BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The invention relates to a stamp unit and method of manufacturing a stamp unit having a holding unit which holds a stamp material. The stamp unit is positionable in a stamp manufacturing device where the holding unit is pressed while a stamp is manufactured from the stamp material. More specifically, the invention relates to providing a uniform pressure applied to a stamp material during manufacture regardless of the size of the stamp material. 
     2. Description of Related Art 
     The conventional stamp unit comprises a grip, a holder and a skirt member. The holder member is connected to the grip member, and is capable of moving vertically within the skirt member. The stamp material is thermally adhered to a lower end portion of the holder member. In such a conventional stamp unit, the stamp material is formed of two layers. The lower layer is made of a soft porous resin formed with a light energy absorption material, such as carbon black, dispersed therein. The upper layer, which supplies ink to the lower layer and is capable of pressing the lower layer uniformly, is made of a hard porous resin. 
     In the case of manufacturing a stamp, a roll-shaped transparent film is transported into the stamp manufacturing device. Then, character and image data is printed by a thermal head and ink transfer ribbon onto the transparent film to create a positive original film. The holder member is placed into the stamp manufacturing device so that the positive original film and the stamp material oppose each other with a transparent acrylic plate between them. When an irradiation unit, such as a xenon tube, emits light, the lower layer of the stamp material is illuminated or exposed through the positive original film. Only the portion which is illuminated through the non-printed or transparent portion of the positive original film is melted and solidified by the heat generated by the light energy absorption material that is, the carbon black, to create a seal so that ink does not permeate. On the other hand, the portion which is not illuminated, melted or solidified forms an image, such as the characters and symbols on the positive original film. Thus, the stamp is manufactured on the lower layer, and contains sealed and unsealed portions according to the desired pattern. 
     An ink pack is stored in an ink pack storing portion within the holder member. The ink pack storing portion has an uneven bottom formed in a lattice shape. The ink pack is opened when it is sandwiched and pressed between the uneven bottom and a plate attached to the grip member, by moving the grip member downward. Ink flowing from the ink pack is stored in the upper and lower layers of the stamp material. The ink flows out from the unsealed portion, but does not flow out from the sealed portion. 
     In the case of printing characters using the stamp unit, the grip member is moved downward to place the skirt member at the desired position on a printing sheet. The grip member moves the holder member downward within the skirt member so that the stamp material is pressed against the printing sheet. Ink attaches to the printing sheet through the unsealed portion of the stamp material so that various kind of images, such as characters and symbols, can be printed. 
     As described above, the stamp unit, including the holding unit, the skirt member and the grip member, are placed in the stamp manufacturing device where the holding unit is pressed while a stamp is manufactured. In such a case, it is necessary to provide a holding unit storing portion which can store the holding unit. Accordingly, it is necessary to provide enough space to insert the various members associated with the stamp unit. 
     Therefore, a stamp unit has been proposed, wherein only the stamp material and the holder member are placed into the stamp manufacturing device. After a stamp is manufactured with the stamp manufacturing device, the holder member which holds the stamp material, is inserted into the skirt member and attached to the grip member so as to be movable vertically within the skirt member. 
     Such a stamp manufacturing device has an irradiation unit on which the holding unit comprising at least the stamp material and the holder member is placed. A presser unit comprising a lid encloses the holding unit within the stamp manufacturing device, and presses the holding unit, and in particular the stamp material, at a predetermined position onto the irradiation unit, when the lid is closed. 
     However, in the conventional device, the holding unit that is placed into the stamp manufacturing device has a fixed height regardless of the stamp material size. However, the stamp material has to be pressed uniformly onto the irradiation unit while a stamp is being produced. When the holding unit is placed into the stamp manufacturing device and the lid is closed, the holding unit is pressed against the irradiation unit. A reaction force then acts on the irradiation unit and the presser unit in proportion to the stamp material size. A large reaction force causes portions of the irradiation unit and the presser unit to bend. This bending leads to a reduction in the pressure urging the stamp material against the irradiation unit, reducing the image quality of the manufactured stamp. 
     SUMMARY OF THE INVENTION 
     Therefore, it is an object of the invention to solve the above-mentioned problem, and to provide a method of manufacturing a stamp unit where the pressure on a stamp material is uniform regardless of the size of the stamp material where a holding unit having a holder member holds the stamp material, and the holding unit is placed into a stamp manufacturing device and pressed to manufacture a stamp from the stamp material. 
     In order to accomplish the object of the invention, the height of the holding unit is heightened in proportion to the stamp material size. That is, even if the stamp material is pressed with a fixed pressure, the reaction force differs according to the stamp material size. In response to the reaction force, portions of an irradiation unit and a presser unit bend in proportion to the reaction force. 
     By changing the height of the holding unit, the stamp material can be pressed uniformly onto an irradiation unit because the bending of the presser unit and irradiation unit is eliminated. 
     Preferably, the stamp material of the stamp unit comprises an elastic and transformable soft porous resin having a light energy absorption material at a lower end portion. The elastic and transformable soft porous resin projects from the lower edge of the holder member. In such a holding unit, it is effective to heighten the holding unit in proportion to the stamp size as the reaction force differs according to the stamp size. 
     Further, according to a preferred embodiment of the invention, the stamp unit comprises a skirt member, a holder member movably disposed within the skirt member for movement in an up and down (defined as axial) direction and configured to hold a stamp material at a lower end portion, and a grip member that moves the holder member downward within the skirt member. The holding unit includes the holder member and the stamp material. Because of the small size of the holding unit, the stamp material can be pressed properly, and the stamp manufacturing device can be miniaturized. Further, positioning grooves and marks for detecting the stamp size can be provided on the holder member, which is inserted within the skirt member, and do not effect its outward appearance. 
     The stamp manufacturing device into which the holding unit is placed preferably includes an original film making unit, an irradiation unit and a presser unit. 
     The stamp manufacturing device is easily affected by the reaction force, as the holding unit is sandwiched and pressed between the irradiation unit and the presser unit. The holding unit can be pressed uniformly by changing its height, thereby, adjusting the pressure on the stamp material. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above mentioned and other aspects and advantages of the invention will become apparent from the following detailed description of preferred embodiments when taken in conjunction with the accompanying drawings, in which: 
     FIG. 1 is a general exploded perspective view of a stamp unit according to a preferred embodiment of the invention; 
     FIG. 2 is a sectional side view of the stamp unit after ink has been supplied to the stamp unit; 
     FIGS. 3A-3K are perspective views of various sizes of stamp units according to the invention; 
     FIG. 4 is a side view of a skirt member according to a preferred embodiment of the invention; 
     FIG. 5 is an end view of the skirt member of FIG. 4; 
     FIG. 6 is a sectional side view of the skirt member of FIG. 4; 
     FIG. 7 is a perspective view of a holder member according to a preferred embodiment of the invention; 
     FIG. 8 is a side view of the holder member of FIG. 7; 
     FIG. 9 is a sectional side view of the holder member of FIG. 7; 
     FIG. 10 is a top view of the holder member of FIG. 7; 
     FIG. 11 is a bottom view of the holder member of FIG. 7; 
     FIG. 12 is a side view of a grip member according to a preferred embodiment of the invention; 
     FIG. 13 is a bottom view of the grip member of FIG. 12; 
     FIG. 14 is a sectional side view of the grip member of FIG. 12; 
     FIG. 15 is a side view of a cap member according to a preferred embodiment of the invention; 
     FIG. 16 is a sectional side view of the cap member of FIG. 15; 
     FIG. 17 is a general perspective view of a stamp manufacturing device according to a preferred embodiment of the invention; 
     FIG. 18 is a perspective view of the frame structure of the stamp manufacturing device of FIG. 17; 
     FIGS. 19 and 20 are perspective views showing a presser unit of the stamp manufacturing device of FIG. 17; 
     FIG. 21 is a sectional side view of an irradiation unit of the stamp manufacturing device; 
     FIG. 22 is a top view of the irradiation unit FIG. 21; 
     FIG. 23 is a top view schematically showing the holding unit placed in a predetermined stamp making position of the holding unit storage part in the stamp manufacturing device according to a preferred embodiment of the invention; 
     FIG. 24 is a side view schematically showing a state where the holding unit is set to a predetermined stamp making position of the holding unit storage part in the stamp manufacturing device according to a preferred embodiment of the invention; 
     FIGS. 25 and 26 are cross sectional views schematically showing the holding unit placed in a predetermined stamp making position of the holding unit storage part in the stamp manufacturing device according to a preferred embodiment of the invention; and 
     FIG. 27 is a perspective view showing the holding unit is being placed in the holding unit storage part when a front and an upper lid are opened. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     For a general understanding of the features of the invention, reference is made to the drawings. In the drawings, like reference numerals have been used throughout to designate like elements. 
     FIG. 1 is a general exploded perspective view of a stamp unit according to a preferred embodiment of the invention and FIG. 2 is a sectional side view of the stamp unit of FIG. 1 soon after an ink pack is opened. As shown in FIGS. 1 and 2, stamp unit  1  comprises a skirt member  2 , which supports the stamp unit  1  during stamp printing; a holder member  4 , which is movably disposed within the skirt member  2  for movement in an up and down (defined as axial) direction and which holds a stamp material  3  thermally adhered to a lower end portion of the holder member  4 ; a grip member  5  that moves the holder member  4  downward to press the stamp material  3  against a printing paper (not shown); and a cap member  60 , which protects the stamp material  3 . 
     The stamp material  3 , held at the lower end portion of the holder member  4 , is preferably formed having a three layer structure. The upper layer  71  is preferably made of a hard porous resin approximately 3 mm thick, such as, for example, a polyvinyl formal of 90% porosity. However, other materials and thicknesses may also be appropriate. The middle layer  72  is preferably made of a hard porous resin preferably approximately 2 mm thick. The middle layer  72  may be formed of the same material as the upper layer  71 . However, other materials and thicknesses may also be appropriate. The lower layer  73  is preferably made of a soft porous resin, for example, a urethane resin of 65% porosity; however, other materials and thicknesses may also be appropriate. The middle layer  72  and the lower layer  73  are preferably adhered to each other by an adhesive agent pasted in a lattice shape. The upper layer  71  and the middle layer  72  are not adhered to each other. 
     Holes  74 , preferably 1 to 2 mm in diameter, are provided on the upper layer  71  so that ink flows immediately from the upper layer  71  to the middle layer  72  through the holes  74 . The ink slowly impregnates the middle layer  72  reaching down to the lower layer  73 . It takes nearly the same time to fill the stamp material  3  with ink as it takes to fill the thin stamp material having a two layer structure, even though the stamp material  3  is thick, because of the three layer structure. Referring to FIG. 2, the circumferential edge portion of the lower layer  73  and the lower end portion of the holder member  4  are pressed together and thermally adhered to each other. At the same time the circumferential edge portion of the lower layer  73  is inclined and sealed. Because the pores in the inclined edge portion of the lower layer  73  are closed by heat or resin, ink does not flow from the edge portion. The stamp is manufactured on the surface of the lower layer  73 , except at its circumferential edge portion. 
     A holding unit U, shown in FIG. 1, comprises the holder member  4 , which holds the stamp material  3 . The holding unit U is placed into the stamp manufacturing device  101  (see FIGS. 17-20 and  27 ). The holding unit U is heightened in proportion to the size of the stamp material  3 . FIGS. 3A to  3 K show stamp units that accommodate various sizes of the stamp material  3 ;  11  types of stamp units are illustrated. These include a minimum sized holding unit shown in FIG. 3A, having an approximately 12 mm×12 mm =144 mm 2  stamp area, and a maximum sized holding unit shown in FIG. 3K, having an approximately 40 mm×90 mm=3600 mm 2  stamp area. FIGS. 3C and 3G show holding units having a standard height H and approximately 900 mm 2  stamp areas. The holding unit of FIG. 3E has an approximately 600 mm 2  stamp area and the holding unit of FIG. 3H has an approximately 1320 mm 2  stamp area. The holding units of FIGS. 3E and 3H are treated as having the standard height H, as they are almost as broad as the standard type holding units of FIGS. 3C and 3G. 
     The holding unit shown in FIG. 3F has an approximately 532 mm 2  stamp area, and is (H−0.2) mm high (smaller than H). The holding unit, shown in FIG. 3B has an approximately 400 mm 2  stamp area, and is (H−0.3) mm high. The holding unit shown in FIG. 3A has an approximately 144 mm 2  stamp area, and is (H−0.4) mm high. On the other hand, the holding unit shown in FIG. 3I has an approximately 1890 mm 2  stamp area, and the holding unit shown in FIG. 3J has an approximately 1972 mm 2  stamp area. Both holding units are (H+0.3) mm high (larger than H). The holding unit shown in FIG. 3K has an approximately 3600 mm 2  stamp area, and is (H+0.5) mm high. In other words, the height of the holding unit U is changed gradually according to the stamp size. The relationship of the holding unit U to the stamp manufacturing device  101  is discussed hereinafter. Next, the skirt member  2  will be described with reference to FIGS. 4 to  6 . FIG. 4 is a side view, FIG. 5 is an end view, and FIG. 6 is a sectional side view of the skirt member  2  according to a preferred embodiment of the invention. 
     As shown in FIGS. 4 and 6, the skirt member  2  preferably has a rectangular-shaped opening portion  10  and an inner wall  11 . The holder member  4  slides relative to the surface of the inner wall  11  within the opening portion  10 . The skirt member  2  is integrally formed of an upper skirt portion  13  and a lower skirt portion  15 . The upper skirt portion  13  has an outer wall  12  and an inner wall  11 . The lower skirt portion  15  has an outer wall  14  formed continuously to the outer wall  12  but has a larger circumference so that it is stepped with respect to the outer wall  12 . 
     A spring engaging portion  17 , which engages an end of a torsion spring  16 , is formed at an upper portion of the inner wall  11  at both the left and right end surfaces of the upper skirt member  13 . A positioning protrusion  18 , which preferably has a half-moon shape, receives the coil portion of the torsion spring  16 . The positioning protrusion  18  is formed below and inclined or offset from the spring engaging portion  17  (FIG.  5 ). Further, a vertical groove  19 , which receives movably therein an inclined rib  35  (described hereinafter), is formed in both of the end surfaces of the skirt member  2  at the center portion of the inner wall  11 . The vertical grooves  19  act to guide ribs  35  of the holder member  4  in the axial direction when the holder member  4  is moved downward while printing. A spring shift suppression member  9  has an aperture portion (not shown), to prevent disengagement of the torsion spring  16 , through which the other end of the torsion spring  16  passes. Further, the lower end of the inclined rib  35  engages the other end of the torsion spring  16  during up and down movement to regulate that movement, as the end of the torsion spring  16  moves in the aperture portion of the spring shift suppression member  9 . The spring shift suppression member  9  is provided between the vertical groove  19  and the position protrusion  18 . 
     The lower skirt portion  15  is placed on a print sheet and supports the stamp unit  1  during stamp printing. Support ribs  20  support the lower edge of the outer wall  14 , keeping it away from the surface of the print sheet, and are disposed at lower corner portions of the outer wall  14 . Preferably, down arrow  21 , which shows a stamp printing direction, is formed at the center portion of the outer wall  14 . 
     The holder member  4  will be described using FIGS. 7 to  11 . FIG. 7 is a perspective view, FIG. 8 is a side view, FIG. 9 is a sectional side view, FIG. 10 is a top view, and FIG. 11 is a bottom view of the holder member  4  according to a preferred embodiment of the invention. 
     As shown in FIGS. 7 to  11 , the holder member  4  is complementary in shape to the upper skirt portion  13  and the lower skirt portion  15  of the skirt portion  2 . The holder member  4  comprises an upper holder portion  30  and a lower holder portion  31  formed as a single body. The upper holder portion  30  includes a side wall  32 , which preferably has a substantially rectangular circumferential shape when viewed from above. Three grooves  33  are provided in a line horizontally at the upper portion of the front side wall and the rear side wall of the circumferential side wall  32 . (The front wall or the rear wall is shown in FIG. 8.) A regulating protrusion  34 , which is preferably wedge-shaped and inclined from the surface of the side wall  32  to be narrower away from the surface, is provided at both sides of the center groove  33 . A rib protrusion  54  (described hereinafter) of the grip member  5  is fitted into each groove  33 , whereby the holder member  4  and the grip member  5  are connected to form a body. The regulating protrusions  34  contact the upper edge of the outer wall  12  of the upper skirt portion  13  of the skirt member  2  and act to regulate downward movement of the holder member  4 . 
     The inclined rib  35 , which is preferably wedge-shaped and inclines outwardly in the axial direction from the surface of the circumferential side wall  32 , is provided at each end wall of the circumferential side wall  32  (the left and right end surfaces as shown in FIG. 8) of the upper holder portion  30 . The inclined ribs  35  are inserted into the vertical grooves  19  of the upper skirt portion  13  to be movable in the axial direction when the holder member  4  is inserted from the bottom into the skirt member  2 . The other end of the torsion spring  16  is fixed at the lower end of the inclined rib  35  (at each end of the stamp unit  1 ). The holder member  4  is supported to be movable in an axial direction within the skirt member  2  by cooperation between the inclined ribs  35  and the vertical grooves  19 . One end of the torsion spring  16  is engaged by the spring engaging portion  17  of the upper skirt portion  13 , and the other end of the torsion spring  16  is engaged by the lower end of inclined rib  35 . The holder member  4  is always energized upwardly within the skirt member  2 . 
     The ink pack storing portion  22 , which is preferably rectangular and surrounded by the side wall  32 , has a flat bottom surface  23  with an ink flow hole  24  in the center. Further, a cutting rib  25  for cutting and opening the ink pack  6  protrudes a little beyond the bottom surface  23 . 
     As shown in FIG. 11, four ink supply holes  26  are provided inside the circumferential side wall  32  and extend from proximate the upper end of the circumferential side wall  32  of the holder member  4  to the bottom of the support rods  27  such that the bottoms of the support rods  27  and ink supply holes  26  define a to plane. The ink supply holes  26  are used to supply ink supplementally when the amount of ink stored in the stamp material  3  decreases. In such a case, ink is poured through the ink supply holes  26  when the grip member  5  is detached. 
     Further, as shown in FIG. 11, the plurality of support rods  27 , which are several millimeters in length, are provided so as to form a lattice on the lower holder portion  31  of the holder member  4 . The support rods  27  extend to and contact the stamp material  3  held by the holder member  4  and the bottom ends of the support rods  27  substantially form a plane. The lower holder portion  31  is integrally formed with the upper holder portion  30  as a single body and has a circumferential side wall  38  which is larger than the circumferential side wall  32 . The holder member  4  is preferably made of ABS resin, polyolefine resin, such as, for example, polyacetal copolymer, polypropylene, polyethylene, nylon, or PC resin. 
     The cutting rib  25  is used to cut and open the ink pack  6  when the ink page  6  is pressed downward via a thick paper plate  37  by the grip member  5 . The edge of the cutting rib  25  is sharp so that the ink pack  6  can be reliably opened. The ink flow hole  24  guides the ink flowing from the ink pack  6  which is opened by the cutting rib  25 , downward so that the ink impregnates the stamp material  3 . 
     Inclined grooves  43  are preferably formed, having an inwardly directed wedge shape at the upper center of outer surface of the front and rear walls of the circumferential side wall  38  constituting the lower holder portion  31 . One or two detecting grooves  44  are preferably formed beside the inclined grooves  43 . The inclined grooves  43  are used to position the holder member  4  at a predetermined stamp making position in a stamp manufacturing device, then a stamp is manufactured on the stamp material  3  therein. As both sides of the inclined grooves  43  are inclined surfaces, the holder member  4  is moved to ensure that the positioning projection  177  (FIGS. 23 and 24) contacts the center portion of the inclined grooves  43  based on a cam effect between the positioning projection  177 , which provides a positioning member, and the inclined surfaces of the inclined grooves  43 . Therefore, the holder member  4  is positioned in a predetermined stamp making position. 
     The number of grooves and the position of the detecting grooves  44  differ based on the size of holder member  4 . The detecting grooves  44  are used to specify the size of holder member  4  in association with a groove sensor (not shown) disposed in the positioning mechanism  170  of the stamp manufacturing device. The positions of the inclined grooves  43  and the detecting grooves  44  on the outer surface of the circumferential side wall  38  are configured to be rotationally symmetrical so that the holding unit U can be positioned from either direction, without having to consider the orientation of the holding unit U. 
     As shown in FIG. 8, a pair of engaging protrusions  45  are formed at the lower portion of the circumferential side wall  38 . The engaging protrusions  45  engage with engaging grooves  62  (FIG. 16) of the cap member  60  and are used to set the cap member  60  to cover the lower end of the lower holder portion  31  (FIGS. 1,  15  and  16 ). Thereby, the surface of the stamp material  3 , supported on the lower end of the side wall  38 , is protected by the cap member  60 . 
     Ink pack  6  (shown in FIG.  1 ), which is preferably bag-shaped and made of a film material, is stored in the ink pack storing portion  22 . The ink pack  6  is substantially fully filled with ink. The thick paper plate  37  is arranged between the ink pack  6  and the bottom of the grip member  5 . The film material is preferably polyethylene, polypropylene, polyester, or nylon alone, or two types laminated together. 
     The grip member  5  will be described with reference to FIGS. 12 to  14 . FIG. 12 is a side view, FIG. 13 is a bottom view, and FIG. 14 is a transverse sectional view of the grip member  5  according to a preferred embodiment of the invention. 
     In FIGS. 12 to  14 , a label portion  50  is formed on the upper surface of the grip member  5 . A label, which indicates the contents of the stamp formed on the stamp material  3 , is pasted on the label portion  50 . 
     An insertion portion  51 , which is inserted into the circumferential side wall  32  of the upper holder portion  30  of the holder member  4 , is formed on the inside surface of the top of the grip member  5 , as shown in FIGS. 2,  13  and  14 . The insertion portion  51  acts to press against the ink pack  6 , disposed in the holder member  4 , via the thick paper plate  37 . 
     The insertion portion  51  preferably has a substantially rectangular shape when viewed from the bottom, as shown in FIG.  13 . Four concave portions  52  are preferably formed at opposed positions at a center peripheral portion of the insertion portion  51 . The concave portions  52  permit the insertion portion  51  to bypass the wall portion of the ink supply holes  26  disposed on a surface of the circumferential side wall  32  when the insertion portion  51  of the grip member  5  is inserted into the circumferential side wall  32  of the holder member  4 . Two pairs of concave portions  52  are formed to prevent the wall portion of the ink supply holes  26  from being an obstacle and to allow the grip member  5  to be inserted with either side opposing the ink supply holes  26 . Further, a plurality of ribs  53  (twelve ribs  53 , for example, as shown in FIG. 13) are formed in a vertical direction on the inner surface of the outer wall of the grip member  5 . A rib protrusion  54  is integrally formed at the lower end of each rib  53 . A rib protrusion  54  is received in an opposed groove  33  formed on the upper surface of the outer wall of the circumferential side wall  32 , whereby the holder member  4  and the grip member  5  are integrated or assembled. 
     In addition, four ribs  53  are found on the inside of the short sides of the grip member. Steps  55  are formed on the ribs  53  that are arranged on the inside of the short sides of the grip member  5 . When the holder member  4  is moved downward within the skirt member  2  to press the stamp material  3  onto a sheet for printing, the steps  55  strike the upper end of the opening portion  10  formed with the inner wall  11  of the skirt member  2 . Thus, the steps  55  prevent the holder member  4  from moving to far downward and causing excessive printing, i.e., excess ink leading to blurring. 
     The cap member  60  disposed at the lower end portion of the lower holder portion  31  of the holder member  4  will be described with reference to FIGS. 15 and 16. FIG. 15 is a side view, and FIG. 16 is a sectional side view of the cap member  60  according to a preferred embodiment of the invention. 
     The cap member  60  is preferably box-shaped having an opening upward as shown in FIGS. 1,  15  and  16 . The hand holding portion  61 , which is held by the operator&#39;s fingers when fixing the cap member  60  onto or detaching the cap member  60  from the holder member  4 , is preferably formed substantially at the center portion of both sides of the surface of the outer wall, as shown in FIG.  15 . Further, a pair of engaging grooves  62 , which are engaged with the engaging protrusions  45  formed on the circumferential side wall  38 , is preferably provided on both sides of the inner surface of the peripheral wall of the cap member  60 . The cap member  60  is attached to the circumferential side wall  38  by each engaging groove  62  of the cap member  60  being engaged with an opposed engaging protrusion  45  of the side wall  38 . Thereby, the surface of the stamp material  3 , which is held at the lower end of the circumferential side wall  38 , is protected by the cap member  60 . 
     Next, the stamp manufacturing device  101  in which the holding unit U, formed of the stamp material  3  and the holder member  4  is inserted will be described in detail. FIG. 17 is a general perspective view of the stamp manufacturing device  101  according to a preferred embodiment of the invention. 
     The stamp manufacturing device  101  has a film magazine  102  storing transparent films; an inlet  103  for a label cut sheet called CS hereinafter formed near the film magazine  102 ; a printing portion  104  having a thermal head  105  therebeneath; a stamp making portion  106 ; and an outlet  158  for the CS and the original film near the stamp making portion  106 . The film magazine  102 , which stores transparent films  108 , can be attached to and removed from the device  101 . A stamp is manufactured from the stamp material  3  held at the lower end portion of the holding unit U, to reflect the design, characters or images, of the original film in the stamp making portion  106 . 
     An original film making unit  1040 , which includes the film magazine  102  and the printing portion  104 , creates a desired image on the transparent film by placing an untransparent material on it. A head holder unit  152  includes a thermal head  105  therebeneath, and is capable of rotating upward around an axis  160  (refer to FIG.  18 ). The stamp making unit  106  comprises a presser unit formed of an upper lid  136  and a front lid  156 , which contains the holding unit U within the stamp making portion  106  of the stamp manufacturing device  101 , when closed, and presses the stamp material  3  downward against an irradiation unit  110 . The irradiation unit  110  is arranged beneath the stamp making portion of the device  101 , and can be attached to and removed from the stamp manufacturing device by moving a slide lever  151  upward. 
     The stamp manufacturing device  101  is connected to and controlled by a personal computer so as to execute various commands, such as creating a positive image onto the film  108 , printing the label onto the CS, and producing a stamp according to the original film. The film  108  is transported from the film magazine  102  to the printing portion  104  and a positive image, such as characters and symbols, is printed onto the film  108  by the thermal head  105  according to an image data printed on the original film. The original film, on which the positive image is printed, is transported to the stamp making portion  106  so that the original film is placed above the irradiation unit  110 . The holding unit U holding the stamp material  3  is placed above the original film, and then, the front lid  156  and the upper lid  136  are closed so that the stamp material is pressed against the original film. The stamp is manufactured by illuminating or exposing the stamp material  3  through the original film. 
     In the case of printing a label, a positive image data is printed onto the CS. The CS is fed from the inlet  103  and discharged from the outlet  158 . The CS, on which the positive image has been printed and which indicates the contents of the stamp formed on the stamp material  3 , is pasted as a label onto the label portion  50  on the top of the grip member  5 , shown in FIGS. 2 and 12. 
     The presser unit  141  arranged in the stamp making unit  106  will be described in detail with reference to FIG.  18 . FIG. 18 is a perspective view of the frame structure of the stamp manufacturing device  101 . 
     A head holder unit  152  is supported by an axis  160  so as to rotate upward around the axis  160 , in front of a main frame having a concave section. The presser unit  141  is attached to the rear side of the main frame  140  with bolts  162 . The presser unit  141  is composed of a frame unit  144  comprising both side frames  142  and a front frame  143 , an upper lid  136  and a front lid  156 . A positioning mechanism  170  for the holding unit U is provided in the frame unit  144 . 
     A rotation axis  136   a  of the upper lid  136  is supported by both side frames  142 . The upper lid  136  is attached to the main frame  140  by a torsion spring  136   b  wound around the rotation axis  136   a , so as to be opened vertically. The front lid  156  is attached to the front end of the upper lid  136  by a torsion spring (not shown), and is capable of moving forward when it is opened. Thus, the holding unit U can be positioned without being obstructed by the upper lid  136  and the front lid  156 . 
     Arcing cuts  156   c  are provided in a rib  156   b  so as to extend toward the back of the front lid  156 . When the upper lid  136  and the front lid  156  are moved against the urging of a spring (not shown) so as to be closed, the cuts  156   c  are hooked by a hook pole  145 , which is attached to the front frame. A photo sensor PS 1 , formed of an emitting element (not shown) and an accepting element (not shown), is obstructed by the rib  156   b  when the lids are closed. Thus, whether the upper lid  136  and the front lid  156  are opened or closed can be detected. 
     A metallic presser plate  146  is fixed on the bottom side of the upper lid  136 . The presser plate  146  presses the holding unit U against the stage  133  (FIGS. 21,  22  and  27 ) of the irradiation unit  110  so as to press the stamp material  3  held at the lower end portion of the holding unit U, when the holding unit U is attached to the positioning mechanism  170  and the lids  136 ,  156  are closed. 
     Next, the assembly process of the presser unit  141  in the stamp manufacturing device according to a preferred embodiment of the invention will be described referring to FIGS. 19 and 20. 
     The presser unit  141  is inserted in the predetermined position in the main frame  140 , as shown in FIG.  19 . An adjustment fixture  161 , which has a fixed height, is placed on the bottom of the main frame  140  by opening the positioning mechanism  170 . After the presser unit  141  is fixed to the main frame  140  with bolts  162 , the adjustment fixture  161  is removed from the main frame  140 . The irradiation unit  110  (described later) is also placed in the main frame  140  with an error of less than 0.1 mm. Thus, the positional relations between the main frame  140  and the presser unit  141 , and between the irradiation unit  110  and the presser unit  141  are always the same. As a result, it is possible to change the height of the holding unit U according to the stamp size in every stamp manufacturing device according to the invention. 
     Further, an irradiation unit  110  according to the preferred embodiment of the invention, which can be positioned in and removed from the frame unit  144 , will be described referring to FIGS. 21 and 22. FIG. 21 is a sectional view, and FIG. 22 is an end view of the irradiation unit  110  according to a preferred embodiment of the invention. 
     The irradiation unit  110  has a xenon tube  111 ; a stage  133 , which is preferably a transparent acrylic plate located between the holding unit U and the xenon tube  111 ; and a reflector box  134  surrounding the xenon tube  111 . The xenon tube  111 , the stage  133  and the reflector box  134  are preferably formed as a single body. 
     A connector  149 , which connects the irradiation unit  110  with the stamp manufacturing device  101 , is formed of a female connector  149 A, which is arranged in the stamp manufacturing device  101 , and a male connector  149 B, which is arranged in the irradiation unit  110 . The male and female connectors  149 A,  149 B each include eight terminals  149 C, four terminals are for irradiation of the xenon tube  111  (two terminals supplying power to the xenon tube and two terminals for generating light) and four terminals are for detecting and identifying the xenon tube. A radiation amount indicating portion  148 , which indicates a radiation amount per unit electric power (radiation performance) of the xenon tube  111  and which is measured in advance, is connected to the male connector  149 B. As the irradiation unit  110  can be attached to and removed from the stamp manufacturing device  101 , the xenon tube  111 , for example, can be replaced easily. Maintenance, such as cleaning the transparent surface, can also be done easily. The irradiation unit is placed in the main frame with an error of less than 0.1 mm. Thus, the positional relationship between the stage  133  and the presser plate  146  is always kept the same. 
     The positioning mechanism  170  and size detecting system  180  arranged in the positioning mechanism  170  will be described with reference to FIGS. 23 to  26 . FIG. 23 is a top view, FIG. 24 is a side view, and FIGS. 25 and 26 are cross sectional views schematically showing a state where the holding unit is positioned in a predetermined stamp making position of a holding unit storage part  169  in the stamp manufacturing device  101  according to a preferred embodiment of the invention. As mentioned above, the holder member  4  of the holding unit U has the inclined grooves  43  and the detecting grooves  44 . The positioning mechanism  170  can detect the existence and the size of the holding unit U in association with the inclined grooves  43  and the detecting grooves  44 . 
     As shown in FIGS. 23 to  26 , the positioning mechanism  170  comprises two holder fixing members  171 ,  172 . The holding unit U is positioned and held by sandwiching it between the holder fixing members  171 ,  172 . The holder fixing member  171  is fixed within the positioning mechanism  170 . Then, a switch plate  174  is attached to the fixing member  171  by three screws  173 . Preferably, six microswitches  175 A,  175 B,  175 C,  175 D,  175 E and  175 F are arranged along an edge of the switch plate  174 ; however, other numbers of microswitches may also be appropriate. Switch terminals of each microswitch  175 A,  175 B,  175 C,  175 D,  175 E and  175 F oppose the holding unit U. The switch terminals protrude a little toward the position of the holding unit U when the holding unit U is not positioned in the positioning mechanism  171 . According to the ON-OFF state of the microswitches  175 A,  175 B,  175 C,  175 E and  175 F, the size or type of the holding unit U can be detected. The microswitch  175 D can be used to detect the existence of the holding unit U. The microswitches  175 A,  175 B,  175 C,  175 E and  175 F and the detecting grooves  44  form the size detecting system  180 . The positioning projection  177  is formed in the center of the longitudinal portion of the holder fixing member  171  and above the microswitch  175 D. The positioning projection  177  properly mates with the inclined grooves  43 . A set mark M is provided in a position corresponding with the positioning projection  177 , and is used as a general index for positioning the holding unit U. The holder fixing member  172  is arranged so as to be capable of moving against the holder fixing member  171 , and is attached by a spring (not shown) in the direction of an arrow shown in FIG.  23 . 
     To position the holding unit U in the predetermined stamp making position in the positioning mechanism  170 , the fixing member  172  is moved in the direction opposite to the arrow shown in FIG. 23 against the urging spring (not shown). This opens the positioning mechanism  170  and the predetermined stamp making position becomes available. Using the set mark M as a general index, the holding unit U is placed approximately in the middle of the holding unit storage part  169  so that the center of the longitudinal side of the circumferential side wall  38  (rear wall), namely the inclined grooves  43  can mate with the positioning projection  177 . The holding unit U is sandwiched and held between the holder fixing members  171  and  172 . 
     As both sides of inclined grooves  43  are inclined surfaces, the holding unit U is moved to ensure that the positioning projection  177  contacts the center portion of the inclined grooves  43  based on a cam effect. Thus, contact is made between the positioning projection  177  of the positioning mechanism  170  and the inclined surfaces even in the case that the center of the longitudinal side of the circumferential side wall  38  is somewhat erroneously positioned to the set mark M. Therefore the holding unit U is placed in a predetermined stamp making position. In this position, the stamp is manufactured on the surface of the stamp material. 
     As shown in FIG. 23, when the holding unit U is placed in the positioning mechanism  170  and the positioning projection  177  properly mates with the inclined grooves  43 , the terminal  176 D of the microswitch  175 D contacts with the circumferential side wall  38  and stays in the inner part of the microswitch  175 D. The terminals  176 A and  176 F of the microswitches  175 A and  175 F also contact with the circumferential side wall  38  and stay in the inner part of the microswitches  175 A and  175 F. On the other hand, the terminals  176 B,  176 C and  176 E of the microswitches  175 B,  175 C and  175 E project into the detecting grooves  44  and are positioned out of microswitches  175 B,  175 C and  175 E, as shown in FIG.  25 . In this case, the microswitches  175 A,  175 D and  175 F are in an ON state and the microswitches  175 B,  175 C and  175 E are in an OFF state. According to the combination of the ON-OFF states of the microswitches, the type and size of the holding unit U is detected. The existence of the holding unit U in the positioning mechanism  170  is also detected according to the ON-OFF state of the microswitch  175 D. 
     Further, as shown in FIG. 23, the inclined grooves  43  and the detecting grooves  44  are rotational-symmetrically provided on both of the longitudinal sides of the holding unit U. Therefore, the holding unit U can be placed in the holding unit storage part  169  from either direction, without it being necessary for a user to take into account the orientation of the holding unit U. 
     Finally, the process by which the holding unit U is placed into the holding unit storage part  169  according to a preferred embodiment of the invention will be described with reference to FIG.  27 . As shown in the FIG. 27, the holding unit U is placed on the stage  133  of the irradiation unit  110 , by opening the upper lid  136 , the front lid  156  and the holder fixing members  171  and  172  in the positioning mechanism  170 . The original film has previously been fed from the film printing unit (not shown) and placed on the stage  133  by a feeding unit (not shown) of the film printing unit. The holding unit U is fixed in its proper position, above the original film, and its size is detected by the positioning mechanism  170 . After the upper lid  136  and front lid  156  are closed, the stamp material  3  is pressed by the presser plate  146 . 
     As mentioned above with reference to FIGS. 19 and 20, every stamp manufacturing device is formed to have almost the same distance between the presser plate  146  and the stage  133  when the upper lid  136  and front lid  156  are closed. However, the presser plate  146  and the stage  133  are subjected to a reaction force in proportion to the size of the stamp material  3  of the holding unit U. The presser plate  146  and the stage  133  bend according to an amount of the reaction force. As the result, an amount of pressure applied to the holding unit U during exposure of the stamp material may be insufficient and the quality of the manufactured stamp may be reduced. 
     To avoid insufficient pressure, the holding unit U is heightened in proportion to the size of the stamp material  3 , as shown and described with reference to FIG. 3 so as to increase the amount of pressure or to absorb the decrease in pressure caused by the bending operation. Thus, in the stamp manufacturing device  101  according to the preferred embodiment of the invention, the stamp material  3  is pressed uniformly for every size holding unit U. The heat generated at the exposed portion by the light energy absorption material is transferred to a portion of the elastic and transformable porous resin around the light energy absorption material. As a result, sealing is performed at a desired portion without requiring an increase in the amount of heat generated at the exposed light energy absorption material. For example, without increasing the energy of the exposure or having to develop a light energy absorption material that generates a higher amount of heat, a stamp having high quality can be manufactured regardless of its size. 
     Further, in the preferred embodiment of the invention, the size of the holding unit U is minimized, including the holder member  4 , which holds the stamp material  3 . Therefore, the space needed for the holding unit U in the stamp manufacturing device  101  can be small and the stamp manufacturing device  101  can be miniaturized. Further, since the positioning grooves  43  for positioning the holding unit U and the detecting grooves  44  for detecting the stamp size are provided on an upper portion of the circumferential side wall  38  of the holder member  4  and such portion is inserted and masked within the skirt member  2  when the holder member  4  is attached to grip member  5  during use, a good outward appearance is maintained. Also, since the holding unit U is formed substantially from only the holder member  4 , it is easy to maintain high reliability while heightening the holding unit U in proportion to the size of the stamp material  3  being utilized. 
     While the invention has been described in conjunction with a specific embodiment thereof, it is evident that many alternatives, modifications and variations may be apparent to those skilled in the art. Accordingly, the preferred embodiment of the invention as set forth herein is intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the invention as defined in the following claims.
A stamp unit comprising a holding unit, and a method of manufacturing a stamp unit, comprising, holding a stamp material in the holder member to create a holding unit; positioning the holding unit in a stamp manufacturing device so that the holding unit is disposed between a presser unit and an irradiation unit of the stamp manufacturing device; and pressing the holding unit by means of the presser unit so as to force a surface of the stamp material against the irradiation unit to form a desired image on a surface of the stamp material when irradiated by the irradiation unit to thereby create a stamp surface. The height of the holder member is selected in proportion to a size of the stamp material to provide a uniform pressure on the holding unit irrespective of the size of the stamp material. When the holding unit is pressed in the presser unit, a reaction force works on portions of the presser unit and the irradiation unit in proportion to the stamp material size. The reaction force causes portions of the presser unit and irradiation unit to bend. Thus, the height of the holding unit is selected in proportion to the stamp material size so as to absorb the bending or to increase the amount of pressure. Thus, the stamp material can be pressed uniformly in the stamp manufacturing device regardless of the stamp material size ensuring a good quality manufactured stamp surface.