Patent Application
20140293188
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 displays contain a thin layer of liquid crystal material interposed between a color filter layer and a thin-film transistor layer. Polarizer layers are located above the color filter layer and below the thin-film transistor layer.
Liquid crystal displays typically include passive display pixels that can alter the amount of light that is transmitted through the display but do not produce light themselves. As a result, it is often desirable to provide backlight for a display with passive pixels such as liquid crystal display pixels.
When it is desired to display images 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 the 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, which in turn controls the transmission of light through the display when displaying images for a user.
It can be difficult to achieve a satisfactory contrast ratio in a liquid crystal display. In edge-lit liquid crystal displays, a light source such as an array of light-emitting diodes emits light into the edge of a light guide plate located behind the display. The light guide plate is used to distribute the backlight uniformly across the display. Thus, in order to display dark colors such as black, the liquid crystal display pixels block light from transmitting through the display to give the appearance of zero luminance. However, the structure of the liquid crystal material is inherently imperfect and some light will always leak through the display. Different regions of a display will also allow different amounts of light to escape in the dark state, resulting in a non-uniform black screen (a phenomenon sometimes referred to as light leakage).
Some displays employ a full array backlight instead of an edge-lit backlight. With this type of configuration, an array of light-emitting diodes is formed directly behind the display. This allows the display to switch off the backlight in the regions where dark colors are being displayed so that the dark colors appear closer to true black. However, full array displays of this type are often thicker than edge-lit displays and typically consume a large amount of power. Moreover, there are a limited number of zones on a full array display that can be locally darkened. This results in a brightened halo around bright objects that are surrounded by darker pixels on the display.
It would therefore be desirable to be able to provide improved displays for electronic devices.
An electronic device is provided with a display such as a liquid crystal display mounted in an electronic device housing. The display includes a display module having an array of display pixels. The display module includes 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.
A backlight unit is used to provide backlight illumination to the display module. The backlight unit may include a light guide plate and a light source that emits light into an edge of the light guide plate. The light guide plate is used to distribute the light uniformly across the display.
The display includes a shutter module having local dimming elements. The local dimming elements are configured to control the amount of light that is transmitted through an overlapping region of the array of display pixels. The local dimming elements may be arranged in a uniform array having rows and columns or the local dimming elements may have different shapes and sizes and may be located in specific regions of the display. For example, the shutter module may include first and second local dimming elements having different sizes. As another example, the shutter module may include one or more elongated local dimming elements that run along one or more edges of the display. Local dimming elements that run along the upper and lower edges of a display can be used to minimize light leakage in these regions (e.g., during a wide-screen movie mode).
The local dimming elements may include liquid crystal display structures, polymer-dispersed liquid crystal display structures, photovoltaic material, electrowetting display structures, and/or other suitable types of light controlling elements.
In one suitable arrangement, the shutter module is located behind the display module (e.g., the shutter module is interposed between the display module and the backlight unit). In another suitable embodiment, the shutter module is arranged in front of the display module (e.g., the display module is interposed between the shutter module and the backlight unit).
Further features, their nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments.
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
Electronic device 10 of
In the example of
The illustrative configurations for device 10 that are shown in
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 schematic diagram of electronic device 10 is shown in
Display pixels 46P may be formed from reflective components, liquid crystal display (LCD) components, organic light-emitting diode (OLED) components, or other suitable display pixel structures. To provide display 14 with the ability to display color images, display pixels 46P may include color filter elements. Each color filter element may be used to impart color to the light associated with a respective display pixel 46P in pixel array of display 14.
Shutter module 62 is used to help control the amount of light that is emitted by display 14. Shutter module 62 includes local dimming elements 62L, which may be arranged in an array of rows and columns or may have other suitable arrangements. Each local dimming element 62 is used to selectively lighten or darken a localized region of display 14. For example, when it is desired to display black in a selected region of display 14, local dimming elements 62L in a corresponding region of shutter module 62 are manipulated to block light from transmitting through display 14 in the selected region. Local dimming elements 62L may be formed from liquid crystal display structures, polymer-dispersed liquid crystal display structures, reflective display structures, electrowetting display structures, electrophoretic display structures, microelectromechanical systems-based shutter elements, photovoltaic materials, and/or other suitable light-controlling structures.
Display control circuitry 29 may include a graphics controller (sometimes referred to as a video card or video adapter) that may be used to provide video data and control signals to display 14. Video data may include text, graphics, images, moving video content, or other content to be presented on display 14.
Display control circuitry 29 may also include display driver circuitry. Display driver circuitry in circuitry 29 may be implemented using one or more integrated circuits (ICs) and is sometimes be referred to as a driver IC, display driver integrated circuit, or display driver. If desired, the display driver integrated circuit may be mounted on an edge of a thin-film-transistor substrate layer in display 14 (as an example). Display control circuitry 29 may include timing controller (TCON) circuitry such as a TCON integrated circuit. The timing controller may be used to supply pixel signals to display pixels 46P and local dimming signals to local dimming elements 62L.
the timing controller supplies data line and gate line signals to both display module 46 and shutter structures 62.
Display control circuitry 29 may be coupled to additional circuitry in device 10 such as storage and processing circuitry 33. Storage and processing circuitry 33 in device 10 may include microprocessors, microcontrollers, digital signal processor integrated circuits, application-specific integrated circuits, and other processing circuitry. Volatile and non-volatile memory circuits such as random-access memory, read-only memory, hard disk drive storage, solid state drives, and other storage circuitry may also be included in circuitry 33. Display calibration information may be stored using circuitry 33 or may be stored using display control circuitry 29 or other circuitry associated with display 14.
Circuitry 33 may use wireless communications circuitry 35 and/or input-output devices 37 to obtain user input and to provide output to a user. Input-output devices 37 may include speakers, microphones, sensors, buttons, keyboards, displays, touch sensors, and other components for receiving input and supplying output. Wireless communications circuitry 35 may include wireless local area network transceiver circuitry, cellular telephone network transceiver circuitry, and other components for wireless communication.
A cross-sectional side view of an illustrative configuration for display 14 of device 10 (e.g., for display 14 of the devices of
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 as 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. Display layers 46 are sometimes referred to herein collectively as “display module.”
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.
Display module 46 is illuminated with backlight 44 provided by backlight structures 42. In the example of
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. The use of a reflector in backlight 42 is, however, merely illustrative and may not be needed in some configurations.
The configuration of
To enhance backlight performance for backlight structures 42, backlight structures 42 optionally 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
Display 14 includes a shutter module such as shutter module 62. Shutter module 62 is used to help control the amount of backlight 44 that is transmitted through display 14 (upwards in dimension Z in the configuration of
Shutter module 62 includes local dimming elements 62L (
Each local dimming element 62L is configured to control light transmission independently of the other local dimming elements in shutter module 62. Local dimming elements 62L can be controlled using data line signals on data lines and gate line signals on gate lines. Because shutter module 62 is used to control the transmission of light from display 14, shutter module 62 need not include color filter elements (e.g., shutter module 62 may include monochromatic display structures). However, if desired, shutter module 62 can include color filter elements.
Shutter module 62 may be assembled with other display structures in display 14 in any suitable fashion. In one suitable embodiment, shutter module 62 is laminated to display module 46 using an adhesive such as optically clear adhesive 84. In another suitable embodiment, layer 84 is an air gap that separates display module 46 from shutter module 62. If desired, display module 46 and shutter module 62 may be manufactured as a single panel and layer 84 may be omitted.
During operation of display 14, control circuitry in device 10 (e.g., circuitry 33 of
If desired, a single display control circuit (e.g., a timing controller (TCON) integrated circuit in circuitry 29 of
The use of a single timing controller integrated circuit to control both display module 46 and shutter module 62 is merely illustrative. If desired, a first timing controller integrated circuit can be used to control display module 46 and a second timing controller integrated circuit can be used to control shutter module 62.
In the example of
This is however, merely illustrative. If desired, shutter module 62 may be located in front of display module 46. This type of configuration is shown in
In another suitable embodiment, shutter module 62 is located behind backlight structures 42. This type of configuration is shown in
If desired, backlight structures 42 may be omitted. With this type of configuration, shutter module 62 operates in the same manner described above. However, rather than blocking or transmitting light from a backlight, shutter module 62 is used to control the transmission of ambient light. When a region of shutter module 62 is transmissive, ambient light will pass through that region of shutter module 62 and will be reflected by reflector 84. The reflected light will illuminate a corresponding region of display module 46. When a region of shutter module 62 is not transmissive, the corresponding region of display module 46 will be dark (e.g., black) because ambient light will be unable to reach reflector 84 behind shutter module 62.
In one suitable embodiment, local dimming elements 62L in shutter module 62 are formed from liquid crystal display structures. This type of configuration is shown in
Layers 66 and 86 are formed from transparent substrate layers such as clear layers of glass or plastic. Layers 86 may, for example, be 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). Conductive traces, transistors, and other circuits and structures are formed on substrate layer 86 (e.g., to form a thin-film transistor layer). If desired, layer 66 may be a thin-film transistor layer. The configuration of
Because shutter module 62 is used for controlling light transmission rather than displaying images, local dimming element 62L need not include color filter elements. However, if it is desired to provide shutter module 62 with the ability to filter light of different wavelengths, layer 66 may be 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).
Layer 86 can include one or more thin-film transistors and associated electrodes (local dimming electrodes) for applying electric fields to liquid crystal layer 68 and thereby controlling the amount of light transmitted through local dimming element 62L.
As light 88 passes through lower polarizer 82, lower polarizer 82 polarizes light 88. As polarized light 88 passes through liquid crystal material 68, liquid crystal material 68 rotates the polarization of light 88 by an amount that is proportional to the electric field through liquid crystal material 68. If the polarization of light 88 is aligned in parallel with the polarization of upper polarizer 64, the transmission of light 88 through layer 64 will be maximized. If the polarization of light 88 is aligned so as to run perpendicular to the polarization of polarizer 64, the transmission of light 88 through layer 64 will be minimized (i.e., light 88 will be blocked). Display control circuitry 29 (e.g., a timing controller) that controls display module 46 can also be used in adjusting the voltages across the local dimming electrodes in local dimming element 62L, thereby selectively lightening and darkening localized regions of display 14.
In another suitable embodiment, local dimming elements 62L in shutter module 62 are formed from polymer-dispersed liquid crystal display structures. This type of configuration is shown in
Polymer-dispersed liquid crystal layer 94 includes liquid crystal droplets 96 dispersed in solid polymer matrix 102. Layer 94 is interposed between upper substrate 90 and lower substrate 100. Upper and lower substrate layers 90 and 100 are formed from transparent substrate layers such as clear layers of plastic or glass. Upper substrate layer 90 is coated with a conductive material such as transparent conductive material 92 (e.g., a thin coating of indium tin oxide or other transparent conductive material). Lower substrate layer 100 is also coated with a conductive material such as transparent conductive material 98 (e.g., a thin coating of indium tin oxide or other transparent conductive material). Polymer-dispersed liquid crystal layer 94 is sandwiched between conductive coatings 92 and 98 (sometimes referred to herein as upper and lower ITO coatings).
Upper and lower ITO coatings are used for applying electric fields to polymer-dispersed liquid crystal layer 94 and thereby controlling the amount of light transmitted through local dimming element 62L. The transmission of light through layer 94 of local dimming element 62L depends on the amount of scattering that occurs as light strikes layer 94. The amount of light scattering in turn depends on the orientation of liquid crystal droplets 96. In the absence of an applied voltage, liquid crystal droplets 96 are dispersed in polymer 102 in a random array. This maximizes the amount of scattering that occurs as light is incident on layer 94 and therefore minimizes the transmission of light through local dimming element 62L. When a voltage is applied across layer 94, the electric field that is produced across layer 94 causes liquid crystal droplets 96 to align with the electric field. This minimizes the amount of scattering that occurs as light is incident on layer 94 and therefore maximizes the transmission of light through local dimming element 62L.
Display control circuitry 29 (e.g., a timing controller) that controls display module 46 can also be used in adjusting the electric field across layer 94 in local dimming element 62L, thereby selectively lightening and darkening localized regions of display 14.
In another suitable embodiment, local dimming elements 62L in shutter module 62 are formed from electrowetting display structures. This type of configuration is shown in
In an equilibrium state (i.e., in the absence of an applied voltage), colored oil 106 forms a flat film on the surface of insulator 108. When a voltage is applied across insulator 108, the equilibrium state changes and it requires less energy for water 104 to rest on the surface of insulator 108. Thus, colored oil 106 is pushed to the side when a voltage is applied across hydrophobic insulator 108.
If desired, colored oil 106 may be opaque such as black and electrode 110 may be a transparent electrode. With this type of configuration, light transmission through local dimming element 62L is minimized when no voltage is applied across insulator 108 so that opaque oil 106 forms a flat film on the surface of insulator 108. Light transmission through shutter module 62 is maximized when a voltage is applied across insulator 108 so that opaque oil 106 moves to the side and light is allowed to pass through local dimming element 62L.
In another suitable embodiment, local dimming elements 62L in shutter module 62 are formed from polymer-dispersed liquid crystal structures and photovoltaic material. This type of configuration is shown in
Conductive structure 92 and photovoltaic material 112 are used for applying electric fields to polymer-dispersed liquid crystal layer 94 and thereby controlling the amount of light transmitted through local dimming element 62L. The transmission of light through layer 94 of local dimming element 62L depends on the amount of scattering that occurs as light strikes layer 94. The amount of light scattering in turn depends on the orientation of liquid crystal droplets 96. In the absence of an applied voltage, liquid crystal droplets 96 are dispersed in polymer 102 in a random array. This maximizes the amount of scattering that occurs as light is incident on layer 94 and therefore minimizes the transmission of light through local dimming element 62L. When a voltage is applied across layer 94, the electric field that is produced across layer 94 causes liquid crystal droplets 96 to align with the electric field. This minimizes the amount of scattering that occurs as light is incident on layer 94 and therefore maximizes the transmission of light through local dimming element 62L.
The voltage across layer 94 is proportional to the intensity of backlight 88 as it strikes photovoltaic material 112. Upper conductive coating 92 is electrically grounded such that, when backlight 88 strikes photovoltaic material 112, a voltage difference ΔV is produced across layer 94. The corresponding electric field produced across layer 94 in turn controls liquid crystal droplets 96 in layer 94. When it is desired to display darker colors such as black, the intensity of backlight 88 (e.g., backlight 88 that is transmitted through display module 46) is minimized, which in turn minimizes the voltage difference ΔV that is produced across layer 94. Liquid crystal droplets 96 will therefore be arranged in a random array, thereby preventing backlight 88 from passing through shutter module 62.
With this type of configuration, it may not be required to supply control signals (e.g., control signals that are synchronized with the display control signals provided to display pixels 46P in display module 46) to local dimming elements 62L of shutter module 62. Transmission of light through local dimming elements 62L of shutter module 62 is controlled by the voltage difference ΔV across layer 94, which in turn is controlled by the intensity of backlight 88 as it strikes photovoltaic material 112. This type of configuration is sometimes referred to as “passive timing” because local dimming elements 62L in shutter module 62 are operated automatically by backlight 88 from backlight structures 42.
Local dimming elements 62L of shutter module 62 can be arranged in any suitable pattern and can have any suitable resolution. As shown in
In the example of
If desired, the shape, size, number, and location of local dimming elements 62L in shutter module 62 can be customized for display 14. For example, local dimming elements 62L can be located in regions that tend to be more susceptible to light leakage. For example, display 14 may sometimes be used to display movies in a wide-screen viewing mode. In this type of viewing mode, the upper and lower borders of the display may remain black while the movie is displayed in a central region of the display. If desired, shutter module 62 can be customized based on specific display usage modes such as the wide-screen movie display mode. For example, as shown in
The example of
The arrangement of local dimming elements 62L may be customized based on display performance information that is gathered from display 14 during manufacturing. For example, a camera may be used to capture one or more images of display 14 in a given mode of operation (e.g., while display 14 is completely black). The captured images may in turn be used to determine which regions of display 14 exhibit light leakage. Local dimming elements 62L of shutter module 62 can be arranged based on the display performance information such that light leakage in display 14 is minimized.
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.
