Laminated electro-optic display and method of manufacturing the same

Abstract

A method of forming an electrophoretic display is provided, including forming a front plane laminate having a first substrate, a first conductive layer, an electrophoretic medium layer, and an adhesive, and coating an insulating layer and a second conductive layer onto a second substrate to provide a backplane. The first substrate and the first conductive layer can be transparent, and the second substrate can include a plurality of conductors. The method can further include scribing the second substrate to provide a removable portion, laminating the front plane laminate to the backplane, removing the portion from the second substrate to provide an opening in the backplane, and filling the opening with a conductive material to provide an electrical connection between the first conductive layer and one of the plurality of conductors. Electrophoretic displays manufactured according to various methods are also provided.

Description

[0001] Cross Reference to Related Applications

[0002] This application claims the benefit of and priority to U.S. Provisional Application Serial No. 62 / 427,970, filed November 30, 2016, the contents of which are incorporated herein in their entirety. TECHNICAL FIELD

[0003] The present invention relates to laminated electro-optic displays and processes for producing electro-optic displays. More particularly, in one aspect, the present invention relates to a method of manufacturing a laminated electro-optic display to provide a top-plate connection (TPC), i.e., an electrical connection between a conductor in a backplane and a conductive layer of a frontplane laminate. BACKGROUND

[0004] The term "electro-optic" as applied to a material or a display, is used herein in its conventional meaning, that is, a material having first and second display states differing in at least one optical property, the material being changed between the two states by application of an electric field to the material. Although the optical property is usually color perceptible to the human eye, it can be another optical property, such as optical transmission, reflectance, luminescence, or, where the display is for machine reading, reflectance of electromagnetic wavelengths outside the visible range.

[0005] Several types of electro-optic display are known. One type of electro-optic display is the rotating bichromal member type, as described, for example, in U.S. Patents 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 (although this type of display is often referred to as a "rotating bichromal ball" display, the term "rotating bichromal member" is preferred as the rotating members are not necessarily spherical). Such a display uses a large number of small bodies (typically spheres or cylinders) which are suspended from suspensions within the display. Each body includes two or more portions having different light transmission properties. The bodies are suspended in pockets of liquid within the display, the liquid being present so as to allow the bodies to rotate freely. The appearance of the display is changed by applying an electric field to the display, thereby rotating the bodies to various positions and changing which portions of the bodies are seen through the viewing surface.

[0006] Another type of electro-optic display uses an electrochromic medium, for example, in the form of a nanochromic film having at least one light- absorbing layer including an electrochromic material, and a plurality of dyed regions held in proximity to the light- absorbing layer; see, for example, O'Regan, B., et al., Nature 1991, 353, 737, as well as Wood, D., Information Display, 18(3), 24 March 2002. See also Bach, U., et al., Adv. Mater., 2002, 14(11), 845. This type of nanochromic film has also been described, for example, in U.S. Patents Nos. 6,301,038, 6,870,657, and 6,950,220. This type of medium is also typically bistable.

[0007] Another type of electro-optic display is an electrowetting display, developed by Philips, and described in Hayes, R. A., et al., "Video-Speed Electronic Paper Based on Electrowetting", Nature, 425, 383-385 (2003). This type of electrowetting display can be made bistable by using a surface treatment such as described in U.S. Patent No. 7,420,549.

[0008] Another type of electro-optic display that has been the subject of intense research and development for many years is the 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 with liquid crystal displays.

[0009] Many patents and applications assigned to, or in the public domain of, the Massachusetts Institute of Technology (MIT), E Ink Corporation, E Ink California, LLC and related companies and / or individuals describe various technologies for encapsulated and microencapsulated electrophoretic and other electro-optic media. Encapsulated electrophoretic media comprise a plurality of small capsules, each of which itself comprises an internal phase and a capsule wall surrounding the internal phase, wherein the internal phase comprises electrophoretically mobile particles in a fluid medium. Typically, these capsules themselves are held in a binder to form a coherent layer positioned between two electrodes. In microencapsulated electrophoretic displays, the charged particles and fluid are not encapsulated within microcapsules, but are held in a plurality of cavities formed in a carrier medium, typically a polymeric film. The technologies described in these patents and applications include:

[0010] (a) electrophoretic particles, fluids and fluid additives; see for example U.S. Patents Nos. 7,002,728 and 7,679,814;

[0011] (b) capsules, binders and encapsulation processes; see for example U.S. Patents Nos. 6,922,276 and 7,411,719;

[0012] (c) microcell structures, wall materials and methods of forming microcells; see for example U.S. Patents Nos. 7,072,095 and 9,279,906;

[0013] (d) methods for filling and sealing microcells; see for example U.S. Patents Nos. 7,144,942 and 7,715,088;

[0014] (e) films and sub-assemblies containing electro-optic materials; see for example U.S. Patents Nos. 6,982,178 and 7,839,564;

[0015] (f) backlights for displays, adhesive layers and other auxiliary layers and methods; see for example U.S. Patents Nos. 7,116,318 and 7,535,624;

[0016] (g) color formation and color adjustment; see for example U.S. Patents Nos. 7,075,502 and 7,839,564;

[0017] (h) methods for driving displays; see for example U.S. Patents Nos. 7,012,600 and 7,453,445;

[0018] (i) applications of displays; see for example U.S. Patents Nos. 7,312,784 and 8,009,348; and

[0019] (j) non-electrophoretic displays, as described in U.S. Patents Nos. 6,241,921 and 2015 / 0277160, and applications of encapsulation and microcell technology other than displays; see for example U.S. Patent Application Publication Nos. 2015 / 0005720 and 2016 / 0012710.

[0020] Many of the aforementioned patents and applications recognize that the walls surrounding discrete microcapsules in an encapsulated electrophoretic medium can be replaced by a continuous phase, thus producing a so-called polymer-dispersed electrophoretic display, in which the electrophoretic medium comprises a plurality of discrete droplets of an electrophoretic fluid and a continuous phase of a polymeric material, and that such a polymer-dispersed electrophoretic display can be viewed as equivalent to a display in which the discrete droplets of electrophoretic fluid are surrounded by a continuous phase, even if no discrete capsule membrane is associated with each individual droplet; see for example the aforementioned U.S. Patent No. 6,866,760. Thus, for the purposes of the present application, such a polymer-dispersed electrophoretic medium can be regarded as a sub-class of an encapsulated electrophoretic medium.

[0021] Encapsulated electrophoretic displays are generally free from the aggregation and settling failure modes of conventional electrophoretic devices and provide additional benefits such as the ability to print or coat displays on a variety of flexible and rigid substrates. (The use of the word "print" is intended to include all forms of printing and coating, including but not limited to: pre-metered coating such as die coating, slot or extrusion coating, slide or curtain coating, curtain coating; roll coating such as knife over roll, forward and reverse roll coating; gravure coating; dip coating; spray coating; meniscus coating; spin coating; brushing; air knife coating; screen printing processes; electrostatic printing processes; thermal printing processes; inkjet printing processes; electrophoretic deposition (see U.S. Patent No. 7,339,715); and other like techniques.) Thus, the resulting display can be flexible. In addition, because the display medium can be printed (using a variety of methods), the display itself can be inexpensively manufactured.

[0022] Other types of electro-optic media can also be used in displays of the present application.

[0023] Electro-optic displays typically comprise a layer of electro-optic material and at least two other layers, one of which is an electrode layer. In most such displays, both layers are electrode layers, and one or both electrode layers is patterned to define pixels of the display. For example, one electrode layer can be patterned into elongate row electrodes, and the other electrode layer is patterned into elongate column electrodes extending 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 pixel electrode defining one pixel of the display. In another type of electro-optic display, intended for use with a stylus, print head or similar movable electrode separate from the display, only one of the layers adjacent the electro-optic layer includes an electrode, the layer on the opposite side of the electro-optic layer typically being a protective layer to protect the electro-optic layer from damage from the movable electrode.

[0024] The manufacture of a three-layer electro-optic display typically involves at least one lamination operation. For example, in several of the patents and applications of MIT and E Ink referred to above, a process for manufacturing an encapsulated electrophoretic display is described in which an encapsulated electrophoretic medium comprising capsules in a binder is coated onto a flexible substrate comprising an indium tin oxide (ITO) or similar conductive coating (which serves as one electrode of the final display) on a plastic film, the capsule / binder coating is dried to form a coherent layer of electrophoretic medium firmly adhered to the substrate. Separately, a backplane is prepared comprising an array of pixel electrodes and appropriate conductor arrangements to connect the pixel electrodes to drive circuitry. To form the final display, the substrate with the capsule / binder layer is laminated to the backplane using a lamination adhesive. (By replacing the backplane with a simple protective layer (e.g., a plastic film), a very similar process can be used to prepare an electrophoretic display that can be used with a stylus or similar movable electrode that can be slid over the protective layer.) In one preferred form of this process, the backplane itself is flexible and is prepared by printing the pixel electrodes and conductors on a plastic film or other flexible substrate. The obvious lamination technique for mass production of displays by this process is roll lamination using a lamination adhesive. Similar manufacturing techniques can be used with other types of electro-optic display. For example, microcell electrophoretic media or rotating bichromal member media can be laminated to a backplane in essentially the same manner as an encapsulated electrophoretic medium.

[0025] Electro-optic displays, including electrophoretic displays, can be expensive to produce; for example, the cost of a color LCD in a portable computer is often a significant fraction of the total cost of the computer. As the use of such displays expands to devices such as cellular telephones and personal digital assistants (PDAs) that are much less expensive than portable computers, the pressure to reduce the cost of such displays is great. As noted above, the ability to form a layer of electrophoretic medium on a flexible substrate by printing techniques opens up the possibility of reducing the cost of the electrophoretic component of a display by using mass production techniques such as roll-to-roll coating using commercial equipment for producing coated paper, polymeric films and similar media. However, the ability to utilize roll-to-roll coating for the mass production of electro-optic displays having a relatively large size is limited by the need for precise alignment of the front plane lamination plate and the backplane.

[0026] Thus, there is a need for improved mass production techniques relating to the manufacture of laminated electro-optic displays. SUMMARY

[0027] According to one embodiment of the present invention, a method of forming an electro-optic display is provided. The method can include forming a front plane laminate including, in order, a first substrate, a first conductive layer, an electro-optic medium layer, and an adhesive, and coating an insulating layer and a second conductive layer onto a second substrate to provide a backplane. The first substrate and the first conductive layer can be transparent, and the second substrate can include a plurality of conductors. The method can further include scribing the second substrate to provide a removable portion, laminating the front plane laminate to the backplane, removing the portion from the second substrate to provide an opening in the backplane, and filling the opening with a conductive material to provide an electrical connection between the first conductive layer and one of the plurality of conductors.

[0028] According to another embodiment of the present invention, a laminated electro-optic display is provided. The display can include a front transparent substrate, a back substrate having a plurality of conductors, and a plurality of layers between the front substrate and the back substrate. The plurality of layers can include an electro-optic medium layer, a first conductive layer between the front substrate and the electro-optic medium, and a second conductive layer between the electro-optic medium and the back substrate. The back substrate can further include a via filled with a conductive material such that at least one of the plurality of conductors is electrically connected to the first conductive layer via the conductive material.

[0029] According to yet another embodiment of the present invention, a method of forming an electro-optic display is provided. A first step of the method can include forming a front plane laminate including, in order, a first substrate, a first conductive layer, an electro-optic medium layer, and an adhesive, the first substrate and the first conductive layer being transparent. The method can further include the steps of providing a backplane including a conductor on a surface of the backplane, applying a conductive material to at least one of the conductor and the adhesive, and laminating the front plane laminate to the backplane such that the conductive material penetrates the electro-optic medium layer to provide an electrical connection between the first conductive layer and the conductor.

[0030] These and other aspects of the present invention will become evident to those skilled in the art in view of the following description. BRIEF DESCRIPTION OF DRAWINGS

[0031] The accompanying drawings, which are included to provide a further understanding of the concepts as described herein and are incorporated in and constitute a part of this application, illustrate embodiments in which:

[0032] Figure 1 is a schematic cross-section of a front plane laminate used in a process according to an embodiment of the present invention;

[0033] Figure 2A is a schematic top view of a substrate of a backplane used in a process according to an embodiment of the present invention;

[0034] Figure 2B is a backplane coated with an insulating layer Figure 2Aschematic top view of the substrate of

[0035] Figure 2C is a backplane coated with a bottom conductive layer Figure 2B schematic top view of the substrate of

[0036] Figure 2D is a backplane having exposed regions of a top conductive layer Figure 1 schematic bottom view of the front planar laminate of

[0037] Figure 3A is a schematic bottom view of a backplane laminated to a front planar laminate according to another embodiment of the application;

[0038] Figure 3B is a magnified view of a tab of the backplane of Figure 3A

[0039] Figure 3C is a magnified view of another embodiment of a tab for a backplane;

[0040] Figure 3D is a magnified view of yet another embodiment of a cutout for a backplane;

[0041] Figure 3E is a magnified view of yet another embodiment of a cutout for a backplane;

[0042] Figure 4 is a schematic cross-section along the axis I-I of the laminate of Figure 3A

[0043] Figure 5 is a schematic cross-section of the laminate of Figure 4 after removal of a tab from the backplane;

[0044] Figure 6 is a schematic cross-section of the laminate of Figure 5 after removal of a portion of the electro-optic medium;

[0045] Figure 7 is a schematic cross-section of the laminate of Figure 6 after filling the void with a conductive material;

[0046] Figure 8 is a schematic cross-section of the laminate according to another embodiment of the application after filling the void with a conductive material;

[0047] Figure 9 is a schematic cross-section of the laminate according to yet another embodiment of the application after filling the void with a conductive material; and

[0048] Figure 10 is a schematic cross-section side view of an electro-optic display manufactured according to another embodiment of the application.​​ DETAILED DESCRIPTION

[0049] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the relevant teachings. However, it will be apparent to one skilled in the art that the present teachings can be practiced without these details.

[0050] Various examples described in this section relate to methods of forming displays by non-precision lamination techniques while also allowing for small, precisely positioned top plane connections. Generally, in accordance with embodiments of the present invention, a backplane can be provided with a hole that extends through an end of a conductor formed in the backplane. After lamination, a top conductive layer of a front plane lamination can be cleaned of electro-optic medium and lamination adhesive through the hole in the backplane. This exposes the top conductive layer and allows for the installation of a conductive non-essential filler into the hole to form an electrical connection between the top conductive layer and the conductor embedded in the backplane.

[0051] Generally, with reference to the drawings, a laminated electro-optic display is provided that includes a front transparent substrate; a back substrate having a plurality of conductors; and a plurality of layers between the front substrate and the back substrate, the plurality of layers including an electro-optic medium layer, a first conductive layer between the front substrate and the electro-optic medium, and a second conductive layer between the electro-optic medium and the back substrate, wherein the back substrate includes a via filled with a conductive material such that at least one of the plurality of conductors is electrically connected to the first conductive layer via the conductive material.

[0052] Various embodiments of the present invention also include methods of forming an electro-optic display. The method includes forming a front plane lamination that includes, in order, a first substrate, a first conductive layer, an electro-optic medium layer, and an adhesive, the first substrate and the first conductive layer being transparent; coating an insulating layer and a second conductive layer onto a second substrate that includes a plurality of conductors to provide a backplane; scribing the second substrate to provide a removable portion; laminating the front plane lamination to the backplane; removing the portion from the second substrate to provide an opening in the backplane; and filling the opening with a conductive material to provide an electrical connection between the first conductive layer and one of the plurality of conductors.

[0053] The portion in the second substrate in the above method can be cut proximate to one of the conductors. The scribing step can also be performed before or after coating the second substrate with the insulating layer and the second conductive layer. The removing step can expose the electro-optic medium and the adhesive within the opening such that at least some of the electro-optic medium and the adhesive within the opening after the lamination step to expose the first conductive layer can be cleaned and / or removed. The portion of the second substrate can be cut in the form of a tab. Further, the second conductive layer can be applied to both opposing surfaces of the second substrate.

[0054] Reference will now be made in detail to the examples illustrated in the accompanying drawings and discussed below.

[0055] In Figure 1 In the following, a schematic cross-section of a front plane laminate ("FPL") 100 is provided. The FPL 100 is similar to those described in the aforementioned U.S. Patent No. 6,982,178, the contents of which are incorporated herein by reference. The FPL 100 can include, in order, a light-transmissive conductive layer; a solid state electro-optic medium layer in electrical contact with the conductive layer; an adhesive layer; and a release sheet. Typically, the light-transmissive conductive layer 104 is applied to a light-transmissive substrate 102, which is preferably flexible in the sense that the substrate can be manually wrapped around a drum having a diameter of 10 inches (254 mm), e.g., without permanent deformation.

[0056] The term "light-transmissive" as used throughout the specification and claims means that the layer so designated transmits sufficient light to enable an observer to view changes in the display state of the electro-optic medium through the layer, which will typically be viewed through the conductive layer and an adjacent substrate, if present; in the case of an electro-optic medium that displays a change in reflectivity at non-visible wavelengths, the term "light-transmissive" is of course to be interpreted as referring to transmission of the relevant non-visible wavelengths. The substrate 102 can be made of glass or a polymer film, for example, and can have a thickness of about 1 to about 25 mils (25 to 634 μm), preferably about 2 to about 10 mils (51 to 254 μm). The top conductive layer 104 can comprise a thin metal or metal oxide layer, e.g., ITO, or can be a conductive polymer, e.g., PEDOT.

[0057] A coating of electro-optic medium 106 is applied over the top conductive layer 104 so that the electro-optic medium 106 is in electrical contact with the top conductive layer 104. The electro-optic medium 106 can preferably be in the form of a reverse electrophoretic encapsulated electrophoretic medium of the type described in U.S. Patent Application 2002 / 0185378, the contents of which are incorporated herein by reference. The medium can include a dispersion medium encapsulated in a binder. The dispersion medium can contain a hydrocarbon-based liquid in which negatively charged white particles and positively charged black particles are suspended. Upon application of an electric field across the electro-optic medium 106, the white particles can move to the positive electrode and the black particles can move to the negative electrode, e.g., so that the electro-optic medium 106 appears white or black to an observer viewing the display through the substrate 102 depending on whether the top conductive layer 104 is positive or negative relative to the backplane at any point within the final display. Instead of black and / or white particles, the electro-optic medium 106 can alternatively include a plurality of colored particles, e.g., each color having a respective charge polarity and intensity.

[0058] The laminate adhesive layer 108 can be coated on the electro-optic medium layer 106, and a release layer 110 can be coated on the adhesive layer 108. The release layer 110 can be a PET film, for example, about 7 mils thick, which can be provided with any suitable release coating, such as a silicone coating. The presence of the laminate adhesive layer affects the electro-optic properties of the display. In particular, the electrical conductivity of the laminate adhesive layer affects the low temperature performance and resolution of the display. The low temperature performance of the display can be improved by increasing the electrical conductivity of the laminate adhesive layer, for example, by doping the layer with tetrabutylammonium hexafluorophosphate or other material, as described in U.S. Patent Nos. 7,012,735 and 7,173,752, the contents of which are incorporated herein by reference. A FPL can optionally include a thin second conductive layer (preferably aluminum) between the release sheet 110 and the laminate adhesive 108, which can be removed with the release sheet 110. The second conductive layer can be used to test the electro-optic medium.

[0059] The FPL can also be provided in other forms, such as the "double release sheet" described in U.S. Patent No. 7,561,324 or the "inverted front plane laminate" described in U.S. Patent No. 7,839,564, the contents of both of which are incorporated herein by reference in their entirety.

[0060] Referring now to Figures 2A to 2C , a schematic diagram of a direct drive backplane 200 is shown. Like the FPL 100, the backplane 200 can include a plurality of layers that can be flexible. The underlying substrate can be formed of an ablatable polymeric material, such as polyimide. The substrate can also include other optional layers, such as a reflective / moisture barrier layer. The backplane for use in the laminating process and laminated displays of the present invention can be manufactured using any method known to those skilled in the art, such as U.S. Patent 7,223,672, the contents of which are incorporated herein by reference.

[0061] Backplanes come in three main types: active matrix, passive matrix, and direct drive backplanes. Any type of backplane can be used in various embodiments of the present invention in order to provide top plane connections within the perimeter of the laminated panel.

[0062] For an active matrix backplane, an array of thin film transistors (TFTs) is formed on the surface of the substrate, and each transistor acts as a switch for a pixel. The TFTs are addressed by a set of narrow multiplexing electrodes (gate lines and source lines). A pixel is addressed by applying a voltage to a gate line, which turns on the TFT and allows charge from a source line to flow to the back electrode. This sets a voltage on the pixel and turns it on.

[0063] Passive matrix backplanes use a simple grid to supply charge to specific pixels on a display. The grid is formed on both the top and bottom substrates. One substrate forms the "columns" and the other substrate forms the "rows." The column or row wiring is made of a transparent conductive material, typically indium tin oxide (ITO). The rows or columns are connected to integrated circuits that control when charge is sent to a specific column or row.

[0064] In the direct drive backplane 200, the bottom substrate 202 can include electrical connectors 204 on the edge of the substrate 202 from which a plurality of conductors 206, 207, 208 extend. The conductors 206, 207, 208 can be traced onto the surface of the substrate 202 using any method known to those skilled in the art, such as an electroplating method. Of the plurality of conductors, one of the conductors 206 is used to form a top plane connection to the top conductive layer of the FPL. According to various embodiments of the present application, the conductor 206 used to form the top plane connection can include a cutout 214, which will be described in more detail below.

[0065] The substrate 202 of the direct drive backplane 200 will then be coated with an insulating layer 210, as shown in Figure 2B The insulating layer 210 is preferably made of a dielectric material, such as silicon nitride, an insulating polymer, or a cross-linkable monomer or oligomer. The insulating layer 210 is applied to cover most of the conductive material while leaving the ends of the conductors 206, 207, 208 exposed. A segmented conductive layer 212a, 212b is then applied over the conductors 207, 208 that will not form part of the top plane connection, as shown in Figure 2C The segmented conductive layer 212a, 212b is applied such that each segment is electrically connected to the corresponding conductor 207, 208, which can be accomplished by leaving areas of the insulating material 210 between the segments 212a, 212b. The conductive layer is also applied in a manner that avoids electrical connection with the conductors 206 that will form part of the top plane connection. For example, the conductive layer 212b can be applied such that a border of the insulating layer 210 will remain between the conductors 206 and the conductive layer 212b, as shown in Figure 2C

[0066] Assembly of an electro-optic display using the FPL 100 can be accomplished by removing the release sheet 110 and contacting the adhesive layer 108 with the backplane 200 under conditions effective to cause the adhesive layer 108 to adhere to the backplane 200, thereby securing the adhesive layer 108, the electro-optic medium layer 106, and the conductive top layer 104 to the backplane 200, and then cutting into pieces of any size desired for use with a particular backplane. However, reference is made to Figure 2C and 2D ​The backplate 200 and FPL 100 must be laminated so that the ends of the conductor 206 are electrically connected only to specific areas of the top conductive layer 104 exposed through the adhesive layer 108, such as... Figure 2D As shown. Previously, this was achieved by cutting or removing the FPL to expose a specific portion of the top conductive layer that would contact the corresponding conductor in the backplane. If the portion in the FPL is cut and removed before lamination to the backplane, the FPL must be precisely aligned with the backplane. This is particularly difficult for large displays, especially when manufacturing prototypes or custom displays without alignment jigs. Alignment jigs are impractical for disposable displays and may even be impossible for some oddly shaped displays. If the portion in the FPL is made after lamination, the removal process can damage the top and / or backplane conductive layers.

[0067] The process according to various embodiments of the invention overcomes the disadvantages of prior lamination techniques by utilizing a notch 214, which is etched within the periphery of the end of the conductor forming part of the top-plane connection. To produce a display module according to embodiments of the invention, the FPL must first be laminated to a backplate with the notch. The FPL can be cut larger than the final display size, and can even be a continuous sheet like a roll-to-roll process. This allows for coarse tolerances in the alignment of the FPL and the backplate, which is particularly useful for large displays. Once laminated, the display can be cut to its final size, possibly using alignment marks or pins on the backplate to precisely align the cut to the backplate. Figures 3A to 3C As shown, the cut 214 in the rear surface of the backplate 200 can form a tab or wing, allowing for easy removal of the cut 214 after the backplate is laminated to the FPL. The cut can be provided in various shapes, such as rectangular, circular, etc., and can be made using any method known to those skilled in the art for scribing the backplate material, such as laser cutting. If the backplate is made of glass, laser cutting can be used, as well as other methods, such as cutting or drilling with a diamond saw or drill bit. If a diamond saw is used, the rectangular tab can be made from two substantially parallel cuts originating from the edge of the backplate, for example... Figure 3E The tab 214 is shown. Alternatively, the cuts can converge to form a tapered tab, such as one resembling a triangle or trapezoid. In a less preferred embodiment, a hole can be drilled in the backing plate and covered with a removable cover (e.g., a sticker with an area at least as large as the opening). The removable cover will serve as a removable tab.

[0068] In another embodiment of the invention, the cut 214 may be a segmented circle and may include a groove 215 near the center of the segmented circle 214. The groove 215 may be sized to receive a tool, such as a flathead screwdriver, and the thin strip of material separating the segments of the circle 214 may be thin enough that rotating the cut 214 with a tool will cause the thin strip of material to break and allow the cut 214 to be removed from the base 202. The cut 214 may be divided into any number of segments, preferably at least two, and the groove 215 may be any shape capable of engaging with a tool. For example, the groove 215 may be cross-shaped to receive a Philips screwdriver or hexagonal to receive an Allen wrench.

[0069] The lamination of the FPL to the backplane can advantageously be achieved through vacuum lamination. Vacuum lamination effectively removes air between the two materials being laminated, thus avoiding unwanted air bubbles in the final display; such bubbles can introduce undesirable artifacts into the image produced on the display. However, vacuum laminating the two parts of an electro-optic display in this way places stringent requirements on the lamination adhesive used, especially in the case of displays using encapsulated electrophoretic media. The lamination adhesive should have sufficient adhesive strength to bond the electro-optic layer to the backplane, and in the case of encapsulated electrophoretic media, the adhesive should also have sufficient adhesive strength to mechanically hold the capsule together. The adhesive is preferably chemically compatible with all other materials in the display. If the electro-optic display is of a flexible type, the adhesive should have sufficient flexibility to prevent the introduction of defects into the display when it is bent. The lamination adhesive should have sufficient fluidity at the lamination temperature to ensure high-quality lamination. Furthermore, the lamination temperature is preferably as low as possible. Examples of useful laminating adhesives that may include an aqueous polyurethane dispersion referred to as a “TMXDI / PPO” dispersion in various embodiments of the present invention are described in U.S. Patent Application Publication No. 2005 / 0107564, the contents of which are incorporated herein by reference.

[0070] Now for reference Figures 4 to 7 The process for making a top-plane connection according to an embodiment of the present invention will now be described. Figures 4 to 7 It is along Figure 3A A partial schematic cross-section of axis II. For example... Figure 4 As shown, a cutout 214 is incorporated into the substrate 202 of the backplate before the conductor 206 is formed.

[0071] As a result of the electroplating operation that forms conductor 206, the material of conductor 206 fills the space between cutout 214 and substrate 202. Therefore, it is preferable to form cutout 214 before forming conductor 206. Figure 7It is also preferred to provide cutouts 214 in the form of tabs instead of through holes in the substrate 202 to provide backing for the FPL during the lamination process and reduce the likelihood of turfing or distortion in the surface of the FPL over the area of the through hole. The cutouts 214 can be filled with a conductive material 216, such as a conductive paste, prior to lamination. The conductive material 216 can be any conductive material known to one skilled in the art, such as silver or carbon filled epoxy. The conductive material 216 can be applied to the cutouts 214 in any manner known to one skilled in the art, such as screen printing, dispensing, or any other method of applying a conductive material to a substrate. The cutouts 214 can be filled with the conductive material 216 to increase the surface contact area of the portion of the conductor that will form the top planar connector. It is also preferred to provide cutouts 214 in the form of tabs instead of through holes in the substrate 202 to provide backing for the FPL during the lamination process and reduce the likelihood of turfing or distortion in the surface of the FPL over the area of the through hole.

[0072] After the lamination step, the cutouts 214 can be removed, as shown in Figure 5 Because the adhesive layer 108 is laminated to the substrate 202, removing the cutouts 214 will also result in the removal of sections of the adhesive layer 108. Thus, removing the cutouts 214 will complete most of the clean-up required to expose the top conductive layer 104. To expose the top conductive layer 104, a solvent can be used in a manual or automated clean-up process to expose a portion of the electro-optic medium 106 within the boundaries of the through hole, as shown in Figure 6 The solvent should be selected to dissolve the electro-optic layer without damaging the top conductive layer. The size of the cutouts should be selected so that after their removal, sufficient space is provided to allow for ease and efficiency of clean-up and to maximize the surface area for electrical contact with the overlying conductor.

[0073] Once the top conductive layer 104 is exposed, a conductive material 216 can be filled in the open space to electrically connect the conductor 206 to the top conductive layer 104, forming a top planar connection. The conductive material can be any conductive filler known to one skilled in the art, such as silver or carbon filled epoxy. In a final step, an insulating barrier (not shown) can be applied over any conductive filler by laminating or dispensing a thin layer of insulating material over an area at least as large as the area of the conductive filler on the exposed side of the backplane.

[0074] In another embodiment of the present invention, a double-sided backplane can be incorporated into the laminated panel. The double-sided backplane differs from the backplane shown in Figures 4 to 7 in that the material used to form the conductors for the top planar connections can be printed on both sides of the backplane substrate. As shown in the example of Figure 8 , the material used to form the conductors 206 has been printed on both sides of the substrate 202, so that the conductors 206 will generally cover the entire through hole formed after the cutouts are removed. The remaining steps of the top planar connection process will be the same as described above. By using a double-sided backplane, the surface area of the conductors is greater relative to the embodiment shown in Figures 4 to 7 . This allows for more connection surface area between the conductors in the backplane and the conductive filler material that will be dispensed into the plated through holes.

[0075] Like the single-sided backplane, the double-sided backplane can be produced by known PCB or flexible PCB technology and by silk screening. An additional silk screening step, in which a conductor material is applied to the bottom side of the substrate around the cutout, will add an additional area for top plane connections, improving overall display reliability.

[0076] Figure 9 Another embodiment including a double-sided backplane is shown in FIG. 12. For certain configurations of silk screened backplanes, the via created by removing the cutout to form a top plane connection can not be the ideal size such that it can simultaneously function as a conductive via. Figure 9 The embodiment shown in FIG. 12 provides two separate paths through the substrate 202 for the conductor 206, one conductive via 220 silk screened on both sides of the substrate 202 and covered with an insulating layer 210, and one via filled with a conductive material 216 to form a top plane connection between the conductor 206 and the top conductive layer 104. In this embodiment, the laminate can include multiple vias to ensure connectivity between the silk screened conductors on either side of the backplane substrate, and a conductive layer on the via wall for the top plane connection is not necessary.

[0077] In yet another embodiment of the present application, an electro-optic display can be manufactured according to a process in which a FPL is laminated to a backplane after a conductive material is applied to an adhesive layer of the FPL positioned on the backplane.

[0078] For example, referring to FIG. 11, Figure 10 A conductive material 1180 can first be applied to one of the plurality of conductors 1140, 1160 positioned on the surface of a substrate 1120 forming a backplane. The backplane can then be laminated to a FPL, the FPL in turn including a light-transmissive substrate 102 (e.g., PET), a light-transmissive conductive layer 1040 (e.g., ITO), an electro-optic medium layer 1060, and a layer of lamination adhesive 1080. The lamination step is performed such that the conductive material 1180 penetrates the electro-optic medium layer 1060 to provide an electrical connection between the conductor 1160 and the conductive layer 1040, thereby forming a TPC.

[0079] Preferably, the conductive material 1180 contacts both the conductive layer 1040 and the conductor 1160 after lamination. However, if the conductivity of the conductive material 1180 is sufficiently high, the conductive material 1180 in close proximity to but not in contact with one or both of the conductive layer 1040 and the conductor 1160 can still provide a TPC.

[0080] As mentioned above, the conductive material 1180 can alternatively be applied to the layer of lamination adhesive 1080 prior to the lamination step. However, it is preferred that the conductive material 1180 be applied to the conductor 1160 positioned on the backplane to avoid potential misalignment of the TPC after lamination.

[0081] The conductive material can include various materials known to those skilled in the art. For example, the conductive material can include conductive particles of carbon or non- reactive metals, such as gold, and / or anisotropic epoxy conductors. The average particle size of the conductive particles is preferably 50 microns. The anisotropic epoxy material can preferably be cast into a specific shape prior to lamination, before being applied to the backplane or FPL. The shape can be designed to facilitate penetration of the electro-optic medium layer. During high temperature lamination, the epoxy can remain rigid enough to replace inks and adhesives, but deform as the lamination rollers press the FPL and backplane together.

[0082] Accordingly, various embodiments of the present application simplify the production of custom large area displays where alignment jigs and other equipment cannot be used for precision alignment lamination. It can also use continuous roll of FPL and backplane for roll-to-roll production of displays. Because the area of the exposed top conductive layer is relatively large, the electrical connection between the top conductive layer and the backplane will be robust and reliable. For architectural applications of electro-optic displays that require large and sometimes unique footprint areas, small batch orders can be done with high yield, especially in applications where the TPC cannot be hidden behind a bezel or frame and must be small. In these applications, small TPCs provided using the process according to various embodiments of the present application can be highly desirable.

[0083] While the preferred embodiments of the application have been shown and described herein, it is to be understood that these embodiments are merely exemplary of the principles of the application. Numerous variations, changes and substitutions will occur to those skilled in the art without departing from the spirit of the application. Therefore, the appended claims are intended to cover all such variations as fall within the spirit and scope of the application.

Claims

1. An electro-optical device, comprising: a front transparent substrate; a back substrate having a plurality of conductors; a light-transmissive conductive layer coupled to the front transparent substrate; a back conductive layer coupled to the back substrate; an insulating layer adjacent to the back substrate; and a top planar connection material disposed in a via through the back substrate such that at least one of the plurality of conductors is electrically connected to the light-transmissive conductive layer through the top planar connection material, and the at least one of the plurality of conductors is separated from the back conductive layer by the insulating layer such that no electrical connection is made to the back conductive layer. The via also passes through the insulating layer.

2. The electro-optical device of claim 1, wherein, The insulating layer surrounds the top planar connection material and forms a boundary with the back conductive layer.

3. The electro-optical device of claim 2, wherein, The electro-optical device comprises an electrophoretic medium.

4. The electro-optical device of claim 1, wherein, The electro-optical device is an electro-wetting device.

5. The electro-optical device of claim 1, wherein, The insulating layer comprises a dielectric material.

6. The electro-optical device of claim 1, wherein, The dielectric material comprises silicon nitride, an insulating polymer, a cross-linkable monomer, or a cross-linkable oligomer.

7. The electro-optical device of claim 6, wherein, The via is formed with a laser, a drill bit, or a diamond saw.

8. The electro-optical device of claim 1, wherein, The via is a slot cut at an edge of the back substrate.

9. The electro-optical device of claim 1, wherein, The top planar connection material comprises silver or carbon-filled epoxy.

10. The electro-optical device of claim 1, wherein, 11. A method of establishing a top planar connection in an electro-optical device, the method comprising: providing a front transparent substrate having a light-transmissive conductive layer coupled thereto; providing a back substrate having a plurality of conductors, and a separate back conductive layer coupled to the back substrate; disposing an insulating layer between the front transparent substrate and the back substrate; cutting a hole through the back substrate to provide a conductive path between at least one of the plurality of conductors and the light-transmissive conductive layer; and filling the hole with a top planar connection material to establish an electrical connection between the at least one of the plurality of conductors and the light-transmissive conductive layer, separating at least one of the plurality of conductors from the back conductive layer by the insulating layer such that no electrical connection is established between the back conductive layer and the light-transmissive conductive layer. The hole passes through the insulating layer.

12. The method of claim 11, wherein, The insulating layer surrounds the top planar connection material and forms a boundary with the back conductive layer.

13. The method of claim 12, wherein, The electro-optical device comprises an electrophoretic medium.

14. The method of claim 11, wherein, The electro-optical device is an electro-wetting device.

15. The method of claim 11, wherein, The hole is cut with a laser, a drill bit, or a diamond saw.

16. The method of claim 11, wherein, The cutting comprises establishing a slot cut at an edge of the back substrate.

17. The method of claim 11, wherein, The top planar connection material is silver or carbon-filled epoxy.

18. The method of claim 11, wherein, ​

Images