JP2007152871A - Nozzle plate, manufacturing method for nozzle plate and liquid delivering head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nozzle plate which has a flat delivering face that enables correct and stable delivering of a liquid from minute nozzles by a low application voltage by using a liquid droplet delivering technique of an electrostatic sucking system, and to provide a manufacturing method for a nozzle plate, and a liquid delivering head using the nozzle plate. <P>SOLUTION: In the nozzle plate which includes the nozzles where the liquid is delivered from delivering holes as liquid droplets, and which is used for the liquid delivering head, a first face formed of a glass whose volume resistivity is not smaller than 10<SP>15</SP>Ω×m and where the delivering holes of the nozzles are formed is flat. The nozzle plate has small diameter parts and large diameter parts. The small diameter part has the delivering hole made one opening. The large diameter part communicates with the other opening of the small diameter part and has an opening in a second face opposite to the first face. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a nozzle plate, a method for manufacturing the nozzle plate, and a liquid discharge head using the nozzle plate.

  In recent years, with the progress of high-definition image quality in inkjet recording methods and the expansion of the application range in industrial applications, there is an increasing demand for fine pattern formation and high-viscosity ink ejection. In order to solve these problems with the conventional ink jet recording method, it is necessary to improve the liquid discharge force by reducing the size of the nozzle and discharging the high viscosity ink, and accordingly, the drive voltage for discharging the ink is increased. As a result, the cost of the head and device becomes very expensive, and a device suitable for practical use has not been realized.

  Therefore, in response to the above request, as a technology for discharging not only low viscosity but also high viscosity droplets from a miniaturized nozzle, various kinds of objects that are charged with the liquid in the nozzle and receive the impact of the nozzle and the droplet 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 the substrate and the substrate (see Patent Document 1).

  However, when using a liquid discharge head with a flat droplet discharge surface in the electrostatic suction type droplet discharge technology, the degree of electric field concentration on the liquid in the nozzle and the meniscus of the discharge hole is small, and the required electrostatic suction In order to obtain force, it was necessary to apply a very high voltage as a voltage applied between the liquid discharge head and the substrate.

Therefore, a droplet discharge device using a so-called electric field assist method, which combines this droplet discharge technology with a technology that discharges a droplet by using pressure due to deformation of a piezo element or generation of bubbles inside the liquid. Development is progressing (see, for example, Patent Documents 2 to 5). This electric field assist method uses a meniscus forming means and electrostatic attraction force to raise a liquid meniscus at the nozzle discharge hole, 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.
WO03 / 070381 pamphlet JP-A-5-104725 JP-A-5-278212 JP-A-6-134992 JP 2003-53977 A

  However, these liquid ejection devices using the electric field assist method have better ejection efficiency than conventional ink jet recording methods using the piezo method and thermal method, but the electrostatic attraction force due to the electric field is utilized to the maximum. Therefore, meniscus formation and droplet ejection are not performed efficiently, and when trying to meet demands for fine pattern formation and high-viscosity ink ejection, ink ejection is similar to conventional inkjet recording methods. For this reason, it is necessary to increase the drive voltage for the head, and the cost of the head and device becomes high. Further, when the applied voltage is increased in order to increase the electrostatic attraction force, there is a problem that dielectric breakdown occurs between the head and the substrate, and the apparatus cannot be driven.

  In these liquid discharge devices using the electric field assist method, when a flat liquid discharge head is used as a liquid discharge head provided with a nozzle for discharging a liquid, the structure is simple, so that the productivity is excellent. There is a great advantage that the nozzle does not get caught in the wiper when wiping the discharge surface when cleaning the liquid discharge head.

  However, a flat liquid discharge head generates pressure due to deformation of the piezo element, so that the liquid meniscus is raised in the discharge hole of the nozzle, and the electric field is selectively concentrated on the raised meniscus, and the liquid is attracted by electrostatic attraction force. Even in the case of a liquid ejecting apparatus using an electric field assist method for ejecting liquid, since the electric field concentration is small, the action of drawing out the meniscus due to electrostatic attraction force is small when forming the meniscus, resulting in a piezoelectric element actuator such as a piezoelectric element. There is a problem that it is necessary to apply a high voltage to the pressure generating means.

  In the present invention, a flat nozzle, a nozzle plate, and a liquid discharge head mean that the protrusion of the nozzle from the discharge surface of the nozzle plate is 30 μm or less, which causes troubles such as damage during the wiping. In other words, the nozzle protrusion is small and the electric field concentration effect due to the protrusion cannot be expected.

  Therefore, in order to eliminate the problems of the flat liquid discharge head, in the liquid discharge apparatus using the electric field assist method, the nozzle protrudes from the nozzle plate of the liquid discharge head to the discharge surface side like a lightning rod, and the tip of the nozzle protrusion In many cases, a liquid discharge head is used in which the electric field is concentrated to increase the discharge efficiency of the nozzle.

  However, since a number of lightning rod-like nozzles having a height of about several tens of μm must be erected from the nozzle plate of the liquid ejection head to the ejection surface side, the structure becomes complicated and productivity is lowered. In addition, there is a problem in that the operability is inferior, for example, the nozzle standing at the time of cleaning the liquid discharge head is broken.

  In recent years, the application of industrial patterning using an ink jet recording method has been widely considered. The reason is that by using the ink jet recording method, there is a great advantage that patterning can be performed directly on a substrate or the like. Conventionally, when patterning on a substrate, a lithography process is required, and when the lithography process is not used, printing or the like can be considered. However, in the printing process, a plate is generally required, and a process such as washing of the plate is performed. Is also necessary. On the other hand, patterning by the ink jet recording method eliminates the need for a lithography process, a plate, and the like, and the process becomes very simple. In such patterning, high definition with a landing diameter of 30 μm or less is desired. To meet this demand, the diameter of the ink droplets ejected from the inkjet head needs to be approximately 15 μm or less. It is said that there is.

  Accordingly, the present invention provides a nozzle plate having a flat ejection surface capable of accurately and stably ejecting liquid from minute nozzles, a method for manufacturing the nozzle plate, and a liquid ejection head using the nozzle plate. Objective.

  The above object can be achieved by any of the following means.

1. In a nozzle plate that has a nozzle that discharges liquid as droplets from a discharge hole and is used in a liquid discharge head,
It consists of glass with a volume resistivity of 10 ¹⁵ Ω · m or more,
The first surface on which the discharge holes of the nozzle are formed is flat,
A nozzle plate comprising: a small-diameter portion having one of the discharge holes as an opening; and a large-diameter portion having an opening in a second surface opposite to the first surface through the other opening of the small-diameter portion. .

  2. The nozzle plate according to 1, wherein a diameter of the large diameter portion is larger than a diameter of the small diameter portion.

  3. The nozzle plate according to 1 or 2, wherein a liquid repellent layer is provided on the first surface.

  4). The nozzle plate according to any one of 1 to 3, wherein the liquid discharge head is an electrostatic suction type liquid discharge head.

5. In a method of manufacturing a nozzle plate having a nozzle that discharges liquid as droplets from a discharge hole and used in a liquid discharge head,
A glass substrate having a volume resistivity of 10 ¹⁵ Ω · m or more, the first surface of the glass substrate and the first surface through the small diameter portion having the discharge hole as one opening and the other opening of the small diameter portion Forming the nozzle composed of a large-diameter portion having an opening on the second surface opposite to the second surface,
Performing a photolithography process on the first surface of the glass substrate to form a pattern mask for the ejection holes;
Performing a dry etching process using the pattern mask of the discharge holes to form a small diameter portion longer than a desired length of the small diameter portion, and a first step including:
Forming a pattern mask of the large diameter portion on a second surface opposite to the first surface by photolithography,
A step of forming the large-diameter portion having a desired length by a dry etching method in addition to the sand blasting method or the sand blasting method using the pattern mask of the large-diameter portion. The manufacturing method of the nozzle plate.

6). The first step includes
Providing a metal film on the first surface of the glass substrate;
Performing a photolithography process and an etching process on the metal film to form a pattern mask of the metal film of the discharge hole;
A step of performing a dry etching process using a pattern mask of the metal film of the discharge hole to form a small diameter portion longer than a desired length of the small diameter portion; and
6. The method for producing a nozzle plate according to 5, wherein the metal film is removed.

  7). The method for producing a nozzle plate according to 5 or 6, further comprising a liquid repellent treatment step of providing a liquid repellent layer on the first surface.

  8). The method of manufacturing a nozzle plate according to any one of 5 to 7, wherein the liquid discharge head is an electrostatic suction type liquid droplet discharge head.

9. A nozzle plate having nozzles for discharging liquid as droplets from the discharge holes;
A body plate having a cavity groove formed as a cavity communicating with each of the nozzles by being bonded to the nozzle plate,
The droplets are ejected and landed on the substrate by an electrostatic attraction force received from an electric field formed between the liquid in the nozzle and the substrate provided opposite to the droplet ejection surface of the nozzle plate. In the liquid discharge head,
The nozzle plate is a nozzle plate manufactured according to any one of 1 to 4 or a nozzle plate manufactured according to any one of 5 to 8;
A liquid discharge head, comprising: an electrostatic voltage applying unit that generates an electrostatic attraction force by applying an electrostatic voltage between the liquid discharged from the discharge hole and the substrate.

  10. 10. The liquid discharge head according to 9, further comprising pressure generating means for applying a pressure to the liquid in the nozzle to form a meniscus.

  According to the first aspect of the invention, since the nozzle plate is first made of glass, the following effects can be obtained. Since fine processing can be performed with high accuracy, even if there are a plurality of discharge holes with a small diameter, they can be made into holes with uniform shapes, so that the discharged droplets are aligned and high recording is achieved. Quality can be. In addition, since high rigidity is ensured compared to resin, it is difficult to cause deformation of the nozzle wall due to the pressure applied to the liquid in the nozzle when the liquid is discharged. The liquid can be discharged well. Furthermore, since the ejected liquid hardly absorbs, the volume resistivity is hardly lowered due to the absorption of the ejected liquid, so that the high volume resistivity described below can be maintained.

Further, since the volume resistivity of the glass forming the nozzle plate is 10 ¹⁵ Ω · m or more, even if the surface on which the discharge holes are formed is flat, an electric field is applied to the liquid in the nozzle to generate a strong electric field. Can be generated in the liquid around the discharge unit, and therefore, it can be used in an electrostatic suction type liquid discharge head in which minute droplets can be discharged. In addition, since the ejection surface is flat, the nozzle plate is easy to manufacture, and the nozzle is not damaged by wiping or the like when cleaning the head. Therefore, it is possible to provide a nozzle plate having a stable liquid ejection state and a long life.

  According to invention of Claim 5, in addition to being able to provide the manufacturing method of the nozzle plate which has said effect, there exists the following effect. When forming the nozzle of the nozzle plate, it is divided into two parts, a small diameter area that requires high precision and avoids damage due to processing, and a large diameter part that does not require high accuracy and damage due to processing. An appropriate processing method can be selected for each of the dry etching method around the portion and the sand blast method for the large diameter portion. Therefore, it is possible to provide a nozzle plate manufacturing method with good productivity while sufficiently securing necessary functions and accuracy.

  According to the ninth aspect of the present invention, the liquid discharge head has the nozzle plate having the above-described effects and includes the electrostatic voltage applying means, and therefore has the following effects. First, since a liquid can be discharged from a discharge hole having a uniform shape even with a plurality of minute diameters, it is possible to form a high-definition and high-quality pattern using discharged liquid droplets. In addition, since a nozzle plate with high productivity is used, a liquid discharge head with high productivity can be provided.

Further, since the nozzle plate has a volume resistivity of 10 ¹⁵ Ω · m or more, even if the surface on which the discharge holes are formed is flat, the electrostatic voltage application means can reduce the static resistance within a practical range. By applying an electric field to the liquid in the nozzle, it is possible to generate a strong electric field in the liquid around the discharge unit, so that electrostatic discharge that can efficiently discharge minute droplets is possible. A suction-type liquid discharge head can be obtained. In addition, since the ejection surface is flat, the liquid is easy to manufacture and the nozzle is not damaged by wiping during cleaning of the liquid ejection head. A discharge head can be provided.

  Hereinafter, an embodiment of a liquid discharge head according to the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view illustrating an overall configuration of a liquid ejection apparatus 1 configured using a liquid ejection head 2 which is an example of the present embodiment. The liquid discharge head 2 of FIG. 1 can be applied to various liquid discharge apparatuses such as a so-called serial method or line method.

  The liquid ejecting apparatus 1 includes a liquid ejecting head 2 on which a nozzle 10 for ejecting a droplet D of a chargeable liquid L such as ink is formed, an operation control unit 4, and an opposing surface facing the nozzle 10 of the liquid ejecting head 2. And a counter electrode 3 that has a surface and supports a substrate K that receives the landing of the droplet D on the opposite surface.

  The liquid discharge head 2 is composed of a nozzle plate 11 and a body plate 19, and is flat so that the nozzle 10 does not protrude from the discharge surface 12 facing the counter electrode 3 of the nozzle plate 11 or the nozzle 10 protrudes only about 30 μm. The head has a discharge surface (for example, see FIG. 4C described later).

  Each nozzle 10 is formed by perforating a nozzle plate 11. Each nozzle 10 has a small-diameter portion 14 having a discharge hole 13 in the discharge surface 12 of the nozzle plate 11 and a large-diameter large diameter located behind the small-diameter portion 14. A two-stage structure with the diameter portion 15 is adopted. In the liquid ejection head 2 as an example of the present embodiment, the small diameter portion 14 of the nozzle 10 is formed in a cylindrical shape, and the large diameter portion 15 is formed in a tapered shape having a circular cross section and a smaller diameter on the counter electrode 3 side. The internal diameter of the discharge hole 13 of the portion 14 (hereinafter referred to as the nozzle diameter) is 8 μm, and the internal diameter of the opening end on the side farthest from the small diameter portion 14 of the large diameter portion 15 is 100 μm. .

  Here, the manufacture of the nozzle plate 11 will be described. FIG. 2 is a diagram schematically showing a process of manufacturing the nozzle plate 11 of FIG. 1 with a sectional view, and the completed nozzle plate is shown as a nozzle plate 2-1b in FIG. 2 (b4). The manufacture of the nozzle plate 2-1b has two steps, a first step for forming the small diameter portion 2-4 and a second step for forming the large diameter portion 2-7, which will be described below. The order of the two steps may be interchanged.

The substrate 2-1 to be the nozzle plate 2-1b is made of glass having a volume resistivity of 10 ¹⁵ Ω · m or more. The volume resistivity will be described later. A glass having a volume resistivity of 10 ¹⁵ Ω · m or more is hereinafter referred to as a high resistance glass. Specific examples of the high-resistance glass material include high-purity glass materials such as quartz and synthetic quartz.

First, the formation of the small diameter portion 2-4 as the first step will be described with reference to FIG. In the present embodiment, a small-diameter portion having discharge holes is formed on a quartz substrate (approximately volume resistivity 10 ¹⁶ Ω · m) that is a high-resistance glass.

  First, a metal film 2-2 is formed on one side of the quartz substrate 2-1 as a mask by a known sputtering method. Here, examples of the metal to be used include Cr, Ni, Al, Cu, Pt, Mo, Ti, and the like. However, the metal is not limited to these, and can be used as a mask in consideration of the etching rate ratio described below. Good. The film thickness of the metal is the length (depth) of the small diameter portion formed on the quartz substrate and the etching rate ratio between the quartz and the metal film (the ratio at which the quartz and the metal film are removed, also referred to as the etching selectivity). It may be determined as appropriate. For example, when the metal film is made of Cr, the etching rate ratio is about 10 to 30. When a 10 μm deep hole is formed in a quartz substrate by etching, the thickness of the Cr film is 0 when the etching rate ratio is 20. .5 μm is sufficient. Actually, the metal and thickness to be used may be determined by conducting experiments in advance. In this embodiment, the mask is a metal film in order to improve the processing accuracy by the etching process, but a known photoresist film such as a dry film can be used.

Next, a photoresist pattern 2-3 ′ for forming the discharge hole 13 and the small diameter portion 14 is formed on the metal film 2-2 by a known photolithography technique. Next, using this photoresist pattern 2-3 ′ as a mask, the metal film 2-2 ′ patterned by removing the unmasked metal film using a known reactive dry etching method using chlorine gas is formed. Form. Thereafter, the resist pattern 2-3 ′ is removed by a known ashing method using oxygen plasma. Next, the small-diameter portion 14 of the nozzle plate 11 in FIG. 1 is formed by using a known reactive dry etching method using CF ₄ gas with the metal film 2-2 ′ patterned as described above as an etching mask. A hole 2-4 having a small diameter part deeper than a desired length (depth of the cylindrical hole) is formed (FIG. 2 (a5)). In the present embodiment, the desired length is 20 μm, which is the length of the small diameter portion 14 in FIG. 1, and the length of the hole 2-4 that becomes the small diameter portion formed in the step of forming the small diameter portion 14 is 25 μm. It is said. Finally, by removing the metal film 2-2 ′, the quartz substrate 2-1a is obtained, and the formation of the small diameter portion is completed.

  Next, formation of the large diameter portion 2-6 as the second step will be described with reference to FIG. The large diameter portion 2-6 is formed so as to communicate with the hole 2-4 using a quartz substrate 2-1a in which the hole 2-4 serving as a small diameter portion is formed. The diameter of the large-diameter portion 2-6 to be formed is larger than the diameter of the hole 2-4, and the partition wall such that interference of the pressurizing force on the liquid in the nozzle, for example, of the adjacent large-diameter portion 2-6 does not become a problem. It is preferable that the diameter has a thickness that can ensure strength, and when there are a plurality of holes 2-4 serving as a small diameter portion, the diameter may be appropriately determined in consideration of the pitch.

  First, the large-diameter portion 2-6 is provided on the surface opposite to the surface provided with the hole 2-4 serving as the small-diameter portion of the quartz substrate 2-1a by a known photolithography technique (resist coating, exposure, development). A photoresist pattern 2-5 ′ is formed (FIG. 2B2). Next, using the photoresist pattern 2-5 'as a mask, a hole is formed using the sandblast method so that the large diameter portion 2-6 has a desired depth. As a result, by setting the length of the hole 2-4 to be the small diameter portion to be a desired length or more, the large diameter portion 2-6 and the small diameter portion are formed when the large diameter portion 2-6 is formed to a desired depth. The hole 2-4 penetrates and a desired nozzle is completed (FIG. 2 (b3)). Finally, by removing the photoresist pattern 2-5 ', the nozzle plate 2-1b is completed (FIG. 2 (b4)).

Here, the desired length of the small diameter portion is 20 μm in this embodiment, and this length is also the thickness of the bottom of the hole of the large diameter portion 2-6. Therefore, when forming this large diameter part 2-6 using the sand blast method which processes with a micro spray particle, a micro crack may arise in this bottom part, and the fall of a yield may be caused. On the other hand, the formation of the large-diameter portion 2-6 by the sand blasting method is made to a thickness at which the occurrence of minute cracks is not a concern, and thereafter, a desired reactive dry etching method using CF ₄ gas is used to obtain a desired thickness. The depth is preferred.

  The formation of the large-diameter portion 2-6 is difficult to form a deep hole because there is no mask material having the required etching rate ratio, and the processing time is very long because the etching rate of the glass is slow. Therefore, the above dry etching method, which excels at precise processing, cannot be handled.

  Here, as described above, the order of the first step for forming the discharge hole 2-4 serving as the small diameter portion and the second step for forming the large diameter portion 2-6 may be interchanged. That is, first, as shown in FIG. 3C, the large-diameter portion 2-6 is formed on the quartz substrate 2-1 using the same sand blasting method or the sand blasting method as described above, and then using the dry etching method (FIG. 3C4). ). Next, as shown in FIG. 3 (D), a hole 2-4 having a small diameter is formed in a quartz substrate 2-1c having a large diameter by using the same dry etching method as described above, and a hole longer than a desired length is formed. What is necessary is just to form.

  After completion of nozzle processing on the quartz substrate, a liquid repellent layer is provided on the surface of the quartz substrate on which the discharge holes are formed, and then separated into individual nozzle plates using a dicer or the like.

  In actual processing, if a quartz substrate, for example, a silicon or glass substrate, is used as a base plate, workability is fixed on the base plate using grease or an adhesive whose adhesiveness is relatively weak such as grease. Is preferable. As a specific example of the temporary fixing method, for example, heat conductive grease such as cool grease (trade name) or a heat conductive adhesive sheet may be used.

  Here, the liquid repellent layer will be described. A liquid repellent layer 28 is preferably provided on the surface of the nozzle plate 11 shown in FIG. By providing the liquid repellent layer 28, it is possible to prevent the liquid L from seeping out and spreading due to the liquid L becoming familiar with the discharge surface 12 from the discharge hole 13. Specifically, for example, if the liquid L is aqueous, a material having water repellency is used, and if the liquid L is oily, a material having oil repellency is used, but in general, FEP (ethylene tetrafluoride, hexafluoroethylene) is used. Fluorine resin such as propylene fluoride), PTFE (polytetrafluoroethylene), fluorine siloxane, fluoroalkylsilane, and amorphous perfluoro resin is often used, and is formed on the discharge surface 12 by a method such as coating or vapor deposition. Yes. The thickness of the film is not particularly limited, but is preferably about 0.1 μm to 3 μm.

  The liquid repellent layer 28 may be formed directly on the ejection surface 12 of the nozzle plate 11 or may be formed through an intermediate layer in order to improve the adhesion of the liquid repellent layer 28. . The liquid repellent layer 28 of the nozzle plate 11 shown in FIG. 1 as an example of this embodiment is made of tetrafluoroethylene having a thickness of 0.2 μm.

  In addition, the shape of the nozzle 10 of the nozzle plate 11 is not limited to the shape shown in FIGS. 1 and 2, and for example, various nozzles 10 having different shapes are used as shown in FIGS. Is possible. Further, the nozzle 10 may have a polygonal cross-section, a cross-sectional star shape, or the like instead of forming a circular cross-section. In addition, when the cross-sectional shape is not a circle, for example, the larger diameter than the small diameter means that the cross-sectional area of the large-diameter portion is replaced with a circle with the same area from the diameter when the cross-sectional area of the small-diameter portion is replaced with a circle with the same area. The case diameter is large.

  Next, as shown in FIG. 1, the surface of the completed nozzle plate 11 joined to the body plate 19 and the inner peripheral surface 17 of the large-diameter portion 15 are arranged in a nozzle made of a conductive material such as NiP, Pt, or Au. A charging electrode 16 serving as an electrostatic voltage applying means for charging the liquid L is provided in a layered manner. By providing the charging electrode 16 in a layered manner in this way, the single charging electrode 16 comes into contact with the liquid in all the large diameter portions 15 on the nozzle plate, and charging is performed from the electrostatic voltage source 18. When an electrostatic voltage is applied to the electrode 16, the liquid L in all the large diameter portions 15 is simultaneously charged, and between the liquid ejection head 2 and the counter electrode 3, in particular, between the liquid L and the substrate K. An electrostatic attractive force can be generated.

  The method for providing the charging electrode 16 is not particularly limited, and a known vacuum deposition method, sputtering method, or the like may be used. Moreover, what is necessary is just to select suitably as a conductive material what does not produce corrosion etc. by contact | connecting a liquid.

  A body plate 19 made of silicon is provided behind the charging electrode 16 of the liquid discharge head 2 shown in FIG. A portion of the body plate 19 facing the opening end of the large diameter portion 15 of each nozzle 10 is formed with a substantially cylindrical space having an inner diameter substantially equal to the opening end, and each space is a liquid to be discharged. The cavity 20 is used for temporarily storing L.

  In the body plate 19, a flow path (not shown) for supplying the liquid L to the cavity 20 is formed. Specifically, the cavity 20, the common flow path, and the flow path connecting the common flow path and the cavity 20 can be provided on the silicon substrate using a known photolithography technique and etching technique.

  A supply pipe (not shown) that supplies the liquid L from an external liquid tank (not shown) communicates with the common flow path, and is supplied by a supply pump (not shown) provided in the supply pipe or by a differential pressure depending on the position of the liquid tank. A predetermined supply pressure is applied to the liquid L such as the passage, the cavity 20 and the nozzle 10.

  Piezo elements 22 that are piezoelectric element actuators as pressure generating means are provided on the back surface portions corresponding to the respective cavities 20, and a drive voltage is applied to the piezo elements 22 to the piezo elements 22. A driving voltage power supply 23 for deforming the is connected. 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 in the discharge hole 13 of the nozzle 10. . Here, as described above, the liquid repellent layer 28 is provided on the flat discharge surface where the discharge hole 13 exists, so that the liquid meniscus formed in the discharge hole 13 portion of the nozzle is surrounded by the discharge hole 13. It is possible to effectively prevent a reduction in electric field concentration on the meniscus tip due to spreading on the discharge surface 12. In addition to the piezoelectric element actuator as in the present embodiment, for example, an electrostatic actuator, a thermal method, or the like can be adopted as the pressure generating means.

  The drive voltage power supply 23 and the electrostatic voltage power supply 18 that applies an electrostatic voltage to the charging electrode 16 are connected to the operation control means 4, respectively, and are controlled by the operation control means 4.

  In this embodiment, the operation control means 4 is composed of a computer in which a CPU 25, a ROM 26, a RAM 27, and the like are connected by a BUS (not shown). The CPU 25 is based on a power control program stored in the ROM 26. The power supply 18 and each drive voltage power supply 23 are driven to discharge the liquid L from the discharge hole 13 of the nozzle 10.

  Below the liquid discharge head 2, a plate-like counter electrode 3 that supports the substrate K is disposed in parallel to the discharge surface 12 of the liquid discharge head 2 and separated 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 mm.

  In the present embodiment, 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 source 18 to the charging electrode 16, an electric field is generated between the liquid L in the ejection hole 13 of the nozzle 10 and the opposing surface of the counter electrode 3 facing the liquid ejection head 2. Has come to occur. When the charged droplet D 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. The droplets D discharged from each nozzle 10 can be landed on the surface of the substrate K at an arbitrary position.

The liquid L discharged by the liquid discharge apparatus 1 is, for example, water, COCl ₂ , HBr, HNO ₃ , H ₃ PO ₄ , H ₂ SO ₄ , SOCl ₂ , SO ₂ Cl ₂ , or FSO ₃ H as an inorganic liquid. Etc.

  Examples of the organic liquid include methanol, n-propanol, isopropanol, n-butanol, 2-methyl-1-propanol, tert-butanol, 4-methyl-2-pentanol, benzyl alcohol, α-terpineol, ethylene glycol, Alcohols such as glycerin, diethylene glycol and triethylene glycol; phenols such as phenol, o-cresol, m-cresol and p-cresol; dioxane, furfural, ethylene glycol dimethyl ether, methyl cellosolve, ethyl cellosolve, butyl cellosolve, ethyl carbitol, Ethers such as butyl carbitol, butyl carbitol acetate, epichlorohydrin; acetone, methyl ethyl ketone, 2-methyl-4-pentanone, Ketones such as tophenone; fatty acids such as formic acid, acetic acid, dichloroacetic acid, trichloroacetic acid; methyl formate, ethyl formate, methyl acetate, ethyl acetate, acetic acid-n-butyl, isobutyl acetate, acetic acid-3-methoxybutyl, acetic acid- n-pentyl, ethyl propionate, ethyl lactate, methyl benzoate, diethyl malonate, dimethyl phthalate, diethyl phthalate, diethyl carbonate, ethylene carbonate, propylene carbonate, cellosolve acetate, butyl carbitol acetate, ethyl acetoacetate, cyanoacetic acid Esters such as methyl and ethyl cyanoacetate; nitromethane, nitrobenzene, acetonitrile, propionitrile, succinonitrile, valeronitrile, benzonitrile, ethylamine, diethylamine, ethylenediamine, aniline, N-methylanily , N, N-dimethylaniline, o-toluidine, p-toluidine, piperidine, pyridine, α-picoline, 2,6-lutidine, quinoline, propylenediamine, formamide, N-methylformamide, N, N-dimethylformamide, Nitrogen-containing compounds such as N, N-diethylformamide, acetamide, N-methylacetamide, N-methylpropionamide, N, N, N ′, N′-tetramethylurea, N-methylpyrrolidone; dimethyl sulfoxide, sulfolane, etc. Sulfur-containing compounds: benzene, p-cymene, naphthalene, cyclohexylbenzene, cyclohexene and other hydrocarbons; 1,1-dichloroethane, 1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,1, 2-tetrachloroethane, 1,1,2,2-te Lachloroethane, pentachloroethane, 1,2-dichloroethylene (cis-), tetrachloroethylene, 2-chlorobutane, 1-chloro-2-methylpropane, 2-chloro-2-methylpropane, bromomethane, tribromomethane, 1-bromopropane And halogenated hydrocarbons. Two or more of the above liquids may be mixed and used.

  Furthermore, when using a conductive paste containing a large amount of high electrical conductivity substance (silver powder or the like) as the liquid L and performing discharge, the above-mentioned substance dissolved or dispersed in the liquid L is as follows: Except for coarse particles that cause clogging in the nozzle 10, there is no particular limitation.

  Here, the discharge principle of the liquid L in the liquid discharge head 2 is demonstrated using the liquid discharge apparatus 1 which FIG. 1 shows.

  In the liquid ejection device 1, an electrostatic voltage is applied from the electrostatic voltage power supply 18 to the charging electrode 16 that is an electrostatic voltage application unit for the liquid L, and the liquid L in the ejection hole 13 of the nozzle 10 and the liquid ejection of the counter electrode 3 are performed. An electric field is generated between the facing surface facing the 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 in the discharge hole 13 of the nozzle 10 with the pressure generated in the liquid L.

  When the insulating property of the nozzle plate 11 is increased as in the present embodiment, as shown by the equipotential line 4-1 by simulation in FIG. The equipotential lines 4-1 are arranged, and a strong electric field is generated toward the liquid L in the small diameter portion 14 of the nozzle 10 and the meniscus portion of the liquid L.

  In particular, as can be seen from the fact that the equipotential lines 4-1 are dense at the tip of the meniscus in FIG. 5, 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 D. Further, the droplet D 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 D attempts to land closer by the action of electrostatic force, the angle at the time of landing on the base material K is stabilized and accurately performed.

The inventors configured the electric field strength of the electric field between the electrodes to be a practical value of 1.5 kV / mm using the liquid discharge apparatus 1 ′ shown in FIG. In an experiment conducted by forming the plate 11 ′ and based on the following experimental conditions, there were cases where the droplet D ′ was ejected from the nozzle 10 ′ and sometimes was not ejected.
[Experimental conditions]
Distance between discharge surface 12 'of nozzle plate 11' and facing surface of counter electrode 3 ': 1.0 mm
Nozzle plate 11 'thickness: 125 μm
Nozzle diameter: 10 μm
Electrostatic voltage: 1.5 kV
Drive voltage: 20V
The nozzle 10 ′ of the liquid discharge head 2 ′ used in the experiment has a taper angle of 4 °. The taper angle indicates an angle that spreads in a direction away from the discharge surface 12 ′ from a perpendicular to the discharge surface 12 ′ in the cross section of the nozzle 10 ′.

In the experiment using the liquid discharge apparatus 1 ′, the electric field strength at the tip of the meniscus was obtained for all cases where the droplet D ′ was stably discharged from the nozzle. Actually, since it is difficult to directly measure the electric field strength at the tip of the meniscus, the electric field simulation software “PHOTO-VOLT” (trade name, manufactured by Photon Co., Ltd.) was used for calculation. The electric field strength here refers to the electric field strength 300 seconds after voltage application in the current distribution analysis mode. As a result, in all cases, the electric field strength at the meniscus tip was 1.5 × 10 ⁷ V / m or more. In this experiment, even when the droplet D ′ was not stably ejected from the nozzle, the electric field strength at the meniscus tip was calculated by the same simulation as described above. As a result, it was less than 1.5 × 10 ⁷ V / m.

Further, as a result of calculating the electric field strength at the meniscus tip by inputting the same parameters as the above experimental conditions into the software, as shown in FIG. 7, the electric field strength is the volume resistance of the insulator used for the nozzle plate 11 ′. It turned out to be strongly dependent on the rate. Moreover, in order to stably discharge the droplet D ′ from the nozzle 10 ′, it is obtained from the above experiment that the electric field strength at the tip of the meniscus needs to be 1.5 × 10 ⁷ V / m or more. Therefore, as apparent from FIG. 7, it was found that the volume resistivity of the nozzle plate 11 ′ should be 10 ¹⁵ Ω · m or more.

  The relationship between the volume resistivity of the nozzle plate 11 ′ and the electric field intensity at the tip of the meniscus becomes a characteristic relationship as shown in FIG. 7 because an electrostatic voltage is applied when the volume resistivity of the nozzle plate 11 ′ is low. Even in this case, the equipotential lines in the nozzle plate 11 ′ are not aligned in the direction substantially perpendicular to the ejection surface 12 as shown in FIG. 5, but the liquid L ′ and liquid L in the nozzle 10 ′ are not aligned. This is probably because the electric field is not sufficiently concentrated on the meniscus.

Theoretically, even if the nozzle plate 11 ′ has a volume resistivity of less than 10 ¹⁵ Ω · m, there is a possibility that the droplet D ′ is ejected from the nozzle 10 ′ if the electrostatic voltage is made very large. Since the substrate K ′ may be damaged due to the occurrence of sparks, it is not preferable to increase the electrostatic voltage very much.

The characteristic relationship between the electric field strength at the tip of the meniscus and the volume resistivity of the nozzle plate 11 ′ as shown in FIG. 7 can be obtained in the same way even when simulation is performed with various nozzle diameters. In all cases, it is known that the electric field strength at the meniscus tip is 1.5 × 10 ⁷ V / m or more when the volume resistivity is 10 ¹⁵ Ω · m or more.

On the other hand, even if the nozzle plate 11 ′ is manufactured using an insulator having a volume resistivity of 10 ¹⁵ Ω · m or more, the droplet D ′ may not be discharged from the nozzle 10 ′. As shown in Table 1, which is the result of experiments conducted by the inventors, when a liquid containing a conductive solvent such as water is used as the liquid L ′, the liquid absorption rate of the nozzle plate 11 ′ is 0.6%. It turns out that it is necessary to:

  The experiment of Table 1 will be described below. Whether or not the nozzle plate 11 ′ of the liquid discharge head 2 ′ shown in FIG. 6 is actually manufactured using various materials shown in Table 1 and the droplet D ′ is discharged from the discharge hole 13 ′ of the nozzle 10 ′. Is ejected onto the substrate K ′, and in Table 1, the case where it was ejected is indicated by “◯”, and the case where it was not possible is denoted by “X”.

  There are three types of liquid L ′ to be ejected: two types of conductive liquid and one type of insulating liquid. Liquid L1 was prepared as a conductive liquid containing 52% by mass of water, 22% by mass of ethylene glycol and propylene glycol, 3% by mass of dye (CI Acid Red 1), and 1% by mass of surfactant. The liquid L3 was prepared as a liquid in which Ag particles were dispersed in tetradecane and charged particles were dispersed in an insulating solvent.

  The volume resistivity was calculated from the electrical resistance value when voltage was applied between the surfaces of the sheet-like object to be measured in accordance with JISC2151. In addition, the liquid absorption rate of the nozzle plate 11 ′ is determined by immersing the nozzle plate 11 ′ or a substitute sheet-like object to be measured in the liquid L ′ to be used at 23 ° C. for 24 hours. It was calculated from the mass change rate of the object to be measured. When the liquid L ′ is a water-soluble ink, it is possible to substitute a water absorption rate according to ASTM D570.

  The experimental results for the liquids L1 to L3 are as shown in Table 1 above. In the column of absorption rate in Table 1, the upper row represents the absorption rate for water (water absorption rate), and the lower row represents the absorption rate for ethanol. “Yes” after the presence or absence of ejection indicates a case where a liquid absorption prevention layer is provided, and “No” indicates a case where no liquid absorption prevention layer is provided. Here, FIG. 8 shows an example in which the liquid absorption preventing layer 8-1 is provided on the nozzle plate 11 'of FIG. The liquid absorption preventing layer 8-1 is provided to prevent the volume resistivity from being lowered by the liquid being absorbed from the inner peripheral surface of the nozzle made of a material whose absorption rate is not 0.6% or less. Yes.

From the results shown in Table 1, when a conductive solvent is contained as in the liquid L1 or the liquid L2, the material having a volume resistivity of less than 10 ¹⁵ Ω · m is used for the liquid L ′ from the nozzle 10 ′ even if the liquid absorption is low. It can be seen that is not discharged. This shows the same result as that of the above simulation. In addition, it is understood that the liquid L can be discharged from the nozzle 10 ′ if the volume resistivity is 10 ¹⁵ Ω · m or more, but the liquid L is not discharged unless the absorption rate is at least 0.6%.

Further, when discharging a liquid in which particles that can be charged in an insulating solvent are discharged, such as the liquid L3, the liquid is discharged from the nozzle 10 'as long as the volume resistivity is 10 ¹⁵ Ω · m or more. I know you get.

  The above results are considered as follows. First, when the nozzle plate 11 ′ absorbs the conductive solvent from the liquid L ′, molecules such as water molecules that are a conductive liquid exist in the nozzle plate 11 ′ that is inherently insulating. In addition, the electrical conductivity of the nozzle plate 11 ′ is increased, the value of the effective volume resistivity at the local portion in contact with the liquid L ′ is decreased, the electric field strength at the meniscus tip is weakened according to the relationship shown in FIG. This is thought to be because the electric field concentration necessary for 'discharge' cannot be obtained.

When a liquid in which particles that can be charged are dispersed in an insulating solvent is used like the liquid L3 in Table 1, the nozzle plate 11 ′ has a volume resistivity of 10 ¹⁵ regardless of the absorption rate of the liquid. It was found that the liquid L is ejected when Ω · m or more. This is because even if the insulating solvent is absorbed in the nozzle plate 11 ′, the electric conductivity of the insulating solvent is low, so that the electric conductivity of the nozzle plate 11 ′ does not change greatly, and the effective volume resistivity does not decrease. This is probably because of this.

Note that the chargeable particles dispersed in the insulating solvent, such as the Ag particles of the solution L3, are not absorbed by the nozzle plate 11 ′ even if they are metal particles having extremely high electrical conductivity. It does not increase the electrical conductivity of 11 '. Note that the above insulating solvent means a solvent that is not discharged by an electrostatic attraction alone, and specifically includes xylene, toluene, tetradecane, and the like. Further, the conductive solvent means a solvent having an electric conductivity of 10 ⁻¹⁰ S / cm or more.

Here, the nozzle plate 11 ′ of this embodiment uses quartz, which is a high-resistance glass having a volume resistivity of about 1.0 × 10 ¹⁶ Ω · m. In addition, since quartz hardly absorbs liquid, it is not necessary to consider a decrease in electrical conductivity due to liquid to be discharged. Therefore, the liquid to be discharged is a case where an inorganic liquid such as the liquid L1, the liquid L2, and the liquid L3, an organic liquid, or a solution containing a large amount of a substance having high electrical conductivity (such as silver powder) is used. However, the volume resistivity of 1.0 × 10 ¹⁵ Ω · m or more necessary for ejection is maintained, and stable liquid ejection can always be achieved.

  Further, in a simulation using a nozzle having steps such as a small diameter portion and a large diameter portion, such as the nozzle plate 11 as an example of the present embodiment, as a parameter for setting the thickness of the nozzle plate 11 to 10 μm, 20 μm, 50 μm, and 100 μm. FIG. 9 shows the electric field strength at the tip of the meniscus when the nozzle diameter is changed. The length of the small diameter part at this time is 10 μm.

  FIG. 9 shows that the electric field strength at the meniscus tip increases as the nozzle diameter decreases and the nozzle plate increases in thickness.

In order to stably discharge the droplet D from the nozzle 10, the electric field strength at the tip of the meniscus needs to be 1.5 × 10 ⁷ V / m or more. For example, when the thickness of the nozzle plate is 10 μm Can stably discharge the droplet D by setting the nozzle diameter to less than 2 μm. Further, for example, when the nozzle plate thickness is 20 μm, the nozzle diameter is less than 3 μm, the nozzle plate thickness is 50 μm, the nozzle diameter is less than 5 μm, and the nozzle plate thickness is 100 μm, By making the nozzle diameter less than 7 μm, the droplet D can be stably discharged.

  Further, FIG. 10 shows the electric field strength at the tip of the meniscus when the nozzle diameter is changed as a parameter for setting the length of the small diameter portion 14 to 5 μm, 10 μm, 15 μm, and 20 μm. The thickness of the nozzle plate 11 at this time is 100 μm. FIG. 10 shows that the electric field strength at the meniscus tip increases as the nozzle diameter decreases and the length of the small diameter increases.

In order to stably discharge the droplets D from the nozzle 10, the electric field strength at the meniscus tip needs to be 1.5 × 10 ⁷ V / m or more as described above, so the length of the small diameter portion is set to 5 μm. In this case, the droplet D can be stably discharged by setting the nozzle diameter to less than 6 μm. Furthermore, for example, when the small diameter portion is 10 μm, the nozzle diameter is less than 7 μm, when the small diameter portion is 15 μm, when the nozzle diameter is less than 8 μm, and when the small diameter portion is 20 μm, the nozzle diameter is When the thickness is less than 9 μm, the droplet D can be stably discharged.

  Therefore, the length of the small-diameter portion of the nozzle and the thickness of the nozzle plate may be appropriately determined based on the simulation results in FIGS. 9 and 10 described above.

  In the simulations in FIGS. 9 and 10, the nozzle hole angle is set to 5 °. However, the influence of the angle of the tip of the nozzle hole is small, and the dependence on the conditions for stably discharging the droplets is not large. .

  Next, driving of the liquid discharge head 2 of the present embodiment will be described with reference to FIGS. The operation control means 4 of the liquid ejection apparatus 1 applies a constant electrostatic voltage Vc from the electrostatic voltage power supply 18 to the charging electrode 16. As a result, a constant electrostatic voltage Vc is always applied to each nozzle 10 of the liquid ejection head 2, and an electric field is generated between the liquid ejection head 2 and the counter electrode 3.

  Further, the operation control means 4 applies a pulsed drive voltage Vd to the piezo element 22 from the drive voltage power supply 23 corresponding to the nozzle 10 for each nozzle 10 to which the droplet D is to be ejected. When such a driving voltage Vd is applied, the piezo element 22 is deformed to increase the pressure of the liquid L inside the nozzle, and the meniscus starts to rise from the state of FIG. As shown in FIG. 11B, the meniscus is greatly raised.

  Then, as described above, a high electric field concentration occurs at the meniscus tip and the electric field strength becomes very strong, and a strong electrostatic force is applied to the meniscus from the electric field formed by the electrostatic voltage Vc. The meniscus is torn off as shown in FIG. 11C by the suction by the strong electrostatic force and the pressure by the piezo element 22 to form a droplet D. The droplet D is accelerated by an electric field, sucked in the direction of the counter electrode, and lands on the substrate K supported by the counter electrode 3.

  At that time, although air resistance or the like is applied to the droplet D, as described above, since the droplet D attempts to land closer due to the action of electrostatic force, the landing direction with respect to the substrate K is not blurred. It is stable and landed on the substrate K accurately.

  In the liquid ejection device 1, the constant electrostatic voltage Vc applied to the charging electrode 16 from the electrostatic voltage power supply 18 is set to 1.5 kV, and the pulse voltage applied from the drive voltage power supply 23 to the piezo element 22 is set. The drive voltage Vd is set to 20V.

  As described above, according to the liquid ejection head 2 of the present embodiment, the liquid ejection head 2 is a head having a flat ejection surface 12 and is not shown in the drawings, but when cleaning the liquid ejection head 2 Even if a member such as a blade or a wiper comes into contact with the discharge surface 12, the nozzle 10 is not damaged, and the operability is excellent.

  In addition, since it is not necessary to form a fine structure such as the protrusion of the nozzle 10 in the manufacture of the liquid discharge head 2, the structure is simple, so that it can be easily manufactured and the productivity is excellent.

Further, since the nozzle plate 11 on which the nozzles 10 are formed is made of high resistance glass, even if the electrostatic voltage applied to the charging electrode 16 is a low voltage of about 1.5 kV, the piezoelectric element 22 is deformed. The electric field can be concentrated on the meniscus of the liquid L formed in the discharge hole portion of the nozzle 10, and the electric field strength at the tip of the meniscus is 1.5 × 10 ⁷ V / m at which the droplet D is stably discharged. This is possible. Further, since the nozzle plate made of glass has a higher rigidity than that of the resin, the deformation of the piezo element 22 when the liquid is discharged causes the deformation of the nozzle wall due to the pressure applied to the liquid in the nozzle. Since the pressure loss is small, the liquid can be efficiently discharged without causing a decrease in the discharge speed.

  As described above, the liquid discharge head 2 of the present embodiment is a flat head, but can effectively cause electric field concentration similar to that of the head from which the nozzle protrudes at the tip of the meniscus. Even when an electrostatic voltage is applied, the liquid can be discharged efficiently and accurately.

  In this embodiment, the meniscus formed by deformation of the piezo element 22 is separated into droplets by electrostatic attraction force, accelerated by an electric field by the electrostatic voltage Vc, and landed on the substrate K. In addition, by adopting a configuration in which an electrostatic voltage can be selectively applied to each nozzle, the electrostatic voltage is not applied to the charging electrode of the non-ejection nozzle, and only the charging electrode of the ejection nozzle is static. Applying a constant bias voltage that does not lead to discharge to the charging electrodes of all nozzles as a method of applying an electric voltage or a configuration that can selectively apply an electrostatic voltage to each nozzle, and discharging only to the nozzles that discharge A method may be used in which discharge is performed by superimposing possible voltages.

  Further, in the present embodiment, the case where the pressure generating means is the piezo element 22 has been described. However, the pressure generating means only needs to have this function. Besides this, for example, the inside of the nozzle 10 or the cavity 20 is used. It is also possible to generate bubbles by heating the liquid L and use the pressure.

  In the liquid ejection apparatus 1 using the liquid ejection head 2 of the present embodiment, the case where the counter electrode 3 is grounded has been described. For example, a voltage is applied to the counter electrode 3 from a power source, and the charging electrode 16 and It is also possible to configure the power supply to be controlled by the operation control means 4 so that the potential difference becomes a predetermined potential difference such as 1.5 kV.

  An example in which a nozzle plate is manufactured and used for a liquid discharge head will be described below.

Example 1
In this embodiment, a nozzle plate having a nozzle diameter of 8 μm, a small diameter portion of the nozzle of 20 μm, and a nozzle plate thickness of 150 μm will be described in detail with reference to FIG.

First, the base material was a quartz glass substrate (thickness 150 μm, diameter 76 mm, manufacturer nominal volume resistance value 10 ¹⁶ Ω · m). Next, an Al film 2-2 having a thickness of 1 μm was formed on one side of the quartz substrate 2-1 by a known sputtering method. In this embodiment, the etching rate ratio between quartz and the Al film was set to 30 based on experiments performed in advance.

Next, a photoresist pattern 2-3 ′ for forming discharge holes and small diameter portions was formed on the Al film by a known photolithography technique. Next, using this photoresist pattern 2-3 ′ as a mask, the unmasked Al film is removed by using a known reactive dry etching method using chlorine gas to form a patterned Cr film 2-2 ′. Formed. Thereafter, the resist pattern 2-3 ′ was removed by a known ashing method using oxygen plasma. Next, a desired length (cylindrical shape) of the small-diameter portion 14 is formed by using a well-known reactive dry etching method using CF ₄ gas with the Al film 2-2 ′ patterned as described above as a mask for etching processing. The hole 2-4 having a small diameter portion of about 25 μm deeper than 20 μm was formed (FIG. 2 (a5)). Finally, the quartz film 2-1a was obtained by removing the Al film 2-2 ′ (FIG. 2 (a6)).

Next, the large-diameter portion 2-6 was formed so as to communicate with the hole 2-4 substantially concentrically using the quartz substrate 2-1a. The diameter of the large diameter portion 2-6 to be formed was 100 μm. First, a large-diameter portion is formed on a surface opposite to the surface provided with the hole 2-4 serving as the small-diameter portion 15 of the quartz substrate 2-1a by a known photolithography technique (exposure and development) using a dry film resist having a thickness of 50 μm. A photoresist pattern 2-5 ′ for providing 2-7 was formed (FIG. 2B2). Next, using the photoresist pattern 2-5 ′ as a mask, a hole was formed using a sandblast method so that the large diameter portion 2-6 had a depth of 100 μm. Thereafter, a hole is further formed by about 30 μm using a known reactive dry etching method using CF ₄ gas to form a desired diameter 130 μm large diameter part 2-7. As a result, the small diameter part and the large diameter part are formed. The part is in a penetrating state (FIG. 2 (b3)). Finally, the photoresist pattern 2-5 ′ was removed to complete the nozzle plate 2-1c (FIG. 2 (b4)).

  Next, a NiP film having a thickness of about 0.3 μm is provided as a charging electrode 16 on the inner peripheral surface 17 of the large-diameter portion 15 by known sputtering. Further, tetrafluoride is formed on the surface having the discharge holes 2-4 by vacuum deposition. A liquid repellent layer having a thickness of 0.2 μm of ethylene was formed and separated into individual nozzle plates using a dicer.

  Next, a body plate was manufactured. Using a silicon substrate, using known photolithography techniques (resist coating, exposure, development) and anisotropic dry etching techniques, cavity grooves that form a plurality of cavities that respectively communicate with the nozzles, and a plurality of cavities that respectively communicate with the cavities An ink supply groove serving as an ink supply path, a common ink chamber groove serving as a common ink chamber communicating with the ink supply, and an ink supply port were formed.

  Next, as shown in FIG. 1, the nozzle plate and the body plate prepared so far are bonded together using an adhesive, and a piezoelectric element 22 that is a pressure generating means is attached to the back surface of each cavity 20 of the body plate 19. The droplet discharge head 2 was attached. The droplet discharge head 2 is installed at a position facing the counter electrode 3 as in the liquid discharge apparatus 1 shown in FIG. 1, and each piezo element 22 and each drive voltage power source 23, electrostatic voltage power source 18 and charging electrode. 16, the drive voltage power supply 23 and the electrostatic voltage power supply 18 and the operation control means 4 are connected to form the liquid ejection apparatus 1. The counter electrode 3 and the negative terminal of the electrostatic voltage power source 18 were grounded.

  The electrostatic voltage Vc applied from the electrostatic voltage power supply 18 is 1.5 kV, the drive voltage Vd from each drive voltage power supply 23 supplied to each piezo element 22 is 20 V, and the liquids to be discharged are the liquid L1 and the liquid L2 described above. When the droplet discharge head 2 was operated as the liquid L3, it was confirmed that stable discharge was possible.

(Example 2)
The electric field strength at the tip of the meniscus shown in FIG. 9 and FIG. 10 obtained by simulation of the nozzle diameter, the length of the small diameter portion of the nozzle, and the thickness of the nozzle plate is 1.5 × 10 ⁷ V / m or more. Nozzle plates varied according to conditions were manufactured, and after that, a liquid ejection apparatus having the same conditions as in Example 1 was configured, and the presence or absence of ejection of the liquid L1 was ejected onto the substrate K and confirmed. In addition, a nozzle plate having an electric field strength of less than 1.5 × 10 ⁷ V / m was also manufactured for reference, and whether or not the liquid L1 was discharged was discharged onto the substrate K and confirmed. The results of the experiment are shown in Table 2.

  In Table 2, a mark ◯ indicating the liquid discharge state indicates that a stable discharge state was confirmed by applying an electrostatic voltage of 1.5 kV. In addition, the Δ mark indicating the liquid discharge state indicates that the discharge of droplets could not be confirmed by applying an electrostatic voltage of 1.5 kV, but the discharge was confirmed by applying a higher voltage. Yes.

From the results of Table 2, from the liquid discharge head having the nozzle plate that satisfies the conditions of the nozzle diameter, the length of the small diameter portion of the nozzle, and the nozzle plate thickness, the electric field strength is 1.5 × 10 ⁷ V / m or more by simulation. In all cases, stable droplet ejection was confirmed. On the other hand, in a liquid discharge head having a nozzle plate with an electric field strength of less than 1.5 × 10 ⁷ V / m, droplet discharge is not confirmed at the same applied voltage as in the simulation. However, it was necessary to apply a higher voltage.

  From these things, it turns out that the result by simulation is the same result as the discharge experiment result by an actual machine.

1 is a diagram illustrating a cross section of a liquid discharge head according to an embodiment and an overall configuration of a liquid discharge apparatus. It is a figure explaining an example of the manufacturing process of the nozzle plate in this embodiment with a sectional view. It is a figure explaining an example of the manufacturing process of the nozzle plate in this embodiment with a sectional view. It is a figure which shows the modification of the nozzle from which a shape differs in sectional drawing. It is a figure which shows typically the electric potential distribution of the discharge hole vicinity of the nozzle by simulation. It is a figure which shows the whole structure of the liquid discharge apparatus which experimented with the actual machine. It is a figure which shows the relationship between the volume resistivity of a nozzle plate, and the electric field strength of a meniscus front-end | tip part. It is a figure which shows the cross section of the example of the nozzle plate which provided the liquid absorption prevention layer. It is a figure which shows the relationship between the nozzle diameter and the electric field strength of a meniscus front-end | tip part by making the thickness of a nozzle plate into a parameter. It is a figure which shows the relationship between a nozzle diameter and the electric field strength of a meniscus front-end | tip part by making the length of the small diameter part of a nozzle into a parameter. It is a figure explaining the drive example of the liquid discharge head of an example shown in this Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid discharge apparatus 2 Liquid discharge head 3 Counter electrode 4 Operation control means 10 Nozzle 11 Nozzle plate 12 Discharge surface 13 Discharge hole 14 Small diameter part 15 Large diameter part 16 Charging electrode 17 Inner peripheral surface of large diameter part 18 Electrostatic voltage power supply 19 Body plate 20 Cavity 22 Piezo element 23 Drive voltage power supply 25 CPU
26 ROM
27 RAM
28 Liquid repellent layer D Droplet K Base material L Liquid

Claims (10)

In a nozzle plate that has a nozzle that discharges liquid as droplets from a discharge hole and is used in a liquid discharge head,
It consists of glass with a volume resistivity of 10 ¹⁵ Ω · m or more,
The first surface on which the discharge holes of the nozzle are formed is flat,
A nozzle plate comprising: a small-diameter portion having one of the discharge holes as an opening; and a large-diameter portion having an opening in a second surface opposite to the first surface through the other opening of the small-diameter portion. . The nozzle plate according to claim 1, wherein a diameter of the large diameter portion is larger than a diameter of the small diameter portion. The nozzle plate according to claim 1, wherein a liquid repellent layer is provided on the first surface. The nozzle plate according to claim 1, wherein the liquid discharge head is an electrostatic suction type liquid discharge head. In a method of manufacturing a nozzle plate having a nozzle that discharges liquid as droplets from a discharge hole and used in a liquid discharge head,
A glass substrate having a volume resistivity of 10 ¹⁵ Ω · m or more, the first surface of the glass substrate and the first surface through the small diameter portion having the discharge hole as one opening and the other opening of the small diameter portion Forming the nozzle composed of a large-diameter portion having an opening on the second surface opposite to the second surface,
Performing a photolithography process on the first surface of the glass substrate to form a pattern mask for the ejection holes;
Performing a dry etching process using the pattern mask of the discharge holes to form a small diameter portion longer than a desired length of the small diameter portion, and a first step including:
Forming a pattern mask of the large diameter portion on a second surface opposite to the first surface by photolithography,
A step of forming the large-diameter portion having a desired length by a dry etching method in addition to the sand blasting method or the sand blasting method using the pattern mask of the large-diameter portion. The manufacturing method of the nozzle plate. The first step includes
Providing a metal film on the first surface of the glass substrate;
Performing a photolithography process and an etching process on the metal film to form a pattern mask of the metal film of the discharge hole;
A step of performing a dry etching process using a pattern mask of the metal film of the discharge hole to form a small diameter portion longer than a desired length of the small diameter portion; and
The method of manufacturing a nozzle plate according to claim 5, further comprising a step of removing the metal film. The method of manufacturing a nozzle plate according to claim 5, further comprising a liquid repellent treatment step of providing a liquid repellent layer on the first surface. The method for manufacturing a nozzle plate according to claim 5, wherein the liquid discharge head is an electrostatic suction type liquid droplet discharge head. A nozzle plate having nozzles for discharging liquid as droplets from the discharge holes;
A body plate having a cavity groove formed as a cavity communicating with each of the nozzles by being bonded to the nozzle plate,
The droplets are ejected and landed on the substrate by an electrostatic attraction force received from an electric field formed between the liquid in the nozzle and the substrate provided opposite to the droplet ejection surface of the nozzle plate. In the liquid discharge head,
The nozzle plate is a nozzle plate manufactured by the nozzle plate according to any one of claims 1 to 4 or the nozzle plate according to any one of claims 5 to 8,
A liquid discharge head, comprising: an electrostatic voltage applying unit that generates an electrostatic attraction force by applying an electrostatic voltage between the liquid discharged from the discharge hole and the substrate. The liquid discharge head according to claim 9, further comprising pressure generating means for applying a pressure to the liquid in the nozzle to form a meniscus.