JPH05116307A - Ink jet recording method, ink jet record head, and ink jet recording device - Google Patents

Abstract

PURPOSE:To control discharging quantity stably in an ink jet recording method wherein the bubbles are generated in ink by heat energy and the ink is discharged when the bubbles are exposed to the air and burst. CONSTITUTION:A bubble 6 gnerated in the neighborhood of a heater 21 as shown in (b) supplied with a pulse for generation expands and burst when exposed to the outside air as shown in (c) at a discharge outlet 5. As shown in (d), ink particle 7 is discharged. Tere, the ink staying between the discharge outlet 5 and the heater 21 becomes the ink particle 7. In such a constitution, for example, as shown in (e), when discharging is performed by applying pulses to a heater 22, the ink staying between the discharge outlet 5 and the heater 22 is discharged as the ink particle 7 and the volume thereof becomes larger than when the heater 21 is used.

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 method, an ink jet recording head and an ink jet recording apparatus for ejecting ink by utilizing heat energy.

[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, relatively high recording quality, and low noise. Have advantages. Further, this method has many excellent advantages that color images can be recorded relatively easily, it can be recorded on plain paper, and that the apparatus can be easily downsized.

A recording apparatus using such an ink jet recording method is generally provided with an ejection port for ejecting ink as a flying ink drop, an ink path communicating with this ejection port, and a part of this ink path. And a recording head having an energy generating unit that gives ejection energy for ejecting the ink in the ink path. For example,
Japanese Patent Publication No. 61-59911, Japanese Patent Publication No. 61-59912
No. 61-59913 and 61-5991
Each of the gazettes of No. 4 discloses a method in which an electrothermal converter is used as the energy generating means, and the thermal energy generated by the electric pulse is applied to the ink to eject the ink.

That is, in the recording methods disclosed in the above publications, the ink subjected to the action of thermal energy causes a state change accompanied by a sharp increase in volume, and the action force based on this state change causes the recording. Ink is ejected from the ejection port at the tip of the head portion, and the ejected ink droplets adhere to the recording medium to form an image. According to this method, since the ejection openings in the recording head can be arranged at a high density, it is possible to record an image of high resolution and high quality at high speed. A recording apparatus using this method is a copying machine, It can be used as information output means in printers, facsimiles and the like.

On the other hand, as an ink jet recording method which uses heat energy but does not have any realization conditions, there is a method described in JP-A-54-161935. In this publication, as shown in FIG. 1, the cylindrical heating element 30 gasifies the ink 31 in the liquid chamber (FIG. 1, (a)).
The gas 32 is ejected together with the ink droplet 33 from the ink ejection port (FIGS. 1B and 1C). According to this method
The gas 32 is ejected in the form of fine droplets from or near the discharge port, resulting in poor image quality. It is recognized that the bubbles in this publication are bubbles formed by nucleate boiling.

The same nucleate boiling, for example, Japanese Patent Laid-Open No.
According to the publication No. 1-185455, as shown in FIG. 2, the heating element head 42 heats the liquid ink 44 filled in the minute gap 43 between the heating element head 42 and the plate-shaped member 41 having the small opening 40 ( 2A and 2B, the generated bubble 45 causes the ink droplet 46 to fly from the small opening 40, and the gas that has formed the bubble 45 whose volume is rapidly increasing due to nucleate boiling is also small opening. It is ejected from 40 (FIG. 2C) to form an image on the recording paper.

Furthermore, Japanese Patent Laid-Open No. Sho 6-1994 discloses the same nucleate boiling.
In JP-A 1-249768, as shown in FIG. 3, thermal energy is applied to the liquid ink 50 to form a considerably large bubble, and an ink droplet 58 is generated based on the expansion force of the bubble.
There is simply described an ink jet recording apparatus that forms and flies, and at the same time ejects gas that has formed bubbles also into the atmosphere from the large opening 52.

However, the above-mentioned JP-A-54-1619 is used.
No. 35, No. 61-185455, No. 61-24976.
The configuration common to No. 8 is that the gas forming bubbles is ejected as fine ink droplets into the atmosphere together with the ejection of the main ink droplets. As a result, the jetting of this gas gasifies the ink to generate splashes or mists, which may result in background stains on the recording paper or stains inside the apparatus.

Further, for example, Japanese Patent Laid-Open No. 61-197246 discloses a thermal transfer recording apparatus using a modified method of the conventional inkjet recording method using thermal energy. That is, in this apparatus, as shown in FIG. 4, the ink 62 held by the plurality of holes 61 provided in the recording medium 60 is heated by the recording head 64 having the heating element 63, and the ink droplet 65 is recorded. It is ejected onto the medium 66. This recording apparatus discharges ink only once and, in addition, it is difficult to completely bring the recording medium 60 and the heating element 63 into close contact with each other. Therefore, as compared with the inkjet recording method using the conventional recording head having a discharge port. However, there is a problem that the thermal efficiency is likely to decrease and it is not suitable for high speed recording.

[0010]

BACKGROUND OF THE INVENTION In order to solve the problems of the ink jet recording method as described above, the applicant of the present invention has taken advantage of the fact that bubbles caused by film boiling generated by heating ink for ejection are exposed to the outside air near the ejection port. An ink jet recording method (hereinafter, this method is also referred to as a continuous discharge method) in which discharge is performed by communicating with each other has been proposed (Japanese Patent Application No. 2-112832,
Japanese Patent Application No. 2-112833, Japanese Patent Application No. 2-112834
No. 2, Japanese Patent Application No. 2-114472).

According to the above continuous discharge method, the gas forming the bubbles does not jet together with the discharged ink droplets, so that the generation of splash and 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.

The above-mentioned continuous discharge method will be described below with reference to FIGS.

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

The ink path structure shown in FIG. 5 (a) comprises a heating resistance layer (heater) 2 on a substrate (not shown), and a partition or a top plate is provided on this substrate to form a common liquid chamber C. 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 during the growth process (the ink in the ink path B is continuous with the ink protruding from the ejection port 5), the refill 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. 5B, the ink passage B is formed into a bent shape, and a 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. 5 (b), a vapor film (about 300.degree. C.) is generated to generate bubbles 6 as in the structure of FIG. 5 (a).
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 realized basically by bringing the position of 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 outside air pressure, the ink scattering near the discharge port, such as splash, which occurs when the bubbles are communicated under the condition that the inside pressure of the bubbles is higher than the outside 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 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 ≧ 1 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 recording 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 the 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).

Further, for example, when the time of communication is viewed in terms of the volume of bubbles, the maximum volume of bubbles that will be reached when the bubbles do 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 a different expression of the above-mentioned first condition, that is, the condition that the bubble communicates with the outside air when the first 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.

Referring 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 of the volume V is 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 above-mentioned 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 ejected from the ink and is excessively accelerated so that the ink is separated from the main ink droplet. 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.

[0037]

DISCLOSURE OF THE INVENTION The present invention is an inkjet recording method and an inkjet recording in which the continuous discharge method is improved so that the volume of the discharged ink can be controlled easily and good gradation recording can be performed. An object is to provide a head and an inkjet recording device.

[0038]

Therefore, according to the present invention,
In an ink jet recording method for ejecting ink from the ejection port using a recording head having an ejection port for ejecting ink and an ink channel communicating with the ejection port, a plurality of arrays arranged in the ink channel are used. A step of generating bubbles in the action part by selectively applying heat energy to the ink of the heat energy action part, and a process of ejecting ink from the ejection port based on the generation of the bubbles in the action step. And a step of communicating the bubble with the outside air at the discharge port.

In addition, the ink jet head further comprises another ejection port for ejecting ink, an ink passage communicating with the ejection port, and a plurality of thermal energy acting portions arranged in the ink passage. By selectively applying thermal energy to the ink, bubbles are generated in the action part,
It is characterized in that, in the process of ejecting ink from the ejection port based on the generation of the bubble, the bubble is used for communicating with the outside air at the ejection port for ejection.

Further, in the ink jet recording apparatus for recording by ejecting ink from the ejection port using a recording head having an ejection port for ejecting ink and an ink path communicating with the ejection port, A plurality of thermal energy acting portions arranged in the ink path, the thermal energy acting means for generating bubbles in the acting portion by selectively acting thermal energy on the ink,
In the process of ejecting ink from the ejection port based on the generation of the bubble, the bubble is communicated with outside air at the ejection port.

[0041]

According to the above structure, the ink from the thermal energy acting portion such as the heater, to which the thermal energy is selectively applied, to the ejection port is ejected as almost an ink droplet. This makes it possible to control the amount of ejected ink in accordance with the selection of the action section that exerts thermal energy.

[0042]

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

FIG. 9 is a schematic sectional view of a main part of a recording head for explaining the ink jet recording method of the present invention.

In this recording head, in the ink path 12 communicating with the ejection port 5, three heaters are provided along the ejection direction.
In series (each heater is capable of communicating bubbles formed by independent foaming to the outside air, and is in the vicinity of the discharge port 5) (from the heater near the discharge port 5 to the heater 21, the heater 22, and the heater 23). Yes).

FIG. 9A shows the state before foaming. In this state, first, when a current is momentarily applied to the heater 21 to heat the ink near the heater in a pulsed manner,
The ink causes film boiling, and bubbles 6 are generated vigorously to start expansion (FIG. 9B). The bubble 6 continues to expand, grows particularly toward the ejection port 5 side where the inertia is smaller due to the ink, penetrates through the ejection port 5 and communicates with the outside air (FIG. 9).
(C)). At this time, the ink on the ejection port 5 side of the bubble 6 is ejected forward due to the momentum given from the bubble 6 up to this moment, and eventually becomes an independent droplet 7 to a recording medium such as paper. Fly (Fig. 9 (d)). As a result, the gap created at the tip of the ejection port 5 side is filled with new ink due to the surface tension of the ink behind and the wetting of the ink path wall, and the state before ejection is restored.

At this time, the volume of the ejected ink droplet 7 is
In the method of the present invention in which the bubbles 6 communicate with the outside air, sufficient kinetic energy can be transmitted from the heater to the ink on the ejection port side, so that the heater 21 ejects the ejection port 5 from the ink.
Up to almost all of the ink up to. Therefore, when an electric current is applied to the heater 22 to generate bubbles, the volume of ink droplets to be similarly ejected corresponds to almost the entire volume of ink from the heater 22 to the ejection port 5 (FIG. 9). (E)). Similarly, when an electric current is passed through the heater 23 to generate bubbles, the heater 23 discharges the discharge port 5
Almost all the ink up to is discharged (see FIG. 9).
(F)).

As described above, the volume of the discharged liquid droplets can be changed by appropriately selecting the heater to be driven according to the recording information. Further, in the above case, since the volume of the ejected ink droplet is determined by the geometric structure of the ink path 12 and the like, it is not dependent on the change in the ambient environment temperature and the physical properties of the ink, and always maintain a stable ejected volume. Is possible.

On the other hand, FIG. 10 shows a conventional ink jet recording system in which air bubbles do not communicate with the outside air during ejection.

In the recording head of this system, three heaters are arranged in series along the ink path 12 communicating with the ejection port 5 (similar to the structure shown in FIG. 9 (from the heater near the ejection port 5 to the heater 21, the heater 22). , Heaters 23), but the length from each heater to the discharge port 5 is different from that used in the present invention in FIG. That is, this length is set longer than that shown in FIG. 9 so that the communication of bubbles does not occur.

FIG. 10A shows the state before foaming. First, when an electric current is momentarily applied to the heater 21 to heat the ink in the vicinity of the heater in a pulsed manner, the ink causes film boiling and vigorously generates bubbles 61 to start expansion (FIG. 10B). The bubble 61 continues to expand, but does not reach the discharge port 5, and eventually the pressure inside the bubble decreases and starts to contract due to the pressure difference with the outside air. At this time, the ink column protruding from the ejection port 5 is separated into a portion that is pulled back by the defoaming of the bubble 61 and a portion that becomes an ink droplet (FIGS. 10C and 10D).

At this time, it is possible to change the ink droplet volume to some extent by appropriately selecting the heater to be driven (FIGS. 10 (e) and 10 (f)). The variable range of the ink drop volume is narrow because the volume of the ink drop is determined by being separated into the part that is pulled back by the bubble and the part that becomes the ink drop, and the changes in the ambient environment temperature, the physical properties of the ink, and other external factors Since the separation position changes due to the change, the volume of the ink droplet changes, and it is relatively difficult to control the volume of the ejected ink droplet. In this way, the excellent effect of the present invention can be understood from the comparison between FIGS. 9 and 10.

In the case of carrying out the recording method of the present invention, when ejecting ink from the heater 22 to the ejection port 5 in FIG. 9, only the heater 22 is driven in the above description. However, in order to facilitate the communication of air bubbles with the outside air, the heater 21 on the discharge port 5 side and the heater 22 simultaneously,
Alternatively, the driving may be performed by appropriately shifting the timing (according to the expansion of the bubbles toward the ejection port). Therefore, similarly, for example, when ejecting ink from the heater 23 to the ejection port 5, not only the heater 23 but also the heater 21, or both the heater 21 and the heater 22 may be appropriately driven. In this case, it is preferable that the heater on the discharge port side be foamed later.

In the above, the case where three heaters are arranged in series along the ink path communicating with the ejection port has been described, but the present invention is not limited to such an embodiment, and the heater is not limited to this embodiment. You can arrange two or more. Further, in the above description, the variable ink droplet volume depends on the number of heaters. That is, when three heaters are used, four-value gradation recording is possible. In order to increase the efficiency of communication of the generated bubbles to the outside air,
You may increase the number of heaters as needed. That is, even when four-valued printing is performed, four or more heaters may be arranged in series and selectively driven for use.

The present invention includes all that can achieve the bubble communication discharge method using a plurality of heaters (including all that can independently drive the heat generating portion), and at least the discharge port side closest contact. As long as the air bubbles in the heat generating portion are in communication with the outside air, the air bubbles in the other heat generating portions do not have to communicate with the outside air alone. In this case, it is indispensable to form bubbles in the heat generating part closest to the discharge port when driving multiple heaters, but the number of gradations is greater than the number of other multiple heaters by changing the discharge volume with any combination of other multiple heaters. It is an advantage that there are many.

In the bubbles caused by film boiling, adjacent bubbles do not communicate with each other at the growth stage by adiabatic expansion, so that the discharge amount can be obtained corresponding to the formed bubbles and the change in the bubble internal pressure at the time of communication can be prevented. Therefore, it is preferable.
In the case of a structure in which bubbles communicate with each other as included in the technical concept of the present invention, the bubble growth may cause interference with each other and become unstable, but the gradation is superior to the conventional one.

As described above, according to the present invention, the bubble generated in the thermal energy acting portion of the heater or the like is communicated with the outside air at the ejection port to eject the ink droplet. Therefore, the volume of the ejected ink droplet is , Thermal energy is determined by the geometrical dimension from the action part to the outlet. Therefore, it is possible to always stably control the volume of the ink droplet without depending on the change of the environment at the time of recording and the physical properties of the ink. As a result, it is possible to stably control the gradation and the partial density in the recorded image.

Further, in order to completely suppress the generation of ink mist and increase the efficiency of communication of bubbles with the outside air by the above-mentioned bubble communication and discharge method according to the present invention, more preferably, for example, “Background Art” is used. It is preferable that the bubbles are communicated with the outside air and discharged under the conditions of any one of the cases 1 to 3 described in the section.

Specific examples based on the ink jet system of the present invention will be described in detail below.

<Example 1> Recording was performed using the recording head shown in FIG.

In this recording head, the partition walls 8 are formed on the substrate 1 so as to separate the ink passages 12, the transparent glass top plate 4 bonded to the partition walls 8, and the substrate 1 in each ink passage 12 are separated.
It is composed of three heaters (indicated by reference numerals 21, 22, and 23 from the side closer to the discharge port 5) formed in series above. The three heaters 21, 22, and 23 are appropriately selected according to an image signal by an electrode (not shown) and are energized. The size of each ink passage 12 having the heaters 21, 22 and 23 and communicating with the ejection port 5 is 20 μm in height and 30 μm in width, and the size of the heater 21 is 25 μm in width.
m × length 7 μm, size of heater 22 is width 25 μm × length 10 μm, size of heater 23 is width 25 μm × length 2
The heater has a length of 0 μm and is farther from the discharge port 5, and has a longer length. This is so that the bubbles generated by the heating of each heater alone can be sufficiently communicated. The position of the heater 21 is 5 μm from the end on the discharge port side to the discharge port 5, and the position of the heater 22 is 17 μm from the end on the discharge port side to the discharge port 5. The position of 23 is from the end on the discharge port side to the discharge port 5
Up to 33 μm. Also, 3 per inch
48 ink channels were arranged at a density of 60.

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 consisting of 77.0% by weight is stirred in a container and uniformly mixed and dissolved. And then filtered with a filter made of polyfluoroethylene fiber having a pore size of 0.45 μm to obtain a viscosity of 2.0 cps
An ink of (20 ° C.) was supplied to the liquid chamber 10 through the ink supply port 11 to try to eject the ink.

First, only the heater 21 of the recording head was driven. The driving conditions are a driving pulse voltage of 9.0 V and a pulse width of 2.5 μsec, and the driving frequency is 2 kHz.
applied at z.

Observation of the state in which ink was ejected from 16 continuous ejection ports using a pulse light source and a microscope confirmed that bubbles were communicating with the outside air about 2 μsec after the start of foaming. Furthermore, the volume of the independently ejected ink droplets was within the range of 5 ± 1 pl for each nozzle.

Next, the heater 22 of the recording head is set to 9.0.
It was driven at 2 kHz with a pulse of V, 2.5 μsec. When the ink was ejected from 16 consecutive ejection ports under this condition, it was observed with a pulse light source and a microscope, and it was confirmed that the bubbles were communicating with the outside air about 2 μsec after the start of foaming. Further, the volume of the independently ejected ink droplet was within the range of 14 ± 1 pl for each nozzle.

Next, the heater 23 of the recording head is set to 9.0.
It was driven at 2 kHz with a pulse of V, 2.5 μsec. When the ink was ejected from 16 consecutive ejection ports using a pulse light source and a microscope, it was confirmed that the bubbles were communicating with the outside air about 2 μsec after the start of foaming. Furthermore, the volume of the independently ejected ink droplet was within the range of 26 ± 1 pl for each nozzle.

It was confirmed that the volume of the ejected ink droplet was changed by selecting the heater to be driven as described above.

Example 2 Recording was performed using the same recording head as shown in FIG.

In this recording head, the ink path 12 has a height of 20 μm and a width of 30 μm, the heater 21 has a size of width 25 μm × length 10 μm, and the heater 22 has a size of width 25 μm × length 10 μm. The size of 23 is 25 μm wide × 20 μm long, and the length is the same for all three heaters. The position of the heater 21 is 5 μm from the discharge port side to the discharge port 5, and the position of the heater 22 is
The length is 20 μm, and the heater 23 position has a similar length of 35 μm. Also, 48 ink paths were arranged at a density of 360 per inch.

With this recording head, first, only the heater 21 was driven. The condition was a pulse of 9.0 V and 2.5 μsec, which was driven at 2 kHz. 16 consecutive
When observing the situation where ink was ejected from each ejection port using a pulse light source and a microscope, about 2 μse
After c, it was confirmed that the bubbles were communicating with the outside air. Furthermore, the volume of ink droplets ejected independently is 6 ± 1 for each nozzle.
It fell within the pl range.

Next, the heater 22 was heated, and the heater 21 was driven with a delay of 1 μm. The conditions are all 9.0.
The pulse was V, 2.5 μsec, and it was driven at 2 kHz. When observing the situation where ink was ejected from 16 consecutive ejection ports using a pulse light source and a microscope,
It was confirmed that the bubbles communicated with the outside air about 3 μsec after the start of foaming by the heater 22. Furthermore, the volume of the independent ejected ink droplets was within the range of 15 ± 1 pl for each ejection port.

Next, the heater 23 was driven, then the heater 22 was driven with a delay of 1 μsec, and the heater 21 was further driven with a delay of 1 μsec. All driving conditions are 9.0V, 2.5μse
It was driven at 2 kHz with a pulse of c. When a state in which ink was ejected from 16 consecutive ejection ports was observed using a pulse light source and a microscope, it was confirmed that bubbles were communicating with the outside air about 4 μsec after the start of foaming by the heater 23. Furthermore, the volume of the independently ejected ink droplets was within the range of 28 ± 1 pl for each nozzle.

When a plurality of heaters are driven to communicate and discharge as described above, the heaters can have the same size.

It was confirmed that the volume of the discharged liquid droplets was changed by selecting the heater to be driven as described above.

<Comparative Example 1> Ejection was performed using the same recording head as that shown in FIG.

In this recording head, the ink path 12 has a height of 20 μm, a width of 30 μm, the size of the heater 21 is width 25 μm × length 60 μm, and the size of the heater 22 is width 2.
5 μm × length 60 μm, heater 23 size is width 25 μm
m × length 60 μm. The heater 21 has a length from the discharge port side to the discharge port 5 of 80 μm, which is longer than in the first and second embodiments, and the heater 22 has the same length of 170 μm, and the heater 23 position. Has a similar length of 270 μm. Also, 48 ink paths were arranged at a density of 360 per inch.

First, only the heater 21 was driven. The condition was a pulse of 9.0 V and 2.5 μsec, which was driven at 2 kHz. When the state where ink was ejected from 16 consecutive ejection ports was observed using a pulse light source and a microscope, it was confirmed that the bubbles did not communicate with the outside air and were defoamed. Further, the volume of the independently ejected ink droplet was 18 pl for each ejection port.

Next, the heater 22 was driven, and the heater 21 was driven with a delay of 1 μsec. The driving conditions were 9.0 V, 2.5 μsec pulse, and 2 k
It was driven at Hz. When the state where ink was ejected from 16 consecutive ejection ports was observed using a pulse light source and a microscope, it was confirmed that the bubbles did not communicate with the outside air and were defoamed. Further, the volume of the independent ejected ink droplet was about 20 pl at each ejection port.

Further, the heater 23 was driven, then the heater 22 was driven with a delay of 1 μsec, and the heater 21 was further driven with a delay of 1 μsec. All driving conditions are 9.0V, 2.5μs
It was driven at 2 kHz with a pulse of ec. 16 consecutive
When observing the situation where ink was ejected from each ejection port using a pulse light source and a microscope, the bubbles did not communicate with the outside air,
The appearance of defoaming was confirmed. Further, the volume of the independently ejected ink droplet was about 21 pl at each ejection port.

As described above, when the continuous discharge method is not used, a large change in ink droplet volume cannot be realized even if the heater to be driven is appropriately selected.

FIG. 12 is a schematic perspective view showing a main part of an ink jet recording apparatus capable of executing the recording of the above-mentioned Examples 1 and 2.

In FIG. 12, the recording head 101 has 48 ink ejection ports (not shown) on the surface facing the recording paper 107 in the transport direction of the recording paper 107. Also,
The recording head 101 is provided with an ink path (not shown) communicating with each of the 48 ejection ports, and heat for ink ejection is applied to a substrate constituting the recording head 101 corresponding to each ink path. Three heaters that generate energy are formed respectively. As described above, these heaters generate heat by the electric pulse applied to the heaters in accordance with the recording data, thereby forming a boiling film in the ink and generating bubbles by the boiling films. While communicating with the outside air, air bubbles are communicated with the ejection port and ink is ejected. Each ink path is provided with a common liquid chamber that communicates with them in common, and the ink stored therein is supplied to the ink path according to the ejection operation in each ink path.

The carriage 102 carries the recording head 101, and slidably engages with a pair of guide rails 103 extending parallel to the recording surface of the recording paper 107. As a result, the recording head 101 can move along the guide rail 103, and along with this movement, recording is performed by ejecting ink toward the recording surface at a predetermined timing. After the above movement, the recording paper 107 is conveyed by a predetermined amount in the direction of the arrow in the drawing, and the above movement is performed again to perform recording. By repeating such an operation, the recording paper 10
In 7, we will record sequentially.

The above-mentioned conveyance of the recording paper 107 is carried out by a pair of conveying rollers 1 arranged above and below the recording surface.
This is done by rotating 04 and 105. Further, a platen 106 for maintaining the flatness of the recording surface is arranged on the back side of the recording surface of the recording paper 107.

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

FIG. 13 is a block diagram showing the control arrangement of the ink jet recording apparatus shown in FIG.

In FIG. 13, the CPU 200 executes control processing and data processing of the operation of each part of the apparatus. ROM
The processing procedure and the like are stored in the 200A, and the drive pulse data of each of the heaters 21, 22, and 23 described above is stored. The RAM 200B is used as a work area for executing the above processing.

Ink ejection in the recording head 101 is
The CPU 200 supplies print data and drive control signals for driving the heater to the head driver 101A. Further, the CPU 200 has a carriage motor 220 for moving the carriage 102.
The rotation of the paper feed (PF) motor 50 for rotating the feed rollers 104 and 105 is controlled via motor drivers 220A and 50A, respectively.

In carrying out the present invention, the bubble communicating and discharging method which is one of the features of the present invention, that is,
In the process of generating bubbles for ink ejection, a method in which the bubbles communicate with the outside air at the ejection port is used, but the conditions described in the above-mentioned “Background Art” are preferable for further carrying out the present invention. 1 to 3 and the condition that the ink path is not blocked until the bubble communicates with the outside air in the generation process (the ink lump protruding from the ejection port due to the generation of the bubble is continuous with the ink in the ink path). Is desirable.

As the heat energy generating means for generating bubbles, for example, laser light can be used in addition to 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 which can be recorded by the 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 shown in FIG. 12, the recording head fixed to the main body of the apparatus or the ink jet from the main body of the apparatus is electrically connected to the main body of the apparatus by mounting the recording head. 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 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 ejection recovery means of the recording head, preliminary auxiliary means and the like 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 or 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 a form of the ink jet recording apparatus of the present invention, other than the one used as an image output terminal of an information processing apparatus such as a computer, a copying apparatus combined with a reader or the like, and a facsimile apparatus having a transmitting / receiving function are provided. It may be in a form or the like.

[0095]

As is apparent from the above description, according to the present invention, the ink from the thermal energy acting portion such as the heater to which the thermal energy is selectively applied to the ejection port is ejected as almost an ink droplet. It This makes it possible to control the amount of ejected ink in accordance with the selection of the action section that exerts thermal energy.

As a result, gradation recording and partial density control can be performed satisfactorily and stably.

[Brief description of drawings]

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

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

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

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

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 schematic cross-sectional view of a main part of a recording head for explaining an inkjet recording method of the present invention.

FIG. 10 is a schematic cross-sectional view of a main part of a recording head for explaining a comparison with a conventional recording method.

11A and 11B are respectively an exploded perspective view and a top view of a recording head used in an embodiment of the present invention.

FIG. 12 is a schematic perspective view of an ink jet recording apparatus capable of implementing each of the embodiments of the present invention.

13 is a block diagram showing an example of a control configuration of the device shown in FIG.

[Explanation of symbols]

 1 Substrate 4 Top Plate 5 Discharge Port 6, 61, 62, 63 Bubble 7 Ink Droplet 8 Partition 10 Liquid Chamber 11 Ink Supply Port 12 Ink Passage 21, 22, 23 Heater 101 Recording Head 200 CPU 200A ROM 200B RAM

Front Page Continuation (72) Inventor Toshiharu Inui 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Katsuhiro Shirota 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Nao Yaegashi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Norio Okuma 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Invention Person Masayoshi Miyakawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Akira Akira 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (10)

[Claims] 1. A recording head comprising an ejection port for ejecting ink, and an ink path communicating with the ejection port,
In an inkjet recording method for ejecting ink from the ejection port, bubbles are generated in the action portion by selectively exerting heat energy on the ink of a plurality of heat energy action portions arranged in the ink path. An ink jet recording method comprising: a step; and a step of communicating the bubble with outside air at the ejection port in the process of ejecting ink from the ejection port based on the generation of the bubble by the step. 2. The ink jet recording according to claim 1, wherein the selective action of the thermal energy on the ink of the plurality of thermal energy action portions has different action timings among the selected action portions. Method. 3. The ink jet recording method according to claim 1, wherein the ink path is not blocked by the bubbles during the communication. 4. The ink jet recording method according to claim 1, wherein at the time of the communication, the bubbles are communicated with the outside air under the condition that the internal pressure of the bubbles is equal to or less than the outside atmospheric pressure. 5. The bubble according to any one of claims 1 to 4, wherein during the communication, the bubble is communicated with the outside air under a condition that the acceleration of the moving speed of the tip of the bubble in the discharge direction is not positive. Inkjet recording method. 6. The thermal energy generating means has a planar shape, and a distance La between an end on the ejection port side of the plane and an end on the ejection port side of the bubble is an end on the side opposite to the ejection port side of the plane. The bubble is communicated with the outside air at the discharge port under a condition of La / Lb ≧ 1 with respect to a distance Lb between the portion and the end of the bubble opposite to the discharge port side. Item 6. The inkjet recording method according to any one of Items 1 to 5. 7. A plurality of thermal energy acting portions, each of which has another ejection opening for ejecting ink, an ink passage communicating with the ejection opening, and a plurality of thermal energy acting portions arranged in the ink passage. By selectively applying thermal energy to the ink, a bubble is generated in the action portion, and in the process of ejecting the ink from the ejection port based on the generation of the bubble, the bubble is exposed to the outside air at the ejection port. An inkjet recording head characterized by being used for communicating and ejecting. 8. An inkjet recording apparatus for recording by ejecting ink from the ejection port using a recording head having an ejection port for ejecting ink and an ink path communicating with the ejection port, A plurality of thermal energy acting portions arranged in the ink passage, the heat energy acting means for generating bubbles in the acting portions by selectively acting thermal energy on the ink, based on the generation of the bubbles. In the process of ejecting the ink from the ejection port, the bubble is communicated with the outside air at the ejection port. 9. The ink jet recording apparatus according to claim 8, wherein the selective action of the thermal energy is performed according to an ejection amount to be ejected. 10. The selective action of the thermal energy on the ink of the plurality of thermal energy acting portions has different timings of action between the selected acting portions. Inkjet recording device.