluids, and fluid additives (see, e.g., U.S. Pat. Nos. 7,002,728 and 7,679,814) (b) Microcapsules, Binders, and Encapsulation Processes (see, e.g., U.S. Pat. Nos. 6,922,276 and 7,411,719) (c) Microcell structures, wall materials, and methods of forming the microcells (see, e.g., U.S. Pat. Nos. 7,072,095 and 9,279,906). (d) Methods for filling and sealing microcells (see, e.g., U.S. Pat. Nos. 7,144,942 and 7,715,088) (e) Films and subassemblies containing electro-optical materials (see, e.g., U.S. Pat. Nos. 6,982,178 and 7,839,564) (f) backplanes, adhesive layers, and other auxiliary layers and methods used in displays (see, e.g., U.S. Pat. Nos. 7,075,703, 7,116,318, 7,535,624, 7,554,712, 7,561,324, 7,649,674, 7,733,554, 8,034,209, 8,610,988, and 9,835,925). (g) Color formation and color control (see, e.g., U.S. Pat. Nos. 7,075,502 and 7,839,564) (h) Methods for driving displays (see, e.g., U.S. Pat. Nos. 7,012,600 and 7,453,445) (i) Display applications (see, e.g., U.S. Pat. Nos. 7,312,784 and 8,009,348) (j) Non-electrophoretic displays and non-display applications of encapsulation and microcell technology, such as those described in U.S. Pat. No. 6,241,921 and U.S. Patent Application Publication No. 2015 / 0277160 (see, e.g., U.S. Pat. No. 7,615,325 and U.S. Patent Application Publication Nos. 2015 / 0005720 and 2016 / 0012710)

[0011] Many of the aforementioned patents and applications recognize that the walls surrounding the discrete microcapsules in an encapsulated electrophoretic medium may be replaced by a continuous phase, thus producing so-called polymer-dispersed electrophoretic displays, in which the electrophoretic medium comprises a plurality of discrete droplets of electrophoretic fluid and a continuous phase of polymeric material, and that the discrete droplets of electrophoretic fluid in such polymer-dispersed electrophoretic displays may be considered capsules or microcapsules even though no discrete capsule membrane is associated with each individual droplet. See, for example, the aforementioned U.S. Patent No. 6,866,760. Thus, for purposes of this application, such polymer-dispersed electrophoretic media are considered a subspecies of encapsulated electrophoretic media.

[0012] A related type of electrophoretic display is the so-called "microcell electrophoretic display." In a microcell electrophoretic display, the charged particles and fluid are not encapsulated in microcapsules, but instead are held within a number of cavities formed in a carrier medium, typically a polymeric film. See, for example, U.S. Patent Nos. 6,672,921 and 6,788,449, both assigned to SiPix Imaging, Inc.

[0013] Encapsulated or microcell electrophoretic displays typically do not suffer from the clustering and settling failure modes of conventional electrophoretic devices and offer additional advantages such as the ability to print or coat displays on a wide variety of flexible and rigid substrates. The use of the word "printing" is intended to include all forms of printing and coating, including, but not limited to, patch die coating, slot or extrusion coating, slide or cascade coating, pre-metered coating such as curtain coating, roll coating such as knife-over-roll coating, forward and reverse roll coating, gravure coating, dip coating, spray coating, meniscus coating, spin coating, brush coating, air knife coating, silk screen printing processes, electrostatic printing processes, thermal printing processes, inkjet printing processes, electrophoretic deposition, and other similar techniques. Thus, the resulting display can be flexible. Furthermore, because the display medium can be printed (using a variety of methods), the display itself can be made inexpensively.

[0014] An electro-optic display typically comprises a layer of electro-optic material and at least two other layers, one of these two layers being an electrode layer, disposed on opposite sides of the electro-optic material layer. In most such displays, both layers are electrode layers, and one or both of the electrode layers are patterned to define the pixels of the display. For example, one electrode layer may be patterned into elongated row electrodes and the other into elongated column electrodes that run at right angles to the row electrodes, the pixels being defined by the intersections of the row and column electrodes. Alternatively, and more commonly, one electrode layer has the form of a single continuous electrode and the other electrode layer is patterned into a matrix of pixel electrodes, each of which defines one pixel of the display. In another type of electro-optic display, where the display is intended for use with a separate stylus, print head, or similar movable electrode, only one of the layers adjacent to the electro-optic material layer comprises an electrode; the layer on the opposite side of the electro-optic material layer is typically a protective layer intended to prevent the movable electrode from damaging the electro-optic material layer. Summary of the Invention [Means for solving the problem]

[0015] The present invention provides displays that include patterned areas of electro-optical material. The electro-optical material is typically an encapsulated electrophoretic material, i.e., an electrophoretic medium encapsulated in a capsule, an array of sealed microcells, or dispersed in a polymer that is not miscible with the electrophoretic medium. Alternatively, the encapsulated electro-optical material may include rotating particles, liquid crystals, or electrochromic materials. Nevertheless, the patterned material can be made to change its optical state with the application of an electric field, typically created between a top transparent electrode and a bottom electrode, which may include a single electrode, or may include several (e.g., segmented) electrodes, or may include an array of pixel electrodes that are individually addressable, for example, using an array of thin film transistors (TFTs).

[0016] A method for making such a display using a double peel laminate electro-optic medium as well as stainless steel is also described.

[0017] In a first aspect, an electrophoretic display comprises a first continuous light-transmissive electrode disposed on a first light-transmissive substrate, a second continuous light-transmissive electrode disposed on a second light-transmissive substrate, a first portion of an encapsulated electrophoretic medium disposed between the first continuous light-transmissive electrode and the second continuous light-transmissive electrode, and a second portion of the encapsulated electrophoretic medium disposed between the first continuous light-transmissive electrode and the second continuous light-transmissive electrode. In the display, the first portion of the encapsulated electrophoretic medium does not contact the second portion of the encapsulated electrophoretic medium, and application of an electric field between the first continuous light-transmissive electrode and the second continuous light-transmissive electrode causes a change in the optical state of both the first portion of the encapsulated electrophoretic medium and the second portion of the encapsulated electrophoretic medium. In some embodiments, the first portion of the encapsulated electrophoretic medium includes a first type of electrophoretic particles and the second portion of the encapsulated electrophoretic medium includes the first type of electrophoretic particles. In some embodiments, a first portion of the encapsulated electrophoretic medium includes a first type of electrophoretic particles and a second portion of the encapsulated electrophoretic medium includes a second type of electrophoretic particles, the first and second types of electrophoretic particles having different optical properties. In some embodiments, both the first portion of the encapsulated electrophoretic medium and the second portion of the encapsulated electrophoretic medium include more than one type of electrophoretic particles. In some embodiments, the first portion of the encapsulated electrophoretic medium is encapsulated in microcapsules and the microcapsules are held together using a polymeric binder. In some embodiments, the microcapsules include gelatin or polyvinyl alcohol. In some embodiments, the polymeric binder includes polyurethane or acrylate. In some embodiments, the first portion of the encapsulated electrophoretic medium is encapsulated in microcells and sealed using a polymeric sealing layer. In some embodiments, the microcells include an acrylic polymer or a (meth)acrylic polymer. In some embodiments, the display further comprises a light-transmissive semi-conductive adhesive disposed between the first continuous light-transmissive electrode and the second continuous light-transmissive electrode.In some embodiments, the optically transparent semiconductive adhesive comprises a polyurethane doped with an inorganic salt. In some embodiments, the optically transparent semiconductive adhesive comprises a polyurethane doped with an inorganic salt at a concentration between 2% (wt:wt) and 0.05% (wt:wt). In some embodiments, the optically transparent semiconductive adhesive separates the first portion of the encapsulated electrophoretic medium and the second portion of the encapsulated electrophoretic medium. In some embodiments, the first portion of the encapsulated electrophoretic medium and the second portion of the encapsulated electrophoretic medium are separated by a distance of at least 5 mm when measured parallel to the first continuous optically transparent electrode and the second continuous optically transparent electrode.

[0018] In another aspect, a method of making an electrophoretic display includes providing a layer of encapsulated electrophoretic medium disposed between a first release sheet and first adhesive layer and a second release sheet and second adhesive layer; patterning the layer of encapsulated electrophoretic medium by cutting through the first release sheet, the first adhesive layer, and the layer of encapsulated electrophoretic medium to create a first portion of the encapsulated electrophoretic medium and a second portion of the encapsulated electrophoretic medium; and disposing the first portion of the encapsulated electrophoretic medium and the second portion of the encapsulated electrophoretic medium between a first continuous light-transmissive electrode disposed on a first light-transmissive substrate and a second continuous light-transmissive electrode disposed on a second light-transmissive substrate such that the first portion of the encapsulated electrophoretic medium does not contact the second portion of the encapsulated electrophoretic medium. In some embodiments, an optically transparent semiconductive adhesive is disposed between the first continuous optically transparent electrode and the second continuous optically transparent electrode, separating the first portion of the encapsulated electrophoretic medium from the second portion of the encapsulated electrophoretic medium. In some embodiments, the first portion of the encapsulated electrophoretic medium and the second portion of the encapsulated electrophoretic medium are separated by a distance of at least 5 mm as measured parallel to the first continuous optically transparent electrode and the second continuous optically transparent electrode. In some embodiments, the patterning includes cutting through the second release sheet and the second adhesive layer. In some embodiments, the patterning is performed with a laser, scissors, a knife, or a die. In some embodiments, the step of patterning further includes creating a remaining portion of the encapsulated electrophoretic medium, and the method further includes removing the remaining portion of the encapsulated electrophoretic medium from the layer of encapsulated electrophoretic medium. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 shows a side view of a double peel stack of an encapsulated electrophoretic medium.

[0020] [Diagram 2]FIG. 2 illustrates the creation of patterned features of an encapsulated electrophoretic medium by cutting completely through the dual peel stack of FIG.

[0021] [Diagram 3] 3 is a top view showing various shapes that can be cut from a single sheet of dual release laminate. In practice, the shapes can be cut very close to each other so that little of the dual release laminate is wasted.

[0022] [Figure 4] FIG. 4 shows the cut shapes after they have been removed from the double peel laminate.

[0023] [Diagram 5] FIG. 5 shows the cut feature affixed to a back conductor, in this case PET-ITO, after one of the two release layers has been removed from the patterned feature and an adhesive layer has been used to laminate the patterned feature to the back conductor.

[0024] [Figure 6] FIG. 6 shows a side view of a cutting shape affixed to a back conductor as in FIG.

[0025] [Figure 7] FIG. 7 shows a side view of FIG. 6 after the second release layer has been removed from the patterned features laminated to the back conductor.

[0026] [Figure 8] FIG. 8 illustrates a top transparent conductor coated with a doped transparent adhesive laminated to the structure of FIG.

[0027] [Figure 9]Figure 9 shows a side view of the completed patterned display including the encapsulated electrophoretic medium. Importantly, the doped transparent adhesive is not conductive enough to provide an electrical path between the top and bottom conductors. The doped transparent adhesive provides a smooth surface despite the gaps between the patterned encapsulated electrophoretic medium.

[0028] [Figure 10] FIG. 10 shows a top view of a completed patterned display including an encapsulated electrophoretic medium. In embodiments where the top and bottom conductors are light-transmitting, e.g., PET-ITO, the intervening spaces between the patterned encapsulated electrophoretic material are transparent. If the electrophoretic medium includes, for example, colored particles, the patterned areas can switch between colors. If the electrophoretic medium is of the shuttering type, the patterned display including the encapsulated electrophoretic medium can switch between a darkened state and a light-transmitting state.

[0029] [Figure 11] 11 shows an alternative embodiment of a patterned display including an encapsulated electrophoretic medium in which the bottom electrode is interrupted with a laser cut that goes only through the bottom electrode, thereby creating two independently addressable segments, each containing multiple patterned electro-optical portions. Notably, each bottom electrode requires a separate lead for control, while only a single connection is required for the top electrode, which covers both segments.

[0030] [Figure 12]12 shows an alternative method for making a patterned display containing an encapsulated electrophoretic medium. In this method, a stencil (mask) is cut corresponding to the desired patterned encapsulated electro-optic medium. The stencil is then placed over the bottom electrode and, for example, a slurry of capsules containing electrophoretic particles in a non-polar fluid is slot or bar coated over the stencil, and the stencil can be removed after coating is completed.

[0031] [Figure 13] FIG. 13 is a top view of a back conductor patterned with an encapsulated electrophoretic medium after the stencil has been removed.

[0032] [Figure 14] FIG. 14 is a side view of FIG. 13 showing that an alternative method allows for the creation of patterned capsules without the need for a second adhesive layer.

[0033] [Figure 15] Figure 15 shows the addition of a top light-transmissive electrode and substrate such as PET-ITO to the patterned assembly of Figure 13. The light-transmissive electrode layer is affixed using a doped transparent adhesive that maintains the relative positions of the patterned electro-optic medium and the top light-transmissive electrode layer.

[0034] [Figure 16] FIG. 16 shows a side view of a completed patterned display containing an encapsulated electrophoretic medium using an alternative method of processing.

[0035] [Figure 17]FIG. 17 illustrates the addition of one or more barrier layers that may be used to reduce water vapor transport into a patterned display containing an encapsulated electrophoretic medium, or to reduce damage caused by UV light, or to provide mechanical protection, or some combination thereof. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] Detailed Description The present invention describes a method for forming a patterned display including isolated portions of an encapsulated electrophoretic medium, and a patterned display including the resulting portions of the encapsulated electrophoretic medium. See, for example, FIG. 5. When the resulting portions of the encapsulated electrophoretic medium are placed between two continuous light-transmitting electrodes, a display is created that allows a viewer to see through a portion of the display while receiving information from the encapsulated electrophoretic medium portion of the display. See, for example, FIGS. 9 and 10. In addition, when the display is placed against a secondary surface or used to hide an object, areas of the display are transparent (and optionally flexible) so that the areas of the display that are transparent will take on the appearance of the surface or object behind the display. (For confirmation, a "continuous light-transmissive electrode" spans both the first and second portions of the encapsulated electrophoretic medium, with a gap between the first and second portions (see FIG. 9).) In some embodiments, portions of the encapsulated electrophoretic medium may transition between light reflecting and light transmitting (i.e., variable transmission), while in other embodiments, portions of the encapsulated electrophoretic medium may transition between light absorbing and light transmitting. The encapsulated electrophoretic medium may include one, two, three, four, or more different types of electrophoretic particles.

[0037] In one embodiment, a patterned display including an encapsulated electrophoretic medium is formed from a dual release laminate 100 of the type described in U.S. Patent No. 7,561,324 (incorporated by reference in its entirety). Such a structure is depicted in FIG. 1 , which shows a first release sheet 110, a first adhesive layer 115, a second release sheet 120, and a second adhesive layer 125. Disposed between the first release sheet 110 and first adhesive layer 115 and the second release sheet 120 and second adhesive layer 125 is a layer 130 of encapsulated electrophoretic medium. The layer 130 of encapsulated electrophoretic medium may be any of the types discussed above and may include a first type of electrophoretic particles 142 and a second type of electrophoretic particles 145 disposed in a non-polar solvent 147. In addition, it should be understood that the electrophoretic medium may include one, two, three, four, five, or six charged particles that move toward or away from the electrodes in the presence of an applied electric field. In some embodiments, the electrophoretic medium is of a shuttering type in that it has a first mode in which the pigment is distributed throughout the container (e.g., microcapsules or microcells), creating a darkened state, and a second mode in which the pigment is collected in a smaller volume, reducing the amount of transmitted light absorbed, thereby providing a light-transmitting medium. It is also possible to use the techniques described herein to include a mixture of patterned electro-optical materials, such as black and white switching media in a first portion of the encapsulated electrophoretic medium and blue and white switching media in a second portion of the encapsulated electrophoretic medium. It is also possible to mix different types of electrophoretic media, such as black and white switching patterned portions and shuttering switching portions. In some embodiments, the patterned capsules or partitioned microprocesses may additionally be colored, for example, using inkjet printing, before an additional conductive layer is adhered to the capsules. In some embodiments, different portions of the encapsulated electrophoretic medium contain the same type of electrophoretic particles. In some embodiments, different portions of the encapsulated electrophoretic medium contain different types of electrophoretic particles.

[0038] To create the encapsulated electrophoretic display of the present invention, the dual release stack 100 can be patterned to create a first portion 220 of encapsulated electrophoretic medium and a second portion 240 of encapsulated electrophoretic medium, as shown in FIG. 2. The patterning can be done, for example, with a laser, scissors, a knife, or a die, represented by a narrow wedge in FIG. 2. The patterning may completely penetrate the dual release stack 100, as shown in FIG. 2, or the patterning may only partially penetrate the dual release stack 100, which allows the second release sheet 120 and the second adhesive layer 125 to remain intact. Such precision cuts are best achieved with a laser cutting assembly that uses a wavelength absorbed by the pigments of the electrophoretic medium. Because the pigments are very dense, when the correct laser wavelength is chosen, the pigments in the electrophoretic medium layer essentially stop the laser from progressing beyond the layer 130 of encapsulated electrophoretic medium. Such a laser cutting system may include, for example, a Nd:YAG laser operating at a fundamental wavelength in the near IR. Such a laser cutting system is available from Trotec Laser, Inc. (Plymouth, Michigan).

[0039] As shown in FIG. 3, various portions of the encapsulated electrophoretic medium can be cut from a single sheet of the dual release laminate 100. One or more of the remnants 250 may be removed from the dual release laminate 100 to isolate a first portion 220 of the encapsulated electrophoretic medium and a second portion 240 of the encapsulated electrophoretic medium (and others, as appropriate), as shown in FIG. 4. When the dual release laminate 100 is cut completely through both release layers, the resulting portion of the encapsulated electrophoretic medium is essentially a double-sided sticker. In a subsequent step, the second release sheet 120 of each isolated portion can be removed and that portion of the encapsulated electrophoretic medium can be affixed to a sheet of PET-ITO, for example, using a second adhesive layer 125. The PET-ITO base thus becomes the second continuous light-transmitting electrode 310 and the second light-transmitting substrate 320 of the claimed display, as shown in FIGS. 5 and 6. In accordance with the present invention, first portion 220 of the encapsulated electrophoretic medium and second portion 240 of the encapsulated electrophoretic medium do not contact because they are separated by a gap, i.e., as shown in Figure 6. The gap between first portion 220 of the encapsulated electrophoretic medium and second portion 240 of the encapsulated electrophoretic medium is typically at least 5 mm as measured parallel to the first continuous light-transmissive electrode and the second continuous light-transmissive electrode. In some cases, the gap is larger, e.g., at least 1 cm, e.g., at least 5 cm, e.g., between 1 cm and 10 cm.

[0040] After first portion 220 of encapsulated electrophoretic medium and second portion 240 of encapsulated electrophoretic medium are positioned on second continuous light-transmitting electrode 310, first release sheet 110 can then be removed from all of the portions of encapsulated electrophoretic medium, as shown in Figure 7. First continuous light-transmitting electrode 340 and first light-transmitting substrate 350 (e.g., a second sheet of PET-ITO) are coated with light-transmitting semi-conductive adhesive 360, and the assembly of first continuous light-transmitting electrode 340, first light-transmitting substrate 350, and light-transmitting semi-conductive adhesive 360 ​​is applied to the assembly of first portion 220 of encapsulated electrophoretic medium, second portion 240 of encapsulated electrophoretic medium, second continuous light-transmitting electrode 310, and second light-transmitting substrate 320, as shown in Figure 8. The resulting electrophoretic display is shown in side profile in FIG. 9 and from above in FIG.

[0041] The optically transparent semiconductive adhesive 360 ​​can be made from several different optically transparent adhesives, such as acrylic and polyurethane, however polyurethane is typically preferred. It is important that the optically transparent semiconductive adhesive 360 ​​is sufficiently conductive that it does not create a dielectric layer between the first continuous optically transparent electrode 340 and the layer of electrophoretic medium, however it must not be sufficiently conductive so as to create a short circuit path between the first continuous optically transparent electrode 340 and the second continuous optically transparent electrode 310, particularly in the gap between the first portion 220 of the encapsulated electrophoretic medium and the second portion 240 of the encapsulated electrophoretic medium. Thus, the optically transparent semiconductive adhesive 360 ​​is typically doped with a salt or a charged polymer. The salt may be, for example, an inorganic salt, an organic salt, or a combination thereof. In one embodiment, the salt comprises potassium acetate. In alternative embodiments, the salt may include a quaternary ammonium salt, for example, a tetraalkylammonium salt such as tetrabutylammonium chloride or hexafluorophosphate. A suitable optically transparent semiconductive adhesive 360 ​​is available from Merck KGaA. The volume resistivity of the optically transparent semiconductive adhesive 360 ​​is typically less than 1×10 5~1×10 12 It is in ohms cm.

[0042] The present invention is not limited to the embodiment shown in Figures 9 and 10. There are several variations that are useful and alternative methods can be used to fabricate such displays, as described below. In one embodiment, the final assembly of the first portion 220 of the encapsulated electrophoretic medium and the second portion 240 of the encapsulated electrophoretic medium, disposed between the first continuous light-transmitting electrode 340 and the second continuous light-transmitting electrode 310, can be made to switch optical states separately, as shown in Figure 11. It is possible to use different types of lasers or knives to cut through only one of the two continuous light-transmitting electrodes, thereby dividing the display into areas that can be controlled separately with different power connections. Using this method, an assembly with, for example, eight different switching areas, each with multiple portions of the encapsulated electrophoretic medium, can be made.

[0043] An alternative method of fabricating a display of the present invention involves using a mask, template, or stencil 410 as shown in FIG. 12. In this embodiment, the starting substrate is a second continuous light-transmissive electrode 310 on a second light-transmissive substrate 320, however, a stencil 410 is placed over the light-transmissive electrode 310 and a layer 130 of encapsulated electrophoretic medium is applied over the entire stencil, for example, using a bar coating method or spray coating of the electrophoretic medium. Once the stencil is removed, the first portion 220 of the encapsulated electrophoretic medium and the second portion 240 of the encapsulated electrophoretic medium remain on the second continuous light-transmissive electrode 310 on the second light-transmissive substrate 320, very similar to the structure shown in FIG. 5, however, the structure of FIG. 13 lacks the first release sheet 110 and the first adhesive layer 115. Compare FIGS. 5 and 6 with FIGS. 13 and 14. It should be noted that this alternative method of making an electrophoretic display only works with encapsulated electrophoretic media encapsulated in microcapsules that can be coated over a stencil as a slurry or sprayed on with a spray gun (see U.S. Pat. No. 9,835,925, incorporated by reference in its entirety). As with the first method, the alternative method is completed with the addition of a first continuous light-transmitting electrode 340 and a first light-transmitting substrate 350 coated with a light-transmitting semiconductive adhesive 360, a first portion 220 of the encapsulated electrophoretic medium, a second portion 240 of the encapsulated electrophoretic medium, a second continuous light-transmitting electrode 310, and a second light-transmitting substrate 320. Compare FIG. 8 and FIG. 15. The final structure of FIG. 14 is very similar to the final structure using the first method, however, the first adhesive layer 115 is missing from FIG. 16. Compare FIG. 9 and FIG. 16. In some cases, removing the adhesive layer is optically beneficial since every layer of differential material presents a new scattering interface. In particular, the design of Figure 16 may have lower haze and better transmission when the electrophoretic medium is of the shuttering type.

[0044] The electrophoretic material layer of the present invention may comprise an electrophoretic medium. The electrophoretic medium may be compartmentalized in microcapsules or microcells. The electrophoretic material layer has a top surface, a bottom surface and a perimeter. The top surface and bottom surface are on opposite sides of the electrophoretic material layer. The top surface of the electrophoretic material layer is defined by a perimeter. The perimeter has a length and a width.

[0045] The electro-optical device of the present invention may include a first adhesive layer and / or a second adhesive layer. The first adhesive layer has an upper surface, a lower surface, and a peripheral surface. The adhesive can be made from a variety of materials, such as acrylic and polyurethane, however, polyurethane is typically preferred. The upper and lower surfaces are on opposite sides of the first adhesive layer. The term "length and width of the first adhesive layer" refers to the length and width dimensions of the upper surface of the first adhesive layer. The second adhesive layer has an upper surface, a lower surface, and a peripheral surface. The upper and lower surfaces are on opposite sides of the second adhesive layer. The term "length and width of the second adhesive layer" refers to the length and width dimensions of the upper surface of the second adhesive layer.

[0046] The electro-optical device of the present invention comprises a backplane, which may be used interchangeably with the second electrode layer. The backplane has a top surface, a bottom surface, and a perimeter surface. The top surface and the bottom surface are on opposite sides of the backplane. The term "length and width of the backplane" refers to the length and width of the top surface of the backplane.

[0047] The term "active display area" is the area of ​​the viewing surface of an electrophoretic display on which a changeable image may be displayed. A changeable image of an electrophoretic display is an image that may be created as a result of application of an electric field across the electrophoretic material layer of the electrophoretic display.

[0048] In some embodiments, the electro-optic material is an electrophoretic medium that is compartmentalized in microcapsules. Alternatively, the electrophoretic medium may be compartmentalized in microcells. The electrophoretic medium may comprise electrophoretic particles in a non-polar liquid.

[0049] For example, in some of the aforementioned E Ink patents and applications, a process for manufacturing an encapsulated electrophoretic display is described in which an encapsulated electrophoretic medium comprising microcapsules in a binder is coated onto a flexible substrate, i.e., as described above, with an indium tin oxide (ITO) or similar conductive coating or adhesive bonded to a release sheet. In some embodiments, the conductive coating is the first light-transmissive electrode layer. Drying or curing of the microcapsule / binder coating forms an electro-optic material layer that is firmly adhered to the first light-transmissive layer. Microcapsules suitable for use with the present invention may include gelatin-acacia microcapsules as described in U.S. Patent Nos. 7,230,750 and 10,983,410, both of which are incorporated by reference in their entirety. Alternative microcapsule materials include non-ionic polymers such as polyvinyl alcohol, as described in U.S. Patent Publication No. 2021 / 0191226, which is incorporated by reference in its entirety. The binder is typically cured using heat or UV light and may be crosslinked as necessary for the application. Suitable binders for use with the encapsulated electrophoretic medium include polyurethanes sold by Merck KGaA and others and acrylics sold by Sartomer (a division of Arkema) and others. Further examples of suitable binders can be found in U.S. Patent No. 9,777,201 (incorporated by reference in its entirety).

[0050] In an alternative embodiment, the encapsulated electrophoretic medium is encapsulated within a plurality of microcells. The microcells may be square, round, or polygonal, such as a honeycomb structure. The microcells are typically fabricated by micro-embossing sheets of acrylic or methacrylic sheet material, as described in U.S. Pat. No. 6,930,818 (incorporated by reference in its entirety). Each microcell includes an opening that is spanned by a polymeric sealing layer. The polymeric sealing layer may be constructed from a variety of materials, such as acrylates, methacrylates, polycarbonates, polyvinyl alcohol, cellulose, poly(N-isopropylacrylamide) (PNIPAAm), poly(lactic-co-glycolic acid) (PLGA), polyethylene, polypropylene, or polystyrene. The encapsulated electrophoretic medium within the microcells may be prepared as a double peel laminate, or the microcells may be bonded to a light-transmitting electrode layer on a light-transmitting substrate, such as PET-ITO.

[0051] The light-transmitting top (or bottom) conductive layer (electrode) may be carried on a light-transmitting substrate, which is preferably flexible in the sense that the substrate may be, for example, manually wound around a 25 mm diameter drum without permanent deformation. The substrate is typically a polymeric film and will usually have a thickness within the range of about 1 to about 25 mils (25 to 634 μm), preferably about 2 to about 10 mils (51 to 254 μm). The light-transmitting electrode may conveniently be a thin metal layer, for example, of aluminum or indium tin oxide (ITO), or may be a conductive polymer. Polyethylene terephthalate (PET) films coated with aluminum or ITO are commercially available, for example, as "aluminized Mylar" ("Mylar" is a registered trademark) from EI du Pont de Nemours & Company, Wilmington Del., and such commercial materials may be used with good results in front plane lamination. However, the optically transparent substrate need not be flexible. The optically transparent substrate can be, for example, glass or a transparent rigid polymer such as a crosslinked acrylic or another rigid optically transparent polymer.

[0052] Assembly of an electro-optical device using such a front plane laminate may be effected by removing the release sheet from the front plane laminate and contacting the backplane with the first adhesive layer under conditions effective to adhere the first adhesive layer to the backplane, thereby affixing the first adhesive layer, the electrophoretic medium, and the conductive layer to the backplane. The process is highly suitable for mass production, since the front plane laminate can typically be mass produced using roll-to-roll coating techniques and then cut into pieces of any size required for use with a specific backplane. An edge seal composition is then dispensed around the pieces to create a conductive edge seal after drying or curing of the edge seal composition. The device is typically exposed to a humidity conditioning step at a temperature and relative humidity prior to edge sealing.

[0053] The patterned display containing the encapsulated electrophoretic medium may additionally include an edge seal. The edge seal composition may include a polymer or a combination of polymers. Drying or curing the edge seal composition forms the edge seal of the device. Non-limiting examples of polymers are polyurethane, epoxy, dimethylpolysiloxane, polyacrylate, polymethacrylic acid, polycarbonate, polyvinyl chloride, polystyrene-alkylene copolymer, polyamide, polyester, polystyrene, polyethylene, polypropylene, polyisobutylene, poly(ethylene terephthalate), poly(ethylene naphthalate), ethylene-vinyl alcohol copolymer, poly(ethylene-co-norbornene), styrene-isobutylene-styrene block copolymer, and mixtures thereof. The edge seal composition may include conductive fillers such as metal particles, metal nanoparticles, metal wires, metal nanowires, metal nanofibers, conductive carbon black particles, carbon nanotubes, graphite, and combinations thereof. The edge seal composition may also include a conductive polymer. Non-limiting examples of conductive polymers are poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT-PSS), polyacetylene, polyphenylene sulfide, polyphenylene vinylene, and combinations thereof. The display of the present invention may additionally include a barrier layer 510, as shown in FIG. 17, which is typically a light-transmitting sheet that is impermeable to water (i.e., has a very low WVTR). The barrier layer may also protect against physical damage, for example, due to contact with a sharp object. Suitable barrier materials include polyethylene, polyimide, glass, and vapor-deposited ceramics such as indium tin oxide and silicon nitride. An additional layer of optically clear adhesive (OCA) may be used to adhere the barrier layer 510 to the first light-transmitting substrate 350.

[0054] It will be apparent to those skilled in the art that numerous changes and modifications may be made in the specific embodiments of the invention described above without departing from the scope of the invention, and therefore the whole of the foregoing description is intended to be interpreted in an illustrative sense, rather than a restrictive one.

Claims

1. 1. An electrophoretic display, comprising: a first continuous light-transmitting electrode (340) disposed on a first light-transmitting substrate (350); a second continuous light-transmitting electrode (310) disposed on a second light-transmitting substrate (320); a first portion (220) of an encapsulated electrophoretic medium disposed between the first continuous light-transmitting electrode (350) and the second continuous light-transmitting electrode (310); a second portion (240) of encapsulated electrophoretic medium disposed between the first continuous light-transmitting electrode and the second continuous light-transmitting electrode; Equipped with the first portion (220) of the encapsulated electrophoretic medium does not contact the second portion (240) of the encapsulated electrophoretic medium; application of an electric field between the first continuous light-transmitting electrode and the second continuous light-transmitting electrode (310) causes a change in the optical state of both the first portion (220) of the encapsulated electrophoretic medium and the second portion (240) of the encapsulated electrophoretic medium; The electrophoretic display further comprises a light-transmitting semi-electrically conductive adhesive (360) having a volume resistivity of 1×10 5 to 1×10 12 ohm-cm disposed between the first continuous light-transmitting electrode and the second continuous light-transmitting electrode.

2. 2. The electrophoretic display of claim 1, wherein the first portion of the encapsulated electrophoretic medium includes electrophoretic particles and the second portion of the encapsulated electrophoretic medium includes electrophoretic particles, and the electrophoretic particles included in the first portion of the encapsulated electrophoretic medium and the electrophoretic particles included in the second portion of the encapsulated electrophoretic medium have identical optical properties.

3. 10. The electrophoretic display of claim 1, wherein a first portion (220) of the encapsulated electrophoretic medium includes a first type of electrophoretic particles (142) and a second portion (240) of the encapsulated electrophoretic medium includes a second type of electrophoretic particles (145), the first and second types of electrophoretic particles (142, 145) having different optical properties.

4. 4. An electrophoretic display as described in any one of claims 1 to 3, wherein the first portion (220) of the encapsulated electrophoretic medium and the second portion (240) of the encapsulated electrophoretic medium both contain more than one type of electrophoretic particles (142, 145) having different optical properties.

5. 10. The electrophoretic display of claim 1, wherein the first portion of the encapsulated electrophoretic medium is encapsulated in microcapsules, the microcapsules being held together with a polymeric binder.

6. 6. The electrophoretic display of claim 5, wherein the microcapsules comprise gelatin or polyvinyl alcohol.

7. 7. The electrophoretic display of claim 6, wherein the polymeric binder comprises a polyurethane or an acrylate.

8. 10. The electrophoretic display of claim 1, wherein the first portion of the encapsulated electrophoretic medium is encapsulated within a microcell and sealed with a polymeric sealing layer.

9. 9. The electrophoretic display of claim 8, wherein the microcells comprise an acrylic or (meth)acrylic polymer.

10. The electrophoretic display of claim 1, wherein the optically transparent semi-electrically conductive adhesive (360) having a volume resistivity of 1×10 5 to 1×10 12 ohm-cm comprises polyurethane doped with an inorganic salt.

11. An electrophoretic display as described in claim 10, wherein the optically transparent semi-electrically conductive adhesive (360) having a volume resistivity of 1x105 to 1x1012 ohm-cm comprises polyurethane doped with an inorganic salt at a concentration of 2% (wt:wt) to 0.05% (wt:wt).

12. An electrophoretic display as described in claim 1, 10 or 11, wherein the optically transparent semi-electrically conductive adhesive (360) having a volume resistivity of 1x105 to 1x1012 ohm-cm separates the first portion (220) of the encapsulated electrophoretic medium and the second portion (240) of the encapsulated electrophoretic medium.

13. 2. The electrophoretic display of claim 1, wherein the first portion (220) of the encapsulated electrophoretic medium and the second portion (240) of the encapsulated electrophoretic medium are separated by a distance of at least 5 mm when measured parallel to the first continuous light-transmitting electrode and the second continuous light-transmitting electrode.

14. 1. A method of making an electrophoretic display, comprising: providing a layer (130) of encapsulated electrophoretic medium disposed between a first release sheet (110) and first adhesive layer (115) and a second release sheet (120) and second adhesive layer (125), wherein the first release sheet (110) is on the first adhesive layer (115) and the second adhesive layer (125) is on the second release sheet (120); patterning the layer of encapsulated electrophoretic medium (130) by cutting through the first release sheet (110), the first adhesive layer (115), and the layer of encapsulated electrophoretic medium (130) to create a first portion of encapsulated electrophoretic medium (220) and a second portion of encapsulated electrophoretic medium (240); disposing the first portion (220) of the encapsulated electrophoretic medium and the second portion (240) of the encapsulated electrophoretic medium between a first continuous optically transparent electrode (340) disposed on a first optically transparent substrate (350) and a second continuous optically transparent electrode (310) disposed on a second optically transparent substrate (320) (320) such that the first portion (220) of the encapsulated electrophoretic medium does not contact the second portion (240) of the encapsulated electrophoretic medium; A method comprising:

15. The method of claim 14, wherein an optically transparent semi-electrically conductive adhesive (360) having a volume resistivity of 1x105 to 1x1012 ohm-cm is disposed between the first continuous optically transparent electrode (340) and the second continuous optically transparent electrode (310), separating the first portion (220) of the encapsulated electrophoretic medium from the second portion (240) of the encapsulated electrophoretic medium.

16. 16. The method of claim 14 or 15, wherein the first portion (220) of the encapsulated electrophoretic medium and the second portion (240) of the encapsulated electrophoretic medium are separated by a distance of at least 5 mm when measured parallel to the first continuous optically transparent electrode (340) and the second continuous optically transparent electrode (310).

17. 15. The method of claim 14, wherein patterning comprises cutting through the second release sheet (120) and the second adhesive layer (125).

18. 18. The method of claim 14 or 17, wherein the patterning is performed using a laser, scissors, a knife, or a die.

19. 15. The method of claim 14, wherein the patterning step further comprises creating a remaining portion (250) of the encapsulated electrophoretic medium, and the method further comprises removing the remaining portion (250) of the encapsulated electrophoretic medium from the layer (130) of the encapsulated electrophoretic medium.

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