WO2002056104A2

WO2002056104A2 - Lcd substrate with protrusions and method of making

Info

Publication number: WO2002056104A2
Application number: PCT/US2002/000998
Authority: WO
Inventors: Yukihiko Sasaki; Philip Yi Zhi Chu
Original assignee: Avery Dennison Corporation
Priority date: 2001-01-15
Filing date: 2002-01-15
Publication date: 2002-07-18
Also published as: WO2002056104A3; WO2002056104A9

Abstract

A first liquid crystal display (LCD) substrate includes protrusions for holding a second substrate spaced apart from the first substrate. The protrusions (302) may be posts which are located in gaps between adjacent pairs of electrodes (316) on the first substrate, and are configured to contact the second substrate in gaps between adjacent pairs of electrodes (326) on the second substrate. The protrusions may be posts or ridges that have a shape, such as a tapered shape, with surface area for contacting the second substrate which is smaller that a cross-sectional area away from distal ends of the protrusions. The first substrate may include an opaque material throughout or in a layer of the substrate. Electrodes on the first substrate element may be formed from an opaque material. The substrate element may include a sputtered alignment barrier layer.

Description

TITLE: LCD SUBSTRATE WITH PROTRUSIONS, AND METHOD OF MAKING

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The invention relates substrates for liquid crystal display (LCD) devices, and to methods for making the same.

2. Background of the Related Art

Liquid crystal display (LCD) devices are well known and are useful in a number of applications where light weight, low power and a flat panel display are desired. Typically, these devices comprise a pair of sheet-like, glass substrate elements or "half-cells" overlying one another with liquid crystal material confined between the glass substrates. The substrates are sealed at their periphery with a sealant to form the cell or device. Transparent electrodes are generally applied to the interior surface of the substrates to allow the application of an electric field at various points on the substrates thereby forming addressable pixel areas on the display. Various types of liquid crystal materials are known in the art and are useful in devices referred to as twisted nematic (TN), super twisted nematic (STN), cholesteric, and ferroelectric display devices.

It is desirable to be able to manufacture large area displays of relatively light weight for use in portable devices such as computers, electronic books, personal digital assistants, and the like. Certain organic, polymeric substrates are much lighter than glass while being transparent and are therefore preferred for use over glass in large area, lightweight displays. However, one problem with the use of polymeric materials as substrates for large-area liquid crystal displays is that these substrates tend to be more flexible than glass and must be separated by a dense population of spacers in order to maintain uniform separation between the closely spaced substrates forming the liquid crystal display device. In order to produce a uniform electric field at low voltages and show uniform contrast across the entire display area, precise control of the shallow cavity containing the liquid crystal material is required.

Prior art means for achieving spacing uniformity have included using precisely dimensioned, short-length polymeric fibers or spheres as in U.S. Patent No. 4,501 ,471 or spacing members made of photoresist material bonded to the substrate as in U.S. Patent No. 4,720,173. Each of these methods has deficiencies. Fiber and spheroidal spacing particles are not easily placed uniformly on the substrate to maintain even spacing over the entire area and fibers may overlap increasing the spacer height. Moreover, when the device flexes or is otherwise physically stressed, the spacers may shift or migrate to cause starved areas in the display cell. Bonded structural members require that they be precisely positioned on each substrate with exactly the same height, a feat that is difficult given the dimensions and tolerances required for effective liquid crystal displays. Members having different chemical composition from the substrate may suffer from differential thermal expansion causing possible fracture of the bond at the interface and shifting of the spacing member.

U.S. Patent No. 5,268,762 discloses polymeric sheet substrate elements which include spacing ribs which are physically and chemically integral with the sheets. However, electrode material on the spacing ribs disclosed may cause short circuits in the opposite substrate element to which the ribs are connected, thus resulting in low yields of devices.

SUMMARY OF THE INVENTION A first liquid crystal display (LCD) substrate includes protrusions for holding a second substrate spaced apart from the first substrate. The protrusions may be posts which are located in gaps between adjacent pairs of electrodes on the first substrate, and are configured to contact the second substrate in gaps between adjacent pairs of electrodes on the second substrate. The protrusions may be posts or ridges that have a shape, such as a tapered shape, with surface area for contacting the second substrate which is smaller than a cross-sectional area away from distal ends of the protrusions. The first substrate may include an opaque material throughout or in a layer of the substrate. Electrodes on the first substrate element may be formed from an opaque material. The substrate element may include a sputtered alignment barrier layer.

According to an aspect of the invention, an LCD substrate element includes columns or posts for holding another substrate spaced apart therefrom.

According to another aspect of the invention, a first LCD substrate element includes protrusions such as posts for holding a second substrate spaced apart therefrom, electrodes on the first substrate facing electrodes on the second substrate. The posts are not in contact with and do not overlap the electrodes of either substrate. According to another aspect of the invention, the posts extend to the edge of the electrodes on the first substrate element, and the electrode material may extend onto a lower part of the posts. According to yet another aspect of the invention, an LCD substrate element has a sputtered alignment layer.

According to still another aspect of the invention, an alignment layer for an LCD substrate is made from SiO_x, where x is a value between 1 and 2.

According to a further aspect of the invention, an opaque LCD substrate includes protrusions for holding a second substrate spaced apart therefrom.

According to a still further aspect of the invention, an LCD substrate which includes protrusions for holding a second substrate spaced apart therefrom, also includes a layer of an opaque material.

According to another aspect of the invention, an LCD substrate which includes protrusions for holding a second substrate spaced apart therefrom, has opaque electrodes thereupon.

According to yet another aspect of the invention, an LCD substrate which includes protrusions for holding a second substrate spaced apart therefrom, is formed from an opaque polymer material or from a polymer material made opaque by addition of a pigment or dye.

According to still another aspect of the invention, a method of making an LCD substrate element includes forming a substrate from an opaque material, with protrusions thereupon from a major surface of the substrate, depositing a layer of conductive material on the substrate, and using laser etching to remove the conductive material from distal ends of the protrusions.

According to a further aspect of the invention, a method of forming a substrate element includes forming protrusions on a major surface of a substrate by printing a curable material on the substrate, and curing the printed curable material.

According to a still further aspect of the invention, a method of forming a substrate element includes forming protrusions on a major surface of a substrate by a photolithography process. The photoresist for the photolithography process may be a black matrix material of the type commonly used for producing color filters. According to another aspect of the invention, a liquid crystal display includes a pair of substrates each having a plurality of electrodes on respective major surfaces thereof, one of the substrates having protrusions on its major surface for supporting the substrates in a spaced-apart relationship with the major surfaces facing each other, wherein the protrusions are not in contact with and do not overlap the electrodes.

According to yet another aspect of the invention, a method of making an LCD substrate element includes the steps of forming protrusions on a polymer substrate, the protrusions rising to a common level defined by a plane spaced apart from a main body of the substrate; depositing a conductive material on the substrate; and laser etching the conductive material off of top surfaces of the protrusions.

According to still another aspect of the invention, a method of making an LCD substrate element includes the steps of forming protrusions on a polymer substrate, the protrusions rising to a common level defined by a plane spaced apart from a main body of the substrate, the protrusions being narrower at the plane than below the plane; depositing a conductive material on the substrate; and etching the conductive material off of top surfaces of the protrusions.

According to a further aspect of the invention, an LCD substrate element includes a polymer sheet having protrusions on a major surface thereof, the protrusions rising to a common level defined by a plane spaced apart from the main body, the protrusions thereby forming a support for a second substrate spaced apart from the major surface, wherein the protrusions have a contoured shape, being narrower at the plane than below the plane.

According to a still further aspect of the invention, an LCD substrate element includes a polymer sheet having protrusions on a major surface thereof, the protrusions rising to a common level defined by a plane spaced apart from the main body, the protrusions thereby forming a support for a second substrate spaced apart from the major surface, and an alignment layer on the polymer sheet and the protrusions, wherein the alignment layer is formed from SiO_x, wherein x is between 1 and 2. According to another aspect of the invention, an LCD substrate element includes a polymer sheet having protrusions on a major surface thereof, the protrusions rising to a common level defined by a plane spaced apart from the main body, the protrusions thereby forming a support for a second substrate spaced apart from the major surface, and an alignment layer on the polymer sheet and the protrusions, wherein the alignment layer is a sputtered alignment layer.

According to yet another aspect of the invention, an LCD substrate element includes a polymer sheet having protrusions on a major surface thereof, the protrusions rising to a common level defined by a plane spaced apart from the main body, the protrusions thereby forming a support for a second substrate spaced apart from the major surface, electrodes on the major surface, and an alignment layer on the electrodes and the protrusions, wherein the polymer sheet and the protrusions include an opaque material. According to still another aspect of the invention, an LCD substrate element includes a polymer sheet having protrusions on a major surface thereof, the protrusions rising to a common level defined by a plane spaced apart from the main body, the protrusions thereby forming a support for a second substrate spaced apart from the major surface, electrodes on the major surface, and an alignment layer on the electrodes and the protrusions, wherein the electrodes include an opaque material.

According to further aspect of the invention, a liquid crystal display includes first and second substrates each having a plurality of electrodes on respective major surfaces thereof, the first substrate having protrusions on its major surface for supporting the substrates in a spaced-apart relationship with the major surfaces facing each other. The protrusions are not in contact with and do not overlap the electrodes of the second substrate.

According to further aspect of the invention, a method of making a liquid crystal display includes the steps of forming protrusions on a first substrate, the protrusions rising to a common level defined by a plane spaced apart from a main body of the first substrate; and ultrasonically bonding a second substrate to distal ends of the protrusions.

To the accomplishment of the foregoing and related ends, the invention comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative embodiments of the invention. These embodiments are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the annexed drawings:

Fig. 1 is a perspective view of a prior art liquid crystal display (LCD) device; Fig. 2 is a perspective view of the general structure of an LCD device; Fig. 3 is a side sectional view of a substrate element having an opaque material layer; Fig. 4 is a schematic view of a manufacturing process for fabricating the substrate element of Fig. 3;

Fig. 5 is a schematic side view of a sputtering process for depositing an alignment layer on an LCD substrate;

Fig. 6 is a side sectional view showing a substrate with protrusions that have tapered sections;

Fig. 7 is a diagrammatic end view of one type of embossing equipment which may be used to form the protrusions on the underlying substrate;

Fig. 8 is a perspective view of a tool for forming a substrate, with female cavities for forming the protrusions located thereon; Figs. 9 and 10 are plan views of substrate elements of an LCD which utilizes posts to maintain electrodes in a spaced-apart relationship;

Fig. 11 is a schematic plan view illustrating a mosaic arrangement of electrodes for a color display; and

Fig. 12 is a schematic plan view illustrating a triad delta arrangement of electrodes for a color display.

DETAILED DESCRIPTION An LCD substrate includes protrusions for holding another substrate a set distance away. The protrusions may have any of a variety of suitable placements and/or configurations. In addition, the substrate may be made of any of a variety of suitable materials, possibly including being made in whole or in part from a suitable opaque material. The electrodes may alternatively be made from an opaque material. The use of opaque materials in the substrate and/or the electrodes may facilitate removal of electrode materials from the tops of the protrusions, for example by laser etching.

Referring initially to Fig. 1 , basic operation of an LCD device is illustrated by explanation of the operation of a prior art twisted nematic display device 10. The device 10 includes a cell or envelope formed by placing a pair of transparent, planar substrates 12 and 14, in register, overlying and spaced apart from one another. The periphery of the substrates are joined and sealed with an adhesive sealant. The shallow space or cavity between the substrates is filled with liquid crystal material 28 just prior to final sealing. Conductive, transparent electrodes 16(a) through 16(e) and 18(a) through 18(d) are arranged on the inside surface of the substrates in either a segmented or X-Y matrix design (shown), as is well known in the art, to form a plurality of picture elements (pixels). Although only a few electrodes are shown, in practice a large number of electrodes are incorporated in the cell and the number will generally increase as the areal dimensions of the cell increase. Alignment coatings 20, 22 are applied to portions of the interior surface of the liquid crystal display cell to cause a desired orientation of the liquid crystal material at its interface with the surface of the display. This ensures that the liquid crystal rotates light through angles which are complementary to the alignment of the polarizers associated with the cell. Polarizing elements 24, 26 are optional depending on the type of display and may be associated with one or more surfaces of the display when used. A reflector element (not shown) may be associated with the bottom substrate 12 when a reflective rather than a transmissive display is desired.

The components and assembly techniques of liquid crystal displays as described above are well known. Liquid crystal material fills the space between substrates 12 and 14, but for purposes of illustration, only one column of liquid crystal material 28 is shown corresponding to the area overlying common areas of crossed electrodes 16(d) and 18(a). Arrows 30(a) through 30(e) show how the molecules of the liquid crystal are aligned in a 90 degree twist by the alignment layers 20, 22 in the absence of an electric field. Arrows 30(a) and 30(e) also correspond to the direction of polarization of the polarizers 24 and 26, respectively. Electrode leads 32(a) through 32(e) and 36(a) through 36(c) are shown connected to bus leads 34 and 38, respectively, which in turn are connected to addressing electronics shown schematically at 40.

Twisted nematic liquid crystal devices have a helical or twisted molecular orientation, turned by 90 degrees in the device as shown by arrows 30(a) through 30(e) in Fig. 1. When an electric field is applied to the liquid crystal material by electrodes incorporated into the device, the molecules re-orient and "unwind" due to the electrical anisotropy of the molecules. This behavior allows the molecules to rotate polarized light when in the twisted state and thereby pass light without rotation when in the untwisted state. When used in combination with polarizers, this ability to rotate polarized light allows the display to act as a light valve, either blocking or passing transmitted or reflected light. The surface 42 represents a pixel area which can be turned on or off by addressing electrodes 16(d) and 18(a) simultaneously When individually addressable electrodes are incorporated into the display, the display device has the ability to display images.

The electrodes may be addressed independently to create an electric field at selected pixels. In some addressing schemes, the electrodes are sequentially and repeatedly scanned at a rapid rate to provide moving images similar to television images. This requires "refreshing" the display at short time intervals to rapidly turn pixels on and off. In order to switch the pixels on and off rapidly with reasonable voltage levels, the layer of liquid crystal material should be uniformly thin and, thus, the spacing between the substrates becomes critical if a uniform appearance is to be achieved.

In order to allow the preparation of large area displays with uniform spacing and resulting appearance the present invention employs one or more substrates with integral spacers provided as microstructure elements integral with the substrates.

Referring to Fig. 2, illustrated generally is a portion of a liquid crystal display device 50 utilizing protrusions. The device 50 includes a bottom substrate 52 and a top substrate 54. Protrusions such as ribs 56 rise up to a common level away from the bottom substrate 52, to support top substrate 54. Conductive electrodes 58 and 60 are located on the interior facing surfaces of the bottom and top substrates, respectively, and are connected to a voltage source for creating an electric field between opposed electrodes. Alignment material layers 62, 64 and 66 are shown in various locations. The alignment material 64 on the top surfaces of the ribs 56 is covered by adhesive/sealant 68. Thus, the alignment material 64 performs no alignment function and can be eliminated if desired. The top substrate 54 is bonded to the tops of spacing ribs 56 by the adhesive/sealant 68 which also seals the periphery of the LCD cell. The spacing ribs 56 together with the substrates 52 and 54 form a cavities in which liquid crystal material (not shown) is disposed before the cell is sealed at its periphery with the adhesive/sealant 68 to form a complete display device 50.

The display device 50 may have one or more features similar to those described in U.S. Patent 5,268,782, U.S. Patent No. 5,399,390, U.S. Patent No. 5,545,280, or International Publication No. WO 99/08151 , the entire disclosures of which are incorporated herein by reference. Thus the substrates 52 and 54 may be made of a thermoplastic, optically-transparent polymeric material such as polycarbonate, polyvinyl chloride, polystyrene, polymethyl methacrylate, polyurethane polyimide and polysulfuric polymers. More broadly, the substrate may be a flexible plastic such as a material selected from the group consisting of polyether sulfone (PES), polyethylene terephthalate (PET), polycorbonate, polybutylene terephthalate, polyphenylene sulfide (PPS), polypropylene, aramid, polyamide-imide (PAI), polyimide, aromatic polyimides, polyetherimide, acrylonitrile butadiene styrene, and polyvinyl chloride. Further details regarding substrates and substrate materials may be found in International Publication Nos. WO 00/46854, WO 00/49421 , WO 00/49658, WO 00/55915, and WO 00/55916, the entire disclosures of which are herein incorporated by reference. The electrodes 58 and 60 may include commonly-known transparent conducting oxides, such as indium-tin-oxide (ITO). The alignment compositions may include a variety of well- known polymeric materials, for example a polyimide which can be spin coated or printed from solvent, and (if necessary) rubbed with cloth, such as velvet, to provide a useful alignment layer. A wide variety of adhesive/sealant materials may be used, such as polymerizable organic materials, heat curing epoxies, light curing adhesives, and acrylate adhesives.

The alignment layer may be a conventional suitable material, such as SiO₂. Alternatively, the alignment layer may be SiO_x, where 1 <x<2. Using SiO_x instead of Si0₂ provides an additional moisture barrier for the display, acting to prevent moisture from being transported through the display. The value x for the SiO_x may be controlled, for example, by controlling the oxide ratio in the material used in sputtering the oxide layer, by adding oxygen to an SiO material.

Generally speaking, it will be appreciated that a wide variety of suitable liquid crystal materials may be employed, such as twisted nematic, super twisted nematic, double layer super twisted nematic, cholesteric, and ferroelectric materials.

One of the substrates may be made of an opaque material. As described in greater detail below, a black or other-colored opaque substrate material may facilitate laser etching of electrode material off tops (distal ends) of protrusions of the substrates, in that the opaque material better absorbs the laser light, thereby producing heat that etches away the electrode material from the tops of the protrusions. The opaque material may be any of a variety of polymer materials with suitable pigments.

Alternatively or in addition, the electrode material itself may be opaque. For example, the electrode material may be aluminum or copper, which is opaque when deposited on the polymer substrate material. The depositing of the electrode material may be by sputtering, for example.

It will be appreciated that a suitable opaqueness may alternatively be achieved by printing an opaque ink between all or a portion of the substrate and the electrode material. For example, the ink may be printed on the tops of the protrusions, prior to the deposition of the electrode material. The opaque substrate and/or electrode material may be used for display devices where light is not transmitted therethrough, but is either reflected by the liquid crystal material or is absorbed by the opaque substrate and/or electrode material. An exemplary suitable liquid crystal material for such a display is a zero field multistable cholesteric liquid crystal mix, such as that described in U.S. Patent No. 5,889,566, which is incorporated herein by reference. Displays including zero field multistable liquid crystal display (FMLCD) technology have many advantages, such as inherent stability in the display without the need to refresh the display, thus allowing a display that can maintain an image in a no-power mode; excellent sunlight readability; and fast switching operation, for example on the order of 30 milliseconds per frame; and the ability to display various gray scales.

The color and/or other characteristics of the opaque substrate material, the opaque electrode material, and/or the opaque ink may be selected in conjunction with the characteristics of the laser used in laser etching, so as to enhance the performance of the laser etching. For example, an IR laser may be used and the substrate material, electrode material, and/or ink may be selected to provide good results when used with the IR laser. It will be appreciated that the color of the substrate, electrode material, and/or ink may be selected for its visual effect in the resulting display device. The opaque material may be useful as an alternative to tinting the display, such tinting being conventionally used to provide a background for the display.

Turning now to Fig. 3, an alternate embodiment substrate 100 is shown. The substrate 100 has protrusions 102, which may be ribs or posts. The substrate 100 includes an opaque material layer 110 joined to a transparent material 112. The opaque material layer 110 may be a polymer material with a pigment or dye added, as described above. It will be appreciated that the opaque material layer 110 may be, as shown in Fig. 3, placed on top of the transparent material 112, forming part of the protrusions 102. Alternatively , the opaque material layer 110 may be underneath or within the transparent material. The opaque material may be of the same polymer type as the transparent material, or may be a different type of polymer. The opaque material layer may be joined to the transparent material by a variety of suitable, well- known methods. For instance, as illustrated in Fig. 4, molten opaque material (black or another color) may be introduced along a surface of the transparent substrate material 112 (for example being introduced by an appropriate means 120) prior to a microreplication process (hot rolling the layers 110 and 112 between a pair of rollers 122 and 124, the top roller 122 having a textured surface) to form the protrusions on the substrate. This material may be cured by thermal means or actinic radiation. Thus the opaque material layer 110 may be joined to the transparent layer 112 as part of a microreplicating or embossing process, such as that described in greater detail below. As observed above, the alignment layer material may be deposited by sputtering. An example of such a sputtering process is illustrated in Fig. 5, for formation of an alignment layer 150 on a substrate 152 having protrusions 154. The alignment layer 152 may be formed by one or more angled sputterings, such as angled sputterings 160 and 162, which are performed at an inclination angle α from the a line perpendicular to the substrate 152. The value of α may be between 30 degrees and 80 degrees. The angled sputtering may also alleviate the need for a post-deposition rubbing of the alignment layer, since the sputtering directions may be selected to provide, from the sputterings themselves, a desired alignment to the alignment layer 150.

As an alternative to sputtering, the alignment layer may be deposited using other suitable methods, such as physical vapor deposition (PVD). Turning now to Fig. 6, a substrate 200 is shown which has protrusions 202. The protrusions 202 have respective distal ends 204 for contacting the other substrate of an LCD device. Immediately beneath the distal ends 204 are tapered sections 206 with increase in cross-sectional area when compared with the area of the distal ends 204. The tapered sections 206 thus have upper surfaces 208 which are exposed to laser light 210 directed downward at the substrate 200. The upper surfaces 208 are thus amenable to laser etching, which as noted above is used to remove electrode material from the distal ends 204. The removal of electrode material from the distal ends 204 prevents shorting of electrodes on the other substrate (the substrate to which the distal ends 204 are to be joined). Such shorting may lead to device failure. In prior devices, where distal ends of the protrusions are abutted by side surfaces (side walls) of the protrusions which are substantially perpendicular to a major surface of the substrate, shorting may still occur due to the presence of conductive electrode material on the side walls of the protrusions, along the edges of the distal ends. The tapered sections 206 of the protrusions 202 facilitate removal of the electrode material not only from the distal ends 204, but also from the adjacent top surfaces 208. Thus the protrusions 202 with tapered sections 206 aid in avoiding the shorting problems which may occur due to use of protrusions without tapered sections.

It will be appreciated that the sections with exposed upper surfaces may be any of a variety of shapes. It will also be appreciated that sections with exposed or other upper surfaces may be used with a variety of protrusion shapes, including ribs and posts. Further, it will be appreciated that the advantages of tapered or other-shaped protrusions may be advantageous for a variety of methods of removing electrode material from the distal ends of the surfaces.

One technique of microreplicating arrays with very small surfaces requiring a high degree of accuracy, is found in the use of continuous embossing to form cube corner sheeting, as used by applicants' assignee. A detailed description of equipment and processes to provide optical quality sheeting are disclosed in U.S. Patent Nos. 4,486,363 and 4,601 ,861. Tools and a method of making a tool used in those techniques are disclosed in U.S. Patent Nos. 4,478,769; 4,460,449; and 5,156,863. The disclosures of all such patents are incorporated herein by reference; all are assigned to applicants' assignee.

A machine 500 for producing a substrate such as that described above, for example, the embossed substrate 200, is shown in elevation in Fig. 7, suitably mounted on a floor 502. The machine 500 includes a frame 504, centrally located within which is an embossing means 505.

A supply reel 508 of unprocessed thermoplastic web 510 is mounted on the right-hand side of the frame 504; so is a supply reel 512 of flexible plastic film such as Mylar film 515. The flat web 510 and the film 515 are fed from the reels 508 and 512, respectively, to the embossing means 505, over guide rollers 520, in the direction of the arrows.

The embossing means 505 includes an embossing tool 522 in the form of an endless metal belt 530 which may be about 0.020 inches (0.051 cm) in thickness. The width and circumference of the belt 530 will depend in part upon the width or material to be embossed and the desired embossing speed and the thickness of the belt 530. The belt 530 is mounted on and carried by a heating roller 540 and a cooling roller 550 having parallel axes. The rollers 540 and 550 are driven by chains 545 and 555, respectively, to advance belt 530 at a predetermined linear speed in the direction of the arrow. The belt 530 is provided on its outer surface with a continuous female embossing pattern 560, as shown in Fig. 8, that matches the general size and shape of the particular protrusions 202 to be formed in the substrate 200.

Evenly spaced sequentially around the belt, for about 180° around the heating roller 540, are a plurality, at least three, and as shown five, of pressure rollers 570 of a resilient material, preferably silicone rubber, with a durometer hardness ranging from Shore A 20 to 90, but preferably, from Shore A 60 to 90.

While rollers 540 and 550 may be the same size, in the machine 500 as constructed, the diameter of heating roller 540 is about 10.5 inches (26.7 cm) and the diameter of cooling roller 550 is about 9 inches (22.9 cm). The diameter of each pressure roller 570 is about 6 inches (15.2 cm).

It may be desirable to maintain additional pressure about the tool and substrate during cooling, in which case the cooling roller 550 could be larger in diameter than the heating roller, and a plurality of additional pressure rollers, (not shown) also could be positioned about the cooling roller.

Either or both heating roller 540 or cooling roller 550, has axial inlet and outlet passages (not shown) joined by an internal spiral tube (not shown) for the circulation therethrough of hot oil (in the case of heating roller 540) or other material (in the case of cooling roller 550) supplied through appropriate lines (not shown).

The web 510 and the film 515, as stated, are fed to the embossing means 505, where they are superimposed to form a laminate 580 which is introduced between the belt 530 and the leading roller of the pressure rollers 570, with the web 510 between the film 515 and the belt 530. From thence, the laminate 580 is moved with the belt 530 to pass under the remaining pressure rollers 570 and around the heating roller 540 and from thence along belt 530 around a substantial portion of cooling roller 550. Thus, one face of web 510 directly confronts and engages embossing pattern 560 and one face of the film 515 directly confronts and engages pressure rollers 570. The film 515 provides several functions during this operation. First, it serves to maintain the web 510 under pressure against the belt 530 while traveling around the heating and cooling rollers 540 and 550 and while traversing the distance between them, thus assuring conformity of the web 510 with the precision pattern 560 of the tool during the change in temperature gradient as the web (now embossed substrate) drops below the glass transition temperature of the material. Second, the film 515 maintains what will be the outer surface of substrate in a flat and highly finished surface for other processing, if desired. Finally, the film 515 acts as a carrier for the web 510 in its weak "molten" state and prevents the web from adhering to the pressure rollers 570 as the web is heated above the glass transition temperature. The embossing means 505 finally includes a stripper roller 585, around which laminate 580 is passed to remove the same from the belt 530, shortly before the belt 530 itself leaves cooling roller 550 on its return path to the heating roller 540.

The laminate 580 is then fed from stripper roller 585 over further guiding rollers 520, eventually emerging from frame 504 at the lower lefthand corner thereof. Laminate 580 is then wound onto a storage winder 590 mounted on the outside of frame 504 at the lefthand end thereof and near the top thereof. On its way from the lower lefthand corner of frame 504 to winder 590, the laminate 580 is guided by additional guiding rollers. The heating roller 540 is internally heated (as aforesaid) so that as belt 530 passes thereover through the heating station, the temperature of the embossing pattern 560 at that portion of the tool is raised sufficiently so that web 510 is heated to a temperature above its glass transition temperature, but not sufficiently high as to exceed the glass transition temperature of the film 515.

The cooling roller 550 is internally "fueled" (as aforesaid) so that as belt 530 passes thereover through the cooling station, the temperature of the portion of the tool embossing pattern 560 is lowered sufficiently so that web 510 is cooled to a temperature below its glass transition temperature, and thus becomes completely solid prior to the time laminate 580 is stripped from tool 530.

It has been found that the laminate 580 can be processed through the embossing means 505 at the rate of about 3 to 4 feet per minute, with satisfactory results in terms of the accuracy and dimensional stability and other pertinent properties of the finished substrate. It should be noted that reference numeral 510 may refer indiscriminately herein to the embossed substrate 200 or web 510 in its initial form, to its in-process form or to its final embossed form, as appropriate.

It will further understood that temperatures of the heating roller and cooling rollers may need to be adjusted within certain ranges depending upon the web material selected. Certain materials have higher glass transition temperature T_G than others. Others may require cooling at a higher temperature then normal and for a longer time period. Preheating or additional heating at the entrance of the nips may be accomplished by a laser by flameless burner or other device and by adjusting the temperature of the heating roller to run at higher preselected temperature. Similar adjustments may be made at the cooling level.

A preferred material for the embossing tool disclosed herein is nickel. The very thin tool (about 0.010 inches (0.025 cm) to about 0.030 inches (0.076 cm)) permits the rapid heating and cooling of the tool 530, and the web 510, through the required temperatures gradients while pressure is applied by the pressure rolls and the carrier film. The result is the continuous production of a precision pattern where flatness and angular accuracy are important while permitting formation of sharp corners with minimal distortion of other surfaces, whereby the finished substrate provides an array of protrusions 202 formed with high accuracy. An alternative means of forming the protrusions is by printing UV-curable resins on a substrate, and then curing the resins to form the protrusions. An example of a suitable material is a black matrix material commonly used in making color filters, such as the OPTIMER CR Series Pigment Dispersed Color Resist available from JSR Corporation of Japan. Another example of UV-curable resins is UV-curable epoxy acrylates. The printing may be accomplished by ink jet printing or screen printing, for example. Further information regarding ink jet printing and screen printing may be found in U.S. Patent No. 5,889,084, and U.S. Patent No. 5,891 ,520, the disclosures of which are incorporated herein by reference. Other methods of forming microstructures with UV-curable resins may be found in International Publication No. WO 99/08151.

A further method of forming a substrate element includes forming protrusions on a major surface of a substrate by a photolithography process. The photoresist for the photolithography process may be a black matrix material of the type commonly used for producing color filters. A preferred material of this type is OPTMER CR Series Pigment Dispersed Color Resist available from JSR Corporation (Japan).

Figs. 9 and 10 illustrate portions of an LCD device which uses posts 302 to separate the electrodes of substrates 310 and 312. The posts 302 are microreplicated or otherwise formed on the substrate 310 at locations in gaps 314 between electrodes 316. The electrodes 316 may be row electrodes, for example. The substrates 310 and 312 are configured so that the posts 302 contact the substrate 312 at locations 320 which in gaps 324 between electrodes 326. The electrodes 326 may be column electrodes, for example. Thus the LCD device of the substrates 310 and 312 avoids protrusions which are in contact with or overlap the electrodes, thus reducing the likelihood of any shorting of electrodes caused by the protrusions. It will be appreciated that known ultrasonic bonding methods may be used to weld the posts 302 to the substrate 310 and/or to the substrate 312. For instance, the posts 302 may be integrally formed with the substrate 310 and ultrasonically welded to the substrate 312.

In an exemplary embodiment, the electrodes may each have a width of 200 microns, with a 20 micron gap between electrodes, thus resulting in a display having pixels that are 200 microns by 200 microns in size, although it will be appreciated that other electrode sizes and gap sizes may be employed. It will be appreciated that spacers, such as spherical spacers made from a polymer material, may be used in addition to the posts described above, if desired. In particular, additional spacers may be utilized where large pixel sizes are used. Such additional spacers may be deposited by well-known methods, for example by spraying. Figs. 11 and 12 show alternate configurations of electrodes, such as electrodes for a color FMLCD display. In the figures R stands for red portions of the display, B for blue portions of the display, and G for green portions of the display. Fig. 11 shows the electrodes in a mosaic configuration, while Fig. 12 shows the electrodes in a triad configuration. Further information on such a tried configuration may be found in the paper titled "A High Performance Delta Arrangement Cell PDP With Meander Barrier Ribs," by O. Toyoda et al., which herein is incorporated by reference in its entirety.

Displays of the sort described above may be generally made by a process including: 1 ) forming the substrates, for example by extrusion of polymeric material; 2) formation of protrusions on one of the substrates, the protrusions being formed for example by microreplication or embossing, or by selective deposition and curing of a resin; 3) deposition of the electrode material on the substrates, for example by sputtering or vapor deposition; 4) selective removal of the electrode material, for example by selective etching, to define the electrodes and to remove electrode material from the protrusions; 5) deposition and rubbing (if necessary) of the alignment material; 6) deposition of adhesives, such as an adhesive on the protrusions for coupling the substrates together, and a sealing material, such as an epoxy, for retaining the liquid crystal material between the substrates; 7) joining together of the substrates; and 8) filling of the area between the substrates with liquid crystal material. Some of the steps described above may be performed by roll forming operations. Displays of the sort described above may be coupled to other components as a part of a wide variety of devices, for display of various types of information. For example, a display may be coupled to a microprocessor, as part of a computer, electronic display device such as an electronic book, cell phone, calculator, smart card, appliance, etc., for displaying information. Although the invention has been shown and described with respect to a certain embodiment or embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In particular regard to the various functions performed by the above described elements (components, assemblies, devices, compositions, etc.), the terms (including a reference to a "means") used to describe such elements are intended to correspond, unless otherwise indicated, to any element which performs the specified function of the described element (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary embodiment or embodiments of the invention. In addition, while a particular feature of the invention may have been described above with respect to only one or more of several illustrated embodiments, such feature may be combined with one or more other features of the other embodiments, as may be desired and advantageous for any given or particular application.

Claims

What is claimed is:

1. A liquid crystal display comprising first and second substrates each having a plurality of electrodes on respective major surfaces thereof, the first substrate having protrusions on its major surface for supporting the substrates in a spaced-apart relationship with the major surfaces facing each other, wherein the protrusions are not in contact with and do not overlap the electrodes of the second substrate.

2. The display of claim 1 , wherein the protrusions are not in contact with and do not overlap the electrodes of the first substrate.

3. The display of claim 1 , wherein the protrusions are in contact with the electrodes of the first substrate.

4. The display of any of claims 1 to 3, wherein one of the substrates has row electrodes thereupon, and the other of the substrates has column electrodes thereupon.

5. The display of any of claims 1 to 4, wherein the protrusions are posts.

6. The display of claim 5, wherein the posts are located adjacent to corners of pixels of the liquid crystal display.

7. The display of claim 5 or claim 6, wherein the posts are chemically and physically integral to the first substrates.

8. The display of any of claims 5 to 7, wherein the substrates are made of a polymer material and the posts are made of a curable resin.

9. The display of any of claims 4 to 8, wherein the posts rise to a common level defined by a plane spaced apart from a main body of the first substrate, the posts having a contoured shape, being narrower at the plane than below the plane.

10. The display of claim 9, wherein the posts each have respective tapered sections.

11. The display of any of claims 1 to 10, further comprising spacers between the substrates, wherein the spacers are not attached to either of the substrates.

12. The display of claim 11 , wherein the spacers are spherical.

13. The display of claim 11 or claim 12, wherein the spacers are made of a polymeric material.

14. The display of any of claims 11 to 13, wherein at least some of the spacers are in contact with respective of the electrodes.

15. The display of any of claims 1 to 14, further comprising an alignment layer on at least one of the substrates.

16. The display of claim 15, wherein the alignment layer is a sputtered alignment layer.

17. The display of claim 16, wherein the alignment layer is formed by angled sputtering.

18. The display of any of claims 15 to 17, wherein the alignment layer includes SiO_x, wherein x is between 1 and 2.

19. The display of any of claims 15 to 18, wherein the alignment layer is on the first substrate.

20. The display of any of claims 1 to 19, wherein one of the substrates includes an opaque material.

21. The display of claim 20, wherein the first substrate is the substrate which includes the opaque material.

22. The display of claim 21 , wherein the opaque material is an opaque layer which is joined to a transparent polymer material.

23. The display of any of claims 20 to 22, wherein the protrusions include the opaque material.

24. The display of any of claims 1 to 19, further comprising an opaque electrode material deposited on one of the substrates.

25. The display of any of claims 1 to 19, further comprising an opaque ink deposited on one of the substrtates.

26. A method of making the display of any of claims 1 to 24, wherein the method comprises: forming the protrusions on the first substrate; depositing a conductive material on the first substrate; and etching the conductive material off of top surfaces of the protrusions.

27. The method of claim 26, wherein the etching includes laser etching.

28. The method of claim 26 or claim 27, wherein the forming includes depositing a resin and curing the resin.

29. The method of claim 28, wherein the resin includes a UV-curable resin.

30. The method of claim 29, wherein the UV-curable resin includes a UV- curable epoxy acrylate.

31. The method of claim 28, wherein the resin includes a black matrix material commonly used in making color filters.

32. The method of any of claims 28 to 31 , wherein the depositing the resin includes printing the resin.

33. The method of any of claims 26 to 32, wherein the forming includes a rolling process.

34. The method of any of claims 26 to 33, further comprising ultrasonically bonding the protrusions and the second substrate.

35. A method of making an LCD substrate element, the method comprising: forming protrusions on a polymer substrate, the protrusions rising to a common level defined by a plane spaced apart from a main body of the substrate; depositing a conductive material on the substrate; and laser etching the conductive material off of top surfaces of the protrusions.

36. The method of claim 35, wherein the protrusions includes posts.

37. A method of making an LCD substrate element, the method comprising: forming protrusions on a polymer substrate, the protrusions rising to a common level defined by a plane spaced apart from a main body of the substrate, the protrusions being narrower at the plane than below the plane; depositing a conductive material on the substrate; and etching the conductive material off of top surfaces of the protrusions.

38. The method of claim 37, wherein the etching includes laser etching.

39. The method of claim 37 or claim 38, wherein the etching includes etching the conductive material off of distal surfaces and tapered surfaces of the protrusions.

40. The method of any of claims 37 to 39, wherein the protrusions include ribs.

41. The method of any of claims 37 to 39, wherein the protrusions include posts.

42. An LCD substrate element comprising a polymer sheet having protrusions on a major surface thereof, the protrusions rising to a common level defined by a plane spaced apart from the main body, the protrusions thereby forming a support for a second substrate spaced apart from the major surface, wherein the protrusions have a contoured shape, being narrower at the plane than below the plane.

43. The substrate element of claim 42, wherein the protrusions include respective tapered sections.

44. An LCD substrate element comprising a polymer sheet having protrusions on a major surface thereof, the protrusions rising to a common level defined by a plane spaced apart from the main body, the protrusions thereby forming a support for a second substrate spaced apart from the major surface, and an alignment layer on the polymer sheet and the protrusions, wherein the alignment layer is formed from SiO_x, wherein x is between 1 and 2.

45. An LCD substrate element comprising a polymer sheet having protrusions on a major surface thereof, the protrusions rising to a common level defined by a plane spaced apart from the main body, the protrusions thereby forming a support for a second substrate spaced apart from the major surface, and an alignment layer on the polymer sheet and the protrusions, wherein the alignment layer is a sputtered alignment layer.

46. The substrate element of claim 45, wherein the alignment layer is formed by angled sputtering.

47. An LCD substrate element comprising a polymer sheet having protrusions on a major surface thereof, the protrusions rising to a common level defined by a plane spaced apart from the main body, the protrusions thereby forming a support for a second substrate spaced apart from the major surface, electrodes on the major surface, and an alignment layer on the electrodes and the protrusions, wherein the polymer sheet and the protrusions include an opaque material.

48. The substrate element of claim 47, wherein the opaque material is an opaque layer which is joined to a transparent polymer material.

49. An LCD substrate element comprising a polymer sheet having protrusions on a major surface thereof, the protrusions rising to a common level defined by a plane spaced apart from the main body, the protrusions thereby forming a support for a second substrate spaced apart from the major surface, electrodes on the major surface, and an alignment layer on the electrodes and the protrusions, wherein the electrodes include an opaque material.

50. An LCD substrate element comprising a polymer sheet having protrusions on a major surface thereof, the protrusions rising to a common level defined by a plane spaced apart from the main body, the protrusions thereby forming a support for a second substrate spaced apart from the major surface, and electrodes on the major surface, wherein the electrodes are arranged in a mosaic pattern.

51. An LCD substrate element comprising a polymer sheet having protrusions on a major surface thereof, the protrusions rising to a common level defined by a plane spaced apart from the main body, the protrusions thereby forming a support for a second substrate spaced apart from the major surface, and electrodes on the major surface, wherein the electrodes are arranged in a delta pattern.

52. The substrate element of claim 51 wherein cells or pixels of the delta pattern each have a substantially hexagonal shape.

53. The substrate element of claim 52, wherein the protrusions are ribs, adjacent of the ribs combining to define the substantially hexagonal shape of the cells or pixels.

54. The substrate element of claim 53, wherein the ribs are substantially continuous from one edge of the substrate element to an opposite edge of the substrate element.

55. A method of making a liquid crystal display, the method comprising: forming protrusions on a first substrate, the protrusions rising to a common level defined by a plane spaced apart from a main body of the first substrate; and ultrasonically bonding a second substrate to distal ends of the protrusions.

56. The method of claim 55, wherein the protrusions include posts.