JPS60124254A - Removal of electrostatic charge from nozzle surface of recording head - Google Patents

Abstract

PURPOSE:To prevent jetted ink drops from being deflected by Coulomb interaction by jetting ink drops from an inkjet nozzle during the stand-by period for printing to remove electrostatic charges on the nozzle surface of a recording head. CONSTITUTION:When the power source of a recorder is turned ON, a head 1 is retracted at the cap position and the nozzle surface 2 separates from a cap roller 15. Ink is fed to the head from a tank 8 flowing out of a nozzle to form an ink column between the nozzle surface 2 and the cap roller 15 and subsequently, running ink is sucked with an air pump 23 from tubule 19. After the supply of ink is stopped to return the liquid pressure to the normal level, the cap roller 15 is rotated to clean up the outer surface of the head. The head 1 is moved to the spitting postion and ink drops is made to jet one at a time from each nozzle to be checked with a spit sensor 14. Then, ink drops are jetted from all nozzles simultaneously for a specified time to remove electric charges on the nozzle surface, i.e. a condition under which printing is awaited.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the drive control of a recording device in an inkjet recording device, and particularly to the nozzle surface of the recording device in an on-demand type inkjet recording device. The present invention relates to a static electricity removal method.

[Prior art]

Among the above-mentioned on-demand type inkjet recording devices that eject ink droplets only when necessary, the
2. Description of the Related Art In recent years, recording apparatuses that eject ink using pressure waves from piezoelectric transducers have been put into practical use, as disclosed in Japanese Patent Publication No. 12138, Japanese Patent Publication No. 51-39495, Japanese Patent Publication No. 53-45698, and the like.

In these types of on-demand type inkjet recording devices, ink droplet ejection failures are more likely to occur than inkjet recording devices that constantly eject ink droplets from nozzles.

This may be due to dust such as paper powder adhering to the nozzle surface because the recording nozzle is close to the recording paper, air bubbles entering the inside of the recording head, or the ink inside the nozzle drying out or changing over time. This is caused by clogging caused by solidification, etc., and these causes cause injection accidents such as incorrect injection direction, unstable injection, or inability to inject.

These ejection failures cause ink droplets, misaligned ink dots, and ink dots on the recording paper.

Print quality may deteriorate due to insufficient print size, etc.

As a means to solve the above problems, JP-A-52-15
No. 0035, JP-A-56-42662, JP-A-54-9928, etc. have been proposed.

On the other hand, the substrate containing the nozzle surface of the recording head is made of an insulator such as ceramics or plastic, and the nozzle surface is sometimes treated to be water repellent to prevent ink from building up. Water repellent treatment on the nozzle surface includes silicone face and oil coating treatment; 7. Coating treatment is applied to the thread polymer or oligomer.

In addition, the composition of the ink used is, in the case of water-based ink,
The main components are distilled water, ethylene glycol, dyes, etc., and conductivity is generally more dominant than dielectric constant.

Note that in the case of oil-based ink, the dielectric constant is generally even higher.

Japanese Patent Application Laid-open No. 52-150035 discloses that in order to keep the nozzle surface of the recording head clean at all times when not printing, an elastic cap member is placed in close contact with the nozzle surface to prevent air bubbles from being sucked in and dirt to be absorbed. This prevents the adhesion of ink or solidification of ink.

However, if the nozzle surface is made of an insulator or is further treated to be water repellent as described above, separate charging occurs when the elastic cap member separates from the close contact state.

Next, Japanese Patent Application Laid-Open No. 56-42662 discloses that in order to wash out impurities and air bubbles mixed into the ink flow path of the recording head,
The inside of the ink flow path is cleaned by forcibly increasing the liquid pressure within the ink flow path and causing the ink to flow out from the nozzle. In this case, charging occurs due to friction between the ink flowing out from each nozzle at the tip of the recording head and the inner wall surface of the nozzle.

Now, the ink droplets ejected from the nozzles of the recording head are
For one pulse signal, several satellite drops occur in addition to the main drop, which is not necessarily one drop. Such main drops and satellite drops have different flight speeds, causing a trailing phenomenon on the recording paper surface and causing a decrease in the resolution of the recorded image.

This phenomenon depends on the distance between the nozzle and the recording paper, the flying speed of the ink droplets, and the relative speed between the dot and the recording paper, but it does not significantly impede high-speed, high-quality image recording. be.

Furthermore, if the recording head is made of an insulator such as ceramic, and the nozzle surface at its tip is water-repellent with a silicone-based or fluorine-based resin coating, frictional electrification and Due to the separate charging, the nozzle surface is charged, and the ink droplets ejected from the nozzle are charged with a polarity opposite to that of the nozzle surface. That is, both the main rope and the satellite drones are electrically charged, and Coulomb interaction occurs with the nozzle surface, which deflects the flight direction of the satellite drones, which have a particularly small mass, and even the main drones. is deflected, significantly deteriorating the image recording quality.

[Purpose of the invention]

The present invention quickly and easily removes static electricity that occurs on the nozzle surface and ink droplets of an inkjet recording device, so that the ink droplets (main drop and satellite droplets) ejected from the nozzle can interact with the coulombs. The purpose of this is to prevent the particles from being deflected by the action and to reach the surface of the recording paper by normal flight, thereby obtaining high-quality image recording.

[Structure of the invention]

To achieve this object, the present invention provides an inkjet recording method in which a recording head having at least one ink ejecting nozzle is moved relative to a recording material, and characters and figures are selectively recorded from each nozzle at At least one of the above record and do is in a standby state when the record is in a non-printing state.
A method for removing static electricity from a nozzle surface of a recording head, characterized by ejecting one or more ink droplets from each of the ink jetting nozzles to remove static electricity on the nozzle surface of the recording head. It provides:

〔Example〕

The present invention will be explained below by showing specific examples thereof.

FIG. 1 is a diagram illustrating the outline of an inkjet recording apparatus according to the present invention, and FIG. 2 is a diagram showing the system configuration thereof.

In these figures, record the pressure chamber 4 at the nozzle.
, a common ink chamber 5, a piezoelectric transducer 6, etc., and is fluidly connected to an ink supply pipe 7 and an ink tank 8. Further, the piezoelectric transducer 6 is electrically connected to an external electric pulse generator 9.

Further, 10 is a cylindrical platen for feeding the recording paper P. The platen 10 is driven and rotated by a motor or the like (not shown) K, and conveys the recording paper P in close contact with the platen 10.

For recording with a plurality of nozzles 3, the drive is carried, the direction 11
The recording paper P approaches the recording paper P and moves from side to side in a direction parallel to the axis of the platen 10 by means of a conductive member such as a wire or belt connected to the platen 10 and a motor 13 that drives it. During recording, the dot 1 ejects ink droplets from the nozzle 3 toward the recording paper P during this horizontal movement, thereby forming characters or images in the form of a dot matrix on the recording paper P.

If air bubbles or solidified matter form in the ink flow path of the print head, good print recording will not be possible. Before printing, the ink in the ink tank B is forced into the ink tank B to forcibly eliminate (purge) air bubbles and foreign matter in the ink flow path.

To this end, for recording, the carriage 11 on which the drive 1 is mounted is moved in the direction of the cap roller 15 rotatably provided in the axial direction of the platen 10. This Ryoya, Prote 1
The nozzle surface 2 of the drum 1 is closely opposed to the outer peripheral surface of the drum 5 (purge position). FIG. 1 is a schematic diagram of this state. The cap roller 15 is rotatable in the direction of the arrow by being powered by a worm wheel 16 fixed coaxially, a worm 17 meshing with the worm wheel 17, and a drive motor 18. It is connected to a tube in which a thin tube 19 is provided below the cap roller 15 and close to the outer peripheral surface of the roller 15, and is further connected to a sealed waste liquid tank 21. The waste liquid tank 21 is further provided with a suction tank.
It is connected to the air pump for exhaust through.

When the air bubbles and foreign matter inside the dome 1 are discharged together with the pressurized ink by the above-mentioned purge operation, they are transferred to the outer circumferential surface of the carrier and growler 15 and the record that faces closely thereto. It is made of a water-repellent coating layer between the nozzle surface 2 and the cap roller 150, and the surface of the cap roller 150 is made of a hydrophilic material. Note that this water-repellent treatment may be applied to the entire nozzle surface 2, or may be applied only to the periphery of the nozzle 3.

FIGS. 4(a) and 4(b) are enlarged perspective views showing the vicinity of the nozzle surface 2 of the recording head. FIG. 4(a) shows a recording head in which a plurality of nozzles 3 are arranged in one row.
FIG. 4(b) shows recording in which a plurality of nozzles 3 are arranged in two rows.

The ink column A formed between the nozzle surface 2 and the roller 15 is sucked from the thin tube 19 by the suction air flow by the air pump B, and is stored in the waste liquid tank 21 through the tube (9). .

When such a purging operation is carried out for a predetermined period of time, for example, about 5 seconds, air bubbles and foreign matter in the recording medium are removed and clogging is eliminated. Then stop supplying the pressurized ink flow and wait for a predetermined period of time.
For example, when suction by the air pump is started after approximately 10 seconds have elapsed, the ink column disappears, the ink liquid pressure returns to normal, and normal ink droplet ejection becomes possible again.

However, in the above purging operation, when the insulating nozzle surface 2 and the cap roller 15 are separated to separate the ink column A, the nozzle surface 2 is negatively charged at the time of separation, and the ink is positively charged.

However, the ink is swept away by the suction air flow of the thin tube 19 and does not affect others. Further, the ink in each nozzle 3 communicates with the ink flow path and is grounded to maintain zero potential.

When only this nozzle surface 2 is negatively charged and a single ink droplet or a group of ink droplets consisting of multiple ink droplets is formed and ejected in response to a specific electrical signal, these ink droplet groups are activated by the nozzle. It flies in a positively charged state with a polarity opposite to that of surface 2.

Figure 5 shows ink droplets being ejected from the nozzle 3 of the printer for recording.
FIG. 3 is a schematic diagram showing the formation over time. When a specific electric pulse signal is applied to the piezoelectric transducer 6, the ink liquid pressure in the pressure chamber 4 begins to rise, causing the ink in the nozzle 3 to flex. Transition from protrusion a) to (e). Further, the ink column reaches its maximum speed and protrudes, and its tip becomes a trailing ink droplet and separates, and the remaining ink column is sucked into the nozzle 3 and becomes as shown in the diagram (d). After a further short period of time has elapsed, the tip of the ink droplet becomes a spherical main drop due to the surface tension of the liquid, and the tail is cut off from the tip and becomes a satellite drop (e). During the flight, the main drop, the satellite drop, and the satellite drop gradually form into a spherical shape (f).

According to one experimental example, the state (f) above occurs at a position where the satellite drops are 300 to 700 μm away from the nozzle surface 2 at 100 to 150 μB after the electric pulse signal is applied. At this time, the diameter of the main drop is 75 to 85.
The diameter of a μm1 satellite drop is 1 μm. In addition, the droplet velocity at the time of satellite drop (d) is 2
．． 5 to 3.5rrI/II, and varies depending on the electrical pulse waveform applied to the main domain. That is, the larger the diameter of the nozzle 3 is, and the greater the energy given by the applied electric pulse signal, the larger the main drop and satellite drops tend to be.

FIG. 6 is a diagram showing an applied electric pulse waveform, which corresponds to the formation of an ink droplet in FIG. 5.

Fig. 7 is a velocity diagram of the satellite drop and pu.
The graph shows the flight speed of the satellite drop on the y-axis. As mentioned above, the satellite drop is placed on the nozzle surface 2.
It appears at a position of eo from and has an initial velocity of V. It has a temperature of ℃. Thereafter, the motion of this satellite drop is due to the Coulomb force between it and the nozzle surface 2, and as shown in the curve (a) in the figure, it flies away from the nozzle surface 2 at a deceleration rate up to a distance of 4, but after point e1 it flies at a deceleration (b). It is pulled back like a curve and finally adheres to the nozzle surface 2. Or like the curve (C), there are some that take a flight direction that is decelerated to some extent but further away from the nozzle surface.Whether it becomes (b) or (e) depends on the mass of the satellite drone. , varies depending on the initial velocity v0 and the amount of charge on the nozzle surface 2, which determines the magnitude of the Coulomb force.
Depending on the charge distribution on the nozzle surface 2, the position at which the satellite drops are pulled back is not uniquely determined but is stochastic.

Furthermore, the above-mentioned separated electrification and frictional electrification of the fist vary depending on subtle differences in surface conditions, and also vary depending on environmental conditions, such as temperature, φ, humidity, etc. Furthermore, the diameter of the droplets formed varies due to individual differences in the manufacturing process, and therefore the degree of effectiveness also varies.

Satellite mud flying along the above (b) curve.

The drop adheres to the nozzle surface 2, and the negative charge on the nozzle surface 2 is electrically neutralized by the positive charge of the satellite drop, and the charge is gradually removed to the extent that it is not affected by Coulomb interaction. As described above, in the present invention, the static electricity on the nozzle surface 2 can be easily eliminated by actively utilizing the pulling back of the satellite drop due to the Coulomb interaction as described above.

As mentioned above, the effect of static electricity removal on the nozzle surface by satellite drops and drops varies depending on the recording process, charge generation status, and environmental conditions.Therefore, there are many so-called blank prints in which ink is ejected during non-printing to remove static electricity. In some cases, it may not be possible to remove static electricity sufficiently without firing.

In the present invention, in the case of a plurality of nozzles, the static elimination effect on each nozzle surface 2 increases, but of course the effect is produced even when only a specific nozzle is used. However, the water-repellent surface of the nozzle surface 2, which is an insulating surface,
Electrostatic charges do not move easily within this plane, and in the above-mentioned method of eliminating static electricity by ejecting ink only from specific nozzles, only specific parts of the nozzle surface 2 are neutralized, but other areas may not be sufficiently eliminated. be. Therefore, it is desirable to eject ink uniformly from all nozzles. As a result, the withdrawn satellite drops randomly adhere to the entire surface of the nozzle surface 2 and are uniformly neutralized.

- In order to eliminate static electricity from the nozzle surface 2 by the above-described method, there is a condition for setting the distance from the nozzle surface 2 when performing the above-mentioned blank printing. In other words, if there is some kind of obstacle before the satellite drops, which are attracted by the Coulomb interaction, are pulled back to the nozzle surface 2 (point 21 in Figure 7), the satellite drops will collide with this and pull back onto the nozzle surface. Returning to step 2, static electricity removal is not performed.Therefore, during blank printing, there must be a space where there are no obstacles within a certain distance in front of the nozzle surface 2. ,
varies depending on the mass and flight speed of the ink droplets, but is approximately 0.
5. m or more is required. The position where such charge removal is performed is at the position of the cap roller 15 before recording.

It is also possible to set the dots to be separated by 0.5 days or more.

In addition, there are other positions, such as a position where blank printing is ejected at regular intervals to prevent clogging of the nozzle 3 (spit position), or a position where a spit sensor 14 is installed to detect nozzle clogging, but which one is the best? In this case, the distance between the nozzle surface 2 and these opposing objects needs to be 0.5u or more.

An example of an inkjet recording apparatus using the method for removing static electricity from a nozzle surface according to the present invention will be described below.

(1) First, when you turn on the power of the device, the nozzle head 2 moves back to record at the capture and pull positions, and the nozzle surface 2 moves to the capture and pull positions.
15 (uncapped).

(2) Pressurized ink is sent from the ink tank 8 to the recording
The ink is supplied into the ink flow path and flows out from the nozzle 3, an ink column is formed between the nozzle surface 2 and the cap roller 15, and the outflowing ink is subsequently sucked from the thin tube 19 by the air pump blade (for about 5 seconds). ).

(3) Stop the pressurized ink supply and return to steady liquid pressure (for about 10 seconds).

(Suction stops after pressurized ink supply stops.) (4
] The cap roller 15 rotates to clean the outer peripheral surface.

(5) The recording head l is moved to the spit position, and ink droplets are ejected one by one from each nozzle, and detected and confirmed by the spit sensor 14.

(6) At this position, ink droplets are ejected from all the nozzles at the same time for a predetermined period of time to eliminate static electricity from the nozzle surface.Then, the printer waits here for recording until a print signal is input.

(7) When the print signal is input, the C moves to the left margin position and printing continues.

(8) For a predetermined period of time, for example (a) every second, the do moves to the spit position, confirms the injection with the spit sensor, and continues printing again.

(9) When the printing end signal is input, the print head moves to the left margin position and then to the spit position, and waits by intermittently spraying at predetermined time intervals until the next signal is input.

α0) When the power is turned off, the recording starts and the dot is turned off.

After moving to the purge position and performing the above-mentioned purge operation, the nozzle surface 2 is pressed against the outer peripheral surface of the cap roller 15 to put it in the cap state.

During such recording, the main drop and satellite drops do not go straight to the regular recording position on the recording paper surface, and are deflected by the Coulomb interaction, causing them to move to different positions on the recording paper surface. This may cause the so-called n-splatter phenomenon.This is because each ink droplet receives a pullback force due to Coulomb force, but if the mass of the ink droplet is thick to a certain extent, it may cause the so-called n-splatter phenomenon. This is because the flight speed is considerably reduced without being pulled back, and the flight speed deviates from the normal position by the time delay caused by the travel of the carry and the ji 11.When such a problem occurs, K is Pal resonant Cfl:&I shown in Figure 6
r3K -&+ 411m7 'z ++ L If
)-l +/ A am Mole 7 Remove static electricity by completely pulling back to the aperture surface. That is, this is achieved by reducing the diameter of the ink droplet by lowering the voltage, increasing the rise time constant, and slowing down the flight speed.

As for the pulse voltage waveform, during printing, the voltage is 120V, the rising time constant is 120 μsec, and the falling time constant is 40 μsec.
” It is about 100 p see, but if you increase the voltage to 90 p.
V (25% reduction), the ink drop velocity is typically 2.5-3.5 ITJ/! What was I was 0.5 ~
1. By falling into the orry'tr, the nozzle surface 2
By pulling back and adhering to the ink, static electricity can be removed in a shorter time or with fewer ink droplets. Also, by keeping the voltage constant, the rise time constant is ~100μI! By making ee longer, the same effect as above can be obtained.

Next, we will describe experimental data on the static elimination effect of blank printing. This shows the number of ink droplets ejected from each nozzle and the change in the amount of charge on the nozzle surface using a dot for recording with a large number of nozzles.

Measure the amount of charge in the United States! rREK'IN (!, E manufactured by
The measurement was carried out using an electrostatic voltmeter Model 3601.

However, since it is affected by environmental conditions, the error in the above data is approximately ±5V.

By the way, if you look at the printed dots on the recording paper, the satellite dots, which were 0.3 to 1 m away from the regular print position, were about 1/1 of the distance from the o and i exposures.
If it goes from 0 to 15 and approaches the normal position,
It can be said that the print quality was sufficiently usable without any scattering phenomenon, and that it had a static neutralizing effect.

In order to obtain this static elimination effect, as shown in the experimental data, by ejecting nine ink droplets from each nozzle 3 to eliminate static electricity on the nozzle surface 2, the satellite during printing is ■The scattering phenomenon caused by this phenomenon completely disappeared, and good print quality was obtained. However, even with 10 or 30 shots, the deflection of the satellite drop is considerably reduced, and it is possible to provide print quality that is sufficiently usable. ``Of course, being able to shoot more than 90 shots improves stability and increases effectiveness.

The amount of charge after blank printing injection for static elimination is 1 of the initial charge amount.
If it is reduced to /2 to 1/15, preferably /4 to 115, there is a complete static elimination effect.

Also, according to repeated experiments, the potential after static elimination is -70 to -5
0V was the most common, and the amount of charge did not decrease below this value, resulting in a saturated state.

The driving frequency of the piezoelectric transducer 6 used in the above experiment is
At 2000H2 or less, almost uniform effects were obtained, and furthermore, at 1000)IZ or less, almost no difference in effect was observed.

Next, FIGS. 8 and 9 are diagrams showing changes in the amount of charge of ink droplets over time. In FIG. 8, the amount of charge on an ink droplet generally decreases by about 10% due to spontaneous discharge, and then becomes almost saturated. Figure 9 shows the change in the amount of charge when the satellite mud is reversely attached to the nozzle surface 2.

When the ink droplet starts to adhere, the amount of charge on the nozzle surface 2 rapidly decreases, and as a result, the charge remaining on the ink droplet also rapidly decreases.

In recent years, in order to improve printing quality, it has become necessary to extremely reduce the diameter of ink droplets and perform high-density recording, but the method of removing static electricity from the nozzle surface of the present invention can provide a great effect even in this case. . That is, even if the above-mentioned satellite drop does not occur, if the ink droplet itself becomes small, the print quality will deteriorate as in the satellite cI91, so using the static elimination method is better than K.

Further, even when a plurality of small ink droplets are ejected and formed by a single electric pulse signal, the static elimination effect of the present invention is significant.

As another example, if the waveform of the applied electric signal is changed only during blank printing to generate only smaller ink droplets, the satellite droplets will be drawn back and attached to the nozzle surface, and the static elimination effect will be more significant.

Further, the static electricity removal method of the present invention is also useful in so-called continuous injection type charge amount control systems and charge deflection systems in that it prevents unnecessary charging on the nozzle surface.

〔Effect of the invention〕

As explained above, the method for eliminating electricity from the nozzle surface of a recording head according to the present invention involves keeping a predetermined distance from an opposing object at a non-printing position and facing the nozzle surface of the do, and depositing a predetermined number of ink droplets from each nozzle. By this, the amount of charge on the nozzle surface is rapidly reduced, and a high quality print image can be stably ensured by normal ink jetting. In particular, this effect is remarkable for high-resolution inkjet recording and color image recording using ink droplets with reduced diameters.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an inkjet recording apparatus according to the present invention, FIG. 2 is a system configuration diagram thereof, FIG. 34 is an enlarged perspective view of the vicinity of the nozzle surface, and FIG. 5 is a schematic diagram showing the progress of ink droplet formation. FIG. 6 is an electric pulse signal waveform diagram, FIG. 7 is a velocity diagram of a satellite drop, and FIGS. 8 and 9 are diagrams showing changes in the charge level of an ink droplet over time. l... To record, do 2... Nozzle surface 3... Nozzle 14... Spit sensor 15... Cap roller agent Yoshimi Kuwabara Figure 5 1 Figure 6

Claims (1)

[Scope of Claims] (1) In an inkjet recording method in which characters and figures are selectively recorded from each nozzle in a recording having at least one ink ejecting nozzle, with relative transfer to a solid recording material. , during standby when the recording head is in a non-printing state, one or more ink droplets are ejected from each ink jet nozzle of the recording head to reduce static electricity on the nozzle surface of the recording head and the recording head. (2) In the non-printing state, ink droplets ejected from the nozzles facing the nozzle surface of the recording head collide. The distance between the opposing object to be collected and the nozzle surface is 0.5
2. A method for removing static electricity from a nozzle surface of a recording head according to claim 1, wherein the static charge is equal to or greater than vm. (3) Claim 1 or 2, wherein the opposing object is a part of an ink recovery device that recovers jetted ink to prevent ink clogging in a non-printing state.
Method for removing static electricity from the nozzle surface of a recording head described in Section 1. (4) The recording nozzle according to claim 1 or 2, wherein the opposing object is a part of a device for detecting ink droplet ejection failure in a non-printing state. How to remove static electricity from a surface. (5) When the recording field is in a non-printing state and before printing starts, ink droplets are ejected to record 2. 5. A method for removing static electricity from a nozzle surface of a recording head according to any one of claims 1 to 4, characterized in that static electricity on a nozzle surface of a recording head is removed. (6) After separating the pink member from the nozzle surface of the nozzle surface of the recording head, ejecting ink droplets to remove static electricity on the nozzle surface of the recording head. To the record set forth in any one of claims 1 to 5, characterized in that
How to remove static electricity from the nozzle surface. (7) After a purge process for removing ink clogging in the recording head, ink droplets are ejected onto the recording head to remove static electricity on the nozzle surface of the recording head. A method for eliminating static electricity from a nozzle surface for recording according to any one of items 1 to 5. (8) At least one ink ejecting nozzle of each of the dos ejects 10 or more ink droplets onto the recording to remove static electricity on the nozzle surface of the do. A method for eliminating static electricity from a nozzle surface according to any one of claims 1 to 7. (9) When the recording is in the non-printing state, by controlling the ink droplet ejection drive signal, either the ink droplet size or the ink droplet ejection speed, or both, can be changed to the particle size at the time of printing or the ink droplet ejection speed. A recording device according to any one of claims 1 to 8, characterized in that static electricity on a nozzle surface of a recording head is removed by reducing the jetting speed to a speed lower than that of a jetting speed. How to remove static electricity from the nozzle surface. The drive voltage of the drive signal for ink droplet ejection of α during non-printing is lower than the voltage during printing (by doing so, electrostatic charge on the nozzle surface of D is removed during recording). A method for eliminating electricity from a nozzle surface of a recording head according to claim 1 or 9. α1) The rise time constant of the drive voltage of the ink droplet ejection drive signal during non-printing is determined from the rise time constant of the drive voltage during non-printing. In the recording according to claim 1 or 9, the electrostatic charge on the nozzle surface of the recording head is removed by lowering the nozzle surface of the recording head. Static elimination method. (1) Ink droplets are ejected onto the recording until the amount of static electricity on the nozzle surface of the dot becomes equal to or less than Z of the amount of charge before the static electricity is removed. A method for removing static from a nozzle surface for recording according to any one of items 1 to 11.