JPH07125259A - Ink jet recording head and its gradation recording control method - Google Patents

Abstract

PURPOSE:To obtain an ink jet recorder capable of carrying out multiple gradation recording by a method wherein a dot is enabled to be drawn in a plurality of density gradation with respective nozzles. CONSTITUTION:Low density ink 13 is supplied from an ink passage 12, and high density ink 23 is supplied from an ink passage 22. Before a tip of a discharge nozzle 10 is refilled with the low density ink 13 in the ink passage 12 after discharging an ink drop from a tip of the discharge nozzle 10 by heating with a discharge heater 11, the high density ink 23 is made to flow in the discharge nozzle 10 by driving a micro-pump 24. The micro-pump 24 is operated with a bubble of the high density ink generated by heating with a driving heater 21. By driving the driving heater 21 by using PWM control or the like according to recording density, inflow of the high density ink 23 with the micro-pump 24 is controlled, and the recording density is varied according to a mixing ratio between the low density ink 13 and the high density ink 23.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording head for executing multi-value gradation recording in an ink jet recording apparatus for recording by ejecting ink from the recording head, and a gradation control method therefor.

[0002]

2. Description of the Related Art A recording device such as a printer, a copying machine or a facsimile is constructed to record an image consisting of a dot pattern on a recording material such as paper or a plastic thin plate based on image information.

Such a recording apparatus has an ink jet type, a wire dot type, a thermal type, a
It can be divided into a laser beam type and the like. Of these, the inkjet type (inkjet recording device) is
An ink (recording liquid) droplet is ejected and ejected from the ejection port of the recording head, and the ink droplet is adhered to a recording material for recording.

In recent years, a large number of recording devices have been used, and high speed recording, high resolution, high image quality, low noise, etc. are required for these recording devices. As an example of a recording device that meets such a demand, the inkjet recording device can be cited. In this ink jet recording apparatus, since ink is ejected from the recording head to perform recording, non-contact printing is possible, and therefore a very stable recorded image can be obtained.

[0005]

However, in the conventional ink jet recording system, binary images are the mainstream and lack in gradation. Further, as an attempt to obtain a multi-valued gradation image in the ink jet system, an area gradation method in which the area of dots is modulated to reproduce gradation, or gradation using a plurality of types of inks with different dye concentrations is used. There is a density gradation method for reproducing However, these conventional area gradation method and density gradation method have the following drawbacks.

First, in the area gradation method, it is very difficult to stably form an ink droplet having a small drop diameter only by the ink jet technique, and in addition, only gradation values of about 4 are practically obtained. I can't. Furthermore,
No recorded image having remarkably improved graininess has been obtained. Also, regarding the printing time, it is necessary to perform overwriting with small ink droplets in area gradation, and it is necessary to scan the carriage multiple times at almost the same location, which results in a very long printing time. There are drawbacks.

Further, in order to solve the above-mentioned defect of area gradation, a method using a density gradation method has been proposed. According to this, the graininess on the image is improved as compared with that of the area gradation method, but in order to increase the gradation, it is necessary to provide a plurality of inks having different dye concentrations such as dye concentration. . In reality, only two kinds of dye concentrations were provided, and it could not be said that it was multivalued.

The present invention has been made in view of the above problems, and provides an ink jet recording apparatus capable of multi-value recording by enabling each nozzle to draw dots at a plurality of density gradation levels. It is an object of the present invention to provide an inkjet recording head and a gradation recording control method for the same, which are capable of obtaining the same.

[0009]

To achieve the above object, an ink jet recording head according to the present invention has the following constitution. That is, an inkjet recording head having nozzles for ejecting ink droplets for recording dots, the first nozzle having a first density at the nozzles.
Second supplying means for supplying the ink of the
Second supply means for supplying the second ink having a density of 2 and a control means for controlling the supply amount of the second ink by the second supply means based on the density of the dots printed by the nozzles. An inkjet recording head characterized by the above.

The gradation recording control method of the present invention for achieving the above object is a gradation recording control method for recording dots having multi-value gradation by ejecting ink droplets from a nozzle. A first supplying step of supplying a first ink having a first density to the nozzle, a second supplying step of supplying a second ink having a second density to the nozzle, and the nozzle The control step of controlling the supply amount of the second ink in the second supply step based on the density of the dots to be recorded in step 2.

[0011]

With the above-described structure, the nozzle for ejecting ink droplets, the ink having the first density and the ink having the second density are supplied to this nozzle. Here, the inflow amount of the ink having the second density into the nozzle is controlled based on the gradation of the dots printed by the nozzle. in this way,
By feeding inks having different densities into the nozzles, the density of the inks in the nozzles is changed, and the density of the ejected ink droplets is changed in multiple stages to perform recording.

For example, an ink having a low dye concentration is used as the ink having the first density, and an ink having a high dye concentration is used as the ink having the second density. Then, the supply amount of the high-density ink is determined based on the signal of the density gradation degree included in the multi-valued image data, and the high-density ink is mixed with the low-density ink by this supply amount. In this way
It is possible to control the dye density in multiple steps based on the density gradation signal, and it is possible to obtain a multi-step density gradation image.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the accompanying drawings.

<Embodiment 1> FIG. 1 is a configuration diagram showing an ejection nozzle of an ink jet recording head in Embodiment 1.

This discharge nozzle 10 has two ink flow paths 1
2 and 22, which are independently connected to the ink supply system. These ink flow paths 12 and 22 are
The low density ink 13 and the high density ink 23 are supplied respectively. First, the ink flow path 12 that supplies the low-concentration ink 13 will be described.

A meniscus 14 is formed at the tip of the discharge nozzle 10 by a capillary force. The tip of the discharge nozzle 10 is subjected to a hydrophilic treatment, and has a meniscus shape as illustrated. The Si substrate 2 is provided at the center of the discharge nozzle 10.
A discharge heater 11 formed by a semiconductor process is provided on the substrate 0. The discharge heater 11 is electrically heated to induce bubble growth due to film boiling of the low-efficiency ink 13 on the discharge heater 11 to discharge ink droplets.

On the other hand, the ink flow path 22 for supplying the high-concentration ink is provided with a micro pump 24 formed by a micromachine technique at the tip. A driving heater 2 for driving the micro pump 24 on the Si substrate 20 on which the above-mentioned discharge heater 11 is formed as a driving source thereof.
1 is provided. The ink flow path 22 is connected to an ink supply system separate from the ink flow path 12 for the low-concentration ink 13 described above, and has respective ink tanks (not shown).

Next, details of the micropump 24 will be described with reference to FIG. FIG. 2 is a diagram showing details of the micro pump 24 of the first embodiment. The micro pump is driven by the piston 26 being pushed up by the bubbling of the high-concentration ink 23 caused by the electric heating of the driving heater 21.
When the piston 26 is pushed up and opened, the high-concentration ink 23 flows into the nozzle. This micro pump 24 is provided with a stopper 25, and the piston 2
The rear end of the piston 26 is hooked in order to prevent 6 from entering the discharge nozzle 10 more than a predetermined amount. Further, the up-and-down movement of the piston 26 controls the inflow amount of the high-concentration ink 23.
The WM control controls the inflow amount of the high-concentration ink 23 in the same way as controlling the ink ejection amount.

Further, an actuator 27 for suppressing the movement of the piston is provided within the operating range of the piston 26. The actuator 27 is used when controlling an area that cannot be set by PWM control, that is, an area in which the ejection amount of the high density ink 23 is small. That is, the actuator 27 is operated during the operation of the piston 26, and the operation of the piston 26 is stopped during the operation. This makes it possible to control the inflow amount of the high-concentration ink 23 into the ejection. Specifically, a shape memory alloy actuator is used as the actuator 27. A shape memory alloy actuator is a metal that returns to a shape set in advance at a high temperature when it exceeds a transformation point. For example, there is a nitome which is an alloy of nickel and titanium. Since this shape memory alloy actuator can change its shape by self-heating due to the electric power when energized, by setting the transformation point higher than the amount of heat generated by the driving heater 21, strict electrical control becomes possible. Furthermore, a plurality of actuators 2
By selectively using 7 to operate, the stop position of the piston 26 can be accurately controlled. As a result, the ink inflow amount can be effectively controlled particularly in a region where the inflow amount is small.

3 to 7 are views for explaining each process of ink ejection, mixing and refilling in the recording head of the first embodiment.

FIG. 3 shows a state in which printing is started. An electric signal is sent to the discharge heater 11, and nucleate boiling of the low-concentration ink 13 is starting to occur on the surface of the discharge heater 11. Further, as shown in FIG. 4, the ink is film-boiling to form a large bubble as the current continues to flow. At the tip of the discharge nozzle 10, the retracted meniscus gradually rises as the bubble grows. Figure 3,
The time is several μsec through FIG. FIG. 5 shows a state in which ink droplets have been ejected. The bubbles on the discharge heater 11 are beginning to disappear. The low density ink 13 is refilled with this, and the normal ink ejection process is completed.

In the first embodiment, in this state, the driving heater 21 of the micropump 24 is energized to grow bubbles on the driving heater 21. It should be noted that, in actuality, in FIG. 4 described above, the energization to the driving heater 21 has been started, and the state where nucleate boiling has occurred in the high-concentration ink 23 on the driving heater 21 is shown in FIG. . Then, in FIG. 5, the grown bubbles are the piston 2 of the micro pump 24.
6 is starting to be pushed up. Further, in FIG. 6, the piston 26 is pushed all the way to inject the high-concentration ink 23 into the ejection nozzle 10, especially in the vicinity of the ejection port. This timing is set just before the previous ejection is completed and the low-density ink is refilled. The amount of high-concentration ink 23 flowing into the ejection nozzle 10 is controlled by PWM (separation pulse width modulation) control or operation control of the piston 26 by an actuator 27 in the micropump 24.

The piston 26 is pushed up by foaming due to the heating of the driving heater 21, and is pulled down by the ink flow at the time of refilling the low density ink 13, the negative force on the high density ink 23 side and the meniscus force. In addition, the high density ink 23
When a large amount of the high density ink 23 is required, the micro pump is driven a plurality of times before the low density ink 13 is refilled, and an appropriate amount of the high density ink 23 is poured. The driving frequency of the micro pump 24 is higher than the driving frequency of the normal discharge heater 11, and it can be driven at ten and several kHz. That is, the driving heater 21 can be sufficiently driven even at a high frequency because the flow rate of ink at one time is very small. In this embodiment, the ejection amount per drive by the ejection heater 11 on the low density ink 13 side is set to about 80 ng, and the ejection amount per drive heater 21 is set to about 10 ng. It is possible to perform various combinations depending on the setting of.

Finally, FIG. 7 shows a state in which the high density ink 23 and the low density ink 13 are mixed at the tip of the discharge nozzle 10 and the next discharge can be performed. The high density ink 23 flowing into the nozzle mixes with the refilled low density ink 13. This mixing is promoted by the surface of the low-density ink 13 at the time of refilling, the vibration wave, and the meniscus vibration. When the next ejection is performed, the ink to be ejected next time at the tip of the nozzle has an ink with a substantially uniform density. However, the ink droplets thus ejected collide with the surface of the recording medium when landing on the recording medium, and are thus mixed by the impact force at that time. Therefore,
Even if the low-density ink 13 and the high-density ink 23 are not sufficiently mixed in the refilled state of the low-density ink 13, the print quality is hardly affected.
Then, returning to FIG. 3A in which the next discharge is started,
Recording is performed by repeating the cycle of FIG. 3 to FIG. 7 described above. In this embodiment, since the inner diameter of the ink flow path is small when not in use, the meniscus force on the high density ink side is strong,
As a result, the high density ink 23 and the low density ink 13 can be reliably separated by the piston 26.

FIG. 8 shows the relationship between the dye density and the optical reflection density in the image having the density gradation formed by the above process. The optical reflection density increases with the increase of the dye concentration up to 5%, but the optical reflection density exceeds the limit, and it is in a capped state and cannot be changed largely. Therefore, in this embodiment, the high-concentration ink has a dye concentration of 20%,
The low-concentration ink has a dye concentration of 1%, and the final ink concentration of the ejected ink can be controlled within a range of 1 to 10%. Further, in the present embodiment, the discharge amount from the discharge nozzle 10 by the discharge heater 11 is 80 ng,
The maximum inflow amount of the high-concentration ink into the ejection nozzle 10 by driving the micropump 24 once is set to 10 ng.

Further, FIG. 9 shows changes in the dye concentration with respect to the inflow amount of the high concentration ink in this case. This figure shows the case where the high density ink uses dyes of 20% and 10%. The dye concentration can be linearly controlled by the inflow amount of high-concentration ink. This suggests that by controlling the inflow amount of high density ink, the dye density can be changed, the optical reflection density of the obtained image can be changed, and density gradation can be performed. Further, the high-concentration ink 23 used in this embodiment cannot be normally used because the dye or the like is fixed in the nozzle portion, but in this embodiment, the high-concentration ink hardly touches the outside air directly. Since almost always faces the low-density ink, it is possible to prevent the problem of fixing the high-density ink. Further, at the ejection port, the ink having a lower density is exposed to the outside air. this is,
This is because the high density ink is refilled so as to be wrapped with the low density ink. For this reason, even when compared with the ink used in a normal ink jet recording apparatus, for example, the ink having a dye concentration of about 3%, the fixing problem is considerably improved.

Further, the ink may be a dye type or a pigment type, or both may be used in combination. Furthermore, not only the density gradation but also the area gradation may be combined to obtain more gradation. In this embodiment, a low-concentration ink having a dye concentration of 1% is used, but by using an ink having a lower dye concentration, the control range of the density gradation is expanded. Further, the same control can be performed by using a clear ink containing no dye.

Next, the discharge control method by PWM control will be described in detail.

FIG. 10 is a diagram for explaining a divided pulse according to one embodiment of the present invention. In the figure, VOP is the drive voltage, P1 is the pulse width of the first pulse (hereinafter referred to as preheat pulse) of the plurality of divided heat pulses, P2 is the interval time, and P3 is the second pulse (hereinafter referred to as the main heat pulse). That is) pulse width. T1, T2, and T3 indicate times for determining P1, P2, and P3. The drive voltage VOP generates thermal energy for causing the electrothermal converter (ejection heater 11) to which this voltage is applied to cause bubbling in the ink in the ink flow path formed by the heater board and the top plate. It provides the necessary electrical energy for. The voltage value is determined by the area of the electrothermal converter, the resistance value, the film structure and the flow path structure of the recording head.

The divided pulse width modulation driving method means P1, P
Pulses are sequentially applied with a width of 2 and P3. Here, the preheat pulse is a pulse mainly for controlling the ink temperature in the flow path, and plays an important role in controlling the ejection amount in this embodiment. The preheat pulse width is set to a value such that the bubbling phenomenon does not occur in the ink due to the thermal energy generated by the electrothermal converter when it is applied.

The interval time is provided in order to set a predetermined time interval so that the pre-heat pulse and the main heat pulse do not interfere with each other, and to make the temperature distribution of the ink in the ink flow path uniform. The main heat pulse is for causing bubbling in the ink in the flow path to eject the ink from the ejection port, and its width P3 is the area of the electrothermal converter, the resistance value, the film structure and the ink of the recording head. It depends on the structure of the flow path.

For example, the action of the preheat pulse in the recording head having the structure shown in FIGS. 11 and 12 will be described. 11 and 12 are views showing a configuration example of the recording head in the present embodiment. FIG. 11 is a schematic vertical sectional view taken along the ink flow path, and FIG. 12 is a schematic front view of the recording head. The electrothermal converter (ejection heater 11) generates heat by applying the divided pulse. The discharge heater 11 is arranged on the heater board together with electrode wiring for applying a divided pulse to the discharge heater 11. The heater board is made of silicon (Si) and is supported by an aluminum plate (Al) which is a substrate of the recording head.

Grooves for forming the ink flow path 12 and the like are formed in the grooved top plate 30, and the ink flow path and the ink flow path are formed by joining the grooved top plate 30 and the heater board (aluminum plate). A common liquid chamber for supplying ink to this is configured. In addition, a discharge hole 31 is formed in the grooved top plate 30,
The ink flow path 12 communicates with each of the ejection holes 31.

In the recording head shown in FIGS. 11 and 12, the driving voltage VOP is 18.0 (V), the main heat pulse width P3 is 4.114 [μsec], and the preheat pulse width P1 is 0 to 3.000. When changed in the range of [μsec], the discharge amount Vd [n as shown in FIG.
The relationship between g / dot] and the preheat pulse width P1 [μsec] can be obtained.

FIG. 13 is a diagram showing the dependency of the discharge amount on the preheat pulse. In FIG. 13, V0 is P1 = 0 [μ
sec], and this value is determined by the head structure shown in FIGS. 11 and 12. Incidentally, V0 in the first embodiment is V0 = 1 when the ambient temperature TR = 25.degree.
It was 8.0 [ng / dot]. As shown by the curve a in FIG. 13, as the pulse width P1 of the preheat pulse increases, the ejection amount Vd linearly increases from the pulse width P1 of 0 to P1LMT, and the passing width P1 of P1LMT. In the larger range, the change loses its linearity and the pulse width P1
It is saturated at 1MAX and becomes maximum.

As described above, the range up to the pulse width P1LMT in which the change in the discharge amount Vd with respect to the change in the pulse width P1 shows linearity is effective as a range in which the discharge amount can be easily controlled by changing the pulse width P1. Is. Incidentally, in the present embodiment shown by the curve a, P1LMT = 1.87 (μs), and the discharge amount at this time was VLMT = 24.0 [ng / dot]. Further, the pulse width P1MAX when the ejection amount Vd becomes saturated was P1MAX = 2.1 [μs], and the ejection amount VMAX at this time was 25.5 [ng / dot].

When the pulse width is larger than P1MAX, the ejection amount Vd becomes smaller than VMAX. When a preheat pulse having a pulse width in the above range is applied, this phenomenon causes minute foaming (a state immediately before film boiling) on the electrothermal converter, and the next main heat pulse is generated before the bubbles disappear. This occurs because the minute bubbles are applied and disturb the foaming due to the main heat pulse, so that the discharge amount becomes small. This area is called a pre-foaming area, and in this area, it becomes difficult to control the ejection amount through the preheat pulse.

If the slope of the straight line showing the relationship between the discharge amount and the pulse width in the range of P1 = 0 to P1LMT [μs] shown in FIG. 13 is defined as the preheat pulse dependence coefficient, the preheat pulse dependence coefficient KP is KP = ΔVDP / ΔP1 [ng / μsec ・ d
ot]. This coefficient KP is determined by the head structure, driving conditions, ink physical properties, etc., regardless of temperature. That is, the curves b and c in FIG. 8 show the case of other recording heads, and it can be seen that the ejection characteristics change when the recording heads are different. As described above, since the upper limit P1LMT of the preheat pulse P1 is different when the recording heads are different, the ejection amount control is performed by setting the upper limit P1LMT for each recording head as described later.
Incidentally, in the recording head and ink shown by the curve a in this embodiment, KP = 3.209 [ng / μsecd
ot].

Another factor that determines the ejection amount of the ink jet recording head is the temperature of the recording head (ink temperature). FIG. 14 is a diagram showing the temperature dependence of the discharge amount. As indicated by the curve a in the figure, the ejection amount Vd increases linearly with the increase of the environmental temperature TR (= head temperature TH) of the recording head. If the slope of this straight line is defined as the temperature dependence coefficient, the temperature dependence coefficient KT is KT = ΔVdt / ΔTH [ng / ° C · dot]. This coefficient KT is determined by the structure of the head, the physical properties of the ink, etc., not by the driving conditions. Also in FIG. 14, curves of other recording heads are shown by curves b and c. In the recording head of this embodiment, KT = 0.3 [ng / ° C.
・ Dot].

13 and 14 as described above.
The discharge amount control according to the present invention can be performed by using the relationship shown in. In addition, although the ejection amount control of the ink by the PWM described above is described with respect to the ejection nozzle 10, the same characteristics can be obtained also in the micro pump 24 that causes the high concentration ink to flow into the ejection nozzle.
It is obvious that the above PWM can be applied to the control of the inflow amount of the high density ink.

Next, a suitable ink jet recording apparatus main body IJRA to which the present invention is applied or applied will be described.

FIG. 15 is an example of an external view of an ink jet recording apparatus IJRA applied to the present invention. In the figure, the carriage HC that engages with the spiral groove 5004 of the lead screw 5005 that rotates via the driving force transmission gears 5011 and 5009 in conjunction with the forward and reverse rotation of the drive motor 5013 has pins (not shown). , And is reciprocated in the directions of arrows a and b. An inkjet cartridge IJC is mounted on the carriage HC. A paper pressing plate 5002 presses the paper against the platen 5000 in the carriage movement direction. 5007, 5008
Is a photo coupler, which is a home position detecting means for confirming the existence of the carriage lever 5006 in this area and switching the rotation direction of the motor 5013. Fifty
16 is a cap member 5 for capping the front surface of the recording head.
Numeral 5015 is a member for supporting 022, and a suction means 5015 sucks the inside of the cap to perform suction recovery of the recording head through the opening 5023 in the cap.

5017 is a cleaning blade,
Reference numeral 19 denotes a member that allows the blade to move in the front-rear direction, and these members are supported by the main body support plate 5018.
Needless to say, a well-known cleaning blade can be applied to this example instead of this form. 5024
Is a temperature or humidity sensor, which can detect the temperature and humidity of the ink jet recording apparatus. It is also possible to predict the temperature of the ink recording head. This may be attached to the inkjet cartridge IJC, and may be directly attached to the inkjet unit IJC.
It may be attached to U for detection.

Reference numeral 5021 denotes a lever for starting suction for suction recovery, which is a cam 5020 fitted with the carriage.
And the driving force from the drive motor is controlled by known transmission means such as clutch switching.

The capping, cleaning, and suction recovery are configured such that the desired processing can be performed at their corresponding positions by the action of the lead screw 5005 when the carriage comes to the home position side area. Any of these can be applied to this example as long as the desired operation is performed.

Further, in the present embodiment, when the suction recovery is performed, the suction pressure is set to be considerably higher than the negative pressure in the ink tank, so that the low density ink and the high density ink can be obtained by one suction recovery. Both can be recovered by suction at the same time. Also,
The preliminary ejection of the high-concentration ink can be performed by controlling the preliminary ejection of the low-concentration ink. After the printing is completed, the sticking is made as difficult as possible, so that the high density ink is prevented from flowing in, and the nozzle tip is left standing and capped while being filled with the low density ink.

Inkjet cartridge IJ in this example
C has a large ink storage ratio, and has a sufficient volume to store a plurality of types of ink. It has a shape in which the tip of the inkjet unit slightly projects from the front surface of the ink tank. The inkjet cartridge IJC is a type that is fixedly supported by the positioning means of the carriage HC mounted on the inkjet recording apparatus main body IJRA and electrical contacts, and is removable from the carriage HC.

Next, FIG. 16 is a block diagram for explaining the flow of print data inside the printing apparatus. Host computer 5
The recording data sent from 0 is stored in the receiving buffer 52 inside the recording apparatus via the interface 51. The reception buffer 52 has a capacity of several k to several tens of kbytes. The command analysis unit 53 performs command analysis on the recorded data stored in the reception buffer 52 to obtain text data. The obtained text data is sent to the text buffer 54. In the text buffer 54, one line of recorded data is held in an intermediate format, and a process of adding a printing position of each character, a type of decoration, a size, a character (code), a font address, etc. is performed. The capacity of the text buffer 54 differs depending on each model, and has a capacity of several lines in the case of a serial printer and a capacity of one page in the case of a page printer. Further, the expanding section 55 is
The recorded data stored in the text buffer 54 is expanded to obtain multi-valued or binarized image data. The obtained image data is stored in the print buffer 56 and then transmitted to the recording head 57 as recording data.
Recording is done.

In the first embodiment, a signal is sent from the multivalued data stored in the print buffer 56 to the micropump 24 to control the density gradation. Depending on the type of recording device, there is also a device that does not have the text buffer 54, expands the recording data accumulated in the reception buffer 52 at the same time as the command analysis, and writes it in the print buffer 56.

FIG. 17 is a flow chart showing the procedure of the density gradation control of the first embodiment. As described above, the print data transmitted from the host computer 50 is expanded into multivalued image data (multivalued data) and stored in the print buffer 56. When multi-valued data is stored in the print buffer 56, steps S1 to S2
Go to. In step S2, the density gradation degree is set for each pixel from the multivalued data stored in the print buffer 56. In step S3, from the density gradation degree shown in FIG.
The high density ink amount is set in accordance with the high density ink amount setting table. FIG. 18 is a control table determined from the relationship between the dye density and the optical reflection density and the relationship between the high density ink and the dye density shown in FIG. 4 and FIG. 5, and can be adapted to 9 levels of density gradation. There is.

In step S4, the PWM control value and the number of times the micro pump 24 is driven are set. In the first embodiment, the stopper 24 is provided so that the high-concentration ink can flow in about 10 ng by driving the micro pump 24 once. Therefore, the control of each density gradient is performed as follows.

When the density gradient is 7 or 8, the operating conditions are set so that the micropump 24 is driven twice or four times while performing the PWM control. When the density gradient is 5 or 6, the operating condition is set to adjust the high density ink amount by PWM control. In the PWM control, as shown in FIG. 13, the inflow amount of the high density ink is controlled by the pulse width of the preheat pulse.

When the density gradient is 1, 2, 3 or 4, the operating condition is set so as to control the ink inflow amount by controlling the actuator 27 (step S5). As described above, the micropump 24 is driven in step S6 under the operating conditions set in steps S4 and S5. Then, recording is performed in step S7.

The inflow of the high-concentration ink by driving the micropump 24 in step S6 is performed during the refilling of the low-concentration ink to the tip of the ejection nozzle after the ejection of the ink for recording. There is. Therefore, the time when the high density ink is exposed to the atmosphere is extremely short. Further, when the first printing is performed, the high density ink is made to flow in after the preliminary ejection just before that.

As described above, by using the ink jet recording apparatus in which the micro pump is mounted in the ink flow path, it becomes possible to flow the inks having different densities into the ink flow path, and one recording head can print the density level. It is possible to provide an ink jet recording apparatus capable of multi-valued recording with tone.

<Embodiment 2> Embodiment 2 is an example in which a micropump having improved controllability in the inflow direction of high density ink is used as compared with Embodiment 1. FIG. 19 is a configuration diagram showing the ejection nozzles of the inkjet recording head in the second embodiment. In the figure, the same components as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted here. Figure 1
In FIG. 9A, 241 is an ink direction control type micro pump, which is operated by the driving heater 21 as in the first embodiment.

FIG. 19B shows a state in which the piston of the ink direction control type micro pump 241 is pushed up by the driving heater 21 and the high concentration ink 23 is flowing in. The tip of the piston is formed obliquely, and the high-concentration ink 23 is discharged from the ejection nozzle 1 according to this shape.
It is flowing into 0. The inflow amount of the high-concentration ink 23 is controlled by PWM control and actuator control as in the first embodiment. In the second embodiment, the low density ink 1
Both the direction in which 3 is refilled and the direction in which the high-concentration ink 23 flows are toward the tip of the ejection nozzle 10. Further, since the refilling force of the low-density ink 13 contributes to pushing down the piston of the micro pump 241, the low-density ink is more reliably prevented from flowing into the high-density ink side. Furthermore, since the piston is pulled by the negative pressure of the ink tank for the high density ink 23 as in the first embodiment, the piston is reliably separated from the low density ink side.

By using the ink direction control type micro pump 241 described above, the high-concentration ink 23 flows into the tip portion of the ejection nozzle 10 more reliably. For this reason, the low-concentration ink 13 is more reliably mixed at the tip portion of the ejection nozzle 10, and highly reliable control can be performed.

<Third Embodiment> The third embodiment is characterized in that the tip of the micropump has a valve shape. Figure 20
6 is a configuration diagram showing ejection nozzles of an inkjet recording head in Embodiment 3. FIG. In the figure, the same components as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted here.
In FIG. 20A, 242 is a valve type micro pump, which is operated by the driving heater 21 as in the first embodiment.

FIG. 20B shows a valve type micro pump 242.
The valve is opened, and the high-concentration ink 23 is flowing into the ejection nozzle 10. The flow rate control of the high density ink 23 is the same as in the first and second embodiments. In the third embodiment, the tip of the micropump has a valve shape. Compared to the embodiment in which the piston moves up and down as in the first and second embodiments, the valve only opens and closes, so sliding resistance is small and energy loss of the micropump is small.
Further, as is clear from FIG. 20B, the characteristic of the high-concentration ink 23 in the inflow direction is also excellent. Low density ink 1
As for the separation of the high-concentration ink 23 and the high-concentration ink 23, the negative pressure of the ink tank on the high-concentration ink side pulls the valve similarly to the second embodiment, so that reliable separation is performed. In the third embodiment, since there is a valve-shaped ink inflow portion having a small sliding resistance, it is particularly excellent in high frequency drive. That is, it is more effective when used in an ink jet recording apparatus driven by a higher frequency or when used with a large inflow amount of high-concentration ink (for example, when density gradation degree = 8 in the high-density ink amount setting table of FIG. 18). Micro pump.

As described above, according to each of the above-described embodiments, it is possible to send the ink droplets having different densities into the ejection nozzles by the micro pump, and to change the densities of the ink droplets in the ejection nozzles. Therefore, it is possible to provide an inkjet recording apparatus capable of recording multi-valued images having density gradations with one recording head, and it is possible to obtain a high-quality image having a smaller size and more gradations than ever before.

In the above-mentioned embodiment, among the ink jet recording methods, the one in which flying droplets are formed by thermal energy is described, but it goes without saying that it may be applied to other ink jet recording methods. Nor.

The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of a single device. Further, it goes without saying that the present invention can also be applied to a case where it is achieved by supplying a program that causes a system or an apparatus to execute the processing defined by the present invention.

[0064]

As described above, according to the ink jet recording head and gradation recording control method of the present invention, each nozzle of the ink jet recording head can draw dots with a plurality of density gradation degrees. It is possible to provide an inkjet recording device capable of multi-value recording.

[0065]

[Brief description of drawings]

FIG. 1 is a diagram illustrating ejection nozzles of an inkjet recording head according to a first exemplary embodiment.

FIG. 2 is a diagram illustrating details of a micro pump 24 according to the first embodiment.

FIG. 3 is a diagram illustrating the ejection of ink in the recording head according to the first embodiment.
It is a figure explaining each process of mixing and refilling.

FIG. 4 is a diagram showing the ejection of ink in the recording head of Example 1.
It is a figure explaining each process of mixing and refilling.

FIG. 5 is a diagram showing the ejection of ink in the recording head of Example 1.
It is a figure explaining each process of mixing and refilling.

FIG. 6 is a diagram illustrating the ejection of ink in the recording head according to the first embodiment.
It is a figure explaining each process of mixing and refilling.

FIG. 7 is a diagram showing the ejection of ink in the recording head of Example 1.
It is a figure explaining each process of mixing and refilling.

FIG. 8 is a diagram showing a relationship between dye density and optical reflection density in an image having density gradation.

FIG. 9 is a diagram showing a change in dye concentration with respect to an inflow amount of high-concentration ink.

FIG. 10 is a diagram for explaining a divided pulse in the present embodiment.

FIG. 11 is a schematic cross-sectional view along an ink flow path showing a configuration example of the recording head in the present embodiment.

FIG. 12 is a schematic front view of the recording head in this embodiment.

FIG. 13 is a diagram showing the preheat pulse dependency of the ejection amount in the present embodiment.

FIG. 14 is a diagram showing temperature dependence of discharge amount in the present embodiment.

FIG. 15 is a diagram illustrating an example of an external view of an inkjet recording device IJRA applied to the present invention.

FIG. 16 is a configuration diagram illustrating a flow of print data inside the printing apparatus.

FIG. 17 is a flowchart showing a procedure of density gradation control according to the first embodiment.

FIG. 18 is a diagram showing a high density ink amount setting table.

FIG. 19 is a diagram showing ejection nozzles of an ink jet recording head in Example 2.

FIG. 20 is a diagram illustrating ejection nozzles of an inkjet recording head according to a third embodiment.

[Explanation of symbols]

 10 Discharge Nozzle 11 Discharge Heater 12, 22 Ink Flow Path 13 Low Concentration Ink 14 Meniscus 20 Si Substrate 21 Drive Heater 23 High Concentration Ink 24 Micro Pump 25 Stopper

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Haruyuki Yanagi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Osamu Sato 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Within the corporation

Claims (10)

[Claims] 1. An inkjet recording head having a nozzle for ejecting ink droplets for recording dots, the first supplying means supplying a first ink having a first density to the nozzle. A second supply means for supplying a second ink having a second density to the nozzle, and a second ink supply amount by the second supply means based on the density of dots recorded by the nozzle. An ink jet recording head, comprising: a control unit for controlling. 2. An inkjet recording head having a nozzle for ejecting a droplet of ink for recording a dot, the first ink communicating with the nozzle and having a first density. First supply means for supplying, second supply means for communicating with the nozzle and supplying second ink having a second density to the nozzle, and partitioning the second supply means with the nozzle Inkjet recording, comprising: partitioning means for controlling the inflow amount of two inks into the nozzle; and control means for controlling the inflowing amount by the partitioning means based on the density of dots recorded by the nozzles. head. 3. The partition means separates the second supply means from the nozzle by a micropump provided at an inflow portion of the second supply means to the nozzle, and the nozzle of the second ink. The inkjet recording head according to claim 2, wherein the amount of inflow to the inkjet recording head is controlled. 4. The ink jet recording head according to claim 3, wherein the micro pump is driven by a dedicated heating element. 5. The ink jet recording head according to claim 3, wherein the micro pump has a direction control unit that controls a flow direction of the second ink into the nozzle. 6. The ink jet recording head according to claim 3, wherein the micro pump has a prevention unit that prevents the first ink from flowing into the second supply unit from the nozzle. 7. The ink jet recording head is a recording head for ejecting ink by utilizing thermal energy, and is provided with a thermal energy converter for generating thermal energy applied to the ink. Claim 1
7. The inkjet recording head according to any one of 6 to 6. 8. The ink jet recording head causes a state change in ink due to thermal energy applied by the thermal energy converter, and ejects the ink from an ejection port based on the state change. The inkjet recording head described. 9. A gradation recording control method for recording dots having multi-value gradation by ejecting ink droplets from a nozzle, wherein the nozzle has a first density having a first density. A first supplying step of supplying ink, a second supplying step of supplying a second ink having a second density to the nozzle, and a second supplying step based on the density of dots recorded by the nozzle And a control step of controlling the supply amount of the second ink. 10. A gradation recording control method for recording dots having multi-valued gradations by ejecting ink droplets from a nozzle, which is in communication with the nozzle and has a first density. A first supplying step of supplying a first ink to the nozzle; a second supplying step of communicating with the nozzle and supplying a second ink having a second density to the nozzle; and a second supplying step. A control step of controlling the inflow amount by controlling a partition part for separating the nozzle from the nozzle and controlling an inflow amount of the second ink into the nozzle based on the density of dots recorded by the nozzle; A gradation recording control method comprising: