JP2012196894A - Liquid ejecting apparatus and liquid ejection head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid ejection head that can improve liquid ejection characteristics by heating the ejected liquid to a desired temperature, and to provide a liquid ejecting apparatus.SOLUTION: The liquid ejection head includes: a nozzle plate 48 in which a nozzle opening 47 that ejects the liquid is provided; a flow channel formation substrate 40 in which a pressure generating chamber 42 that communicates to the nozzle opening 47; a pressure generating means 11 that causes pressure change in the pressure generating chamber 42. The nozzle plate 48 is composed of a PTC heat generating material that has the PTC characteristics, and in the nozzle plate 48, an electrode 80 that supplies the current to the PTC heat generating material is provided.

Description

The present invention relates to a liquid ejecting head that ejects liquid from nozzle openings and a liquid ejecting apparatus using the same, and more particularly to an ink jet recording head and an ink jet recording apparatus that eject ink as liquid.

A typical example of a liquid ejecting head that ejects droplets is an ink jet recording head that ejects ink droplets. As an ink jet recording head, for example, a nozzle plate having nozzles formed therein, a channel forming substrate on which a liquid channel including a plurality of pressure generating chambers communicating with the nozzles is formed, and one of the channel forming substrates are provided. Some have pressure generating means formed on the direction side.

The liquid ejected from such a recording head has a viscosity suitable for ejection depending on the type of the liquid. Since the viscosity of the liquid has a correlation with the temperature, there is a characteristic that the lower the temperature, the higher the viscosity, and the higher the temperature, the lower the viscosity. For this reason, when a recording head designed to suit the viscosity of a liquid that is normally used is placed in a low-temperature (high-temperature) environment or when a high-viscosity (low-) liquid is discharged, the liquid is heated ( Cooling). Specifically, a structure in which heating means is provided in contact with the nozzle plate (see, for example, Patent Document 1), or a structure in which a heater is provided in a metal stack in the head (for example, see Patent Document 2) is proposed. Has been.

JP 2010-023258 A JP 2008-296498 A

However, when a heater is brought into contact with the nozzle plate, there is a problem that heat transfer loss occurs between the nozzle plate and the heater, and temperature distribution occurs in the nozzle plate. In addition, when a heater is provided in the metal stack in the head, there is a problem that temperature distribution and heat loss occur between the heater installation site and the nozzle plate that ejects ink.

In any case, since the temperature of the ink at the time of ejection cannot be controlled with high precision, there is a problem that desired ink ejection characteristics cannot be obtained and print quality is deteriorated.

Such a problem is not limited to an ink jet recording head that ejects ink, but also exists in a liquid ejecting head that ejects liquid other than ink.

SUMMARY An advantage of some aspects of the invention is that it provides a liquid ejecting head and a liquid ejecting apparatus that can improve the liquid ejecting characteristics by heating the ejected liquid to a desired temperature.

According to a first aspect of the present invention for achieving the above object, there is provided a nozzle plate provided with a nozzle opening for ejecting liquid, a flow path forming substrate provided with a pressure generating chamber communicating with the nozzle opening, and the pressure generation. Pressure generating means for causing a pressure change in the liquid in the chamber, the nozzle plate is made of a heat generating material having PTC characteristics, and an electrode for supplying current to the heat generating material is provided on the nozzle plate. The liquid ejecting head is characterized by the above.
In this aspect, since the liquid immediately before being discharged is heated to a predetermined temperature by the nozzle plate made of a heat generating material having PTC characteristics, the discharged liquid is heated to a desired temperature to improve the liquid discharge characteristics. be able to.

Here, it is preferable that the electrode is provided at an opposite edge of the nozzle plate. According to this, since the current is uniformly supplied to the heat generating material having the PTC characteristic constituting the nozzle plate, the entire nozzle plate is heated more uniformly.

Moreover, it is preferable that the said electrode is provided in the corner | angular part which the edge part which the said nozzle plate opposes. According to this, since the current is uniformly supplied to the heat generating material having the PTC characteristic constituting the nozzle plate, the entire nozzle plate is heated more uniformly.

The heat generating material is preferably a ceramic having PTC characteristics or a mixed material containing silicon having PTC characteristics and stainless steel. According to this, the desired rigidity of the nozzle plate can be ensured.

According to another aspect of the invention, there is provided a liquid ejecting apparatus including the liquid ejecting head according to the above aspect.
According to this, since the liquid immediately before being discharged can be efficiently heated, the viscosity of the discharged liquid can be efficiently reduced, and a liquid ejecting apparatus having a head with improved discharge characteristics can be realized.

FIG. 2 is an exploded perspective view of a recording head according to Embodiment 1 of the invention. FIG. 3 is a top view of the recording head according to the first embodiment of the invention. FIG. 3 is a cross-sectional view of the recording head according to the first embodiment of the invention. FIG. 3 is a cross-sectional view of the recording head according to the first embodiment of the invention. It is a top view which shows schematic structure of the nozzle plate of this invention. 1 is a perspective view illustrating a schematic configuration of a recording apparatus according to Embodiment 1. FIG.

Hereinafter, the present invention will be described in detail based on embodiments.
(Embodiment 1)
FIG. 1 is an exploded perspective view of an ink jet recording head which is an example of a recording head according to Embodiment 1 of the present invention, FIG. 2 is a top view of the ink jet recording head, and FIG.
FIG. 4 is a sectional view taken along the line BB ′ of FIG.

As shown in FIG. 1, the ink jet recording head 1 of the present embodiment (hereinafter referred to as the recording head 1).
Also includes a pair of actuator units 2, a case 4 made of a resin material provided with an accommodating portion 3 capable of accommodating the actuator unit 2 therein, and a flow path unit 5 joined to the front end surface of the case 4. And a cover head 6 covering the flow path unit 5 side.

As shown in FIGS. 3 and 4, the actuator unit 2 of the present embodiment includes a piezoelectric element forming member 13 in which a plurality of piezoelectric elements 11 that are actuators of the present embodiment are arranged in parallel in the width direction, and piezoelectric element formation. The base plate (other end portion) side of the member 13 is joined as a fixed end so that the distal end portion (one end portion) side of the member 13 becomes a free end.

The piezoelectric element forming member 13 includes a piezoelectric material layer 15 and internal electrodes constituting two poles of the piezoelectric element 11, that is, individual internal electrodes 16 constituting individual electrodes electrically independent of the adjacent piezoelectric elements 11, It is formed by alternately stacking common internal electrodes 17 constituting common electrodes that are electrically common to adjacent piezoelectric elements 11.

The piezoelectric element forming member 13 includes a plurality of slits 18 using, for example, a wire saw.
Is formed, and the tip end side is cut into a comb-like shape to form a row of piezoelectric elements 11. A positioning portion 19 having a width wider than each piezoelectric element 11 is provided on both outer sides of the row of piezoelectric elements 11. The positioning portion 19 is a non-driving vibrator that is formed of the piezoelectric element forming member 13 and is not substantially driven, like the piezoelectric element 11, and is positioned when the actuator unit 2 is incorporated into the recording head 1. The portion 19 is brought into contact with the side surface of the accommodating portion 3 provided in the case 4 to position the actuator unit 2 with high accuracy.

Here, the region joined to the fixed plate 14 of the piezoelectric element 11 is an inactive region that does not contribute to vibration, and when a voltage is applied between the individual internal electrode 16 and the common internal electrode 17 constituting the piezoelectric element 11. Only the region on the tip side that is not joined to the fixed plate 14 vibrates. And
The front end surface of the piezoelectric element 11 is fixed to an island portion 49 of a diaphragm 46 described later via an adhesive or the like.

Further, each piezoelectric element 11 of the actuator unit 2 is connected to a circuit board 30 such as a COF on which a drive circuit 29 such as a drive IC for driving the piezoelectric element 11 is mounted.

The flow path unit 5 includes a flow path forming substrate 40, a vibration plate 46 and a nozzle plate 48.

The flow path forming substrate 40 is made of a silicon single crystal substrate, and a pressure generation chamber 42 defined by a plurality of partition walls 41 is provided in parallel on the surface layer portion on one side thereof (hereinafter referred to as this arrangement). Direction is referred to as a juxtaposed direction or a first direction).

Further, as shown in FIG. 3, a direction (hereinafter, referred to as a direction substantially orthogonal to the parallel direction of the pressure generating chambers 42).
On one end side (this direction is referred to as a second direction), a manifold 44 for supplying ink, which is an example of liquid, to each pressure generating chamber 42 is communicated via an ink supply path 45, which is an example of a liquid supply path. Has been. In addition, the opening surface side of the pressure generating chamber 42 of the flow path forming substrate 40 is sealed with a vibration plate 46, and a nozzle plate 48, which is an example of a nozzle forming member having a nozzle opening 47 formed on the other surface side, is bonded. It is bonded via an agent or a heat welding film. The nozzle opening 47 of the nozzle plate 48 and the pressure generating chamber 42 communicate with each other through a nozzle opening communication hole 43 provided through the flow path forming substrate 40.

Here, the nozzle plate 48 is made of PTC (Positive Temperature).
It is composed of a PTC heating element made of a material having a characteristic of Coefficient (positive temperature coefficient). The PTC heating element is preferably made of a material that secures a desired rigidity, specifically, ceramic having PTC characteristics, or silicon and stainless steel having PTC characteristics (
SUS) and the like. A PTC heating element is a material containing conductive particles such as carbon, and is a material that exhibits conductivity through conductive particles. However, when a predetermined temperature is reached, the chain of conductive particles is cut off, and current flows. It is a material that becomes difficult (resistance increases). Since the PTC heating element can be set so as to generate heat to a predetermined constant temperature by appropriately adjusting its Curie temperature, there is an advantage that it is not necessary to provide a temperature control means such as a thermostat.

As described above, since the nozzle plate 48 is composed of a PTC heating element and the nozzle plate 48 itself is a heating element, the droplet immediately before discharge contacting the nozzle plate 48 is heated to a predetermined temperature to maintain a predetermined viscosity. Thus, the discharge characteristics can be improved.

As shown in FIGS. 1 and 5A, the opposite edges of the nozzle plate 48 are
An electrode 80 for supplying current to the PTC heating element is provided along the side, and current is supplied from a power source (not shown). By providing the electrodes 80 on the opposite sides in this way, a current can be supplied uniformly to the PTC heating element, and the nozzle plate 48 can be heated more uniformly. The surfaces of the nozzle plate 48 and the electrode 80 are insulated so as not to be electrically connected to a cover head 6 and a liquid described later.

The electrode 80 is not necessarily provided along the side. For example, as shown in FIG. 5B, the electrode 80 </ b> A may be disposed at an opposite angle. Also by this, a current can be supplied uniformly to the PTC heating element, and the nozzle plate 48 can be heated more uniformly.

The diaphragm 46 is, for example, an elastic film 4 that is a first member made of an elastic member such as a resin film.
6a and a support plate 46b that is a second member made of, for example, a metal material that supports the elastic film 46a. The elastic film 46a side is joined to the flow path forming substrate 40. Yes. For example, in the present embodiment, the elastic film 46a as the first member is made of a PPS (polyphenylene sulfide) film having a thickness of about several μm, and the support plate 4 as the second member.
6b consists of a stainless steel plate (SUS) having a thickness of about several tens of μm.

In addition, in the region of the diaphragm 46 that faces each pressure generating chamber 42, an island portion 49 is provided in which the tip of the piezoelectric element 11 contacts. That is, a thin portion 50 having a thickness smaller than that of other regions is formed in a region of the diaphragm 46 that faces the peripheral portion of each pressure generating chamber 42, and island portions 49 are provided inside the thin portion 50. Yes. In such an island portion 49, the tip end portion of the piezoelectric element 11 of the actuator unit 2 described above is fixed via an adhesive or the like, for example.

Further, in the region facing the manifold 44 of the vibration plate 46, similarly to the thin portion 50, a compliance portion 54 that is substantially composed only of the elastic film 46 a is provided by removing the support plate 46 b by etching. . The compliance portion 54 absorbs the pressure change by the deformation of the elastic film 46a of the compliance portion 54 when a pressure change occurs in the manifold 44, and always keeps the pressure in the manifold 44 constant. Fulfill.

In the present embodiment, the diaphragm 46 is constituted by the elastic film 46a and the support plate 46b, and the island portion 4 is formed.
The peripheral portion 9 and the compliance portion 54 are configured by only the elastic film 46a. However, the present invention is not particularly limited to this. For example, a single plate-like member is used as the diaphragm, and the thickness of the plate-like member is one. The island portions 49 and the compliance portions 54 may be formed by providing the concave thin portions 50 and 52 and the like from which the portions are removed.

The case 4 is fixed on the vibration plate 46 of the flow path forming substrate 40, and is connected to an ink supply pipe connected to an ink storage unit (not shown) for storing ink, and the manifold 44.
An ink supply path 45 is provided for supplying ink.

The case 4 is provided with two accommodating portions 3 that penetrate in the thickness direction, and the actuator unit 2 is positioned and fixed to each accommodating portion 3.

As shown in FIG. 1, the housing portion 3 of the case 4 includes a fixed plate holding portion 3 a that is wider than the width of the fixed plate 14 on the side where the fixed plate 14 is fixed, and a piezoelectric element forming member. 13 has a piezoelectric element holding portion 3b that is narrower than the fixed plate holding portion 3a and slightly wider than the piezoelectric element forming member 13. The width here refers to the direction in which the piezoelectric elements 11 (pressure generation chambers 42) are arranged side by side. As shown in FIG. 3, the fixing plate holding portion 3 a of the housing portion 3 is provided with a step portion 3 c so that the diaphragm 46 side becomes narrow in the penetrating direction.
4, the end surface from which the piezoelectric element 11 protrudes contacts and is fixed to the stepped portion 3c.

Further, the case 4 is provided with a compliance space 55 having a concave shape that opens in a region facing the compliance portion 54. The compliance portion 54 is deformably held by the compliance space 55.

Such a case 4 is formed of a resin material. In addition, the case 4 can be manufactured at a low cost by molding and can be easily mass-produced.

Further, a reinforcing plate 60 is embedded in the case 4. In the present embodiment, the reinforcing plate 60 is embedded in a partition wall 61 that is provided between the two storage portions 3 of the case 4 and partitions the storage portion 3.

On the other hand, as shown in FIGS. 1 and 3 to 4, the recording head 1 is provided with a cover head 6 that covers the ejection surface side with the nozzle openings 47 exposed on the surface side where the nozzle openings 47 open. It has been.

The cover head 6 includes an opening 70 that exposes the nozzle opening 47 and a frame 71 that defines the opening 70.

In this embodiment, the frame portion 71 is provided over the periphery of the ejection surface.
Is provided with a side wall 72 extending so as to bend over the outer peripheral edge of the ejection surface.

Further, the side wall portion 72 is provided with fixing portions 73 extending on both sides of the nozzle opening 47 in the juxtaposition direction. The fixing portion 73 is bent from the side wall portion 72 and is fixed to a flange portion 74 protruding from the side surface of the case 4 via a fixing screw 75. This
The cover head 6 is integrated with the recording head 1.

As the cover head 6, for example, a metal material such as stainless steel can be used. Further, the cover head 6 may be formed by pressing a metal plate or may be formed by molding.

In such a recording head 1, the piezoelectric element 11 and the diaphragm 46 are ejected when ink droplets are ejected.
Due to this deformation, the volume of each pressure generating chamber 42 is changed and ink droplets are ejected from a predetermined nozzle opening 47. Specifically, when ink is supplied from an ink cartridge (not shown) to the manifold 44 through the ink introduction hole 56 provided in the case 4, the ink is distributed to each pressure generating chamber 42 through the ink supply path 45. The In practice, the piezoelectric element 1
The piezoelectric element 11 is contracted by applying a voltage to 1. As a result, the diaphragm 46 is deformed together with the piezoelectric element 11 to expand the volume of the pressure generating chamber 42, and ink is drawn into the pressure generating chamber 42. Then, after the ink is filled up to the nozzle opening 47, the voltage applied to the electrodes 16 and 17 of the piezoelectric element 11 is released in accordance with a recording signal supplied via the circuit board 30. As a result, the piezoelectric element 11 is expanded to return to the original state, and the diaphragm 46 is also displaced to return to the original state. As a result, the volume of the pressure generation chamber 42 contracts, the pressure in the pressure generation chamber 42 increases, and ink droplets are ejected from the nozzle openings 47.

The ink jet recording head 1 of each of these embodiments constitutes a part of an ink jet recording head unit having an ink flow path communicating with an ink cartridge or the like, and is mounted on an ink jet recording apparatus. FIG. 6 is a schematic view showing an example of the ink jet recording apparatus.

As shown in FIG. 6, the ink jet recording apparatus 200 has a main body 201, a plurality of ink jet recording head units 202 (liquid ejecting head units), and the plurality of ink jet recording head units 202 relatively positioned. A carriage 203 that is held in a heated state, and an ink storage portion 205 that supplies ink via an ink supply tube 204 formed of a flexible tube. The ink storage unit 205 is provided with a heating means (not shown) for heating the ink stored inside.

The carriage 203 is provided so as to be movable in the axial direction on a pair of carriage shafts 206 attached to the apparatus main body 201. Further, a drive motor 207 is provided on one end side of the carriage shaft 206, and the driving force by the drive motor 207 is generated by the carriage shaft 20.
6 is transmitted to the carriage 203 via a timing belt 210 spanned between a pair of pulleys 208 and 209 provided on both end sides of the carriage 6, whereby the carriage 203 on which a plurality of ink jet recording head units 202 are mounted. Is moved along the carriage shaft 206 (main scanning direction).

On the other hand, the apparatus main body 201 is provided with a platen 211 along the carriage shaft 206, and the recording medium S such as recording paper fed by a paper feeding roller (not shown) is placed on the platen 21.
1 is conveyed.

Further, in the non-printing area of the ink jet recording apparatus 200, the recording head unit 20 is provided.
And a suction member 214 such as a vacuum pump connected to the cap member 212 via a suction pipe 213.

The cap member 212 having such a configuration is brought into contact with the ejection surface of the recording head unit 202 to cause the suction unit 214 to perform a suction operation, thereby setting the inside of the cap member 212 to a negative pressure, and the nozzles of the recording head unit 202. A suction operation (cleaning operation) is performed by sucking the ink in the flow path together with bubbles from the opening. The cap member 212 of the present embodiment includes a heating unit that heats the ejection surface of the recording head unit 202 during non-printing, as will be described in detail later.

Note that the cap member 212 abuts on the outer edge portion of the ejection surface of the recording head unit 202 and covers the ejection surface at a desired timing. Therefore, in this embodiment, the cap member 212 is provided to be movable in the vertical direction. It has been. The cap member 212 can be moved by a moving means such as a drive motor or an electromagnet (not shown).

In the above-described example, the head unit 202 having a plurality of recording heads 1 is mounted on the ink jet recording apparatus 200. However, one recording head 1 may be mounted on each head unit 202. In addition, one or a plurality of recording heads 1 may be directly mounted on the ink jet recording apparatus 200.

In the above-described embodiment, an ink jet recording head has been described as an example of a liquid ejecting head. However, the present invention is widely intended for all liquid ejecting heads and ejects liquids other than ink. Of course, the present invention can also be applied to a liquid ejecting head. Other liquid ejecting heads include, for example, various recording heads used in image recording apparatuses such as printers, color material ejecting heads used in the manufacture of color filters such as liquid crystal displays,
Examples thereof include an electrode material ejecting head used for forming an electrode such as an organic EL display and FED (field emission display), and a bio-organic matter ejecting head used for biochip production.

DESCRIPTION OF SYMBOLS 1 Inkjet recording head (liquid ejecting head), 2 Actuator unit, 3 Housing | casing part, 4 Case, 5 Flow path unit, 11 Piezoelectric element (actuator), 13 Piezoelectric element formation member, 14 Fixed plate, 16 Individual internal electrode, 17
Common internal electrode, 18 slit, 19 positioning part, 30 circuit board, 40
Flow path forming substrate, 42 pressure generating chamber, 46 diaphragm, 47 nozzle opening, 48 nozzle plate, 80, 80A electrode, 200 ink jet recording apparatus (liquid ejecting apparatus), 202 ink jet recording head unit (liquid ejecting head unit)

Claims (5)

A nozzle plate provided with nozzle openings for ejecting liquid;
A flow path forming substrate provided with a pressure generating chamber communicating with the nozzle opening;
Pressure generating means for causing a pressure change in the liquid in the pressure generating chamber;
Comprising
The liquid ejecting head according to claim 1, wherein the nozzle plate is made of a heat generating material having PTC characteristics, and an electrode for supplying a current to the heat generating material is provided on the nozzle plate. The liquid ejecting head according to claim 1,
The liquid ejecting head according to claim 1, wherein the electrodes are provided at opposite edges of the nozzle plate. The liquid ejecting head according to claim 1,
The liquid ejecting head according to claim 1, wherein the electrodes are provided at opposing corners of opposing edges of the nozzle plate. In the liquid jet head according to any one of claims 1 to 3,
The liquid ejecting head, wherein the heat generating material is ceramic having PTC characteristics or a mixed material including silicon having PTC characteristics and stainless steel. A liquid ejecting apparatus comprising the liquid ejecting head according to claim 1.

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