PATENT DOCUMENT

Publication Number: US-9395589-B2
Application Number: US-201213424950-A
Country: US
Kind Code: B2

Title: Electronic device with inverted liquid crystal display

Abstract:
An electronic device may have a liquid crystal display with backlight structures. The backlight structures may produce backlight that passes through an array of display pixels. The display pixels may include electrode structures and thin-film transistor structures for controlling electric fields in a layer of liquid crystal material. The liquid crystal material may be formed between an outer display layer and an inner display layer. The inner display layer may be interposed between the backlight structures and the liquid crystal material. Thin-film transistor structures, electrodes, and conductive interconnection lines may be deposited in a layer on the inner surface of the outer display layer. A layer of color filter elements may be used to provide the display with color pixels. The color filter elements may be formed on top of the thin-film transistor layer or on a separate color filter array substrate such as the inner display layer.

Claims:
What is claimed is: 
     
       1. A display having an active area surrounded by a peripheral border region, the display comprising:
 an outer display layer comprising:
 a substrate having first and second opposing surfaces; 
 an opaque masking layer formed on the substrate only in the peripheral border region of the display such that the substrate is free of the opaque masking layer in the active area; 
 a thin-film transistor layer formed on the substrate, the thin-film transistor layer including one or more thin-film transistors and one or more electrode structures, wherein the one or more thin-film transistors are associated with one or more display pixel structures; and 
 a planarization layer formed on the substrate, wherein at least a portion of the opaque masking layer is interposed between the planarization layer and the substrate such that the planarization layer forms a planar surface on which the thin-film transistor layer is formed; 
 
 an inner display layer comprising:
 a color filter layer including one or more color filter elements and an opaque masking material that separates a first one of the one or more color filter elements from a second one of the one or more color filter elements; 
 
 a layer of liquid crystal material between the outer display layer and the inner display layer; and 
 backlight structures, wherein the inner display layer is interposed between the layer of liquid crystal material and the backlight structures. 
 
     
     
       2. The display defined in  claim 1  wherein the inner display layer comprises a layer of clear material selected from the group consisting of: clear glass and clear plastic. 
     
     
       3. The display defined in  claim 2  wherein the thin-film transistors are formed on an inner surface of the substrate and wherein the thin-film transistors are interposed between the color filter layer and the substrate. 
     
     
       4. The display defined in  claim 3  wherein the substrate comprises a layer of glass. 
     
     
       5. The display defined in  claim 4  wherein the planarization layer is interposed between the substrate and the thin-film transistors. 
     
     
       6. The display defined in  claim 4  further comprising a display driver integrated circuit mounted on the substrate, wherein at least some of the opaque masking layer overlaps the display driver integrated circuit. 
     
     
       7. The display defined in  claim 6  wherein the opaque masking layer hides the display driver integrated circuit from view. 
     
     
       8. The display defined in  claim 1  wherein the outer display layer comprises a peripheral border region that extends laterally beyond the inner display layer and the backlight structures, and wherein the display further comprises a display driver integrated circuit mounted to the outer display layer in the peripheral border region. 
     
     
       9. The display defined in  claim 1  wherein the opaque masking layer comprises an organic material and wherein the planarization layer comprises a spin-on coating on the organic material. 
     
     
       10. A display having an active area and an inactive area, the display comprising:
 an outer display layer having a first substrate, wherein the first substrate comprises a thin-film transistor layer having one or more electrode structures and one or more thin-film transistors formed thereon; 
 an inner display layer having a second substrate, wherein a color filter layer comprising a plurality of color filter elements and an opaque material that separates first and second color filter elements in the plurality of color filter elements are formed on the second substrate; 
 a layer of liquid crystal material between the outer display layer and the inner display layer; 
 backlight structures, wherein the inner display layer is interposed between the layer of liquid crystal material and the backlight structures; and 
 an opaque masking material formed directly on a peripheral portion of the first substrate in the inactive area of the display, wherein the opaque masking material does not extend into the active area of the display. 
 
     
     
       11. The display defined in  claim 10  wherein the outer display layer comprises a layer of clear material selected from the group consisting of: clear glass and clear plastic. 
     
     
       12. The display defined in  claim 10  wherein the outer display layer comprises a layer of glass. 
     
     
       13. The display defined in  claim 12  further comprising a planarizing layer that covers the opaque masking material, wherein the planarizing layer is interposed between the layer of glass and the thin-film transistors. 
     
     
       14. The display defined in  claim 12  further comprising a display driver integrated circuit mounted on the layer of glass, wherein at least some of the opaque masking material overlaps the display driver integrated circuit. 
     
     
       15. The display defined in  claim 14  wherein the display driver integrated circuit is mounted on an edge of the layer of glass that does not overlap the backlight structures. 
     
     
       16. The display defined in  claim 10  wherein the one or more electrode structures comprise one or more gate lines and one or more data lines. 
     
     
       17. An electronic device, comprising:
 a housing having sidewalls with uppermost edges; and 
 a display mounted in the housing such that at least a portion of the display extends over the uppermost edges of the sidewalls, wherein the display comprises:
 a substrate having an upper surface and a lower surface; 
 a thin-film transistor layer that is formed on the lower surface of the substrate, wherein the thin-film transistor layer comprises thin-film transistors, one or more electrode structures, and associated display pixel structures in an active area of the display; 
 backlight structures configured to produce backlight for the display, wherein the lower surface of the substrate is interposed between the upper surface of the substrate and the backlight structures; 
 color filter elements that are interposed between the thin-film transistors and the backlight structures, wherein each of the color filter elements are separated by an opaque material; and 
 
 an opaque masking material in a peripheral border region of the display that surrounds the active area, wherein the opaque masking material is interposed between the lower surface of the substrate and the thin-film transistor layer and does not overlap the active area of the display. 
 
     
     
       18. The electronic device defined in  claim 17  further comprising a display driver integrated circuit mounted on the substrate, wherein the opaque masking material overlaps the display driver integrated circuit and blocks the display driver integrated circuit from view through the substrate. 
     
     
       19. The electronic device defined in  claim 18  further comprising a planarizing layer that covers the opaque masking material and that is interposed between the substrate and the thin-film transistors. 
     
     
       20. The electronic device defined in  claim 17  wherein the thin-film transistor layer has an upper surface and a lower surface and wherein the lower surface of the thin-film transistor layer is interposed between the upper surface of the thin-film transistor layer and the backlight structures; and
 a display driver integrated circuit mounted on the lower surface of the thin-film transistor layer.

Description:
BACKGROUND 
     This relates generally to electronic devices and, more particularly, to displays for electronic devices. 
     Electronic devices such as computers and cellular telephones are generally provided with displays. Displays such as liquid crystal displays contain a thin layer of liquid crystal material. Color liquid crystal displays include color filter layers. The layer of liquid crystal material in this type of display is interposed between the color filter layer and a thin-film transistor. Polarizer layers may be placed above and below the color filter layer, liquid crystal material, and thin-film transistor layer. 
     When it is desired to display an image for a user, display driver circuitry applies signals to a grid of data lines and gate lines within the thin-film transistor layer. These signals adjust electric fields associated with an array of pixels on the thin-film transistor layer. The electric field pattern that is produced controls the liquid crystal material and creates a visible image on the display. 
     Image quality in conventional displays can be degraded during off-axis viewing, because off-axis viewing angles can allow light from display pixels of one color to bleed into adjacent display pixels of another color. Although off-axis quality can be improved somewhat by incorporating wide black matrix structures into the display, the use of excessively large black matrix masking lines can adversely affect display brightness. 
     It would therefore be desirable to be able to provide improved electronic device displays. 
     SUMMARY 
     Electronic devices may be provided with displays such as liquid crystal displays. A display may have an array of display pixels. The display pixels may be controlled using a grid of data lines and gate lines. Each pixel may receive display data on a data line and may have a thin-film transistor that is controlled by a gate line signal on a gate line. The thin-film transistors may be controlled to apply electric fields to a layer of liquid crystal material. 
     A liquid crystal display may be provided with backlight structures. The backlight structures may produce backlight that passes through an array of display pixels. The display pixels may include electrode structures and thin-film transistor structures for controlling electric fields in the layer of liquid crystal material. The liquid crystal material may be formed between an outer display layer and an inner display layer. 
     The inner display layer may be interposed between the backlight structures and the liquid crystal material. Thin-film transistor structures, electrodes, and conductive interconnection lines may be deposited in a layer on the inner surface of the outer display layer. 
     A layer of color filter elements may be used to provide the display with color pixels. With one suitable configuration, the color filter elements may be formed on the thin-film transistor layer. In this type of configuration, the inner display layer may be formed from a layer of clear glass or plastic. In another suitable configuration, the color filter elements may be formed on the inner display layer. 
     A patterned layer of opaque masking material may be formed in a peripheral border region of the outer display layer. A planarization layer may be used to cover the opaque masking layer. The thin-film transistors and other display pixels structures may be formed on the planarization layer. 
     Further features of the invention, its 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 diagram of an illustrative electronic device with a display such as a portable computer in accordance with an embodiment of the present invention. 
         FIG. 2  is a diagram of an illustrative electronic device with a display such as a cellular telephone or other handheld device in accordance with an embodiment of the present invention. 
         FIG. 3  is a diagram of an illustrative electronic device with a display such as a tablet computer in accordance with an embodiment of the present invention. 
         FIG. 4  is a diagram of an illustrative electronic device with a display such as a computer monitor with a built-in computer in accordance with an embodiment of the present invention. 
         FIG. 5  is a circuit diagram showing circuitry that may be used in operating an electronic device with a display in accordance with an embodiment of the present invention. 
         FIG. 6  is a circuit diagram of an illustrative display pixel in accordance with an embodiment of the present invention. 
         FIG. 7  is a cross-sectional side view of a portion of an illustrative liquid crystal display with backlight structures in accordance with an embodiment of the present invention. 
         FIG. 8  is a cross-sectional view of an illustrative electronic device having a display that overlaps housing sidewall structures in accordance with an embodiment of the present invention. 
         FIG. 9  is a cross-sectional view of an illustrative electronic device having a display that overlaps housing sidewall structures and having a display cover layer in accordance with an embodiment of the present invention. 
         FIG. 10  is a cross-sectional view of an illustrative electronic device having a display with edges that are mounted between opposing housing sidewalls in accordance with an embodiment of the present invention. 
         FIG. 11  is a cross-sectional view of an illustrative electronic device having a display with edges that are mounted between opposing housing sidewalls and having a display cover layer in accordance with an embodiment of the present invention. 
         FIG. 12  is a cross-sectional side view of a display showing how backlight structures may be used to provide the display with backlight in accordance with an embodiment of the present invention. 
         FIG. 13  is a cross-sectional view of an illustrative display having a substrate layer on which thin-film transistor structures and color filter structures have been formed in accordance with an embodiment of the present invention. 
         FIG. 14  is a cross-sectional side view of an illustrative display having an upper layer on which thin-film transistor structures have been formed and having a lower layer that serves as a color filter in accordance with an embodiment of the present invention. 
         FIG. 15  is a top view of a portion of a display showing how a black matrix may be used to separate color filter elements in accordance with an embodiment of the present invention. 
         FIG. 16  is a cross-sectional side view of a portion of a display showing how black matrix structures in the display may be used to cover underlying structures such as conductive lines on a thin-film transistor substrate in accordance with an embodiment of the present invention. 
         FIG. 17  is a cross-sectional side view of an illustrative display showing how formation of a layer of color filter elements on top of underlying thin-film structures such as electrode structures on a thin-film-transistor substrate may help improve off-axis display performance in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     An illustrative electronic device of the type that may be provided with a display is shown in  FIG. 1 . Electronic device  10  may be a computer such as a computer that is integrated into a display such as a computer monitor, a laptop computer, a tablet computer, a somewhat smaller portable device such as a wrist-watch device, pendant device, or other wearable or miniature device, a cellular telephone, a media player, a tablet computer, a gaming device, a navigation device, a computer monitor, a television, or other electronic equipment. 
     As shown in  FIG. 1 , device  10  may include a display such as display  14 . Display  14  may be a touch screen that incorporates capacitive touch electrodes or other touch sensor components or may be a display that is not touch sensitive. Display  14  may include image pixels formed from liquid crystal display (LCD) components or other suitable display pixel structures. Arrangements in which display  14  is formed using liquid crystal display pixels are sometimes described herein as an example. This is, however, merely illustrative. Any suitable type of display technology may be used in forming display  14  if desired. 
     Device  10  may have a housing such as housing  12 . Housing  12 , which may sometimes be referred to as a case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of any two or more of these materials. 
     Housing  12  may be formed using a unibody configuration in which some or all of housing  12  is machined or molded as a single structure or may be formed using multiple structures (e.g., an internal frame structure, one or more structures that form exterior housing surfaces, etc.). 
     As shown in  FIG. 1 , housing  12  may have multiple parts. For example, housing  12  may have upper portion  12 A and lower portion  12 B. Upper portion  12 A may be coupled to lower portion  12 B using a hinge that allows portion  12 A to rotate about rotational axis  16  relative to portion  12 B. A keyboard such as keyboard  18  and a touch pad such as touch pad  20  may be mounted in housing portion  12 B. 
     In the example of  FIG. 2 , device  10  has been implemented using a housing that is sufficiently small to fit within a user&#39;s hand (i.e., device  10  of  FIG. 2  may be a handheld electronic device such as a cellular telephone). As show in  FIG. 2 , device  10  may include a display such as display  14  mounted on the front of housing  12 . Display  14  may be substantially filled with active display pixels or may have an active portion and an inactive portion. Display  14  may have openings (e.g., openings in the inactive or active portions of display  14 ) such as an opening to accommodate button  22  and an opening to accommodate speaker port  24 . 
       FIG. 3  is a perspective view of electronic device  10  in a configuration in which electronic device  10  has been implemented in the form of a tablet computer. As shown in  FIG. 3 , display  14  may be mounted on the upper (front) surface of housing  12 . An opening may be formed in display  14  to accommodate button  22 . 
       FIG. 4  is a perspective view of electronic device  10  in a configuration in which electronic device  10  has been implemented in the form of a computer integrated into a computer monitor. As shown in  FIG. 4 , display  14  may be mounted on the front surface of housing  12 . Stand  26  may be used to support housing  12 . 
     Other configurations may be used for electronic device  10  if desired. The examples of  FIGS. 1, 2, 3, and 4  are merely illustrative. 
     A diagram showing circuitry of the type that may be used in device  10  is shown in  FIG. 5 . As shown in  FIG. 5 , display  14  may be coupled to device components  28  such as input-output circuitry  30  and control circuitry  32 . Input-output circuitry  30  may include components for receiving device input. For example, input-output circuitry  30  may include a microphone for receiving audio input, a keyboard, keypad, or other buttons or switches for receiving input (e.g., key press input or button press input from a user), sensors for gathering input such as an accelerometer, a compass, a light sensor, a proximity sensor, touch sensor (e.g., touch sensors associated with display  14  or separate touch sensors), or other input devices. Input-output circuitry  30  may also include components for supplying output. Output circuitry may include components such as speakers, light-emitting diodes or other light-emitting devices for producing light output, vibrators, and other components for supplying output. Input-output ports in circuitry  30  may be used for receiving analog and/or digital input signal and may be used for outputting analog and/or digital output signals. Examples of input-output ports that may be used in circuitry  30  include audio ports, digital data ports, ports associated with 30-pin connectors, and ports associated with Universal Serial Bus connectors and other digital data connectors. 
     Control circuitry  32  may be used in controlling the operation of device  10 . Control circuitry  32  may include storage circuits such as volatile and non-volatile memory circuits, solid state drives, hard drives, and other memory and storage circuitry. Control circuitry  32  may also include processing circuitry such as processing circuitry in a microprocessor or other processor. One or more integrated circuits may be used in implementing control circuitry  32 . Examples of integrated circuits that may be included in control circuitry  32  include microprocessors, digital signal processors, power management units, baseband processors, microcontrollers, application-specific integrated circuits, circuits for handling audio and/or visual information, and other control circuitry. 
     Control circuitry  32  may be used in running software for device  10 . For example, control circuitry  32  may be configured to execute code in connection with the displaying of images on display  14  (e.g., text, pictures, video, etc.). 
     Display  14  may include a pixel array such as pixel array  34 . Pixel array  34  may be controlled using control signals produced by display driver circuitry such as display driver circuitry  36 . Display driver circuitry  36  may be implemented using one or more integrated circuits (ICs) and may sometimes be referred to as a driver IC, display driver integrated circuit, or display driver. Display driver integrated circuit  36  may be mounted on an edge of a thin-film transistor substrate layer in display  14  (as an example). The thin-film transistor substrate layer may sometimes be referred to as a thin-film transistor (TFT) layer. 
     During operation of device  10 , control circuitry  32  may provide data to display driver  36 . For example, control circuitry  32  may use a path such as path  38  to supply display driver  36  with digital data corresponding to text, graphics, video, or other images to be displayed on display  14 . Display driver  36  may convert the data that is received on path  20  into signals for controlling the pixels of pixel array  34 . 
     Pixel array  34  may contain rows and columns of display pixels  40 . The circuitry of pixel array  34  may be controlled using signals such as data line signals on data lines  42  and gate line signals on gate lines  44 . 
     Pixels  40  in pixel array  34  may contain thin-film transistor circuitry (e.g., polysilicon transistor circuitry or amorphous silicon transistor circuitry) and associated structures for producing electric fields across liquid crystal material in display  14 . The thin-film transistor structures that are used in forming pixels  40  may be located on a substrate (sometimes referred to as a thin-film transistor layer or thin-film transistor substrate). The thin-film transistor (TFT) layer may be formed from a planar glass substrate, a plastic substrate, or a sheet of other suitable substrate materials. 
     Gate driver circuitry  46  may be used to generate gate signals on gate lines  44 . Circuits such as gate driver circuitry  46  may be formed from thin-film transistors on the thin-film transistor layer. Gate driver circuitry  46  may be located on both the left and right sides of pixel array  34  (as shown in  FIG. 5 ) or may be located on only one side of pixel array  34 . 
     The data line signals in pixel array  34  carry analog image data (e.g., voltages with magnitudes representing pixel brightness levels). During the process of displaying images on display  14 , display driver integrated circuit  36  may receive digital data from control circuitry  18  via path  38  and may produce corresponding analog data on path  48 . The analog data signals on path  48  may be demultiplexed by demultiplexer circuitry  50  in accordance with control signals provided by driver circuitry  36 . This demultiplexing process produces corresponding color-coded analog data line signals on data lines  42  (e.g., data signals for a red channel, data signals for a green channel, and data signals for a blue channel). 
     The data line signals on data lines  42  may be provided to the columns of display pixels  40  in pixel array  34 . Gate line signals may be provided to the rows of pixels  40  in pixel array  34  by gate driver circuitry  46 . 
     The circuitry of display  14  such as demultiplexer circuitry  50  and gate driver circuitry  46  and the circuitry of pixels  40  may be formed from conductive structures (e.g., metal lines and/or structures formed from transparent conductive materials such as indium tin oxide) and may include transistors that are fabricated on the thin-film transistor substrate layer of display  14 . The thin-film transistors may be, for example, polysilicon thin-film transistors or amorphous silicon transistors. 
       FIG. 6  is a circuit diagram of an illustrative display pixel in pixel array  34 . Pixels such as pixel  40  of  FIG. 6  may be located at the intersection of each gate line  44  and data line  42  in array  34 . 
     A data signal D may be supplied to terminal  50  from one of data lines  42  ( FIG. 5 ). Thin-film transistor  52  (e.g., a thin-film polysilicon transistor or an amorphous silicon transistor) may have a gate terminal such as gate  54  that receives gate line signal G from gate driver circuitry  46  ( FIG. 5 ). When signal G is asserted, transistor  52  will be turned on and signal D will be passed to node  56  as voltage Vp. Data for display  14  may be displayed in frames. Following assertion of signal G in one frame, signal G may be deasserted. Signal G may then be asserted to turn on transistor  52  and capture a new value of Vp in a subsequent display frame. 
     Pixel  40  may have a signal storage element such as capacitor Cst or other charge storage element. Storage capacitor Cst may be used to store signal Vp between frames (i.e., in the period of time between the assertion of successive signals G). 
     Display  14  may have a common electrode coupled to node  58 . The common electrode (which is sometimes referred to as the Vcom electrode) may be used to distribute a common electrode voltage such as common electrode voltage Vcom to nodes such as node  58  in each pixel  40  of array  24 . Capacitor Cst may be coupled between nodes  56  and  58 . A parallel capacitance Clc arises across nodes  56  and  58  due to electrode structures in pixel  40  that are used in controlling the electric field through the liquid crystal material of the pixel (liquid crystal material  60 ). As shown in  FIG. 6 , electrode structures  62  may be coupled to node  56 . Capacitance Clc is associated with the capacitance between electrode structures  62  and common electrode Vcom at node  58 . During operation, electrode structures  62  may be used to apply a controlled electric field (i.e., a field having a magnitude proportional to Vp-Vcom) across a pixel-sized portion of liquid crystal material  60  in pixel  40 . Due to the presence of storage capacitor Cst, the value of Vp (and therefore the associated electric field across liquid crystal material  60 ) may be maintained across nodes  56  and  58  for the duration of the frame. 
     The electric field that is produced across liquid crystal material  60  causes a change in the orientations of the liquid crystals in liquid crystal material  60 . This changes the polarization of light passing through liquid crystal material  60 . The change in polarization may be used in controlling the amount of light that is transmitted through each pixel  40  in array  34 . 
     A portion of display  14  illustrating how changes in the light polarization produced by liquid crystal material  60  can be used to affect the amount of light that is transmitted through display  14  is shown in  FIG. 7 . As shown in  FIG. 7 , backlight structures  64  may be used to produce backlight  66  that travels upwards (outwards) in dimension Z through display layers  81  of display  14 . Display layers  81  may include an upper polarizer layer such as layer  68  and a lower polarizer layer  74 . Upper polarizer layer  68  may be attached to one or more substrate layers such as layer  70 . Lower polarizer layer  74  may be attached to one or more substrate layers such as layer  72 . Layers  70  and/or  72  may be formed from transparent layers such as layers of glass, plastic, or other sheets of material. Layers  70  and/or  72  and other layers of display  81  may include thin-film transistor layers, color filter layers, layers that include thin-film transistor structures and color filter elements, planarization layers, opaque masking patterns, clear layers, or other suitable display layers. 
     As light  66  passes through lower polarizer  74 , lower polarizer  74  polarizes light  66 . As polarized light  66  passes through liquid crystal material  60 , liquid crystal material  60  may rotate the polarization of light  66  by an amount that is proportional to the electric field through liquid crystal material  60 . If the polarization of light  66  is aligned in parallel with the polarization of polarizer  68 , the transmission of light  66  through layer  68  will be maximized. If the polarization of light  66  is aligned so as to run perpendicular to the polarization of polarizer  68 , the transmission of light  66  through layer  68  will be minimized (i.e., light  66  will be blocked). The display circuitry of  FIG. 5  may be used in adjusting the voltages Vp across the electrodes  62  of display pixels  40  in display pixel array  34 , thereby selectively lightening and darkening pixels  40  in pixel array  34  and presenting an image to a user of device  10  such as viewer  76 , viewing display  14  in direction  78 . 
     Displays such as display  14  may be mounted on one or more surfaces of device  10 . For example, displays such as display  14  may be mounted on a front face of housing  12 , on a rear face of housing  12 , or on other portions of device  10 . 
     As shown in  FIG. 8 , display  14  may be mounted in housing  12  so that some or all of the edges of display  14  overlap housing sidewalls  12 ′. Internal electrical components  82  (e.g., input-output components  30 , control circuitry  32 , etc.) may be mounted on one or more substrates such as substrate  80  within housing  12 . Substrate  80  may be formed from one or more printed circuits. For example, substrate  80  may include a rigid printed circuit board (e.g., a printed circuit board formed from a material such as fiberglass-filled epoxy) and/or a flexible printed circuit (“flex circuit”) such as a printed circuit formed from patterned conductive traces on a sheet of polyimide or other flexible polymer. 
     If desired, some or all of the outermost surface of display  14  may be covered with a display cover layer such as display cover layer  84  of  FIG. 9 . Display cover layer  84  may be formed from a layer of glass, a layer of plastic, a layer of ceramic, or other suitable transparent materials. One or more additional display layers may also be included in display  14  if desired (e.g., antireflection films, scratch-resistance coating layers, fingerprint-reducing layers, layers that perform multiple functions such as reducing reflection, reducing scratches, and reducing fingerprints, etc.). 
       FIG. 10  is a cross-sectional view of device  10  in a configuration in which display  14  has been mounted between respective housing sidewalls  12 ′ (i.e., without overlapping upper edges  12 ″ of sidewalls  12 ′).  FIG. 11  shows how display cover layer  84  may be used to cover display  14  in a configuration in which display  14  is mounted between housing sidewalls  12 ′. 
     The illustrative mounting arrangements of  FIGS. 8, 9, 10, and 11  are merely illustrative examples of ways in which display  14  may be mounted in housing  12  of device  10 . Other mounting configurations may be used if desired. 
       FIG. 12  is a cross-sectional view of display  14  showing how backlight structures  86  may be used in producing backlight  66  for display  14 . As shown in  FIG. 12 , a light source such as light source  92  may produce light  94 . Light source  92  may include, for example, one or more light-emitting diodes. Backlight structures  86  may include a light guide plate and other layers  88  (e.g., a diffuser and other optical films). A reflective layer such as reflector  90  may be placed on the rear surface of the light guide plate. As light  94  travels through the light guide plate, some of light  94  scatters upwards in direction Z towards viewer  76  and serves as backlight  66  for display  14 . Light that scatters downwards may be reflected upwards by reflector  90  to serve as additional backlight  66 . 
     Display layers  81  may include thin-film transistors such as transistor  52  of  FIG. 6  and conductive structures (e.g., electrodes such as electrode  62 , gate lines, data lines, and other lines and conductive structures formed from metal and/or indium tin oxide or other transparent conductive materials). Display layers  81  may also include color filter structures for imparting colors such as red, blue, and green colors to pixels  40  in pixel array  34 . The color filter structures may be formed in an array (e.g., an array of alternating red, green, and blue color filter elements) and are therefore sometimes referred to as a color filter array or color filter array structures. 
     Color filter array structures may be formed using colored substances such as dye or pigment (e.g., colored red, blue, and green ink or materials of other suitable colors). Color filter structures may be formed by ink-jet printing, screen printing, pad printing, photolithographic patterning, or other suitable deposition and patterning techniques. Color filter structures may be formed on the same substrate as the thin-film transistors and conductive structures of display pixels  40  or may be formed separately (e.g., on a color filter layer that is separated from a thin-film transistor substrate layer). 
       FIG. 13  is a cross-sectional view of an illustrative configuration that may be used for display  14  in which color filter elements for the color filter array in display  14  have been formed on the same substrate as the thin-film transistors and conductive structures of display pixels  40 . As shown in  FIG. 13 , display  14  may be provided with backlight  66  using backlight structures  86 . During operation, backlight  66  may travel vertically upwards (outwards in dimension Z) through display layers  81  of display  14  to be viewed by a user such as viewer  76  looking at display  14  in direction  78 . 
     Display layers  81  may include a substrate such as substrate  96 . Substrate  96  may be formed from glass, plastic, ceramic, or other suitable transparent materials. Substrate  96  may have a rectangular outline or other suitable shape. The surfaces of substrate  96  such as outer (upper) surface  106  and inner (lower) surface  104  may be planar (as shown in  FIG. 13 ) or may be curved. 
     An opaque (e.g., black) masking material such as an inorganic opaque material (e.g., chrome) or an organic opaque material (e.g., black ink or black plastic) may be used to form peripheral border mask  98  in peripheral border region  100  (e.g., a rectangular ring surrounding a central rectangular active area of display  14 ). Opaque masking material may also be used to form an opaque matrix (e.g., a black matrix) that separates individual pixels  40 . As shown in  FIG. 13 , masking material  98  may be formed on interior surface  104  of substrate  96  in peripheral border region  100  (as an example). 
     An optional planarization layer such as layer  102  may be formed over the inner surface of substrate  96  following formation of opaque masking material  98  (e.g., layer  102  may be deposited so as to cover masking material  98 ). Planarization layer  102  may be formed from a layer of silicon oxide, silicon nitride, silicon oxynitride, an organic material such as acrylic, other transparent planarizing materials, or a combination of two or more of these materials. Layer  102  may be deposited by screen printing, spin-on coating, spray coating, physical vapor deposition, chemical vapor deposition, or other suitable deposition techniques. If desired, layer  102  may be polished to help planarize layer  102 . 
     Layer  108  may be formed on planarization layer  102 . Layer  108 , which may sometimes be referred to as a thin-film transistor layer, may include display pixel structures such as structures  110  and conductive structures such as traces  112 . Structures  110  may include thin-film transistors such as thin-film transistor  52  of  FIG. 6  and electrodes such as electrode structures  62  of  FIG. 6 . Traces  112  may include gate lines  44 , data lines  42 , and other conductive lines. Structures  110  and  112  may be formed from thin-film transistor materials (e.g., polysilicon or amorphous silicon), conductive materials such as metal and transparent conductors such as indium tin oxide, or other suitable materials. 
     Solder connections such as solder bumps  114  may be used in connecting display driver integrated circuit  36  or other external circuitry to traces  112  in thin-film transistor layer  108 . Integrated circuit  36  may be mounted on substrate  96  so that integrated circuit  36  is fully or partly covered by overlapping portions of masking material  98  (i.e., so that integrated circuit  36  is blocked from view by viewer  76  by overlapping masking layer  98 ). 
     Color filter layer  116  may be formed on layer  108 . Color filter layer  116  may, for example, be deposited on layer  108  using physical vapor deposition, chemical vapor deposition, ink-jet printing, spraying, pad printing, screen printing, spin-on coating, or other deposition techniques. Color filter layer  116  may include an array of color filter elements  116 ′ each of which may be associated with a different respective display pixel  40  in pixel array  34 . Three elements  116 ′ (labeled as red R, green G, and blue B) are shown in  FIG. 13 . In general, color filter array layer  116  may include any suitable number of pixels (e.g., hundreds or more, thousands or more, tens of thousands or more, etc.). Layers  116  and  108  may have any suitable thicknesses. For example, layers  116  and  108  may each be less than 20 microns thick, less than 10 microns thick, or less than 4 microns thick (as examples). 
     Liquid crystal layer  60  may be sandwiched between substrate  96  (and the structures formed on lower surface  104  of substrate  96  such as thin-film transistor layer  108  and color filter layer  116 ) and inner display layers such as inner display layer  118 . Layer  118  may be formed from a material such as glass, ceramic, plastic, or other substance that is sufficiently transparent to allow backlight  66  to pass through the display pixels of display layers  81 . Layer  118  may, for example, be formed from a rectangular sheet of clear glass or plastic (as an example). As described in connection with  FIG. 7 , the upper surface of display  14  such as surface  106  of substrate  96  may be covered with an upper polarizer layer such as upper polarizer  68  and may (as described in connection with  FIGS. 9 and 11 ) be covered with an optional display cover layer such as display cover layer  84  and/or coatings such as smudge-resistance coatings, scratch-resistance coatings, and antireflection coatings. The lower surface of display  14  in  FIG. 13  (e.g., lower surface  120  of layer  118 ) may be covered with a lower polarizer layer such as layer  74 . 
       FIG. 14  is a cross-sectional view of display  14  in a configuration in which color filter layer  116  has been implemented using a substrate layer that is separate from thin-film transistor substrate layer  96 . In this configuration, liquid crystal material  60  may be interposed between thin-film transistor layer  108  and color filter array layer  116 . As with display  14  of  FIG. 13 , display  14  of  FIG. 14  may be provided with backlight  66  using backlight structures  86 . Backlight  66  may travel vertically upwards (outwards) in dimension Z through display layers  81  of display  14  to be viewed by a user such as viewer  76  looking at display  14  in direction  78 . 
     Display layers  81  may include a substrate such as substrate  96 . As with substrate  96  of  FIG. 13 , substrate  96  of  FIG. 14  may be formed from glass, plastic, ceramic, or other suitable transparent materials. Substrate  96  may have a rectangular outline or other suitable shape. The surfaces of substrate  96  such as outer (upper) surface  106  and inner (lower) surface  104  may be planar (as shown in  FIG. 14 ) or may be curved. 
     An opaque masking material such as an inorganic opaque material (e.g., chrome) or an organic opaque material (e.g., black ink or black plastic) may be used to form peripheral border mask  98  in peripheral border region  100 . Opaque masking material may also be used to form an opaque matrix that separates individual pixels  40 . Black masking material  98  may be formed on interior surface  104  of substrate  96  (as an example). 
     An optional planarization layer such as layer  102  may be formed over the inner surface of substrate  96  following formation of opaque masking material  98 . Planarization layer  102  may be formed from a layer of silicon oxide, silicon nitride, silicon oxynitride, an organic material such as acrylic, other transparent planarizing materials, or a combination of two or more of these materials. Layer  102  may be deposited over masking material  98  and other features on substrate  96  using screen printing, spin-on coating, spray coating, physical vapor deposition, chemical vapor deposition, or other suitable deposition techniques. If desired, layer  102  may be polished to help planarize layer  102 . 
     Layer  108  may be formed on planarization layer  102 . Layer  108 , which may sometimes be referred to as a thin-film transistor layer, may include display pixel structures such as structures  110  and conductive structures such as traces  112 . Structures  110  may include thin-film transistors such as thin-film transistor  52  of  FIG. 6  and electrodes such as electrode structures  62  of  FIG. 6 . Traces  112  may include gate lines  44 , data lines  42 , and other conductive lines. Structures  110  and  112  may be formed from thin-film transistor materials (e.g., polysilicon or amorphous silicon), conductive materials such as metal and transparent conductors such as indium tin oxide, or other suitable materials. 
     Solder connections such as solder bumps  114  may be used in connecting display driver integrated circuit  36  or other external circuitry to traces  112  in thin-film transistor layer  108 . Display driver integrated circuit  36  may be mounted under masking layer  98  so that masking layer  98  blocks integrated circuit  36  from view by viewer  76 . 
     Color filter array  116  may be formed from a substrate that is separated from layer  108  by an interposed layer of liquid crystal material such as liquid crystal layer  60 . Color filter array  116  may, for example, be formed from an array of color filter elements that are deposited on a substrate such as a layer of glass, plastic, ceramic, or other transparent sheet of material using physical vapor deposition, chemical vapor deposition, ink-jet printing, spraying, pad printing, screen printing, spin-on coating, or other deposition techniques. 
     Color filter layer  116  of  FIG. 14  may include an array of color filter elements  116 ′ each of which may be associated with a different respective display pixel  40  in pixel array  34 . Illustrative elements  116 ′ (labeled as red R, green G, and blue B) are shown in  FIG. 14 . In general, color filter array layer  116  may include any suitable number of color filter elements  116 ′ corresponding to any suitable number of respective display pixels  40  (e.g., hundreds or more, thousands or more, tens of thousands or more, etc.). 
     As shown in  FIG. 14 , liquid crystal layer  60  may be sandwiched between upper display layers such as substrate  96  (and the structures formed on lower surface  104  of substrate  96  such as thin-film transistor layer  108 ) and lower display layers such as color filter array  116 . A substrate layer in color filter array  116  may be formed from a material such as glass, ceramic, plastic, or other substance that is sufficiently transparent to allow backlight  66  to pass through the display pixels of display layers  81 . Layer  116  may, for example, be formed from a rectangular sheet of clear glass or plastic (as an example). The upper surface of display  14  such as surface  106  of thin-film transistor substrate  96  may be covered with an upper polarizer layer such as upper polarizer  68  and may be covered with an optional display cover layer such as display cover layer  84  and/or coatings such as smudge-resistance coatings, scratch-resistance coatings, and antireflection coatings. The lower surface of display  14  in  FIG. 14  (e.g., lower surface  122  of color filter array  116 ) may be covered with a lower polarizer layer such as layer  74 . 
     Color filter elements  116 ′ in color filter array  116  may be separated by lines of opaque material (sometimes referred to as black matrix material or opaque masking material). The black matrix may be used to block metal lines and other structures from view by the user of device  10  and may help reduce light leakage between adjacent pixels. The black matrix may be formed from opaque organic or inorganic materials such as chrome and black ink (as examples). The top view of color filter array  116  in  FIG. 15  shows how black matrix  124  may form a grid of opaque masking lines laterally interposed between respective color filter elements  116 ′. The width of the masking lines (shown as width W in  FIG. 15 ) may be less than 50 microns, less than 30 microns, less than 20 microns, less than 15 microns, less than 10 microns, less than 7 microns, less than 3 microns, or any other suitable width. The lateral dimensions of color filter elements  116 ′ may be 500 microns or less, 100 microns or less, 50 microns or less, or 25 microns or less (as examples). For example, rectangular color filter elements  116 ′ in array  116  may be provided with pixel dimensions of 25 microns by 75 microns (as an example). 
     It may be desirable to reduce the magnitude of black matrix line width W relative to the lateral dimensions D of color filter elements  116 ′ to improve display brightness (i.e., brightness efficiency). Using arrangements of the type shown in  FIG. 13  in which a layer of color filter elements  116 ′ has been deposited on thin-film transistor layer  108 , color filter array layer  116  may be formed in close proximity to the thin-film transistors, electrodes, and other structures of thin-film transistor layer  108 . This may facilitate accurate alignment between the black matrix in the color filter array and underlying structures in layer  108 , thereby allowing the magnitude of black matrix line width W to be minimized. 
     As shown in  FIG. 16 , thin-film transistor layer  108  may be formed on substrate  96 . Each electrode  62  (i.e., each set of three common electrode finger structures in the example of  FIG. 16 ) may be configured to overlap with a corresponding color filter element  116 ′. Color filter elements  116 ′ may be used to impart colors to backlight  66  before backlight  66  passes through the pixels of thin-film transistor layer  108  and is viewed in direction  78  by viewer  76 . Lines of black matrix material  124  may be configured to overlap structures in thin-film transistor layer  108  such as structures  126  (e.g., gate lines  44 , data lines  42 , etc.) and thereby block structures  126  from view. The thickness T of thin-film transistor layer  108  and therefore the vertical separation in dimension Z between color filter layer  116  and the thin-film structures on surface  104  of substrate  96  may be relatively small (e.g., less than 25 microns, less than 5 microns, less than 2 microns, etc.). The small thickness T and the ability to form color filter layer  116  on layer  108  allows black matrix lines  124  to be accurately aligned with respect to structures  126 . This accurate alignment allows the size W of black matrix lines  124  to be minimized (e.g., so be less than 50 microns, less than 30 microns, less than 20 microns, less than 15 microns, less than 10 microns, less than 7 microns, less than 3 microns, or other suitable width). By minimizing W relative to the lateral dimensions (e.g., dimension D) of color filter elements  116 ′, display brightness (e.g., the efficiency with which display  14  transmits a given amount of backlight  66 ) may be enhanced. 
     Configuring display  14  so that viewer  76  views display pixels  40  through thin-film transistor substrate  96  and electrodes  62  rather than color filter  116  may reduce light leakage effects between adjacent pixels. Consider, as an example, display  14  of  FIG. 17 . As shown in  FIG. 17 , viewer  76  may view display  14  through substrate  96  and thin-film transistor layer  108  by viewing in directions such as direction  78 A and  78 B. (Polarizer layers, cover glass, backlight structures and other layers have been omitted from  FIG. 17  for clarity). Backlight  66  passes through liquid crystal material  60 . Electrodes  62  are located in thin-film transistor layer  108  on substrate  96 , so the electric field that is produced in liquid crystal material  60  is strongest near layer  108  and is weakest near layer  118 . Color filter array  116  and color filter elements  116 ′ may be deposited on thin-film transistor layer  108 . Layer  118  may be formed from clear glass, clear plastic, or other transparent material. 
     The gradual weakening of the electric field strength in layer  60  with increasing distance from layer  108  is illustrated for the green “G” pixel in  FIG. 17 . In the  FIG. 17  example, the red pixel “R” and the blue pixels “B” are not receiving signals on their respective electrodes  62 , so the liquid crystals  60 ′ in the portions of liquid crystal layer  60  that are associated with the R and B pixels has not been rotated, as illustrated in  FIG. 17 . The electrode  62  that is associated with the green (“G”) pixel is, however, receiving a signal (in this example) and is therefore producing an electric field in an adjacent portion of layer  60 . As a result, liquid crystals  60 ′ above electrode  62  in the green (“G”) pixel are rotated. Because the electric field strength in the green pixel decreases with increasing distance into layer  60  away from thin-film layer  108  and electrode  62 , the amount of rotation of liquid crystals  60 ′ in the green pixel decreases by a corresponding amount at increasing distances into layer  60  away from layer  108 , as shown in  FIG. 17 . 
     When viewing the pixels of display  40  “on axis” (i.e., along a direction that is parallel to the surface normal n for substrate  96 ), backlight  66  will generally not leak appreciably into adjacent pixels and the pixel colors will tend not to bleed into each other. When, however, viewer  76  views display  14  along an off-axis angle such as the angle associated with directions  78 A and  78 B of  FIG. 17 , there is a risk that the viewer will view part of the liquid crystal material associated with one pixel through the color filter of another pixel. If not well controlled, this effect can reduce display performance by reducing color accuracy. 
     With a display of the type show in  FIG. 17 , off-axis performance may be enhanced, because off-axis light rays that have the potential to cause interference have relatively low intensities. When viewer  76  views light  66  traveling along viewing axis  78 B, viewer  76  will observe light  66  that has travelled through strongly rotated (i.e., strongly “on”) liquid crystals  60 ′ and a corresponding portion of the green (“G”) color filter element  116 ′ in color filter layer  116 . The viewer observing the center of the green pixel along axis  78 B will therefore correctly observe that the green pixel is emitting green backlight  66  and has a green color. When viewer  76  views light  66  traveling along viewing axis  78 A, however, viewer  76  will observe light  66  that has travelled through a weakly rotated (i.e., weakly “on”) liquid crystals  60 ′ and a corresponding portion of the red (“R”) color filter element  116 ′ in color filter layer  116 . The red pixel in the  FIG. 17  example has been turned “off” (i.e., the red pixel&#39;s liquid crystals  60 ′ have not been rotated), so the viewer should not be observing any red light through the red color filter element  116 ′. The red light  66  that the viewer observes along axis  78 A therefore represents a source of color error and tends to degrade display performance. Nevertheless, because the liquid crystals  60 ′ through which the red light traveling along axis  78 A has passed are weakly rotated, the magnitude (intensity) of the erroneous red light that is observed by viewer  76  will tend to be small. The reduced tendency for display  14  to exhibit color bleeding between adjacent pixels may be exploited to enhance color accuracy and/or to reduce the width of black matrix  124  and thereby improve display brightness efficiency. 
     In conventional displays, there is more potential for color interference between adjacent pixels. Consider, as an example, a situation in which layer  118  of  FIG. 17  is used to implement a conventional color filter array and color filter layer  116  is omitted. Conventional backlight  66 ′ in this scenario would pass through strongly rotated liquid crystals  60 ′ in the green pixel before passing through red color filter element portion  150  of layer  118  along axis  78 ′. Off-axis viewer  76 ′ of the conventional display would therefore observe a significant erroneous red light component when the green pixel is turned on. 
     The foregoing is merely illustrative of the principles of this invention and various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention.

Metadata:
Filing Date: 20120320
Publication Date: 20160719
Grant Date: 20160719
Priority Date: 20120320
Inventors: QI JUN
MATHEW DINESH C.
POSNER BRYAN W.
HENDREN KEITH J.
AUGENBERGS PETERIS K.
GARELLI ADAM T.
YIN VICTOR H.
WILSON, JR. THOMAS W.
Assignee: APPLE INC
CPC Classifications: [{"code": "G02F2001/136222", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/1362", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F2001/133562", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133512", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133512", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/133562", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133509", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/1362", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/1368", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133562", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133357", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/136222", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/1362", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/136222", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133512", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/13454", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/136209", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133514", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/1362", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 48014329