JP2000301713A - Ink jet recording head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a small size high density ink jet recording head employing a shape memory material by increasing variation in the volume of ink cavity. SOLUTION: The ink jet recording head 10 comprises a tubular body 21 made of a shape memory material having an inner ink cavity 33, means for heating the tubular body 21, and a nozzle 39 communicating with the ink cavity 33. The tubular body 21 contracts in the axial direction to pressurize ink in the ink cavity 33 thus ejecting an ink drop from the nozzle 39.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording head for discharging ink droplets to a recording medium by pressing ink in an ink channel by utilizing deformation of a shape memory material.

[0002]

2. Description of the Related Art Conventionally, an ink jet recording head using a shape memory material has been proposed.

For example, Japanese Patent Application Laid-Open No. Hei 6-91865 describes an ink jet recording head shown in FIGS. In this ink jet recording head, the upper opening of each ink channel 1 in the drawing is closed by a bias spring layer 2 having an elastic restoring force which tends to bulge upward. 2, a shape memory alloy layer 3 is formed on the entire surface. In FIG. 12, reference numeral 4 denotes a nozzle, and reference numeral 5 denotes a driving circuit for generating a resistance heat by energizing the shape memory alloy layer 3.

At room temperature, the shape memory alloy layer 3, which is a martensite phase, is bent in a state of bulging upward in the figure due to the elastic restoring force of the bias spring layer 2. When the temperature of the shape memory alloy layer 3 rises to the transformation temperature or higher due to energization from the drive circuit 5, the shape memory alloy layer 3 which has become the austenitic phase is shown by a dotted line in the drawing against the urging force of the bias spring layer 2. Deforms into a flat plate as shown. As a result, the volume of the ink channel 1 is reduced, the ink is pressurized, and the ink droplet is ejected from the nozzle 4.

[0005]

In general, the amount of expansion and contraction of the shape memory alloy constituting the shape memory alloy layer 3 before and after transformation is of the order of several percent, whereas the amount of expansion and contraction of the material constituting the bias spring layer 2 is several percent. The amount of expansion and contraction is only on the order of 0.1%, which is very small compared to the amount of expansion and contraction of the shape memory alloy before and after transformation.

Therefore, when the bias spring layer 2 is provided on the entire surface of the shape memory alloy layer 3 as in the ink jet recording head shown in FIG. 12, deformation of the shape memory alloy layer 3 is restrained by the bias spring layer 2. Therefore, the amount of expansion and contraction of the shape memory alloy layer 3 before and after transformation is limited to the order of 0.1%, and the volume change rate of the ink channel 1 is reduced. When the rate of change in the volume of the ink channel 1 is small, it is necessary to increase the volume of the ink channel 1 in order to secure the amount and speed of ink ejection. In the ink jet recording head shown in FIG. 12, the volume of the ink channel 1 before and after the transformation changes in proportion to the cube of the change in the width of the shape memory alloy layer 3, and the width of the shape memory alloy layer 3 is reduced. Then, the volume change rate of the ink channel 1 is greatly reduced. Therefore, it has been difficult to increase the density and reduce the size of this type of conventional inkjet recording head.

Accordingly, an object of the present invention is to increase the rate of change in the volume of an ink channel by increasing the amount of expansion and contraction of a shape memory material before and after transformation, thereby increasing the density and miniaturization of an ink jet recording head. I have.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a cylindrical body made of a shape memory material, the inside of which forms an ink cavity; a heating means for heating the cylindrical body; The present invention provides an ink jet recording head which has a nozzle communicating with a cavity, and presses ink in the ink cavity by discharging the ink droplet from the nozzle by contracting the cylinder in the axial direction.

In the ink jet recording head of the present invention,
Since the volume of the ink cavity changes when the cylindrical body made of the shape memory material expands and contracts in the axial direction, the expansion and contraction of the shape memory material is efficiently converted into a change in the volume of the ink cavity. That is, the amount of change in the volume of the ink cavity is determined by the product of the volume of the ink cavity and the expansion and contraction rate of the shape memory material forming the cylinder, and even if the dimension (width) in the direction orthogonal to the axial direction of the cylinder is reduced, The rate of volume change of the cavity does not drop significantly. Therefore, in the ink jet recording head of the present invention, the volume of the ink cavity can be reduced, and high density and small size can be achieved.

In particular, when a bias spring or the like is not laminated on the outer periphery of a cylindrical body made of a shape memory material, expansion and contraction of the cylindrical body is not restricted, and the cylindrical body has a large expansion and contraction on the order of several percent inherent in the shape memory material. It expands and contracts at a rate. Therefore, in this case, the volume change rate of the ink cavity becomes larger.

[0011] Further, the above-mentioned ink jet recording head comprises:
It is preferable to include a shape regulating unit that urges the cylindrical body so as to expand or contract in a direction opposite to that in the heating by the heating unit.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention shown in the drawings will be described in detail.

(First Embodiment) FIG. 1 shows an ink jet recording apparatus 11 having an ink jet recording head 10 according to a first embodiment of the present invention.

The ink jet recording apparatus 11 has a moving mechanism 13 for moving the carriage 12 in the main scanning direction indicated by arrows X1 and X2, and a feeding mechanism for moving the recording paper 14 as a recording medium in the sub-scanning direction indicated by arrow Y. 15 is provided.

In the carriage 12, an ink jet recording head 10 for ejecting ink droplets onto recording paper 14 and a cartridge type ink tank (not shown) storing ink to be supplied to the ink jet recording head 10 are housed. ing.

As shown in FIGS. 2 to 4, the ink jet recording head 10 has a cylindrical body 21, a support wall 23, and an end wall 2.
5, a bias spring member 27, a heating resistor 29, and a channel plate 31 are provided.

The cylindrical body 21 is made of Ti which is a shape memory alloy.
It is a square cylinder made of a thin film of a Ni (titanium / nickel) alloy, the upper end of which is closed and the lower end is open in the figure,
The internal space forms an ink cavity 33.
Gaps are provided between adjacent cylinders 21 and between each cylinder 21 and the support wall 23. No bias spring layer or the like is provided on the outer periphery of the cylindrical body 21. That is, the side wall of the cylindrical body 21 is composed of only the thin film of the TiNi alloy. Note that, in the present embodiment, Ti
The Ni alloy has a composition ratio of 50% -50% and a transformation temperature of about 7%.
At 0 ° C., the maximum strain is about 5%, and the generated stress is about 600 MPa.

The support wall 23 includes walls 23a, 23a opposed to each other with the cylindrical body 21 interposed therebetween, and these walls 23a, 23a.
and a wall 23b for connecting a. On the other hand, the end wall 25 is formed on the entire closed end of each cylindrical body 21. The support wall 23 and the end wall 25 are formed by etching a Si (silicon) substrate as described later.

The bias spring member 27 is formed by etching a plate made of Si.
And a pair of parallel support portions 27a, 27a fixed to the upper end in the drawing of the wall portions 23a, 23a, and a shape regulating portion 27b (book) provided in parallel with each other so as to connect these support portions 27a, 27a. Constituting the shape regulating means of the invention).

There is a step between the lower end of the supporting portions 27a and 27a in the drawing and the lower end of the shape regulating portion 27 in the drawing. Each shape regulating portion 27b is joined to the end wall 25 attached to the upper end of each of the cylindrical bodies 21 in a state where the shape regulating portion 27b is pushed downward in the figure by this step difference (the pushing amount D). For this reason, an elastic biasing force that acts in the axial direction (the direction of the axis N) acts on each cylindrical body 21 by the corresponding shape regulating portion 27b.

The heating resistor 29 is made of NiCr (nickel
(Chromium) and is formed on each shape regulating portion 27b of the bias spring member 27. Each heating resistor 29
Has one end grounded via a common electrode 35 and the other end connected to a drive circuit 37 via an individual electrode 36.

The channel plate 31 is provided on the opening side (the lower side in the figure) of the cylindrical body 21.
The channel plate 31 is formed by laminating three plates 31a, 31b, 31c made of electroformed nickel. The nozzle 39 communicates with the ink cavity 33, the supply chamber 41 communicates with the ink tank, and the supply chamber 41. And an inlet 43 communicating with the ink cavity 33.

The method of manufacturing the ink jet recording head will be described. First, as shown in FIG.
One surface 45a of the Si substrate 45 is etched to form a rectangular parallelepiped concave portion 45b.

Next, as shown in FIG. 5B, a 5 μm thick thin film 4 of TiNi is formed on the entire surface 45 a of the substrate 45 on which the concave portion 45 a is formed by sputtering.
7 is formed. The substrate 4 on which the thin film 47 is formed
5 was annealed at 500 ° C. to form TiN
The shape is stored in i.

Next, as shown in FIG. 5 (C), the thin film 47 formed on the
The nozzle plate 31 is formed by sequentially attaching the plates 31a, 31b, and 31c.

Thereafter, as shown in FIG.
The surface 45c opposite to the surface 45a on which the thin film 47 and the nozzle plate 31 of No. 5 are provided is coated with SF ₆ (sulfur hexafluoride).
Gas Ion Etching Using Reactive Gas (RI
Etching is performed by E) to form a cylindrical body 21 made of TiNi. The portions of the substrate 45 that remain without being etched become the support wall 23 and the end wall 25.

Next, as shown in FIG. 6, the support portion 27a of the bi-ice spring member 27 in which the heating resistor 29, the common electrode 35, and the individual electrode 36 are provided in advance in a state where the heating temperature is higher than the transformation temperature of TiNi. It joins to the upper end in the figure of the wall part 23a of the support wall 23. Also, the bias spring member 2
7 is joined to the end wall 25. At this time, since the upper surface of the support wall 23 and the upper surface of the end wall 25 are on the same plane, the shape regulating portion 27b is joined to the end wall 25 in a state where it is pushed downward by the pushing amount D. You.
Therefore, an elastic restoring force for the shape restricting portion 27 b to return to the original shape acts on the cylinder 21 via the end wall 25. This restoring force acts in a direction in which the cylinder 21 is pulled in the axial direction.

When the ink jet recording head 10 is cooled to a normal temperature lower than the transformation temperature, the cylindrical portion 21 in the martensitic phase becomes the shape regulating portion 27 of the bias spring member 27.
The extension in the axial direction is caused by the urging force of b, and the dimension in the axial direction is increased by the pushing amount D as shown in FIG.

The operation of the ink jet recording head 10 will be described. In a normal temperature state in which the power supply to the heating resistor 29 is stopped, as shown in FIGS. Due to the elastic restoring force, the cylinder 21 which is a martensite phase
Is in a state of being extended in the axial direction by the pushing amount D.

When the heating resistor 29 is energized by the drive circuit 37 to generate heat and the temperature of the cylinder 21 rises to the transformation temperature or higher, the cylinder 21 in the austenite phase has a shape as shown in FIG. Against the restoring force of the restricting portion 27b, it contracts in the axial direction by the pushing amount D. As a result, the volume of the ink cavity 33 decreases, and the pressurized ink is ejected from the nozzle 39.

The energization of the heating resistor 29 is stopped,
When the cylinder 21 is cooled to below the transformation temperature and returns to the martensite phase, the cylinder 2 is pressed by the urging force of the shape regulating portion 27b.
1 extends in the axial direction by the pushing amount D, and returns to the state shown in FIGS. As a result, the volume of the ink cavity 33 increases, and ink is supplied from the supply chamber 41 to the ink cavity 33 via the inlet 43.

As described above, the power supply to the heating resistor 29
The non-energization causes the cylindrical body 21 made of the shape memory alloy to be repeatedly deformed by heating and cooling, whereby the ejection of ink droplets is repeated.

The ink jet recording head 1 of the present embodiment
At 0, the volume of the ink cavity 33 changes due to the axial expansion and contraction of the cylindrical body 21 made of the shape memory material. Therefore, the expansion and contraction of the shape memory material is efficiently converted into a change in the volume of the ink cavity 33. That is, the amount of change in the volume of the ink cavity 33 is determined by the product of the volume of the ink cavity 33 and the expansion and contraction rate of the shape memory material forming the cylinder 21, and the dimension (width) of the cylinder 21 in the direction orthogonal to the axial direction is reduced. However, the rate of change of the volume of the ink cavity 33 does not decrease significantly. Further, since no bias spring or the like is laminated on the outer periphery of the cylindrical body 21 made of the shape memory material, the expansion and contraction of the cylindrical body is not restricted, and the cylindrical body has a few% that the shape memory material originally has.
It expands and contracts at a large expansion and contraction rate on the order of. Therefore, in the ink jet recording head of the present embodiment, the volume of the ink cavity 33 can be reduced, and high density and small size can be achieved.

Further, since the bias spring, the heating resistor and the like are not laminated on the outer periphery of the cylindrical body 21, it is possible to prevent them from being broken by repeating expansion and contraction with the cylindrical body.

The means for heating the cylindrical body 21 is not limited to the means for energizing the heating resistor 29, but is divided by each of the cylindrical bodies 21 and the resistance heat generated by energizing the individual cylindrical bodies 21 is generated. It may be heated.

(Second Embodiment) FIGS. 7 to 9 show an ink jet recording head 10 according to a second embodiment.

The cylindrical body 21 is made of a NiTi alloy thin film having a thickness of 5 μm, and has a cylindrical shape with openings at both ends. As shown in FIG. 7, one end of the cylindrical body 21 is grounded, and the other end is connected to a drive circuit 37.
It is connected to the.

One opening (upper opening in the figure) of the cylindrical body 21 is closed by a nozzle plate 49 made of an electroformed nickel plate. In the nozzle plate 49,
A nozzle 39 communicating with an ink cavity 33 formed inside each cylinder 21 is formed. Cylinder 2
1 (opening on the lower side in the figure) corresponds to FIG.
Is closed by a bias spring member 27 shown in FIG. The support wall 23 made of Si is interposed between the nozzle plate 49 and the bias spring member 27. On the other hand, an elastic film 53 is provided on the surface of the bias spring member 27 opposite to the cylindrical body 21. A channel plate 3 is provided on the stretch film 53 side of the bias spring member 27 made of Si.
1 is attached.

As in the first embodiment, the bias spring member 27 includes a pair of parallel support portions 27a, 27a.
And a shape regulating portion 27 provided in parallel with each other so as to connect the supporting portions 27a, 27a corresponding to the respective cylindrical members 21.
b. Each shape restricting portion 27 b is
Are joined to the lower end in each of FIGS.
1 exerts an elastic force that is pulled in the axial direction (the direction of the axis N). In addition, each shape regulating portion 27b has a through hole 2
7c is provided.

The elastic film 53 is provided on the entire surface of the bias spring member 27, and is provided with a through hole 53a so as to communicate with each through hole 27c provided in the shape regulating portion 27b. These through-holes 27c and 53a are provided with an ink cavity 33 formed inside the cylinder 21 and
An ink inlet 43 is provided to communicate with the supply chamber 41 formed in the channel plate 31. However, an opening or the like corresponding to the slit between the shape regulating portions 27b is not formed in the elastic film 53, and the supply chamber 41 is closed by the elastic film 53 except for the inlet 43. The stretch film 53 is made of a resin material such as polyimide, vinyl chloride, Teflon, natural rubber, and silicon.

The operation of the ink jet recording head 10 will be described. In a normal temperature state in which the power supply to the cylinder 21 is stopped, as shown in FIGS. 8 and 9, the elastic restoring force of each shape regulating portion 27b is obtained. As a result, the cylindrical body 21 in the martensite phase is in a state of being extended in the axial direction.

When the cylinder 21 energized by the drive circuit 37 generates heat and rises in temperature to the transformation temperature or higher, the cylinder 21 in the austenite phase is subjected to the restoring force of the shape regulating portion 27b as shown in FIG. On the contrary, it contracts in the axial direction by the pushing amount D. As a result, the volume of the ink cavity 33 decreases, and the pressurized ink is ejected from the nozzle 39.

When the energization is stopped and the cylinder 21 is cooled below the transformation temperature, the cylinder 2 returns to the martensitic phase.
1 is extended in the axial direction by the urging force of the shape regulating portion 27b of the bias spring member 27, and returns to the state shown in FIG.
As a result, the volume of the ink cavity 33 increases, and the ink cavity 3 is supplied from the supply chamber 41 through the inlet 43.
3 is supplied with ink.

As described above, the heating and cooling of the cylinder 21 made of a shape memory alloy are repeated and deformed by the energization / de-energization of the cylinder 21, thereby repeatedly discharging the ink droplets.

As in the first embodiment, in the ink jet recording head 10 of the second embodiment, the volume of the ink cavity 33 changes due to the axial expansion and contraction of the cylindrical body 21 made of the shape memory material. The expansion and contraction of the material is efficiently converted into a change in the volume of the ink cavity 33. Further, since no bias spring or the like is laminated on the outer periphery of the cylindrical body 21 made of the shape memory material, expansion and contraction of the cylindrical body is not restricted. Therefore, the volume of the ink cavity 33 can be reduced, and higher density and smaller size can be achieved. In addition, since the bias springs and the like are not stacked on the outer periphery of the cylindrical body 21, it is possible to prevent the springs from being broken by repeatedly expanding and contracting with the cylindrical body.

A heating resistor similar to that of the first embodiment is provided on the outer periphery of the cylindrical body 21 in such a shape and size that does not affect the expansion and contraction of the cylindrical body 21. The temperature of the cylindrical body 21 may be raised by using.

The present invention is not limited to the above embodiment, and various modifications are possible. First, the shape memory material forming the cylinder is not limited to the thin film of the TiNi alloy, but may be TiN.
An alloy obtained by adding Pb or Cu to i or another shape memory alloy such as a Cu-Zn-Al alloy may be used. Further, the cylindrical body may be made of a shape recording resin and a shape recording fiber. Further, the shape memory material layer may be formed of a composite material containing at least one of a shape memory alloy, a shape recording resin, and a shape recording fiber.

The heating resistor is limited to NiCr.
TaN (tantalum nitride), HfB _Two, TaAl, etc.
Other materials may be used. Also, the heating resistor layer and the cylindrical body
It may be provided between the bias spring members.

A protective film for improving the durability may be formed on a portion of the cylinder made of the above shape memory material which comes into contact with the ink, that is, on a portion constituting the peripheral surface of the ink cavity of the cylinder. For example, a metal film such as Au, Ni, Cr, and Pt having relatively good ink resistance may be formed on the shape memory material layer by sputtering or vapor deposition. Alternatively, a resin-based material that does not reduce the elasticity of the shape memory material may be formed as a protective layer by vapor deposition.

In the above embodiment, the cylinder made of the shape memory material shrinks when heated, but may have a configuration in which the cylinder is more elongated during heating than at room temperature. In this case, when the ink is not ejected, the cylinder is heated and the cylinder is cooled at the time of ejecting the ink, thereby reducing the volume of the ink cavity.

[0051]

As is apparent from the above description, in the ink jet recording head of the present invention, the volume of the ink cavity is changed by compressing the ink by expanding and contracting the cylinder made of the shape memory material in the axial direction. Therefore, expansion and contraction of the shape memory material are efficiently converted into a change in the volume of the ink cavity. That is, the amount of change in the volume of the ink cavity is determined by the product of the volume of the ink cavity and the expansion and contraction rate of the shape memory material constituting the cylinder, and even if the dimension of the cylinder in the direction perpendicular to the axial direction is reduced, the volume of the ink cavity is reduced. The rate of change does not drop significantly. Therefore, in the ink jet recording head of the present invention, the volume of the ink cavity can be reduced, and high density and small size can be achieved.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating an inkjet recording apparatus including an inkjet recording head according to a first embodiment of the present invention.

FIG. 2 is a partial cross-sectional partial perspective view showing the ink jet recording head of the first embodiment.

FIG. 3 is a sectional view taken along line III-III in FIG. 2;

FIG. 4 is a sectional view taken along line IV-IV in FIG.

FIG. 5 (A), (B), (C) and (D) show the first
FIG. 4 is a cross-sectional view for explaining the method for manufacturing the ink jet recording head of the embodiment.

FIG. 6 is a cross-sectional view taken along the line III-III in FIG. 2 when an ink droplet is ejected.

FIG. 7 is a partial cross-sectional partial perspective view illustrating an inkjet recording head according to a second embodiment of the present invention.

FIG. 8 is a sectional view taken along line VIII-VIII in FIG. 7;

FIG. 9 is a sectional view taken along line XI-XI in FIG. 7;

FIG. 10 is a partial cross-sectional partial perspective view showing a bias spring member and an elastic film.

FIG. 11 is a view illustrating a state where ink droplets are ejected.
It is sectional drawing in the I line.

FIG. 12A is a plan view showing a conventional inkjet recording head, and FIG. 12B is a cross-sectional view taken along line XII-XII of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Ink jet recording head 11 Ink jet recording apparatus 21 Cylindrical body 23 Support wall 25 End wall 27 Bias spring member 27a Support part 27b Shape regulation part 29 Heating resistor 31 Channel plate 33 Ink cavity 35 Common electrode 36 Individual electrode 37 Drive circuit 41 Supply Chamber 43 Inlet 49 Nozzle plate 53 Stretchable film

Claims (2)

[Claims] 1. A cylinder made of a shape memory material, the interior of which forms an ink cavity, a heating means for heating the cylinder, and a nozzle communicating with the ink cavity, wherein the cylinder is contracted in the axial direction. By pressurizing the ink in the ink cavity,
An ink jet recording head that ejects ink droplets from the nozzles. 2. The ink jet recording head according to claim 1, further comprising a shape regulating means for urging the cylindrical body so as to expand or contract in a direction opposite to that of the heating by the heating means.