JP2011046155A - Thermal printer and printing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal printer which improves a printing quality by preventing contact marks of a feed roller from being impressed on a printing surface, and to provide a printing method. <P>SOLUTION: The thermal printer 1 includes a first thermal head 11 for printing one surface Pa of a paper P, a second thermal head 13 arranged on the opposite side to the first thermal head 11 with respect to the paper P and for printing another surface Pb of the paper P, and the feed roller 15 which conveys the paper P through contact with either of one surface Pa and another surface Pb. A distance on a pass line T between the feed roller 15 and either of the first thermal head 11 arranged on the same side as the feed roller 15 with respect to the paper P and the second thermal head 13 is set to be longer than a print length PL of the paper P. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a thermal printer and a printing method, and more particularly to a thermal printer and a printing method for performing duplex printing.

  There has been proposed a thermal printer that prints on a printing medium such as paper by using an ink ribbon to which ink is applied. An example of a thermal printer is a sublimation printer. In a sublimation type printer, a print medium and an ink ribbon are simultaneously conveyed and heated by a thermal head in a superposed state. As a result, the ink applied to the ink ribbon is sublimated and transferred to the paper, thereby printing the print medium.

  The ink ribbon is formed with an ink layer to which inks of three colors Y (yellow), M (magenta), and C (cyan) are applied. In addition, an overcoat layer is formed on the YMC print area in order to protect the print surface after the YMC ink is printed on the print medium.

  In such a sublimation printer, a printer capable of printing on both sides of a sheet has been proposed. For example, Japanese Patent Laid-Open No. 10-76713 (Patent Document 1) describes a sublimation heat transfer type double-sided simultaneous printing printer apparatus. This double-sided simultaneous printing printer apparatus includes a sublimation heat transfer type front surface printing head and a back surface printing head, and the front surface printing head and the back surface while a sheet of printing paper is staying in the apparatus. Printing is performed on both sides of the printing paper by simultaneously driving the printing head.

JP-A-10-76713

  In the sublimation thermal transfer type double-sided simultaneous printing printer apparatus disclosed in the above publication, a feed roller is applied to the front surface on which the overcoat (laminate) layer is printed after the YMC ink is printed. The third feed roller is in contact.

  When the feed roller comes into contact with the print surface, the surface of the feed roller is pressed against the print surface, so that contact marks of the feed roller are conspicuous on the print surface, and the print quality deteriorates.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a thermal printer and a printing method for improving print quality by not making contact marks of a feed roller on a print (print) surface. is there.

  A thermal printer according to the present invention includes a first head for printing one side of a print medium, a print head disposed on the opposite side of the first head, and for printing the other side of the print medium. A second head and a feed roller for conveying the print medium in contact with one of the one side and the other side are provided. The distance on the pass line between either the first head or the second head arranged on the same side as the feed roller with respect to the print medium and the feed roller is longer than the print length of the print medium.

  According to the thermal printer of the present invention, the distance on the pass line between the head and the feed roller located on the same side as the feed roller with respect to the print medium of the first head and the second head is the print medium print. It is set to be longer than the length. For this reason, it is possible to prevent the feed roller from coming into contact with the print (print) surface of the print medium. Thereby, since the contact trace of a feed roller does not adhere to the printing surface of a printing medium, print quality can be improved.

  In the above thermal printer, the distance on the pass line between either the first head or the second head and the feed roller is preferably set so that the same side is shorter than the opposite side. As a result, not only the feed roller but also the pinch roller can be prevented from contacting the printing surface of the printing medium.

  In the above thermal printer, the distance on the pass line between either the first head or the second head and the feed roller is preferably set so that the same side is longer than the opposite side. As a result, the thermal printer can be made smaller because the distance between the feed roller and the head on the opposite side can be shortened compared to the case where the head on the same side as the feed roller is arranged closer to the head on the opposite side. Can do.

  In the above thermal printer, the feed roller preferably has a protrusion on the surface. As a result, the position of the print medium is fixed by the protrusion on the surface of the feed roller, so that the print medium can be conveyed more accurately.

  The printing method of the present invention includes a step of printing with a first head for printing one side of a print medium, a side opposite to the first head with respect to the print medium, and the other side of the print medium A step of printing with a second head for printing, and a step of bringing the print medium into contact with one of the one side and the other side with a feed roller. The feed roller contacts a portion different from the portion of the print medium printed by the first head and the second head.

  According to the printing method of the present invention, since the feed roller contacts a part different from the part of the print medium printed by the first head and the second head, the feed roller is placed on the printed part of the print medium. It can be prevented from touching. As a result, since the contact mark of the feed roller is not formed on the printed portion of the print medium, the print quality can be improved.

  In the present invention, the pass line means a paper transport path from the paper roll to the paper cutter.

  As described above, according to the present invention, it is possible to improve the print quality by not providing the contact mark of the feed roller on the print (print) surface.

1 is a side view schematically showing a configuration of a printing unit of a thermal printer in an embodiment of the present invention. It is a top view which shows roughly the structure of the 1st and 2nd ink ribbon used with the thermal printer in one embodiment of this invention. 1 is a block diagram schematically showing a system configuration of a thermal printer in an embodiment of the present invention. It is a side view which shows schematically the printing method in one embodiment of the present invention, Comprising: The printing start state (A) of one side, the printing end state (B) of one side, and the printing start state of the other side ( It is a side view which shows C) and the printing completion state (D) of the other side. It is a side view which shows roughly the structure of the printing part of the thermal printer in the modification of one embodiment of this invention. FIG. 9 is a side view schematically showing a printing method in a modification of an embodiment of the present invention, in which a printing start state (A) on one side, a printing end state (B) on one side, and printing on the other side It is a side view which shows a start state (C) and the printing completion state (D) of the other side. It is a side view which shows roughly the protrusion of the feed roller of the thermal printer in one embodiment of this invention. It is a top view which shows roughly the protrusion of the feed roller of the thermal printer in one embodiment of this invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
First, the configuration of a thermal printer according to an embodiment of the present invention will be described.

  First, the configuration of the printing unit 10 of the thermal printer 1 according to the embodiment of the present invention will be described. Referring to FIG. 1, a printing unit 10 of a thermal printer 1 according to an embodiment of the present invention includes a one-side printing mechanism 101, the other-side printing mechanism 102, a printing medium transport mechanism 103, a paper roll 19, The paper cutter 29 is mainly included.

  The one-side printing mechanism 101 is disposed on one side of the paper P that has been unwound from the paper roll 19 and is a printing mechanism for printing the one side Pa. The other side printing mechanism 102 is disposed on the other side of the sheet P opposite to one side, and is a printing mechanism for printing the other side Pb. Both the one side Pa and the other side Pb of the paper P can be printed by the one side printing mechanism 101 and the other side printing mechanism 102.

  The print medium transport mechanism 103 is a transport mechanism for feeding the paper P to the one-side printing mechanism 101 and the other-side printing mechanism 102 and moving the paper P during printing. The print medium transport mechanism 103 is a transport mechanism for discharging the printed paper P. The paper roll 19 is for winding and holding the paper P conveyed by the printing medium conveyance mechanism 103 in a roll shape. The paper cutter 29 has a predetermined size corresponding to a print length PL (FIG. 4A) that is a length corresponding to one printing unit of the paper P printed by the one-side printing mechanism 101 and the other-side printing mechanism 102. It is for cutting with.

  The one-side printing mechanism 101 includes a first thermal head (head) 11, a first platen roller 12, a first ink ribbon supply roller 17a, a first ink ribbon take-up roller 17b, The ink ribbon R1 is mainly included.

  The first thermal head 11 for printing the one side Pa is arranged on the one side Pa side of the paper P supplied from the paper roll 19. On the side of the paper cutter 29 of the first thermal head 11, a first ink ribbon supply roller 17a in which an unused first ink ribbon R1 is wound in a roll shape is disposed. On the paper roll 19 side of the first thermal head 11, a first ink ribbon take-up roller 17b around which a used first ink ribbon R1 is wound is disposed.

  The first ink ribbon R1 (unused first ink ribbon R1) unwound from the first ink ribbon supply roller 17a is guided by the ink ribbon guide roller 17c and overlapped with the paper P to be the first. The thermal head 11 and the first platen roller 12 are arranged so as to be conveyed. The first platen roller 12 is configured to press the paper P against the heating resistor of the first thermal head 11. The first ink ribbon R1 (used first ink ribbon R1) heated by the first thermal head 11 is guided by the ink ribbon guide roller 17d and taken up by the first ink ribbon take-up roller 17b. Is arranged to be.

  The other-side printing mechanism 102 includes a second thermal head (head) 13, a second platen roller 14, a second ink ribbon supply roller 18a, a second ink ribbon take-up roller 18b, It mainly has an ink ribbon R2.

  The second thermal head 13 for printing the other surface Pb of the paper P is disposed on the other surface Pb side opposite to the first thermal head 11 with respect to the paper P. On the side of the paper cutter 29 of the second thermal head 13, a second ink ribbon supply roller 18a in which an unused second ink ribbon R2 is wound in a roll shape is disposed. On the paper roll 19 side of the second thermal head 13, a second ink ribbon take-up roller 18b in which a used second ink ribbon R2 is wound in a roll shape is disposed.

  The second ink ribbon R2 (unused second ink ribbon R2) unwound from the second ink ribbon supply roller 18a is guided by the ink ribbon guide roller 18c and overlapped with the paper P to be second. The thermal head 13 and the second platen roller 14 are arranged so as to be conveyed. The second platen roller 14 is configured to press the paper P against the heating resistor of the second thermal head 13. The second ink ribbon R2 (used second ink ribbon R2) heated by the second thermal head 13 is guided by the ink ribbon guide roller 18d and taken up by the second ink ribbon take-up roller 18b. Is arranged to be.

  Each side of the one-side printing mechanism 101 and the other-side printing mechanism 102 is disposed on the opposite side of the paper P. The first thermal head 11 and the second thermal head 13 each have a heating resistor provided corresponding to each dot for one line of the image. Note that the heating resistors may be arranged on a plurality of lines, respectively.

  The print medium transport mechanism 103 mainly includes a feed roller 15 and pinch rollers 16a and 16b. The feed roller 15 is configured to contact one surface Pa of the paper P, and the pinch rollers 16a and 16b are configured to contact the other surface Pb. The feed roller 15 and the pinch rollers 16a and 16b are configured to convey with the paper P interposed therebetween. The feed roller 15 and the pinch rollers 16a and 16b are configured to convey the paper P to the paper roll 19 side when printing the paper P.

  The feed roller 15 may have a protrusion on the surface. As shown in FIGS. 7 and 8, for example, the protrusion 151 may be formed with a height PH of 20 μm or more and 100 μm or less. The protrusion 151 may be formed with Ra (arithmetic mean roughness) of 20 μm or more and 100 μm or less. A plurality of protrusions 151 may be formed on the surface. The protrusions 151 may be formed at the end portions FA on both sides of the feed roller 15. For example, the length FL of the feed roller 15 may be 200 mm, and the lengths of the end portions FA on both sides may be 40 mm. In addition, the diameter of the feed roller 15 may be formed with 16-20 mm, for example.

  For example, the plurality of protrusions 151 may be arranged at intervals of 0.5 mm in the circumferential direction of the feed roller 15. Further, for example, the plurality of protrusions 151 may be arranged at intervals PW of 0.5 mm in the axial direction of the feed roller 15. Since the protrusions 151 are formed on the surface in this way, the feed roller 15 can control the transport position of the paper P more accurately.

  The feed roller 15 is disposed on the same side (one surface Pa side) of the first thermal head 11 and the paper P. Pinch rollers 16 a and 16 b are disposed on the opposite side of the paper P from the feed roller 15. The feed roller 15 is configured to be rotationally driven by a paper transport motor 28 (FIG. 3). The pinch rollers 16 a and 16 b are configured to be driven to rotate by being driven by the feed roller 15 when the rotation of the feed roller 15 is transmitted across the paper P.

  A paper roll guide roller 19 a is disposed along the paper P from the feed roller 15 toward the paper roll 19. A paper roll guide roller 19b is disposed between the paper roll guide roller 19a and the paper P.

  The paper roll 19 is configured to unwind and supply the paper (print medium) P. The paper P is supplied toward the feed roller 15 through the paper roll guide rollers 19a and 19b. The paper P is sandwiched between the feed roller 15 and the pinch rollers 16 a and 16 b and is supplied to the first thermal head 11. The paper P passes between the first thermal head 11 and the first platen roller 12 and is supplied to the second thermal head 13. The paper P passes between the second thermal head 13 and the second platen roller 14 and is supplied to the paper discharge side where the paper cutter 29 is disposed.

  A path from the paper roll 19 to the paper cutter 29 forms a paper transport path (pass line) T. The paper roll 19 is positioned upstream of the pass line T (paper supply side).

  The paper cutter 29 is disposed on the paper discharge side opposite to the paper roll 19 along the pass line T. The paper cutter 29 is located downstream of the pass line T (paper discharge side).

  The feed roller 15 is arranged at a position away from the print length PL on the pass line T from the first thermal head 11 arranged on the same side with respect to the paper P. The feed roller 15 is disposed on the upstream side of the pass line T from the first thermal head 11. As a result, even when the paper P is printed upstream by the first thermal head 11, the first feed roller 15 is arranged at a position away from the print length PL, and the paper P is printed. After that, since it is conveyed downstream, the feed roller 15 is configured not to contact the printing surface PS of the paper P (FIG. 4B).

  The print length PL is a length obtained by combining the length in the extending direction of the printed paper P and the length of the extension. The print length PL has a contact point between the thermal head and the paper P as a measurement reference position. The distance from the measurement reference position to the contact point between the feed roller 15 and the paper P is set to be longer than the print length PL. The print length PL varies depending on the size of the paper P to be printed. When a plurality of sizes of paper P are used, the print length PL can be a length corresponding to one printing unit of the maximum size of paper P to be used.

  Referring to FIG. 2, each of the first ink ribbon R1 and the second ink ribbon R2 includes three ink layers of Y (yellow), M (magenta), and C (cyan), and OP (overcoat). Layer) is periodically arranged in the extending direction. By providing YMC three colors of ink, it is possible to print in full color. By providing the overcoat layer OP, it is possible to protect the print area of YMC ink. The first ink ribbon R1 and the second ink ribbon R2 have the same configuration. Each ink of YMC of the ink layer is formed by, for example, a dye-based sublimation ink. The overcoat layer OP is formed of a laminate material, for example.

  Next, the system configuration of the thermal printer according to the embodiment of the present invention will be described. Referring to FIG. 3, a thermal printer (printer) 1 includes a main control unit 21, an image buffer 22, a print control unit 23, an energization pulse generation unit 24, a thermal head 25, and a motor drive control unit 26. Ink ribbon supply side motor 27a, ink ribbon take-up side motor 27b, paper transport motor 28, paper cutter 29, and print unit 10 are mainly included.

  The main control unit 21 includes, for example, a CPU and is configured to control each unit. The image buffer 22 receives an image to be printed as image data such as YMC (Y (yellow), M (magenta), C (cyan)) from an external control device such as a host (host computer) 2. It is configured to store temporarily.

  The print control unit 23 is configured to perform control for printing each image corresponding to the image data transmitted from the host 2. The print controller 23 includes a print image data generator 23a, an ink ribbon take-up / rewind processor 23b, a roll paper drive processor 23c, a thermal head heating controller 23d, and an ink ribbon diameter calculator 23e. have.

  The print image data generation unit 23a is a processing unit for converting the image data stored in the image buffer 22 into print image data corresponding to the inks Y, M, and C of the ink ribbon.

  The ink ribbon winding / rewinding processing unit 23b outputs a command signal to the motor drive control unit 26 based on the printing image data generated by the printing image data generating unit 23a, and the ink ribbon supply side motor 27a and a processing unit for driving the ink ribbon winding side motor 27b.

  The roll paper drive processing unit 23c outputs a command signal to the motor drive control unit 26 based on the print image data generated by the print image data generation unit 23a, and drives the paper transport motor 28 to make the paper It is a processing unit that performs control so that P is transported at a predetermined transport speed and transport amount. Further, the roll paper drive processing unit 23c is configured to control the drive of the paper cutter 29 for performing the paper P cutting process.

  The thermal head heating control unit 23d is a control for controlling the amount of heat output from the thermal head 25 according to the density gradation of each image, based on the print image data generated by the print image data generation unit 23a. A signal is generated and output to the thermal head 25 via the energization pulse generator 24.

  The energization pulse generator 24 is configured to energize the heat generating resistor in the thermal head 25 with an energization pulse pattern corresponding to the gradation (density) based on a control signal from the thermal head heating controller 23d. Has been.

  The thermal head 25 is configured to heat the heating resistor based on pulse energization from the energization pulse generator 24. The thermal head 25 is a functional block including the first thermal head 11 and the second thermal head 13. The first thermal head 11 is configured such that the heating resistor is pulse-energized based on the print image data printed on the one surface Pa of the paper P. The second thermal head 13 is configured such that the heating resistor is pulse-energized based on print image data printed on the other side Pb of the paper P.

  The ink ribbon diameter calculator 23e calculates the diameter of the first ink ribbon R1 from the transport amount of the paper P and the rotation speeds of the first ink ribbon supply roller 17a and the first ink ribbon take-up roller 17b. It is an operation part. The ink ribbon diameter calculator 23e calculates the diameter of the second ink ribbon R2 from the transport amount of the paper P and the rotation speeds of the second ink ribbon supply roller 18a and the second ink ribbon take-up roller 18b. It is a calculating part for.

  The ink ribbon diameter calculation unit 23e is configured to acquire the transport amount of the paper P based on an input from the roll paper drive processing unit 23c. The ink ribbon diameter calculation unit 23e rotates the first ink ribbon supply roller 17a and the first ink ribbon take-up roller 17b, and rotates the second ink ribbon supply roller 18a and the second ink ribbon take-up roller 18b. Configured to get a number.

  The ink ribbon diameter calculator 23e sets the transport amount of the paper P as the transport amount A of the first ink ribbon R1, and the respective rotation angles θ (rad) of the first ink ribbon supply roller 17a and the ink ribbon take-up roller 17b. Thus, the ink ribbon diameter B of the first ink ribbon R1 is obtained by calculation according to the relationship B = A / θ. The ink ribbon diameter calculator 23e is configured to obtain the ink ribbon diameter of the second ink ribbon R2 by the same calculation as that of the first ink ribbon R1.

  The motor drive control unit 26 is configured to drive and control the ink ribbon supply side motor 27a, the ink ribbon take-up side motor 27b, and the paper transport motor 28. The motor drive control unit 26 is configured to feed back the rotational speeds of the ink ribbon supply side motor 27a and the ink ribbon winding side motor 27b to the print control unit 23 in a timely manner.

  The ink ribbon supply side motor 27a drives the first ink ribbon supply roller 17a (FIG. 1) and the second ink ribbon supply roller 18a (FIG. 1), and the first ink ribbon R1 (FIG. 1) and the first ink ribbon R1 (FIG. 1). The second ink ribbon R2 (FIG. 1) is supplied at a predetermined transport speed and transport amount. The ink ribbon supply side motor 27a is provided with an encoder for detecting the rotation angle. This encoder is configured to detect the rotational speeds of the first ink ribbon supply roller 17a (FIG. 1) and the second ink ribbon supply roller 18a (FIG. 1). The detection result is output to the ink ribbon diameter calculation unit 23e by the motor drive control unit 26.

  The ink ribbon take-up motor 27b drives the first ink ribbon take-up roller 17b and the second ink ribbon take-up roller 18b to move the first ink ribbon R1 and the second ink ribbon R2 to a predetermined level. It is configured to wind up at a conveyance speed and a conveyance amount. The ink ribbon winding side motor 27b is provided with an encoder for detecting a rotation angle. This encoder is configured to detect the rotational speeds of the first ink ribbon take-up roller 17b (FIG. 1) and the second ink ribbon take-up roller 18b (FIG. 1). The detection result is output to the ink ribbon diameter calculation unit 23e by the motor drive control unit 26.

  The paper transport motor 28 is configured to transport the paper P by driving the feed roller 15. The paper cutter 29 is configured to receive a command signal from the roll paper drive processing unit 23c and cut the paper P. The printing unit 10 is a mechanism unit that performs a printing operation as described above, and is controlled by the above-described units.

Next, the operation of the thermal printer according to the embodiment of the present invention will be described.
1 to 3, when the print control unit 23 acquires image data from the external host 2 via the image buffer 22, the print image data generation unit 23 a generates print image data. The print control unit 23 performs each process in the ink ribbon winding / rewinding processing unit 23b and the roll paper drive processing unit 23c based on the generated image data for printing.

  That is, when the command signal is input from the roll paper drive processing unit 23c to the motor drive control unit 26, the paper transport motor 28 is rotationally driven. The paper transport motor 28 rotates the feed roller 15. The paper P is sandwiched between the feed roller 15 and the pinch rollers 16a and 16b, the feed roller 15 is rotationally driven, and the paper P is conveyed along the pass line T. The sheet P is sent to the downstream side (paper cutter 29 side) by one printing unit corresponding to the printing image data. The length corresponding to one printing unit corresponds to the print length PL.

  Subsequently, when the roll paper drive processing unit 23c inputs a command signal to the motor drive control unit 26, the paper transport motor 28 is rotationally driven, and the fed paper P is fed by the feed roller 15 and the pinch rollers 16a and 16b. It is transported at a predetermined transport speed and transport amount toward the upstream side (paper roll 19 side).

  When the ink ribbon take-up / rewind processing unit 23b inputs a command signal to the motor drive control unit 26, the ink ribbon supply side motor 27a and the ink ribbon take-up side motor 27b are driven to have a predetermined tension and transport amount. The first ink ribbon R1 and the second ink ribbon R2 are conveyed. The ink ribbon winding / rewinding processing unit 23b controls the first ink ribbon R1 and the second ink ribbon R2 to be arranged at appropriate positions when printing.

  The ink ribbon diameter calculation unit 23e inputs the calculation results of the ink ribbon diameters of the first ink ribbon R1 and the second ink ribbon R2 to the ink ribbon winding / rewinding processing unit 23b. Accordingly, the first ink ribbon R1 and the second ink ribbon R2 are sent out with reference to the ink ribbon diameters of the first ink ribbon R1 and the second ink ribbon R2 on the supply side and the take-up side.

  Timely detection results are output from the encoders provided in the ink ribbon supply side motor 27a and the ink ribbon take-up side motor 27b, and the motor drive control unit 26 feeds back the detection results to provide feedback to the ink ribbon supply side motor 27a. And the ink ribbon winding side motor 27b is controlled.

  Thus, when one side Pa of the paper P is printed, the one side Pa of the paper P and the first ink ribbon R1 are transported upstream at the same transport speed. Further, when the other side Pb of the paper P is printed, the paper P is transported upstream at the same transport speed in a state where the other surface Pb of the paper P and the second ink ribbon R2 are overlapped. Thus, the double-sided printing of the paper P is performed by printing the one side Pa and the other side Pb of the paper P.

  The thermal head heating control unit 23d selectively causes the heating resistors of the first thermal head 11 and the second thermal head 13 to generate heat, whereby the first and second ink ribbons R1 are first formed on the paper P. , R2 ink layer Y (yellow) ink is transferred in a predetermined pattern. Subsequently, the paper P is again conveyed downstream. By repeating the above operation, Y (yellow), M (magenta), and C (cyan) inks are transferred to the same printing range on the paper P. Thereby, a desired color image is printed on the paper P. Further, the overcoat layer OP is transferred onto the YMC color image by the same operation.

  With reference to FIGS. 4A to 4D, a printing method according to an embodiment of the present invention will be described. 4A to 4D, the feed roller 15, the pinch rollers 16a and 16b, the first thermal head 11, the first platen roller 12, and the second thermal head are shown for ease of viewing. 13, the second platen roller 14, and only the paper P are illustrated as being linearly arranged.

  Referring to FIG. 4A, the feed roller 15 is in contact with one surface Pa of the paper (print medium) P. The pinch rollers 16a and 16b are in contact with the other side Pb of the paper P. The feed roller 15 is rotationally driven with the paper P sandwiched between the feed roller 15 and the pinch rollers 16a and 16b, and the paper P is conveyed in the direction of the second thermal head 13. The paper P is sent out in accordance with the print length PL corresponding to the print image data on the one side Pa.

  Referring to FIG. 4B, the first thermal head 11 prints one side Pa of the paper P. When the paper P is conveyed to the feed roller 15 side, the YMC inks and the overcoat layer OP are transferred to one side Pa of the paper P to form a printing surface PS. The distance D1 on the pass line T between the feed roller 15 and the first thermal head 11 is set to be longer than the print length PL of the paper P. More specifically, the distance D1 on the pass line T from the contact point between the feed roller 15 and the paper P to the contact point between the first thermal head 11 and the paper P is longer than the print length PL of the printing surface PS of the paper P. It is set to be. Therefore, even if the paper P is conveyed to the feed roller 15 side, the feed roller 15 does not contact the printing surface PS.

  Referring to FIG. 4C, the paper P is conveyed to the second thermal head 13 side by the feed roller 15. The paper P is conveyed from the contact point between the second thermal head 13 and the paper P to the paper cutter 29 (FIG. 1) side in accordance with the print length PL corresponding to the image data for printing on the other side Pb.

  Referring to FIG. 4D, the second thermal head 13 prints the other side Pb of the paper P. On the other side Pb of the paper P, the YMC inks and the overcoat layer OP are printed to form a printing surface PS. The distance D2 on the pass line T between the feed roller 15 and the second thermal head 13 is also set to be longer than the print length PL of the print surface PS.

  As shown in FIGS. 4A to 4D, the feed roller 15 conveys the paper P in contact with a portion different from the printing surface PS that is a printed portion of the one surface Pa of the paper P. Therefore, the feed roller 15 does not come into contact with the printing surface PS on both surfaces (one surface Pa and the other surface Pb) of the paper P. Thereafter, the printing surface PS corresponding to the print length PL formed at the leading end of the paper P is cut off by a paper cutter 29 (FIG. 1) (not shown).

  In the above description, the distance on the pass line T with respect to the feed roller 15 is such that the first thermal head 11 disposed on the same side as the feed roller 15 with respect to the paper P is disposed on the opposite side. It is configured to be shorter than 13. However, as in the modification shown in FIG. 5, the distance on the pass line T with respect to the feed roller 15 is opposite to the second thermal head 13 arranged on the same side as the feed roller 15 with respect to the paper P. The first thermal head 11 may be configured to be longer than the first thermal head 11.

  Referring to FIG. 5, in the modification, the feed roller 15 is disposed on the other side Pb side of the paper P. The pinch rollers 16a and 16b are arranged on the one surface Pa side of the paper P. The second thermal head 13 is disposed on the other surface Pb side that is the same side as the feed roller 15 with respect to the paper P. The first thermal head 11 is disposed on the one surface Pa side opposite to the feed roller 15 with respect to the paper P. The distance on the pass line T between the second thermal head 13 and the feed roller 15 is set to be longer than the distance between the first thermal head 11 and the feed roller 15.

  With reference to FIGS. 6A to 6D, a printing method according to a modification of the embodiment of the present invention will be described. 6A to 6D, the feed roller 15, the pinch rollers 16a and 16b, the first thermal head 11, the first platen roller 12, and the second thermal head are shown for ease of viewing. 13, the second platen roller 14, and only the paper P are illustrated as being linearly arranged.

  Referring to FIG. 6A, the feed roller 15 is in contact with the other side Pb of the paper P. The pinch rollers 16a and 16b are in contact with one side Pa of the paper P. The feed roller 15 is rotationally driven with the paper P sandwiched between the feed roller 15 and the pinch rollers 16a and 16b, and the paper P is conveyed in the direction of the second thermal head 13. The paper P is sent out in accordance with the print length PL corresponding to the print image data on the one side Pa.

  Referring to FIG. 6B, the first thermal head 11 prints one side Pa of the paper P. When the paper P is conveyed to the feed roller 15 side, the YMC inks and the overcoat layer OP are transferred to one side Pa of the paper P to form a printing surface PS. The distance D1 on the pass line between the feed roller 15 and the first thermal head 11 is set to be shorter than the print length PL of the one side Pa of the paper P. More specifically, the distance D1 on the pass line T from the contact point between the feed roller 15 and the paper P to the contact point between the first thermal head 11 and the paper P is shorter than the print length PL of the printing surface PS of the paper P. It is set to be.

  Therefore, when the paper P is conveyed to the feed roller 15 side, a part of the printing surface PS on one side Pa comes into contact with the pinch rollers 16a and 16b. However, since the pinch rollers 16a and 16b are not driven by the paper transport motor 28 (FIG. 3), the force that presses the printing surface PS is weaker than that of the feed roller 15, so that contact marks are conspicuous even when contacting the printing surface PS. Absent. On the other hand, since the feed roller 15 is disposed on the other surface Pb side opposite to the first thermal head 11 with the paper P interposed therebetween, it does not contact the printing surface PS of the one surface Pa. Even when the protrusions 151 (FIG. 7) are formed on the feed roller 15, the feed roller 15 does not come into contact with the printing surface PS of the one surface Pa of the paper P, so that the protrusions 151 are not marked.

  With reference to FIG. 6C, the feed roller 15 comes into contact with the other surface Pb of the paper P, and the paper P is conveyed in the direction of the second thermal head 13. The paper P is conveyed from the contact point between the second thermal head 13 and the paper P to the paper cutter 29 (FIG. 1) side in accordance with the print length PL corresponding to the image data for printing on the other side Pb.

  Referring to FIG. 6D, the second thermal head 13 prints the other side Pb of the paper P. On the other side Pb of the paper P, the YMC inks and the overcoat layer OP are printed to form a printing surface PS. A distance D2 on the pass line T between the feed roller 15 and the second thermal head 13 is set to be longer than the print length PL of the print surface PS of the other side Pb of the paper P. Accordingly, the feed roller 15 does not contact the printing surface PS of the other side Pb of the paper P.

  As shown in FIGS. 6A to 6D, the feed roller 15 conveys the paper P in contact with a portion different from the printing surface PS that is a printed portion of the other side Pb of the paper P. Therefore, the feed roller 15 does not come into contact with the printing surface PS on both surfaces (one surface Pa and the other surface Pb) of the paper P. According to the modification, since the distance D1 on the pass line between the feed roller 15 and the first thermal head 11 can be shortened, the thermal printer 1 can be made small.

Next, the function and effect of the embodiment of the present invention will be described.
By printing on both sides of the paper P, the degree of freedom of printing can be improved. When the both sides of the paper P are printed, the feed roller 15 comes into contact with the paper P. When the paper P comes into contact with the printed surface PS on which the paper P is printed, the contact marks of the feed roller 15 become conspicuous.

  According to the thermal printer of one embodiment of the present invention, the first thermal head (head) 11 and the second thermal head (head) arranged on the same side as the feed roller 15 with respect to the paper (print medium) P. ) The distance on the pass line T between any one of 13 and the feed roller 15 is set to be longer than the print length PL of the paper P. When the paper P is printed by the head on the same side as the feed roller 15, the paper P is moved to the feed roller 15 side according to the print length PL. For this reason, even if the paper P is conveyed to the feed roller 15 side, the feed roller 15 can be prevented from coming into contact with the printing surface PS of the paper P. Thereby, since the contact mark of the feed roller 15 is not attached to the printing surface PS of the paper P, the print quality can be improved.

  Further, the distance on the pass line T between either the first thermal head (head) 11 or the second thermal head (head) 13 and the feed roller 15 is set so that the same side is shorter than the opposite side. Has been. Thereby, not only the feed roller 15 but also the pinch rollers 16a and 16b can be prevented from contacting the printing surface PS of the paper P.

  Also, the distance on the pass line T between either the first thermal head (head) 11 or the second thermal head (head) 13 and the feed roller 15 is set so that the same side is longer than the opposite side. Has been. Thereby, even when the distance between the feed roller 15 and the head on the opposite side to the paper P is shorter than the print length PL of the printing surface PS on the opposite side to the feed roller 15, the feed roller 15 does not contact the printing surface PS. Can be. Therefore, compared with the case where the head on the same side as the feed roller 15 with respect to the paper P is disposed closer to the head on the opposite side, the distance between the feed roller 15 and the head on the opposite side can be shortened. Therefore, the thermal printer 1 can be made small.

  The feed roller 15 has a protrusion 151 on the surface. As a result, the position of the paper P is fixed by the protrusions 151 on the surface of the feed roller 15, so that the paper P can be conveyed more accurately. Therefore, the print quality can be improved.

  According to the printing method of the embodiment of the present invention, the feed roller 15 is a portion of the sheet (print medium) P printed by the first thermal head (head) 11 and the second thermal head (head) 13 ( The feed roller 15 can be prevented from coming into contact with the printing surface PS of the paper P since the printing surface PS is in contact with a portion different from the printing surface PS). Thereby, since the contact mark of the feed roller 15 is not attached to the printing surface PS of the paper P, the print quality can be improved.

  Although the sublimation type printer has been described above, the present invention is not limited to this, and the printer may be a thermal printer.

  In the above description, the application to the case where the overcoat layer is overcoated is described. However, the present invention may be applied to printing that does not require relative positional accuracy different from YMC printing.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention can be applied particularly advantageously to a thermal printer and a printing method for performing duplex printing.

  DESCRIPTION OF SYMBOLS 1 Thermal printer, 2 Host, 10 Print part, 11 1st thermal head, 12 1st platen roller, 13 2nd thermal head, 14 2nd platen roller, 15 Feed roller, 16a, 16b Pinch roller, 17a First ink ribbon supply roller, 17b Second ink ribbon take-up roller, 18a First ink ribbon supply roller, 18b Second ink ribbon take-up roller, 19 Paper roll, 21 Main control unit, 22 Image buffer, 23 print control unit, 23a print image data generation unit, 23b ink ribbon winding / rewinding processing unit, 23c roll paper drive processing unit, 23d thermal head heating control unit, 23e ink ribbon diameter calculation unit, 24 energization pulse generation unit , 25 Thermal head, 26 Motor drive controller 27a ink ribbon supply side motor, 27b ink ribbon take-up side motor, 28 paper transport motor, 29 paper cutter, 101 one side printing mechanism, 102 other side printing mechanism, 103 print medium transport mechanism, 151 protrusion, P paper, R1 first Ink ribbon, R2 Second ink ribbon, T pass line (paper transport path).

Claims (5)

A first head for printing one side of the print medium;
A second head disposed on the opposite side of the print medium from the first head and for printing the other side of the print medium;
A feed roller that conveys the print medium in contact with either the one surface or the other surface;
The distance on the pass line between the feed roller and any one of the first head and the second head disposed on the same side as the feed roller with respect to the print medium is longer than the print length of the print medium, Thermal printer.   2. The thermal printer according to claim 1, wherein a distance on a pass line between one of the first head and the second head and the feed roller is shorter on the same side than on the opposite side.   2. The thermal printer according to claim 1, wherein a distance on a pass line between one of the first head and the second head and the feed roller is longer on the same side than on the opposite side.   The thermal printer according to claim 1, wherein the feed roller has a protrusion on a surface. Printing with a first head for printing one side of the print medium;
Printing with a second head disposed on the opposite side of the print medium from the first head and for printing the other side of the print medium;
A step of contacting the print medium with a feed roller in contact with either the one surface or the other surface;
The printing method, wherein the feed roller is in contact with a portion different from the portion of the print medium printed by the first head and the second head.

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