Patent Publication Number: US-9835888-B2

Title: Connecting a liquid crystal display to a circuit board using a flexible circuit board

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is Bypass Continuation of international patent application PCT/JP2013/005683, filed: Sep. 25, 2013 designating the United States of America, the entire disclosure of which is incorporated herein by reference. Priority is claimed based on Japanese patent application JP2012-244100, filed: Nov. 6, 2012. The entire disclosure of Japanese patent application JP2012-244100 is incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present application relates to a liquid crystal display device and a method of manufacturing a liquid crystal display device. 
     BACKGROUND 
     A liquid crystal display device displays an image on a display surface by controlling transmittance and non-transmittance of backlight through a liquid crystal material sealed in a liquid crystal display. A circuit board on which a drive circuit for driving the liquid crystal display is provided is connected to the liquid crystal display via a flexible circuit board (flexible board). In the existing liquid crystal display devices it may be difficult to couple the circuit board to the liquid crystal display. Hence a liquid crystal display device is designed that can make the coupling of the circuit board to the liquid crystal display easier. 
     SUMMARY 
     In one general aspect, the instant application describes a liquid crystal display device comprising: a liquid crystal display; a circuit board including a top surface, a bottom surface, and a drive circuit for driving the liquid crystal display; and a flexible circuit board for connecting the liquid crystal display and the circuit board to each other. The flexible circuit board includes a first end connected to the liquid crystal display and a second end connected to the bottom surface of the circuit board. The flexible circuit board is configured to wrap around the circuit board, covering the top surface and the bottom surface of the circuit board. The top surface of the circuit board is fixed to the flexible circuit board. 
     The above general aspect may include one or more of the following features. For example, the flexible circuit board may be configured to cover a side surface of the circuit board. The liquid crystal display device may further include a touch panel having a top surface and a bottom surface provided to cover a display surface of the liquid crystal display. The flexible circuit board may include a first portion extending along the bottom surface of the touch panel and located between the touch panel and the circuit board, a second portion extending from the first portion and folding away from the bottom surface of the touch panel to wrap around the circuit board, and a third portion extending from the second portion and along the bottom surface of the circuit board. 
     The circuit board may be separated from the liquid crystal display by a predetermined distance. The liquid crystal display may include a TFT substrate; and a driver IC provided on the TFT substrate. The liquid crystal display device may further include a backlight unit provided on a surface located on an opposite side to a display surface of the liquid crystal display. The top surface of the circuit board may be directly fixed to the flexible circuit board with pressure-sensitive adhesive tape. 
     The top surface of the circuit board may be directly fixed to the flexible circuit board with double-sided pressure-sensitive adhesive tape. The top surface of the circuit board may be directly fixed to the flexible circuit board with a clip. The top surface of the circuit board may be fixed to the flexible circuit board with solder. 
     In another general aspect, the instant application describes a liquid crystal display device including a liquid crystal display; a circuit board including a top surface, a bottom surface, and a drive circuit for driving the liquid crystal display; a flexible circuit board for connecting the liquid crystal display and the circuit board to each other; and a touch panel provided to cover a display surface of the liquid crystal display. The flexible circuit board has a first end connected to the liquid crystal display and a second end connected to the bottom surface of the circuit board. The circuit board is fixed to the touch panel. The flexible circuit board is not located between the top surface of the circuit board and the touch panel. 
     The above general aspect may include one or more of the following features. The flexible circuit board may include a first portion extending along the bottom surface of the touch panel, a second portion extending from the first portion and folding away from the bottom surface of the touch panel, and a third portion extending from the second portion and along the bottom surface of the circuit board. 
     In another general aspect, the instant application describes a method of manufacturing a liquid crystal display device. The liquid crystal display device includes a liquid crystal display; a circuit board including a top surface, a bottom surface, and a drive circuit for driving the liquid crystal display; a flexible circuit board for connecting the liquid crystal display and the circuit board to each other; a touch panel provided to cover a display surface of the liquid crystal display; and a backlight unit provided on a surface located on an opposite side to the display surface of the liquid crystal display. The flexible circuit board has a first end connected to the liquid crystal display and a second end connected to the bottom surface of the circuit board. The method comprises steps of: folding the flexible circuit board so that a first portion of the flexible circuit board covers the top surface of the circuit board and second portion of the flexible circuit board covers the bottom surface of the circuit board; fixing the top surface of the circuit board to the flexible circuit board; and setting, after the folding step, the backlight unit on the surface located on the opposite side to the display surface of the liquid crystal display. 
     In another general aspect, the instant application describes a method of manufacturing a liquid crystal display device. The liquid crystal display device includes: a liquid crystal display; a circuit board including a top surface, a bottom surface, and a drive circuit for driving the liquid crystal display; a flexible circuit board for connecting the liquid crystal display and the circuit board to each other; a touch panel provided to cover a display surface of the liquid crystal display; and a backlight unit provided on a surface located on an opposite side to the display surface of the liquid crystal display. The flexible circuit board includes a first end connected to the liquid crystal display and a second end connected to the circuit board. The method includes steps of: fixing the circuit board to the touch panel without placing the flexible circuit board between the top surface of the circuit board and the touch panel; and setting the backlight unit on the surface located on the opposite side to the display surface of the liquid crystal display. 
     These general and specific aspects may be implemented using a system, a method, or a computer program, or any combination of systems, methods, and computer programs. Additional advantages and novel features will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following and the accompanying drawings or may be learned by production or operation of the examples. The advantages of the present teachings may be realized and attained by practice or use of various aspects of the methodologies, instrumentalities and combinations set forth in the detailed examples discussed below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an exemplary configuration of a liquid crystal display device of the present application. 
         FIG. 2  illustrates an exemplary method of manufacturing the liquid crystal display device shown in  FIG. 1 . 
         FIGS. 3-5  illustrate exemplary manufacturing processes of the liquid crystal display device shown in  FIG. 1 . 
         FIG. 6  illustrates an exemplary configuration of a liquid crystal display device without a touch panel. 
         FIG. 7  illustrates another exemplary configuration of a liquid crystal display device without a touch panel. 
         FIGS. 8-10  illustrate exemplary manufacturing steps of the liquid crystal display device including a touch panel. 
         FIG. 11  illustrates a liquid crystal display device in which a circuit board is fixed to a flexible circuit board with single-sided pressure-sensitive adhesive tape. 
         FIG. 12  illustrates a liquid crystal display device in which the circuit board is fixed to the flexible circuit board with solder. 
         FIG. 13  illustrates a liquid crystal display device in which the circuit board is fixed to the flexible circuit board with a clip. 
         FIG. 14  illustrates a sectional view of the liquid crystal display device shown in  FIG. 13 . 
         FIG. 15  illustrates another exemplary configuration of a liquid crystal display device of the present invention. 
         FIG. 16  illustrates an exemplary method of manufacturing the liquid crystal display device shown in  FIG. 15 . 
         FIGS. 17-18  illustrate a manufacturing process of the liquid crystal display device shown in  FIG. 15 . 
         FIG. 19  illustrates a liquid crystal display device in which a circuit board is fixed with single-sided pressure-sensitive adhesive tape. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, numerous specific details are set forth by way of examples in order to provide a thorough understanding of the relevant teachings. However, it should be apparent to those skilled in the art that the present teachings may be practiced without such details. In other instances, well known methods, procedures, components, and/or circuitry have been described at a relatively high-level, without detail, in order to avoid unnecessarily obscuring aspects of the present teachings. 
     The various systems and methods disclosed herein relate to a liquid crystal display device and a method of manufacturing a liquid crystal display device. 
       FIG. 1  illustrates an exemplary configuration of a liquid crystal display device  1000  of the present application. The liquid crystal display device  1000  includes a touch panel  1100 , a liquid crystal display  1200 , and a backlight unit  1300 . The touch panel  1100  is provided so as to cover a display surface of the liquid crystal display  1200 . In one implementation, the touch panel  1100  has an area larger than that of the display surface of the liquid crystal display  1200 , and protrudes from the liquid crystal display  1200 . The touch panel  1100  detects user&#39;s contact (touch operation) to the surface of the touch panel  1100 , which is performed in accordance with the display of the liquid crystal display  1200 . Based on the detection result, the touch panel  1100  generates an electrical signal and outputs the generated electrical signal to a control section (not shown) or the like of the liquid crystal display device  1000 . 
     The liquid crystal display  1200  includes polarizing plates  1201  and  1204 , color filter glass  1202 , a TFT substrate  1203 , and a driver IC  1205 . The driver IC  1205  is provided on the TFT substrate  1203 . Examples of a method of mounting the driver IC  1205  include COF (chip on film) and COG (chip on glass). COF refers to mounting of a chip of the driver IC  1205  on a thin film such as a flexible board. When COG is employed as in this implementation, a problem of disconnection may be more easily prevented and the yield may be better than the case of COF. 
     The backlight unit  1300  includes an optical sheet  1301 , a light guide plate  1302 , a reflective sheet  1303 , a light source  1304 , and a frame  1305  made of iron or aluminum. The backlight unit  1300  is provided on a surface of the liquid crystal display  1200  located on the opposite side to the display surface of the liquid crystal display  1200  on which the touch panel  1100  is provided. 
     The liquid crystal display  1200  and a circuit board  1209  including a drive circuit for driving the liquid crystal display  1200  are connected to each other via a flexible circuit board  1206 . The flexible circuit board  1206  includes a first portion  1208 , a second portion  1220 , and a third portion  1207 . The first portion  1208  extends parallel to the bottom surface of the touch panel  1100  and is located between the circuit board  1209  and the touch panel  1100 . The second portion  1220  extends from the first portion  1208  and is folded to extend away from the bottom surface of the touch panel  1100 . The third portion  1207  extends from the second portion  1220  and extends parallel to the bottom surface  1210  of circuit board  1209 . To this end, the flexible circuit board  1206  is configured to wrap around the circuit board  1209 , covering the top surface  1211  of the circuit board  1209 , the side surface  1213  of the circuit board  1209  and the bottom surface  1210  of the circuit board  1209 . The top surface  1211  of the circuit board  1209  may be directly fixed to the flexible circuit board  1206  with double-sided pressure-sensitive adhesive tape  1212 . The bottom surface  1210  of the circuit board  1209  may be connected to the third portion  1207  of the flexible circuit board  1206 . The flexible circuit board  1206  at a first end is connected to the liquid crystal display  1200  and at a second end is connected to a bottom surface  1210  of the circuit board  1209 . Next, a method of manufacturing the liquid crystal display device  1000  is described. 
       FIG. 2  illustrates an exemplary method of manufacturing the liquid crystal display device  1000  shown in  FIG. 1 .  FIGS. 3-5  illustrate exemplary manufacturing processes of the liquid crystal display device  1000  shown in  FIG. 1 . Referring to  FIG. 2 , first, the liquid crystal display  1200  is constructed (S 201 ). Next, the touch panel  1100  is coupled to the liquid crystal display  1200  (S 202 ).  FIG. 3  illustrates a state in which the touch panel  1100  is coupled to the liquid crystal display  1200 . 
     Next, the double-sided pressure-sensitive adhesive tape  1212  for fixation is attached to the circuit board  1209  of the liquid crystal display  1200  (S 203 ).  FIG. 4  illustrates a state in which the double-sided pressure-sensitive adhesive tape  1212  is attached to the circuit board  1209 . Then, as indicated by the arrows of  FIG. 4 , the flexible circuit board  1206  of the liquid crystal display  1200  is folded so that the top surface  1211  of the circuit board  1209  is opposed to the surface of the flexible circuit board  1206  (S 204 ). Next, with use of the double-sided pressure-sensitive adhesive tape  1212  attached in Step S 203 , the top surface  1211  of the circuit board  1209  is directly fixed to the flexible circuit board  1206  (S 205 ). 
     Next, the backlight unit  1300  is coupled to the liquid crystal display  1200  (S 206 ).  FIG. 5  illustrates a step of coupling the backlight unit  1300  to the liquid crystal display  1200 . The backlight unit  1300  is provided on surface of the liquid crystal display  1200  located opposite to the display surface of the liquid crystal display  1200 . In this way, manufacturing method of the liquid crystal display device  1000  can be completed. To this end, the liquid crystal display device  1000  includes the circuit board  1209  that is fixed to the flexible circuit board  1206  without using the backlight unit  1300 . 
       FIG. 6  illustrates an exemplary configuration of a liquid crystal display device  2000  without a touch panel.  FIG. 7  illustrates another exemplary configuration of a liquid crystal display device  3000  without a touch panel. In applications taking priority in downsizing (area saving), as illustrated in  FIG. 6 , the circuit board  1209  is fixed to a part of the frame  1305  of the backlight unit  1300  on the opposite side to the liquid crystal display  1200  with use of the double-sided pressure-sensitive adhesive tape  1212  or the like. In this case, the thickness is increased by the thickness of the circuit board, but the outer shape of the liquid crystal display device can be reduced. On the other hand, in applications taking priority in thinning, as illustrated in  FIG. 7 , the circuit board  1209  is fixed to a part of the frame  1305  of the backlight unit  1300 , which is protruded in the side surface direction of the liquid crystal display  1200 , with use of a screw  1213 . Therefore, the outer shape is increased on the protruded part, but the thickness of the liquid crystal display device can be reduced. 
     However, in the configuration for applications taking priority in thinning illustrated in  FIG. 7 , the position of the circuit board  1209  is determined based on the bending of the flexible circuit board  1206 , and hence it is difficult to align a screw hole  1214  of the circuit board  1209  with a screw hole  1306  of the frame  1305 . 
     When the touch panel  1100  is further provided, it is difficult to fix the circuit board  1209  to the part of the frame  1305  of the backlight unit  1300 , which is protruded in the side surface direction of the liquid crystal display  1200 , with use of the screw  1213  as illustrated in  FIG. 7 . This point is described below. 
       FIGS. 8-10  illustrate exemplary manufacturing steps of the liquid crystal display  3000  device including a touch panel  1100 . The surface of the liquid crystal display  1200  may be flat when the touch panel  1100  is attached thereto. The touch panel  1100  may be attached to the liquid crystal display device  3000  before mounting the backlight unit  1300 . Therefore, when the circuit board  1209  is fixed with use of the frame  1305  of the backlight unit  1300 , the fixing is carried out under a state in which the touch panel  1100  has been already set. However, the touch panel  1100  has an area larger than that of the display surface of the liquid crystal display  1200 , and hence, unlike  FIG. 7 , it may be impossible to perform screwing from the upward direction as shown in  FIG. 8 . Furthermore, when screwing is performed from the downward direction as shown in  FIG. 9 , the touch panel  1100  may be damaged. This is because an interval from a position of the frame  1305 , which is closest to the touch panel  1100 , to the touch panel  1100  may be as small as 1 mm or less. In addition, in this scenario, it may be difficult to bend the flexible circuit board  1206  into a shape as illustrated in  FIG. 8 . When the flexible circuit board  1206  is bent into a shape as illustrated in  FIG. 8 , in order to insert the circuit board  1209  between the flexible circuit board  1206  and the frame  1305 , it is necessary to once warp the flexible circuit board  1206  in the upward direction of the figure. However, the touch panel  1100  is present in the upward direction, and hence the flexible circuit board  1206  cannot be sufficiently warped. As shown in  FIG. 10 , the flexible circuit board  1206  also cannot be sufficiently wrapped in the downward direction. Therefore, the circuit board  1209  cannot be inserted between the flexible circuit board  1206  and the frame  1305  as shown in  FIG. 10 . Further, when the flexible circuit board  1206  is warped upward, the touch panel  1100  may be damaged. 
     As a countermeasure, in one implementation, the circuit board  1209  of the instant application may be directly fixed to the flexible circuit board  1206  with the double-sided pressure-sensitive adhesive tape  1212 . Therefore, adjustment of the position of the screw hole may be unnecessary, and the accuracy that is required for the bending shape in the manufacturing steps can be reduced. Since the screw  1213  is not used, the touch panel  1100  may not be damaged by the screw  1213  as shown in  FIGS. 8 and 9 . Furthermore, the flexible circuit board  1206  may only be required to be bent in the downward direction of the figure, thereby avoiding damage to the touch panel  1100 , which would have been caused in bending the flexible circuit board  1206  in the upward direction. 
     Although in the above-described implementation the circuit board  1209  is fixed to the flexible circuit board  1206  with the double-sided pressure-sensitive adhesive tape  1212 , the instant application is not limited thereto. For example, the circuit board  1209  may be fixed to the flexible circuit board  1206  with single-sided pressure-sensitive adhesive tape, solder, a clip, or the like. 
       FIG. 11  illustrates a liquid crystal display device  4000  in which a circuit board  1209  is fixed to a flexible circuit board  1206  with single-sided pressure-sensitive adhesive tape  1215 .  FIG. 12  illustrates a liquid crystal display device  5000  in which the circuit board  1209  is fixed to the flexible circuit board  1206  with solder  1216 .  FIG. 13  illustrates a liquid crystal display device  6000  in which the circuit board  1209  is fixed to the flexible circuit board  1206  with a clip  1207 .  FIG. 14  illustrates a sectional view of the liquid crystal display device  6000 , which is taken along the dashed-dotted line of  FIG. 13 . 
     Referring again to  FIG. 1 , the top surface  1211  of the circuit board  1209  is shown to be fixed to the flexible circuit board  1206  in the liquid crystal display device, the instant application is not limited thereto. For example, the side surface of the circuit board  1209  may be fixed to an opposed region (bent region) of the surface of the flexible circuit board  1206 . Furthermore, in order to fix the circuit board  1209  without a backlash, it is desired that the interval d of  FIG. 1  between the circuit board  1209  and the liquid crystal display  1200  be set to a desired value or less. The desired value may be determined based on the hardness of the flexible circuit board  1206 . Alternatively or additionally, the desired value may be determined so that the circuit board  1209  comes into contact with the frame  1305 . The value of d may be more than 0 mm and 1.5 mm or less. When the interval is provided, disconnection is less likely to occur as compared to the case where no interval is provided (e.g., d=0). 
       FIG. 15  illustrates another exemplary configuration of a liquid crystal display device  7000  of the present invention. The liquid crystal display device  7000  includes a touch panel  7100 , a liquid crystal display  7200 , and a backlight unit  7300 . The touch panel  7100  is a touch panel provided to cover a display surface of the liquid crystal display  7200 , and detects user&#39;s contact (touch operation) to the surface of the touch panel  7100 , which is performed in accordance with the display of the liquid crystal display  7200 . Based on the detection result, the touch panel  7100  generates an electrical signal, and outputs the generated electrical signal to a control section (not shown) or the like of the liquid crystal display device  7000 . 
     The liquid crystal display  7200  includes polarizing plates  7201  and  7204 , color filter glass  7202 , a TFT substrate  7203 , and a driver IC  7205 . The driver IC  7205  is provided on the TFT substrate  7203 . Examples of a method of mounting the driver IC include COF and COG COF refers to mounting of a chip of the driver IC on a thin film such as a flexible board. When COG is employed as in this implementation, a problem of disconnection may be more easily prevented and the yield may be better than the case of COF. 
     The backlight unit  7300  includes an optical sheet  7301 , a light guide plate  7302 , a reflective sheet  7303 , a light source  7304 , and a frame  7305  made of iron or aluminum. The backlight unit  7300  is provided on a surface of the liquid crystal display  7200  located on an opposite side to a display surface of liquid crystal display  7200 , on which the touch panel  7100  is provided. 
     The liquid crystal display  7200  and a circuit board  7209  including a drive circuit for driving the liquid crystal display  7200  are connected to each other via a flexible circuit board  7206 . In this case, a first end of the flexible circuit board  7206  is connected to the liquid crystal display  7200 , and a second end of the flexible circuit board  7206  is connected to a first surface  7210  of the circuit board  7209 . The flexible circuit board  7206  has a shape of being folded. To this end, the flexible circuit board  7206  includes a first portion  7220 , a second portion  7222 , and a third portion  7224 . The first portion  7220  extends parallel to the bottom surface of the touch panel  7100 . The second portion  7222  extends from the first portion  7220  and is folded to extend away from the bottom surface of the touch panel  7100 . The third portion  7224  extends from the second portion  7222  and extends parallel to the bottom surface  7210  of circuit board  7209 . 
     Unlike the implementation shown in  FIG. 1 , the flexible circuit board  7206  is not placed between the top surface  7211  of the circuit board  7209  and the touch panel  7100 . To this end, the top surface  7211  of the circuit board  7209  is not fixed to the flexible circuit board  7206  with double-sided pressure-sensitive adhesive tape. Instead, in  FIG. 15 , the top surface  7211  of the circuit board  7209  is directly fixed to the bottom surface of the touch panel  7100  with double-sided pressure-sensitive adhesive tape  7212 . The bottom surface  7210  of the circuit board  7209  may be connected to the third portion  7224  of the flexible circuit board  7206 . Next, a method of manufacturing the liquid crystal display device  7000  is described. 
       FIG. 16  illustrates an exemplary method of manufacturing the liquid crystal display device  7000  shown in  FIG. 15 .  FIGS. 17-18  illustrate a manufacturing process of the liquid crystal display device  7000  shown in  FIG. 15 . First, the liquid crystal display  7200  is constructed (S 1601 ). Next, the touch panel  7100  is coupled to the liquid crystal display  7200  (S 1602 ). Next, the double-sided pressure-sensitive adhesive tape  7212  for fixation is attached to the touch panel  7100  (S 1603 ). Then, the flexible circuit board  7206  of the liquid crystal display  7200  is folded so that the top surface  7211  of the circuit board  7209  is opposed to the touch panel  7100  (S 1604 ). 
       FIG. 17  illustrates a step of attaching the double-sided pressure-sensitive adhesive tape  7212  to the touch panel  7100  and folding the flexible circuit board  7206 . The flexible circuit board  7206  is folded so that the circuit board  7209  moves as indicated by the arrows to be opposed to the double-sided pressure-sensitive adhesive tape  7212 . Next, the top surface  7211  of the circuit board  7209  is directly fixed to the touch panel  7100  with the double-sided pressure-sensitive adhesive tape  7212  attached in Step S 1603  (S 1605 ).  FIG. 18  illustrates the liquid crystal display device  7000  in which the top surface  7211  of the circuit board  7209  is directly fixed to the touch panel  7100  with the double-sided pressure-sensitive adhesive tape  7212 . Next, the backlight unit  7300  is coupled to the liquid crystal display  7200  (S 1606 ). In this way, method of manufacturing the liquid crystal display device  7000  shown in  FIG. 15  is completed. 
     With the above-mentioned configuration, the circuit board  7209  on which the drive circuit for driving the liquid crystal display  7200  is provided is fixed without using the backlight unit  7300 . According to this configuration, even in the liquid crystal display device  7000  including the touch panel  7100 , the circuit board  7209  is fixed. Therefore, similar to the liquid crystal display device  1000  shown in  FIG. 1 , the liquid crystal display device  7000  can obtain such an effect that the circuit board  7209  is fixed without damaging the touch panel  7100 . 
     Referring again to  FIG. 15 , although the circuit board  7209  is fixed with the double-sided pressure-sensitive adhesive tape  7212 , the present application is not limited thereto. For example, the circuit board  7209  may be fixed with single-sided pressure-sensitive adhesive tape, solder, a clip, or the like.  FIG. 19  illustrates a liquid crystal display device  8000  in which the circuit board  7209  is fixed with single-sided pressure-sensitive adhesive tape  7215 . 
     The configuration of the liquid crystal display device provided with a touch panel, in which the circuit board is fixed without using the backlight unit, is described herein, but it is needless to say that the configuration according to the present application is applicable to a liquid crystal display device not provided with a touch panel.