JP2007160735A - Liquid droplet ejection head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid droplet ejection head which can eject a high-viscosity liquid at a high drive frequency at room temperature. <P>SOLUTION: When the buckling reversion movement of a beam member 14 reaches the highest point to be convex in the ejection direction along with the rotation of a rotary encoder 20, ink droplets 2 are ejected by the inertia disengagement as shown in Fig. 3(d). The ink in a passage 13 is refilled by centrifugal force, and refilling is performed at the same time as the ejection even if high-viscosity ink is used, thereby preventing troubles such as no-ejection due to the shortage of ink in the vicinity of nozzles 16. Furthermore, when returning back to the initial state from the Fig. 3(g), namely when the buckling reversion movement of the beam member becomes concave in the ejection direction, the beam member 14 is buckled and reversed to send the ink from the end portion of the ink passage 13 to the vicinity of the nozzles 16 by centrifugal force. Therefore, as long as the ink ejecting operation is continued, no ink shortage in the vicinity of the nozzles 16 occurs all the time, thereby attaining sure ejection of ink. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a droplet discharge head, and more particularly to a droplet discharge head that discharges high-viscosity ink as droplets.

  A currently marketed aqueous inkjet printer known as a droplet discharge device employs a dye ink or a pigment ink having a viscosity of about 5 cps or so and an order of 10 cps at most. Reasons such as prevention of ink bleeding when landing on the medium, increase in optical color density, suppression of swelling / short time drying of the medium due to reduced water content, or greater freedom in total design of such high quality ink Therefore, it is known that the printing performance can be improved by increasing the ink viscosity.

  On the other hand, in order to eject high-viscosity ink, a high-output pressure generation mechanism is required, which causes adverse effects such as an increase in cost and head size. Conventionally, a technique for forcibly lowering the ink viscosity at the time of ejection by separately providing a heater in the ejector is known (see, for example, Patent Document 1). However, the above-described method of heating ink causes ink deterioration and flow path damage. There is a fundamental problem to be accelerated, and the ink that can be used is limited to one that does not deteriorate due to heat.

  In addition, a technique (for example, see Patent Document 2) is disclosed in which ink flow in the reverse direction when ink is ejected is suppressed by a beam-like valve and ink with higher viscosity is ejected.

  As a method of powering up the pressure generation mechanism itself using a seat bending beam that can obtain a large deformation, a technique using a diaphragm actuator that deforms due to a difference in thermal expansion with the heating element layer (see, for example, Patent Document 3), Further, a technique using a cantilever-like actuator with the same configuration (for example, see Patent Document 4) is disclosed.

  For example, the ink jet recording head 100 shown in FIG. 14 rapidly pressurizes the ink 101 in the ink chamber 106 by deforming the actuator 102 as shown in FIGS. It is made to discharge as.

  However, even with the above-described prior art, it is extremely difficult to stably eject a high viscosity ink having a viscosity of 50 to 100 cps, which greatly exceeds 10 cps, at room temperature.

The inventors of the present application provide an ink jet recording head that applies a compressive and rotational motion to a beam and makes a high-viscosity ink droplet inertially release from a nozzle in a desired direction by using a steep vertical motion when the seat bending direction is reversed. (See Patent Documents 5 to 8).
As a result of investigation by the inventors of the present application, as a method of discharging high-viscosity ink at a higher speed / higher frequency with this head, back pressure (back pressure) is applied to the ink flow path, and the nozzle moves in the discharge direction and in the reverse direction. At the same time, they found out a discharge method that generates the buckling reversal motion of the beam in both motion directions in the reciprocating movement of the flow path.

  The present invention further develops the prior application. For example, when a holding member that holds both ends of a beam and a rotary encoder that applies compression and rotation to the holding member are combined, an offset from the encoder rotation center is set to zero or small. The beam is buckled and reversed in the ejection direction and in the opposite direction for each ink ejection by providing the beam with initial deflection in advance.

  In the conventional method, the flow resistance is increased due to the viscosity of the high-viscosity ink, so refill (refilling ink or returning to the meniscus) is delayed, and it is impossible to discharge by high-speed high-frequency driving. Ink flow toward the nozzles can be increased, and in addition to the effect of adding back pressure, refilling can be performed in a shorter time than the conventional method.

The object of the present invention is to apply a compressive and rotational motion to the beam and use a steep vertical motion when the seat bending direction is reversed to remove a highly viscous droplet (ink droplet) from the nozzle at a high drive frequency by inertial detachment. It is to provide a liquid droplet ejection head that is ejected by the above method.
JP 2003-220702 A (FIG. 1, pages 4 to 6) Japanese Patent Laid-Open No. 9-327918 (FIG. 1, pages 8 to 9) JP 2003-118114 A (FIG. 3, pages 4 to 5) JP 2003-34710 A (FIG. 13, pages 6 to 8) Japanese Patent Application No. 2004-322341 Japanese Patent Application No. 2004-322342 Japanese Patent Application No. 2004-322343 Japanese Patent Application No. 2004-322344

  In consideration of the above facts, an object of the present invention is to provide a droplet discharge head capable of discharging a high-viscosity liquid at a high drive frequency at room temperature.

  The liquid droplet ejection head according to claim 1 includes a nozzle that ejects liquid droplets, a liquid flow path member that includes the nozzle, and a joint or liquid flow path member that is joined to the liquid flow path member in the liquid droplet ejection direction. A beam that, after being buckled and inverted so as to be concave, is buckled and inverted so as to be convex in the droplet discharge direction, and gives the liquid in the vicinity of the nozzle the inertia in the discharge direction, thereby discharging the droplet from the nozzle. And a member.

  In the invention with the above-described configuration, the ink drops are buckled during both the ink drop ejection processes, and an inertial flow toward the nozzles is generated in the ink inside the flow path, so that ink refilling is performed faster and ink droplets can be ejected at high speed and high frequency. It becomes.

  The droplet discharge head according to claim 2, wherein both ends or one end in the longitudinal direction of the beam member are rotatably held in the droplet discharge direction, and the beam member is recessed in the droplet discharge direction. A holding member that is compressed in the longitudinal direction of the member and buckled and reversed and then buckled and reversed so that both ends or one end in the longitudinal direction of the beam member are rotated to be convex in the droplet discharge direction is provided. Features.

  In the invention with the above-described configuration, the ink drops are buckled during both the ink drop ejection processes, and an inertial flow toward the nozzles is generated in the ink inside the flow path, so that ink refilling is performed faster and ink droplets can be ejected at high speed and high frequency. It becomes.

  The droplet discharge head according to claim 3, further comprising: a rotary encoder that rotatably supports one or both of the holding members in a droplet discharge direction and rotates the beam member, and the holding member is the beam member in advance. Is supported in a position offset from the rotation center or the rotation center of the encoder in a state of being compressed and bent in the longitudinal direction, so that the rotation of the encoder causes the beam member to be concave and convex in the droplet discharge direction. The beam member is buckled and reversed in both of the operations to be performed.

  In the invention with the above-described configuration, the ink drops are buckled during both the ink drop ejection processes, and an inertial flow toward the nozzles is generated in the ink inside the flow path, so that ink refilling is performed faster and ink droplets can be ejected at high speed and high frequency. It becomes.

  The liquid droplet ejection head according to claim 4 is characterized in that a back pressure is applied to the liquid in the liquid flow path.

  In the invention with the above configuration, refilling can be performed in a short time by applying a back pressure to the ink in the ink flow path.

  The liquid droplet ejection head according to claim 5 is characterized in that the liquid in the liquid channel is constantly pumped through the liquid channel by back pressure.

  In the invention having the above-described configuration, the back pressure is applied to the ink in the ink flow path, so that the refill can be performed in a short time, and the convex amount of the meniscus, that is, the refill speed after the discharge is determined by the pressure difference between the upstream side and the downstream side of the nozzle. Can be changed.

  The droplet discharge head according to claim 6, wherein the beam member or the liquid flow path includes a liquid discharge portion that discharges the liquid overflowing from the nozzle to the opposite side of the droplet discharge direction. .

  In the invention with the above configuration, it is possible to accurately discharge even during ink pressure feeding by discharging the overflowed excess ink to the side opposite to the discharge.

  According to a seventh aspect of the present invention, there is provided a liquid droplet ejection head comprising a liquid recovery means for recovering the liquid discharged from the liquid discharge portion.

  In the invention with the above-described configuration, in addition to buckling inversion in the direction opposite to the ejection, surplus ink can be reliably removed by suction assistance using suction means such as air flowing from the nozzle side to the back surface side.

  Since the present invention has the above-described configuration, a droplet discharge head capable of discharging droplets having a high viscosity at room temperature at a high driving frequency can be obtained.

<Basic configuration>
FIG. 1B shows an ink jet recording head according to the first embodiment of the present invention.

  As shown in FIG. 1B, the ink jet recording head 10 includes an ink flow path 13 therein, an ink flow path member 12 including a nozzle 16 at a substantially central portion or an end in the length direction, and the ink flow path member 12. The beam member 14 that supports the structure is joined in a columnar shape, and the holding member 18 supports both ends.

  A piezo element 30 is joined to the beam member 14, and an individual electrode 32 is joined to the piezo element 30, and the beam member 14, the piezo element 30, and the individual electrode 32 constitute an actuator 36. The beam member 14 also serves as a common electrode of the piezo element 30, and has a structure in which the piezo element 30 is sandwiched between the beam member 14 and the individual electrode 32. An electrode pad 33 is provided at one end of the individual electrode 32 and connected to a switching IC (not shown) by wiring. The piezo element 30 is driven by a signal from the switching IC, and the beam member 14 is controlled to be bent / not bent.

  The ink flow path member 12 can be bent in the ink discharge direction (upper in the drawing) and in the reverse direction, and is supplied from the ink pool 24 provided inside the holding member 18 and reaches the nozzle 16 through the ink flow path 13. Ink is ejected as ink droplets in the ejection direction due to inertia.

  FIG. 1C shows an ink jet recording head according to the second embodiment of the present invention.

  The vicinity of the nozzle 16 in FIG. 1C is enlarged and shown in FIG. The end face of the flow path member 12 is formed as a cut end cut as it is vertically or on an angled taper as shown in FIG.

  As described above, the ink used here prevents ink bleeding when landing on the medium, increases the optical color density, suppresses the swelling of the medium by reducing the water content, or dries for a short time, or totals such high quality ink. For example, it is a high viscosity ink having a very high ink viscosity, for example, a viscosity much higher than 20 cps, for example, 50 to 100 cps due to a large degree of freedom in designing.

The holding member 18 is fixed to the rotary encoder 20 and is pressed from both sides as the rotary encoder 20 rotates, or a force is applied in the bending direction to join the beam member 14 in the ink discharge direction or in the opposite direction. 12 is bent.
<Refill by centrifugal force>
2 to 4 show refills of high viscosity ink according to the first embodiment of the present invention.

  Conventionally, in normal pressure wave discharge, that is, ink discharge using a piezo method or thermal method, ink droplets are discharged from the nozzles 16 by pressure waves as shown in FIG. 2 (FIGS. 2B to 2C), and the ink droplets 2 are formed. After the separation due to the free surface particle speed, the ink was refilled by the surface tension as indicated by the white arrow in FIG. However, if high-viscosity ink is used, the refill cannot catch up with the surface tension and there is a risk of non-ejection.

  On the other hand, in the present invention, as shown in FIG. 3, by using centrifugal force, refilling can be performed in a shorter time than the conventional method while using high-viscosity ink.

  The graph of FIG. 3 shows the movement of the central portion of the beam member 14 in the ink ejection direction. Assuming that the state immediately before buckling reversal is time 0, at this time, the ink droplet discharge has not started in the vicinity of the nozzle 16 as shown in FIG. 3A, and the beam member 14 (channel member) as shown in FIG. 12) is convex on the side opposite to the ejection direction (lower side in the figure).

  From here, the buckling reversal of the beam member 14 starts with the rotation of the rotary encoder 20, and a liquid flow due to centrifugal force is generated in the ink in the flow path 13, and the meniscus becomes convex. At this time, as shown in FIG. 3 (f), the centrifugal force also acts on the ink in the vicinity of the nozzle 16 among the ink in the flow path 13, and is directed toward the nozzle 16 in the direction indicated by the white arrow in FIG. 3 (f). Ink is pushed out.

  As shown in FIGS. 3B to 3C, an ink liquid column is formed by inertia in the ejection direction, and when the buckling reversal movement of the beam member 14 reaches the highest point that is convex in the ejection direction (FIG. 3G 3) As shown in FIG. 3D, the ink droplet 2 is ejected by inertial separation. At this time, the ink in the flow path 13 is also refilled by centrifugal force as described above, and refilling is performed at the same time as ejection even when high-viscosity ink is used. Problems such as occurrence can be prevented.

Further, when returning to the initial state from FIG. 3G, that is, when it becomes concave in the ejection direction, the beam member 14 is also buckled and reversed, so that the ink is also applied to the vicinity of the nozzle 16 from the end of the ink flow path 13 by centrifugal force. Can be sent out. As a result, as long as the ink ejection operation continues, there is no shortage of ink in the vicinity of the nozzle 16 at all times, and reliable ejection can be performed.
<Offset presence and number of buckling reversals>
4 and 5 show the relationship between the support position of the beam member and the number of buckling reversals according to the present invention.

  As shown in FIG. 4, when the holding member 18 that supports the beam member 14 is held at a position offset from the rotation center of the rotary encoder 20, the buckling reversal is performed once in one cycle of the discharge operation.

  That is, by causing the encoder 20 to rotate in the direction opposite to the discharge direction in FIG. 4 (b) from the initial state of FIG. 4 (a), the beam member 14 generates an initial deflection in the anti-discharge direction (convex downward in the figure), In FIG. 4C, the encoder 20 is rotated in the discharge direction to increase the deflection (convex downward in the figure) of the beam member 14.

  When the encoder 20 continues to rotate in the discharge direction, the beam member 14 undergoes buckling reversal, and the downward convex deflection reverses in the discharge direction, and becomes convex upward in the figure. At this time, ink droplets 2 are ejected.

  On the other hand, as shown in FIG. 5, when the holding member 18 that supports the beam member 14 is held at a position that is not offset from the rotation center of the rotary encoder 20, buckling reversal occurs twice in one discharge operation cycle. Can do.

  At this time, as shown in FIG. 5 (a), when the rotary encoder 20 is in the neutral position, if the beam member 14 extends straight, the buckling reversal will occur regardless of whether the rotary encoder 20 is rotated up or down. In order not to occur, it is necessary to compress the beam member 14 in the length direction from both ends, that is, from the rotary encoder 20 in advance as shown in FIG.

  That is, when the initial deflection is given, for example, downward convex as shown in FIG. 5B, and the rotary encoder 20 is rotated as shown in FIG. 5C, the amount of downward convex deflection increases.

  When the rotary encoder 20 is further rotated, buckling inversion occurs from the downward convex to the upward convex as shown in FIG. 5D, and the ink droplet 2 is ejected from the nozzle 16 (not shown).

  In this state, the beam member 14 is convex upward, so that the rotary encoder 20 is reversed and the upward convex deflection is increased as shown in FIG. It can be buckled and reversed in the direction. That is, as shown in FIG. 5F, the beam member 14 is buckled and reversed by further rotating the rotary encoder 20 in the reverse direction (rotating in the direction opposite to that during the discharge operation), and in the vicinity of the center of the beam member 14 in the length direction. An inertial flow is generated in the ink in the flow path 13 toward the nozzle 16 (not shown) provided in the flow path.

As a result, the ink in the flow path 13 in the vicinity of the nozzle 16 consumed for the ink droplet 2 ejected from the nozzle 16 is quickly refilled, and the non-ejection accompanying the shortening of the ink droplet ejection interval, that is, the improvement of the ejection frequency. Such as image failure can be prevented.
<Back pressure application and constant pumping>
6 to 8 show the relationship between the back pressure applied to the ink according to the present invention and the meniscus.

  As shown in FIG. 6, when positive back pressure is applied to the ink inside the ink flow path 13 from both sides and the back pressures P1 and P2 from both directions in the vicinity of the nozzle 16 are substantially equal, the ink droplets as shown in FIG. Even if the meniscus 3 is concave immediately after ejection, the ink is pushed from both sides of the flow path 13 by the back pressures P1 and P2, and the ink is pushed out from the nozzle 16 as shown in FIG. Become.

  In this state, if the ink droplets are left without being ejected, the meniscus 3 is enlarged as shown in FIG. 6C, and if more time passes, the ink overflows in the vicinity of the nozzles 16 as shown in FIG. 6D. Result.

  In contrast, when the ink is pumped from one side of the flow path 13 to the other as shown in FIG. 7, that is, the back pressure P2 that pumps the ink toward the nozzle 16 as shown in FIG. Consider a case where ink is pumped from the middle right direction to the left direction. At this time, if the back pressures P1 and P2 have a relationship of P1 ≦ P2, the meniscus 3 protrudes from the nozzle 16 due to the back pressure P2 from FIG. 7A immediately after ink droplet discharge, but simultaneously the back pressures P1 and P2 The ink in the ink flow path 13 is pumped to the P1 side (the left side in the figure), which is the low back pressure side. As a result, the meniscus 3 does not protrude more than a certain value and moves while maintaining a certain height as shown in FIG. 7C. Therefore, the meniscus 3 protrudes from the nozzle 16 as shown in FIGS. 6C and 6D. The situation where ink overflows around the nozzle 16 can be avoided.

  Furthermore, the protrusion amount of the meniscus can be controlled by the magnitude relationship between the back pressures P1 and P2. As shown in FIGS. 8A and 8B, the amount of protrusion of the meniscus 3 is determined by the difference between the back pressures P1 and P2.

  That is, if the back pressures P1 and P2 are P1 ≦ P2, the difference between the two is small and the amount of protrusion of the meniscus 3 is small. If P1 << P2, the difference between the two is large and the amount of protrusion of the meniscus 3 is large. That is, because the ink is pumped at a high pressure by P2, the height of the meniscus protruding from the nozzle 16 is also increased.

  Since a conventional pressure wave type head requires an ink supply path, it is difficult to adopt such a pressure supply type. In the configuration of the present invention, since ink droplets are ejected with inertia, no aperture is required in the vicinity of the nozzle, which can be said to be a particularly effective supply method.

  Alternatively, when the nozzle 16 is provided not at the center in the length direction of the ink flow path member 12 but at the end, the meniscus 3 is raised from the nozzle 16 as shown in FIG. Ink overflows from 16. This is because the surface tension that pushes the ink back against the positive back pressure P for refilling is weak, and the overflowed ink accumulates in the vicinity of the nozzle as liquid dripping, so that the meniscus 3 is maintained in this configuration. The end nozzle structure is undesirable.

From the above, in order to maintain the meniscus 3 in a constantly convex state, the nozzle 16 is provided in the center of the ink flow path 13, the back pressure P applied from both ends is increased and decreased, and the ink inside is unidirectional. It can be said that the configuration of FIG.
<Back pressure applied and buckling reversal count>
9 to 10 show the relationship between the back pressure applied to the ink according to the second embodiment of the present invention and the number of buckling reversals.

  As shown in FIG. 9, the beam member 14 that supports the ink flow path member 12 of the end face nozzle structure is buckled and reversed when the positive back pressure P is applied to the ink inside the ink flow path 13, so that the ink is discharged from the nozzle 16. FIG. 10 shows changes in the ink refill state and meniscus state depending on the magnitude of the back pressure P and the number of buckling reversals in the configuration for ejecting droplets.

  As an example, when high-viscosity ink of 100 cps is used, a nozzle is formed at an angle of 45 degrees on the end face of a tubular ink flow path having an inner diameter of 80 μm, and the nozzle is driven at 20 Hz. As in e), the ink is not sufficiently refilled, and the ink to be ejected does not exist in the vicinity of the nozzle 16, so that an image failure such as non-ejection occurs. That is, even if the ejection operation by buckling reversal of the beam member 14 is performed in FIG. 10 (e-2), the ink is not refilled in the nozzles 16 and the ink is not ejected. As in 3), the ink flow path 13 remains a gap.

  On the other hand, when the back pressure P is applied slightly (here, 5 mmHg), ink refilling is performed as shown in FIG. However, since the refill is not sufficient, the ink droplet 2 has a small volume around a droplet diameter of 10 μm, and the meniscus after ejection does not return correctly. That is, in FIG. 10D-2, the ink droplet 2 is ejected by the ejection operation by the buckling reversal of the beam member 14, but at this time, the ink amount in the ink flow path 13 is insufficient due to insufficient refilling. The size of the ink droplet 2 is also insufficient with respect to the diameter of the ink flow path and the nozzle. Even when the ejection operation is completed, as shown in FIG. 10D-3, the ink flow path 13 is not refilled and the meniscus does not return, so the ink droplet diameter for each ejection is not stable.

  When the back pressure P is further increased (here, 10 mmHg), the ink droplet 2 becomes relatively large with a droplet diameter of about 20 to 30 μm as shown in FIG. 10C, but the refill is insufficient. That is, in FIG. 10C-2, the ink droplet 2 is ejected by the ejection operation by buckling inversion of the beam member 14, but at this time, the ink amount in the ink flow path 13 is insufficient due to insufficient refill. The size of the ink droplet 2 is still insufficient. Further, even when the ejection operation is completed, as shown in FIG. 10C-3, the ink flow path 13 is not refilled correctly so that the meniscus does not return correctly, so the ink droplet diameter for each ejection is not stable.

  Therefore, when the beam member 14 is added at the time of ink ejection and buckled and reversed at the time of return (see FIG. 5) with this back pressure P maintained, the size of the ink droplet 2 is sufficient as a droplet diameter of 40 to 50 μm, and the seat The refilling by the reversal operation sufficiently replenishes the ejected ink, so that the meniscus is also restored. That is, in FIG. 10B-2, the ink droplet 2 is ejected by the ejection operation by the buckling reversal of the beam member 14. At this time, the amount of ink in the ink flow path 13 is sufficient, so there is no shortage. The size of the droplet 2 is not insufficient with respect to the ink flow path and the nozzle diameter. When the discharge operation is completed, ink refilling is performed by buckling reversal at the time of return, so that the ink channel 13 is refilled with a sufficient amount of ink as shown in FIG. Return. For this reason, the ink droplet diameter for each ejection is stable.

  Alternatively, the refill can be promoted by further increasing the back pressure P. When the back pressure P is further increased (here, 20 mmHg), the ink droplet 2 becomes as large as a droplet diameter of about 50 μm as shown in FIG. That is, in FIG. 10A-2, the ink droplet 2 is ejected by the ejection operation by the buckling reversal of the beam member 14. At this time, the amount of ink in the ink flow path 13 is high, and the refill is not performed. The size of the ink droplet 2 is sufficient with respect to the ink flow path and the nozzle diameter. After the discharge operation is completed, the ink flow path of the ink flow path 13 also returns to the meniscus correctly due to the back pressure P as shown in FIG.

  However, if the back pressure P is increased so that the refill follows even at a high drive frequency, the amount of ink discharged from the nozzle 16 increases accordingly, and even if it operates without problems during continuous discharge, the discharge stops. Then, there is a risk that the ink discharged from the nozzles 16 will cause ink dripping due to the back pressure P. Therefore, a configuration in which the number of buckling reversals is increased rather than simply increasing the back pressure P is desirable in terms of preventing ink dripping.

Further, even in a configuration in which the buckling reversal operation as shown in FIG. 10B is performed a plurality of times in one cycle, it is not always necessary to perform the operation of one discharge and one return. Needless to say, it may be one cycle such as three turns.
<Ink collection>
11 to 12 show an ink recovery method according to the third embodiment of the present invention.

  As shown in FIG. 11, when the back pressure P is applied to the ink inside the ink flow path 13, the beam member 14 that supports the ink flow path member 12 of the end face nozzle structure is buckled and reversed, whereby the ink droplets are ejected from the nozzle 16. A method of processing ink overflowing from the nozzle 16 due to the back pressure P in the configuration of ejecting 2 will be described.

  When the nozzle 16 is open at the end of the ink flow path member 12 provided on the beam member 14 as shown in FIG. 11A, the back pressure P operates as described above without any problem during continuous discharge. Even if the discharge is stopped, there is a risk that the ink discharged from the nozzle 16 due to the back pressure P causes ink dripping.

  In the above case, since the ink in the flow path 13 overflows from the nozzle 16, by providing the discharge portion 17 as shown in FIG. 11A, it can be processed so as not to interfere with the ink droplet ejection. .

  As shown in the side view of FIG. 11B, if the ink overflowing from the nozzle 16 is discharged from the discharge portion 17 as indicated by a white arrow, the ink overflowing in the vicinity of the nozzle 16 may hinder ink droplet ejection. Never become. That is, when the beam member 14 (ink flow path member 12) buckles and reverses downward, the overflowed ink is collected by the ink collection unit 19 through the discharge unit 17 and is prevented from affecting the subsequent processes.

  The process at this time is shown in FIG. As shown in FIG. 12A, the ink to which the back pressure P is applied starts to overflow from the nozzle 16, and ink dripping occurs from the discharge portion 17 as shown in FIG. 12B. At this time, the ink droplet ejection operation is started, and the beam member 14 is buckled and reversed in the downward direction (the direction opposite to the ink ejection direction).

  As a result, as shown in FIG. 12C, the ink dripping is discharged as ink droplets 2B. As a result, the ink overflowing and overflowing around the nozzle 16 is eliminated, and there is no possibility of adversely affecting the formation of the ejected ink droplet 2.

  Subsequently, the beam member 14 undergoes buckling reversal in the ink droplet ejection direction, that is, in the upward direction in the figure. For this reason, the ink in the ink flow path 13 is refilled as shown in FIG. 12D, and the ink discharged in FIG. 12C is replenished, and the meniscus returns to normal.

  Further, when the buckling inversion in the ejection direction is completed in FIG. 12E, an ink droplet 2 is formed in the ejection direction, and ejection is performed in FIG. At this time, the ink is refilled by the buckling reversal operation, and the ink in the ink flow path 13 is replenished without shortage together with the pumping by the back pressure P.

  At this time, the ink recovery unit 19 shown in FIG. 11B may be a mechanism that generates a negative pressure by a vacuum mechanism or the like and actively collects the ink when the overflowed ink falls from the discharge unit 17. Alternatively, an ink absorbing member such as a sponge may be attached to the bottom surface more simply.

  However, when the back pressure P is constantly applied to the ink and the ink is constantly pumped, the ink that overflows from the nozzle 16 consumes a great deal of ink unless it is collected / reused, and the user is troublesome in terms of cost / ink replenishment. Therefore, it is preferable that the overflowed ink is recovered by the ink recovery unit 19 and then sent to the ink flow path 13 again to be circulated so that the overflowed ink is also reused.

  Further, as shown in FIG. 11C, the shape of the discharge portion 17 may be a portion in which both sides in the width direction are shaved and the width is narrowed instead of the nozzle shape. In this case, the overflowed ink is discharged from both sides toward the ink collecting unit 19.

  Or the discharge part 17 may be comprised not with one hole but with several holes, and the structure of using a mesh-shaped member etc. may be sufficient.

  FIG. 13 shows an ink recovery method according to the fourth embodiment of the present invention.

  That is, as shown in FIG. 13, the above-described ink recovery portion 19 can be applied even in a configuration in which the nozzle 16 is provided in the approximate center in the length direction instead of the end of the ink flow path member 12.

  That is, as shown in FIG. 13A, the ink flow path 13 is provided on the side opposite to the ejection direction (lower side in the figure), and the ejection direction side where the nozzles 16 are provided is flush to reduce unevenness. It can be set as a structure advantageous to. A nozzle 16 penetrating the actuator 36 is formed. As shown in FIG. 13C, a protective film 23 is deposited on the nozzle surface (surface) and the inner wall of the nozzle, and a water-repellent film 21 is further sprayed on the surface. By forming it, the ink resistance can be further increased.

At this time, the discharge portion 17 may be a rectangular hole that can be easily formed by slit scanning or the like, as shown in FIG. 13B. Moreover, the position of the discharge part 17 should just be in the vicinity of the nozzle 16 even if it is not directly under the nozzle 16 like FIG.13 (c).
<Others>
In addition, this invention is not limited to said embodiment.

For example, in the above-described embodiment, the actuator includes the piezo element 30 and the beam member 14, but an actuator that uses a heating resistor instead of the piezo element 30 and bends and deforms due to a difference in thermal expansion may be used. However, it may be one using electrostatic force or magnetic force. Or the actuator of another form may be sufficient.
Moreover, in the said embodiment, although the nozzle 16 and the ink flow path 13 were each formed in the separate resin film and adhesively joined, it is not limited to this. For example, the nozzle and the ink supply path may be integrally formed. Alternatively, the beam member 14 may be an integral structure. Alternatively, other forms may be used.

  In addition, although the ink jet recording head is taken as an example of the droplet discharge head in the present specification, it is not necessarily limited to recording characters and images on recording paper using ink. That is, the recording medium is not limited to paper, and the ejected liquid is not limited to ink. For example, industrial uses such as creating color filters for displays by discharging ink onto polymer films or glass, or forming bumps for component mounting by discharging liquid solder onto a substrate The present invention can be applied to all types of liquid droplet ejecting apparatuses.

It is a figure which shows the inkjet recording head which concerns on this invention. It is a figure which shows the refill of the high viscosity ink which concerns on 1st Embodiment of this invention. It is a figure which shows the refill of the high viscosity ink which concerns on 1st Embodiment of this invention. It is a figure which shows the relationship between the support position of the beam member which concerns on this invention, and the frequency | count of buckling reversal. It is a figure which shows the relationship between the support position of the beam member which concerns on this invention, and the frequency | count of buckling reversal. It is a figure which shows the relationship between the back pressure concerning the ink which concerns on this invention, and a meniscus. It is a figure which shows the relationship between the back pressure concerning the ink which concerns on this invention, and a meniscus. It is a figure which shows the relationship between the back pressure concerning the ink which concerns on this invention, and a meniscus. It is a figure which shows the relationship between the back pressure concerning the ink which concerns on 2nd Embodiment of this invention, and the number of buckling reversals. It is a figure which shows the relationship between the back pressure concerning the ink which concerns on 2nd Embodiment of this invention, and the number of buckling reversals. It is a figure which shows the ink collection method which concerns on 3rd Embodiment of this invention. It is a figure which shows the ink collection method which concerns on 3rd Embodiment of this invention. It is a figure which shows the ink collection method which concerns on 4th Embodiment of this invention. It is a figure which shows the conventional inkjet recording head.

Explanation of symbols

2 Ink Drop 3 Meniscus 10 Inkjet Recording Head 12 Ink Channel Member 13 Ink Channel 14 Beam Member 16 Nozzle 18 Holding Member 20 Rotary Encoder 30 Piezo Element 32 Individual Electrode 36 Actuator

Claims (7)

A nozzle for discharging droplets;
A liquid flow path member including the nozzle;
In the vicinity of the nozzle, including the liquid flow path member or including the liquid flow path member, buckling and reversing deformation so as to be concave in the droplet discharge direction, and then buckling and reversing deformation so as to be convex in the liquid discharge direction A beam member for discharging liquid droplets from the nozzle by giving inertia in the discharge direction to the liquid;
A liquid droplet ejection head comprising: Both ends or one end of the beam member in the longitudinal direction are held rotatably in the droplet discharge direction, and the beam member is compressed in the longitudinal direction of the beam member so as to be concave in the droplet discharge direction and buckled and inverted. 2. The droplet discharge according to claim 1, further comprising a holding member that rotates and reverses both ends or one end in the longitudinal direction of the beam member so as to be convex in the droplet discharge direction. head. A rotary encoder that rotatably supports one or both of the holding members in a droplet discharge direction and rotates the beam member;
The holding member supports the beam member at a position offset from the rotation center or the rotation center of the encoder in a state where the beam member is previously compressed and bent in the longitudinal direction. The droplet discharge head according to claim 2, wherein the beam member is buckled and reversed in both the concave and convex operations in the droplet discharge direction. 4. The liquid droplet ejection head according to claim 1, wherein a back pressure is applied to the liquid in the liquid channel. The liquid droplet ejection head according to claim 4, wherein the liquid in the liquid channel is constantly pumped through the liquid channel by back pressure. The said beam member or the said liquid flow path is provided with the liquid discharge part which discharges | emits the liquid overflowing from the said nozzle to the opposite side of a droplet discharge direction, The said any one of Claim 1 thru | or 5 characterized by the above-mentioned. Droplet discharge head. The liquid droplet ejection head according to claim 6, further comprising a liquid recovery unit that recovers the liquid discharged from the liquid discharge unit.

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