JP2001138523A - Liquid jet head, liquid jet apparatus and liquid jet method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the discharge quantity ratio of liquid drops and to make the discharge speeds of respective liquid drops almost equal. SOLUTION: A liquid jet head is equipped with a liquid jet orifice 7, the liquid flow channels 3 always communicating with the jet orifice 5 at one end parts thereof, the liquid supply port communicating with a common liquid supply chamber 6 storing the liquid supplied to the liquid flow channel 3, a plurality of heating elements 4a, 4b generating an air bubble in the liquid supplied to the liquid flow channel 3 and the movable member 8 provided on the liquid flow channel 3 so as to provide a gap with respect to the liquid supply port and supported in such a state that the end on the side of the jet orifice 5 is set as a free end. By driving the heating element generating an air bubble having the smallest volume among a plurality of the heating elements 4a, 4b, of the liquid jet head, the liquid supply port 5 is hermetically closed by the movable member 8 to be cut off substnatially.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid discharge head, a liquid discharge apparatus, and a liquid discharge method for discharging liquid by applying heat energy to liquid to generate bubbles.

[0002] The present invention also relates to a facsimile having a printer, a copier, a communication system, and a printer for performing recording on a recording medium such as paper, thread, fiber, cloth, leather, metal, plastic, glass, wood, ceramics and the like. The present invention can be applied to a device such as a word processor having a unit, and further to an industrial recording device combined with various processing devices.

In the present invention, “recording” means not only giving an image having a meaning such as a character or a figure 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 Conventionally, in a recording device such as a printer,
Applying energy such as heat to the liquid ink in the flow path to generate air bubbles, and the ink is ejected from the ejection ports by the action force based on the steep volume change that accompanies it and adheres to the recording medium to form an image. Ink-jet recording method,
A so-called bubble jet (registered trademark) recording method is known. As disclosed in U.S. Pat. No. 4,723,129 and the like, a recording apparatus using this bubble jet recording method includes a discharge port for discharging ink, a flow path communicating with the discharge port, An electrothermal converter (heater) as an energy generating means for discharging ink disposed in the flow path is generally disposed.

According to such a recording method, a high-quality image can be recorded at high speed and with low noise, and in a head performing this recording method, ejection ports for ejecting ink are arranged at a high density. Therefore, it has many advantages that a high-resolution recorded image and a color image can be easily obtained with a small device. For this reason, this bubble jet recording method has recently been used in many office devices such as printers, copiers, and facsimile machines, and has also been used in industrial systems such as textile printing devices.

As described above, various demands are increasing as the bubble jet technology is used for products in various fields.
For example, in order to obtain a high-quality image, a drive condition for providing a liquid discharge method or the like in which the ink discharge speed is high and a good ink discharge based on stable bubble generation is proposed. From the viewpoint, there has been proposed an improved flow path shape in order to obtain a liquid discharge head having a high filling (refilling) speed of the discharged liquid into the liquid flow path.

Further, in order to simultaneously increase the detail of a recorded image and increase the printing speed, one liquid flow path (nozzle)
There is also proposed a device in which a plurality of electrothermal transducers are arranged in such a manner that droplets having different sizes are discharged from the same nozzle.

The liquid discharge characteristics such as the discharge amount, discharge speed, and refill frequency of the liquid discharge head generally include a flow resistance in front of the heater (downstream side in the flow direction of the liquid in the liquid flow path) and a flow resistance behind the heater (upstream side). ) Flow resistance,
The ratio of the flow resistance in front of the heater to the flow resistance behind the heater,
Is determined by the following three factors. Therefore, the liquid discharge head is configured such that the above three elements are appropriately changed by adjusting the structure of the liquid flow path, the size and the arrangement position of the heater, and the desired discharge characteristics are obtained. .

[0009]

A liquid discharge head (hereinafter referred to as "discharge amount modulation") in which a plurality of electrothermal transducers are arranged in one nozzle and droplets having different sizes are discharged from the same nozzle. Head)), it is necessary to further increase the ejection amount modulation ratio (volume ratio between small droplets and large droplets) in order to achieve higher definition of a recorded image and higher printing speed. is there.

However, when the discharge amount modulation ratio is increased,
Since the difference between the ejection speeds of the small droplet and the large droplet increases and the landing position of the droplet on the recording medium shifts, it is necessary to eject the small droplet and the large droplet within one scanning stroke. In some cases, or it may be necessary to perform an advanced image processing step such as changing the ejection timing according to the size of the droplet to be ejected. In addition, if the size ratio between the heaters arranged in one nozzle is increased, the length of the nozzle must be increased, which may greatly affect the discharge characteristics such as a decrease in the refill frequency.

The ejection volume modulation head is required to have approximately the same ejection speed of each droplet, while the ejection volume modulation head ejects droplets of different sizes from the same nozzle. It is difficult to make a configuration that is optimal for discharging droplets of each size. Further, in the ejection amount modulation head, since a plurality of heaters are arranged in one nozzle, the degree of freedom of the size and arrangement position of the heater may be limited.

As described above, the discharge amount modulation head requires much higher design conditions than a general liquid discharge head in which one heater is arranged for one nozzle. Conventionally, if these conditions are to be satisfied, the ejection efficiency is reduced and the temperature of the head is easily increased, and the dimensional accuracy and the assembly accuracy of the components need to be increased.

Accordingly, the present invention provides a liquid discharge head, a liquid discharge method, and a liquid discharge method capable of increasing the discharge amount ratio of liquid droplets, making the discharge speed of each liquid droplet substantially equal, and increasing the refill frequency after discharge. An object is to provide a discharge device.

[0014]

In order to achieve the above object, a liquid discharge head of the present invention has a discharge port for discharging a liquid, and one end of the discharge port is always in communication with the discharge port to generate bubbles in the liquid. A liquid flow path having a plurality of bubble generation regions to be caused,
A liquid supply port arranged in the liquid flow path and communicated with a common liquid supply chamber that stores the liquid supplied to the liquid flow path, and bubbles are formed in the liquid disposed in the liquid flow path. A plurality of bubble generating means to be generated, provided in the liquid flow path in a state where the discharge port side is supported as a free end with a gap of 10 μm or less with respect to the liquid flow path side of the liquid supply port,
A plate-shaped movable member having a projection area larger than an opening area of the liquid supply port, wherein the discharge port and the bubble generation unit are in a linear communication state, and the volume of the plurality of bubble generation units is the largest. The movable member hermetically closes and substantially shuts off the liquid supply port by driving a bubble generation unit that generates a small bubble.

According to another aspect of the present invention, there is provided a liquid discharge head having a discharge port for discharging a liquid, and a plurality of bubble generating regions having one end constantly connected to the discharge port and generating bubbles in the liquid. A flow path, a liquid supply port disposed in the liquid flow path, communicating with a common liquid supply chamber for storing the liquid supplied to the liquid flow path, and the liquid supply port disposed in the liquid flow path. A plurality of bubble generating means for generating bubbles in the liquid, and the liquid flow path supported by the discharge port side as a free end with a gap of 10 μm or less with respect to the liquid flow path side of the liquid supply port. And a plate-shaped movable member having a projection area larger than the opening area of the liquid supply port, wherein the discharge port and the bubble generation means are in linear communication with each other, and By choosing one of them,
In generating bubbles, the movable member hermetically closes and substantially shuts off the liquid supply port when driving any of the bubble generation means.

According to the liquid discharge head of the present invention having the above-described structure, a part of the liquid filling the liquid flow path is heated by the heating element (bubble generating means), and almost simultaneously with the generation of bubbles due to film boiling. In addition, the movable member comes into close contact with the peripheral portion of the liquid supply port to close the liquid supply port, and the inside of the liquid flow path is substantially closed except for the discharge port.

Therefore, the propagation of the pressure wave is prevented from going to the liquid supply port side, and the liquid does not move to the rear of the heating element when discharging the liquid, so that the flow resistance behind the heating element is almost infinite. Can be considered. Furthermore, since the flow resistance behind (upstream) the heating element is almost infinite, the ratio of the flow resistance in front of the heating element to the flow resistance behind the heating element is the flow resistance in front (downstream side) of the heating element. Is almost always zero even if changes. Therefore, in the liquid discharge head of the present invention, the liquid discharge characteristics are determined only by the “flow resistance in front (downstream side) of the heating element” among the three elements that determine the liquid discharge characteristics.

The discharge speed of the liquid is inversely proportional to the flow resistance in front of the heating element and proportional to the foaming power determined by the effective foaming area of the heating element. In addition, since the discharge amount of the liquid discharged from the discharge port is proportional to the effective foaming area of the heating element, in the liquid ejection head of the present invention, the liquid ejection head in front (downstream side) of each heating element provided in the same liquid flow path. By making the ratio between the flow resistance and the ejection amount equal, the ejection speed of each droplet ejected by heating each heating element becomes equal. Thus, according to the present invention, it becomes easy to make the ejection speeds of the respective droplets equal even if the ejection amount ratio of the droplets is increased.

Further, the plurality of bubble generating means provided in the liquid flow path may be arranged in an order in which a foaming area gradually increases from a downstream side to an upstream side of the liquid flow path. preferable.

Further, a gap may be provided between the liquid flow path wall constituting the liquid flow path and the movable member.

The liquid may be discharged by driving the plurality of bubble generating means. In this case, the liquid may be discharged by simultaneously driving the plurality of bubble generating units. Alternatively, the liquid may be discharged by first driving the bubble generating means closest to the discharge port out of the plurality of bubble generating means. Alternatively, the liquid may be ejected by first driving the bubble generating unit closest to the movable member among the plurality of bubble generating units.

Further, a liquid discharge apparatus according to the present invention includes the above liquid discharge head according to the present invention, and drive signal supply means for supplying a drive signal for discharging liquid from the liquid discharge head.

According to another aspect of the present invention, there is provided a liquid ejecting apparatus including the liquid ejecting head of the present invention described above, and a recording medium transport means for transporting a recording medium receiving the liquid ejected from the liquid ejecting head.

Further, the recording may be performed by discharging ink from the liquid discharge head and attaching the ink to a recording medium.

Further, according to the liquid discharge method of the present invention, there is provided a liquid flow path having a discharge port for discharging a liquid, and a plurality of bubble generation regions, one end of which is always in communication with the discharge port and which generates bubbles in the liquid. A liquid supply port disposed in the liquid flow path and communicating with a common liquid supply chamber that stores the liquid supplied to the liquid flow path; and the liquid flow path provided in the liquid flow path. A plurality of bubble generating means for generating bubbles in the liquid disposed in the liquid flow path wall and the liquid supply port between the liquid flow path wall and the liquid supply port constituting the liquid flow path; A movable member having a projection area larger than an opening area of the liquid supply port, the movable member being provided in the liquid path in a state where the discharge port side is supported as a free end with a minute gap with respect to the liquid flow path side; A liquid ejection method using a liquid ejection head comprising: By driving the bubble generating means for generating the smallest volume of bubbles among the number of bubble generating means to generate bubbles, the entire bubble grows substantially isotropically after the driving voltage is applied to the bubble generating means. The movable member hermetically closes and substantially shuts off the liquid supply port until the end of the period.

According to another liquid discharging method of the present invention, there is provided a liquid flow path having a discharging port for discharging a liquid, and a plurality of bubble generating regions, one end of which is always in communication with the discharging port, for generating bubbles in the liquid. A liquid supply port disposed in the liquid flow path and communicating with a common liquid supply chamber that stores the liquid supplied to the liquid flow path; and the liquid flow path provided in the liquid flow path. A plurality of bubble generating means for generating bubbles in the liquid disposed in the liquid flow path wall and the liquid supply port between the liquid flow path wall and the liquid supply port constituting the liquid flow path; A movable member having a projection area larger than an opening area of the liquid supply port, the movable member being provided in the liquid path in a state where the discharge port side is supported as a free end with a minute gap with respect to the liquid flow path side; A liquid discharge method using a liquid discharge head comprising: When generating a bubble by selecting one of the bubble generating means, when driving any of the bubble generating means, the entire bubble is substantially equal after a driving voltage is applied to the bubble generating means. The movable member hermetically closes and substantially shuts off the liquid supply port until the growth period ends.

As a result, the liquid flows into the liquid flow path earlier than the retreat amount of the meniscus formed at the discharge port becomes maximum, and the flow of rapidly drawing the meniscus into the liquid flow path is sharply reduced. As the amount of meniscus retreat decreases, the meniscus starts to return to the position before foaming at a relatively low speed. As a result, the time required for the meniscus to return to the initial state after the discharge is very short, that is, the time required to complete the replenishment (refill) of the ink in the liquid flow path is short, so that the ink discharge with high precision (quantity) can be performed. In the implementation, the ejection frequency (drive frequency) can also be dramatically improved.

Further, the discharge port side and the liquid supply port side in the bubble generation area may have a structure in which the growth volume change of the bubbles and the time from the generation of the bubbles to the disappearance of the bubbles are greatly different.

Further, the air bubble generating region may not be opened to the atmosphere.

The liquid may be discharged by driving the plurality of bubble generating means. In this case, the liquid may be discharged by simultaneously driving the plurality of bubble generating units. Alternatively, the liquid may be discharged by first driving the bubble generating means closest to the discharge port out of the plurality of bubble generating means. Alternatively, the liquid may be ejected by first driving the bubble generating unit closest to the movable member among the plurality of bubble generating units.

The 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 flow direction of a liquid from a liquid supply source to a discharge port through a bubble generation region (or a movable member).
Alternatively, it is expressed as an expression regarding this structural direction.

The "downstream side" of the bubble itself is as follows.
With respect to the center of the bubble, it means a bubble that is generated on the downstream side in the flow direction or the configuration direction, or on the downstream side of the area center of the heating element.

The expression "the movable member seals and substantially shuts off the liquid supply port" in the present invention does not necessarily mean that the movable member is in close contact with the periphery of the liquid supply port.
This includes the movable member approaching the liquid supply port without limit.

[0035]

Next, embodiments of the present invention will be described with reference to the drawings.

(First Embodiment) FIG. 1 is a cross-sectional view of a liquid discharge head according to an embodiment of the present invention, taken along one liquid flow direction. FIG. 2 is a cross-sectional view of the liquid discharge head shown in FIG. −
1. FIG. 3 is a cross-sectional view taken along the line X ', and FIG. 3 is a cross-sectional view taken along the line YY' shifted from the center of the discharge port of the liquid discharge head shown in FIG.

In the liquid discharge head in the form of a plurality of flow paths and a common liquid chamber shown in FIGS. 1 to 3, the element substrate 1 and the top plate 2 are fixed in a stacked state via the flow path side wall 10, and the two plates 1 , 2, a liquid flow path 3 having one end communicating with the discharge port 7 is formed. The liquid flow paths 3 are provided in large numbers in one head. Further, the element substrate 1 is provided with heating elements 4a and 4b as bubble generating means for generating bubbles in the liquid replenished in the liquid flow path 3 for each liquid flow path 3. Heating element 4
a and 4b are arranged for each of the liquid flow paths 3 respectively.
In this embodiment, two heating elements are arranged in each liquid flow path 3, but the number of heating elements arranged in each liquid flow path 3 is two.
The number is not limited to one and may be more. Heating element 4a,
A heating element 4 is provided in a region near a surface where the liquid 4b contacts the discharge liquid.
There is a bubble generation region 11 in which a and 4b are rapidly heated to cause foaming in the discharge liquid.

Each of the plurality of liquid flow paths 3 has a supply portion forming member 5
A liquid supply port 5 formed in A is provided, and a common liquid supply chamber 6 communicating with each liquid supply port 5 is provided. That is, the flow path has a shape branched from a single common liquid supply chamber 6 to a number of liquid flow paths 3, and has an amount corresponding to the liquid discharged from the discharge port 7 communicating with each liquid flow path 3. Liquid is received from this common liquid supply chamber 6. The symbol S indicates the liquid supply port 5
3 shows a substantial opening area for supplying a liquid to the liquid flow path 3 of FIG.

A movable member 8 is provided between the liquid supply port 5 and the liquid flow path 3 so as to be substantially parallel to the opening area S of the liquid supply port 5 with a small gap α (for example, 10 μm or less). Have been. The projected area of the movable member 8 is larger than the opening area S of the liquid supply port 5 (see FIG. 3), and a small gap is formed between the side portion of the movable member 8 and each of the flow path side walls 10 on both sides. β (see FIGS. 2 and 3).

The supply section forming member 5A described above has a gap γ with respect to the movable member 8 as shown in FIG. The gaps β and γ differ depending on the pitch of the flow path. However, if the gap γ is large, the movable member 8 can easily block the opening area S, and if the gap β is large, the movable member 8 can be moved from the steady state located through the gap α. Also easily moves toward the element substrate 1 with the defoaming. In this embodiment, the gap α is 3 μm, the gap β is 3 μm, and the gap γ is 4 μm.

The movable member 8 has a width W1 larger than the width W2 of the opening region in the width direction between the flow path side walls 10, and has a width enough to sufficiently seal the opening region. . 8A of the movable member 8 is a continuous part (a part of which is shown in FIG. 1) in which the upstream end of the opening area of the liquid supply port 5 is continuous in the direction in which the plurality of movable members intersect the plurality of flow paths. As shown in FIG. 3) on the extension of the free end. In this embodiment,
As shown in FIGS. 3 and 2, the thickness of a portion of the supply portion forming member 5 </ b> A along the movable member 8 is set smaller than the thickness of the channel side wall 10 itself. The supply section forming member 5A is stacked. The discharge port 7 side of the movable member of the supply section forming member 5A with respect to the free end 8B is set to have the same thickness as the liquid flow path wall 10 itself, as shown in FIG.

As a result, the movable member 8 can be moved in the liquid flow path 3 without frictional resistance, while displacement toward the opening area S can be restricted at the periphery of the opening area S. Thereby, the opening area S is substantially closed and the common liquid supply chamber 6
While it is possible to prevent the liquid from flowing into the liquid flow path, the liquid can be moved from the substantially closed state to the refillable state with the defoaming of the air bubbles. In the present embodiment, the movable member 8 is also positioned parallel to the element substrate 1 with respect to the element substrate 1. An end 8B of the movable member 8 is a free end located near the heating elements 4a and 4b of the element substrate 1, and the other end is supported by a fixed member 9. Further, the end of the liquid flow path 3 opposite to the discharge port 7 of the movable member 8 (ie, the end on the upstream side) is closed by the fixing member 9.

As shown in FIG. 4, in the present embodiment, there is no obstacle such as a valve between the heating elements 4a and 4b as the electrothermal transducers and the discharge port 7, and the liquid flow is reduced. On the other hand, it is in a “linear communication state” in which a straight channel structure is maintained. This is more preferably achieved by linearly matching the direction of propagation of the pressure wave generated when bubbles are generated and the direction of flow of the liquid with the direction of discharge of the liquid, so that the direction of discharge of the droplets and the discharge speed of the droplets are adjusted. This is because it is desirable to form an ideal state in which the state is stabilized at an extremely high level. In the present invention, as one definition for achieving or approximating this ideal state, the discharge port 7 and the heat generating elements 4a and 4b, particularly the discharge port side (downstream side) of the heat generating element having an influence on the bubble discharge port side. ) May be directly connected with a straight line. This is because if there is no fluid in the flow path, observe the heating element, particularly the downstream side of the heating element, as viewed from the outside of the discharge port 7. (See FIG. 4).

Next, the discharge operation of the liquid discharge head of the present embodiment will be described. FIGS. 5 and 6 show a liquid discharge head in a cutaway view along the liquid flow path direction to explain the discharge operation of the liquid discharge head having the structure shown in FIGS. (A) to (d) of FIG. 5, FIG.
(A) to (c). Further, in FIGS. 5 and 6, the symbol M represents a meniscus formed by the ejection liquid. 5 and 6 show an example in which the front (downstream) heating element 4a generates heat.

FIG. 5A shows a state before energy such as electric energy is applied to the heating element 4a, and shows a state before the heating element generates heat. In this state, there is a small gap (10 μm or less) between the movable member 8 provided between the liquid supply port 5 and the liquid flow path 3 and the surface on which the liquid supply port 5 is formed.

FIG. 5B shows a state in which a part of the liquid filling the liquid flow path 3 is heated by the heating element 4a, film boiling occurs on the heating element 4a, and the bubbles 21 grow isotropically. Here, "isotropic bubble growth" refers to a state where the bubble growth rates in the direction perpendicular to the bubble surface are almost equal at various places on the bubble surface.

In the isotropic growth process of the bubble 21 at the initial stage of the bubble generation, the movable member 8 is brought into close contact with the peripheral portion of the liquid supply port 5 to close the liquid supply port 5, and the inside of the liquid flow path 3 is discharged. Except for the outlet 7, it is substantially closed. This sealed state
This is maintained during any period of the isotropic growth process of the bubbles 21. In addition, the heating element 4
To the end of the process of isotropic growth of the bubbles 21 after the application of the electric energy to the air. Also,
In this closed state, the inertance of the liquid flow path 3 on the liquid supply port side from the center of the heating element 4 (the difficulty in moving the stationary liquid when it suddenly starts moving) becomes substantially infinite. At this time, the inertance from the heating element 4 to the liquid supply port side approaches infinity as the distance between the heating element 4 and the movable member 8 increases.

FIG. 5C shows a state in which the bubbles 21 continue to grow. As described above, when the inside of the liquid flow path 3 is substantially closed except for the discharge port 7, the liquid does not flow to the liquid supply port 5 side. Therefore, among the bubbles that have grown isotropically on the heating element 4a, the bubbles on the liquid supply port 5 side cannot grow, and the growth energy of the bubbles is consumed only for the growth of the bubbles on the discharge port 7 side.

Here, the bubble growth process in FIGS. 5A to 5C will be described in detail with reference to FIG. FIG.
When the heating element 4 is heated as shown in (a), initial boiling occurs on the heating element 4 and then changes to film boiling in which film-like bubbles cover the heating element 4 as shown in FIG. 7 (b). I do. The bubbles in the film boiling state continue to grow isotropically as shown in FIGS. 7B to 7C. Called). However, as shown in FIG. 5 (b), when the inside of the liquid flow path 3 is substantially closed except for the discharge port 7, the liquid cannot move to the upstream side. Some of the bubbles on the side (liquid supply port side) do not grow, and only the remaining downstream (discharge port side) part grows. FIGS. 5C, 7D and 7E show this state.

Here, for convenience of explanation, when the heating element 4a is being heated, the area on the heating element 4a where bubbles do not grow is defined as area B, and the area on the discharge port 7 side where bubbles grow is defined as A.
Area. In the region B, the foam volume during isotropic bubble growth is maximized.

FIG. 5D shows a state in which bubble growth continues in the region A and bubble contraction starts in the region B. In this state, in the region A, the bubbles grow larger toward the ejection port side. Then, the volume of bubbles in the region B starts to decrease. Accordingly, the movable member 8 starts to be displaced downward to the steady state position by the restoring force due to its rigidity and the defoaming force of the bubbles in the B region. As a result, the liquid supply port 5 is opened, and the common liquid supply chamber 6 and the liquid flow path 3 are in communication.

FIG. 6A shows a state in which the bubble 21 has grown to a maximum. In this state, the bubbles grow in the region A to the maximum, and the bubbles in the region B almost disappear. Further, the ejection droplet 22 ejecting from the ejection port 7 is still connected to the meniscus M in a long tail state.

FIG. 6B shows a stage in which the growth of the bubble 21 stops and only the defoaming step is performed.
Indicates a state in which it is divided. Immediately after changing from bubble growth to bubble elimination in the region A, the contraction energy of the bubbles 21 acts as a force for moving the liquid in the vicinity of the discharge port 7 in the upstream direction as an overall balance. Therefore, the meniscus M is drawn into the liquid flow path 3 from the discharge port 7 at this point, and the discharge droplet 22
The liquid column that is connected to is separated. On the other hand, the movable member 8 is displaced downward due to the contraction of the bubble, and the liquid rapidly flows into the liquid flow path 3 from the common liquid supply chamber 6 via the liquid supply port 5 as a large flow. As a result, the flow of drawing the meniscus M into the liquid flow path 3 rapidly drops abruptly, so that the retreat amount of the meniscus M can be reduced and the meniscus M returns to the position before foaming at a relatively low speed. start. As a result, the convergence of the vibration of the meniscus M is very good as compared with the liquid ejection method having no movable member according to the present invention.

In FIG. 6C, the bubble 21 completely disappears.
The state where the movable member 8 has also returned to the steady state position is shown. In this state, the movable member 8 is displaced upward by the elastic force (in the direction of the solid arrow in FIG. 6B). In this state, the meniscus M has already returned near the discharge port 7.

Next, the correlation between the time change of the bubble volume in the regions A and B shown in FIGS. 5 and 6 and the behavior of the movable member will be described with reference to FIG. FIG. 8 is a graph showing the correlation. Curve A shows the time change of the bubble volume in the A region, and curve B shows the time change of the bubble volume in the B region.

As shown in FIG. 8, the change over time in the growth volume of bubbles in the region A draws a parabola having a maximum value. That is,
From the start of foaming to the defoaming, the bubble volume increases with time, reaches a maximum at some point, and then decreases. On the other hand, in the region B, the time required from the start of foaming to the defoaming is shorter than that in the region A, the maximum growth volume of the bubble is small, and the time to reach the maximum growth volume is short. That is, in the A region and the B region, the time required from the start of foaming to the defoaming and the change in the growth volume of the bubbles are greatly different, and the B region is smaller.

In particular, in FIG. 8, since the bubble volume increases at the same time change in the initial stage of bubble generation, the curves A and B overlap. That is, in the initial stage of the generation of the bubble, a period in which the bubble is growing isotropically (semi-Purro-like) occurs.
Thereafter, the curve A draws a curve that increases to the maximum point, but at some point the curve B branches off from the curve A and draws a curve in which the bubble volume decreases. That is, while the volume of the bubble increases in the region A, a period in which the volume of the bubble decreases in the region B (a partial growth partial contraction period) occurs.

Based on the above-described bubble growth method, when the free end of the movable member covers a part of the heating element as shown in FIG. 1, the movable member behaves as follows. That is, in the period of FIG. 8, the movable member is displaced upward toward the liquid supply port. In the period shown in the figure, the movable member is in close contact with the liquid supply port, and the inside of the liquid flow path is substantially closed except for the discharge port. The start of the closed state is performed during a period when the bubbles are growing isotropically. Next, during the period shown in the figure, the movable member is displaced downward toward the steady state position. The opening of the liquid supply port by the movable member is started after a lapse of a predetermined time from the start of the partial growth partial contraction period. Next, during the period shown in the figure, the movable member is further displaced downward from the steady state. Next, during the period shown in the figure, the downward displacement of the movable member is substantially stopped, and the movable member is in an equilibrium state at the open position. Finally, during the period shown in the figure, the movable member is displaced upward toward the steady state position.

The correlation between the bubble growth and the behavior of the movable member is affected by the relative position between the movable member and the heating element. Therefore, with reference to FIGS. 9 and 10, the correlation between the bubble growth and the behavior of the movable member in the liquid ejection head having the movable member and the heating element at different relative positions from the present embodiment will be described.

FIG. 9 is a diagram for explaining the correlation between the bubble growth and the behavior of the movable member when the free end of the movable member covers the entire heating element.
(B) shows a graph of the correlation. When the area in which the heating element 4a is covered with the movable member 8 is large as in the mode shown in FIG. 9A, the period in FIG. 9 is shorter than that in the mode in FIG. This is more preferable because the sealed state is obtained in a short time after heating 4a. In addition, the behavior of the movable member in each period from to in FIG. 9 is the same as the behavior described with reference to FIG. 9, the movable member 8 is more susceptible to the reduction in the volume of air bubbles. Therefore, as can be seen from the start of the period shown in FIG. 9, the opening of the liquid supply port 5 by the movable member 8 starts with partial growth. Immediately after the start of the partial contraction period. That is, the opening timing of the movable member 8 is earlier than in the case of the embodiment of FIG. For the same reason, the amplitude of the movable member 8 increases.

FIGS. 10A and 10B are diagrams for explaining the correlation between the bubble growth and the behavior of the movable member when the heating element and the movable member are separated from each other. FIG.
Shows a graph of the correlation. (A) of FIG.
When the heating element 4a is located closer to the discharge port than the position below the free end of the movable member 8 as in the form shown in FIG.
As is apparent from the start of the period shown in the figure, the opening of the liquid supply port 5 by the movable member 8 is considerably delayed from the start of the partial growth partial contraction period. That is, the opening timing of the movable member 8 is later than in the case of the embodiment of FIG. For the same reason, the amplitude of the movable member 8 decreases. In addition, the behavior of the movable member 8 in each of the periods from to in FIG. 10 is the same as the behavior described with reference to FIG.

The positional relationship between the movable member 8 and the heating element 4a has been described for general operation, and each operation differs depending on the position of the movable member, the rigidity of the movable member, and the like.

As described above, the head configuration and the liquid discharging operation of the present embodiment have been described. According to such a mode, the growth component of the bubble toward the downstream side and the growth component toward the upstream side are not uniform. Almost no growth component flows to the upstream side, and the movement of the liquid to the upstream side is suppressed. Since the flow of the liquid to the upstream side is suppressed, most of the bubble growth component is directed to the discharge port without loss to the upstream side,
The discharge force is significantly improved. Further, the retreat amount of the meniscus after the discharge is reduced, and the amount of the meniscus protruding from the orifice surface at the time of refilling is also reduced accordingly. Therefore, meniscus vibration is suppressed, and stable ejection can be performed at all driving frequencies from a low frequency to a high frequency.

Although the case where the heating element 4a on the downstream side of the liquid flow path 3 generates heat has been described above, the above-described discharge operation also occurs when the heating element 4b on the upstream side is heated. This is because, in the present invention, since the effective heating area of the upstream heating element 4b is larger than that of the downstream heating element 4a as described later, bubbles generated when the downstream heating element 4a generates heat are generated. If the movable member 8 is configured to be in close contact with the liquid supply port 5 during the growth process, the movable member 8 is similarly connected to the liquid supply port 5 even when the heating element 4b on the upstream side is heated. This is because they are adhered.

As described above, according to the liquid discharge head of the present embodiment, when a part of the liquid filling the liquid flow path 3 is heated by the heating element 4 and bubbles accompanying the film boiling become bubbles, The movable member 8 is brought into close contact with the peripheral portion of the liquid supply port 5 and
And the inside of the liquid flow path 3 becomes substantially closed except for the discharge port 7. Therefore, propagation of the pressure wave to the liquid supply port 5 side is suppressed. Therefore, in the liquid ejection head of the present embodiment, the ink does not move to the rear of the heating element when ejecting the liquid, so that the flow resistance behind the heating element can be considered to be almost infinite.

Therefore, the flow resistance in front of the heating element (downstream side), the flow resistance in the rear side (upstream side) of the heating element, and the flow resistance in the rear side of the heating element determine the liquid ejection characteristics of the liquid ejection head. Of the three elements of the flow resistance ratio
The flow resistance behind (upstream) the heating element becomes infinite,
The ratio of the flow resistance at the front of the heating element to the flow resistance at the rear of the heating element is such that the flow resistance at the front (downstream side) of the heating element changes because the flow resistance at the back (upstream side) of the heating element is infinite. But it is always zero. Therefore, the liquid discharge characteristics of the liquid discharge head of the present embodiment are determined only by the flow resistance in front (downstream) of the heating element.

Here, as shown in FIG.
The case where the cross-sectional area of the (nozzle) is constant over its entire length will be described. FIG. 11A is a cross-sectional view along one liquid flow direction of the liquid discharge head.
FIG. 2B is a cross-sectional view taken along line AA ′ of FIG.

The maximum foaming volume Vo of the bubbles by the heating element is:
It is proportional to the pressure generated on the heating element during foaming. When the configuration of the nozzle is not significantly different, the foaming pressure is substantially proportional to the effective foaming area Se of the heating element. In addition, since the area of about 4 μm from the outer edge of the heating element does not become high temperature even when an electric current is applied and does not contribute to foaming, the effective foaming area Se is an area excluding the outer edge portion from the entire area of the heating element.

Further, in this embodiment, since the liquid hardly moves to the rear of the heating element, substantially all of the liquid moves in the direction of the discharge port when foaming occurs. Vd becomes substantially equal. That is, the discharge amount Vd and the effective foaming area Se are in a proportional relationship, and the following equation is obtained.

Vd = a · Se (a is a proportional constant) Expression (1) Further, the discharge speed v of the liquid droplet is determined by the acceleration at which the liquid moves forward of the heating element. Therefore, the discharge speed v is proportional to the foaming power determined by the effective foaming area Se of the heating element, and is inversely proportional to the flow resistance Rf in front of the heating element.
Therefore, the discharge speed v is given by the following equation.

V = b · Se / Rf (b is a proportional constant) Expression (2) Here, when Expression (1) is substituted into Expression (2), v = c · Vd / Rf (c = b / a Equation (3) is obtained. The flow resistance Rf is obtained by integrating the reciprocal of the cross-sectional area of the nozzle over the distance in front of the heating element from the discharge port, and is given by the following equation.

Rf = ∫ [ρ / S (x)] dx = [ρ / S] · OH (4) where ρ is the density of the liquid, and S (x) is the cross-sectional area of the nozzle at the position x. , OH are distances from the discharge port to the center of gravity of the heating element. From the above equation (4), if the cross-sectional area of the nozzle is constant (S), the flow resistance Rf is the distance O from the discharge port to the center of gravity of the heating element.
It can be seen that it is proportional to H.

From the equations (3) and (4), v = c ′ · Vd / OH (c ′ = c · S / ρ) (5) Vd and OH
It can be seen that the distance and the distance are easily obtained.

In the liquid discharge head in which one heating element is provided with two heating elements as in the present embodiment, the ejection amount Vd1 of the first heating element 4a and the ejection amount Vd2 of the second heating element 4b are determined. When the liquid is ejected from the same nozzle, when the arrangement position of the heating elements is determined so that Vd1 / Vd2 = OH1 / OH2 Equation (6), the ejection speeds v1, v2 of the droplets ejected by each heating element are determined. about,
The relationship v1 = v2 holds. For example, when the discharge amount ratio of the droplets is 1: 4, the ratio of the effective foaming area of the first heating element 4a and the second heating element 4b is 1: 4, and the first heating element 4a and the second heating element 4b are set to the first ejection element. If the ratio of the distance to the heating element 4a and the distance from the ejection port to the second heating element 4b is 1: 4, the ejection speed v1 of the small droplet and the ejection speed v2 of the large droplet can be made equal. it can.

Next, a case where the sectional area of the liquid flow path 3 (nozzle) changes in the longitudinal direction as shown in FIG. 12 will be described. FIG. 12A is a cross-sectional view along one liquid flow direction of the liquid discharge head.
FIG. 2B is a cross-sectional view taken along line BB ′ of FIG.

The liquid flow path 3 of the liquid discharge head shown in FIG.
Has a cross-sectional area S1 downstream from the position of the distance L from the discharge port 7 and a cross-sectional area S2 upstream.

Also in the example shown in FIG. 12, the effective heating area of the first heating element 4a is Se1, the discharge amount is Vd1, the discharge speed is v1, and the flow resistance of the liquid flow path 3 in the region where the sectional area is S1 is Rf1. Then, Vd1 = a.Se1 (a is a proportional constant)... Equation (7) v1 = b.Se1 / Rf1 (b is a proportional constant)... Equation (8) v1 = c.Vd1 / Rf1 (c = b / a) ) Equation (9) Rf1 = [ρ / S1] · OH1 Equation (10) v1 = c ′ · Vd1 / OH1 (c ′ = c · S1 / ρ) Equation (11) is obtained. The effective heating area of the second heating element 4b is Se2, the discharge amount is Vd2, the discharge speed is v2, and the sectional area is S2.
Assuming that the flow resistance of the liquid flow path 3 in the region is Rf2, Vd2 = a.Se2 (a is a proportional constant)... (12) v2 = b.Se2 / Rf2 (b is a proportional constant)... (13) v2 = C · Vd2 / Rf2 (c = b / a) Equation (14) Rf2 = [ρ / S1] · L + [ρ / S2] · (OH2-L) Equation (15) v2 = c ′ · Vd2 · (L / S1 + (OH2−L) / S2) ⁻¹ Equation (16) is obtained.

Here, when OH1 <L <OH2, Se1 · (S1 / OH1) = Se2 · (L / S1 + (OH2
−L) / S2) When each value is set so as to be ⁻¹ , v1 = v2, and the ejection speed of the small droplet and the ejection speed of the large droplet that are ejected by the heat generated by the heating elements 4a and 4b are equalized. Can be.

The mode of the liquid discharge operation by the liquid discharge head of the present invention includes a mode in which one of the heating elements 4a and 4b is driven, and a mode in which both the heating elements 4a and 4b are driven. . In the mode in which both the heating elements 4a and 4b are driven, the ejection state may be different from the mode in which one of the heating elements 4a and 4b is driven.

The modes for driving the heating elements 4a and 4b include a mode for driving the heating elements 4a and 4b simultaneously, a mode for driving the heating element 4a on the downstream side first, and a mode for driving the heating element 4a on the upstream side first. There is a driving mode. Both heating elements 4
a and 4b are driven at the same time.
The ejection amount is smaller than the sum of the ejection amounts when a and 4b are individually driven. In the mode in which the downstream heating element 4a is driven first, the downstream heating element 4a can be driven twice while the liquid flow path 3 is kept substantially closed except for the discharge port. Thereby, the ejection amount can be made larger than in the mode in which two droplets are ejected and both the heating elements 4a and 4b are simultaneously driven. Further, in the mode in which the heating element 4a on the upstream side is driven first, the movable member can be displaced downward more quickly than in the mode in which both the heating elements 4a and 4b are simultaneously driven, so that the refill characteristics can be further improved. Can be.

Hereinafter, the discharge state in the mode for driving both of the heating elements 4a and 4b will be sequentially described with reference to the drawings.

First, a droplet discharging operation in a mode in which both the heating elements 4a and 4b are driven simultaneously will be described. FIGS. 13 and 14 show the characteristic phenomena of the droplet discharge operation in the mode in which both heating elements 4a and 4b are driven simultaneously, FIGS. 13 (a) to 13 (c) and FIGS. 14 (a) to 14 (c). Are shown separately.

FIG. 13A shows that the two heating elements 4a and 4b are simultaneously driven so that a part of the liquid filling the liquid flow path 3 is heated by the two heating elements 4a and 4b.
This shows a state in which film boiling has occurred on a and 4b and bubbles 21a and 21b have grown isotropically. Here, “isotropic bubble growth” refers to a state in which bubble growth speed in any direction on the bubble surface in the direction perpendicular to the bubble surface is substantially equal.

In the initial stage of the bubble generation, the bubbles 21a and 21b
In the isotropic growth process, the movable member 8 is in close contact with the peripheral portion of the liquid supply port 5 to close the liquid supply port 5, and the inside of the liquid flow path 3 is substantially closed except for the discharge port 7. .

FIG. 13B shows a state where the bubbles 21a and 21b continue to grow. At this time, the downstream heating element 4
The bubbles in the region A on the downstream heating element 4a grow faster and the bubbles in the region B shrink faster than when only a is driven. In other words, the transition of the bubble 21a on the upstream side heating element 4a to the partial growth partial contraction period is quick. Further, the foam volume of the bubbles 21b on the heating element 4b on the upstream side is small.

FIG. 13C shows a state in which bubble growth is conducted in the A region of each of the bubbles 21a and 21b on both heating elements 4a and 4b, and bubble contraction has begun in the B region.
In this state, in region A, bubbles 21 are directed toward the ejection port side.
a and 21b grow greatly. Then, the volume of the bubbles 21a and 21b in the region B starts to decrease. At this time, if the foaming pressure of the bubbles in the area A on the upstream heating element 4b is larger than the sum of the defoaming forces of the bubbles in the areas B on the heating elements 4a and 4b, the movable member 8 is displaced downward. Without this, the sealed state is maintained. Note that this does not apply when the tip of the movable member is located on the upstream side of the center of the heating element 4b on the upstream side.

FIG. 14A shows a state in which the bubbles 21a on the downstream side heating element 4a have grown almost to the maximum. In this state, the bubble grows maximally in the region A on the downstream heating element 4a, and the bubble in the region B continues to contract.
At this time, when the foaming pressure of the bubbles in the region A on the upstream heating element 4b decreases, the movable member 8 starts to be displaced downward. Further, the ejection droplet 22 ejecting from the ejection port 7
Is still connected to meniscus M in a long tailed state. As a result, the liquid supply port 5 is opened, and the common liquid supply chamber 6 is opened.
And the liquid flow path 3 are in communication.

FIG. 14B shows a state in which the growth of the bubbles 21a on the downstream heating element 4a has stopped and only the defoaming step has been performed, and the discharge droplet 22 and the meniscus M are separated. In this state, the movable member 8 is quickly displaced downward due to the defoaming force of the bubbles in the B region on the upstream heating element 4b and the defoaming force of the bubbles in the A region and the B region on the downstream heating element 4a. I do. Immediately after changing from bubble growth to defoaming in the region A on the upstream heating element 4a, the contraction energy of the bubbles acts as a force to move the liquid in the vicinity of the discharge port 7 in the upstream direction as an overall balance. Therefore, meniscus M
At this time, the liquid column is drawn into the liquid flow path 3 from the discharge port 7, and the liquid column connected to the discharge liquid droplet 22 is quickly separated with a strong force. At this time, the discharge amount is determined by each of the heating elements 4a, 4
The discharge amount is smaller than the total discharge amount when b is individually driven. On the other hand, the movable member 8
Is displaced downward, and the liquid rapidly flows into the liquid flow path 3 from the common liquid supply chamber 6 via the liquid supply port 5 as a large flow. As a result, the flow of drawing the meniscus M rapidly into the liquid flow path 3 is suddenly reduced, so that the retreat amount of the meniscus M is reduced and the meniscus M starts to return to the position before foaming at a relatively low speed. As a result, the convergence of the vibration of the meniscus M is very good as compared with the liquid ejection method having no movable member according to the present invention.

FIG. 14 (c) shows a state in which the bubbles on the downstream heating element 4a are almost completed, and the bubbles on the upstream heating element 4b have been completely defoamed. In this state, the liquid flows from the liquid supply chamber 6 via the liquid supply port 5, and the defoaming of the bubbles proceeds and the meniscus M returns. After this state, the movable member is displaced upward by the restoring force due to its rigidity, and returns to the steady state position.

As described above, in the mode in which both the heating elements 4a and 4b are simultaneously driven, it is possible to discharge droplets having a smaller ejection amount than the total ejection amount when the respective heating elements 4a and 4b are individually driven. it can.

Next, the droplet discharging operation in the mode in which the downstream heating element 4a is driven first will be described. FIGS. 15 and 16 show the characteristic phenomena of the droplet discharge operation in the mode in which the downstream-side heating element 4a is driven first.
(C), which is shown in steps (a) to (c) of FIG.

FIG. 15A shows that, by driving only the heating element 4a on the downstream side, a part of the liquid filling the liquid flow path 3 is heated by the heating element 4a on the downstream side, and a film is formed on the heating element 4. This shows a state where boiling has occurred and bubbles 21a have grown isotropically. Here, “isotropic bubble growth” refers to a state in which bubble growth speed in any direction on the bubble surface in the direction perpendicular to the bubble surface is substantially equal.

In the isotropic growth process of the bubble 21a at the initial stage of bubble generation, the movable member 8 is in close contact with the peripheral portion of the liquid supply port 5 to close the liquid supply port 5, and the inside of the liquid flow path 3 is discharged. Except for the outlet 7, it is substantially closed.

FIG. 15B shows that the bubble growth continues in the region A on the downstream heating element 4a, the bubble contraction starts in the region B, and the bubble is substantially isotropic on the upstream heating element 4b. Shows a growing state. By driving the upstream heating element 4b at the time when the bubble on the downstream heating element 4a shifts to the partial growth partial contraction period, the bubble defoaming force in the region B on the downstream heating element 4a is reduced. , Upstream heating element 4b
The foaming pressure of the bubbles on the upper side is superior, the movable member 8 is not displaced, and the sealed state is maintained.

FIG. 15 (c) shows a state in which the bubble 21a on the downstream heating element 4a has grown to a maximum and the bubble 21b on the upstream heating element 4b has partially grown and partially contracted.
In this state, the bubbles in the region B on the downstream heating element 4a contract quickly due to the growth of the bubbles on the upstream heating element 4b. Also, the ejection droplet 2 ejecting from the ejection port 7
2 is still connected to the meniscus M in a long tail state. Further, the hermetically sealed state is maintained.

FIG. 16A shows a state where the bubble 21a on the downstream heating element 4a has been completely defoamed. In this state, the bubble 21b on the upstream heating element 4b continues the partial growth and partial contraction period, and the foaming pressure of the bubble in the area A on the upstream heating element 4b increases the defoaming force of the bubble in the area B. , The movable member 8 is not displaced, and the hermetically sealed state is still maintained. Also, the droplet 22a is ejected from the ejection port,
Due to the bubbling pressure of the bubbles in the region A on the upstream side heating element 4b, the meniscus M returns without retreating much.

FIG. 16B shows a state in which bubbles grow substantially isotropically on the downstream heating element 4a, and bubbles on the upstream heating element 4b disappear. A on the heating element 4b on the upstream side
By driving the downstream heating element 4a again at the point in time when the bubbles in the area shift to bubble disappearance, the downstream heating element 4a is driven again.
The foaming pressure of the bubbles on the upstream heating element 4b exceeds the defoaming force of the bubbles on the upper surface a, the movable member 8 is not displaced, the hermetically sealed state is still maintained, and the meniscus M
Will return further.

FIG. 16 (c) shows that the bubbles on the upstream heating element 4b have already been defoamed and the bubbles on the downstream heating element 4a have been removed.
In the region, the bubble growth continues, and in the region B, the bubble contraction starts. In this state, the movable member 8 starts to be displaced to the steady state position due to the restoring force due to its rigidity and the defoaming force of the bubbles in the region B on the downstream heating element 4a. As a result, the liquid supply port 5 is opened, and the common liquid supply chamber 6 is opened.
And the liquid flow path 3 are in communication.

Thereafter, the second droplet 22b is subjected to substantially the same process as the liquid discharge operation shown in FIGS. 6 (a) to 6 (c).
Is discharged.

As described above, in the mode in which the downstream heating element 4a is driven first, two droplets can be ejected in a series of liquid ejection operations, and both heating elements 4a and 4b are simultaneously driven. The discharge amount can be made larger than in the driving mode.

Next, the droplet discharge operation in the mode in which the upstream heating element 4b is driven first will be described. FIGS. 17 and 18 show the characteristic phenomena of the droplet discharge operation in the mode in which the downstream heating element 4a is driven first, and FIGS.
(C) and the steps shown in FIGS. 18 (a) to (c).

FIG. 17A shows that, by driving only the heating element 4b on the upstream side, part of the liquid filling the liquid flow path 3 is heated by the heating element 4b on the upstream side. This shows a state in which boiling has occurred and bubbles 21b have grown isotropically. Here, “isotropic bubble growth” refers to a state in which bubble growth speed in any direction on the bubble surface in the direction perpendicular to the bubble surface is substantially equal.

In the isotropic growth process of the bubble 21b at the initial stage of bubble generation, the movable member 8 is in close contact with the peripheral portion of the liquid supply port 5 to close the liquid supply port 5, and the inside of the liquid flow path 3 is discharged. Except for the outlet 7, it is substantially closed.

FIG. 17B shows that the bubbles on the upstream heating element 4b drive the downstream heating element 4a during the entire growth period, and the air bubbles on the downstream heating element 4a. This shows a state in which bubbles are growing substantially isotropically. After this state, FIG.
As shown in (c), bubbles 21 on both heating elements 4a, 4b
Both a and 21b shift to the partial growth partial contraction period. Further later, the bubbles on the upstream heating element 4b shift to the contraction period earlier due to the bubbling pressure of the bubbles on the downstream heating element 4a.

FIG. 18 (a) shows a state in which the bubble 21a on the downstream heating element 4a continues the partial growth and partial contraction period, and the bubble 21b on the upstream heating element 4b disappears. . In this state, the movable member 8 has the restoring force due to its rigidity or the area B on the downstream heating element 4a and the upstream heating element 4b.
Due to the defoaming force of the air bubbles in the upper region A and the upper region B, the downward movement of the heating elements 4a and 4b to the steady state position is started more quickly than in the mode in which both the heating elements 4a and 4b are simultaneously driven. As a result, the liquid supply port 5 is opened, and the common liquid supply chamber 6 and the liquid flow path 3 are in communication.

FIG. 18B shows a state where only the bubble defoaming step is performed, and the discharge droplet 22 and the meniscus M are separated. Immediately after changing from bubble growth to bubble elimination in the region A, the contraction energy of the bubbles 21 acts as a force for moving the liquid in the vicinity of the discharge port 7 in the upstream direction as an overall balance. Therefore, the meniscus M is drawn into the liquid flow path 3 from the discharge port 7 at this time, and the liquid column connected to the discharge droplet 22 is cut off. On the other hand, the movable member 8 is displaced downward due to the contraction of the bubble, and the liquid rapidly flows into the liquid flow path 3 from the common liquid supply chamber 6 via the liquid supply port 5 as a large flow. As a result, the flow of rapidly drawing the meniscus M into the liquid flow path 3 suddenly decreases.
The amount of retraction of the meniscus M can be reduced, and the meniscus M starts to return to the position before foaming at a relatively low speed. As a result, the convergence of the vibration of the meniscus M is very good as compared with the liquid ejection method having no movable member according to the present invention.

FIG. 18C shows a state in which the bubbles have completely disappeared and the movable member 8 has returned to the steady state position. In this state, the movable member 8 is displaced upward by its elastic force.
In this state, the meniscus M has already returned near the discharge port 7.

As described above, in the mode in which the heating element 4b on the upstream side is driven first, the movable member can be displaced downward more quickly than in the mode in which the heating elements 4a and 4b are simultaneously driven. It can be further improved.

(Other Embodiments) Various embodiments suitable for a head using the above-described liquid discharging method will be described below.

<Element Substrate> The configuration of the element substrate 1 provided with the heating element 4 for applying heat to the liquid will be described below. In the following, for convenience, 1
A description will be given using a configuration in which two heating elements 4 are provided.

FIG. 19 is a side sectional view of a main part of a liquid discharge apparatus according to the present invention. FIG. 19A shows a head having a protective film described later, and FIG. Is shown.

A top plate 2 is arranged on the element substrate 1, and a liquid flow path 3 is formed between the element substrate 1 and the top plate 2.

The element substrate 1 is formed by forming a silicon oxide film or a silicon nitride film 106 for insulation and heat storage on a substrate 107 such as silicon, and forming a hafnium boride (HfB) constituting the heating element 4 thereon. ₂ ) The electric resistance layer 105 (0.01 to 0.2 μm thick) such as tantalum nitride (TaN) or tantalum aluminum (TaAl) and the wiring electrode 104 (0.2 to 1.0 μm thick) such as aluminum are shown. 1
Patterning is performed as shown in FIG. A voltage is applied to the resistance layer 105 from the wiring electrode 104, and the resistance layer 105
To cause the heating element 4 to generate heat. Wiring electrode 104
A protective film 103 of, for example, silicon oxide or silicon nitride is formed to a thickness of 0.1 to 2.0 μm on the intervening resistance layer 105, and a cavitation-resistant layer 102 (0.1 ~ 0.6 μm thick)
The resistance layer 105 is protected from various liquids such as ink.

In particular, the pressure and shock waves generated during the generation and defoaming of air bubbles are extremely strong, and significantly reduce the durability of a hard and brittle oxide film.
Are used as the anti-cavitation layer 102.

Further, depending on the combination of the liquid, the flow path configuration, and the resistance material, a configuration in which the above-described resistance layer 105 does not require the protective film 103 may be employed. An example is shown in FIG.
Examples of the material of the resistance layer 105 that does not require such a protective film 103 include an iridium-tantalum-aluminum alloy.

As described above, the configuration of the heating element 4 in each of the above-described embodiments includes the above-described resistance layer 1 between the electrodes 104.
05 (heat generating portion) alone, or may include a protective film 103 for protecting the resistance layer 105.

In each of the embodiments, the heating element 4 having a heating portion composed of the resistance layer 105 that generates heat in response to an electric signal is used. However, the present invention is not limited to this.
What is necessary is just to generate bubbles in the foaming liquid sufficient to discharge the discharge liquid. For example, a light-to-heat converter that generates heat by receiving light from a laser or the like, or a heat generator that has a heat generating portion that generates heat by receiving a high frequency may be used.

The element substrate 1 includes, in addition to the heating element 4 including the resistance layer 105 constituting the heating section and the wiring electrode 104 for supplying an electric signal to the resistance layer 105, Functional elements such as a transistor, a diode, a latch, and a shift register for selectively driving the heating element 4 (electrothermal conversion element) may be integrally formed by a semiconductor manufacturing process.

Further, in order to drive the heat generating portion of the heat generating element 4 provided on the element substrate 1 as described above and to discharge the liquid, the above-described resistance layer 105 is connected to the above-described resistance layer 105 via the wiring electrode 104 as shown in FIG. A rectangular pulse as shown is applied, and the wiring electrode 1
The resistance layer 105 between the layers 04 is heated rapidly. In the above-described liquid ejection head, the voltage is 24 V and the pulse width is 7 μs.
The heating element was driven by applying an electric signal of ec, a current of 150 mA at 6 kHz, and the liquid ink was ejected from the ejection port 4 by the operation described above. However, the condition of the drive signal is not limited to this, and any drive signal can be used as long as it can appropriately foam the foaming liquid.

<Discharged Liquid> Among such liquids, as a liquid (recording liquid) used for recording, an ink having a composition used in a conventional bubble jet apparatus can be used.

However, the properties of the discharged liquid are:
It is desired that the liquid is not a liquid that hinders ejection, foaming, or operation of the movable member.

As the ejection liquid for recording, a high-viscosity ink or the like can be used.

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 was increased due to the improvement of the discharge force, the liquid was discharged. Drop landing accuracy is improved, and a very good recorded image can be obtained.

[0124]

[Outside 1]

<Liquid Discharge Apparatus> FIG. 21 shows a schematic configuration of an ink jet recording apparatus which is an example of a liquid discharge apparatus to which the liquid discharge head having the structure described in the present embodiment can be mounted. The head cartridge 601 mounted on the ink jet recording apparatus 600 shown in FIG. 21 has a liquid ejection head having the above-described structure, and a liquid container for holding liquid supplied to the liquid ejection head. The head cartridge 601 is shown in FIG.
As shown in FIG. 1, it is mounted on a carriage 607 that engages with a spiral groove 606 of a lead screw 605 that rotates via driving force transmission gears 603 and 604 in conjunction with forward and reverse rotation of a driving motor 602. . Drive motor 602
Causes the head cartridge 601 to reciprocate along the guide 608 along with the carriage 607 in the directions of arrows a and b. Inkjet recording device 600
Includes a print sheet P as a recording medium for receiving a liquid such as ink discharged from the head cartridge 601.
And a recording medium conveying means (not shown) for conveying the recording medium. The platen 609 is moved by the recording medium conveying means.
The paper holding plate 610 of the printing paper P conveyed above is
Print paper P over the moving direction of carriage 607
Is pressed against the platen 609.

In the vicinity of one end of the lead screw 605, photocouplers 611 and 612 are provided. The photocouplers 611 and 612 are home position detection means for confirming the presence of the lever 607a of the carriage 607 in the region of the photocouplers 611 and 612 and switching the rotation direction of the drive motor 602. Near one end of the platen 609, the head cartridge 6
A support member 613 that supports a cap member 614 that covers the front surface having the 01 discharge port is provided. In addition, an ink suction unit 615 that sucks ink that has been idly discharged from the head cartridge 601 and accumulated inside the cap member 614 is provided. This ink suction means 615
Thus, the suction recovery of the head cartridge 601 is performed through the opening of the cap member 614.

The ink jet recording apparatus 600 is provided with a main body support 619. The main body support 619 has a moving member 618 in the front-rear direction, that is, the carriage 60.
7 is supported so as to be movable in a direction perpendicular to the moving direction. The moving member 618 includes the cleaning blade 6.
17 are attached. Cleaning blade 61
Reference numeral 7 is not limited to this form, and may be another form of a known cleaning blade. Further, the ink suction means 61
5 is provided with a lever 620 for starting suction when the suction recovery operation is performed by the control unit 5. The movement is controlled by a known transmission means such as the like. A signal is given to a heating element provided in the head cartridge 601,
An ink jet recording control unit that controls the driving of each mechanism described above is provided on the main body of the recording apparatus.
1 is not shown.

In the ink jet recording apparatus 600 having the above-described configuration, the head cartridge 601 reciprocates over the entire width of the print paper P with respect to the print paper P transported on the platen 609 by the recording medium transport means. When a drive signal is supplied from a drive signal supply unit (not shown) to the head cartridge 601 during this movement, ink (recording liquid) is ejected from the liquid ejection head unit to the recording medium in accordance with the signal, and recording is performed. Done.

FIG. 22 is a block diagram of the entire recording apparatus for performing ink jet recording by the liquid ejection apparatus of the present invention.

The recording device receives print information from the host computer 300 as a control signal. The print information is temporarily stored in the input interface 301 inside the printing apparatus, and at the same time, is converted into data that can be processed in the recording apparatus.
It is input to a CPU (central processing unit) 302 which also serves as a head drive signal supply unit. The CPU 302 stores data input to the CPU 302 based on a control program stored in a ROM (Read Only Memory) 303, into a RAM (Random Access Memory) 304.
And the like, and converted into data (image data) to be printed.

Further, the CPU 302 drives the drive motor 306 for moving the carriage 607 on which the recording paper and the head cartridge 601 are mounted in synchronization with the image data in order to record the image data at an appropriate position on the recording paper.
Create driving data to drive. The image data and the motor drive data are transmitted to the head cartridge 60 via the head driver 307 and the motor driver 305, respectively.
1 and the driving motor 306, and each is driven at a controlled timing to form an image.

Examples of the recording medium 150 used in such a recording apparatus, to which a liquid such as ink is applied, include various papers, OHP sheets, plastic materials used for compact discs, decorative plates, etc., cloth, aluminum, etc. Metal materials such as copper and copper, leather materials such as cow skin, pig skin and artificial leather, wood such as wood and plywood, ceramic materials such as bamboo materials and tiles, and three-dimensional structures such as sponges can be targeted.

As the recording apparatus, various types of paper and O
A printer device for recording on an HP sheet or the like, a recording device for a plastic for recording on a plastic material such as a compact disc, a recording device for a metal for recording on a metal plate,
A recording device for leather that records on leather, a recording device for wood that records on wood, a recording device for ceramic that records on ceramic materials, a recording device that records on a three-dimensional network structure such as a sponge, or a fabric Also includes a textile printing device for performing recording on the paper.

Further, as a discharge liquid used in these liquid discharge devices, a liquid suitable for each recording medium and recording conditions may be used.

FIG. 23 is a sectional view showing another embodiment of the liquid discharge head of the present invention.

In the liquid discharge head of the embodiment shown in FIG.
The element substrate 1 and the top plate 2 are joined, and the element substrate 1 and the top plate 2 are joined.
A liquid flow path 3 having one end communicating with the discharge port 7 is formed between them. Heating elements 4a and 4b are provided as bubble generating means for generating bubbles in the liquid replenished in the liquid flow path 3. A liquid supply port 5 is provided in the liquid flow path 3, and a liquid supply chamber communicating with the liquid supply port 5 is provided.

The movable member 8 has a small gap α between the liquid supply port 5 and the liquid flow path 3 with respect to the surface on which the liquid supply port 5 is formed.
(For example, 10 μm or less). A region surrounded by at least the free end of the movable member 8 and both ends continuous with the movable member 8 is larger than an opening region of the liquid supply port 5 with respect to the liquid flow path. Each of the side walls 10 has a minute gap β. Thereby, the movable member 8 can move in the liquid flow path 3 without frictional resistance, while the displacement into the liquid supply port 5 is regulated at the peripheral portion of the opening area S, and the liquid supply port 5 is closed to close the liquid supply port 3.
From the liquid supply chamber 6 to the liquid supply chamber 6, the bubbles can be moved from the substantially closed state to the refillable state toward the liquid flow path side with the defoaming of the bubbles. Further, in the present embodiment, the movable member 8 is located to face the element substrate 1.
One end of the movable member 8 is connected to the heating elements 4a, 4a of the element substrate 1.
b is a free end displaced to the b side, and the other end side is a fixed member 9
It is supported by.

[0138]

As described above, the liquid discharge head and the liquid discharge apparatus of the present invention have a plurality of bubble generating means in the liquid flow path and generate the smallest volume bubble among the plurality of bubble generating means. The movable member is configured to hermetically close and substantially shut off the liquid supply port by driving the bubble generating means, or generate bubbles by selecting one of the plurality of bubble generating means. When driving any of the bubble generating means, the movable member is configured to seal and substantially shut off the liquid supply port, so that each liquid discharged by driving each of the bubble generating means The droplet ejection speed can be made equal.

Further, according to the liquid discharge method of the present invention, the bubble generating means for generating the smallest volume among the plurality of bubble generating means is driven to generate the bubbles.
During the period from when the driving voltage is applied to the bubble generating means to when the period in which the entire bubble is growing substantially isotropically ends, the movable member hermetically closes and shuts off the liquid supply port, or When generating a bubble by selecting one of the plurality of bubble generating means, when driving any of the bubble generating means, the whole of the bubble is substantially reduced after a driving voltage is applied to the bubble generating means. By the end of the period during which the isotropic growth is completed, the movable member closes and substantially shuts off the liquid supply port, thereby improving the convergence of the vibration of the meniscus, and after discharging the droplet. The refill frequency can be increased.

[Brief description of the drawings]

FIG. 1 shows a liquid ejection head 1 according to an embodiment of the present invention.
FIG. 4 is a cross-sectional view along one liquid flow direction.

FIG. 2 is a sectional view taken along line XX ′ of the liquid discharge head shown in FIG.

FIG. 3 is a sectional view taken along line YY ′ of the liquid discharge head shown in FIG. 1;

FIG. 4 is a cross-sectional view of a flow path for explaining a “linear communication state”.

FIG. 5 is a view for explaining an ejection operation of the liquid ejection head having the structure shown in FIGS. 1 to 3;

FIG. 6 is a view for explaining an ejection operation of the liquid ejection head having the structure shown in FIGS. 1 to 3;

FIG. 7 is a diagram showing an isotropic growth state of bubbles in FIG. 5 (b).

8 is a graph showing a correlation between a time change of bubble growth in a region A and a region B shown in FIG. 4 and a behavior of a movable member.

9 is a graph showing a correlation between a time change of bubble growth and a behavior of the movable member in a liquid ejection head having a different form from the relative position of the movable member and the heating element shown in FIG.

10 is a graph showing a correlation between a time change of bubble growth and a behavior of the movable member in a liquid ejection head having a different form from the relative position of the movable member and the heating element shown in FIG.

FIG. 11 is a cross-sectional view showing an example of the liquid discharge head of the present invention in which the cross-sectional area of the liquid flow path (nozzle) is constant over its entire length.

FIG. 12 is a cross-sectional view showing an example in which the cross-sectional area of the liquid flow path (nozzle) of the liquid discharge head of the present invention changes in the length direction.

FIG. 13 is a view for explaining an ejection operation of the liquid ejection head having the structure shown in FIGS. 1 to 3;

FIG. 14 is a view for explaining an ejection operation of the liquid ejection head having the structure shown in FIGS. 1 to 3;

FIG. 15 is a view for explaining an ejection operation of the liquid ejection head having the structure shown in FIGS. 1 to 3;

FIG. 16 is a view for explaining an ejection operation of the liquid ejection head having the structure shown in FIGS.

FIG. 17 is a view for explaining an ejection operation of the liquid ejection head having the structure shown in FIGS. 1 to 3;

FIG. 18 is a view for explaining an ejection operation of the liquid ejection head having the structure shown in FIGS. 1 to 3;

FIG. 19 is a longitudinal sectional view of the liquid discharge head of the present invention,
FIG. 3A shows a case where a protective film is provided, and FIG. 3B shows a case without a protective film.

FIG. 20 is a waveform diagram of a pulse wave for driving a heating element used in the present invention.

FIG. 21 is a diagram showing a schematic configuration of a liquid ejection device equipped with the liquid ejection head of the present invention.

FIG. 22 is a block diagram of an entire apparatus for performing liquid discharge recording in a liquid discharge method and a liquid discharge head of the present invention.

FIG. 23 is a sectional view showing another embodiment of the liquid ejection head of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Element board 2 Top plate 3 Liquid flow path 4, 4a, 4b Heating element 5 Liquid supply port 6 Common liquid supply chamber 7 Discharge port 8 Movable member 9 Fixed member 10 Channel side wall 11 Bubble generation area 21, 21a, 21b Bubbles 22 , 22a, 22b Droplet 102 Anti-cavitation layer 103 Protective film 104 Wiring electrode 105 Resistive layer 106 Silicon nitride film 107 Substrate 300 Host computer 301 Input / output interface 302 CPU 303 ROM 304 RAM 305 Motor driver 307 Head driver 600 Ink jet recording device 601 Head cartridge 602 Drive motor 603, 604 Drive transmission gear 605 Lead screw 606 Spiral groove 607 Carriage 607a Lever 608 Guide 609 Platen 610 Paper press plate 611, 612 Photocoupler 613 supporting member 614 cap member 615 ink suction means 617 cleaning blade 618 moves member 619 main support 620 lever 621 cams

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masahiko Kubota 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Masanori Takenouchi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inside (72) Inventor Masami Ikeda 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hiroshi Sugitani 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. ( 72) Inventor Takashi Saito 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc.

Claims (19)

[Claims] 1. A discharge port for discharging a liquid, a liquid flow path having one end constantly connected to the discharge port, and having a bubble generation region for generating bubbles in the liquid, and provided in the liquid flow path. A liquid supply port that communicates with a common liquid supply chamber that stores the liquid supplied to the liquid flow path; and a plurality of bubble generation units that generate bubbles in the liquid disposed in the liquid flow path. The liquid supply port is provided in the liquid flow path in a state where the discharge port side is supported as a free end with a gap of 10 μm or less from the liquid flow path side with respect to the liquid flow path side, and the liquid supply port is larger than the opening area of the liquid supply port A plate-shaped movable member having a large projection area, wherein the discharge port and the bubble generation unit are in a linear communication state, and a bubble generation unit that generates a bubble having the smallest volume among the plurality of bubble generation units. By driving the movable member A liquid discharge head, characterized in that substantially block to seal the serial liquid supply port. 2. A liquid outlet for discharging a liquid, a liquid flow path having one end always connected to the discharge port, and having a plurality of bubble generation regions for generating air bubbles in the liquid; A liquid supply port that is provided and communicates with a common liquid supply chamber that stores the liquid supplied to the liquid flow path; and a plurality of bubbles that generate bubbles in the liquid disposed in the liquid flow path. An opening area of the liquid supply port, the liquid supply port being provided in the liquid flow path in a state where the discharge port side is supported as a free end with a gap of 10 μm or less with respect to the liquid flow path side of the liquid supply port; A plate-shaped movable member having a larger projection area, wherein the discharge port and the bubble generation means are in a linear communication state, and the bubbles are formed by selecting one of the plurality of bubble generation means. When generating, any air bubble generation means When moving also the liquid discharge head in which said movable member is substantially shut off by sealing the liquid supply port. 3. The liquid crystal device according to claim 1, wherein the plurality of bubble generating means provided in the liquid flow path are arranged in an order in which a foaming area gradually increases from a downstream side to an upstream side of the liquid flow path. 3. The liquid discharge head according to 2. 4. The liquid discharge head according to claim 1, wherein a gap is also provided between a liquid flow path wall forming the liquid flow path and the movable member. 5. The liquid discharge head according to claim 1, wherein the liquid is discharged by driving the plurality of bubble generating units. 6. The liquid discharge head according to claim 5, wherein the liquid is discharged by simultaneously driving the plurality of bubble generating means. 7. The liquid ejection head according to claim 5, wherein the liquid ejection head is configured to eject the liquid by driving a bubble generation unit closest to the ejection port first among the plurality of bubble generation units. . 8. The liquid ejection device according to claim 5, wherein the liquid ejection device is configured to eject the liquid by first driving the bubble generation device closest to the movable member among the plurality of bubble generation devices. head. 9. A liquid discharge apparatus comprising: the liquid discharge head according to claim 1; and a drive signal supply unit that supplies a drive signal for discharging liquid from the liquid discharge head. 10. A liquid ejection apparatus comprising: the liquid ejection head according to claim 1; and a recording medium transport unit that transports a recording medium that receives the liquid ejected from the liquid ejection head. apparatus. 11. The liquid ejecting apparatus according to claim 9, wherein recording is performed by ejecting ink from the liquid ejecting head and attaching the ink to a recording medium. 12. A liquid outlet for discharging a liquid, a liquid flow path having one end always connected to the discharge port, and having a plurality of bubble generating regions for generating air bubbles in the liquid; A liquid supply port that is provided and communicates with a common liquid supply chamber that stores the liquid that is supplied to the liquid flow path; and that the liquid that is provided in the liquid flow path and is disposed in the liquid flow path has bubbles. A plurality of bubble generating means for generating the liquid flow path, the liquid flow path wall forming the liquid flow path and the liquid supply port, the liquid flow path wall and the liquid discharge port being minute relative to the liquid flow path side. A movable member provided in the liquid flow path in a state where the discharge port side is supported as a free end with a gap, and having a projection area larger than an opening area of the liquid supply port. The liquid discharging method used, wherein the plurality of bubble generating means are used. By driving the bubble generating means for generating the bubble with the smallest volume to generate the bubbles, from the time when the driving voltage is applied to the bubble generating means to the end of the period in which the entire bubble is growing substantially isotropically Wherein the movable member hermetically closes and substantially shuts off the liquid supply port. 13. A liquid outlet for discharging a liquid, a liquid flow path having a plurality of bubble generation regions, one end of which is always in communication with the discharge port, for generating bubbles in the liquid; A liquid supply port that is provided and communicates with a common liquid supply chamber that stores the liquid that is supplied to the liquid flow path; and that the liquid that is provided in the liquid flow path and is disposed in the liquid flow path has bubbles. A plurality of bubble generating means for generating the liquid flow path, the liquid flow path wall forming the liquid flow path and the liquid supply port, the liquid flow path wall and the liquid discharge port being minute relative to the liquid flow path side. A movable member provided in the liquid flow path in a state where the discharge port side is supported as a free end with a gap, and having a projection area larger than an opening area of the liquid supply port. The liquid discharging method used, wherein the plurality of bubble generating means are used. When generating a bubble by selecting one of the above, when driving any of the bubble generating means, the entire bubble has grown substantially isotropically after the drive voltage is applied to the bubble generating means. The liquid discharging method, wherein the movable member hermetically closes and substantially shuts off the liquid supply port until a period ends. 14. The method according to claim 1, wherein the change in the growth volume of the bubbles in the bubble generation region and the time from the generation of the bubbles to the defoaming are significantly different between the discharge port side and the liquid supply port side.
14. The liquid discharging method according to 2 or 13. 15. The liquid discharging method according to claim 12, wherein the bubble generation region is not opened to the atmosphere. 16. The liquid discharging method according to claim 12, wherein the liquid is discharged by driving the plurality of bubble generating units. 17. The liquid discharging method according to claim 16, wherein the liquid is discharged by simultaneously driving the plurality of bubble generating means. 18. The liquid discharging method according to claim 16, wherein the liquid is discharged by first driving the bubble generating means closest to the discharge port among the plurality of bubble generating means. 19. The liquid discharging method according to claim 16, wherein the liquid is discharged by first driving the bubble generating means closest to the movable member among the plurality of bubble generating means.