JP2000301712A - Ink jet recording head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a small and high density ink jet recording head by increasing expansion/contraction before and after transformation of a shape memory material layer. SOLUTION: The ink jet recording head 10 comprises a shape memory material layer 18 constituting a part of the wall part of an ink channel 23, means 20 for heating the shape memory material layer 18, a shape regulating means 19b for resiliently urging the shape memory material layer 18 to be deformed reversely to heating, and a nozzle communicating with the ink channel 23. The ink channel 23 is elongated to have longitudinal and widthwise directions and the shape regulating means 19b is provided, at least on one side of the shape memory material layer 18, to occupy a part of the ink channel 23 in the widthwise direction with a gap being provided between the opposite end parts of the ink channel 23 in the widthwise direction.

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 Laid-Open Publication No. Hei 6-91865 describes an ink jet recording head shown in FIGS. 15A and 15B. 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. 15, reference numeral 4 denotes a nozzle, and reference numeral 5 denotes a drive 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. 15, the 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. If the rate of change in the volume of the ink channel 1 is small, it is necessary to set the volume of the ink channel 1 large in order to secure the amount and speed of ink ejection. It is difficult to plan.

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

[0008]

In order to solve the above-mentioned problems, the present invention provides a shape memory material layer constituting a part of a wall portion of an ink channel, a heating means for heating the shape memory material layer, In an ink jet recording head including a shape regulating means for elastically urging the shape memory material layer to deform in a direction opposite to a shape at the time of heating, and a nozzle communicating with the ink channel, the ink channel is disposed in a longitudinal direction. And an elongated shape having a width direction and
The shape regulating means is provided on at least one surface side of the shape memory material layer so as to occupy a part of the width direction of the ink channel, and to have a gap between both ends in the width direction of the ink channel. It is intended to provide an ink jet recording head characterized in that:

In the ink jet recording head of the present invention having the above-described structure, only the shape memory material layer exists in the gap between the shape regulating means and the both ends in the width direction of the ink channel, and the shape regulating portion does not exist. Therefore, in this portion, since the expansion and contraction of the shape memory material layer in the ink channel width direction is not restricted by the shape restricting portion, the expansion and contraction amount of the shape memory material layer in the width direction is large. Therefore, in the ink jet recording head of the present invention, the rate of change in the volume of the ink channel between normal temperature and heating is large, and the volume of the ink channel can be reduced to achieve higher density and smaller size.

Further, in the ink jet recording head of the present invention, since the volume change rate of the ink channel is large as described above, the length of the ink channel can be reduced. Therefore, the characteristic of the natural oscillation cycle of the ink contained in the ink channel is improved, and smaller ink droplets can be made to fly at a higher ejection speed.

Further, in the ink jet recording head of the present invention, since the shape regulating portion is provided only in a part of the shape memory material layer in the width direction of the ink channel, the deformation amount of the shape regulating portion before and after the deformation of the shape memory material layer is reduced. small. Therefore, it is possible to prevent the destruction caused by the deformation of the shape regulating member together with the shape memory material layer.

[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 includes a flow path substrate 17, a shape memory material layer 18, a bias spring layer 19, a heating resistor layer 20, and a nozzle plate 21.

The channel substrate 17 is a flat plate made of Si (silicon) having a thickness of 0.2 mm, and a plurality of elongated slots 17a penetrating in the thickness direction are provided in parallel with each other. On one surface 17b (upper surface in the figure) of the flow path substrate 17, the shape memory material layer 18 is provided on the entire surface, and the shape memory material layer 18 closes one opening of the slot 17a. I have. Further, a nozzle plate 21 is attached to the other surface 17c (the lower surface in the figure) of the flow path substrate 17, and the nozzle plate 21 closes the other opening of the slot 17a. Thus, the shape memory material layer 18
The inside of each slot 17 a in which the upper and lower openings in the figure are closed by the nozzle plate 21 forms an ink channel 23. That is, each of the ink channels 23 has an elongated rectangular parallelepiped shape, and the side walls in the longitudinal and width directions are made of the flow path substrate 17, the upper wall is made of the shape memory material layer 18, and the bottom wall is made of the nozzle plate 21.

In the first embodiment, the ink channel 23 has a width W1 of 300 μm and a length L1 of 1 mm.

The shape memory material layer 18 is formed of a thin film of TiNi alloy having a thickness of 10 μm, and is deformed into a planar shape when heated to a transformation temperature or higher to form an austenite phase as described later.

The bias spring layer 19 has a thickness of 20 μm.
And a 10 μm thick silicon nitride film 25 formed on the shape memory material layer 18 and a 10 μm thick silicon oxide film 2 formed on the silicon nitride film 25.
7 The bias spring layer 19 is formed in parallel with each other so as to connect a pair of support portions 19a, 19a formed with a gap from each end in the longitudinal direction of the ink channel 23, and to connect these support portions 19a, 19a. And a provided shape regulating portion 19b (constituting the shape regulating means of the present invention). Each shape regulating portion 19b is provided corresponding to each ink channel 23, and is formed so as to pass above the ink channel 23 in the longitudinal direction in the drawing.

The shape regulating portion 19 of the bias spring layer 19
The width W2 of the ink channel 23 is 200 μm.
Is smaller than the width W1. The shape regulating portions 19b are provided with gaps 24 in the width direction with respect to the both ends in the width direction of the ink channel 23, that is, the side walls formed of the flow path substrate 17.

At room temperature, the silicon nitride film 25 of the bias spring layer 19 is a tensile film to which a tension indicated by an arrow A1 acts in FIG. 3, while the silicon oxide film 27 of the bias spring layer 19 is an arrow A2 in FIG. This is a compression film on which the tension indicated by. Therefore, the shape regulating portion 19b of the bias spring layer 19 has an elastic restoring force that tends to elastically deform in the direction in which the volume of the ink channel 23 increases, that is, in the direction in which the upper side swells in the drawing.

The heating resistor layer 20 is made of NiCr (nickel / chromium), and has a heating portion 20a formed on each shape regulating portion 19b of the bias spring layer 19 and one support portion 19a of the bias spring layer 19. A common electrode section 20b formed on the top and grounding one end of each heat generating section 20a;
An individual electrode section 20c is formed on the other support section 19a and connected to the other end of each heat generating section 20a. Each individual electrode section 20c is connected to a drive circuit 29 shown only in FIG.

The nozzle plate 21 has a thickness of 0.2 m.
A nozzle 21a communicating with the ink channel 23 and an ink supply passage 21b for communicating the ink tank with the ink channel 23 are formed.

A method of manufacturing the ink jet recording head 10 will be described. First, a shape memory material layer 18 made of a thin film of TiNi is provided on the entire one surface 17b of the flow path substrate 17 made of Si by a sputtering method.
Next, a silicon nitride film 25 and a silicon oxide film 27 are sequentially formed on the shape memory material layer 18 by a sputtering method. Further, the heating resistor layer 20 made of NiCr is formed on the silicon oxide film 27 by a sputtering method. In this state, annealing is performed at 500 ° C. to store the planar shape in the shape memory material layer 18.

Thereafter, a slit is formed on the surface of the flow path substrate 17 opposite to the shape memory material layer 18 by a reactive gas plasma ion etching method (RIE) using SF ₆ (sulfur hexafluoride). Further, the silicon nitride film 25 and the silicon oxide film 27 are etched by RIE using CHF ₃ (carbon trifluoride) and CF ₄ (carbon tetrafluoride), respectively, and the bias spring layer 19 is formed as described above. Is formed into a shape having a supporting portion 19a and a shape regulating portion 19b. Further, the nozzle plate 21 is attached to the other surface of the flow path substrate 17.

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 layer 20 is stopped, as shown in FIGS. 3 and 4, each shape regulating portion 19b of the bias spring layer 19 is formed. Due to the elastic restoring force, the upper wall portion of the ink channel 23 of the shape memory material layer 18, which is a martensite phase, has a shape bulging upward.

When the heating resistor layer 20 is energized by the drive circuit 29 to generate heat and the temperature of the shape memory material layer 18 rises to the transformation temperature or higher, the upper wall portion of the shape memory material layer 18 in the austenite phase is removed. As shown in FIG. 5 and FIG. 6, the constituting portion has a planar shape against the restoring force of the shape regulating portion 19 b of the bias spring layer 19. As a result, the volume of the ink channel 23 decreases, and the pressurized ink is ejected from the nozzle 21a.

When the energization of the heating resistor layer 20 is stopped and the shape memory material layer 18 is cooled below the transformation temperature and returns to the martensite phase, the upper wall of the ink channel 23 of the shape memory material layer 18 is formed. The portion returns to the upwardly bulged shape shown in FIGS. 3 and 4 by the urging force of the shape regulating portion 19b. As a result, the volume of the ink channel 23 increases, and ink is supplied to the ink channel 23 via the ink supply path 21b.

As described above, the heating and cooling of the shape memory material layer 18 are repeated by applying and removing electricity to and from the heating resistor layer 20, thereby deforming the shape memory material layer 18, thereby repeatedly discharging ink droplets.

In the first embodiment, as described above, the width W2 of the shape restricting portion 19b of the bias spring layer 19 is smaller than the width W1 of the ink channel 23 and the shape restricting portion 19b.
b is provided with a gap 24 between both ends in the width direction of the ink channel 23. That is, in the vicinity of both ends in the width direction of the ink channel 23, the upper opening in the drawing of the ink channel 23 is
And the shape regulating portion 19 does not exist. Therefore, when the shape memory material layer 18 is repeatedly deformed by repeating heating and cooling, the shape memory material layer 18 in the gap 24 expands and contracts on the order of several percent without being restricted by the shape restricting portion 19. be able to. Therefore, in the first embodiment, the amount of expansion and contraction of the shape memory material layer 18 in the width direction of the ink channel 23 is large, and the volume change rate of the ink channel 23 before and after energizing the heating resistor layer 20 is correspondingly large. . Therefore, in the ink jet recording head 10 of the first embodiment, the volume of the ink channel 23 can be reduced, and the density and the size can be reduced.

Also, as described above, the ink channel 23
Is large, the length L1 of the ink channel 23 can also be reduced. Therefore, the characteristic of the natural oscillation period of the ink contained in the ink channel 23 is improved, and smaller ink droplets can be made to fly at a higher ejection speed.

Further, as described above, since the shape regulating portion 19b is provided only in a part of the shape memory material layer 18 in the width direction of the ink channel 23, the shape regulating portion 19b before and after the deformation of the shape memory material layer 18 is formed. The amount of deformation is small. For this reason, destruction due to repeated deformation of the shape regulating portion 19 together with the shape memory material layer 18 is prevented.

(Second Embodiment) An ink jet recording head 10 according to a second embodiment of the present invention shown in FIGS.
The configuration of the bias spring layer 19 is different from that of the first embodiment.

That is, the bias spring layer 19 of the second embodiment is formed of an aluminum plate 31 having a thickness of 70 μm on the shape memory material layer 18, that is, the ink channel 23 side. A 70 μm nickel plate 33 is laminated. The aluminum plate 31 and the nickel plate 33 are processed into a shape having a support portion 19a and a shape regulating portion 19b, respectively. Then, the aluminum plate 31 is joined to the shape memory material layer 18 under the temperature condition of 500 ° C., and the nickel plate 33 is further joined to the aluminum plate 31. Thermal expansion coefficient of aluminum plate 31 (23.2 × 10 ⁶ (1 / ° C.))
Is the coefficient of thermal expansion of the nickel plate 33 (12.7 × 10 ⁶ (1
/ ° C)), so in a state where the temperature has dropped to room temperature,
As in the case of the first embodiment, the shape regulating portion 19b has an upwardly bulging shape, and applies an upward urging force to a portion of the shape memory material layer 18 that forms the upper wall of the ink channel 23.

The ink channel 23 has a length L1.
Is 1 mm, the width W1 is 100 μm, the thickness of the shape memory material layer 18 is 5 μm, and the width W2 of the shape regulating portion 19 b is 40 μm.
It is.

When the characteristics of the ink jet recording head of the second embodiment were tested using the aqueous ink,
The flying of the 1 ink drop was confirmed.

In the ink jet recording head of the second embodiment as well, the shape restricting portion 19b of the bias spring layer 19 has the width W2 smaller than the width W1 of the ink channel 23, and is provided at both ends in the width direction of the ink channel 23. The gaps 24 are provided in the shape memory material layer 1
When the deformation is repeated, the shape memory material layer 18 can expand and contract in the vicinity of both ends in the width direction of the ink channel 23 without being restricted by the shape restriction part 19. The amount of expansion and contraction in the width direction is large, and the volume change rate of the ink channel 23 is large. Therefore, the volume of the ink channel 23 is reduced,
Higher density and smaller size can be achieved.

Further, as in the first embodiment, the characteristic period of the ink is improved by reducing the length of the ink channel 23, and the shape regulating portion 19 is formed by the shape memory material layer 18.
In addition, it is possible to prevent destruction due to repeated deformation.

(Third Embodiment) A third embodiment of the present invention shown in FIG.
In the ink jet recording head 10 of the embodiment, the bias spring layer 19 includes only one support portion 19a,
One end of each shape regulating portion 19b is connected to the supporting portion 19a, and the other end is a free end. In the heating resistor layer 20, the free end side of each shape regulating portion 19b is grounded.

In the third embodiment, the shape regulating portion 19b
The deformation of only one end is restricted by the support portion 19a. Therefore, compared to the case where both ends of each shape regulating portion 19b are connected to the support portion 19a as in the first embodiment, The upward swelling amount of the shape regulating portion 19b is increased. Then, the volume of the ink channel 23 at the time of non-energization increases by that amount, so that the volume change rate increases, and the volume of the ink droplet increases.

Other configurations and operations of the third embodiment are the same as those of the first embodiment.

(Fourth Embodiment) In an ink jet recording head 10 according to a fourth embodiment of the present invention shown in FIG. 10, the bias spring layer 19 does not have a support as in the first embodiment, and each ink channel has A rectangular parallelepiped shape regulating portion 19b is provided for each 23. The heating resistor layer 20
Has one end connected to the drive circuit 29 and the other end grounded for each shape regulating portion 19b.

In the third embodiment, each shape regulating portion 19
Since the deformation of both ends is not constrained, the volume of the ink channel 23 at the time of non-energization is further increased, the volume change rate is increased, and the volume of the ink droplet is increased as compared with the first embodiment.

Other configurations and operations of the fourth embodiment are the same as those of the first embodiment.

(Fifth Embodiment) An ink jet recording head 10 according to a fifth embodiment of the present invention shown in FIGS.
Then, the shape memory material layer 18 is provided for each ink channel 23.
In the figure, a rectangular second bias spring layer 19 and a heating resistor layer 20 are also provided on the lower surface side. In the second bias spring layer 19, a silicon oxide film 27 is formed on the lower surface of the shape memory material layer 18, and a silicon nitride film 25 is further formed on the lower surface of the silicon oxide film 27. Are elastically urged to bulge upward in the figure. The second bias spring layer 19 is provided with a gap 24 between both ends in the width direction of the ink channel 23.

The other structure of the fifth embodiment is the same as that of the first embodiment.

(Sixth Embodiment) An ink jet recording head 10 according to a sixth embodiment of the present invention shown in FIGS.
Then, a silicon nitride film 25 is provided in each ink channel 23.
The bias spring layer 19 and the heating resistor layer 20 are provided, and the bias spring layer 19 and the heating resistor layer 20 are not provided on the upper surface side of the ink channel 23.

The other configuration of the sixth embodiment is the same as that of the first embodiment.

Also in the third to sixth embodiments, the shape restricting portion 19b of the bias spring layer 19 has the width W2 smaller than the width W1 of the ink channel 23, and is provided at both ends in the width direction of the ink channel 23. Because the gap 24 is provided with the gap 2, the gap 2 of the shape memory material layer 18 is formed.
The amount of expansion and contraction in the width direction of the ink channel 23 in the portion corresponding to No. 4 is large. As a result, the rate of change in the volume of the ink channel 23 increases, so that the volume of the ink channel 23 can be reduced and the density and size of the ink jet recording head can be increased. Further, as in the first embodiment, it is possible to improve the characteristic period characteristic of the ink by reducing the length of the ink channel 23 and to prevent destruction caused by the shape restricting portion 19 being repeatedly deformed together with the shape memory material layer 18. Can be planned.

The present invention is not limited to the above embodiment, and various modifications are possible. First, the shape memory material layer is
Not limited to the above thin film of TiNi alloy,
Other shape memory alloys such as an alloy to which Cu and Cu are added, and a Cu—Zn—Al alloy may be used. Further, the shape memory material layer may be made of a shape memory resin and a shape memory fiber. Further, the shape memory material layer may be formed of a composite material including at least one of a shape memory alloy, a shape memory resin, and a shape memory fiber.

The heating resistor layer is not limited to NiCr, but may be another material such as TaN (tantalum nitride), HfB ₂ , TaAl. Further, a heating resistor layer may be provided between the shape memory material layer and the bias spring layer.

The means for heating the shape memory material layer is not limited to the means for energizing the heat generating resistor. The means for heating the shape memory material layer is divided for each ink channel, and the energized current is applied to each of the divided shape memory material layers. The temperature of the shape memory material layer may be increased by the generated resistance heat.

A protective film for improving the durability may be formed on a portion of the shape memory material layer which comes into contact with the ink. 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 shape memory material layer becomes flat when heated, but may protrude into the ink channel when heated. Further, the shape memory material layer may be flat at normal temperature, and may protrude into the ink channel when heated.

[0056]

As is apparent from the above description, in the ink jet recording head of the present invention, the shape regulating means occupies a part of the width of the ink channel on at least one surface side of the shape memory material layer, and Since there is a gap between both ends in the width direction of the ink channel, only the shape memory material layer exists in the gap between the shape regulating means and the both ends in the width direction of the ink channel. However, there is no shape regulating portion. Therefore, in this portion, the elasticity of the shape memory material layer in the ink channel width direction is not restricted by the shape restricting portion, and the deformation amount of the shape memory material layer is large. Therefore, in the ink jet recording head of the present invention, the rate of change in the volume of the ink channel between normal temperature and heating is large, and the volume of the ink channel can be reduced to achieve higher density and smaller size.

Further, in the ink jet recording head of the present invention, since the volume change rate of the ink channel is large as described above, the length of the ink channel can be reduced. Therefore, the characteristic of the natural oscillation cycle of the ink contained in the ink channel is improved, and smaller ink droplets can be made to fly at a higher ejection speed.

Further, in the ink jet recording head of the present invention, since the shape regulating portion is provided only in a part of the shape memory material layer in the width direction of the ink channel, the amount of deformation of the shape regulating portion before and after the deformation of the shape memory material layer is reduced. small. Therefore, it is possible to prevent the destruction caused by the deformation of the shape regulating member together with the shape memory material layer.

[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 perspective view showing an ink jet recording head of the present invention.

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

FIG. 6 is a cross-sectional view taken along line IV-IV of FIG. 2 when an ink droplet is ejected.

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

FIG. 8 is a cross-sectional view illustrating an inkjet recording head according to a second embodiment of the present invention.

FIG. 9 is a perspective view illustrating an inkjet recording head according to a third embodiment of the present invention.

FIG. 10 is a perspective view illustrating an inkjet recording head according to a fourth embodiment of the present invention.

FIG. 11 is a longitudinal sectional view showing an inkjet recording head according to a fifth embodiment of the present invention.

FIG. 12 is a cross-sectional view illustrating an inkjet recording head according to a fifth embodiment of the present invention.

FIG. 13 is a longitudinal sectional view showing an ink jet recording head according to a sixth embodiment of the present invention.

FIG. 14 is a cross-sectional view illustrating an inkjet recording head according to a sixth embodiment of the invention.

15A is a plan view showing a conventional inkjet recording head, and FIG. 15B is a cross-sectional view taken along line XV-XV in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Ink jet recording head 11 Ink jet recording apparatus 17 Flow path substrate 18 Shape memory material layer 19 Bias spring layer 19a Support part 19b Shape regulating part (shape regulating means) 20 Heating resistor layer 21 Nozzle plate 21a Nozzle 21b Ink supply path 23 Ink channel Reference Signs List 25 silicon nitride film 27 silicon oxide film 29 drive circuit 31 aluminum plate 33 nickel plate

Claims (1)

[Claims] 1. A shape memory material layer constituting a part of a wall portion of an ink channel, heating means for heating the shape memory material layer, and a shape memory material layer deformed in a direction opposite to a shape at the time of heating. An ink jet recording head comprising: a shape regulating means for elastically urging the ink channel; and a nozzle communicating with the ink channel, wherein the ink channel has an elongated shape having a longitudinal direction and a width direction, and Is provided on at least one surface side of the shape memory material layer so as to occupy a part of the width direction of the ink channel and to have a gap between both end portions in the width direction of the ink channel. An ink jet recording head characterized by the following.