JP2020151939A - Droplet discharge device - Google Patents

Abstract

To stably and reliably detect droplets from plural discharge ports by one light receiving element.SOLUTION: A droplet discharge device has: droplet discharge means in which plural discharge ports are arranged along an arrangement line; control means which controls discharge timing of droplets discharged from each discharge port; one light ray irradiation means which keeps a prescribed interval with respect to the arrangement line, and radiates droplet detection light ray in parallel to the arrangement line; and one light receiving means which receives the droplet detection light ray. The control means keeps a prescribed deviation time between adjacent discharge ports, and repeats plural times an operation for discharging the droplets from a discharge port on one end side on the arrangement line toward a discharge port on the other end side in order, and controls so that a discharge interval time of the droplets discharged from any discharge port becomes longer than a total time of the deviation time for one cycle.SELECTED DRAWING: Figure 3

Description

The present invention relates to a liquid drop ejection device.

In an inkjet type droplet ejection device, as a method of simultaneously detecting a plurality of ejected droplets, for example, a method of irradiating a droplet with a laser beam and detecting the generated scattered light with a light receiving means is known (for example). , Patent Document 1).

However, in the method of detecting droplets by scattered light, in order to detect a plurality of droplets ejected at the same timing, they are simultaneously ejected at a position deviating from the optical path of the laser beam, that is, in the direction in which the scattered light is directed. It is necessary to provide more light receiving elements than the number of droplets, which is costly and there is a concern that the device will become large.

On the other hand, a method is also known in which one light receiving element is provided on the optical path of the laser beam and the droplet is detected by detecting a temporary input blockage of the laser beam due to the droplet passing on the optical path. Since the droplet is detected by one light receiving element, it is possible to obtain a droplet ejection device that can be miniaturized at low cost.

As described above, in the method of detecting the droplets with one light receiving element, it is necessary to sequentially eject the plurality of droplets with a predetermined time difference (deviation time) from each other. However, since the meniscus on the liquid surface at the discharge port vibrates up and down for a certain period of time immediately after the droplets are ejected, the ejection timing tends to shift if the droplet ejection interval is short, and one light receiving element. There is a problem that it is difficult to stably detect droplets ejected from a plurality of ejection ports.

An object of the present invention is to provide a liquid drop ejection device capable of stably and surely detecting a plurality of droplets ejected from a plurality of ejection ports with one light receiving unit.

The droplet ejection device of the present invention as a means for solving the above problems includes a droplet ejection means in which a plurality of ejection ports are arranged along an array line and ejection of droplets ejected from the respective ejection ports. A control means for controlling the timing, one light beam irradiating means for irradiating the droplet detection ray in parallel with the array line at a predetermined interval with respect to the array line, and one light receiving the droplet detection ray. The control means has a light receiving means, and the control means keeps a predetermined deviation time between adjacent discharge ports, and sequentially describes the discharge port from one end side to the other end side discharge port on the array line. The operation of ejecting the droplets is repeated for a plurality of cycles, and the ejection interval time of the droplets ejected from an arbitrary ejection port is controlled to be longer than the total time of the deviation time for one cycle.

The present invention makes it possible to stably and reliably detect droplets ejected from a plurality of ejection ports with one light receiving element.

FIG. 1 is a schematic view showing an example of the liquid drop model of the present invention. FIG. 2 is a plan view of the liquid drop ejection means of FIG. 1 when viewed from below. FIG. 3 is a schematic view showing a droplet detection operation in the droplet ejection device of the present invention. FIG. 4 is an explanatory diagram showing the time transition of the vibration amplitude of the meniscus of the solution at the discharge port. FIG. 5 is a flowchart showing a flow in which the control means controls the drive unit.

Hereinafter, the liquid drop ejection device according to the embodiment of the present invention will be described with reference to the drawings. It should be noted that each of the embodiments shown below is specifically described in order to better understand the gist of the invention, and is not limited to the present invention unless otherwise specified. Further, in the drawings used in the following description, in order to make the features of the present invention easy to understand, the main parts may be enlarged and shown, and the dimensional ratios of the respective components are the same as the actual ones. Is not always the case.

FIG. 1 is a schematic view showing an example of a liquid drop model of the embodiment of the present invention.
FIG. 2 is a plan view of the liquid drop ejection means of FIG. 1 when viewed from below.
The droplet ejection device 1 of the present embodiment includes a droplet ejection means 10, a droplet detecting means 20, and a controlling means 30.

The droplet ejection means 10 includes a substantially cubic liquid holding portion 11 in which the liquid R forming the droplet D is stored, and a plurality of ejection ports (nozzles) 12 formed on the bottom surface 11a of the liquid holding portion 11. The upper part of the liquid holding portion 11 includes a plurality of driving portions 13 formed at positions corresponding to the respective discharge ports, and a film-like member 14 formed so as to be in contact with the driving portions 13.

The discharge port 12 is formed of, for example, a circular through-hole, and the opening diameter thereof is such that the liquid R does not flow out from the discharge port 12 due to surface tension. In the present embodiment, three discharge ports 12a, 12b, and 12c are formed at equal intervals with each other along the array line L1 which is a virtual line set along the longitudinal direction of the bottom surface 11a of the liquid holding portion 11. ..
The number of discharge ports 12 formed is not limited to three, and any number of discharge ports 12 may be formed in any number of two or more.

The drive unit 13 is composed of, for example, a piezo element, and a film-like member 14 formed adjacent to the drive unit 13 is locally vibrated to apply pressure to the liquid R stored in the liquid holding unit 11, thereby causing the liquid R to be applied. Is discharged as a droplet D from the discharge port 12. In the present embodiment, the drive unit 13 includes three drive units 13a, 13b, and 13c, and discharges the liquid drop D corresponding to each of the discharge ports 12a, 12b, and 12c. The drive units 13a, 13b, and 13c are independently ejected by the ejection command signal output from the control means 30.

The shape of the drive unit 13 is not particularly limited, and can be appropriately designed according to the shape of the film-like member. As the drive unit 13, for example, a piezoelectric element can be applied. The piezoelectric element may have, for example, a structure in which electrodes for applying a voltage are provided on the upper surface and the lower surface of the piezoelectric material. In this case, by applying a voltage between the drive unit 13 and the upper and lower electrodes of the piezoelectric element, compressive stress is applied in the lateral direction of the film surface, and the film-like member 14 can be vibrated in the vertical direction.

The piezoelectric material when the drive unit 13 is a piezoelectric element is not particularly limited and may be appropriately selected depending on the intended purpose. For example, lead zirconate titanate (PZT), bismuth iron oxide, and metal niobate. Examples include materials, barium titanate, or these materials with metals or different oxides added. Among these, lead zirconate titanate (PZT) is preferable.

The film-like member 14 is a member that discharges the liquid R held by the liquid holding portion 11 as droplets D from the discharge port 12 by vibration due to amplitude movement. When the droplet ejection means 10 is a closed head as in the present embodiment, the film-like member 14 is fixed to the upper end portion of the liquid holding portion 11. When the droplet ejection means 10 has an open head, the film-like member 14 may be fixed to the lower end of the liquid holding portion 11. The liquid R held in the liquid holding portion 11 is discharged as droplets D from the discharge port 12 by the vibration of the film-like member 14.

The planar shape, size, material, and structure of the film-like member 14 are not particularly limited and may be appropriately selected depending on the intended purpose. The planar shape of the film-like member 14 may match the shape of the liquid holding portion 11, and examples thereof include a circle, an ellipse, a rectangle, a square, and a rhombus.

As the material of the film-like member 14, if it is too soft, the film-like member easily vibrates, and it is difficult to immediately suppress the vibration when it is not discharged. Therefore, it is preferable to use a material having a certain degree of hardness. Examples of the material of the film-like member 14 include metals, ceramics, and polymer materials, and specific examples thereof include stainless steel, nickel, aluminum, silicon dioxide, alumina, and zirconia.

The liquid holding portion 11 is a member that stores (holds) the liquid R for forming the droplet D, and when the droplet discharging means 10 is set to an open head, the liquid holding portion 11 is open to the atmosphere on the upper side of the liquid holding portion 11. A part may be formed.

The shape, size, material, and structure of the liquid holding portion 11 are not particularly limited and may be appropriately selected depending on the intended purpose. As the material of the liquid holding portion 11, it is preferable to use a material having low adhesion to the liquid R stored in the liquid holding portion 11.

Specific examples of the material of the liquid holding portion 11 include stainless steel, nickel, aluminum and the like, silicon dioxide, alumina, zirconia and the like. In addition to these, it is also conceivable to reduce the adhesiveness to the liquid R by coating the surface of the material. For example, the surface of the material can be coated with the aforementioned metal or metal oxide material.

In the present embodiment, the liquid holding portion 11 is composed of one liquid tank common to the plurality of discharge ports 12, but in addition to this, three liquid chambers for each discharge port 12 are provided by a partition wall. It can also be configured separately. In such a configuration, liquid drops having different components can be discharged for each discharge port 12.

The liquid R stored in the liquid holding unit 11 may be any liquid as long as it does not transmit the laser beam described later. For example, ion-exchanged water in which particles such as cells are dispersed, distilled water, pure water, physiological saline and the like can be mentioned.

The operation method of the droplet ejection means 10 is not limited to the above-described configuration, and can be appropriately selected depending on the intended purpose. For example, a piezoelectric pressurization method using a piezoelectric element or a thermal method using a heater. Examples thereof include an inkjet head using a method, an electrostatic method that pulls a liquid by electrostatic attraction, and the like. Among these, the piezoelectric pressurization method is preferable because the heat and electric field damage to the particles are relatively small.

The droplet detecting means 20 detects the flying droplet D ejected from the arbitrary ejection ports 12a, 12b, 12c. The term “flying” as used herein refers to a state between the time when the liquid drop model D is discharged from the discharge port 12 and the time when the liquid drop model D is deposited on the object to be adhered.
The droplet detecting means 20 has one light emitting means 21 and one light receiving means 22.

The light beam irradiating means 21 irradiates the droplet detection ray Ls so as to be parallel to the array line L1 while maintaining a predetermined distance W1 with respect to the array line L1 in which the plurality of discharge ports 12 are arranged. The droplet detection ray Ls may be a laser beam, and the light beam irradiating means 21 uses a laser light source capable of irradiating the laser beam.

The light beam irradiating means 21 is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include a solid-state laser device, a semiconductor laser device, and a dye laser device. Examples of the solid-state laser device include a YAG laser device, a ruby laser device, a glass laser device, and the like.

The spot diameter of the laser beam, which is the droplet detection ray Ls, is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 100 μm or more and 2000 μm or less. When the spot diameter is 100 μm or more and 2000 μm or less, the probability that the laser beam is irradiated to the liquid drop D is high even when the ejection variation of the liquid drop D occurs, so that the liquid drop D can be detected with high accuracy. There are advantages.

The droplet detection ray Ls may be a continuous ray or a pulsed ray. When a pulsed ray is used as the droplet detection ray Ls, the pulse width is not limited and can be appropriately selected depending on the intended purpose. For example, 10 μs or less is preferable, and 1 μs or less is more preferable.

The wavelength range of the droplet detection light Ls preferably does not include an optical component having a wavelength that destroys (decomposes) the constituents of the droplet D to be detected. Therefore, the droplet detection ray Ls is preferably selected according to the properties of the droplet D to be detected.

Further, in the present embodiment, the light filter 23 is provided on the emission side of the light irradiation means 21. Such an optical filter 23 removes, for example, an optical component having a wavelength that destroys the constituents of the liquid drop model D. As a result, even if the droplet detection light Ls emitted from the light irradiation means 21 contains a light component having a wavelength that destroys the constituents of the droplet D, the light component is removed by the optical filter 23 and the liquid is removed. It is possible to prevent the constituents of the droplet D from being destroyed by the droplet detection light Ls.

The light receiving means 22 is arranged on the optical path of the liquid drop detection light Ls emitted from the light irradiation means 21 and receives the liquid drop detection light Ls. The light receiving means 22 is not particularly limited and may be appropriately selected depending on the intended purpose. Specific examples of the light receiving means 22 include a photodiode, a photo sensor, and the like. Among these, photomultiplier tubes and avalanche photodiodes are preferable. Further, as the light receiving means 22, an image pickup device such as a CCD (Charge Coupled Device), a CMOS (Complementary Metal Oxide Semiconductor) image pickup device, or a gate CCD can be used.

The droplet detection means 20 of the present embodiment continuously irradiates the droplet detection light Ls from the light irradiation means 21 during the discharge of the droplet D. Then, when the incident of the droplet detection ray Ls is interrupted by the light receiving means 22, the droplet D is detected. That is, when a flying droplet passes through the optical path of the droplet detection ray Ls, the droplet detection ray Ls is absorbed by the droplet D or the droplet detection ray Ls is reflected in a direction other than the light receiving means 22. At the timing when the incident of the liquid drop detection ray Ls is momentarily blocked, the light receiving means 22 outputs the liquid drop detection signal to the control means 30.

The control means 30 includes a CPU, a storage memory, a driver circuit, and the like. The control means 30 operates the plurality of drive units 13 at arbitrary timings, controls the light irradiation means 21, and inputs the droplet detection signal output from the light receiving means 22.

Hereinafter, the operation of the liquid drop ejection device of the present embodiment will be described with reference to FIGS. 1 to 3.
FIG. 3 is a schematic view showing a droplet detection operation in the droplet ejection device.
In the following description, among the plurality of discharge ports 12, the operation of sequentially discharging the liquid drops D from the discharge port 12a on the one end side toward the discharge port 12c on the other end side is set as one cycle, and such a cycle is repeated a plurality of times. Assuming operation.

First, the control means 30 outputs a discharge command signal to the drive unit 13a to discharge the liquid drop model Da1 from the discharge port 12a. Next, after the elapse of the preset deviation time dt1, the control means 30 outputs a discharge command signal to the drive unit 13b to discharge the liquid drop Db1 from the discharge port 12b. Further, after the elapse of the preset deviation time dt2, the control means 30 outputs a discharge command signal to the drive unit 13c to discharge the liquid drop Dc1 from the discharge port 12c. In this way, the liquid drop ejection operation of the first cycle is completed.

When the flying droplets Da1, Db1, and Dc1 reach the optical path of the droplet detection ray Ls irradiated from the light ray irradiating means 21, they block the droplet detection ray Ls and do not enter the light receiving means 22. To do. The light receiving means 22 detects the ejection of each droplet D by momentarily blocking the incident of the droplet detection ray Ls.

At this time, since the droplets Da1, Db1, and Dc1 are sequentially ejected with a deviation time dt from each other, the plurality of droplets D do not overlap on the optical path of the droplet detection ray Ls. Therefore, the droplet detecting means 20 including one light emitting means 21 and one light receiving means 22 can individually recognize and detect a plurality of droplets D ejected from the plurality of ejection ports 12.

Further, in the control means 30, each of the droplets D ejected is liquid from the preset ejection speed (flying speed) of the droplet D and the distance W1 between the ejection port 12 and the optical path of the droplet detection ray Ls. Even if the detection time elapses after the detection time for reaching the optical path of the droplet detection ray Ls is set and the ejection command signal for the droplet D is output to each ejection port 12, the light receiving means 22 detects the droplet. When the signal is not output, it is memorized that the non-ejection that the droplet is not ejected from the corresponding ejection port 12 has occurred.

Next, the control means 30 operates the drive unit 13a to discharge the liquid drop model Da2 in the second cycle from the discharge port 12a. At this time, the control means 30 discharges the liquid drop model Da from the discharge port 12a (cycle), for example, from the discharge of the liquid drop model Da1 in the first cycle to the discharge of the liquid drop model Da2 in the second cycle. The discharge interval time T'1 of is controlled to be longer than the total time (dt1 + dt2) of the deviation time for one cycle (dt1 + dt2 <T'1).

Since the ejection speeds of all the liquid drops D are the same, by performing such control, when the first cycle droplet Dc1 ejected from the ejection port 12c reaches the liquid drop detection ray Ls, the ejection port The liquid drop model Da2 of the second cycle discharged from 12a flies with respect to the liquid drop model Dc1 at a sufficient interval along the discharge direction.

As a result, the droplet Dc1 and the droplet Da2 do not overlap on the optical path of the droplet detection ray Ls at the same time. Therefore, the light receiving means 22 reliably recognizes the first cycle liquid drop Dc1 discharged from the discharge port 12c and the second cycle liquid drop Da2 discharged from the discharge port 12a as separate droplets. It becomes possible to detect.

For the other discharge ports 12b and 12c, the discharge interval times T'2 and T'3 are controlled to be longer than the total time (dt1 + dt2) of the deviation time for one cycle, respectively (dt1 + dt2 <T'2, dt1 + dt2). <T'3). As a result, the second cycle droplets Db2 and Dc2 also pass on the optical path of the droplet detection ray Ls without overlapping with other droplets.

By performing such control by the control means 30, even if the ejection cycle is repeated at all the ejection ports 12, all the ejected droplets D may overlap each other on the optical path of the droplet detection ray Ls. However, all the ejected droplets D can be reliably detected individually by the light receiving means 22.

FIG. 4 is an explanatory diagram showing the time transition of the vibration amplitude of the meniscus of the solution at the discharge port.
As shown in FIG. 4, when the discharge interval time T1 of the discharge port 12a is short, the next droplet D is discharged before the vibration amplitude of the meniscus of the discharge port 12a due to the discharge of the droplet D is completely contained. Will be done. In such a state, the ejection is not stable, and when the ejection intervals T1, T2, and T3 deviate from each other, the droplet D is ejected at the respective ejection ports 12 with different vibration states of the meniscus. Therefore, a discharge port 12 in which the discharge is normal and a discharge port 12 in which the discharge is abnormal occur.

However, in the present embodiment, the discharge port 12 discharges the second cycle at the discharge interval times T'1, T'2, and T'3 where the discharge of the first cycle is completed and the vibration of the meniscus is contained. Therefore, even if the ejection is repeated for a plurality of cycles, the droplet D can be ejected stably.

Next, an example of a method of controlling the drive unit by the control means will be described.
FIG. 5 is a flowchart showing a flow in which the control means controls the drive unit.
The control means 30 first sets the target droplet velocity sp1 when ejecting the droplet D (S1). Next, the applied voltage v1 applied to the drive unit 13 is set (S2). Then, a discharge command signal is output to the drive unit 13 that discharges the droplet D (S3). At the same time, the time t1 at which the discharge command signal is output is recorded in the memory (S4).

The drive unit 13 to which the discharge command signal is input vibrates the liquid R at the set applied voltage v1. As a result, the liquid drop D is discharged from the corresponding discharge port 12 (S5). Next, the control means 30 irradiates the droplet detection light Ls from the light irradiation means 21 and hits the discharged droplet D (S6). Then, when the light receiving means 22 detects the droplet D, the light receiving means 22 outputs the droplet detection signal to the control means 30 (S7).

The control means 30 is based on the time t1 from which the ejection command signal is output to the time (detection time) t2 until the droplet detection signal is input and the distance W1 between the ejection port 12 and the optical path of the droplet detection ray Ls. The actual liquid drop ejection speed (flying speed) sp2 is calculated (S8). Then, when sp2 is equal to sp1, the initially set applied voltage v1 is applied to the drive unit 13 to eject the liquid droplet D (S9). On the other hand, when sp2 is different from sp1, the applied voltage v1 to be applied to the drive unit 13 is set again (S2).

As described above, the control means 30 is the actual liquid based on the detection time t2, which is the time difference between the discharge command signal of the droplet D for the arbitrary discharge port 12 and the droplet detection signal output from the light receiving means 22. The liquid drop discharge rate sp2 is calculated.

Then, the control means 30 corrects the applied voltage v1 applied to the drive unit 13 constituting the liquid drop ejection means 10 based on the droplet ejection speed sp2, and the control means 30 corrects the applied voltage v1 of the droplets D ejected from all the ejection ports 12. The liquid drop ejection speed sp2 is controlled to be uniform.

As a result, the ejection speed of the droplet D is stable, the droplet D can be detected stably and accurately by the droplet detecting means 20, and the droplet D can be detected even if a driving voltage is applied to the driving unit 13. It is possible to suppress the occurrence of non-discharge in which is not discharged.

Although one embodiment of the present invention has been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. Such an embodiment can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention as well as the invention described in the claims and the equivalent scope thereof.

The present invention includes the following aspects.
[1] A liquid drop ejection means in which a plurality of ejection ports are arranged along an array line, a control means for controlling the ejection timing of droplets ejected from the respective ejection ports, and predetermined arrangement lines. It has one light beam irradiating means for irradiating the droplet detection light beam in parallel with the array line at intervals, and one light receiving means for irradiating the liquid drop detection light beam.
The control means performs a plurality of operations of ejecting the droplets in order from the ejection port on one end side to the ejection port on the other end side on the array line while maintaining a predetermined deviation time between adjacent ejection ports. It is a liquid drop ejection device characterized in that the cycle is repeated and the ejection interval time of droplets ejected from an arbitrary ejection port is controlled to be longer than the total time of the deviation time for one cycle. ..
[2] The droplet ejection device according to the above [1], wherein the light beam irradiating means includes an optical filter for removing a light component having a wavelength that destroys the constituents of the droplet.
[3] The control means calculates the liquid drop ejection speed based on the detection time, which is the time difference between the droplet ejection command signal for an arbitrary ejection port and the droplet detection signal output from the light receiving means. The droplet ejection device according to the above [1] or [2].
[4] The control means corrects the drive voltage applied to the drive unit constituting the liquid drop ejection means based on the droplet ejection speed, and the ejection speed of the droplets ejected from all the ejection ports is adjusted. The droplet ejection device according to the above [3], which is controlled so as to be uniform.
[5] If the light receiving means does not detect a liquid drop model even after the detection time has elapsed after the control means has caused a discharge operation to an arbitrary discharge port, the liquid drop model is not discharged from the discharge port. The liquid drop ejection device according to the above [3] or [4], wherein the liquid drop model is recorded.

1 Droplet ejection device 10 Droplet ejection means 11 Liquid holding unit 12 Discharge port (nozzle)
13 Drive unit 14 Membrane-like member 20 Droplet detection means 21 Light irradiation means 22 Light receiving means 23 Optical filter 30 Control means D Droplet R Liquid

JP-A-2018-17700

Claims (5)

A liquid drop ejection means in which a plurality of ejection ports are arranged along the array line, a control means for controlling the ejection timing of the droplets ejected from the respective ejection ports, and a predetermined interval with respect to the array line are maintained. It has one light beam irradiating means for irradiating the droplet detection light beam in parallel with the array line, and one light receiving means for receiving the liquid drop detection light beam.
The control means performs a plurality of operations of ejecting the droplets in order from the ejection port on one end side to the ejection port on the other end side on the array line while maintaining a predetermined deviation time between adjacent ejection ports. A droplet ejection device characterized in that the cycle is repeated and the ejection interval time of droplets ejected from an arbitrary ejection port is controlled to be longer than the total time of the deviation times for one cycle. The droplet ejection device according to claim 1, wherein the light irradiation means includes an optical filter that removes an optical component having a wavelength that destroys the constituents of the droplet. The control means is characterized in that the droplet ejection speed is calculated based on the detection time, which is the time difference between the droplet ejection command signal for an arbitrary ejection port and the droplet detection signal output from the light receiving means. The droplet ejection device according to claim 1 or 2. The control means corrects the drive voltage applied to the drive unit constituting the liquid drop ejection means based on the droplet ejection speed, and the ejection speed of the droplets ejected from all the ejection ports becomes uniform. The liquid drop ejection device according to claim 3, wherein the liquid drop model is controlled in such a manner. When the light receiving means does not detect the liquid drop model even after the detection time elapses after the control means causes the discharge operation to the arbitrary discharge port, the liquid drop model is not discharged at the discharge port. The liquid drop ejection device according to claim 3 or 4, wherein the liquid drop model is recorded.

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