JPH11291500A - Liquid delivery method and liquid delivery head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent non-delivery from occurring unexpectedly in a liquid delivery head of the side shooter type. SOLUTION: A liquid delivery head comprising a plurality of heaters 1, a plurality of delivery ports 4 arranged densely each in opposition to the heaters 1, and a plurality of liquid passages 5 in communication with the ports 4 is used. When bubbles each having an internal pressure of less than atmospheric pressure are brought into communication with the atmosphere, droplets each having a small volume are separated from a liquid, whereby the liquid is delivered at a frequency of 7 kHz or more. The height Tn of the liquid passage 5 is 6 μm or more, and a distance between the upper surface and lower surface of the port 4 is half the minimum distance in the port 4 or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid discharging method for performing recording by discharging liquid droplets of ink or the like toward various recording media such as paper, and more particularly to a liquid discharging method for realizing high resolution. The present invention relates to a liquid discharge method and a liquid discharge head that discharge extremely small droplets at a high frequency by using a recording head having a plurality of liquid flow paths arranged at a high density.

[0002]

2. Description of the Related Art Among liquid discharge methods, a bubble jet type liquid discharge method in which bubbles are rapidly generated in a liquid and the liquid is discharged as droplets from a discharge port by utilizing the pressure at the time of the growth of the bubbles. It has been known. In this bubble jet type liquid discharging method, the liquid discharging response is high,
Excellent for high speed recording and high density recording.

[0003] Among the bubble jet type liquid discharge methods, among others, a liquid discharge method in which bubbles generated on a heating element are communicated with the atmosphere at an edge of a discharge port is known. For example, JP-A-4-10940, JP-A-4-10941, JP-A-4-10742 and the like are known as gazettes.

[0004] The characteristic of this type of liquid discharge method is that
Second, since the liquid discharge speed can be increased, the discharge reliability can be improved. Second, since almost all of the liquid between the heating element and the discharge ports can be discharged, the discharge for each discharge port can be performed. The droplet volume can be made substantially uniform, and density unevenness of a recorded image can be reduced.

[0005] By the way, with the advance of recording technology, droplets of smaller volume (for example, 1.5 × 10 ^-15 m ³ or less) are deposited on a recording medium at a high density (for example, 600 dots / 2 dots).
(5.4 mm or more) and high-quality recording. In the case of performing such high-definition printing, it is necessary to arrange the ejection ports from which the liquid droplets are ejected and the liquid flow paths communicating with the ejection ports at a high density. For example, the above 600
In order to achieve a recording density of dot / 25.4 mm,
The arrangement of the discharge ports is staggered in two rows (consisting of two rows of discharge ports extending in the same direction, with one row being displaced in the extending direction by half a pitch with respect to the other row). Even if they are arranged, the liquid flow paths and the discharge ports must be arranged at a high density of 300 pieces per row / 25.4 mm.

In order to prevent a decrease in recording speed due to an increase in the number of ejected droplets by performing recording using smaller droplets, droplets are ejected from one ejection port in a unit time. It is necessary to increase the number of times (hereinafter, referred to as a discharge frequency). For example, in the above configuration, the ejection frequency is required to be at least about 7 kHz.

In addition, in order to perform high-quality recording by discharging such small volumes of droplets, it is necessary to further enhance the reliability of droplet discharge.

On the other hand, as a method of discharging a bubble jet, there is a method of communicating bubbles to the atmosphere. For example, Japanese Patent Application Laid-Open No. Hei 5-16365 discloses a sufficient technical disclosure about the condition of the droplet at the time of ejection and the communication condition of the bubble with the atmosphere.

[0009]

By the way, an ink jet head which discharges extremely small droplets such as 1.5 × 10 ^-15 m ³ is a bubble jet type liquid discharging method in which the bubbles are communicated with the atmosphere. When I checked the discharge state by applying to, the discharge port that was performing proper discharge was
A phenomenon that the ejection was suddenly stopped occurred. This did not occur with conventional ejection. When investigating the cause, the recording liquid suddenly clogged the discharge port between the time when the air bubble communicated with the atmosphere and the time when the refill was completed, and unless the recovery process was performed using the recovery mechanism of the printing apparatus main body thereafter,
It is impossible to discharge the recording liquid from the discharge port.

FIG. 5 is a sectional view showing this state. FIG.
As shown in (2), immediately after the bubbles communicate with the atmosphere and the recording liquid 501 is discharged, the recording liquid 501 is clogged in the discharge port 4. At this time, although the recording liquid 501 remains in the middle of the ink supply path, the recording liquid 501 does not exist in the vicinity of the electrothermal transducer 1 because it has just been ejected, and only the atmospheric pressure air 502 exists. doing. In this state, even if an electric pulse is applied to the electrothermal converter 1, the electrothermal converter 1
, The recording liquid 501 cannot be discharged, so that it is impossible to remove the clogging of the discharge port 4.

Further, the present invention provides a method of driving a head having a high density and a large number of liquid flow paths at a high frequency by using this type of head. It turned out that we had to pay attention to the variation. The object of the present invention is to use a so-called side shooter type liquid discharge head in which discharge ports for discharging extremely small droplets at a high frequency are arranged at high density and have discharge ports at positions opposed to the heating element. The present invention is to provide a liquid ejection method of a bubble jet method for communicating bubbles with the atmosphere, and a liquid ejection method capable of performing high-speed recording while maintaining ejection reliability that sudden ejection failure does not occur. .

[0012]

A typical requirement of the present invention to achieve the above object is as follows.

According to the present invention, an electrothermal conversion element for generating thermal energy sufficient to foam a liquid, and discharge ports provided at positions facing the electrothermal conversion element are arranged in a line of 25.4 m.
Using a liquid ejection head including a plurality of liquid flow paths arranged at a density of 300 or more per m and communicating with the ejection ports, bubbles generated by thermal energy of the electrothermal conversion element have an internal pressure of atmospheric pressure. Less than 15
In a liquid discharging method for discharging droplets having a volume of × 10 ⁻¹⁵ m ³ or less by driving a frequency of 7 kHz or more, the liquid discharging head has a height of the liquid flow path of 6 μm or more, and The distance between the upper surface and the lower surface is not more than half of the minimum opening distance passing through the center of the discharge port.

According to the present invention, there are provided a plurality of electrothermal transducers for generating thermal energy for foaming a liquid, and a plurality of discharge ports provided at positions facing the electrothermal transducers for discharging droplets. A plurality of liquid flow paths communicating with the discharge ports, and the plurality of electrothermal conversion elements and the plurality of discharge ports are arranged at an array density of 300 or more per 25.4 mm. Is applied with a drive signal at a frequency of 7 kHz or more, generates bubbles in the liquid in the liquid flow path, communicates with the atmosphere when the internal pressure of the bubbles is lower than the atmospheric pressure, and is 15 × 10 ⁻¹⁵ m ³ or less. In the liquid discharge head that discharges a droplet having a volume, the height of the liquid flow path is 6 μm or more, and the distance between the upper surface and the lower surface of the discharge port is less than half the minimum opening distance passing through the center of the discharge port. There is a feature.

Further, according to the present invention, there is provided an electrothermal conversion element for generating thermal energy sufficient for foaming a liquid, and a discharge port provided at a position facing the electrothermal conversion element in a line.
Using a liquid ejection head that is arranged at a density of 300 or more per 5.4 mm and includes a plurality of liquid passages respectively communicating with the ejection ports, bubbles generated by thermal energy of the electrothermal conversion element have an internal pressure of 7k droplets having a volume of 15 × 10 ⁻¹⁵ m ³ or less, communicating with the atmosphere under atmospheric pressure
A liquid discharging method for discharging at a frequency drive of not less than Hz, a step of maintaining the liquid remaining in the discharge port after the bubble communicates with the outside air in communication with the liquid retreated from the discharge port in the liquid flow path. Combining the residual liquid with the liquid in the liquid flow path and refilling the inside of the discharge port.

[0016] In such a configuration, a so-called side port having a discharge port for discharging liquid droplets in accordance with the bubbling pressure is provided at a position facing the electrothermal conversion element for applying heat energy to the liquid to generate bubbling. By preventing the sudden ejection failure in the shooter type liquid ejection head, high-speed recording and high-quality recording can be performed while maintaining ejection reliability.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIGS. 1A and 1B
1 is a diagram showing a schematic configuration of a liquid ejection head to which the liquid ejection method of the present invention can be applied, FIG. 1 (a) is a perspective view showing an appearance, and FIG. 1 (b) is FIG. FIG. 3 is a cross-sectional view taken along line AA of FIG.

In FIG. 1, reference numeral 2 denotes a Si element substrate in which a heater as an electrothermal conversion element described later and discharge ports are formed by a thin film technique. This element substrate 2 has a structure shown in FIG.
As shown in (a), a plurality of discharge ports 4 arranged in two rows are provided in a staggered manner. The element substrate 2 is bonded and fixed to a part of the support member 102 processed into an L-shape. Similarly, a wiring board 104 is fixed on the support member 102,
The wiring portion of the wiring substrate 104 and the wiring portion of the element substrate 2 are electrically connected by bonding. The support member 102 is formed of an aluminum material from the viewpoint of cost, workability, and the like. The mold member 103 has a part of the support member 102 inserted therein to support the support member 102 and a liquid supply path 107 formed therein.
This is a member for supplying a liquid (for example, ink) from a liquid storage unit (not shown) to a discharge port provided on the above-described element substrate 2 through the liquid storage unit. Further, the mold member 103 serves as a mounting and positioning member for detachably fixing the entire liquid ejection head of the present embodiment to a liquid ejection device described later.

A mold member 10 is provided inside the element substrate 2.
The communication path 105 for further supplying the liquid supplied through the liquid supply path 107 of the third substrate to the discharge port is provided on the element substrate 2.
Are provided to pass through. The communication passage 105 communicates with a liquid flow path that communicates with each discharge port, and has a role as a common liquid chamber.

FIGS. 2 (a) and 2 (b) are views showing a main part of the liquid discharge head shown in FIGS. 1 (a) and 1 (b), and FIG. FIG. 2B is a side sectional view as viewed, and FIG. 2B is a top view of FIG.

As shown in FIG. 2, a rectangular heater 1 as an electrothermal conversion element is provided at a predetermined position on the element substrate 2. An orifice plate 3 is provided on the heater 1, and the orifice plate 3 has a discharge port 4 opening in a rectangular shape at a position facing the center of the heater 1. The discharge port area of this discharge port 4 is
It is represented by So as shown in FIG. Note that 41
Denotes an upper surface of the discharge port, and 42 denotes a lower surface of the discharge port. In this embodiment, the upper surface and the lower surface are virtual surfaces formed by extensions of the orifice plate.

The distance between the heater 1 and the orifice plate 3 is equal to the height Tn of the liquid flow path 5 and is defined by the height of the liquid flow path wall 6, as shown in FIG. I have. When the liquid flow path 5 extends in the x direction as shown in FIG. 2B, the discharge port 4 communicating with the liquid flow path 5
Are arranged in the y direction orthogonal to the x direction. The plurality of liquid flow paths 5 communicate with a communication path 105 that also functions as a common liquid chamber illustrated in FIG. The thickness of the orifice plate 3 corresponding to the distance between the upper surface 41 and the lower surface 42 of the discharge port is assumed to be To.

Next, an embodiment of the liquid discharge method of the present invention using the liquid discharge head having the above-described configuration will be described.

FIGS. 3A to 3G are sectional views for explaining the operation of the liquid discharge head to which the liquid discharge method of the present invention is applied.

As shown in FIG. 3A, the meniscus 11 reaches the upper end of the discharge port 4 in a steady state.
At this time, first, a driving voltage is applied to the heater 1.
As a driving condition, it is desirable to perform short-pulse driving so that bubbles do not grow excessively and the meniscus receding amount does not become too large. The width of the discharge electric pulse given to the heater 1 is preferably 3.5 μsec or less. This is because if the pulse width exceeds 3.5 μsec, the growth of bubbles becomes excessive, the meniscus receding after the bubbles are involved in the ejection of liquid becomes large, and the refill time becomes long, so that high-speed recording cannot be performed. Because. Also,
Driving such as a so-called double pulse using two or more driving pulses can also be adopted. In this case, the length of the pre-pulse applied before the ejection main pulse is preferably 1.5 μsec or less. The interval between the pre-pulse and the main pulse is preferably 2.0 μsec.
It is as follows. Here, the length of the pre-pulse is 1.5 μs
If ec or the interval between the pre-pulse and the main pulse exceeds 2.0 μsec, the growth of bubbles becomes remarkably large, the amount of meniscus retreat becomes large, and it becomes unsuitable for high-frequency driving. It is difficult to achieve.

As for the driving voltage, 1.1 to 1.3 times the threshold voltage Vth of the droplet discharge is a suitable value for achieving the object of the present invention. Drive voltage is 1.1 Vt
If it is lower than h, the droplet discharge speed is too low even if foaming / discharge occurs, causing the droplet to be distorted or the driving at a high frequency to be unstable. If it is higher than 1.3 Vth, the bubble length is too large and the meniscus retreat amount becomes large, and the refill time becomes long, or the droplet discharge speed becomes too high and the amount of the droplet rebounding on the recording medium. May be large. Therefore, the driving voltage is one of the preferable conditions for the present invention.

Next, as shown in FIG. 3B, bubbles 301 start to be generated in the liquid on the heater 1 by the application of the driving voltage, and as the bubbles 301 grow, the upper side of the bubbles 301 is discharged. The liquid in the outlet 4 and the liquid flow path 5 rises upward from the upper end of the discharge port 4. In this process, the pressure of the bubble 301 which has been higher than the atmospheric pressure turns to a pressure lower than the atmospheric pressure.

Next, as shown in FIG.
When 1 further grows, the liquid in the discharge port 4 above the bubble 301 and the liquid flow path 5 is discharged upward from the upper end of the discharge port 4. However, at this stage, the bubble 301 has not yet communicated with the atmosphere, and the meniscus in the liquid flow path 5 continues to recede due to the further growth of the bubble 301. At this time, bubbles 301
Immediately before the liquid communicates with the atmosphere, the recording liquid in the liquid flow path 5 exists up to the lower surface 42 of the discharge port 4, and the recording liquid on the lower surface 42 of the discharge port remains on the inner wall of the discharge port. It is in communication with the recording liquid. Until the bubble 301 communicates with the atmosphere, the internal pressure of the bubble 301 is maintained at a level lower than the atmospheric pressure. When the bubble 301 communicates with the atmosphere while the internal pressure of the bubble 301 is equal to or higher than the atmospheric pressure, the liquid scatters in an unstable manner in the vicinity of the discharge port during the communication, and the unstable liquid is removed. The force for drawing into the flow channel does not work at all, and the effect of preventing the unstable liquid from scattering cannot be obtained.

Next, as shown in FIG.
Simultaneously with or immediately after 1 communicates with the atmosphere, the droplet 12 leaves the upper end of the ejection port 4 and is ejected. At this time, when the droplet is cut at the left side of the discharge port 4 in the figure, most of the recording liquid remaining on the inner wall of the discharge port remains on the lower surface 42 of the discharge port having a negative pressure. The liquid is drawn by the liquid and finally merges with the recording liquid in the liquid flow path 5 and moves into the liquid flow path 5. It should be noted that a little after the time of the communication, the meniscus 1
3 retreats the maximum, reaches the maximum meniscus retreat amount, and after this, as shown in FIGS. 3 (e) to 3 (g), the liquid is discharged. Return to

This step, that is, the step of maintaining the state of communication of the liquid remaining in the discharge port after the bubbles communicate with the outside air with the liquid receding from the discharge port in the liquid flow path; And refilling the inside of the discharge port by combining with the liquid in the liquid flow path, even if the recording liquid adheres to the vicinity of the upper surface 41 of the discharge port, Since the recording liquid is united with the recording liquid on the inner wall of the discharge port, it is possible to move the liquid adhering to the inside of the liquid flow path 5 and perform stable discharge without causing the non-discharge phenomenon.

The volume of the droplet 12 to be ejected is appropriately determined according to the size of the ejection port of the liquid ejection head used for ejection. × 10 ⁻¹⁵ m ³ or less.

One more preferable condition for stably communicating the bubble 301 with the atmosphere is (To + T
n) ≦ heater size. Here, the heater size is defined as (S
h) It means ^1/2 .

Conversely, in the case of "(To + Tn)> (Sh) ^1/2 ", even if the bubble communicates with the atmosphere, (To + Tn)
As n) becomes relatively large, an unstable element tends to be more likely to appear in the balance between air and bubbles. Therefore, it is a preferable condition to take a correlation between (To + Tn) and (Sh) ^1/2 . In addition, (To + Tn) ≫ (Sh)
^In the case of ^1/2, the discharge method is such that the atmosphere and the bubble do not communicate with each other, and the precondition of the present invention is eliminated.

A step of maintaining a state in which the liquid remaining in the nozzle portion after the bubbles communicate with the outside air is communicated with the liquid retreated from the discharge port in the flow path; The following configuration can be cited as an embodiment in which the step of refilling the inside of the nozzle portion by combining with a liquid can be realized more reliably.

(1) Regarding the cross-sectional shape of the discharge port, a so-called tapered discharge port, in which the minimum opening distance passing through the center of the upper surface of the discharge port is smaller than the minimum opening distance passing through the center of the lower surface of the discharge port, is effective. It is.

FIG. 6 shows a cross section of this.
Due to the tapered shape, not only is the recording liquid remaining on the inner wall of the ejection port easier to communicate with the ink in the liquid flow path, but also the diameter is larger at the lower surface of the ejection port in terms of the geometric distance. Therefore, the recording liquid does not block the discharge port.

(2) With respect to the discharge port planar shape, for example, a star-shaped discharge port is more likely to cause the recording liquid to remain on the inner wall of the discharge port as compared with the circular or square discharge port. Is easy to realize. This is because the liquid remaining near the apex angle of the star-shaped outlet becomes easier to communicate with the liquid on the lower surface of the outlet, and the effective outlet diameter when discharging ink is determined by the diameter of the concave portion of the star-shaped outlet. That's why.

(3) Meniscus Locality Ratio In order to easily combine the liquid remaining on the inner wall of the discharge port with the liquid in the liquid flow path, it is desirable that the negative pressure of the meniscus formed in the liquid flow path is large. To this end, it is preferable that the height of the liquid flow path is low and narrow within a range that does not greatly increase the refill time.

In order to further improve the preferred embodiments (1) to (3), the inner wall of the liquid flow path, particularly the lower surface of the discharge port, is easily wetted by the recording liquid (hydrophilic treatment is applied). Is desirable.

(4) Volume of Adhered Droplet In order to prevent the recording liquid from clogging the discharge port, it is desirable to minimize the supply of excess liquid on the upper surface of the discharge port. To this end, it is important to perform a water-repellent treatment on the discharge port surface so as to increase the water repellency on the discharge port surface as much as possible so that the liquid attached to the discharge port surface does not become large due to the coalescence. It is also effective to partially provide a hydrophilic region at a position distant from the discharge port on the discharge port surface having water repellency.

Next, the factors that determine the ejection state of the liquid ejection head will be considered more specifically from the viewpoint of the structure of the orifice plate.

The liquid remaining on the inner wall of the discharge port after discharging the recording liquid tends to form a meniscus (interface) in the discharge port. The relative pressure P of the recording liquid at this time is r1 (1/2 of the minimum opening distance formed by the meniscus when the discharge port is viewed from above, r2 (the curvature formed by the meniscus when the discharge port is viewed from the cross-sectional direction) Radius) and the surface tension γ of the recording liquid, P = −γ ((1 / r1) − (1 / r2)), where r1 <r2 → P <0 r1> r2 → P> 0, and when P> 0, even when the recording liquid is near the upper surface of the ejection port, it is difficult to draw the liquid into the ejection port, so that the recording liquid is less likely to be clogged in the ejection port.

R1 is the discharge aperture (口 (So)
^1/2 ) and r2 are respectively proportional to the thickness To.

In view of the above relationship, as structural conditions under which the recording liquid does not clog the above-mentioned discharge port, the inventors particularly consider the minimum opening distance passing through the center of the discharge port and the thickness of the orifice plate. As a result of performing various trials with attention, the liquid in the liquid flow path reaches the lower surface of the discharge port immediately after the bubbles communicate with the atmosphere, regardless of the wetting in the liquid flow path or the water repellent state of the upper surface of the discharge port. Even if it does not reach, it has been found that the occurrence rate of the recording liquid clogging phenomenon changes extremely when the minimum opening distance passing through the center of the discharge port is twice the thickness of the orifice plate. That is, if the minimum opening distance passing through the center of the discharge port is larger than twice the thickness of the orifice plate (if the distance between the upper surface and the lower surface of the discharge port is less than half the minimum opening distance passing through the center of the discharge port), The occurrence rate of the above phenomenon is very low, and conversely, the minimum opening distance passing through the center of the discharge port is smaller than twice the thickness of the orifice plate (the distance between the upper surface and the lower surface of the discharge port is the minimum opening distance passing through the center of the discharge port). Is greater than half), the occurrence rate of the above phenomenon increases rapidly, and non-discharge occurs to such an extent that it becomes a practical problem.

The "minimum opening distance passing through the center of the discharge port" in the present invention is defined by its diameter when the cross-sectional shape in the direction perpendicular to the discharge direction is a substantially perfect circle, and is defined by its diameter when it is a square. It is the length of one side, the length of the short side in the case of a rectangle, the length of the short side in the case of an ellipse, and the minimum diameter if the cross-sectional shape in the direction along the ejection direction is tapered.

Next, conditions for driving at a high frequency will be described. For this purpose, it is essential to shorten the refill time. The refill time is determined by (1) the maximum meniscus retreat amount, (2) the capillary force as a driving force during refill,
(3) Determined by the viscous resistance of the liquid flow path during refill.

The smaller the maximum meniscus retreat amount in (1), the shorter the refill time. The smaller the maximum meniscus retreat amount is, the better the droplets of a desired volume are ejected stably. In order to satisfy this condition, the driving pulse width is 3.5 μ
sec.

Since the capillary force of (2) is a driving force for the ink during refilling, it is generally better to increase the capillary force. That is, the surface tension of the recording liquid is desirably high, and is preferably 0.025 N / m or more.

In general, the smaller the viscosity resistance of the liquid channel, the better.

Note that the above conditions facilitate the communication between the liquid in the liquid flow path and the liquid remaining on the inner wall of the discharge port. In such a case, a more reliable liquid discharge head is used. Can be provided.

However, regarding (2) and (3), the setting should be made so that the vibration of the meniscus does not increase significantly after the refilling.

As a condition at a practical level that enables high-frequency driving by suppressing the viscous resistance of the liquid flow path during refilling, 6 μm ≦ Tn (the height of the liquid flow path) was found. Was. If 6 μm> Tn, the height of the liquid flow path is too low, the flow resistance becomes large, and a long time is required for refilling, so that high-frequency driving cannot be supported. Furthermore, it is necessary that the viscosity of the recording liquid is not too high in order to suppress the viscous resistance of the liquid flow path. 5 × 10 ⁻² N / s or less is desirable.

Further, as a condition for obtaining a good image with little deviation, the discharge speed of the droplet is 10 m / s or more and 30 m / s or less, preferably 10 m / s or more and 20 m / s or less.
s or less. When the discharge speed of the droplet is less than 10 m / s, the discharged droplet is likely to be distorted, and the print quality may be degraded. If the discharge speed of the droplets exceeds 30 m / s, the droplets related to printing tend to be mist-like due to the rebound of the droplets on the recording medium. Even if the above conditions are satisfied, if the thickness of the orifice plate 3 is too small, the problem that the ejection direction of droplets becomes unstable and the problem that the mechanical strength of the orifice plate 3 itself decreases may occur. A certain thickness is required. Specifically, 4 μm or more is preferable.

The liquid discharge head according to the embodiment described above can be mounted on, for example, the liquid discharge device shown in FIG. 4 to carry out the liquid discharge method of the present invention.

Hereinafter, an example of the liquid ejection apparatus will be described with reference to FIG.

In FIG. 4, reference numeral 200 denotes a carriage for detachably mounting the above-described liquid discharge head.
In this example, four types of liquid ejection heads are mounted according to the type of ink color as liquid, and each head has a yellow ink tank 201Y and a magenta ink tank 201.
It is mounted on the carriage 200 together with the M and cyan ink tanks 201C and the black ink tank 201B.

The carriage 200 is mounted on the guide shaft 20
The guide shaft 2 is supported by an endless belt 204 supported by the motor 2 and driven in a forward or reverse direction by a motor 203.
02 is reciprocable on arrow A in the direction of arrow A. Endless belt 204 is wound between pulleys 205 and 206.

The recording paper P as a recording medium is conveyed intermittently in the direction of arrow B perpendicular to the direction of arrow A. The recording paper P includes a pair of roller units 207 and 208 on the upstream side,
The sheet is nipped by a pair of roller units 209 and 210 on the downstream side, is applied with a constant tension, and is conveyed while ensuring flatness with respect to the head. The application of the driving force to each roller unit is performed by the driving unit 211,
The roller unit may be driven by using the above-described drive motor.

The carriage 200 stops at the home position as needed at the start of printing or during printing. At this position, a cap member 212 for capping the ejection opening surface of each head is provided.
Is connected to suction recovery means (not shown) for forcibly suctioning the discharge port on the discharge port surface to prevent clogging in the discharge port.

(Examples 1 and 2) FIGS. 2A and 2B
Was manufactured, and the results are shown in Table 1. As shown in FIGS. 1 (a) and 1 (b), the discharge ports are arranged in two rows, both discharge port rows are arranged in parallel to each other, and one discharge port row is shifted in a staggered manner by 300 dpi (25.4m pitch). And consequently 600 dpi (600 per 25.4 mm) in the main scanning direction of the head.
Density. The minimum opening distance passing through the center of each outlet is 2
2 μm, and the opening area S
o was set to 484 μm ² (= 22 μm × 22 μm). In this case, the length 26 of the effective foaming area in the liquid flow direction is set.
μm, and the length from the center to the end on the liquid supply side is 1
The area Sh of each heater of 3 μm is 936 μm ² (= 26 μm).
m × 36 μm).

In the first and second embodiments, the height Tn of the liquid flow path is set to 1
The thickness of the orifice plate was 9 μm and 11 μm. An unillustrated 0.6 μm thick insulating film (SiO ₂ ) and a 0.3 μm thick passivation resistant film (Ta) were formed on each heater.

The recording ink used had a composition of thiodiglycol 5%, glycerin 5%, urea 5%, isopropyl alcohol 4%, and the balance of water, and had a viscosity of 1.8 × 10 ⁻² N /
s, surface tension is 0.038 N / m, density is 1040 kg
/ M ³ .

Using a power supply voltage such that a voltage of Vop = 12 V is applied to the heater of the liquid discharge head (recording head) having such a configuration, a drive pulse having a width of 1.9 μsec was applied and the heater was driven at a frequency of 7 kHz. When a 1.9 μsec drive pulse was applied to the heater, the minimum voltage (threshold voltage) Vth required for ink ejection was 9.9 V. Therefore, Vop / Vth = 1.21. Table 1 shows various characteristics when such driving (12 V / 1.9 μsec) was performed.

Under the above conditions, A3 size recording paper was continuously fed, and actual printing was continuously performed. The minimum opening distance D passing through the center of the discharge port is 22 μm, which is twice or more the thickness To of the orifice plate corresponding to the distance between the upper surface and the lower surface of the discharge port, and at least one A3 actual print can be continuously and normally performed. Therefore, the reliability was at a level having no practical problem.

[0066]

[Table 1]

Further, since the ink ejection speed was sufficiently high, it was possible to cope with the case where the viscosity of the ink was increased by leaving the head unattended. Specifically, the viscosity of the ink is 5 × 10 ^-2 N /
s. If the viscosity of the ink exceeds 10 × 10 ⁻² N / s, the viscosity is too high, and the ejection speed is reduced to 10 m / s or less, and the deflection is increased. In order to further ensure the object of the present invention, the higher the surface tension of the ink, the more desirable,
The upper limit is not a problem as long as it can be determined by taking into account the droplet formation behavior of the droplet on the recording medium, preferably 30 × 10 ⁻² N / m or more, as long as the droplet can be ejected.
When the surface tension of the ink is less than 30 × 10 ⁻² N / m,
Insufficiency of the capillary force as a driving force during refilling causes an inconvenience that the refilling time becomes longer and high-frequency driving becomes difficult.

The refill time in the above embodiment was 75 μsec from the start of the application of the ejection pulse. Subsequent meniscus vibration was at a level that was not observed, and had no effect on print record quality.

In this embodiment, the growth amount of bubbles could be suppressed to a relatively small value by making the heater protective layer thinner and making the pulse width shorter. That is, the refill time was shortened by reducing the amount of meniscus retreat instead of increasing the refill speed.

In this embodiment, the protective layer of the heater 1 is formed of SiO ₂ (0.6 μm thick), and the passivation-resistant film is formed of Ta (0.3 μm thick). The thinner the film, the better. By reducing the thickness of the protective layer, the total amount of heat energy transmitted from the heater to the ink can be reduced from the start of pulse application to the bubbling, and the growth amount of bubbles after bubbling can be suppressed. is there. In the case where a protective layer of SiO ₂ or SiN is provided, it is desirable that the film thickness is less than 1 μm. Of course, if the heater material is made of a material such as platinum having strong corrosion resistance, the protective layer may be omitted.

In the head of the present invention in which bubbles in the liquid flow path of the liquid discharge head communicate with the atmosphere through the discharge port, the ink discharge volume is determined by the heater, the liquid flow path, and the geometrical shape of the discharge port. It is almost determined by the conditions, and there is a wide range in which the ejection amount is not affected even when the bubble growth amount is small.

(Comparative Examples 1 to 4) Comparative Examples 1 to 4 shown in Table 1 as in Examples 1 and 2 are examples in which the height of the liquid flow path was changed from that of Example 1. That is, while the heights Tn of the liquid flow paths in Examples 1 and 2 are 12 μm and 6 μm,
Comparative Examples 1 to 4 were 6 μm, 4 μm, 6 μm, and 5 μm, respectively.
5 μm. The orifice plate thicknesses To of Comparative Examples 1 to 4 were 12 μm, 9 μm, 11 μm, and 11 μm, respectively.
m. In these comparative examples 1 to 4, the minimum opening distance D passing through the center of the discharge port is less than twice the orifice plate thickness To. That is, non-discharge frequently occurs in Comparative Examples 1 and 3, in which the orifice plate thickness To set to correspond to the distance between the upper surface and the lower surface of the discharge port exceeds half of the minimum opening distance D passing through the center of the discharge port. Become like Also,
In Comparative Examples 2 and 4 in which the height of the liquid flow path was less than 6 μm, it was found that the refill time was long and was unsuitable for high frequency driving.

On the other hand, although not described in Table 1,

[0074]

[Outside 1]

The behavior of the droplet and the meniscus when the air bubble communicates with the atmosphere becomes unstable, and adversely affects the printing.

(Examples 3 to 5 and Comparative Examples 5 to 10) A liquid discharge head having the structure shown in FIGS. 2A and 2B was manufactured, and the results are shown in Table 2. Fig. 1
As shown in FIG. 1A and FIG. 1B, two rows are arranged in parallel with each other, and one row of
The density was set to be 00 dpi, and arranged in a zigzag manner with a shift of half a pitch in the length direction of the ejection port row with respect to the other ejection port row, resulting in a density of 1200 dpi in the main scanning direction of the head. The opening area So of the discharge port of Examples 3-5, respectively ^{227μm 2 (= φ17μm), 225μm} 2
(15 μm square) and 324 μm ² . In this case, the area Sh of each heater is set to 576 μm ² (24 μm × 2
4 μm).

In Examples 3 to 5, the same inks as those used in Examples 1 and 2 were used.

In the third and fourth embodiments, the height Tn of the liquid passage is set to 12
μm, and in Example 5, it was 6 μm. The thickness To of the orifice plate was set to 7 μm in the third embodiment, 6 μm in the fourth embodiment, and 9 μm in the fifth embodiment.

[0079] Further, each of the opening area So of the discharge port of Comparative Example 5~10 200μm ^2, 314μm ^2, 227
μm ^2, 202μm ² (14.2μm square), 324μ
m ² and 324 μm ² . The opening area Sh of each heater is 576 μm ² (24 μm
× 24 μm). The height Tn of each liquid flow channel of Comparative Examples 5 to 10 was 12 μm, 4 μm, 8 μm, 12 μm, respectively.
6 μm, 5.0 μm, orifice plate thickness To
Of 9 μm, 11 μm, 9 μm, 9 μm, and 9.5, respectively.
μm and 9 μm.

The sheet resistance of the heater is 53Ω.

Using a power supply voltage such that a voltage of Vop = 9.0 V is applied to the heater of the liquid ejection head (recording head) having such a configuration, a drive pulse having a width of 2.7 μsec is applied and the heater is driven at a frequency of 10 kHz. did. 2.7μse
When a drive pulse having a width c was given, the minimum voltage (threshold voltage) Vth required for ink ejection was 7.2 V. Therefore, Vop / Vth = 1.25. Table 2 shows various characteristics and the normal ejection sustained number of sheets (A3 size recording paper) when such driving (9 V / 2.7 μsec) was performed.

[0082]

[Table 2]

As is clear from Table 2, Examples 3 to 5
In, the number of continuous normal ejections is much larger than in the other comparative examples. This indicates that the occurrence of streaks due to non-ejection during printing is prevented.

Further, focusing on D / To, Examples 3 to
5 is 2 or more, while other Comparative Examples 5 to 9 are less than 2. In these Comparative Examples 5 to 9, the number of normally ejected sheets is small, and streaks due to non-ejection are noticeable when printing is performed. Therefore, D / To is preferably 2 or more. D / T of Comparative Example 10
Although o is 2.0, the occurrence of the phenomenon of sudden ejection failure is reduced, but in Comparative Example 10, the height Tn of the liquid flow path is as low as 5.0 μm, and ink refilling is performed at a frequency drive of 10 kHz or more. Is not in time, and printing blur occurs, so that the number of continuous normal ejections is reduced.

Further, in the refill time, the drive frequency of Comparative Example 7 is 95 μs, which is sufficient, and the drive frequency of Comparative Example 6 is 920 μs, which does not reach the drive frequency of 10 kHz. This is because Tn is as small as 4 μm.
As for the refill time, Tn is preferably 6 μm or more.

The shape of the discharge port of Example 4 and Comparative Example 8 is square, which is different from the true circle of the other examples.
Also in Comparative Example 6 having such a discharge port shape, non-discharge occurs suddenly as in the case of another true circular shape. Example 4
In the above, D / To is preferably 2.5 or more, which is 2 or more, and the shape of the discharge port is square, but no non-discharge has occurred suddenly. The thickness To of the orifice plate is desirably 4 μm or more in consideration of deformation due to foaming pressure.

In each of the above Examples and Comparative Examples, solid printing is evaluated in order to accurately determine the occurrence of blurring during printing and sudden non-ejection.

In the present embodiment, the solid printing means that the A3 size paper is continuously fed in accordance with the Japanese Industrial Standards and ink dots are printed at an A3 size of 100%. The important thing as this criterion is that at least the normal ejection sustained number is one or more.
When blurring or sudden ejection failure occurs during printing of one sheet (defective), it is necessary to perform a recovery operation or the like on the same sheet, and it takes time to recover even after recovery. Such is not practical. That is, one sheet (A
3) print quality and maintaining print quality
It is important.

In any case, the present invention finds a new problem that occurs when ink droplets having a volume of 15 × 10 ⁻¹⁵ m ³ or less are ejected in a system in which air communicates with air bubbles, and solves this problem. A practical configuration and method are provided as conditions for performing the above.

(Others) It should be noted that the present invention includes a means (for example, an electrothermal converter or a laser beam) for generating thermal energy as energy used for discharging ink, particularly in an ink jet recording system. An excellent effect is obtained in a recording head and a recording apparatus of a type in which the state of ink is changed by the thermal energy. This is because according to such a method, it is possible to achieve higher density and higher definition of recording.

The typical structure and principle are described in, for example, US Pat. Nos. 4,723,129 and 4,740.
It is preferable to use the basic principle disclosed in the specification of Japanese Patent No. 796. This method is a so-called on-demand type,
Although it can be applied to any type of continuous type, in particular, in the case of the on-demand type, it can be applied to a sheet holding liquid (ink) or an electrothermal converter arranged corresponding to the liquid path. By applying at least one drive signal corresponding to the recorded information and providing a rapid temperature rise exceeding nucleate boiling, heat energy is generated in the electrothermal transducer, and film boiling occurs on the heat acting surface of the recording head. Liquid (ink) corresponding to this drive signal on a one-to-one basis.
This is effective because air bubbles inside can be formed. The liquid (ink) is ejected through the ejection opening by the growth and contraction of the bubble to form at least one droplet. When the drive signal is formed into a pulse shape, the growth and shrinkage of the bubble are performed immediately and appropriately, so that the ejection of a liquid (ink) having particularly excellent responsiveness can be achieved, which is more preferable. As the pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. Further, if the conditions described in US Pat. No. 4,313,124 relating to the temperature rise rate of the heat acting surface are adopted, more excellent recording can be performed.

As the configuration of the recording head, in addition to the combination of the discharge port, the liquid path, and the electrothermal converter (the right-angled liquid flow path) as disclosed in the above-mentioned specifications, the heat acting portion is bent. U.S. Pat. No. 455, which discloses an arrangement located in a region
A configuration using the specification of US Patent No. 8333 and US Patent No. 4,459,600 is also included in the present invention. in addition,
Japanese Patent Laid-Open No. 59-1 discloses a configuration in which a common slit is used as a discharge section of an electrothermal converter for a plurality of electrothermal converters.
No. 23670 and JP-A-59-13, which disclose a configuration in which an opening for absorbing a pressure wave of thermal energy is made to correspond to a discharge portion.
The effect of the present invention is effective even if the configuration is based on No. 8461. That is, according to the present invention, recording can be reliably and efficiently performed regardless of the form of the recording head.

Further, the present invention can be effectively applied to a full-line type recording head having a length corresponding to the maximum width of a recording medium on which a recording apparatus can record. Such a recording head may have a configuration that satisfies the length by a combination of a plurality of recording heads, or a configuration as one integrally formed recording head.

In addition, even in the case of the serial type as described above, the recording head fixed to the apparatus main body or the electric connection with the apparatus main body and the ink from the apparatus main body when attached to the apparatus main body. The present invention is also effective when a replaceable chip-type recording head that can be supplied or a cartridge-type recording head in which an ink tank is provided integrally with the recording head itself is used.

Further, it is preferable to add ejection recovery means for the recording head, preliminary auxiliary means, and the like as the constitution of the recording apparatus of the present invention since the effect of the present invention can be further stabilized. If these are specifically mentioned, the recording head is heated using capping means, cleaning means, pressurizing or suction means, an electrothermal transducer, another heating element or a combination thereof. Pre-heating means for performing the pre-heating and pre-discharging means for performing the discharging other than the recording can be used.

Further, the types and the number of the recording heads to be mounted are, for example, not only one provided for a single color ink but also a plurality of inks having different recording colors and densities. A plurality may be provided. That is, for example, the printing mode of the printing apparatus is not limited to a printing mode of only a mainstream color such as black, but may be any of integrally forming a printing head or a combination of a plurality of printing heads. The present invention is also very effective for an apparatus provided with at least one of the recording modes of full color by color mixture.

In addition, in the embodiments of the present invention described above, the ink is described as a liquid. However, an ink which solidifies at room temperature or lower and which softens or liquefies at room temperature may be used. In general, the ink jet method generally controls the temperature of the ink itself within a range of 30 ° C. or more and 70 ° C. or less to control the temperature so that the viscosity of the ink is in a stable ejection range. Sometimes, the ink may be in a liquid state. In addition, in order to positively prevent temperature rise due to thermal energy by using it as energy for changing the state of the ink from a solid state to a liquid state, or to prevent evaporation of the ink, the ink is solidified in a standing state and heated. May be used. In any case, the application of heat energy causes the ink to be liquefied by the application of the heat energy according to the recording signal and the liquid ink to be ejected, or to start solidifying when it reaches the recording medium. The present invention is also applicable to a case where an ink having a property of liquefying for the first time is used. In such a case, the ink
JP-A-54-56847 or JP-A-60-7
As described in Japanese Patent Publication No. 1260, it is also possible to adopt a form in which the sheet is opposed to the electrothermal converter in a state where it is held as a liquid or solid substance in the concave portion or through hole of the porous sheet. In the present invention, the most effective one for each of the above-mentioned inks is to execute the above-mentioned film boiling method.

In addition, the form of the ink jet recording apparatus of the present invention is not only used as an image output terminal of an information processing apparatus such as a computer, but also for a copying apparatus combined with a reader or the like, and a facsimile apparatus having a transmission / reception function. It may take a form.

[0099]

As described above, according to the present invention,
In the side shooter type liquid discharge head that communicates air bubbles with the atmosphere, by preventing the recording liquid from clogging in the discharge port, it is possible to reliably prevent the occurrence of streaks during recording and to cause sudden ejection failure It is possible to perform high-speed and high-quality printing while maintaining the ejection reliability that there is no printing, and to enable high-quality printing.

[Brief description of the drawings]

FIGS. 1A and 1B are diagrams showing a schematic configuration of a liquid ejection head to which a liquid ejection method of the present invention can be applied, wherein FIG. 1A is a perspective view showing an external appearance, and FIG. ) Is (a)
FIG. 3 is a cross-sectional view taken along line AA of FIG.

FIGS. 2A and 2B are diagrams showing a main part of the liquid ejection head shown in FIGS. 1A and 1B, wherein FIG. FIG. 2B is a top view of FIG. 2A.

FIGS. 3A to 3G are cross-sectional views illustrating the operation of a liquid ejection head to which the liquid ejection method of the present invention is applied.

FIG. 4 is a schematic perspective view showing an example of a liquid discharge apparatus to which a liquid discharge head to which the liquid discharge method of the present invention can be applied is mounted.

FIG. 5 is an enlarged cross-sectional view showing a main part of a liquid ejection head for describing a problem newly found in the present invention.

FIG. 6 is an enlarged cross-sectional view showing a main part of a liquid ejection head for describing a problem newly found in the present invention.

[Explanation of symbols]

Reference Signs List 1 heater (electrothermal conversion element) 2 element substrate 3 orifice plate To Distance between upper and lower surfaces of discharge port (corresponding to the thickness of orifice plate in the embodiment) 4 discharge port So discharge port area 5 liquid flow path Tn liquid flow Path height 6 Liquid flow path wall 11 Meniscus 12 Droplet 13 Bubbles 102 Support member 103 Mold member 104 Wiring board 105 Communication path 200 Carriage 201Y, 201M, 201C, 201B Liquid discharge head 202 Guide shaft 203 Drive motor 204 Endless belt 205 , 206 Pulley 207, 208, 209, 210 Roller unit 211 Drive unit 212 Suction recovery unit 301 Bubble

Claims (29)

[Claims] 1. An electrothermal transducer for generating thermal energy sufficient for foaming a liquid and discharge ports provided at positions facing the electrothermal transducer at a density of 300 or more per 25.4 mm in a row. Using a liquid discharge head including a plurality of liquid flow paths respectively communicating with the discharge ports, bubbles generated by the heat energy of the electrothermal transducer, the internal pressure is communicated with the atmosphere in a state of less than atmospheric pressure, 15 × 10
A liquid discharge method for discharging droplets having a ^-15 m ³ or less of the volume at frequencies above drive 7 kHz, the liquid discharge head, the height of the liquid flow path is at 6μm or more, and the upper surface of the discharge port A liquid ejection method, wherein the distance to the lower surface is equal to or less than half the minimum opening distance passing through the center of the ejection port. 2. The liquid discharging method according to claim 1, wherein a sum of a distance between an upper surface and a lower surface of the discharge port and a height of the liquid flow path is equal to or smaller than a size of the electrothermal conversion element. 3. The liquid discharging method according to claim 1, wherein the volume of the droplet is 10 × 10 ⁻¹⁵ m ³ or less. 4. The liquid discharging method according to claim 1, wherein the height of the liquid flow path of the liquid discharging head is 20 μm or less. 5. The liquid discharging method according to claim 1, wherein the flying speed of the discharged droplet is 20 m / s or less. 6. The liquid discharging method according to claim 1, wherein the width of the discharging electric pulse given to the electrothermal transducer is 3.5 μsec or less. 7. The liquid ejection device according to claim 1, wherein a driving voltage of an electric pulse applied to the electrothermal conversion element is in a range of 1.1 to 1.3 times a threshold voltage of droplet ejection. Method. 8. The method according to claim 7, wherein the electric pulse includes a plurality of pulses. 9. The plurality of pulses include a main pulse and a pre-pulse applied before the main pulse, and the length of the pre-pulse is 1.5 μsec or less. 9. The liquid discharging method according to item 8. 10. The liquid discharging method according to claim 9, wherein an interval between the pre-pulse and the main pulse is 2.0 μsec or less. 11. The surface tension of the liquid to be ejected is 0.1.
2. The liquid discharging method according to claim 1, wherein the viscosity is not less than 025 N / m and the viscosity is not more than 5 × 10 ⁻² N / s. 12. The liquid discharging method according to claim 1, wherein said electrothermal conversion element is means for generating heat energy for causing film boiling of said liquid. 13. A plurality of electrothermal conversion elements for generating thermal energy for foaming a liquid, a plurality of discharge ports provided at positions facing the electrothermal conversion elements to discharge droplets, and the discharge ports And a plurality of liquid flow paths communicating with the
The plurality of electrothermal transducers and the plurality of discharge ports are 25.
Arranged at an array density of 300 or more per 4 mm,
A drive signal is applied to the electrothermal conversion element at a frequency of 7 kHz or more to generate bubbles in the liquid in the liquid flow path, and the bubbles communicate with the atmosphere when the internal pressure of the bubbles is lower than the atmospheric pressure.
In a liquid discharge head that discharges a droplet having a volume of 10 ⁻¹⁵ m ³ or less, the height of the liquid flow path is 6 μm or more, and the distance between the upper surface and the lower surface of the discharge port passes through the center of the discharge port. A liquid ejection head, wherein the length is not more than half of the minimum opening distance. 14. The liquid discharge head according to claim 13, wherein a sum of a distance between an upper surface and a lower surface of the discharge port and a height of the liquid flow path is equal to or smaller than a size of the electrothermal transducer. 15. The volume of the droplet is 10 × 10 ⁻¹⁵ m ^3.
14. The liquid discharge head according to claim 13, wherein: 16. The liquid discharge head according to claim 13, wherein the height of the liquid flow path is 20 μm or less. 17. The liquid discharge head according to claim 13, wherein the flying speed of the discharged droplet is 20 m / s or less. 18. The liquid discharge head according to claim 13, wherein the width of the discharge electric pulse given to the electrothermal transducer is 3.5 μsec or less. 19. A driving voltage of an electric pulse applied to the electrothermal transducer is 1.1 times to 1.3 times a threshold voltage of droplet discharge.
14. The liquid discharge head according to claim 13, wherein the range is twice as large. 20. The liquid discharge head according to claim 19, wherein the electric pulse is composed of a plurality of pulses. 21. The plurality of pulses are composed of a main pulse and a pre-pulse applied before the main pulse, and the length of the pre-pulse is 1.5 μsec or less. 20. The liquid ejection head according to 20. 22. The liquid discharge head according to claim 21, wherein an interval between the pre-pulse and the main pulse is 2.0 μsec or less. 23. The discharged liquid has a surface tension of 0.1.
14. The liquid ejection head according to claim 13, wherein the viscosity is not less than 025 N / m and the viscosity is not more than 5 × 10 ⁻² N / s. 24. The liquid discharge head according to claim 13, wherein said electrothermal conversion element is means for generating heat energy for causing film boiling of said liquid. 25. An electrothermal conversion element for generating thermal energy sufficient to foam a liquid, and discharge ports provided at positions facing the electrothermal conversion element are arranged at a density of 300 or more per 25.4 mm in a row. Using a liquid discharge head including a plurality of liquid flow paths respectively communicating with the discharge ports, bubbles generated by the thermal energy of the electrothermal transducer, communicate with the atmosphere in a state where the internal pressure is less than atmospheric pressure, 15 × 10
A liquid discharge method for discharging droplets having a ^-15 m ³ or less of the volume at frequencies above drive 7 kHz, the discharge port liquid bubbles from remaining in the discharge port after the communication with the outside air in the liquid flow path A liquid discharging method comprising: a step of maintaining a state of communication with the liquid retreated from the liquid channel; and a step of combining the residual liquid with the liquid in the liquid flow path and refilling the inside of the discharge port. 26. The liquid discharging method according to claim 25, wherein a minimum opening distance passing through the center of the upper surface of the discharge port is smaller than a minimum opening distance passing through the center of the lower surface of the discharge port. 27. A discharge port surface provided with the discharge port upper surface is subjected to a water-repellent treatment.
3. The liquid discharging method according to item 1. 28. The liquid discharging method according to claim 27, wherein the discharge port surface has a parent waterlogging area. 29. The method according to claim 25, wherein the lower surface side of the discharge port of the liquid flow path is subjected to a friendship processing.
The liquid discharging method according to any one of the above.