Patent Publication Number: US-2013250190-A1

Title: Back light unit integrated digitizer

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Korean Patent Application No. 10-2012-0029319, filed on Mar. 22, 2012, entitled “Back Light Unit Integrated Digitizer” which is hereby incorporated by reference in its entirety into this application. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to a back light unit integrated digitizer. 
     2. Description of the Related Art 
     In accordance with the growth of computers using a digital technology, devices assisting computers have also been developed, and personal computers, portable transmitters and other personal information processors execute processing of text and graphics using a variety of input devices such as a keyboard and a mouse. 
     While the rapid advancement of an information-oriented society has widened the use of computers more and more, it is difficult to efficiently operate products using only a keyboard and a mouse currently serving as an input device. Therefore, the necessity for a device that is simple, has minimum malfunction, and is capable of easily inputting information has increased. 
     In addition, current techniques for input devices have progressed toward techniques related to high reliability, durability, innovation, designing and processing beyond the level of satisfying general functions. To this end, a digitizer has been developed as an input device capable of inputting information such as text, graphics, or the like. 
     Meanwhile, like Patent Document described in the following Citation List, the digitizer according to the prior art uses a sensing pad disposed under a liquid crystal display (LCD) as a sensor. 
     However, the digitizer according to the prior art includes the sensing pad separately from the LCD, and therefore has a thick thickness to make it difficult to slim, consumes much manufacturing costs to degrade price competitiveness, and the like. 
     [Prior Art Document] 
     [Patent Document] 
     (Patent Document 1) US2004-0223089 A1 
     SUMMARY OF THE INVENTION 
     The present invention has been made in an effort to provide a back light unit integrated digitizer capable of reducing an overall thickness and saving manufacturing costs by integrally forming the digitizer in a back light unit of a liquid crystal display. 
     According to a preferred embodiment of the present invention, there is provided a back light unit integrated digitizer, including: a cover disposed on one surface of the back light unit to cover the back light unit; and a loop coil formed on the cover. 
     The loop coil may be formed in the back light unit direction in both surfaces of the cover. 
     The loop coil may include: a first loop coil formed on one surface of the cover; and a second loop coil formed on an insulating layer disposed on one surface of the cover. 
     The first loop coil and the second loop coil may intersect vertically to each other. 
     In the back light unit, a reflector, a housing, a light guide, and a sheet material may be stacked in order and the cover may be disposed under the reflector. 
     The sheet material may include a diffusion sheet, a prism sheet, and a protective sheet. 
     The other surface of the back light unit may be provided with a LCD panel. 
     The LCD panel may include a liquid crystal module (LCM) and polarizers disposed on both sides of the LCM. 
     A touch panel may be disposed over the LCD panel. 
     The touch panel may be a capacitive type touch panel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is an exploded perspective view of a back light unit integrated digitizer according to a preferred embodiment of the present invention; 
         FIG. 2  is an exploded perspective view of a cover illustrated in  FIG. 1 ; 
         FIG. 3  is a plan view of a cover illustrated in  FIG. 1 ; 
         FIG. 4  is a block diagram of a digitizer according to a preferred embodiment of the present invention; and 
         FIG. 5  is an exploded perspective view of a back light unit integrated digitizer according to a modified example of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The objects, features and advantages of the present invention will be more clearly understood from the following detailed description of the preferred embodiments taken in conjunction with the accompanying drawings. Throughout the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant descriptions thereof are omitted. Further, in the following description, the terms “first,” “second,” “one side,” “the other side” and the like are used to differentiate a certain component from other components, but the configuration of such components should not be construed to be limited by the terms. Further, in the description of the present invention, when it is determined that the detailed description of the related art would obscure the gist of the present invention, the description thereof will be omitted. 
     Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. 
       FIG. 1  is an exploded perspective view of a back light unit integrated digitizer according to a preferred embodiment of the present invention,  FIG. 2  is an exploded perspective view of a cover illustrated in  FIG. 1 , and  FIG. 3  is a plan view of a cover illustrated in  FIG. 1 . 
     As illustrated in  FIGS. 1 to 3 , a back light unit integrated digitizer  100  according to a preferred embodiment of the present invention is configured to include a cover  120  disposed on one surface of a back light unit  110  to protect the back light unit  110  and a loop coil  130  formed on the cover  120 . 
     The back light unit  110  is disposed under a liquid crystal display (LCD) panel to supply light having uniform brightness in the LCD panel  160  direction. In detail, the back light unit  110  has a structure in which a reflector  113 , a housing  115 , a light guide  117 , and a sheet material  119  are stacked in order. In this configuration, the housing  115  serves to accurately couple and support internal components such as the light guide  117  and the sheet material  119 . Further, the light guide  117  receives light diffused from a light source using a transparent acrylic panel, and the like, to uniformly distribute light over the whole region through patterns formed on a surface thereof. In addition, the reflector  113  is coupled with the housing  115  by so as to be disposed under the light guide  117  and again reflects light emitted from the light guide  117  to the light guide  117 . Meanwhile, the sheet material  119  includes a diffusion sheet  119   a,  a prism sheet  119   b,  and a protective sheet  119   c.  In this configuration, the diffusion sheet  119   a  is disposed over the light guide  117  to scatter the light emitted from the light guide  117  in a predetermined direction and uniformly diffuse the scattered light over the overall surface of the light guide  117 . Further, the prism sheet  119   b  collects light emitted from the diffusion sheet  119   a  to increase brightness and the protective sheet  119   c  prevents a scratch from occurring on the prism sheet  119   b  and a moiré phenomenon from occurring. 
     The cover  120  is disposed under the back light unit  110  to protect the lower part of the back light unit  110  and may be formed of metal, but the preferred embodiments of the present invention is not limited thereto. Further, the cover  120  is provided with the loop coil  130  to sense an input unit  140  (a stylus pen, and the like) and the detailed description of the loop coil  130  will be described below. 
     Meanwhile, the other surface of the back light unit  110  (a surface opposite to one surface of the back light unit  110  on which the cover  120  is disposed) is provided with the LCD panel  160 . In this configuration, the LCD panel  160  includes a liquid crystal module (LCM)  163  and polarizers  165  disposed on both surfaces of the LCM  163 . In this case, two polarizers  165  disposed on both surfaces of the LCM  163  polarize the light incident from the back light unit  110  vertically to each other. 
     The loop coil  130  that is one component of the digitizer along with the input unit  140  is disposed on the cover  120 . In this configuration, the input unit  140  may be, for example, an electromagnetic induction type stylus pen and the user instructs coordinates using the input unit  140 . In detail, the input unit  140  includes a resonance circuit resonated at a specific frequency and the resonance circuit resonates with a signal of a specific frequency transmitted through the loop coil  130  to generate induced voltage. In addition, when a signal of a specific frequency transmitted through the loop coil  130  stops, the induced voltage generated by the resonance circuit generates an electromagnetic wave from a position detection coil configuring the resonance circuit. In this case, the input unit  140  transmits the electromagnetic wave generated from the coil of the resonance circuit to the loop coil  130 , such that the loop coil  130  may finally recognize coordinates. 
     Meanwhile, the loop coil  130  may be formed in the back light unit  110  direction in both surfaces of the cover  120  so as not to be exposed to the outside. Herein, the loop coil  130  may include a plurality of first loop coils  130   a  disposed in parallel in a Y-axis direction and a plurality of second loop coils  130   b  disposed in parallel in an X-axis direction (see  FIGS. 2 and 3 ). In this case, the first loop coil  130   a  and the second loop coil  130   b  may intersect vertically each other, and the first loop coil  130   a  is directly formed on one surface of the cover  120  and the second loop coil  130   b  may be directly formed on an insulating layer  131  disposed on one surface thereof. As described above, the loop coil  130  may be directly formed on the cover  120  of the back light unit  110  to integrally form the digitizer in the back light unit  110 , thereby reducing the overall thickness to implement slimness and saving the manufacturing costs to secure price competitiveness. 
     Further,  FIG. 4  is a block diagram of a digitizer according to a preferred embodiment of the present invention and the digitizer will be described in more detail with reference to  FIG. 4 . As illustrated in  FIG. 4 , the plurality of first loop coils  130   a  and the plurality of second loop coils  130   b  are connected with a selection circuit  141  that selects any loop coil  130 . Here, the selection circuit  141  is connected with a transmitting and receiving conversion circuit  142 . A receiving terminal R of the transmitting and receiving conversion circuit  142  is connected to an amplifier  143 , the amplifier  143  is connected to a detection circuit  144 , the detection circuit  144  is connected to a sample and hold circuit  146  through a low-pass filter  145 . In addition, the sample and hold circuit  146  is connected to an analog/digital conversion circuit  147  and the analog/digital conversion circuit  147  is connected to a central processing unit (CPU)  148 . In this case, the CPU  148  supplies a control signal to the selection circuit  141 , the sample and hold circuit  146 , the analog/digital conversion circuit  147 , and the transmitting and receiving conversion circuit  142 , respectively. 
     Further, the digitizer includes an oscillator  150  that generates an AC signal of a frequency and a current driver  151  that converts an AC signal into current. Herein, the current driver  151  is connected to a transmitting terminal T of the transmitting and receiving conversion circuit  142 . Therefore, when a contact of the transmitting and receiving conversion circuit  142  is switched to the transmitting side by the control signal supplied from the CPU  148 , a magnetic field is generated from the loop coil  130 . 
     When the transmitting and receiving conversion circuit  142  is connected to the transmitting terminal T, the resonance circuit embedded in the input unit  140  is resonates to generate the induced voltage as the input unit  140  approaches the loop coil  130 . Next, when the terminal of the transmitting and receiving conversion circuit  142  is switched to the receiving terminal R according to the control signal supplied from the CPU  148 , the magnetic field is not supplied to the input unit  140  from the loop coil  130  and the magnetic field is generated from a position detection coil embedded in the input unit  140 . In this case, the loop coil  130  detects the magnetic field generated from the input unit  140 . In detail, the coordinates instructed by the input unit  140  may be detected from the position of the loop coil  130  in which the magnetic field generated from the input unit  140  is strongest detected, among the loop coils  130  selected by the selection circuit  141 . 
     However, the foregoing digitizer is only by way of example, and therefore the preferred embodiment of the present invention is not limited thereto, but all the types of electromagnetic induction type known to those skilled in the art may be applied. 
     Meanwhile,  FIG. 5  is an exploded perspective view of a back light unit integrated digitizer according to a modified example of the present invention. As illustrated in  FIG. 5 , a back light unit integrated digitizer  200  according to the modified example of the preferred embodiment of the present invention may include a touch panel  170  disposed over the LCD panel  160 . Herein, the type of the touch panel  170  is not particularly limited, but may be a capacitive type touch panel, such as a self capacitive type touch panel, a mutual capacitive type touch panel, and the like. When the capacitive type touch panel is touched by a user, the capacitive type touch panel measures variations in capacitance to recognize touched coordinates. As such, the touch panel  170  is disposed over the LCD panel  160 , such that the modified example of the preferred embodiment of the present invention may use the touch screen function along with the digitizer function. 
     According to the preferred embodiments of the present invention, the digitizer can be integrally formed in the backlight unit of the liquid crystal display, thereby reducing the overall thickness to implement the slimness and saving the manufacturing costs to secure the price competitiveness. 
     According to the preferred embodiments of the present invention, the touch panel can be disposed over the liquid crystal display, thereby using the function of the touch screen while using the function of the digitizer. 
     Although the embodiments of the present invention have been disclosed for illustrative purposes, it will be appreciated that the present invention is not limited thereto, and those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention. 
     Accordingly, any and all modifications, variations or equivalent arrangements should be considered to be within the scope of the invention, and the detailed scope of the invention will be disclosed by the accompanying claims.