Patent Application
20140085576
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. An electronic device may have a housing such as a housing formed from plastic or metal. Components for the electronic device such as display components may be mounted in the housing.
It can be challenging to incorporate a display into the housing of an electronic device. Size and weight are often important considerations in designing electronic devices. If care is not taken, displays may be bulky or may be surrounded by overly large borders. The housing of an electronic device can be adjusted to accommodate a bulky display with large borders, but this can lead to undesirable enlargement of the size and weight of the housing and unappealing device aesthetics.
It would therefore be desirable to be able to provide improved ways to provide displays for electronic devices.
An electronic device may be provided with a display. The display includes display layers for displaying images. The display also includes backlight structures that provide backlight illumination to the display layers.
The display backlight structures include a light source such as an array of light-emitting diodes. Light from the light source is coupled into an edge of a light guide plate. The light guide plate distributes the backlight laterally across the display layers.
One or more optical films such as brightness enhancement films and diffuser layers are interposed between the display layers and the light guide plate.
The optical films include optical film alignment features that are configured to mate with corresponding light guide plate alignment features on the light guide plate. The mating alignment features are used to align the optical films with respect to the light guide plate.
The optical film alignment features may include openings such as notches or holes. The openings may be formed at opposing edges of the optical films. The light guide plate alignment features may include protrusions that each extend into a respective opening in the optical films. Portions of the optical films may partially or completely surround the light guide plate protrusions.
If desired, the light guide plate may have a protruding portion that extends around the entire periphery of the light guide plate. With this type of configuration, the protruding portion of the light guide plate completely surrounds a perimeter of the optical films. The protruding portion laterally aligns the optical films with respect to the light guide plate and helps protect the optical films from moisture and other contaminants.
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.
Electronic devices may include displays. The displays may be used to display images to a user. Illustrative electronic devices that may be provided with displays are shown in
The illustrative configurations for device 10 that are shown in
Housing 12 of device 10, which is sometimes referred to as a case, may be 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.
Displays for device 10 may, in general, include image pixels formed from light-emitting diodes (LEDs), organic LEDs (OLEDs), plasma cells, electrowetting pixels, electrophoretic pixels, liquid crystal display (LCD) components, or other suitable image pixel structures. In some situations, it may be desirable to use LCD components to form display 14, so configurations for display 14 in which display 14 is a liquid crystal display are sometimes described herein as an example. It may also be desirable to provide displays such as display 14 with backlight structures, so configurations for display 14 that include a backlight unit may sometimes be described herein as an example. Other types of display technology may be used in device 10 if desired. The use of liquid crystal display structures and backlight structures in device 10 is merely illustrative.
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. A display cover layer or other outer display layer may be formed from a transparent glass sheet, a clear plastic layer, or other transparent member.
Touch sensor components such as an array of capacitive touch sensor electrodes formed from transparent materials such as indium tin oxide may be formed on the underside of a display cover layer, may be formed on a separate display layer such as a glass or polymer touch sensor substrate, or may be integrated into other display layers (e.g., substrate layers such as a thin-film transistor layer).
A schematic diagram of an illustrative configuration that may be used for electronic device 10 is shown in
Control circuitry 29 may be used to run software on device 10, such as operating system software and application software. Using this software, control circuitry 29 may present information to a user of electronic device 10 on display 14. When presenting information to a user on display 14, sensor signals and other information may be used by control circuitry 29 in making adjustments to the strength of backlight illumination that is used for display 14.
Input-output circuitry 30 may be used to allow data to be supplied to device 10 and to allow data to be provided from device 10 to external devices. Input-output circuitry 30 may include communications circuitry 32. Communications circuitry 32 may include wired communications circuitry for supporting communications using data ports in device 10. Communications circuitry 32 may also include wireless communications circuits (e.g., circuitry for transmitting and receiving wireless radio-frequency signals using antennas).
Input-output circuitry 30 may also include input-output devices 34. A user can control the operation of device 10 by supplying commands through input-output devices 34 and may receive status information and other output from device 10 using the output resources of input-output devices 34.
Input-output devices 34 may include sensors and status indicators 36 such as an ambient light sensor, a proximity sensor, a temperature sensor, a pressure sensor, a magnetic sensor, an accelerometer, and light-emitting diodes and other components for gathering information about the environment in which device 10 is operating and providing information to a user of device 10 about the status of device 10.
Audio components 38 may include speakers and tone generators for presenting sound to a user of device 10 and microphones for gathering user audio input.
Display 14 may be used to present images for a user such as text, video, and still images. Sensors 36 may include a touch sensor array that is formed as one of the layers in display 14.
User input may be gathered using buttons and other input-output components 40 such as touch pad sensors, buttons, joysticks, click wheels, scrolling wheels, touch sensors such as sensors 36 in display 14, key pads, keyboards, vibrators, cameras, and other input-output components.
A cross-sectional side view of an illustrative configuration that may be used 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 may 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 may include a liquid crystal layer such a liquid crystal layer 52. Liquid crystal layer 52 may be sandwiched between display layers such as display layers 58 and 56. Layers 56 and 58 may be interposed between lower polarizer layer 60 and upper polarizer layer 54.
Layers 58 and 56 may be formed from transparent substrate layers such as clear layers of glass or plastic. Layers 56 and 58 may be layers such as a thin-film transistor layer and/or a color filter layer. Conductive traces, color filter elements, transistors, and other circuits and structures may be 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 may be 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 may be 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 29 (e.g., one or more integrated circuits such as components 68 on printed circuit 66 of
Display driver integrated circuit 62 may be 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 may be 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 may be 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 may include a light guide plate such as light guide plate 78. Light guide plate 78 may be 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 may generate light 74. Light source 72 may be, for example, an array of light-emitting diodes.
Light 74 from light source 72 may be coupled into edge surface 76 of light guide plate 78 and may be distributed in dimensions X and Y throughout light guide plate 78 due to the principal of total internal reflection. Light guide plate 78 may include light-scattering features such as pits or bumps. The light-scattering features may be 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 may serve as backlight 44 for display 14. Light 74 that scatters downwards may be reflected back in the upwards direction by reflector 80. Reflector 80 may be 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 may include optical films 70. Optical films 70 may 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 may 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
Light guide plate 78 may have a rectangular footprint when viewed in direction 50 of
It may be desirable to operate device 10 over a range of operating temperatures from a low operating temperature of T1 to a high operating temperature of T2. The value of T1 may be, for example, 0° C., −30° C., −10° C., etc. The value of T2 may be, for example, 100° C., 90° C., or 60° C., etc. With one suitable arrangement, the temperature range over which device 10 is designed to operate satisfactorily may be −20° C. to 85° C. (as an example). When operating over a range of temperatures (e.g., over a range of temperatures spanning 50° C. or more, 80° C. or more, or 100° C. or more), housing 12 and the layers in display 14 may expand and contract.
Housing 12 and the structures in display 14 may have different rates of thermal expansion. As examples, housing 12 may be formed from metal such as aluminum, which has a coefficient of thermal expansion (CTE) value of about 20 ppm. Light guide plate 78 may be formed from polymer such as polymethyl methacrylate, which has a CTE value of about 65 ppm.
Other backlight structures such as optical films 70 may also expand or contract at different rates than housing 12. For example, optical films 70 may have a coefficient of thermal expansion that exceeds that of housing 12.
In conventional electronic devices, optical films are sometimes coupled directly to the housing of the electronic device. In some situations, the optical films include tabs having holes that receive portions of the housing. In other situations, the optical films include tabs that protrude into recesses in the housing. Because the optical films expand at a faster rate than the housing, the optical film tabs adjacent to the housing run the risk of contacting the inner edges of the housing at higher temperatures, thereby potentially damaging the optical films and the display. Some devices include an air gap to help avoid this type of failure, but excessive gap size can lead to undesirable increases in the size of a device.
To help minimize the air gaps between housing 12 and backlight structures 42 and thereby implement display 14 and device 10 in a compact arrangement, light guide plate 78 may be used to laterally align optical films 70 with respect to light guide plate 78. For example, light guide plate 78 may include alignment features such as light guide plate alignment features 78T. Light guide plate alignment features 78T may be configured to mate with corresponding alignment features in optical films 70 such as optical film alignment features 70P. In the example of
The example of
Optical films 70 may be formed from materials that have a first coefficient of thermal expansion (CTE) such as CTE1, whereas light guide plate 78 may have a second coefficient of thermal expansion CTE2. CTE1 of optical films 70 may, for example, be less than CTE2 of light guide plate 78. With this type of arrangement, gaps between optical films 70 and light guide plate 78 may be minimized and the risk of damaging optical films 70 may be reduced. This is, however, merely illustrative. If desired, CTE1 of optical films 70 and light guide plate 78 may be configured to exhibit coefficients of thermal expansion that do not differ significantly (e.g., such that CTE2 is within 100% of CTE1, within 70% of CTE1, within 50% of CTE1, within 30% of CTE1, within 20% of CTE1, within 10% of CTE1, within 5% of CTE1, or within 1% of CTE1).
In configurations in which the coefficient of thermal expansion of optical films 70 and light guide plate 78 are closely matched, optical films 70 and light guide plate 78 will exhibit comparable changes in size (e.g., in the X-Y plane that lies parallel to the other layers of display 14). By exhibiting comparable changes in size with changes in temperature, situations can be avoided in which optical films 70 are forced against light guide plate 78 sufficiently to cause damage.
As shown in
If desired, light guide plate alignment structures 78T may be formed on one side of optical films 70, on two sides of optical films 70, on three sides of optical films 70, or on all four sides of optical films 70. There may be one, two, three or more than three light guide plate alignment structures 78T on a given side of optical films 70. The example of
Light guide plate alignment structures 78T are formed from the same material that light guide plate 78 is formed from (e.g., a polymer such as polymethyl methacrylate). Light guide plate alignment structures 78T may be molded as integral parts of light guide plate 78 (e.g., using an injection molding process such as insert molding or overmolding).
In the example of
Because optical films 70 have a lower coefficient of thermal expansion than light guide plate 78, gaps G2 between optical films 70 and light guide plate alignment structures 78T may be minimized and damage to optical films 70 may be avoided.
Each optical film tab 70T includes a corresponding optical film alignment feature 70P. As shown in
With this type of configuration, light guide plate 78 aligns optical films 70 in the X-Y plane with respect to light guide plate 78. Light guide plate fence portion 78T also forms a barrier around optical films 70 that helps protect optical films 70 from moisture and other contaminants.
The example of
Illustrative equipment for forming a polymer light guide plate having alignment structures that are configured to laterally align an optical film stack is shown in
Molding tool 92 molds polymer 90 into a substrate such as planar substrate 78 having alignment structures such as light guide plate alignment structures 78T. Light guide plate alignment structures 78T are integrally molded at the edges of light guide plate 78 and protrude outward from planar surface 78S of light guide plate 78 (e.g., alignment structures 78T are perpendicular to planar surface 78S of light guide plate 78).
Following formation of light guide plate 78 having alignment structures 78T, light guide plate 78, other layers of display 14, housing 12, and other parts in electronic device 10 (shown as parts 94 of
In another suitable embodiment, light guide plate 78 and light guide plate alignment structures 78T may be formed from a two-step molding process such as a two-shot injection molding process, an overmolding process, an insert molding process, or other suitable two-step molding process. Illustrative equipment for forming a polymer light guide plate having alignment structures using a two-step molding process is shown in
Molding tool 92 molds polymer 90 into a substrate such as planar substrate 78. This may include, for example, using an injection molding tool to inject a first shot of polymer 90 in the form of molten plastic into a mold cavity having the shape of light guide plate 78.
Following formation of light guide plate 78, molding tool 92 receives additional polymer material 90. Molding tool 92 molds additional polymer 90 onto edge portions of light guide plate 78 to form light guide plate alignment structures 78T (e.g., as part of an insert molding process or overmolding process). This may include, for example, using an injection molding tool to inject a second shot of polymer 90 into a mold cavity having the shape of light guide plate alignment structures 78T. The second shot of polymer that forms alignment structures 78T may be performed during the same molding cycle that forms light guide plate 78 or may be performed after light guide plate 78 has been molded. As shown in
Following formation of light guide plate 78 having alignment structures 78T, light guide plate 78, other layers of display 14, housing 12, and other parts in electronic device 10 (shown as parts 94 of
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.
