Backlighting apparatus for a keypad assembly

A keypad assembly including a dome configured to operatively engage a switch sensor; a dome overlay guide operatively coupled by to the dome; a key corresponding to the dome and configured to operatively engage the dome; and a light emitting source, configured to emit light. The dome overlay guide is configured to receive the light emitted by the light emitting source and direct the received light toward the keys.

RELEVANT FIELD

The field of this disclosure relates generally to keypads and keypad backlighting, with particular but by no means exclusive application to keypads of mobile communications devices.

BACKGROUND

It is often desirable to provide backlighting to the keys of a keypad assembly used in electronic devices such as mobile communications devices during darkened conditions. Light may be emitted from a light source located within the electronic device, and directed toward one or multiple keys illuminating such key(s).

DETAILED DESCRIPTION

In one broad aspect, there is provided a keypad assembly. The keypad assembly includes a dome configured to operatively engage a switch sensor; a dome overlay guide operatively coupled to the dome; a key corresponding to the dome, and configured to operatively engage the dome; and a light emitting source configured to emit light. The dome overlay guide is configured to receive the emitted light and direct the received light toward the key.

The dome overlay guide may include a light guide film. The keypad assembly may also include a reflector layer configured to reflect light escaping the dome overlay guide. The reflector layer may be configured to reflect the escaping light toward the key. The dome overlay guide may be between the reflector layer and the key.

The operative coupling may include an adhesive. The keypad assembly may also include a deflection web configured to seat the key, wherein the deflection web is between the key and the dome overlay guide.

The light emitting source may include a side firing light emitting diode. The keypad assembly may include a plurality of keys, and a plurality of corresponding domes.

In another broad aspect, there is provided a mobile device comprising the keypad assembly.

In a third broad aspect, there is provided a keypad assembly. The keypad assembly includes a dome configured to operatively engage a switch sensor; a dome overlay guide operatively coupled to the dome; a key corresponding to the dome, and configured to operatively engage the dome; a deflection web configured to seat the key; and a side firing light emitting source configured to emit light. The dome overlay guide is configured to receive the emitted light, and direct the received light toward the key; and an actuator is adjacent a portion of an upper surface of the dome overlay guide.

The dome overlay guide may include a light guide film. The keypad assembly may also include a reflector layer configured to reflect light escaping the dome overlay guide. The reflector layer may be configured to reflect the escaping light toward the key.

The keypad assembly may also include a printed circuit board, wherein the reflector layer is positioned between the printed circuit board and the dome overlay guide. The dome overlay guide may be adhered to the reflector layer.

The dome overlay guide may include at least one cavity configured to emit the received light in a direction toward the key. The side firing light emitting source may include a light emitting diode.

In another broad aspect, there is provided a method for providing backlighting for a keypad assembly, the keypad assembly comprising a printed circuit board having a switch sensor, a key corresponding to the switch sensor, and a light emitting source configured to emit light. The method includes providing a dome corresponding to the switch sensor; adhering a light guide film to the dome; and securing the light guide film within the keypad assembly, wherein the film is configured to receive the emitted light, and wherein the dome is configured to operatively engage the switch sensor.

The method may also include adhering a reflector layer to the light guide film.

Some embodiments of the system and methods described herein make reference to a mobile device. A mobile device may be a two-way communication device with advanced data communication capabilities having the capability to communicate with other computer systems. A mobile device may also include the capability for voice communications. Depending on the functionality provided by a mobile device, it may be referred to as a data messaging device, a two-way pager, a cellular telephone with data messaging capabilities, a wireless Internet appliance, or a data communication device (with or without telephony capabilities), for example. A mobile device may communicate with other devices through a network of transceiver stations.

To aid the reader in understanding the structure of a mobile device, reference is made toFIG. 1.

FIG. 1is a block diagram of a mobile device in one example implementation, shown generally as100. Mobile device100comprises a number of components, the controlling component being microprocessor102. Microprocessor102controls the overall operation of mobile device100. Communication functions, including data and voice communications, may be performed through communication subsystem104. Communication subsystem104may be configured to receive messages from and send messages to a wireless network200. In one example implementation of mobile device100, communication subsystem104may be configured in accordance with the Global System for Mobile Communication (GSM) and General Packet Radio Services (GPRS) standards. The GSM/GPRS wireless network is used worldwide and it is expected that these standards may be supplemented or superseded eventually by Enhanced Data GSM Environment (EDGE) and Universal Mobile Telecommunications Service (UMTS), and Ultra Mobile Broadband (UMB), etc. New standards are still being defined, but it is believed that they will have similarities to the network behaviour described herein, and it will also be understood by persons skilled in the art that the embodiments of the present disclosure are intended to use any other suitable standards that are developed in the future. The wireless link connecting communication subsystem104with network200represents one or more different Radio Frequency (RF) channels, operating according to defined protocols specified for GSM/GPRS communications. With newer network protocols, these channels are capable of supporting both circuit switched voice communications and packet switched data communications.

Although the wireless network associated with mobile device100is a GSM/GPRS wireless network in one example implementation of mobile device100, other wireless networks may also be associated with mobile device100in variant implementations. Different types of wireless networks that may be employed include, for example, data-centric wireless networks, voice-centric wireless networks, and dual-mode networks that can support both voice and data communications over the same physical base stations. Combined dual-mode networks include, but are not limited to, Code Division Multiple Access (CDMA) or CDMA2000 networks, GSM/GPRS networks (as mentioned above), and future third-generation (3G) networks like EDGE and UMTS. Some older examples of data-centric networks include the Mobitex™ Radio Network and the DataTAC™ Radio Network. Examples of older voice-centric data networks include Personal Communication Systems (PCS) networks like GSM and Time Division Multiple Access (TDMA) systems. Other network communication technologies that may be employed include, for example, Integrated Digital Enhanced Network (iDEN™), Evolution-Data Optimized (EV-DO), and High Speed Packet Access (HSPA), etc.

Some of the subsystems of mobile device100perform communication-related functions, whereas other subsystems may provide “resident” or on-device functions. By way of example, display110and keyboard116may be used for both communication-related functions, such as entering a text message for transmission over network200, as well as device-resident functions such as a calculator or task list. Operating system software used by microprocessor102is typically stored in a persistent store such as flash memory108, which may alternatively be a read-only memory (ROM) or similar storage element (not shown). Those skilled in the art will appreciate that the operating system, specific device applications, or parts thereof, may be temporarily loaded into a volatile store such as RAM106.

Mobile device100may send and receive communication signals over network200after network registration or activation procedures have been completed. Network access may be associated with a subscriber or user of a mobile device100. To identify a subscriber, mobile device100may provide for a Subscriber Identity Module (“SIM”) card126to be inserted in a SIM interface128in order to communicate with a network. SIM card126may be one example type of a conventional “smart card” used to identify a subscriber of mobile device100and to personalize the mobile device100, among other things. Without SIM card126, mobile device100may not be fully operational for communication with network200. By inserting SIM card126into SIM interface128, a subscriber may access all subscribed services. Services may include, without limitation: web browsing and messaging such as e-mail, voice mail, Short Message Service (SMS), and Multimedia Messaging Services (MMS). More advanced services may include, without limitation: point of sale, field service and sales force automation. SIM card126may include a processor and memory for storing information. Once SIM card126is inserted in SIM interface128, it may be coupled to microprocessor102. In order to identify the subscriber, SIM card126may contain some user parameters such as an International Mobile Subscriber Identity (IMSI). By using SIM card126, a subscriber may not necessarily be bound by any single physical mobile device. SIM card126may store additional subscriber information for a mobile device as well, including datebook (or calendar) information and recent call information.

Mobile device100may be a battery-powered device and may comprise a battery interface132for receiving one or more rechargeable batteries130. Battery interface132may be coupled to a regulator (not shown), which assists battery130in providing power V+ to mobile device100. Although current technology makes use of a battery, future technologies such as micro fuel cells may provide power to mobile device100. In some embodiments, mobile device100may be solar-powered.

Microprocessor102, in addition to its operating system functions, enables execution of software applications on mobile device100. A set of applications that control basic device operations, including data and voice communication applications, may be installed on mobile device100during its manufacture. Another application that may be loaded onto mobile device100is a personal information manager (PIM). A PIM has functionality to organize and manage data items of interest to a subscriber, such as, but not limited to, e-mail, calendar events, voice mails, appointments, and task items. A PIM application has the ability to send and receive data items via wireless network200. PIM data items may be seamlessly integrated, synchronized, and updated via wireless network200with the mobile device subscriber's corresponding data items stored and/or associated with a host computer system. This functionality may create a mirrored host computer on mobile device100with respect to such items. This can be particularly advantageous where the host computer system is the mobile device subscriber's office computer system.

Additional applications may also be loaded onto mobile device100through network200, auxiliary I/O subsystem112, serial port114, short-range communications subsystem122, or any other suitable subsystem124. This flexibility in application installation increases the functionality of mobile device100and may provide enhanced on-device functions, communication-related functions, or both. For example, secure communication applications may enable electronic commerce functions and other such financial transactions to be performed using mobile device100.

Serial port114enables a subscriber to set preferences through an external device or software application and extends the capabilities of mobile device100by providing for information or software downloads to mobile device100other than through a wireless communication network. The alternate download path may, for example, be used to load an encryption key onto mobile device100through a direct and thus reliable and trusted connection to provide secure device communication.

Short-range communications subsystem122provides for communication between mobile device100and different systems or devices, without the use of network200. For example, subsystem122may include an infrared device and associated circuits and components for short-range communication. Examples of short range communication include standards developed by the Infrared Data Association (IrDA), Bluetooth®, and the 802.11 family of standards (Wi-Fi®) developed by IEEE.

In use, a received signal such as a text message, an e-mail message, or web page download is processed by communication subsystem104and input to microprocessor102. Microprocessor102then processes the received signal for output to display110or alternatively to auxiliary I/O subsystem112. A subscriber may also compose data items, such as e-mail messages, for example, using keyboard116in conjunction with display110and possibly auxiliary I/O subsystem112. Auxiliary subsystem112may include devices such as: a touch screen, mouse, track ball, optical trackpad infrared fingerprint detector, or a roller wheel with dynamic button pressing capability. Keyboard116may comprise an alphanumeric keyboard and/or telephone-type keypad, for example. A composed item may be transmitted over network200through communication subsystem104.

For voice communications, the overall operation of mobile device100may be substantially similar, except that the received signals may be processed and output to speaker118, and signals for transmission may be generated by microphone120. Alternative voice or audio I/O subsystems, such as a voice message recording subsystem, may also be implemented on mobile device100. Although voice or audio signal output is accomplished primarily through speaker118, display110may also be used to provide additional information such as the identity of a calling party, duration of a voice call, or other voice call related information.

Referring now toFIG. 2, a keypad assembly according to an embodiment is shown generally as400. The keypad assembly400may be used within electronic devices, such as the mobile device100described above. For example, the keypad assembly400may comprise part of the keyboard116.

The keypad assembly400comprises a plurality of keys (or keycaps)415which may be arranged on a deflection web445. Each of the keys415is operatively coupled to at least one switch sensor440. The switch sensor440detects if the corresponding key has been pressed and if so it generates a corresponding signal on a printed circuit board450.

Separating a key415from its corresponding switch sensor440may be a corresponding dome425that is operatively coupled to the switch sensor440. The dome425may be made of metal or another suitable material (or a combination thereof) and may be configured to collapse and contact the switch sensor440when the corresponding key415is depressed in the key press direction480(i.e. the direction480in which a key415may be depressed). To this end, the key415may be configured to operatively engage the dome425via an actuator435. The actuator435may comprise part of and extend from the deflection web445. Specifically, the actuator435may be positioned between the key415and the dome425and it may transfer the key depression force, onto the dome425. Persons skilled in the art will understand that the domes425and the switch sensors440may operate like dome switches known in the art.

The keypad assembly400includes a light emitting source410configured to emit light for illuminating the keys415. To distribute the light emitted by the light emitting source410(referred to hereinafter as “emitted light”460) to the plurality of keys415, a dome overlay guide420is provided. The dome overlay guide420is configured to receive the emitted light460(referred to hereinafter as “received light”465) and direct the received light toward the keys (FIG. 3). To this end, the dome overlay guide420may comprise a light guide film.

The dome overlay guide420may also serve to keep the domes425aligned with their corresponding switch sensors440. To this end, the dome overlay guide420may overlay and be operatively coupled, by adhesive or otherwise, to the domes425.

Persons skilled in the art will appreciate that the keys415may be held in place in any suitable manner. For example, the keys415may be adhered (using an adhesive or otherwise) to the deflection web445. In some embodiments (not shown), one or both of the deflection web445and the actuators435may be configured to seat the keys415. In such a “seating” embodiment, the keys415and the one or both of the deflection web445and the actuators435may be provided with complementary male (such as a post) and female (such as a seat) features to permit the keys415to sit within the one or both of the deflection web445and the actuators435.

Referring now toFIG. 3, the illumination of the keys415by the light emitting source410is discussed in more detail. The light emitting source410is positioned adjacent and oriented towards an edge455of the dome overlay guide420, such that light460emitted from the light emitting source410is received by the dome overlay guide420through its edge455.

To redirect the received light465out of the dome overlay guide420toward the keys415, the dome overlay guide420may be provided with several micro features470. The micro features470may be provided at predetermined locations of the dome overlay guide420so as to align with the keys415. When the received light465traveling through the dome overlay guide420intersects with a micro feature470, a portion of the received light465is redirected toward the key415which is aligned with that micro feature470.

Persons skilled in the art will understand that the micro features470have been illustrated schematically and that any micro features suitable for redirecting received light465may be used. For example, the micro features470may comprise one or more cavities etched into a surface of the dome overlay guide420. These cavities may, for example, comprise v-shaped cuts, or white printing dots (or micro dots). In some variants, a two dimensional array of micro features470on the surface of the dome overlay guide420may be provided to help evenly redirect received light465toward the keys415.

Received light465traveling through the dome overlay guide420may escape (or leak) from the dome overlay guide420toward one or more of the printed circuit board450and the domes425. The escape of light from the dome overlay guide420may be most common wherever the dome overlay guide420is adhered to another surface using an adhesive. The escape of light caused by the use of an adhesive on the dome overlay guide420is sometimes referred to as wet out.

In some embodiments, to recapture at least a portion of the received light465, which escapes the dome overlay guide420toward the domes425and the printed circuit board450, the domes425and the printed circuit board450may be configured to be sufficiently reflective to reflect such escaped light back toward the keys415. For example, the domes425may be one of polished, provided with a reflective coating (for example, silver plating) or naturally reflective. Similarly, a reflector layer430may be provided between the dome overlay guide420and the printed circuit board450. The reflector layer430may be configured to reflect escaping light back toward the keys415. The side of the reflector layer430, which faces the dome overlay guide420, may be provided with a reflective coating or may be naturally reflective. In some embodiments, the reflector layer430may comprise a polymeric specular reflector film, such as for example Vikuiti™ Enhanced Specular Reflector film, as distributed by 3M Optical Systems.

The deflection web445and the actuators435may be made from a substantially translucent (or semitransparent) material. This may permit a relatively high portion of light emitted from the dome overlay guide420to pass through the deflection web445and the actuators435and reach the key(s)415.

The light emitting source410may comprise a side firing (or side emitting) light emitting diode (LED) as may be known in the art. Persons skilled in the art will understand that a side firing LED typically comprises a housing for the LED that is mountable at a base of the housing and an LED configured to emit light from a side wall—adjacent the base—of the housing. In contrast, the housing of a top firing LED, which is also mountable at its base, contains an LED configured to emit light from a top surface—opposite the base—of the housing.

Persons skilled in the art will appreciate that LEDs typically require there to be a certain amount of clearance (or space) between the surface of the LEDs, from which the light is emitted, and a light guide or other object in order for the LEDs to function efficiently. This space is typically referred to as the LED leading space gap. When using side firing LEDs (i.e. LEDs which emit light in a direction that is generally perpendicular to the key press direction480), as opposed to top firing LEDs (i.e. LEDs which emit light in a direction that is generally parallel to the key press direction480), as the light emitting source410within a keypad assembly400, any required leading space gap is lateral (i.e. generally perpendicular to the key press direction480) rather than vertical (i.e. generally parallel to the key press direction480). Consequently, the thickness of the keypad assembly400may be reduced by using side firing LEDs instead of top firing LEDs as the light emitting source410within a keypad assembly400.

Referring now toFIG. 4, the alignment and configuration of the reflector layer430is discussed in greater detail.FIG. 4shows an exploded view of the dome overlay guide420, the reflector layer430, and the printed circuit board450with the domes425. The reflector layer430is provided with apertures475, each of which corresponds to a dome425. Specifically, when the reflector layer430is coupled to the printed circuit board450, by adhesive or otherwise, the domes425each project out of their corresponding aperture475. Further, when the dome overlay guide420is coupled to the domes425, those areas of the dome overlay guide420that are not coupled to the domes425may be optionally adhered to the reflector layer430.

Persons having ordinary skill in the art will understand that the reflector layer430may comprise any number and arrangement of apertures475. Similarly the keypad assembly400may comprise any number and arrangement of keys415. For example,FIG. 4shows an example reflector layer430with twelve apertures475for use with a standard alphanumeric twelve-key keypad assembly (0-9, #, *). Those of ordinary skill the art will appreciate that other configurations of the reflector layer430and keys415may also exist to correspond to keypad assemblies with different numbers and/or arrangements of keys (e.g. a full QWERTY keypad assembly).

Referring now to the logical flow diagram ofFIG. 5, a method (referred to generally as700) for providing backlighting for a keypad assembly400comprising a printed circuit board450having a switch sensor440, a key415corresponding to the switch sensor440and a light emitting source410will now be discussed. A dome425corresponding to the switch sensor440, is provided at Block710. The dome425is configured to operatively engage the switch sensor440when the key415corresponding to the switch sensor440is depressed.

At Block720, a dome overlay guide420is adhered or otherwise coupled to the dome425. The dome overlay guide420may comprise a light transmissive film such as a light guide film and be configured to receive light emitted (or emitted light460) from the light emitting source(s)410and direct light460toward the key(s)415of the keypad assembly400.

At Block730, the dome overlay guide420is secured within the keypad assembly. The dome overlay guide420may be secured to the printed circuit board450by adhering or otherwise coupling the dome overlay guide420to the reflector layer430which in turn may be adhered or otherwise coupled to the printed circuit board450.

In some instances, a keyboard assembly as described herein may be thinner than keyboard assemblies of alternate design, for example designs comprising separate (e.g. laminate) dome overlay guides and light guiding means.

The steps of a method in accordance with any of the embodiments described herein may not be required to be performed in any particular order, whether or not such steps are described in the claims or otherwise in numbered or lettered paragraphs.

The keypad assembly has been described with regard to a number of embodiments. However, it will be understood by persons skilled in the art that other variants and modifications may be made without departing from the scope of the disclosure as defined in the claims appended hereto.