JP2005271322A - Thermal printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal printer that provides a high quality print while controlling the temperature of a thermal head by a simple structure and a method. <P>SOLUTION: The color thermal printer 2 has a temperature sensor 24 to measure the temperature of the thermal head 17, and a system controller 21 turning on a heater 23 to heat the thermal head 17 when Tm is smaller than Ta and turning off the heater 23 when Tm is equal to or larger than Ta during a non-image recording time when an image is not recorded by the thermal head 17, and turning on the heater 23 to heat the thermal head 17 and turning off the heater 23 during the image recording time when an image is recorded by the thermal head 17, monitoring the periodical variation pattern 30 of Tm caused by the turning-on and off of the heater 23, and controlling the driving of the thermal head 17 so as to start the recording of an image when the variation pattern 30 shows a specific behavior when the target temperature of the thermal head 17 is Ta and the temperature of the thermal head 17 measured by the temperature sensor 24 is Tm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a thermal printer having a thermal head for recording an image on a recording material and a heating unit for heating the thermal head.

  In a thermal printer, for example, a color thermal printer, a heat generating element array provided in a thermal head is pressed against color thermal recording paper, and each heat generating element generates heat in accordance with print data, so that multi-tone and multi-color printing can be performed. Is going.

  In order to obtain a print having an appropriate density and color balance, it is necessary to heat each heating element to a temperature corresponding to the print data. However, since the temperature of the thermal head is low immediately after the start of recording, it is impossible to develop a color with sufficient density.

  In order to solve the above problems, in the conventional thermal printer, a heater for preheating the thermal head during recording standby and a temperature sensor for measuring the temperature of the thermal head are provided, and the temperature of the thermal head is always the target temperature. The driving of the heater is controlled according to the measurement result of the temperature sensor (see Patent Documents 1 to 3).

JP 7-125295 A JP 7-137326 A JP-A-9-174852

  As in the thermal printers described in Patent Documents 1 to 3, when controlling the heater drive according to the measurement result of the temperature sensor, PID control is used as a method for keeping the temperature of the thermal head constant at the target temperature. Conceivable. However, when PID control is employed, there is a problem that a great deal of labor is required to select control parameters and production costs increase.

  On the other hand, since the method of simply on / off controlling the heater is simpler than the PID control, the aforementioned control can be performed at a low production cost. However, the amplitude of the temperature fluctuation increases accordingly, and there is a time lag between the measurement of the thermal head temperature by the temperature sensor and the start of image recording, so the temperature of the thermal head at the start of image recording is There is a problem that variations and density unevenness due to the variations occur.

  The present invention has been made in view of the above problems, and an object thereof is to provide a thermal printer capable of obtaining high-quality prints while performing temperature control of the thermal head with a simple configuration and technique.

  In order to achieve the above object, the present invention provides a thermal printer having a thermal head for recording an image on a recording material and a heating unit for heating the thermal head, and a temperature measuring unit for measuring the temperature of the thermal head. When the target temperature of the thermal head is Ta and the measurement temperature of the thermal head by the temperature measuring unit is Tm, the non-image recording is not performed by the thermal head. When Tm <Ta, the heating unit is turned on. When Tm ≧ Ta, the heating unit is turned off, and when recording an image with a thermal head, the heating unit is turned off, and a periodic variation pattern of Tm generated by turning on and off the heating unit is monitored, In order to start image recording when the variation pattern exhibits a certain behavior, Characterized by comprising a control means for controlling driving of heads or others.

  The control means preferably compares the previous measurement temperature Tmo with the current measurement temperature Tmn and performs the control when the same comparison result continues for a predetermined number of times.

  According to the thermal printer of the present invention, when the temperature measurement means for measuring the temperature of the thermal head, the target temperature of the thermal head is Ta, and the measurement temperature of the thermal head by the temperature measurement means is Tm, the thermal head records an image. During non-image recording, the heating means for heating the thermal head is turned on when Tm <Ta, the heating means is turned off when Tm ≧ Ta, and the heating means is turned off when recording an image with the thermal head. Control means for monitoring the periodic variation pattern of Tm caused by turning on and off the heating means and controlling the driving of the thermal head so as to start image recording when the fluctuation pattern shows a certain behavior With a simple configuration and method, the thermal head temperature is controlled and high-quality printing is performed. It is possible to obtain.

  In FIG. 1, a color thermal printer 2 to which the present invention is applied uses a long color thermal recording paper (hereinafter simply referred to as recording paper) 10 as a recording material. The recording paper 10 is set in the color thermal printer 2 in the form of a recording paper roll 11 wound in a roll shape.

  As is well known, the recording paper 10 has a structure in which a cyan thermosensitive coloring layer, a magenta thermosensitive coloring layer, a yellow thermosensitive coloring layer, and a protective layer are sequentially formed on a support. The yellow thermosensitive coloring layer, which is the uppermost layer, has the highest thermal sensitivity and develops yellow with a small amount of heat energy. The cyan thermosensitive coloring layer, which is the lowermost layer, has the lowest thermal sensitivity and develops cyan with large heat energy.

  The yellow thermosensitive coloring layer loses its coloring ability when irradiated with near ultraviolet rays of 420 nm. The magenta thermosensitive coloring layer develops magenta with intermediate thermal energy between the yellow thermosensitive coloring layer and the cyan thermosensitive coloring layer and loses the coloring ability when irradiated with 365 nm ultraviolet rays. For example, a recording paper having a four-layer structure provided with a black thermosensitive coloring layer may be used.

  A paper feed roller 13 rotated by the transport motor 12 is in contact with the outer peripheral surface of the recording paper roll 11. The carry motor 12 is a stepping motor and is driven by drive pulses input from the motor driver 14. When the paper feed roller 13 rotates counterclockwise in the figure, the recording paper roll 11 rotates clockwise in the figure, and the recording paper 10 is sent out from the recording paper roll 11. When the paper supply roller 13 rotates clockwise in the figure, the recording paper roll 11 rotates counterclockwise in the figure, and the recording paper 10 is rewound onto the recording paper roll 11.

  The recording paper 10 sent out from the recording paper roll 11 is sent into a conveyance path arranged in the horizontal direction. In this transport path, a transport roller pair 15 and a paper discharge roller pair 16 are disposed that sandwich and transport the recording paper 10. The conveyance roller pair 15 and the paper discharge roller pair 16 are composed of capstan rollers 15a and 16a rotated by the conveyance motor 12 and pinch rollers 15b and 16b pressed against the capstan rollers 15a and 16a. In the figure, the sheet is reciprocated in the A direction (paper feeding direction) and the B direction (rewinding direction).

  A thermal head 17 and a platen roller 18 disposed below the transport path so as to face the thermal head 17 are provided between the paper feed roller 13 and the transport roller pair 15. A heating element array 20 in which a plurality of heating elements are arranged in a line is provided on the surface of the thermal head 17 facing the recording paper 10 of the head substrate 19. The heating element array 20 generates heat based on the drive data input from the system controller 21 to the head driver 22, and colors each thermosensitive coloring layer of the recording paper 10.

  The platen roller 18 is driven and rotated in accordance with the conveyance of the recording paper 10 to stabilize the contact state between the recording paper 10 and the heating element array 20. Further, the platen roller 18 is movable in the vertical direction, and is urged in a direction in which it is pressed against the heating element array 20 by a spring (not shown). When the recording paper 10 is fed and discharged, the platen roller 18 is lowered by a shift mechanism (not shown) including a cam and a solenoid, and the nipping of the recording paper 10 with the thermal head 17 is released.

  On the head substrate 19 of the thermal head 17, a plate-like heater 23 for heating the thermal head is attached. A temperature sensor 24 for measuring the temperature of the thermal head 17 is embedded in the head substrate 19.

  The temperature sensor 24 measures the temperature of the thermal head 17 every predetermined time, for example, every 10 msec, and sequentially transmits the measurement result to the system controller 21. When the temperature measured by the temperature sensor 24 is Tm, the target temperature of the thermal head 17 is Ta, and the non-image recording is not performed by the thermal head 17, the system controller 21 turns on the heater 23 when Tm <Ta. The temperature of the thermal head 17 is raised. When Tm ≧ Ta, the heater 23 is turned off and the temperature of the thermal head 17 is lowered. On the other hand, when recording an image with the thermal head 17, the heater 23 is turned off. Note that Ta is stored in advance in a memory (not shown) in the system controller 22.

  When on / off control of the heater 23 is performed by the system controller 21 as described above, Tm, that is, the temperature of the thermal head 17 has a characteristic having a periodic variation pattern 30 as shown in FIG. The system controller 21 monitors this periodic variation pattern 30, stocks the previous measured temperature Tmo in the memory, and compares the magnitude relationship between this Tmo and the current measured temperature Tmn.

  The system controller 21 increments a count value when the comparison result between Tmo and Tmn is Tmo ≧ Tmn, and a counter (not shown) that initializes the count value to 0 when Tmo <Tmn. I have. When the count value of this counter is a predetermined value, for example, 5 or more, and Tmn ≦ Ta at that time, that is, in FIG. 2, Tm has passed Ta between time t0 and t1. Then, the driving of the thermal head 17 is controlled via the head driver 22 so that image recording is started when the head is lowered. Note that ts in FIG. 2 represents the time when the count value of the counter is 5 or more and a signal instructing the start of image recording is transmitted from the system controller 21 to the head driver 22, and tp is actually measured by the thermal head 17. Each represents the time when image recording was started.

  In FIG. 1, a fixing device 25 is arranged facing the recording surface of the recording paper 10 on the downstream side in the A direction of the conveying roller pair 15. A cutter 26 for cutting the recording paper 10 into a predetermined print size is disposed between the fixing device 25 and the paper discharge roller pair 16. Further, on the downstream side in the A direction of the paper discharge roller pair 16, a paper discharge port 27 for discharging the recording paper 10 on which the image has been recorded to the outside is provided.

  The fixing device 25 includes a yellow fixing light source 25a that emits near-ultraviolet light having an emission peak of 420 nm to fix the yellow thermosensitive coloring layer, and a magenta fixing light source that emits ultraviolet light having an emission peak of 365 nm to fix the magenta thermosensitive coloring layer. It comprises a light source 25b and a reflector 25c that reflects light from these light sources 25a and 25b toward the recording paper 10. Each light source 25a, 25b is driven by a lamp driver 28.

  Next, the operation of the color thermal printer 2 having the above configuration will be described with reference to the flowchart of FIG. When the image recording start operation is executed, the feed roller 13 is rotated counterclockwise by the forward rotation of the transport motor 12, and the recording paper 10 is sent out from the recording paper roll 11 in the A direction. The leading edge of the recording paper 10 moves in the conveyance path, is nipped by the conveyance roller pair 15, and is further conveyed downstream in the A direction.

  When the recording paper 10 reaches the image recording start position, the rotation of the transport motor 12 is temporarily stopped. Next, the platen roller 18 is raised by the shift mechanism, and the recording paper 10 is sandwiched between the heating element array 20. In this state, the conveyance motor 12 is driven again, and the yellow thermosensitive coloring layer of the recording paper 10 is generated by the heating element array 20 that generates heat based on the driving data input to the head driver 22 while the recording paper 10 is conveyed in the A direction. A yellow image is recorded in

  When the recording of the yellow image is completed, the trailing end of the recorded image is conveyed to a position facing the yellow fixing light source 25a of the fixing device 25, and the rotation of the conveying motor 12 is stopped. At this time, the platen roller 18 is lowered by the shift mechanism, and the holding of the recording paper 10 by the thermal head 17 is released. Next, the yellow fixing light source 25a is turned on by the lamp driver 28, the conveyance motor 12 is rotated in the reverse direction, and the recording paper 10 is rewound in the B direction, whereby the yellow thermosensitive coloring layer on which the image has been recorded is fixed.

  After fixing the yellow thermosensitive coloring layer, the leading edge of the recorded image is conveyed to a position facing the heating element array 20, and the rotation of the conveying motor 12 is stopped. As in the yellow image recording, the platen roller 18 is raised by the shift mechanism, and the recording paper 10 is sandwiched between the heating element array 20. In this state, the conveyance motor 12 is driven again, and a magenta image is recorded on the magenta thermosensitive coloring layer of the recording paper 10 while the recording paper 10 is conveyed in the A direction.

  When the recording of the magenta image is completed, the rear end of the recorded image is conveyed to a position facing the magenta fixing light source 25b of the fixing device 25, and the rotation of the conveying motor 12 is stopped. Similarly to the yellow image fixing, the magenta fixing light source 25b is turned on by the lamp driver 28, the conveyance motor 12 is reversed, and the recording paper 10 is rewound in the B direction. Is established.

  After fixing the magenta thermosensitive coloring layer, the leading edge of the recorded image is conveyed to a position where it faces the heating element array 20, and the rotation of the conveying motor 12 is stopped. A cyan image is recorded on the cyan thermosensitive coloring layer of the recording paper 10 in the same manner as when recording yellow and magenta images.

  The recording paper 10 after image recording is conveyed in the A direction by the conveying roller pair 15, cut to a predetermined print size by the cutter 26, and then discharged to the outside from the paper discharge outlet 27 by the paper discharge roller pair 16.

  During non-image recording where no image is recorded by the thermal head 17, the temperature of the thermal head 17 is measured by the temperature sensor 24 at regular intervals. The measurement results are sequentially transmitted to the system controller 21 and stocked in the memory in the system controller 21.

  When Tm <Ta, the heater 23 is turned on and the temperature of the thermal head 17 is raised. When Tm ≧ Ta, the heater 23 is turned off and the temperature of the thermal head 17 is lowered.

  The system controller 21 compares the magnitude relationship between Tmo and Tmn that have been stored in the memory so far. When the comparison result is Tmo ≧ Tmn, the count value of the counter is incremented. On the other hand, when Tmo <Tmn, the count value is initialized to 0 and the process is returned. .

  When the count value of the counter is equal to or greater than a predetermined value and Tmn ≦ Ta at that time, the heater 23 is turned off by the system controller 21 and the drive of the thermal head 17 is controlled so that image recording is started. . On the other hand, if the count value of the counter is equal to or smaller than the predetermined value or Tmn> Ta, the process is returned.

  As described above, since image recording is started at a substantially constant timing, temperature fluctuations between time lags from when the temperature of the thermal head 17 is measured by the temperature sensor 24 until image recording is started. As a result, the temperature of the thermal head 17 at the start of image recording does not vary, and density unevenness can be prevented. Further, since the heater 23 is on / off controlled, it is not necessary to perform complicated operations such as setting control parameters as in the case of PID control.

  Further, since the previous measurement temperature Tmo is compared with the current measurement temperature Tmn, and when the same comparison result continues for a predetermined number of times, image recording is started, it is possible to ensure that the Tm variation pattern 30 is surely present. It is possible to grasp whether or not the behavior is shown.

  In the above embodiment, in FIG. 2, the image recording is started when the time Tm is lower than Ta between time t0 and time t1, but for example, Tm is increased after Ta is increased. In other words, it is only necessary to start image recording only when the Tm variation pattern 30 exhibits a certain behavior. Moreover, in the said embodiment, although only the heater 23 which heats the thermal head 17 is provided, you may provide cooling means, such as a fan and a heat sink, as needed.

  In the above embodiment, the color thermal printer 2 has been described as an example of the thermal printer. However, the present invention is not limited to this and can be applied to other thermal printers such as a thermal transfer printer.

1 is a schematic diagram illustrating a configuration of a color thermal printer to which the present invention is applied. It is a graph which shows the time change of the measurement temperature by a temperature sensor. It is a flowchart which shows the process sequence of the color thermal printer at the time of non-image recording.

Explanation of symbols

2 Color thermal printer 10 Color thermal recording paper (recording paper)
17 Thermal Head 21 System Controller 23 Heater 24 Temperature Sensor 25 Fixing Device 30 Fluctuation Pattern

Claims (2)

In a thermal printer having a thermal head for recording an image on a recording material and a heating means for heating the thermal head,
Temperature measuring means for measuring the temperature of the thermal head;
When the target temperature of the thermal head is Ta and the measurement temperature of the thermal head by the temperature measuring means is Tm, when non-image recording is not performed with the thermal head, the heating means is turned on when Tm <Ta, When Tm ≧ Ta, the heating unit is turned off, and when the image is recorded with the thermal head, the heating unit is turned off,
Monitoring a periodic variation pattern of Tm caused by turning on and off the heating means;
A thermal printer comprising: control means for controlling driving of the thermal head so that image recording is started when the fluctuation pattern exhibits a specific behavior.   2. The thermal printer according to claim 1, wherein the control unit compares the previous measurement temperature Tmo with the current measurement temperature Tmn and performs the control when the same comparison result continues a predetermined number of times. .

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