Abstract:
A mold structure has a first mold, a second mold relatively connectable to and disconnectable from the first mold, a heater on at least one of the first and second molds, a transfer member on at least one of the first and second molds, that is relatively movable and separable from the at least one of the first and second molds on which the transfer member is disposed, a transfer surface formed on the transfer member that is placed in contact with a resin sheet fed between the first and second molds to perform transfer molding onto the resin sheet, and a moving mechanism that moves the at least one of the first and second molds on which the transfer member is disposed and the transfer member relative to each other.

Description:
BACKGROUND 
       [0001]    1. Field 
         [0002]    The present invention relates to a mold structure, a transfer molding apparatus, and a transfer molding method. 
         [0003]    2. Related Art 
         [0004]    Transfer molding apparatuses known in the art heat and pressurize a resin film to transfer a pattern of minute protrusions and recesses from a transfer plate onto the resin film (refer to, for example, Patent Literature 1). 
         [0005]    Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2005-310286 
       SUMMARY 
       [0006]    However, such a transfer molding apparatus known in the art includes a transfer plate integrated in a mold. When the transfer plate needs replacement due to damage for example, the replacement work is allowed only within the mold that can be open and closed. If the replacement is performed during the molding process, the mold at high temperature may burn the worker. The workability in replacing the transfer plate is thus low. 
         [0007]    With the transfer plate being integrated with the mold, the entire structure needs to be heated and cooled. The efficiency of heat exchange is low. 
         [0008]    One or more embodiments of the present invention provides a structure that allows easy and quick replacement of a transfer member and improves the efficiency of heat exchange. 
         [0009]    One or more embodiments of the present invention provides a mold structure including a first mold, a second mold relatively connectable to and disconnectable from the first mold, a heater on at least one of the molds, a transfer member on at least one of the molds, and a mechanism. The transfer member is relatively movable and separable from the at least one mold. The transfer member has a transfer surface that is placed in contact with a resin sheet fed between the molds to perform transfer molding onto the resin sheet. The mechanism is configured to move the mold and the transfer member relative to each other. 
         [0010]    This structure allows only the transfer member that undergoes micro processing to move relatively and separate from the mold, and thus allows easy replacement of the transfer member at a position to which the transfer member has been moved and separated from the mold. 
         [0011]    One or more embodiments of the present invention provides a transfer molding apparatus including the mold structure. 
         [0012]    According to one or more embodiments of the present invention, the transfer member further includes a cooling unit configured to cool the transfer member that is maintained in contact with the resin sheet and has been moved and separated from the mold. 
         [0013]    This structure allows transfer molding from the transfer surface of the transfer member to the resin sheet, moves and separates the transfer member from the mold, and cools the resin sheet via the transfer member with the cooling unit. This enables efficient cooling in a short period of time while preventing the resin sheet from being affected by heat from the molds. 
         [0014]    According to one or more embodiments of the present invention, the cooling unit is located in a non-transfer area at least when transfer molding is not being performed. 
         [0015]    This structure prevents the cooling unit and the molds from thermally affecting each other. In particular, the molds are not cooled by the cooling unit when transfer molding is not being performed. This allows the subsequent transfer molding to start smoothly. 
         [0016]    According to one or more embodiments of the present invention, the cooling unit may include an intake unit configured to supply air to a surface of the transfer member opposite to the transfer surface of the transfer member moved and separated from the mold. 
         [0017]    This structure allows the resin sheet to be cooled with a simple mechanism of supplying air to the transfer member. The transfer member is separate from the mold. Thus, the molds are not cooled with air supplied from the intake unit. This allows the subsequent transfer molding to start smoothly as compared with the mold structure that is cooled entirely. 
         [0018]    According to one or more embodiments of the present invention, the cooling unit may include a cooling member configured to come in contact with a surface of the transfer member opposite to the transfer surface of the transfer member moved and separated from the mold. 
         [0019]    This structure more efficiently cools the resin sheet with the cooling member placed in contact with the transfer member. The cooling member may be water-cooling, or may use other cooling methods. 
         [0020]    According to one or more embodiments of the present invention, the cooling member has a temperature not more than a glass-transition temperature. 
         [0021]    According to one or more embodiments of the present invention, the cooling member has one surface coming in contact with the surface of the transfer member opposite to the transfer surface, and the other surface having a heat insulator thereon. 
         [0022]    In this structure, the heat insulator prevents the cooling member from absorbing heat from parts other than the resin sheet. This structure thus effectively cools the resin sheet via the transfer member. This shortens the time taken for the cooling process of the resin sheet, and thus shortens the cycle time for the transfer molding. 
         [0023]    According to one or more embodiments of the present invention, the mold located opposite to the cooling unit across the resin film includes a heater, and a heat insulator arranged between the resin film and the heater. 
         [0024]    In this structure, the heat insulator reduces the amount of heat released from the molds to the cooling member. More specifically, each mold is prevented from being cooled more than necessary, whether or not the cooling member is arranged. This allows the subsequent transfer molding to start smoothly. 
         [0025]    According to one or more embodiments of the present invention, the cooling member is movable in a direction intersecting with a direction in which the molds are connected and disconnected. 
         [0026]    This structure allows the cooling member to move to a retracted position so that the cooling member is prevented from cooling the molds when the resin sheet is not cooled. 
         [0027]    According to one or more embodiments of the present invention, the transfer member includes transfer members on both sides of the resin sheet in a manner relatively movable and separable from the respective molds, and the cooling unit includes two members each configured to cool a surface of the transfer member opposite to the transfer surface of the transfer member moved and separated from the mold, and the molds have substantially the same temperature. 
         [0028]    This structure allows uniform cooling of the two surfaces of the resin sheet, and thus allows the resin sheet to undergo curing in an appropriate state without uneven heat deformation of the resin sheet due to cooling. 
         [0029]    According to one or more embodiments of the present invention, at least one of the upper mold and the lower mold is reciprocable in a direction intersecting with a direction in which the molds are connected and disconnected. 
         [0030]    This structure allows cooling of the resin sheet or replacement of the transfer member to be performed at a position where the resin sheet or the transfer member has been moved laterally, and improves the workability. 
         [0031]    According to one or more embodiments of the present invention, the cooling unit includes a member configured to cool a surface of the transfer member opposite to the transfer surface, and the mold located where cooling is provided by the cooling unit is configured to have a higher temperature than the opposing mold. 
         [0032]    This structure allows the transportation line for the resin sheet to be installed near the mold at a lower temperature. This allows the mold structure to be compact. 
         [0033]    One or more embodiments of the present invention provides a transfer molding method including placing a resin sheet between a first mold and a second mold facing each other, supporting the resin sheet between the molds with at least one surface of the resin sheet being in contact with a transfer surface of a transfer member, performing transfer molding on the resin sheet by heating at least one of the molds, releasing the molds and moving and separating the transfer member from the mold, and cooling the transfer member moved and separated from the mold. 
         [0034]    According to one or more embodiments of the present invention, the cooling step includes supplying air to a surface of the transfer member opposite to the transfer surface. 
         [0035]    According to one or more embodiments of the present invention, the cooling step includes placing the cooling member in contact with the surface of the transfer member opposite to the transfer surface. 
         [0036]    One or more embodiments of the present invention allows the transfer member to be moved and separated from the mold, and thus allows easy replacement of the transfer member. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0037]      FIG. 1  is a schematic front view of a light guide plate manufacturing system according to a first embodiment. 
           [0038]      FIG. 2  is a schematic partially exploded perspective view of a transfer molding apparatus shown in  FIG. 1 . 
           [0039]      FIG. 3(   a ) is a partial plan view of a transfer plate for an upper mold shown in  FIG. 2 ,  FIG. 3(   b ) is a schematic partial cross-sectional view of the mold shown in  FIG. 2 , and  FIG. 3(   c ) is a partially enlarged view of  FIG. 3(   b ). 
           [0040]      FIG. 4(   a ) is a diagram illustrating the relationship between semifinished plates and a first cutting tool and a second cutting tool, and  FIGS. 4(   b ) and  4 ( c ) are diagrams illustrating the relationship between the semifinished plates and the first cutting tool. 
           [0041]      FIG. 5(   a ) is a photograph showing the illumination state of a light guide plate according to the first embodiment,  FIG. 5(   b ) is a photograph showing the illumination state of a conventional light guide plate, and  FIG. 5(   c ) is a graph showing the amount of light transmission in the states shown in  FIGS. 5(   a ) and  5 ( b ). 
           [0042]      FIG. 6  is a schematic perspective view of a light guide plate manufacturing system according to a second embodiment. 
           [0043]    FIGS.  7 A(a)- 7 A(f) are diagrams illustrating the operation of each plate of the transfer molding apparatus shown in  FIG. 6 . 
           [0044]    FIG.  7 B(a) is a graph showing changes in the elastic modulus of a resin sheet  25  as the temperature of the resin sheet changes, and FIG.  7 B(b) is a graph showing changes in the residual stress of the resin sheet as the temperature of the resin sheet changes. 
           [0045]      FIG. 8  is a graph showing the relationship between the temperature and the applied pressure in the molds of the transfer molding apparatus shown in  FIG. 6 . 
           [0046]      FIGS. 9(   a ) to  9 ( d ) are diagrams illustrating the operation of each plate of the transfer molding apparatus according to a third embodiment. 
           [0047]      FIGS. 10(   a ) to  10 ( c ) are diagrams illustrating the operation of each plate of the transfer molding apparatus according to a third embodiment. 
           [0048]    FIGS.  11 A(a) to  11 A(d) are schematic views illustrating a method for forming a thick portion of a resin sheet according to another embodiment. 
           [0049]    FIGS.  11 B(a) and  11 B(b) are schematic views illustrating a method for forming a thick portion of a resin sheet according to another embodiment. 
           [0050]    FIGS.  11 C(a) and  11 C(b) are schematic views illustrating a method for forming a thick portion of a resin sheet according to another embodiment. 
           [0051]    FIGS.  11 D(a)- 11 D(d) are schematic partial cross-sectional views of a transfer plate and a resin sheet according to another embodiment. 
           [0052]      FIG. 11E  is a cross-sectional view of a liquid crystal display including the light guide plate according to the first embodiment. 
           [0053]      FIG. 11F  is a perspective view of a surface light source device including a light guide plate according to another embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0054]    Embodiments of the present invention will now be described with reference to the accompanying drawings. In embodiments of the invention, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to one of ordinary skill in the art that the invention may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid obscuring the invention. The terms indicating specific directions or positions used herein (e.g., the terms including upper, lower, side, and edge) for easy understanding of the invention with reference to the drawings do not limit the technical scope of the invention. The description herein is merely exemplary in nature, and is not intended to limit the invention, its applications, or uses. 
       First Embodiment 
     Configuration 
       [0055]      FIG. 1  is a schematic view of a light guide plate manufacturing system according to a first embodiment. The light guide plate manufacturing system includes a material feeder  1 , a transfer molding apparatus  2 , a film applicator  3 , a cutter  4 , and a shaping apparatus  5 . 
         [0056]    The material feeder  1  rewinds a resin sheet  25  from a main roller  6  and feeds the sheet to the transfer molding apparatus  2 . The resin sheet  25  is transported by a plurality of rollers  7  arranged midway to the transfer molding apparatus  2 . Immediately after passing the second one of the rollers  7 , a protective sheet bonded to the resin sheet  25  is separated and wound by a winding roller  8 . The resin sheet  25  is made of polycarbonate (with a melting point of about 240° C. and a glass-transition temperature of about 150° C.). 
         [0057]    As shown in  FIG. 2 , the transfer molding apparatus  2  includes a lower mold  9  and an upper mold  10 . The lower mold  9  includes a lower mold support  11 , on the upper surface of which a lower mold intermediate plate  12 , a lower mold heat insulating plate  13 , and a lower mold transfer plate  14  are arranged in this order. 
         [0058]    The lower mold support  11  is a stainless steel (SUS) plate that is rectangular as viewed from above. The lower mold support  11  has a plurality of through-holes extending across its both sides, through which heaters  15  and thermocouples (not shown) are arranged. When energized, the heaters  15  can heat the lower mold support  11 , which then eventually heats the lower mold transfer plate  14  to an intended temperature via the lower mold intermediate plate  12  and the lower mold heat insulating plate  13 . In the first embodiment, the temperature to which the lower mold support  11  is heated by the energized heaters  15  is regulated to about 180° C. 
         [0059]    Like the lower mold support  11 , the lower mold intermediate plate  12  is a stainless steel (SUS) plate that is rectangular as viewed from above. 
         [0060]    The lower mold heat insulating plate  13  includes a plurality of heat insulating sheets  13   a  that are laminated together ( FIG. 2  shows the sheets as vertically separate from each other). The heat insulating sheets  13   a  are made of resin material such as polyimide. The degree of heat insulation may be adjusted by changing the number of heat insulating sheets. In the first embodiment, the lower mold heat insulating plate  13  includes five heat insulating sheets to allow the lower mold transfer plate  14  to be heated to about 150° C. but the lower mold support  11  to be heated to about 180° C. This prevents the resin sheet  25  from deforming under heat from the lower mold support  11 . This structure thus allows the transportation line for the resin sheet  25  to be installed near the lower mold  9 , and eliminates the need to increase the distance between the molds when the molds are released, and thus downsizes the transfer molding apparatus  2 . When the molds are closed to heat the resin sheet  25 , the lower mold heat insulating plate  13  further prevents heat from the upper mold  10  from escaping toward the lower mold. The lower mold heat insulating plate  13  further prevents the lower mold support  11  from being cooled when the resin sheet  25  is cooled. 
         [0061]    The lower mold transfer plate  14  is a nickel-chromium alloy plate that is rectangular as viewed from above. The lower mold transfer plate  14  has an upper surface functioning as a transfer surface, which has a plurality of hemispherical recesses with a depth in the order of submicrometers at predetermined intervals in X-direction and Y-direction. This sheet can form a plurality of hemispherical protrusions on the lower surface of the resin sheet  25 , onto which the transfer is to be performed. The surface with such protrusions serves as a reflecting surface that reflects light emitted from a light source toward the upper surface to allow the light to be emitted from the upper surface. The recesses may not be hemispherical but may be in other shapes. For example, the recesses may be conical. The transfer surface may not have the recesses but may have protrusions. 
         [0062]    The lower mold  9  is movable on a horizontal plane in X-direction and Y-direction when driven by, for example, a servo motor (not shown). The amount of movement of the lower mold  9  is detected by a micrometer  16 , and is used to finely adjust the positions of the lower mold  9  in X-direction and Y-direction. The lower mold may be moved manually. 
         [0063]    The upper mold  10  includes an upper mold support  17 , on the lower surface of which an upper mold intermediate plate  18 , an upper mold heat insulating plate  19 , and a retainer plate  21  retaining an upper mold transfer plate  20  are arranged in this order. 
         [0064]    Like the lower mold support  11 , the upper mold support  17  is a stainless steel (SUS) plate that is rectangular as viewed from above. The upper mold support  17  has a plurality of through-holes extending across its both sides, through which heaters  22  and thermocouples (not shown) are placed. When energized, the heaters  22  can heat the upper mold support  17  to about 280° C. 
         [0065]    Like the upper mold support  17 , the upper mold intermediate plate  18  is a stainless steel (SUS) plate that is rectangular as viewed from above. 
         [0066]    Like the lower mold heat insulating plate  13 , the upper mold heat insulating plate  19  includes a plurality of heat insulating sheets  19   a  that are laminated together. The heat insulating sheets  19   a  are made of resin material such as polyimide. The upper mold heat insulating plate  19  includes two heat insulating sheets. This structure allows the upper mold transfer plate  20  to be heated to about 240° C. When supported between the upper mold  10  and the lower mold  9 , the resin sheet  25  can melt sufficiently. 
         [0067]    Like the lower mold transfer plate  14 , the upper mold transfer plate  20  is a nickel-chromium-alloy plate that is rectangular as viewed from above. As shown in  FIGS. 3(   a ) to  3 ( c ), the upper mold transfer plate  20  has a recess  23  extending in the width direction in its lower surface. As shown in  FIG. 3(   c ), the recess  23  is defined by a perpendicular surface  23   a , a bottom surface  23   b , an inclined surface  23   c , and both end faces (not shown). The inclined surface  23   c  includes a plurality of arc-shaped areas  24 , which are aligned in the width direction. Each arc-shaped area  24  includes a plurality of protrusions (not shown), which are arranged circumferentially. Each protrusion has a substantially triangular cross section and extends radially. 
         [0068]    The recess  23  receives a molten portion of the resin sheet  25  and forms a thick portion  26 . Examples of the resin sheet  25  may range from an extremely thin film and a film with a thickness of 0.2 to 0.3 mm used in the first embodiment to a still thicker film. The thick portion  26  has a height in the order of submillimeters. In the first embodiment, the thick portion  26  has a height of 0.2 mm. The protrusions on the inclined surface have a height (surface roughness) in the order of submicrometers. In the first embodiment, the protrusions have a height of 0.2 μm. The area including such protrusions serves as a transfer surface, which bends light from a plurality of light sources arranged on the end face near the thick portion  26  to reduce leaking of the light from the inclined surface. 
         [0069]    The upper mold transfer plate  20  has a plurality of grooves  27  on its lower surface. The grooves  27  communicate with the recess  23  and extend to the side of the upper mold transfer plate  20 . According to one or more embodiments of the present invention, each groove  27  extends in a direction (X-direction) perpendicular to the width direction in which the recess  23  extends (Y-direction). This minimizes the length of the groove  27 . Each groove  27  is located between the adjacent arc-shaped areas  24 , because the molten resin flows most slowly between the adjacent arc-shaped areas  24  and thus bubbles easily remain there. This structure effectively removes bubbles from the recess  23 . Each groove  27  only needs to have a depth of not less than the depth of the recess  23 . In the first embodiment, each groove  27  is as deep as the recess  23 . Each groove  27  has a width to minimize the overflow of the molten resin (resin sheet  25 ) from the recess  23  and also to prevent bubbles from remaining in the recess  23 . 
         [0070]    The grooves  27  communicating with the recess  23  and extending to the outside are located between the adjacent arc-shaped areas  24 . Such grooves  27  efficiently guide air in the recess  23  toward the outside when the molten resin flows into the recess  23 . The resin flowing into the recess  23  also partially flows into the grooves  27 . The grooves  27  have a depth not less than the depth of the recess  23  and thus prevent the air from remaining in the area connecting the recess  23  and the grooves  27  (if the grooves  27  have a smaller depth than the recess  23 , the grooves  27  and the recess  23  may form steps between them, where air may be trapped). This structure prevents air from remaining in the recess  23 , and prevents voids from forming in the thick portion  26 . Although a little air may remain in the recess  23 , such air would not cause resin burning. Additionally, a pressure may be applied to eliminate such air in the molten resin and prevent the air from forming voids. 
         [0071]    As shown in  FIG. 2 , the retainer plate  21  is a rectangular stainless steel (SUS) frame with an opening  28  formed in its center. The retainer plate  21  retains the upper mold transfer plate  20  placed on its lower surface and allows the upper mold transfer plate  20  to be exposed upward through the opening  28 . The upper surface of the upper mold transfer plate  20  exposed through the opening is irradiated with soft X-rays by a soft X-ray irradiation unit  29 . The irradiation removes static electricity from the resin sheet  25  to prevent the surrounding dust or other matter from being attracted to the resin sheet  25  by electrostatic attraction. The retainer plate  21  has rods  30  connected to its two sides, which are driven by, for example, a cylinder (not shown) to raise or lower the retainer plate  21  independently of the operation of raising and lowering the entire upper mold. 
         [0072]    The entire upper mold is raised or lowered by a press  31  arranged on the upper surface of the upper mold-retainer plate  17 . The press  31  is supplied with air or the air is discharged from the press  31  by an air supply  32  to raise or lower the rods  30  (not shown) and to raise or lower the entire upper mold with the upper mold support  17 . 
         [0073]    The resin sheet  25  fed by the material feeder  1  is transported between the upper mold  10  and the lower mold  9 . The transportation line for the resin sheet  25  includes support rollers  33 , which support the lower surface of the resin sheet  25 , and positioning grippers  34 , which each grip the resin sheet  25  from above and below, in this order at positions near the molds toward the entry side and the exit side of the molds. The support rollers  33  and the positioning grippers  34  can be raised and lowered. The transportation line further includes a transporting gripper  35  downstream. The transporting gripper  35  also grips the resin sheet  25  from above and below like the positioning grippers  34 . The transporting gripper  35  reciprocates along the transportation line when driven by a driver (not shown). To transport the resin sheet  25 , the positioning gripper  34  is released, and the resin sheet  25  gripped by the transporting gripper  35  is moved downstream on the transportation line. The operations of the support rollers  33  and these grippers will be described below. 
         [0074]    An intake duct  36  is arranged above at a position upstream from the molds, and an exhaust duct  37  is arranged above at a downstream position. The intake duct  36  blows out the air supplied from, for example, a compressor (not shown). The air is blown to the resin sheet  25  located between the upper mold  10  and the lower mold  9  obliquely from above. The exhaust duct  37 , which is sucked by, for example, a compressor (not shown), sucks the air blown to the resin sheet  25  from the intake duct  36 . The air supplied from the intake duct  36  is clean, and the flow of air from the intake duct  36  to the exhaust duct  37  not only cools the resin sheet  25  but also serves as a barrier to prevent dust or other matter from adhering to the surface of the resin sheet  25 . As described above, the irradiation with soft X-rays has removed static electricity from the resin sheet  25 , and thus prevents dust from being attracted to the resin sheet  25  by electrostatic attraction. 
         [0075]    As shown in  FIG. 1 , application rollers  38 , which come in contact with the upper and lower surfaces of the resin sheet  25 , are arranged upstream from the molds. The application rollers  38  rotate to transport the resin sheet  25  while removing dust or other matter adhering to each surface of the resin sheet  25 . 
         [0076]    The film applicator  3  applies a protective film  39  on each of the upper and lower surfaces of the resin sheet  25  that has undergone transfer molding. The protective film  39  protects the resin sheet  25  from damage when colliding with other parts or from dust adhering to the surface of the resin sheet  25  and causing failures. 
         [0077]    The cutter  4  cuts the resin sheet  25  that has undergone transfer molding into rectangular portions. The peripheral four sides of the rectangular portions of the resin sheet  25  cut by the cutter  4  are removed by a stamping device (not shown) to form semifinished plates  46 . The resulting semifinished plates  46  each include a thick portion  26 , and a cutting margin on its end face opposite to the thick portion  26 . 
         [0078]    The shaping apparatus  5  includes a cutting member  41  for cutting both ends of each semifinished plate  46  (its thick portion  26  and its side opposite to the thick portion  26 ). The cutting member  41  includes a first cutting tool  48   a  and a second cutting tool  48   b  as shown in  FIG. 4(   a ). The cutting tools  48   a  and  48   b  rotate when driven by a driver (not shown). The first cutting tool  48   a  is cylindrical, and includes cutting blades  49   a  arranged on its outer circumferential surface at positions symmetric to each other with respect to a point about the rotation axis. The first cutting tool  48   a  is used for rough finishing. The second cutting tool  48   b  is disk-shaped, and includes cutouts at two symmetric positions on its outer circumference, and includes cutting blades  49   b  extending radially on its front surface. The second cutting tool  48   b  is used for mirror finishing. A specific method for cutting with the cutting member  41  will be described later. 
         [0079]    Operation 
         [0080]    The operation of the light guide plate manufacturing system with the above structure will now be described. 
         [0081]    Preparation Process 
         [0082]    The upper mold  10  is raised to open the molds, and the distal end of the resin sheet  25  fed from the material feeder  1  is gripped by the transporting gripper  35 . The transporting gripper  35  is moved, and then the resin sheet  25  is gripped by the positioning gripper  34  to locate the resin sheet  25  within an area where the upper mold  10  and the lower mold  9  face each other (transporting process). 
         [0083]    The molds are preheated by energizing the heaters  15 . With the heat insulating plate incorporated in each of the upper mold  10  and the lower mold  9  as described above, the upper mold transfer plate  20  in the upper mold  10  is heated to about 240° C., whereas the lower mold transfer plate  14  in the lower mold  9  is heated to about 150° C. For the lower mold  9  located near the resin sheet  25 , the temperature of the upper surface is regulated substantially to the glass-transition temperature. This prevents failures of the resin sheet  25 , or prevents the resin sheet  25  from bending downward under heat to come in contact with the lower mold transfer plate  14  (preheating process). 
         [0084]    Transfer Molding Process 
         [0085]    The support roller  33  and the positioning gripper  34  are lowered to place the resin sheet  25  onto the lower mold transfer plate  14  of the lower mold  9 . The press  31  is driven to lower the upper mold  10  so that the transfer surface of the upper mold transfer plate  20  comes in contact with the resin sheet  25 . In this state, the press  31  applies a small pressure so that the resin sheet  25  is loosely supported between the upper and lower molds. In this state, the resin sheet  25  is heated to remove water content at its surface portion (preheating process). 
         [0086]    When a predetermined time (a first set time) elapses from the start of the preheating process, the press  31  increases its applied pressure. As described above, the resin sheet  25  is made of polycarbonate (with a melting point of about 250° C. and a glass-transition temperature of about 150° C.). The upper mold transfer plate  20  has been heated to 240° C., and thus can heat the resin sheet  25  to a temperature exceeding its melting point. As a result, the resin sheet  25  is molten. Although the lower mold transfer plate  14  in the lower mold  9  has been heated to 180° C., the lower mold heat insulating plate  13  prevents heat from escaping from the lower mold. Thus, the entire area of the resin sheet  25  supported between the molds is heated to a temperature exceeding the melting point, and the resin sheet  25  is molten (heating and pressurizing process). 
         [0087]    The resin sheet  25  receives a pressure from the upper mold  10 , which is applied by the press  31 . This causes a portion of the resin sheet  25  supported between the molds to be thin, and causes a part of the resin sheet  25  (its upper surface part) to flow into the recess  23  formed in the upper mold transfer plate  20 . When the molten resin flows into the recess  23 , the air in the recess  23  flows along the grooves  27  and is removed outside. The recess  23  is completely filled with the molten resin, which partially flows into the grooves  27 . The grooves  27  are as deep as or deeper than the recess  23  (as deep as the recess  23  in the first embodiment). In this case, the air is smoothly removed outside without remaining in the recess  23 . The air is not compressed in the recess  23 , and thus would not cause burning. If a small amount of air remains in the recess  23 , a sufficient pressure is applied to eliminate such air and prevent voids from forming in the molten resin. 
         [0088]    When a predetermined time (a second set time) elapses from the start of the heating and pressurizing process, the upper mold  10  is raised. In this state, the upper mold transfer plate  20  remains in contact with the resin sheet  25  as the cylinder is driven. Air is then supplied through the intake duct  36  onto the upper mold transfer plate  20 . The heated upper mold support  17  is located away from the resin sheet  25 , and the air is blown onto the upper mold transfer plate  20  from the intake duct  36 . In this case, the resin sheet  25  is cooled only with the upper mold transfer plate  20 . The resin sheet  25  is cooled efficiently in a short time without being affected by heat from the upper mold support  17 . More specifically, the resin sheet  25  can be cooled in a short period to 150° C., which is the glass-transition temperature of polycarbonate used for the resin sheet  25 , or to a lower temperature. This structure does not cool the upper mold support  17  and the upper mold intermediate plate  18 , and thus reduces energy loss and enables the subsequent transfer molding process to start smoothly in a short time (cooling process). 
         [0089]    When a predetermined time (a third set time) elapses from the start of the cooling process, or specifically when the molten resin is cooled to solidify into a stable shape, the upper mold transfer plate  20  is raised and released from the molded piece. The support rollers  33  are also raised to release the molded portion from the lower mold transfer plate  14 . This forms the thick portion  26  having a height in the order of submillimeters, or with a thickness of 0.2 mm, on the upper surface of the resin sheet  25 . The inclined surface of the thick portion  26  includes a plurality of sawtooth-like protrusions of the order of submicrometers, or specifically with a size of 14 μm. In contrast, semicircular protrusions are formed on the lower surface of the resin sheet  25  at constant intervals in X-direction and Y-direction (releasing process). 
         [0090]    Although protrusions of the order of submicrometers can be formed on the resin sheet  25  by conventional transfer molding, such conventional molding cannot form the thick portion  26  of the order of submillimeters on the resin sheet  25  at the same time. The transfer molding apparatus  2  including the above mold structure enables both protrusions of the order of submicrometers and the thick portion  26  of the order of submillimeters to be formed in the resin sheet  25  at the same time. The above transfer molding process melts the entire resin sheet  25  supported between the molds, and thus generates no internal stress in the semifinished plate  46  resulting from the subsequent curing. This allows light from a plurality of LEDs arranged on the end face near the thick portion  26  to be transmitted through the structure to illuminate uniformly on the entire upper surface of the structure excluding the thick portion  26  without uneven illumination. 
         [0091]    Film Applying Process 
         [0092]    The resin sheet  25  that has undergone transfer molding with the transfer molding apparatus  2  is further transported downstream, and a protective film  39  is applied to each of the upper and lower surfaces of the resin sheet  25  by the film applicator  3 . The protective film  39  protects the semifinished plate  46  from damage or scratches when colliding with other parts, or from the surrounding dust or other matter adhering to the surfaces of the semifinished plate  46  and causing failures. After the semifinished plate  46  undergoes subsequent machining to complete the light guide plate, the protective films  39  are removed in the process of assembling the light guide plate with a liquid crystal panel. 
         [0093]    Cutting Process 
         [0094]    The resin sheet  25  having the protective films  39  on its both sides is further transported downstream, and is cut with the cutter  4  into rectangular portions in the direction of transportation in units of semifinished plates. Each semifinished plate  46  includes a thick portion  26 , and a cutting margin used in the shaping process on its end face opposite to the thick portion  26  (its cut surface). The cut surface of each semifinished plate  46  includes a beveled surface  46   a  on its edge in the direction of cutting performed by the first cutting tool  48   a  described below. The beveled surface  46   a  forms an angle of about 3 degrees with the cut surface and extends such that a beveled portion will remain after the cutting margin is removed. 
         [0095]    Shaping Process 
         [0096]    Eight semifinished plates  46  obtained through the cutting process are stacked on one another such that the thick portions  26  of adjacent plates are on the different sides. Dummy plates  47  are placed on the upper and lower surfaces of the stacked semifinished plates  46 . 
         [0097]    The semifinished plates  46  and the dummy plates  47  are cut on their one end face first with the first cutting tool  48   a , and then with the second cutting tool  48   b.    
         [0098]    As shown in  FIG. 4(   a ), the first cutting tool  48   a  is arranged to have its rotating axis parallel to the cut surfaces of the semifinished plates  46 , and cuts the end faces of the semifinished plates  46  with its cutting blades arranged on the outer circumference while it is rotating clockwise in the figure. The semifinished plates  46  stacked on one another are sandwiched between the dummy plates  47 , and thus can be cut smoothly without chattering during the cutting process. The semifinished plates  46  have the beveled surface  46   a  on their edge in the direction of cutting performed by the first cutting tool  48   a . The beveled surface  46   a  extends beyond the cutting margin on the cut surface of the semifinished plates  46 . The semifinished plates  46  will not have burrs at their edge when cut by the first cutting tool  48 . 
         [0099]    As shown in  FIG. 4(   b ), the second cutting tool  48   b  is arranged to have its rotating axis perpendicular to the cut surfaces of the semifinished plates  46 . The second cutting tool  48   b  having cutting blades arranged on its surface provides mirror finish on the cut surfaces of the semifinished plates  46 . The cutting blades cut the cut surfaces of the stacked semifinished plates  46  while rotating. Without the dummy plates  47  arranged on the upper and lower surfaces, burrs will form on the upper and lower edges of the outermost two semifinished plates  46 . In the first embodiment, the upper and lower edges of the outermost two semifinished plates  46  are covered by the dummy plates  47 . The dummy plates  47  may have burrs but the semifinished plates  46  do not form burrs. 
         [0100]    The completed light guide plate includes a thin portion with a thickness of 0.2 mm and a thick portion with a thickness of 0.5 mm. The thick portion has a substantially trapezoidal cross section. The light guide plate includes a plurality of hemispherical recesses (or protrusions) on its bottom surface. The light guide plate serves as one component of a liquid crystal display, and is assembled with other parts as described below. 
         [0101]    As shown in  FIG. 11E , the light guide plate  61  is placed on the upper surface of a base  62 . A diffusion plate  63 , a prism sheet  64 , and a liquid crystal panel  65  are then placed on the upper surface of the light guide plate  61  in this order. An LED  66 , which serves as a light source, is then arranged on the surface lateral to the perpendicular surface of the thick portion  61   a . This completes a liquid crystal display  60 . 
         [0102]    In the completed liquid crystal display  60 , light emitted from the LED  66  is guided to the thin portion  61   b  while the protrusions of the thick portion  61   a  prevent the light from leaking outside. The light is uniformly diffused by the hemispherical recesses at the bottom, and illuminates the liquid crystal panel  65  after passing through the diffusion plate  63  and the prism sheet  64 . 
         [0103]    The light guide plate may not be combined with the liquid crystal panel  65  but may be used simply as a surface light source device. 
         [0104]    The state of double refraction of the light guide plate will now be described. As described above, the resin sheet  25  supported between the upper and lower molds is entirely molten in the transfer molding process. This generates no internal stress in the resulting product and the product has the homogenous composition. Thus, the light guide plate can emit light uniformly from its entire upper surface as shown in  FIG. 5(   a ). However, a conventional light guide plate emits light unevenly from its upper surface as shown in  FIG. 5(   b ).  FIG. 5(   c ) is a graph showing the difference in the amount of light transmission between p-polarized light and s-polarized light of each of these light guide plates. As the graph shows, the difference in the amount of light transmission is significantly smaller for the light guide plate according to the first embodiment than for the conventional light guide plate. 
       Second Embodiment 
       [0105]    The system shown in  FIG. 6  uses a direct cooling method for cooling an upper mold transfer plate  20  by direct contact with a cooling plate  50 , instead of using the air cooling method of cooling the upper mold transfer plate  20  with air blown from the intake duct  36 . 
         [0106]    The cooling plate  50  can reciprocate between a transfer area defined in the molds and a non-transfer area defined outside the molds by a horizontal moving mechanism (not shown). An auxiliary heat insulating plate  51  is formed integrally with the upper surface of the cooling plate  50 . When an upper transfer plate is retained on the retainer plate  21 , the lower surface of the upper transfer plate can come in contact with the upper surface of the resin sheet  25 , and the upper surface of the upper transfer plate can come in contact with the lower surface of the cooling plate  50 . The cooling plate  50  is water-cooling, and uses a fluid flowing through a pipe (not shown) to maintain the surface temperature to a constant value (e.g., 20° C.). The other components such as the molds are the same as those in the first embodiment, and the corresponding components are given the same reference numerals and will not be described. 
         [0107]    The structure including the cooling plate  50  performs cooling as described below after heating and pressurizing the resin sheet  25 . The transfer molding process includes shifting from the state shown in FIG.  7 A(a) to cooling performed by raising the upper mold  10  while maintaining the upper mold transfer plate  20  in contact with the resin sheet  25  as shown in FIG.  7 A(b), and then laterally placing the cooling plate  50  between the upper mold transfer plate  20  and the upper mold intermediate plate  18  as shown in FIG.  7 A(c). 
         [0108]    First Cooling Process 
         [0109]    As shown in FIG.  7 A(d), the lower surface of the cooling plate  50  is placed in contact with the upper surface of the upper mold transfer plate  20  to hold the cooling plate  50  and the auxiliary heat insulating plate  51  between the upper mold transfer plate  20  and the upper mold intermediate plate  18 . As shown in  FIG. 8 , a high pressure (but a lower pressure than in the process of heating and pressurizing) is applied to eliminate bubbles (voids) from the resin sheet  25 . In one example, the applied pressure may be not less than 0.8 MPa based on the combined gas law to reduce the diameter of bubbles from about 0.4 mm to about 0.1 mm. 
         [0110]    Second Cooling Process 
         [0111]    Subsequently, when the resin sheet  25  is cooled to a temperature equal to or less than its melting point (e.g., to 200° C.) (based on time in the second embodiment, or specifically when a first set time elapses from the start of the first cooling process), the pressure is lowered drastically (for example, to 0.1 MPa). As shown in FIG.  7 B(a), the resin sheet  25  has a greater elastic modulus and thus undergoes elastic deformation less easily as its temperature decreases. The resin sheet  25  solidifies and loses fluidity at about 150° C., which is the glass-transition temperature. As shown in FIG.  7 B(b), when cooled to about 150° C. under pressure applied from the molds, the resin sheet  25  generates residual stress. The resin sheet  25  then becomes elastic like rubber at about 200° C. and generates residual stress. In the second embodiment, the applied pressure is reduced when the resin sheet  25  is cooled to about 200° C. to eliminate residual stress. 
         [0112]    Third Cooling Process 
         [0113]    When the resin sheet  25  is further cooled to a temperature equal to or less than the glass-transition temperature (e.g., to 150° C.) (based on time in the second embodiment, or specifically when a second set time elapses from the start of the second cooling process), the pressure is raised again (to, for example, not less than 0.5 MPa). The resin sheet  25  is cooled at its upper surface, and thus the temperature distributes unevenly. When the upper surface of the resin sheet  25  is cooled to a temperature equal to or less than the glass-transition temperature and solidifies, the lower surface of the resin sheet  25  may yet to be cooled to such a temperature. In this case, the solidified upper surface portion of the resin sheet  25  cannot shrink when the lower surface portion of the resin sheet  25  shrinks by heat. As a result, the lower surface portion of the resin sheet  25  would warp and have a ridged central portion. To prevent this, the pressure is raised again to forcibly cancel such shrinkage stress. 
         [0114]    As described above, the cooling method according to the second embodiment allows the cooling time to be shorter than the air cooling in the first embodiment. More specifically, the direct cooling in the second embodiment takes the cooling time of 55 seconds, whereas the air cooling in the first embodiment takes the cooling time of 110 seconds. In addition to the heat-insulation plates arranged on the upper mold  10  and the lower mold  9 , the auxiliary heat insulating plate  51  is arranged on the upper surface of the cooling plate  50 . This structure prevents the upper mold  10  from being affected by the low-temperature cooling plate  50 , and shortens the recovery time to the subsequent heating and pressurizing. 
         [0115]    The resin sheet  25  is cooled in the manner described above, and then the upper mold  10  is raised and the cooling plate  50  is retracted by moving horizontally as shown in FIG.  7 A(e). As shown in FIG.  7 A(f), the upper mold transfer plate  20  is then raised to complete the single cycle. 
       Third Embodiment 
       [0116]    The system according to a third embodiment includes a cooling mechanism that cools the resin sheet  25  both from above and below, or specifically cools the upper surface of the upper mold transfer plate  20  and the lower surface of the lower mold transfer plate  14  as shown in  FIGS. 9(   a ) to  10 ( c ). 
         [0117]    Whereas the system of the second embodiment includes the cooling plate  50  formed integrally with the auxiliary heat insulating plate  51  on its upper surface, the system of the third embodiment includes not only a first cooling plate  52  formed integrally with an auxiliary heat insulating plate  53  on its upper surface, which corresponds to the cooling plate  50 , but also a second cooling plate  54  formed integrally with an auxiliary heat insulating plate  55  on its lower surface. The lower mold excluding the lower mold transfer plate  14  is entirely movable to a position at which the lower mold is retracted in the horizontal direction. The first cooling plate  52  and the second cooling plate  54  facing each other in the vertical direction can be placed respectively above and below the resin sheet  25 , with the upper surface being in contact with the upper mold transfer plate  20  and the lower surface being in contact with the lower mold transfer plate  14 . 
         [0118]    The operation of a transfer molding apparatus  2  including the above cooling mechanism will now be described. As in the first and second embodiments, the preheat process and the transfer molding process are complete as shown in  FIG. 9(   a ), and then the upper mold  10  is raised while the upper mold transfer plate  20  is in contact with the upper surface of the resin sheet as shown in  FIG. 9(   b ). As shown in  FIG. 9(   c ), while the lower mold transfer plate  14  is in contact with the lower surface of the resin sheet  25 , the lower mold  9  excluding the lower transfer plate  14  is moved to the retracted position in the horizontal direction. The upper mold transfer plate  20  and the lower mold transfer plate  14  facing each other in the vertical direction are moved in the horizontal direction, and are respectively arranged above and below the resin sheet  25 , with the upper surface being in contact with the upper mold transfer plate  20  and the lower surface being in contact with the lower mold transfer plate  14 . In this state, the upper mold  10  is lowered to allow the resin sheet  25 , having the upper surface in contact with the upper mold transfer plate  20  and the lower surface in contact with the lower mold transfer plate  14 , to be supported between the first cooling plate and the second cooling plate as shown in  FIG. 9(   d ). Then, a pressure is applied to the resin sheet  25  to start the cooling process of the resin sheet  25 . 
         [0119]    As described above, the cooling process uniformly cools the resin sheet  25  from above and below. The process thus eliminates the need to respond to warps in the first to third cooling processes in the second embodiment. More specifically, the single cooling process completes the semifinished plate  46  without warps. 
         [0120]    After the cooling process, the first cooling plate  52 , the second cooling plate  54 , and the lower mold  9  excluding the lower mold transfer plate  14  are moved horizontally to their original positions as shown in  FIG. 10(   a ). When the resin sheet  25  having the upper surface in contact with the upper mold transfer plate  20  and the lower surface in contact with the lower mold transfer plate  14  is placed on the lower mold  9  as shown in  FIG. 10(   b ), the upper mold transfer plate  20  is raised to complete the single cycle as shown in  FIG. 10(   c ). 
       OTHER EMBODIMENTS 
       [0121]    The present invention is not limited to the structures described in the above embodiments, but may be modified in various forms. 
         [0122]    For example, although the thick portion  26  is formed by the molten resin sheet  25  partially flowing into the recess in the upper mold transfer plate  20  in one or more of the above embodiments, the thick portion  26  may be formed in the manner described below. 
         [0123]    The structure in FIG.  11 A(a) allows a non-product portion of the molten resin sheet  25  (excluding its portion corresponding to the light guide plate) to mainly flow into the recess  23 . More specifically, the recess  23  formed in the upper mold transfer plate  20  has a side wall  20   a  corresponding to the non-product portion, and the side wall  20   a  is higher than other portions of the recess  23 . The sidewall  20   a  defines an inner surface  20   b , which is an inclined surface  20   b  inclined to gradually increase the opening from the bottom surface of the recess  23 . 
         [0124]    As shown in FIG.  11 A(b), the molds are placed close to each other to apply a pressure to the resin sheet  25  in the transfer molding process. This causes the non-product portion of the molten resin to move along the inclined surface  20   b  of the side wall portion  20   a  and flow into the recess  23  as shown in FIG.  11 A(c). Subsequently, the product portion of the molten resin also moves partially along the inclined surface  20   c  of the opposite side wall and flows into the recess  23 . The side wall  20   a  is high, and thus allows a sufficiently large amount of molten resin in the non-product portion flows into the recess  23 . This reduces the amount of resin to be wasted, and reduces the cost. As a result, the recess  23  is filled with the molten resin as shown in FIG.  11 A(d). The subsequent cooling and other processes are the same as described in one or more of the above embodiments, and will not be described. 
         [0125]    In the structure shown in FIG.  11 B(a), the resin sheet  25  is not melted to partially flow into the recess  23 , but the upper mold transfer plate  20  is provided with an additional material (e.g., a resin piece  25   a ) for filling the recess  23 . This structure allows the thick portion  26  to be easily and efficiently formed as shown in FIG.  11 B(b). 
         [0126]    The structure shown in FIG.  11 C(a) includes an additional material formed integrally with the resin sheet  25 , or specifically includes a protrusion  25   b  as a part of the resin sheet  25 . According to one or more embodiments of the present invention, the protrusion  25   b  is thinner than the thick portion  26  and thicker than the resin sheet  25  that has yet to undergo transfer molding. The structure including the protrusion  25   b  eliminates the need for a mechanism for placing an additional material and thus improves the workability. 
         [0127]    Although the upper mold transfer plate  20  has the recess  23  in one or more of the above embodiments, the recess  23  may be formed in the lower mold transfer plate  14 , or the recess  23  may be formed in both the upper and lower mold transfer plates. 
         [0128]    Although the mold structure includes the upper mold  10  and the lower mold  9  in one or more of the above embodiments, the mold structure may include molds that are open and closed in the horizontal direction. 
         [0129]    Although each of the upper mold transfer plate  20  and the lower mold transfer plate  14  has the transfer surface in one or more of the above embodiments, the transfer surface may be formed in one of the upper and lower mold transfer plates. Alternatively, the upper and lower mold transfer plates may be eliminated, and the mold(s) may directly have a transfer surface (e.g., its intermediate plate may have a transfer surface). 
         [0130]    Although the entire upper mold transfer plate  20  is heated uniformly in one or more of the above embodiments, the upper mold transfer plate  20  may not be heated uniformly. For example, the upper mold transfer plate  20  may be heated locally in the vicinity of the recess  23 . This improves the molten state of the resin in the recess  23 , and forms the thick portion  26  in an appropriate manner without sink marks or other defects. 
         [0131]    In one or more of the above embodiments, the resin sheet  25  supported between the upper mold transfer plate  20  and the lower mold transfer plate  14  is heated and pressurized to melt the entire resin sheet  25 . According to one or more embodiments of the present invention, at least one of the transfer plates  20  and  14  includes a resin flow regulator on its peripheral portion to regulate the flow of the molten resin. 
         [0132]    As shown in FIGS.  11 D(a)- 11 D(d), the lower mold transfer plate  14  may include a flow regulator on a peripheral portion of its upper surface. The flow regulator that can prevent the resin from flowing into the surrounding areas may not surround the four sides, but may be discontinuous or may cover only two sides. 
         [0133]    FIG.  11 D(a) shows the structure including a protrusion  14   a  as a flow regulator extending from the upper surface of the lower mold transfer plate  14 . FIG.  11 D(b) shows the structure including a groove  14   b  as a flow regulator formed in the upper surface of the lower mold transfer plate  14 . FIG.  11 D(c) shows the structure including a large number of minute protrusions  14   c  as a flow regulator extending from the upper surface of the lower mold transfer plate  14 . FIG.  11 D(d) shows the structure including a large number of minute recesses  14  as a flow regulator formed in the upper surface of the lower mold transfer plate  14 . Each of these structures may be formed in the upper mold transfer plate  20  or may be formed in each of the transfer plates  14  and  20 . The flow regulator is not limited to these examples, but may be in any form that can increase resistance to the flow of the molten resin. 
         [0134]    Although the applied pressure in the cooling process is determined as shown in  FIG. 8  in one or more of the above embodiments, the pressure may be changed as described below. 
         [0135]    For example, the first cooling process may use an applied pressure P 1  determined in accordance with the combined gas law (where PV/T is constant) as described below to reduce the diameter of bubbles from 0.4 mm to 0.1 mm. 
         [0000]        P   0   ×V   0   /T   0   =P   1   ×V   1   /T   1   (1)
 
         [0000]    where
 
P 0 =101325 Pa (the atmospheric pressure)
 
V 0 =3.35×10 −11  m 3  (the volume of bubbles with a diameter of 0.4 mm)
 
       T 0 =240° C.=513K 
       [0136]    V 1 =5.23×10 −13  m 3  (the volume of bubbles with a diameter of 0.1 mm) 
       T 1 =190° C.=463K 
       [0137]    As a result, P 1 =5.85 MPa.
 
With the applied pressure of not less than 5.85 MPa, the diameter of bubbles is reduced from 0.4 mm to 0.1 mm or less.
 
         [0138]    In the second cooling process, the resin sheet  25  (polycarbonate) is cooled to 190° C. to lower the applied pressure to 0.02 MPa (or to 0 MPa to apply no pressure). This prevents residual stress from being generated. 
         [0139]    In the third cooling process, the applied pressure P 2  corresponds to the shrinkage stress produced when the resin sheet  25  (polycarbonate) is cooled from 150° C., which is the glass-transition temperature, to 130° C., at which the resin sheet can be released from the molds. 
         [0000]    More specifically, P 2 =E×α
 
E (elastic coefficient)=2.45 GPa
 
α (linear expansion coefficient of polycarbonate)=7×10 −5  
 
As a result, P 2 =3.4 MPa. With a pressure higher than this value (e.g., 6.2 MPa), the resin sheet  25  is prevented from deforming due to shrinkage stress generated by cooling.
 
         [0140]    Although the preparation process, the transfer molding process, the film applying process, and the cutting process are performed continuously with devices installed in a series in one or more of the above embodiments, these processes may be performed independently, or only some of the processes may be performed continuously. It is only required that the processes are performed in sequence, irrespective of whether these processes are performed continuously or discontinuously. The processes included in the transfer molding process may be performed independently, or some of the processes may be performed continuously. 
         [0141]    Although the protrusions and recesses on the transfer surface have maximum heights in the order of submircons in one or more of the above embodiments, the protrusions and recesses may have maximum heights in the order of micrometers (e.g., 200 μm) or in the order of submillimeters (e.g., 1 mm). It is only required that the thick portion  26  has the thickness greater than the maximum height of the protrusions and recesses. In particular, according to one or more embodiments of the present invention, the thick portion  26  has the thickness at least 10 times greater than the maximum height of the protrusions and recesses. The thick portion  26  may have the thickness in the order of submicrometers when the thickness is at least 10 times greater. 
         [0142]    Although the resin sheet  25  has a continuous band-like shape in one or more of the above embodiments, a plurality of separate rectangular resin sheets  25  may be used for transfer molding of a single semifinished plate  46  (or two or more semifinished plates) onto each separate resin sheet  25 . In this case, rollers that can rotate when driven may be arranged above and below to allow transportation of such separate rectangular resin sheets  25 . 
         [0143]    Although the transfer molding method is used to prepare the light guide plate in one or more of the above embodiments, the method may be used to prepare a variety of optical components such prism sheets. 
         [0144]    Although the light guide plate is incorporated into the liquid crystal display with the structure shown in  FIG. 11E  in one or more of the above embodiments, the light guide plate may be modified for use in a surface light source device as shown in  FIG. 11F . 
         [0145]    The light guide plate  70  shown in  FIG. 11F  includes a light guide plate member  71  with a substantially uniform thickness, and a wedge-shaped light directing part  72 . The light guide plate member  71  has a deflection pattern or a diffusion pattern on its back surface, and includes a lenticular lens  73  having a semicircular cross section on its front surface. The light directing part  72  has an inclined surface  74 , which is included from the light directing part  72  toward the light guide plate member  71 . The thickness of the light directing part  72  at its end face (light incident surface) is greater than the height of a light source  75 . 
         [0146]    The surface light source device  11  including the light guide plate  70 , in which the thickness of the light directing part  72  at its end face is greater than the height of the light source  75 , allows light emitted from the light source  75  to efficiently enter the light directing part  72 . The light entering the light directing part  72  is directed toward the light guide plate member  71  while it is widened into planar light. The light is reflected on the deflection pattern or the diffusion pattern and is emitted out of the light guide plate member  71  through its light emitting surface. The light emitted through the light emitting surface undergoes widening of the directivity with the lenticular lens  73 . 
         [0147]    The surface light source device with this structure can be thin and can improve the light use efficiency of the light source  75 . 
         [0148]    Although the light guide plate  70  includes the lenticular lens  73  having a semicircular cross section on the surface of the light guide plate member  71 , the light guide plate  70  may include a lens with another cross section, such as a prism lens with a triangular cross section. 
         [0149]    While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           1  material feeder 
           2  transfer molding apparatus 
           3  film applicator 
           4  cutter 
           5  shaping apparatus 
           6  main roller 
           7  roller 
           8  winding roller 
           9  lower mold 
           10  upper mold 
           11  lower mold support 
           12  lower mold intermediate plate 
           13  lower mold heat insulating plate 
           14  lower mold transfer plate 
           15  heater 
           16  micrometer 
           17  upper mold support 
           18  upper mold intermediate plate 
           19  upper mold heat insulating plate 
           20  upper mold transfer plate 
           21  retainer plate 
           22  heater 
           23  recess 
           24  arc-shaped area 
           25  resin sheet 
           26  thick portion 
           27  groove 
           28  opening 
           29  soft X-ray irradiation unit 
           30  rod 
           31  press 
           32  air supply 
           33  support roller 
           34  positioning gripper 
           35  transporting gripper 
           36  intake duct 
           37  exhaust duct 
           38  application roller 
           39  protective film 
           40  jig 
           41  cutting member 
           42  groove 
           43  mounting recess 
           44  clamp member 
           45  clamp plate 
           46  semifinished plate 
           47  dummy plate 
           48  cutting tool 
           49  cutting blade 
           50  cooling plate 
           51  auxiliary heat insulating plate