JP4878640B2 - Inkjet recording apparatus and inkjet recording method - Google Patents

Description

  The present invention relates to an ink jet recording apparatus and an ink jet recording method for recording an image using a recording head capable of discharging different inks.

  Conventionally, as a recording apparatus for recording on a recording medium such as paper and an OHP sheet, forms using various types of recording heads have been proposed. The recording head includes a wire dot method, a heat sensitive method, a thermal transfer method, an ink jet method, and the like. In particular, the ink jet method is attracting attention as a method that allows a recording operation with low running cost and excellent quietness because ink is directly jetted onto a recording medium.

  An ink jet recording head that ejects ink using thermal energy can be manufactured using a semiconductor manufacturing process such as etching, vapor deposition, or sputtering. That is, a nozzle that forms an ink discharge port by forming an electrothermal converter (hereinafter also referred to as a “heater”), an electrode, a liquid path wall, a top plate, and the like formed on a substrate as discharge energy generating means. Can be easily manufactured.

  By the way, in the ink jet recording head using such heat energy, it is known that the characteristics relating to the ejection of the ink ejection section including the heater change according to the number of times of driving, and with long-term use. The recording head may be deteriorated with time. One of the main factors is that ink burns on the heater, and there is a possibility that the discharge performance may be deteriorated due to an increase in deposits on the heater. As a result of the change in the ejection characteristics as described above, the minimum drive energy required for ejecting ink changes, and further, there is a possibility that the quality and quality of the recorded image may be deteriorated by changing the ink ejection amount and ejection speed.

  Conventionally, as a method for solving such a problem, Patent Documents 1 and 2 propose a method of changing a drive pulse to be applied according to an increase in the number of times of driving.

JP 2000-37681 A JP 2001-138498 A

  By the way, the change tendency of the ejection characteristics due to the above-described deterioration with time and the accumulation of scorch varies depending on the type of ink. However, this tendency is not a problem with dye inks. On the other hand, in the case of water-based pigment ink (ink in which pigment particles are dispersed in water), the dispersion stability of the pigment particles is destroyed by heat, and the ejection characteristics are changed by the deposition of the dispersion and destruction products on the heater. In this case, the tendency of change varies greatly depending on the type of ink.

  However, the techniques described in Patent Documents 1 and 2 described above merely change drive pulses to be applied uniformly according to the increase in the number of times of driving regardless of the type of ink to be ejected. For this reason, when the ejection characteristics of the ink ejection unit differ greatly depending on the type of ink, there is a possibility that ejection of a specific ink may be uncertain.

  An object of the present invention is to provide an ink jet recording apparatus and an ink jet recording method capable of stably maintaining the discharge performance for different inks over a long period of time.

  The inkjet recording apparatus of the present invention is an inkjet recording apparatus that records an image using a recording head including a plurality of ink ejection units that eject black ink, cyan ink, magenta ink, and yellow ink, respectively. A drive unit for driving the unit, a measuring unit for measuring the number of times each of the plurality of ejection units is driven, and a change for changing the drive energy for ejecting ink according to the number of times of driving in each of the plurality of ink ejection units And (A) the drive energy for discharging the black ink is changed from a relatively high drive energy when the drive count reaches a predetermined drive count. The drive energy is changed to a lower value, and after the predetermined number of times of driving, the driving energy is gradually increased according to the number of times of driving. Together be modified to increase the Energy, and changes so as to increase gradually in accordance with the number of times of driving the driving energy for discharging (B) said cyan ink, magenta ink, yellow ink.

  The inkjet recording method of the present invention uses the recording head including a plurality of ink discharge units that discharge black ink, cyan ink, magenta ink, and yellow ink, respectively, and drives the plurality of ink discharge units to generate the black ink, In an inkjet recording method for recording an image by discharging cyan ink, magenta ink, and yellow ink, a measurement step of measuring the number of times of driving of each of the plurality of ejecting units, and the number of times of driving in each of the plurality of ink ejecting units. And changing the driving energy for discharging the ink according to the changing step. In the changing step, (A) the driving energy for discharging the black ink is changed to the predetermined number of driving times. When it reaches a relatively low drive energy from a relatively high drive energy. And is changed so as to gradually increase the driving energy in accordance with the number of driving times, and (B) driving energy for discharging the cyan ink, magenta ink, and yellow ink. Is changed so as to gradually increase in accordance with the number of times of driving.

  As described above, according to the present invention, by changing the drive condition of the ink discharge unit according to the type of ink, the drive condition of the ink discharge unit is optimally set according to the characteristics for each type of ink. As a result, it is possible to record a high-quality image while maintaining stable ejection performance for a long period of time regardless of the type of ink, and to extend the life of the recording head. .

  In addition, since the driving conditions of the ink discharge unit can be optimally set according to the characteristics of each type of ink, the good discharge performance of the ink discharge unit can be maintained over the life of the recording head. . In addition, since driving conditions can be set for each type of ink to be ejected, there is no need to allow for a driving condition that considers the characteristics of all types of ink from the initial stage of use of the recording head. Longer life of the recording head can be realized.

  In addition, by changing the drive timing of the ink ejection unit for each type of ink to be ejected, the drive condition can be set at an appropriate timing according to the tendency of the ink ejection unit to change over time due to the characteristics of each ink type. As a result, the driving conditions can be set more optimally.

  In the case where the recording head is driven by a single power source as in a general recording apparatus by changing the waveform of the driving pulse without changing the driving voltage of the driving pulse applied to the ink ejection unit. Also, different drive pulses can be set for each type of ink.

  Further, by setting the drive condition of the ink discharge unit based on the detection result of the ink discharge state from the ink discharge unit, it is possible to set a more optimal drive condition.

1 is a schematic perspective view of an ink jet recording apparatus according to a first embodiment of the present invention. FIG. 2 is a schematic configuration diagram of a control system in the recording apparatus of FIG. 1. 2 is a flowchart for explaining a change process of a drive pulse change in the recording apparatus of FIG. 1. It is explanatory drawing of the example of a change of the drive pulse in the 1st Embodiment of this invention. It is explanatory drawing of the relationship between the drive energy regarding the nozzle which discharges different ink, and discharge speed. It is explanatory drawing of the relationship between the drive energy regarding the nozzle for cyan ink discharge, and discharge speed. It is explanatory drawing of the time-dependent change of the minimum drive voltage regarding the nozzle for cyan ink discharge. It is explanatory drawing of the time-dependent change of the discharge speed regarding the nozzle which discharges a different ink. It is explanatory drawing of the relationship between the drive energy regarding the nozzle for yellow ink discharge, and discharge speed. It is a schematic perspective view of the principal part in the inkjet recording device of the 2nd Embodiment of this invention.

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
(Basic configuration of recording device)
First, the overall configuration and operation of an inkjet recording apparatus to which the present invention can be applied will be described.

FIG. 1 is a schematic diagram showing the entire inkjet recording apparatus of this example.
In FIG. 1, the pair of paper feed rollers 101 convey the recording medium 102 in the sub-scanning direction indicated by the arrow Y by rotating so as to sandwich the recording medium 102. The ink jet recording head 105 is detachably attached to the carriage 104, and has an ink ejection port on a surface facing the platen 106. The carriage 104 is moved in the main scanning direction indicated by an arrow X along the main scanning guide 103 by carriage driving means (not shown). The recording head 105 moves together with the carriage 104 and ejects ink droplets from the ejection ports while scanning the recording medium 102 (hereinafter also referred to as “main scanning”). The recording head 105 is connected to an ink supply device (not shown) and supplied with ink. The platen 106 is provided below the recording head 105. At the time of recording, the recording medium 102 is held on the platen 106 so as to be positioned between the platen 106 and the recording head 105, and the interval between the recording medium 102 and the recording head 105 is appropriately maintained. Although not shown in FIG. 1, in the ink jet recording apparatus of this example, the recording medium supply unit that supplies the recording medium 102 to the paper feed roller 101 and the state around the ejection port of the recording head 105 are appropriately set. There are provided recovery means for maintaining a good ink discharge state and recording medium discharging means for discharging the recording medium 102 after recording.

The recording operation is performed as follows.
When a recording start command signal is input to the ink jet recording apparatus, the recording medium 102 is supplied from the upper right direction in FIG. 1 by a recording medium supply means (not shown), and the tip of the recording medium 102 is the position of the paper feed roller 101. Sent to. Thereafter, the paper feed roller 101 is operated according to the recording signal, and the recording medium 102 is fed in the sub-scanning direction so that the recording head 105 is positioned at the recording start position on the recording medium 102. Subsequently, recording is performed by ejecting ink droplets onto the recording medium 102 from the ejection port of the recording head 105 while moving the recording head 105 together with the carriage 104 in the main scanning direction. Thereafter, the recording medium 102 is fed by a predetermined amount in the sub-scanning direction by the paper feed roller 101 (hereinafter, this operation is also referred to as “sub-scanning”), and the recording head 105 is moved in the main scanning direction together with the carriage 104 again. Ink droplets are ejected onto the recording medium 102. In this way, after the sub-scan and the main scan are alternately repeated to record an image on the recording medium 102, the recording medium 102 is discharged in the lower left direction in FIG.

  In the recording head 105, the method for discharging ink from the discharge port is not particularly limited, and various methods using discharge energy generating elements such as electrothermal transducers (heaters) and piezoelectric elements (piezo elements) are available. Things can be adopted. In the case of this example, a heater was used as the discharge energy generating element. By applying a driving pulse to the heater to generate heat, the ink is foamed using the thermal energy, and thereby the ink can be discharged from the discharge port. The heat energy generated by the heater will change according to the drive pulse applied to it. A functional unit (including a discharge energy generating element such as a heater) for discharging ink from the discharge port is also referred to as an ink discharge unit. The recording head 105 can be configured by one or a plurality of recording chips. In the case of this example, the recording head 105 is composed of a plurality of recording chips, and the ink ejection portions for ejecting different colors of ink are divided into the respective recording chips. Therefore, the type of ink to be ejected differs for each recording chip.

  Also, paper is often used as the recording medium, but other materials may be used. The recording medium may be an OHP sheet or a compact disk. Furthermore, in the case of a DNA chip manufacturing apparatus or a display manufacturing apparatus using an ink jet technology, a substrate made of a material suitable for each manufacturing apparatus is used. There may be.

(Basic configuration of control system)
FIG. 2 is an explanatory diagram of a schematic configuration of a control system in the ink jet recording apparatus.
The control unit 200 includes a CPU, a ROM, a RAM, and the like, and recording is performed by outputting recording data received from the outside to the driving unit 202. The measuring means 204 in the control means 200 measures the number of times the heater is driven as its usage history (driving history) for each recording chip constituting the recording head 105. The measurement result is stored and updated in the storage unit 206. At the start of recording, based on the number of times of driving for each recording chip stored in the storage unit 206, the determining unit 205 determines the drive pulse change timing for each recording chip. For the recording chip that has reached the change timing, the drive pulse changing means 207 changes the drive pulse. When changing the drive pulse, the optimum drive pulse for each recording chip is selected based on the measurement result of the measuring means 204 and the data of the drive condition table (drive pulse table) 203. As will be described later, the driving condition table 203 associates the number of times of driving as a measurement result of the measuring unit 204 with a driving pulse (driving energy), and selects the driving pulse according to the former number of times of driving. be able to. The driving unit 202 drives the heater for each recording chip by the selected driving pulse.

  The recording head 105 is provided with a memory 107 capable of writing head information including a use history (driving history) for each recording chip. When the recording head 105 is mounted, the control unit 200 acquires a use history for each recording chip from the head information stored in the memory 107. In addition, the control unit 200 appropriately stores information in the storage unit 206 in the memory 107 as head information. Thereby, even when the recording head 105 is attached / detached, the usage history for each recording chip in the recording head 105 so far is grasped, and an appropriate driving pulse corresponding to the usage history is set for each recording chip. Can do.

(Basic driving condition change method)
Next, a basic method of changing the drive pulse in the ink jet recording apparatus of this example will be described based on the flowchart of FIG.

  When the control unit 200 receives the recording data and further receives a recording start command (step S100), the determination unit 205 drives the heater for each recording chip based on the number of times the heater is driven for each recording chip in the storage unit 206. It is determined whether the number of times exceeds a predetermined comparison reference number (step S101). The comparison reference number is set for each recording chip as described later. If the number of drive times of any recording chip does not exceed the comparison reference number, step S102 for changing drive conditions (drive pulse change) is skipped, and a recording operation is started (step S103).

  If it is determined in step S101 that there is a recording chip in which the heater driving frequency exceeds the comparison reference frequency, only the driving pulse for the heater in the recording chip is changed (step S102), and the recording operation is started (step S102). S103). After the end of the recording operation (step S104), the measuring unit 204 measures the number of times the heater has been driven in the current recording operation, and adds it to the number of times the heater has been driven for each recording chip so far (step S105). . The measuring unit 204 may sequentially measure the number of times the heater is driven for each recording chip, and add the measurement result to the number of times of driving so far in step 105. The measurement results obtained by the measuring unit 204 are stored in the sequential storage unit 206.

  In this example, the drive pulse change determination (step S102) is performed immediately after reception of the recording start command (step S100). However, the present invention is not limited to this, and the drive pulse change may be determined at any timing such as after recording as long as the recording pulse is not affected even if the drive pulse is not changed.

(First embodiment)
The first embodiment of the present invention in the basic configuration as described above will be described below.

  In the present embodiment, the following pigment inks 1, 2, 3, and 4 were used.

<Pigment ink 1: Black ink>
(1) Composition and Production Method of Dispersion Styrene-acrylic acid copolymer (number average molecular weight: about 4000): 10 parts Potassium hydroxide: 1 part Glycerin: 5 parts Ion exchange water: 64 parts

  First, the above components were mixed in a container, and heated to 70 ° C. in a water bath to completely dissolve the resin component. Next, 20 parts of carbon black was added to this solution, premixed for 30 minutes, charged into a batch type sand mill (manufactured by Imex), filled with 0.8 mm diameter zirconia beads as a medium, and cooled with water. The dispersion treatment was performed for 3 hours.

  Further, the dispersion obtained in this manner was centrifuged (10,000 rpm, 30 minutes) to remove non-dispersed materials containing coarse particles to obtain a black dispersion. The resulting black dispersion had a pigment concentration of 8% and a dispersant concentration of 4%.

(2) Preparation of ink Using the above black dispersion liquid, the following components were added to obtain a predetermined concentration, and after these components were sufficiently mixed and stirred, a microfilter having a pore size of 2.5 μm (manufactured by Fuji Film) The pigment ink 1 was prepared by filtration under pressure.
Black dispersion liquid: 50 parts Glycerin: 8 parts Diethylene glycol: 4 parts Ethylene glycol: 5 parts Surfynol 440 (manufactured by Kawaken Fine Chemicals): 0.1 part Polyoxyethylene oleyl ether (EO 10, HLB 14.5): 1. 5 parts Ion exchange water: 31.4 parts

<Pigment ink 2: Cyan ink>
(1) Composition and Production Method of Dispersion Styrene-methyl acrylate (number average molecular weight: about 3000): 10 parts Potassium hydroxide: 1 part Diethylene glycol: 5 parts Ion exchange water: 64 parts

  First, the above components were mixed in a container, and heated to 80 ° C. with a water bath to completely dissolve the resin component. Next, C.I. I. After adding 20 parts of Pigment Blue 15: 3 and premixing for 30 minutes, the same dispersion treatment as in the case of preparation of the black dispersion used for the pigment ink 1 was performed to prepare a cyan dispersion. The obtained cyan dispersion had a pigment concentration of 10% by mass and a dispersant concentration of 4% by mass.

(2) Preparation of ink Using the above cyan dispersion liquid, the following components were added to obtain a predetermined concentration, and after mixing and stirring these components sufficiently, a microfilter having a pore size of 2.5 μm (manufactured by Fuji Film) The pigment ink 2 used in this embodiment was prepared by filtration under pressure.
Cyan dispersion liquid: 30 parts Glycerin: 10 parts Triethylene glycol: 5 parts EO adduct of acetylene glycol: 0.5 parts (Product name: Acetylenol E100; manufactured by Kawaken Fine Chemicals)
Polyoxyethylene cetyl ether (EO 20): 1 part Ion exchange water: 53.5 parts

<Pigment ink 3: Magenta ink>
(1) Composition / Production Method of Dispersion Styrene-methyl acrylate (number average molecular weight: about 3000): 10 parts Potassium hydroxide: 1 part Diethylene glycol: 5 parts Ion exchange water: 64 parts.

  First, the above components were mixed in a container, and heated to 80 ° C. with a water bath to completely dissolve the resin component. Next, C.I. I. After adding 20 parts of Pigment Red 122 and premixing for 30 minutes, the same dispersion treatment as in the case of preparation of the black dispersion used for the pigment ink 1 was performed to prepare a magenta dispersion. The obtained magenta dispersion had a pigment concentration of 10% by mass and a dispersant concentration of 4% by mass.

(2) Preparation of ink Using the above magenta dispersion liquid, the following components were added to obtain a predetermined concentration, and after these components were sufficiently mixed and stirred, a microfilter having a pore size of 2.5 μm (manufactured by Fuji Film) The pigment ink 3 used in the present embodiment was prepared by filtration under pressure.
Magenta dispersion: 30 parts Glycerin: 10 parts Triethylene glycol: 5 parts EO adduct of acetylene glycol: 0.5 parts (trade name: Acetyleneol E100; manufactured by Kawaken Fine Chemicals)
Polyoxyethylene cetyl ether (EO 20): 1 part Ion exchange water: 53.5 parts

<Pigment ink 4: Yellow ink>
(1) Composition and Production Method of Dispersion Styrene-acrylic acid copolymer (number average molecular weight: about 4000): 10 parts Potassium hydroxide: 1 part Glycerin: 5 parts Ion exchange water: 64 parts

  First, the above components were mixed in a container, and heated to 70 ° C. in a water bath to completely dissolve the resin component. Next, C.I. I. After adding 20 parts of Pigment Yellow 128 and premixing for 30 minutes, the same dispersion treatment as in the preparation of the black dispersion used for the pigment ink 1 was performed to prepare a yellow dispersion. The resulting yellow dispersion had a pigment concentration of 8% and a dispersant concentration of 4%.

(2) Preparation of ink Using the above yellow dispersion, the following components were added to obtain a predetermined concentration, and after these components were sufficiently mixed and stirred, a microfilter having a pore size of 2.5 μm (manufactured by Fuji Film) The pigment ink 4 was prepared by filtration under pressure.
Yellow dispersion liquid: 50 parts Glycerin: 8 parts Diethylene glycol: 4 parts Ethylene glycol: 5 parts Surfynol 440 (manufactured by Kawaken Fine Chemicals): 0.1 part Polyoxyethylene oleyl ether (EO 10, HLB14.5): 1. 5 parts Ion exchange water: 31.4 parts

  When such pigment inks 1, 2, 3, and 4 are used in an ink jet recording apparatus, according to the experiment of the present inventor, a change in ejection characteristics as shown in FIG. 5 was recognized.

  FIG. 5 shows a case where the drive pulse width applied to the heater of the recording head 105 is fixed (1.0 μs: the drive pulse width that provides the minimum ejection energy at the drive voltage of 16.24 V is set), and the drive voltage is changed. It is the result of evaluating the change of the ink discharge speed. The horizontal axis represents the ratio to the reference voltage (16.24 V) (hereinafter, this ratio is referred to as “K value”).

(Evaluation results of cyan ink (C) and black ink (Bk))
Increasing the K value from 1 (minimum drive energy leading to ejection) causes the ink ejection speed to rise steeply, giving a stable ejection speed regardless of the K value since the K value exceeded 1.05. There is a flat area that can be In this experiment, the rising region where the K value is between 1 and 1.05 is not evaluated in detail. The ejection speed in a flat region where the ejection speed is stable is determined by the nozzle structure of the recording head 105 rather than by the type of ink, and the dynamics of the liquid such as viscosity, surface tension, and density as the basic physical performance of the ink. If the general properties are equivalent, they are almost the same. Therefore, when a discharge speed lower than the value in the flat region is measured, the ink itself can be regarded as having a chemical defect.

  When the K value is further increased, the pigment burns on the surface of the heater or the heater changes in quality, and the ink discharge speed decreases, and eventually the heater does not burn out and discharge. This tendency is the same for dye inks.

(Evaluation result of magenta ink (M))
Until the K value is approximately 1.13, there is a flat region where the ink ejection speed is stable, as in the case of the cyan ink and the black ink. However, in the region where the K value is near 1.17, the ink ejection speed is reduced by about 2 m / s at the maximum. Further, after the K value exceeds 1.20, there is a flat region where the ink ejection speed becomes stable again.

(Evaluation result of yellow ink (Y))
In the region where the K value is low (up to about 1.13), the ink ejection speed is stable, but it can be confirmed that the ink ejection speed itself is about 4 m / s slower than the other color inks. . As the K value is further increased, the ink discharge speed starts to increase again around 1.17 from 1.13, and when it exceeds 1.17, the discharge speed reaches the same discharge speed as that of the other color inks. When the K value is further increased, there is a flat region where the ink ejection speed is stable.

  In the experiment of this example, the drive pulse width was fixed and the drive voltage was adjusted for evaluation. However, the present invention is not limited to this, and conversely, the driving voltage may be fixed and the width of the driving pulse may be changed.

  In the present embodiment, in accordance with the ejection characteristics of each ink obtained from such experimental results, the driving conditions (driving pulse changing conditions) of the recording head 105 for each ink color are set as shown in FIG. . The horizontal axis in FIG. 4 is the number of times the recording head 105 is driven, and the vertical axis is the driving energy of the heater of the recording head 105. The drive energy is displayed as a K value {drive voltage / (minimum drive voltage leading to ejection)} along the horizontal axis of FIG. In the present invention, the number of driving times 4 × 108 is assumed to be an average head life. Such K value changing conditions are stored in the driving condition table 203 of FIG. The value of the driving energy on the vertical axis is a value when attention is paid to a single nozzle (corresponding to “one ink discharge portion”) that is most likely to discharge ink in the recording chip. In the setting, the following two points are taken into consideration.

  In actual recording, when the heaters for each nozzle are driven simultaneously to simultaneously eject ink from a plurality of nozzles, the voltage effect of the drive voltage occurs and drive energy fluctuates.

  Due to design variations among the nozzles in the recording chip, the drive conditions for each nozzle vary. As described above, when setting according to the nozzle that is most likely to eject ink, it is necessary to consider nozzles that are least likely to eject ink.

  In the present embodiment, in consideration of these circumstances, the drive pulse is set so as to guarantee the ink ejection performance even under the worst conditions where the adverse conditions overlap. FIG. 4 shows the set K value of a single nozzle at that time.

  For the yellow ink ejection nozzles, the K value is greatly changed stepwise from 1.17 to 1.24 as the number of times of driving increases. For the nozzles for cyan ink and magenta ink discharge, the K value is greatly changed stepwise from 1.17 to 1.21 as the number of times of driving increases. For the black ink ejection nozzle, the K value is set to 1.24 until the number of times of driving reaches around 1 × 10 6 times, and thereafter the K value is changed to 1.17 before the cyan ink and magenta Similar to the nozzles for ejecting ink, the K value is greatly changed stepwise as the number of times of driving increases. On an actual printing apparatus, since it is difficult to vary the drive voltage according to the ink type and the number of times each ink is ejected, the drive energy (K value) is switched as described above. In this method, the drive voltage is switched while the drive voltage is fixed.

  In FIG. 4, for simplification, the drive pulse switching point for each ink type is the same. However, the present invention is not limited to this, and it is preferable to optimize according to the characteristics for each ink type.

  Such K value changing conditions were set based on the following setting methods 1, 2, 3, and 4.

(Setting method 1)
This setting method 1 is a design method of a K value change condition for a type of ink that exhibits K value dependency like the cyan ink (C) in FIG.

  FIG. 6 shows the same evaluation results as FIG. 5 in the initial stage of use of the nozzles of the recording head for discharging the cyan ink and the time when the end of the service life is reached. Although the entire characteristic curve in FIG. 5 shifts to the right due to the change over time until the life of the recording head, the tendency of the ejection speed to depend on the K value does not change much. In view of this, with respect to cyan ink, the shift is made in consideration of only the shift amount of the entire characteristic curve of FIG. 5, that is, the change in the minimum drive energy necessary for ink discharge during the life of the cyan ink discharge recording head. The condition change condition is determined.

  FIG. 7 shows the experiment result of the present inventor who evaluated the change in the minimum drive energy necessary for ink ejection with respect to the nozzle for cyan ink ejection. The relationship between the number of times of driving (horizontal axis) and the minimum driving voltage (vertical axis) necessary for ink ejection when the pulse width of the driving pulse is made constant is shown. The time when the drive frequency exceeds 5 * 108 and the drive voltage finally increases sharply is the time when the heater in the recording chip starts to be disconnected, and it can be determined that the life of the recording head is exhausted. .

  In the present setting method 1, considering the characteristics of this type of ink, as shown in FIG. 4, the K value of the cyan ink (C) is largely changed stepwise as the number of times of driving increases. In addition, as shown in FIG. 7, the fluctuation is particularly large in the initial stage (up to 1 * 108), and the latter half (after 2 * 108) hardly changes until the end of the service life. It is set so that the switching is not performed in the second half.

(Setting method 2)
This setting method 2 is a method for setting the K value for the ink of the setting method 1 and for the type of ink in which the discharge speed decreases at the initial use of the recording head, such as the black ink described later.

  FIG. 8 is a graph showing changes in ink ejection speed (vertical axis) with respect to the number of driving operations (horizontal axis) at the initial use of the recording head nozzles for ejecting cyan, magenta, yellow, and black ink (C, M, Y, Bk). Axis). The driving conditions are the results of evaluation performed under the conditions shown in FIG. 4 (the total ink K value is 1.17). For cyan, magenta, and yellow inks (C, M, Y), the ejection speed hardly fluctuates from the beginning of use of the recording head. On the other hand, in the black ink (Bk), a temporary tendency to significantly decrease the ejection speed is observed. In the case of an ink of a type in which the change in the discharge speed is seen at the beginning of use, such as this black ink, the familiar discharge process is performed in order to avoid recording during a period during which the discharge speed is reduced (discharge unstable period). There is a need. When an initial familiar discharge period is required, it is preferable to set the driving condition in the initial use of the recording head so that the period can be shortened as much as possible. Generally, the effect can be improved by increasing the driving energy from the time of recording, and the process can be completed in a short period of time. The shortening of the initial conforming ejection period shortens the number of times of driving (the number of times of ink ejection) and the time required for shifting to the driving conditions for the normal recording operation. Also, when there are many inks with different ejection instability periods at the initial use of the recording head, the familiar ejection process for these inks can be efficiently completed by sharing the initial familiar ejection period for those inks. Can be made.

  In this setting method 2, the K value of the black ink (C) is changed as shown in FIG. 4 in consideration of the characteristics of such type of ink.

(Setting method 3)
This setting method 3 is a K value setting method for ink of a type that exhibits K value dependency such as yellow ink.

  In the case of yellow ink, as shown in FIG. 5, although the discharge speed is slightly lower than that of the other inks on the low K value side, in the range in which such a slightly lower discharge speed is maintained, Recording can be performed. FIG. 9 shows the same evaluation results as in FIG. 5 at the initial stage of use of the nozzles of the recording head for discharging yellow ink and at the time when the lifetime was exhausted. As shown in FIG. 9, at the time when the life of the recording head is exhausted, the entire characteristic curve is shifted, and the discharge speed in the range where the K value is small is significantly lower than in the initial use. May not be possible.

  If the K value of such yellow ink is set by the same method as the setting method 1 described above, the following problem may occur. In other words, when recording is performed, if adverse conditions in driving the recording head overlap, there is a nozzle that is driven in a K value range in which the discharge speed decreases, and the nozzle is defective in ink discharge. There is a risk of causing. As described above, the adverse conditions in driving the recording head include a large variation in ink ejection performance between nozzles, and a severe driving condition in which a voltage drop of the driving voltage is caused by simultaneously driving a large number of nozzles. .

  Therefore, for such yellow ink, it is necessary to set the K value in consideration of the tendency of the discharge speed to decrease in a range where the K value is small. This setting method 3 changes the K value of yellow ink (Y) as shown in FIG. 4 in consideration of the characteristics of this type of ink.

(Setting method 4)
This setting method 4 is a design method of a K value change condition for a type of ink that exhibits K value dependency, such as magenta ink (M).

  As shown in FIG. 5, the magenta ink has a lower discharge speed in a region where the K value is near 1.17. If the level of decrease in the ejection speed is not a problem, the K value of magenta ink may be set in the same manner as in setting method 1 described above. In this embodiment, as shown by magenta ink (M) in FIG. 4, it is set by the setting method 1 described above. However, when the degree of the decrease in the discharge speed becomes a problem, it is preferable to exclude the drive condition that causes such a decrease in the discharge speed and set the drive condition.

(Second Embodiment)
FIG. 10 is a perspective view of an essential part for explaining a second embodiment of the present invention.

  The recording head 105 of this example is provided with six recording chips 301, and each recording chip 301 has a plurality of ejection ports 301 formed in a row along the sub-scanning direction. Different ink is supplied to each recording chip 301 via the tube 303 and the joint 302. The recording chip 301 is provided with heaters (discharge energy generating means) corresponding to the respective discharge ports 301A, and ink droplets are discharged from the discharge ports 301A downward in FIG. 10 by the heat energy of the heaters. To do. These heaters, the discharge ports 301A, and the like constitute an ink discharge unit. Reference numeral 304 denotes an ejection port surface of the recording head 105 on which the ejection port 301A is located.

  In this example, the ink jet recording apparatus is provided with detection means for detecting the ink ejection state, and the drive condition (drive pulse) is set based on the detection result of the detection means.

  The detection means of this example arranges a photo sensor at a position facing a discharge port array (hereinafter also referred to as “nozzle array”) of the recording head 105, and drops ink droplets discharged from the discharge port 301 </ b> A of the recording head 105. It is a transmissive photo interrupter that directly detects optically. The light emitting unit 305 uses an infrared LED as a light emitting element, and projects parallel light on the optical axis 307 toward the light receiving unit 306 through a lens integrally formed on the light emitting surface. The light receiving unit 306 uses a phototransistor as a light receiving element. Reference numeral 308 denotes a frame on which the light emitting unit 305 and the light receiving unit 306 are arranged to face each other.

  When detecting the ink ejection state, first, the recording head 105 and the detection unit are set so that the ink droplets ejected from the ejection port 301A to be detected pass between the light emitting unit 305 and the light receiving unit 306. Move relative. Then, an ink droplet is ejected from the ejection port 301 </ b> A and is passed between the light emitting unit 305 and the light receiving unit 306. The ink droplets block light from the light emitting unit 305 side and reduce the amount of light received on the light receiving unit 306 side, whereby the output of the phototransistor in the light receiving unit 306 changes. Based on the change in the output, ejection or non-ejection of ink from the ejection port 301A is detected. Such detection is performed in units of ejection ports 301 for each nozzle row that ejects different inks.

  More specifically, with respect to the recording chip 301 that has reached a predetermined driving pulse change timing, an ink droplet from the ejection port 301A is switched while switching the driving pulse width while fixing the driving voltage of the ejection port 301A in the recording chip 301. And the ejection state of the ink droplet is detected. The switching of the drive pulse width starts from a drive pulse width that reliably ejects ink droplets from the ejection port 301A, gradually decreases the drive pulse width, and gradually decreases the amount of ink droplet ejection energy supplied. The ink droplet ejection state is detected while gradually switching the drive pulse width until the time when ink non-ejection is first detected or until the time when ink non-ejection of all ejection ports 301A is detected. The drive pulse is finally determined as a drive condition based on a table that records the results of accumulating and calculating the print head control error, print head design error, and the like with respect to the drive pulse width. To do.

  As a result, an appropriate drive pulse can be set for each recording chip 301 that ejects different inks based on the actual ink droplet ejection state when the drive pulse is changed.

(Other embodiments)
In the second embodiment, the drive pulse change timing can be set in the same manner as in FIG. 4, and the same K value as in FIG. 4 is corrected based on the detection result of the ink ejection state. Also good.

  The present invention only needs to be able to set the drive conditions for the ink discharge portion according to the type of ink to be discharged. The drive conditions are set in common for all the ink discharge portions that discharge the same type of ink. Correction may be made for each ink discharge unit in accordance with the detection result of the discharge state.

In addition, the ink ejection unit that ejects different inks may be configured for each recording chip, or may be configured for one recording chip. In addition, the ink discharge section for discharging different inks may be divided into a plurality of recording heads in addition to a single recording head. In any case, it suffices if the drive conditions of the ink discharge unit can be set according to the type of ink to be discharged,
In addition to the so-called serial scan type recording apparatus, the present invention is also applicable to a so-called full line type recording apparatus using a long recording head extending over the entire recording width of the recording medium. Can do.

  The embodiments of the present invention are listed below.

[Embodiment 1] In an inkjet recording apparatus for recording an image using a recording head capable of ejecting different inks from a plurality of ink ejection units,
Driving means for driving the plurality of ink ejection units;
Changing means for changing the driving condition by the driving means for each ink discharge portion corresponding to the type of ink to be discharged;
An ink jet recording apparatus comprising:

  [Embodiment 2] The change unit changes a drive condition by the drive unit for each of the ink discharge units corresponding to the type of ink to be discharged, based on a drive history of the plurality of ink discharge units. The inkjet recording apparatus according to Embodiment 1.

  [Embodiment 3] The inkjet recording apparatus according to Embodiment 2, wherein the driving history of the recording head is the number of times of driving for each of the ink ejection units.

  [Embodiment 4] The inkjet recording apparatus according to Embodiment 3, further comprising a measuring unit that measures the number of times of driving for each of the ink ejection units.

  [Embodiment 5] Any one of Embodiments 1 to 4, wherein the changing unit sets a change time of a driving condition by the driving unit for each of the ink discharge units corresponding to the type of ink to be discharged. 2. An ink jet recording apparatus according to 1.

[Embodiment 6] The driving means applies a driving pulse to drive the ink ejection unit,
The inkjet recording apparatus according to any one of claims 1 to 5, wherein the changing unit changes a pulse waveform of the drive pulse.

  [Embodiment 7] The inkjet recording apparatus according to Embodiment 6, wherein the changing unit changes the pulse width without changing the drive voltage of the drive pulse.

[Embodiment 8] A detection means for detecting an ink discharge state from the ink discharge portion is provided,
The inkjet recording apparatus according to any one of claims 1 to 7, wherein the changing unit changes a driving condition of the driving unit based on a detection result of the detecting unit.

  [Embodiment 9] The inkjet recording according to any one of Embodiments 1 to 8, wherein the plurality of ink discharge units are configured to be divided on a plurality of chips according to the type of ink to be discharged. apparatus.

  [Embodiment 10] Embodiments 1 to 9 are characterized in that the ink discharge section includes discharge energy generation means for generating energy for discharging ink from the discharge port in accordance with the driving condition of the drive means. Any one of the inkjet recording apparatuses.

  [Embodiment 11] The inkjet recording apparatus according to Embodiment 10, wherein the discharge energy generating means is an electrothermal converter that generates thermal energy.

[Embodiment 12] In an inkjet recording method for recording an image using a recording head capable of ejecting different inks from a plurality of ink ejection portions,
An ink jet recording method, wherein the drive condition of the ink discharge section is changed for each ink discharge section corresponding to the type of ink to be discharged.

DESCRIPTION OF SYMBOLS 101 Feed roller 102 Recording medium 103 Main operation guide 104 Carriage 105 Recording head 106 Platen 107 Memory 200 Control means 202 Driving means 203 Driving condition table 204 Measuring means 205 Change measuring means 206 Storage means 301 Recording chip 301A Discharge port 302 Joint 303 Tube 304 Discharge port surface 305 Light emitting part 306 Light receiving part 307 Optical axis

Claims (8)

In an inkjet recording apparatus that records an image using a recording head that includes a plurality of ink ejection units that eject black ink, cyan ink, magenta ink, and yellow ink, respectively.
Driving means for driving the plurality of ink ejection units;
Measuring means for measuring the number of times of driving each of the plurality of ejection units;
Changing means for changing drive energy for discharging ink in accordance with the number of times of driving in each of the plurality of ink discharge portions,
The changing means is
(A) The drive energy for discharging the black ink is changed from a relatively high drive energy to a relatively low drive energy when the drive count reaches a predetermined drive count, and the predetermined drive count Thereafter, the driving energy is gradually increased according to the number of times of driving, and
(B) The inkjet recording apparatus, wherein the drive energy for discharging the cyan ink, magenta ink, and yellow ink is changed so as to gradually increase in accordance with the number of times of driving. The changing means is
Each ink is discharged so that the driving energy for discharging the yellow ink is greater than the driving energy for discharging the black ink, cyan ink, and magenta ink at a driving frequency that is greater than the predetermined driving frequency. The ink jet recording apparatus according to claim 1, wherein the driving energy for changing is changed. The driving unit drives the ink ejection unit by applying a driving pulse,
The inkjet recording apparatus according to claim 1, wherein the changing unit changes a pulse waveform of the drive pulse.   The inkjet recording apparatus according to claim 3, wherein the changing unit changes a pulse width without changing a driving voltage of the driving pulse. The recording head has a plurality of chips in which a plurality of ejection openings are formed in a row,
The inkjet recording apparatus according to claim 1, wherein the plurality of ink ejection units are configured on different chips.   The inkjet recording apparatus according to claim 1, wherein the plurality of ink ejection units include ejection energy generation means for generating energy for ejecting ink from ejection ports.   The inkjet recording apparatus according to claim 6, wherein the discharge energy generating unit is an electrothermal converter that generates thermal energy. The black ink, cyan ink, magenta ink, and yellow ink are driven by using a recording head having a plurality of ink discharge sections that respectively discharge black ink, cyan ink, magenta ink, and yellow ink. In an ink jet recording method for recording an image by discharging
A measuring step of measuring the number of times each of the plurality of ejection units is driven;
A change step of changing drive energy for discharging ink according to the number of times of driving in each of the plurality of ink discharge portions,
In the changing step,
(A) The drive energy for discharging the black ink is changed from a relatively high drive energy to a relatively low drive energy when the drive count reaches a predetermined drive count, and the predetermined drive count Thereafter, the driving energy is gradually increased according to the number of times of driving, and
(B) An inkjet recording method, wherein driving energy for discharging the cyan ink, magenta ink, and yellow ink is changed so as to gradually increase in accordance with the number of times of driving.

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