Patent Publication Number: US-8524516-B2

Title: Liquid crystal display device and fabricating and driving method thereof

Description:
This application is a divisional application of application Ser. No. 11/386,773, filed on Mar. 23, 2006, now U.S. Pat. No. 7,944,429, which claims the benefit of Korean Patent Application No. P2005-0132268 filed on Dec. 28, 2005, which are hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a display device, and more particularly to a liquid crystal display device, and fabricating and driving method thereof. 
     2. Description of the Related Art 
     A liquid crystal display (hereinafter referred to as “LCD”) device controls light transmittance of liquid crystal cells in accordance with a video signal to display a picture. The LCD device utilizes an active matrix of cells in which a switching device is used in each cell. The LCD device can be configured for use in several different types of display devices, such as computer monitor, television monitor and cellular phone display. A thin film transistor (hereinafter referred to as “TFT”) is mainly used as the switching device in the active matrix of the LCD device. 
       FIG. 1  represents a driving device of an LCD device of the related art. Referring to  FIG. 1 , the driving device of the LCD device of the related art includes a liquid crystal panel  152  where m×n number of liquid crystal cells Clc are arranged in an active matrix having m number of data lines D 1  to DM crossing n number of gate lines G 1  to Gn, and a TFT formed adjacent to each of the crossings; a data driver  64  for supplying a data signal to the data lines D 1  to Dm of the liquid crystal panel  152 ; a gate driver  66  for supplying a scan signal to the gate lines G 1  to Gn; a gamma voltage supplier  68  for supplying a gamma voltage to the data driver  64 ; a timing controller  60  for controlling the data driver  64  and the gate driver  66  using a synchronization signal supplied from a system  70 ; a DC/DC converter  74  for generating voltages supplied to the liquid crystal panel  52  from a voltage supplied by a power supplier  62 ; and an inverter  76  for driving a backlight  78 . The system  70  supplies a vertical/horizontal synchronization signal Vsync, Hsync, a clock signal DCLK, a data enable signal DE and data RGB to the timing controller. 
     The liquid crystal panel  52  includes a plurality of liquid crystal cells Clc that are arranged in a matrix shape defined by the crossing of data lines D 1  to Dm and gate lines G 1  to Gn. A TFT is respectively formed in each of the liquid crystal cells Clc to switch the data signal from the data lines D 1  to Dm in response to the scan signal supplied from the gate line G. Further, a storage capacitor Cst is formed in each of the liquid crystal cells Clc. The storage capacitor Cst is formed between the pre-stage gate line and the pixel electrode of the liquid crystal cell Clc, or formed between a common electrode line and the pixel electrode of the liquid crystal cell Clc, thereby fixedly sustaining the voltage of the liquid crystal cell Clc. 
     The gamma voltage supplier  68  supplies a plurality of gamma voltages to the data driver  64 . The data driver  64  converts the digital video data RGB to an analog gamma voltage (data signal) corresponding to the gray level value in response to the control signal CS from the timing controller, and supplies the analog gamma voltage to the data lines D 1  to Dm. The gate driver  66  sequentially supplies a scan pulse to the gate lines G 1  to Gn in response to the control signal CS from the timing controller  60 , thereby selecting a horizontal line of the liquid crystal panel  52  to which the data signal is supplied. 
     The timing controller  60  generates the control signal CS for controlling the gate driver  66  and the data driver  64  by use of the vertical/horizontal synchronization signal Vsync, Hsync and the clock signal DCLK which are inputted from the system  70 . Herein, the control signal CS for controlling the gate driver  66  includes gate start pulse GSP, gate shift clock GSC, and gate output signal GOE. And the control signal CS for controlling the data driver  64  includes source start pulse GSP, source shift clock SSC, source output signal SOE, and polarity signal POL. The timing controller  60  also re-arranges the data RGB supplied from the system  70  for supply to the data driver  64 . 
     The DC/DC converter  74  boosts or reduces the voltage of 3.3V input from the power supplier  62  and generates a voltage to be supplied to the liquid crystal panel  52 . The DC/DC converter  72  generates a gamma reference voltage, a gate high voltage VGH, a gate low voltage VGL, and a common voltage Vcom. 
     The inverter  76  drives the backlight  78  by use of the drive voltage Vinv supplied from any one of the power supplier  62  or the system  70 . The backlight  78  is controlled by the inverter  76  to generate light to supply to the liquid crystal panel  52 . 
     In the liquid crystal display  52  of the liquid crystal display device of the related art, constant light is always supplied from the backlight  78  regardless of the amount of available light in the external environment. Thus, the backlight may provide insufficient lighting to the liquid crystal panel in a bright light environment or waste power in a low light environment. To solve these problems, a technique is proposed in that the external light is sensed by use of a photo-sensor, such as a photodiode, and the brightness of the backlight  18  is adjusted by a user&#39;s manipulation. However, the photo-sensor is not located within the liquid crystal panel  52  such that its reliability is decreased. Further, there is cost increase if the photo-sensor is separately added to the LCD device. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to a liquid crystal display device and fabricating and driving method thereof that substantially obviates one or more of the problems due to limitations and disadvantages of the related art. 
     An object of the present invention to provide a liquid crystal display device that has reduced manufacturing cost, and fabricating and driving method thereof. 
     Another object of the present invention to provide a liquid crystal display device that has improved visibility and reducing power consumption, and fabricating and driving method thereof. 
     Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
     To achieve these and other objects of the invention, a liquid crystal display device according to an aspect of the present invention includes a liquid crystal display device includes a liquid crystal panel divided into a non-display area and a display area where pixel cells are arranged in a matrix, a backlight for supplying light to the liquid crystal panel, and a photo-sensing device in the non-display area for sensing an external light to control light output from the backlight in accordance with the sensed external light. 
     In another aspect, a fabricating method of a liquid crystal display device includes: forming a gate pattern having of a gate line and a first gate electrode of a thin film transistor connected to the gate line in a display area of a thin film transistor array substrate and a second gate electrode of a photo-sensing device in a non-display area of the thin film transistor array substrate; forming a gate insulating film on the gate pattern; forming a first semiconductor pattern of the thin film transistor and a second semiconductor pattern of the photo-sensing device on the gate insulating film; forming a source/drain pattern having a first source electrode and a first drain electrode connected to the first semiconductor pattern, second source electrodes and second drain electrodes connected to the second semiconductor pattern, and a data line crossing the gate line; forming a passivation film having a contact hole that exposes the first drain electrode of the thin film transistor; forming a pixel electrode that is connected to the first drain electrode through the contact hole; forming a color filter array substrate having a color filter array; and bonding the color filter array substrate and the thin film transistor array substrate with liquid crystal therebetween. 
     In yet another aspect, a driving method of a liquid crystal display device includes sensing an external light with a photo-sensing device formed on the thin film transistor array substrate and controlling a light output of a backlight supplied to the liquid crystal display device in accordance with the sensed result. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. 
         FIG. 1  is a diagram representing a driving device of a liquid crystal display device of the related art. 
         FIG. 2  is a diagram of a corner portion of a liquid crystal display device according to a first embodiment of the present invention. 
         FIG. 3  is a plan of an area A in  FIG. 2 . 
         FIG. 4  is a cross-sectional view of the liquid crystal display device taken along line I-I′ of  FIG. 3 . 
         FIG. 5  is a plan view of area B in  FIG. 2 . 
         FIG. 6  is a cross-sectional view of the liquid crystal display device along the line II-II′ of  FIG. 5 . 
         FIG. 7  is a diagram representing a driver of the liquid crystal display device and an inverter printed circuit board that drives a backlight of the liquid crystal display device. 
         FIG. 8  is a diagram representing that a voltage sensed by a photo-sensing device is supplied to the inverter printed circuit board through an interconnection circuit. 
         FIG. 9  is a diagram representing that the voltage sensed by the photo-sensing device is converted into and modulated a digital signal within a data printed circuit board, and then supplies the digital signal to the inverter printed circuit board. 
         FIG. 10  is a diagram representing a driving characteristic of a photo-sensing device. 
         FIGS. 11A to 11E  are process charts representing a fabricating process of a thin film transistor array substrate of a liquid crystal display device according to an embodiment of the present invention. 
         FIG. 12  is a diagram representing a liquid crystal display device according to a second embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     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. 2 to 12 , embodiments of the present invention will be explained as follows. 
       FIG. 2  is a diagram of a corner portion of a liquid crystal display device according to a first embodiment of the present invention. The liquid crystal display (LCD) device shown in  FIG. 2  has a photo-sensing device  177  formed on a thin film transistor array substrate  170  of a liquid crystal panel  152 . Thus, a photo-sensor device, such as a separate photo diode, mounted outside of the thin film transistor substrate is not required so that the manufacturing cost of the LCD device can be reduced. The photo-sensing device  177  is formed within the liquid crystal panel  152 , thereby improving the reliability of the photo-sensing device  177 . Hereinafter, in reference to  FIGS. 2 to 6 , the configuration and operation of embodiments of the present invention will be described in detail. 
     As shown in  FIG. 2 , the LCD device includes a liquid crystal panel  152  having a thin film transistor array substrate  170  on which a thin film transistor array is formed, a color filter substrate  180  on which a color filter array is formed, a data driver  172  for supplying a data signal to the liquid crystal display panel  152 , and a gate driver  182  for supplying a gate signal to the liquid crystal display panel  152 . The thin film transistor array substrate  170  is bonded to the color filter substrate  180 . 
     The gate driver  182  and the data driver  172  are integrated into the LCD device as a plurality of integrated circuits IC. That is to say, each gate driver  182  is integrated into gate integrated circuits  184  mounted on a gate TCP (tape carrier package)  186  connected to the liquid crystal panel  152  by a TAB (tape automated bonding) method, or mounted on the liquid crystal panel  152  by a COG (chip on glass) method. Each data driver  172  is integrated into data integrated circuits  174  mounted on the data TCP (tape carrier package)  176  connected to the liquid crystal panel  152  by a TAB (tape automated bonding) method, or mounted on the liquid crystal panel  152  by a COG (chip on glass) method. The integrated circuits  174  and  184  connected to the liquid crystal panel  152  by the TAB method through the TCP  176 ,  186  receive the control signals and DC voltages input from the outside through the signal lines mounted in PCB (printed circuit board) (not shown) connected to the TCPs  176  and  186  and are connected to each other. 
     The liquid crystal panel  152  includes a thin film transistor array substrate  170  having a gate line  102  and a data line  104  crossing each other to define a pixel cell. The gate line  102  is electrically connected to the gate integrated circuit  184  that drives the gate lines  102 . And the data line  104  is electrically connected to the data drive IC  174  that drives the data line  104 . 
     The liquid crystal panel  152  is divided into a display area P 1  where a picture is realized and a non-display area P 2 . In the display area P 1 , the pixel cells (or liquid crystal cells) defined by the gate line  102  and the data line  104  are arranged in a matrix shape. In the non-display area P 2 , a photo-sensing device  177  is located in an area of the thin film transistor array substrate  170  that is not overlapped by either the gate line  102  or the data line  104 . 
       FIG. 3  is a plan of an area A in  FIG. 2 . More particularly,  FIG. 3  is a plan view of one pixel cell in a thin film transistor array substrate, and  FIG. 4  is a cross-sectional view of the liquid crystal display device along the line I-I′ of  FIG. 3 . For the sake of convenience,  FIG. 3  only shows the thin film transistor array substrate, and  FIG. 4  shows both the thin film transistor array substrate and the color filter array substrate. Referring to  FIGS. 3 and 4 , each of the pixel cells are arranged in a matrix shape within the display area P 1 . The color filter array substrate  180  is bonded to the thin film transistor array substrate  170  with the liquid crystal  175  therebetween. Each of the pixel cells have a color filter  136  on the color filter array substrate  180  and a pixel electrode  118  on the thin film transistor array substrate  170  with the liquid crystal  175  between the color filter  136  and the pixel electrode  118 . 
     The thin film transistor array substrate  170  includes a gate line  102  and a data line  104 , which are formed to cross each other and have a gate insulating film  144  therebetween; a thin film transistor  106 A formed at each of the crossings; the pixel electrode  118  formed in a pixel area defined by the crossings; and a storage capacitor  120  formed where the pixel electrode  118  and a pre-stage gate line  102  overlap. 
     The thin film transistor  106   a  includes a first gate electrode  108   a  connected to the gate line  102 , a first source electrode  110   a  connected to the data line  104 , a first drain electrode  112   a  connected to the pixel electrode  118 , an active layer  114   a , which overlaps the first gate electrode  108   a  and forms a channel between the first source electrode  110   a  and the first drain electrode  112   a . The active layer  114   a  partially overlaps the first source electrode  110   a  and the first drain electrode  112   a  and further includes a channel part between the first source electrode  110 A and the second drain electrode  112   a . A first ohmic contact layer  147   a  for being in ohmic contact with the first source electrode  110   a  and the second drain electrode  112   a  is further formed on the first active layer  114   a . Herein, the first active layer  114   a  and the first ohmic contact layer  147  are called a first semiconductor pattern  148   a.    
     The thin film transistor  106   a  transmits the pixel voltage signal charged and maintained on the data line  104  in response to the gate signal supplied to the gate line  102 . The pixel electrode  118  is connected to the first drain electrode  112   a  of the thin film transistor  106   a  through the contact hole  117  that penetrates a passivation film  150 . The pixel electrode  118  generates a potential difference with a common electrode  138  in response to receiving the charged pixel voltage. The potential difference causes a liquid crystal  175  located between the thin film transistor array substrate  170  and the upper substrate  132  to rotate by dielectric anisotropy, thereby transmitting incident light through the LCD device. 
     The storage capacitor  120  includes the pre-stage gate line  102  and the pixel electrode  118 , which overlaps the gate line  102  with the gate insulating film  144  and the passivation film  150  therebetween. The storage capacitor  120  stably maintains the pixel voltage charged in the pixel electrode  118  until the next pixel voltage is received. 
     The color filter array substrate  180  includes a black matrix  134  bounding a pixel cell area on the upper substrate  132 , a color filter  136  which is divided by the black matrix  134  and faces the pixel electrode  118  of the thin film transistor array substrate  170 , and the common electrode  138  on the entire surface of the color filter  136  and the black matrix  134 . The black matrix  134  is formed on the upper substrate  132  corresponding to the gate lines  102  and the data line  104 , and provides defines a cell area where the color filter  136  is to be formed. The black matrix  134  prevents light leakage and absorbs the external light to increase contrast ratio. The color filter  136  is formed in a cell area defined by the black matrix  134  and corresponds to the pixel electrode  118  of the thin film transistor array substrate  170 . The color filter  136  is formed for each of red, green and blue colors to realize a color display. The common electrode  138  is formed over the entire surface of the upper substrate  132  where the color filter  136  is formed for making a vertical electric field with the pixel electrode  118 . On the thin film transistor array substrate  170  and the color filter array substrate  180 , alignment films (not shown) are further formed and a cell gap is sustained by a spacer (not shown). 
       FIG. 5  is a plan view of area B of  FIG. 2 . More particularly,  FIG. 5  is a plan view of a photo-sensing device  177  located in a non-display area P 2  of a liquid crystal panel  152 .  FIG. 6  is a cross-sectional view of the liquid crystal display device along line II-II′ of  FIG. 5 . For the sake of convenience,  FIG. 5  only shows the thin film transistor array substrate, and  FIG. 6  both the thin film transistor array substrate and the color filter array substrate. 
     The photo-sensing device  177  includes a second gate electrode  108   b  connected to a first output pad  187   b  of the TCP  176 ,  186 , a gate insulating film  144  formed to cover the second gate electrode  108   b ; a second semiconductor pattern  148   b  having an active layer  114   b  and a second ohmic contact layer  147   b  that overlaps the second gate electrode  108   b  with the gate insulating film  144  therebetween, second source electrodes  110   b  and second drain electrodes  112   b  that face each other with a channel of the second semiconductor pattern  148  therebetween; a source line  181  connected to the second source electrodes  110   b  and to a second output pad  187   a  of the TCP  176 ; and a drain line  183  that is connected to the second drain electrodes  112 B and a first input pad  187   c  of the TCP  176 ,  186 . 
     A first drive voltage is supplied to the second gate electrode  108   b  through the first output pad  187   b  of the TCP  176 ,  186  from a separate voltage source for driving the photo-sensing device  177 . The source line  181  also receives a second drive voltage from a separate voltage source through the second output pad  187   a  of the TCP for driving the photo-sensing device  177 . The drain line  183  supplies the voltage sensed by the photo-sensing to the first input pad  187   c  of the TCP  176 ,  186 . The second source electrodes  110   b  are formed to extend from the source line  181  so as to face the drain line  183 , and the second drain electrode  112   b  is formed to extend from the drain line  183  so as to face the source line  181 . The second source electrodes  110   b  and the second drain electrodes  112   b  are interleaved and have channels  151  in between. The photo-sensing device  177  in embodiments of the present invention has a structure in which a plurality of parallel connected thin film transistors  106   b  are configured to commonly share the second gate electrode  108   b , second drain electrodes  112   b , second source electrodes  110   b  and the second semiconductor pattern  148   b  such that their channels  151  acts as a light receiving part of a photo-sensing device  177 . 
     The black matrix  134  formed in the color filter array substrate  180  which faces the photo-sensing device  177  exposes the channels  151  of the photo-sensing device  177 . Thus, the black matrix  134  has an opening at light receiving area P 3  that corresponds to the light receiving part of the photo-sensing device  177 . Accordingly, the external light can irradiate the photo-sensing device  177  through the light receiving area P 3  of the color filter array substrate  180  so that the photo-sensing device  177  can sense the amount of the external light. Hereinafter, the process that the photo-sensing device  177  senses the external light will be explained. 
     A path of photo current flows to the second drain electrodes  112   b  through the channels  151  from the second source electrodes  110   b  of the photo-sensing device  177  in accordance with the received light amount if a first drive voltage Vdrv, e.g., a voltage of about 10V, is applied to the source electrode  110   b  through the source line  181  of the photo-sensing device  177 , a second drive voltage Vbias, e.g., a reverse bias voltage of about −5V, is applied to the second gate electrode  108 B of the photo-sensing device  177 , and light is received in the channel  151  area of the photo-sensing device  177 . The voltage by the photo current path is supplied to the first input pad  187   c  through the second drain electrode  112   b  of the photo-sensing device  177 . 
       FIG. 7  is a diagram representing an inverter printed circuit board which drives a driver and a backlight of the liquid crystal display device. The sensing voltage supplied to the first input pad  187   c , as shown in  FIG. 5 , is transmitted to the inverter PCB  230  through a FPC (flexible printed circuit) (or connector)  220  which connects the data PCB  210  to the inverter PCB  230 , as shown in  FIG. 7 . The inverter  230  converts the sensing voltage from the PCB  230  into a digital signal through an analog-digital converter ADC  232 , and then supplies the digital signal to an inverter controller  234 . The inverter controller  234  controls the inverter  236  that uses the digital signal corresponding to the sensing voltage supplied to the ADC  232 . The inverter  236  controls the light output of the backlight  238  in response to the control signal from the inverter controller  234 . 
     The inverter controller  234  can include a Look-up table for modulating the digital signal from the ADC  232 . The inverter controller  234  compares the digital signal from the ADC  232  with a reference value and chooses the modulated digital signal corresponding to the compared result from the Look-up table, and then supplies the digital signal to the inverter  236  by use of the selected modulation digital signal. The inverter  236  controls the light output of the backlight  238  by use of the digital signal from the inverter controller  234 . 
       FIG. 8  is a diagram representing that a voltage sensed by a photo-sensing device is supplied to the inverter printed circuit board through an interconnection circuit. The sensing voltage supplied to the first input pad  187   c  is directly transmitted to the inverter PCB  230 , as shown in  FIG. 8 , by use of a flexible printed circuit (FPC) (or connector)  221 . Thus, the sensing voltage does not pass through the data PCB. 
       FIG. 9  is a diagram representing that the voltage sensed by the photo-sensing device is converted into and modulated a digital signal within a data printed circuit board, and then supplies the digital signal to the inverter printed circuit board. A method of transmitting the sensing voltage supplied to the first input pad  187   c  to the inverter PCB is not limited to method described with regard to  FIG. 7 . For example, as shown in  FIG. 9 , the analog-digital converter ADC  232  is mounted on the data PCB  210  and a signal for controlling the backlight  238  is formed by use of a timing controller positioned on the data PCB  210 . In other words, the sensing voltage supplied to the first input pad  187   c  is converted into the digital signal through the analog-digital converter ADC  232  positioned on the data PCB  210  and then supplies the digital signal to the timing controller  242 . The timing controller  242  compares the digital signal from the ADC  232  with a reference value and chooses the modulated digital signal corresponding to the compared result from the Look-up table, and then supplies the selected modulation digital signal to the inverter  230  through the FPC  220 . The inverter controller  234  and the inverter  236  of the inverter PCB  230  controls the light output of the backlight  238  by use of the modulated digital signal. Hereinafter, the light output from the backlight  238  is explained in reference with the characteristic of the thin film transistor. 
       FIG. 10  is a diagram representing a driving characteristic of a photo-sensing device. The photo current (or “off” current) generated by the photo-sensing device  177 , as shown in  FIG. 10 , becomes larger in size because the sensed light amount is larger as it goes from a dark environment to a bright environment. Accordingly, the light output of the backlight  238  is adjusted in proportion to the size of the current amount that is sensed by the photo-sensing device  177 . For example, in the case of driving a transmissive liquid crystal display device in a bright environment where there is a lot of external light, the photo-sensing device  177  sense a large amount of light from the external light and controls the light output of the backlight  238  in accordance with the amount of sensed voltage. More specifically, a higher intensity light, which can make a displayed picture clearly visible in the bright environment, is supplied to the liquid crystal display panel  152  from the backlight  238 , thereby improving visibility. In another example, in the case of driving a transmissive liquid crystal display device in the dark environment, the photo-sensing device  177  senses a small amount of light and the light intensity of the backlight  238  can be proportionally reduced in accordance with the amount of the sensed sensing voltage, thereby reducing power consumption. 
     On the other hand, in the case of using a transflective liquid crystal display device, rather than the general transmissive liquid crystal display device, a contrary method of light amount control is used. That is, in the case of the transflective display, a picture is realized by use of the external light in the bright environment so that the supply of the light from the backlight  238  is minimized and the supply of the light from the backlight  238  should be increased in an environment where the external light is low. Thus, in the case of driving a transflective liquid crystal display device in the bright environment where the external light is large, the photo-sensing device  177  senses a lot of light from the external light and the amount of the light supply of the backlight  238  is inversely proportional to the amount of the sensed sensing voltage, and the light supply of the backlight  238  is increased in the dark environment. 
     The liquid crystal display device according to embodiments of the present invention forms the photo-sensing device  177  within the liquid crystal display panel  152  and controls the brightness of the backlight  238  by use of a sense signal from the photo-sensing device  177 . Accordingly, when the liquid crystal display panel  152  is located in a bright place, the light of the backlight  238  is adjusted to improve the visibility, and if the ambient brightness is dark, the light of the backlight  238  is reduced to lower power consumption. Further, the photo-sensing device  177  in the present invention can be simultaneously formed with the thin film patterns such as the thin film transistor  106   a  within the liquid crystal display panel  152 , thus in comparison with the related art, the separate photo-sensing device  177  is not necessary to be added to the outside, thereby reducing manufacturing cost. 
       FIGS. 11A to 11E  are process charts representing a fabricating process of a thin film transistor array substrate of a liquid crystal display device according to an embodiment of the present invention. Hereinafter, in reference with  FIGS. 11A to 11E , a fabricating method of the thin film transistor array substrate  170  where the photo-sensing device  177  is formed on the liquid crystal panel will be described according to an embodiment of the present invention. 
     After a gate metal layer is formed on the lower substrate  142  by a deposition method, such as sputtering, the gate metal layer is patterned by a photolithography process and etching process, thereby forming the gate patterns having a first gate electrode  108   a  of the thin film transistor  106   a , the gate line  102  in the display area P 1 , and the second gate electrode  108   b  of the photo-sensing device  177  in the non-display area P 2 , as shown in  FIG. 11A . Then, the gate insulating film  144  is formed by the deposition method, such as PECVD or sputtering, on the lower substrate  120  where the gate patterns are formed. Subsequently, an amorphous silicon layer and n+ amorphous silicon layer are sequentially formed on the lower substrate  142  where the gate insulating film  144  is formed. The amorphous silicon layer and the n+ amorphous silicon layer are patterned by a photolithography process and an etching process using a mask, as shown in  FIG. 11B , to form the first semiconductor pattern  148   a  for the thin film transistor  106   a  of the display are P 1  and the second semiconductor pattern  148   b  for the photo-sensing device  177  of the non-display area P 2 . The first semiconductor pattern  148   a  is made of a double layer of the active layer  114   a  and the ohmic contact layers  147   a . The second semiconductor pattern  148   b  is made of a double layer of the active layer  114   b  and the ohmic contact layers  147   b.    
     After sequentially forming a source/drain metal layer on the lower substrate  142  where the first and second semiconductor patterns  148   a  and  148   b  are formed, a source/drain pattern having the source line  181  and the drain line  183 , the second source electrode  110   b  and the second drain electrode  112   b  of the photo-sensing device  177  is formed, the data line  104  is formed, and the first source electrode  110   a  and the first drain electrode  112   a  of the thin film transistor  106   a  is formed, as shown in  FIG. 11C , by a photolithography process and an etching process using the mask. 
     A passivation film  150  is formed by a deposition method, such as plasma enhanced chemical vapor deposition (PECVD), on the entire surface of the gate insulating film  144  where the source/drain patterns are formed. Then, the passivation film  150  is patterned by a photolithography process and an etching process to form a contact hole  117 , which exposes the first drain electrode  112 A of the thin film transistor  106 A, as shown in  FIG. 11D . 
     A transparent electrode material is deposited on the entire surface of the passivation film  150  by a deposition method, such as sputtering. Then, the transparent electrode material is patterned by a photolithography process and an etching process, thereby forming the pixel electrode  118 , as shown in  FIG. 11E . Accordingly, the thin film transistor arrays are formed in the display area P 1  of the thin film transistor array substrate  170 , and at the same time, the photo-sensing device  177  is formed in the non-display area P 2 . 
     The liquid crystal cell area on the color filter array substrate  180  is formed by a separate process. The color filter array substrate  180  has the black matrix  134  that prevents light leakage when driving the liquid crystal display device. The color filter array substrate  180  also has the color filter  136  formed in the liquid crystal cell area divided by the black matrix  134  and corresponding to the pixel area where the pixel electrode  118  is located. The black matrix  134  is not formed in an area corresponding to the pixel electrode  118   a  or in the light receiving area P 3  of the photo-sensing device  177  in the non-display area P 2 . The thin film transistor array substrate  170  and the color filter array substrate  180  are bonded with liquid crystal therebetween, thereby completing the liquid crystal display panel  152  inclusive of the photo-sensing device  177 . 
       FIG. 12  is a plan view of a liquid crystal display device according to a second embodiment of the present invention. The liquid crystal display device shown in  FIG. 10  has the same components as the liquid crystal display device according to the first embodiment of the present invention, as shown in  FIGS. 2 to 6 , except that the photo-sensing device  177  is positioned so as not to be covered by the color filter array substrate  180  but rather is exposed directly to the outside such that no separate light receiving area P 2  is provided in the black matrix  134 . Thus the same reference numerals are given to the same components as  FIGS. 2 to 6  and a detail description will be omitted. 
     Referring to  FIG. 12 , in the second embodiment of the present invention, the photo-sensing device  177  is not covered by the color filter array substrate  180 , so that the entire channel  151  area might be exposed to the external light. Accordingly, in case that the external light is incident to the photo-sensing device  177  in the second embodiment, external light does not pass through the color filter array substrate  180 , thus the efficiency of the external light sensing is increased and the reliability of the sensed light can be improved. Further, in the first embodiment, the incident light supplied to the photo-sensing device  177  first passes through a polarizer that is located at the rear surface of the color filter array substrate  180 . In the second embodiment, the incident light supplied to the photo-sensing device  177  does not pass through a polarizer, thereby making the photo-sensing more precise and reliable. 
     As described above, the liquid crystal display device and the fabricating method thereof according to embodiments of the present invention forms a photo-sensing device on the liquid crystal panel and controls the brightness of the backlight using a sensed signal from the photo-sensing device. Thus, in the case when a transmissive LCD device is located in a bright place, the light of the backlight is made bright to improve visibility, and if the ambient light is dark, the light of the backlight is made dark to reduce power consumption. Further, the photo-sensing device of the present invention is made to be simultaneously formed with the thin film patterns, thus the separate photo-sensor is not later added to liquid crystal panel like in the related art, thereby reducing manufacturing cost. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.