JPH05116341A - Method for driving ink jet recording head - Google Patents

Abstract

PURPOSE:To realize the stable emission of ink, in an ink jet recording system emitting ink by an air bubble formed by heat energy, by reducing the irregularity of the foaming time of the air bubble. CONSTITUTION:The heat value Q(t) of a heating element for forming an air bubble is made constant during the period t20-t1 before foaming time and set to the increase function of a time (t) during the period t1-t2 in the vicinity of the foaming time. By this constitution, the irregularity of the foaming time is suppressed to stably emit ink.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of driving an ink jet recording head which applies thermal energy to ink and ejects ink based on the generation of bubbles generated thereby.

[0002]

2. Description of the Related Art Conventionally, in a recording apparatus for recording by heating ink to generate bubbles and ejecting ink based on the generation of the bubbles, various measures have been taken regarding heating conditions. The general structure of such a recording head is as follows: an ejection port for ejecting ink, an ink channel communicating with the ejection port and filled with ink, and an electric path for generating the thermal energy provided in the ink channel. It is equipped with a heat conversion element (heating element). The heating element is generally made of a thin film resistor, and heat energy is generated by energizing (applying a driving pulse) in a pulsed manner to the heating element through electrode wiring.

Therefore, when devising a heating condition, the waveform of the driving pulse (driving signal) applied to the heating element is mostly considered. By devising such a drive signal, the amount of ejected ink is optimally controlled to improve the quality of a recorded image, and the life of the heating element is improved.

Hereinafter, some of the conventional structures relating to the drive signal waveform will be described.

For example, Japanese Patent Application Laid-Open No. 55-132263 discloses a method of varying the ink ejection amount by using a plurality of rectangular voltage pulses as a drive signal waveform.

Further, JP-A-63-278858, JP-A-63-297049. In Japanese Patent Laid-Open No. 64-38245, the drive signal waveform is made into a plurality of rectangular voltage pulses, and at least one of the pulses is made to have its current direction opposite to that of other pulses. A method for improving the durability of a recording head is disclosed.

Further, Japanese Patent Laid-Open No. 30545/1990 discloses a method of varying the ink ejection amount by causing a heating element to generate heat so as to include two or more different heating conditions.

Further, in the above method, in order to perform stable recording with good image quality, Japanese Patent Laid-Open No. 58-1
As disclosed in 571, it is desirable to set the drive signal voltage to 1.02 to 1.3 times the lowest voltage for generating bubbles.

[0009]

However, since the heat generation amount Q (t) of the heating element is generally proportional to the square of the voltage value of the drive pulse, when the drive pulse is a rectangular wave as in the conventional example described above. , Q (t) is almost constant at the time of foaming t = t ₀

[0010]

[Outer 1]

Therefore, the temperature rise rate of the ink at t = t ₀

[0012]

[Outside 2]

Cannot be so large. For this reason, there are cases in which the variation in the bubbling start time becomes large for the reasons described below, which causes a change in the ejection amount and the like, which deteriorates the image quality. The temperature rise rate

[0014]

[Outside 3]

Although it is conceivable to increase the absolute value of the heat generation amount Q (t) in order to increase, the problem is that if Q (t) is increased, the foaming start time becomes earlier and the degree of freedom in bubble control decreases. Occurs.

Ink temperature rise rate at t = y ₀

[0017]

[Outside 4]

The reason why the variation of the foaming start time becomes large when is small is as follows.

The foaming probability of the ink depends on the temperature distribution in the ink, but roughly speaking, the temperature T of the highest temperature part in the ink is a temperature zone T ₁ <T <where the temperature T is near the overheat limit.
The foaming probability is 0 when T ₂ changes from the low temperature side to the high temperature side.
It can be said that it changes from 1 to 1. If you follow this,
The variation δt of bubbling time is

[0020]

[Equation 1]

Is given by

Therefore, the temperature rise rate

[0023]

[Outside 5]

When is small, δt is large.

Further, the thinner the protective film of the thin film resistor forming the foam, the higher the temperature rise rate.

[0026]

[Outside 6]

In some cases, the tendency becomes remarkable especially when the protective film is not present. This is because, when viewed at the same time interval, the thinner the protective film is, the more quickly the heat generated by the heating element is transferred to the ink, so the temperature rise immediately after the start of heating, but the temperature rise slows in a relatively early time. This is because

FIGS. 1 (a) and 1 (b) are views showing this state. FIG. 1 (a) shows a temperature rise curve in the case where a protective film is present, and FIG. 1 (b) does not have a protective film. A temperature rise curve in the case of or extremely thin is shown.

As is clear from these figures, the rate of temperature rise at the time of foaming t = T ₀ , despite the case of heating to the same temperature for the same heating time.

[0030]

[Outside 7]

(The slope of the tangent line at the point of t = t _{0 on} the curve) becomes smaller when there is no protective film or when it is extremely thin.

According to the present invention, the amount of heat acting on the ink for ejecting the ink is made to be a function of the increase in time when bubbles are generated, thereby increasing the temperature rise rate of the ink at the time of bubbling to start bubbling. It is an object of the present invention to provide a method for driving an inkjet recording head, which makes it possible to perform stable ink ejection with a small time variation.

[0033]

Therefore, according to the present invention,
An ink ejection port for ejecting ink and an ink path communicating with the ejection port are provided, and the ink in the ink path is heated to generate bubbles, and the ink is ejected from the ejection port based on the generation of the bubbles. In the method of driving the inkjet recording head, the amount of heat supplied to the ink by the heating is increased before and after the generation of the bubbles.

[0034]

According to the above construction, the amount of heat supplied to the ink for ejecting the ink is increased before and after the bubble is generated, so that it is possible to suppress the variation in the time of bubble generation. As a result, it becomes possible to perform stable discharge such as stable discharge amount.

[0035]

Embodiments of the present invention will now be described in detail with reference to the drawings.

Before describing specific examples of the present invention, the technical idea of the present invention will be described.

In this description, the following heat conduction model is used. That is, at time t = 0, the semi-infinite region Z ≧ 0 filled with the ink of the constant temperature T _amb is converted into the end Z = 0.
Heat flux proportional to the m-th power of time t

[0038]

[Number 2] q (t) = q (t / t 0) Consider models heated by ^m (2).

In this model, the distance Z from the heater and the ink temperature T at time t after the start of heating
(Z, t) is the one-dimensional heat conduction equation

[0040]

[Equation 3]

The initial condition T (z, t = 0) = T _amb ,
boundary condition

[0042]

[Equation 4]

Solution solved under

[0044]

[Equation 5]

Is given by In particular, the ink temperature T (t, Z = 0) ≡T (t) of the portion in contact with the heater is

[0046]

[Equation 6]

Is given by When this equation (6) is expressed using the Γ function,

[0048]

[Equation 7]

It becomes

Here, if T (t) reaches the foaming temperature Tg at time t = t ₀ , from equation (7),

[0051]

[Equation 8]

Is required. Therefore, it is obtained by differentiating the equation (7) with respect to time t and substituting the equation (8) with t = t ₀ . Temperature rise rate at t = t ₀

[0053]

[Outside 8]

Is

[0055]

[Equation 9]

It becomes

From the equation (9), the larger m is, the higher the temperature rise rate is.

[0058]

[Outside 9]

It can be seen that becomes large. Therefore, rather than heating with a constant heat flow end (m = 0 in the equation (2)), heating so that the heat generation amount is an increasing function of time (m> 0 in the equation (2))

[0060]

[Outside 10]

Becomes larger.

In the above discussion, the case where q (t) is an increasing function (αt ^m , m> 0) of t throughout the entire time from the start of foaming to the foaming was considered for simplification. Since the temperature rise rate at the time of foaming is a problem in carrying out
It suffices if (t) is an increasing function of t.

FIG. 2 is a diagram showing the time change of the heat generation amount of the heating element according to the first embodiment of the present invention.

As is clear from the figure, in this example, t =
A constant calorific value is obtained from 0 to t = t ₁ , and a calorific value Q (t) is obtained from t = t ₁ to t = t _2, which is the foaming time range.
Is an increasing function. The drive pulse V (t) for generating such heat generation amount Q (t) is shown by the one-dot chain line in the figure.

As the heating element, as shown in FIG.
On a 525 μm-thick Si substrate 1 on which a 2.7 μm-thick surface oxide layer 2 is formed, a 0.1 μm-thick Ta film is formed.
A resistance layer 3 and an Al electrode 4 having a thickness of 0.6 μm were used. By energizing the electrodes 4 of the heating element, the Ta resistance layer 3 is heated to heat the ink in contact with the Ta resistance layer 3. Here, the protective film is made of SiO _{2 and} has a thickness of 1.0 μm. In addition, the Ta resistance layer 3
Of these, the area that actually generates heat is a 60 μm × 60 μm square area 6.

Here, between the heat generation amount Q (t) and the voltage V (t) applied between the electrodes 4,

[0067]

[Equation 10]

Since there is a relation of, the heat generation amount Q (t) is controlled by controlling the waveform of the drive pulse, that is, the voltage value.
Can be controlled as shown in FIG. Where R
_H is the resistance value of the resistor formed by the Ta resistance layer 3 and the like, and in this embodiment, R _H = 25Ω.

FIG. 4 shows the time change of the ink temperature (from the start of heating to the bubbling) obtained by controlling the heat generation amount as shown in FIG. As is clear from the figure, at the time t ₀ (t ₁ <t ₀ <t ₂ ) at which foaming occurs, the temperature rise rate

[0070]

[Outside 11]

It can be seen that is large.

Parameters t ₁ , t related to the driving pulse
₂ , Q ₁ and Q ₂ may be set so that the ink reaches the bubbling temperature T _g at the time t ₁ <t <t ₂ .

For example, when water is used instead of ink for simplification, t ₁ = 4 μsec, t ₂ = 6 μsec,
Q = 2.3 W, defines the waveform of the driving pulse such that Q ₂ = 4.6 W.

As described above, the calorific value is kept constant until the preset (desired) foaming time is approached,
(Be careful not to cause foaming) Near the foaming time,
By using the amount of heat generation as an increasing function, the probability of foaming is increased, and thereby the foaming time can be accurately determined. According to this, the following additional effects can be obtained.

That is, referring to FIGS. 2 and 4, t ₁ and Q ₁ can be freely set to some extent until the desired foaming time. Here, at time 0 <t <t ₁ ,
The total amount of heat applied to the ink is proportional to Q ₁ t ₁ , while the temperature of the ink at t = t ₁ is proportional to Q ₁ √t ₁ . Therefore, the total amount of heat given to the liquid can be increased while satisfying the constraint that the ink does not foam at t = t ₁ .

That is, by increasing the value of t ₁ in proportion to Q ₁ ^-2 while suppressing the amount of heat generation Q ₁ , the total amount of heat can be increased while increasing the temperature to the same extent as in other cases. It can be increased in proportion to Q ₁ ^-1 .

As described above, since the total amount of heat given to the liquid can be increased, it is possible to increase the energy of bubbles generated thereafter. This has advantages such as improving reproducibility of foaming. In addition, this increase in bubble energy is an effective configuration in the so-called bubble communication discharge method proposed by the present applicant.

That is, this discharge-communication discharge system is an ink jet recording system in which bubbles caused by film boiling generated by heating ink for discharge are communicated with the outside air in the vicinity of the discharge port for discharge. Applicant filed Japanese Patent Application No. 2
-112832, Japanese Patent Application No. 2-112833, Japanese Patent Application No. 2-112834, Japanese Patent Application No. 2-114472.

According to the above-mentioned continuous discharge method, the gas forming bubbles does not jet out together with the discharged ink droplets, so that the generation of splash or mist is reduced,
It is possible to prevent background stains on the recording medium and stains inside the apparatus.

Further, as a basic operation of the above-mentioned continuous discharge method, there is a principle that all the ink on the discharge port side of the portion where bubbles are generated is discharged as ink droplets. Therefore, the amount of ejected ink can be determined by the structure of the recording head, such as the distance from the ejection port to the bubble generating portion. As a result, according to the above-described continuous discharge method, it is possible to perform stable discharge of the discharge amount without being affected by the change in the ink temperature.

Hereinafter, the continuous discharge method will be described with reference to FIGS.

FIGS. 5 (a) and 5 (b) show a recording head suitable for applying the above-mentioned continuous discharge method and its discharging method, and show two examples of specific ink path configurations of this recording head. .. However, it goes without saying that the present invention is not limited to this configuration.

The ink path structure shown in FIG. 5A comprises a heating resistance layer (heater) 2 on a substrate (not shown), and a partition or a top plate is provided on this substrate, whereby the common liquid chamber C is formed. And the ink path B is formed. At the same time, the ejection port 5 is formed at the end of the ink path B. E1 and E2 are
A selection electrode and a common electrode for applying a pulsed electric signal to the heater 2 are shown respectively. Further, D is a protective layer.

In response to the application of the electric signal based on the recording data via the electrodes E1 and E2, the heater 2 between the electrodes E1 and E2 generates a rapid temperature rise that causes a vapor film in a short time. (About 300 ° C.), whereby bubbles 6 are generated. The bubbles 6 grow and eventually communicate with the atmosphere at the end A of the ejection port 5 on the substrate side. After this communication, stable ejected ink droplets (broken line 7) are formed.

In this ejection, since the bubble 6 does not completely block the ink path B in the growth process (the ink in the ink path B is continuous with the ink protruding from the ejection port 5), refilling for the subsequent ejection is performed. Be done promptly,
Further, since the heat of the bubbles having a relatively high temperature of 300 ° C. or higher is also released to the outside air, a large problem of heat storage (ink viscosity lowering due to heat storage and destabilization of bubble formation) does not occur, and each heater is driven. The duty can be increased.

Although the common liquid chamber C is not shown in FIG. 5 (b), the ink passage B has a bent shape, and the heating resistor portion (heater) 2 is provided on the substrate surface of the bent portion. There is. The discharge port 5 has a shape that reduces its cross-sectional area in the discharge direction, and has an opening facing the heater 2. The discharge port 5 is formed in the orifice plate OP.

Also in FIG. 5B, a vapor film (about 300.degree. C.) is generated to generate bubbles 6 as in the structure of FIG. 5A.
To generate. By generating the bubbles, the ink in the thickness portion of the orifice plate OP is pushed in the ejection direction, and the ink in the portion is diluted. After that, the bubbles 6 communicate with the atmosphere in the range from the outer peripheral edge A1 of the discharge port 5 to the discharge port vicinity region A2 on the inner side. At this time, since the growth of the bubbles 6 does not block the ink path, the ink that does not need to go in the ejection direction can remain as a continuous body with the ink in the ink path B, and the ejection amount of the ink droplet 7 can be reduced. It is possible to achieve stabilization and stabilization of the discharge speed.

According to such a continuous discharge method, bubble growth in the vicinity of the discharge port can be performed rapidly and surely, so that the refilling property of the ink path in the non-blocking state is also assisted and high stable high speed recording is possible. Can be achieved. Further, by communicating the air bubbles with the atmosphere, the defoaming process of the air bubbles is eliminated, and it is possible to prevent the heater and the substrate from being damaged by cavitation.

The above-described communication between the bubbles and the atmosphere associated with the ink ejection can be basically realized by bringing the heater 2 closer to the ejection port 5. However, the conditions that ensure the suppression of the above-described splash and the like and the stabilization of the discharge amount, which are preferable when applied to the configurations shown in FIGS. 5A and 5B, are listed below.

The first condition is that the bubbles communicate with the outside air under the condition that the internal pressure of the bubbles is lower than the outside pressure.

That is, by causing the bubbles to communicate with the outside air under the condition that the internal pressure of the bubbles is lower than the external pressure, the ink scattering near the discharge port, such as splash, which occurs when the internal pressure of the bubbles is communicated under the condition that the internal pressure of the bubbles is higher than the external pressure. In comparison with the case where the above two pressures are equal, the force of drawing unstable ink into the ink passage at the time of ejection is small, but works more stably, and more stable ink ejection and prevention of unnecessary ink scattering Can be planned.

As a condition different from the above-mentioned first condition, the second condition that the bubble and the outside air are communicated with each other under the condition that the first-order differential value of the moving speed of the bubble at the end portion on the discharge port side is negative, and the discharge condition Distance L _a from the discharge port side end of the energy generating means to the bubble discharge port side end and from the end of the discharge energy generating means on the side opposite to the discharge port to the end on the side opposite to the bubble discharging port. It is more preferable that the bubble and the outside air are communicated with each other by satisfying the third condition that the distance L _b of is equal to L _a / L _b ≧ l, or both of them.

The first condition will be described in more detail with reference to FIGS.

The relationship between the elapsed time t from foaming and the bubble volume V and the bubble internal pressure P is as shown in FIG. 6, but in reality, since the bubbles communicate with each other during their growth, these relations are As shown in FIG. That is, in FIG. 7, the bubbles communicate with the outside air at time t = tb (t1 ≦ tb: t1 is the time when the bubble internal pressure p becomes equal to the pressure of the outside air). The first condition is a condition that the pressure P inside the bubble is smaller than the pressure (OATM) of the outside air at this time.

When the ink is ejected under this condition, compared with the case where the bubble is communicated with the outside air and the ink droplet is ejected under the condition that the pressure P inside the bubble is higher than the outside pressure (the gas is ejected into the atmosphere), As described above, it is possible to prevent the recording paper and the inside of the device from being contaminated by the mist and splash of ink. Further, when the bubble internal pressure P is made smaller than the atmospheric pressure to communicate with each other in this way, the bubble can be communicated with the outside air after the volume of the bubble is relatively increased. Thereby, sufficient kinetic energy can be transmitted to the ink, and the effect of increasing the ejection speed can also be obtained.

The print head satisfying the first condition is provided, for example, at a position where the position of the heater 2 is close to the direction of the ejection port 5 in FIG. This is the simplest method for communicating air bubbles with the outside air. However, the first condition cannot be satisfied simply by bringing the heater 2 closer to the ejection port 5. That is, in order to satisfy the above conditions, the amount of heat energy generated by the heater (depending on the heater configuration, forming material, driving conditions, area, heat capacity of the substrate on which the heater is provided, etc.), ink physical properties, and various parts of the recording head By appropriately setting the size (the distance between the discharge port and the heater, the width and height of the discharge port and the liquid passage), it is possible to communicate with the outside air in a state where the first condition is satisfied.

Specifically, for example, the ink path shape contributes to the communication between air bubbles and the atmosphere as follows. In other words, although the width of the ink path shape is almost determined by the shape of the thermal energy generating element used, the specific relationship is often set by empirical rules. However, it has been clarified that the height of the ink path affects the conditions for the communication of the bubbles with the atmosphere. Therefore, in order to reduce the influence of the environment and the like on the outside and to further stabilize the communication between the air bubbles and the atmosphere, the width W of the ink path is
It is preferable to lower the height H of the ink path (H> W).

Also, for example, when the time of communication is viewed as the volume of bubbles, the maximum volume of bubbles that would be reached if the bubbles did not communicate with the outside air, or 70% or more, and more preferably 80% or more of the maximum volume. It is preferable that the bubbles communicate with the outside air when the volume is reached.

Next, the above-mentioned second condition, which is another expression of the above-mentioned first condition, that is, the condition that the bubble communicates with the outside air when the primary differential of the expansion velocity of the bubble becomes negative will be described.

FIG. 8 shows changes in the bubble volume V and the bubble internal pressure P and changes in the bubble expansion velocity dV / dt from the time when the ink starts foaming until the bubble communicates with the outside air.
Shown in.

From this figure, it is possible to know the magnitude relationship between the internal pressure and the external pressure of the bubble by obtaining the first derivative of the expansion velocity, that is, the second derivative of the volume V d ² V / dt ² . That is, the expansion velocity dV / dt of the bubble increases during the period of d ² V / dyt ² > 0, and the velocity dV / dt decreases when d ² V / dt ² <0. Therefore, when d ² V / dt ² = 0, it can be said that the bubble internal pressure P becomes equal to the external atmospheric pressure.
That is, when d ² V / dt ² > 0, the bubble internal pressure P is higher than the external pressure, and when d ² V / dt ² ≦ 0, the bubble internal pressure P is equal to or lower than the external pressure.

Explaining with reference to FIG. 8, from the start of foaming t = t ₀ to t = t ₁ , the bubble internal pressure P is higher than the external pressure d.
² V / dt ² > 0, and the internal pressure of the bubble is equal to or lower than the external atmospheric pressure until t = t _b from t = t ₁ until the bubble communicates with the external air, and d ² V / dt ² ≦ 0. Normally, this general theory holds, but since the bubble volume changes due to the ink material or the resistance of the ink path, there may be a slight difference in the relationship with the external atmospheric pressure.
Therefore, as conditions other than the first condition, d ² / V / dt ² <
It is preferable to satisfy 0, and the sum of the first condition and the second condition becomes more preferable.

As described above, the second derivative d ² V /
When dt ² <0, that is, when the first derivative of the expansion velocity is negative,
By allowing the bubbles to communicate with the outside air, the bubbles can communicate with each other under the condition that the pressure inside the bubbles is lower than the outside pressure.

According to the second condition, when the air bubble and the outside air are communicated with each other, the ink in the vicinity of the communication portion is separated from the main ink droplet due to the excessive acceleration due to the ejection of the ink. You can also do it. When the above separation occurs, it becomes noticeable that the ink in the vicinity thereof is splashed in the form of splash, or is scattered as a mist,
Moreover, in a high-density ejection port arrangement, ejection failure may occur due to ink adhering to the ejection port surface.
Can be settled according to the conditions.

One of the most characteristic constitutions of the bubble communicating and discharging method explained above is that the ink path length between the heater and the discharge port of the recording head is different from that of the other type of recording head in order to facilitate the bubble communication. It is set shorter than the comparison. However, if the driving method of the present invention is used, the energy of bubbles can be increased as described above, so that reliable communication can be performed even if the ink path length between the heater and the ejection port is relatively long. ..

FIG. 9 is an explanatory diagram showing both the time variation of the heat generation amount of the heating element and the waveform of the drive pulse for realizing this heat generation amount in the second embodiment of the present invention.

In this embodiment, the drive pulse is composed of a large number of rectangular pulse groups each having a pulse width of 0.1 μs,
By changing the pulse density per unit time, as shown by the broken line, the same change in the calorific value as in Example 1 was realized in the average sense, and the same effect was obtained.

FIG. 10 shows the liquid temperature T in the second embodiment.
It can be seen that the change is similar to that of the first embodiment.

FIG. 11 is a diagram, which is similar to FIG. 9 (changes in heat generation amount are omitted). The operation of the present invention,
Some examples of drive pulse waveforms that can obtain the effect are shown.

(Others) The present invention can be effectively applied not only to a serial type apparatus but also to a full line type recording head having a length corresponding to the maximum width of a recording medium which can be recorded by a recording apparatus. .. 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 recording head integrally formed.

In addition, even in the case of the serial type, when it is attached to the recording head fixed to the apparatus main body or the apparatus main body, it becomes possible to electrically connect to the apparatus main body and supply the ink from the apparatus main body. The present invention is also effective when a replaceable chip type recording head or a cartridge type recording head in which an ink tank is integrally provided in the recording head itself is used.

Further, as the constitution of the recording apparatus of the present invention, it is preferable to add the ejection recovery means of the recording head, the auxiliary auxiliary means, etc. because the effects of the present invention can be further stabilized. Specifically, heating is performed by using a capping means, a cleaning means, a pressure or suction means for the recording head, an electrothermal converter or a heating element other than this, or a combination thereof. Examples thereof include a preliminary heating unit for performing the discharge and a preliminary discharge unit for performing discharge different from the recording.

Regarding the type and the number of recording heads to be mounted, for example, only one is provided corresponding to a single color ink, or a plurality of inks having different recording colors and densities are supported. A plurality of pieces may be provided. That is, for example, the recording mode of the recording apparatus is not limited to the recording mode of only the mainstream color such as black, but may be either integrally formed of the recording heads or a combination of a plurality of them. The present invention is also very effective for an apparatus provided with at least one of full-color recording modes by color mixing.

In addition, as the form of the ink jet recording apparatus of the present invention, other than the one used as an image output terminal of information processing equipment such as a computer, a copying apparatus combined with a reader or the like, and a facsimile apparatus having a transmitting / receiving function can be used. It may be in a form or the like.

[0115]

As is apparent from the above description, according to the present invention, the amount of heat supplied to the ink for ejecting the ink is increased before and after the generation of the bubbles.
It is possible to suppress variations in the time of bubble generation. As a result, it becomes possible to perform stable discharge such as stable discharge amount.

As a result, it is possible to record a high-quality image without uneven density.

[Brief description of drawings]

FIG. 1A and FIG. 1B are diagrams showing changes in ink temperature according to a difference in thickness of a protective film with respect to a heating resistance film for heating ink.

FIG. 2 is a diagram showing a change in heat generation amount of the heating element according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a heating element used in the first embodiment of the present invention.

FIG. 4 is a diagram showing a change in ink temperature according to a change in heat generation amount in the first embodiment.

5A and 5B are cross-sectional views of a main part of the recording head for explaining a suitable recording head to which the present invention is applied and a discharge method thereof.

FIG. 6 is a diagram showing changes in bubble internal pressure and bubble volume according to the ejection method of the present invention.

FIG. 7 is a diagram showing changes in the bubble internal pressure, bubble volume, and bubble expansion rate according to the discharge method of the present invention.

FIG. 8 is a diagram showing changes in bubble internal pressure, bubble volume, and bubble expansion rate according to the ejection method of the present invention.

FIG. 9 is a diagram showing both drive pulses according to the second embodiment of the present invention and changes in the amount of heat generated thereby.

FIG. 10 is a diagram showing a change in ink temperature due to a change in heat generation amount.

FIG. 11 is a waveform diagram showing some examples of drive pulses that produce the effect of the present invention.

[Explanation of symbols]

 1 Si substrate 2 Surface oxide layer of Si substrate 3 Ta resistor layer 4 Al electrode 5 Protective film 6 Heating area

Claims (1)

[Claims] 1. An ejection port for ejecting ink, and an ink passage communicating with the ejection port, wherein ink in the ink passage is heated to generate bubbles, and the ejection is performed based on the generation of the bubbles. An inkjet recording head driving method for ejecting ink from an outlet, wherein the amount of heat supplied to the ink by the heating is increased before and after the generation of the bubbles.