JP2006231613A - Inkjet recording device and inkjet recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording method to prevent picture quality from deteriorating due to variation in a discharge quantity involved in increase in head temperature, and an inkjet recording device. <P>SOLUTION: The inkjet recording device has a recording head which performs recording by discharging an ink by thermal energy generated by a heating element by applying a driving signal. The device has a driving signal control means to control the driving signal, a head temperature detection means to detect the temperature of the recording head, and a head temperature control means to control the temperature of the head on the basis of the result of the detection, and controls the temperature of the head to ensure that the range of variation of a discharge quantity involved in variation of the temperature of the head is not larger than the range of modulation of a discharge quantity by the control of the driving signal. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ink jet recording method for performing recording by ejecting ink using thermal energy, and an ink jet recording apparatus to which the ink jet recording method can be applied.

  2. Description of the Related Art Conventionally, as an image forming apparatus that performs recording on a recording medium such as paper or an OHP sheet, there have been proposed forms in which recording heads using various recording methods are mounted. This recording head includes a wire dot method, a thermal method, a thermal transfer method, an ink jet method, and the like. In particular, since the ink jet method directly ejects ink onto recording paper, the running cost is low and quiet. It is attracting attention as a method capable of recording operation with excellent characteristics.

  The recording apparatus as described above is a carriage scanning type in which a carriage on which a recording head is mounted moves in the horizontal direction. In a carriage scanning type ink jet printer, a large number of recording heads are provided in the recording head by carriage scanning. The nozzle is driven based on the recording information, and after recording one scanning recording area, the recording medium is fed by one scanning recording area in a direction perpendicular to the traveling direction of the carriage. A predetermined image is formed by alternately conveying the recording medium.

  A large number of nozzles (discharge ports) are formed inside the recording head in order to eject ink droplets. The nozzles are filled with ink used for recording on a recording medium. In the case of recording an image or the like, the one corresponding to the image data is selected from each nozzle as appropriate, and ink dots are ejected to perform recording.

  In the ink jet system, bubbles are generated in the ink by the heat energy generated by the heating of the heater, and the ink is ejected by the growth of the bubbles. Therefore, the ink jet system is easily affected by the head temperature, and the ejection amount varies accordingly. Using this, according to Japanese Patent No. 3253107, a method for optimizing the head temperature adjustment range according to the ink to be used and further according to the recording medium is disclosed in Japanese Patent Laid-Open No. 5-77424. In order to obtain the ink amount (recording density), a method of controlling the head temperature is disclosed.

  On the other hand, however, since the temperature rise of the head causes a large discharge amount fluctuation, there arises a problem that image quality deterioration (print density change or density unevenness) occurs.

On the other hand, as disclosed in, for example, Japanese Patent No. 3247412, there is a method of providing a plurality of drive signals composed of two pulse portions and changing them according to the temperature of the print head (hereinafter referred to as PWM control). It has been. According to this method, the discharge amount fluctuation due to the temperature rise of the head is reduced, and the temperature rise of the recording head can be suppressed as compared with the case of single driving. Furthermore, by making the ejection amount modulation range based on the drive signal correspond to a temperature range that is considered to be frequently used in actual printing, it is possible to obtain more effective image quality stabilization.
Patent Registration No. 3253107 Japanese Patent Laid-Open No. 5-77424 Japanese Patent Registration No. 3247212

  However, in the above method, the discharge amount fluctuation range due to the head temperature rise is larger than the range in which the discharge amount can be modulated by PWM control, and when the head becomes high temperature due to continuous printing, the constant drive condition is set outside the control range. This is not sufficient when a stable image quality is always required.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to stabilize the discharge amount regardless of the temperature rise due to printing.

  In order to solve the above problem, according to the ink jet recording apparatus according to claim 1, in the ink jet recording apparatus provided with a recording head that performs recording by discharging ink with heat energy generated by a heating element by applying a driving signal, the driving A drive signal control means for controlling the signal; a head temperature detection means for detecting the temperature of the recording head; a head temperature control means for controlling the head temperature based on the detection result; and a discharge amount fluctuation range accompanying the head temperature fluctuation However, the head temperature control is performed so that the discharge amount modulation range is less than or equal to the drive signal control.

  Further, according to the ink jet recording apparatus of claim 2, the head temperature control unit performs temperature control by heating when the head temperature detection result is equal to or lower than the lower limit set temperature, and reaches the upper limit set temperature or higher. In such a case, the temperature control is performed such that printing is stopped by the temperature rise protection, and the printer is on standby until the temperature falls below the upper limit set temperature.

  Further, according to the ink jet recording apparatus of the third aspect, the drive signal control means switches a plurality of drive signals in stages and controls the discharge amount.

  According to the present invention, the head temperature control is performed so that the discharge amount fluctuation amount due to the temperature rise of the head is within the discharge amount modulation range by the PWM control that is grasped in advance. The image quality (printing density) can always be made uniform during the interval.

  Further, the drive signal control according to the present invention is not always uniquely associated with the head temperature, but is divided and assigned within the head temperature control range and changes with the control temperature setting region. For example, when 4-step drive control is performed, the first drive signal is applied to 30-35 ° C if the temperature control region is 30-50 ° C, and 50-55 ° C if the temperature control region is 50-70 ° C. Applies to

  Furthermore, the discharge amount modulation possible range in the present invention is the amount that can be modulated by PWM control and the amount of discharge amount variation error due to the number of drive signal switching steps in PWM control (the temperature range that is driven by each drive signal as the number of switching steps increases) Represents a range in which the discharge amount modulation error is reduced due to narrowing).

  According to the ink jet recording apparatus of any one of claims 4 to 9, the control temperature range by the head temperature control means is different for each print mode (claim 4), and is set by the head temperature control means. The upper limit temperature is a maximum reached temperature assumed for each printing mode (Claim 5). The control temperature range by the head temperature control means is different for each environmental temperature (Claim). Item 6).

  The upper limit temperature set by the head temperature control means is a maximum reached temperature assumed for each environmental temperature (Claim 7).

  The control temperature range by the head temperature control means is different for each printing mode and environmental temperature (claim 8).

  The upper limit temperature set by the head temperature control means is a maximum attainable temperature assumed for each printing mode and environmental temperature condition (claim 9).

  According to the present invention, the head control range is effectively set and the printing efficiency is improved.

  The head temperature rise profile when performing continuous printing differs depending on the printing mode and conditions with additional environmental conditions. Therefore, by setting the head temperature control area according to this, the printing efficiency is improved. It is. Furthermore, by setting the maximum reachable (convergence) temperature assumed for each condition as the head temperature control upper limit, even if continuous printing is performed, the print standby by the temperature rise (upper limit) protection is eliminated and the printing efficiency is improved. is there.

  In addition, according to the ink jet recording method of the tenth aspect, the upper limit temperature set by the head temperature control means is a maximum temperature that is assumed from all print modes and environmental temperatures.

  According to the present invention, in addition to the printing efficiency, the drive signal changed by the PWM control uniquely corresponds to the head temperature. Therefore, the image quality (all environments, all printing modes) is always maintained regardless of printing conditions (all environments, all printing modes). (Print density) can be made uniform.

  As described above, according to the present invention, the discharge amount can be stabilized regardless of the temperature rise due to printing. Furthermore, by setting the upper limit of the set temperature range for head temperature control to the maximum temperature that can be assumed from the printing conditions (printing mode or printing mode discharge environment temperature), printing standby due to temperature rise protection during continuous printing is avoided. Therefore, it is possible to stabilize the discharge amount without reducing the printing efficiency.

  Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

<Outline of recording device>
First, the overall configuration and operation of the ink jet recording apparatus of the present invention will be described.

  FIG. 8 is a schematic diagram showing the entire inkjet recording apparatus of the present invention.

  In FIG. 8, the paper feed roller 101 is configured to sandwich the recording medium 102 between a pair of rollers, and moves the recording medium in the sub-scanning direction by rotating. The recording head has an ejection port on the surface facing the platen 106. The recording head 105 is detachably attached to the carriage 104, and the carriage is moved along the main scanning guide 103 by carriage driving means (not shown), so that the recording medium is scanned (hereinafter referred to as "main scanning"). Ink droplets can be ejected. The recording head is coupled to an ink supply device (not shown) and is supplied with ink. The platen 106 is provided under the ink recording head. During recording, the recording medium is positioned between the platen and the recording head, and is held by the platen 106 so that the interval between the recording medium and the recording head is appropriate. Retained. Although not shown in FIG. 8, this ink jet recording apparatus has a recording medium supply means for supplying the recording medium to the paper feed roller, a recovery means for maintaining the state around the ejection opening of the recording head, and recording. A recording medium discharge means for taking out the finished recording medium is provided.

  The recording operation is performed as follows.

  When a recording start command signal is input to the ink jet recording apparatus, the recording medium is supplied from the upper right direction in FIG. 8 by a recording medium supply means (not shown) until the leading end comes to the position of the paper feed roller. In response to the recording signal, the recording medium is fed by the paper feed roller so that the recording head is positioned at the printing start position on the recording medium. Subsequently, printing is performed by spraying ink droplets onto the recording medium while the carriage and the recording head perform main scanning. Thereafter, the recording medium is fed by a predetermined amount by the paper feed roller (this operation is hereinafter referred to as “sub scanning”), and the carriage and the recording head again spray ink droplets on the recording medium while performing the main scanning. After recording is performed on the recording medium by repeating the sub-scanning and main scanning, the recording medium is discharged in the lower left direction in FIG. Note that paper is often used as the recording medium, but other materials may be used. Further, in the case of an OHP sheet, a compact disk, and a DNA chip manufacturing apparatus and a display manufacturing apparatus using an ink jet, a substrate made of a material suitable for each may be used.

<Drive Signal Control (PWM Control) Method According to Embodiment of Present Invention>
FIG. 9 shows a drive signal according to the present invention, where VOP is a drive voltage, P1 is a pulse width of the first pulse of a plurality of divided heat pulses (hereinafter referred to as preheat pulse), P2 is an interval time, P3 is the pulse width of the second pulse (hereinafter referred to as the main heat pulse).

  The drive voltage VOP gives electric energy necessary for the electrothermal transducer to which this voltage is applied to generate heat energy in the ink on the heater board. The value is determined by the area of the electrothermal transducer, the resistance value, the film structure, and the liquid path structure of the recording head.

  The drive signal according to the present invention sequentially applies pulses in the widths P1, P2, and P3.

  The preheat pulse is a pulse mainly for controlling the ink temperature in the liquid path, and plays an important role in controlling the ejection amount. The preheat pulse width is set to a value that does not cause a foaming phenomenon in the ink due to the heat energy generated by the electrothermal transducer when applied.

  The interval time is provided in order to provide a certain time interval so that the preheat pulse and the main heat pulse do not interfere with each other, and to make the temperature distribution of the ink in the ink liquid path uniform.

  The main heat pulse is for causing foaming in the ink in the liquid path and ejecting the ink from the ejection port, and its width P3 is the area of the electrothermal transducer, the resistance value, the film structure and the ink of the recording head. It depends on the structure of the liquid channel.

  The discharge amount control based on the above parameters will be described in more detail.

  In order to increase the amount of ink discharged, it is necessary to increase the foam growth area, that is, the foam volume.Therefore, not only the ink temperature in the vicinity of the heater but also the surrounding ink temperature is increased to expand the foam growth boundary area. It is necessary to keep. Therefore, a variable energy for increasing the ink temperature is given by a variable preheat pulse P1, and this energy is diffused at an interval time P2 to form a desired ink temperature distribution, and a desired ink discharge amount is set by the main heat pulse P3. Is to get. That is, by controlling P1 and P2 (input energy and elapsed time after input), the ink temperature distribution, that is, the foaming region is controlled, and the discharge amount is controlled.

  Next, an example of a method for determining P1, P2, and P3 will be described.

(1) A drive pulse (P1, P2, P3) determination voltage (a voltage reduced at a constant ratio with respect to the printing apparatus main body drive voltage) is set.

  (2) Fix to a certain P1 and P2, change the P3 width sequentially, and print a test pattern.

(P2 sets a sufficient interval time for P1.)
For example, the value is multiplied by a predetermined ratio.

  (3) The minimum value at which ejection is confirmed in (2) is determined as P3.

  (4) Subsequently, P1 is changed, and (1) to (3) are performed.

  The above (1) to (4) are sequentially performed within a range in which preheat pulse foaming due to P1 does not occur, and the combination of P1, P2, and P3 is determined.

  The constant ratio in (1) corresponds to the voltage difference between the drive pulse evaluation step and the actual use in the printing apparatus main body, and the drive energy margin is sufficiently added to compensate for sufficiently stable ejection. It is set. According to the present inventor, 1.17 is desirable, but not limited thereto.

  The PWM control method is a method of controlling the drive signal by switching the determined drive pulse table step by step for the discharge amount modulation. At this time, as described above, the discharge amount can be increased by lengthening P1.

  FIG. 10 shows that the driving voltage VOP = 16.24 [V] (the printer body has a driving voltage 19.00 [V]), and the preheat pulse width P1 is in the range of 0 to 0.4 [μsec] and 0.1 [μsec]. The combination table of P1, P2, and P3 when changing in increments (P2 is set to P1 * 1.33) is shown. Note that the preheat pulse width P1 is set to 0.4 [μsec] in consideration of preheat pulse foaming.

  FIG. 11 is a diagram showing the relationship between the head ejection amount Vd [pl / dot] and the preheat pulse width P1 [μsec] when the drive pulse shown in FIG. 10 is applied.

  10 and 11 show an example of a head having a certain structure, which is different if the structure is changed.

  Next, FIG. 12 shows the temperature dependence of the head ejection amount Vd [pl / dot] when the drive pulse shown in FIG. 10 is applied. The discharge amount Vd increases linearly as the recording head temperature TH increases. If the slope of this straight line is defined as a temperature dependence coefficient, the temperature dependence coefficient KT is 0.47 pl / 10 ° C. This coefficient is determined by the structure of the head, the physical properties of the ink, etc., regardless of the driving conditions.

In view of FIG. 11 and FIG.
Discharge amount modulation amount by drive signal control (PWM control): ~ 0.75pl
Head temperature fluctuation amount ΔT corresponding to the modulation amount (˜0.75 pl): ˜16 ° C.
I understand that.

  FIG. 13 is a diagram showing the relationship between the head temperature and the discharge amount.

  In the following, embodiments that characterize the present invention will be described using the above data as an example.

  FIG. 1 is a diagram for explaining head temperature control according to an embodiment of the present invention.

  At this time, the PWM control is performed in four stages as shown in FIG.

As shown in FIG. 1, the head temperature control is configured in the following three modes. That is, according to the temperature TH of the recording head,
(1) TH ≤ T0 ... Temperature control by heating (no printing)
When the head temperature is T0 or less, the temperature of the recording head is adjusted by heating and printing is performed. The temperature of the recording head by heating may be controlled by applying a pulse in a range that does not lead to ejection using a discharge heater, or by providing a separate temperature control heater in the head and applying a pulse thereto. You may adjust the temperature with.

(2) T0 <TH ≤ TL ... No control (printing while controlling the discharge rate by PWM control)
In the temperature range of the head temperature T0 to TL, the discharge amount is controlled by PWM control. In this region, the temperature sensor detects the head temperature and changes the drive signal according to the table shown in FIG. FIG. 3 shows a pulse width modulation sequence at this time.

(3) TL <TH <Tc ... Temperature rise protection (printing standby until the head temperature falls below TL)
Here, Tc indicates the use limit temperature of the head. If the head temperature exceeds TL, the temperature rise protection is applied to the printing, this is stopped, and the printer is on standby until the head temperature falls below TL.

  As shown in FIG. 1, the head temperature control range ΔT (head temperature TL−T0) is ΔT ′ (head temperature fluctuation amount corresponding to the modulation range by PWM drive signal control: ˜16 ° C.) + Α (number of PWM control steps) The head temperature fluctuation amount corresponding to the Vd control error due to (˜5.5 ° C.) is set to ˜21.5 ° C. However, the absolute values of T0 and TL are not particularly limited as long as TL <Tc.

  Hereinafter, the head temperature acquisition and the pulse width modulation sequence based thereon will be described with reference to FIG.

  The sequence shown in FIG. 3 is activated by an interrupt every 40 msec, for example. First, the print head temperature is detected in step S401. Next, in step S402, in order to prevent erroneous detection of the temperature due to heat flux entering the temperature sensor or electrical noise, a process of setting the average value of the past three head temperatures and the head temperature detected in step S401 as Tm is performed. . In the next step S403, this average value is compared with the drive pulse table to which Tm belongs and the drive pulse table to which the previously obtained average value Tm-1 of the head temperature belongs. If the difference is 0, the pulse is left as it is in step S405. If the difference is positive, the process proceeds to step S406, and P1 is shortened by incrementing the table number referred to in the table of FIG. If the difference is negative, the process proceeds to step S404, where P1 is increased by decreasing the table number by one to increase the discharge amount, and the discharge amount always becomes a constant amount Vd0. Control as follows. The reason why the change of the drive table that is changed in accordance with the temperature change in the above process is set as one unit is to prevent a malfunction of feedback (such as erroneous detection of the sensor temperature) and prevent the occurrence of density jump. In this embodiment, the average value of the two left and right temperature sensors is used as the temperature of the recording head.

  Furthermore, the average value detected four times for temperature detection is used to prevent false detection due to sensor noise, etc., and to smoothly perform feedback, to minimize density fluctuation due to control, and to connect by serial printing method This is to make the change in density (connection streaks) inconspicuous.

  By performing the above control, the discharge amount can be controlled within a range of ± ΔV in the temperature range that can be managed by the table of FIG. 2 with respect to the central discharge amount Vd0. The state of the change in the discharge amount changes, for example, as indicated by an arrow a shown in FIG.

  At this time, FIG. 2 shows an example of four-step PWM control, but by increasing the number of control tables, the discharge amount modulation amount per step is further reduced, that is, switching at each step switching. It is possible to suppress the change discharge amount step (± ΔV) to be smaller, and to further stabilize the image quality.

  FIG. 4 is a diagram for explaining the head temperature control according to the second embodiment of the present invention.

  In this embodiment, the head temperature control range described in [Embodiment 1] is set for each print mode.

  FIG. 5 shows a head temperature rise profile when continuous continuous printing is performed on A0 paper in the printing mode C in a large format printer. In this way, the input energy and the heat radiation energy approach equilibrium and converge to a certain temperature. In FIG. 5, since the print is A0, the first sheet converges to the maximum temperature. FIG. 6 shows the results of the same evaluation performed in a plurality of print modes. FIG. 4 shows the result of setting the head control temperature range based on the result of FIG.

  FIG. 4 shows an example in which the head temperature control region is set based on the evaluation results of FIGS. 5 and 6 in the room temperature environment. However, the maximum temperature reached in consideration of the highest environment temperature assumed as the printer use environment. It is more desirable to set the head temperature control range based on this. As a result, when continuous printing is performed under a normal printer usage environment, the printing standby time due to the temperature rise protection can be eliminated, and the printing efficiency can be improved. Furthermore, the head temperature control area may be shifted in accordance with the ambient temperature based on the thermistor temperature measurement result associated with the printer body.

  FIG. 8 is a diagram for explaining the head temperature control according to the third embodiment of the present invention.

  In this embodiment, in contrast to the method in which the head temperature control range is set for each print mode as in [Embodiment 2], the full print mode is considered (the mode shown in FIG. The maximum reached temperature (here, print mode C), which is the most severe condition for the head temperature rise, is set as the head temperature control upper limit value (TL). FIG. 7 shows the maximum temperature reached results calculated in consideration of the highest environmental temperature (assumed to be 30 ° C. in this case) assumed as the printer use environment for each print mode in FIG. FIG. 8 shows the result of setting the head temperature control region based on this.

  According to this embodiment, as shown in FIG. 8, all printing is performed while applying one head temperature control range. As a result, the discharge amount variation (center discharge amount difference) between the print modes existing in the second embodiment can be eliminated without reducing the printing efficiency as much as possible with respect to the second embodiment.

It is a figure for demonstrating Example 1 of this invention. It is an example of a PWM control table for demonstrating Example 1 of this invention. It is a flowchart of the pulse width modulation sequence concerning one Example of this invention. It is a figure for demonstrating Example 2 of this invention. FIG. 10 is a diagram showing a head temperature increase profile when continuous printing is performed at a maximum printing density on an A0 size medium in a printing mode C. The maximum temperature rise reached by printing mode is shown (room temperature). The maximum temperature rise temperature for each printing mode is shown (30 ° C environment). It is a figure for demonstrating Example 3 of this invention. 1 is a schematic perspective view illustrating an ink jet recording apparatus according to an embodiment of the present invention. It is a figure showing the drive signal waveform in the embodiment of the present invention. It is a figure showing the drive signal table in the embodiment of the present invention. It is a figure which shows the relationship between P1 evaluated based on the drive signal table shown in FIG. 10, and discharge amount. It is a figure which shows the relationship between head temperature and discharge amount.

Claims (20)

In an ink jet recording apparatus including a recording head that performs recording by discharging ink with heat energy generated by a heating element by application of a drive signal,
Drive signal control means for controlling the drive signal;
Head temperature detecting means for detecting the temperature of the recording head;
Head temperature control means for controlling the head temperature based on the detection result is provided, and the head temperature control is performed so that the discharge amount fluctuation range accompanying the head temperature fluctuation is less than or equal to the discharge amount modulation possible range by the drive signal control. An ink jet recording apparatus.   The head temperature control means performs temperature control by heating when the detection result of the head temperature is equal to or lower than the lower limit set temperature, and stops printing by temperature increase protection when the temperature reaches the upper limit set temperature. 2. The ink jet recording apparatus according to claim 1, wherein temperature control is performed so as to wait until the temperature falls below the upper limit set temperature.   The inkjet recording apparatus according to claim 1, wherein the drive signal control unit switches a plurality of drive signals stepwise and controls the discharge amount.   The inkjet recording apparatus according to any one of claims 1 to 3, wherein a control temperature range by the head temperature control unit is different for each print mode.   5. The ink jet recording apparatus according to claim 4, wherein the upper limit temperature set by the head temperature control means is a maximum temperature expected for each printing mode.   4. The ink jet recording apparatus according to claim 1, wherein a control temperature range by the head temperature control unit is different for each environmental temperature. 5.   7. The ink jet recording apparatus according to claim 6, wherein the upper limit temperature set by the head temperature control means is a maximum temperature reached for each environmental temperature.   4. The ink jet recording apparatus according to claim 1, wherein a control temperature range by the head temperature control unit is different for each printing mode and environmental temperature. 5.   9. The ink jet recording apparatus according to claim 8, wherein the upper limit temperature set by the head temperature control means is a maximum temperature reached for each printing mode and environmental temperature condition.   4. The ink jet recording apparatus according to claim 1, wherein the upper limit temperature set by the head temperature control means is a maximum reached temperature assumed from all print modes and environmental temperatures. 5. .   In an ink jet recording method for performing recording by discharging ink by heat energy generated by a heating element by application of a driving signal, the method includes a step of modulating an ejection amount by controlling a driving signal, and a step of detecting the temperature of the recording head, An ink jet recording method comprising: a head temperature control step of performing temperature control based on the detection result of the head temperature so that a discharge amount fluctuation range accompanying a head temperature change is equal to or less than a discharge amount modulation possible range by the drive signal control. .   In the head temperature control step, when the head temperature detection result is equal to or lower than the lower limit set temperature, the step of adjusting the temperature by heating is performed. 12. The ink jet recording method according to claim 11, further comprising a step of performing temperature adjustment so as to wait until the temperature falls below the upper limit set temperature.   12. The ink jet recording method according to claim 11, wherein the ejection amount modulation step by controlling the drive signal is a step of switching a plurality of drive signals in stages.   The inkjet recording method according to any one of claims 11 to 13, wherein a control temperature region in the head temperature control step is different for each print mode.   15. The ink jet recording method according to claim 14, wherein, in the head temperature control step, the upper limit set temperature is a maximum reached temperature assumed for each printing mode.   The inkjet recording method according to claim 11, wherein a control temperature region in the head temperature control step is different for each environmental temperature.   17. The ink jet recording method according to claim 16, wherein, in the head temperature control step, the upper limit set temperature is a maximum reached temperature assumed for each environmental temperature.   14. The ink jet recording method according to claim 11, wherein a control temperature region in the head temperature control step is different for each printing mode and environmental temperature.   19. The ink jet recording method according to claim 18, wherein, in the head temperature control step, the upper limit set temperature is a maximum temperature reached for each printing mode and environmental temperature condition.   14. The ink jet recording method according to claim 11, wherein, in the head temperature control step, the upper limit set temperature is a maximum temperature reached from all printing modes and environmental temperatures.

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