Abstract:
A signal processing circuit board includes a board body, a variable electronic element, and a hole. The variable electronic element is mounted in a mounting side of the board body. The variable electronic element has an operating member to control an output outputted from the variable electronic element in a single side of the variable electronic element. The hole is provided in the board body. The operating member is positioned in the hole such that the operating member points in the other side opposite to the mounting side of the board body.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a division of application Ser. No. 09/739,236, filed on Dec. 19, 2000 now U.S. Pat. No. 6,853,409, the entire contents of which are hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a signal processing circuit board and a liquid crystal display apparatus and particularly to a signal processing circuit board and a liquid crystal display apparatus equipped with a variable resistor which has a control knob. 
     2. Description of the Related Art 
     A signal processing circuit board has been proposed which has a variable resistor (referred to as VR hereinafter) mounted thereon for adjusting the supply potential to an optimum level. For example, such signal processing circuit boards are installed in a liquid crystal panel used as the liquid crystal display (LCD) of a notebook computer or the like. 
       FIG. 1A  is a front view of a liquid crystal panel unit employing a conventional signal processing circuit board.  FIG. 1B  is a back view and  FIG. 1C  is a side view of the same.  FIG. 1D  is a cross sectional view taken along the line D—D of  FIG. 1A . 
     As shown in  FIGS. 1A to 1D , the liquid crystal panel unit  1  has a liquid crystal panel  2  of a rectangular plate shape mounted on a front side  1   a  thereof and a (front) shield sheet  3  of a frame form exposed on the outer edge of the liquid crystal panel  2 . The liquid crystal unit  1  also has a pair of signal processing circuit boards  4   a  and  4   b  (two printed circuit boards) mounted along a horizontal edge and a vertical edge respectively on a back side  1   b  thereof. The signal processing circuit board  4   a  is designed for applying a data signal to each pixel of the liquid crystal panel  2  while the signal processing circuit board  4   b  is designed for applying a horizontal scan signal to each pixel of the liquid crystal panel  2 . 
     As shown in  FIG. 1D , the shield plate  3  is made of a frame-like metal plate having an L shape in cross section. The shield plate  3  has an upright wall  3   a  thereof which extends along the outer edge of the liquid crystal panel  2  to determine an outer edge of the crystal panel unit  1 . As best shown in  FIGS. 1A and 1D , the shield plate  3  has a VR adjustable aperture  5   a  provided in a vertical side  3   k  thereof and communicated with a notch in the upright wall  3   a.  As shown in  FIGS. 1A ,  1 B, and  1 D, the signal processing circuit board  4   a  has a VR mounted extension  4   c  extending from a side thereof. A VR  6   a  of single-side controllable type is mounted on the mounting side of the VR mounting extension  4   c  (the front side  1   a  of the liquid crystal panel unit  1 ) for adjusting the supply potential to an optimum level. 
     As shown in  FIG. 1D , a light guiding plate  7  is disposed on the back side of the liquid crystal panel  2  have a layers structure. The liquid crystal panel  2  is accommodated with the light guiding plate  7  in a frame-shaped back light chassis  8 . A light reflecting sheet  7   a  is bonded to the back side of the light guiding plate  7  covering the entire surface. As the back light chassis  8  is inserted beneath the back side  3   c  of the shield plate  3 , the outer edge  2   d  of the liquid crystal panel  2  is protected with the shield plate  3 . There is provided a space for the VR  6   a  between the outer side  8   a  of the back light chassis  8  and the upright wall  3   a  of the shield plate  3 . 
     As described, the VR  6   a  of single-side controllable type is mounted with its control knob  6   b  at the upper on the mounting side of the VR mounting extension  4   c  which extends from the side of the signal processing circuit board  4   a.    
     In action, the single-side control VR  6   a  of single-side (one-side) controllable type can be adjusted to a desired setting of resistance with its control knob  6   b  turned by an adjusting tool, such as a screwdriver, inserted into the VR adjusting aperture  5   a  in the shield plate  3 . Using the VR  6   a  of single-side controllable type, the supply potential can be adjusted to an optimum level from the front side  1   a  of the liquid crystal panel unit  1 . 
     The VR adjustment has to be conducted for each AC driven crystal panel to set the driving voltage to a desired level. If the adjustment is inadequate, the panel may exhibit flickers, burns, or other visual irregularities. 
       FIG. 2A  is a front view of another liquid crystal panel unit employing a conventional signal processing circuit board.  FIG. 2B  is a back view and  FIG. 2C  is a side view of the same.  FIG. 2D  is a cross sectional view taken along the line E—E of  FIG. 2B .  FIG. 2E  is an enlarged view of a VR mounting extension. 
     As shown in  FIG. 2D , the liquid crystal panel unit  9  has a VR  6   d  of double-side controllable type, not single-side type  6   a,  mounted thereon with its control knob  6   c  exposed from the back side of the signal processing circuit board  4   a.  As shown in  FIGS. 2B and 2D , the VR aperture  5   a  provided in the shield plate  3  is replaced by a VR adjusting aperture  5   b  provided in the signal processing circuit board  4   a  on which the VR  6   d  is mounted so that the control knob  6   c  is exposed from the back side of the signal processing circuit board  4   a  (opposite to the components mounting side.). The other arrangement and functions of this model is identical to the liquid crystal panel unit  1  ( FIG. 1 ). 
     In action, the VR  6   d  of double-side controllable type can be adjusted to a desired setting of resistance with its control knob  6   c  turned by an adjusting tool, such as a screwdriver, inserted into the VR adjusting aperture  5   b  in the signal processing circuit board  4 . Using the VR  6   d  of double-side controllable type, the supply potential can be adjusted to an optimum level from the back side  9   b  of the liquid crystal panel unit  9 . 
     As the liquid crystal panel units  1  and  9  are reduced in the thickness and the peripheral marginal area, their structure holds a larger area for display hence matching the down sizing and the light weighing of notebook computers with the liquid crystal display. It is now feasible that, for example, the thickness is less than 8 mm while the effective pixel area covers substantially 90% of the entire panel surface. It is essential that since the VR  6   a  or  6   b  is controlled by visual manipulation with the signal processing circuit board  4   a  mounted to the liquid crystal panel  2 , its control knob  6   a  or  6   d  is exposed from the front side  1   a  or the back side  1   b  of the liquid crystal panel unit  1 . 
     However, the VR  6   a  of single-side controllable type which has a height of about 1 mm and is lower than the VR  6   d  of double-side controllable type of about 1.5 mm in height is suitable for minimizing the thickness but has to have the VR adjusting aperture  5   a  provided in the shield plate  3  (See  FIG. 1D ). 
     After the signal processing circuit board  4   a  is assembled with its VR mounting side (the components mounting side) to face the back side of the liquid crystal panel  2 , the VR  6   a  has to be adjusted through viewing the display side of the liquid crystal panel  2 . For exposing the control knob  6   b  of the VR  6   a  to be adjusted, the VR  6   a  is shifted to the mounting location outside the liquid crystal panel  2  or beneath the shield plate  3  before the aperture  5   a  is provided in the shield plate  3 . 
     Also, since the distance between the back side of the liquid crystal panel  2  and the upper center side of the signal processing circuit board  4   a  is smaller than 1.5 mm (which is equal to the height of the VR  6   d ), the VR  6   d  of double-side controllable type is hardly located in substantially a center region of the signal processing circuit board  4   a.  This allows the VR  6   d  of double-side controllable type to be located only beneath the shield plate  3  where there is provided a sufficient room (See  FIGS. 2B and 2D ). 
     As the shield plate  3  has the VR adjusting aperture  5   a  provided therein, the physical strength of its metal material may be declined. Also, as the VR is located at the edge of the signal processing circuit board  4   a  and the room for its installation is preserve in the limited space beneath the back side of the shield plate  3  ( FIGS. 1D and 2D ), the back light chassis  8  has to be reduced in the thickness thus declining the physical strength. This is a critical condition when the shield plate  3  of the frame-narrowed structure is minimized in the frame width to provide a generous size of the effective pixel area. 
     For avoiding the drilling of the shield plate  3  or the thinning of the back light chassis  8 , it is desirable to locate the VR beneath the back side of the liquid crystal panel  2 . There is no room (depth) for installation of the VR between the signal processing circuit board  4   a  and the light guiding plate  7  bonded on the back side of the liquid crystal panel  2 . Preserving any room for installation of the VR between the two members involves reducing the thickness of the liquid crystal panel  2 . As the reduction of the thickness may degrade the optical characteristics the liquid crystal panel  2 , it is impossible to develop any room. The VR has to stay beneath the shield plate  3 . 
     Since the control knob  6   c  of the VR  6   d  of double-side controllable type is exposed from the back side of the signal processing circuit board  4   a,  it can readily be accessed by the adjusting tool without difficulty. The VR  6   a  of single-side controllable type is accessed by the adjusting tool inserting deeply through the VR adjusting aperture  5   a  and may be injured when being groped by the tip of the adjusting tool. 
     Accordingly, as the conventional liquid crystal panel units  1  and  9  are limited in the installation of the VR, they may be declined in the physical strength and injured at the VR during the assembling process. 
     SUMMARY OF THE INVENTION 
     The present invention is accomplished in view of the above mentioned problems. Therefore, an object of the present invention is to provide a signal processing circuit board and a liquid crystal display apparatus which are hardly declined in the mechanical strength while its variable resistor is not limited to one particular location for the installation but successfully inhibited from being injured during the assembling process. 
     In order to achieve an aspect of the present invention, a signal processing circuit board, includes a board body; a variable electronic element mounted in a mounting side of the board body, the variable electronic element having an operating member to control an output outputted from the variable electronic element in a single side of the variable electronic element; and a hole provided in the board body, and wherein the operating member is positioned in the hole such that the operating member points in the other side opposite to the mounting side of the board body. 
     In this case, the variable electronic element has the operating member in only the single side of the variable electronic element. 
     Also in this case, the variable electronic element is a variable resistor. 
     Further in this case, the variable electronic element is a variable capacitor. 
     In this case, the operating member does not project from the other side. 
     Also in this case, the variable electronic element is mounted through an attachment member electronically and mechanically connected to the mounting side. 
     Further in this case, the attachment member is a flexible printed circuit connected to the mounting side to cover the hole. 
     In this case, the flexible printed circuit is soldered to the mounting side in a substantially center position of one end of the flexible printed circuit and two different locations of the other end of the flexible printed circuit respectively which are equally spaced from the center position of the same. 
     Also in this case, the variable electronic element is floated on the flexible printed circuit. 
     Further in this case, the flexible printed circuit has a flexibility to protect the variable electronic element from mechanical stress. 
     In this case, the attachment member includes a strip on which the variable electronic element is mounted and a supporting member to attach to the mounting side. 
     Also in this case, the supporting member includes one of a conductive bump and a conductive pin. 
     Further in this case, the attachment member includes a recessed block having a recess in which the variable electronic element is mounted. 
     In this case, the recessed block is formed of a single board. 
     Also in this case, the recessed block is formed of a number of layers. 
     In order to achieve another aspect of the present invention, a liquid crystal display apparatus controlling method, includes: providing a liquid crystal display screen; providing a board used for the liquid crystal display screen; providing a variable electronic element mounted in a mounting side of the board, the variable electronic element having an operating member to control an output outputted from the variable electronic element in a single side of the variable electronic element; forming a hole in the board; positioning the operating member in the hole such that the operating member points in the other side opposite to the mounting side of the board, the other side being opposite to the liquid crystal display screen; displaying an image on the liquid crystal display screen; and operating the operating member through the hole from the other side while viewing the image. 
     In this case, the operating member does not project from the other side. 
     Also in this case, the variable electronic element is mounted through a flexible printed circuit electronically and mechanically connected to the mounting side. 
     Further in this case, the flexible printed circuit covers the hole. 
     In this case, the variable electronic element is floated on the flexible printed circuit. 
     Also in this case, the flexible printed circuit has a flexibility to protect the variable electronic element from mechanical stress when the operating member is operated such that the mechanical stress is not applied to the liquid crystal display screen. 
     Further in this case, the variable electronic element is provided to overlap with the liquid crystal display screen. 
     In order to achieve still another aspect of the present invention, a liquid crystal display apparatus, includes a signal processing circuit board; and a liquid crystal display screen electronically connected to the signal processing circuit board, an image being displayed on a displaying side of the liquid crystal display screen, and wherein the signal processing circuit board includes: a board body; a variable electronic element mounted in a mounting side of the board body, the variable electronic element having an operating member to control an output outputted from the variable electronic element in a single side of the variable electronic element; and a hole provided in the board body, and wherein the operating member is positioned in the hole such that the operating member points in the other side opposite to the mounting side of the board body, and wherein the variable electronic element is provided in a opposed side opposed to the displaying side of the liquid crystal display screen such that the operating member is exposed in the opposed side through the hole. 
     In this case, the variable electronic element is mounted through an attachment member electronically and mechanically connected to the mounting side. 
     Also in this case, the attachment member is a flexible printed circuit connected to the mounting side to cover the hole. 
     Further in this case, the attachment member includes a strip on which the variable electronic element is mounted and a supporting member to attach to the mounting side. 
     In this case, the attachment member includes a recessed block having a recess in which the variable electronic element is mounted. 
     According to the present invention, a variable resistor of single-side controllable type having a control knob thereof on single side is mounted on the components mounting side of a signal processing circuit board with its control knob locating in an adjusting aperture provided in the signal processing circuit board to open at the components mounting side and simultaneously facing in a direction opposite to the components mounting side. This allows the variable resistor installed in a liquid crystal display panel of a thin, frame-narrowed structure to be mounted at a proper location without unnecessary limitation and protected from being injured during the assembling process without declining the mechanical strength. 
     A liquid crystal display apparatus of the present invention can be implemented using the signal processing circuit board described above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a front view showing a liquid crystal panel unit employing a conventional signal processing circuit board; 
         FIG. 1B  is a back view showing the liquid crystal panel unit employing the conventional signal processing circuit board; 
         FIG. 1C  is a side view showing the liquid crystal panel unit employing the conventional signal processing circuit board; 
         FIG. 1D  is a cross sectional view taken along the line D—D of  FIG. 1A ; 
         FIG. 2A  is a front view showing a liquid crystal panel unit employing another conventional signal processing circuit board; 
         FIG. 2B  is a back view showing the liquid crystal panel unit employing the another conventional signal processing circuit board; 
         FIG. 2C  is a side view showing the liquid crystal panel unit employing the another conventional signal processing circuit board; 
         FIG. 2D  is a cross sectional view taken along the line E—E of  FIG. 2A ; 
         FIG. 2E  is an enlarged view of a VR mounting region shown in  FIG. 2A ; 
         FIG. 3A  is a front view showing a liquid crystal panel unit employing a signal processing circuit board according to an embodiment of the present invention; 
         FIG. 3B  is a back view showing the liquid crystal panel unit employing the signal processing circuit board according to the embodiment of the present invention; 
         FIG. 3C  is a side view showing the liquid crystal panel unit employing the signal processing circuit board according to the embodiment of the present invention; 
         FIG. 4  is an exploded view of a liquid crystal display module including the liquid crystal panel unit show in  FIGS. 3A to 3C ; 
         FIG. 5  is a longitudinally cross sectional view showing an internal arrangement of the liquid crystal display module shown in  FIG. 4 ; 
         FIG. 6A  is a plan view showing a portion of the components mounting side of the signal processing circuit board of the embodiment on which a VR is mounted; 
         FIG. 6B  is a cross sectional view taken along the line A—A of  FIG. 6A ; 
         FIG. 6C  is a plan view showing a portion of the back side of the signal processing circuit board of the embodiment on which the VR is mounted; 
         FIG. 7A  is a cross sectional view explaining a step for mounting the VR on the signal processing circuit board shown in  FIGS. 6A to 6C ; 
         FIG. 7B  is a cross sectional view explaining another step for mounting the VR on the signal processing circuit board shown in  FIGS. 6A to 6C ; 
         FIG. 7C  is a cross sectional view explaining a further step for mounting the VR on the signal processing circuit board shown in  FIGS. 6A to 6C ; 
         FIG. 7D  is a cross sectional view explaining a still further step for mounting the VR on the signal processing circuit board shown in  FIGS. 6A to 6C ; 
         FIG. 7E  is a cross sectional view explaining a still further step for mounting the VR on the signal processing circuit board shown in  FIGS. 6A to 6C ; 
         FIG. 8A  is a plan view showing a portion of the components mounting side of the signal processing circuit board of the embodiment on which the VR is mounted with modifications; 
         FIG. 8B  is a cross sectional view taken along the line B—B of  FIG. 8A  showing one modification; 
         FIG. 8C  is a cross sectional view taken along the line B—B of  FIG. 8A  showing another modification; 
         FIG. 8D  is a plan view showing a portion of the back side of the signal processing circuit board of the embodiment on which the VR is mounted with the modifications; 
         FIG. 9A  is an overall perspective view of a recessed block showing a still further modification; 
         FIG. 9B  is an overall perspective view of another form of the recessed block showing a still further modification; 
         FIG. 9C  is a cross sectional view showing the VR mounted on the recessed block of the still further modification; 
         FIG. 9D  is a cross sectional view showing the VR mounted on the another form of the recessed block of the still further modification; 
         FIG. 10A  is a plan view showing a portion of the components mounting side of the signal processing circuit board of the embodiment on which the VR is mounted by the recessed block shown in  FIGS. 9A to 9D ; 
         FIG. 10B  is a cross sectional view taken along the line C—C of  FIG. 10A ; and 
         FIG. 10C  is a plan view showing a portion of the back side of the signal processing circuit board of the embodiment on which the VR is mounted by the recessed block shown in  FIGS. 9A to 9D . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preferred embodiments of the present invention will be described referring to the relevant drawings. 
       FIG. 3A  is a front view of a liquid crystal panel unit including a signal processing circuit board according to an embodiment of the present invention.  FIG. 3B  is a back view and  FIG. 3C  is a side view of the same. 
     As shown in  FIGS. 3A and 3B , the liquid crystal (LC) panel unit  10  has a liquid crystal panel  11  of a rectangular shape and a (front) shield plate  12  of a frame-like shape on the outer edge of the liquid crystal panel  11  to be exposed in a front side  10   a  of the liquid crystal panel unit  10 . The liquid crystal panel unit  10  includes a pair of signal processing circuit boards (two printed circuit boards of a source circuit board and a gate circuit board)  13  and  14  mounted on a back side  10   b  thereof along a horizontal side and a vertical side respectively. 
     As the liquid crystal panel unit  10  is reduced in the thickness and the peripheral marginal area, their structure holds a larger area for display hence matching the down sizing and the light weighing of a notebook computer with the liquid crystal display. Preferably, the liquid crystal panel unit  10  may be 4 to 8 mm in the thickness and its effective pixel area may be about 90% of the entire panel surface. 
     The shield plate  12  is made of a frame-like shaped metal material having an L shape in cross section. The shield plate  12  has an upright wall  12   a  thereof which extends along the outer edge of the liquid crystal panel  11  to determine an outer edge of the crystal panel unit  10 . A variable resistor (VR)  15  of single-side controllable type is mounted on a components mounting side of the signal processing circuit board  13  with its control knob exposed from the back side of the same. 
     The VR  15  is joined by a flexible printed circuit (FPC)  16  to the signal processing circuit board  13  and its control knob is exposed from the back side  10   b  of the liquid crystal panel unit  10 . The VR  15  can hence be adjusted to a desired level of resistance by an adjusting tool, such as a screwdriver, engaging and turning its control knob. 
       FIG. 4  is an exploded view of a liquid crystal module including the liquid crystal panel shown in  FIGS. 3A to 3C . As shown in  FIG. 4 , the liquid crystal module  17  consists mainly of the liquid crystal panel  10 , the shield plate  12 , and a back light unit  18 . The liquid crystal panel unit  10  is sandwiched from both sides between the shield plate  12  and the back light unit  18  and assembled together, to form the liquid crystal module  17 . 
     The paired signal processing circuit boards  13  and  14  are mounted along a long edge and a short edge respectively on the liquid crystal panel  11  of the liquid crystal panel unit  10 . A plurality of tape carrier packages (TCPs)  19  of driver integral circuits (IC) are provided to one of long sides of the signal processing circuit board  13  along the long side. Similarly, a plurality of tape carrier packages (TCPs)  20  of driver integral circuits (IC) acre provided to one of long sides of the signal processing circuit board  14  along the long side. 
     The TCP  19  and the TCP  20  join the signal processing circuit boards  13  and  14  respectively to the liquid crystal panel  11 . Accordingly, the two signal processing circuit boards  13  and  14  can be folded down onto the back side of the liquid crystal panel  11  at their respective TCPs  19  and  20  (See  FIG. 3B ). 
     The back light unit  18  includes a light guiding plate  22 , a light diffusing sheet  23 , a light reflecting sheet  29 , and a back light module  24  joined to one another to have a rectangular unit ( FIG. 5 ). A lamp (not shown) is installed in a lowermost region of the light guiding plate  22 . A lamp cable  25  extends from one end of the lowermost region which is connected at a distal end with a connector  25   a . The light guiding plate  22 , the light diffusing sheet  23 , and the light reflecting sheet  29  are bonded in layer relationship and fixedly joined at the outer edge with the back light module  24 . 
       FIG. 5  is a longitudinal cross sectional view showing an internal arrangement of the liquid crystal module  17 . As shown in  FIG. 5 , the liquid crystal module  17  has a layer arrangement where placed one over the other in an order, from the liquid crystal display screen or the front side  10   a  of the liquid crystal panel unit  10  to the signal processing circuit board  13 , are the liquid crystal panel  11  which includes four layers of a polarizing plate  26   a,  an opposite substrate  27 , a thin film transistor (TFT) substrate  28 , and another polarizing plate  26   b,  the light guiding plate  22 , the light reflecting sheet  29 , and the signal processing circuit board  13 . 
     The signal processing circuit board  13  includes the VR  15 , a variable capacitor, a resistor, a capacitor and other circuitry components which are not shown in  FIG. 5 , in addition to the driver IC, resistors, and capacitors and the like. 
     The liquid crystal module  17  is protected at the outer edge with the shield plate  12  extending over the back light mold  24 . A lamp  30  is provided along the lowermost part  22   b  of the light guiding plate  22 . The light guiding plate  22  is arranged of a tapered cross section which becomes gradually thicker from the upper end to the lower end. The back side of the light guiding plate  22  is spaced by a small gap  40  from the signal processing circuit board  13 . The small gap  40  is developed and maintained by the thickness of the back light mold  24  provided above for accepting some components. 
     The TCP  19  mounted at the uppermost of the signal processing circuit board  13  has a front end  19   a  thereof extending in an arc-shape and along the outer edge of the back light mold  24  and connected with the TFT substrate  28  of the liquid crystal panel  11 . 
       FIG. 6A  is a plan view showing a portion of the components mounting side  13   a  of the signal processing substrate  13  on which the VR  15  is mounted.  FIG. 6B  is a cross sectional view taken along the line A—A of  FIG. 6A .  FIG. 6C  is a plan view showing a portion of the back side  13   b  of the signal processing circuit board  13  on which the VR  15  is mounted. 
     As shown in  FIGS. 6A to 6C , the VR  15  is mounted at a particular location on the components mounting side  13   a  of the signal processing circuit board  13  which thus has a VR adjusting opening  31  (e.g. of a rectangular shape) provided therein for access to the VR  15 . 
     The VR adjusting opening  31  is shaped to a minimum size suited for avoiding the VR  15  from being damaged by the adjusting tool during the adjusting process and allowing its control knob  15   a  to be manipulated by the adjusting tool without difficulty while being free from the signal processing circuit board  13  (See  FIGS. 6B and 6C ). The size of the VR adjusting opening  31  may be equal to a sum of the size of the control knob  15   a  of the VR  15  and a discrepancy from of the installation area of the VR  15 . 
     The VR  15  is not directly joined to the signal processing circuit board  13  but mounted on the FPC  16 , which exhibits a level of flexibility, against the applied stress as is spaced above from the signal processing circuit board  13  ( FIG. 6B ). The control knob  15   a  of the VR  15  faces the VR adjusting opening  31  and points in the direction of the back side  13   b  of the signal processing circuit board  13  opposite to the components mounting side  13   a  ( FIGS. 6B and 6C ). 
     The FPC  16  has a rectangular shape which is greater in the size than the mounting side  15   b  facing opposite to the control knob  15   a  of the VR  15 . The VR  15  is fixedly joined at its mounting side  15   a  to substantially the center of the FPC  16 . The FPC  16  is in turn joined to the components mounting side  13   a  of the signal processing circuit board  13  so as to shut off the VR adjusting opening  31  entirely. More particularly, the FPC  16  carrying the VR  15  is soldered at its edge to the components mounting side  13   a  of the signal processing circuit board  13  by three VR terminal soldering sections  32   a,    32   b,  and  32   c  which are connected to connection terminals  15   c  of the VR  15  respectively ( FIGS. 6A and 6B ). 
     The VR terminal soldering section  32   a  is located at substantially the center of one end of the FPC  16  while the other two VR terminal solders  32   b  and  32   c  are located at two different locations of the other end of the FPC  16  respectively which are equally spaced from the center of the same. 
     As shown in  FIG. 6B , when the FPC  16  is soldered by the VR terminal solders  32   a,    32   b,  and  32   c  to the components mounting side  13   a  of the signal processing circuit board  13 , the FPC  16  is formed such that the control knob  15   a  of the VR  15  is supported so as not to project from the VR adjusting opening  31  in the direction of the back side  13   b.    
     More specifically, the FPC  16  bent to a predetermined shape by forming process holds the VR  15  in the VR adjusting opening  31  so that its control knob  15   a  is flush with the back side  13   b  of the signal processing circuit board  13 . The FPC  16  may preferably be made of a sheet material which can easily be shaped by an known forming process. 
     The function of the FPC  16  hence includes electrical and mechanical connection of the VR  15  to the signal processing circuit boards  13 , leveling the VR  15  with the signal processing circuit board  13 , and serving as a resistor mounting member, hence contributing to the minimum thickness of the liquid panel unit  10  on which the signal processing circuit board  13  is mounted and thus of the liquid crystal display. 
       FIGS. 7A to 7E  are cross sectional views explaining a procedure of mounting the VR onto the signal processing circuit board shown in  FIGS. 6A  to  6 C. Referring to  FIGS. 7A to 7C , the VR  15  is first mounted on the FPC  16  ( FIG. 7A ) with its mounting side  15   b  down ( FIG. 7B ). Then, both ends of the FPC  16  are lightly bent until they tilts downwardly at an angle ( FIG. 7C ). 
     The FPC  16  is then subjected to the forming process where its two regions on both sides of the VR  15  are curved upwardly, leaving the two ends leveled with the VR  15  ( FIG. 7D ). The formed FPC  16  is supported beneath the signal processing circuit board  13  with the control knob  15   a  of the VR  15  positioned just in the VR adjusting opening  31  and soldered at both ends to the components mounting side  13   a  of the signal processing circuit board  13 . The mounting of the FPC  16  on the signal processing circuit board  13  is now completed. 
     During the forming process of the FPC  16 , care should be taken so that the control knob  15   a  of the VR  15  mounted thereon stays in the VR adjusting opening  31  but not projects upwardly from the back side  13   b  of the signal processing circuit board  13 . 
     As described above, the FPC  16  mounted to the signal processing circuit board  13  allows the control knob  15   a  of the VR  15  to be exposed at the VR adjusting opening  31  from the back side, opposite to the display side, of the liquid crystal module  17 . The control knob  15   a  can easily be accessed and controlled by an adjusting tool, such as a screwdriver, inserting from the back side of the liquid crystal module  17  into the VR adjusting opening  31 . More particularly, the VR  15  can be adjusted to a desired level of resistance with the adjusting tool for determining the optimum supply potential while observing the display of the liquid crystal module  17 . 
     Also, the FPC  16  is selected from flexible materials of a thickness which can be bent in a short stroke for inhibiting declination of the efficiency of the mounting process and can bear a stress (of pressure and turning) during the VR adjustment while the VR  15  is of single-side controllable type. 
     The VR  15  of single side controllable type which is lower in the height is mounted on the FPC  16  and located in the VR adjusting opening  31  provided in the signal processing circuit board  13  of the liquid crystal panel  11  in the liquid crystal display. This permits the VR  15  to be accessed and controlled from the back side opposite to the components mounting side of the signal processing circuit board  13  or the back side of the liquid crystal display for adjusting the supply potential to an optimum level. 
     Also, as the VR  15  is mounted on the FPC  16 , it can be protected from being intensively stressed during the adjustment of resistance of the VR  15  by the flexibility of the FPC  16 . While the VR  15  is inhibited from being injured, the direct transmission of stress to the back light unit  18  can favorably be avoided and the performance of the liquid crystal display will be ensured without declining its image quality. 
     The VR  15  is mounted as overlapped with the liquid crystal panel  11  and its installation is not limited by the back light chassis (See  FIGS. 1D and 2D ). Since the VR  15  is enabled to sit at any location where its room or space is provided, the freedom for designing the signal processing circuit board  13  can significantly be increased. 
     The signal processing circuit board on which the VR  15  is mounted with some modifications will now be described referring to  FIGS. 8A to 8D . 
       FIG. 8A  is a plan view showing a portion of the components mounting side of the signal processing circuit board on which the VR is mounted with the some modifications.  FIG. 8B  is a cross sectional view taken along the line B—B of  FIG. 8A  showing one modification.  FIG. 8C  is a cross sectional view taken along the line B—B of  FIG. 8A  showing another modification.  FIG. 8D  is a plan view showing a portion of the back side of the signal processing circuit board. 
     As shown in  FIGS. 8A to 8D , this arrangement and function is identical to that shown in  FIGS. 6A to 6C , except that the VR  15  is mounted to the signal processing circuit board  13  by a combination of a board  33  and supporting member  34  which replace the FPC  16 . 
     The board  33  may be made of the same material as of the signal processing circuit board  13 . The board  33  on which the VR  15  is mounted at its mounting side  15   b  is joined to the components mounting side  13   a  of the signal processing circuit board  13  by the pillar or wall-like supporting member  34  which are arranged of, for example, a bump  34   a  ( FIG. 8B ) or a pin  34   b  ( FIG. 8C ) made of a conductive material. The supporting member  34  of the bump  34   a  are directly solder to or the supporting member  34  of the pin  34   b  are soldered by VR terminal solders  32   a,    32   b,  and  32   c  to the components mounting side  13   a.    
     The signal processing circuit board on which the VR  15  is mounted with further modifications will be described referring to  FIGS. 9A to 9D . 
       FIG. 9A  is an overall perspective view of a recessed block showing one modification.  FIG. 9B  is an overall perspective view of another form of the recessed block.  FIG. 9C  is a cross sectional view of the VR mounted on the recessed block.  FIG. 9   d  is a cross sectional view of the VR mounted on the another form of the recessed block. As shown in  FIGS. 9A to 9D , this arrangement and function is identical to that shown in  FIGS. 6A to 6C , except that the VR  15  is mounted on the signal processing circuit board  13  by the concave-type board  35  which replaces the FPC  16 . 
     The concave-type board  35  may be made of the same material as of the signal processing circuit board  13 . The concave-type board  35  has a (installation) concave section  35   a  provided in the center thereof for installation of the VR  15  and three vertical flutes  36  provided in both sides thereof for electrical and mechanical connection with the signal processing circuit board  13  ( FIG. 9A ). The concave section  35   a  may be replaced by a slot section  35   b  with a pair of opposite side walls eliminated ( FIG. 9B ). The number of the vertical flutes  36  is not limited to three but may be more if desired. The concave-type board  35  may be formed of a single board or a number of layers. 
     Before mounting the VR  15  on the concave-type board  35 , a conductive pattern  37  is provided on the bottom of the concave section  35   a  for connecting connection terminals  15   c  of the VR  15  to the components mounting side  13   a  of the signal processing circuit board  13  ( FIG. 9C ). The conductive pattern  37  may be provided on the back side of the concave-type board  35  as extended from the concave section  35   a  ( FIG. 9D ). 
       FIG. 10A  is a plan view showing a portion of the components mounting side of the signal processing circuit board  13  where the VR  15  is mounted by the recessed block shown in  FIGS. 9A to 9D .  FIG. 10B  is a cross sectional view taken along the line C—C of  FIG. 10A .  FIG. 10C  is a plan view showing a portion of the back side of the signal processing circuit board  13  where the VR  15  is mounted by the recessed block shown in  FIGS. 9A to 9D . 
     As shown in  FIGS. 10A to 10C , the concave-type board  35  is joined at its vertical flutes  36  by soldering to the signal processing circuit board  13 . 
     According to the embodiments, the VR  15  of single-side controllable type which is shorter in the height than the double-side controllable type and lower in price is enabled to sit on the signal processing circuit board  13  of the liquid crystal panel  11  of a liquid crystal display, such as a notebook computer, having basically a thin, frame-narrowed arrangement and can favorably be adjusted while observing the display. 
     Also, as the VR  15  is mounted by the FPC  16  to the signal processing circuit board  13 , it can be protected from being intensively stressed during the adjustment of resistance by the flexibility of the FPC  16  which also dissipates the stress to the signal processing circuit board  13 . This will minimize the injury of the VR  15  and the fracture of the FPC  16 . As the VR  15  of single-side controllable type is low in the height and its control knob  15   a  stays in the VR adjusting opening  31  provided in the signal processing circuit board  13  but not exceeding the thickness of the board ( FIG. 6B ), the installation of the VR  15  can be decreased in the overall height. 
     Since the height of the VR which is a major target to be tackled for minimizing the overall thickness and implementing the frame-narrowed structure is decreased, such tall, troubled components are eliminated and the minimizing the overall thickness and the implementing the frame-narrowed arrangement can be accelerated. The VR  15  on the signal processing circuit board  13  remains not projected outwardly of the back side of the board ( FIG. 6B ), hence preventing any event of injury by the physical collision or short-circuit by the electrical contact at the back side of the signal processing circuit board  13  during the assembling process of the liquid crystal panel unit  10  at either the manufacturer&#39;s plant or the client&#39;s workshop. 
     While being free from preparing a particularly raised VR mounting area off the shield plate  3  or at an edge region thereof so that the VR  15  does not overlap the liquid crystal panel  11 , the signal processing circuit board  13  is arranged of a simple rectangular shape without extensions thus decreasing the margin of a material and contributing to the cost down of the overall assembly. 
     This allows the liquid crystal display to be minimized in the height of components mounted on the signal processing circuit board  13  while its effective area in the overall display surface remaining wide and its structure remaining narrow in the marginal area, hence decreasing the overall thickness and the cost of production. Also, the adjustment on the VR can be manipulated from the back side of the signal processing circuit board  13  or of the liquid crystal display. As the control knob  15   a  of the VR  15  is highly visible and accessible in the VR adjusting opening  31 , its adjusting action can be improved in the efficiency. In particular, when different types or sizes of the display are flexibly manufactured on a single production line, the above mentioned advantage will be more emphasized. 
     The use of the FPC  16  is also advantageous. This permits the bump  34   a  which may hardly be controlled in the size along the vertical direction to be favorably employed under appropriate control. If the pin  34   b  is selected, any conventional manner requires three consecutive steps for mounting the VR  15  to the board  33 , mounting the pins  34   b  to the board  33 , and mounting the pins  34   b  to the signal processing circuit board  13 . Using the FPC  16 , the procedure may duly be replaced by two steps or mounting the VR  15  to the FPC  16  and mounting the FPC  16  to the signal processing circuit board  13 . 
     When the concave-type board  35  is used, its fabrication is not an easy task and requires steps of seat preparation and bonding multiple layers to form a layer structure. The FPC  16  can readily be fabricated by punching process. The FPC  16  is flexible enough as compared with the bumps  34   a,  the pins  34   b,  and the concave-type board  35  and can hardly be fractured because it absorbs a force of impact developed by the adjusting too. 
     The mounting of the component on the signal processing circuit board  13  is not limited to the VR  15  but any other similar component, such as a variable capacitor of single-side controllable type, may successfully be mounted on the signal processing circuit board  13  by the foregoing manner. 
     While the VR  15  is mounted on the signal processing circuit board  13  throughout the embodiments, it may be mounted on the signal processing circuit board  14  or another substrate (not shown) for controlling different voltages which are applied for operating the liquid crystal display. 
     As set forth above, the present invention allows the variable resistor of single-side controllable type having a control knob thereof on single side to be mounted on the components mounting side of the signal processing circuit board with its control knob locating in the adjusting aperture provided in the signal processing circuit board to open at the components mounting side and simultaneously facing in a direction opposite to the components mounting side. Accordingly, the variable resistor installed in a liquid crystal display panel of a thin, frame-narrowed structure can favorably be mounted at a proper location without unnecessary limitation and protected from being injured during the assembling process without declining the mechanical strength because the shield plate and the chassis have not openings nor notches. 
     The liquid crystal display apparatus of the present invention can be implemented using the signal processing circuit board described above.