Abstract:
A backlight unit is adapted for increasing the brightness uniformity and life span of a light source, and a liquid crystal module using the same. A light unit includes a light source; a temperature sensor for sensing a temperature of the light source; a peltier device for increasing and decreasing the temperature of the light source; and a controller for controlling the peltier device in correspondence to an output of the temperature sensor.

Description:
This application claims the benefit of the Korean Patent Application No. P2005-0072886 filed on Aug. 9, 2006, which is hereby incorporated by reference. 
     FIELD 
     The present invention relates to a liquid crystal module, and more particularly to a backlight unit that is adaptive for increasing the brightness uniformity and life span of a light source, and a liquid crystal module using the same. 
     BACKGROUND 
     A CRT (cathode ray tube) is one of display devices which are generally used in a monitor of a measuring instrument, an information terminal etc. as well as a TV, but it cannot actively corresponds to the demand of making an electronic appliance small and light due to the CRT&#39;s own weight and size. 
     Accordingly, the display devices, which are expected to replace the CRT which has a certain limit in weight and size when various electronic appliances are on the trend of being made small and light, include a liquid crystal display LCD using an electric field optical effect, a plasma display panel PDP using a gas discharge, an organic light emitting diode OLED using an field effect luminous effect. Among them, the liquid crystal display device has actively been researched. 
     In order to replace the CRT, the liquid crystal display device having advantages such as compact size, light weight and low power consumption has recently been developed to act sufficiently as a flat panel display and is used in a monitor of a desktop computer and a large-size display device as well as a monitor of a notebook computer, thus the demand for the liquid crystal display device is continuously increasing. 
     The liquid crystal display device like this generally includes a liquid crystal module LCM, a drive circuit part for driving the liquid crystal module, and a case. And, the liquid crystal module includes a liquid crystal display panel where liquid crystal cells are arranged in amatrix shape, and a backlight unit which irradiates light to the liquid crystal display panel. 
     The liquid crystal display device not being a self-luminous display device needs a separate light source like a backlight unit. And the liquid crystal display device is divided into an edge type and a direct type in accordance with a location where the light source is installed. 
     The light source of the backlight unit can be a cold cathode fluorescent lamp CCFL, a hot cathode fluorescent lamp HCFL, an external electrode fluorescent lamp EEFL, a light emitting diode LED, etc, and the CCFL or the LED are mainly used among them. 
     Additionally, in case of the liquid crystal display device which uses the CCFL or LED as the light source device, there is generated a problem in that brightness is decreased in accordance with a temperature as shown in  FIGS. 1 and 2 . 
       FIG. 1  represents a brightness change of a CCFL in accordance with a temperature, and  FIG. 2  represents a brightness change of an LED in accordance with a temperature. 
     Referring to  FIGS. 1 and 2 , it is known that the brightness is remarkably deteriorated when a temperature is high or low in the CCFL and when a temperature is high in the LED. 
     Further, the temperature of the light source has a close relationship with an operation life span to be directly connected to the reliability of the product as well as being a problem of the brightness deterioration. 
     SUMMARY 
     Accordingly, it is an objective of the present invention to provide a backlight unit that is adaptive for increasing the brightness uniformity and life span of a light source, and a liquid crystal module using the same. 
     A backlight unit according to an aspect of the present invention includes a light source and a temperature sensor that senses a temperature of the light source. The backlight unit further comprises a peltier device that increases or decreases the temperature of the light source and a controller that controls the peltier device in correspondence to an output of the temperature sensor. 
     A liquid crystal module according to another aspect of the present invention includes a backlight unit. The backlight unit includes a light source, a temperature sensor that senses a temperature of the light source, a peltier device that increases or decreases the temperature of the light source and a controller that controls the peltier device in correspondence to an output of the temperature sensor. The liquid crystal module further comprises a liquid crystal display-panel that receives a light irradiated from the backlight unit to realize a picture, a support main within which the backlight unit of the liquid crystal display panel is deposited, a cover bottom that encompasses the bottom and side surfaces of one side of the support main, and a case top that encompasses the edge of the liquid crystal display panel and the cover bottom. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other objectives of the invention will be apparent from the following detailed description of the embodiments of the present invention with reference to the accompanying drawings, in which: 
         FIG. 1  is a diagram representing a brightness deterioration in accordance with a temperature of a cold cathode fluorescent lamp; 
         FIG. 2  is a diagram representing a brightness deterioration in accordance with a temperature of a light emitting diode; 
         FIG. 3  is a diagram representing a liquid crystal module according to a first embodiment of the present invention; 
         FIG. 4  is a diagram representing a peltier device; 
         FIG. 5  is a block diagram representing a flow of temperature control; and 
         FIG. 6  is a diagram representing a liquid crystal module according to a second embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. 
     With reference to  FIGS. 3 to 6 , embodiments of the present invention will be explained as follows. 
     Referring to  FIG. 3 , a liquid crystal module according to a first embodiment of the present invention includes a support main  102 ; a backlight unit and a liquid crystal display panel  105  which are deposited inside the support main  102 ; a cover bottom  109  which encompasses the bottom and side surfaces of one side of the support main  102 ; and a case top  101  which encompasses the edge of the liquid crystal display panel  105  and the cover bottom  109 . 
     The support main  102  acts to support the whole of the liquid crystal module and has the backlight unit and the liquid crystal display panel  105  deposited therewithin. 
     The liquid crystal display panel  105  includes an upper plate  103  where a black matrix, a color filter array, a common electrode and an alignment film are sequentially formed on a substrate; a lower plate  104  where a TFT array, a pixel electrode and an alignment film are sequentially formed on a substrate; an upper polarizer  107   a  stuck onto the upper plate  103 ; a lower polarizer  107   b  stuck under the lower plate  104 ; a spacer (not shown) for keeping a gap between the upper and lower plates; and a liquid crystal injected into a space between the upper and lower plates  103 ,  104 . And, the upper plate  103  and the lower plate  104  are bonded by a sealant. 
     The case top  101  is installed to encompass the surface edge and side surface of the optical sheets  114  and the liquid crystal display panel  105 . The case top  101  encompasses the edge of the liquid crystal display panel  105  to protect the liquid crystal display panel  105  from an external impact. 
     The cover bottom  109  is installed to encompass the side surface and the bottom surface of one side of the support main  102 . The cover bottom  109  is formed of a metal material, e.g., aluminum. 
     The backlight unit includes a lamp  108  which generates light; a lamp holder  106  which fixes the lamp  108 ; a housing  111  installed in a form of encompassing the lamp  108 ; a peltier device  110  stuck to the housing  111  for controlling the temperature of the lamp  108 ; a light guide panel  112  for converting the light incident from the lamp  108  into a surface light; a reflection plate  113  located in the lower part of the light guide panel  112  for reflecting the light progressing to the lower and side surfaces of the light guide panel  112  to the upper surface; and optical sheets  114  for controlling the diffusion and progress direction of the light which passes through the light guide panel. 
     A cold cathode fluorescent lamp is mainly used as the lamp  108  which is used in the backlight unit, and the light generated at the lamp  108  is incident to the light guide panel  112  through the incidence surface of the light guide panel  112 . 
     On the other hand, it is possible to use a light emitting diode, a hot cathode fluorescent lamp, an external electrode fluorescent lamp, etc. as the lamp  108  used in the backlight unit. 
     The housing  111  has a specular surface in the inner surface thereof to reflect the light from the lamp  108  to the incidence surface of the light guide panel  112 . 
     The reflection plate  113  is installed to face in the rear surface of the light guide panel  112 . The light guide panel  112  makes the light incident from the lamp  108  reach a place which is far from the lamp  108 . The light guide panel  112  is formed of PMMA (polymethylmethacrylate) which is high in strength so as not to be deformed or broken and is good in transmissivity. 
     The reflection plate  113  re-reflects the light incident to itself through the rear surface of the light guide panel  112 , thereby acting to reduce light loss. The light from the lamp  108  is reflected at a designated tilt angle at the reflection plate  112  of the rear surface to progress uniformly to an exiting surface if the light is incident to the light guide panel  112 . At this moment, the light progressing to the lower and side surfaces of the light guide panel  112  is reflected to the light guide panel  112  to progress to the exiting surface. 
     The light exiting through the exiting surface of the light guide panel  112  has its diffusion and progress direction controlled by the optical sheets  114 . To this end, the optical sheets  114  include a diffusion sheet for diffusing the light exiting through the exiting surface of the light guide panel  112  to the whole area; first and second prism sheets for getting the progress angle of the light exiting from the light guide panel to be vertical to the liquid crystal display panel  105 ; and a protection sheet for protecting the second prism sheet. 
     The peltier device  110  is formed in a shape of encompassing the part or whole of the external surface of the housing  111  to control a surrounding temperature of the lamp  108 . 
     The peltier device  110  is a circuit device made by use of a peltier effect. The peltier effect is a phenomenon that when a current flows in two different metals of which both cut ends are connected, a temperature difference is generated in the both cut ends, that is to say, emission or decalescence of heat is generated at the joined part of the both cut ends of the two metals. The emission or decalescence of heat at the joined part of the both cut ends of the two metals is reversible in accordance with a direction of a current between two electrodes of the peltier device. The peltier effect and the peltier device using the same has already been known to the public, thus a detail explanation will be omitted. 
     A peltier device using a ceramic substrate is shown in  FIG. 4  as an example of the peltier device. 
     Referring to  FIG. 5 , two electrodes of a peltier device  110  are connected to a controller which controls the direction and amount of the current flowing between the two electrodes of the peltier device  110 , and an output terminal of a thermistor is connected to the controller. 
     The thermistor is installed at a location which is suitable for measuring the temperature of the lamp  108 , and the output terminal of the thermistor is connected to the controller. 
     The controller makes a suitable current flow in the peltier device so as for the temperature sensed at the thermistor to be always kept at a fixed level. The temperature of the lamp  108  is suitable to be kept at around 10° C.˜70° C., as shown in  FIG. 1 , in order for the lamp  108  to keep a suitable brightness, and it is desirable for the controller to control the peltier device so that the lamp  108  can keep the temperature. The controller can be mounted on any one of an inverter printed circuit board (hereinafter, referred to as ‘PCB’), a source PCB and a gate PCB which are generally embedded in the liquid crystal module. 
       FIG. 6  represents a liquid crystal module according to a second embodiment of the present invention. 
     Referring to  FIG. 6 , the liquid crystal module according to the second embodiment of the present invention includes a support main  202 ; a backlight unit and a liquid crystal display panel  205  which are deposited inside the support main  202 ; a cover bottom  209  which encompasses the bottom and side surfaces of one side of the support main  202 ; and a case top  201  which encompasses the edge of the liquid crystal display panel  205  and the cover bottom  209 . 
     The support main  202  acts to support the whole of the liquid crystal module and has the backlight unit and the liquid crystal display panel  205  deposited therewithin. 
     The liquid crystal display panel  205  includes an upper plate  203  where a black matrix, a color filter array, a common electrode and an alignment film are sequentially formed on a substrate; a lower plate  204  where a TFT array, a pixel electrode and an alignment film are sequentially formed on a substrate; an upper polarizer  207   a  stuck onto the upper plate  203 ; a lower polarizer  207   b  stuck under the lower plate  204 ; a spacer (not shown) for keeping a gap between the upper and lower plates; and a liquid crystal injected into a space between the upper and lower plates  203 ,  204 . And, the upper plate  203  and the lower plate  204  are bonded by a sealant. 
     The case top  201  is installed to encompass the surface edge and side surface of the optical sheets  214  and the liquid crystal display panel  205 . The case top  201  encompasses the edge of the liquid crystal display panel  205  to protect the liquid crystal display panel  205  from an external impact. 
     The cover bottom  209  is installed to encompass the side surface and the bottom surface of one side of the support main  202 . The cover bottom  209  is formed of a metal material, e.g., aluminum. 
     The backlight unit includes a light emitting diode (hereinafter, referred to as ‘LED’)  208  which generates light; an LED PCB  206  to which the LED  208  is stuck; a housing  211  installed in a form of encompassing the LED unit  208 ; a peltier device  210  stuck to the housing  211  for controlling the temperature of the LED  208 ; a light guide panel  212  for converting the light incident from the LED  208  into a surface light; a reflection plate  213  located in the lower part of the light guide panel  212  for reflecting the light progressing to the lower and side surfaces of the light guide panel  212  to the upper surface; and optical sheets  214  for controlling the diffusion and progress direction of the light which passes through the light guide panel. 
     The LED is a self-luminous device controlled in accordance with the current amount, and the light generated in the LED  208  is incident to the light guide panel  212  through the incidence surface of the light guide panel  212 . 
     The housing  211  has a specular surface in the inner surface thereof to reflect the light from the LED  208  to the incidence surface of the light guide panel  212 . 
     The reflection plate  213  is installed to face in the rear surface of the light guide panel  212 . The light guide panel  212  makes the light incident from the LED  208  reach a place which is far from the LED  208 . The light guide panel  212  is formed of PMMA (polymethylmethacrylate) which is high in strength so as not to be deformed or broken and is good in transmissivity. 
     The reflection plate  213  re-reflects the light incident to itself through the rear surface of the light guide panel  212 , thereby acting to reduce light loss. The light from the LED  208  is reflected at a designated tilt angle at the reflection plate  213  of the rear surface to progress uniformly to an exiting surface if the light is incident to the light guide panel  212 . At this moment, the light progressing to the lower and side surfaces of the light guide panel  212  is reflected to the light guide panel  212  to progress to the exiting surface. 
     The light exiting through the exiting surface of the light guide panel  212  has its diffusion and progress direction controlled by the optical sheets  214 . To this end, the optical sheets  214  include a diffusion sheet for diffusing the light exiting through the exiting surface of the light guide panel  212  to the whole area; first and second prism sheets for getting the progress angle of the light exiting from the light guide panel  212  to be vertical to the liquid crystal display panel  205 ; and a protection sheet for protecting the second prism sheet. 
     The peltier device  210  is formed in a shape of encompassing the part or whole of the external surface of the housing  211  to control a surrounding temperature of the LED  208 . A description for the peltier device  210  is the same as that of the foregoing first embodiment, thus a detain explanation for this will be omitted. 
     In the same manner as the first embodiment, two electrodes of a peltier device  210  are connected to a controller which controls the direction and amount of the current flowing between the two electrodes of the peltier device  210 , and an output terminal of a thermistor is connected to the controller. 
     The thermistor is installed at a location which is suitable for measuring the temperature of the LED  208 , and the output terminal of the thermistor is connected to the controller. 
     The controller makes a suitable current flow in the peltier device so as for the temperature sensed at the thermistor to be always kept at a fixed level. The temperature of the LED  208  is suitable to be kept at below 60° C., as shown in  FIG. 2 , in order for the LED  208  to keep a suitable brightness, and it is desirable for the controller to control the peltier device so that the LED  208  can keep the temperature. The controller can be mounted on any one of an inverter printed circuit board (hereinafter, referred to as ‘PCB’), a source PCB and a gate PCB which are generally embedded in the liquid crystal module. 
     As described above, the temperature of the light source is controlled by use of the peltier device, thus the backlight unit and the liquid crystal module using the same can keep a uniform brightness under the environment of various temperatures and increase the operation life span and reliability. 
     Although the embodiments above describe backlight unit and liquid crystal module using the same, the present invention is not limited thereto. Other preferred embodiments include frontlight or sidelight unit, and liquid crystal modules using the same. 
     Although the present invention has been explained by the embodiments shown in the drawings described above, it should be understood to the ordinary skilled person in the art that the invention is not limited to the embodiments, but rather that various changes or modifications thereof are possible without departing from the spirit of the invention. Accordingly, the scope of the invention shall be determined only by the appended claims and their equivalents.