JP2009274415A - Nozzle plate and liquid discharge head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a durable nozzle plate which is prevented from generating a crack and a rupture in a resin part of the nozzle plate in which a nozzle hole is formed. <P>SOLUTION: The nozzle plate comprises a nozzle having a discharge port from which a liquid is discharged as a droplet and is used for a liquid discharge head employing an electrostatic suction method. The nozzle plate comprises a resin layer in which is formed a first hole using the discharge port as an opening and a silicon plate which is put on the resin layer and in which a second hole is formed, the second hole communicating with the first hole and having a larger diameter than the first hole. The shape distortion index C in a portion covering the second hole of the resin layer satisfies a predetermined formula. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a nozzle plate.

  In recent years, the demand for fine pattern formation and high-viscosity ink ejection has been increasing with the progress of high-definition image quality using inkjet recording heads and the expansion of the application range in industrial applications. In order to solve these problems Development of a liquid ejection apparatus and a method for manufacturing the same are progressing (for example, see Patent Document 1).

  Among them, in response to the above requirements, as a technology for discharging not only low viscosity but also high viscosity droplets from a miniaturized nozzle, the liquid in the nozzle is charged, There is known a so-called electrostatic attraction type droplet discharge technique in which discharge is performed by an electrostatic attraction force received from an electric field formed between various types of base materials (see, for example, Patent Document 2).

  Furthermore, a droplet discharge device using a so-called electric field assist method, which combines this droplet discharge technology with a technology that discharges droplets using pressure due to deformation of a piezo element or generation of bubbles inside the liquid. Development is progressing.

  In this electric field assist method, the meniscus forming means and electrostatic attraction force are used to raise the liquid meniscus at the nozzle outlet, thereby increasing the electrostatic attraction force against the meniscus and overcoming the liquid surface tension to drop the meniscus into droplets. This is a method of forming and discharging.

  In the electric field assist method, a droplet is formed from the nozzle by the resultant force of the pressure and the electrostatic attraction force, and the formed droplet is caused to fly to the substrate by the electrostatic attraction force. For example, the diameter is 5 μm. From the conventional piezo method and thermal method, the adhesion of fine droplets ejected from a minute ejection port of about 10 μm to 10 μm is superior.

In the conventional piezo method and thermal method, the total energy for forming a meniscus, causing droplets to fly and landing on a substrate must be covered with pressure due to deformation of the piezo element. On the other hand, the energy required to generate the pressure required for the electric field assist method is only the energy required to form a meniscus and form a droplet, so pressure generation from a piezoelectric actuator such as a piezo element is generated. The driving voltage of the means is advantageous in that it requires a lower voltage than the conventional method.
JP 2005-249436 A JP 2006-110757 A

  In an electric field assisted ink jet recording head aiming at high-precision recording by discharging fine droplets, a plate in which nozzle holes having discharge ports as openings are formed in order to improve insulation between the ink and the recording medium ( In some cases, the nozzle plate or a part of the nozzle plate is made of resin as described in Patent Document 1, for example.

  In order to cope with the discharge of minute droplets, when the nozzle hole diameter (the diameter of the hole having the discharge port as an opening) is reduced from about 5 μm to about 10 μm, the injection resistance increases, and the injection resistance is favorably emitted against this injection resistance. It is necessary to increase the injection pressure. However, since the Young's modulus of the resin is about two orders of magnitude smaller than that of metal or silicon (Si), if the injection pressure is increased, the resin part where the nozzle is formed will be cracked and fractured, and good recording will not be performed. There was a problem that quality deteriorated.

  The present invention has been made in view of the above-described problems, and the object of the present invention is to provide durability by preventing cracks and tears in the resin portion in which the nozzle holes of the nozzle plate are formed. It is an object to provide a nozzle plate and a liquid discharge head with good characteristics.

  Said subject is solved by the following structures.

1. In a nozzle plate that has a nozzle that discharges liquid as droplets from a discharge port, and that is used in an electrostatic suction type liquid discharge head,
A resin layer in which a first hole having the discharge port as an opening is formed;
A silicon plate overlaid on the resin layer and having a second hole larger in diameter than the first hole communicating with the first hole;
A shape deformation index C indicating a deformation state of a portion covering the second hole of the resin layer satisfies the following expression.
C ≦ k1 × d × 10 ⁻²³
However,
5μm ≦ d ≦ 10μm
d: Diameter of the first hole (μm)
k1 = 0.3 (1 / μm)
C = k2 × D ⁶ / (E × t ³ ) (m ³ / Pa)
k2 = 0.0069
D: Diameter of the second hole (m)
E: Young's modulus of resin layer (Pa)
t: thickness of resin layer (m)
2. 2. The nozzle plate according to 1, wherein the resin layer has a volume resistivity of 10 ¹⁵ Ωm or more.

  3. The nozzle plate according to 1 or 2, wherein the water absorption rate of the resin layer is 0.3% or less.

4). The nozzle plate according to any one of 1 to 3, and
A body plate in which a space serving as a cavity communicating with the nozzle is formed by bonding with the nozzle plate;
Pressure generating means for generating pressure in the liquid in the cavity by changing the volume of the cavity;
An electrostatic voltage generating means for generating an electrostatic attraction force by applying an electrostatic voltage between the nozzle and the liquid in the cavity and the substrate.

  According to the nozzle plate and the liquid discharge head of the present invention, durability can be improved by preventing cracks and tears from occurring in the resin portion where the nozzle holes of the nozzle plate are formed.

  Although the present invention will be described based on the illustrated embodiment, the present invention is not limited to the embodiment.

  FIG. 1 is a schematic cross-sectional view illustrating the entire configuration of an electric field assist type liquid ejection apparatus 1 using an electrostatic attraction force according to the present embodiment. The liquid discharge head 2 according to the present invention can be applied to various liquid discharge devices such as a so-called serial method or line method.

  The liquid ejection apparatus 1 has a liquid ejection head 2 on which nozzles 5 to be described later for ejecting droplets Q of a chargeable liquid L such as ink are formed, and a facing surface facing the nozzles 5 of the liquid ejection head 2. The counter electrode 3 that supports the base material K that receives the landing of the droplet Q on the counter surface is provided.

  A nozzle plate 4 in which a plurality of nozzles 5 are formed is provided on the side of the liquid discharge head 2 facing the counter electrode 3.

  As shown in FIG. 1, each nozzle 5 is formed by perforating the nozzle plate 4 and is a second hole that communicates with a liquid supply port 9 through which a liquid L is supplied from a cavity 20 described later. It has a two-stage structure including a diameter portion (liquid supply port side) 10 and a small diameter portion (discharge port side) 12 that is a first hole communicating with a part of the bottom surface of the large diameter portion 10. Further, the nozzle diameter of the large diameter portion 10 is configured to be larger than the nozzle diameter of the small diameter portion 12. In addition, the opening cross-sectional shape of the large diameter part 10 and the small diameter part 12 is circular.

  The small-diameter portion 12 has the discharge port 11 of the discharge surface 6 as an opening, and discharges the droplet Q from the discharge port 11 to the counter electrode 3.

  The nozzle plate 4 has a laminated structure including a silicon layer 41 and a resin layer 42 formed of, for example, a thermosetting fluoropolymer. The small diameter portion 12 of each nozzle 5 is formed by perforating the resin layer 42, and the large diameter portion 10 is formed by perforating the silicon layer 41.

The thermosetting fluoropolymer that forms the resin layer 42 has physical properties such as a volume resistivity of 10 ¹⁵ Ωm or more, a relative dielectric constant of 3 or less, and a glass transition temperature of 350 ° C. or more. For example, Asahi Low-K polymer ( Asahi Glass Co., Ltd.) can be used.

  By making the nozzle plate 4 have such a laminated structure, the nozzle plate 4 can obtain smoothness and rigidity by the silicon layer 41, and can concentrate the electric field on the nozzle tip of the resin layer 42.

  The water absorption rate of the liquid L in the resin layer 42 is set to 0.3% or less. Thereby, a strong electrostatic attraction force can be generated stably for a long time without being affected by the physical properties of the liquid L.

  The resin layer 42 is formed to have a thickness of 5 μm or more so as to increase electric field concentration around the nozzle 5 and to generate a stronger electrostatic attraction force.

  On the discharge surface 6 of the nozzle plate 4, a liquid repellent layer 61 for suppressing the oozing of the liquid L from the discharge port 11 is provided on the entire surface of the discharge surface 6 except the discharge port 11 as a preferred form. For the liquid repellent layer 61, for example, a material having water repellency is used if the liquid L is aqueous, and a material having oil repellency is preferably used if the liquid L is oily. Generally, fluororesins such as FEP (tetrafluoroethylene / hexafluoropropylene), PTFE (polytetrafluoroethylene), fluorosiloxane, fluoroalkylsilane, amorphous perfluororesin, etc. are often used, and coating and vapor deposition, etc. The film is formed on the discharge surface 6 by the method described above.

An intermediate layer (not shown) made of SiO ₂ may be provided on the critical surface between the liquid repellent layer 61 and the resin layer 42 in order to improve the adhesion of the liquid repellent layer 61.

  The liquid discharge head 2 is configured as a head having a flat discharge surface where the nozzle 5 does not protrude from the discharge surface 6 facing the counter electrode 3 of the nozzle plate 4.

  On the surface opposite to the ejection surface 6 of the nozzle plate 4, a charging electrode 14 made of a conductive material such as NiP, for example, for charging the liquid L in the nozzle 5 is provided in layers. In the present embodiment, the charging electrode 14 extends to the inner peripheral surface 15 of the large diameter portion 10 of the nozzle 5 and is in contact with the liquid L in the nozzle.

  The charging electrode 14 is connected to an electrostatic voltage power supply 16 that is an electrostatic voltage generating means. Since the single charging electrode 14 is in contact with the liquid L in all the nozzles 5, when an electrostatic voltage is applied between the charging electrode 14 and the counter electrode 3 by the electrostatic voltage power supply 16, The liquid L in all the nozzles 5 is charged at the same time, and an electrostatic attraction force is generated between the liquid discharge head 2 and the counter electrode 3, particularly between the liquid L and the base material K.

  A body plate 19 is provided behind the charging electrode 14. A portion of the body plate 19 facing the opening end of the large diameter portion 10 of each nozzle 5 is formed with a substantially cylindrical space having an inner diameter substantially equal to the opening end, and each space is discharged. The cavity 20 is used for temporarily storing the liquid L.

  Behind the body plate 19 is provided a flexible layer 21 made of a flexible metal thin plate, silicon, or the like. The flexible layer 21 defines the cavity 20 from the outside.

  A channel (not shown) for supplying the liquid L to the cavity 20 is formed at the boundary between the body plate 19 and the flexible layer 21. Specifically, the body plate 19 is provided with a common channel and a channel connecting the common channel and the cavity 20 by etching a silicon substrate. A supply pipe (not shown) for supplying the liquid L from an external liquid tank (not shown) is connected to the common flow path, and is arranged by a supply pump (not shown) provided in the supply pipe or the arrangement of the liquid tank. A predetermined supply pressure is applied to the liquid L such as the flow path, the cavity 20 and the nozzle 5 by the differential pressure depending on the position.

  Piezo elements 22, which are piezoelectric element actuators as pressure generating means, are provided at portions corresponding to the cavities 20 on the outer surface of the flexible layer 21, and a drive voltage is applied to the piezo elements 22. A drive voltage power source 23 is connected to apply and deform the element. The piezo element 22 is deformed by the application of a drive voltage from the drive voltage power source 23 to generate a pressure on the liquid L in the nozzle, thereby forming a meniscus of the liquid L at the discharge port 11 of the nozzle 5. . In addition to the piezoelectric element actuator as in the present embodiment, for example, a thermal method or the like can be adopted as the pressure generating means.

  The driving voltage power supply 23 and the electrostatic voltage power supply 16 for applying an electrostatic voltage to the charging electrode 14 are respectively connected to the operation control means 24 and are controlled by the operation control means 24, respectively.

  The operation control means 24 is composed of a computer in which a CPU 25, a ROM 26, a RAM 29, etc. are connected by a BUS (not shown). The CPU 25 is operated based on a control program stored in the ROM 26. The liquid L is discharged from the discharge port 11 of the nozzle 5 by driving the voltage power source 23 and the like.

  Below the liquid ejection head 2, a plate-like counter electrode 3 that supports the substrate K is disposed in parallel to the ejection surface 6 of the liquid ejection head 2 and spaced apart by a predetermined distance. The separation distance between the counter electrode 3 and the liquid ejection head 2 is appropriately set within a range of about 0.1 to 3.0 mm.

  The counter electrode 3 is grounded and is always maintained at the ground potential. Therefore, when an electrostatic voltage is applied from the electrostatic voltage power supply 16 to the charging electrode 14, the liquid L in the discharge port 11 of the nozzle 5 and the surface facing the liquid discharge head 2 of the counter electrode 3 are between. An electric field is generated. Further, when the charged droplet Q lands on the substrate K, the counter electrode 3 releases the electric charge by grounding.

  The counter electrode 3 or the liquid ejection head 2 is provided with positioning means (not shown) for positioning the liquid ejection head 2 and the substrate K by relatively moving them, whereby each nozzle of the liquid ejection head 2 is attached. The droplet Q ejected from 5 can land on the surface of the substrate K at an arbitrary position.

  As the liquid L to be ejected by the liquid ejection device 1, a conductive paste or the like containing a large amount of an inorganic liquid such as water, an organic liquid such as methanol, and a substance having a high electrical conductivity (such as silver powder) is used.

  The discharge principle of the liquid L in the liquid discharge head 2 of the present invention will be described with reference to FIGS.

  An electrostatic voltage is applied from the electrostatic voltage power supply 16 to the charging electrode 14, and an electric field is generated between the liquid L in the ejection port 11 of the nozzle 5 and the opposed surface of the counter electrode 3 facing the liquid ejection head 2. Further, a driving voltage is applied from the driving voltage power source 23 to the piezo element 22 to deform the piezo element 22, thereby forming a meniscus of the liquid L at the discharge port 11 of the nozzle 5 with the pressure generated in the liquid L.

  When the insulation property of the nozzle plate 4 is increased as in the present embodiment, the equipotential lines in the nozzle plate 4 are substantially perpendicular to the ejection surface 6 as shown by equipotential lines by simulation in FIG. And a strong electric field is generated toward the liquid L in the small diameter portion 12 of the nozzle 5 and the meniscus portion of the liquid L.

  In particular, as can be seen from the fact that equipotential lines are dense at the tip of the meniscus M in FIG. 2, a very strong electric field concentration occurs at the tip of the meniscus. Therefore, the meniscus is torn off by the electrostatic force of the electric field and separated from the liquid L in the nozzle to become a droplet Q. Further, the droplet Q is accelerated by the electrostatic force, and is attracted and landed on the base material K supported by the counter electrode 3. At that time, since the droplet Q tries to land at a closer place by the action of electrostatic force, the angle at the time of landing on the substrate K is stabilized and accurately performed.

According to the droplet discharge experiments so far, in order to stably discharge the droplet, the electric field strength at the tip of the meniscus needs to be 1.5 × 10 ⁷ V / m (1.5 kV / mm) or more. I know that. Further, it has been found that when the volume resistivity of the nozzle plate 4 is 10 ¹⁵ Ωm or more, the electric field strength at the tip of the meniscus is 1.5 × 10 ⁷ V / m or more. For this reason, the volume resistivity of the resin material forming the resin layer 42 is preferably 10 ¹⁵ Ωm or more. Theoretically, even if the nozzle plate 4 has a volume resistivity of less than 10 ¹⁵ Ωm, there is a possibility that the droplet Q is ejected from the nozzle 5 if the electrostatic voltage is made very large. As a result, the substrate K may be damaged.

The electric field strength at the meniscus tip depends on the thickness and relative dielectric constant of the resin layer 42. In order to set the electric field strength at the meniscus tip to about 1.5 × 10 ⁷ V / m or more, the resin layer It has been found that the thickness of 42 is preferably 5 μm or more and the relative dielectric constant is 3 or less.

  As described above, the meniscus of the liquid L is formed in the discharge port 11 by driving the piezo element 22 to deform the flexible layer 21 and applying pressure to the liquid L in the nozzle 5. The lid 421, which is a portion that covers the opening of the large-diameter portion 10 of the resin layer 42 in which the small-diameter portion 12 is formed, is raised as shown by the dotted line in FIG. 3 due to the pressure applied to form the meniscus. Transforms into The deformation of the lid 421 usually returns from the state indicated by the dotted line to the original state when the applied pressure is lost. However, in some cases, the lid 421 may be cracked or broken during the uplift. If the lid 421 is cracked, broken, or the like, the subsequent meniscus formation is not performed well, and the droplets cannot be discharged well, and the recording quality on the substrate K is deteriorated.

  The above cracks and breaks are presumed to be caused by the deformation of the lid 421 exceeding the elastic deformation range and entering a region where plastic deformation occurs.

In order to cause cracks and breaks in the lid 421, the diameter d of the small diameter portion 12, the diameter D of the large diameter portion 10, the Young's modulus E of the resin layer 42 forming the lid 421, and the thickness of the resin layer 42 corresponding to the thickness of the lid 421. It can be obtained that t has a certain relationship. Hereinafter, as shown in the equation (1), it was found that when the shape deformation index C is equal to or less than a numerical value determined by the diameter d of the small diameter portion 12, cracks and fractures do not occur. The resin layer 42 was formed using Asahi Low-K polymer (Asahi Glass Co., Ltd.) (Young's modulus E = 3.5 GPa).
C ≦ k1 × d × 10 ⁻²³ (1)
However,
5μm ≦ d ≦ 10μm
d: Diameter (μm) of the small diameter portion (first hole)
k1 = 0.3 (1 / μm)
C = k2 × D ⁶ / (E × t ³ ) (m ³ / Pa) (2)
k2 = 0.0069
D: Diameter (m) of the large diameter part (second hole)
E: Young's modulus of resin layer (Pa)
t: thickness of resin layer (m)
The shape deformation index C indicates the deformation state of the lid 421 when pressure is applied to the lid 421. The amount h of protrusion (see FIG. 3) of the lid 421 is measured in a state where a certain pressure is applied. Was converted per unit pressure. By preventing the shape deformation index C from exceeding a certain value, the lid 421 is not cracked or broken. In addition, the protruding amount h was measured in the vicinity of the discharge port of the small diameter portion 12 as shown in FIG.

The thickness h and the diameter D of the resin layer 42 were changed as appropriate, a certain pressure was applied, and the protruding amount h of the lid 421 was measured with reference to the ejection surface. As a result of examining the data obtained by such experiments, it was found that the shape deformation index C has the following relationship.
(A) It is proportional to the sixth power of the diameter D.
(B) It is proportional to the inverse of the cube of the thickness t.
(C) It is proportional to the reciprocal of Young's modulus E.

  The coefficient k2 is determined so that the above relationships (a), (b), and (c) are best matched to the amount of protrusion per unit pressure, and this is defined as equation (2).

  It was found that when the diameter d of the small diameter portion 12 is in the range of 5 μm to 10 μm and the shape deformation index C satisfies the relationship of the diameter d of the small diameter portion 12 and the formula (1), the lid 421 does not crack or break. If the diameter d of the small diameter portion is small and less than 5 μm, it is difficult to form droplets and it becomes impossible to discharge well, and if it exceeds 10 μm, the meniscus M (see FIG. 2) is difficult to form normally. Will not be able to discharge properly.

  Next, a method for forming the nozzle plate 4 of the liquid ejection head 2 of this embodiment will be described.

  First, as shown in FIG. 4A, for example, an oxide film (thermal oxide film) 32 having a thickness of 2 μm, for example, is formed on the upper surface (A surface) and the lower surface (B surface) of a double-sided mirror surface having a thickness of 200 μm, for example. A silicon substrate 30 corresponding to the formed silicon layer 41 is prepared.

  Next, as shown in FIG. 4B, the oxide film 32 on the A surface of the silicon substrate 30 is removed, and a corresponding thermosetting fluoropolymer layer is formed as a resin layer 42 by spin coating.

  Next, an oxide film 33 is formed on the resin layer 42 by a CVD method using TEOS (tetraethoxysilane) gas or the like, and using the lithography technique, as shown in FIG. An opening 341 is formed in the substrate. An opening 361 is formed in the oxide film 32 on the B surface.

  Next, on the surface A, as shown in FIG. 4D, the opening 342 is formed in the thermosetting fluoropolymer layer by etching the resin layer 42 until the silicon substrate 30 is reached using the oxide film 33 as a mask. After that, the oxide film 33 is removed.

  Next, as shown in FIG. 5A, cool grease (not shown) or the like is used on the dummy wafer 50 made of silicon so that the B surface of the silicon substrate 30 is on the upper side. And fix.

  Next, as shown in FIG. 5B, the silicon substrate 30 is anisotropically etched through the opening 361 by an ICP (Inductively Coupled Plasma) method using the oxide film 32 as a mask. Then, an opening 362 is formed by digging down until the silicon substrate 30 is penetrated.

  Next, as shown in FIG. 5C, the oxide film 32 is removed by reactive ion etching, and surface treatment is performed as necessary, and this is used as the nozzle plate 4. The opening 362 corresponds to the large diameter portion 10 of the nozzle 5, and the opening 342 corresponds to the small diameter portion 12 of the nozzle 5.

  In the above, the opening 342 is formed first, and then the opening 362 is formed. However, after the opening 362 is formed on the B surface, the opening 342 is formed on the resin layer 42 on the A surface. Also good.

  The charging electrode 14 is formed on the nozzle plate 4 manufactured as described above, and the liquid ejection head 2 is formed by bonding a separately molded body plate 19 by the anodic bonding method via the charging electrode 14. .

  This joining is performed as follows. First, the nozzle plate 4 with the charging electrode 14 and the body plate 19 are brought into contact with each other. Next, in this state, the nozzle plate 4 and the body plate 19 are joined by heating to 350 ° C. to 450 ° C. and applying a voltage just before a leakage current flows between the nozzle plate 4 and the body plate 19. By joining the nozzle plate 4 and the body plate 19, a liquid flow path connected to the nozzle 5 is formed.

  Further, after the liquid flow path is formed, the piezo element 22 is attached, the operation control means 24 is attached, necessary wiring connection and packaging are performed, and the liquid discharge head 2 is completed.

  The nozzle plate 4 was manufactured according to the nozzle formation method described above with reference to FIGS. In manufacturing, the resin layer 42 provided with the opening 342 corresponding to the small-diameter portion 12 uses Asahi Low-K polymer (Asahi Glass Co., Ltd.) (Young's modulus E = 3.5 GPa), and the diameter of the small-diameter portion 12. d, the diameter D of the large diameter portion 10, and the thickness t of the resin layer 41 were appropriately changed. Using the nozzle plate 4 thus obtained, the liquid discharge head 2 was manufactured, and liquid discharge was performed 10 million times (piezo element drive frequency 30 kHz) to confirm the presence or absence of cracks and breaks. The distance between the discharge surface 6 of the nozzle plate 4 and the opposing surface of the counter electrode 3 is 1.0 mm, and the applied electrostatic voltage is 1 from 1.5 kV / mm, which is a practical value of the electric field strength between the electrodes. 0.5 kV. The results are shown in Tables 1 to 3. The item of the formula (1) is marked with “◯” when it conforms to the formula (1), and “x” when it does not fit.

From the results of Tables 1 to 3, it can be seen that if the shape deformation index C shown in the equation (1) is equal to or smaller than the value determined by the diameter d of the small diameter portion, cracks and fractures do not occur. That is, when d = 5 μm in Table 1, C ≦ 1.5 × 10 ⁻²³ (hereinafter, units are omitted), and when d = 7 μm in Table 2, C ≦ 2.1 × 10 ⁻²³ , d in Table 3 In the case of = 10 μm, cracks and breakage did not occur when C ≦ 3 × 10 ⁻²³ .

  In addition, when the diameter d of the small diameter portion is in the range of 5 μm to 10 μm, it is possible to discharge the droplets satisfactorily in the range satisfying the conditional expression (1). On the other hand, when the diameter d of the small-diameter portion is less than 5 μm, it is difficult to form a droplet, and when it exceeds 10 μm, it is difficult to form a meniscus normally, and good ejection cannot be performed.

It is a cross-sectional schematic diagram which shows the whole structure of the liquid discharge apparatus which concerns on this embodiment. It is a schematic diagram which shows the electric potential distribution of the discharge opening vicinity of the nozzle by simulation. It is a figure explaining a deformation | transformation of a small diameter part peripheral part. It is sectional drawing which shows a part of formation process of the liquid discharge head which concerns on this embodiment. It is sectional drawing which shows a part of formation process of the liquid discharge head which concerns on this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid discharge apparatus 2 Liquid discharge head 3 Counter electrode 4 Nozzle plate 41 Silicon layer 42 Resin layer 5 Nozzle 6 Discharge surface 61 Liquid repellent layer 9 Liquid supply port 10 Large diameter part 11 Discharge port 12 Small diameter part 14 Charging electrode 15 Inner circumference Surface 16 Electrostatic voltage power supply (electrostatic voltage generating means)
19 body plate 20 cavity 21 flexible layer 22 piezo element (pressure generating means)
23 drive voltage power supply 24 operation control means 25 CPU
26 ROM
29 RAM
30 Silicon substrate 32, 33 Oxide film 42 Resin layer 421 Lid d, D Diameter K Base material L Liquid M Meniscus

Claims (4)

In a nozzle plate that has a nozzle that discharges liquid as droplets from a discharge port, and that is used in an electrostatic suction type liquid discharge head,
A resin layer in which a first hole having the discharge port as an opening is formed;
A silicon plate overlaid on the resin layer and having a second hole larger in diameter than the first hole communicating with the first hole;
A shape deformation index C indicating a deformation state of a portion covering the second hole of the resin layer satisfies the following expression.
C ≦ k1 × d × 10 ⁻²³
However,
5μm ≦ d ≦ 10μm
d: Diameter of the first hole (μm)
k1 = 0.3 (1 / μm)
C = k2 × D ⁶ / (E × t ³ ) (m ³ / Pa)
k2 = 0.0069
D: Diameter of the second hole (m)
E: Young's modulus of resin layer (Pa)
t: thickness of resin layer (m) 2. The nozzle plate according to claim 1, wherein the resin layer has a volume resistivity of 10 ¹⁵ Ωm or more. The nozzle plate according to claim 1 or 2, wherein the water absorption of the resin layer is 0.3% or less. The nozzle plate according to any one of claims 1 to 3,
A body plate in which a space serving as a cavity communicating with the nozzle is formed by bonding with the nozzle plate;
Pressure generating means for generating pressure in the liquid in the cavity by changing the volume of the cavity;
An electrostatic voltage generating means for generating an electrostatic attraction force by applying an electrostatic voltage between the nozzle and the liquid in the cavity and the substrate.

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