Patent Publication Number: US-8988636-B2

Title: Methods for trimming polarizers in displays

Description:
This patent application claims the benefit of provisional patent application No. 61/703,719, filed Sep. 20, 2012, which is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     This relates generally to electronic devices and, more particularly, to electronic devices with displays. 
     Electronic devices often include displays. For example, cellular telephones and portable computers often include displays for presenting information to a user. 
     Displays such as liquid crystal display have polarizers. The polarizers are formed from polymer layers that are laminated to glass display layers. It may be desirable to ensure that a polarizer layer has the same size as an associated glass display layer. If the polarizer is too large, the edge of the polarizer will overhang the edge of the glass display layer. If the polarizer is too small, the edge of the display will have an unsightly visible polarizer edge. Although the polarizer edge may be covered with a plastic bezel, the use of a bezel reduces the visible area of a display and can make the display unattractive. 
     It would therefore be desirable to be able to provide improved displays with polarizers for electronic devices. 
     SUMMARY 
     An electronic device is provided with a display such as a liquid crystal display mounted in an electronic device housing. The display has a layer of liquid crystal material sandwiched between an upper display layer such as a color filter layer and a lower display layer such as a thin-film-transistor layer. 
     An upper polarizer is formed on the upper surface of the color filter layer. A lower polarizer is formed on the lower surface of the thin-film-transistor layer. Additional display structures provide backlight for the display. 
     To protect display layers such as a glass color filter layer substrate for the color filter layer from damage during polarizer trimming operations, a coating is deposited on a peripheral edge of the glass color filter layer substrate. The coating is formed from an elastomeric polymer such as silicone or other material that coats and protects the peripheral edge. The coating may remain in place following polarizer trimming or may be removed following trimming operations. 
     Further features, their nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device such as a laptop computer with display structures in accordance with an embodiment. 
         FIG. 2  is a perspective view of an illustrative electronic device such as a handheld electronic device with display structures in accordance with an embodiment. 
         FIG. 3  is a perspective view of an illustrative electronic device such as a tablet computer with display structures in accordance with an embodiment. 
         FIG. 4  is a perspective view of an illustrative electronic device such as a computer display with display structures in accordance with an embodiment. 
         FIG. 5  a cross-sectional side view of an illustrative display of the type that may be used in devices of the types shown in  FIGS. 1 ,  2 ,  3 , and  4  in accordance with an embodiment. 
         FIG. 6  is a cross-sectional side view of an illustrative polarizer layer in accordance with an embodiment. 
         FIG. 7  is a diagram of an illustrative system being used to form a display layer such as a glass substrate layer for a liquid crystal display color filter layer in accordance with an embodiment. 
         FIG. 8  is a diagram of an illustrative system that is forming an edge coating on a display layer of the type shown in  FIG. 7  in accordance with an embodiment. 
         FIG. 9  is a top view of an illustrative display layer with an edge coating in accordance with an embodiment. 
         FIG. 10  is a diagram of an illustrative system being used to laminate a polarizer to a display layer with protective edge coating structures in accordance with an embodiment. 
         FIG. 11  is a diagram of an illustrative system being used to laminate a polarizer to a display layer and coat the peripheral edge of the display layer with a coating layer in accordance with an embodiment. 
         FIG. 12  is a cross-sectional side view of an illustrative display layer with an edge coating in accordance with an embodiment of the present invention. 
         FIG. 13  is diagram of an illustrative system in which laser-based equipment is being used to trim a polarizer on a display layer in accordance with an embodiment. 
         FIG. 14  is side view of an illustrative focusing lens and focused laser beam of the type used in laser trimming a polarizer on a display layer with the equipment of  FIG. 13  in accordance with an embodiment. 
         FIG. 15  is a cross-sectional side view of an illustrative polarizer being laser trimmed from a display layer with a protective edge coating in accordance with an embodiment. 
         FIG. 16  is a cross-sectional side view of an illustrative polarizer trimming system having a cutting blade in accordance with an embodiment. 
         FIG. 17  is a diagram of a system in which an edge coating layer is being removed following polarizer trimming in accordance with an embodiment. 
         FIG. 18  is a flow chart of illustrative steps involved in forming electronic devices and displays by trimming polarizers on displays in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Displays in electronic devices such as liquid crystal displays may be provided with polarizers. Illustrative electronic devices that have displays with polarizers are shown in  FIGS. 1 ,  2 ,  3 , and  4 . 
     Electronic device  10  of  FIG. 1  has the shape of a laptop computer and has upper housing  12 A and lower housing  12 B with components such as keyboard  16  and touchpad  18 . Device  10  has hinge structures  20  to allow upper housing  12 A to rotate in directions  22  about rotational axis  24  relative to lower housing  12 B. Display  14  is mounted in upper housing  12 A. Upper housing  12 A, which may sometimes referred to as a display housing or lid, is placed in a closed position by rotating upper housing  12 A towards lower housing  12 B about rotational axis  24 . 
       FIG. 2  shows an illustrative configuration for electronic device  10  based on a handheld device such as a cellular telephone, music player, gaming device, navigation unit, or other compact device. In this type of configuration for device  10 , housing  12  has opposing front and rear surfaces. Display  14  is mounted on a front face of housing  12 . Display  14  may have an exterior layer that includes openings for components such as button  26  and speaker port  28 . 
     In the example of  FIG. 3 , electronic device  10  is a tablet computer. In electronic device  10  of  FIG. 3 , housing  12  has opposing planar front and rear surfaces. Display  14  is mounted on the front surface of housing  12 . As shown in  FIG. 3 , display  14  has an external layer with an opening to accommodate button  26 . 
       FIG. 4  shows an illustrative configuration for electronic device  10  in which device  10  is a computer display or a computer that has been integrated into a computer display. With this type of arrangement, housing  12  for device  10  is mounted on a support structure such as stand  27 . Display  14  is mounted on a front face of housing  12 . 
     The illustrative configurations for device  10  that are shown in  FIGS. 1 ,  2 ,  3 , and  4  are merely illustrative. In general, electronic device  10  may be a laptop computer, a computer monitor containing an embedded computer, a tablet computer, a cellular telephone, a media player, or other handheld or portable electronic device, a smaller device such as a wrist-watch device, a pendant device, a headphone or earpiece device, or other wearable or miniature device, a television, a computer display that does not contain an embedded computer, a gaming device, a navigation device, an embedded system such as a system in which electronic equipment with a display is mounted in a kiosk or automobile, equipment that implements the functionality of two or more of these devices, or other electronic equipment. 
     Housing  12  of device  10 , which is sometimes referred to as a case, is formed of materials such as plastic, glass, ceramics, carbon-fiber composites and other fiber-based composites, metal (e.g., machined aluminum, stainless steel, or other metals), other materials, or a combination of these materials. Device  10  may be formed using a unibody construction in which most or all of housing  12  is formed from a single structural element (e.g., a piece of machined metal or a piece of molded plastic) or may be formed from multiple housing structures (e.g., outer housing structures that have been mounted to internal frame elements or other internal housing structures). 
     Display  14  may be a touch sensitive display that includes a touch sensor or may be insensitive to touch. Touch sensors for display  14  may be formed from an array of capacitive touch sensor electrodes, a resistive touch array, touch sensor structures based on acoustic touch, optical touch, or force-based touch technologies, or other suitable touch sensor components. 
     Display  14  for device  10  includes display pixels formed from liquid crystal display (LCD) components or other suitable image pixel structures. 
     A display cover layer may cover the surface of display  14  or a display layer such as a color filter layer or other portion of a display may be used as the outermost (or nearly outermost) layer in display  14 . The outermost display layer may be formed from a transparent glass sheet, a clear plastic layer, or other transparent member. 
     A cross-sectional side view of an illustrative configuration for display  14  of device  10  (e.g., for display  14  of the devices of  FIG. 1 ,  FIG. 2 ,  FIG. 3 ,  FIG. 4  or other suitable electronic devices) is shown in  FIG. 5 . As shown in  FIG. 5 , display  14  includes backlight structures such as backlight unit  42  for producing backlight  44 . During operation, backlight  44  travels outwards (vertically upwards in dimension Z in the orientation of  FIG. 5 ) and passes through display pixel structures in display layers  46 . This illuminates any images that are being produced by the display pixels for viewing by a user. For example, backlight  44  illuminates images on display layers  46  that are being viewed by viewer  48  in direction  50 . 
     Display layers  46  may be mounted in chassis structures such as a plastic chassis structure and/or a metal chassis structure to form a display module for mounting in housing  12  or display layers  46  may be mounted directly in housing  12  (e.g., by stacking display layers  46  into a recessed portion in housing  12 ). Display layers  46  form a liquid crystal display or may be used in forming displays of other types. 
     In a configuration in which display layers  46  are used in forming a liquid crystal display, display layers  46  include a liquid crystal layer such a liquid crystal layer  52 . Liquid crystal layer  52  is sandwiched between display layers such as display layers  58  and  56 . Layers  56  and  58  are interposed between lower polarizer layer  60  and upper polarizer layer  54 . 
     Layers  58  and  56  are formed from transparent substrate layers such as clear layers of glass or plastic. Layers  56  and  58  are layers such as a thin-film transistor layer (e.g., a thin-film-transistor substrate such as a glass layer coated with a layer of thin-film transistor circuitry) and/or a color filter layer (e.g., a color filter layer substrate such as a layer of glass having a layer of color filter elements such as red, blue, and green color filter elements arranged in an array). Conductive traces, color filter elements, transistors, and other circuits and structures are formed on the substrates of layers  58  and  56  (e.g., to form a thin-film transistor layer and/or a color filter layer). Touch sensor electrodes may also be incorporated into layers such as layers  58  and  56  and/or touch sensor electrodes may be formed on other substrates. 
     With one illustrative configuration, layer  58  is a thin-film transistor layer that includes an array of thin-film transistors and associated electrodes (display pixel electrodes) for applying electric fields to liquid crystal layer  52  and thereby displaying images on display  14 . Layer  56  is a color filter layer that includes an array of color filter elements for providing display  14  with the ability to display color images. If desired, layer  58  may be a color filter layer and layer  56  may be a thin-film transistor layer. 
     During operation of display  14  in device  10 , control circuitry (e.g., one or more integrated circuits such as components  68  on printed circuit  66  of  FIG. 5  and/or other circuitry) is used to generate information to be displayed on display  14  (e.g., display data). The information to be displayed is conveyed from circuitry  68  to display driver integrated circuit  62  using a signal path such as a signal path formed from conductive metal traces in flexible printed circuit  64  (as an example). 
     Display driver circuitry such as display driver integrated circuit  62  of  FIG. 5  is mounted on thin-film-transistor layer driver ledge  82  or elsewhere in device  10 . A flexible printed circuit cable such as flexible printed circuit  64  is used in routing signals between printed circuit  66  and thin-film-transistor layer  58 . If desired, display driver integrated circuit  62  may be mounted on printed circuit  66  or flexible printed circuit  64 . Printed circuit  66  is formed from a rigid printed circuit board (e.g., a layer of fiberglass-filled epoxy) or a flexible printed circuit (e.g., a flexible sheet of polyimide or other flexible polymer layer). 
     Backlight structures  42  include a light guide plate such as light guide plate  78 . Light guide plate  78  is formed from a transparent material such as clear glass or plastic. During operation of backlight structures  42 , a light source such as light source  72  generates light  74 . Light source  72  may be, for example, an array of light-emitting diodes. 
     Light  74  from one or more light sources such as light source  72  is coupled into one or more corresponding edge surfaces such as edge surface  76  of light guide plate  78  and is distributed in dimensions X and Y throughout light guide plate  78  due to the principal of total internal reflection. Light guide plate  78  includes light-scattering features such as pits or bumps. The light-scattering features are located on an upper surface and/or on an opposing lower surface of light guide plate  78 . 
     Light  74  that scatters upwards in direction Z from light guide plate  78  serves as backlight  44  for display  14 . Light  74  that scatters downwards is reflected back in the upwards direction by reflector  80 . Reflector  80  is formed from a reflective material such as a layer of white plastic or other shiny materials. 
     To enhance backlight performance for backlight structures  42 , backlight structures  42  include optical films  70 . Optical films  70  include diffuser layers for helping to homogenize backlight  44  and thereby reduce hotspots, compensation films for enhancing off-axis viewing, and brightness enhancement films (also sometimes referred to as turning films) for collimating backlight  44 . Optical films  70  overlap the other structures in backlight unit  42  such as light guide plate  78  and reflector  80 . For example, if light guide plate  78  has a rectangular footprint in the X-Y plane of  FIG. 5 , optical films  70  and reflector  80  preferably have a matching rectangular footprint. 
     The outermost layer of display  14  may be a protective display layer such as a layer of glass that covers layers  46  or a display layer such as color filter layer  56  (e.g., a glass substrate layer in layer  56 ) may serve as the outermost structural layer in display  14 . When display layer  56  is used as the outermost substrate layer in display  14 , visible border structures in display  14  can be minimized by accurately trimming polarizer  54  along the edge of layer  56 . Polarizing trimming operations can be performed using lasers, cutting blades (knife edges), or other trimming equipment. Care should be taken during trimming operations not to damage display layer  56 . As an example, care should be taken not to induce thermal damage to a glass substrate in layer  56  during laser trimming operations or mechanical damage to a glass substrate in layer  56  during cutting blade trimming operations. 
     A cross-sectional side view of an illustrative polarizer layer in display  14  is shown in  FIG. 6 . Polarizer layer  54  of  FIG. 6  is an upper polarizer such as upper polarizer  54  of  FIG. 5 . Lower polarizer layers such as lower polarizer  60  may be constructed similarly. 
     In the example of  FIG. 6 , polarizer  54  is formed from multiple layers of material that are attached together. Polarizer film  94  is formed from a stretched polymer such as stretched polyvinyl alcohol (PVA) and may therefore sometimes be referred to as a PVA layer. Iodine may be placed on the stretched PVA film so that iodine molecules align with the stretched film and form the polarizer. Other types of polarizer films may be used if desired. 
     Polarizer film  94  is sandwiched between layers  92  and  96 . Layers  92  and  96  may be formed from a material such as tri-acetyl cellulose (TAC) and may sometimes be referred to as TAC films or may be formed from other polymers. The TAC films may help hold the PVA film in its stretched configuration and may protect the PVA film. Other films may be attached to polarizer film  94  if desired. 
     Coating layer  90  includes one or more films of material that provide polarizer  54  with desired surface properties. For example, layer  90  may be formed from materials that provide polarizer  54  with antiglare (light diffusing) properties, antireflection properties, scratch resistance, fingerprint resistance, and other desired properties. Layer  90  preferably is formed from one or more layers of material such as antireflection (AR) layers (e.g., films formed from a stack of alternating high-index-of-refraction and low-index-of-refraction layers), antiglare layers, antireflection-antiglare layers, oleophobic layers, antiscratch coatings, and other coating layers. The functions of these layers need not be mutually exclusive. For example, an antiglare film in coating  90  may help provide polarizer  54  with scratch resistance. 
     Polarizer  54  can be provided with a layer of adhesive such as adhesive layer  98  to help attach polarizer  54  to the upper surface of display layers  46  (i.e., color filter  56  of  FIG. 5 ). The thickness of polarizer  54  may be about 50-200 microns or 90-180 microns (as examples). During manufacturing operations, adhesive  98  attaches polarizer  54  to the upper surface of color filter layer  56 . 
     Trimming operations are preferably used to trim the edge of polarizer  54  to match the edge of color filter layer  56 . 
     As shown in  FIG. 7 , color filter substrates such as substrate  108  can be formed from larger sheets of material such as layer  100 . Layer  100  may be a layer of glass, a ceramic layer, a polymer layer, or other suitable display layer substrate. As an example, layer  100  may be a glass layer. 
     Initially, glass layer  100  will be oversized (i.e., layer  100  will be larger than needed for forming display  14 ). Equipment such as equipment  122  is used to divide layer  100  into smaller pieces such as substrate  108 . Equipment  122  may be substrate cutting equipment such as water-jet cutting equipment, laser cutting equipment, sawing equipment, machining equipment, or other equipment for dividing layer  100  into smaller pieces. In the illustrative configuration of  FIG. 7 , equipment  122  includes a computer-controlled positioner such as positioner  104  and a scribing tool such as scribing tool  102 . Positioner  104  moves scribing tool  102  in a desired pattern over the surface of layer  100  to form scribe lines. Manual and/or automated equipment may then be used to break layer  100  along the scribe lines to form separate pieces of layer  100  such as pieces  106  and  108 . Pieces  106  and  108  have the size and shape of display  14  (e.g., a rectangular display-sized piece of glass). 
     Following the use of scribing operations or other operations to separate out individual glass layers such as display-sized glass layer  108  from glass layer  100  using equipment  122 , machining equipment  124  or other edge treatment equipment is used to modify edge surface  100  of the peripheral edge of glass layer  108 . In the illustrative configuration of  FIG. 7 , equipment  124  includes computer-controlled positioner  112  and machining tool head  114 . Head  114  has a surface profile that is configured to ease the sharp corners in layer  108  (e.g., by rounding the upper and lower edges of layer  108 , by beveling the upper and lower edges of layer  108 , etc.). 
     During operation, positioner  112  rotates machining tool head  114  about rotational axis  116  in direction  118  while moving head  114  along the edge of layer  108 , thereby machining edge surface  110  of layer  108  into a desired shape. As shown at the bottom of  FIG. 7 , equipment  124  can provide layer  108  with a machined profile for surface  110  such as an edge profile that includes one or more bevels such as bevel  120 . 
     Machined glass layer  108  is used as a substrate for one or more layers in display  14 . For example, layer  108  may serve as a color filter layer substrate for color filter layer  56  or other display layer in display  14 . If desired, substrate layer  108  may be formed form plastic, ceramic, or other transparent materials. The use of clear glass for forming layer  108  is merely illustrative. 
     To protect glass layer  108  from damage while supporting the edge of polarizer  54  during polarizer trimming operations, it may be desirable to provide glass layer  108  with edge protection. With one suitable arrangement, peripheral edge  110  of layer  108  is covered with a protective coating. The protective coating may be formed from plastic (e.g., silicone or other elastomeric polymer, hard plastic, etc.), ceramic, metal, or other coatings. As an example, peripheral edge  110  can be covered with black or clear silicone. 
       FIG. 8  is a diagram showing how edge  110  of glass layer  108  can be covered with a protective coating. In the example of  FIG. 8 , coating deposition equipment  126  is being used to dispense coating material  132  onto edge  110  of glass layer  108 . Equipment  126  includes computer-controlled positioner  128 , dispensing head  130 , and nozzle  132 . During operation, coating material  134  is dispensed onto edge surface  110  via nozzle  132  while positioner  128  runs head  130  around the periphery of glass layer  108 , thereby forming edge coating  136 . Equipment for dispensing material  134  may include dipping equipment, spraying equipment, ink-jet printing equipment, pad printing equipment, screen printing equipment, painting equipment, physical vapor deposition equipment, electrochemical deposition equipment, etc. 
       FIG. 9  is a top view of an illustrative display layer such as glass substrate layer  108  following coating of peripheral edge  110  with coating structures  136 . In the illustrative configuration of  FIG. 9 , substrate layer  108  has a rectangular footprint so that edge coating  136  has a rectangular ring shape. The rectangular shape of illustrative substrate  108  in  FIG. 9  allows substrate  108  to be used in forming rectangular displays. Displays of other shapes may be formed if desired. 
       FIG. 10  is a system diagram showing how polarizer  54  may be attached to substrate layer  108 . In the illustrative configuration of  FIG. 10 , lamination equipment  138  is being used to laminate polarizer  54  to substrate layer  108 . Lamination equipment  138  may include a roller laminator, vacuum lamination equipment, or other equipment for attaching polarizer  54  to substrate  108 . When attached using roller-based lamination equipment or other lamination equipment, adhesive layer  98  attaches the lower surface of polarizer  54  to the upper surface of display layer  108  to form display structures  140 , as shown in the bottom of  FIG. 10 . 
     In display structures  140 , polarizer  54  has larger lateral dimensions than the corresponding lateral dimensions of substrate layer  108 . As a result, portions of polarizer layer  54  extend laterally beyond edge  110  of substrate  108  to form overhanging (overlapping) edge portions  142  of layer  54 . Coating structures  136  may be configured to support at least some of the portion of polarizer  54  that extends laterally beyond edges  110  of substrate layer  108 , as shown in  FIG. 10 . 
     Following attachment of polarizer  54  to the upper surface of glass layer  108 , polarizer  54  may be trimmed to remove excess portions such as protruding portions  142 . If desired, polarizer  54  may be attached to glass substrate  108  before equipment  126  is used to apply coating material  132 . This type of configuration is shown in  FIG. 11 . With a configuration of the type shown in  FIG. 11 , lamination equipment  138  receives polarizer material  54  and glass substrate  108  and laminates layer  54  to layer  108  to form structures  140 . Equipment  126  includes computer-controlled positioner  128  and dispensing structures  130  with nozzle  132  or other coating equipment. Positioner  128  runs nozzle  132  along the edge of layer  108  to dispense a bead of coating material  134 . Because structures  140  are inverted (i.e., because layer  108  rests on top of layer  54  in the configuration of  FIG. 11 ), coating material  134  is supported by portion  144  of polarizer lower surface  146 . The presence of portion  144  therefore helps to control the flow of coating material  134 . 
     As shown in  FIG. 12 , coating material  134  is preferably thin enough to wick into recesses such as recess  148  (formed by the presence of bevel  120 ). 
     A system such as system  150  of  FIG. 13  or other trimming equipment is used to trim the edges of polarizer  54  following attachment of polarizer  54  to substrate layer  108 . In a configuration of the type shown in  FIG. 13 , system  150  includes a camera such as camera  154  for capturing images of layers  54  and  108 . Camera  154  includes a digital image sensor that captures digital image data for processing by control unit  152 . Camera  154  preferably has sufficient resolution for capturing images of edge  110 . Layers  108  and  54  are supported by support structures  164  during digital imaging operations. Light source  165  in support structures  164  generates polarized and/or unpolarized backlight  167  for illuminating layers  108  and  54 . The use of polarized light in illuminating layers  108  and  54  can help delineate the location of edge  110  for camera  154 . 
     Data from camera  154  is analyzed by control unit  152  to determine the position of edge  110  relative to laser  160  and laser beam  162 . Laser  160  may be an infrared leaser such as a carbon dioxide laser operating at a wavelength of 9.6 microns (as an example). Control unit  152  may be one or more computers, embedded processors, networked computing equipment, online computing equipment, and/or other computing equipment for processing digital image data from camera  154  or other sensors to determine the location of edges  110  and for issuing corresponding control signals on outputs  170 ,  172 , and  174 . 
     The control signals on outputs  170   172 , and  174  control the operation of computer-controlled positioners  156 ,  158 , and  166 , respectively. For example, control commands on path  170  control the operation of positioner  156 , which is used in adjusting the position of camera  154 . Control signals on path  172  are used in controlling the operation of positioner  166 , which is used in adjusting the position of support  164  (and therefore layers  108  and  54 ) relative to laser beam  162 . Control signals on line  174  are used to control positioner  158  and thereby adjust the position of laser  160  and laser beam  162  relative to edge  110 . If desired, different arrangements of positioners may be used. As an example, the position of machine vision equipment such as camera  154  may be fixed and/or positioner  158  and/or positioner  166  may be omitted. Additional positioners (e.g. to control mirrors or other optical structures that direct beam  162  onto layer  54 ) may also be used. The configuration of  FIG. 13  is shown as an example. 
     Optical structures such as lens  176  of  FIG. 14  are used to focus laser beam  162 . In the configuration of  FIG. 14 , the position of lens  176  is controlled by positioner  178 . Positioner  178  is a computer-controlled positioner that receives control signals from control unit  152  via input  180 . In response, positioner  178  positions lens  176  and therefore laser beam  162  relative to layer  54  and edge  110  ( FIG. 13 ). As shown in  FIG. 14 , lens  176  focuses laser beam  162  to produce a spot of diameter D over a length L. Outside of length L, laser beam  162  becomes unfocused and is characterized by an enlarged spot size and reduced power density. The length of L may be determined by the configuration of lens  176  (e.g., L may be 50 to 2000 microns or less than 100 microns or more than 100 microns). The diameter D may be about 60-100 microns (as an example). 
     Using polarizer trimming system  150  of  FIG. 14 , focused laser beam  162  of  FIG. 14  is applied to polarizer  54  to trim away excess portions of polarizer  54  and thereby ensure that the lateral dimensions of polarizer  54  in dimensions X and Y match the respective lateral dimensions of glass layer  108  in dimensions X and Y. Laser beam  162  is preferably focused on the portion of polarizer  54  that lies just outside of edge  110  of glass layer  108 . As shown in  FIG. 15 , this type of configuration ensures that laser beam  162  strikes portion  188  of edge coating  134 , rather than being focused on portions  184  of glass layer  108  inside of peripheral edge  110  and on the surface of peripheral edge  110 . Glass layer  108  can be damaged by excessive exposure to laser light and resulting heating of layer  108 , so using system  150  of  FIG. 13  to ensure that laser beam  162  is focused on coating layer  134  rather than layer  108  avoids degrading the strength and reliability of layer  108  from exposure to laser beam  162 . 
     The profile of focused laser beam  162  of  FIG. 14  generally causes polarizer  54  to acquire an angled (non-vertical) edge surface such as edge surface  190  of  FIG. 15  when excess polarizer portions such as portion  54 ′ are trimmed away from polarizer  54 . Following trimming, the portion of edge  190  where edge  190  meets inner surface  55  of polarizer  54  (point  191  of  FIG. 15 ) lies on coating layer  134  (as shown in  FIG. 15 ) or lies directly over edge  110 . 
     If desired, other types of polarizer trimming equipment may be used to remove excess portions of polarizer  54  and thereby ensure that polarizer  54  has a size and shape that matches that of glass layer  108 . As shown in  FIG. 16 , for example, equipment  196  that includes a cutting blade such as knife  192  may be used in trimming polarizer  54  along edge  110  of glass layer  108 . Equipment  196  includes computer-controlled positioner  194 . Positioner  194  receives control commands from control unit  152  ( FIG. 13 ) and/or support structures such as support structures  164  may be used to move polarizer  54  and glass layer  108  relative to blade  192 . In this way, blade  192  cuts polarizer  54  along edge  110  of glass layer  108 , above protective coating  134 . Due to the presence of coating  134 , the tip of blade  192  will not contact and damage glass layer  108 . 
       FIG. 17  shows how coating layer  134  may be removed following trimming. As shown in the upper portion of  FIG. 17 , this type of approach involves forming coating  134  on glass layer  108  and trimming away excess material  54 ′ to form trimmed polarizer  54  on glass layer  108 . During trimming operations, layer  134  can help protect edge  110  of glass layer  108  from damage. Following formation of trimmed polarizer  54  on glass layer  108  so that edge  190  of polarizer  54  is aligned with edge  110  of glass layer  108 , edge coating removal equipment  198  uses chemical material removal techniques (e.g., wet and/or dry etching), light-based material removal techniques such as application of laser beam  162  or other laser light to edge  110 , mechanical removal techniques, heat-based material removal techniques, and/or other material removal techniques to remove coating  134  from edge  110 . Following removal of material  134 , edge  110  is free of material  134  and is aligned with edge  190  of polarizer  54 , as shown in the lower portion of  FIG. 17 . 
       FIG. 18  is a flow chart of illustrative steps involved in forming display  14  and electronic device  10 . As shown in  FIG. 18 , display layers such as display layer  108  (e.g., a color filter substrate for color filter layer  56  for display layers  46  in display  14  of  FIG. 5 ) may be formed at step  200 . The formation of display layer  200  may involve scribing and breaking glass layers such as layer  100  to form glass layers such as glass layer  108 . Edges  110  of glass layer  108  may be machined using equipment  124 . 
     Following formation of glass layer  108  at step  200 , the edges of glass layer  108  such as peripheral edge  110  are coated with coating  134  at step  200 . Polarizer layer  54  is then attached to the upper surface of glass layer  108 . If desired, polarizer  54  may be attached to layer  108  before coating edge  110  with coating  134 , as shown by steps  210  and  212 . 
     At step  206 , laser-based or cutting-blade-based trimming techniques are used to trim excess polarizer from the edges of glass layer  108 . By trimming excess polarizer material away, the lateral dimensions of polarizer  54  are trimmed to match the lateral dimensions of glass layer  108 . 
     As described in connection with  FIG. 17 , coating material  134  can be removed from edge  110 . For example, during the operations of step  214 , polarizer  54  may be attached to glass layer  108  and material  134  may be deposited as a coating on edge  110 , followed by trimming of polarizer  54  to align edge  190  of polarizer  190  with edge  110  of glass layer  108  (step  214 ). Edge coating removal tool  198  ( FIG. 17 ) may then be used to remove coating  134  (step  216 ). 
     Substrate  108  may form a liquid crystal display color filter layer substrate for color filter layer  56  of display  14  of  FIG. 5 . At step  208 , the layers of display  14  may be assembled to form display  14  of  FIG. 5  and display  14  may be installed in device housing  12  of electronic device  10  with other device components. 
     The foregoing is merely illustrative and various modifications can be made by those skilled in the art without departing from the scope and spirit of the described embodiments. The foregoing embodiments may be implemented individually or in any combination.