JP2007168352A - Droplet discharge head and droplet discharge apparatus - Google Patents

Abstract

A droplet discharge head and a droplet discharge device are provided that reduce the flow resistance in an ink flow path and prevent choking of the ink flow in the middle of the ink flow path.
SOLUTION: A cavity substrate 3 on which a bottom wall forms a vibration plate 8 and a pressure chamber 7 in which droplets are collected and discharged, and an individual electrode 17 that faces the vibration plate 8 and drives the vibration plate 8 are formed. The electrode substrate 4, the reservoir 10 for supplying droplets to the pressure chamber 7, the supply hole 9 for transferring droplets from the reservoir 10 to the pressure chamber 7, and the droplets from the pressure chamber 7 to the nozzle hole 5 are transferred. The reservoir substrate 2 having the nozzle communication hole 11 is laminated, and the area of the cross section of the pressure chamber 7 is S0, and the area of the cross section of the communication path leading from the supply hole 9 to the pressure chamber 7 is S1. The ink flow path was formed so that S2>S1> S0 or S2 <S1 <S0, where S2 is the area of the cross-section of the hole 7.
[Selection] Figure 3

Description

  The present invention relates to a droplet discharge head and a droplet discharge device, and more particularly to a droplet discharge head and a droplet discharge device with an improved ink supply port structure for supplying ink from a reservoir to a pressure chamber.

  In recent years, electrostatic drive type droplet discharge heads have been required to increase the density of nozzles and pressure chambers (also referred to as discharge chambers) for discharging droplets in order to pursue high printing performance. Along with this, the cross section of the ink flow path through which the ink flows becomes smaller. If the cross section of the ink flow path is reduced, it is difficult to simultaneously adjust the acoustic resistance and inertance. In addition, bubbles tend to stay in the ink flow path.

  In order to solve such a problem, for example, “a common ink chamber, an ink pressure chamber, an ink nozzle communicating with the ink pressure chamber, and ink is supplied from the common ink chamber to the ink pressure chamber. And an ink supply port for ejecting ink droplets from the ink nozzles due to a change in the volume of the ink pressure chamber. The ink supply unit includes at least a first ink supply port and a second ink. There has been proposed an “inkjet head” including a supply port, wherein the first ink supply port has a cross-sectional area larger than that of the second ink supply port (see, for example, Patent Document 1). .

JP 2002-301818 (page 5 and FIG. 2)

  In the ink jet head described in Patent Document 1, the acoustic resistance that is the ink flow path characteristic of the ink supply port can be adjusted by the second ink supply port, and the inertance can be adjusted by the first and second ink supply ports. It has become. Accordingly, the responsiveness and print quality of the ink jet head can be improved, and a rapid change in the cross-sectional area in the ink flow path can be prevented, so that the retention of bubbles can be suppressed, and the adverse effects caused by this can be avoided. .

  However, although the acoustic resistance and inertance can be adjusted, the flow path resistance generated in the ink flow path has not been considered. That is, a sudden change in the cross-sectional area in the ink flow path is prevented, but this alone cannot solve the problem of ink choking in the middle of the ink flow path. The choking of the ink flow means that a rapid flow velocity change point is generated in the ink flow.

  The present invention has been made in order to solve the above-described problem, and is a droplet in which the flow of ink in the ink flow path is reduced while the flow of ink is not choked in the middle of the ink flow path. An object of the present invention is to provide a discharge head and a droplet discharge device.

  The droplet discharge head according to the present invention includes a cavity substrate on which a bottom wall forms a vibration plate and a pressure chamber for collecting and discharging droplets, and an individual electrode that faces the vibration plate and drives the vibration plate. An electrode substrate, a reservoir for supplying droplets to the pressure chamber, a supply hole for transferring droplets from the reservoir to the pressure chamber, and a reservoir substrate having nozzle communication holes for transferring droplets from the pressure chamber to the nozzle holes; Is a droplet discharge head configured by stacking S0, the area of the cross section of the pressure chamber, S1, the area of the cross section of the communication path from the supply hole to the pressure chamber, S1, and the cross section of the supply hole The ink flow path is formed so that S2> S1> S0, where S2 is the area of the ink.

  Accordingly, since it is possible to reduce the flow path resistance of the ink flow path from the supply hole to the discharge chamber, it is possible to solve the shortage of ink supply even in a droplet discharge head driven at a high drive frequency. . In addition, since the ink flow path from the supply hole to the discharge chamber is gradually increased, it is possible to prevent the occurrence of choke at that portion. For this reason, while staying of a bubble can be suppressed, the harmful effect resulting from this can be avoided. That is, it is possible to provide a droplet discharge head that can discharge ink droplets uniformly and stably.

  The droplet discharge head according to the present invention includes a cavity substrate on which a bottom wall forms a vibration plate and a pressure chamber for collecting and discharging droplets, and an individual electrode that faces the vibration plate and drives the vibration plate. An electrode substrate, a reservoir for supplying droplets to the pressure chamber, a supply hole for transferring droplets from the reservoir to the pressure chamber, and a reservoir substrate having nozzle communication holes for transferring droplets from the pressure chamber to the nozzle holes; Is a droplet discharge head configured by stacking S0, the area of the cross section of the pressure chamber, S1, the area of the cross section of the communication path from the supply hole to the pressure chamber, S1, and the cross section of the supply hole The ink flow path is formed so that S2 <S1 <S0, where S2 is the area.

  Accordingly, since it is possible to reduce the flow path resistance of the ink flow path from the supply hole to the discharge chamber, it is possible to solve the shortage of ink supply even in a droplet discharge head driven at a high drive frequency. . In addition, since the ink flow path from the supply hole to the discharge chamber is gradually increased, it is possible to prevent the occurrence of choke at that portion. For this reason, while staying of a bubble can be suppressed, the harmful effect resulting from this can be avoided. That is, it is possible to provide a droplet discharge head that can discharge ink droplets uniformly and stably.

  The droplet discharge head according to the present invention is characterized in that the planar shape of the supply hole in the reservoir substrate is elongated in the long side direction of the pressure chamber to form a long hole shape. By so doing, the cross-sectional area can be increased compared to a circular shape having the same diameter as the length of the supply hole in the short side direction. Therefore, it is possible to reduce the flow path resistance in the supply hole. In addition, it is possible to deal with a cavity substrate having a predetermined area and a high density and a narrow width.

  The droplet discharge head according to the present invention is characterized in that one supply hole is provided for a pressure chamber for transferring a droplet from the supply hole. That is, a predetermined cross-sectional area is ensured by one supply hole. In this way, when a plurality of supply holes are formed to ensure a cross-sectional area, it is possible to prevent ink from flowing only into one of the supply holes and not being uniformly supplied to the pressure chamber. .

  In the droplet discharge head according to the present invention, the area S1 of the cross section of the flow path leading from the supply hole to the pressure chamber is smaller than 0.85 times the area S0 of the vertical cross section of the pressure chamber, and the long hole-shaped cross section of the supply hole It is characterized by being formed larger than 1.05 times the area S2. In this manner, the area S1 of the cross section of the flow path leading from the supply hole to the pressure chamber is determined, so that choke generation is prevented while reducing flow path resistance.

  A droplet discharge apparatus according to the present invention includes the above-described droplet discharge head. Therefore, it has all the effects of the above-described droplet discharge head.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an exploded perspective view showing a state in which a droplet discharge head 100 according to an embodiment of the present invention is disassembled. FIG. 2 is a longitudinal sectional view showing a cross section AA ′ in a state where the droplet discharge head 100 is assembled. The configuration and operation of the droplet discharge head 100 will be described with reference to FIGS. In addition, in the following drawings including FIG. 1, the relationship of the size of each component may be different from the actual one. Also, the upper side of the figure will be described as the upper side, and the lower side will be described as the lower side.

  The droplet discharge head 100 is a face that discharges droplets from nozzle holes provided on the surface side of a nozzle substrate as a representative of a device equipped with an electrostatic drive type electrostatic actuator driven by electrostatic force. An eject type droplet discharge head will be described as an example. In FIG. 1, a part of an FPC (Flexible Printed Circuit) for supplying drive power is shown. In addition, a driver IC 15 that supplies a drive signal to the individual electrode 17 is provided.

  As shown in FIG. 1, the droplet discharge head 100 is configured as a four-layer structure in which four substrates of an electrode substrate 4, a cavity substrate 3, a reservoir substrate 2 and a nozzle substrate 1 are joined in order. Yes. That is, the nozzle substrate 1 is bonded to one (upper) surface of the reservoir substrate 2, and the cavity substrate 3 is bonded to the other (lower) surface of the reservoir substrate 2. An electrode substrate 4 is bonded to the opposite surface of the surface where 2 is bonded. The electrode substrate 4 and the cavity substrate 3 are bonded by anodic bonding, and the cavity substrate 3 and the reservoir substrate 2 and the reservoir substrate 2 and the nozzle substrate 1 are bonded by using an adhesive such as an epoxy resin. To do.

[Electrode substrate 4]
For example, the electrode substrate 4 may be formed of glass such as borosilicate glass having a thickness of 1 mm as a main material. Here, a case where the electrode substrate 4 is formed of borosilicate glass is shown as an example, but the present invention is not limited to this. For example, the electrode substrate 4 may be formed of single crystal silicon. A plurality of recesses (grooves) 12 are formed in the electrode substrate 4 in accordance with a pressure chamber 7 of the cavity substrate 3 described later. The recess 12 may be formed with a depth of 0.3 μm, for example.

  In addition, inside the recess 12 (particularly at the bottom), the individual electrodes 17 serving as fixed electrodes are opposed to respective pressure chambers 7 (vibrating plates 8) of the cavity substrate 3 to be described later with a certain interval. Have been made. And the recessed part 12 is pattern-formed by the slightly large shape similar to these shapes so that the one part can mount | wear with the separate electrode 17. FIG. The individual electrode 17 may be manufactured by sputtering ITO (Indium Tin Oxide) with a thickness of 0.1 μm, for example.

  Further, the individual electrode 17 is produced by integrating the lead portion 17a and the terminal portion 17b. One end (terminal portion 17 b) of the individual electrode 17 is connected to the driver IC 15, and a drive signal is supplied from the driver IC 15 to the individual electrode 17. It should be noted that unless specifically distinguished, the lead portion 17a and the terminal portion 17b are combined to be described as the individual electrode 17.

  When the electrode substrate 4 and the cavity substrate 3 are bonded and laminated, a certain gap (gap) 13 that allows the vibration plate 8 to bend (displace) is formed between the vibration plate 8 and the individual electrode 17. It is formed by the recess 12 of the substrate 4. The gap 13 is preferably formed to have a depth of 0.2 μm, for example. The electrode substrate 4 is provided with ink supply holes 11 for taking in liquid supplied from an external ink tank (not shown).

  In the droplet discharge head 100, a plurality of individual electrodes 17 are formed in a rectangular shape having long sides and short sides, and the individual electrodes 17 are arranged so that their long sides are parallel to each other. FIG. 1 shows one electrode row extending in the short side direction of the individual electrode 17. In addition, when the short side of the individual electrode 17 is formed obliquely with respect to the long side and the individual electrode 17 has an elongated parallelogram shape, an electrode array extending in a direction perpendicular to the long side direction is formed. What should I do?

  In the droplet discharge head 100, the driver IC 15 is provided between the two electrode rows of the individual electrode 17, and is connected to both electrode rows. Therefore, it becomes possible to supply drive signals from the driver IC 15 to the two electrode rows, and it is easy to increase the number of electrode rows. Furthermore, since the number of driver ICs 15 can be reduced, the cost required for manufacturing can be reduced, and the droplet discharge head 100 can be downsized.

  On the electrode substrate 4, wiring (IC input mounting unit 20) for supplying an input signal for driving the driver IC 15 from the FPC 30 and the FPC mounting unit 21 are formed, and the FPC 30 and the driver IC 15 are connected. ing. In addition, after joining the electrode substrate 4 and the cavity substrate 3, the sealing member 14 for sealing the gap 13 is formed (refer FIG. 2). Further, the number of driver ICs 15 for supplying drive signals may be determined according to the number of individual electrodes 17.

[Cavity substrate 3]
The cavity substrate 3 is composed of, for example, a silicon single crystal substrate (hereinafter simply referred to as a silicon substrate) having a thickness of about 50 μm (micrometer) as a main material. The cavity substrate 3 is formed with a plurality of pressure chambers (or discharge chambers) 7 whose bottom wall is the diaphragm 8. The pressure chambers 7 are formed corresponding to the electrode rows of the individual electrodes 17. In addition, a first hole 22 is formed in the cavity substrate 3 so as to penetrate the cavity substrate 3 between the electrode arrays. The ink flow path in the pressure chamber 7 will be described in detail later (see FIG. 3).

  Further, a TEOS film (here, tetraethylsilane: tetraethoxysilane) for electrically insulating the diaphragm 8 and the individual electrodes 17 is formed on the lower surface of the cavity substrate 3 (the surface facing the electrode substrate 4). An insulating film (not shown), which is (referred to as a SiO2 film formed using ethyl silicate), is formed to a thickness of 0.1 μm by using a plasma CVD (also referred to as Chemical Vapor Deposition: TEOS-pCVD) method. This is for preventing dielectric breakdown and short-circuit when the diaphragm 8 is driven, and for preventing etching of the cavity substrate 3 by droplets of ink or the like.

Although the case where the insulating film is a TEOS film is shown here, the present invention is not limited to this, and any material that improves the insulating performance may be used. For example, Al ₂ O ₃ (aluminum oxide (alumina)) may be used. The cavity substrate 3 is also provided with an ink supply hole 11 (in communication with the ink supply hole 11 provided in the electrode substrate 4). Furthermore, a common electrode 16 is provided as a terminal for supplying charges having a polarity opposite to that of the individual electrode 17 from the external power supply means (not shown) to the diaphragm 8.

The diaphragm 8 may be formed of a high concentration boron doped layer. The etching rate in etching single crystal silicon with an alkaline solution such as an aqueous potassium hydroxide solution is very small in a high concentration region of about 5 × 10 19 atoms / cm ³ or more when the dopant is boron. For this reason, when the diaphragm 8 is made of a high-concentration boron-doped layer and the pressure chamber 7 is formed by anisotropic etching with an alkaline solution, the boron-doped layer is exposed and the etching rate becomes extremely small, so-called etching stop. By using the technique, the diaphragm 8 can be formed in a desired thickness.

[Reservoir substrate 2]
The reservoir substrate 2 is made of, for example, single crystal silicon as a main material, and a reservoir 10 for supplying droplets such as ink to the pressure chambers 7 is formed. A supply hole 9 for transferring a droplet from the reservoir 10 to the pressure chamber 7 is formed on the bottom surface of the reservoir 10 according to the position of each pressure chamber 7. The supply hole 9 is formed in a long hole shape or a substantially rectangular shape, and communicates with the pressure chamber 7. The ink flow path (portion A shown in FIG. 2) transferred from the supply hole 9 to the pressure chamber 7 will be described in detail with reference to FIG.

  An ink supply hole 11 that penetrates the bottom surface of the reservoir 10 is formed on the bottom surface of the reservoir 10. The ink supply hole 11 formed in the reservoir substrate 2, the ink supply hole 11 formed in the cavity substrate 3, and the ink supply hole 11 formed in the electrode substrate 4 are the reservoir substrate 2, the cavity substrate 3, and the electrode substrate 4. Are connected to each other in a joined state, and droplets are supplied from an external ink tank.

  Further, the reservoir substrate 2 becomes an ink flow path between each pressure chamber 7 and the nozzle hole 5 provided in the nozzle substrate 1, and a flow for transferring the liquid droplet pressurized in the pressure chamber 7 to the nozzle hole 5. A plurality of nozzle communication holes 6 serving as paths are provided in accordance with the respective nozzle holes 5 (each pressure chamber 7). The reservoir substrate 2 is formed with a second hole 23 that penetrates the reservoir substrate 2. The second hole portion 23 communicates with the first hole portion 22 of the cavity substrate 3 so that the driver IC 15 can be accommodated.

[Nozzle substrate 1]
The nozzle substrate 1 is made of, for example, a silicon substrate having a thickness of 100 μm as a main material, and a plurality of nozzle holes 5 communicating with the respective nozzle communication holes 6 are formed. Each nozzle hole 5 discharges the liquid droplets transferred from each nozzle communication hole 6 to the outside. In addition, when the nozzle hole 5 is formed in a plurality of stages (for example, two stages), it can be expected that straightness is improved when a droplet is ejected. The nozzle substrate 1 may be provided with a diaphragm for buffering the pressure applied to the liquid on the reservoir 10 side by the vibration plate 8.

  As shown in FIG. 2, the first hole portion 22 provided in the cavity substrate 3 and the second hole portion 23 provided in the reservoir substrate 2 communicate with each other to form the accommodating portion 24. Yes. The driver IC 15 is accommodated in the accommodating portion 24. Further, the nozzle communication hole 6 penetrates the reservoir substrate 2 and communicates with one end on the opposite side of one end with which the supply hole 9 of the pressure chamber 7 communicates.

  In this droplet discharge head 100, the driver IC 15 is accommodated in the accommodating portion 24, and the accommodating portion 24 is closed by the nozzle substrate 1, the reservoir substrate 2, the cavity substrate 3 and the electrode substrate 4. That is, the nozzle substrate 1 forms the upper surface of the housing portion 24, the electrode substrate 4 forms the lower surface of the housing portion 24, and the cavity substrate 3 and the reservoir substrate 2 form the side surfaces of the housing portion 24, thereby closing the housing portion 24. It is like that. In addition, it is desirable that the accommodating portion 24 be sealed in order to protect the driver IC 15 from liquid droplets and outside air.

The sealing member 14 seals the gap 13 between the diaphragm 8 and the individual electrode 17. The sealing member 14 is formed of, for example, silicon oxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), silicon oxynitride (SiON), silicon nitride (SiN), polyparaxylylene, or the like having low moisture permeability. Good. In addition, polyparaxylylene is a crystalline polymer resin and has properties that are excellent in moisture permeation prevention and chemical resistance.

Next, the operation of the droplet discharge head 100 will be briefly described.
A droplet such as ink is supplied to the reservoir 10 from the outside through the ink supply hole 11. In addition, droplets are supplied from the reservoir 10 to the pressure chamber 7 through the supply hole 9. A drive signal (pulse voltage) is supplied to the driver IC 15 from a control unit (not shown) via the FPC internal wiring (IC input) 32 of the FPC 30 and the IC input mounting unit 20 provided on the electrode substrate 4.

  A pulse voltage of about 0 V to 40 V is applied to the individual electrode 17 selected by the driver IC 15 to charge the individual electrode 17 positively. At this time, a drive signal (pulse voltage) having a negative polarity is supplied to the cavity substrate 3 through the FPC internal wiring 31 (COM) and the common electrode 16, and the diaphragm corresponding to the positively charged individual electrode 17 is supplied. 8 is relatively negatively charged. Therefore, an electrostatic force is generated between the selected individual electrode 17 and the diaphragm 8. If it does so, the diaphragm 8 will be attracted | sucked by the individual electrode 17 side by an electrostatic force, and will be bent. Thereby, the volume of the pressure chamber 7 is expanded.

  Next, when the supply of the pulse voltage is stopped, the electrostatic force between the diaphragm 8 and the individual electrode 17 disappears, and the diaphragm 8 is restored to the original state. At this time, the pressure inside the pressure chamber 7 rises rapidly, and the droplets in the pressure chamber 7 pass through the nozzle communication hole 6 and are discharged from the nozzle hole 5. Thereafter, the droplet is replenished from the reservoir 10 into the pressure chamber 7 through the supply hole 9 and returns to the initial state.

  The supply of droplets to the reservoir 10 of the droplet discharge head 100 is performed by, for example, a droplet supply tube (not shown) connected to the ink supply hole 11. The FPC 30 is connected to the driver IC 15 so that the longitudinal direction of the FPC 30 is parallel to the short side direction of the individual electrodes 17 forming the electrode array. For example, when the short side of the individual electrode 17 is inclined with respect to the long side and the individual electrode 17 has an elongated parallelogram shape, the FPC 30 is connected in a direction perpendicular to the long side of the individual electrode 17. That's fine.

  Here, an ink flow path of ink transferred from the supply hole 9 to the pressure chamber 7, which is a characteristic part of the droplet discharge head 100 according to this embodiment, will be described. FIG. 3 is an explanatory diagram for explaining the relationship between the supply hole 9 and the pressure chamber 7. FIG. 3A shows an enlarged plan view of the portion A shown in FIG. 2 as viewed from above. FIG. 3B shows an enlarged cross-sectional view of a portion A shown in FIG.

  As shown to Fig.3 (a), the supply hole 9 is produced as a long hole shape. By so doing, the area of the channel cross section (c-c ′ cross section) can be increased compared to a circular shape having the same diameter as the length in the short side direction. As described above, if the area of the cross section of the flow path of the supply hole 9 is increased, the flow path resistance of the ink transferred to the pressure chamber 7 can be decreased. In other words, in order to secure the same cross-sectional area of the flow path as that of the long hole shape in a circular shape, the diameter of the circle must be increased. As a result, it becomes impossible to cope with the cavity substrate 3 having a high density and a narrow width.

  In addition, alignment between the wafers on which the substrates are stacked becomes difficult. If it does so, the incidence rate of inferior goods will become high and it will become a thing with a low yield. Therefore, by making the cross section of the flow path of the supply hole 9 into a long hole shape, the flow path resistance of the ink is efficiently reduced, and the alignment between the wafers on which the substrates are stacked is facilitated. The elongated hole shape is a shape obtained by extending a circular shape in the long side direction. Here, a case where the supply hole 9 is formed in a long hole shape will be described as an example, but the present invention is not limited to this. For example, it may be formed as an oval (ellipse) shape or a substantially rectangular shape.

  Next, the ink flow path of the ink transferred from the supply hole 9 to the pressure chamber 7 will be described. In FIG. 3B, the area of the flow passage cross section (aa ′ cross section) of the pressure chamber 7 is S0, and the area of the flow passage cross section (bb ′ cross section) of the communication path that leads from the supply hole 9 to the pressure chamber 7. Is shown as S1, and the area of the flow path cross section (cc ′ cross section) of the supply hole 9 is shown as S2. Here, these areas are formed such that S2 <S1 <S0. This is to prevent choking (sudden change point of flow velocity) in the ink flow in the ink flow path (from S2 to S0).

  That is, when the cross-sectional area from S2 to S0 increases or decreases, choke is generated in the ink flow, and the ink is not filled when the pressure chamber 7 is filled with the initial ink. Or bubbles are likely to remain (see FIG. 4). Therefore, the ink flow path (from S2 to S0) is gradually expanded to prevent the occurrence of choke. Here, the case where the area is gradually expanded as S2 <S1 <S0 has been described as an example. However, the area may be gradually decreased as S2> S1> S0 to prevent generation of choke.

  Although it is conceivable to form a plurality of supply holes 9 for one pressure chamber 7 to secure an area, an ink flow occurs only in one supply hole 9 and pressure is evenly supplied from each supply hole 9. It occurs that ink is not supplied to the chamber 7. That is, the supply of ink in each supply hole 9 is biased, and air bubbles remain in the other supply hole 9 without being filled with ink (see FIG. 7). It has been found that this phenomenon occurs remarkably when the cavity substrate 3 has a high density and a narrow cross section. Therefore, it is desirable to form one supply hole 9 for one pressure chamber 7.

  FIG. 4 is an explanatory diagram showing the results of investigating the relationship between the cross-sectional area of the ink flow path and the flow path resistance. Based on FIG. 4, the relationship between the cross-sectional area (S0, S1, and S2) of the ink flow path and the ink flow velocity will be described in detail. Here, it is assumed that the average speed when the ink passes through S0 is V0, the average speed when the ink passes through S1 is V1, and the average speed when the ink passes through S2 is V2.

  The relationship of S0 × V0 = S1 × V1 = S2 × V2 is established by the continuity of the ink flow rate. In order to prevent the occurrence of choke in the ink flow path (from S2 to S0), it is effective to satisfy S2 <S1 <S0 or S2> S1> S0 as described above. The relationship between the flow velocities at this time is V2> V1> V0 when S2 <S1 <S0 and V2 <V1 <V0 when S2> S1> S0. That is, if the flow velocity is gradually increased or decreased gradually, the generation of choke in the middle of the ink flow path can be prevented.

  In the droplet discharge head 100 according to this embodiment, as shown in FIG. 3, the ink flow path has a relationship of S2 <S1 <S0. In order to make the relationship between the flow rates V2> V1> V0, the cross-sectional area ratio (S1 / S0) between S1 and S0 and the cross-sectional area ratio (S2 / S1) between S2 and S1 must be smaller than predetermined values. Is required. It can be derived from the survey results shown in FIG. FIG. 4 shows the channel resistance (R ratio shown in the figure) when S1 / S0 and S2 / S1 are variously changed.

  A boundary line X in FIG. 4 indicates a boundary where choke occurs. That is, the region α divided by the boundary line X indicates a region where choke (abrupt flow velocity change point) does not occur, and the region β indicates a region where choke occurs. Here, it is shown that the points a to u exist in the region α, and the points d to k exist in the region β. Therefore, if S0 to S2 are set so that the values of points a to c can be obtained, the occurrence of choke can be prevented.

  Further, in order to reduce the ink flow path resistance while preventing the occurrence of choke, it is desirable to set S0 to S2 so that the values of point i and point u can be obtained. The points A and U are within a range in which S1 is smaller than 0.85 times S0 (S1 <0.85 × S0) and S1 is larger than 1.05 times S2 (S1> 1.05 × S2). This can be realized by satisfying S2 <S1 <S0.

  5 to 7 are simulation diagrams showing the flow velocity of ink flowing in the ink flow path (from S2 to S0). FIG. 5 shows an example when choke is generated. The flow velocity simulation shown in FIG. 5 corresponds to the point d shown in FIG. That is, although the relationship of S2 <S1 <S0 or S2> S1> S0 is satisfied, the relationship of S1 <0.85 × S0 and S1> 1.05 × S2 is not satisfied, and choke is generated. ing.

  On the other hand, FIG. 6 shows an example when no choke is generated. The flow velocity simulation shown in FIG. 6 corresponds to the point c shown in FIG. In other words, choke is not generated because the relationship of S2 <S1 <S0 or S2> S1> S0 is satisfied, and the relationship of S1 <0.85 × S0 and S1> 1.05 × S2 is also satisfied. It is like that.

  FIG. 7 is a simulation diagram showing the flow rate of ink when two supply holes 9 are formed. In order to reduce the flow path resistance, it is conceivable to form a plurality of supply holes 9 (two in this case) for one pressure chamber 7 as a method of increasing the cross-sectional area of the supply holes 9. However, as shown in FIG. 7, the ink flows only in one supply hole 9, and the ink is not uniformly supplied from all the supply holes 9 to the pressure chamber 7. That is, the supply of ink is biased in each supply hole 9, and air bubbles remain in the other supply hole 9 without being filled with ink. Therefore, as described above, it is desirable to form one supply hole 9 for one pressure chamber 7.

  FIG. 8 is a perspective view showing an example of a droplet discharge device 150 on which the above-described droplet discharge head 100 is mounted. FIG. 9 is a diagram illustrating an example of main components of the droplet discharge device 150. The droplet discharge device 150 is a so-called general serial type inkjet printer for printing by a droplet discharge method (inkjet method). Further, as described above, the mounted droplet discharge head 100 has a small flow channel resistance in the ink flow channel (from S2 to S0) and prevents the occurrence of choke. 150 can also obtain the same effect.

  The droplet discharge device 150 is mainly composed of a drum 101 on which a print paper 110 that is a printing object is supported, and a droplet discharge head 100 that discharges ink to the print paper 110 and performs recording. In addition, there is an ink supply unit (not shown) for supplying ink to the droplet discharge head 100. The print paper 110 is held by being pressed against the drum 101 by a paper press roller 103 provided parallel to the axial direction of the drum 101. The droplet discharge head 100 is held by a feed screw 104 provided parallel to the axial direction of the drum 101.

  The droplet discharge head 100 moves in the axial direction of the drum 101 by rotating the feed screw 104. On the other hand, the drum 101 is rotated by a motor 106 via a belt 105 or the like. The print control means 107 drives the feed screw 104 and the motor 106 based on the print data and the control signal. Further, the print control unit 107 is configured to print on the print paper 110 while driving the oscillation drive circuit (not shown) to control the diaphragm 4.

  Here, a case where liquid is ejected as ink onto the print paper 110 has been described as an example, but the present invention is not limited to this. For example, in an application for discharging to a substrate to be a color filter, a liquid containing a color filter pigment may be used. Moreover, in the use discharged to the board | substrate of the display panel (OLED etc.) using electroluminescent elements, such as an organic compound, the liquid containing the compound used as a light emitting element may be sufficient. Furthermore, in the use for wiring on a substrate, a liquid containing a conductive metal may be used.

  On the other hand, when the droplet discharge head 100 is used as a dispenser and is used for discharging onto a substrate that is a microarray of biomolecules, DNA (Deoxyribo Nucleic Acids), RNA (Ribo Nucleic Acid), PNA (Phosphorus Nucleic Acid). You may make it discharge the liquid containing protein probes, such as Peptide Nucleic Acids (peptide nucleic acid). In addition, it can also be used for discharging dyes such as cloth.

  In this embodiment, the case where the droplet discharge head 100 is configured by stacking four substrates of the electrode substrate 4, the cavity substrate 3, the reservoir substrate 2, and the nozzle substrate 1 has been described as an example. Is not to be done. For example, the present invention can also be applied to a droplet discharge head in which the pressure chamber 7 and the reservoir 10 are formed on the same substrate and three substrates are stacked.

FIG. 3 is an exploded perspective view showing a state in which the droplet discharge head according to the embodiment is disassembled. It is A-A 'sectional view in the state where a droplet discharge head was assembled. It is explanatory drawing for demonstrating the relationship between a supply hole and a pressure chamber. It is explanatory drawing which shows the investigation result of the relationship between the cross-sectional area of an ink flow path, and flow path resistance. It is a simulation figure which shows the flow velocity of the ink which flows through the inside of an ink flow path. It is a simulation figure which shows the flow velocity of the ink which flows through the inside of an ink flow path. It is a simulation figure which shows the flow velocity of the ink which flows through the inside of an ink flow path. It is the perspective view which showed an example of the droplet discharge apparatus carrying a droplet discharge head. It is a figure showing an example of the main structural means of a droplet discharge apparatus.

Explanation of symbols

1 nozzle substrate, 2 reservoir substrate, 3 cavity substrate, 4 electrode substrate, 5 nozzle hole, 6 nozzle communication hole, 7 pressure chamber, 8 diaphragm, 9 supply hole, 10 reservoir, 11 ink supply hole, 12 recess (glass groove) ), 13 Gap (vibration chamber), 14 Sealing member, 15 Driver IC, 16 Common electrode, 17 Individual electrode, 17a Lead part, 17b Terminal part, 20 IC input mounting part, 21 FPC mounting part, 22 First hole Part, 23 second hole part, 24 container part, 100 droplet discharge head, 101 drum, 103 paper pressure roller, 104 feed screw, 105 belt, 106 motor, 107 print control means, 110 print paper, 150 droplet discharge apparatus.

Claims (6)

A cavity substrate on which a bottom wall forms a vibration plate and a pressure chamber for storing and discharging droplets is formed;
An electrode substrate formed with individual electrodes facing the diaphragm and driving the diaphragm;
A reservoir substrate having a reservoir for supplying droplets to the pressure chamber, a supply hole for transferring droplets from the reservoir to the pressure chamber, and a nozzle communication hole for transferring droplets from the pressure chamber to the nozzle holes; A droplet discharge head configured by being laminated,
The area of the flow passage cross section of the pressure chamber is S0,
The area of the cross section of the communication path that leads from the supply hole to the pressure chamber is S1,
When the area of the cross section of the flow path of the supply hole is S2,
An ink flow path is formed so as to satisfy S2>S1> S0. A cavity substrate on which a bottom wall forms a vibration plate and a pressure chamber for storing and discharging droplets is formed;
An electrode substrate formed with individual electrodes facing the diaphragm and driving the diaphragm;
A reservoir substrate having a reservoir for supplying droplets to the pressure chamber, a supply hole for transferring droplets from the reservoir to the pressure chamber, and a nozzle communication hole for transferring droplets from the pressure chamber to the nozzle holes; A droplet discharge head configured by being laminated,
The area of the flow passage cross section of the pressure chamber is S0,
The area of the cross section of the communication path that leads from the supply hole to the pressure chamber is S1,
When the area of the cross section of the flow path of the supply hole is S2,
A liquid droplet ejection head, wherein an ink flow path is formed so that S2 <S1 <S0. 3. The droplet discharge head according to claim 1, wherein a planar shape of the supply hole in the reservoir substrate is elongated in a long side direction of the pressure chamber to have a long hole shape. The supply hole,
The droplet discharge head according to any one of claims 1 to 3, wherein the number of the pressure chambers is one for the droplets transferred from the supply hole. The area S1 of the cross-section of the communication path that leads from the supply hole to the pressure chamber is:
Smaller than 0.85 times the area S0 of the flow path cross section of the pressure chamber,
The droplet discharge head according to claim 1, wherein the droplet discharge head is formed to be larger than 1.05 times the area S2 of the flow path cross section of the supply hole. A droplet discharge apparatus comprising the droplet discharge head according to claim 1.

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