JP3170326B2 - Ink jet recording head and ink jet recording apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording head for discharging ink using thermal energy and an ink jet recording apparatus using the head.

[0002]

2. Description of the Related Art An ink-jet recording method in which ink droplets are ejected and deposited on a recording medium to form an image is capable of high-speed recording, has relatively high recording quality, and has low noise. Has advantages. Further, this method has many excellent advantages such as relatively easy recording of a color image, recording on plain paper and the like, and further, easy downsizing of the apparatus.

A recording apparatus using such an ink jet recording method is generally provided with a discharge port for discharging ink as flying ink droplets, an ink path communicating with the discharge port, and a part of the ink path. A recording head having energy generating means for applying ejection energy to the ink in the ink path for ejection. For example,
JP-B-61-59911, JP-B-61-59912
No., JP-B-61-59913, JP-B-61-5991
No. 4 discloses a method in which an electrothermal converter is used as energy generating means, and the thermal energy generated by the application of an electric pulse is applied to the ink to eject the ink.

In other words, according to the recording methods disclosed in the above publications, the ink that has been subjected to the action of thermal energy undergoes a state change accompanied by a sharp increase in volume. Ink is ejected from an ejection port at the tip of the head, and the ejected ink droplets adhere to a recording medium to form an image. According to this method, the ejection ports in the recording head can be arranged at a high density, so that a high-resolution, high-quality image can be recorded at a high speed. A recording apparatus using this method includes a copier, It can be used as information output means in a printer, facsimile, or the like.

On the other hand, as an ink jet recording method which uses heat energy but has no realization conditions, there is a method described in Japanese Patent Application Laid-Open No. 54-161935. In this publication, as shown in FIG. 1, an ink 31 in a liquid chamber is gasified by a cylindrical heating element 30 (FIG. 1, (a)).
The gas 32 is ejected from the ink ejection port together with the ink droplet 33 (FIGS. 1B and 1C). According to this method,
The gas 32 is ejected in the form of minute droplets from the discharge port or the vicinity of the discharge port, resulting in poor image quality. The bubbles in this publication are recognized as bubble formation due to nucleate boiling.

A similar nucleate boiling is described in, for example,
In Japanese Patent Application Laid-Open No. 1-185455, as shown in FIG. 2, a liquid ink 44 filled in a minute gap 43 between a plate-shaped member 41 having a small opening 40 and a heating element head 42 is heated by the heating element head 42 ( 2 (a) and 2 (b)), the generated bubbles 45 cause the ink droplets 46 to fly from the small openings 40, and the gas forming the bubbles 45 whose volume has rapidly increased due to nucleate boiling is also reduced to the small openings. An image is formed on recording paper by ejecting the ink from the recording paper 40 (FIG. 2C).

Further, Japanese Unexamined Patent Publication No. Sho 6 discloses a similar nucleate boiling.
In Japanese Patent Application Laid-Open No. 1-249768, as shown in FIG. 3, thermal energy is applied to the liquid ink 50 to form a considerably large bubble, and the ink droplet 58 is formed based on the expansion force of the bubble.
An ink jet recording apparatus is described in which a gas that forms a bubble is ejected into the atmosphere through the large opening 52 at the same time that the gas is formed and flies.

[0008] However, the above-mentioned Japanese Patent Application Laid-Open No. 54-1619
No. 35, No. 61-185455, No. 61-24976
The configuration common to No. 8 is that the gas forming the bubbles is ejected as fine ink droplets into the atmosphere together with the ejection of the main ink droplets. As a result, the gas is ejected and gasified to generate ink splash or mist, and as a result, the recording paper may be stained or the inside of the apparatus may be stained.

[0009] For example, Japanese Patent Application Laid-Open No. 61-197246 discloses a thermal transfer type recording apparatus using a modification of a conventional ink jet recording method using thermal energy. That is, in this apparatus, as shown in FIG. 4, an ink 62 held by a plurality of holes 61 provided in a recording medium 60 is heated by a recording head 64 having a heating element 63, and an ink droplet 65 is recorded. The ink is discharged onto the medium 66. This recording apparatus is a one-shot ink discharge, and in addition, it is difficult to completely adhere the recording medium 60 and the heat generating element 63 to each other. Therefore, compared to the conventional ink jet recording method using a recording head having a discharge port, In addition, there is a problem that thermal efficiency is apt to decrease and is not suitable for high-speed recording.

[0010]

BACKGROUND OF THE INVENTION In order to solve the problems of the ink jet recording system as described above, the present applicant converts bubbles caused by film boiling generated by heating ink for ejection to outside air near an ejection port. An ink jet recording system that performs discharge by communicating (hereinafter, this system is also referred to as a continuous discharge system) has been proposed (Japanese Patent Application No. 2-112832,
Japanese Patent Application No. 2-112833, Japanese Patent Application No. 2-112834
No., Japanese Patent Application No. 2-114472).

[0011] According to the above-described communication discharge method, the gas forming the bubble is not ejected together with the ejected ink droplets, so that the generation of splash and mist is reduced.
Background dirt on the recording medium and dirt in the apparatus can be prevented.

In addition, as a basic operation of the above-described communication and discharge method, there is a case where all ink located on the discharge port side from a portion where bubbles are generated is discharged as ink droplets in principle. Therefore, the amount of ink to be ejected can be determined by the structure of the recording head, such as the distance from the ejection port to the bubble generation site. As a result, according to the above-described continuous ejection method, it is possible to perform ejection with a stable ejection amount without being significantly affected by a change in ink temperature or the like.

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

FIGS. 5 (a) and 5 (b) show a print head suitable for applying the above-described continuous discharge method and a discharge method thereof. Two examples of specific ink path configurations of this print head are shown. . However, it goes without saying that the present invention is not limited to this configuration.

The ink path configuration shown in FIG. 5A includes a heating resistor layer (heater) 2 on a substrate (not shown), and a partition and a top plate are provided on the substrate to form a common liquid chamber C. And an ink path B are formed. At the same time, an 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. 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 causing a vapor film in a short time. (About 300 ° C.), whereby bubbles 6 are generated. The bubble 6 grows and eventually communicates with the atmosphere at the end A of the discharge port 5 on the substrate side. After this communication, stable ink droplets (broken line 7) are formed.

In this discharge, the bubble 6 does not completely block the ink path B during its growth process (the ink in the ink path B is continuous with the ink protruding from the discharge port 5), so that refill for the subsequent discharge is not performed. Be done promptly,
In addition, since the heat of the air bubbles having a relatively high temperature of 300 ° C. or more is released to the outside air, a large heat storage problem (a decrease in ink viscosity and unstable bubble formation due to the heat storage) does not occur. The duty can be increased.

In FIG. 5B, the common liquid chamber C is not shown, but the ink path B is formed in a bent shape, and the heat generating resistance portion (heater) 2 is provided on the substrate surface of the bent portion. I have. The discharge port 5 has a shape whose cross-sectional area decreases in the discharge direction, and has an opening facing the heater 2. The discharge port 5 is formed in the orifice plate OP.

In FIG. 5B, a vapor film (about 300 ° C.) is generated and bubbles 6 are formed similarly to the configuration of FIG. 5A.
Generate Due to the generation of the bubbles, the ink in the thickness portion of the orifice plate OP is pushed in the ejection direction, and the ink in that portion is diluted. Thereafter, the bubbles 6 communicate with the atmosphere in the range from the outside air side peripheral edge A1 of the discharge port 5 to the area A2 near the discharge port on the inner side. At this time, the growth of the bubble 6 does not block the ink path, and the ink that does not need to go in the discharge direction can be left as a continuous body with the ink in the ink path B. Stabilization and stabilization of the discharge speed can be realized.

According to such a continuous discharge method, since the bubble growth near the discharge port can be performed rapidly and reliably, the refilling by the ink path in the non-blocking state is also helped, and the high-speed and high-speed recording is performed. Can be achieved. In addition, by communicating the air bubbles with the atmosphere, the process of defoaming the air bubbles is eliminated, and damage to the heater and the substrate due to cavitation can be prevented.

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

The first condition is that the bubble communicates with the outside air under the condition that the inside pressure of the bubble 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 outside pressure, the ink scatters in the vicinity of the discharge port such as splash, which has occurred when the inside pressure of the bubbles is communicated under the condition that the inside pressure is higher than the outside pressure. In addition, as compared with the case where the above two pressures are equal to each other, the force for drawing the unstable ink into the ink path at the time of ejection is slightly applied, so that more stable ink ejection and prevention of unnecessary ink scattering are achieved. Can be achieved.

As another condition different from the first condition, a second condition that the bubble communicates with the outside air under the condition that the first derivative of the moving speed of the bubble at the discharge port side end is negative is obtained. from the end opposite to the discharge port of the distance L _a between the discharge energy generating means from the discharge port-side end portion to the discharge port side end of the bubble energy generating means to the end portion opposite to the bubble discharge port third condition and the distance L _b of satisfies L _a / L _b ≧ l, or be in communication with air bubbles and the outside air by satisfying both conditions more preferred.

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

FIG. 6 shows the relationship between the elapsed time t from the foaming, the bubble volume V, and the pressure P in the bubble. In fact, since the bubbles communicate during the growth thereof, these relationships are as follows. As shown in FIG. That is, in FIG. 7, the bubble communicates with the outside air at the time t = tb (t1 ≦ tb: t1 is the time when the pressure p in the bubble becomes equal to the pressure of the outside air). The first condition is that the pressure P in the bubble is smaller than the pressure of the outside air (OATM).

When the ink is ejected under these conditions, the ink droplets are ejected by discharging the ink droplets (gas is ejected into the atmosphere) as described above, in which the bubbles communicate with the outside air under the condition that the pressure P inside the bubbles is higher than the outside air pressure. As described above, it is possible to prevent the recording paper and the inside of the apparatus from being stained by ink mist or splash. Further, in the case where the bubble pressure P is made lower than the atmospheric pressure for communication as described above, 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 be obtained.

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

Specifically, for example, the shape of the ink path contributes to the communication between the air bubbles and the atmosphere as described below. That is, 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 an empirical rule. However, it has been found that the height of the ink path affects the conditions for communicating the bubbles with the atmosphere. Therefore, the ink path width W is less susceptible to external influences such as the environment and the like.
It is preferable to lower the height H of the ink path (H> W).

Further, for example, when the communication time is viewed in terms of the volume of the bubble, the maximum volume of the bubble which would be reached when the bubble does not communicate with the outside air, or 70% or more of the maximum volume, more preferably 80% or more. It is preferable that the bubbles communicate with the outside air when they have a volume.

Next, the above-mentioned second condition, which is another expression of the above-mentioned first condition, that is, the condition that the air bubbles communicate with the outside air when the first derivative of the expansion speed of the air bubbles becomes negative will be described.

FIG. 8 shows the change in the bubble volume V, the pressure P in the bubble, and the change in the bubble expansion speed dV / dt during the time from the start of the foaming of the ink until the bubble communicates with the outside air.
Shown in

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

Referring to FIG. 8, from the start of foaming t = t ₀ to t = t ₁ , the pressure P in the bubble is higher than the outside pressure and d
² V / dt ² > 0, and the internal pressure of the bubble is equal to or less than the outside pressure until t = t _b from t = t ₁ until the bubble communicates with the outside air, and d ² V / dt ² ≦ 0. Normally, this general theory holds, but since the volume of the bubble changes depending on the material of the ink or the resistance of the ink path, the relationship with the outside air pressure may slightly differ.
Therefore, as a condition 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 is more preferable.

As described above, the second derivative d ² V /
When dt ² <0, that is, when the first derivative of the expansion rate is negative,
By communicating the bubbles with the outside air, the bubbles can be communicated under the condition that the pressure in the bubbles is lower than the outside pressure.

According to the second condition, it is possible to solve the problem that the ink in the vicinity of the communication portion is separated from the main ink droplet due to excessive acceleration due to ejection of the ink when the air bubbles communicate with the outside air. You can also. When the above separation occurs, the ink in the vicinity scatters in a splash-like manner, and becomes remarkable to scatter as a mist,
In addition, when the ejection openings are arranged at a high density, the ejection failure due to the adhesion of the ink to the ejection opening surface may be caused.
Can be solved by the requirement.

[0037]

SUMMARY OF THE INVENTION The present invention is intended to further improve the above-mentioned invention, and has as its object to make bubbles more efficiently communicate with the outside air.

Another object of the present invention is to improve the return of the ink meniscus, which has retreated to the rear of the discharge port by the continuous discharge, to the position of the discharge port.

Still another object of the present invention is to improve the ejection characteristics and to enable ink ejection at a higher frequency.

[0040]

For this purpose, an ink jet recording head according to the present invention comprises: a discharge port for discharging ink; a substantially straight liquid path communicating with the discharge port;
Comprising a liquid chamber communicating with the liquid passage and a heat acting portion for applying thermal energy for causing discharge from the discharge port to the ink supplied to the liquid path, i in the liquid passage
From the upstream end of the heat acting portion with respect to the supply direction of the ink
The upstream side has a fluid resistance element on the side opposite to the discharge port with respect to the heat acting section, and the internal pressure of the bubble generated in the ink by the film boiling based on the action of the heat energy is equal to or less than the external pressure. The ink is ejected by communicating the bubble with the outside air.

Here, the fluid resistance element may be a constricted portion provided on a member forming the liquid passage to narrow the cross-sectional area of the liquid passage.

The recording head further comprises a liquid chamber for supplying ink in communication with the liquid path, wherein a portion of the recording head at the narrowest portion of the constricted portion and a portion of the heat acting portion closest to the liquid chamber are located. The distance is L ₁ , the distance between the discharge port and the portion of the heat acting portion closest to the discharge port is L ₂ , and the distance between the portion of the heat acting portion closest to the liquid chamber and the liquid chamber is L ₃ . Then, L ₁ <2 × L ₂ and L ₃ <10 × L ₂ can be satisfied.

Also, it is assumed that the liquid path is not interrupted by the bubble at the time of the communication.
It is assumed that the bubble communicates with the outside air under the condition that the acceleration of the moving speed of the tip of the bubble in the discharge direction is not positive, and further, the bubble grows to the discharge port side,
Can communicate with the outside air.

Further, the ink jet recording apparatus of the present invention comprises such an ink jet recording head, means for relatively moving the ink jet recording head and the recording medium, and generating bubbles in the ink by applying the heat energy. Means for discharging the ink toward the recording medium by communicating the bubble with the outside air.

[0045]

According to the present invention, the image quality is improved by stabilizing the volume of droplets and preventing mist and splash, and the life of the head is reduced by the invention already filed by the present applicant (Japanese Patent Application No. 2-112832). While making the most of the effect of the improvement of ink jetting, it is possible to perform communication ejection more efficiently, and further accelerate the speed of returning the ink surface (meniscus) retreated from the orifice to the orifice position after ejection, thereby realizing ejection at a higher frequency. You can do it.

Therefore, it is possible to realize a recording head, an ink jet recording method and an apparatus capable of performing more stable and advanced image recording.

[0047]

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

FIG. 9 schematically shows a main part of an embodiment of the ink jet recording head according to the present invention. The recording head has a heating element such as an electrothermal conversion element for generating thermal energy for causing film boiling of the ink in response to energization on a base 314 as a means for generating energy used for discharging ink. Then, a thermal action section (hereinafter, referred to as a heater) 331 above the element faces the liquid path 335 defined by the wall 338W to apply thermal energy to the ink. The recording head according to the present embodiment includes a discharge port 33 on a wall 338W of a liquid path between the heater 331 and the liquid chamber 334.
3 has a constricted portion 332 as a fluid resistance element including a surface 332A that sharply narrows the cross section of the liquid path and a surface 332B that gradually expands the cross section from the sharply narrowed portion toward the liquid chamber. are doing. 342 is a top plate.

FIGS. 10A to 10F illustrate an ink jet recording method (liquid jet recording method) in which recording is performed using the recording head shown in FIG.

In FIGS. 10A to 10E, 33
6 is ink, 338 is a bubble, and 337 is a droplet.

FIG. 10A shows an initial state, in which the liquid path is filled with ink 336. First, for example, an electric current is instantaneously passed through the electrothermal converter, and the heater 331 is pulsed.
When the nearby ink 3 is rapidly heated, air bubbles (bubbles) 338 are generated on the heater 331 due to so-called film boiling, and rapidly expand (FIG. 10B). Further bubble 338
Continues to expand and grows mainly toward the discharge port 5 side having a small inertia resistance, and finally exceeds the discharge port 333, and the outside air and the bubble 3
38 communicate with each other (FIG. 10 (c)). At this time, the outside air is in equilibrium with the internal pressure of the bubble 338 or higher, and flows into the bubble 338.

The ink 33 extruded from the discharge port 333
6 continues to fly further forward by this moment due to the momentum provided by the expansion of the bubble 338, and eventually flies as independent liquid droplets 337 toward a recording medium such as paper, while in the liquid path. Is supplied from the heater 331 to the liquid chamber 3.
The meniscus 339 is formed with the ink surface pulled toward the side 42 (FIG. 10D). Further, after the liquid is ejected, the ink 3
The ink 336 is supplied rightward in the drawing due to the surface tension of the ink 36 and the wettability of the member forming the liquid path.
37 returns (refills) toward the discharge port 333 (FIG. 10E). Then, the meniscus completely returns to the discharge port 333, and when the meniscus returns to the initial state, the next discharge becomes possible (FIG. 10F).

In FIG. 10 (c), when the bubble 338 communicates with the outside air, the outside air flows into the bubble. For this purpose, the bubble 338 is provided under the conditions disclosed in Japanese Patent Application No. 2-112,832. Can be communicated with the outside air. For example, if the bubble communicates with the outside air under the condition that the internal pressure of the bubble is equal to or lower than the outside air pressure, the gas in the bubble blows out to the outside air and does not adversely affect the discharged droplet. Here, if the bubble 338 is efficiently communicated with the outside air from the ejection port 333, the speed of the ejected droplet is increased, and clogging of the ink can be effectively prevented. In addition, there is no problem that ink remains around the discharge port after the droplet is discharged, and as a result, air is taken in and the non-discharge is caused.

The fluid resistance element according to the present invention, that is, FIG.
First, the constricted portion 332 has a function of efficiently communicating the bubble with the outside air. That is,
In FIG. 10B, a bubble 338 is generated due to the film boiling and grows toward the discharge port side having a smaller inertial resistance than the liquid chamber side, but due to an increase in the fluid resistance in the liquid chamber direction due to the constricted portion 332. The growth of the bubble 338 in the direction of the liquid chamber is further inhibited, and the growth of the bubble 338 toward the ejection port is promoted. As a result, the bubbles 338 communicate with the outside air more efficiently, and the ink discharge characteristics such as stabilization of the ink discharge amount and improvement of the discharge speed are further improved.

The phenomenon of the meniscus 9 returning in FIGS. 10D to 10F is governed by the surface tension of the ink and the force of wetting the inner wall of the nozzle.
That is, when the meniscus returns, the meniscus has a curved surface, so that the meniscus has a force to make the meniscus a flat surface with a minimum area by surface tension, and the contact angle is to be kept small by the wetting of the ink with the inner wall of the nozzle. The meniscus is restored by the synergistic action with the force.

It is preferable that the speed of the meniscus return (ink refill) is higher, so that the ejection frequency can be increased.

The fluid resistance element according to the present invention does not hinder at least ink refilling due to its presence.
Rather, it is more preferable to be configured so as to be able to increase the refill speed, and in combination with the effect of improving the efficiency of the continuous discharge described above, further stabilization of the discharge or improvement of the discharge frequency is realized, and the discharge efficiency is further improved. It can be improved.

The forces that govern the refilling of ink are all characteristics that depend on the ink and the material of the inner wall of the nozzle. Conventional means for increasing the refilling speed include:
Other than improving these materials, only passive methods such as reducing the flow resistance of the nozzle have been used.

The present inventors have found through various experiments a means capable of positively improving the refill speed.

The principle of speeding up the refill will be described. FIG. 11 is a top view of the recording head of FIG. 9 viewed from the top plate 342 side, and shows a state at the moment of FIG. 10D. In the head used in this example, the meniscus 33
The present inventors have found that the meniscus 339 jumps out of the constricted portion 332 to the liquid chamber 334 side as shown in the figure when 9 retreats to the maximum. As shown in FIG. 11, the shape of the meniscus at this time is characterized in that the radius of curvature of the portion protruding from the constricted portion 332 is smaller than that without the constricted portion. In this state, the restoring force of the portion protruding from the constricted portion 332 is substantially controlled only by the surface tension of the ink because the ink is not separated from the inner wall of the nozzle. Since the surface tension acts in a direction to reduce the surface area as much as possible, the smaller the radius of curvature, the larger the restoring force. Therefore, the meniscus returns quickly in such a state.

In addition, the presence of the constricted portion makes it easier for ink to remain on the inner wall of the nozzle, thereby suppressing the cause of refilling due to the wetting of the contact line between the ink and the inner wall of the nozzle.

In FIG. 9, the structure for narrowing is provided only on the wall defining the liquid path, but it may be provided on the inner wall of the nozzle on the top plate side or the heater substrate side, or may be provided in the flow path. . Further, the flow path cross-sectional area of the narrowest portion is preferably set to
30% to 90% of the cross-sectional area of the flow path in the portion is preferable. If this value is large, the effect is small. FIGS. 12A to 12D show structural examples of the constricted portion.

FIGS. 13 (a) and 13 (b) also show triangular constrictions 332 having different postures as two examples of the structure of the constriction as a fluid resistance element applicable to the present invention. When the flow velocity of the ink pushed to the liquid chamber side due to bubble growth or meniscus receding is equal, as is clear from the streamlines, FIG. 12A shows a larger vortex toward the liquid chamber side than FIG. Is generated, the fluid resistance toward the liquid chamber side is large. Therefore, (a) more effectively prevents the growth of bubbles toward the liquid chamber side, and the amount of meniscus retreat is also smaller than (b). The meniscus return force is determined by the perimeter of the portion that restricts the meniscus (the narrowest portion when the meniscus is closer to the liquid chamber than the narrowest portion, and the discharge port when the meniscus is closer to the discharge port). It does not change depending on the amount of retreat. In other words, if the opening shape of the narrowest portion is the same, the restoring force is the same regardless of the shape before and after the opening, so that the meniscus preferably jumps out of the narrowest portion toward the liquid chamber, but the smaller the amount, the more Refill in a short time.

That is, FIG. 13 showing the opening shape of the constricted portion.
When (a) and (b) are proportional, it can be said that (a) has higher communication discharge efficiency and shorter refill time. The same can be said, for example, when comparing FIG. 12 (b) with FIG. 11, but the shape, dimensions, etc. of the fluid resistance element can be appropriately selected according to the ejection characteristics, ink properties, etc. desired for the recording head. It is.

FIG. 14 shows the experimental results of ink ejection every 20 μsec from the initial state (FIG. 13A) when the fluid resistance element, that is, the constriction 2 is provided as shown in FIG. 13A. As shown in FIG. 13B, the constriction 332 is effectively acting on the communication discharge or the subsequent meniscus retreat, and the subsequent refilling process (FIG.
After (d)), it was confirmed that refilling was almost completed after 80 μsec.

As described above, the present inventors have found that by providing a constriction at a predetermined position, the radius of curvature of the meniscus can be reduced, and as a result, the refill speed can be improved. As a result of further research on the head structure capable of causing the meniscus to protrude toward the liquid chamber from the constriction, the measurement was performed along the flow path between the narrowest position of the constriction and the portion of the heater 331 closest to the liquid chamber. The distance measured along the flow path between the discharge port and the portion of the heater 331 closest to the discharge port is L _2, and the distance from the portion of the heater 331 closest to the liquid chamber 34 to the liquid chamber 34 is L ₁ . When L ₃ , L ₁ <2 × L ₂ and L ₃ <1
It has been found that if the recording head satisfies the condition of 0 × L _2, the effect of improving the refill speed can be achieved irrespective of the ink and the material of the nozzle wall.

The structure of the constricted portion 332 having such a function may be such that its narrowest portion is within a range satisfying the above-mentioned conditional expression, and the shape of the slope before and after the constricted structure is arbitrary, and May be.

Hereinafter, a specific study example regarding such numerical values will be described.

<Examination Example 1> FIG. 15 is a diagram showing the structure of a recording head manufactured in this investigation example, and FIG. 16 is a top view of the structure near the discharge port projected from the top plate side. . The recording head includes a partition 343 disposed on the heater substrate 334 so as to separate each liquid flow path 335,
It comprises a transparent top plate 342 made of glass in contact with the partition wall 343 and a heater 331 provided on the substrate 341 of each liquid flow path. The electrothermal conversion element corresponding to the heater 331 is energized according to an image signal by an electrode (not shown). The structure near the discharge port 333 has a structure in which no narrowing structure is provided on the substrate 341 side and the surface of the top plate 342 opposed thereto, and a pair of narrowing structures is provided only on the side wall side. ing. The detailed structure of the narrowed structure is as shown in FIG. The length (L ₁ ) from the heater 331 to the narrowest portion of the narrowed portion 332 is 15 μm in design value, and the discharge port 3
The length (L ₂ ) from 33 to the front edge of the heater 331 is 2
5 μm, the length from the heater 331 to the liquid chamber 334 (L
₃ ) is 150 μm, the narrowest part of the constricted part 332 is 20 μm wide, and has a cross-sectional area of 50% of the flow path cross-sectional area of the heater 331 part. The narrowed structure extends as shown in the drawing to a position of 20 μm from the narrowest portion toward the liquid chamber, and extends to a position of 10 μm in the discharge direction. The height of the liquid path is constant at 25 μm, and the width of the flow path is 40 μm at portions other than the constricted portion. The shape of the heater 331 is 32 μm in width and 40 μm in length. On one recording head, 48 liquid paths are provided at intervals of 63.5 μm. In addition, this recording head is a liquid jet recording method which has been applied by the present applicant and ejects ink by causing bubbles generated by a heater to communicate with the outside air under a condition lower than the outside pressure (Japanese Patent Application No. 2-112832). , Which satisfies the conditional expression of the present invention.

Next, a method for manufacturing the recording head will be described. Using a known semiconductor process on a flat silicon wafer, a dry film is adhered to a heater substrate 341 on which heaters, electrodes, and other protective films provided at predetermined intervals are formed to form a constricted portion structure. The partition wall 343 was formed by exposure and development using a mask of a nozzle. Further, a top plate 42 made of glass is adhered to the upper portion. Thereafter, the laminated chip is cut off using a dicing saw to form a head chip. An electric circuit, an ink supply tube, and the like were attached to the chip manufactured as described above to manufacture a recording head in this embodiment.

Printing was performed using the recording head thus manufactured.

C. I. Food Black 2 3.0% by weight Diethylene glycol 15.0% by weight N-methyl-2-pyrrolidone 5.0% by weight Ion-exchanged water 77.0% by weight Each component is stirred in a container and uniformly mixed and dissolved. After that, the mixture was filtered through a polyfluoroethylene fiber filter having a pore diameter of 0.45 μm to obtain a viscosity of 2.0 cps (20 cps).
° C), and a voltage of 9 V and a pulse width of 2.5 µm were applied together with the image signal. At this time, when the driving frequency was gradually increased, the liquid was discharged stably up to a frequency of 18 kHz. When printing on paper in this state,
Regardless of the head used, a stable high-quality image could be obtained.

At this time, the state of the ink in the nozzle was observed with a microscope while illuminating the state of the discharge with a strobe in synchronization with the discharge from the top plate side. When the communication bubble reduction process is not observed and the meniscus further retreats to the maximum, the portion of the meniscus closest to the liquid chamber is constricted portion 33.
It was observed that it protruded to the liquid chamber 334 side from the narrowest position of No. 2.

<Examination Example 2> FIG. 17 is a view showing the structure of a recording head manufactured in another investigation example of the present invention, and FIG. 18 schematically shows the structure near the discharge port. . Similarly to the print head manufactured in the first embodiment, this print head includes a partition 343 arranged on the heater substrate 341 so as to separate the liquid paths 33, a transparent top plate 342 made of glass in contact with the partition, and It is composed of a heater 331 provided on the substrate 341 in the flow path. Heater 331
Are supplied with an electrode (not shown) according to the image signal. The detailed structure of the constriction 332 is as shown in FIG. That is, a structure having a regular triangular cross section with a side of 15 μm is provided at a position 10 μm away from the liquid chamber side of the heater 331 such that one side faces the heater 331 side. The constriction structure is formed on the substrate 34.
1 and the top plate 342. The length from the heater 331 to the narrowest portion of the narrowed portion 332 (L
₁ ) is a design value of 15 μm, and the heater 33
The length (L ₂ ) to the front edge portion of the heater 1 is 25 μm,
The length (L ₃ ) from 1 to the liquid chamber 334 is 150 μm. This nozzle is 63.5 μm on one recording head.
48 are provided at intervals. Note that this recording head is also a liquid jet recording method that has been applied by the present applicant and that ejects ink under the condition that bubbles generated by the heater are communicated with the outside air (Japanese Patent Application No. 2-112832).
, Which satisfies the above conditional expression.

This recording head was manufactured in the same manner as in Example 1, and was driven at a voltage of 10 V and a pulse width of 2.5 μs using the same ink as in Study Example 1. As a result, the recording head was stably ejected up to a frequency of 15 kHz. . When printing was performed on paper in this state, a stable high-quality image could be obtained using any of the heads.

At this time, the state of ink in the nozzles was observed with a microscope while illuminating the state of discharge with a strobe in synchronization with the discharge from the top plate side. No reduction process of the communicating bubble was observed, and further, when the meniscus retracted to the maximum, it was observed that the meniscus was divided into two sides on both sides of the stenosis structure and jumped out to the liquid chamber side.

<Examination Example 3> FIG. 19 schematically shows a structure near a discharge head of a recording head manufactured in another investigation example of the present invention. This recording head has the same configuration as the recording head manufactured in Study Example 1. Heater 33
1 is energized by an electrode (not shown) in accordance with an image signal. The detailed structure of the constricted portion is such that the constricted structure is not provided on the substrate side and the surface of the top plate opposed thereto, and the constricted structure is provided only on the side wall side. Length (L ₁ ) from heater 331 to narrowest portion of narrowed portion 332
Is a design value of 20 μm, the length (L ₂ ) from the discharge port 333 to the front edge of the heater 331 is 25 μm, and the length (L ₃ ) from the heater 331 to the liquid chamber 334 is 200 μm. The narrow part is 20 μm wide. The narrowed structure extends as shown in the drawing to a position of 20 μm from the narrowest portion toward the liquid chamber side, and on the other hand, extends in the discharge direction so as to be orthogonal to the side wall. The side wall between the nozzle heater 331 and the discharge port 333 narrows toward the discharge port, and the width at the orifice is 34 μm. The height of the nozzle is constant at 25 μm, and the width of the flow path is 40 μm at portions other than the narrowed portion. The shape of the heater 331 is 32 μm in width and 40 μm in length. On one recording head, these nozzles are arranged at intervals of 63.5 μm.
Eight are provided. Note that this recording head also performs ejection by a liquid ejection recording method (Japanese Patent Application No. 2-112832 or the like) which has already been filed by the present applicant and which ejects ink under the condition that bubbles generated by the heater communicate with the outside air. A recording head having a structure, which further satisfies the conditional expression in the present invention.

This recording head was manufactured in the same manner as in Study Example 1, and was driven with the same ink as in Study Example 1 at a voltage of 10 V and a pulse width of 2.5 μs. As a result, stable ejection was performed up to a frequency of 11 kHz. . When printing was performed on paper in this state, a stable high-quality image could be obtained using any of the heads.

At this time, the state of ink in the nozzles was observed with a microscope while illuminating the state of discharge with a strobe in synchronization with the discharge from the top plate side. No reduction process of the communicating bubble was observed, and further, when the meniscus retracted to the maximum, it was observed that the meniscus protruded to the liquid chamber side from the narrowest part.

<Examination Example 4> FIG. 20 schematically shows the structure near the ejection port of a print head manufactured in another investigation example of the present invention. Nozzle width 3 other than constriction
0 μm and the nozzle height is 20 μm. The shape of the heater 331 is 20 μm in width and 20 μm in length. The narrowed structure is not provided on the substrate side and the surface of the top plate facing the substrate, and the narrowed structure is provided only on the side wall side. From the heater 331 to the narrowest portion of the narrowed portion 332 (L
The length up to ₁ ) is 6 μm in design value, the length (L ₂ ) from the discharge port 333 to the front edge of the heater 331 is 20 μm, and the length (L ₃ ) from the heater 331 to the liquid chamber 334 is 80 μm.
m, the narrowest part of the constriction 332 is 12 μm wide. From the narrowest portion, it extends in the ejection direction so as to be orthogonal to the side wall, and conversely, 10
The constriction structure extends as shown in the figure to the position of μm. Also, this nozzle is provided on one recording head.
48 nozzles are provided at intervals of 5 μm. Note that this recording head also employs a liquid jet recording method that has been filed by the present applicant and ejects ink under the condition that bubbles generated by a heater are communicated with outside air (Japanese Patent Application No. 2-11 / 1990).
No. 2832), which satisfies the conditional expression of the present invention.

The method of manufacturing this recording head is the same as the method of Study Example 1. When this head was driven with the same ink as in Study Example 1 at a voltage of 7 V and a pulse width of 3.0 μs, stable ejection was possible up to 17 kHz. When printing was performed on paper in this state, a stable high-quality image could be obtained.

At this time, the state of the ink in the nozzles was observed with a microscope while illuminating the state of the discharge with a strobe in synchronization with the discharge from the top plate side. When the meniscus retreated to the maximum, the meniscus was most narrowed. It was observed that it protruded from the part to the liquid chamber side.

<Embodiment 5> FIG. 21 is a view showing the structure of a recording head according to Embodiment 5 of the present invention. This is a head having a structure in which the position of the constricted portion 332 of the head used in Study Example 1 is shifted to the liquid chamber side. The distance between the heater 331 and the narrowest part (L
₁ ) is 60 μm, the length (L ₂ ) from the discharge port 333 to the front edge of the heater 331 is 25 μm, and the length (L ₃ ) from the liquid chamber side end of the heater 331 to the liquid chamber 334 is 150 μm.
The width of the passage and the height of the nozzle during this period are constant and the width is 40
μm and a height of 25 μm. The shape of the heater 331 is 32 μm in width and 40 μm in length. On one recording head, the nozzles are arranged at intervals of 63.5 μm.
Nozzles are provided. Note that this recording head has a structure in which the present applicant has already applied for a liquid ejection recording method (such as Japanese Patent Application No. 2-112832) that ejects ink under the condition that bubbles generated by a heater are communicated with the outside air. The recording head satisfies the conditional expression L ₃ <10 × L _2, but does not satisfy the conditional expression L ₁ <2 × L ₂ .

This recording head was manufactured in the same manner as in Study Example 1. With this head, a stable ejection state was obtained up to a frequency as high as 5 kHz, but ejection became unstable at frequencies higher than this.

When the state of the ink in the nozzles was observed with a microscope while illuminating the state of the discharge with a strobe in synchronization with the discharge from the top plate side, even when the meniscus retreated to the maximum, the meniscus was heated by the heater. 35 μm from rear end
It was only retracted to a degree and did not reach the most constricted part.

<Study Example 6> FIG. 22 is a view showing the structure of a recording head according to a further study example of the present invention. This is a head having a structure in which the liquid flow path of the head used in Study Example 1 is extended. The distance (L ₁ ) between the heater 331 and the narrowest part is 1
5 μm, the length (L ₂ ) from the discharge port 333 to the front edge of the heater 331 is 25 μm, and the length (L ₃ ) from the liquid chamber side end of the heater 331 to the liquid chamber 334 is 300 μm. The width of the path and the height of the nozzle are constant, 40 μm in width and 25 μm in height. The shape of the heater 331 is 32 μm in width.
m, length 40 μm. On one print head, 48 nozzles are provided at intervals of 63.5 μm. Note that this recording head has a structure in which the present applicant has already applied for a liquid ejection recording method (such as Japanese Patent Application No. 2-112832) that ejects ink under the condition that bubbles generated by a heater are communicated with the outside air. The recording head satisfies the conditional expression L ₃ <10 × L ₂ ,
This head does not satisfy the conditional expression L ₃ <10 × L ₂ .

When this recording head was manufactured in the same manner as in Study Example 1 and ejection was attempted, stable ejection was observed up to a high frequency of 5 kHz, but ejection was not stable at frequencies higher than 5 kHz.

At this time, the state of the ink in the nozzle was observed with a microscope while illuminating the state of the discharge with a strobe in synchronization with the discharge from the top plate side. Even when the meniscus retreated to the maximum, the meniscus was heated by the heater. 12-3 from rear end
It receded only to a position of about μm and did not reach the most constricted part.

FIG. 23 is a schematic perspective view showing a main part of an embodiment of an ink jet recording apparatus constituted by using the recording head according to the above embodiment.

In FIG. 23, the recording head 101 has a plurality of ink ejection ports (not shown) on a surface facing a recording medium (hereinafter, referred to as recording paper) 107 such as paper in the conveying direction of the recording paper 107. . The printhead 101 is provided with a liquid path (not shown) communicating with each of the plurality of discharge ports, and is used for discharging ink on a substrate constituting the printhead 101 corresponding to each liquid path. A heater for applying the heat energy is formed. The electrothermal conversion element corresponding to the heater generates heat by the electric pulse applied thereto according to the recording data as described above, thereby generating a boiling film in the ink and generating bubbles by the boiling film. As a result, ink is ejected from the ejection port. Each liquid path is provided with a common liquid chamber that is commonly communicated with them, and the ink stored therein is supplied to the ink path in accordance with the ejection operation in each ink path. The recording head is configured as described above.

The carriage 102 has the recording head 101 mounted thereon and slidably engages with a pair of guide rails 103 extending in parallel with the recording surface of the recording paper 107. Accordingly, the recording head 101 can move along the guide rail 103, and performs recording by discharging ink toward the recording surface at a predetermined timing along with the movement. After the above movement, the recording paper 107 is conveyed by a predetermined amount in the direction of the arrow in the figure, and is again moved to perform recording. By repeating such operations, the recording paper 10
7, recording is performed sequentially.

The recording paper 107 is conveyed by a pair of conveying rollers 1 disposed above and below the recording surface.
This is performed by rotation of 04 and 105. A platen 106 for maintaining the flatness of the recording surface is provided on the back side of the recording surface of the recording paper 107.

The above-described movement of the carriage 102 is made possible by driving, for example, a belt (not shown) attached to the carriage 102 by a motor. Similarly, the rotation of the transport rollers 104 and 105 is also controlled by the rotation of the motor. This is made possible by being transmitted to

FIG. 24 is a block diagram showing a control configuration of the ink jet recording apparatus shown in FIG.

Referring to FIG. 24, a CPU 200 executes control processing of each unit operation, data processing, and the like. ROM
The processing procedure and the like are stored in 200A, as well as driving pulse data that terminates the action of heat by the heater before the bubbles communicate with the atmosphere after the film boiling as described with reference to FIG. . Further, the RAM 200B is used as a work area for executing the above processing.

The ink discharge from the recording head 101 is as follows.
This is performed by the CPU 200 supplying print data and a drive control signal for driving the heater to the head driver 101A. The CPU 200 further includes a carriage motor 220 for moving the carriage 102.
The rotation of the paper feed (PF) motor 50 for rotating the paper feed rollers 104 and 105 is controlled via motor drivers 220A and 50A, respectively.

In carrying out the present invention, a bubble communicating discharge system which constitutes one feature of the present invention,
In other words, in the process of generating bubbles for ink ejection,
A method in which bubbles communicate with the outside air at the discharge port is used.However, in order for the present invention to be more suitably implemented, the conditions 1 to 3 described in the section of the above “Background Art” and the bubbles are connected to the outside air in the generation process. It is desirable to satisfy the condition that the ink path is not interrupted until communication is established (the ink mass protruding from the ejection port due to the generation of bubbles is continuous with the ink in the ink path).

As the thermal energy generating means for generating bubbles, for example, a laser beam can be used other than the electrothermal converter (heater) shown in the above embodiment.

(Others) 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 shown in FIG. 23, a recording head fixed to the apparatus main body or an electric connection with the apparatus main body or ink from the apparatus main body by being mounted on 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 effects 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 recording heads to be mounted are not limited to those provided only for one color ink, for example, and for 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.

Further, the form of the ink jet recording apparatus of the present invention is not limited to those used as image output terminals of information processing equipment such as a computer, a copying apparatus combined with a reader or the like, and a facsimile apparatus having a transmission / reception function. It may take a form.

[0104]

As described above, according to the present invention,
While utilizing the effects of stabilizing the volume of droplets, improving image quality by preventing mist and splash, and improving the life of the head according to the invention already filed by the applicant (Japanese Patent Application No. 2-112832), This makes it possible to perform the communication discharge more efficiently, further increase the speed of returning the ink surface (meniscus) retreated from the orifice to the orifice position after the discharge, and realize the discharge at a higher frequency. At that time, the fluid resistance element creates bubbles.
Also discharges ink because it also functions to efficiently communicate with outside air
Further improve ink ejection characteristics such as stabilizing the amount and improving the ejection speed.
Can be improved.

Accordingly, it is possible to realize a recording head, an ink jet recording method and an apparatus capable of performing more stable and advanced image recording.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a recording head for explaining a conventional example of an ink discharging method.

FIG. 2 is a schematic cross-sectional view of a recording head for explaining another conventional example of an ink discharging method.

FIG. 3 is a schematic cross-sectional view of a recording head for explaining still another conventional example of an ink discharging method.

FIG. 4 is a schematic cross-sectional view of a recording head for explaining still another conventional example of an ink discharging method.

FIGS. 5A and 5B are main-portion cross-sectional views of a recording head for describing a recording head suitable for applying the present invention and a discharge method thereof;

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

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

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

FIG. 9 is an explanatory view schematically showing a main part of one embodiment of the ink jet recording head of the present invention.

FIGS. 10A to 10F are explanatory views for explaining a liquid jet recording method for performing recording by using the recording head shown in FIG. 9;

FIG. 11 is an explanatory diagram for explaining an operation of the head shown in FIG. 10;

FIGS. 12 (a) to (d) show other four types of the recording head of the present invention.
It is a schematic diagram which shows an Example.

FIGS. 13 (a) and (b) are illustrations showing still another two embodiments of the recording head of the present invention, and comparing the operations of the two.

FIGS. 14A to 14E are explanatory diagrams showing states from the initial state of the head shown in FIG. 13A to the completion of refilling.

FIG. 15 is a perspective view of a recording head according to Study Example 1 of the invention.

FIG. 16 is a schematic view of the main part.

FIG. 17 is a perspective view of a recording head according to Study Example 2 of the invention.

FIG. 18 is a schematic view of the main part.

FIG. 19 is a schematic diagram of a recording head according to Study Example 3 of the invention.

FIG. 20 is a schematic diagram of a recording head according to Example 4 of the invention.

FIG. 21 is a schematic diagram of a recording head according to Study Example 5 of the invention.

FIG. 22 is a schematic diagram of a recording head according to Study Example 6 of the invention.

FIG. 23 is a schematic perspective view of an ink jet recording apparatus capable of performing each of the embodiments of the present invention.

24 is a block diagram illustrating an example of a control configuration of the device illustrated in FIG.

[Explanation of symbols]

 101 Recording Head 200 CPU 200A ROM 200B RAM 331 Heater 332 Constriction 333 Discharge Port 334 Liquid Chamber 335 Liquid Channel 336 Ink 337 Ink Drop 338 Bubble 339 Meniscus 341 Substrate

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-54-161935 (JP, A) JP-A-61-185455 (JP, A) JP-A-61-249768 (JP, A) JP-A-62 222854 (JP, A) Patent 2783647 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41J 2/05 B41J 2/175

Claims (7)

(57) [Claims] A discharge port for discharging ink; a substantially straight liquid path communicating with the discharge port; and a liquid path communicating with the liquid path.
A liquid chamber, and a heat acting portion for applying heat energy for causing the ink supplied in the liquid path to be discharged from the discharge port, and a heat acting portion in a direction in which the ink is supplied in the liquid path.
With respect to the heat working portion,
A fluid resistance element on the opposite side of the discharge port with respect to the discharge port, and communicates the bubble with the outside air under the condition that the internal pressure of the bubble generated in the ink by the film boiling based on the action of the heat energy is equal to or lower than the external pressure. An ink jet recording head characterized in that the ink is ejected by causing the ink to be ejected. Wherein said fluid resistance element, an ink jet recording head according to claim 1, characterized in that provided on the member forming the liquid path is a constriction for constricting the cross-sectional area of the fluid passage. 3. A liquid chamber for supplying ink in communication with the liquid path, wherein a position of the narrowest portion of the constricted portion of the recording head and a portion of the heat acting portion which is closest to the liquid chamber are arranged. The distance is L _{1 , the} distance between the discharge port and the portion of the heat acting portion closest to the discharge port is L ₂ , and the distance between the portion of the heat acting portion closest to the liquid chamber and the distance to the liquid chamber is L ₃ . When L ₁ <
_3. The ink jet recording head according to claim 1, wherein 2 × L ₂ and L ₃ <10 × L ₂ . . 4. The liquid passage is not interrupted by the bubble at the time of the communication.
4. The ink jet recording head according to any one of items 3 to 3. 5. The communication device according to claim 1, wherein the communication of the bubble with the outside air is performed under a condition that the acceleration of the moving speed of the tip of the bubble in the discharge direction is not positive.
5. The ink jet recording head according to any one of items 1 to 4 . 6. The bubble grows to the discharge port side,
An ink jet recording head according to any one of claims 1 to 5, characterized in that communicating with the outside air. 7. A ink jet recording head according to any one of claims 1 to 6, and means for relatively moving the recording medium with the ink jet recording head, the bubble the heat by the action of energy in the ink Means for causing the bubbles to occur and communicating the bubbles with the outside air to cause ink to be ejected toward the recording medium.