Abstract:
A printer avoids scratching or damaging the platen and print defects caused by adhesive. The printer  1  prints to thermal paper S that has an adhesive area  150  formed on one side with the edges of the paper adhesive-free, and color layers formed on the other side of the paper. The thermal paper S is wound sequentially into a roll so that the other side is on the outside without applying a liner protecting the adhesive area  150  on the one side. The printer  1  has a platen  18 , a heating element unit  43 , and a guide incline  45 . The platen  18  is disposed to a main cover, rotates in the thermal paper S transportation direction, and applies pressure to the thermal paper S from the one side. The heating element unit  43  selectively heats the other side of the paper. The guide incline  45  guides the thermal paper S in a prescribed direction without contacting the area on the back of the adhesive area  150  on the other side of the thermal paper S after the thermal paper S passes the heating element unit  43 , and guides the platen  18  to a prescribed position so that the platen  18  does not contact the heating element unit  43  when the main cover is closed.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of Invention 
         [0002]    The present invention relates to a printer that prints by selectively heating thermal paper that reacts to heat energy. 
         [0003]    2. Description of Related Art 
         [0004]    Thermal printers are one type of printer known from the literature. Thermal printers print using a direct thermal printing method that prints to thermosensitive paper (commonly called “thermal paper”) as a result of the print head, which has small heating elements to which an electrical current is selectively applied arranged in a line, selectively fusing the color layers of the thermal paper, causing the heated dot to change to a particular color. As taught in Japanese Unexamined Patent Appl. Pub. JP-A-2004-98699 and Japanese Unexamined Patent Appl. Pub. JP-A-2001-322304, the thermal print head that prints by this direct thermal method has a pressure mechanism that urges the print head towards an opposing platen disposed to a heat radiation plate. The thermal paper is inserted between the thermal head and the platen, and is selectively heated while pressure is applied by the pressure mechanism to selectively fuse the color layers of the paper to print. The printed thermal paper is then conveyed outside the printer with the side of the paper having the color layers in contact with a guide member disposed to the heat radiation plate downstream from the thermal head. 
         [0005]    Label paper is one type of thermal paper that is printed by such thermal printers. Such label paper has an adhesive coating on the opposite side as the side containing the color layers, and a web (liner) that protects the adhesive area. Information is printed in the thermosensitive area of the label paper, and the labels can then be peeled from the liner and applied to some other object. 
         [0006]    If the platen is disposed to the main cover of the thermal printer, a mechanism for preventing the cover from hitting and damaging the thermal head when the cover is closed is needed. So that pressure can be accurately applied to the thermal paper when printing, the platen opposing the thermal head must be protected from scratching and damage particularly in the middle area where printing becomes lighter. This is commonly accomplished by providing a guide member to guide the platen to a prescribed position. However, as the cover is repeatedly opened and closed and repeatedly contacts the guide member, the platen gets scratched and damaged so that pressure is not accurately applied to the platen, contact between the platen and thermal paper therefore deteriorates, and print defects occur. 
         [0007]    A newer type of thermal paper is linerless label paper that does not have a liner protecting the adhesive area. However, because linerless label paper is wound into a roll and the adhesive side of the paper is necessarily wound against the color layer side of the paper, a small amount of the adhesive from the adhesive side inevitably adheres to the surface of the color layer side behind the adhesive side. When the surface containing the color layers of the printed linerless label paper then passes over the guide member, the adhesive sticking to the color layer surface transfers to the guide member. As the adhesive accumulates, smooth transportation of the thermal paper is impeded, contact between the thermal head and the thermal paper deteriorates, and print defects occur. 
       SUMMARY OF THE INVENTION 
       [0008]    A printer according to the present invention has a roller unit that is rotatably supported on a main cover, rotates in a thermal paper feeding direction, and applies pressure to one side of the thermal paper, a heating element unit that is disposed opposite the roller unit with the thermal paper therebetween, and selectively heats the color layers of the thermal paper, and a guide unit that guides the roller unit in a prescribed direction when the main cover closes. The guide unit has a contact unit that contacts both end parts of the roller unit. 
         [0009]    By having a contact unit rendered so that the guide unit contacts both end parts of the roller unit when the main cover closes, the middle part of the roller unit does not contact the guide unit, and is guided to a prescribed position without being scratched or damaged. 
         [0010]    A printer according to another aspect of the invention prints to thermal paper that has an adhesive side formed on one surface with a non-adhesive area formed along both edge portions and an adhesive area therebetween, and a color layer side on which color layers are formed, and is wound sequentially into a roll so that the color layer side is to the outside without a liner protecting the adhesive area on the adhesive side. A roller unit applies pressure to one side of the thermal paper while advancing the paper. A heating element unit is disposed opposite the roller unit with the thermal paper therebetween, and selectively heats the other side of the thermal paper to selectively fuse the color layers to print. The guide unit guides the thermal paper in a prescribed direction by contacting the area that is not behind the adhesive area on the color layer side of the thermal paper that is heated and conveyed. 
         [0011]    This aspect of the invention guides the printed thermal paper in the direction in which it is to travel from the other side of the paper without touching the area on this other side of the paper that is on the back of the adhesive area. In addition not touching to the adhesive area where the adhesive is coated on the one side of the paper, the guide unit therefore also does not contact the area on the other side of the thermal paper to which some adhesive from the one side is transferred as a result of the thermal paper being wound in a roll. As a result, problems caused by adhesive on the guide unit, such as the direction in which the paper is guided being skewed, poor contact between the heating element unit and the thermal paper, and print defects caused by such poor contact, can be avoided. 
         [0012]    In a printer according to another aspect of the invention, the guide unit preferably has an inclined part that causes the roller unit to slide without contacting the heating element unit to a position opposite the heating element unit, and the contact unit is disposed at an end part of the inclined part. 
         [0013]    The roller unit thus slides and is guided to a position opposite the heating element unit without colliding with the heating element unit, and damage to the heating element unit caused by collision with the roller unit can be avoided. 
         [0014]    Yet further preferably, the contact unit has curved surfaces that contact the other side of the thermal paper and the end parts of the roller unit. 
         [0015]    Because the contact unit contacts the thermal paper and the roller unit with a curved surface, the thermal paper and roller unit can be guided without creasing or marring. 
         [0016]    Other objects and attainments together with a fuller understanding of the invention will become apparent and appreciated by referring to the following description and claims taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  is an oblique view showing the appearance of a printer according to a preferred embodiment of the invention. 
           [0018]      FIG. 2  is an oblique view of the print mechanism unit when the cover frame is open. 
           [0019]      FIG. 3  is an oblique view of the print mechanism unit when the cover frame is closed. 
           [0020]      FIG. 4  is a side section view of the print mechanism unit. 
           [0021]      FIG. 5  is a section view showing the thermal head in detail. 
           [0022]      FIG. 6A  is a plan view from the platen side of the heating unit of the thermal head, and  FIG. 6B  is a section view of the middle part of the thermal head. 
           [0023]      FIG. 7  describes a roller of linerless label paper. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0024]    A preferred embodiment of the present invention is described below with reference to the accompanying figures. 
         [0025]      FIG. 1  is an oblique view showing the appearance of a printer  1  according to a preferred embodiment of the invention. The printer  1  is a thermal printer that is used as a receipt printer in a POS system, for example. The printer  1  uses thermal paper S that is wound in a roll (see  FIG. 7 ), and has a print mechanism unit  8  ( FIG. 2 ) for printing information on the thermal paper S, a paper cutting unit for cutting the printed thermal paper S, and a roll paper compartment for storing the thermal paper S. 
         [0026]    The print mechanism unit  8  ( FIG. 2 ) is attached to a bottom case  4  made of plastic, the side and back portions are covered by a top case  3 , and the front portion is covered by a panel  2 . A paper cutter unit is disposed at the top of the panel  2 . The paper cutter unit is covered by a cutter cover  6 , and the cutter cover  6  can be slid out in the direction of arrow A. 
         [0027]    An open button  7  that drives an internal cover opening lever  9  to rotate an internal cover frame  10  ( FIG. 2 ) in order to remove the thermal paper S is disposed at one side of the top case  3 . This cover frame  10  ( FIG. 2 ) is connected to a top cover  5 . When the open button  7  is pressed in the direction of arrow B, the cover opening lever  9  rotates clockwise and a lock mechanism disengages so that the top cover  5  can open in the direction of arrow C and the roll paper compartment  17  ( FIG. 2 ) is exposed. 
         [0028]    The thermal paper S used in this embodiment of the invention is linerless label paper that has an adhesive area on the opposite side as the printing surface, and is wound into a roll with the printing surface to the outside without having a web (liner) protecting the adhesive area. As shown in  FIG. 7 , the thermal paper S has an adhesive area  150  of a prescribed width W formed substantially in the center of the inside surface S 2  of the roll, and a nonadhesive area  155  from along each edge of the inside surface S 2 . A color layer having a plurality of colorants held separated by a binder is formed on the outside surface S 1  of the roll. As described above, a small amount of adhesive from the adhesive area  150  adheres to the outside surface S 1  opposite the adhesive area  150  of this thermal paper S. 
         [0029]      FIG. 2  and  FIG. 3  are oblique views of the print mechanism unit  8 ,  FIG. 2  being an oblique view of the print mechanism unit  8  when the cover frame  10  is open, and  FIG. 3  being an oblique view of the print mechanism unit  8  when the cover frame  10  is closed. 
         [0030]    The print mechanism unit  8  has a cover frame  10  that opens and closes freely to the top of a main frame  13  that is typically metal, and an automatic paper cutter unit  11  that houses a movable knife  32  and a drive means for the movable knife. When the thermal paper S is not cut, the movable knife  32  is stored inside the automatic paper cutter unit  11  and the movable knife  32  is not exposed. When thus positioned, the movable knife  32  is said to be in the standby position. 
         [0031]    A fixed knife  33  that crosses the movable knife  32  with a scissor action is disposed to the cover frame  10  opposite the automatic paper cutter unit  11 . A blade shutter  34  is disposed above the fixed knife  33 . The blade shutter  34  is urged by a shutter spring  35  in the direction covering the cutting edge of the fixed knife  33 , but when the cover frame  10  is closed as shown in  FIG. 3 , part of the blade shutter  34  contacts an engaging part disposed to the main frame  13  so that the blade shutter  34  is lifted slightly open. The cutting edge of the fixed knife  33  is thus exposed so that the movable knife  32  can move across the fixed knife  33  with a scissor action to cut the paper. 
         [0032]    The cover frame  10  is attached to pivot, that is, open and close freely, on support pins  14  provided at the top part on both sides of the main frame  13 . A cover part  15  disposed to the cover frame  10  is curved so that the cover part  15  does not contact the thermal paper S when the cover frame  10  is closed. When the orientation of the printer installation is changed, this cover part  15  also functions as a holding member that receives the thermal paper S. 
         [0033]    A cover detector  44  that detects if the cover frame  10  is closed is disposed on the right side of the main frame  13 . This cover detector  44  is a transmission type photodetector, and detects whether or not the cover frame  10  is closed correctly based on whether the light beam from the detector is interrupted by a part of the cover frame  10 . 
         [0034]    A near-end detector  24  and a paper detector  30  described below are also provided in addition to this cover detector  44 . Leads  12  from these detectors, the automatic paper cutter unit  11 , and a paper transportation motor  23  described below are connected to a relay board  16  attached to the right side of the main frame  13 . The relay board  16  and a main circuit board (not shown in the figure) that controls the printer  1  are connected by a flat flexible cable, for example. 
         [0035]      FIG. 2  is an oblique view from the left side of the print mechanism unit  8 , and shows the cover frame  10  open and the blade shutter  34  covering the fixed knife  33 . This arrangement is to prevent the operator from touching and being cut by the fixed knife  33  when the cover frame  10  is open. The movable knife  32  is housed inside the automatic paper cutter unit  11  and does not present a safety problem. 
         [0036]    A plastic roll paper compartment  17  is disposed inside the open cover frame  10 . The paper detector  30  for detecting if paper is present is disposed to the roll paper compartment  17 . The paper detector  30  is a reflection type photodetector, and a group of holes  31  is disposed on the upstream side of the paper detector  30 . The holes  31  allow foreign matter and chaff clinging to the thermal paper S to drop out so that the paper dust or other foreign matter does not interfere with detector operation. Slots  27  for engaging the right and left side panels of the main frame  13  are also rendered in the roll paper compartment  17 . When these slots  27  engage the right and left side panels of the main frame  13 , the widthwise position of the roll paper compartment  17  is fixed and the inside of the roll paper compartment is held at a width suitable to the thermal paper S. 
         [0037]    A platen  18 , which is a roller unit having a cylindrical rubber roller, is supported rotatably on the cover frame  10  by a platen shaft  20 . A platen gear  19  is press fit to one end of the platen  18 . A groove part  21  is rendered to the main frame  13  so that when the cover frame  10  closes, the platen shaft  20  is guided by a guide incline  45  of the heat radiation plate  47  ( FIG. 4 ) and then contacts the groove part  21 , and the platen  18  is positioned in a prescribed position. Pressure from the thermal head  39  ( FIG. 4 ) on the platen  18  works to push down on the cover frame  10  and determine the position of the platen  18 . The platen gear  19  and paper transportation transfer gear  22  also mesh and power is transmitted from the paper transportation motor  23  to the platen  18 . 
         [0038]    The near-end detector  24  for detecting if the thermal paper S is near the end of the roll is disposed freely rotatably on a support pin  25  on the left side of the main frame  13 . This arrangement enables the near-end detector  24  to be optimally positioned according to the orientation angle of the printer. For example, when the printer is used with the bottom  28  of the cover frame  10  down as shown in  FIG. 2 , the actuator  26  of the near-end detector  24  is fixed inside a hole  32   a  rendered in the cover frame  10 . When the printer is used with the back  29  of the cover frame  10  down, however, the actuator  26  is fixed in position in a separate hole  32   b . A support channel unit  50  that supports the thermal head  39  ( FIG. 4 ) and the head pressure plate  41  ( FIG. 4 ) is rendered at the left and right sides of the main frame  13 . 
         [0039]      FIG. 4  is a side section view of the print mechanism unit  8 , and shows the thermal paper S roll paper compartment  17  held in the roll paper compartment  17  with the leading end delivered in the discharge direction (D).  FIG. 4  shows the thermal paper S when the diameter is large. As the paper is advanced and the diameter of the thermal paper S becomes small enough, the thermal paper S drops into the recess  38  and the near-end detector  24  thus detects that the roll diameter of the thermal paper S has become a certain small size. 
         [0040]      FIG. 5  is a section view showing the thermal head  39  in detail. As shown in this figure, a head support pin  40  is disposed on both sides of the thermal head  39 , and the head support pins  40  are supported on a part of the support channel unit  50  disposed to the main frame  13 . The heating element unit  43  disposed to the thermal head  39  is urged by a spring  42  toward the platen  18 . The spring  42  is affixed to the head pressure plate  41 , and the head pressure plate  41  is supported by the support channel unit  50   b  disposed to the main frame  13 . With this arrangement the thermal paper S is held between the platen  18  and the heating element unit  43  with the platen  18  pressing the thermal paper S from the inside surface S 2  side to the thermal head  39 , and the heating element unit  43  of the thermal head  39  opposite the platen  18  pressed against the outside surface S 1  of the thermal paper S. 
         [0041]      FIG. 6A  is a plan view from the platen  18  side of the heating element unit  43  area of the thermal head  39 , and  FIG. 6B  is a section view through approximately the middle of  FIG. 6A . The thermal head  39  uses the heat radiation plate  47  as a base, and a guide incline  45  is formed as a guide unit on one end part on the side of the heat radiation plate  47  facing the platen  18 . When the cover frame  10  closes, the platen  18  slides along the guide incline  45  and is guided thereby to a prescribed position. The slope of the guide incline  45  is an angle preventing the platen  18  from colliding with the heating element unit  43 . This guide unit is also disposed so that the platen does not strike the end part of the heating element unit  43  and the heating element unit is not damaged. As also shown in  FIG. 6B , a notched part  110  of a prescribed width L is disposed and in this embodiment of the invention a surface of substantially the same thickness as the flat part of the heat radiation plate  47  is formed in the center at the end where the platen  18  slides across the guide incline  45 . The prescribed width L is set to be longer than the width M of the adhesive area  150  of the thermal paper S. The inclined face of the guide incline  45  is set at approximately the same height as the heating element unit  43  disposed proximally to the guide incline  45 . 
         [0042]    The heating element unit  43  is described next with reference to  FIG. 5  and  FIG. 6 . The heating element unit  43  is formed on a base substrate made from an alumina ceramic, for example, and though not shown in the figures, an underglaze layer, metal electrodes, a common electrode, and a protective film are formed in layers on the substrate surface. A linear heating resistor  140  that converts an applied current to heat is embedded protected by the protective film along the length of the heating element unit  43 . This heating resistor  140  has hundreds of fine heating elements arrayed in a line. When the heating elements are selectively energized, only the energized heating elements instantaneously emit heat. When the heating element is de-energized, the heat is instantly dissipated by the heat radiation plate  47 . The heating resistor  140  is embedded substantially at the point of tangency between the platen  18  and the thermal head  39 . 
         [0043]    An epoxy molding  130  containing a sealed driver chip for selectively energizing the heating resistor  140  is disposed near the other end of the heat radiation plate  47  as the surface where the heat radiation plate  47  faces the platen  18 , and a glass epoxy circuit board  135  wired to the epoxy molding  130  extends beyond this other end. A connector  46  connected by a flat flexible cable, for example, to the main circuit board (not shown in the figure) that controls the printer  1  is disposed to the end part of the glass epoxy circuit board  135 . 
         [0044]    The thermal paper S is thus sequentially advanced in the discharge direction (D) by the platen  18  while pressed against the heating resistor  140  of the heating element unit  43 . As the paper advances, the heating resistor  140  emits heat from the heating elements in response to signals sent from the main circuit board (not shown in the figure) through the connector  46 . The thermal paper S is thus selectively heated across the width so that the color layers formed on the outside surface S 1  are selectively fused as the thermal paper S advances sequentially lengthwise and information is printed to the thermal paper S according to the applied signals. After passing the heating element unit  43 , both edge parts on the outside surface S 1  of the thermal paper S contact the distal end parts  120  formed with a curve at the ends of the guide incline  45  so that the thermal paper S is guided upward without curling, and are guided into the paper cutter unit by the guide portions  48  disposed to the cover frame  10 . 
         [0045]    Because a notched part  110  is disposed to the guide incline  45 , the part of the outside surface S 1  on the back of the adhesive area  150  formed in the middle of the inside surface S 2  is guided upward without touching the guide incline  45 . More particularly, adhesive material sticking to the area of the outside surface S 1  behind the adhesive area  150  does not stick to the guide incline  45 , and the paper is discharged with the adhesive remaining on the outside surface S 1 . The thermal paper S guided to the paper cutter unit passes between the movable knife  32  and fixed knife  33 , and is discharged from the printer  1 . 
         [0046]    The invention is described above with reference to a preferred embodiment thereof, but is not limited to this embodiment and can be varied in many ways, including the variations described below. 
         [0047]    (1) The heat radiation plate  47  can be a thin plate that is bent to form the guide incline  45 . The notched part  110  is not limited to a flat surface, and can be any shape that does not contact the area of the outside surface S 1  behind the adhesive area  150 . 
         [0048]    (2) The width L of the notched part  110  can be adjusted according to the width M of the adhesive area  150  of the thermal paper S. 
         [0049]    (3) The platen  18  is not limited to being supported on the top cover  5 . For example, the thermal head could be disposed to the top cover  5  and the platen could be disposed to the main frame. 
         [0050]    The invention being thus described, it will be obvious that it may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.