Patent Abstract:
An exemplary liquid crystal display device ( 2 ) includes a liquid crystal panel ( 21 ) and a heating system. The heating system heats the liquid crystal panel when the temperature of the liquid crystal panel is below a predetermined threshold temperature. The liquid crystal display device can work normally without being adversely influenced by the surrounding temperature.

Full Description:
FIELD OF THE INVENTION 
     The present invention relates to liquid crystal display (LCD) devices, and particularly to an LCD device having a temperature control system. 
     BACKGROUND 
     Because LCD devices have the advantages of portability, low power consumption, and low radiation, they have been widely used in various portable information products such as notebooks, personal digital assistants (PDAs), video cameras, and the like. Furthermore, LCD devices are considered by many to have the potential to completely replace cathode ray tube (CRT) monitors and televisions. 
       FIG. 3  is a schematic, exploded side view of a conventional LCD device. The LCD device  1  includes a liquid crystal (LC) panel  11 , and a backlight module  12  arranged under the LC panel  11 . The backlight module  12  provides light beams to the LC panel  11  so that the LC panel  11  is able to display images. 
     The LC panel  11  includes a top substrate  191 , a bottom substrate  192  parallel to the top substrate  191 , and a liquid crystal layer  190  sandwiched between the top substrate  191  and the bottom substrate  192 . 
     The backlight module  12  includes an optical film unit  13 , a light guide plate (LGP)  15 , a reflective plate  17 , and a light source  16 . The LGP  15  includes a light incident surface  151 , a top light emitting surface  152  adjoining the light incident surface  151 , and a bottom surface  153  adjoining the light incident surface  151 . The light source  16  is a set of light emitting diodes (LEDs), and is disposed adjacent to the light incident surface  151  of the LGP  15 . The optical film unit  13  is disposed adjacent to the light emitting surface  152 . The reflective plate  17  is disposed adjacent to the bottom surface  153 . 
     Light beams emitted by the light source  16  enter the LGP  15  through the light incident surface  151 . Most of the light beams are reflected by the bottom surface  153  of the LGP  16 , and then transmit through the light emitting surface  152 . Some of the light beams transmit out of the LGP  15  through the bottom surface  153 , are reflected by the reflective plate  17  back into the LGP  15 , and then transmit through the light emitting surface  152 . The light beams emitting from the light emitting surface  152  transmit through the optical film unit  13  to illuminate the LC panel  11 . 
     When the light beams illuminate the LC panel  11 , simultaneously, an electric field is applied between the top substrate  191  and the bottom substrate  192 . Liquid crystal molecules of the liquid crystal of the liquid crystal layer  190  are driven by the electric field to rotate from one direction to another direction. The liquid crystal molecules work as light switches, and allow certain parts of the light beams to pass through the LC panel  11 . Thereby, the LC panel  11  displays images. 
     The freezing point of the liquid crystal is about −40° C. When the temperature of the liquid crystal is in the range from −10° C. to −30° C., the liquid crystal layer  190  becomes stickier, and the liquid crystal molecules rotate slower than normal. This is liable to cause flicker and image delay. That is, the display quality of the LCD device  1  is impaired. Furthermore, when the temperature of the liquid crystal is below −40° C., the liquid crystal layer  190  may even freeze, whereupon the LCD device  1  stops working. 
     Accordingly, what is needed is an LCD device that can circumvent the above-described difficulties. 
     SUMMARY 
     An exemplary LCD device includes a liquid crystal panel and a heating system. The heating system heats the liquid crystal panel when the temperature of the liquid crystal panel is below a predetermined temperature. 
     Another exemplary LCD device includes a liquid crystal panel and a temperature control system. The temperature control system is used for maintaining the temperature of the liquid crystal panel in a predetermined threshold range. 
     Other novel features and advantages will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. In the drawings, all the views are schematic. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded, side view of an LCD device according to a preferred embodiment of the present invention, the LCD device including a backlight module. 
         FIG. 2  is a top plan view of certain parts of the backlight module of  FIG. 1 . 
         FIG. 3  is an exploded, side view of a conventional LCD device. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to  FIG. 1  and  FIG. 2  show aspects of an LCD device according to a preferred embodiment of the present invention. The LCD device  2  includes an LC panel  21 , a backlight module  22  arranged under the LC panel  21  for providing light beams to the LC panel  21 , and a heating system (not labeled) for heating the LC panel  21 . 
     The LC panel  21  includes a top substrate  291 , a bottom substrate  292  parallel to the top substrate  291 , and a liquid crystal layer  290  sandwiched between the top substrate  291  and the bottom substrate  292 . A main central area of the LC panel  21  is defined as a display area (not labeled). 
     The backlight module  22  includes an optical film unit  23 , an LGP  25 , a reflective plate  27 , and a light source  26 . The LGP  25  includes a light incident surface  251 , a top light emitting surface  252  adjoining the light incident surface  251 , and a bottom surface  253  adjoining the light incident surface  251 . The light source  26  is preferably a set of LEDs, and is disposed adjacent to the light incident surface  251  of the LGP  25 . The optical film unit  23  is disposed adjacent to the light emitting surface  252 . The reflective plate  27  is disposed adjacent to the bottom surface  153 . 
     Referring also to  FIG. 2 , the heating system includes a temperature sensor  280 , a set of infrared ray-emitting diodes  28 , and an infrared ray absorbing film  24 . The temperature sensor  280  is arranged on an edge portion of a bottom surface of the bottom substrate  292 . Thereby, the temperature sensor  280  indirectly senses the temperature of the liquid crystal layer  290  by detecting the temperature of the LC panel  21 . The infrared ray-emitting diodes  28  are arranged adjacent to the light incident surface  251  of the LGP  25 . In the illustrated embodiment, the infrared ray-emitting diodes  28  and the LEDs of the light source  26  are arranged alternately along a length of the light incident surface  251 . The infrared ray-emitting diodes  28  can emit infrared rays with a specific wavelength, typically over 800 nm. The LEDs of the light source  26  emit visible light with wavelengths in the range from 380 nm to 780 nm. The infrared ray absorbing film  24  is arranged between the LC panel  21  and the optical film unit  23 , and faces the display area of the LC panel  21 . 
     The infrared ray absorbing film  24  is a transparent film with high visible light transparence. The infrared ray absorbing film  24  can absorb infrared rays with a specific wavelength over 800 nm, and convert the energy of the infrared rays into thermal energy. In particular, the energy conversion occurs as follows. When infrared rays with specific frequencies irradiate the infrared ray absorbing film  24 , some atomic groups or molecular groups of the infrared ray absorbing film  24  that have the same oscillation frequency as the infrared rays resonate with the infrared rays and gain kinetic energy from the infrared rays. With the accumulation of the kinetic energy, the atomic groups or the molecular groups jump from a ground state with a lower energy level to an excited state with a higher energy level. Accordingly, the temperature of the infrared ray absorbing film  24  rises to a higher temperature. 
     In operation of the LCD device  2 , visible light beams emitted by the light source  26  enter the LGP  25  through the light incident surface  251 . Most of the light beams are reflected by the bottom surface  253  of the LGP  25 , and then transmit through the light emitting surface  252 . Some of the light beams transmit out of the LGP  25  through the bottom surface  253 , are reflected by the reflective plate  27  back into the LGP  25 , and then transmit through the light emitting surface  252 . The light beams emitting from the light emitting surface  252  transmit through the optical film unit  23  and the infrared ray absorbing film  24  to illuminate the LC panel  21 . 
     The temperature sensor  280  detects the temperature of the LC panel  21 . When the temperature of the LC panel  21  is below a first predetermined threshold temperature (e.g. −10° C.), the infrared ray-emitting diodes  28  are turned on and emit infrared rays. The infrared rays transmit into the LGP  25  through the light incident surface  251  and emit from the light emitting surface  252 . Then the infrared rays irradiate the infrared ray absorbing film  24 . The infrared ray absorbing film  24  gains energy from the infrared rays, so that the temperature of the infrared ray absorbing film  24  rises. Because the infrared rays absorbing film  24  abuts or is close to the LC panel  21 , the thermal energy of the infrared ray absorbing film  24  is transferred to the LC panel  21  and heats the liquid crystal layer  290  to a higher temperature. 
     When the temperature of the LC panel  21  is higher than a second predetermined threshold temperature, (e.g. 20° C.), the infrared ray-emitting diodes  28  are turned off and stop emitting infrared rays. 
     The above-described configuration provides the LCD device  2  with the heating system. The heating system detects the temperature of the LC panel  21 , and heats up the LC panel  21  when the temperature is below a predetermined threshold. This ensures that the liquid crystal layer  290  is maintained in a predetermined temperature range in which the LCD device  2  can work normally. 
     It is to be understood, however, that even though numerous characteristics and advantages of the present embodiments have been set out in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.

Technology Classification (CPC): 6