JP5587088B2 - Droplet discharge head and liquid discharge apparatus - Google Patents

Description

  The present invention relates to a liquid discharge head and a liquid discharge apparatus including the liquid discharge head.

  The so-called continuous type droplet discharge device applies a constant pressure to the liquid with a pump, pushes it out of the nozzle, and further vibrates it with vibration means, so that the state of the liquid discharged from the nozzle regularly drops into droplets. Form. In this method, since the liquid droplets are continuously discharged from the nozzle, it is necessary to select the liquid droplets used for printing and the liquid droplets not used according to the print data. In the so-called charge deflection method, the droplets are selectively charged, deflected by an electric field, and selected so as to fly on a different trajectory from the uncharged droplets. The sorted non-printed droplets are captured and collected by a gutter. In order to realize these functions, a charging electrode, a deflection electrode, and a gutter are provided along the droplet flight trajectory from the nozzle.

  Patent Document 1 discloses a method for sorting droplets without charging, which is different from the charge deflection method. Specifically, large droplets and small droplets are separated by a nozzle and passed through a liquid curtain made of mist-like droplets formed in the droplet flight path to capture small droplets. Discloses a configuration in which only the recording medium is landed on a recording medium. Japanese Patent Application Laid-Open No. 2004-228561 discloses a technique for causing another droplet to collide with a flying droplet, although it is not a continuous type liquid ejection device. Specifically, the droplets from the first discharge port collide with the droplets (main droplet) from the first discharge port and deflect the flight direction, thereby causing the satellite droplets (minimum) from the first discharge port. A configuration is disclosed in which only the droplets) are landed on a recording medium so as to reduce the size of the recording dots.

JP 2003-334957 A JP 2008-143188 A

  By the way, if the recording droplets are charged, there is a problem that the landing trajectory shifts due to electrostatic interaction with the charged droplets before and after and the charged mist adhering to the wall surface, resulting in poor landing accuracy. There is. Even when the recording droplet is not charged, the recording droplet may be charged by electrostatic induction due to the influence of the preceding charged droplet.

  In the method disclosed in Patent Document 1, since the recording droplet also passes through the liquid curtain, the landing position may be shifted due to the influence of the liquid curtain. In addition, in the method disclosed in Patent Document 2, another droplet is caused to fly and land on a gutter for capturing non-recording droplets. There was a fear.

  An object of the present invention is to provide a liquid discharge head capable of improving the landing accuracy of used droplets (recording droplets) and suppressing the occurrence of mist in the droplet flight path, and the liquid discharge head. It is an object to provide a liquid ejection apparatus provided.

  The liquid ejection head of the present invention includes a first nozzle that continuously ejects liquid droplets, and a recovery unit that collects unused liquid droplets among liquid droplets continuously ejected from the first nozzle. A second nozzle capable of projecting the liquid surface so that the liquid ejected from the first nozzle is located on a trajectory on which the liquid droplets fly. The liquid level is projected from the second nozzle, the unused liquid droplets ejected from the first nozzle collide with the projected liquid level, and the projected liquid level is retracted. Thus, the unused droplets are collected.

  The liquid ejection apparatus according to the present invention includes a first nozzle that continuously ejects liquid droplets, and a recovery that collects unused liquid droplets among liquid droplets that are continuously ejected from the first nozzle. And a second nozzle capable of projecting the liquid level so that the liquid droplet ejected from the first nozzle is located on a trajectory on which the liquid is ejected, the liquid from the second nozzle The unused liquid droplets are recovered by causing the surface to protrude, causing the unused liquid droplets discharged from the first nozzle to collide with the protruding liquid surface, and then retreating the protruding liquid surface. It comprises: the recovery means; and transport means for transporting a recording medium on which recording is performed by the used droplets among the droplets continuously ejected from the first nozzle. .

  According to the present invention, since it is possible to selectively collect unused droplets (non-recording droplets) without affecting the used droplets (recording droplets), the landing accuracy of the used droplets (recording droplets) is improved. It is possible to increase. In addition, since the liquid surface protruding from the second nozzle for sorting does not fly into droplets, it is possible to suppress the occurrence of mist in the droplet flight path and improve the reliability of the head. Can be made.

It is a system outline figure of the liquid discharge device of the present invention. 1 is an exploded perspective view of a first embodiment of a liquid ejection apparatus of the present invention. It is sectional drawing of 1st Embodiment of the liquid discharge apparatus of this invention. It is sectional drawing explaining operation | movement of the liquid discharge apparatus of this invention. It is a perspective exploded view of another embodiment of the liquid ejection apparatus of the present invention. 3 is a simulation model of the operation of the liquid ejection apparatus of the present invention. It is a figure showing the simulation result of operation of the liquid discharge device of the present invention. It is sectional drawing of the liquid discharge apparatus which concerns on the 2nd Example of this invention. It is a system outline | summary figure of the liquid discharge apparatus which concerns on the 3rd Example of this invention. It is sectional drawing of the liquid discharge apparatus which concerns on the 3rd Example of this invention. It is sectional drawing of the liquid discharge apparatus which concerns on the 4th Example of this invention.

[First Embodiment]
A first embodiment of the present invention will be described. The discharge target of the liquid discharge head of the present invention is not limited to printing ink using a color material, and can be applied to all liquids. In addition, although the droplet discharge head of the present invention is described as an example in which droplets are landed on a recording medium and used for recording, the use is not limited to printing, but a liquid made of a conductive material or a polymer is used. The present invention can be widely applied to a manufacturing apparatus and an analysis apparatus using a liquid containing protein.

  FIG. 1 is a system schematic diagram of a liquid discharge apparatus equipped with a liquid discharge head of the present invention. The liquid ejection apparatus according to the present invention includes an ink tank 001, a pressure pump 002, a vibration mechanism 003, a head 004, a controller 005, a recovery pump 006, and an ink adjustment unit 007. 2 is an exploded perspective view of the configuration of the head portion of the present invention, and FIG. 3 is a cross-sectional view. The head unit 004 includes a discharge nozzle 101 (first nozzle), a recovery nozzle 102 (second nozzle), and a liquid level drive mechanism 103 (drive mechanism). As shown in FIG. 3, the recovery nozzle 102 can cause the liquid level driven by the liquid level driving mechanism 103 to protrude from the opening of the recovery nozzle 102, and the protruding liquid level is continuously from the discharge nozzle 101. It is arranged so as to be positioned on the trajectory 117 of the droplets discharged to the surface.

  Next, the operation of the liquid ejection apparatus of the present invention will be described based on the cross-sectional view of the head shown in FIG. The ink stored in the ink tank 001 is pressurized by the pressure pump 002 and supplied to the head 004. The ink supplied to the head 004 is vibrated by the vibration mechanism 003 and ejected from the ejection nozzle 101. When the ink ejected from the nozzle 101 flies about 500 to 800 μm, it splits from the liquid column into droplets and flies along the droplet flight trajectory 117. On the other hand, in the recovery nozzle 102, the liquid level is held in the vicinity of the recovery nozzle 102 by balancing the negative pressure by the recovery pump 006 and the meniscus force (FIG. 4A).

  When a liquid droplet not used for recording (unused liquid droplet) passes in the vicinity of the recovery nozzle 102, the liquid level driving mechanism 103 causes a liquid droplet flight trajectory from the opening of the recovery nozzle 102 by a signal from the controller 005. It is made to collide with the unused droplet which protrudes and flies so that it may be located on 117 (FIG.4 (b)).

  Thereafter, the protruding liquid surface is united with the collided droplet, and both return to the original position due to the surface tension of the liquid surface. By maintaining the pressure constant by the recovery pump 006, the liquid level of the recovery nozzle 102 is maintained at a constant position even after capture. In particular, the amount of displacement of the liquid level driving mechanism 103 is controlled so that the protruding liquid level does not drop. The captured droplet is gradually sent to the ink adjusting unit 007, and after removing dust and adjusting the viscosity, it is pressurized again by the pressure pump 002 and circulated to the head 004 for reuse. . On the other hand, when a droplet (used droplet) used for recording passes, the liquid surface of the recovery nozzle 102 does not protrude (advance) and does not intersect with the droplet flight trajectory 117. The liquid droplets land on the recording medium 008 as they are.

  As described above, by controlling the liquid level driving mechanism 103 according to the recording data, the liquid droplets that are not used for recording are collected by the protruded liquid surface, and only the liquid droplets used for recording are transferred to the recording medium 008. Can land. The recording medium 008 on which recording has been performed is transported by a transport unit (not shown).

  When performing high-speed recording, the subsequent droplets may pass before the liquid level of the recovery nozzle 102 has returned to the position at the time of stabilization. Even in such a case, if the difference between the forward and backward positions of the liquid surface of the recovery nozzle 102 is sufficient, and the unused droplet can be captured and the used droplet can pass, the liquid ejection device of the present invention can be used. Function.

  In the present embodiment, the case where the negative pressure is maintained by the recovery pump 006, the liquid level is moved backward by the recovery nozzle 102, and the liquid level is advanced by the liquid level driving mechanism 103 when the unused droplets pass is described. Conversely, the positive pressure may be maintained by the recovery pump 006, the liquid level may be advanced by the recovery nozzle 102, and the liquid level may be retracted by the liquid level driving mechanism 103 when the used droplets pass. In this case, it is preferable that the outer surface of the recovery nozzle 102 is subjected to a water repellent treatment so that the liquid surface does not spread by wetting the outer surface in a state where positive pressure is applied. This method is effective in reducing power consumption and heat generation in a state where all of the ejected ink is collected without performing recording, such as during standby.

  In FIG. 2, the droplet flight path is slit-shaped and common to each nozzle row. However, as shown in FIG. 5, a separate partition may be provided for each nozzle. The slit-shaped flight path as shown in FIG. 2 has an advantage that cleaning is easy when mist or the like adheres. On the other hand, the individual flight paths as shown in FIG. 5 are not easily affected by the wake of the droplet air from the adjacent discharge nozzles 101, and have the advantage that the landing accuracy is further improved.

In FIG. 2, the liquid level driving mechanism 103 uses a piezoelectric element on a thin film, but other types of driving means may be used. For example, if the piezoelectric element, it may be used by laminating bulk piezoelectric elements may be utilized deformation of d ₁₅ direction by using the piezoelectric element on the side walls (shear mode). Alternatively, the driving means may be a heater, and the liquid level may be driven by foaming due to film boiling. When a heater is used, a large displacement can be easily obtained and the size can be reduced as compared with the case where a piezoelectric material is used, so that the nozzle density can be increased. On the other hand, when a piezoelectric element is used, the liquid level can be accurately controlled by optimizing the drive waveform.

  A first embodiment of the present invention will be described. As in the embodiment, the liquid ejection device in this example is a perspective exploded view of the configuration of the head portion, and FIG. 3 is a sectional view. As shown in FIG. 2, the head portion is configured by laminating plate-like members. Silicon, stainless steel, resin material, etc. can be used for the member. By producing these plate-like members by patterning by exposure, etching, or pressing, even when the number of nozzles is increased, batch processing is possible, and the number of parts is not increased, and a head can be manufactured at low cost. In this embodiment, a thin film piezoelectric element is used as the liquid level driving mechanism 103. Specifically, the upper electrode 111, the piezoelectric element 112, and the lower electrode 113 are formed on the diaphragm 114. Sputtering or the like can be used for film formation, and dry etching can be used for patterning.

  In FIG. 2, the nozzle interval in the depth direction is 500 μm, and the nozzle interval in the horizontal direction is 3 mm. A liquid having a viscosity of 1 to 40 cP and a surface tension of 30 mN / m is used. If the diameter of the discharge nozzle 101 is 7.4 μm, the pressure of the ink tank 002 is 0.8 MPa, and the vibration frequency of the vibration mechanism 003 is 50 kHz, the droplet size is 4 pL (diameter about 20 μm) and the discharge speed is about 10 m / s. It is. In the discharge nozzle 101, first, a liquid column is formed, and droplets are formed at locations separated from the discharge nozzle 101 by about 500 to 800 μm. The diameter of the recovery nozzle 102 is 80 μm, and is provided at a point 1 mm away from the discharge nozzle 101 in the droplet flight direction. The discharged liquid droplets are decelerated to about 8 m / s when passing through the vicinity of the recovery nozzle 102 due to air resistance. Further, the droplet flight trajectory 117 is 30 μm away from the recovery nozzle 102. The ink in the recovery nozzle 102 is controlled to a constant negative pressure by the recovery pump 006 (about −1.4 kPa with respect to the atmospheric pressure), and an ink meniscus is formed in the recovery nozzle 102. When the unused droplet passes, the liquid level driving mechanism 103 advances the liquid level of the recovery nozzle 102 and collides with the droplet.

  A state in which the liquid surface protruding from the recovery nozzle 102 collides with the flying droplet was analyzed by general-purpose fluid analysis software Fluent (ANSYS). The model used for the analysis is shown in FIG. In the center of the figure, there is a recovery nozzle 102 having a diameter of 80 μm and a thickness of 80 μm, the left side is filled with ink (40 cP), and the right side is the atmosphere. A pressure boundary condition corresponding to the case where the diaphragm 114 in FIG. 2 was displaced by about 40 nm was given to the left wall, and the liquid level was advanced. Further, a 4 pL droplet was ejected from above at a position perpendicular to the axis of the recovery nozzle 102 at a distance of 30 μm from the recovery nozzle 102 at 8 m / s and collided with the liquid surface advanced from the recovery nozzle 102. FIG. 7 shows the state of the liquid surface and the liquid droplets over time. The liquid surface advanced in 6 μs collides with the droplet 118. Thereafter, the droplets are united with the liquid surface without being scattered and absorbed by the liquid surface. Further, the liquid level that has advanced from the recovery nozzle 102 does not become droplets.

  Here, the liquid level of the recovery nozzle 102 is then returned to the original position by the surface tension of the nozzle portion. By controlling the liquid level driving mechanism 103, if the liquid chamber is expanded, the liquid level can be returned to the original position at a higher speed. By absorbing the droplet 118, the ink amount of the recovery nozzle 102 increases, but the pressure of the recovery pump 006 is kept constant, so that the ink meniscus position of the recovery nozzle 102 is held at the same position. The Excess ink is sent to the ink adjustment unit 007 via the recovery pump 006, and after being adjusted in viscosity and density, is circulated to the discharge nozzle 101 again.

  The diameter of the recovery nozzle 102 is preferably at least twice the diameter of the droplet discharged from the discharge nozzle 101. If it is smaller than that, the liquid surface that has advanced at the time of collision with the droplet may be split. On the other hand, it is preferable that the amount of advance of the liquid level from the recovery nozzle 102 is about the same as the diameter of the recovery nozzle 102. If the advance amount is larger than that, droplet formation may occur or the liquid level may not be retracted.

  If the diameter of the recovery nozzle 102 is too large, it becomes difficult to maintain a meniscus in the nozzle portion. Further, when the diameter of the recovery nozzle 102 is increased, it takes time for the liquid level that has advanced to return to the original position, and high-speed driving becomes difficult. For example, when a liquid having a viscosity of 40 cP and a surface tension of 30 mN / m is used, the diameter of the recovery nozzle 102 that can keep the liquid level stable even when the pressure setting of the recovery pump 006 is changed is up to about φ160 μm.

  A second embodiment of the present invention will be described. A cross-sectional view of the liquid discharge head of this embodiment is shown in FIG. As shown in FIG. 2, the liquid level driving mechanism 103 of the first embodiment is arranged between the recovery nozzle 102 and the discharge nozzle 101, whereas in the second embodiment, the liquid level driving mechanism 103 is It is arranged facing the lowermost surface of the head, that is, the recording medium 008. In the configuration of the first embodiment, since the piezoelectric element 112 and the electrode do not face the outside, the structure is protected against mist and rubbing and has high durability. Further, by storing the liquid level driving mechanism 103 in a space until the droplet 118 is formed into a droplet, there is an advantage that the distance between the discharge nozzle 101 and the recording medium 008 can be shortened. On the other hand, the shape of the second embodiment has the advantage that the upper electrode 111 and the lower electrode 113 are exposed on the outer surface of the head as compared with the configuration of the first embodiment. ing. The droplet discharge and sorting functions are the same as those in the first embodiment.

  A third embodiment of the present invention will be described. FIG. 9 is a schematic system diagram of the present embodiment, and FIG. 10 is a sectional view of the liquid discharge head. In this embodiment, two recovery channels to the recovery nozzle 102 are provided, and the first recovery channel 211 (recovery supply channel) is always circulated from the second recovery channel 212 (discharge channel). ing.

Here, the set pressure of the first recovery pump 201 is P ₁ , the set pressure of the second recovery pump 202 is P ₂ , the pressure of the recovery nozzle 102 is P ₃ , and the pressure from the first recovery pump 201 to the recovery nozzle 102 is The flow resistance of the first recovery flow path 211 is R ₁ , the flow resistance of the second recovery flow path 212 from the second recovery pump 202 to the recovery nozzle 102 is R ₂ , and the circulating flow rate is Q. At this time, the following two expressions hold.
Q = (P ₁ −P ₂ ) / (R ₁ + R ₂ ) (1)
_{P 3 = (P 1 R 2} -P 2 R 1) / (R 1 + R 2) ··· (2)
When the above two equations are combined, P ₁ and P ₂ can be solved as follows.

Maintaining the meniscus at the recovery nozzle 102 while obtaining a desired circulation flow rate by appropriately performing the set pressures of the first recovery pump 201 and the second recovery pump 202 according to the equations (3) and (4). Is possible. Specific numerical values of Q and P ₃ per nozzle include, for example, Q = 2 × 10 ⁻⁹ m ³ / s and P ₃ = −1.4 kPa (based on atmospheric pressure).

  By always circulating the collected liquid as in this embodiment, it is possible to prevent dust from being collected in the vicinity of the collection nozzle 102 and the collected ink from being thickened without being circulated easily. In addition, by using a diluted liquid or diluted ink as the liquid supplied to the first recovery flow path 211, it is possible to prevent the ink from sticking near the recovery nozzle 102 and improve the fluidity.

  A fourth embodiment of the present invention will be described. In this embodiment, a plurality of recovery nozzles are provided for one discharge nozzle, thereby supporting high-speed recording. FIG. 11 shows a cross-sectional view of the liquid discharge head of this embodiment. A first recovery nozzle 301 and a second recovery nozzle 302 are arranged with respect to the discharge nozzle 101. The liquid levels of the first recovery nozzle 301 and the second recovery nozzle 302 are driven independently by the first liquid level driving mechanism 311 and the second liquid level driving mechanism 312, respectively. Each collecting nozzle collects every other unused droplet so that the frequency of the vibration mechanism 003 is increased and high-speed printing can be performed reliably.

  The liquid discharge head of the present invention has little impact on the flying of the droplets used during the selection and recovery of the droplets, so that high landing accuracy can be obtained and used for the production of a high-definition liquid discharge head can do.

004 Head 101 Discharge nozzle 102 Recovery nozzle 103 Liquid level driving mechanism 115 Supply flow path 116 Recovery flow path 117 Droplet flight trajectory 118 Droplet

Claims (5)

A liquid ejection head comprising: a first nozzle that continuously ejects droplets; and a recovery unit that collects unused droplets among droplets continuously ejected from the first nozzle. There,
The recovery means has a second nozzle capable of projecting the liquid level so that the liquid droplet ejected from the first nozzle is located on a trajectory on which the liquid droplets fly, and the liquid from the second nozzle The unused liquid droplets are recovered by causing the surface to protrude, causing the unused liquid droplets discharged from the first nozzle to collide with the protruding liquid surface, and then retreating the protruding liquid surface. A liquid discharge head. The second nozzle is provided with a supply flow path for supplying liquid to the second nozzle and a discharge flow path for discharging liquid from the second nozzle,
2. The liquid discharge head according to claim 1, wherein liquid is circulated from the supply flow path toward the discharge flow path at least while liquid droplets are discharged from the first nozzle.   The liquid ejection head according to claim 1, wherein the recovery unit includes a plurality of the second nozzles with respect to one of the first nozzles.   2. The liquid ejection head according to claim 1, wherein the diameter of the second nozzle is at least twice the diameter of an unused droplet ejected from the first nozzle. A first nozzle that continuously ejects droplets;
Among the droplets continuously discharged from the first nozzle, the recovery means recovers unused droplets that are not used, and is located on a trajectory along which the droplets discharged from the first nozzle fly. A second nozzle capable of projecting the liquid level to cause the liquid level to project from the second nozzle, and the unused liquid discharged from the first nozzle to the projected liquid level The recovery means for recovering the unused droplets by causing the droplets to collide and coalesce and retreating the protruding liquid surface;
Transport means for transporting a recording medium on which recording is performed by using used droplets among liquid droplets continuously discharged from the first nozzle;
A liquid ejection apparatus comprising:

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