JP2016010862A - Ink jet head and ink jet device equipped with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet head in which discharge stability owing to circulation of ink and reduction in ink material loss are compatible; and to provide an ink jet device equipped with the ink jet head.SOLUTION: An ink jet head includes: an ink supply flow passage 101 to which ink is supplied through an ink introducing port; an ink discharge flow passage 102 from which ink is discharged to an ink collecting port; ink chambers 110 through which the ink supply passage and the ink discharge flow passage are communicated with each other and which each have at least one nozzle to discharge ink; and actuators displacing oscillation plates 130 in the ink chambers to apply pressure on the ink in the ink chambers. The ink jet head is characterized in that a minimum opening length at the flow passage cross-section at the nozzle downstream side is smaller than the minimum opening length at the flow passage cross-section at the nozzle upstream side.

Description

  The present invention relates to an inkjet head and an inkjet apparatus including the inkjet head.

  An inkjet head is known as a head that can apply a necessary amount of ink toward an object at an arbitrary timing in accordance with an input signal. In particular, piezoelectric (piezo) ink jet heads are being actively developed because they can apply a wide variety of inks while controlling them with high precision.

 In general, a piezoelectric inkjet head includes an ink supply channel, a plurality of ink chambers having nozzles that communicate with the ink supply channel, and a piezoelectric element that applies pressure to the ink filled in the ink chamber. Is done. A drive voltage is applied to the piezoelectric element to cause mechanical distortion in the piezoelectric element, and ink is ejected from the nozzle by applying pressure to the ink in the ink chamber.

  For example, as a typical inkjet head configuration, a configuration in which the entire surface of an actuator (piezoelectric element) is installed on a resin film (wall surface of an ink chamber) is known, and the resin film is pressed by driving the piezoelectric element, There is a technique in which ink droplets are ejected from nozzles by pressurizing ink filled in an ink chamber (see Patent Document 1).

As an invention aiming at increasing the density of ink droplets, an ink jet recording head described in Patent Document 2 is known. The ink jet recording head is a technique for ejecting ink from ink nozzles by pressing a Si protrusion by a piezoelectric actuator and displacing the SiO ₂ film to change the volume of an ink pressurization chamber formed by a cavity plate. It is.
Japanese Patent Application Laid-Open No. 2004-228561 discloses a technique for providing an ink supply channel on the upstream side of an ink chamber having nozzles and an ink discharge channel on the downstream side of the ink chamber to circulate ink.

JP 2006-096042 A JP-A-3-015555 JP 2011-218784 A

  However, the conventional ink jet head has the following problems.

  First, Patent Documents 1 and 2 do not have an idea of circulating ink in an ink jet head, and disclose only a configuration in which ink is supplied from a supply channel to an nozzle through an ink chamber. In such a configuration, since the amount of ink discharged from the nozzle is replenished by capillary force, the ink solute component aggregates or settles, and the ink solvent component evaporates or hardens. The nozzles may be clogged, and the configuration is not sufficient for an inkjet head.

Furthermore, the technique described in Patent Document 3 is based on the premise that there is no special description regarding the minimum opening length in the cross section of the ink circulation flow path, and that the supply side and the discharge side are basically the same. In such a configuration, it is possible to uniformly eject ink in which particles are uniformly dispersed, but it is not possible to eject the ink volume necessary for filling the ink circulation flow path, and the material Loss occurs. If the particles dispersed in the ink are relatively expensive materials,
This is not a preferable mode because the material cost increases.

  SUMMARY An advantage of some aspects of the invention is that it provides an ink-jet head and an ink-jet apparatus including the ink-jet head, which are compatible with ejection stability due to ink circulation and ink material loss reduction.

  The ink jet head of the present invention and the ink jet apparatus including the ink jet head have the following characteristics.

  [1] An ink supply channel through which ink is supplied from an ink inlet, an ink discharge channel that discharges ink to an ink recovery port, the ink supply channel, and the ink discharge channel communicate with each other, and An ink chamber having a nozzle for discharging the ink, and an actuator for displacing a vibration plate of the ink chamber and applying pressure to the ink in the ink chamber, and having a minimum opening length in the cross section of the flow channel upstream of the nozzle In comparison, the ink jet head is characterized in that the minimum opening length in the cross section of the flow path on the downstream side of the nozzle is small.

  With this configuration, it is possible to realize an ink jet head that achieves both ejection stability by ink circulation and reduction of ink material loss.

  [2] In the above [1], if the minimum opening length in the cross section of the flow path on the downstream side of the nozzle is smaller than the minimum opening length of the nozzle, the ink chamber in the vicinity of the nozzle Since the concentration of the ink-containing particles can be increased to a certain level or more, it is preferable from the viewpoint of material loss without discarding the ink-containing particles.

[3] In the above [1] or [2], it is preferable that the nozzle position is arranged on the downstream side of the ink chamber.
[4] In the above [1] to [3], it is preferable that there are a plurality of the ink discharge holes.

  [5] In the above [1] to [4], it is preferable that the ink chamber includes a plurality of ink chambers, and the plurality of ink chambers are arranged in parallel to the ink supply channel and the ink discharge channel. is there.

    [6] In the above [1] to [5], it is preferable that the ink contains particles.

  [7] In the above [1] to [6], it is preferable that the minimum opening length of the ink discharge hole is not more than twice the diameter of the particle.

  [8] In the above [1] to [7], it is preferable that the minimum opening length of the cross section in the ink flow channel upstream of the nozzle is smaller than three times the minimum opening length of the nozzle. is there.

  [9] In the above [1] to [8], the minimum opening length of the cross section in the ink flow path on the downstream side of the nozzle is larger than one-tenth of the minimum opening length of the nozzle. A configuration smaller than the minimum opening length is preferred.

  [10] An inkjet apparatus including the inkjet head according to any one of [1] to [9] is preferable.

  In the present invention, the ink supply flow path is provided on the upstream side of the ink chamber having the nozzle, and the ink discharge flow path is provided on the downstream side of the ink chamber. Can do. Furthermore, since the minimum opening length in the channel cross section on the downstream side of the nozzle is smaller than the minimum opening length in the channel cross section on the upstream side of the nozzle, the concentration of the ink-containing particles is constant in the vicinity of the nozzle. Since it can be increased as described above, the material loss can be reduced without discarding the ink-containing particles.

1 is a perspective view of an inkjet head according to a first embodiment. Sectional drawing of the inkjet head of Embodiment 1 (A) Top view of the inkjet head of Embodiment 1, (b) to (c) Enlarged view of corner A of (a) (A)-(b) Sectional drawing of the inkjet head of Embodiment 2 and 3 (A)-(i) Sectional drawing of the ink discharge hole of Embodiment 1 Distribution diagram of ink-containing particles in cross section of inkjet head of Patent Document 3 Distribution diagram of ink-containing particles in the cross section of the ink jet head of Embodiment 1.

1. About the inkjet head of the present invention:
The inkjet head of the present invention is a drop-on-demand type piezoelectric inkjet head having a plurality of ink chambers. A drop-on-demand ink jet head is known as an ink jet head that can apply a necessary amount of ink toward an object at an arbitrary timing in accordance with an input signal. In particular, piezoelectric (piezo) drop-on-demand ink jet heads can apply a wide variety of inks while controlling them with high accuracy. The present invention also relates to an ink circulation type inkjet head in which ink flows in an ink chamber.

  The ink jet head of the present invention is configured to include an ink supply channel, an ink discharge channel, a plurality of ink chambers, and a plurality of laminated piezoelectric elements. The plurality of ink chambers are arranged in parallel, and a piezoelectric element is arranged via a vibration plate corresponding to each ink chamber. The material loss of the ink-containing particles can be reduced by devising the minimum opening length and nozzle arrangement position of the cross section of the ink circulation flow path.

<Basic configuration of inkjet head>
Hereinafter, components of the inkjet head will be described.

  The ink supply channel is a channel that has an ink introduction port through which ink is supplied from the outside and through which the ink supplied to the ink chamber flows. The ink supply amount supplied to the ink supply channel is not particularly limited, and may be several μl / min or more. The ink supplied to the ink supply channel through the ink inlet is distributed and provided to each of the plurality of ink chambers.

  The ink discharge channel is a channel that has an ink collection port for discharging ink to the outside, and flows the ink discharged from the plurality of ink chambers.

  The ink chamber is a space for storing ink ejected from the nozzles. The ink chamber communicates with the ink supply channel and the ink discharge channel. The maximum number of ink chambers communicating with one ink supply channel and ink discharge channel is usually 1024.

  The ink chamber and the ink supply channel are connected by an ink supply hole. The ink chamber and the ink discharge channel are connected by an ink discharge hole. Therefore, ink flows from the ink supply hole to the ink discharge hole in the ink chamber. As a result, new ink is always supplied into the ink chamber. In this way, by constantly supplying new ink into the ink chamber, it is possible to prevent stagnation and clogging of the ink in the ink chamber and the retention and mixing of bubbles. The ink flow rate in the ink chamber is preferably 0.1 to 20 μl / min. The direction in which the ink flows in the ink chamber may be the same as the direction in which ink is ejected from the nozzle (hereinafter simply referred to as “ejection direction”) (see FIG. 2), and is substantially perpendicular to the ink ejection direction. May be in any direction (see FIG. 4A).

  The ink chamber has a nozzle. The nozzle is a tube that communicates with the outside and has a discharge hole. One ink chamber may have one nozzle or two or more nozzles. The ink in the ink chamber passes through the inside of the nozzle and is discharged to the outside from the discharge hole. The diameter of the discharge hole is not particularly limited and is, for example, about 10 to 100 μm.

  The type of ink stored in the ink chamber is not particularly limited, and is appropriately selected depending on the type of product. For example, when the product is a biological structure, examples of the ink stored in the ink chamber include a particle dispersion containing cells, a bioabsorbable material, a cell adhesive protein, a culture solution, and the like. As described above, the ink jet head of the present invention can be applied without discarding the ink-containing particles by devising the minimum opening length and nozzle arrangement position in the cross section of the ink circulation flow path.

  The piezoelectric element is an operating device that converts an electric control signal including a driving voltage into a mechanical operation and displaces a wall surface (vibrating plate) of the ink chamber. By applying a voltage to the piezoelectric element, the height of the piezoelectric element increases, and pressure is applied to the ink in the ink chamber via the vibration plate. Thereby, ink can be discharged from the discharge hole of the nozzle.

  The piezoelectric element in the present invention may be a thin film piezoelectric element or a laminated piezoelectric element, but is preferably a laminated piezoelectric element. The thin film piezoelectric element has a fast output response to the input, but the output tends to be low. Therefore, the ratio of the loss of ejection force to the ink supply channel and the ink discharge channel tends to increase. Therefore, depending on the type of ink, proper ejection may not be possible. On the other hand, the laminated piezoelectric element has a slow output response to the input, but it is easy to increase the output. Therefore, the laminated piezoelectric element is hardly affected by the ink pressure in the ink chamber to be ejected, and stable ejection can be realized. The height (length in the stacking direction) of the multilayer piezoelectric element is not particularly limited, but is usually 100 to 1000 μm.

  The laminated piezoelectric element may be produced by laminating a plurality of sheets of lead zirconate titanate (PZT) and a conductive film on a piezoelectric plate to produce a driver, and then dividing the driver. In order to divide the drive body, a dicing apparatus incorporating a rotating blade may be used.

<Positions and shapes of main components>
Hereinafter, in the ink jet head of the present invention, the ink supply channel, the ink discharge channel, the ink chamber, the nozzle, the wall surface (vibration plate) of the ink chamber, and the arrangement position of the piezoelectric element will be described in detail.

  The ink circulation flow path is configured to communicate from the ink supply flow path to the ink chamber via the ink supply hole and further to the ink discharge flow path via the ink discharge hole. The ink chamber is provided with a nozzle communicating with the outside, and the piezoelectric element is provided on the wall surface (vibration plate) of the ink chamber. The piezoelectric element and the vibration element may be in contact with each other, or may be in contact with each other. In the inkjet head of the present invention, the minimum opening length of the flow path cross section in the ink discharge flow path including the ink discharge hole is smaller than the minimum opening length of the flow path cross section in the ink supply flow path including the ink supply hole. It is small.

With such a configuration, the ink supply flow path, the ink discharge flow path, the ink chamber, the nozzle, the wall surface (vibration plate) of the ink chamber, and the piezoelectric element are arranged, so that ejection stability due to ink circulation and ink material loss are reduced. It is possible to achieve both.
Here, the minimum opening length of the cross section of the flow path in the flow path means the narrowest interval (length) in the cross section of the opening of the flow path.

2. About the inkjet device of the present invention:
The ink jet apparatus of the present invention is characterized by including the above-described ink jet head, but otherwise has members of known ink jet apparatuses as appropriate. For example, it has a member for fixing the ink jet head, a moving stage for placing and moving an object to which ink is applied, and the like.

  The ink jet device includes an ink circulation device (not shown). The ink circulation device circulates ink by supplying a driving pressure to the ink. A pump may be used to supply the driving pressure to the ink, but it is preferable to use a regulator that supplies pressure using compressed air. The reason is that the use of a regulator makes the driving pressure constant and stabilizes the ink circulation flow rate. In the ink jet apparatus of the present invention, it is preferable that the ink of the ink jet head is continuously circulated during the operation of the apparatus.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to these embodiments.
(Embodiment 1)
FIG. 1 is a perspective view of an inkjet head 100 according to Embodiment 1 of the present invention. As shown in FIG. 1, the inkjet head 100 includes an ink supply channel 101, an ink discharge channel 102, and a plurality of ink chambers 110. The ink supply channel 101 has an ink inlet 103. The ink discharge channel 102 has an ink recovery port 104.

  2 is a cross-sectional view taken along line A of the inkjet head 100 shown in FIG. 3A is a cross-sectional view (top view) of the inkjet head 100 shown in FIG. 1 taken along line B. FIG.

  As shown in FIGS. 2 and 3A, the ink chamber 110 has a nozzle 111. The ink chamber 110 stores ink that is ejected from the ejection hole 112 of the nozzle 111. In addition, the ink chamber 110 communicates with the ink supply channel 101 via the ink supply hole 107 and communicates with the ink discharge channel 102 via the ink discharge hole 108.

  As shown in FIG. 2, the ink discharge hole 108 is disposed on the nozzle side with respect to the ink supply hole 107. Further, the ink discharge hole 108 is disposed on the nozzle side with respect to a laminated piezoelectric element 113 described later. By adopting such a configuration, the distance between the ink discharge hole 108 and the nozzle 111 can be designed to be short, and the ink flow in the vicinity of the nozzle 111 can be performed more smoothly. In particular, as shown in FIG. 2, it is preferable that the ink discharge hole 108 is on the same plane as the discharge hole 112.

Furthermore, the ink supply hole 107 and the ink discharge hole 108 are both provided on the wall surface of the ink chamber 110 along the ink ejection direction X. Further, since the ink supply hole 107 is disposed vertically upward and the ink discharge hole 108 is disposed vertically downward in the ink chamber 110, the ink flow in the ink chamber 110 is directed vertically downward. Therefore, the dispersed particle component in the ink can be supplied to the vicinity of the nozzle 111 without any stagnation.
<Minimum opening length of channel cross section in ink circulation channel>
Here, the minimum opening length of the flow path cross section in the ink discharge flow path 102 including the ink discharge holes 108 is smaller than the minimum opening length of the flow path cross section in the ink supply flow path 101 including the ink supply holes 107. It is small.

The minimum opening is usually the ink supply hole 107 and the ink discharge hole 108 in many cases.
Although not particularly limited, it is desirable that the minimum opening length of the channel cross section in the ink supply channel 101 including the ink supply hole 107 is larger than the diameter of the nozzle 111 in order to realize smooth ink circulation.

  When there are a plurality of nozzles 111, the diameter is the diameter when the total area of the nozzles is a circle. The same applies hereinafter.

  In view of the ink ejection force, the minimum opening length of the cross section of the ink supply flow path 101 including the ink supply hole 107 is preferably smaller than three times the diameter of the nozzle 111. This is because the ink pressure in the ink chamber due to the displacement of the laminated piezoelectric element can be efficiently converted into the ink ejection energy from the nozzle 111 without being lost by propagating to the ink supply channel 101 side.

  If it becomes three times or more, the force due to the displacement of the piezoelectric element is propagated from the nozzle to the ink supply channel 101 side.

  Further, the minimum opening length of the cross section of the ink discharge channel 102 including the ink discharge hole 108 is larger than one tenth of the diameter of the nozzle 111 from the viewpoint of smooth ink circulation, and the material of the ink-containing particles. From the viewpoint of loss, it is preferable that the diameter is smaller than the diameter of the nozzle 111.

  For example, when the diameter is equal to or less than one-tenth of the diameter of the nozzle 111, the pressure loss resistance greatly changes depending on the concentration of the ink-containing particles, and it becomes difficult to stably realize ink circulation.

  When the diameter is larger than the diameter of the nozzle 111, most of the ink-containing particles pass without staying on the upstream side of the ink discharge hole 108, and the concentration of the ink-containing particles in the vicinity of the nozzle 111 cannot be increased.

  Further, although not particularly limited, for example, the minimum opening length of the flow path cross section in the ink supply hole 107 is preferably at least twice the diameter of the ink-containing particles. This is because the ink containing particles are greatly affected by properties such as elastic modulus and pressure resistance, but mechanical damage to the ink containing particles becomes a problem.

  On the other hand, the minimum opening length of the cross section of the flow path in the ink discharge hole 108 is preferably not more than twice the diameter of the ink-containing particles. This is greatly influenced not only by the elastic modulus and pressure resistance characteristics of the ink-containing particles, but also by various properties such as ease of aggregation and adhesion to the channel wall surface. This is because rate reduction becomes a problem.

<Pressure loss resistance>
From the viewpoint of ink circulation stability, the ratio of the pressure loss resistance of the ink discharge flow path 102 including the ink discharge holes 108 to the pressure loss resistance of the ink supply flow path 101 including the ink supply holes 107 is 0.5˜. It is preferable to be configured within a range of about 1.5.

  In general, the pressure loss resistance of the flow path is often determined mainly by the opening area and length of the ink supply hole 107 and the ink discharge hole 108. However, if the ink circulation path including the ink chamber 110 from the ink introduction port 103 to the ink recovery port 104 is long, thin, and is bent in a complicated manner, it is also affected.

  For example, if the minimum opening length of the cross section of the ink discharge flow path 102 including the ink discharge holes 108 is relatively small, the minimum opening is long, and a bent flow path structure is used, This is because the ink flow is not smoothly performed and a stagnation portion is generated, and the risk that the dispersed particle component in the ink adheres, aggregates, or settles increases.

  In particular, in the case of a particle-containing ink that easily aggregates or settles and has a relatively unstable dispersion, the ink flow in the ink circulation channel needs to be performed more smoothly, and therefore the minimum ink supply hole 107 and ink discharge hole 108 and the like. The length of the opening in the ink flow direction is short, and it is preferable that the opening is not bent and the cross-sectional shape is small.

  As shown in FIGS. 2 and 3A, the inkjet head 100 displaces a wall surface 130 of the ink chamber 110 (hereinafter referred to as “vibrating plate 130”) along the ink ejection direction X. A laminated piezoelectric element (piezo element) 113 is included. The laminated piezoelectric element 113 is disposed outside the ink chamber 110 and is provided via an island portion 105 provided on the vibration plate 130. The island portion 105 is disposed so as to straddle the nozzle 111, and may be a separate member from the diaphragm 130 and the laminated piezoelectric element 113, or may be the same member.

<Operation>
Next, the operation of the inkjet head 100 according to the first embodiment will be described with reference to FIGS.

  First, ink is supplied from an ink tank (not shown) to the ink supply channel 101. The ink tank preferably has a pressure adjustment mechanism (not shown). Since the ink tank has a pressure adjustment mechanism, the ink in the ink tank is consumed and the ink is supplied from the ink tank to the ink supply channel 101 at a constant pressure even when the ink liquid level in the ink tank drops. Can do. The pressure adjusting mechanism may make the pressure of the supplied ink constant by adjusting the height of the ink tank and making the height of the ink liquid surface constant.

  The ink supplied to the ink supply channel 101 is supplied to the ink chamber 110 through the ink supply hole 107. The ink supplied to the ink chamber 110 is further discharged to the ink discharge channel 102 through the ink discharge hole 108. For this reason, ink flows in the ink chamber 110. As a result, new ink is always supplied into the ink chamber 110.

  In the ink supply channel 101 of the present embodiment, the most downstream portion (corner portion A in FIG. 3) of the ink supply channel 101 is tapered as shown in FIG. It is preferable that the shape is a curved surface as in c). The reason is that when ink flows from the ink supply channel 101 to the ink chamber 110, ink or bubbles may stay in the corner portion of the ink supply channel 101. Although not shown, based on the same idea, it is preferable from the viewpoint of ink flow that a taper shape or a curved surface shape is provided in the most upstream portion (corner portion B in FIG. 3) of the ink discharge channel 102.

  Further, as described above, the ink discharge hole 108 is provided on the nozzle side with respect to the ink supply hole 107. The direction in which ink flows in the ink chamber 110 is the same as the direction X in which ink is ejected from the nozzle 111 (ejection direction X). For this reason, a force in the same direction as the ejection direction X is applied to the ink in the ink chamber 110 in advance.

  Next, a driving voltage is applied to the laminated piezoelectric element 113. As a result, the height of the laminated piezoelectric element 113 increases, the capacity of the ink chamber 110 decreases, and pressure is applied to the ink in the ink chamber 110.

  In the present embodiment, the laminated piezoelectric element 113 is disposed outside the ink chamber 110 and deforms the diaphragm 130 via the island part 105. Thereby, the pressure of the ink chamber 110 is changed. By propagating this generated pressure along the flow path structure, a force in the same direction as the ink ejection direction X shown in FIG. 2 is generated. Further, as described above, a force in the same direction as the ejection direction X is applied to the ink in the ink chamber 110 in advance by flowing the ink. For this reason, the ink in the ink chamber 110 is ejected by a force that is a combination of a force in a direction acting in advance on the ink and a force generated by driving the laminated piezoelectric element 113.

  As described above, according to the present embodiment, in addition to the force generated by driving the multilayered piezoelectric element 113, the force acting on the ink in advance by the ink flowing in the ink chamber 110 is used as the ink ejection force. Therefore, the ink can be stably discharged while circulating the ink.

  In addition, as described above, the ink flow path in the present embodiment has a downstream side of the nozzle as compared with the minimum opening length in the cross section of the upstream side of the nozzle (the cross section of the ink circulation path upstream of the nozzle 111). The minimum opening length in the flow path cross section (the cross section of the ink circulation flow path on the downstream side of the nozzle 111) is set to be small.

  In this example, the ink discharge hole 108 has a small flow path cross section on the downstream side of the nozzle. The cross-sectional shape of the ink discharge hole 108 may be, for example, a quadrangle as shown in FIG. 5A or a circle as shown in FIG. It may be a triangle or a star as shown in (d). Furthermore, you may have a some opening as shown in FIG.5 (e)-FIG.5 (f). A mechanism that can reduce ink material loss by using such a configuration will be described below.

  FIG. 6 shows the distribution state of the ink-containing particles 140 in the ink circulation channel in the technique described in Patent Document 3. Since the minimum opening length in the nozzle cross section on the upstream side and downstream side of the nozzle is about the same, the uniformly dispersed ink flows in the entire ink circulation channel without any stagnation. It has become.

  In such a case, a large amount of ink and contained particles remain in the ink circulation channel even in a situation where the ink remaining in the ink tank runs out and ink cannot be ejected, and must be discarded. Therefore, in the ink jet head as in Patent Document 3, the ink material loss increases.

  On the other hand, FIG. 7 shows the distribution state of the ink-containing particles 140 in the ink circulation channel in the present embodiment. As described above, the ink flow path in the present embodiment is configured such that the minimum opening length in the flow path cross section on the downstream side of the nozzle is smaller than the minimum opening length in the flow path cross section on the upstream side of the nozzle. . Therefore, while the ink solvent component can pass through a portion where the flow passage cross section on the ink discharge side is small, the ink-containing particles 140 cannot pass through the portion where the flow passage cross section on the ink discharge side is small. It will remain near the nozzle 111 in the chamber 110.

  5 (e) to 5 (f) show a plurality of opening shapes of the same shape and size in the ink discharge hole 108, but have a configuration in which any one of the shape, size, and opening ratio is different. It does not matter. Although not particularly limited, for example, as shown in FIG. 5G, the upstream side and the downstream side of the ink flow in the ink chamber 110 may have different opening shapes. Further, as shown in FIG. 5H, the upstream opening length of the ink flow in the ink chamber 110 may be larger than the downstream opening length. Further, as shown in FIG. 5I, the upstream side opening ratio of the ink flow in the ink chamber 110 may be larger than the downstream side opening ratio.

  With the configuration as described above, a larger amount of ink is provided in the vicinity of the nozzle 111 arranged near the most downstream of the ink flow in the ink chamber 110 without hindering the flow of the solvent component having a smaller specific gravity than the ink-containing particles. It is preferable because ink-containing particles can be supplied, and it is possible to more efficiently realize both ejection stability by ink circulation and reduction of ink material loss.

  By continuing the ink circulation, the above phenomenon is repeated, and the particle concentration can be increased in the vicinity of the nozzle 111. In addition, since the ink-containing particles 140 are agitated by ink circulation and ejection operation, there is no fear of aggregation or sedimentation. Therefore, since it is possible to discharge with high-concentration ink until the ink-containing particles 140 disappear, it is possible to reduce the waste loss of the most expensive ink-containing particles 140 among the ink components.

  Note that the minimum opening length in the flow path cross section on the downstream side of the nozzle is smaller than the diameter of the nozzle 111. In particular, it is possible to more effectively achieve both the discharge stability by ink circulation and the reduction of ink material loss. Can be made. This idea is also effective for the embodiments described later.

(Embodiment 2)
As the second embodiment, there may be an inkjet head as shown in FIG. That is, the inkjet head 100 according to the first embodiment has a configuration in which the nozzle 111 is formed in the ink chamber 110 in the direction in which the ink flows. As the second embodiment, the nozzle 111 ejects ink from the ink supply hole 107. There may be a form in which the ink flowing toward the hole 108 and the nozzle plate 120 in a substantially vertical direction are formed.

  In the first embodiment, the laminated piezoelectric element 113 is driven to push the ink in the ink chamber 110 in the direction of the nozzle 111 (or the ejection hole 112), and from the ink supply hole 107 to the ink discharge hole 108. The force that the ink flows in the direction overlaps, and the ink can be pushed out from the nozzle 111 with a strong ejection force. On the other hand, in the case of this embodiment, the ink in the ink chamber 110 flows with a force that pushes the ink in the ink chamber 110 in the direction of the nozzle 111 when the laminated piezoelectric element 113 is driven. is there.

  In the case of the inkjet head 100 of the present embodiment, unlike the above-described first embodiment, a structure that creates an ink flow in the direction of the nozzle 111 in the upstream portion of the ink chamber 110 (in FIG. 2, ink is supplied from the ink supply hole 107. When the ink is supplied to the chamber 110, a structure that changes the ink flow at a substantially right angle is unnecessary, and therefore the distance between the laminated piezoelectric element 113 and the nozzle 111 (or the discharge hole 112) can be designed to be short. it can. Therefore, in the case of this example, the force for pushing the ink in the ink chamber 110 from the nozzle 111 by driving the laminated piezoelectric element 113 is stronger than that in the first embodiment. As a result, the ink jet head 100 of the present example can realize an ink ejection force comparable to that of the first embodiment.

(Embodiment 3)
As the third embodiment, there may be an ink jet head 100 as shown in FIG. That is, like the inkjet head of the first embodiment, the nozzle 111 is formed in the ink chamber 110 in the direction in which the ink flows. Further, since the ink flow direction in the ink chamber is vertically downward, the ink-containing particles are less likely to stagnate and can be stably supplied from the vicinity of the nozzle 111.

  In the first embodiment, the laminated piezoelectric element 113 is driven to push the ink in the ink chamber 110 in the direction of the nozzle 111 (or the ejection hole 112), and from the ink supply hole 107 to the ink discharge hole 108. The force that the ink flows in the direction overlaps, and the ink can be pushed out from the nozzle 111 with a strong ejection force. On the other hand, in the case of this embodiment, the ink in the ink chamber 110 flows with a force that pushes the ink in the ink chamber 110 in the direction of the nozzle 111 when the laminated piezoelectric element 113 is driven. is there.

  In the case of the inkjet head 100 of this example, unlike the above-described first embodiment, the distance between the laminated piezoelectric element 113 and the nozzle 111 (or the discharge hole 112) can be designed to be short. Therefore, in the case of this example, the force for pushing the ink in the ink chamber 110 from the nozzle 111 by driving the laminated piezoelectric element 113 is stronger than that in the first embodiment. As a result, the ink jet head 100 of the present example can realize an ink ejection force comparable to that of the first embodiment.

  In the ink jet head and the ink jet apparatus of the present invention, it is possible to realize both the ejection stability by ink circulation and the reduction of ink material loss. Therefore, for example, in the production of biological structures, it is preferably used as an inkjet head and an inkjet apparatus for coating and forming a particle-dispersed ink material containing cells, a bioabsorbable material, a cell adhesive protein, a culture solution and the like.

DESCRIPTION OF SYMBOLS 100 Inkjet head 101 Ink supply flow path 102 Ink discharge flow path 103 Ink introduction port 104 Ink collection port 105 Island part 107 Ink supply hole 108 Ink discharge hole 110 Ink chamber 111 Nozzle 112 Ejection hole 113 Stacked piezoelectric element 120 Nozzle plate 130 Vibration plate 140 Ink-containing particles

Claims (10)

An ink supply channel from the ink inlet to the ink supply hole;
An ink discharge channel from the ink discharge hole to the ink recovery port;
An ink chamber communicating with the ink supply hole and the ink discharge hole and having a discharge hole for discharging ink;
A piezoelectric element that applies pressure to the ink in the ink chamber,
An inkjet head characterized in that a minimum opening length in an ink flow path downstream of the discharge holes is smaller than a minimum opening length in an ink flow path upstream of the discharge holes. The minimum opening length in the ink discharge flow path is smaller than the minimum opening length of the ejection holes,
The inkjet head according to claim 1. The ejection hole is disposed closer to the ink discharge hole than the ink supply hole.
The inkjet head according to claim 1 or 2. The inkjet head according to claim 1, wherein there are a plurality of the ink discharge holes. The ink chamber includes a plurality of ink chambers, and the plurality of ink chambers are arranged in parallel to the ink supply channel and the ink discharge channel.
The inkjet head according to any one of claims 1 to 4. The inkjet head according to claim 1, wherein the ink includes particles. The inkjet head according to claim 6, wherein a minimum opening length of the ink discharge hole is not more than twice a diameter of the particle. The inkjet head according to any one of claims 1 to 7, wherein a minimum opening length of a cross section in the ink flow path upstream of the ejection holes is smaller than three times a minimum opening length of the ejection holes. The minimum opening length of the channel cross section in the ink channel on the downstream side of the ejection holes is larger than one tenth of the minimum opening length of the ejection holes and smaller than the minimum opening length of the ejection holes. The inkjet head of any one of 1-8. An ink jet apparatus comprising the ink jet head according to claim 1.

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