HK1132553A1 - Components and methods for use in electro-optic displays - Google Patents

Abstract

A sub-assembly for use in forming an electro-optic display comprises (in this order) a light-transmissive substrate (120); discrete areas (204) of electro-optic material separated by gutter areas (205) essentially free from the electro-optic material; and an adhesive layer (122) and/or a release layer (124) peelable from the sub-assembly. A second sub-assembly comprises (in this order) a peelable release sheet (102); discrete areas of electro-optic material (204) separated by gutter areas (205) essentially free from the electro-optic material, and an adhesive layer (206) and/or a peelable release layer (208). Processes for producing these sub-assemblies and for using them to form electro-optic displays are also described.

Description

Component and method for use in electro-optic displays

Cross Reference to Related Applications

The present application relates to: (a) U.S. patent publication nos. 2006/0291034; (b) U.S. patent nos. 7,236,292; (c) U.S. Pat. Nos. 6,982,178; (d) U.S. patent publication nos. 2004/0155857; (e) U.S. patent nos. 7,110,164; (f) U.S. patent publication nos. 2007/0109219; (g) U.S. patent publication nos. 2007/0152956; (h) international application No. pct/US 2007/063551; and (g) International application No. PCT/US 2006/061141.

For convenience, the aforementioned patents, publications and applications may be referred to hereinafter as "electro-optic display manufacturing" or "EODM" patents.

Technical Field

The present application relates to components and methods for use in electro-optic displays. More particularly, the present application relates to methods for the manufacture of electro-optic displays, and some sub-assemblies produced in such methods. The present invention relates generally to such methods and sub-assemblies for forming electro-optic displays comprising a solid electro-optic medium in the sense that it has a solid outer surface (for convenience such displays will hereinafter be referred to as "solid electro-optic displays"), although the medium may, and typically does, have an internal liquid or gas filled space; the invention also relates to a method of assembling a display using such an electro-optic medium. Accordingly, the term "solid state electro-optic display" includes encapsulated electrophoretic displays, encapsulated liquid crystal displays, and other types of displays described below.

Background

Background terminology and status regarding the art of electro-optic displays is discussed in detail in the aforementioned EOMD patents to which the reader is referred for more information. Accordingly, this term and state of the art will be briefly summarized below.

The term "electro-optic" as used herein as applied to materials or displays is its conventional meaning in the imaging arts, and refers to a material having first and second display states differing in at least one optical property, the material being transitioned from the first display state to the 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 any given element is driven to assume either its first or second display state by an addressing pulse having a finite duration which, after the addressing pulse has terminated, 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.

Several types of electro-optic displays are known, for example: (a) rotating two-color element 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, for example, Nature1991, 353, 737 to O' Regan, b. et al; Information Display, 18(3), 24(March 2002) to Wood, d.; adv. mater, 2002, 14(11), 845 to Bach, u. et al; and U.S. patent 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", Nature, 425, 383-; (d) particle-based electrophoretic displays in which a plurality of electrically charged particles move 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 No. 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 Nos. 1,099,207B 1; 1,145,072B 1; and other patents and applications for MIT and E Ink discussed in the aforementioned U.S. Pat. No.7,012,600).

There are several different variations of electrophoretic media. Electrophoretic media can use liquid or gaseous fluids; see, for example, "movement of electronic Toner in electronic Paper-like display" by Kitamura, T.et al, IDW Japan, 2001, Paper HCS1-1, and "Toner display using electrostatically charged insulating particles" by Yamaguchi, Y.et al, IDW Japan, 2001, Paper AMD 4-4. U.S. patent publication nos. 2005/0001810; european patent applications 1,462,847, 1,482,354, 1,484,635, 1,500,971, 1,501,194, 1,536,271, 1,542,067, 1,577,702, 1,577,703 and 1,598,694; and international applications WO 2004/090626, WO2004/079442 and WO 2004/001498. The medium may be encapsulated, comprising a plurality of capsules, each of which itself comprises an internal phase containing electrophoretically-mobile particles suspended in a liquid suspending medium, and a capsule wall surrounding the internal phase. Typically, these capsules are themselves held in a polymeric binder to form an adhesive layer between two electrodes, see the aforementioned patents and applications for M I T and E INK. Alternatively, the walls surrounding the separation microcapsules in an encapsulated electrophoretic medium comprising a plurality of separate droplets of an electrophoretic fluid and a continuous phase of a polymeric material may be replaced by a continuous phase, thus yielding a so-called dispersed polymer (polymer-dispersed) electrophoretic display, 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 opaque and one display state is transmissive. See, for example, the aforementioned 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 also operate in a similar mode; see U.S. patent No.4,418,346. Other types of electro-optic displays can also operate in a shutter mode.

Other types of electro-optic media, such as encapsulated liquid crystal media, may also be used in the method of the present invention.

Typically, an electrophoretic display comprises a layer of electrophoretic material and at least two further layers arranged on opposite sides of the electrophoretic material, one of the two layers being an electrode layer. In most such displays both layers are electrode layers, and one or both of the electrode layers is patterned to define the pixels of the display. For example, one electrode layer is patterned as elongate row electrodes and the other electrode layer is patterned as 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 is in the form of a single continuous electrode, while the other electrode layer is patterned as a matrix of pixel electrodes, each defining one pixel of the display. In another type of electrophoretic display intended to employ a stylus, printhead or similar movable electrode separate from the display, only one of the layers adjacent to the electrophoretic layer comprises an electrode, the layer on the opposite side of the electrophoretic layer generally acting as a protective layer to prevent damage to the electrophoretic layer by the movable electrode.

Most prior art methods for lamination of the various layers required to form an electro-optic display are essentially batch methods in which the electro-optic medium, lamination adhesive and backplane are brought together just prior to final assembly, and thus there is a need for methods that are better suited for high volume production.

The aforementioned U.S. patent No.6,982,178 describes a method of assembling solid state electro-optic displays, including particle-based electrophoretic displays, which is well suited for mass production. This patent essentially describes a so-called "front plane laminate" (FPL) comprising, in order, a light-transmissive electrically conductive layer, a layer of solid electro-optic medium in electrical contact with the electrically conductive layer, an adhesive layer, and a release sheet. Typically, the light-transmissive electrically conductive layer is mounted on a light-transmissive substrate, which is preferably flexible in the sense that the substrate can be manually wound onto, say, a drum having a diameter of 10 inches (254 mm) without permanent deformation. The term "light transmissive" as used herein and in this patent means that the layer in question is capable of passing sufficient light to enable a viewer to observe through the layer, typically viewed through the electrically conductive layer and adjacent substrate (if any), a change in the display state of the electro-optic medium. The substrate is typically 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). Suitably, the electrically conductive layer is a thin metal or metal oxide layer, such as aluminium or ITO, or a conductive polymer. Polyethylene terephthalate (PET) films coated with aluminum or ITO are commercially available, for example, "aluminized Mylar" (Mylar "is a registered trademark) from dupont DE Nemours & Company, Wilmington DE, Wilmington, a commercial material that can have good results for front plane lamination.

The combination of electro-optic displays with such front plane lamination can be achieved by: the release sheet is removed from the front plane laminate and the adhesive layer is contacted with the backplane under conditions effective to promote adhesion of the adhesive layer to the backplane, thereby securing the adhesive layer, the layer of electro-optic medium, and the electrically conductive layer to the backplane. The process is well suited for mass production, as front plane lamination is typically mass produced using roll-to-roll coating techniques and then cut into pieces of any size required for use with a particular backplane.

The aforementioned 2004/0155857 describes a so-called "double release panel" which is essentially a simplified version of the front plane lamination 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 sheet comprises a layer of solid electro-optic medium sandwiched between two release layers. Both forms of the dual release film are intended for use in a process substantially similar to that already described for assembling an electro-optic display from a front plane lamination, but involving two separate laminations, typically in a first lamination the dual release sheet is laminated to the front electrode to form a front sub-assembly and then in a second lamination the front sub-assembly is laminated to the backplane to form the final display, although the order of the two laminations can be reversed if desired.

The aforementioned 2007/0109219 describes a so-called "inverted front plane laminate", which is a variation of the front plane laminate described in the aforementioned U.S. Pat. No.6,982,178. The inverted front plane lamination 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 useful for forming 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 generally thin second adhesive layer between the electro-optic layer and the backplane. Such electro-optic displays have both good resolution and good low temperature performance.

However, there are a number of problems in the large scale manufacture of electro-optic displays. The lamination process involved is relatively slow and therefore labour intensive and so in practice, at least for low cost displays, it is desirable to use an "all in one" method of laminating multiple displays in a single operation, with the individual displays being separated from one another at a later stage of the process. To allow proper separation, gaps ("grooves") must be left between adjacent displays. If the electro-optic medium is coated on the substrate as a continuous film, the electro-optic medium in the grooves is wasted because it is not used in any of the final displays. Such waste is a serious problem because the electro-optic medium is expensive, especially when the individual displays are small, such as those used in a blinking drive. For example, lamination of small displays can result in only about 20% of the electro-optic medium being included in the final display, with the remaining 80% or so being wasted. If it is not desired to waste the electro-optic medium in the grooves, the discrete pieces of electro-optic medium (and other layers attached thereto prior to lamination) must be precisely maintained spaced from one another so that they can be laminated to other components of the final display.

Disclosure of Invention

The present invention provides a method for the production of electro-optic displays that reduces or eliminates the aforementioned problems. The present invention also provides subassemblies useful in such methods.

In one aspect, the invention provides a (first) sub-assembly for forming an electro-optic display, the sub-assembly comprising: a light-transmissive substrate; a plurality of discrete regions of adhesive material disposed on the substrate, the discrete regions being separated from one another by a channel region substantially free of adhesive material; a plurality of discrete regions of electro-optic material disposed on the adhesive material, each of the discrete regions of electro-optic material disposed on one of the plurality of discrete regions of adhesive material, the discrete regions of electro-optic material separated from one another by a trench region substantially free of electro-optic material; and on the opposite side of the area of electro-optic material relative to the substrate, at least one of the adhesive layer and the release layer may be peeled from the subassembly without substantial damage thereto.

This first subassembly of the invention may have a second adhesive layer in contact with the region of electro-optic material and a release layer on the opposite side of the adhesive layer from the electro-optic material. The adhesion layer and/or release layer may or may not extend across the trench region. The substrate may include a light-transmissive conductive layer. The first subassembly may further include a removable masking film disposed on an opposite side of the substrate relative to the electro-optic material.

The invention also provides a (second) sub-assembly for use in forming an electro-optic display, the sub-assembly comprising: a release plate; a plurality of discrete regions of electro-optic material disposed on the substrate, the discrete regions being separated from one another by trench regions substantially free of electro-optic material; the release sheet being capable of peeling away from the electro-optic material without substantial damage thereto; and at least one of an adhesive layer and a release layer on an opposite side of the area of the electro-optic material relative to the release sheet, the release layer being peelable from the electro-optic material or the adhesive layer in contact therewith without substantial damage thereto.

This second subassembly of the invention has an adhesive layer in contact with the region of electro-optic material and a release layer on the opposite side of the adhesive layer from the electro-optic material. The adhesion layer and release layer may or may not extend across the trench area, but the latter is generally preferred.

The first and second subassemblies of the present invention may utilize any of the types of solid electro-optic materials discussed above. Thus, for example, either type of subassembly may include a rotating bichromal member or electrochromic material. Alternatively, either type of subassembly may comprise an electrophoretic material with a plurality of 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 charged particles and the fluid are present as a plurality of discrete droplets surrounded by a continuous phase comprising a polymeric material. The fluid may be liquid or gaseous. 【023】 In another aspect, the present invention provides a (first) process for forming a first subassembly of the present invention, the process comprising: forming a plurality of components, each component comprising a layer of electro-optic material and a release layer peelable from the layer of electro-optic material without substantial damage thereto; arranging the plurality of components on a support surface, the components being spaced apart from one another with the layer of electro-optic material facing away from the support surface; and contacting the disposed plurality of components with a light-transmissive substrate under conditions effective to cause the plurality of components to adhere to the substrate.

In a first process of the invention, the support surface may comprise a mould having a plurality of recesses, wherein the component is received within the plurality of recesses. Each of the components further comprises a substrate adhesive layer arranged on the opposite side of the layer of electro-optic material with respect to at least one of the adhesive layer and the release layer, and the components are arranged on the support surface with the substrate adhesive layer facing the substrate such that the substrate adhesive layer acts to adhere the components to the substrate. The first process further includes: forming a subassembly comprising an adhesion layer on a second substrate; and after adhering the component to the light-transmissive substrate, removing the release layer from the component, and contacting the component with an adhesive layer on a second substrate under conditions effective to cause the component and the light-transmissive substrate to adhere to the adhesive layer. The substrate used in the first process includes a light-transmissive conductive layer.

In another aspect, the invention provides a (second) process for forming the first subassembly of the invention, the second process comprising: forming a layer of electro-optic material on the release sheet; severing the layer of electro-optic material on the release sheet to define a plurality of discrete regions separated from one another by trench regions; removing the layer of electro-optic material from the trench regions while leaving the electro-optic material on the release sheet in a plurality of discrete areas; and adhering a light transmissive substrate to the electro-optic material in the plurality of discrete regions after the layer of electro-optic material is removed from the trench regions.

This second process of the present invention may further include: forming an adhesive layer covering the layer of electro-optic material on the release sheet; severing the layer of electro-optic material and the adhesive layer to define a plurality of discrete regions; removing the layer of electro-optic material and the adhesion layer from the trench region; and after the layer of electro-optic material and the adhesive layer are removed from the trench regions, contacting the light-transmissive substrate with the adhesive layer in the plurality of discrete regions, thereby causing the light-transmissive substrate to adhere to the adhesive layer.

Alternatively or additionally, the second process of the present invention may further comprise: providing a release layer overlying the adhesive layer on the release sheet; severing the layer of electro-optic material, the adhesive layer and the release layer to define a plurality of discrete regions; and removing the release layer from the plurality of discrete regions and the trench region prior to contacting the light transmissive substrate with the adhesion layer. The removal of the release layer may be effected in two stages, in the first stage removing the release layer from the trench regions leaving the release layer covering the adhesive layer and the layer of electro-optic material in the plurality of discrete regions, and in the second stage removing the release layer from the adhesive layer and the layer of electro-optic material in the plurality of discrete regions.

Another form of the second process of the present invention further comprises: forming a subassembly comprising an adhesive layer on a second release sheet; and after adhering the light-transmissive substrate to the electro-optic material in the plurality of discrete areas, removing the release sheet from the layer of electro-optic material and contacting the electro-optic material with the adhesive layer of the subassembly, thereby adhering the subassembly to the layer of electro-optic material.

In a second process of the invention, the removal of the layer of electro-optic material from the trench regions is achieved by placing a sheet of material over the plurality of discrete regions and the trench regions and thereafter removing the sheet of material with portions of the electro-optic material from the trench regions to which it is attached, leaving the electro-optic material in the plurality of discrete regions. Alternatively, after severing the layer of electro-optic material, the adhesive layer and the release layer to define the plurality of discrete areas, portions of the release layer in the trench areas may be initially removed, and thereafter a sheet of material is placed over the plurality of discrete areas and the trench areas, and thereafter the sheet of material with the adhesive layer and portions of electro-optic material is removed from the trench areas to which it is attached, leaving the adhesive layer and the electro-optic material in the plurality of discrete areas. The removal of the sheet of material may also remove the release layer from the plurality of discrete regions. The substrate may include a light-transmissive conductive layer.

Drawings

Fig. 1A to 1E show schematic side views of various states of one form of the first process of the present invention for producing the first subassembly of the present invention. 【031】 Fig. 2A to 2F show schematic side views of respective states of one form of a second process of producing the first and second subassemblies of the present invention.

Fig. 3A to 3D show schematic side views of various states of a modified form of the second process of the present invention shown in fig. 2A to 2F, which again produces the first and second subassemblies of the present invention.

Detailed Description

The "loose" and "tight" release plates will be described below. These terms are used in their conventional sense in the art to indicate the magnitude of the force required to peel it from a layer in contact with a release plate, a tight release plate requiring more force than a loose release plate. In particular, if the stack has a tight release plate on one side and a loose release plate on the other side, it is possible to peel the loose release plate from the stack without separating the tight release plate from the stack.

As already noted, some subassemblies of the present invention contain two separate adhesive layers. When needed or desired, the two adhesive layers will be designated as "front" and "back" adhesive layers, these terms designating the location of the relevant adhesive layer in the final display produced by laminating the subassembly to a backplane; the front adhesive layer is an adhesive layer that is positioned between the electro-optic medium and the viewing surface of the display (i.e., the surface through which an observer views the display, typically the surface away from the backplane and considered the "front" of the display), while the back adhesive layer is positioned on the opposite side of the electro-optic layer from the front adhesive layer and adjacent to the backplane. In the usual case, i.e. where the display has a single front electrode between the electro-optic layer and the viewing surface and a plurality of pixel electrodes on the backplane and hence on the opposite side of the electro-optic layer, a front adhesive layer is located between the electro-optic layer and the front electrode and a rear adhesive layer is located between the electro-optic layer and the pixel electrodes.

The dimensions of the drawings are not exact dimensions. In particular, the thicknesses of the various layers are greatly exaggerated relative to their lateral dimensions for ease of explanation. The invention is well suited for the production of thin, flexible electro-optic displays; typically, a subassembly or front plane laminate that is the product of the process described below will have a thickness of about 100 μm (measured without the release sheet remaining, which is discarded prior to final lamination to the backplane), and can be laminated to a flexible backplane of similar thickness.

As already indicated, the figures show the various stages of three different processes of the invention, all of which ultimately result in the first subassembly of the invention; the second process illustrated in fig. 2A-2F also produces a second subassembly of the present invention. Accordingly, it is considered most convenient to describe the various subassemblies of the present invention that result from these processes first, and hereinafter describe the possibilities for producing these subassemblies from the multi-step process of the present invention.

The first subassembly of the present invention resulting from the illustrated process is shown in FIGS. 1D, 1E, 2E and 2F of the drawings; as explained below, the third process illustrated in fig. 3A-3D ultimately results in the same first subassembly as those illustrated in fig. 2E and 2F. The first subassembly shown in fig. 1E and 2F is a particular form of inverted front plane lamination described in the aforementioned 2007/0109219; other first subassemblies (not shown) of the present invention may be of a particular form of "conventional" (i.e., non-inverted) front plane lamination as described in the aforementioned U.S. patent No.6,982,178.

In each of fig. 1D, 1E, 2E and 2F, the first subassembly of the present invention includes a light transmissive substrate 120. Substrate 120 is typically a multilayer structure and typically includes a light-transmissive electrode layer, such as an Indium Tin Oxide (ITO) layer, forming the front electrode of the final display; the electrode layers are not shown separately in the drawings. However, a substrate 120 without an electrode layer may be used, for example in an electro-optic display intended to be written using a stylus or similar external electrode.

The first subassembly of the present invention also includes a plurality of discrete regions (104 in fig. 1D and 1E and 204 in fig. 2E and 2F) of electro-optic material disposed on the substrate 120. The subassembly is shown with a substrate (or front) adhesive layer (106 in fig. 1D and 1E and 206 in fig. 2E and 2F) interposed between the electro-optic material 104 or 204 and the substrate 120, but in some cases the front adhesive layer can be omitted, for example by using an electro-optic material that includes an adhesive that itself serves an adhesive function, as described in the aforementioned U.S. patent No.7,110,164. The discrete areas of electro-optic material 104 or 204 are separated from each other by a trench area (105 in fig. 1D and 1E, 205 in fig. 2E and 2F) that is free of electro-optic material and adhesive layer 106 or 206. Although each figure only shows two discrete areas of electro-optic material separated by a single trench region, in practice each subassembly typically has a large number of discrete areas of electro-optic material; for example, a sub-assembly intended for producing six separate displays may have a 3 x 2 arrangement of such regions separated from each other by two parallel trench regions and a third trench region extending at right angles to the two trench regions. Indeed, as described in more detail below, some subassemblies of the present invention can be in the form of a continuous web of indefinite length having a large number of regions of electro-optic material arranged in a two-dimensional array and separated from each other by two sets of trench regions extending in perpendicular directions.

The first subassembly of the invention further comprises at least one of an adhesive layer and a release layer on the opposite side of the layer of electro-optic material to the substrate. The first subassembly shown in fig. 1D and 2E possesses only the release layer 102 on the opposite side of the layer of electro-optic material relative to the substrate, whereas the subassembly shown in fig. 1E and 2F possesses the adhesive layer 122 in contact with the electro-optic layer 104 or 204 and the release layer 124 on the opposite side of the adhesive layer 122 relative to the electro-optic layer 104 or 204. Note that the release layer 102 is discontinuous in fig. 1D, wherein separate pieces of the release layer 102 only cover adjacent areas of the electro-optic layer 104 and do not extend across the trench regions 105. However in fig. 2E the release layer 102 is continuous and extends across the trench region 205. In fig. 1E and 2F, both the adhesion layer 122 and the release layer 124 are continuous and extend across the trench region 105 or 205.

A second subassembly of the present invention is shown in fig. 2D. The sub-assembly comprises a release sheet 102 supporting a plurality of discrete areas 204 of electro-optic material 204, the discrete areas 204 being separated from each other by channel areas 205 devoid of electro-optic material. The second subassembly also includes an adhesive layer 206 on the opposite side of the electro-optic layer from the release sheet 102 and a release layer or sheet 208 on the opposite side of the adhesive layer 206 from the release sheet 102. For reasons already explained, the adhesion layer 206 may be omitted in some cases. The release plate 208 shown in fig. 2D is discontinuous and does not extend across the channel region 205, but if desired, a second subassembly of the present invention can be produced having a continuous release plate similar to 208.

The method for producing the subassembly of the present invention will be described in detail. The first method of the invention shown in figure 1 is intended exclusively, but not exclusively, for the production of small electro-optic displays. In a first step of the process, an electro-optic medium is coated or otherwise deposited on a tight release sheet 102 to form a continuous electro-optic layer 104. Separately, a continuous front adhesive layer 106 is coated on a release sheet 108. The two resulting subassemblies are then laminated together with the adhesive layer 106 in contact with the electro-optic layer 104 to produce the structure shown in FIG. 1A. These are as described in the aforementioned U.S. patent No.7,110,164, and the resulting assembly is a dual release plate, as described in the aforementioned 2004/0155857.

In the next step in the process, the panel shown in FIG. 1A is cut into pieces of appropriate size to form individual displays. The cutting of the panel is conventionally accomplished by laser cutting, as indicated by lines 110 and 112 in fig. 1A, so as to cause the tab 108A of the release panel 108 to extend outwardly beyond the other layers, although methods such as die cutting may also be used. At this point, a cut may be, and typically is, made completely through the plate to provide any desired apertures or cuts in the front adhesive layer 106 and electro-optic layer 104; for example, the apertures may be cut through the front adhesive layer and electro-optic layer to provide pre-formed connection apertures as described in the aforementioned international application No. pct/US2007/063551, which will ultimately be used (in combination with corresponding apertures in the rear adhesive layer, as described below) to form conductive paths connecting the front electrodes to the backplane in the final display. The release plate 108 is then removed from the assembly by conveniently pulling on the tab 108A.

With the release plate 108 removed, a plurality of these sheets (labeled 114 in fig. 1B) are then placed in a mold or fixture, with the adhesive side facing up, that includes a thin alignment plate 116 adhered to a lamination tray 118. The alignment plate 11 is removable and typically discarded after 3 or 4 laminations (described below), however, the lamination is disk permanent; an advantage of this configuration is that the alignment plate 116 can be quickly changed so that the various parts can be laminated in the same laminator without the need for multiple expensive metal molds. Also, at least in some cases, alignment plate 116, which is typically formed of a polymer film such as polyethylene terephthalate (PET), can be laser cut using the same digital file used for laser cut piece 144. The thickness of the alignment plate 116 should be selected so that the upper (adhesive) surface of the sheet 114 extends slightly beyond the alignment plate 116 (approximately 1-2 mils, 25-51 μm).

As shown in fig. 1B, the sheet 114 held in the molds 116, 118 is then laminated to an oversized plate of the front substrate 120 (i.e., larger than the alignment plate 116). The front substrate 120 is a multi-layer structure including an Indium Tin Oxide (ITO) layer forming the front electrode of the final display. The front substrate also includes a removable masking film that is removed before the final display is placed in use, as described below.

This front substrate structure is designed to provide the front light-transmissive electrode of the final display. The front substrate 120 also provides the necessary mechanical support for the thin and relatively fragile front electrode. Furthermore, it is desirable to protect certain electro-optical layers, especially the electrophoretic layer, the front substrate preferably providing all necessary barriers to water vapor and oxygen, and uv absorption properties. The front substrate can also provide desirable antiglare properties to the viewing surface of the final display. The front substrate 120 has all of these functions while also being sufficiently thin and flexible to enable the formation of a final display that is sufficiently flexible to be wound around a 15mm diameter mandrel, for example. As already explained, the front substrate comprises a masking film; the masking film is provided primarily to increase the thickness of the front substrate to facilitate handling of the substrate during lamination. In a preferred process, the total thickness of the front substrate remaining in the final display (i.e., the masking film removed) is only about 1mil (25 μm), and the masking film is used to add about 2 mils (51 μm) to this thickness for ease of handling. The masking film is also typically used to prevent scratches or dust or debris from adhering to the adjacent anti-glare layer during lamination.

After lamination as shown in fig. 1B, the board with the front substrate 120 of the sheet 114 secured thereto is removed as a single unit from the dies 116, 118. Fig. 1D shows an enlarged view of two sheets 114 on a substrate 120, the sheets 114 and the substrate 120 together forming a first subassembly of the present invention as already described. The base 120 supporting the sheet 114 is then placed on a laser cutter with the sheet 114 facing the laser. A laser cutter is then used to cut the pilot hole through the front substrate 120 at a position aligned with the position of the sheet 114; these locating holes will be used to engage the board with locating pins to locate the board during later lamination, as described below. Alternatively, the registration holes may be pre-cut in the front substrate 120 before the front substrate 120 is laminated to the sheet 114, and if such pre-cut registration holes are provided, they will engage pins provided on the dies 116, 118 to align the front substrate with the sheet 114 during lamination thereof.

Respectively, a rear adhesive layer 122 (fig. 1C) is coated on a release sheet 124, and the exposed surface of the rear adhesive layer is covered by an intermediate layer (actually, another release sheet-not shown in the figure) for preventing contamination of the surface of the adhesive layer during laser cutting. The release layer/adhesive layer/intermediate layer "sandwich" is laser cut with the intermediate layer facing the laser to form pilot holes similar to those previously cut through the front substrate and intended for the same purpose. Laser cutters are also used to cut other apertures through the adhesive layer as needed for a particular display; for example, a laser cutter may cut apertures that constitute pre-formed connecting apertures in communication with corresponding apertures previously cut in the front adhesive layer and electro-optic layer, as described in the aforementioned international application No. pct/US 2007/063551.

In the next step of the process, the intermediate layer is removed from the back adhesive layer 122, and the back adhesive layer 122 is then placed on the base of the laminator with the adhesive release sheet 124, with its locating holes engaged with locating pins (not shown) on the laminator, as shown in fig. 1C. The release sheet 102 is peeled away from the sheet 114 mounted on the substrate 120 and the positioning holes previously cut in the release sheet 120 are also engaged with the positioning pins on the laminator so that the exposed surface of the electro-optic layer 104 faces the back adhesive layer 122. The two panels are then laminated together, thus forming an inverted front plane laminate, as described in the aforementioned 2007/0109219. Fig. 1E is an enlarged view similar to fig. 1D and showing a portion of substrate 120 supporting two sheets 114 at the same stage as fig. 1C. As already explained, the structure shown in fig. 1E constitutes the first subassembly of the invention.

At this time, the masking film is typically removed because it is convenient to remove the film before the individual displays are separated from each other, however, removal of the masking film may be accomplished later if desired. Whether or not the masking film is removed, the next major step is to separate the panel into a plurality of pieces that are laminated in an inverted front plane. The separation is achieved by laser cutting of the laminated sheet, which is held on locating pins to ensure accurate location of the cut. The cut severs the third release sheet 124, the back adhesive layer 122, and the front substrate 120 to form a ready, inverted, front plane laminated discrete sheet for lamination to a backplane to form a final display after removal of the third release sheet 124. It is desirable to cut the laminated sheet to leave the tab of the third release sheet extending beyond the front substrate 120, adhesive layers 107 and 122 and electro-optic layer 104; such a tab facilitates removal of the third release plate 124 during production of the final display.

As shown in fig. 2A-2F of the drawings, the second process of the present invention is primarily intended for producing larger displays than the first process described above with reference to fig. 1A-1E; the portion resulting from the second process is large enough that the loss of electro-optic material present in the trench regions between adjacent displays can be tolerated. As will be set forth in the detailed description of the second process below, the first process differs from the second process primarily in that the second process does not utilize a fixture to align the separate pieces of electro-optic medium on the front substrate; rather, during the second process, successive layers of electro-optic material are severed to produce a plurality of "islands" of electro-optic material separated by trench regions devoid of electro-optic material.

In fig. 2A, the second process of the present invention is the same as the first process, wherein fig. 2A is the same as fig. 1A. However, as can be seen by comparing fig. 1B and fig. 2B, the following cutting steps are different. The cutting step of the second process is accomplished in which the release sheet 108 faces the laser cutter and kiss cutting (kiss cutting) is performed such that the release sheet 108, the front adhesive layer 106, and the electro-optic layer 104 are cut but the tight release sheet 102 is not cut. Also during the first process, also in this step, any through-going apertures for aligning the holes, preformed connections or apertures for other purposes may be cut (but this may also be done later, as described below). Because in some cases it may be possible to implement the entire second process on a roll-to-roll substrate, the through-hole openings formed in this step may include drag-feed holes formed along the side edges of the web of material and serving as locating holes in a later stage of the process.

The continuous portion of the release sheet 108 (i.e., the portion of the release sheet that will become the trench area at a later stage in the process) is then removed, either manually or mechanically, thus leaving the structure shown in FIG. 2B, where the "islands" 208 corresponding to the release sheet of the final display hold the front adhesive layer 106 and electro-optic layer 104 continuous but cut-off above. The next step in the process is to remove the unwanted portions of the front adhesion layer 106 and the electro-optic layer 104, respectively. Because the front adhesive layer and the electro-optic layer possess sufficient mechanical cohesion that they can be manually rolled up on themselves and removed from the underlying tight release sheet 102 in large pieces, the removal can be accomplished manually. However, as shown in FIG. 2C, in a preferred method for removing the unwanted portions of the front adhesive layer and electro-optic layer, a sacrificial plate 210 (which need not be tacky) is cold rolled onto the islands 208 and exposed portions of the front adhesive layer 107. The sacrificial plate 210 is then removed, thus removing the portions of the front adhesive layer 106 and electro-optic layer 104 not covered by the islands 208, and leaving the structure shown in FIG. 2D. As described above, this structure comprises the second subassembly of the present invention in which a plurality of "mesas" (mesas) extend upwardly from the tight release sheet 102, wherein the mesas comprise islands 208 of the tight release sheet and similarly sized regions 206 and 204 underlying the front adhesive layer and electro-optic layer, respectively, the mesas being separated from one another by trench regions 205. As described in the first process of the present invention described above, in some cases, the front adhesive layer 206 may be omitted, for example, when the electro-optic material is capable of acting as an adhesive by itself. Also, as should be clear, each of these mesas will eventually form a separate display. (in some cases, it may be possible to recycle the portion of the front adhesive layer and electro-optic layer removed on the discard plate 210 in other small displays.)

In the next step, the remaining portion 208 of the release plate is peeled off of the structure shown in fig. 2D and the remaining layers of the structure are laminated to the plate of the front substrate 120, which may be the same as that used in the first process of the invention described above, and may be previously provided with any apertures required for engagement with locating pins or the like during a later stage of the process. The first subassembly of the present invention resulting from this lamination is shown in fig. 2E and has been described in more detail above.

Although produced by a very different method, the subassembly shown in FIG. 2E is very similar to that produced in the first process of the present invention after lamination and subsequent laser cutting as shown in FIG. 1B, the only difference being that the tight release sheet 102 is continuous in the structure of FIG. 2E. Thus, the remaining steps of the second process are substantially the same as the first process. Again, a rear adhesive layer 122 is coated on a third release sheet 124, an intermediate layer is applied over the adhesive layer 122 and any desired apertures are cut in the resulting structure. The intermediate layer is then removed, the tight release sheet 102 is removed from the structure of fig. 2E, and the two resulting films are laminated together to produce a final inverted front plane laminate or subassembly shown in fig. 2F, which is the same as that produced by the first process of the present invention.

The third process of the present invention shown in fig. 3A-3D is generally a variation of the second process described above. As shown in fig. 3A and 3B, which are respectively equivalent to fig. 2A and 2B, the third process is equivalent to the second process up to fig. 3B. However, in the next step of the process, rather than discarding the plate 210, the adhesive film 310 (fig. 3C) is rolled up and adhered to the exposed surfaces of the release plate 108 and the front adhesive layer 106. Thus, when the adhesive film 310 is removed, the remaining release sheet 108 and the front adhesive layer 106 and unwanted portions of the electro-optic layer 104 are removed therefrom, thus resulting in the structure shown in FIG. 3D; in fact, the use of the adhesive film 310 allows the steps from fig. 2B and 2C and subsequent removal of the release plate prior to lamination to the front substrate 120 to be combined into a single operation. Once the structure shown in fig. 3D has been produced, the remaining steps of the third process are the same as those of the second step.

It should be noted that in this third process of the invention, all removal of unwanted material is achieved in the form of a plate, or if the process is to use a continuous web of material, in the form of a continuous web. Thus, the third process of the present invention is well suited for use on continuous, roll-to-roll substrates.

However, if the process shown in figures 3A-3D and the subsequent lamination to form the final electro-optic display is to be carried out on a continuous web, care must be taken to maintain proper alignment for the various steps throughout the process. At the time shown in FIG. 3D, a "land" 204, 206 is created at a known location on the release plate 102. If the structure shown in FIG. 3D undergoes lamination similar to that shown in FIG. 1B in order to adhere the mesas to the front substrate, and then laminating the mesas first to the backplane on the front substrate (with or without intermediate lamination of the adhesive layer to the electro-optic layer 204) is achieved on a web, it is obviously necessary to ensure that the mesas are aligned with the backplane on edge. Because of the initial alignment between the table top and the release plate 102, removal of the release plate can disrupt the alignment. To ensure that the table tops are aligned upright with the backplate, the table tops must first be transported to a known position on the front substrate relative to some fixed indicia, and then the front substrate supporting the table tops is brought into contact with the backplate so that the fixed indicia on the front substrate are in known alignment with the backplate. The required alignment is most easily maintained in the desired alignment with each other by providing all the webs to be drawn through the delivery holes and ensuring that the webs are driven by the usual drawing delivery apparatus.

It will be apparent from the foregoing discussion that the method of the present invention can be practiced with any electro-optic layer having a solid external surface to which the adhesive layer and release sheet can adhere and which has sufficient mechanical adhesion to allow the necessary handling of the film containing the electro-optic layer. The method can therefore be implemented using any of the types of electro-optic media described above. For example, the method may utilize a rotating bichromal member, electrochromic or electrophoretic medium, and in the last case, the electrophoretic medium may be of the encapsulated, polymer dispersed or microcell type.

Claims (26)

1. A sub-assembly for use in forming an electro-optic display, the sub-assembly being characterised by, in this order:

a light-transmissive substrate (120);

a plurality of discrete areas (106; 206) of adhesive material disposed on the substrate (120), the discrete areas (106; 206) being separated from one another by a channel area (105; 205) substantially free of adhesive material;

a plurality of discrete areas (104; 204) of electro-optic material disposed on the adhesive material, each of the discrete areas (104; 204) of electro-optic material being disposed on one of the plurality of discrete areas (106; 206) of adhesive material, the discrete areas (104; 204) of electro-optic material being separated from one another by a trench area (105; 205) substantially free of electro-optic material; and

on the opposite side of the area of electro-optic material relative to the substrate, at least one of the second adhesive layer (122) and the release layer (102; 124) may be peeled from the subassembly without substantial damage thereto.

2. A sub-assembly according to claim 1, having a second adhesive layer (122) in contact with the region (204) of electro-optic material and a release layer (124) on the opposite side of the second adhesive layer (122) to the electro-optic material.

3. The sub-assembly of claim 1, wherein the substrate (120) comprises a light-transmissive electrically-conductive layer.

4. A sub-assembly according to claim 1, further comprising a removable masking film arranged on the opposite side with respect to the substrate (120) of electro-optic material.

5. A sub-assembly for use in forming an electro-optic display, the sub-assembly characterized by:

a release plate (102) for releasing the release plate,

a plurality of discrete areas (204) of electro-optic material arranged on a release sheet (102), the discrete areas (204) being separated from one another by channel areas (205) substantially free of electro-optic material;

the release sheet (102) being capable of peeling away from the electro-optic material without substantial damage thereto; and

at least one of an adhesive layer (206) and a release layer (208) on an opposite side of the area (204) of electro-optic material relative to the release plate (102), the release layer (208) being peelable from the electro-optic material (204) or the adhesive layer (206) in contact therewith without substantial damage thereto.

6. A sub-assembly according to claim 5, having an adhesive layer (206) in contact with the region (204) of electro-optic material and a release layer (208) on the opposite side of the adhesive layer (206) to the electro-optic material.

7. The subassembly of claim 6, wherein the adhesive layer (206) and the release layer (208) do not extend across the trench region (205)

8. A sub-assembly according to claim 1 or 5, wherein the electro-optic material comprises a rotating bichromal member or electrochromic material.

9. A sub-assembly according to claim 1 or 5, wherein the electro-optic material comprises an electrophoretic material with a plurality of electrically charged particles disposed in a fluid and capable of moving through the fluid under the influence of an electric field.

10. The subassembly of claim 9, wherein the charged particles and the fluid are confined in a plurality of capsules or microcells.

11. The subassembly of claim 9, wherein the charged particles and the fluid are present as a plurality of discrete droplets surrounded by a continuous phase comprising a polymeric material.

12. The subassembly of claim 9, wherein the fluid is gaseous.

13. A process for forming a subassembly according to claim 1, the process characterized by: forming a plurality of features (114), each feature (114) comprising a layer of electro-optic material (104) and a release layer (102) peelable from the electro-optic material (104) without substantial damage thereto;

arranging the plurality of components (114) on a support surface (118), the components (114) being spaced apart from each other, the layer of electro-optic material (104) facing away from the support surface (118); and

contacting the disposed plurality of components (114) with the light-transmissive substrate (120) under conditions effective to cause the plurality of components (114) to adhere to the substrate (120).

14. A process according to claim 13, wherein the support surface (118) is provided with a mould (116) having a plurality of recesses, wherein the components (114) are received within the plurality of recesses.

15. The process of claim 13, wherein each of the components (114) further comprises a substrate adhesive layer (106), and the components (114) are disposed on the support surface (118), with the substrate adhesive layer (106) facing the substrate (120), such that the substrate adhesive layer (106) functions to adhere the components (114) to the substrate (120).

16. The process of claim 13, further comprising:

forming a subassembly comprising an adhesive layer (122) on a second substrate (124); and

removing the release layer (102) from the component (114) after adhering the component (114) to the light-transmissive substrate (120), and contacting the component (114) with the adhesive layer (122) on the second substrate (124) under conditions effective to cause the component (114) and the light-transmissive substrate (120) to adhere to the adhesive layer (122).

17. The process of claim 13, wherein the substrate (120) comprises a light-transmissive electrically conductive layer.

18. A process for forming a subassembly according to claim 1, the process characterized by:

forming a layer of electro-optic material (104) on the release sheet (102);

severing the layer of electro-optic material (104) on the release sheet (102) to define a plurality of discrete regions (204) separated from one another by trench regions (205);

removing the layer of electro-optic material (104) from the trench regions (205) while leaving the electro-optic material (204) on the release sheet (102) in a plurality of discrete regions;

and adhering a light transmissive substrate (120) to the electro-optic material (204) in a plurality of discrete areas after the layer of electro-optic material (104) is removed from the trench regions (205).

19. The process of claim 18, further comprising:

forming an adhesive layer (106) on the release sheet (102) covering the layer of electro-optic material (104);

severing the layer of electro-optic material (104) and the adhesive layer (106) to define a plurality of discrete regions;

removing the layer of electro-optic material (104) and the adhesive layer (106) from the trench region;

and contacting the light-transmissive substrate (120) with the adhesive layer (206) in a plurality of discrete areas after the layer of electro-optic material (104) and the adhesive layer (106) are removed from the trench areas (205), thereby causing the light-transmissive substrate (120) to adhere to the adhesive layer (206).

20. The process of claim 19, further comprising:

providing a release layer (108) overlying the adhesive layer (106) on the release sheet (102);

severing the layer of electro-optic material (104), the adhesive layer (106), and the release layer (108) to define a plurality of discrete regions; and

removing the release layer (108) from the plurality of discrete regions and the trench regions (205) prior to contacting the light-transmissive substrate (120) with the adhesion layer (206).

21. A process according to claim 20, wherein the removal of the release layer (108) is effected in two stages, in a first stage causing the release layer (108) to be removed from the trench regions (205) leaving the release layer (208) covering the adhesive layer (206) and the layer of electro-optic material (204) in the plurality of discrete regions, and in a second stage causing the release layer (208) to be removed from the adhesive layer (206) and the layer of electro-optic material (204) in the plurality of discrete regions.

22. The process of claim 18, further comprising:

forming a subassembly comprising an adhesive layer (122) on a second release sheet (124); and

after adhering a light transmissive substrate (120) to the electro-optic material (204) in the plurality of discrete areas, removing the release sheet (102) from the layer of electro-optic material (204) and contacting the electro-optic material (204) with the adhesive layer (122) of the subassembly, thereby adhering the subassembly (122, 124) to the layer of electro-optic material (204).

23. A process according to claim 18, wherein the removal of the layer (104) of electro-optic material from the trench regions (205) is by placing a sheet (210) of material over the plurality of discrete regions and the trench regions (205) and thereafter removing the sheet (210) of material with portions of the electro-optic material (104) from the trench regions (205) to which it is attached, leaving the electro-optic material (204) in the plurality of discrete regions.

24. A process according to claim 21, wherein after severing the layer of electro-optic material (104), the adhesive layer (106) and the release layer (108) to define the plurality of discrete areas, the portion of the release layer (108) in the trench areas (205) is first removed, and thereafter a sheet of material (310) is placed over the plurality of discrete areas and the trench areas (205), and thereafter the sheet of material (310) with the adhesive layer (106) and the portion of the electro-optic material (104) is removed from the trench areas (205) to which it is attached, leaving the adhesive layer (206) and the electro-optic material (204) in the plurality of discrete areas.

25. The process of claim 24, wherein the removing of the sheet of material (310) also removes the release layer (108) from the plurality of discrete areas.

26. The process of claim 18, wherein the substrate (120) comprises a light-transmissive electrically-conductive layer.