HK1171815B - Electro-optic displays, and materials and testing methods therefor - Google Patents

Description

Electro-optic displays, materials therefor and methods of testing same

The application is a divisional application of Chinese patent application with application number 200880104642.9, title "electro-optic display and its material and testing method", filed on 26.6.2008.

Technical Field

The present application relates to:

(a) U.S. Pat. Nos. 6,982,178;

(b) U.S. patent publication nos. 2004/0155857;

(c) U.S. patent nos. 7,110,164;

(d) U.S. patent nos. 7,075,703;

(e) U.S. patent publication nos. 2007/0109219;

(f) U.S. patent publication nos. 2007/0152956; and

(g) U.S. patent publication No. 2008/0057252.

This invention relates to electro-optic displays and to materials and methods for manufacturing and testing such displays. The invention is particularly, but not exclusively, intended for use in displays containing encapsulated electrophoretic media. The invention may, however, also be used with various other types of solid electro-optic media, by solid being meant a solid in the sense that they have a solid outer surface, although the media may and typically do have an internal cavity containing a fluid (liquid or gas). Accordingly, the term "solid state electro-optic display" includes encapsulated electrophoretic displays, encapsulated liquid crystal displays, and other types of displays discussed below.

Background

An electro-optic display comprises a layer of electro-optic material, which term is used herein in its conventional sense in the imaging arts to refer to a material having first and second display states differing in at least one optical property, the material being transitioned from its first display state to its second display state by application of an electric field to the material.

The terms "bistable" and "bistability" are used herein in their conventional sense in the art to refer to displays comprising display elements having first and second display states differing in at least one optical property such that, after any given element is driven to assume either its first or second display state by an addressing pulse of finite duration, that state will last at least several times, for example at least four times, the minimum duration of the addressing pulse required to change the state of that display element after the addressing pulse has terminated.

Several types of electro-optic displays are known, for example:

(a) rotating bichromal member displays (see, e.g., U.S. Pat. Nos. 5,808,783; 5,777,782; 5,760,761; 6,054,0716,055,091; 6,097,531; 6,128,124; 6,137,467 and 6,147,791);

(b) electrochromic displays (see, e.g., O' Regan, B. et al, Nature 1991, 353, 737; Wood, D., Information Display, 18(3), 24 (3.2002); Bach, U. et al, adv. Mater., 2002, 14(11), 845; and U.S. Pat. Nos. 6,301,038, 6,870.657 and 6,950,220);

(c) electrowetting displays (see Hayes, r.a. et al, "Video-Speed electronic paper based on Electro wetting" ("Video high Speed electronic paper based on electrowetting technology"), Nature, 425, 383-;

(d) particle-based electrophoretic displays in which a plurality of charged particles are passed through a fluid under the influence of an electric field. (see U.S. Pat. Nos. 5,930,026; 5,961,804; 6,017,584; 6,067,185; 6,118,426; 6,120,588; 6,120,839; 6,124,851; 6,130,773 and 6,130,774; U.S. patent application publication Nos. 2002/0060321; 2002/0090980; 2003/0011560; 2003/0102858; 2003/0151702; 2003/0222315; 2004/0014265; 2004/0075634; 2004/0094422; 2004/0105036; 2005/0062714 and 2005/0270261; and International application publication No. WO 00/38000; WO 00/36560; WO 00/67110 and WO 01/07961; and European patent No.1,099,207B1; and 1,145,072B 1; and patents and applications of the aforementioned U.S. Pat. No.7,012,600, other institute of Martensins (EIMIT) and Yingke (EInk) companies).

There are several different variations of electrophoretic media. The electrophoretic medium may use a liquid or gaseous fluid; see, for gaseous fluids, for example, Kitamura, T.et al, "Electrical Toner movement for electronic Paper-like display" ("movement of electronic Toner in electronic Paper-like display"), IDWJapan, 2001, Paper HCS1-1 and Yamaguchi, Y.et al, "Toner display using triboelectrically charged insulating particles" ("Toner display using triboelectrically charged insulating particles"), IDW Japan, 2001, Paper AMD 4-4); U.S. patent publication nos. 2005/0001810; european patent application 1,462,847; 1,482,354, respectively; 1,484,635, respectively; 1,500,971, respectively; 1,501,194, respectively; 1,536,271, respectively; 1,542,067, respectively; 1,577,702, respectively; 1,577,703 and 1,598,694; and international application WO 2004/090626; WO 2004/079442 and WO 2004/001498. The medium may be encapsulated and comprise a plurality of capsules, each of which itself comprises an internal phase comprising electrophoretically mobile particles suspended in a liquid suspending medium, and a capsule wall surrounding the internal phase. Typically, the capsules themselves are held in a polymeric binder to form an adhesive layer between two electrodes; see the aforementioned patents and applications for MIT and EInk. Alternatively, the walls surrounding the separate microcapsules in the encapsulated electrophoretic medium may be replaced with a continuous phase, thus producing a so-called polymer-dispersed electrophoretic display, in which the electrophoretic medium comprises a plurality of separate droplets of an electrophoretic fluid and a continuous phase of a polymeric material; see, for example, U.S. patent No.6,866,760. For the purposes of this application, such polymer-dispersed electrophoretic media are considered to be a subclass of encapsulated electrophoretic media. Another variation is the so-called "microcell electrophoretic display" in which charged particles and a fluid are held within a plurality of cavities formed within a carrier medium, typically a polymer film, see, for example, U.S. patent nos. 6,672,921 and 6,788,449.

Electrophoretic media may operate in a "shutter mode" in which one display state is substantially non-transmissive and one display state is light-transmissive. See, for example, U.S. Pat. Nos. 6,130,774 and 6,172,798, and U.S. Pat. Nos. 5,872,552, 6,144,361, 6,271,823, 6,225,971, and 6,184,856. Dielectrophoretic displays can operate in a similar mode; see U.S. patent No.4,418,346. Other types of electro-optic displays can also operate in the shutter mode.

Other types of electro-optic materials may also be used in the displays of the present invention.

Most prior art processes for manufacturing electrophoretic displays are essentially batch processes in which the electro-optic medium, the laminating adhesive and the backplane are only combined just before final assembly, and it is therefore desirable to provide a process that is more suitable for mass production.

The aforementioned U.S. patent No.6,982,178 describes a method of assembling a solid state electro-optic display (including particle-based encapsulated electrophoretic displays) that is well suited for mass production. This patent essentially describes a so-called "front plane laminate" (FPL) comprising, in sequence, a light-transmissive electrically conductive layer, a layer of solid electro-optic medium in electrical contact with the electrically conductive layer, a layer of adhesive and a release sheet. Typically, the light-transmissive electrically-conductive layer is carried by a light-transmissive substrate, which is preferably flexible in the sense that the substrate can be manually wound around, say, a 10 inch (254 mm) diameter column without permanent deformation. The term "light transmissive" as used herein and throughout this patent indicates that the layer so designated is capable of passing sufficient light to enable a viewer to see through the layer to observe changes in the display state of the electro-optic medium, typically as viewed through the conductive layer and the adjacent substrate, if any. Where the electro-optic medium exhibits a change in reflectivity at non-visible wavelengths, the term "light transmissive" should of course be construed to mean transmission at the relevant non-visible wavelengths. Typically, the substrate is a polymer film, and typically has a thickness in 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 conductive layer is conventionally a thin metal or metal oxide layer such as aluminum or ITO, or may be a conductive polymer. Polyethylene terephthalate (PET) films coated with aluminum or ITO are commercially available, for example from dupont de Nemours & Company, wilmington de, wilmington, of wilmington, tera, and such commercially available materials can be used and have good effect in the front plane laminate. When a very flexible front plane laminate is desired for use in a flexible display, ITO coated polymer films having a thickness of about 0.5-1 mil (13-25 μm) are commercially available and can be coated with electro-optic materials.

The aforementioned U.S. patent No.6,982,178 also describes a first method for testing the electro-optic medium in the front plane laminate prior to introducing the front plane laminate into the display. In the test method a release plate is provided with a conductive layer and a voltage sufficient to change the optical state of the electro-optical medium is applied between the conductive layer and the conductive layer on the opposite side of the electro-optical medium. Observation of the electro-optic medium subsequently reveals any imperfections in the medium avoids the ultimate cost of laminating a defective electro-optic medium into the display and discarding the entire display rather than just the defective front plane laminate.

The aforementioned U.S. Pat. No.2004/0155857 describes a so-called "double release plate" which is essentially a simplified version of the front plane laminate of the aforementioned U.S. Pat. No.6,982,178. One form of dual release sheet comprises a layer of solid electro-optic medium sandwiched between two adhesive layers, one or both of which are covered by a release sheet. Another form of dual release layer comprises a layer of solid electro-optic medium sandwiched between two release plates. Both forms of the dual release film are intended for use in a process generally similar to that already described for assembling an electro-optic display from a front planar laminate, but which includes two separate laminates. Typically, the dual release sheet is laminated to the front electrode in a first lamination to form a front sub-assembly, and then the front sub-assembly is laminated to the backplane in a second lamination to form the final display, although the order of the two laminations can be reversed if desired.

The aforementioned No.2007/0109219 describes a so-called "inverted front plane stack", which is a variation of the front plane stack described in the aforementioned U.S. patent No.6,982,178. The inverted front plane stack sequentially comprises: at least one of a light-transmissive protective layer and a light-transmissive electrically-conductive layer, an adhesive layer, a layer of solid electro-optic medium, and a release sheet. The inverted front plane laminate is used to form an electro-optic display having a laminate adhesive layer between the electro-optic layer and a front electrode or front substrate; there may or may not be a second, typically very thin, adhesive layer between the electro-optic layer and the backplane. Such electro-optic displays have both good definition and low temperature performance.

The aforementioned No.2008/0057252 also describes various methods designed for the mass production of electro-optic displays using an inverted front plane laminate. The preferred form of these methods is a "multiple up" method designed to allow simultaneous lamination of components for multiple electro-optic displays.

The aforementioned U.S. patent No.6,982,178 also describes a method for forming an electrical connection between a backplane laminated by the front plane stack and a light-transmissive conductive layer in the front plane stack (such a connection is required because the circuitry for controlling the voltage applied to the pixel electrodes also typically controls the voltage applied to the front electrodes). As shown in fig. 21 and 22 of that patent, the formation of the layers of electro-optic medium in the front plane laminate may be controlled so as to leave uncoated areas ("slots") in which there is no layer of electro-optic medium, and some of these uncoated areas may subsequently be used to form the required electrical connections. However, this method for forming the connections is undesirable from a manufacturing perspective, as the arrangement of the connections is of course a function of the backplane design, such that FPLs coated with a particular arrangement of slots can only be used with one or a limited range of backplanes, but for economic reasons it is desirable to produce only one form of FPL that can be used with any backplane.

Accordingly, the aforementioned U.S. Pat. No.6,982,178 also describes a method of forming the required electrical connections by coating the electro-optic medium over the entire FPL area and then removing the electro-optic medium where it is desired to form the electrical connections. However, this removal of the electro-optic medium has its own problems, especially when the FPL is formed by coating a thin (less than about 25 μm) polymer film. Typically, the electro-optic medium must be removed by using a solvent or mechanical cleaning, both of which may damage or remove the conductive layer of the FPL (which is typically a metal oxide layer, such as indium tin oxide having a thickness of less than 1 μm) such that the electrical connection is unsuccessful. In extreme cases, damage to the front substrate (typically a polymer film) used to support and mechanically protect the conductive layer may also be caused. In some cases, it is not easy to solvate the materials forming the electro-optic medium, and it may not be possible to remove them without using corrosive solvents and/or high mechanical pressure, which may exacerbate the aforementioned problems.

Similar methods employing selective coating and/or selective removal of the electro-optic medium may also be applied to the aforementioned dual release film and inverted front plane laminate.

It is common practice to use laser cutting to separate pieces of FPL of the appropriate size for lamination to the respective back sheet from a continuous sheet. Such laser cutting may also be used to prepare areas for electrical connection to the backplane by "kiss cutting" the FPL with a laser from the side of the lamination adhesive so that the lamination adhesive and the electro-optic medium are removed from the connection areas, but the conductive layer is not removed. Such kiss cutting requires precise control of both laser power and cutting speed if the thin and relatively fragile conductive layer is not removed or damaged. In addition, bending the conductive layer and the associated front substrate may break the conductive layer depending on the location of the connection, resulting in an inability to make a suitable connection between the backplate and the conductive layer, and thus an inability to display.

The aforementioned No.2007/0211331 describes a method of forming an electrical connection to the conductive layer of the front plane stack. This application describes a first process for manufacturing a front plane laminate comprising forming a subassembly comprising a layer of laminating adhesive and a layer of electro-optic medium; forming a hole through the subassembly; and then securing a light-transmissive electrode layer extending through the aperture to the exposed surface of the laminating adhesive. The resulting FPL has precut holes through the electro-optic medium and the adhesive layer that facilitate contact with the electrode layer.

The aforementioned No.2007/0211331 also describes a second method for manufacturing a front plane laminate comprising forming a subassembly comprising a layer of laminating adhesive and a layer of electro-optic medium; and subsequently securing a light-transmissive electrode layer to the exposed surface of the lamination adhesive, the electrode layer having a protruding portion extending beyond the perimeter of the lamination adhesive and the layer of electro-optic medium.

Disclosure of Invention

One aspect of the present invention relates to an alternative method for forming electrical connections to the conductive layers of the front plane stack, which is substantially similar to those features described in the aforementioned No.2007/0211331, but does not require the formation of holes through the electro-optic layer or the provision of projections on the electrode layers.

A second aspect of the present invention is directed to reducing the problems experienced in prior art pre-test planar stacks and similar structures. The first test method for front plane lamination described in the aforementioned U.S. patent No.6,982,178 obviously requires making electrical contact to the light-transmissive conductive layer and the conductive layer of the release sheet. The contact to the light-transmissive electrically conductive layer (so-called "top-side connection") can be made as described in the aforementioned No.2007/0211331 by providing pre-cut through-holes through the electro-optic medium and any adhesive layer between the electro-optic medium and the light-transmissive electrically conductive layer. Contact with the conductive layer of the release plate may be achieved by providing a portion of the release plate that extends outwardly beyond the residual layer of the front plane laminate over which extent the conductive layer is exposed.

A typical prior art front plane laminate of this type (generally designated P100) is illustrated in fig. 1 and 2, where fig. 1 is a top view of the front plane laminate and fig. 2 is a schematic cross-section through one of the inspection tabs shown in fig. 1. The FPL P100 has a rectangular main portion P102 and two inspection tabs, each indicated generally as P104; each projection P104 has an inner portion P104A adjacent main portion P102, and an outer portion P104B.

As shown in FIG. 2, the FPL P100 includes several different layers, in the order (viewed) from the top surface of the FPL:

(a) a mask P106 to protect the underlying layers and remove the final display before it is placed in use;

(b) an optically clear adhesive layer P108;

(c) a PET layer P110 serving as a support and protection layer for the support;

(d) a light-transmitting electrode layer P112 formed of Indium Tin Oxide (ITO);

(e) an electro-optical layer P114, illustrated as an encapsulated electrophoretic layer;

(f) a laminating adhesive layer P116;

(g) a conductive aluminum coating P118 consisting of

(h) Supported by a polymer film P120 which, together with the aluminum coating P118, forms a conductive release sheet.

All of the foregoing layers extend through the main portion P102 and the inner portion P104A of each projection P104. However, as shown in fig. 2, only the aluminum coating P118 and the polymer film P120 are present in the outer portion P104B of each projection P104 so that the upper surface of the aluminum coating is exposed in each outer portion P104 (as shown in fig. 2) to enable electrical contact to be made with the coating. To enable contact to be made with the ITO layer P112, each inner protrusion P104A is provided with a top surface connection hole P122 (shown in fig. 2) extending from the lower surface of the FPL P100 through the polymer layer P120, the aluminum coating P118, the adhesive layer P116 and the electro-optic layer P114. The printed silver layer P124 is covered on the portion of the ITO layer P112 exposed through the hole 122, and the silver layer P124 serves to reduce the risk of damaging the relatively fragile ITO layer P112 when electrically contacting the ITO layer P112 with a probe (the silver layer P124 is made by printing silver ink onto the ITO layer P112 supported on the PET layer P110 before the electro-optical layer P114 is coated onto the ITO layer P112).

By contacting the exposed surfaces of the aluminum coating layer P118 and the silver layer P124 with a probe, an FPLP100 having dimensions corresponding to a single display can be tested by the first test method described in the aforementioned U.S. patent No.6,982,178. Subsequent removal of the release sheet, including polymer layer P120 and aluminum coating P118, removes outer ledge P104B, leaving inner ledge P104A, and their holes P122 available to serve as top surface connections in the final display.

The prior art FPL structure shown in FIGS. 1 and 2 provides good results for relatively thick FPLs, such as described in the aforementioned U.S. Pat. No.6,982,178, which is based on a PET layer P110 having a thickness of about 5 mils (127 μm). However, when the prior art FPL structure shown in fig. 1 and 2 is based on a PET layer with a thickness of about 1 mil (25 μm), there is a risk of mechanical damage to the hole P122 or adjacent portions of the silver layer P124 and the ITO layer P112, and because in this structure the hole P122 is used for testing purposes and as a top surface connection in the final display, damage to either the hole or the adjacent conductive layer during testing can affect the performance of the final display.

The structures shown in fig. 1 and 2 have other disadvantages. As described in the aforementioned U.S. patent No.6,982,178, FPLs are typically prepared by coating an electro-optic layer on a polymer film that has been coated with ITO (such ITO-coated films are commercially available); if a silver layer P124 is present, this layer is applied before the electro-optical layer is applied. In addition, an adhesive layer P116 is coated onto a conductive release sheet comprising an aluminum layer P118 and a polymer layer P120, and the resulting adhesive subassembly on the release sheet is laminated to the electro-optic layer, typically under heat and pressure. It has heretofore been desirable to perform this process on material in the form of a thin strip or large sheet, and only after the FPL is prepared, to cut it into pieces suitable for use in forming individual displays.

If the structures shown in fig. 1 and 2 are to be made in this way, it is also necessary to cut the electro-layer on PET and the adhesive on the release sheet separately before laminating them together and then to laminate them, keeping a fine alignment to ensure that the aluminium layer is still exposed on the small outer protrusion P104B, or to cut a piece of laminated FPL into the shape shown in fig. 1 and then to remove the layers P106 to P116 from the outer protrusion P104B. In either case, the hole P122 also needs to be formed. In practice, the laminated FPL is cut into the shape shown in fig. 1, and laser "kiss" cuts are used from both sides of the FPL, both to remove unwanted layers from the outer protrusion P104B and to form the holes 122. Such laser cutting may damage adjacent portions of the silver layer P124 and/or the ITO layer P112, with adverse results as already explained.

Furthermore, the configuration shown in fig. 1 and 2 requires the same top surface connections (holes P122) for testing and use in the final display, while it may be more convenient for engineering reasons to provide separate sets of top surface connections for both purposes, and to leave the inner protrusions P104A on the final FPL after removal of the conductive release sheet P118/P120, while in some cases the presence of these protruding inner protrusions P104A may cause inconvenience.

A second aspect of the present invention seeks to provide a front plane laminate or similar manufactured product which reduces or eliminates the above discussed drawbacks of the prior art arrangements.

Accordingly, in one aspect, the present invention provides a method for producing an article of manufacture for use in the production of an electro-optic display, the method comprising:

providing an electro-optic subassembly comprising a layer of electro-optic medium;

providing an adhesive subassembly comprising an adhesive layer, the adhesive layer being larger in at least one dimension than the electro-optic medium layer, the adhesive layer having at least one aperture extending therethrough; and

adhering the adhesive subassembly to the electro-optic subassembly such that a portion of the adhesive layer adheres to the layer of electro-optic medium but at least one aperture in the adhesive layer is spaced from the layer of electro-optic medium (i.e., such that the electro-optic medium does not block adjacent ends of the aperture in the adhesive layer).

In such a "preformed aperture" approach, the electro-optic subassembly may include a light-transmissive electrically-conductive layer that will form the front electrode in the final display. In addition, in such cases, the layer of electro-optic medium typically also includes at least one support or protective layer on the opposite side of the light-transmissive electrically-conductive layer from the layer of electro-optic medium to support the electrically-conductive layer and to protect it from mechanical damage. The supporting or protective layer may also serve other functions, such as acting as a barrier against moisture and/or ultraviolet radiation, and/or providing a desired surface texture (the electro-optic medium is of course typically viewed from the side bearing the electrically conductive layer). Alternatively, the electro-optic subassembly may comprise a second adhesive layer disposed on one of the surfaces of the layer of electro-optic medium, the adhesive subassembly being adhered to the surface of the layer of electro-optic medium not covered by the second adhesive layer. The surface of the second adhesive layer remote from the layer of electro-optic medium may be covered by a release sheet. The electro-optic sub-assembly further includes a release sheet overlying a surface of the layer of electro-optic medium to be adhered to the adhesive sub-assembly, the release sheet being removed from the layer of electro-optic medium prior to contacting the layer of electro-optic medium with the adhesive sub-assembly.

Typically, the adhesive subassembly includes a release sheet carrying an adhesive layer. It is not necessary that the at least one hole in the adhesive layer extend through the release sheet, but typically the at least one hole is so, as it is often most convenient to form the at least one hole by cutting completely (e.g., by laser cutting or die cutting) through the adhesive subassembly.

The electro-optic medium used in the method of the invention may be any of the types of solid electro-optic medium previously described. Thus, the electro-optic medium may be a rotating bichromal member or an electrochromic medium. The electro-optic medium may also be an electrophoretic material comprising a plurality of electrically charged particles disposed in a fluid and capable of moving through the fluid under the influence of an electric field. The charged particles and the fluid may be confined in a plurality of capsules or microcells. Alternatively, the electrophoretic material may be polymer dispersed, the charged particles and the fluid being present as a plurality of separate droplets surrounded by a continuous phase comprising the polymeric material.

The invention also relates to novel subassemblies and displays produced by the method of the invention. The articles of manufacture and electro-optic displays produced using the method of the present invention may be used in any application where electro-optic displays have previously been employed. Accordingly, the present invention relates to electronic book readers, portable computers, tablet computers, cellular telephones, smart cards, signs, watches, shelf labels and flash drives comprising a display of the present invention or produced using a method or component of the present invention.

The invention also provides a sub-assembly for use in the production of an electro-optic display, the sub-assembly comprising:

a layer of electro-optic medium;

an adhesive layer larger in at least one dimension than the layer of electro-optic medium, the adhesive layer having at least one aperture extending therethrough;

a portion of the adhesive layer adheres to the layer of electro-optic medium but at least one aperture in the adhesive layer is spaced from the layer of electro-optic medium.

In such a sub-assembly a plurality of discrete areas of the layer of electro-optic medium are disposed on the substrate, the discrete areas being separated by zones devoid of the electro-optic medium, and a plurality of apertures may pass through the layer of adhesive, one end of each aperture terminating in one of the zones. A sub-assembly may be included on a light-transmissive electrically-conductive layer disposed on a surface of the layer of electro-optic medium remote from the adhesive layer.

The invention relates to an electro-optic display comprising a subassembly as hereinbefore described and a backplane adhered to the adhesive layer, the backplane comprising at least one first electrode disposed adjacent the layer of electro-optic medium and at least one second electrode spaced from the layer of electro-optic medium, the at least one second electrode being in electrical contact with the light-transmissive electrically-conductive layer via at least one aperture in the adhesive layer. The invention also relates to electronic book readers, portable computers, tablet computers, cellular telephones, smart cards, signs, watches, shelf labels and flash drives comprising such a display.

In a second broad aspect, the invention provides an article of manufacture ("detachable tab front plane laminate" or "DTFPL") for use in the production of an electro-optic display, the article comprising a conductive layer and a layer of electro-optic medium, the conductive layer having a main portion covered by the layer of electro-optic medium, an exposed portion exposing at least a portion of the conductive layer free of the electro-optic medium, and a weakened portion connecting the main portion and the exposed portion, such that the exposed portion can be manipulated to cause fracture of the weakened portion, thereby detaching the exposed portion from the main portion substantially without damage to the main portion.

Typically, in the detachable tab front plane laminate of the present invention, all portions of the conductive layer are supported on a support layer (e.g., a polymer film) and both the conductive layer and the support layer have weakened portions such that the exposed portions of the conductive layer and associated portions of the support layer are detachable from the main portion of the conductive layer and associated portions of the support layer. The support layer also serves other functions, such as acting as a barrier against moisture vapor and/or ultraviolet radiation, and/or providing a desired surface texture.

Although the product provided by the invention is referred to above as a "detachable tab front plane laminate" and is described below primarily with reference to a "full" front plane laminate similar to that shown in fig. 1 and 2, the invention can be applied to other structures having an electro-optic layer and a conductive layer. For example, the foregoing 2004/0155857 describes a dual release film comprising an electro-optic layer sandwiched between two release plates, one or both of which may include a conductive layer for testing purposes. Such a double release membrane may be provided with a detachable tab of the present invention. Similarly, in an FPL of the type shown in fig. 2, the conductive layer P118 of the release plate may be omitted and the conductive layer P112 may be provided with a separable tab, and the FPL may be tested by the second method described in the aforementioned U.S. patent No.6,982,178, with the application of an electrostatic charge to the polymer film P112.

As described above, the front plane stack, which is typically intended for testing, has two separate conductive layers, one (P112 in fig. 2) forming the front electrode in the final display, and the other (P118 in fig. 2) being part of a conductive release sheet, which can be removed from the front plane stack before lamination to the backplane. Desirably, in such a dual conductive layer front plane laminate, each conductive layer is provided with a separable exposed portion. To facilitate removal of the two separable exposed portions, it is desirable that they are offset from one another, i.e. separated from one another in the plane of the layer of electro-optic medium. The exposed portion of the front electrode conductive layer may be provided in the same manner as described in fig. 2, in other words by providing an aperture in the front electrode conductive layer that extends through the front planar stack (and the conductive release plate if the conductive release plate covers the location of the aperture). As in fig. 2, the portion of the front electrode conductive layer exposed by the hole may be enhanced by providing a conductive pad electrically connected to the conductive layer. Although the exposed portions of the two conductive layers may be located on the same detachable tab, it is typically convenient to provide two detachable tabs for the exposed portions of the two conductive layers. As discussed in more detail below, an advantage of providing separate protrusions is that, at least in some cases, exposed portions of the conductive layer on the release sheet can be provided simply by weakening appropriate areas of the FPL and subsequently removing the front substrate with the electro-optic medium and adhesive adhered thereto from the associated protrusions.

One or more of the weakened portions of the DTFPL may have a different form, although of course some electrical connection between the exposed and main portions of the conductive layer needs to be maintained to ensure that the electro-optic medium can still be switched during the testing process. For example, in an FPL of the type shown in fig. 2, the PET layer P110 and the polymer layer P120 are reduced in thickness, for example by bringing them into contact with a heated component. However, it is generally preferred to cut portions of the weakened portion, for example by perforation or perforation; the latter is preferred because it does not produce a large number of small pieces of debris.

The electro-optical medium used in the DTFPL of the invention may be any solid-state electro-optical medium of the type described before. Thus, the electro-optic medium may be a rotating bichromal member or an electrochromic medium. The electro-optic medium may also be an electrophoretic material comprising a plurality of electrically charged particles disposed in a fluid and capable of moving through the fluid under the influence of an electric field. The charged particles and the fluid are confined in a plurality of capsules or microcells. Alternatively, the electrophoretic material may be polymer dispersed, the charged particles and the fluid being present as a plurality of separate droplets surrounded by a continuous phase comprising the polymeric material. The fluid used may be a liquid or a gas.

The electro-optic displays produced using the DTFPL of the invention can be used in any application where electro-optic displays have previously been employed. Accordingly, the present invention relates to electronic book readers, portable computers, tablet computers, cellular telephones, smart cards, signs, watches, shelf labels, and flash drives that include displays produced using the products of the present invention.

Finally, the invention provides a method for testing a layer of electro-optic medium, the method comprising:

providing a product comprising a conductive layer and a layer of electro-optic medium, the conductive layer having a main portion covered by the layer of electro-optic medium, an exposed portion exposing at least a portion of the conductive layer free of the electro-optic medium, and a weakened portion connecting the main portion and the exposed portion;

applying a voltage to the conductive layer sufficient to change the optical state of the layer of electro-optic medium;

observing the appearance of the electro-optic medium layer along with the change; and

subsequently, the exposed portion is manipulated to cause the weakened portion to break, whereby the exposed portion separates from the main portion without substantially damaging the main portion.

In such a method, a product (DTFPL) may comprise first and second conductive layers arranged on opposite sides of the layer of electro-optic medium, each of the first and second conductive layers being provided with an exposed portion and a weakened portion, the voltage being applied between the first and second conductive layers, and subsequently the two exposed portions being operated to cause rupture of the two weakened portions.

Drawings

The drawings are not to scale. In particular, the thickness of the various layers is greatly exaggerated relative to their lateral dimensions for ease of illustration. The invention is suitable for use in the manufacture of thin, flexible electro-optic displays; typically, the thickness of the subassembly used in the method described below is about 100 μm, and may be laminated to a flexible backplane of similar thickness.

As already described, FIG. 1 is a top view of a prior art front plane laminate with inspection tabs;

FIG. 2 is a schematic cross-sectional view through one of the inspection tabs of the front plane laminate shown in FIG. 1;

FIGS. 3A-3E are schematic cross-sectional views through different stages in a preformed hole process of the present invention;

FIG. 4A is a top view schematic of a stage in the pre-formed hole process shown in FIG. 3C;

FIG. 4B is a top view schematic of a stage in the pre-formed hole process shown in FIG. 3E;

FIGS. 5A-5C are schematic cross-sectional views through various stages in a process for converting the product in the process of FIGS. 3A-3E into a finished display;

similar to fig. 3A-3E, fig. 6A-6E are schematic cross-sectional views, respectively, at various stages throughout a process for manufacturing a front plane laminate of separable tabs of the present invention;

fig. 7A and 7B are schematic top views of processing stages corresponding to fig. 6C and 6E, respectively.

Detailed Description

Before describing various embodiments of the present invention in detail, it is useful to specify some definitions. The term "backplane" as used herein, consistent with its conventional meaning in the field of electro-optic displays and in the aforementioned patents and published applications, refers to a rigid or flexible material provided with one or more electrodes. The backplane may also be provided with electronics for addressing the display, or such electronics may be provided in a unit separate from the backplane. In flexible displays (and the invention is particularly, but not exclusively, intended for use in flexible displays), it is highly desirable that the backplane provides sufficient barrier properties to prevent ingress of moisture and other contaminants through the non-viewing side of the display. If it is desired to add one or more additional layers to the backplane to reduce the ingress of moisture and other contaminants, the barrier layer should be located as close to the electro-optic layer as possible so that there is little or no edge profile of the low barrier material between the front and back barrier layers (discussed below).

Hereinafter, reference will be made to "loose" and "tight" release plates. These terms are used in their conventional sense in the art and refer to the amount of force required to peel the associated release sheet in contact with the layer from the layer, with a tight release sheet requiring more force than a loose release sheet. In particular, if the stack of layers has a tight release plate on one side and a loose release plate on the other side, the loose release plate can be peeled from the stack without detaching the tight release plate from the stack.

Some displays or sub-assemblies of the present invention include two separate adhesive layers. When needed or desired, the two adhesive layers may be referred to as "front" and "back" adhesive layers, these terms indicating the location of the relevant adhesive layer in the final display; the front adhesive layer is the adhesive layer located between the electro-optic medium and the viewing surface of the display, while the back adhesive layer is located on the opposite side of the electro-optic layer from the front adhesive layer. In the general case of a display having a single front electrode between the electro-optic layer and the viewing surface and a plurality of pixel electrodes on opposite sides of the electro-optic layer, a front adhesive layer is positioned between the electro-optic layer and the front electrode and a rear adhesive layer is positioned between the electro-optic layer and the pixel electrodes.

As noted above, in one aspect the present invention provides a process of "pre-forming apertures" for use in the manufacture of sub-assemblies for use in the manufacture of electro-optic displays. In this pre-formed aperture process, a separate electro-optic and adhesive subassembly is formed, the former comprising at least a layer of electro-optic medium and the latter comprising at least a layer of adhesive. The adhesive layer has one or more apertures extending therethrough. The two subassemblies are adhered together such that a portion of the adhesive layer adheres to the layer of electro-optic medium, but the electro-optic medium does not block the holes in the adhesive layer.

As already mentioned, the electro-optic sub-assembly used in the process may comprise at least one electrode layer, most commonly a single continuous front electrode extending across the entire display. Typically, the surface of the electro-optic subassembly remote from the adhesive subassembly forms the viewing surface through which an observer views the display. With the backplane, the electro-optic subassembly can provide barrier properties to prevent moisture and other contaminants from passing through the viewing side of the display. If it is desired to add one or more additional layers to the subassembly to reduce the ingress of moisture and other contaminants, the barrier layer should be located as close to the electro-optic layer as possible so that there is little or no edge profile of the low barrier material between the front and back barrier layers. For a more detailed discussion of such barrier layers and other optical layers in the two subassemblies, see 2007/0109219 and 2007/0152956, supra.

Fig. 3A-3E are schematic cross-sectional views through different stages in a preformed hole process of the present invention. In a first step of the process, an electro-optic medium is coated or otherwise deposited onto the tight release sheet 302 to form an electro-optic layer 304. Separately, a front adhesive layer 306 is coated onto a release sheet 308. The two resulting subassemblies are then laminated to one another with the adhesive layer 306 in contact with the electro-optic layer 304 to produce the structure shown in FIG. 3A. These steps are as described in the aforementioned U.S. patent No.7,110,164, and the resulting assembly is a double release plate as described in the aforementioned 2004/0155857.

In the second step of the process, the structure shown in fig. 3A is kiss cut with the release sheet 308 facing a cutting tool (typically a laser cutter), the kiss cut being performed to cut the release sheet 308, the front adhesive layer 306, and the electro-optic layer 304, but not the tight release sheet 302. Successive portions of the release sheet 308, the front adhesive layer 306, and the electro-optic layer 304 are then manually or mechanically removed, leaving the structure shown in FIG. 3B with a plurality of "mesas" extending upward from the tight release sheet 302, the mesas including islands 318 of the release sheet and similarly sized areas 316 and 314 of the front adhesive layer and the electro-optic layer, respectively. Each of these mesas will eventually form a separate display (in some cases, it may be possible in other small displays to be able to reuse the portion of the front adhesive layer and electro-optic layer that is separate from the release sheet 308).

Thus, the stages of the described process are most typically carried out on a continuous web or large sheet of material sufficient to form several final displays. For ease of illustration, fig. 3B shows only two separate mesas, but it will be appreciated that in practice there are more mesas on a single large sheet (sheet) or web. When the process is carried out on a web on a roll-to-roll basis, the web used may include a draw feed hole formed along a side edge of the web of material to act as an alignment hole. Alternatively, reference marks are provided on the web and these reference marks are light sensitive to control the alignment of the web.

In the next step, the remaining portion 318 of the release sheet is peeled from the structure shown in fig. 3B and the remaining layers of the structure are laminated to the sheets of the front substrate 320. The front substrate 320 is a multi-layer structure including an Indium Tin Oxide (ITO) layer forming the front electrode of the final display. The front substrate may also include a removable mask that can be removed prior to placing the final display in use.

The front substrate is designed to provide a front light-transmissive electrode for the final display. The front substrate 320 also provides the required mechanical support for such a thin and relatively fragile front electrode. Furthermore, the front substrate preferably provides all required moisture and oxygen barrier, as well as uv absorbing properties, desired to protect certain electro-optical layers, especially the electrophoretic layer. The front substrate may also provide the desired antiglare properties to the viewing surface of the final display. The front substrate 320 provides all of these functions while still being thin and flexible enough to allow the resulting display to be flexible enough to wrap around a roll of 15mm in diameter (for example). As already explained, the front substrate comprises a mask, which is provided primarily to increase the thickness of the front substrate to facilitate handling of the substrate in the lamination process. In a preferred process, the total thickness of the front substrate when it is left in the final display (i.e. with the mask removed) is only about 1 mil (25 μm) and for ease of handling, about 2 mils (51 μm) are added to this thickness using the mask. Typically, the mask also serves to prevent scratching or adhesion of dust or debris to the adjacent antiglare layer during lamination. Figure 3C shows the structure resulting from this step of the process and including an electro-optical subassembly suitable for use in the process of the present invention.

The steps of the foregoing process are substantially the same as those of the process described with reference to fig. 2A through 2E of 2008/0057252, previously described, which the reader is referred to for further information.

At this point, a thin second adhesive layer 322 is applied to a third release sheet 324 and holes 326 are formed through the adhesive layer 322 and release sheet 324 at locations corresponding to the top surface connections (connections between the backplane and front electrodes) present in the final display, thereby creating an adhesive subassembly suitable for use in the process of the present invention. To carry out the present process, the release sheet 302 is peeled away from the electro-optic subassembly shown in FIG. 3C and an adhesive layer 322 is laminated to the electro-optic layer portion 314 to provide the structure shown in FIG. 3D. Note that the holes 326 in the adhesive layer are arranged so that they are spaced apart from the mesa (i.e., spaced apart from the electro-optic layer portion 314) so that the mesa does not block the holes 326. Fig. 4A shows a top view corresponding to fig. 3D, but only illustrating a single mesa and its associated aperture 326. At this stage of the process, the material is still in the form of a web or large sheet and as indicated by the curved boundary of the front substrate 320 in FIG. 4A, FIG. 4A only illustrates a portion of the web or sheet (for ease of illustration, FIG. 4A only illustrates a single aperture 326 associated with the mesas. in practice, it is often desirable to provide two or more apertures 326 associated with each mesa to provide excess top surface connections in each final display, thereby ensuring that each display can still function properly even if one of the top surface connections is not properly formed or damaged during use).

The next stage in the process is the singulation, i.e., the separation of the sub-assemblies corresponding to the individual displays. Fig. 3E and 4B illustrate the result of this segmentation step. This segmentation step results in three logically separate operations simultaneously, namely:

(a) cutting the sheet or web into pieces of the required size for each display;

(b) forming the required holes through the adhesive layer 322 for mechanical alignment of the subassembly during subsequent lamination to the back sheet; and

(c) holes are formed through the front substrate 320, adhesive layer 322 and release sheet 324 that are ultimately used to mount electronic circuit devices on the backplane of the final display.

As illustrated in fig. 3E and 4B, operation (a) is accomplished by cutting the front substrate 320, adhesive layer 322, and release sheet 324 along the same rectangular perimeter, thereby defining separate units (blocks) that are ultimately laminated to the backplane to form a front plane stack of a single display. In addition to the discrete elements separating the front plane stack, this step creates extended tabs or "tails" of the non-optically active material (the portion of the front plane stack underlying the electro-optic layer 314 as shown in FIG. 4B) that increase the thickness of the corresponding portion of the final display. Without this tail of non-optically active material, the thickness of the final display in this region would be only that of the backplane itself, and in thin flexible displays the thickness of the backplane would be only about 25 μm, with the extended tail portion typically providing an additional thickness of 25 μm, doubling the thickness of the region to about 50 μm. For further discussion regarding the provision of a tab or tail portion of a front electrode layer, and the use of such a tab or tail portion to provide electrical contact with the front electrode layer, see 2007/0211331, supra.

Operation (B) is achieved by providing two small circular holes 328 adjacent to one edge (the lower edge as shown in fig. 4B) of the rectangular front plane stack (although fig. 3E is a cross-sectional view of fig. 4B above, for ease of understanding, holes 328 are shown in phantom in fig. 3E, so in practice holes 328 are not visible in the cross-sectional view of fig. 3E). As shown in FIG. 3E, the hole 328 is located in the tail portion of the FPL and extends through the entire thickness of the FPL, through the front substrate 320, the adhesive layer 322, and the release plate 324. The holes 328 may be used for mechanical alignment or attachment of the FPL during lamination to the backplane or during subsequent manufacturing stages. As described below with reference to fig. 5A-5C, the holes 328 may be used in conjunction with registration pins or similar cooperating members provided on the backplate or the substrate carrying the backplate to ensure accurate registration of the FPL with respect to the backplate. The holes 328 may also be used at a later stage in the manufacturing process to accurately position the final display module relative to the housing or other surrounding portion of the final commercial display unit (e.g., a printed circuit board), or to attach the display module to such a housing or surrounding portion.

Operation (c) is accomplished by providing a rectangular aperture 330 in the tail portion of the FPL, the rectangular aperture 330 extending completely through the FPL, i.e., through the front substrate 320, the adhesive layer 322, and the release plate 324. As discussed below, an FPL of the type shown in FIGS. 3E and 4B is typically employed with a backplane that is substantially the same size as the FPL, such that the FPL covers substantially the entire backplane. Thus, if it is desired to have electrical access to the backplane, for example for mounting a driver chip on the backplane, the holes formed must allow this, and this is the role of the holes 330. Driver chips or other electronic circuit devices may be placed in the holes 330 and the FPLs surrounding the holes provide an area of increased thickness, which contributes to the ruggedness of the display.

Fig. 5A illustrates in a rather schematic way a process in which the blocks of the front plane stack shown in fig. 3E and 4B are laminated to a back plate. As shown in FIG. 5A, the support platform 350 is provided with a pair of pins 352 (only one of which is visible in FIG. 5A). The back plate 354 is provided with holes that engage the pins 352. The release plate 324 (see fig. 3E) is removed from the front planar stack 356 and the front planar stack 356 is then laid flat on the back plate using the holes 328 (see fig. 3E and 4B) that engage the pins 352. Nip roller 358 passes over the front plane laminate 356 thereby attaching the adhesive layer 322 (see fig. 3E) to the adjacent surface of the back plate 354 and thereby laminating the front plane laminate to the back plate to form the display. As described in the aforementioned U.S. patent No.6,982,178, conductive ink may be placed on the backplate at appropriate points prior to the lamination so that during lamination the conductive ink is forced into the holes 326 to form conductive vias (not shown) that connect contact pads (not shown) on the backplate to electrode layers in the front substrate 320. Alternatively, the lamination will bring the electrode layer in the front substrate 320 into electrical contact with one or more contact pads on the back plate, especially if the adhesive layer 322 and the front substrate 320 are thin, without such conductive ink. After this lamination, the laminated FPL and backplane are removed from the support stage 350, as in the structure shown in fig. 5B (the meaning of the arrow in fig. 5B is explained below).

When laminating the front plane stack to the backplane, the FPL typically has to be aligned with respect to the backplane components, e.g. with respect to contact pads designed to provide contact with the electrode layers in the front plane stack. The FPL may be designed to be smaller than the backplane (to facilitate electrical connections over the backplane area not covered by the FPL) or the same size as the backplane, depending on design requirements. If the FPL or the barrier layer laminated on the FPL is the same size as the backplane, it is in practice difficult to achieve a clean edge alignment, since there is always some tendency for the FPL to be not aligned exactly with the backplane. In addition, certain components that are desirable during manufacturing, such as inspection tabs or positioning strips (tapping strips), are undesirable if present in the finished display module.

There is a growing trend to use electro-optic media with thin backplanes based on polymer films (e.g. PET or poly (ethylene naphthalene), PEN under the registered trademark TEONEX from DuPont teijin film of hopewell va) or metal foils. Electro-optic displays based on such thin backplanes can be flexible or rollable and can therefore be used in certain applications where conventional displays cannot be used (e.g. large displays that can be stored in mobile phones-see 2002/0090980 previously mentioned). It has now been found that the FPL laminated to the backplane of such a polymer or metal foil can be readily cut by industrial methods such as laser cutting or die cutting, and that such cutting of the FPL/backplane stack can achieve a precisely matched edge between the FPL (or barrier layer overlying the FPL) and the backplane without adversely affecting the functionality of the final display. Such cutting also allows for the removal of components that are used during manufacturing but are not desired in the final display.

The laminate produced in fig. 5B is then trimmed by laser or die cutting, as schematically indicated by the arrows in fig. 5B, to produce the final display module schematically shown in fig. 5C.

As mentioned above, a second main aspect of the invention relates to a detachable tab front plane laminate comprising a conductive layer and a layer of electro-optic medium, the conductive layer having a main portion covered by the layer of electro-optic medium, an exposed portion exposing at least a portion of the conductive layer free of the electro-optic medium, and a weakened portion connecting the main portion and the exposed portion, such that the exposed portion can be detached from the main portion without substantial damage to the main portion.

Typically, the surface of the DTFPL of the invention that remains exposed after lamination to the backplane will form a viewing surface through which a viewer views the display. With the backplane, the front substrate of the DTFPL can provide barrier properties to prevent moisture or other contaminants from entering through the viewing side of the display. If it is desired to add one or more additional layers to the DTFPL to reduce the ingress of moisture and other contaminants, the barrier layer should be as close as possible to the electro-optic layer so that there is little or no edge profile of the low barrier material between the front and back barrier layers.

Fig. 6A-6E are schematic cross-sectional views through different stages of manufacturing a front plane laminate of separable tabs of the present invention. The process illustrated in fig. 6A-6E is very similar to the process illustrated in fig. 3A-3E above, and therefore only aspects of the process of fig. 6A-6E that differ from corresponding aspects of the process of fig. 3A-3E are described below in a simplified manner. The first two stages of the process illustrated in fig. 6A and 6B are the same as the corresponding stages shown in fig. 3A and 3B, respectively. The next stage shown in fig. 6C is also actually the same as that shown in fig. 3C, but the front electrode layer 621, which will form the light-transmissive electrode in the final display, is shown separately in fig. 6C for the reasons shown below.

The next step in the process employs a third release plate 624 having a conductive layer 625 on one of its surfaces. A thin layer of adhesive 322 is coated on the third release sheet, as in the process illustrated in fig. 3D, but in this case the adhesive layer is deposited on the conductive layer 625. Holes 326 are formed through the adhesive layer 322, the conductive layer 625, and the third release plate 624 at locations corresponding to the top surface connections present in the final display. A second hole 628 is also formed through the adhesive layer 322, the conductive layer 625, and the release plate 624 to facilitate forming a detachable inspection tab as described below. At the same time, the release plate 624 is preferably intermittently cut along a line 627 (see FIG. 7A) to form a positioning strip (discussed further below). The release sheet 302 is peeled away from the structure shown in fig. 6C and an adhesive layer 322 is laminated to the electro-optic layer portion 314 to provide the structure shown in fig. 6D. Fig. 7A shows a corresponding top view illustrating only a single mesa and its associated holes 326 and 628 and lines 627. At this stage of the process, the material is still in the form of a thin strip or large sheet and, as indicated by the curved boundary of the front substrate 320 in fig. 7A, fig. 7A only illustrates a portion of the plate or sheet (although fig. 6D and 6E are cross-sectional views of fig. 7A above, for ease of understanding, the holes 628 are shown in phantom in fig. 6D and 6E, and thus, in fact, the holes 628 are not visible in the cross-sections of fig. 6D and 6E). The adhesive layer 322 must of course be precisely aligned with respect to the mesas to ensure that the apertures 326 and 628 and the lines 627 are in the correct position with respect to their associated mesas, as shown in fig. 7A (for ease of illustration, fig. 7A shows only a single aperture 326 associated with a mesa-indeed, in the configuration shown in fig. 4A, it is often desirable to provide two or more apertures 326 associated with each mesa to provide excessive top surface connections in each final display, thereby ensuring that each display can function properly even if one of the top surface connections is not properly formed or damaged during use).

The next stage in the process is the segmentation, i.e., the separation of the FPL portions corresponding to the individual displays. Fig. 6E and 7B illustrate the result of this segmentation step. The division not only cuts the sheet or web into FPL blocks of the desired size for the individual displays, but also forms separable tabs 630 and 632 on one edge of each FPL block (as shown by the lower edge in fig. 7B). The tab 630 includes only a small rectangular area of the FPL separated from the main portion of the FPL by a stitch (i.e., interrupted cut) line 634. The protrusion 632 surrounds the hole 628 and is separated from the main portion of the FPL by a perforation line 636. The interrupted cuts along lines 634 and 636 extend completely through the FPL and are formed using the same laser cutter that separates the FPL block shown in fig. 6E and 7B from the web. Since the intermittent cutting does not completely cut the conductive layers 621 and 625, the portions of the conductive layers located in the protrusions 630 and 632 are electrically connected to the main portions of the conductive layers in the main portion of the FPL block.

The tabs 630 are intended to provide access to the conductive layer 625 on the release plate 624, i.e., the tabs 630 serve the same function as the outer ledge P104B shown in fig. 1 and 2. Although the conductive layer 625 is still covered by the front substrate 320, the front conductive layer 621, and the adhesive layer 322 as illustrated in fig. 6E and 7B, it has been found that by manually grasping and pulling the front substrate 320, the front conductive layer 621, and the adhesive layer 322 will all break along line 634 to expose the conductive layer 625. On the protrusion 632, the hole 628 exposes the front conductive layer 621 so that the protrusion 632 functions as the inner protrusion P104A shown in fig. 1 and 2.

To test the FPL block shown in fig. 6E and 7B, the conductive layer 625 on the protrusion 630 is exposed as described in the previous paragraph, and the probe is placed in contact with the conductive layer 625 on the protrusion 630 and the conductive layer 621 on the protrusion 632. A varying voltage is applied to the conductive layers 621 and 625 to switch the electro-optic medium between its extreme optical states. The switching of the electro-optical medium is observed by the naked eye or by a mechanical vision system. Once the electro-optic medium is found to be satisfactory, the probe is removed. They are then removed by manually pulling them to remove the tabs 630 and 632, thereby causing tearing along lines 634 and 636 and separating the tabs without damaging the main portion of the FPL block. Alternatively, the release plate 624 may be peeled off from the remaining layers of the FPL using the tab 630 before laminating the FPL to the backplane.

As also shown in fig. 7B, the division of the FPL block from the web results in a line 627 extending proximate to and parallel to one edge of the FPL block, forming a locating bar 629 between the line 627 and the adjacent edge in the form of an elongated region continuous along one edge of the FPL block. Because the release plate 624 is cut along the line 627, the portion of the release plate 624 below the locating bar 629 can be removed without removing the release plate 624 from the main portion of the FPL block. Before laminating the two portions of the backplane and the FPL block to form the display, a positioning bar 629 is provided to aid in positioning the FPL block on the backplane; the portion of the release plate 624 underlying the positioning bar 629 is removed and the portion of the adhesive layer 322 thus exposed may be manually pressed into the correct position for lamination to the backing plate before the main portion of the release plate 624 is removed and the lamination operation is completed.

It will be apparent to those skilled in the art of electro-optic displays that numerous modifications and improvements can be made in the preferred embodiments of the invention described without departing from the scope of the invention. For example, in the preferred method of the invention illustrated in the drawings, the inverted front plane stack can be cut into pieces of the required size for each display before being laminated to the backplane (see fig. 3E, 4B, 6E and 7B). When mass production is desired, it is convenient to reverse the order of these splitting and laminating operations, i.e., to laminate a sheet or web sufficient to form an inverted front plane stack of multiple displays in an aligned manner to a sheet or web to form a backplane of the multiple displays, and then to split it from the sheet or web. In the case of using an inverted front plane stack and a sheet of the backplane, the backplane sheet is typically secured to a support member during lamination, and the singulation operation (and any desired trimming operations, such as described above with reference to fig. 5B and 5C) can be accomplished with the sheet of the display still secured to the support member. Note that in this variation of the DTFPL process, only a single pair of protrusions 630,632 need be provided to allow testing of the complete sheet of electro-optic medium of the FPL.

In addition, in the preferred DTFPL process of the invention shown in fig. 6 and 7, the electro-optic medium does not extend into the removable protrusions. In other variations of the invention the electro-optic medium may extend into a portion of the protrusion. For example, the tabs used in the DTFPL process may be similar to those shown in fig. 1 and 2, but provided with weakened portions similar to those shown in fig. 7B, so that they are removable.

Furthermore, although the separable tabs used in the DTFPL process have been illustrated in the drawings as discrete rectangles protruding from a larger rectangular area defining the final block form of the FPL, the tabs need not protrude in this form. Depending on the required form of the final block FPL, the protrusions may for example be in the form of triangular cross-sections placed in the corners of a rectangular block of the FPL, so that the final block of the FPL is in the form of a rectangle with cut corners.

Claims (7)

1. An article of manufacture for use in an electro-optic display product, the article of manufacture comprising:

a support layer (320);

a light-transmitting conductive layer (621); and

a layer of electro-optic medium (314),

the conductive layer (621) being arranged between the support layer (320) and the layer of electro-optic medium (314),

the support layer (320) has a major portion covered by the layer of electro-optic medium (314),

the support layer (320) having an exposed portion (630,632) that exposes at least a portion of the conductive layer (621) free of the electro-optic medium (314), and a weakened portion (634,636) connecting a main portion of the support layer and the exposed portion (630,632) of the support layer, such that manipulation of the exposed portion (630,632) causes breakage of the weakened portion (634,636), thereby separating the exposed portion (630,632) of the support layer from the main portion of the support layer without substantial damage to the main portion,

wherein the conductive layer (621) is a metal layer, a metal oxide layer, or a conductive polymer layer.

2. An article of manufacture as claimed in claim 1, comprising first and second conductive layers (621,625) disposed on opposite sides of the layer of electro-optic medium (314), each of the first and second conductive layers (621,625) being provided with an exposed portion (630,632) and a weakened portion (634, 636).

3. An article of manufacture according to claim 2 wherein the exposed portions (630,632) of the first and second conductive layers (621,625) are spaced from one another in the plane of the layer of electro-optic medium (314).

4. The article of manufacture of claim 1, wherein the weakened portion is formed by reducing a thickness of the weakened portion.

5. An article of manufacture as defined in claim 1, wherein the weakened portions are formed by perforations or knurls.

6. A method for testing a layer of electro-optic medium, the method comprising:

providing a product comprising a support layer (320), a light-transmissive conductive layer (621) and a layer of electro-optic medium (314), the conductive layer (621) being arranged between the support layer (320) and the layer of electro-optic medium (314), the support layer (320) having a main portion covered by the layer of electro-optic medium (314), the support layer (320) having an exposed portion (630,632) which exposes at least a portion of the conductive layer (621,625) free of the electro-optic medium (314), and a weakened portion (634,636) connecting the main portion of the support layer and the exposed portion (630,632) of the support layer;

applying a voltage to the conductive layer (621) sufficient to change the optical state of the layer of electro-optic medium (314);

observing the appearance of the electro-optic medium layer (314) following the change in the optical state of the electro-optic medium layer (314); and

subsequently, manipulating the exposed portion (630,632) to cause fracture of the weakened portion (634,636), thereby separating the exposed portion (630,632) from the main portion without substantially damaging the main portion,

wherein the conductive layer (621) is a metal layer, a metal oxide layer, or a conductive polymer layer.

7. A method according to claim 6, wherein the product comprises first and second conductive layers (621,625) arranged on opposite sides of the layer (314) of electro-optic medium, each of the first and second conductive layers (621,625) being provided with an exposed portion (630,632) and a weakened portion (634,636), the voltage being applied between the first and second conductive layers (621,625), and the two exposed portions (630,632) being subsequently operated to cause fracture of the two weakened portions (634, 636).