LIQUID DROPLET FORMING APPARATUS

What is provided is a liquid droplet forming apparatus capable of stably ejecting dispersion liquid, as liquid droplets, containing settling particles having constant concentration. A liquid droplet forming apparatus includes an ejection head that has a liquid chamber storing liquid containing settling particles and that ejects a liquid droplet of the liquid, stirrer for stirring the liquid held in the liquid chamber, posture controller for controlling a posture of the stirrer, and a control unit that controls operations of the ejection head, the stirrer, and the posture controller, in which the stirrer includes a tube-like member inserted into the liquid chamber, and a liquid feeding portion that sucks or discharges the liquid stored in the liquid chamber via the tube-like member, and the posture controller controls one or both of the position and the direction in which the stirrer sucks and discharges the liquid in the liquid chamber.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2023-049895, filed Mar. 27, 2023. The contents of which are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a liquid droplet forming apparatus.

Description of Related Art

In the related art, an ink jet type liquid droplet forming apparatus is known as a technique for ejecting a liquid substance (liquid) such as ink to a desired position.

In recent years, there has been demand for a liquid droplet forming apparatus which can eject various types of liquid in place of ink used in two-dimensional printing in the related art. Exemplary examples of the liquid to be ejected include dispersion liquid as well as a solution. Exemplary examples of dispersoids (particles) contained in the dispersion liquid include organic materials such as resin materials, inorganic materials such as metal particles and oxide particles, and biologically derived materials such as cells and genes.

In a case where the above-described dispersion liquid is ejected in a liquid droplet forming apparatus, dispersoids may settle in a liquid chamber. In the following description, the dispersoids that settle in the dispersion liquid may be referred to as “settling particles”. In a case where settling particles settle, the concentration of settling particles contained in the liquid to be ejected changes even in a case where the amount of liquid droplets to be ejected is constant, which makes it difficult to stably eject a desired amount of dispersoids.

In response to such a problem in the related art, in a liquid droplet forming apparatus that stores dispersion liquid containing settling particles, a configuration having two liquid suction-discharge members connected to a liquid holding portion has been proposed (for example, see Japanese Patent No. 7062974). In the apparatus in Japanese Patent No. 7062974, liquid is stirred by synchronizing operations of the two liquid suction-discharge members, suctioning the dispersion liquid stored in the liquid holding portion using one of the liquid suction-discharge members, and discharging the dispersion liquid using the other of the liquid suction-discharge members.

SUMMARY OF THE INVENTION

In the configuration of Japanese Patent No. 7062974, the settling particles are likely to be accumulated in the corner of the liquid holding portion, and it is difficult to stably eject liquid droplets containing settling particles having constant concentration.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a liquid droplet forming apparatus capable of stably ejecting dispersion liquid, as liquid droplets, containing settling particles having constant concentration.

In order to solve the above problems, one aspect of the present invention provides a liquid droplet forming apparatus including: an ejection head that has a liquid chamber storing liquid containing settling particles and that ejects a liquid droplet of the liquid; stirrer for stirring the liquid held in the liquid chamber; posture controller for controlling a posture of the stirrer; and a control unit that controls operations of the ejection head, the stirrer, and the posture controller, in which the stirrer includes a tube-like member inserted into the liquid chamber, and a liquid feeding portion that sucks or discharges the liquid stored in the liquid chamber via the tube-like member, and the posture controller controls one or both of the position and the direction in which the stirrer sucks and discharges the liquid in the liquid chamber.

In the present invention, it is possible to provide a liquid droplet forming apparatus capable of stably ejecting dispersion liquid, as liquid droplets, containing settling particles having constant concentration.

DETAILED DESCRIPTION OF THE INVENTION

First Embodiment

A liquid droplet forming apparatus according to a first embodiment of the present invention will be described below with reference toFIGS.1to5. In all the following drawings, dimensions, proportions, and the like of each constituent element have been appropriately changed in order to make the drawings easier to see.

FIG.1is a schematic view of a liquid droplet forming apparatus1of the present embodiment. As illustrated inFIG.1, the liquid droplet forming apparatus1includes an ejecting portion10, an adhesion portion30, a mounting portion40, and a control unit50.FIG.2is a schematic view illustrating a configuration ofa part of the ejecting portion10.

In the following description, an xyz orthogonal coordinate system is set, and a positional relationship of each member will be described with reference to the xyz orthogonal coordinate system. Here, a predetermined direction within a horizontal plane is defined as an x-axis direction, a direction orthogonal to the x-axis direction within the horizontal plane is defined as a y-axis direction, and a direction (that is, a vertical direction) orthogonal to each of the x-axis direction and the y-axis direction is defined as a z-axis direction.

In addition, an upper part in the vertical direction is defined as a +z direction, and a lower part in the vertical direction is defined as a −z direction. In the following description, the same meanings are applied to the term “up” from “upper part” and “upper surface” and the term “low” from “lower part” and “lower surface”.

Further, in the following description, the term “plan view” refers to viewing a target object from above, and the term “planar shape” refers to a shape of the target object as viewed from above.

Ejecting Portion

As illustrated inFIGS.1and2, the ejecting portion10includes an ejection head110, stirrer120, and moving unit130. The moving unit130corresponds to posture controller in the present invention.

Ejection Head

The ejection head110ejects a liquid droplet L1of liquid containing settling particles. The ejecting portion10may include only one ejection head110or a plurality of ejection heads110.

The ejection head110includes a liquid holding portion111, a nozzle plate (film-like member)112, and vibration applier113.

A space surrounded by the liquid holding portion111, the nozzle plate112, and the vibration applier113is a liquid chamber110A of the ejection head110. The liquid (liquid L) containing settling particles is held in the liquid chamber110A.

The amount of the liquid L held in the liquid chamber110A is not particularly limited. Exemplary examples of the amount of the liquid L held in the liquid chamber110A include substantially 1 μl to 1 ml. When expensive liquid such as cell suspension is ejected from the liquid droplet forming apparatus1, it is preferable that the amount of the liquid L held in the liquid chamber110A is substantially 1 μl to 200 μl.

The liquid L ejected by the liquid droplet forming apparatus1contains dispersoids (particles P), which are settling particles, and a dispersion medium DM in which the particles P are dispersed.

Exemplary examples of the particles P include organic materials such as polymer particles, and inorganic materials such as fine metal particles and inorganic oxide particles. Exemplary examples of the fine metal particles include silver particles and copper particles. Exemplary examples of the inorganic fine particles include titanium oxide particles and silicon oxide particles.

Further, cells can also be used as the particles P. As the cells, plant cells or animal cells can be applied. Exemplary examples of the animal cells include, particularly, human-derived cells.

Exemplary examples of the dispersion medium DM include water and alcohol. The dispersion medium DM may contain a wetting agent for suppressing evaporation or a surfactant for lowering surface tension.

In the present embodiment, the liquid L ejected by the liquid droplet forming apparatus1will be described as dispersion liquid in which cells are dispersed as the particles P in the dispersion medium DM. In this case, as the dispersion medium DM, known buffer solutions such as phosphate buffered saline or Hank's balanced salt solution, or various cell culture media can be used.

Liquid Holding Portion

The liquid holding portion111is a tubular-shaped member of which both end portions are open in the z-axis direction. Exemplary examples of the material of the liquid holding portion111include metal, silicon, ceramics, and polymer materials. In the liquid droplet forming apparatus1that ejects the liquid L in which cells are dispersed, a material to which cells are not easily adhered is preferable as a material of the liquid holding portion111. As such a material, a material having high hydrophilicity is preferable.

Exemplary examples of such materials include metal, ceramics, semiconductor materials, and polymer materials. A fluororesin can be used as the polymer material.

A lower end portion of the liquid holding portion111is blocked by the nozzle plate112and the vibration applier113. It is preferable that, in a case where cells are used as the particles P, an upper end portion of the liquid holding portion111is open. When the upper part of the liquid holding portion111is open, the liquid L held in the liquid holding portion111is less likely to be pressurized during liquid droplet ejection, and damage to cells can be suppressed.

As the liquid holding portion111, for example, a member having a cylindrical shape, a truncated cone shape, or a square tubular shape can be used.

The size of the liquid holding portion111can be selected according to the shape of the adhesion portion30described below. For example, in a case where a known 96 well plate is used as the adhesion portion30, a cylindrical-shaped member having an outer diameter of 6.0 mm or less can be used as the liquid holding portion. In this case, for example, the inner diameter of the liquid holding portion111can be set to 4 mm, and the height can be set to 10 mm.

The volume of the liquid holding portion111is not particularly limited and may be appropriately selected according to the purposes.

The nozzle plate112is a ring-shaped member having an ejection outlet112x. The nozzle plate112blocks the lower end portion of the liquid holding portion111and forms the liquid chamber110A, which holds the liquid L, together with the liquid holding portion111. An upper surface of the nozzle plate112is a bottom surface110xof the liquid chamber110A. The ejection outlet112xcommunicates with the liquid holding portion111.

The planar shape, the size when viewed in a plan view, the material, and the structure of the nozzle plate112are not particularly limited and can be appropriately selected according to the purpose.

Exemplary examples of the planar shape of an outer edge of the nozzle plate112include a circular shape, an elliptical shape, a rectangular shape, a square shape, and a rhombic shape. For example, in a case where the shape of the outer edge of the nozzle plate112is a circular shape, the nozzle plate112is a circular ring-shaped member.

The nozzle plate112is not supported at an end portion on an ejection outlet112xside and is capable of vibrating up and down (z-axis direction). The nozzle plate112vibrates at the end portion on the ejection outlet112xside to apply a downward force to the liquid L in the vicinity of the ejection outlet112x, and the liquid L is ejected from the ejection outlet112xas the liquid droplet L1.

As the material of the nozzle plate112, it is preferable to use a material having a certain degree of hardness because the nozzle plate112may easily vibrate and it may be difficult to immediately suppress the vibration when the nozzle plate112is not in the ejection state, in a case where the nozzle plate112is too soft.

Further, in a case where the liquid L to be ejected is dispersion liquid of cells, the material of the nozzle plate112is preferably a material to which cells do not easily adhere. As such a material, a material having high hydrophilicity is preferable.

Exemplary examples of such materials include metal, ceramics, semiconductor materials, and polymer materials. A fluororesin can be used as the polymer material.

More specifically, exemplary examples of the material of the nozzle plate112include stainless steel, nickel, aluminum, silicon dioxide, alumina, and zirconia. Further, it is possible to use a composite material in which a surface of the nozzle plate112, which is formed with a material different from the above material, is coated with the above-described metal, ceramics, or a synthetic phospholipid polymer (for example, Lipidure, manufactured by NOF Corporation) that mimics the cell membrane.

The opening shape of the ejection outlet112xcan be appropriately selected according to the purpose. Exemplary examples of the opening shape of the ejection outlet112xinclude a circular shape, an elliptical shape, and a square shape. Among them, a circular shape is preferable as the opening shape of the ejection outlet112x.

The average opening diameter of the ejection outlet112xis not particularly limited and can be appropriately selected according to the purpose. In order to prevent clogging of the ejection outlet112xby the dispersoids such as cells dispersed in the liquid L in a case where the liquid L to be ejected is dispersion liquid, it is preferable for the opening shape of the ejection outlet112xto be at least twice the maximum diameter of the dispersoid.

The nozzle plate112having a relatively large diameter (for example, 100 m) of the ejection outlet112xalso has a large diameter of the liquid droplets to be ejected. Such a nozzle plate112is suitable for a case where a large amount of liquid needs to be dispensed because a large amount of liquid can be ejected with a small number of liquid droplets.

On the other hand, the nozzle plate112having a relatively small diameter of the ejection outlet112xhas a relatively small diameter of the liquid droplets to be ejected. Such a nozzle plate112is suitable for the purpose of precisely controlling the number of cells to dispense the cells.

The vibration applier113vibrates the nozzle plate112based on an electrical signal to be input, thereby ejecting the liquid droplet L1from the ejection outlet112x.

The vibration applier113is installed on a lower surface of the nozzle plate112.

The shape, the size, the material, and the structure of the vibration applier113are not particularly limited and can be appropriately selected according to the purpose.

The shape or the disposition of the vibration applier113are not particularly limited as long as the effects of the invention are not impaired, and can be appropriately designed in accordance with the shape of the nozzle plate112. For example, in a case where the planar shape of the nozzle plate112is a circular ring shape, it is preferable to provide the vibration applier113concentrically around the ejection outlet112x.

A piezoelectric element is suitably used as the vibration applier113. As the piezoelectric element, for example, it is possible to employ a structure in which electrodes for applying voltage are provided on an upper surface and a lower surface of a piezoelectric material.

In this case, by applying voltage between the upper and lower electrodes of the piezoelectric element through the control unit50, compressive stress is applied in a lateral direction of a film surface so that it is possible to vibrate the nozzle plate112in the up and down direction of the film surface.

The piezoelectric material is not particularly limited and can be appropriately selected according to the purpose, and exemplary examples thereof include lead zirconate titanate (PZT), bismuth iron oxide, metal niobate, barium titanate, and composites of these materials with metals or different oxides. Among them, lead zirconate titanate (PZT) is preferable.

Further, the vibration applier113may be a heater made of a material having a linear expansion coefficient different from that of the material of the nozzle plate112. Such a heater may be patterned on the nozzle plate112, and the heater may be energized and heated to generate vibration.

The stirrer120includes a nozzle (tube-like member)121and a liquid feeding portion122and stirs the liquid L held in the liquid chamber110A. The nozzle121is inserted into the liquid chamber110A. The liquid feeding portion122sucks or discharges the liquid L stored in the liquid chamber110A via the nozzle121.

The nozzle121is a tube-shaped member that constitutes a flow path of the liquid L in the liquid chamber110A and includes an opening portion121xat the tip. The outer diameter of the nozzle121is smaller than the inner diameter of the liquid holding portion111, and can be, for example, set to ½ or less of the inner diameter of the liquid holding portion111. For example, in a case where a cylindrical-shaped member having an inner diameter of 2.8 mm is used as the liquid holding portion111, a tube with an outer diameter of 0.8 mm can be used as the nozzle121.

The material of the nozzle121is not particularly limited, and the nozzle121can be formed using a resin, a silicon rubber, a metal, or the like. It is preferable to use a general-purpose resin-made thin tube called a disposable tip as the nozzle121because replacement is easy.

The liquid feeding portion122is a pump that sucks or discharges the liquid L in the liquid chamber110A via the nozzle121. A syringe pump or a diaphragm pump can be employed as the liquid feeding portion122in the liquid feeding portion122.

According to such stirrer120, the liquid L in the liquid chamber110A can be stirred by inserting the nozzle121into the liquid chamber110A and sucking or discharging the liquid L in the liquid chamber110A.

Moving Unit

The moving unit130includes a first movement portion131, a second movement portion132, a third movement portion133, a first conveying portion134, and a second conveying portion135. The moving unit130, which is posture controller, controls a posture of the stirrer120. The “posture” of the stirrer120is specifically a relative posture of the stirrer120with respect to the liquid chamber110A of the ejection head110. By controlling the posture of the stirrer120, one or both of the position of the nozzle121of the stirrer120and the opening direction of the nozzle121are controlled. The moving unit130controls the posture of the stirrer120and controls the position and opening direction of the nozzle121.

First Movement Portion

As illustrated inFIG.1, the first movement portion131includes a support member131aand a linear motion portion131b.

The support member131asupports the ejection head110in an attachable and detachable manner. Therefore, when the ejection head110is contaminated or damaged, the ejection head110can be removed from the support member131aand replaced with a new ejection head110.

The linear motion portion131bis an elongated member that is connected to the support member131aand extends in the z-axis direction. The linear motion portion131bmoves the support member131aup and down. The linear motion portion131bcan employ, for example, a known linear actuator including a stepping motor as a drive source.

The linear motion portion131bmay include an encoder that determines a drive amount of the stepping motor and may be configured to be capable of determining a movement amount of the support member131a.

The first movement portion131moves the support member131aup and down by driving the linear motion portion131b. Accordingly, the first movement portion131moves the ejection head110supported by the support member131aup and down. Specifically, the first movement portion131moves the ejection head110to a non-ejection position where the liquid L is not ejected from the ejection head110and an ejection position where the liquid is ejected from the ejection head110.FIG.1illustrates the ejection head110(110A) positioned at the non-ejection position and the ejection head110(110B) positioned at the ejection position.

Second Movement Portion

The second movement portion132includes a support member132aand a linear motion portion132b. The second movement portion132is a pair of members provided at end portions of the first conveying portion134on the +x side and the −x side.

The support member132ais a rectangular member in the field of view when viewed from the +y direction and supports the first movement portion131.

The linear motion portion132bis an elongated member extending in the z-axis direction. The linear motion portion132bmoves the support member132aup and down in the z-axis direction. The linear motion portion132bcan employ, for example, a known linear actuator including a stepping motor as a drive source.

The second movement portion132moves the support member132ain the z-axis direction, thereby moving the ejection head110supported by the first movement portion131in the z-axis direction.

Third Movement Portion

The third movement portion133includes a support member133aand a linear motion portion133b.

The support member133asupports the stirrer120in an attachable and detachable manner. Therefore, when the stirrer120is contaminated or damaged, the stirrer120can be removed from the support member133aand replaced with new stirrer120.

The linear motion portion133bis an elongated member extending in the z-axis direction and moves the support member133aup and down. The linear motion portion133bcan employ, for example, a known linear actuator including a stepping motor as a drive source.

The linear motion portion133bmay include an encoder that determines a drive amount of the stepping motor and may be configured to be capable of determining a movement amount of the support member133a.

The third movement portion133moves the support member133aup and down by driving the linear motion portion133b. Accordingly, the third movement portion133moves the stirrer120supported by the support member133aup and down.

First Conveying Portion

The first conveying portion134includes a support member134aand a linear motion portion134b.

The support member134ais a rectangular member in the field of view when viewed from the +y direction and supports the ejection head110via the first movement portion131.

The linear motion portion134bis an elongated member extending in the x-axis direction. The linear motion portion134bmoves the support member134ahorizontally in the x-axis direction. Both ends of the linear motion portion134bare each supported by the support member132aof the second movement portion132.

The linear motion portion134bcan employ, for example, a known linear actuator including a stepping motor as a drive source.

The first conveying portion134moves the support member134ain the x-axis direction, thereby moving the ejection head110supported by the support member134ain the x-axis direction.

Second Conveying Portion

The second conveying portion135includes a support member135aand a linear motion portion135b.

The support member135ais a rectangular member in the field of view when viewed from the +y direction and supports the stirrer120via the third movement portion133.

The linear motion portion135bis an elongated member extending in the x-axis direction. The linear motion portion135bmoves the support member134ahorizontally in the x-axis direction. The linear motion portion135bcan employ, for example, a known linear actuator including a stepping motor as a drive source.

The second conveying portion135moves the support member135ain the x-axis direction, thereby moving the stirrer120supported by the support member135ain the x-axis direction.

Further, the moving unit130is provided with a mechanism that controls a posture of the stirrer120in the y-axis direction (the relative posture of the stirrer120with respect to the liquid chamber110A).

Such a configuration can be realized, for example, by making the support member132aof the second movement portion132movable in the y-axis direction. Similarly, such a configuration can be realized by making indicating members (not illustrated) that support the linear motion portion135bof the second conveying portion135on both sides in the x-axis direction movable in the y-axis direction.

Further, a configuration may be used in which the support member134ais moved in the y-axis direction and the ejection head110supported by the support member134ais moved in the y-axis direction, or a configuration may be used in which the support member135ais moved in the y-axis direction and the stirrer120supported by the support member135ais moved in the y-axis direction.

When the moving unit130has these configurations, the posture of the nozzle121in the y-axis direction with respect to the liquid chamber110A can be controlled.

Adhesion Portion

The adhesion portion30is disposed in the ejection direction of the liquid droplet L1ejected from the ejecting portion10, and the liquid droplet L1adheres thereto. As the adhesion portion30, it is possible to select a structure object having various materials and shapes according to the purpose of ejecting the liquid.

FIG.3is a schematic perspective view illustrating the adhesion portion30. The adhesion portion30includes a plate-shaped base portion301with a plurality of holes30aand wells302provided to cover the lower part of the hole30a. The well302is a recess portion covered with a wall portion and a bottom portion and open at the hole30a.

The adhesion portion30is a so-called well plate in which a plurality of wells are arranged in a matrix shape at equal intervals.

In a case where such an adhesion portion30is used, when ejection head is disposed an upper part of the base portion301of the adhesion portion30and the liquid is ejected, the distance between the bottom of the well to which the liquid is adhered and the ejection head is large, and the position at which the liquid is adhered tends to shift.

Further, commercially available well plates have various variations with different numbers of wells. For example, the well plate is known to have a configuration in which the number of wells is 6 (6 wells), 12 (12 wells), 24 (24 wells), 48 (48 wells), and 96 (96 wells).

In the 96-well plate, which is the largest number, the opening diameter D of the holes30avaries depending on the shape of the wells302, but is set to substantially 6.5 mm to 7.0 mm. By using a cylindrical-shaped member having an outer diameter of 6.0 mm or less as the liquid holding portion111of the ejection head110, the liquid droplet forming apparatus1can eject liquid droplets in a state in which the ejection head110is inserted into the well.

Mounting Portion

The adhesion portion30is mounted on the mounting portion40. The mounting portion40includes an x-stage41, a y-stage42, and a base43.

The x-stage41supports and fixes the adhesion portion30. Further, the x-stage41moves the adhesion portion30horizontally in the x-axis direction.

The y-stage42moves the x-stage41horizontally in the y-axis direction.

The base43supports the y-stage42.

The mounting portion40can employ a known configuration as the x and y stages.

Control Unit

The control unit50generates an electrical signal for operating each portion of the liquid droplet forming apparatus1, and supplies and controls each portion. For example, the control unit50generates drive signals to be supplied to the ejecting portion and the mounting portion40, and supplies the drive signals to each portion to control the operation of each portion.

Hereinafter, a characteristic operation of the liquid droplet forming apparatus1will be described with reference to the drawings.FIGS.4and5are explanatory views illustrating an operation of the liquid droplet forming apparatus1.

As illustrated inFIG.4, when a time elapses after the liquid holding portion111is filled with the liquid L, there is a case where the particles P settle and are accumulated on the bottom surface110xof the liquid chamber110A. When the liquid droplet ejection is started in such a state, the particles P, which are accumulated on the bottom surface110x(seeFIG.2), especially near the ejection outlet112x(indicated by a symbol a in the figure), are ejected at once, and the liquid droplet ejection becomes difficult in a state where the number of particles is controlled.

Further, even when a certain amount of liquid droplets are ejected in a state where the particles P have settled and the particles P at the position indicated by the symbol a are removed, the particles P tend to remain at the corner of the bottom surface110x, specifically at a position where the liquid holding portion111and the nozzle plate112intersect (indicated by a symbol R in the figure). Therefore, when the liquid droplets are continuously ejected, there is a concern that the particles P at the position indicated by the symbol R may be mixed with the liquid droplets, and the droplet ejection becomes difficult in a state where the number of particles is controlled.

Therefore, in the liquid droplet forming apparatus1, the particles P accumulated on the bottom surface110xare dispersed in the liquid L before the liquid droplets are ejected, and then the liquid droplet ejection is performed.

First, as illustrated inFIG.4, the posture controller (the moving unit130) inserts the nozzle121of the stirrer120into the liquid chamber110A based on a control signal supplied from the control unit50. At this time, the tip of the nozzle121may be brought close to the bottom surface110xwithout coming into contact with the bottom surface110x.

Specifically, it is preferable that the tip of the nozzle121is brought closer to the bottom surface110xto the same extent as the opening diameter of the nozzle121. For example, when the inner diameter of the nozzle121is 0.6 mm, the tip of the nozzle121may be brought closer to a position 0.6 mm above the bottom surface110x. In a case where the shape of the opening portion121x(seeFIG.2) of the nozzle121is not a circular shape, the smallest rectangle that circumscribes the opening portion121xis assumed, and the length of a short side of the rectangle is used as a determination criterion. For example, in a case where the shape of the opening portion121xis an elliptical shape, it is preferable to bring the tip of the nozzle121close to a position above the bottom surface110xby the length of the short side of the rectangle circumscribing the opening portion121x(that is, the length of the short axis of the ellipse).

As a result, the moving unit130controls the position where the stirrer120sucks or discharges the liquid L in the liquid chamber110A, specifically, the position of the nozzle121in the liquid chamber110A.

Next, the stirrer120sucks the liquid L in the liquid chamber110A from the nozzle121based on the control signal supplied from the control unit50.

The suction amount of the liquid L by the stirrer120is preferably an amount by which a liquid surface LS of the liquid L in the liquid chamber110A does not fall downward (on the bottom surface110xside) below the opening portion121x. For example, in a case where the liquid level LS is at a position with height of 6 mm from the bottom surface110xand the opening portion121xis at a position with height of 1 mm from the bottom surface110x, it is preferable that the position of the height position of the liquid level LS is not equal to or lower than 1 mm from the bottom surface110x.

The control unit50calculates a suction amount that satisfies the position of the liquid level LS, based on a liquid feeding amount per unit time by the liquid feeding portion122and the amount of the liquid L stored in the liquid chamber110A. Alternatively, the control unit50stores the calculated suction amount described above. The control unit50can cause the stirrer120to perform a suction operation in which these suction amounts are satisfied.

Next, the stirrer120discharges the sucked liquid L into the liquid chamber110A based on the control signal supplied from the control unit50. As illustrated inFIG.4, the liquid L discharged from the nozzle121forms a flow F of the liquid L and winds up the particles P accumulated on the bottom surface110xfacing the opening portion121x. As a result, the liquid L in the liquid chamber110A is stirred.

At this time, in a case where a set value of the liquid feeding amount at the time of discharge by the liquid feeding portion122exceeds a set value of the liquid feeding amount at the time of suction by the liquid feeding portion122, air bubbles are discharged into the liquid L at the time of discharge. Therefore, it is preferable that the control unit50performs control such that the set value of the liquid feeding amount at the time of discharge does not exceed the set value of the liquid feeding amount at the time of suction.

Next, as illustrated inFIG.5, the moving unit130moves the stirrer120based on the control signal supplied from the control unit50and moves the position of the nozzle121in the liquid chamber110A. The position of the nozzle121after the movement can be the same as the description inFIG.4.

Next, the stirrer120sucks and discharges the liquid L in the liquid chamber110A from the nozzle121based on the control signal supplied from the control unit50. The operation of suction and discharge of the liquid L can be the same as described inFIG.4. Accordingly, the liquid L discharged from the nozzle121winds up the particles P accumulated on the bottom surface110x, and the liquid L in the liquid chamber110A is stirred. The operation of suction and discharge of the liquid L by the stirrer120is performed before the dispersed particles P inFIG.4are accumulated on the bottom surface110xagain.

When the suction and discharge of the liquid L are repeated by the stirrer120, it is preferable to make the discharging amount smaller than the suction amount in the first suction and discharge operation and to hold the liquid L in the stirrer120. In a case where the suction amount and the discharging amount of the liquid L are controlled to be the same amount in the second and subsequent suction and discharge operations in a state in which the stirrer120holds the liquid L, there is no concern about discharging air bubbles into the liquid L at the time of discharge of the liquid L, and the operation is stable.

The control unit50causes the stirrer120to suck and discharge the liquid L at a plurality of places in the liquid chamber110A. For example, the control unit50preferably stirs the liquid L in the entire liquid chamber110A by sucking and discharging the liquid L at the center of the bottom surface110x, which has a circular shape in plan view, and at the plurality of places (for example, 4 places every 900 in the circumferential direction) equally spaced around the center of the bottom surface110x.

When the suction and discharge of the liquid L is performed at the plurality of places in the liquid chamber110A, the order in which the suction and discharge of the liquid L is performed can be appropriately set.

The position where the liquid L is sucked and discharged by the stirrer120is not limited to the position described above and can be appropriately changed according to the shape or size of the liquid chamber110A.

By repeating these operations, the stirrer120can eliminate the accumulation of the particles P on the bottom surface110x, disperse the particles P, and stir the liquid L.

In a case where the stirring of the liquid L by the stirrer120is completed, the control unit50supplies the control signal to the moving unit130and extracts the nozzle121from the liquid chamber110A before the ejection head110ejects the liquid L. Thereafter, the ejection head110ejects the liquid L.

When the liquid L is ejected from the ejection head110, the nozzle plate112vibrates in the ejection head110, and, together, the liquid L in the liquid holding portion111or the liquid chamber110A vibrates. At this time, when the nozzle121is inserted into the liquid chamber110A, the nozzle121also vibrates, and there is a concern that the vibration characteristics of the nozzle121may affect the formation of the liquid droplets. In the liquid droplet forming apparatus1, as described above, by extracting the nozzle121from the liquid chamber110A before the ejection of the liquid droplets, the formation of liquid droplets can be easily stabilized.

Due to these operations, the liquid L held in the liquid chamber110A is stirred and the particles P are suitably dispersed. Therefore, according to the liquid droplet forming apparatus1configured as described above, it is possible to stably eject the dispersion liquid, as liquid droplets, containing the settling particles having constant concentration.

Second Embodiment

FIGS.6to8are explanatory views of a liquid droplet forming apparatus2according to a second embodiment of the present invention. In the present embodiment, the same reference symbols are given to the same component elements as in the first embodiment, and detailed description thereof will be omitted.

FIG.6is a schematic view of a configuration of a part of the ejecting portion20included in the liquid droplet forming apparatus2of the present embodiment and is a view corresponding toFIG.2.

The ejecting portion20includes an ejection head110, stirrer220, and moving unit230. In addition, the ejecting portion20may further have the same configuration as the moving unit130of the first embodiment.

The stirrer220includes a nozzle (tube-like member)221and a liquid feeding portion122and stirs the liquid L held in the liquid chamber110A. The nozzle221is inserted into the liquid chamber110A. The liquid feeding portion122sucks or discharges the liquid L stored in the liquid chamber110A via the nozzle121.

The nozzle221is a tube-shaped member forming a flow path of the liquid L in the liquid chamber110A, and the tip221ais formed as a surface obliquely intersecting a central axis of the nozzle221. Accordingly, the opening portion221xof the nozzle221is open in a direction intersecting the central axis of the nozzle221.

Moving Unit

The moving unit230rotates the stirrer220around the central axis of the nozzle221. As a result, the moving unit230changes an orientation of the opening portion221xin the liquid chamber110A in the circumferential direction of the central axis of the nozzle221.

The moving unit230may rotate the entire stirrer220or may rotate only the nozzle221.

FIGS.7and8are explanatory views illustrating an operation of the liquid droplet forming apparatus2.

First, as illustrated inFIG.7, the moving unit130(seeFIG.1), which is posture controller, inserts the nozzle221of the stirrer220into the liquid chamber110A based on the control signal supplied from the control unit50. For example, the moving unit130positions the tip of the nozzle221at the center of the bottom surface110xin plan view.

The opening portion221xof the nozzle221is open in a direction intersecting the central axis of the nozzle221. Therefore, in the nozzle221positioned at the center of the bottom surface110x, the opening portion221xis open toward the corner of the bottom surface110xinstead of the center of the bottom surface110x.

Next, the stirrer220sucks and discharges the liquid L in the liquid chamber110A from the nozzle221based on the control signal supplied from the control unit50. The liquid L discharged from the nozzle221forms a flow F of the liquid L and winds up the particles P accumulated on the bottom surface110xfacing the opening portion221x. As a result, the liquid L in the liquid chamber110A is stirred.

Next, as illustrated inFIG.8, the moving unit230, which is the posture controller, rotates the stirrer220based on the control signal supplied from the control unit50and changes the opening direction of the nozzle221in the liquid chamber110A. As a result, the moving unit230controls a direction in which the stirrer220sucks or discharges the liquid L in the liquid chamber110A, specifically, an opening direction of the opening portion221xof the nozzle221in the liquid chamber110A.

Next, the stirrer220sucks and discharges the liquid L in the liquid chamber110A from the nozzle221based on the control signal supplied from the control unit50. The operation of suction and discharge of the liquid L can be the same as described inFIG.4. Accordingly, the liquid L discharged from the nozzle221winds up the particles P accumulated on the bottom surface110x, and the liquid L in the liquid chamber110A is stirred.

The control unit50causes the stirrer220to suck and discharge the liquid L in a plurality of directions in the liquid chamber110A. For example, the control unit50preferably stirs the liquid L in the entire liquid chamber110A by sucking and discharging the liquid L in the plurality of directions (for example, 4 directions every 900 in the circumferential direction) equally spaced around the center of the bottom surface110x.

When the suction and discharge of the liquid L is performed at the plurality of directions in the liquid chamber110A, the order in which the suction and discharge of the liquid L is performed can be appropriately set.

The direction in which the liquid L is sucked and discharged by the stirrer220can be appropriately changed according to the shape or size of the liquid chamber110A.

By repeating these operations, the stirrer220can eliminate the accumulation of the particles P on the bottom surface110x, disperse the particles P, and stir the liquid L.

In a case where the stirring of the liquid L by the stirrer220is completed, the control unit50supplies the control signal to the moving unit130and extracts the nozzle221from the liquid chamber110A before the ejection head110ejects the liquid L. Thereafter, the ejection head110ejects the liquid L.

Due to these operations, the liquid L held in the liquid chamber110A is stirred and the particles P are suitably dispersed. Therefore, according to the liquid droplet forming apparatus2configured as described above, it is possible to stably eject the dispersion liquid, as liquid droplets, containing the settling particles having constant concentration.

In the above embodiment, although the posture controller controls any one of the position and the direction where the stirrer sucks and discharges the liquid L in the liquid chamber110A, the present embodiment is not limited to this. For example, in the liquid droplet forming apparatus2of the second embodiment, the tip position of the nozzle221may be changed in the liquid chamber110A using the moving unit130without fixing the tip position of the nozzle221to the center of the bottom surface110xin plan view.

Further, in the above embodiment, although the stirrer discharges the liquid L in the same posture (nozzle position and nozzle opening direction) as when the liquid L is sucked, the present embodiment is not limited to this. For example, after the liquid L is sucked by the stirrer, the posture of the stirrer may be changed by the posture controller, and then the stirrer may discharge the liquid L. Further, in the second embodiment, the orientation of the opening portion221xof the nozzle221may be changed by the moving unit230while the stirrer sucks and discharges the liquid L. Even in a case where the liquid droplet forming apparatus performs such an operation, the effect of the present invention can be exhibited.

As described above, although the preferred examples of the embodiments according to the present invention have been described with reference to the accompanying drawings, the present invention is not limited to such examples. The variety of shapes, combinations, and the like of the individual constituent members described in the above-described examples are examples, and a variety of modifications are permitted based on design requirements and the like without departing from the gist of the present invention.

The present invention includes the following aspects.[1] A liquid droplet forming apparatus includes: an ejection head that has a liquid chamber storing liquid containing settling particles and that ejects a liquid droplet of the liquid; stirrer for stirring the liquid held in the liquid chamber; posture controller for controlling a posture of the stirrer; and a control unit that controls operations of the ejection head, the stirrer, and the posture controller, in which the stirrer includes a tube-like member inserted into the liquid chamber, and a liquid feeding portion that sucks or discharges the liquid stored in the liquid chamber via the tube-like member, and the posture controller controls one or both of the position and the direction in which the stirrer sucks and discharges the liquid in the liquid chamber.[2] In the liquid droplet forming apparatus according to [1], the posture controller changes a position of the tube-like member in the liquid chamber.[3] In the liquid droplet forming apparatus according to [1] or [2], an opening portion of the tube-like member on a tip side is open in a direction intersecting a central axis of the tube-like member, and the posture controller changes an orientation of the opening portion in the liquid chamber in a circumferential direction of the central axis.[4] In the liquid droplet forming apparatus according to any one of [1] to [3], the control unit causes the posture controller to extract the tube-like member from the liquid chamber before the liquid is ejected from the ejection head.[5] In the liquid droplet forming apparatus according to any one of [1] to [4], the ejection head includes a liquid holding portion that holds the liquid, and a film-like member that includes an ejection outlet for ejecting the liquid droplet and that forms the liquid chamber together with the liquid holding portion, the liquid holding portion is a cylindrical-shaped member, and an outer diameter of the liquid holding portion is 6 mm or less.

EXPLANATION OF REFERENCES