JP3535816B2 - Liquid ejection head, liquid ejection device, and liquid ejection method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid ejection head, a liquid ejection device, and a liquid ejection method for ejecting a liquid by causing thermal energy to act on the liquid to generate bubbles.

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

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

[0004]

2. Description of the Related Art Conventionally, in a recording device such as a printer,
Energy such as heat is applied to the liquid ink in the flow path to generate bubbles, and the ink is ejected from the ejection port by the action force based on the resulting abrupt volume change, and this is attached to the recording medium to form an image. An inkjet recording method for performing
A so-called bubble jet (registered trademark) recording method is known. In a recording apparatus using this bubble jet recording method, as disclosed in US Pat. No. 4,723,129, an ejection port for ejecting ink, a flow path communicating with this ejection port, An electrothermal converter (heater) as an energy generating means for ejecting the ink arranged in the flow path is generally arranged.

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

As the bubble jet technology is applied to products in various fields, various demands are increasing,
For example, in order to obtain a high-quality image, driving conditions have been proposed for providing a liquid ejection method, etc., in which the ink ejection speed is fast and good ink ejection is possible based on stable bubble generation. From the point of view, there has been proposed an improved flow passage shape in order to obtain a liquid discharge head having a high filling (refill) speed of the discharged liquid into the liquid flow passage.

Furthermore, in order to simultaneously achieve high definition of the recorded image and high printing speed, one liquid flow path (nozzle)
It has also been proposed that a plurality of electrothermal converters are arranged in the same, and droplets having different sizes are ejected from the same nozzle.

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

[0009]

A plurality of electrothermal converters are arranged in one nozzle, and a liquid ejection head (hereinafter referred to as "ejection amount modulation") configured to eject droplets having different sizes from the same nozzle. Also referred to as a “head”), it is necessary to increase the ejection amount modulation ratio (volume ratio of small droplets to large droplets) in order to realize high-definition recording images and high printing speed. is there.

However, if the ejection amount modulation ratio is increased,
Since the difference in ejection speed between the small droplets and the large droplets becomes large and the landing position of the droplets on the recording medium shifts, the small droplets and the large droplets are ejected within one scanning stroke. In some cases, or it becomes necessary to perform an advanced image processing step such as changing the ejection timing according to the size of the droplets to be ejected. Further, if the size ratio of the heaters arranged in one nozzle is increased, the nozzle length is unavoidably lengthened, which may have a large effect on the ejection characteristics such as a reduction in refill frequency.

In the ejection amount modulation head, it is required that the ejection speeds of the respective liquid droplets are substantially equal, while the ejection amount modulation head ejects liquid droplets of different sizes from the same nozzle. It is difficult to configure each of the droplets of each size to be optimal. Moreover, in the ejection amount modulation head, since a plurality of heaters are arranged in one nozzle, the size of the heaters and the degree of freedom of the arrangement position may be limited.

As described above, the ejection amount modulation head is required to have much higher design conditions than a general liquid ejection head in which one heater is arranged for one nozzle. Conventionally, if these conditions are attempted to be satisfied, the ejection efficiency is lowered, the temperature of the head is likely to rise, and it is necessary to make the dimensional accuracy and assembly accuracy of the component parts highly accurate.

Therefore, according to the present invention, a liquid discharge head, a liquid discharge method, and a liquid which can increase a discharge amount ratio of liquid droplets, can make discharge speeds of respective liquid droplets substantially equal to each other, and can increase a refill frequency after discharge. An object is to provide a discharge device.

[0014]

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

[0015]

According to the liquid discharge head of the present invention having such a configuration, a part of the liquid filling the liquid flow path is heated by the heating element (bubble generating means), and at the same time as the generation of bubbles accompanying film boiling. The movable member is in 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 sealed 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 the liquid is discharged, so that the flow resistance behind the heating element is almost infinite. Can be considered. Furthermore, since the flow resistance behind the heating element (upstream side) 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 of the heating element (downstream side). Even if changes, it is almost zero. Therefore, in the liquid ejection head of the present invention, the liquid ejection characteristic is determined only by the "flow resistance in front (downstream side of the heating element)" of the three elements that determine the liquid ejection characteristic.

The discharge speed of the liquid is inversely proportional to the flow resistance in front of the heating element, and is proportional to the foaming power determined by the effective foaming area of the heating element. Further, since the discharge amount of the liquid discharged from the discharge port is proportional to the effective bubbling area of the heating element, in the liquid discharge head of the present invention, the front portion (downstream side) of each heating element provided in the same liquid flow path is By making the ratio of the flow resistance and the ejection amount equal, the ejection speeds of the droplets ejected by heating the heating elements become equal. As a result, according to the present invention, it becomes easy to equalize the ejection speed of each droplet even if the ejection amount ratio of the droplets is increased.

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

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

The liquid may be ejected by driving the plurality of bubble generating means. In this case, the liquid may be ejected by simultaneously driving the plurality of bubble generating means. Alternatively, the liquid may be ejected by first driving the air bubble generating means closest to the ejection port among the plurality of air 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 liquid ejecting apparatus of the present invention has the above-mentioned liquid ejecting head of the present invention, and drive signal supplying means for supplying a drive signal for ejecting liquid from the liquid ejecting head.

Another liquid ejecting apparatus of the present invention has the above-mentioned liquid ejecting head of the present invention and a recording medium conveying means for conveying a recording medium that receives the liquid ejected from the liquid ejecting head.

Further, recording may be performed by ejecting ink from the liquid ejection head and adhering the ink to a recording medium.

Further, in the liquid discharging method of the present invention, a liquid flow path having a discharge port for discharging the liquid and a plurality of bubble generating regions for continuously generating a bubble in the liquid, one end of which is always communicated with the discharge port. A liquid supply port that is disposed in the liquid flow path and communicates with a common liquid supply chamber that stores the liquid supplied to the liquid flow path; A plurality of bubble generating means for generating bubbles in the liquid arranged in the liquid flow path, and between the liquid flow path wall and the liquid supply port forming the liquid flow path, the liquid flow path wall and the liquid discharge port A movable member that is provided in the liquid flow channel in a state of being supported with the discharge port side as a free end with a minute gap from the liquid flow channel side, and that has a projection region larger than the opening region of the liquid supply port; A liquid ejecting method using a liquid ejecting head comprising: By generating a bubble by driving the bubble generating unit that generates the smallest volume bubble among the number of bubble generating units, the entire bubble grows substantially isotropic after the drive voltage is applied to the bubble generating unit. The movable member hermetically closes and substantially shuts off the liquid supply port until the end of the period.

[0026]

As a result, the liquid flows into the liquid flow path earlier than when the receding amount of the meniscus formed at the discharge port becomes maximum, and the flow that rapidly draws the meniscus into the liquid flow path sharply decreases. As the meniscus receding amount decreases, the meniscus starts to return to the pre-foaming position at a relatively low speed. As a result, the time for the meniscus to return to the initial state after ejection is very short, that is, the fixed amount of ink replenishment (refill) to the liquid flow path is completed quickly, so highly accurate (constant) ink ejection is possible. The ejection frequency (driving frequency) can also be dramatically improved in the implementation.

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

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

The liquid may be ejected by driving the plurality of bubble generating means. In this case, the liquid may be ejected by simultaneously driving the plurality of bubble generating means. Alternatively, the liquid may be ejected by first driving the air bubble generating means closest to the ejection port among the plurality of air 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.

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

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

"Downstream" with respect to the bubble itself means
It means a bubble generated in the downstream side with respect to the center of the bubble in the flow direction or the structural direction, or in the region downstream from the center of the area of the heating element.

Further, the expression "the movable member hermetically closes and substantially blocks the liquid supply port" in the present invention does not necessarily mean that the movable member is in close contact with the peripheral portion of the liquid supply port.
This includes that the movable member approaches the liquid supply port without limit.

[0035]

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

(First Embodiment) FIG. 1 is a sectional view taken along the direction of one liquid flow path of a liquid ejection head according to an embodiment of the present invention, and FIG. 2 is an X of the liquid ejection head shown in FIG. −
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 ′ that is shifted from the center of the ejection port of the liquid ejection head shown in FIG.

In the liquid discharge head in the form of a plurality of channels-common liquid chamber shown in FIGS. 1 to 3, the element substrate 1 and the top plate 2 are fixed in a laminated state via the channel sidewalls 10, and both plates 1 , 2 is formed with a liquid flow path 3 whose one end communicates with the discharge port 7. Many liquid channels 3 are provided 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 liquid flow path 3.
Although two heating elements are arranged in each liquid flow path 3 in this embodiment, 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,
In the area near the surface where 4b and the discharge liquid come into contact, the heating element 4
There is a bubble generation region 11 where a and 4b are rapidly heated and bubbling occurs in the discharge liquid.

A supply portion forming member 5 is provided in each of the plurality of liquid flow paths 3.
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 the single common liquid supply chamber 6 into a large number of liquid flow paths 3, and has an amount of liquid commensurate with the liquid discharged from the discharge ports 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
The substantial opening area for supplying the liquid to the liquid flow path 3 is shown.

The movable member 8 is provided between the liquid supply port 5 and the liquid flow path 3 substantially parallel to the opening area S of the liquid supply port 5 with a minute gap α (for example, 10 μm or less). Has 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 minute gap is provided between the side portion of the movable member 8 and each of the flow path side walls 10 on both sides. It has β (see FIGS. 2 and 3).

The above-mentioned supply portion forming member 5A 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 paths, but if the gap γ is large, the movable member 8 is likely to block the opening region S, and if the gap β is large, the movable member 8 is in a steady state in which the movable member 8 is located via the gap α. Also, it becomes easy to move to the element substrate 1 side with defoaming. In this embodiment, the gap α is 3 μm, the gap β is 3 μm, and the gap γ is 4 μm.

Further, 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 capable of sufficiently sealing the opening region. . 8A of the movable member 8 is a continuous portion where the upstream end of the opening region of the liquid supply port 5 is continuous in the direction in which the plurality of movable members intersect the plurality of flow paths (a part of which is shown in FIG. 1). Is separated from the fixing member 9) on the free end side extension line (see FIG. 3). In this embodiment,
As shown in FIGS. 3 and 2, the thickness of the portion of the supply portion forming member 5A along the movable member 8 is set to be smaller than the thickness of the flow path side wall 10 itself. The supply portion forming member 5A is laminated. As shown in FIG. 3, the portion of the supply portion forming member 5A closer to the discharge port 7 than the free end 8B of the movable member is set to have the same thickness as the thickness of the liquid flow path wall 10 itself.

As a result, the movable member 8 can be moved within the liquid flow path 3 without frictional resistance, while the displacement toward the opening region S can be restricted at the peripheral portion of the opening region S. As a result, the opening region S is substantially closed and the common liquid supply chamber 6 is supplied from inside the liquid flow path 3.
While it is possible to prevent the liquid flow into the liquid flow path, it is possible to move the liquid flow path side from the substantially closed state to the refillable state as the bubbles disappear. In addition, in the present embodiment, the movable member 8 is also positioned parallel to the element substrate 1 with respect to the element substrate 1. The 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 the fixed member 9. Further, the fixed member 9 closes the liquid flow path 3 at the end of the movable member 8 on the side opposite to the discharge port 7 (that is, the end on the upstream side).

As shown in FIG. 4, in this embodiment, there is no obstacle such as a valve between the heating elements 4a and 4b as the electrothermal converters and the discharge port 7, and the liquid flow is prevented. On the other hand, it is in a "linear communication state" in which a straight flow path structure is maintained. More preferably, this is achieved by linearly matching the propagation direction of the pressure wave generated when bubbles are generated and the accompanying flow direction of the liquid with the liquid ejection direction, thereby ejecting the ejection direction and ejection speed of the ejection droplets. This is because it is desirable to form an ideal state that stabilizes the state 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 heating elements 4a, 4b, particularly the discharge port side (downstream side) of the heating element having an influence on the discharge port side of bubbles. ) Is directly connected with a straight line, and this means that when there is no fluid in the flow path, the heating element, particularly the downstream side of the heating element, is viewed from the outside of the discharge port 7. Is possible (see FIG. 4).

Next, the ejection operation of the liquid ejection head of this embodiment will be described. FIGS. 5 and 6 are sectional views of the liquid discharge head along the liquid flow path direction for explaining the discharge operation of the liquid discharge head having the structure shown in FIGS. 5A to 5D and FIG.
It is shown separately in the steps (a) to (c). Further, in FIGS. 5 and 6, the symbol M represents a meniscus formed by the discharge 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 minute 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 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” means a state in which the bubble growth rates in the normal direction of the bubble surface are almost equal in places on the bubble surface.

In the isotropic growth process of the bubble 21 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 in a substantially sealed state. This sealed state is
It is maintained during any of the isotropic growth processes of the bubble 21. It should be noted that the heating element 4 is kept in the closed period.
It may be between the time when the electric energy is applied to and the end of the isotropic growth process of the bubble 21. Also,
In this closed state, the inertance from the center of the heating element 4 in the liquid flow path 3 to the liquid supply port side (difficulty of movement when the stationary liquid 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 bubble 21 continues to grow. As described above, when the inside of the liquid flow path 3 is substantially sealed except for the discharge port 7, the flow of liquid does not go 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 spent only on the growth of the bubbles on the discharge port 7 side.

The bubble growth process in FIGS. 5A to 5C will be described in detail with reference to FIG. Figure 7
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). To do. Then, the bubbles in the film boiling state continue to grow isotropically as shown in FIGS. 7B to 7C (the state in which the bubbles are growing isotropically as described above is referred to as a “semi-plow state”). be called). However, as shown in FIG. 5B, when the inside of the liquid flow path 3 is substantially sealed except for the discharge port 7, the liquid cannot be moved to the upstream side. A part of the bubbles on the side (liquid supply port side) does not grow, and only the remaining downstream side (ejection port side) grows. This state is shown in FIGS. 5C, 7D, and 7E.

For convenience of explanation, when heating the heating element 4a, a region where bubbles do not grow on the heating element 4a is designated as a region B, and a region where the bubbles grow is on the side of the discharge port 7 is designated as A.
The area. In the region B, the foam volume at the time of isotropic bubble growth becomes maximum.

Next, 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 area A, the bubbles grow largely toward the ejection port side. Then, the volume of bubbles in the B region starts to decrease. As a result, the movable member 8 begins to be displaced downward to the steady state position due to 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 with each other.

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

In FIG. 6B, the growth of the bubble 21 is stopped and only the defoaming step is performed. The discharge droplet 22 and the meniscus M are shown.
Shows the state where and are separated. Immediately after the bubble growth is changed to the defoaming in the region A, the contraction energy of the bubble 21 acts as a force for moving the liquid in the vicinity of the ejection port 7 in the upstream direction as a whole balance. Therefore, the meniscus M is drawn into the liquid flow path 3 from the ejection port 7 at this time, and the ejection droplet 22
The liquid column connected to is to be separated. On the other hand, the movable member 8 is displaced downward due to the contraction of the bubbles, and the liquid rapidly flows into the liquid flow path 3 from the common liquid supply chamber 6 through the liquid supply port 5. As a result, the flow that rapidly draws the meniscus M into the liquid flow path 3 suddenly decreases, 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 that does not include the movable member according to the present invention.

In FIG. 6C, the bubbles 21 have completely disappeared,
The movable member 8 is also returned to the steady state position. To this state, the movable member 8 is displaced upward by its elastic force (in the direction of the solid line arrow in FIG. 6B). Further, in this state, the meniscus M has already returned near the ejection port 7.

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

As shown in FIG. 8, the time variation of 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 the passage of time, reaches a maximum at a certain point, and then decreases. On the other hand, in the B region, the time required from the start of foaming to the defoaming is shorter, the maximum growth volume of the bubbles is smaller, and the time to reach the maximum growth volume is shorter than in the A region. 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 significantly different, and the B region is smaller.

In particular, in FIG. 8, since the bubble volume increases with the same time change in the initial stage of bubble generation, the curve A and the curve B overlap. That is, in the initial stage of bubble generation, a period during which the bubble isotropically grows (semi-puro state) occurs.
Then, although the curve A draws a curve that increases to the maximum point, the curve B branches from the curve A at some point and draws a curve in which the bubble volume decreases. That is, there is a period (partial growth partial contraction period) in which the bubble volume increases in the region A, but decreases in the region B.

Based on the above-described bubble growth method, in the form in which 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 sealed except for the discharge port. The start of this closed state is performed during the period when the bubbles are isotropically growing. Next, in 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 certain time from the start of the partial growth partial contraction period. Next, in the period shown in the figure, the movable member is further displaced downward from the steady state. Next, in the period shown in the figure, the downward displacement of the movable member is almost stopped, and the movable member is in the equilibrium state at the open position. Finally, in 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 influenced by the relative position of the movable member and the heating element. Therefore, with reference to FIGS. 9 and 10, a correlation between bubble growth and the behavior of the movable member in the liquid ejection head including the movable member and the heating element at the relative positions different from those of 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 in the form in which the free end of the movable member covers the entire heating element.
(B) has shown the graph of the correlation. If the area where the heating element 4a is covered by the movable member 8 is large as in the configuration shown in FIG. 9A, the period of FIG. 9 becomes shorter than that in the configuration of FIG. 4a is more preferable because it becomes a closed state in a short time after heating 4a. The behavior of the movable member in each of the periods from to in FIG. 9 is the same as the behavior described based on FIG. Further, if the form of FIG. 9 is adopted, the movable member 8 is easily affected by the volume reduction of the bubbles, and therefore, as can be seen from the start of the period in the same figure, the start of opening the liquid supply port 5 by the movable member 8 causes partial growth. Immediately after the start of the partial contraction period. That is, the opening timing of the movable member 8 is earlier than that in the case of the configuration of FIG. For the same reason, the amplitude of the movable member 8 becomes large.

FIG. 10 is a diagram for explaining the correlation between bubble growth and the behavior of the movable member when the heating element and the movable member are separated from each other.
Shows a graph of the correlation. (A) of FIG.
When the heating element 4a is closer to the discharge port than the position below the free end of the movable member 8 as shown in FIG.
Is less affected by the decrease in the volume of the bubbles, the opening of the liquid supply port 5 by the movable member 8 is started considerably later than the start of the partial growth partial contraction period, as can be seen from the start of the period shown in FIG. That is, the opening timing of the movable member 8 is later than that in the case of the configuration of FIG. For the same reason, the amplitude of the movable member 8 becomes small. The behavior of the movable member 8 in each of the periods from to in FIG. 10 is the same as the behavior described based on FIG.

Further, the positional relationship between the movable member 8 and the heating element 4a is for explaining the 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 structure and the liquid discharging operation of the present embodiment have been described. According to such a form, the growth component to the downstream side of the bubble is not equal to the growth component to the upstream side, Almost no growth component to the upstream side is suppressed, and the movement of the liquid to the upstream side is suppressed. Since the flow of liquid to the upstream side is suppressed, most of the bubble growth component is directed toward the discharge port without loss on the upstream side,
The discharge power is significantly improved. Furthermore, the amount of retreat of the meniscus after ejection is reduced, and the amount by which the meniscus projects from the orifice surface during refilling is reduced accordingly. Therefore, meniscus vibration is suppressed, and stable ejection can be performed at any driving frequency from low frequency to high frequency.

In the above description, the case where the heating element 4a on the downstream side of the liquid flow path 3 is caused to generate heat has been described, but the above-mentioned discharge operation also occurs when the heating element 4b on the upstream side is caused to generate heat. In the present invention, the upstream heating element 4b has a larger effective foaming area than the downstream heating element 4a in the present invention, as will be described later, and therefore, bubbles generated when the downstream heating element 4a is heated. If the movable member 8 is configured to be in close contact with the liquid supply port 5 during the lateral growth process, the movable member 8 is similarly attached to the liquid supply port 5 when the upstream heating element 4b is heated. This is because they are closely attached.

As described above, according to the liquid discharge head of this embodiment, when a part of the liquid filling the liquid flow path 3 is heated by the heating element 4 and the bubbles are bubbled due to the film boiling, the bubbles are generated. At the same time when the pressure wave is generated due to the generation of the
Is closed, and the inside of the liquid flow path 3 is substantially sealed except for the discharge port 7. Therefore, the pressure wave is prevented from propagating to the liquid supply port 5 side. Therefore, in the liquid ejection head of the present embodiment, since the ink does not move to the rear of the heating element when ejecting the liquid, it can be considered that the flow resistance behind the heating element is almost infinite.

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

Here, as shown in FIG. 11, the liquid flow path 3
A case where the cross-sectional area of the (nozzle) is constant over the entire length will be described. Note that FIG. 11A is a sectional view taken along one liquid flow path direction of the liquid ejection head.
(B) is a cross-sectional view taken along the line AA ′ of FIG.

The maximum foaming volume Vo of bubbles by the heating element is
It is proportional to the pressure generated on the heating element during foaming. When the nozzle configurations are not so different, the bubbling pressure is substantially proportional to the effective bubbling area Se of the heating element. In addition, since a region of about 4 μm from the outer edge of the heating element does not reach a 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 the present embodiment, since the liquid hardly moves to the rear of the heating element, substantially all the liquid moves toward the discharge port when foaming occurs. Therefore, the maximum bubble foaming volume Vo and the discharge amount are set. Vd becomes almost equal. That is, the discharge amount Vd and the effective bubbling area Se are in a proportional relationship, and the following equation is obtained.

Vd = a · Se (a is a proportional constant) Equation (1) Further, the discharge velocity v of the liquid droplet is determined by the acceleration of the liquid moving in front 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 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) Equation (2) Here, when Equation (1) is substituted into Equation (2), v = c · Vd / Rf (c = b / a ) It becomes Formula (3). The flow resistance Rf is the reciprocal of the cross-sectional area of the nozzle integrated 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 is the distance 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.

Further, from the equations (3) and (4), v = c ′ · Vd / OH (c ′ = c · S / ρ) ... Equation (5) From this result, the ejection speed v is ejected. Quantity Vd and OH
It can be seen that it can be easily obtained by the distance.

In the liquid ejection head in which one nozzle is provided with two heating elements as in this embodiment, the ejection rate Vd1 by the first heating element 4a and the ejection rate Vd2 by the second heating element 4b are set. When the liquid is ejected from the same nozzle, if the arrangement positions of the heating elements are determined so that Vd1 / Vd2 = OH1 / OH2 (6), then the ejection speeds v1, v2 of the droplets ejected by the heating elements are determined. about,
The relationship of v1 = v2 is established. For example, when the ejection amount ratio of droplets is 1: 4, the ratio of the effective bubbling area between the first heating element 4a and the second heating element 4b is 1: 4, and the first opening from the ejection port is When 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 for small droplets and the ejection speed v2 for large droplets can be made equal. it can.

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

Liquid flow path 3 of the liquid discharge head shown in FIG.
With a position at a distance L from the discharge port 7 as a boundary, the cross-sectional area on the downstream side of the position is S1 and the cross-sectional area on the upstream side is S2.

Also in the example shown in FIG. 12, the effective bubbling 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. Further, the effective foaming area of the second heating element 4b is Se2, the discharge amount is Vd2, the discharge speed is v2, and the cross-sectional area is S2.
Vd2 = a · Se2 (a is a proportional constant) equation (12) v2 = b · Se2 / Rf2 (b is a proportional constant) equation (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) Setting the respective values such that ^-1, v1 = v2, and the respective heating elements 4a, equalizing the discharge speed of droplets and large liquid droplets ejected by the heating of 4b You can

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

The modes of driving both heating elements 4a and 4b include a mode of simultaneously driving both heating elements 4a and 4b, a mode of driving the downstream heating element 4a first, and a mode of driving the upstream heating element 4a first. There is a mode to drive. Both heating elements 4
In the mode in which a and 4b are driven at exactly the same time, each heating element 4
The ejection amount is smaller than the total ejection amount when a and 4b are individually driven. Further, 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 substantially sealed except for the discharge port. As a result, the ejection amount can be made larger than in the mode in which two droplets are ejected and both heating elements 4a and 4b are driven simultaneously. Further, in the mode in which the upstream heating element 4a is driven first, the movable member can be displaced downward more quickly than in the mode in which both heating elements 4a and 4b are driven simultaneously, so the refill characteristic is further improved. You can

The ejection state in the mode for driving both heating elements 4a and 4b will be sequentially described below with reference to the drawings.

First, the droplet discharge operation in the mode in which both heating elements 4a and 4b are simultaneously driven will be described. 13 and 14 show characteristic phenomena of the droplet discharge operation in the mode in which both heating elements 4a and 4b are driven simultaneously, (a) to (c) of FIG. 13 and (a) to (c) of FIG. It is shown separately for each step.

In FIG. 13 (a), by driving both heating elements 4a and 4b at the same time, a part of the liquid filling the liquid flow path 3 is heated by both heating elements 4a and 4b, and both heating elements 4a and 4b are heated.
It shows a state where film boiling occurs on a and 4b and bubbles 21a and 21b are isotropically grown. Here, "isotropic bubble growth" means a state in which at any position on the bubble surface, the bubble growth rates in the direction normal to the bubble surface are substantially equal.

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

FIG. 13B shows a state in which the bubbles 21a and 21b continue to grow. At this time, the heating element 4 on the downstream side
Bubbles in the area A on the downstream heating element 4a grow faster and bubbles in the area B shrink faster than when only a is driven. That is, the transition of the bubble 21a on the upstream heating element 4a to the partial growth partial contraction period is early. Further, the bubble volume of the bubbles 21b on the upstream heating element 4b is small.

FIG. 13C shows a state in which bubble growth is passing through in regions A of the bubbles 21a and 21b on both heating elements 4a and 4b, and bubble contraction has started in region B.
In this state, in the area A, the bubbles 21 are directed toward the ejection port side.
a and 21b grow greatly. Then, the volumes of the bubbles 21a and 21b in the B region start 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 both heating elements 4a and 4b, the movable member 8 is displaced downward. Without, the sealed state is maintained. Note that this is not the case when the tip of the movable member is located upstream of the center of the upstream heating element 4b.

FIG. 14 (a) shows a state in which the bubbles 21a on the downstream heating element 4a have grown to the maximum extent. In this state, the bubbles grow maximally in the area A on the heating element 4a on the downstream side, and the bubbles in the area B continue to shrink.
At this time, when the bubbling pressure of the bubbles in the area A on the heating element 4b on the upstream side is weakened, the movable member 8 starts downward displacement. In addition, the ejection droplet 22 that is ejecting from the ejection port 7
Is still connected to the meniscus M with a long tail. As a result, the liquid supply port 5 opens and the common liquid supply chamber 6
And the liquid flow path 3 are in communication with each other.

FIG. 14B shows a state in which the bubble 21a on the downstream heating element 4a stops growing and only the defoaming step is performed, and the discharge droplet 22 and the meniscus M are separated. In this state, the movable member 8 is promptly displaced downward by the defoaming force of bubbles in the area B on the upstream heating element 4b and the defoaming force of bubbles in the areas A and B on the downstream heating element 4a. To do. Immediately after the bubble growth is changed to the defoaming in the region A on the heating element 4a on the upstream side, the contraction energy of the bubbles acts as a force for moving the liquid in the vicinity of the discharge port 7 in the upstream direction as a total balance. Therefore, the meniscus M
At this point, the liquid column is drawn into the liquid flow path 3 from the discharge port 7, and the liquid column connected to the discharged liquid droplet 22 is quickly separated by a strong force. At this time, the discharge amount is determined by the heating elements 4a, 4
The ejection amount is smaller than the total ejection amount when b is individually driven. On the other hand, as the bubbles contract, the movable member 8
Is displaced downward, and the liquid rapidly becomes a large flow from the common liquid supply chamber 6 through the liquid supply port 5 and flows into the liquid flow path 3. As a result, the flow that rapidly draws the meniscus M into the liquid flow path 3 suddenly decreases, so that the retreat amount of the meniscus M is reduced and the meniscus M starts returning 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 that does not include the movable member according to the present invention.

FIG. 14 (c) shows a state in which the air bubbles on the downstream heating element 4a are almost completed and the air bubbles on the upstream heating element 4b are completely defoamed. In this state, the liquid flows from the liquid supply chamber 6 through the liquid supply port 5, the defoaming of the bubbles progresses, 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 heating elements 4a and 4b are driven at the same time, it is possible to eject a droplet having a smaller ejection amount than the total ejection amount when the heating elements 4a and 4b are individually driven. it can.

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

In FIG. 15A, 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 in which boiling has occurred and the bubbles 21a have grown isotropically. Here, "isotropic bubble growth" means a state in which at any position on the bubble surface, the bubble growth rates in the direction normal to the bubble surface are 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 in a substantially sealed state.

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

FIG. 15C shows a state in which the bubbles 21a on the heating element 4a on the downstream side have grown to the maximum extent and the bubbles 21b on the heating element 4b on the upstream side have 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 bubbles on the upstream heating element 4b. In addition, the ejection drop 2 that is being ejected from the ejection port 7
2 is still connected to the meniscus M with a long tail. Moreover, the hermetically sealed state is continuously maintained.

FIG. 16A shows a state in which the defoaming of the bubbles 21a on the downstream heating element 4a is completed. In this state, the bubble 21b on the upstream heating element 4b continues the partial growth partial contraction period, and the foaming pressure of the bubble in the area A on the upstream heating element 4b is the defoaming force of the bubble in the area B. Therefore, the movable member 8 is not displaced and the sealed state is still maintained. Further, the droplet 22a is discharged from the discharge port,
Due to the bubbling pressure of bubbles in the area A on the upstream heating element 4b, the meniscus M returns without much receding.

FIG. 16B shows a state in which the bubbles grow substantially isotropically on the heating element 4a on the downstream side and the bubbles on the heating element 4b on the upstream side are defoamed. A on the heating element 4b on the upstream side
At the time when the bubbles in the area shift to defoaming, the downstream heating element 4a is driven again, so that the downstream heating element 4a is driven.
The defoaming force of the bubbles on a is exceeded by the foaming pressure of the bubbles on the heating element 4b on the upstream side, the movable member 8 is not displaced, the sealed state is still maintained, and the meniscus M
Will return more.

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

After that, the second droplet 22b is formed in almost the same process as the liquid discharging operation shown in FIGS. 6A to 6C.
Is discharged.

As described above, in the mode in which the heating element 4a on the downstream side is driven first, two droplets can be ejected during a series of liquid ejection operations, and both heating elements 4a and 4b can be simultaneously ejected. The ejection amount can be increased as compared with the driving mode.

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

In FIG. 17A, by driving only the heating element 4b on the upstream side, a part of the liquid filling the liquid flow path 3 is heated by the heating element 4b on the upstream side, and a film is formed on the heating element 4. It shows a state in which boiling has occurred and the bubbles 21b have grown isotropically. Here, "isotropic bubble growth" means a state in which at any position on the bubble surface, the bubble growth rates in the direction normal to the bubble surface are substantially equal.

In the isotropic growth process of the bubble 21b at the initial stage of the bubble generation, the movable member 8 comes 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 in a substantially sealed state.

In FIG. 17B, the bubbles on the heating element 4b on the upstream side drive the heating element 4a on the downstream side within a period in which the bubbles are growing on the upstream side. The state where the bubbles are growing isotropically is shown. After this state,
As shown in (c), the bubbles 21 on both heating elements 4a, 4b.
Both a and 21b shift to the partial growth partial contraction period. After that, the bubbles on the upstream heating element 4b move into the contraction period earlier due to the bubbling pressure of the bubbles on the downstream heating element 4a.

FIG. 18A shows a state in which the bubble 21a on the downstream heating element 4a continues the partial growth partial contraction period, and the bubble 21b on the upstream heating element 4b disappears. . In this state, the movable member 8 has a restoring force due to its rigidity, an area B on the heating element 4a on the downstream side and a heating element 4b on the upstream side.
Due to the defoaming force of the bubbles in the upper areas A and B, the downward displacement starts faster than the mode in which both heating elements 4a and 4b are simultaneously driven to the steady state position. 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 with each other.

FIG. 18B shows a state in which only the bubble defoaming step is performed and the discharge droplet 22 and the meniscus M are separated. Immediately after the bubble growth is changed to the defoaming in the region A, the contraction energy of the bubble 21 acts as a force for moving the liquid in the vicinity of the ejection port 7 in the upstream direction as a whole 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 separated. On the other hand, the movable member 8 is displaced downward due to the contraction of the bubbles, and the liquid rapidly flows into the liquid flow path 3 from the common liquid supply chamber 6 through the liquid supply port 5. As a result, the flow that draws the meniscus M into the liquid flow path 3 rapidly decreases,
The amount of retreat of the meniscus M can be reduced, and the meniscus M starts returning to the pre-foaming position 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 that does not include the 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 also returned to the steady state position. To this state, the movable member 8 is displaced upward due to its elastic force.
Further, in this state, the meniscus M has already returned near the ejection port 7.

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

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

<Element Substrate> The structure of the element substrate 1 provided with the heating element 4 for applying heat to the liquid will be described below. It should be noted that in the following, for convenience, the liquid flow path 3 is set to 1
This will be described using a configuration in which one heating element 4 is provided.

FIG. 19 is a side sectional view of the main part of the liquid ejection apparatus of the present invention. FIG. 19A shows a head having a protective film which will be described later, and FIG. 19B shows a device having no protective film. 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.

In the element substrate 1, a silicon oxide film or a silicon nitride film 106 for insulation and heat storage is formed on a substrate 107 such as silicon, and a hafnium boride (HfB) constituting the heating element 4 is formed thereon. ₂ ), tantalum nitride (TaN), tantalum aluminum (TaAl) and other electric resistance layers 105 (0.01 to 0.2 μm thick) and aluminum and other wiring electrodes 104 (0.2 to 1.0 μm thick) are shown. 1
9 (a) is patterned. A voltage is applied from the wiring electrode 104 to the resistance layer 105,
An electric current is applied to the heating element 4 to generate heat. Wiring electrode 104
A protective film 103 made of silicon oxide, silicon nitride, or the like is formed to a thickness of 0.1 to 2.0 μm on the resistance layer 105 between them, and a cavitation resistant layer 102 (0.1, 0.1) made of tantalum or the like is further formed thereon. ~ 0.6 μm thick) is deposited,
The resistance layer 105 is protected from various liquids such as ink.

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

Further, depending on the combination of the liquid, the flow channel structure and the resistance material, the above-mentioned resistance layer 105 may not need the protective film 103, and an example thereof is shown in FIG. 19 (b).
Examples of the material of the resistance layer 105 that does not require the protective film 103 include iridium-tantalum-aluminum alloy.

As described above, as the constitution of the heating element 4 in each of the above-described embodiments, the resistance layer 1 between the electrodes 104 described above is used.
05 (heat generating part) only, or may include the protective film 103 for protecting the resistance layer 105.

In each of the embodiments, the heating element 4 having the heating portion constituted by the resistance layer 105 which generates heat in response to an electric signal is used, but the heating element 4 is not limited to this.
Any material may be used as long as it produces sufficient bubbles in the foaming liquid to eject the ejection liquid. For example, it may be a photothermal converter that generates heat when receiving light from a laser or the like, or a heating element that has a heating portion that generates heat when receiving high frequency.

On the element substrate 1 described above, in addition to the heating element 4 including the resistance layer 105 forming the heating portion 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 heating portion of the heating element 4 provided on the element substrate 1 as described above and eject the liquid, the resistance layer 105 is connected to the resistance layer 105 via the wiring electrode 104, as shown in FIG. Applying a rectangular pulse as shown, wiring electrode 1
The resistance layer 105 between 04 and 40 rapidly generate heat. In the liquid ejection head described above, the voltage is 24 V and the pulse width is 7 μs.
The heating element was driven by applying an electric signal of ec and a current of 150 mA at 6 kHz, and the liquid ink was ejected from the ejection port 4 by the above-described operation. However, the condition of the drive signal is not limited to this, and any drive signal capable of appropriately foaming the foaming liquid may be used.

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

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

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

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

[0124]

[Outer 1]

<Liquid Ejecting Device> FIG. 21 shows a schematic structure of an ink jet recording device which is an example of a liquid ejecting device to which the liquid ejecting head having the structure described in this embodiment can be mounted and applied. The head cartridge 601 mounted in the inkjet recording apparatus 600 shown in FIG. 21 has the liquid ejection head having the above-described structure and a liquid container that holds the 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 association with forward and reverse rotations of a drive motor 602. . Drive motor 602
The head cartridge 601 is reciprocally moved along with the carriage 607 along the guide 608 in the directions of arrows a and b by the power of. Inkjet recording device 600
Is a print paper P as a recording medium that receives a liquid such as ink ejected from the head cartridge 601.
A recording medium conveying means (not shown) for conveying the recording medium is provided. A platen 609 is provided by the recording medium conveying means.
The paper pressing plate 610 of the print paper P conveyed above is
The print paper P is moved in the moving direction of the carriage 607
Are pressed against the platen 609.

Photocouplers 611 and 612 are arranged near one end of the lead screw 605. The photocouplers 611 and 612 are home position detecting means for confirming the existence of the lever 607a of the carriage 607 in the area of the photocouplers 611 and 612 and switching the rotation direction of the drive motor 602. The head cartridge 6 is provided near one end of the platen 609.
A support member 613 that supports a cap member 614 that covers the front surface of the No. 01 discharge port is provided. Further, an ink suction means 615 for sucking ink that has been discharged from the head cartridge 601 and accumulated inside the cap member 614 is provided. This ink suction means 615
As a result, 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 equipped with a main body support 619. A moving member 618 is attached to the main body support 619 in the front-back direction, that is, the carriage 60.
It is movably supported in a direction perpendicular to the moving direction of 7. The moving member 618 includes a cleaning blade 6
17 is attached. Cleaning blade 61
Not limited to this form, 7 may be a known cleaning blade of another form. Further, the ink suction means 61
5, a lever 620 for starting suction in the suction recovery operation is provided. The lever 620 moves in accordance with the movement of the cam 621 that engages with the carriage 607, and the driving force from the driving motor 602 switches the clutch. The movement is controlled by a known transmission means such as. Give a signal to the heating element provided in the head cartridge 601,
The inkjet recording control unit that controls the drive of each mechanism described above is provided on the recording apparatus main body side.
Not shown in 1.

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

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

The recording apparatus 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 printer and at the same time converted into data that can be processed in the recorder.
It is input to a CPU (Central Processing Unit) 302 which also serves as a head drive signal supply means. The CPU 302 stores the data input to the CPU 302 in a RAM (random access memory) 304 based on a control program stored in a ROM (read only memory) 303.
It is processed using peripheral units such as and converted to data (image data) to be printed.

Further, the CPU 302 drives the drive motor 306 which moves the carriage 607 carrying the recording sheet and the head cartridge 601 in synchronization with the image data in order to record the image data at an appropriate position on the recording sheet.
Make drive data to drive. The image data and the motor drive data are sent to the head cartridge 60 via the head driver 307 and the motor driver 305, respectively.
1 and the driving motor 306, and each of them is driven at a controlled timing to form an image.

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

As the recording device, various kinds of paper and O
A printer device for recording on HP sheets, a plastic recording device for recording on a plastic material such as a compact disc, a metal recording device for recording on a metal plate,
A leather recording device for recording on leather, a wood recording device for recording on wood, a ceramic recording device for recording on a ceramic material, a recording device for recording on a three-dimensional network structure such as a sponge, or a cloth. It also includes a printing device and the like for recording on.

As the ejection liquid used in these liquid ejection 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 form shown in FIG. 23,
The element substrate 1 and the top plate 2 are joined together, and the element substrate 1 and the top plate 2 are joined together.
A liquid flow path 3 whose one end communicates with the discharge port 7 is formed between and. Further, heating elements 4a and 4b are provided as a 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.

Between the liquid supply port 5 and the liquid flow path 3, the movable member 8 has a minute gap α 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 end portions continuous with the movable member 8 is larger than the opening region of the liquid supply port 5 with respect to the liquid flow path, and the side portion of the movable member 8 and the liquid flow path. There is a minute gap β between each of the side walls 10. As a result, the movable member 8 can be moved in the liquid flow path 3 without frictional resistance, but the displacement into the liquid supply port 5 is restricted at the peripheral portion of the opening region S, and the liquid supply port 5 is closed to close the liquid flow path 3
While it is possible to prevent the liquid flow from the liquid supply chamber 6 to the liquid supply chamber 6, it is possible to move the liquid flow path side from the substantially closed state to the refillable state along with the defoaming of the bubbles. Further, in this embodiment, the movable member 8 is located so as to face the element substrate 1.
One end of the movable member 8 is provided with the heating elements 4a, 4a of the element substrate 1.
It is a free end displacing to the b side, and the other end side is the fixing member 9
Supported by.

[0138]

As described above, the liquid discharge head and the liquid discharge apparatus of the present invention are provided with a plurality of bubble generating means in the liquid flow path, and generate the smallest volume bubble among the plurality of bubble generating means. than is configured such that the movable member substantially blocks seals the liquid supply port by driving the air bubble generating means, equal to the discharge velocity of the droplet ejected by the drive of each bubble generating means can do.

Further, in the liquid discharge method of the present invention, the bubble generating means for generating the smallest volume of the plurality of bubble generating means is driven to generate the bubbles,
Between the drive voltage is applied to the bubble generating means to the period in which the whole is growing substantially isotropic bubble is completed, to substantially blocked by the movable member seals the liquid supply port < Thus, the convergence of the vibration of the meniscus is improved, and the refill frequency after discharging the droplet can be increased.

[Brief description of drawings]

FIG. 1 is a view of a liquid ejection head 1 according to an embodiment of the present invention.
It is sectional drawing along the direction of one liquid flow path.

2 is a cross-sectional view of the liquid ejection head shown in FIG. 1 taken along line XX ′.

3 is a cross-sectional view of the liquid ejection head shown in FIG. 1 taken along the line YY '.

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

5 is a diagram for explaining the ejection operation of the liquid ejection head having the structure shown in FIGS.

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

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

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

9 is a graph showing the correlation between the time change of bubble growth and the behavior of the movable member in the liquid ejection head having a configuration in which the relative positions of the movable member and the heating element shown in FIG. 1 are different.

FIG. 10 is a graph showing the correlation between the time change of bubble growth and the behavior of the movable member in the liquid ejection head having a configuration in which the relative positions of the movable member and the heating element shown in FIG. 1 are different.

FIG. 11 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 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 diagram for explaining the ejection operation of the liquid ejection head having the structure shown in FIGS.

FIG. 14 is a diagram for explaining the ejection operation of the liquid ejection head having the structure shown in FIGS.

FIG. 15 is a diagram for explaining the ejection operation of the liquid ejection head having the structure shown in FIGS.

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

FIG. 17 is a diagram for explaining the ejection operation of the liquid ejection head having the structure shown in FIGS.

FIG. 18 is a diagram for explaining the ejection operation of the liquid ejection head having the structure shown in FIGS.

FIG. 19 is a vertical cross-sectional view of the liquid ejection head of the present invention,
The figure (a) shows what has a protective film, and the figure (b) shows what has no protective film.

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

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

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

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

[Explanation of symbols]

1 element substrate 2 Top plate 3 liquid flow paths 4,4a, 4b heating element 5 Liquid supply port 6 Common liquid supply chamber 7 outlet 8 movable members 9 fixing member 10 Channel side wall 11 Bubble generation area 21,21a, 21b bubbles 22,22a, 22b Discharged droplets 102 Anti-cavitation layer 103 protective film 104 wiring electrode 105 Resistance layer 106 silicon nitride film 107 base 300 host computer 301 Input / output interface 302 CPU 303 ROM 304 RAM 305 motor driver 307 head driver 600 inkjet 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 holding plate 611,612 Photo coupler 613 support member 614 Cap member 615 Ink suction means 617 cleaning blade 618 Moving member 619 Main body support 620 lever 621 cam

Front page continuation (72) Inventor Masanori Takenouchi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Masami Ikeda 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hiroshi Sugitani 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Takashi Saito 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) Reference Documents JP-A-11-235829 (JP, A) JP-A-2-113950 (JP, A) JP-A-9-52364 (JP, A) JP-A-11-48481 (JP, A) JP-A-10- 202915 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) B41J 2/05 B41J 2/205

Claims (17)

(57) [Claims] 1. A discharge port for discharging a liquid, a liquid flow path having a bubble generation region in which one end is always communicated with the discharge port and generating a bubble in the liquid, and the liquid flow path is disposed 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 means that generate bubbles in the liquid arranged in the liquid flow path. Provided in the liquid flow channel in a state of being supported with the discharge port side as a free end with a gap of 10 μm or less with respect to the liquid flow channel side of the liquid supply port, and more than the opening region of the liquid supply port. A plate-shaped movable member having a large projection area, the discharge port and the bubble generating unit are in linear communication with each other, and a bubble generating unit for generating a bubble having the smallest volume among the plurality of bubble generating units. By driving the movable member A liquid discharge head, characterized in that substantially block to seal the serial liquid supply port. Wherein said plurality of bubble generating means provided in the liquid flow path, the foaming area toward the upstream side from the downstream side of the liquid flow path are arranged in order of progressively increases, to claim 1 The liquid ejection head described. Wherein also a gap between the movable member and liquid flow path wall constituting the liquid flow path, the liquid discharge head according to claim 1 or 2. Wherein said plurality of being configured to eject the liquid by driving the air bubble generating means, the liquid discharge head according to any one of claims 1 to 3. 5. The liquid ejection head according to claim 4 , wherein the liquid ejection head is configured to eject the liquid by simultaneously driving the plurality of bubble generating means. 6. The liquid ejecting head according to claim 4 , wherein the liquid ejecting head is configured to eject the liquid by first driving the bubble generating unit closest to the ejection port among the plurality of bubble generating units. . 7. The liquid is ejected by first driving the bubble generating means closest to the movable member among the plurality of bubble generating means.
4. The liquid ejection head according to item 4 . 8. A liquid discharge head according to any one of claims 1 to 7, the liquid ejection apparatus and a driving signal supplying means for supplying a driving signal for discharging the liquid from the liquid discharging head. 9. Liquid has a liquid discharge head according to any one of claims 1 7, and recording medium conveying means for conveying a recording medium for receiving liquid discharged from said liquid discharging head discharging apparatus. 10. ejecting ink from the liquid discharge head performs recording by attaching the ink onto a recording medium, a liquid ejecting apparatus according to claim 8 or 9. 11. A discharge port 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, and a liquid flow path disposed in the liquid flow path. 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 bubbles in the liquid that is provided in the liquid flow path and that is disposed in the liquid flow path. Between a plurality of bubble generating means for generating the liquid flow path and the liquid flow path wall forming the liquid flow path and the liquid supply port with respect to the liquid flow path side of the liquid flow path wall and the liquid discharge port. And a movable member that is provided in the liquid flow path in a state of being supported with the discharge port side as a free end with a gap, and that has a projection region that is larger than the opening region of the liquid supply port. A liquid discharging method used, comprising: By driving the bubble generating means for generating the bubble having the smallest volume to generate the bubble, from the time when the driving voltage is applied to the bubble generating means until the end of the period in which the entire bubble is isotropically grown. The liquid discharging method, characterized in that the movable member hermetically closes the liquid supply port during the period to substantially shut off the liquid supply port. 12. A time from the generation of the growth volume change and the bubble of the bubble in said bubble generating region to defoaming is significantly different between the discharge port side and said liquid supply port side, claim 1
1. The liquid discharge method described in 1 . 13. The liquid ejection method according to claim 11 , wherein the bubble generation region is not exposed to the atmosphere. 14. ejecting the liquid by driving the plurality of bubble generating means, the liquid ejecting method according to any one of claims 11 to 13. 15. The liquid discharge method according to claim 14 , wherein the liquid is discharged by simultaneously driving the plurality of bubble generating means. 16. The liquid ejecting method according to claim 14 , wherein the liquid is ejected by first driving the bubble generating means closest to the ejection port among the plurality of bubble generating means. 17. The liquid ejecting method according to claim 14 , wherein the liquid is ejected by first driving the bubble generating unit closest to the movable member among the plurality of bubble generating units.