JP2000062182A - Liquid discharge head, liquid discharge method and liquid discharge device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To reduce the number of satellites and suppress meniscus vibration while enabling stable ejection amount modulation.
Furthermore, high-speed printing is realized with high printing quality. SOLUTION: In a liquid flow path 10 communicating with a discharge port 18 for discharging a liquid, two heating elements 2 and 3 for generating bubbles are arranged along a flow direction of the liquid toward the discharge port 18. . In the liquid flow path 10, a movable member 31 is provided at least partially so as to face the bubble generation region 11 on the upstream side, and is displaceable as the bubble grows. Above the bubble generation region 11, a stopper 64 for regulating the displacement of the movable member 31 is provided.
, The liquid flow path 10 is substantially divided in the flow direction of the liquid.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid ejection head for ejecting a desired liquid by the generation of bubbles caused by the action of thermal energy on the liquid, a head cartridge using the liquid ejection head, and a liquid ejection device. In particular, the present invention relates to a liquid ejection head having a movable member that is displaced by utilizing the generation of bubbles, a head cartridge using the liquid ejection head, and a liquid ejection device.

The present invention also provides a printer for performing recording on a recording medium such as paper, thread, fiber, cloth, leather, metal, plastic, glass, wood and ceramics, a copying machine, a facsimile having a communication system, and a printer. The present invention can be applied to a device such as a word processor having a unit, and further to an industrial recording device that is combined with various processing devices.

In the present invention, "recording" means not only giving an image having a meaning such as characters and figures to a recording medium, but also giving an image having no meaning such as a pattern. Also means.

[0004]

2. Description of the Related Art By applying energy such as heat to ink, a state change accompanied by a sharp volume change (generation of bubbles) is caused in the ink, and the ink is ejected from an ejection port by an action force based on the state change. An ink jet recording method, which is a so-called bubble jet recording method, in which an image is formed by adhering this onto a recording medium is conventionally known. In a recording apparatus using this bubble jet recording method, as disclosed in US Pat. No. 4,723,129, an ejection port for ejecting ink and an ink flow communicating with this ejection port are disclosed. The channels and the electrothermal converters as energy generating means for ejecting the ink disposed in the ink flow paths are generally disposed.

According to such a recording method, it is possible to record a high-quality image at high speed and with low noise, and in the head performing this recording method, the ejection openings for ejecting ink are arranged at high density. Therefore, it has many excellent points that a high-resolution recorded image and a color image can be easily obtained with a small apparatus. Therefore, in recent years, this bubble jet recording method has been used in many office devices such as printers, copying machines, and facsimiles, and has also come to be used in industrial systems such as textile printing devices.

As the bubble jet technology has been used for products in various fields as described above, various requirements as described below have been further increased in recent years.

In order to obtain a high-quality image, driving conditions have been proposed for providing a liquid ejection method, etc., in which the ink ejection speed is fast and good ink ejection can be performed based on stable bubble generation, or high-speed recording is performed. From this point of view, there has been proposed a liquid flow head having an improved flow path shape in order to obtain a liquid discharge head having a high filling (refill) speed of the discharged liquid into the liquid flow path.

In addition to such a head, attention is paid to a back wave (pressure directed in the direction opposite to the direction toward the ejection port) generated with the generation of bubbles, and The invention of the structure for preventing is disclosed in JP-A-6-
No. 31918 (particularly FIG. 3). In the invention described in this publication, a triangular portion of a triangular plate member is opposed to a heater that generates bubbles. In the present invention, the back wave is temporarily and slightly suppressed by the plate member. However, since the correlation between the bubble growth and the triangular portion is not mentioned at all and there is no idea of it, the above invention includes the following problems.

That is, in the invention described in the above-mentioned publication, since the heater is located at the bottom of the recess and cannot establish a linear communication with the discharge port, droplet formation cannot be performed stably, and furthermore, bubbles cannot be formed. Growth is allowed around the apex of the triangle, the bubbles grow from one side of the triangular plate to the entire opposite side, resulting in the liquid as if the plate were not present. The normal bubble growth inside is completed. Therefore, the presence of the plate-shaped member has nothing to do with the grown bubbles. On the contrary, since the entire plate-shaped member is surrounded by bubbles, refilling the heater located in the recess causes turbulent flow in the stage of contraction of the bubbles, which causes the accumulation of minute bubbles in the recess.
The principle itself of discharging based on the growing bubbles is disturbed.

On the other hand, EP publication EP0436047A
Reference numeral 1 alternately opens and closes a first valve that shuts off the area near the ejection port and the bubble generating portion, and a second valve that shuts off the air bubble generating portion and the ink supply portion completely. Proposed invention (4th to 9th of EP0436047A1)
Figure). However, in the present invention, since these three chambers are divided into two, the ink that follows the droplets becomes a large trail at the time of ejection, and compared with the normal ejection method in which bubble growth, contraction, and defoaming are performed. Therefore, the satellite dots are considerably increased (it is presumed that the effect of meniscus receding due to defoaming cannot be used). Further, at the time of refilling, the liquid is supplied to the bubble generation part along with the defoaming, but since the liquid cannot be supplied to the area near the discharge port until the next foaming occurs, not only is there a large variation in the discharged droplets. , The ejection response frequency is extremely small, and is not at a practical level. Furthermore, JP-A-9
In JP-52364, a plurality of ejection energy generating elements (electrothermal converters) are provided for one liquid flow path, and a growth direction of bubbles generated by driving these electrothermal converters is controlled. A liquid ejection head in which a valve member is provided commonly to all electrothermal converters or for each electrothermal converter is disclosed. By providing a plurality of electrothermal converters in the liquid flow path in this manner, it becomes possible to control the discharge amount of the liquid and discharge a desired volume of the liquid,
Further, since it is possible to stably eject droplets having a small ejection liquid amount at a high frequency, it is possible to perform high gradation recording at high speed. In particular, by disposing a plurality of electrothermal converters along the flow direction of the liquid toward the discharge port,
The width of the liquid flow path can be reduced, and high density can be achieved.

[0011]

However, it has a direct influence on the process of foaming to defoaming and the formation of discharged liquid droplets, and satellite generation peculiar to the ink jet and continuous discharging operation have been performed, which has been a traditional problem. No proposal has been made to solve the instability of repetition.

Further, even when the valve member is used in the liquid ejection head in which a plurality of ejection energy generating elements are arranged in the liquid flow path, there are actually the following problems to be solved. First, when a plurality of ejection energy generating elements are arranged along the flow direction of the liquid and they are covered with one valve member, when only the energy generating element on the upstream side is driven, bubble growth occurs. Since the pressure due to the action acts near the base of the valve member, the discharge characteristic is not so good, and discharge cannot be performed in a mode in which only the discharge energy on the upstream side is driven. Also,
When a valve member is provided for each discharge energy generating element, when the discharge energy generating element on the upstream side and the discharge energy generating element on the downstream side are simultaneously driven, if the interval between the discharge energies is too small, the valve The displacement of the member and the growth of bubbles influence each other, and the desired ejection cannot be obtained. On the other hand, when the discharge energy generating elements are arranged in parallel and the valve member is provided correspondingly, the width of the liquid flow path needs to be wide, which is not suitable for high-density arrangement.

In the present invention, the fundamental ejection characteristics of the conventional method of ejecting the liquid by forming bubbles (especially bubbles associated with film boiling) in the liquid flow path have not hitherto been considered. From the point of view, the main issue is to raise it to a level that cannot be predicted conventionally.

The inventors return to the principle of liquid ejection,
The present inventors have conducted earnest research to provide a novel droplet discharge method using bubbles that has not been obtained in the past, and a head used for the method. At this time, the first technical analysis starting from the operation of the liquid flow path and the movable member, such as analyzing the principle of the mechanism of the movable member in the liquid flow path, and the starting point of the droplet discharge principle and droplet formation principle by bubbles. It was decided to perform a second analysis technique that uses the above, and a third analysis technique that starts from the bubble formation region of the heating element for bubble formation.

These analyzes show that the free end of the movable member and the entire liquid flow path affect the discharge port side and the supply side part of the bubble, and the discharge droplet shape is made more stable to an ideal shape. We came to establish technology. That is,
Stability of image quality in continuous ejection operation is achieved by reducing the printing quality peculiar to inkjet, reducing satellites that contaminate the device itself and recording medium, achieving high-speed refill, and converging fluctuation of meniscus at high speed. It has reached an extremely high level compared to the conventional technical level of achieving both.

The main objects of the present invention are as follows.

A first object of the present invention is to control the generated bubbles, the liquid on the discharge port side and the liquid on the supply side thereof by the movable member and the structure of the entire liquid flow path, thereby providing a very novel liquid discharge principle. Is to provide.

A second object of the present invention is to provide a liquid ejecting method and a liquid ejecting head in which the satellites are reduced by controlling the ejected droplet forming process and the satellites are completely eliminated in the ejecting operation. .

A third object of the present invention is to control the meniscus speed by controlling the flow in the liquid flow path, to enhance the convergence of high-speed refill and vibration, and to realize ejection stability in high-speed printing and the like. However, it is another object of the present invention to provide a liquid ejection method and a liquid ejection head that improve printing quality.

A fourth object of the present invention is to reduce the load structure on the system of the recording apparatus for eliminating the adverse effects due to the fluctuation of satellites and meniscus.

A fifth object of the present invention is to realize stable ejection amount modulation in the ejection of a liquid using a head having a plurality of heating elements provided in the liquid flow path, and to achieve high-speed printing. It is an object of the present invention to provide a liquid ejection method and a liquid ejection head which are realized at a print quality level.

[0022]

In order to achieve the above object, a liquid ejection head of the present invention comprises an ejection port for ejecting a liquid,
A liquid flow path provided with a plurality of bubble generation regions communicating with the discharge port and for generating bubbles in the liquid along the flow direction of the liquid toward the discharge port, facing the bubble generation region. And a movable member having a free end on the downstream side with respect to the flow direction of the liquid toward the discharge port,
The movable member is provided only in a bubble generation region on an upstream side of the plurality of bubble generation regions in a flow direction of the liquid toward the ejection port.

Further, in particular, it has a regulating portion for regulating the displacement of the movable member due to the growth of the bubbles, and the movable member is displaced to substantially contact the regulating portion, whereby the liquid It is preferable that the flow path is substantially divided in the flow direction of the liquid toward the discharge port.

In the liquid discharge head of the present invention configured as described above, since a plurality of bubble generation regions are provided in the liquid flow path along the flow direction of the liquid toward the discharge port,
If the size of each bubble generation region is different, it is possible to perform gradation recording by individually generating bubbles in each bubble generation region and discharging the liquid from the discharge port.

At the moment when the liquid is discharged from the discharge port due to the generation of bubbles, it is in a state close to a liquid column in which the portion discharged from the discharge port and the liquid in the liquid flow path are connected. When the movable member is displaced by the step of growing bubbles, and the displaced movable member substantially contacts the regulating portion,
The liquid flow path is substantially divided with respect to the liquid flow direction.
Therefore, since the liquid is not supplied from the upstream side of the liquid flow path until the member is separated from the regulating portion due to the bubble defoaming, most of the bubble defoaming energy moves the liquid near the discharge port to the upstream side. It will work as a moving force. As a result, immediately after the defoaming of the bubbles is started, the meniscus formed at the discharge port is rapidly drawn into the liquid flow path from the discharge port, and the trailing portion forming the liquid column is quickly separated. This makes satellite dots smaller,
The printing quality can be improved.

Further, since the trailing portion is quickly separated, the ejection speed does not decrease, and the distance between the ejected droplet and the satellite dot is shortened. Therefore, the satellite dot is formed behind the ejected droplet by a so-called slipstream phenomenon. It is attracted to the ejected droplet. As a result, it is possible to provide a liquid ejection head in which the satellite dots are united with the ejection droplets and the satellite dots are almost absent.

Furthermore, since the movable member is arranged so as to face the bubble generating region on the upstream side, even if a plurality of bubble generating regions are arranged along the flow direction of the liquid, the length of the movable member does not become long. . As a result, the responsiveness of the movable member does not deteriorate.
Moreover, since only one movable member is required for one liquid flow path, the space for supporting the movable member is minimized, and the liquid ejection head does not become large.

In the liquid discharge method of the present invention, the liquid discharge head of the present invention is used, and bubbles are generated in the bubble generation region on the downstream side of the flow direction of the liquid toward the discharge port among the bubble generation regions. After that, bubbles are generated in the bubble generation region on the upstream side, and the liquid is discharged from the discharge ports by the bubbles generated in each bubble generation region.

As described above, by discharging the liquid from the discharge port while shifting the timing of bubble generation in each bubble generation region, the liquid flow to the discharge port is differentially generated, and thus the discharge speed is extremely high. Bubble growth is sustained to the extent that it is not increased. As a result, it becomes possible to eject a further large droplet at a stable ejection speed. In this case, it is preferable to generate bubbles in the bubble generating region on the upstream side while the bubbles are contracting in the bubble generating region on the downstream side.

Other effects of the present invention can be understood from the description of each embodiment.

The terms "upstream" and "downstream" used in the description of the present invention refer to the direction of flow of the liquid from the liquid supply source through the bubble generation region (or movable member) to the discharge port.
Alternatively, it is expressed as an expression regarding this structural direction.

The term "downstream side" with respect to the bubbles themselves means
It means a bubble generated in the downstream side with respect to the center of the bubble in the flow direction or the structural direction, or in the region downstream from the center of the area of the heating element. Similarly, the term "upstream side" regarding the bubble itself means a bubble generated in the upstream side with respect to the flow direction or the above structural direction with respect to the center of the bubble, or in the region upstream from the center of area of the heating element. To do.

Further, the substantial "contact" between the movable member and the regulating portion used in the present invention is a state in which the movable member and the regulating portion are in direct contact with each other even when a liquid of about several μm is interposed between them. May be.

[0034]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 and FIG. 2 are sectional views of the liquid discharge head according to the embodiment of the present invention cut in the liquid flow path direction, and show characteristic phenomena in the liquid flow path (a) to (f). ) Are shown separately. In particular, FIG. 1 shows a characteristic phenomenon when the upstream heating element is driven, and FIG. 2 shows a characteristic phenomenon when the downstream heating element is driven.

In the liquid ejection head of this embodiment, as the ejection energy generating element for ejecting the liquid, the element substrate 1 in which the heating elements 2 and 3 for applying the heat energy to the liquid are smooth
The liquid flow path 10 is disposed on the element substrate 1 in correspondence with the heat generating elements 2 and 3. The heating elements 2 and 3 are arranged along the longitudinal direction of one liquid flow path 10 and can generate heat independently. Downstream heating element 3
Has a smaller area than that of the heating element 2 on the upstream side, and aims to eject a small amount of droplets. By appropriately driving these two heating elements 2 and 3, droplets having different ejection amounts are discharged. It is possible to discharge.

The liquid flow path 10 communicates with the discharge port 18 and also with the common liquid chamber 13 for supplying liquid to the plurality of liquid flow paths 10, and the liquid discharged from the discharge port 18 is connected to the common liquid chamber 13. A commensurate amount of liquid is received from this common liquid chamber 13. Reference symbol M represents a meniscus formed by the discharge liquid, and the meniscus M is relative to the internal pressure of the common liquid chamber 13, which is normally a negative pressure due to the capillary force generated by the discharge port 18 and the inner wall of the liquid flow path 10 communicating with it. They are balanced near the discharge port 18.

The liquid flow path 10 is formed by joining the element substrate 1 having the heating elements 2 and 3 and the top plate 50,
In the vicinity of the surface where the heating elements 2 and 3 come into contact with the discharge liquid, there are bubble generation areas 11 and 12 in which the heating elements 2 and 3 are rapidly heated to generate bubbles in the discharge liquid. At least a part of the movable member 31 faces the upstream bubble generating region 11 in the liquid flow path 10 and is arranged so as to be displaceable as the bubble generated by the heat generation of the heating elements 2 and 3 grows. . The movable member 31 has a free end 32 on the downstream side toward the discharge port 18, and is supported by a support member 34 arranged on the upstream side. In particular, in this embodiment, the free end 32 is arranged near the center of the bubble generation region 11 in order to suppress the growth of the upstream half of the bubble that affects the back wave to the upstream side and the inertial force of the liquid. The fulcrum 3 when the movable member 31 is displaced
3 is a support portion of the movable member 31 in the support member 34.

A stopper (regulating portion) 64 is located above the center of the upstream bubble generating region 11 to suppress the growth of the upstream half of the bubbles generated by the heat generation of the upstream heating element 2. The displacement of the movable member 31 is restricted within a certain range. In the flow from the common liquid chamber 13 to the discharge port 18,
A low flow path resistance region 65 having a flow path resistance relatively lower than that of the liquid flow path 10 is provided on the upstream side of the stopper 64 as a boundary. The flow channel structure in this region 65 has no upper wall or has a large flow channel cross-sectional area, so that the resistance received from the flow channel with respect to the movement of the liquid is reduced.

With the above structure, the displaced movable member 31
By the contact between the stopper 64 and the stopper 64,
It proposes a unique head structure in which the liquid flow path 10 having 12 is a substantially closed space except for the discharge port 18, which has not been achieved in the past.

The ejection operation of the liquid ejection head of this embodiment will be described in detail below. As described above, since the liquid ejection head of this embodiment includes the two heating elements 2 and 3 for one liquid flow path 10, which heating element 2 or 2 is used.
It has a plurality of ejection modes depending on whether 3 is driven.

First, the discharge operation when the heating element 2 on the upstream side is driven will be described with reference to FIG.

FIG. 1 (a) shows a state before energy such as electric energy is applied to the heating element 2, and shows a state before the heating element 2 generates heat. What is important here is that the movable member 31 is provided at a position facing the upstream half of the bubble generated by the heat generation of the heating element 2 and restricts the displacement of the movable member 31. That is, the stopper 64 is provided above the center of the bubble generating region 11 on the upstream side. That is, depending on the liquid flow path structure and the arrangement position of the movable member 31, the upstream half of the bubble is pressed into the movable member 31.

FIG. 1B shows a state in which part of the liquid filling the bubble generation region 11 is heated by the heating element 2 and the bubbles 40 accompanying the film boiling have grown to the maximum. At this time,
The liquid in the liquid flow path 10 moves to the downstream side and the upstream side by the pressure based on the generation of the bubbles 40, and the bubbles 4
The movable member 31 is displaced by the growth of 0, and the discharge droplet 66 is about to be ejected from the discharge port 18 on the downstream side.
Here, the movement of the liquid on the upstream side, that is, in the direction of the common liquid chamber 13 becomes a large flow due to the low flow path resistance region 65, but when the movable member 31 is displaced until it approaches or contacts the stopper 64, further displacement occurs Therefore, the movement of the liquid in the upstream direction is also largely restricted there. At the same time, the growth of the bubbles 40 on the upstream side is also limited by the movable member 31. However, since the moving force of the liquid in the upstream direction is large, the movable member 31 receives a large amount of stress in the form of being pulled in the upstream direction. Further, some of the bubbles 40, the growth of which is restricted by the movable member 31, pass through a slight gap between both side walls forming the liquid flow path 10 and the side portion of the movable member 31,
It is raised on the upper surface side of the movable member 31. This raised bubble will be referred to as "raised bubble (41)" in the present specification.

FIG. 1C shows a state in which the negative pressure inside the bubbles overcomes the movement of the liquid to the downstream side in the liquid flow path after the film boiling described above, and the contraction of the bubbles 40 is started. At this point, since a large force of the liquid in the upstream direction due to bubble growth remains, the movable member 31 is still in contact with the stopper 64 for a certain period after the start of contraction of the bubble 40, and most of the contraction of the bubble 40 occurs. Causes the liquid to move from the discharge port 18 in the upstream direction. That is, immediately after the step shown in FIG. 1B, the liquid flow path 10 having the bubble generation region 11 is brought into contact with the discharge port 1 by the contact between the displaced movable member 31 and the stopper 64.
Since the space is substantially closed except for 8, the contraction energy of the bubble 40 acts as a force for moving the liquid in the vicinity of the discharge port 18 in the upstream direction. Therefore, at this point, the meniscus M is largely drawn into the liquid flow path 10 from the ejection port 18, and the liquid column connected to the ejection droplet 66 is quickly separated with a strong force. As a result, FIG. 1 (d)
As shown in FIG. 7, the droplets, that is, satellites (sub-droplets) 67 left outside the ejection port 18 are reduced.

FIG. 1D shows a state in which the discharge bubble 66 is separated from the meniscus M after the defoaming process is completed. In the low flow path resistance region 65, the repulsive force of the movable member 31 exceeds the moving force of the liquid in the upstream direction, and the downward displacement of the movable member 31 and the subsequent flow in the low flow path resistance region 65 in the downstream direction start. To be done. At the same time, the flow in the downstream direction in the low flow resistance region 65 has a small flow resistance, so that it rapidly becomes a large flow and flows into the liquid flow path 10 via the stopper 64 portion. As a result, the flow that rapidly draws the meniscus M into the liquid flow path 10 suddenly decreases, so that the meniscus M draws the liquid column portion remaining outside from the discharge port 18 to a position before foaming at a relatively low speed. Start returning. Therefore, the vibration of the meniscus can be converged at high speed.

On the other hand, the ejected droplet 66 and the satellite 67 existing immediately thereafter are extremely close to each other due to the rapid meniscus drawing in FIG. 1C, and the ejected droplet 66 becomes an ejected droplet due to the vortex of air generated after the flight of the ejected droplet 66. A phenomenon called a slipstream phenomenon occurs, which receives a force attracted.

This phenomenon will be described in detail. In the conventional liquid ejection head, the droplet does not form a sphere at the moment when the liquid is ejected from the ejection port, and is ejected in a state close to a liquid column having a spherical portion at the tip. It is known that when the trailing portion is pulled by both the main droplet and the meniscus and separated from the meniscus, satellite dots are formed from the trailing portion and fly to the recording medium together with the main droplet. . Since the satellite dots fly after the main droplet, the ejection speed is low because the satellite dot is pulled by the meniscus, and the landing position of the satellite dot deviates from the main droplet, deteriorating the print quality. In the liquid ejection head according to the present invention,
As described above, since the force for retracting the meniscus is larger than that of the conventional liquid ejection head, the force for pulling the tailing portion after the main droplet is ejected is strong, and the force for separating the tailing portion and the meniscus becomes strong, and this separation is performed. The timing will be earlier. Therefore, the satellite dots formed from the trailing portion become smaller, and the distance between the main droplet and the satellite dot becomes shorter. Furthermore, since the trailing portion does not continue to be pulled by the meniscus, the ejection speed does not decrease, and the satellite 67 is attracted by the so-called slipstream phenomenon behind the ejection droplet 66.

FIG. 1E shows a further advanced state of the state of FIG. 1D. The satellite 67 has a further drop 66.
And are attracted at the same time, and the pulling force due to the slipstream phenomenon also increases. On the other hand, from the upstream side, the discharge port 18
The movement of the liquid in the direction causes displacement of the movable member 31 below the initial position to cause the liquid to be drawn in from the upstream side and the liquid to be ejected toward the ejection port 18. In addition, the cross-sectional area of the liquid flow path in which the stopper 64 is present is increased to increase the liquid flow in the direction of the discharge port 18 and accelerate the return of the meniscus M to the discharge port 18.
As a result, the refill characteristics in this embodiment are dramatically improved.

In FIG. 1F, the state of FIG. 1E is further advanced, and the satellite 67 is taken into the ejected droplet 66. The combination of the discharge droplet 66 and the satellite 67 does not always occur in each discharge even in the other embodiments.
It may or may not occur depending on the conditions. However, by at least reducing or eliminating the amount of satellites, the landing positions of the main droplets and satellite dots hardly shift on the recording medium, and the influence on print quality becomes extremely small. That is, the sharpness of the image can be enhanced to improve the printing quality, and the harmful effects such as becoming a mist and contaminating the inside of the printing medium or the recording apparatus can be reduced.

On the other hand, the movable member 31 is displaced in the direction of the stopper 64 again by the reaction of the overshoot.
This converges due to the damping vibration determined by the shape and Young's modulus of the movable member 31, the viscosity of the liquid in the liquid flow path, and the specific gravity, and finally stops at the initial position.

The upward displacement of the movable member 31 controls the flow of liquid from the common liquid chamber 13 side toward the discharge port 18,
The movement of the meniscus M quickly converges near the discharge port. Therefore, it is possible to greatly reduce the factors such as the overshoot phenomenon of the meniscus, which makes the ejection state unstable and deteriorates the printing quality.

Here, further characteristic effects when the heating element 2 on the upstream side is driven will be described.

FIG. 3 is a see-through perspective view of a part of the head shown in FIG. 1 (b), which basically shows the same state as that shown in FIG. 1 (b) except that the nozzle is seen through and shown by a broken line. is there. In this embodiment, there is a slight clearance between both side wall surfaces of the wall forming the liquid flow path 10 and both side portions of the movable member 31 to allow the movable member 31 to be smoothly displaced.
Further, in the step of growing foam by the heating element 2, the bubble 40 displaces the movable member 31 and bulges toward the upper surface side of the movable member 31 through the clearance and slightly enters the low flow path resistance region 65. This rising bubble 41
Wraps around the back surface of the movable member 31 (the surface opposite to the bubble generation region 11) to suppress the blurring of the movable member 31 and stabilize the ejection characteristics.

Further, in the defoaming process of the bubble 40, the raised bubble 41 is moved from the low flow path resistance region 65 to the bubble generation region 11
The liquid flow to the nozzle is accelerated, and the defoaming is promptly completed in combination with the above-described high-speed drawing of the meniscus from the discharge port 18 side. In particular, the liquid flow caused by the raised bubbles 41 hardly accumulates the bubbles in the movable member 31 or the corners of the liquid flow path 10.

Next, the discharge operation when the downstream heating element 3 is driven will be described with reference to FIG.

FIG. 2B shows a state in which a part of the liquid in the bubble generation region 12 is heated by the driving of the heating element 3 on the downstream side, and the bubbles 42 accompanying the film boiling have grown to the maximum. At this time, on the downstream side, the ejection droplet 68 is about to fly out from the ejection port 18. The size of the discharged droplet 66 is the same as that of the discharged droplet 66 (see FIG. 1) that is discharged when the upstream heating element 2 is driven.
Smaller than the size of (see). On the other hand, although a liquid flow is generated on the upstream side, the movable member 31 is displaced to some extent by the flow, so that the liquid flow on the upstream side is restricted.

FIG. 2C shows the process of shrinking the bubbles 42. At this time, the flow path resistance from the bubble 42 to the common liquid chamber 13 is different from the flow path resistance from the bubble 42 to the discharge port 18.
Since the distance is long and the flow passage cross section of the movable member 31 and the stopper 64 is considerably large, the defoaming point of the bubble 42 is displaced upstream from the center of the heating element 3. This means that the pulling-in of the meniscus M is increased, whereby the ejection amount of the ejection droplet 68 can be kept small and the ejection amount can be kept small.

FIG. 2D shows a state in which the discharging bubble 68 and the meniscus M are separated after the defoaming process is completed. In this state, since the movable member 31 is displaced downward after the bubbles 42 are defoamed, the flow path resistance here is also small, and the meniscus M is restored at high speed.

In FIG. 2 (e), the movable member 31 is displaced upward by reaction so that the high-speed liquid flow from the upstream side is suppressed,
The movement of the meniscus M is rapidly converged. this is,
As in the case of FIG. 1, the ejection state can be stabilized by stabilizing the meniscus M, which leads to an improvement in print quality.

As described above, the liquid of the present embodiment is produced by the large droplets discharged by the upstream heating element 2 described in FIG. 1 and the small droplets discharged by the downstream heating element 3 described in FIG. The ejection head realizes high-speed printing with large droplets and high-quality printing with small droplets.

In particular, the heating element 2 for large droplets is located upstream of the heating element 3 for small droplets, and the bubbles 40 generated by the heating element 3 are divided by the stopper 64 and the movable member 31 in the central region. Therefore, large droplets and small droplets can be discharged stably and at high speed, and high-quality printing can be obtained by reducing satellites and meniscus vibration. More specifically, in order to stably eject large and small droplets, it is necessary to set the ejection speed of each droplet to a certain level or higher. In the case of the present invention, the heating element 3 for small liquid droplets is arranged on the side closer to the ejection port 18 to improve the ejection speed, and at the same time, the action of the movable member 31 increases the drawing speed of the meniscus M to increase the ejection amount. I'm suppressing it. Further, when the heating element 2 for large droplets is arranged on the upstream side, the movable member 31 suppresses the large growth of the bubbles 40 to the common liquid chamber 13 side, so that a highly reliable ejection state can be maintained. it can.

Further, since only one movable member 31 is provided for the liquid flow path 10, in order to support the movable member as compared with the case where a movable member is provided for each of the heating elements 2 and 3. The required space on the element substrate 1 is minimized. Further, since the free end 32 of the movable member 31 is located above the heating element 2 on the upstream side, the length of the movable member 31 does not become long, and the movable member 31 is displaced when the bubbles 40 and 42 grow. Responsiveness is also good. Therefore, even if the heating elements 2 and 3 are driven at a high frequency, the movable member 31 reliably acts on the liquid and the bubbles 40 and 42 in the liquid flow path 10.

The case where the two heating elements 2 and 3 are individually driven to eject the liquid has been described above.
It is also possible to drive 3 at the same time to eject a larger droplet. Hereinafter, a method of driving the two heating elements 2 and 3 at the same time to eject larger droplets will be described with reference to FIG.

When the heating elements 2 and 3 are simultaneously driven to eject a large droplet, the ejection amount increases, but
Although the print quality is deteriorated due to an increase in satellites or the like, in the present invention, after the downstream heating element 3 is driven, the upstream heating element 3 is driven at a different timing,
A stable increase in the discharge amount is realized.

First, as shown in FIG. 4A, the heating element 3 on the downstream side is driven to generate bubbles 42, and the heating element 3 is generated.
After about 5 to 15 μs after driving, the bubble 40 is generated by the heating element 3 on the upstream side, as shown in FIG. 4B. At this time, the bubbles 42 generated by the heating element 3 on the downstream side have moved to the shrinking step, but the bubbles 40 having a larger volume than that cause the liquid flow to the discharge port 18 differentially, The post-ejection is continued to the extent that the ejection speed is not extremely increased, and a stable ejection speed (usually 8 to 20 m /
s, preferably 10 to 18 m / s), it is possible to realize ejection of larger droplets.

In FIG. 4 (c), the meniscus M is drawn in at high speed by the defoaming of the bubbles 40 and 42 and the displacement state of the movable member 31, and the satellite is also reduced. Figure 4 (d)
In the subsequent steps, basically, the same operational effects as those in the step of FIG.

(Other Embodiments) Various embodiments applicable to the head using the above-described liquid ejecting method will be described below.

<Movable Member> FIG. 5 shows another shape of the movable member 31. The figure (a) is a rectangular shape, the figure (b) is a shape in which the fulcrum side is narrow and the shape of the movable member is easy to operate, and the figure (c) is wide in the fulcrum side and the movable member is The shape improves the rigidity of the.

In the previous embodiment, the movable member 31 was made of nickel having a thickness of 5 μm. However, the material constituting the movable member is not limited to this, it has solvent resistance to the discharge liquid, and is movable. Any member may be used as long as it has elasticity so that it can operate well as a member.

As the material of the movable member 31, silver, nickel, gold, iron, titanium, aluminum, which has high durability,
Metals such as platinum, tantalum, stainless steel, phosphor bronze, and their alloys, or acrylonitrile, butadiene,
Resins having nitrile groups such as styrene, resins having amide groups such as polyamide, resins having carboxyl groups such as polycarbonate, resins having aldehyde groups such as polyacetal, resins having sulfone groups such as polysulfone, and other liquid crystal polymers, etc. Resin and its compounds,
Metals with high ink resistance such as gold, tungsten, tantalum, nickel, stainless steel, and titanium, alloys of these, and those having ink resistance coated on the surface, resins having amide groups such as polyamide, polyacetal, etc. Resin having aldehyde group, resin having ketone group such as polyetheretherketone, resin having imide group such as polyimide, resin having hydroxyl group such as phenol resin, resin having ethyl group such as polyethylene, alkyl such as polypropylene Resin with a base,
A resin having an epoxy group such as an epoxy resin, a resin having an amino group such as a melamine resin, a resin having a methylol group such as a xylene resin and a compound thereof, and a ceramic such as silicon dioxide and silicon nitride and a compound thereof are preferable.
The thickness of the μm order is targeted as the movable member 31 in the present invention.

Next, the positional relationship between the heating element and the movable member will be described. By the optimal arrangement of the heating element and the movable member,
The flow of the liquid at the time of foaming by the heating element can be properly controlled and effectively used.

By applying energy such as heat to the ink, a state change accompanied by a sharp volume change (generation of bubbles) is generated in the ink, and the action force based on the state change ejects the ink from the ejection port. In the conventional ink jet recording method, that is, a so-called bubble jet recording method, in which an image is formed by adhering the ink onto a recording medium, the conventional method shown in FIG.
As shown in (1), it can be seen that there is a non-foaming effective region S that does not contribute to ink ejection, although the heating element area and the ink ejection amount are in a proportional relationship. Further, from the state of kogation on the heating element, it can be seen that the non-foaming effective area S exists around the heating element. From these results, it is considered that the width of about 4 μm around the heating element is not involved in foaming.

Therefore, in order to effectively use the foaming pressure, the region directly above the foaming effective region of about 4 μm or more from the periphery of the heating element is the region that effectively acts on the movable member.
In the case of the present invention, the action of the bubbles on the upstream side and the downstream side of the bubble in the bubble generation region (actually within a range of ± 10 μm in the liquid flow direction from the center) on the liquid flow in the liquid passage is independently controlled. It can be said that it is extremely important to arrange the movable member so that the upstream side from the central region faces the movable region of the movable member, focusing on the distinction between the stage where the movable member and the stage where the movable member is totally acted on. . In this embodiment,
Although the effective foaming area is set to be approximately 4 μm or more inside from the periphery of the heating element, it is not limited to this depending on the type of the heating element and the forming method.

<Element Substrate> Next, the structure of the element substrate will be described.

7A and 7B are vertical sectional views of the liquid discharge head of the present invention. FIG. 7A shows a head having a protective film described later, and FIG. 7B shows it without a protective film. .

The liquid flow path 10, the discharge port 18 communicating with the liquid flow path 10, the low flow path resistance region 65, and the top plate 50 provided with the groove forming the common liquid chamber 13 are arranged on the element substrate 1. .

The element substrate 1 has a base 107 made of silicon or the like.
A silicon oxide film or a silicon nitride film 106 for the purpose of insulation and heat storage is formed on the above, and heating elements 2, 3 are formed thereon.
Of the hafnium boride (HfB2), tantalum nitride (TaN), tantalum aluminum (TaAl) or the like, and an electric resistance layer 105 (0.01 to 0.2 μm thick) and a wiring electrode 104 (0.2) of aluminum or the like. ~ 1.0 μm thickness)
Is patterned as shown in FIG. A voltage is applied from the wiring electrode 104 to the resistance layer 105, and a current is passed through the resistance layer to generate heat. A protective layer 103 such as silicon oxide or silicon nitride is formed on the resistance layer between the wiring electrodes by 0.1.
˜2.0 μm thick, and a cavitation resistant layer 102 (0.1 to 0.6 μm) made of tantalum or the like.
Is formed to protect the resistance layer 105 from various liquids such as ink.

In particular, the pressure and shock waves generated when bubbles are generated and defoamed are very strong, and the durability of a hard and brittle oxide film is significantly reduced. Therefore, tantalum (Ta) which is a metal material is used.
Etc. are used as the anti-cavitation layer 102.

Further, depending on the combination of the liquid, the liquid flow path structure, and the resistance material, the above-mentioned resistance layer 105 may not need the protective layer 103, and an example thereof is shown in FIG. 7B. Examples of the material of the resistance layer 105 that does not require the protective layer 103 include iridium-tantalum-aluminum alloy.

As described above, as the constitution of the heating element, only the resistance layer (heating portion) between the electrodes may be used.
It may also include a protective layer for protecting the resistance layer.

Although a heating element having a heating portion composed of a resistance layer that generates heat in response to an electric signal is used here, the heating element is not limited to this, and bubbles sufficient to eject the ejected liquid are generated. Any material can be used as long as it can be generated in the foaming liquid.
For example, the heat generating portion may be a photothermal converter that generates heat when receiving light from a laser or the like, or a heat generating body that has a heat generating portion that generates heat when receiving high frequency.

On the element substrate 1 described above, in addition to the electrothermal converter constituted by the resistance layer 105 forming the heating portion and the wiring electrode 104 for supplying an electric signal to the resistance layer, Functional elements such as a transistor, a diode, a latch, and a shift register for selectively driving the electrothermal conversion element may be integrally formed in the semiconductor manufacturing process.

Further, in order to drive the heat generating portion of the electrothermal converter provided on the element substrate 1 as described above and eject the liquid, the resistance layer 105 is connected to the resistance layer 105 via the wiring electrode 104 as shown in FIG. A rectangular pulse as shown by is applied to rapidly generate heat in the resistance layer 105 between the wiring electrodes. In the head of each of the above-described embodiments, the voltage is 24 V, the pulse width is about 4 μsec, the current is about 100 mA, and the electric signal is 6 kHz.
By adding the above, the heating element was driven, and the liquid ink was ejected from the ejection port by the above-described operation. However, the condition of the drive signal is not limited to this, and any drive signal capable of appropriately foaming the foaming liquid may be used.

<Discharge Liquid> Among these liquids, as the liquid used for recording (recording liquid), the ink having the composition used in the conventional bubble jet device can be used.

Further, it is possible to use a liquid having a low foaming property which has been difficult to be ejected conventionally, a liquid which is easily deteriorated or deteriorated by heat, a high viscosity liquid and the like.

However, as the properties of the discharge liquid, the discharge liquid itself is
It is desired that the liquid is not a liquid that hinders ejection, foaming, movement of the movable member, or the like.

High-viscosity ink or the like can also be used as the ejection liquid for recording.

In the present invention, recording was performed using an ink having the following composition as a recording liquid that can be used as the discharge liquid. However, since the discharge speed of the ink increased due to the improvement of the discharge force, the liquid The landing accuracy of the drops is improved, and a very good recorded image can be obtained.

Composition of dye ink (viscosity 2 cP) (C-1. Food Black 2) Dye 3% by weight Diethylene glycol 10% by weight Thiodiglycol 5% by weight Ethanol 5% by weight 77% by weight of water

<Structure of Liquid Discharging Head> FIG. 9 is an exploded perspective view showing the overall structure of the liquid discharging head of the present invention.

An element substrate 1 having a plurality of heating elements 2 is provided on a support 70 made of aluminum or the like. A support member 34 that supports the movable member 31 is provided thereon so as to face the half of each heating element 2 on the common liquid chamber 13 side. Further, a top plate 50 provided with a plurality of grooves forming the liquid flow path 10 and concave grooves of the common liquid chamber 13 is provided thereon.

<Liquid Ejecting Device> FIG. 10 shows a schematic structure of a liquid ejecting device equipped with the liquid ejecting head having the structure described with reference to FIG. In this embodiment, an ink discharge recording apparatus using ink as a discharge liquid will be described in particular. A carriage HC of the liquid ejecting apparatus is equipped with a head cartridge to which a liquid tank section 90 containing ink and a liquid ejecting head section 200 can be attached / detached. It reciprocates in the width direction of the recording medium 150.

When a drive signal is supplied from a drive signal supply means (not shown) to the liquid discharge means on the carriage, the recording liquid is discharged from the liquid discharge head onto the recording medium in response to this signal.

Further, in the liquid ejecting apparatus of this embodiment, the motor 111 as a drive source for driving the recording medium conveying means and the carriage, the gears 112, 113 for transmitting the power from the drive source to the carriage, It has a carriage shaft 115 and the like. With this recording apparatus and the liquid ejecting method performed by this recording apparatus, it is possible to obtain a recorded image with a good image by ejecting liquid onto various recording media.

FIG. 11 is a block diagram of the entire apparatus for operating ink discharge recording in the liquid discharge method and liquid discharge head of the present invention.

The recording apparatus receives print information as a control signal from the host computer 300. The print information is temporarily stored in the input interface 301 inside the printer, and at the same time, converted into data that can be processed in the recorder and input to the CPU 302 which also serves as a head drive signal supply means. The CPU 302 processes the data input to the CPU 302 using a peripheral unit such as the RAM 304 based on a control program stored in the ROM 303,
Convert to print data (image data).

Further, the CPU 302 produces drive data for driving a drive motor that moves the recording sheet and the recording head in synchronization with the image data in order to record the image data at an appropriate position on the recording sheet. . The image data and the motor drive data are respectively sent to the head driver 307.
Is transmitted to the head 200 and the drive motor 306 via the motor driver 305, and driven at each controlled timing to form an image.

The recording medium that can be applied to the recording apparatus as described above and to which liquid such as ink is applied is various kinds of paper, OHP sheets, plastic materials used for compact discs, decorative plates, etc., cloth, aluminum. Metal materials such as copper and copper, leather materials such as cowhide, pigskin and artificial leather, wood materials such as wood and plywood, bamboo materials, ceramic materials such as tiles, and three-dimensional structures such as sponges can be targeted.

As the above-mentioned recording device, a printer device for recording on various kinds of paper or OHP sheets, a recording device for plastics for recording on a plastic material such as a compact disc, a metal for recording on a metal plate, etc. Recording device, recording device for leather for recording on leather, recording device for wood for recording on wood, recording device for ceramics for recording on ceramic material, recording device for recording on three-dimensional mesh structure such as sponge It also includes a printing device for recording on the cloth.

As the ejection liquid used in these liquid ejection devices, a liquid suitable for each recording medium and recording conditions may be used.

[0102]

As described above, according to the liquid discharge head of the present invention, the movable member is displaced and comes into contact with the regulating portion, so that the liquid flow path is substantially in the flow direction of the liquid toward the discharge port. Since it is divided into two parts, it is possible to stably and rapidly discharge the liquid associated with the generation of bubbles in each bubble generation region, and it is possible to reduce satellite dots and meniscus vibration. Further, since the movable member is arranged so that the free end faces the downstream side facing the bubble generation region on the upstream side, the responsiveness of the movable member is also good, and moreover, the movable member has one liquid flow path. Since only one is required, the space for supporting the movable member is minimized and the liquid ejection head does not become large.

According to the liquid ejecting method of the present invention, the liquid ejecting head of the present invention is used to generate bubbles in the bubble generating region on the downstream side of each bubble generating region, and thereafter in the bubble generating region on the upstream side. By generating bubbles and discharging the liquid from the discharge ports by the bubbles generated in each bubble generation region, it is possible to discharge a large droplet at a stable discharge speed. Accordingly, it is possible to stably form droplets having different ejection amounts with one nozzle.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a liquid discharge head according to an embodiment of the present invention cut in the liquid flow path direction, showing a characteristic phenomenon in the liquid flow path when an upstream heating element is driven (a). It is shown separately for the steps (f) to (f).

FIG. 2 is a cross-sectional view showing characteristic phenomena in a liquid flow path when a heating element on the downstream side is driven in the liquid discharge head shown in FIG. 1, divided into steps (a) to (e). Is.

FIG. 3 is a perspective view of a part of the head shown in FIG. 1 (b).

FIG. 4 is a cross-sectional view showing characteristic phenomena in a liquid flow path when two heating elements are driven in the liquid discharge head shown in FIG. 1, divided into steps (a) to (f). is there.

FIG. 5 is a diagram showing another shape of the movable member.

FIG. 6 is a graph showing a relative relationship between a heating element area and an ink discharge amount.

FIG. 7 is a shield cross-sectional view of the liquid ejection head of the present invention,
(A) shows what has a protective film, (b) shows what has no protective film.

FIG. 8 is a drive waveform diagram of a heating element used in the present invention.

FIG. 9 is an exploded perspective view showing the overall configuration of the liquid ejection head of the present invention.

FIG. 10 is a diagram showing a schematic configuration of a liquid ejection apparatus equipped with the liquid ejection head having the structure described in FIG.

FIG. 11 is a block diagram of an entire apparatus for performing an ink ejection operation in the liquid ejection method and liquid ejection head of the present invention.

[Explanation of symbols]

1 element substrate A few heating elements 10 liquid flow paths 11, 12 Bubble generation area 13 Common liquid chamber 18 outlets 31 Movable member 32 Free end 33 fulcrum 34 Support member 40,42 bubbles 41 Raised bubbles 50 top plate 64 stopper 65 Low flow resistance area 66,68 droplets 67 satellites 70 Support 90 ink tank 102 Anti-cavitation layer 103 protective layer 104 wiring electrode 105 Resistance layer 106 silicon nitride film 107 base 111 motor 112, 113 gears 115 Carriage axis 150 recording media 200 heads 300 host computer 301 Input / output interface 302 CPU 303 ROM 304 RAM 305 motor driver 306 Drive motor 307 head driver

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroyuki Sugiyama             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation (72) Inventor Satoshi Shimazu             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation (72) Inventor Sadayuki Sugama             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation F-term (reference) 2C056 EA04 EA15 EA23 FA03                 2C057 AF09 AF23 AF28 AF34 AF39                       AF78 AG12 AR18 BA03 BA13                       CA01

Claims (12)

[Claims] 1. A discharge port for discharging a liquid, and a plurality of bubble generation regions communicating with the discharge port and for generating bubbles in the liquid are provided along a flow direction of the liquid toward the discharge port. A liquid flow path and a movable member that is arranged facing the bubble generation region and has a free end on the downstream side with respect to the flow direction of the liquid toward the discharge port, and the movable member is configured to generate the plurality of bubbles. A liquid ejecting head, wherein the liquid ejecting head is provided only in a bubble generation region on an upstream side in a direction of liquid flow toward the ejection port. 2. The liquid flow path has a restricting portion for restricting displacement of the movable member due to growth of the bubbles, and the movable member is displaced and substantially contacts the restricting portion. The liquid ejection head according to claim 1, wherein the liquid ejection head is substantially divided in a flow direction of the liquid toward the ejection port. 3. The free end of the movable member is substantially located at the central portion of the bubble generating region on the upstream side.
Alternatively, the liquid ejection head according to item 2. 4. The liquid ejection head according to claim 1, 2 or 3, wherein the area of the bubble generating region on the downstream side in the flow direction of the liquid toward the ejection port is smaller than the area of the bubble generating region on the upstream side. 5. The liquid ejection head according to claim 1, wherein a heating element that generates heat for generating bubbles is provided in each of the bubble generation regions. 6. The liquid ejection head according to claim 5, wherein each of the heating elements can be individually driven. 7. The liquid discharge head according to claim 1, wherein, after generating bubbles in a bubble generation region on a downstream side in a flow direction of the liquid toward the discharge port among the bubble generation regions, an upstream side is generated. A bubble is generated in the bubble generating region, and the liquid is discharged from the discharge port by the bubble generated in each bubble generating region. 8. The liquid discharge head according to claim 2, wherein bubbles are generated in a bubble generation region on a downstream side of a flow direction of the liquid toward the discharge port in each bubble generation region. After being generated, a bubble is generated in the bubble generating region on the upstream side, and the liquid is discharged from the discharge port by the bubble generated in each bubble generating region. 9. The liquid ejection method according to claim 7, wherein bubbles are generated in the upstream bubble generating region while the bubbles are contracting in the downstream bubble generating region. 10. In the step of growing bubbles in the bubble generating region on the upstream side, the movable member is brought close to or in contact with the restriction portion to move the liquid in the upstream direction with respect to the flow direction of the liquid toward the discharge port. 9. The liquid ejection method according to claim 8, comprising the step of limiting bubble growth. 11. A liquid, comprising: the liquid ejection head according to claim 1; and a recording medium conveyance unit that conveys a recording medium that receives the liquid ejected from the liquid ejection head. Discharge device. 12. The liquid ejection apparatus according to claim 11, wherein recording is performed by ejecting ink from the liquid ejection head and adhering the ink to a recording medium.