Patent Publication Number: US-2010110335-A1

Title: Display unit with improved backlighting

Description:
FIELD OF THE INVENTION 
     This invention relates to displays. More specifically, this invention relates to liquid crystal displays with backlighting. 
     BACKGROUND 
     Backlighting refers to illumination used in a liquid crystal displays (LCD). Backlighting is often used in small displays such as mobile phone displays to help increase readability in low light conditions. Backlighting is also used in computer displays and LCD televisions. The backlighting used in LCDs typically accounts for more than 80 percent of the display power consumption and can quickly deplete a charged battery. For mobile electronic devices, such as cell phones, PDAs and portable enthronement systems, battery lifetime is of great importance. Accordingly, there has been advances in producing batteries with longer life times as well as developing devices with lower rates of power consumption. 
     The present invention is directed to a display unit that is particularly well suite for mobile electronic devices. The display unit of the present invention exhibits improved light output efficiency and, therefore, can be operated at a reduced rate of power consumption. 
     SUMMARY 
     The present invention is directed to a display unit that includes a liquid crystal structure with a liquid crystal panel and any optical elements or films suitable for the application at hand. For example the liquid crystal panel is coated with one or more of a protective layer and an optical diffuser layer. The liquid crystal panel has light receiving surface and a display surface. 
     The display unit further includes a backlighting structure that eclipses at least a portion of the liquid crystal structure. The backlighting structure includes a backlighting panel with a front light emitting surface and a back reflective surface. The front light emitting surface of the backlighting structure is preferably patterned with hexagonal shaped pixels, which occupy greater than 80% or more of the light emitting surface. The back reflective surface is preferably coated with a reflective material, patterned with a matte surface and/or a combination thereof. 
     The display unit of the present invention is particularly well suited for displays used in portable electronic devices, such as personal digital assistants (PDAs), cellular phones and digital entertainment systems. However, it will be clear to one skilled in the art from the description below that the display unit of the present invention has applications for use computer monitors, television screens and any other device where backlighting is preferred or required to display images from a liquid crystal panel. In a particular embodiment of the invention, the display unit is used to provide lighting for a head mounted display that is for example mounted to a user&#39;s head through a frame, similar to a frame used for corrective eye glasses. 
     The display unit, or backlighting structure, also includes a light source or light sources that are placed around periphery edges of the backlighting panel. The backlighting panel is formed from a glass material, a polymeric material or any other material with that is capable of transmitting light. The light source or light sources are configured to transmit light into the backlighting panel through side walls of the backlighting panel. In operation a portion of the light is emitted through the hexagonal shaped pixels and onto the liquid crystal panel. 
     Preferably, the light transmitted from the light source or light sources and into the backlighting panel is transmitted to the onto the liquid crystal panel with en efficiency of 80% or greater. 
     Suitable light sources include, but are not limited to, incandescent light sources, light emitting diode light sources, electro-luminescent light sources and flourescent light sources. The liquid crystal panel is a thin-film transistor (TFT) liquid crystal panel, an in-plane switching (IPS) liquid crystal panel, a multi-domain vertical alignment (MVA) crystal panel, a patterned vertical alignment (PVA) crystal panel, a continuous pinwheel alignment (CPA) crystal panel or any combination thereof. 
     The display unit in further embodiments of the invention further includes one or more optical diffuser layers, one or more optical polarizer layers and or any other optical element suitable for the application at hand. The one or more optical elements are, for example, sandwiched between the liquid crystal structure and the backlighting structure. 
     The display unit in accordance with the embodiments of the invention further includes means for controlling an output of the light source and/or images displayed on the display unit. For example, the means for controlling an output of the light source and/or images displayed on the display unit includes a micro processor and/or receiver, such as a radio receiver, for receiving the dynamic media data from a transmitting device. Where the display unit includes a receiver, the display unit is configured to display a representation of the dynamic media data. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1A  shows a cross-sectional view of a backlighting construction used in LCD displays. 
         FIG. 1B  shows a cross-sectional view of a backlighting construction used in LCD displays, in accordance with the embodiments of the present invention. 
         FIGS. 2A-B  show a cross-sectional view of a backlighting construction and a front top view of backlighting panel used in LCD displays, in accordance with the embodiments of the present invention. 
         FIG. 3A  illustrates a schematic representation of an LCD display unit with a control unit, in accordance with the embodiments of the present invention. 
         FIG. 3B  illustrates a portable electronic device with LCD display unit shown in  FIG. 3A . 
         FIG. 4  is a block-flow diagram outlining the steps for making a device with a display unit, in accordance with the method of the present invention. 
         FIG. 5  shows a graphical representation comparing light output from a display using backlighting of the present invention to that of a display using convention backlighting. 
         FIG. 6  shows a schematic representation a head mountable system that includes display units of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1A  shows a cross-sectional view of a liquid crystal display configuration  100  with and liquid crystal structure  123  and a backlighting structure  121 . The backlighting structure  121  includes a light source  101 , a diffuser  103 , a prism  105  and a polarizer  107 . The backlighting structure  121  is eclipsed, or partially eclipsed with the liquid crystal structure  123 . The liquid crystal structure  123  includes a liquid crystal panel  109  with one more optical elements or optical films  111  to optically enhance or modify an image produced by the liquid crystal display configuration  100 . The liquid crystal display configuration  100  is too bulky to be suitable for use in very thin or small portable electronic devices. In order to reduce the space required for a liquid crystal display in very thin or small portable electronic devices, a liquid crystal display configuration with an in-plane backlighting structure, such as described below with reference to  FIG. 1B , is preferable. 
       FIG. 1B  shows a liquid crystal display configuration  150  that utilize an in-plane backlighting structure  173 . The term “in-plane backlighting structure” refers to a back lighting structure with a backlighting panel  153  and one or more light sources  151  positioned around a parameter or periphery of the backlighting panel  153 . The liquid crystal display configuration  150  also includes a liquid crystal structure  155  that includes a liquid crystal panel. As described above, the backlighting structure  153  and the liquid crystal structure  155  are at least partially eclipsed. Also, the backlighting structure  153  and the liquid crystal structure  155  include any number of optical elements or films suitable for the application at hand. 
     Still referring to  FIG. 1B , the backlighting panel  153  includes a light emitting surface  152  and a reflective back surface  154 . The light emitting surface  152  is patterned with pixels  161  and  161 ′ that are separated by a distance D 1 , which occupies less than 80% of the light emitting surface  152 . In operation, the one or more light sources  156  emits light, as indicated by the arrow  165 . The light that is emitted by the one or more light sources  156  enters into the backlighting panel  153  through side walls  156  of the back lighting panel  153 . The back lighting panel  153  acts as a wave guide and a portion of the light tunnels through the backlighting panel  153  and strikes the pixels  161  and  161 ′. The pixels bend the light and cause the light to be emitted through the backlighting panel  153  from the light emitting surface  152  as indicated by the arrows  176 . Portions of the light  165  are internally reflected from the back reflective surface  154 , and other structure interfaces within backlighting panel  153  before being emitted from the light emitting surface  152 . The light emitted from the light emitting surface  152  strike the liquid crystal structure to produce an image and/or enhance brightness of an image on a liquid crystal structure  155 . 
     Now referring to  FIG. 2A , in a preferred embodiment of the invention, a display unit  200  includes a liquid crystal structure  205  with a light receiving surface  219  and a display surface  216 . The liquid crystal structure  205  includes a liquid crystal panel that is a thin-film transistor (TFT) liquid crystal panel, an in-plane switching (IPS) liquid crystal panel, a multi-domain vertical alignment (MVA) crystal panel, a patterned vertical alignment (PVA) crystal panel, a continuous pinwheel alignment (CPA) crystal panel or any combination thereof. The liquid crystal structure  205  also includes any number of optical elements or optical films suitable for the application at hand. 
     Still referring to  FIG. 2A , the display unit  200  further includes a backlighting lighting structure  273  that is at least partially eclipsed with a portion of the liquid crystal structure  205 . The backlighting structure  173  includes a backlighting panel  203  with a front light emitting surface  252  and a back surface reflective  204 . The backlighting panel  203  is formed from a glass material, a polymeric material or any other material with that is capable of transmitting light. 
     Referring now to both  FIGS. 2A and 2B  front light emitting surface  205  of the backlighting panel  203  is preferably patterned with hexagonal shaped pixels  211  and  211 ′, wherein the hexagonal shaped pixels  211  and  211 ′ occupy 80% or more of the light emitting surface  252 . Here and throughout the application, the same reference numbers are used for labeling similar or the same elements in separate Figures. The hexagonal shaped pixels  211  and  211 ′ are preferable speared by a distance D 2 . 
     The back reflective surface  204  of the backlighting panel  203  is coated with a reflective material, patterned with a matte surface and/or otherwise modified to allow light that enters into the backlighting panel  203  to be internally reflected, such as described previously with reference to  FIG. 1B . For example, the back reflective surface  204  is coated with a reflective paint, a mirror film and/or a matte film. 
     The backlighting structure  173  also includes a light source or light sources  201  that are placed around one or more edges of the backlighting panel  203  and are configured to transmit light through one or more side walls  256  and  256 ′ of the backlighting panel  203 , such as described above with reference to  FIG. 1B . The one or more light sources  201  include electro-luminescent light sources, flourescent light sources or a combination thereof. Preferably, the one or more light sources  201  include a plurality of light emitting diodes  202 ,  202 ′ and  202 ″ positioned around the entire periphery of the backlighting panel  203 . 
     In operation a portion of the light emitted by the light source or light sources  201  is transmitted though the one or more side walls  256  and  256 ′ of the backlighting panel  203 . The light is then emitted through the hexagonal shaped pixels  211  and  211 ′ and onto the light receiving surface of the liquid crustal structure  205  to generate or enhance an image produced on the a display surface  216  of the liquid crystal structure  205 . Preferably, the light is transmitted to the onto light receiving surface  219  liquid crystal structure  205  is transmitted from the light source or light sources  201  with an efficiency of 80% or greater. 
     Now referring to  FIG. 3A , a display unit  300  in accordance with the embodiments of the invention includes a liquid crystal structure  205  and a backlighting structure  273 , such as described in detail above. The display unit further includes control means  301  for controlling an output of a light source and/or images displayed on the display unit  300 . The control means  301  includes a micro processor  307 , a receiver  305  and a transmitter  303  for receiving and transmitting dynamic media data. In accordance with this embodiment, the display unit  300  is configured to display a representation of the dynamic media data received by the receiver  305  and/or transmitted by the transmitter  303 . 
     In accordance with a specific embodiment of the invention a cellular phone  350  includes the display unit  300 . The cellular phone is configured to receiving the dynamic media data, as indicated by the arrow  371  from a remote device  361 , such as another cellular phone, and is configured to transmit dynamic media data, as indicated by the arrow  373 , to the remote device  361 . The cell phone  350  preferably includes one or more user interfaces for imputing dynamic media data. Suitable user interfaces include, for example, a key pad  353 , a micro-phone  361  and a camera  371 . The cellular phone  350  also includes a speaker  362  for receiving an audio representation of dynamic media data received by the receiver  305  and transmitted from the remote device  361 . 
       FIG. 4  is a block-flow diagram  400  outlining the steps for making a device with a display unit, in accordance with the method of the present invention. In the step  401   a  backlighting structure with a backlighting panel having a light emitting surface with hexagonal pixels, a reflective back surface and a light source positioned around edges of the backlighting panel is formed. The backlighting structure is formed using any suitable method including injection molding and lithographic and/or embossing techniques. In the step  403 , the backlighting structure formed in the step  401  is coupled to a liquid crystal structure comprising a liquid crystal panel, such that backlighting panel and the liquid crystal panel are at least partially eclipsed to form a display unit. After the display unit is formed in the step  403 , in the step  405  the display unit is coupled to a control unit configured to control an output of light from the light source to thereby form a device. The control unit includes a micro processor, receiver, a transmitter (or transducer) and any number of user interfaces, such as described with reference to the cellular phone device  350  in  FIG. 3B   
       FIG. 5  shows a graphical representation  500  comparing light output from a display using backlighting configuration of the present invention as indicated by the line  503  to that of a display using convention backlighting, as indicated by the line  501 . Both of the lines  503  and  501  represent the brightness measurements of rectangular displays acquired diagonally across the rectangular displays from the left bottom corner to the top right corner of the rectangular displays while operating at the same rate of power consumption. Note that the hatched area  505  between the curves  503  and  501  represents the improvement in efficiency achieved by the backlighting configuration of the present invention. 
     While the display unit of the present invention been described as being used for displaying media data on small or thin portable small electronic devices, such as personal digital assistants (PDAs), cellular phones and digital entertainment systems, the display unit of the present invention also has applications for use in computer monitors, television screens and any other device where backlighting in required to display images. 
     Referring now to  FIG. 6 , in a particular embodiment of the invention back lighting structures  300 ′ and  300 ″ similar to the back lighting structure  273  described with reference to  FIGS. 2A and 2B  are used to provide back lighting or lighting for display  600  that is configured to be mounted to a user&#39;s head through a frame  601 , with a strap  603  or other suitable means. 
     The present invention has been described in terms of specific embodiments incorporating details to facilitate the understanding of principles of construction and operation of the invention. Such reference herein to specific embodiments and details thereof is not intended to limit the scope of the claims appended hereto. It will be apparent to those skilled in the art that modifications may be made in the embodiment chosen for illustration without departing from the spirit and scope of the invention.