JP2018183892A - Printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printer that, in a case where printing is carried out with a thermal head having a plurality of heating-element lines, is able to prevent a change in concentration due to a change in pressing force applied to the paper by the head.SOLUTION: In order to achieve the foregoing object, a printer (200) according to the present invention comprises: a thermal head (101) in which at least three heating-element lines (217, 218, 219), in each of which a plurality of heating elements are arranged in a main scanning direction, are arranged in a sub-scanning direction, the thermal head being provided to print ink of an ink ribbon onto paper by supplying power to the heating elements; and control means (201) that controls supply of power to the heating elements of the thermal head. The control means exerts control such that printing is carried out by supplying power to the heating elements while two or more heating-element lines and paper are in contact with each other via the ink ribbon.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a printing apparatus having a thermal head in which a plurality of heating element rows are arranged.

  A thermal transfer recording method using a thermal head is used as a printing method of a printing apparatus and a method for obtaining high-quality image recording with a simple structure. In the thermal transfer recording system using a thermal head, an ink ribbon and paper that have been pre-coated with a dye are superimposed on a long film-like sheet material, and the ink ribbon and paper are conveyed while being pressed by the thermal head. A configuration for printing is common.

  In the thermal head, a plurality of heating elements (resistive elements) are arranged in a line. By selectively energizing these heating elements, the dye applied to the ink ribbon is transferred to the paper, and the paper Printing is performed on In a thermal transfer recording type printing apparatus that performs full-color printing, three colors of yellow, magenta, and cyan applied in sequence to the ink ribbon are sequentially stacked and printed at a constant speed of about 0.4 to 2.0 inches per second. Thus, a full color print is generated. In addition to these colors, ink ribbons to which black, metallic luster color, and a transparent overcoat material for coating the surface are added have been put into practical use.

  Normally, in a general small thermal transfer recording type printing apparatus, a sheet is held by holding a sheet by a grip roller and a pinch roller having protrusions formed on the surface of a metal roller, and controlling the rotation of the grip roller. The printing operation is performed by reciprocating. At this time, since it is necessary to pinch the paper between the grip roller and the pinch roller, a non-printing area where printing cannot be performed is necessary between the position where the thermal head can start printing and the leading edge of the paper. For this reason, it is generally put into practical use that a perforated cut is made on a sheet, and a tab including a margin in the range from the perforation to the end portion is cut out to make a borderless photograph.

  However, adding perforations to the paper increases the number of paper manufacturing processes and requires a longer tab length, which increases costs and requires the user to cut tabs at the perforation. .

  In Patent Document 1, a transport roller capable of rotating in the forward and reverse directions is provided on the upstream side and the downstream side of a printing unit so as to sandwich and transport the substrate, and the conveyance roller is sandwiched when the substrate is being printed by the printing unit. As a configuration in which the mechanism is released, printing on the edge of the sheet is possible.

  By adopting the method as described in Patent Document 1, it is possible to print to the edge of the paper, and it is possible to realize borderless full surface printing without providing a tab on the paper.

JP-A-8-72335

  However, in order to actually perform printing on the edge of the sheet with certainty, it is necessary to take into account positional deviation of the sheet with respect to the thermal head and variations in the dimensions of the sheet. For this reason, it is necessary to start printing from the front side of the front end of the paper and to print to a position past the rear end of the paper. At that time, when the heat of the thermal head is applied to the area where the ink ribbon outside the paper edge is not in contact with the paper, the heat of the ink ribbon cannot be transferred to the paper. The ink ribbon film may be softened and cut off. It is possible to prevent the ink ribbon from being cut by reducing the energy near the edge to less than the energy required for the original image, but in other cases, the density near the edge will be lower than the original image, resulting in poor print quality. Resulting in. Therefore, by using a thermal head substrate having a plurality of heating element arrays in which a plurality of heating elements are arranged in the scanning direction and performing printing multiple times at the same location in one pass, the required energy is reduced. Thus, it is possible to perform printing multiple times with the same color.

  However, when printing is made possible by a plurality of heating element rows, the pressing force necessary for good transfer is applied while ensuring the optimum head touch at each heating element row location on a single substrate. There is a need. For example, when printing with one heating element row, when the leading edge of the paper enters under another heating element row, or when the trailing edge of the paper that was under another heating element row falls out from under the heating element row In addition, fluctuations in the speed of the paper and fluctuations in the pressing force of the entire head against the paper occur. For this reason, density variation called banding occurs in the print result.

  Accordingly, an object of the present invention is to provide a printing apparatus capable of preventing density fluctuations due to fluctuations in the pressing force of the head against the paper when printing is performed using a thermal head having a plurality of heating element arrays. And

  In order to achieve the above object, a printing apparatus according to the present invention is a thermal head in which a plurality of heating element rows in which a plurality of heating elements are arranged in the main scanning direction is arranged in three or more rows in the sub-scanning direction. A thermal head that prints the ink ribbon ink on the paper by energizing the paper, and a control unit that controls the energization of the heating element of the thermal head. The control means is connected to the paper in two rows via the ink ribbon. While the above heating element rows are in contact, the heating element is controlled to be energized to perform printing.

  According to the present invention, when printing is performed using a thermal head having a plurality of heating element arrays, it is possible to provide a printing apparatus capable of preventing density fluctuations due to head pressing force fluctuations on paper. .

Schematic cross section of printing device Block diagram of printing device Schematic model of thermal head with 3 rows of heating elements Print preparation flowchart Configuration diagram of one screen of ink ribbon used in printing device Sectional view of the printing start position of the printing unit of the printing device Flow chart of printing operation of printing device Explanatory drawing which shows the printing data corresponding to each heat generating body row | line | column in 1st Example. Driving timing chart of each heating element row in the first embodiment Sectional view of the print section showing the behavior of the thermal head when the leading edge of the paper is located below the upstream heating element row and below the central heating element row Sectional view of the print section showing the behavior of the thermal head when the leading edge of the paper is located below the central heating element row and below the downstream heating element row Cross section of the print section showing the behavior of the thermal head depending on the position of the trailing edge of the paper Explanatory drawing which shows the printing data corresponding to each heat generating body row | line | column in 2nd Example. Driving timing chart of each heating element row in the second embodiment

(First embodiment)
The first embodiment of the present invention will be described below with reference to FIGS.

  FIG. 1 is a schematic cross-sectional view showing a main part of a printing apparatus according to an embodiment of the present invention.

  Reference numeral 101 denotes a thermal head. The thermal head used in the printing apparatus of the present invention is provided by arranging three heating element rows in which a plurality of heating elements are arranged in a line in the scanning direction on a single substrate in the sub-scanning direction. In addition, it is a multi-row thermal head. In this embodiment, a case where three rows are arranged will be described, but three or more rows may be arranged. The thermal head 101 is fixed to an aluminum block 102. The aluminum block 102 is fixed to a thermal head support frame 103, and is supported rotatably about a rotation shaft 103a provided on a side arm portion of the thermal head support frame 103. Has been. Reference numeral 104 denotes a head drive cam, which pushes down the pressing plate 105 when rotated counterclockwise in the drawing with the shaft portion 104a as a rotation axis.

  Reference numeral 107 denotes an ink ribbon, which is wound and conveyed from a supply bobbin 109 that is rotatably supported in an ink ribbon cassette 108 to a take-up bobbin 110.

  A paper 111 is a recording medium of the printing apparatus of the present invention. The paper 111 is pressed against the platen roller 112 by an urging means (not shown), and can be reciprocally conveyed in synchronization with the rotation of the platen roller 112.

  When the pressing plate 105 is pushed down, the thermal head support frame 103 rotates clockwise in the drawing with the rotation shaft 103 a as a fulcrum, and the thermal head 101 passes through the ink ribbon 107 and the paper 111 and the platen roller 112. Is pushed to. When pressed further, the pressing spring 106 is compressed, and due to its restoring force, the thermal head 101, the ink ribbon 101, and the paper 111 are brought into close contact with each other, and a pressing force necessary for good transfer works. Reference numeral 113 denotes a peeling plate for creating a starting point for peeling the ink ribbon 107 and the paper 111 used in printing.

  In a state where the thermal head 101 presses the ink ribbon 107 and the paper 111 toward the platen roller 112, the electrical signal applied to the heating element of the thermal head 101 is converted into thermal energy, and the dye of the ink ribbon 107 is applied to the paper 111. Transcribed.

  FIG. 2 is a block diagram of the printing apparatus according to the embodiment of the present invention. The system configuration of the printer of this embodiment will be described with reference to FIG.

  Reference numeral 200 denotes a printing apparatus. A main controller 201 performs system control and arithmetic processing of the printing apparatus. A ROM 202 stores a system control program for the printing apparatus. The main controller 201 reads a program from the ROM 202 and controls each unit based on the read program. A RAM 203 temporarily stores image data and is used for data processing work. A portion configured by the main controller 201, the ROM 202, and the RAM 203 is a main control unit that mainly processes each control of the printing apparatus.

  Reference numeral 204 denotes a head temperature detection sensor that measures the temperature of the thermal head 101, and 205 denotes an environmental temperature detection sensor that measures the temperature inside the printing apparatus. In addition, a sheet detection sensor 206 for detecting a sheet is provided as a sensor for detecting each piece of information in the apparatus. In this printing apparatus, paper detection sensors are provided at a plurality of locations to enable accurate paper position control. Further, a ribbon detection sensor 207 for detecting a marker for controlling the screen position of the ink ribbon 107 is provided. Further, based on the sensor information and information programmed in advance, the main controller 201 issues a command to the motor driver 208 to drive and control the three motors that drive each mechanism of the printing apparatus.

  Reference numeral 209 denotes a paper transport motor for transporting paper. Reference numeral 210 denotes a position change motor that drives the head position or drives a phase switching mechanism of a plurality of mechanisms in order to move to a printing pressing position or a retracted position. Reference numeral 211 denotes an ink ribbon transport motor for rotating and winding the winding side bobbin 110 of the ink ribbon 107 to transport the ink ribbon 107. An image data input unit 212 receives image data from a storage medium or wireless information. Reference numeral 213 denotes a display unit, and the image data captured from the image data input unit 212 is displayed on the display unit 213. Reference numeral 214 denotes an operation unit, which is operation instruction information transmitted from an external device through communication with an external device such as a key switch provided in the printing device 200 or a digital camera, personal computer, or portable terminal connected to the printing device. Accept. The operation instruction information input to the operation unit 214 is transmitted to the main controller 201.

  Reference numeral 215 denotes an image processing unit that performs image processing on image data fetched from the image data input unit 212. The image processing unit 215 performs various image processing such as decompression processing on image data, resizing processing according to used paper, and image correction processing, and print data for printing is generated based on the image data subjected to the image processing. Generated.

  A head control driver 216 controls the thermal head 101. The print data generated by the image processing unit 215 is sent to the head control driver 216.

  In the present invention, the thermal head 101 has a plurality of heating element rows, and the image processing unit 215 generates original data that is divided into print data and distributed to each heating element row. An image is formed by combining images.

  Reference numeral 217 denotes an upstream heating element row arranged on the most upstream side of the sheet conveyance, 218 denotes a central heating element row arranged at the center, and 219 denotes a downstream heating element row arranged on the most downstream side, and all three rows. This is a double row configuration.

  The image data input to the head control driver 216 is converted into an electrical signal and output to each heating element array. In the heating element rows 217, 218, and 219, the electric signal is converted into thermal energy, and the dye on the ink ribbon is transferred to the paper.

  Next, details of a three-row thermal head having a three-row configuration, which is characteristic among the components of the printing apparatus of the present invention, will be described.

  FIG. 3 is a schematic model diagram of a three-row configuration thermal head in the present embodiment. FIG. 3B is a front view seen from the heating element surface side, and FIG. 3A is a cross-sectional view taken along the line AA of FIG.

  Reference numeral 220 denotes a substrate constituting the thermal head 101, on which each electrode and driver element described below are mounted.

  Reference numeral 221 denotes an upstream side heating element, which is regularly arranged in the main scanning direction, and forms an upstream side heating element row 217. Similarly, the central heating element 222 is regularly arranged in the main scanning direction to form a central heating element array 218. Reference numeral 223 denotes a downstream heating element, which is regularly arranged in the main scanning direction, and forms a downstream heating element array 219. In each heating element row, five heating elements and individual electrodes corresponding to the heating elements are displayed in the main scanning direction for convenience of explanation, but this is not restrictive.

  224 is an upstream individual electrode of the upstream heating element row 217 located on the most upstream side in the sheet conveying direction, 225 is a central individual electrode of the central heating element row 218 provided in the center where the sheet reaches after 224, Reference numeral 226 denotes a downstream individual electrode of the downstream heating element array 219. 227 common electrode.

  Reference numeral 228 denotes a data transmission line for sending the print data processed by the image processing unit 215 to the head controller driver 216.

  In this embodiment, the head control driver 216 is mounted on a substrate (not shown) different from the substrate 220. From the head control driver 216, individual drivers 216A, 216B mounted on the substrate 220 for individually outputting and driving the heating element rows 217, 218, 219 on the upstream, central, and downstream sides, respectively. It is connected to 216C with individual electrodes. Here, the head control driver 216 controls which of the individual drivers 216A, 216B, and 216C is driven to send data and the timing of sending the data to each individual driver based on the timing determined by the distance between the heating element rows. As described above, the configuration of the head control driver of this embodiment includes individual drivers (216A, 216B, 216C) for driving each heating element array, and further includes a driver 216 for selectively driving each driver. . However, the present invention is not limited to this configuration, and a plurality of heating element rows may be driven by a single driver element.

  Next, operations related to printing of the printing apparatus 200 in this embodiment will be described with reference to FIGS.

  FIG. 4 is a flowchart showing the sequence of the pre-printing preparation operation among the printing operations by the printing apparatus 200. First, a preparatory operation before printing will be described along the flow shown in FIG.

  When image data is input to the image data input unit 212 and print start instruction information is received from the operation unit 214, the printing apparatus 200 starts a printing operation (S1). When the printing operation is started, the printing apparatus 200 operates the paper feed mechanism and starts paper feed conveyance (S2). Then, by driving the paper transport motor 209, the paper is transported toward the main part shown in FIG.

  On the way, when detected by the paper detection sensor 206, the leading edge of the paper is conveyed to the printing start position where the central heating element row 218 of the thermal head 101 can print. The transport distance from the paper detection sensor 206 to the above-described print start position is stored in advance in the apparatus. The sheet transport motor 209 is a stepping motor, and after the sheet detection sensor 206 detects the leading edge of the sheet, it is controlled to transport the sheet a specified number of steps and stop the sheet (S4).

  On the other hand, if a sheet is not detected within a predetermined number of steps determined in advance as being necessary for sheet feeding after the sheet feeding is started, the sheet is processed as a sheet error (S5).

  Subsequently, when the sheet is transported to the printing start position in S4, the head drive cam 104 is rotated counterclockwise in the drawing around the rotation support shaft 104a by the driving force of the position change motor 210.

  As a result, the thermal head 101 is rotated around the rotary shaft 103a against the urging force of the pressing 106 by the pressing plate 105 engaged with the thermal head support frame 103 being pressed by the head drive cam 104. Move the position around. Then, when the head 101 is moved from the position shown in FIG. 1 to the intermediate position between the platen roller 112 and the leading end of the paper 111 and the pressing position for niping via the ink ribbon 107, the driving of the stepping motor is stopped. (S6). Next, in order to detect the marker portion provided at the head of each color of the ink ribbon 107 by driving the ribbon transport motor 211, the ink ribbon winding operation is started.

  When the ribbon transport motor 211 is driven, the take-up bobbin 110 is rotated counterclockwise in the drawing by a drive transmission mechanism (not shown), and the ink ribbon 107 is fed from the supply bobbin 109 side around which the unprinted ink ribbon is wound. It is wound up. FIG. 5 shows a configuration diagram of one screen of the ink ribbon 107. When the marker portions 305 and 306 provided in the front area of the yellow (Y) dye application surface 301 which is the first print color of the ink ribbon 107 shown in FIG. 211 is stopped (S8). When the marker search operation is completed, the position change motor 210 is driven, and the head drive cam 104 is further rotated counterclockwise around the rotation support shaft 104a. The thermal head 101 rotates clockwise in the drawing around the rotation shaft 103 a provided on the side arm portion of the thermal head support frame 103, and presses the ink ribbon 107 and the paper 111 between the platen roller 112. Move to the pressing position (S9). The head position at this time is shown in a sectional view of the printing start position of the printing unit in FIG. Here, the pressing plate 105 compresses the pressing spring 106. The repulsive force of the compressed pressing spring 106 is transmitted to the thermal head 101 through the aluminum block 102, and the heating element of the thermal head 101, the ink ribbon 107, and the paper 111 on the platen roller 112 are pressed. This completes the print preparation (S11).

  FIG. 7 is a flowchart of the printing operation in the printing apparatus of this embodiment. Next, the printing operation will be described with reference to FIG.

  In the state shown in FIG. 6, the sheet 111 and the ink ribbon 107 are conveyed counterclockwise in the figure while being sandwiched between the thermal head 101 and the platen roller 112. At this time, the ink ribbon 107 is simultaneously heated by the thermal head 101, the ink applied to the ink ribbon 107 is transferred to the paper 111, and printing is performed. (S102) At this time, in the present invention, the original image is decomposed and corrected into three heating element rows, and each is driven and synthesized at a timing according to the distance between the heating element rows, thereby printing. To do. Details of the print composition process using each heating element array will be described later.

  During the printing operation, as described above, the ink ribbon 107 and the paper 111 are conveyed at the same speed. For this reason, the ink ribbon transport mechanism provided in the printing apparatus 200 incorporates a torque limiter mechanism (not shown) that slips when a load exceeding a certain torque is applied. When printing is performed by heating by the thermal head 101, the ink ribbon 107 and the paper 111 are conveyed while maintaining a fixed contact state for a certain distance, and then conveyed in directions away from each other. The paper 111 is temporarily transported in a circumferential direction along the outer periphery of the platen roller 112, but the ink ribbon 107 slides on the release plate 113 fixed to the thermal head support frame 103 while the ink wound around the take-up bobbin 110. It is conveyed toward the tangential direction of the ribbon outer periphery. The ink ribbon 107 is in close contact with the paper 111 by being pressed and heated by the thermal head 101, but is conveyed to the position of the peeling plate 113 and peeled off from the paper 111.

  When the printing of the yellow image on the paper 111 is completed, the position change motor 210 is driven to move the thermal head 101 and retract it to an intermediate position separated from the thermal head 101 (S103). Thereafter, the paper conveyance motor 209 is driven and conveyed until the top of the paper 111 reaches the print start position where printing with the thermal head 101 is possible (S104). Next, as in the operation before yellow printing, the ink ribbon 107 is transported to the print start possible position by detecting the marker 307 in front of the magenta plate while winding up by driving the ribbon transport motor 211. Stop (S105). Subsequently, when the marker search operation is completed, the position change motor 210 is driven to move the thermal head 101 to the pressing position shown in FIG. (S106). As in the case of yellow printing, the paper 111 and the ink ribbon 107 are conveyed in the counterclockwise direction in the figure while being held between the thermal head 101 and the platen roller 112. At this time, the ink ribbon 107 is simultaneously heated by the thermal head 101, the ink applied to the ink ribbon 107 is transferred to the paper 111, and magenta (M) printing is performed. (S107). Similarly, cyan (C) and overcoat (OC) printing is performed (S108 to 117). When the printing up to the overcoat is completed, the thermal head 101 is moved to the standby position shown in FIG. 1 by the driving force of the position change motor 210 (S118). Subsequently, the sheet is transported in the direction of the discharge port of the printing apparatus (not shown) and discharged out of the apparatus (S119), and the printing operation ends (S120).

  Next, details of the printing process by image composition using three rows of heating elements, which is one of the features of the present invention, will be described with reference to FIGS.

  FIG. 8 is a schematic diagram showing print data in which each heating element array prints the original image data. FIG. 9 is a drive timing chart of each heating element row for synthesizing image patterns.

  In FIG. 8, reference numeral 400 denotes original image data. The original image data is an example of a solid black image in which black created by the highest density of each color exists on the entire screen. An arrow indicated by PF indicates the sheet feeding direction at the time of printing. The print data 401 is printed with respect to the original image 400 using the upstream heating element row 217. Similarly, the print data to be printed using the central heating element row 218 is 402, and the print data to be printed using the downstream heating element row 219 is 403. At the time of printing, the main controller 201 or the head control driver 216 prints the original image 400 with the thermal head 101 by correcting the print data for each heating element row as follows.

  The print data 401 to be printed using the upstream heating element row 217 is data in which only the portion indicated by 404 is the actual print range. The data 404 is obtained by reducing the density of the rear end region at a distance of L2 from the rear end of the sheet to 80% of the density of the original image data with respect to the printing feed direction PF. Next, the print data 402 to be printed using the central heating element row 218 includes a front end region portion 405 at a distance L1 from the front end of the paper and a rear end at a distance L2 from the rear end of the paper with respect to the printing feed direction PF. The area portion 407 is reduced to 80% density with respect to the original image data. Then, the central region portion 406 having a distance L3 between the other portions is the same as the original image. Also, the print data 403 to be printed using the downstream heating element row 219 is data in which only the portion indicated by 408 is the actual print range, and the distance L1 from the front end of the sheet with respect to the print feed direction PF. The tip region 408 is reduced to 80% density with respect to the original image data.

  L1 coincides with the center distance between the heating element rows of the central heating element row 218 and the downstream heating element row 219. L2 is equal to the distance between the heating element centers of the upstream heating element array 217 and the central heating element array 218.

  L3 is a distance obtained by subtracting L1 and L2 from the total length of the sheet.

  In order to print the original image 400, the printing apparatus 200 of this embodiment prints the print data 401, 402, and 403 using the three heating element rows 217, 218, and 219, respectively, and combines them. It is realized by.

  Next, a printing procedure using three heating element rows will be described following the timing chart of FIG. First, printing of the printing data 405 is started by the central heating element row 218 in the portion of the leading edge region from the leading edge of the sheet to the distance L1. The time for printing the tip region at a distance of L1 is indicated by t1, and the energy applied by the central heating element row 218 at this time is EB, and is possible for printing at a density of 80% of the original image density. This is the correction energy amount. After t1, the leading edge of the paper reaches the downstream heating element row 219. At this timing, the downstream heating element array 219 is driven with the energy EB corresponding to the print data 408, and printing is performed on the tip region. As a result, the central heating element array 218 and the downstream heating element array 219 are printed in the front end region, and these print results are overlapped and combined, whereby an image corresponding to the original image is combined and printed. After elapse of t1, the central heating element array 218 drives and prints for a time t3, which is a printing time corresponding to the distance L3, with EA that is an uncorrected energy amount for printing the printing data 406 as the original image. After t1 has elapsed from the start of printing, printing by the downstream heating element row 219 is started, and when t1 has further passed, printing of the tip region by the downstream heating element row 219 is completed. At this time, the driving of the downstream heating element row 219 is stopped.

  A time corresponding to the printing time of the trailing edge region corresponding to the distance L2 from the trailing edge of the sheet is t2. Prior to the time t2 when the central heating element row 218 finishes driving with the uncorrected energy EA, the upstream heating element row 217 reaches the rear end region. Therefore, the upstream heating element row 217 is driven for a time t2 with the correction energy EB corresponding to the print data 404, and the rear end region of the distance L2 from the rear end of printing is printed. After (t1 + t3) has elapsed from the start of the subsequent printing, the central heating element row 218 completes the printing of the central area and reaches the rear end area. At that timing, the rear end area is driven by the correction energy EB corresponding to the print data 407 by the central heating element array 218, and the print is combined to complete the printing. Further, after the elapse of (t1 + t3) from the start of printing, the upstream side heating element row 217 reaches the rear end of the sheet, so that the driving is stopped.

  As described above, the density of the original image is synthesized and printed by printing twice near the edge of the paper with the data reduced to 80% density using two heating element arrays. The reason is as follows. When trying to print the ink ribbon once printed on the downstream side, the phenomenon that the dye returns from the paper side to the ink ribbon side occurs in the first printed portion, and the density of the first printed portion is It falls temporarily. Further, in the second printing, since the dye has already decreased from the ink ribbon in the first printing, the color developability is deteriorated with respect to the unprinted ink ribbon. In consideration of this phenomenon and the fact that the data obtained by reducing the density of the edges printed by the two heating element rows are the same, the sublimation type generally used experimentally by the present inventor. Experiments were performed using printer ink ribbons and paper. Then, the print result almost equal to the density of 100% of the original image could be obtained by synthesizing the print data with the density reduced to 80% by the two heating element arrays. In addition, when the edge of the paper was printed with a black solid pattern having a density exceeding 90%, damage to the ink ribbon that could hit the edge of the paper was observed. From the above, it is possible to prevent ink ribbon breakage at the end of the paper by reducing the energy applied to the head by reducing the density to 80%, and by printing and synthesizing twice with another heating element array, the desired density can be achieved. It is obtained. However, the concentration reduction amount is not limited to this. For example, if a material or printing system that has a sufficiently high dye content in the ink ribbon and does not cause reverse transfer from the paper to the ink ribbon is used, the desired print data can be synthesized by reducing the density to 50%. Printing is possible. Further, the end print data in the two heating element rows are not necessarily the same. In accordance with the characteristics of the ink ribbon and paper to be used, the characteristics of the printing device, and the thermal head, the density reduction rate of the combined portion, that is, the front end area and the rear end area of each heating element row is optimized for each heating element row. Different density reduction ratios may be used for each column. If the same density reduction data is used in a plurality of heating element arrays as in the present invention, the processing for data generation by the image processing unit 215 can be reduced, and the configuration of the head control driver 216 can be simplified. There is sex.

  In the above description, each of the heating element rows is driven (energized) so that the front end region and the rear end region have a maximum energy amount EB that is smaller than the maximum energy amount EA usable in the central region. ) As for the control method of the maximum energy amount, the maximum drive energy may be changed by changing the voltage or current when driving the heating element. Further, the maximum amount of energy that can be applied per unit time may be controlled by setting the voltage and current constant and limiting the number of energized pulses per unit time.

  In this embodiment, the image is divided into a front end region, a central region, and a rear end region. However, in order to improve the print image quality at the boundary line of the division, an overlap region is provided at each region boundary, and energy is gradually increased. May be changed.

  Next, when the edge of the paper enters under another heating element row, or when the edge of the paper that was under another heating element row comes out from under the heating element row, the pressing force against the paper of the entire head is reduced. The state of fluctuation and the effect of this embodiment will be described with reference to FIGS.

  FIG. 10 is a cross-sectional view of the printing portion showing the behavior of the thermal head when the leading edge of the sheet is located below the upstream heating element row and below the central heating element row. It is sectional drawing of the printing part which showed the behavior of the thermal head in the position under a body row. FIG. 11 is a cross-sectional view of the printing unit showing the behavior of the thermal head 101 according to the position of the trailing edge of the paper.

  FIG. 10A is a cross-sectional view of the printing unit when the leading edge of the sheet 111 reaches below the heating element portion of the upstream heating element row 217. When the sheet 111 is absent, each heating element row is pressed against the platen roller 112 via the ink ribbon 107. However, when the leading edge of the sheet 111 reaches, the upstream heating element row 217 portion , Pushed up in the direction of arrow 501. FIG. 10B is a cross-sectional view of the printing unit when the leading edge of the sheet 111 contacts the central heating element row 218. At this time, the front end of the paper collides with the convex portion of the heating element row 218, so that there is a slight impact. Therefore, when printing is performed by driving the upstream heating element row 217 in the section of the paper position as shown in FIGS. 10A to 10B, the position of FIG. 10B is printed. At this time, the paper conveyance speed fluctuates due to the impact, and banding occurs in the printed image. FIG. 10C is a cross section of the printing unit at the time when the sheet conveyance further proceeds and the leading edge of the sheet 111 reaches below the heating element portion of the central heating element row 218. At this time, as shown in FIG. 10B, since the leading edge of the sheet comes into contact with the central heating element row 218 and then moves under the heating element, the thermal head 101 moves in the direction of the arrow 502. Received force and pushed up. Here, when printing is performed by driving the upstream heat generating element row 217, the head pressing force fluctuates and falls below a desired density.

  FIG. 11A is the same as FIG. 10C, and is a cross section of the printing portion when the leading edge of the paper 111 reaches below the heating element portion of the central heating element row 218. FIG. 11B shows a state in which the leading end of the sheet 111 passes under the heating element portion of the central heating element row 218 and is being conveyed toward the downstream side heating element row 219. At this time, the posture of the thermal head 101 is stable in a state where the upstream heating element row 217 and the central heating element row 218 are pressed against the paper. The downstream heating element row 219 toward which the leading edge of the sheet is directed is not in a state of pressing against the platen roller 112 via the ink ribbon 107. FIG. 11C is a cross section of the printing unit at the time when the leading edge of the sheet 111 reaches below the heating element portion of the downstream heating element row 219. At this time, unlike the state of FIG. 10B, the leading edge of the paper 111 is not in a state where the downstream heating element row 219 of the thermal head 101 excessively blocks the paper traveling path. It can penetrate under the heating element. For this reason, fluctuations in the speed of the paper 111 and fluctuations in the pressing force of the thermal head 101 are very small and thus have little effect on the output image. Accordingly, as shown in FIG. 11A, the two heating element rows of the upstream heating element row 217 and the central heating element row 218 contact the paper 111 via the ink ribbon 107 and press the platen roller 112 side. If it is from the state which is carrying out, favorable printing can be performed.

  FIG. 12A is a cross-sectional view of the printing portion when the rear end of the sheet 111 is under the heating element portion of the upstream heating element row 217. In this state, each heating element row is on the paper 111 and can be stably printed. FIG. 12B is a cross-sectional view of the printing portion when the rear end of the sheet 111 is under the heating element portion of the central heating element row 218. As shown in FIG. 12B, even if the rear end of the sheet 111 passes under the heating element portion of the upstream heating element row 217, the thermal is generated at two locations of the central heating element row 218 and the downstream heating element row 219. Since the posture of the head 101 is maintained, the pressing force does not vary. For this reason, the impact when the rear end of the paper 111 is pulled out from under the upstream side heating element row 217 is small, and the output image is hardly affected. FIG. 12C is a cross-sectional view of the printing unit in a state where the rear end of the sheet 111 passes under the central heating element row 218 and reaches the downstream heating element row 219. When the trailing edge of the sheet passes through the central heating element row 218, only one of the downstream heating element rows 219 is on the sheet, and the posture of the thermal head 101 becomes unstable. Then, the upstream portion where there is no sheet receives the force of the pressing spring and tilts in the direction indicated by the arrow 503 and is pushed into the portion where the sheet is removed on the platen roller 112 side, and the upstream heating element row 217 and the central heating element row 218 contacts the platen roller 112 via the ink ribbon 107. At this time, since the pressing force of the thermal head 101 varies, banding occurs.

  As described above, when printing at the leading edge portion and the trailing edge portion, if the heating element rows of two or more rows are not pressed against the paper via the ink ribbon, the paper speed fluctuations and thermal The head pressing force fluctuates, causing banding and lowering the print quality.

  For this reason, in this embodiment, as described with reference to FIG. 9, the composite printing method in which the timing is such that the edge of the sheet is positioned below the central heating element at the start and end of printing is always obtained. Printing is performed in a state where the above heating element row presses on the paper. In printing, printing is performed using one or two of the heating element rows pressing on the paper via the ink ribbon, that is, using at least one heating element row.

(Second embodiment)
Hereinafter, a second embodiment of the present invention will be described with reference to FIGS. In the present embodiment, the configuration of the apparatus and the basic printing flow are the same as those in the first embodiment. Therefore, the description will be made with reference to the explanatory diagrams in the embodiment.

  FIG. 13 is a schematic diagram showing print data in which each heating element array prints original image data in the present embodiment. FIG. 14 is a drive timing chart of each heating element row for synthesizing an image pattern.

  In FIG. 13, 600 is original image data. The original image data is an example of a solid black image as in the first embodiment. An arrow indicated by PF indicates the sheet feeding direction at the time of printing. The print data 601 is printed with respect to the original image 600 using the upstream heating element row 217. Similarly, the print data to be printed using the central heating element row 218 is 602, and the print data to be printed using the downstream heating element row 219 is 603.

  The print data 601 to be printed using the upstream heating element row 217 is data in which only the portion indicated by 604 is the actual print range. The data 604 is obtained by reducing the density of the rear end area of the distance L2 from the rear end of the sheet to 80% of the density of the original image data with respect to the printing feed direction PF. Next, the print data 602 to be printed using the central heating element array 218 is reduced to a density of 80% of the original image data from the leading edge of the paper to the trailing edge of the paper in the printing feed direction PF. is there. Also, the print data 603 printed using the downstream heating element array 219 is data in which only the portion indicated by 605 is the actual print range, and the portion 605 excluding the rear end region at a distance of L2 from the rear end of the sheet. However, the density is reduced to 80% of the original image data.

  The distance relationship between L1, L2, and L3 is the same as that in the first embodiment.

  In order to print the original image 600, in this embodiment, the print data of 601, 602, and 603 are respectively printed using three rows of heating element rows 217, 218, and 219, and synthesized. Yes.

  Next, a printing procedure using three heating element rows will be described according to the timing chart of FIG. First, printing of the printing data 605 is started by the central heating element row 218 at the portion from the leading edge of the sheet to the distance L1. The time for printing the distance L1 is indicated by t1, and the energy applied by the central heating element array 218 at this time is the amount of correction energy that can be printed with EB at a density of 80% of the original image density. It is. After the elapse of t1, printing is performed at the same location by driving the downstream heating element row 219 with the correction energy EB corresponding to the print data 605 and performing print synthesis. At the same time, the central heating element row 218 is driven by EB, which is a correction energy amount for printing the print data 602, for a time t3 corresponding to the distance L3 and is printed. Thereafter, after the elapse of t1, the same portion is driven by the downstream heating element EB, which is the correction energy amount, for a time t3 corresponding to the distance L3, and is combined and printed.

  The time corresponding to the printing time for the distance L2 from the rear end of the paper is t2. Prior to the time t2 when the central heating element row 218 finishes driving with the correction energy EB, the upstream heating element row 217 is driven for the time t2 with the correction energy EB corresponding to the print data 604, and from the rear end of printing. The range of the distance L2 is printed. Thereafter, the same portion is similarly driven by the correction energy EB by the central heating element row 218, and printing is completed by combining the prints. Also in this embodiment, at the start and end of printing, printing is always performed in a state where the two heating element rows are pressed on the paper. Can be prevented.

  The present embodiment is different from the first embodiment in that the three heating element rows 217, 218, and 219 are all driven by only the correction energy amount in which the density is lowered. With this method, the total energy efficiency is reduced, but the instantaneous maximum energy amount can be reduced as compared with the first embodiment.

  As described above, in the present invention, it is possible to prevent the occurrence of banding when the leading edge of the paper enters the separate heating element row and the trailing edge is detached, which is a problem in the thermal head having a plurality of heating element rows. The printing in the above configuration can be realized without dropping the image. Also, using a thermal head with three rows of heating elements, the energy near the edge of the paper is dropped and then synthesized using two rows of heating elements to output the desired density near the edge. Therefore, it is possible to realize borderless printing without causing the ink ribbon to run out and the density of the end portion to decrease.

(Other examples)
Moreover, although preferable embodiment of this invention was described so far, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

  The present invention supplies a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in a computer of the system or apparatus read and execute the program This process can be realized. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

Claims (12)

A thermal head in which a plurality of heating element rows in which a plurality of heating elements are arranged in the main scanning direction is arranged in three or more rows in the sub-scanning direction, and prints ink ribbon ink on paper by energizing the heating elements. Head,
Control means for controlling energization to the heating element of the thermal head,
The control device controls the printing to be performed by energizing the heating element while two or more heating element rows are in contact with the paper via the ink ribbon.   The control means applies at least one heating element row of the heating element rows in contact with the paper via the ink ribbon while two or more heating element rows are in contact with the paper via the ink ribbon. The printing apparatus according to claim 1, wherein control is performed so that energization is performed.   In the thermal head, heating element rows are arranged in the order of the first heating element row, the second heating element row, and the third heating element row from the upstream side in the transport direction during printing. The printing apparatus according to claim 1.   4. The printing apparatus according to claim 3, wherein the control unit controls to start printing by the second heating element row in response to the leading edge of the sheet being conveyed to the second heating element row.   5. The printing apparatus according to claim 4, wherein the control unit controls to start printing by the third heating element row in response to the leading edge of the sheet being conveyed to the third heating element row.   The control means starts printing by the third heating element row in response to the leading edge of the paper being transported to the third heating element row, and printing to a predetermined area at the leading edge of the paper is completed. The printing apparatus according to claim 5, wherein control is performed to stop energization of the third heating element row in response to the operation.   The control means performs printing on a rear end region of the sheet using the first heating element array, performs printing on the entire sheet using the second heating element array, and the third heating element array. The printing apparatus according to claim 3, wherein control is performed so as to perform printing on a leading end region of the sheet using the heating element array.   The rear end region is a region corresponding to a distance between the first heating element row and the second heating element row, and the front end region is the second heating element row and the third heat generation. The printing apparatus according to claim 7, wherein the printing apparatus is an area corresponding to a distance between the body rows.   2. The printing apparatus according to claim 1, wherein the control unit performs control so that printing is performed with a maximum energy amount smaller in a front end region and a rear end region of the paper than in a central region of the paper. The control means includes
Based on the input print data, control is performed to energize the first heating element row, the second heating element row, the second heating element row,
Printing on the rear end region using the first heating element row, printing on the front end region, the central region, and the rear end region using the second heating element row, Control to perform printing on the tip region using two heating element rows,
The printing apparatus according to claim 9, wherein the rear end region and the front end region are controlled so as to be energized using print data that has been corrected so that the density decreases. Correction means for correcting the print data of the rear end region;
The printing apparatus according to claim 10, wherein the correction unit performs different corrections for the print data for the first heating element array and the print data for the second heating element array. Correction means for correcting the print data of the tip region,
11. The printing apparatus according to claim 10, wherein the correction unit performs different corrections for the print data for the second heating element array and the print data for the third heating element array.

Images