HK1149959B - Electro-optic displays - Google Patents

Description

Electro-optic display

The present application relates to:

(a) U.S. patent nos. 7,349,148;

(b) U.S. Pat. Nos. 7,173,752;

(c) U.S. patent nos. 6,831,769;

(d) U.S. patent application publication No. 2005/0122563;

(e) U.S. Pat. Nos. 7,012,735; and

(f) U.S. patent No.7,110,164.

The above patents and patent applications are hereby incorporated by reference in their entirety, and all U.S. patents and published and co-pending applications described below are also incorporated by reference in their entirety.

Technical Field

The present invention relates to electro-optic displays. More particularly, the invention relates to methods for producing stylus-based and similar electro-optic displays. The invention is particularly, but not exclusively, intended for use in displays containing encapsulated electrophoretic media.

Background

Background terminology and state of the art with respect to electro-optic displays is discussed in detail in U.S. Pat. No.7,012,600, to which the reader is referred for further information. Therefore, the terms and states of the art are briefly summarized as follows.

As applied to materials or displays, the term "electro-optic" 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 changed from its first display state to its second display state by application of an electric field to the material. Some electro-optic materials are solid, which refers to a solid in the sense that the electro-optic material has a solid outer surface, although the material may, and typically does, have an internal liquid or gas-filled space. Such displays using solid electro-optic materials may be referred to hereinafter for convenience as "solid electro-optic displays". Thus, the term "solid state electro-optic display" includes rotating bichromal member displays, encapsulated electrophoretic displays, microcell electrophoretic displays, and encapsulated liquid crystal displays.

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 its first or second display state by means of an addressing pulse having a finite duration, that state will continue for a time at least several times (e.g. at least 4 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 two-color component displays (see, e.g., U.S. Pat. Nos. 5,808,783; 5,777,782; 5,760,761; 6,054,071; 6,055,091; 6,097,531; 6,128,124; 6,137,467; and 6,147,791);

(b) electrochromic displays (see, for example, Nature 1991, 353, 737 to O' Regan, b. et al; Information Display, 18(3), 24 (3.2002), d. Bach, u. et al, 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, for example, Hayes, R.A. et al, Nature, 425, 383-385 (9/25 2003), entitled "Video-Speed Electronic Paper Based on electrowetting" and U.S. patent publication No. 2005/0151709);

(d) particle-based electrophoretic displays in which a plurality of charged particles move through a fluid under the influence of a battery (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 patent application publication No. WO00/38000; WO 00/36560; WO00/67110 and WO 01/07961; and European patent Nos. 1,099,207B1 and 1,145,072B 1; and other MIT and E Ink patents and applications discussed in the aforementioned U.S. Pat. No.7,012,600).

There are several different variations of electrophoretic media. The electrophoretic medium may use a liquid or gaseous fluid; for gaseous fluids see, for example, Kitamura, T.et al, published in IDW Japan, PaperHCS1-1 in 2001, entitled "Electrical inside movement for electronic Paper-like display", and Yamaguchi et al, published in IDW Japan, Paper AMD4-4) in 2001, entitled "inside display using insulating substrates charged plasma"; 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; 1,505,194, 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; WO2004/079442 and WO 2004/001498. The medium may be encapsulated, comprising a plurality of capsules, each capsule itself comprising 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 within a polymeric binder to form an adhesive layer (coherent layer) located between two electrodes; see the MIT and E Ink patents and applications mentioned above. Alternatively, the wall capsules surrounding the discrete microcapsules in the encapsulated electrophoretic medium may be replaced by a continuous phase, thus producing a so-called polymer dispersed electrophoretic display, in which the electrophoretic medium comprises a plurality of discrete droplets of an electrophoretic fluid and a continuous phase of a polymeric material; 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 retained within a plurality of cavities formed within a carrier medium, typically a polymer film; see, for example, U.S. Pat. Nos. 6,672,921 and 6,788,449.

Encapsulated electrophoretic displays generally do not suffer from the failure modes of aggregation and settling of conventional electrophoretic devices and have additional advantages such as the ability to print or coat the display on a variety of different flexible and rigid substrates. (the use of the term "printing" is intended to include all forms of printing and coating including, but not limited to, pre-set coating such as slot or extrusion coating of small die coating (patch die coating), slide or cascade coating, curtain coating, roll coating such as knife-over-roll coating, forward and reverse roll coating, gravure coating, dip coating, spray coating, meniscus coating, spin coating, brushing, air knife coating, screen printing processes, electrostatic printing processes, thermal printing processes, ink jet printing processes, electrophoretic deposition (see U.S. Pat. No.7,339,715), and other similar techniques). thus, the resulting display can be flexible. Further, since the display medium can be printed (using various methods), the display itself can be manufactured at low cost.

The manufacture of a three-layer electro-optic display typically involves at least one lamination operation. For example, in several of the aforementioned MIT and E Ink patents and applications, a method is described for manufacturing an encapsulated electrophoretic display in which a capsule-encapsulated electrophoretic medium comprising a capsule in an adhesive is coated onto a flexible substrate comprising Indium Tin Oxide (ITO) or similar conductive coating (serving as one electrode of the final display) on a plastic film, the capsule/adhesive coating being baked to form an adhesive layer of the electrophoretic medium securely bonded to the substrate. A backplane is separately prepared, which includes an array of pixel electrodes and appropriately laid out conductors connecting the pixel electrodes to drive circuitry. To form the final display, the substrate with the bladder/adhesive layer thereon is laminated to a backplane using a lamination adhesive. Electrophoretic displays using a stylus or other movable electrode that can slide over a simple protective layer, such as a plastic film, can be prepared by replacing the backplane with a very similar method. In a preferred form of the method, the backplane is itself flexible and is prepared by printing the pixel electrodes and conductors on a plastic film or other flexible substrate. For mass production of displays by this method, a obvious lamination technique is roll lamination using a lamination adhesive. Other types of electro-optic displays may use similar manufacturing techniques. For example, a microcell electrophoretic medium or a rotating bichromal member medium may be laminated to the backplane in essentially the same manner as the encapsulated electrophoretic medium.

The present invention relates to so-called "stylus-based displays". As mentioned above, most electro-optic displays are made up of fixed electrodes located on both sides of an electro-optic medium. However, it is known (see for example the aforementioned us patent No.6,473,072) that electro-optic displays can be constructed with fixed electrodes located on only one side of the electro-optic medium, typically on the side opposite the viewing surface of the display. The other electrode, which is required to provide an electric field across the electro-optic medium, is in the form of a stylus, print head or similar moveable device which can be moved manually or mechanically relative to the electro-optic medium (the term "stylus-based display" is used herein to cover in a broad sense all displays having such moveable electrodes, irrespective of the exact nature of the moveable electrode, and the term "stylus" is used to refer to all such moveable electrodes). Such stylus-based displays may be used, among other things, to capture handwritten material, including signatures, since a user can manipulate the movable electrodes and "write" on a viewing surface of the display in a manner similar to a pen.

One problem with producing stylus-based displays is providing a suitable layer between the electro-optic medium and the stylus. Many electro-optic media are susceptible to mechanical damage and some users attempt to hold the stylus in a heavy-handed manner when writing on an electro-optic display, in which case a sufficiently thick and robust protective layer needs to be provided between the electro-optic medium and the stylus to protect the electro-optic medium from mechanical damage. However, because such a protective layer is present between the electrodes of the display, there is a voltage drop across the protective layer, which, for any given operating voltage applied between the electrodes, reduces the voltage across the electro-optic medium itself and thus the electro-optic properties of the medium. Although it appears that the voltage drop across the protective layer can be minimised by using a highly conductive protective layer, the resistance of the protective layer needs to be sufficiently large to prevent lateral flow of current through the protective layer (i.e. flow of current in the plane of the protective layer), which results in a change in the optical state of the electro-optic medium over an area substantially wider than the width of the stylus, and thus in effect "blurs" the lines produced by moving the stylus over the protective layer.

The voltage drop across the protective layer requires a significant increase in the operating voltage of the display to provide satisfactory electro-optic performance. For example, when an encapsulated electrophoretic medium commercially sold by E Ink corporation is used in a display having two sets of fixed electrodes, such that only the electro-optic medium and (relatively thin) laminating adhesive layer are present between the electrodes, the encapsulated electrophoretic medium operates at 15V. To use such an electrophoretic medium in a stylus-based display, it has been considered necessary to date to use a polymer sheet such as Pomalux SD-A (a statically dissipative acetal copolymer manufactured by Westlake Plastics Co., P.O. Box 127, Lenni PA 19052-0127) having a thickness of 5-10 mils (127-. These polymer sheets are very hard and increase the required operating voltage of the display to 100-200V. A disadvantage of such high operating voltages is that they are generally considered by users to be unsafe (although in practice the very low currents required for electrophoretic displays enable such voltages to be used with complete safety). More importantly, one major application of stylus-based displays is electronic notebooks, which need to be highly portable and battery powered. Generating an operating voltage of 100-200V from a battery requires complex and relatively expensive power supply circuitry, and the high voltage uses so much power that battery life is undesirably short. Moreover, the thickness of the protective layer reduces the maximum resolution of the display, since there is inevitably some lateral flow of current within the protective layer, such that the lines written by the stylus are inevitably widened by some fraction of the thickness of the protective layer.

There is therefore a need for a protective sheet for use in a stylus-based electro-optic display that provides adequate protection of the electro-optic medium while reducing the required operating voltage, and the present invention seeks to provide such a protective layer.

Disclosure of Invention

The invention provides a method for making an electro-optic display, the method comprising:

forming a layer of electro-optic material on the electrodes;

depositing a layer of a substantially solvent-free polymerizable liquid material on the layer of electro-optic material;

and

exposing the polymerizable liquid material to conditions effective to polymerize the material, thereby forming a polymer layer on the layer of electro-optic material.

The display so produced is intended to be written using a stylus (the term being broadly defined above). In such a method, the polymerizable liquid material is thermally curable and the conditions effective to cause polymerization of the material may comprise heating the liquid material to a temperature high enough to cure the material. Alternatively, the polymerizable liquid material is radiation curable and the conditions effective to polymerize the material may comprise exposing the liquid material to radiation having a wavelength effective to cure the material; those skilled in the art of solvent-free polymerizable liquid materials will appreciate that typically the polymerizing radiation is ultraviolet light. The polymerizable liquid material may comprise an acrylate, a urethane acrylate mixture or a silica gel.

The method may comprise controlling the thickness of the layer of polymerisable liquid material deposited on the layer of electro-optic material. The thickness of the layer of polymerizable liquid material may be controlled by a doctor blade or pressure application. Alternatively, the thickness of the layer of polymerizable liquid material may be controlled by contacting the layer of liquid material with a release sheet and passing a nip roller over the sheet prior to polymerizing the liquid material.

For the reasons already explained, it is desirable to keep the thickness of the final polymer layer as small as possible and to achieve good protection of the electro-optical material. Thus, the thickness of the polymer layer may be from about 6 to about 250 μm, and preferably from about 8 to about 50 μm. In some cases, the layer of electro-optic material formed on the electrodes has an uneven exposed surface and the final polymer layer levels the layer of electro-optic material such that the exposed surface of the final polymer layer is substantially planar.

The electro-optic material used in the present method may be of any of the types discussed above. Thus, for example, the electro-optic material may comprise a rotating bichromal member or an electrochromic material. Alternatively, the electro-optic material may comprise 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 within a plurality of capsules or microcells. Alternatively, the electrophoretic material may be of the polymer dispersed type, the electrically charged particles and the fluid being present as a plurality of discrete droplets surrounded by a continuous phase comprising a polymeric material. The fluid may be liquid or gaseous.

The invention also provides an electro-optic display capable of being imaged by a stylus, the display comprising: an electrode; a layer of electro-optic material disposed on the electrodes; and a polymer layer on the layer of electro-optic material, the polymer layer comprising a polymerized product of a substantially solvent-free polymerizable liquid material.

Drawings

Figure 1 of the accompanying drawings is a schematic side view showing the application of a polymerisable liquid material to an electro-optic material in a method for forming an electro-optic display of the present invention.

FIG. 2 is a schematic side view similar to FIG. 1 but showing the use of a release sheet and roller to form a uniform layer of polymerizable liquid material.

Detailed Description

As mentioned above, the present invention relates to the use of a substantially solvent-free polymerisable liquid material (a so-called "100% solid" monomer or oligomer) to form a protective layer over a layer of electro-optic material, which protective layer is used to prevent mechanical damage to the electro-optic material when writing on a display using a stylus or similar device. It has been found that the use of a substantially solvent-free polymerizable liquid material to form such a protective layer alleviates or eliminates the problems discussed above with respect to stylus-based displays; in particular, the use of these polymerizable liquid materials allows the formation of a thin, rigid protective layer that provides sufficient mechanical protection for commercial electro-optic materials, but is thin enough to substantially reduce the operating voltage of the display compared to existing stylus-based displays using conventional protective layers. In practice it has been found that the operating voltage of the display of the invention can be 80-90% lower than that of the prior art display. A thinner protective layer also allows higher resolution addressing of the display and enables the manufacture of stylus-based flexible displays.

The stylus-based displays of the present invention may be formed by coating or laminating a layer of electro-optic material directly onto the electrically conductive electrodes (in many cases, particularly where the electrodes need to be light transmissive, it is typically necessary to mechanically support the electrodes on a substrate, typically a polymer film; however, since suitable substrates are well known to those of ordinary skill in the art of electro-optic displays and are discussed, for example, in the aforementioned U.S. Pat. No.6,982,178, such substrates will not be discussed in detail herein). The polymerizable liquid material may be used to form a viewing or non-viewing surface of the display, more typically the former. It is apparent that if the polymerisable liquid material is to form the viewing surface of a display, the polymer layer formed by polymerisation of the liquid material must be light transmissive, and in this case the electrodes on which the layer of electro-optic material is formed may be opaque and can be formed from an inexpensive conductor such as metallised poly (ethylene terephthalate) (PET) or aluminium or other metal foil. However, if the electrode on which the layer of electro-optic material is formed is to comprise the viewing surface of the display, that electrode needs to be light transmissive and may therefore be formed, for example, from Indium Tin Oxide (ITO), CNT or a conductive polymer such as polythiophene.

The polymerizable liquid materials used in the process of the present invention are known in several industries as "hard coat materials," for example, for use as optical adhesives to provide hard surfaces on wood floors and as scratch resistant coatings on eyeglasses and other optical devices. The polymerizable liquid material comprises a radiation or thermally curable monomer or oligomer, typically an acrylate, urethane acrylate blend or silicone. Currently preferred liquid materials are optical adhesives manufactured by Norland Products, 2540Route 130, Suite 100, p.o.box637, Cranbury NJ 08512, particularly those sold under the trademarks NOA 63, NOA71 and NOA 81. The polymerisable liquid material is a relatively low viscosity liquid which is capable of flowing to produce a thin layer of liquid over the electro-optic material. Typically, the polymer layer produced after liquid polymerization will have a thickness in the range from about 6 to 250 μm, desirably in the range from 8 to 50 μm.

An important property of the polymerizable liquid material is the electrical conductivity of the layer formed after polymerization; the polymerized layer should not be too conductive or the display resolution will be lost. It has been found empirically that the loss in resolution is at 5 x 10⁵The range of surface conductivities of ohms/square appears to become significant.

The thickness of the layer of polymerizable liquid material, and thus the thickness of the final polymer layer, can be controlled by several techniques familiar to those skilled in the art of liquid coating. For example, fig. 1 of the accompanying drawings illustrates, in a highly schematic manner, a conductive electrode 102 on which electrode 102 an electrophoretic layer comprising capsules 104 disposed in a binder 106 has been deposited. A polymerizable liquid material 108 is applied (e.g., using a die or slot coater) over the electrophoretic layer and the thickness of the liquid material 108 is controlled by a doctor blade 110. It should be noted that the upper surface of the electrophoretic layer (as illustrated in fig. 1) is not flat due to the capsules 104 protruding upward from the adhesive 106, but the provision of the liquid material 108 enables the final surface of the polymeric protective layer to be flat. (although FIG. 1 suggests that the thickness of the layer of polymerizable liquid material over the center of the capsules 104 may be close to zero, in practice this is undesirable and there should be at least a minimum thickness of the protective layer over the entire electrophoretic layer.)

Figure 2 illustrates in a highly schematic way an alternative method of the invention. The conductive electrode 102, the capsule 104, and the adhesive 106 in this second method are the same as those shown in fig. 1. And a polymerizable liquid material 108 is applied over the electrophoretic layer. However, no doctor blade is employed; rather, a release sheet 212 is applied over the liquid material 108 and the entire assembly is passed between rollers 214 and 216 to control the thickness of the liquid material 108.

Although fig. 2 suggests that the assembly passes horizontally through the nip rollers, it is more convenient in large scale roll-to-roll production that the assembly passes vertically down through the nip rollers, while the polymerizable liquid material may be continuously applied between the electrophoretic medium and the release sheet 212.

Where a release sheet is employed to control the thickness of the liquid material 108, the release sheet may be removed immediately after solidification of the liquid material, or may remain in place until a later time to provide mechanical protection to a polymer layer formed by solidifying the liquid material.

In the present method, the sheet for controlling the thickness of the liquid layer does not have to be a release sheet, and the sheet does not have to be flexible. Moreover, it is not necessary to remove the sheet from the polymer layer formed by curing the liquid material. For example, whether the sheet is rigid or flexible, it may comprise a transparent sheet that is used as a protective layer in the final display. Alternatively, the sheet may contain a conductive layer that can be permanently adhered to the final display by a polymer layer. Typically, such a conductive layer will form the common front electrode of the final display, and in such cases, the conductive layer should be light transmissive so that the change in optical state of the electro-optic medium can be seen through the conductive layer.

The sheet used to control the thickness of the liquid layer can also be in the form of a colour filter array (typically with a conductive layer to form the common front electrode of the final display), which may be flexible or rigid. Such a color filter array needs to be aligned with the pixels of the electrodes on the opposite side of the electro-optic medium. If the color filter array is rigid (e.g., a glass color filter array), the color filter array may be placed on a polymerizable liquid material and roughly aligned with the pixels. The color filter may then be pressed or rolled and a portion of the color filter array is finely aligned with the pixels using a color filter array alignment tool or fixture. After fine alignment, a small region of polymerizable liquid material is spot cured to fix the color filter array in place relative to other components of the display. The display may be treated to remove any trapped gases before the remainder of the polymerizable liquid material is cured (see below).

The flexible color filter array can be adhered in a very similar manner except that to avoid misalignment due to distortion of the flexible color filter array, the fine alignment of the color filter array and subsequent dot curing steps typically need to be repeated multiple times over different regions of the display until all regions of the display are properly fine aligned.

In most cases where the sheet used to control the thickness of the liquid layer is to remain as a permanent part of the display, it is difficult to avoid trapping some air bubbles under the sheet. Techniques for removing such trapped air bubbles are well known in the art (e.g., subjecting the display to autoclaving or placing the display in a vacuum) and any known technique may be used in the present invention. As noted above, if the sheet is a color filter array or similar sheet that requires alignment with the remainder of the display, a spot cure of the polymerizable liquid material should be performed prior to the de-bubbling process to ensure that alignment of the sheet is maintained during de-bubbling. In other cases, such as when the sheet contains only a conductive layer and (optionally) a support for the conductive layer, fine alignment is not required and bubble removal can be performed without the need for a prior spot cure of the polymerizable liquid material.

The following examples are now given by way of illustration only to show details of the presently preferred process of the invention.

Examples of the invention

The bladder/adhesive slurry is slot coated onto the ITO-covered surface of a poly (ethylene terephthalate)/ITO film, and the resulting coated film is dried to produce an adherent layer of bladders in adhesive on the PET/ITO film, substantially as described in the aforementioned U.S. patent No.6,982,178. A plastic release sheet was individually covered over a generally 24 square inch (61 square centimeter) sheet of metal, positioned to expose the release layer. A 12 square inch (30 square centimeter) dried capsule coating film was placed in the center of the top of the release sheet, exposing the capsule layer. A drop of Norland optical adhesive (NOA 63, NOA71, or NOA 81) was placed 13mm from one edge of the capsule coated film, the drop extending to within about 13mm from each side edge of the film to minimize the amount of optical adhesive squeezed out of the display during subsequent steps of the process. A second release sheet is then placed over the optical adhesive-bearing bladder coating film, the second release sheet being positioned so that its release layer faces the bladder coating film, and the second release sheet being sized so that it extends at least 2 inches (51mm) beyond the edges of the bladder coating film around the peripheral perimeter of the bladder coating film to minimize contamination of the laminator rollers upon subsequent lamination.

The entire stack of metal plate, capsule coated film and two release sheets is then placed in a roll laminator with open rollers, the stack being placed so that the rollers close on the release sheet which can be detached from the capsule coated film. The stack was then passed through a roll laminator at room temperature and 50 psi (about 0.48MPa) using 6 inch (152mm) medium hardness silicone rollers at a rate of 0.5 feet per minute (about 2.5 mm/sec). In the process of smoothing the original rough surface of the film, the optical adhesive is spread as a thin layer over the entire capsule coated film via a laminator. The stack was then passed twice under a 150W/inch (6W/mm) uv lamp at a speed of 20 feet/minute (about 100 cm/sec) to partially cure the optical adhesive. The top release sheet was then removed and the remaining layer was passed under an ultraviolet lamp twice under the same conditions to complete the curing of the optical adhesive. Thereafter, the complete PET/ITO/capsule-adhesive layer/optical adhesive display may be removed from the metal plate and adjacent release sheet and cut to the desired size. It will be appreciated that the process described in this example is a small scale laboratory method, while other techniques, particularly roll-to-roll techniques, would be more suitable for mass production.

The use of a polymerizable liquid material that can be cured to a hard and solid appearance, according to a preferred embodiment of the invention, allows the use of a very thin non-conductive protective layer that has a smooth appearance and provides good mechanical protection for the electro-optic layer. Radiation curing allows for fast line speeds and an economical roll-to-roll production process.

Claims (19)

1. A method for making an electro-optic display, the method comprising:

forming a layer (104, 106) of electro-optic material on the electrode (102);

depositing a layer of a substantially solvent-free polymerisable liquid material (108) over the layer of electro-optic material (104, 106) to form a viewing surface of the display; and

exposing the polymerizable liquid material (108) to conditions effective to polymerize the material, thereby forming a polymer layer on the layer of electro-optic material (104, 106).

2. A method according to claim 1, wherein the polymerizable liquid material (108) is thermally curable and the conditions under which the material is polymerized comprise heating the liquid material to a temperature high enough to cure the material.

3. The method of claim 1, wherein the polymerizable liquid material (108) is radiation curable and the conditions that cause polymerization of the material comprise exposing the liquid material to radiation having a wavelength capable of curing the material.

4. A method according to claim 1, wherein the polymerizable liquid material (108) comprises an acrylate, a urethane acrylate blend or a silicone gum.

5. A method according to claim 1, further comprising controlling the thickness of the layer of polymerisable liquid material (108) deposited on the layer of electro-optic material (104, 106).

6. The method according to claim 5, wherein said thickness of said layer of polymerizable liquid material is controlled by a doctor blade (110) or pressure coating.

7. A method according to claim 5, wherein said thickness of said layer of polymerizable liquid material is controlled by placing said layer of liquid material (108) on a release sheet (212) prior to polymerizing said liquid material (108) and passing the layer of liquid material (108) with the release sheet (212) between the nip rollers (214, 216).

8. The method of claim 7, wherein the sheet is a release sheet removed from the final display.

9. The method of claim 7, wherein the sheet comprises a conductive layer that remains as a permanent part of the final display.

10. The method of claim 7 wherein the sheet comprises an array of color filters that remain as a permanent part of the final display.

11. The method according to claim 1, wherein the thickness of the final polymer layer is from 6 to 250 μm.

12. The method according to claim 11, wherein the thickness of the final polymer layer is from 8 to 50 μm.

13. A method according to claim 1, wherein the layer (104, 106) of electro-optic material formed on the electrode (102) has an uneven exposed surface and the final polymer layer levels the layer (104, 106) of electro-optic material such that the exposed surface of the final polymer layer is substantially flat.

14. A method according to claim 1 wherein the electro-optic material comprises a rotating bichromal member or an electrochromic material.

15. A method according to claim 1, wherein the electro-optic material comprises 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.

16. The method of claim 15, wherein the charged particles and the fluid are confined within a plurality of capsules or microcells.

17. The method of claim 15, wherein the electrically charged particles and the fluid are present as a plurality of discrete droplets surrounded by a continuous phase comprising a polymeric material.

18. The method of claim 15, wherein the fluid is gaseous.

19. An electro-optic display capable of being imaged by a stylus, the display comprising:

an electrode (102);

a layer (104, 106) of electro-optic material disposed on the electrode (102); and

a polymer layer located on the layer (104, 106) of electro-optic material and forming a viewing surface of the display,

the polymer layer is formed from a polymerization product of a substantially solvent-free polymerizable liquid material (108).