JP3495649B2 - Inkjet head - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bubble jet type ink jet head in which ink is heated and foamed by a heating element to eject the ink.

[0002]

2. Description of the Related Art Conventionally, there has been a bubble jet type ink jet head as a recording head (inkjet head) of an ink jet printer. In this bubble jet type inkjet head, a pulse current is applied to a heating element (heater) to generate heat, whereby the ink is foamed and ejected to the outside.

In this bubble jet type ink jet head, the heat of the heater is diffused to the substrate of the ink jet head, so that the amount of heat contributing to the heating of the ink is reduced and the rise in the temperature of the ink is hindered. Since it was necessary to increase the amount of electricity to make up for it,
There is a problem that power consumption increases.

Therefore, in order to solve this problem, in the structure disclosed in Japanese Patent Laid-Open No. 7-227968, a heat insulating space as a heat insulating layer is provided below the heater to prevent heat diffusion to the substrate. It is like this.

Further, Japanese Patent No. 2759447 discloses that
It is disclosed that two types of layers having different thermal conductivities are provided between the heater and the substrate to suppress heat diffusion to the substrate. Further, as a technique for obtaining the same effect, there is also a technique in which a glass glaze layer having a low thermal conductivity is arranged below the heater.

[0006]

However, in the ink jet head as described above, it is difficult to lower the temperature of the heater which has once generated heat and has risen in temperature. Therefore, even if a pulse current is applied to the heater, the temperature is not so high. The next pulse current will be applied while it is not decreasing,
There is a problem in that the heater intermittently generates heat and becomes in an overheated state, the response frequency of the heater is lowered, and the ink ejection amount cannot be controlled.

The present invention has been made in order to solve such a problem, and it is possible to prevent the heat diffusion of the heater when the heat is generated and to surely raise the temperature, and to lower the temperature of the heater after the heat is generated. The purpose of this is to make it possible to carry out reliably in a short time.

[0008]

[Means for Solving the Problems] To achieve the above-mentioned object.
The ink jet head of the present invention for, by causing the heating element originating heated, in an inkjet head that ejects ink, a nozzle for ejecting ink is provided
Nozzle plate and spacer facing the nozzle plate
Between the head substrate for encapsulating the ink via
With the heating element interposed, the head substrate is provided with the heating element.
A recess for constituting a covered space in provided, the space portion
A communication hole communicating with the outside atmosphere is provided in the substrate, and the heating element is configured to buckle in the void due to thermal expansion due to temperature rise.

Therefore, when the ink is heated, the heat insulating effect of the voids suppresses the diffusion of the heat of the heating element and enables a rapid temperature rise, and after the ink is ejected, the heating of the heating element is caused by the buckling of the heating element and the head substrate. By radiating heat through
It is possible to reduce the temperature of the heating element in a short time.

The heating element of the present invention comprises a heater, a protective film that protects the heater, and an insulating film that insulates the heater, and each component is formed of materials having substantially the same linear expansion coefficient.

Therefore, it is possible to prevent the occurrence of cracks due to the heat cycle.

The heating element of the present invention is arranged so as to regulate the thickness of both end portions and the movement of the thickness in the direction at right angles.

Therefore, it is possible to reliably buckle the heating element in the void.

The heating element of the present invention is configured to come into contact with the head substrate when buckled in the void.

Therefore, the heat of the heating element can be satisfactorily diffused by heat conduction to the head substrate.

[0016]

[0017]

According to the present invention, the head substrate is provided with a communication hole for communicating the void with the outside.

Therefore, it is possible to radiate the heat in the void to the outside through the communication hole.

[0020] have a bimetal structure consisting of a plurality of metal material to deform the void portion by the temperature rise of the originating heat of the present invention.

Therefore, it is possible to surely deform the heating element into the void.

[0022] to form a shape memory alloy layer to deform into the gap portion when the outgoing heat of the present invention exceeds a predetermined temperature.

Therefore, it is possible to surely deform the heating element into the void portion.

Further , the present invention for achieving the above-mentioned object
Nozurupure Ming inkjet head, by causing the heating element originating heated, in an inkjet head for ejecting ink, the nozzles for ejecting ink provided
And a nozzle corresponding to the nozzle plate via a spacer.
The heating element between the head substrate and the
The interposed, on the head substrate, corresponding to the said nozzle
A recess for constituting the space provided to the piezoelectric element for deforming the heating element to the pressing and the void portion, the Nozurupu
One end is fixed to the rate side and the other end is opposed to the above space.
Are arranged so that

Therefore, it is possible to surely deform the heating element into the void.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of a general bubble jet type ink jet head as an ink jet head of the present invention will be described with reference to FIGS. Figure 1
2 is a top view showing the ink jet head of Embodiment 1, and FIG. 2 is a sectional view.

In the ink jet head of the first embodiment, the heating element 4 is arranged between the nozzle plate 1 and the substrate 2 via the spacers 3 and 3.

A cavity 5 for enclosing the ink is provided between the spacers 3 and 3, and a nozzle 6 for ejecting the ink is provided in the central portion of the nozzle plate 1.

Further, a void portion 7 as a heat insulating layer is formed below the heating element 4. The void 7 is formed on the substrate 2
Is a concave portion formed in the above, and is a space between the substrate 2 and the heating element 4. The void 7 has a function of reducing heat conduction between the heating element 4 and the substrate 2.

The ink jet head having such a configuration is set so that the heating element 4 heats in a pulsed manner by a pulse current applied from a pulse power source (not shown) during ink ejection. As a result, the ink in the cavity 5 is instantaneously boiled and foamed, and the nozzle 6
It is designed to eject ink from.

Next, the heating element 4 of the ink jet head will be described.

As shown in FIG. 2, the heating element 4 has its both ends fixed to the spacer 3 and the substrate 2, and is composed of a protective film 11, a heater 12 and an insulating film 13.

The protective film 11 is for preventing the ink in the cavity 5 from adhering to the heater 12. The insulating film 13 prevents the pulse current applied to the heater 12 from leaking to the substrate 2. The heater 12 is
It is a thin film made of a metal having a high coefficient of thermal expansion and a high electric resistance value.

The heater 12 generates heat by the pulse current applied from the pulse power source, and the temperature of the entire heating element 4 at which the ink in the cavity 5 can be foamed by film boiling (hereinafter referred to as the foaming temperature). It is set to heat up to (referred to).

Wirings 14 for supplying a pulse current from the pulse power source to the heater 12 are arranged at both ends of the heater 12.

Further, when the temperature of the heating element 4 exceeds the bubbling temperature, the heater 12 buckles due to thermal energy (thermal expansion), deforming the entire shape of the heating element 4, and part of it is transferred to the substrate 2. It has the function of contacting.

That is, as shown in FIG. 3, below the foaming temperature, the heating element 4 maintains a horizontal state (adiabatic state) on the substrate 2. When the foaming temperature is exceeded, as shown in FIG. 4, the heating element 4 buckles due to the buckling of the heater 12.
Is in a state of being bent toward the void 7 until it comes into contact with the substrate 2. Due to this bending, part of the heating element 4 (heater 12) comes into contact with the substrate 2 (heat radiation state), and the heat of the heating element 4 (heater 12) is transferred to the substrate. Two
And the heat is dissipated, the heating element 4 returns to the adiabatic state shown in FIG.

The heater 12 is made of nickel having a thickness of 6.5 μm and a length of 150 μm, and is heated to about 500 degrees with respect to the buckling start temperature of 370 degrees to eject ink. .

The nozzle plate 1 is a stainless etching plate, a nickel electroformed plate, a photosensitive glass, precision molded plastic, etc., the spacer 3 is polyimide, nickel plating, a dry film, etc., and the protective film 11 is polyimide, SiO ₂ , SiN, etc.
The wiring 14 is Ta, Ni, Au, Al, etc., the heater 12 is Ta, Ni, HfB _2, etc., the insulating film 13 is polyimide, SiO ₂ , SiN, etc., and the substrate 2 is glass, ceramic, stainless steel, nickel, etc. Materials such as silicon can be used.

As described above, the ink jet head is provided with the void portion 7 between the heating element 4 and the substrate 2, thereby preventing heat conduction between the heating element 4 and the substrate 2. Therefore, the temperature of the heating element 4 can be instantaneously raised to the foaming temperature.

Further, after the foaming temperature is reached, the heater 12
Since the heating element 4 is buckled along with the buckling of the heating element 4 and a part of the heating element 4 contacts the substrate 2, the heat of the heating element 4 is radiated in a very short time, and The temperature drops in a short time and returns to an adiabatic state.

As a result, in the ink jet head of the first embodiment, the response frequency of the heater 12 can be made substantially equal to the frequency of the applied pulse current, so that the ink ejection amount can be controlled very accurately.

In the first embodiment, the heating element 4 is composed of the protective film 11, the heater 12 and the insulating film 13. However, materials having thermal expansion coefficients substantially equal to each other should be used as these materials. Is preferred. This is to suppress the generation of cracks due to heat cycles.

Further, it is preferable to apply silicon oil to the contact portion between the heating element 4 and the substrate 2. Thereby, heat diffusion from the heating element 4 to the substrate 2 can be promoted.

In the first embodiment, both ends of the heating element 4 are fixed to the spacer 3 and the substrate 2.
However, the installation state of the heating element 4 is not limited to this.
The heating element 4 may be installed in any way as long as it is restricted from moving in a direction perpendicular to the thickness direction (direction perpendicular to the plane of the paper in FIG. 2, or left-right direction).

In the first embodiment, when the temperature of the heating element 4 exceeds the buckling temperature, the heater 12 buckles and the heating element 4 comes into contact with the substrate 2.

However, the buckling of the heater 12 does not have to be accompanied by such a large deformation. That is, when the heating element 4 exceeds the buckling temperature, the heater 12 heats the heating element 4
The heating element 4 (heater 12) can be cooled by heat diffusion to the substrate 2 if the distance between the heating element 4 and the substrate 2 is shortened. be able to.

Further, in the first embodiment, the gap 7 is formed on the substrate 2
However, the configuration of the void portion 7 is not limited to this, and for example, as shown in the second embodiment of FIGS. 5 and 6, the substrate 7 communicates the void portion 7 with the outside atmosphere. You may make it provide such a communicating hole 8.

In this way, the pressure rise in the void 7 due to the deformation of the heating element 4 can be avoided, so that the buckling of the heating element 4 is facilitated, and the ventilation in the void 7 communicates with this. Because of the holes 8, the heating element 4 (heater 1
The cooling of 2) can be promoted.

[0050]

In the first embodiment, the heater 12 is made of a metal thin film having a high coefficient of thermal expansion and a high electric resistance, but the heater 12 may be a laminated film made of a plurality of metal thin films.

That is, as shown in the third embodiment of FIG. 7, two kinds of metals A and B having different thermal expansion coefficients can be laminated and used as the heater 12 (in FIG. 7, the insulating film 13 is used). Is omitted).

By forming the heater 12 into such a bimetal structure, the deformation direction of the heater 12 can be controlled well.

In the first embodiment, the heater 12 buckles when the temperature of the heater 12 exceeds the buckling temperature. However, the configuration of the heating element 4 is not limited to this, and for example, as shown in the fourth embodiment of FIG.
Shape memory alloy (SMP: Shape Mem)
You may make it arrange | position the thin film of ory Arrow15.

That is, the shape memory alloy 15 is in a horizontal state (see FIG. 8A) with the substrate 2 at a low temperature, and is in a deformed state (see FIG. 8B) when the deformation temperature is exceeded. When set to, the deformation and cooling of the heating element 4 can be realized well. If such a shape memory alloy 15 is used, it is not necessary to use a material having a high coefficient of thermal expansion as the material of the heater 12.

In the first embodiment, the heating element 4 is connected to the substrate 2
In order to bring the heater 12 into contact with the heater 12 to cool the heater 12, the spontaneous shape change of the heating element 4 is used. That is, the heater 12
Alternatively, the material of the shape memory alloy 15 can be selected so as to be deformed in the void portion 7 at a temperature exceeding the deformation temperature, whereby the contact between the heater 12 and the substrate 2 can be realized.

However, the construction of the ink jet head of the first embodiment is not limited to this, and for example, the ink jet head may be of a type in which the piezoelectric element is used to forcefully push the heating element 4 into the space 7.

FIG. 9 is an explanatory view showing the construction of the fifth embodiment of the ink jet head when this system is adopted. As shown in FIG. 9, in this configuration, the piezoelectric element 21 is provided on the nozzle plate 1 so that the heating element 4 faces the nozzle plate 1.

The piezoelectric element 21 is set so as to extend toward the heating element 4 when a voltage is applied by a power source (not shown). Then, it has a function of pushing the heating element 4 into the space 7 and bringing it into contact with the substrate 2.

According to this structure, it is possible to realize the contact between the heating element 4 and the substrate 2 regardless of the material of the heater 12 and without using the SMP 15. Also, the heating element 4
Since the displacement amount and the contact time with the substrate 2 can be set arbitrarily, the response frequency of the heater 12 can be controlled with extremely high accuracy, and the ink ejection amount can be adjusted with extremely high accuracy.

As the piezoelectric element 21, it is preferable to use a laminated piezoelectric element in which a plurality of piezoelectric elements are laminated. Further, in this case, it is preferable to press the heating element 4 by the displacement of each piezoelectric element in the thickness direction.

In this way, the voltage applied to the piezoelectric element 21 can be reduced to 40 V or less, and the shape of the piezoelectric element 21 can be changed at high speed. Therefore,
The response frequency in the heater 12 can be controlled with higher accuracy.

Further, as the piezoelectric element 21, a thin film piezoelectric element 21 may be used. For example, in the configuration shown in the sixth embodiment of FIG. 10, the piezoelectric element 21 has a laminated structure (bimorph structure) of the first piezoelectric film 22 and the second piezoelectric film 23.
Has become.

The piezoelectric element 21 is set so that the first piezoelectric film 22 extends in the direction parallel to the film surface while the second piezoelectric film 23 contracts in the same direction by the application of a voltage. Accordingly, by applying a voltage, the pressing portion 31 formed at the end of the piezoelectric element 21 presses the heating element 4 downward, and the heating element 4 and the substrate 2 can be brought into contact with each other. By doing so, the structure of the inkjet head can be simplified and the assembling workability can be improved.

The material of the first piezoelectric film 22 and the second piezoelectric film 23 is, for example, PZT (lead zi).
rconium titanate) can be used.

In the configuration shown in FIG. 10, the first
Instead of the piezoelectric film 22, a metal thin film such as stainless steel may be used (unimorph structure). Also in this configuration, the displacement of the piezoelectric element 21 can be favorably realized, and the structure of the piezoelectric element 21 can be simplified to reduce the manufacturing cost.

[0067]

According to the present invention , when the ink is heated, the adiabatic effect of the void portion suppresses the diffusion of heat of the heating element and enables a rapid temperature rise, and after the ink is ejected, the heating element buckles to generate heat. By radiating the heat of the body through the head substrate, the temperature of the heating element can be lowered in a short time, and the ink ejection control can be reliably performed. in this case,
Provide a communication hole to communicate the void of the head substrate with the outside.
Therefore, the heat in the void is radiated to the outside through the communication hole.
Can improve the heat dissipation efficiency of the heating element.
it can.

The heating element of the present invention comprises a heater, a protective film for protecting the heater, and an insulating film for insulating the heater, and each of the constituent members is made of materials having substantially the same linear expansion coefficient. It is possible to prevent the occurrence of cracks due to heat cycles.

[0069]

Since the heating element of the present invention is constructed so as to come into contact with the head substrate when buckling into the void, the heat of the heating element can be diffused satisfactorily by heat conduction due to contact with the head substrate. It is possible to control the ink ejection amount with high accuracy.

[0071]

[0072]

Further , since the heating element has a bimetal structure made of a plurality of metal materials so as to be deformed into a void due to a temperature rise, the direction of deformation of the heating element can be easily set, and the deformation into the void can be ensured. Therefore, it is possible to control the ejection amount of ink with high accuracy.

Further , by providing the shape memory alloy layer on the heating element so as to be deformed toward the void side when the temperature exceeds the predetermined temperature,
The deformation direction of the heating element can be easily set, the heating element can be surely deformed into the void portion, and the ink ejection amount can be controlled with high accuracy.

Further , according to the present invention, a piezoelectric element is provided.
As a result, the heating element can be reliably deformed into the void portion, and the ink ejection amount can be controlled with high accuracy.

[Brief description of drawings]

FIG. 1 is a top view showing a first embodiment of an inkjet head of the present invention.

FIG. 2 is a sectional view showing Embodiment 1 of the inkjet head of the present invention.

FIG. 3 is an explanatory diagram showing a heat insulating state of the first embodiment of the inkjet head of the present invention.

FIG. 4 is an explanatory diagram showing a heat radiation state of the first embodiment of the inkjet head of the present invention.

FIG. 5 is a top view showing Embodiment 2 of the inkjet head of the present invention.

FIG. 6 is a sectional view showing Embodiment 2 of the inkjet head of the present invention.

FIG. 7 is a sectional view showing Embodiment 3 of the inkjet head of the present invention.

FIG. 8A is a sectional view showing a heat insulating state of an inkjet head according to a fourth embodiment of the present invention, and FIG. 8B is a sectional view showing a heat radiating state.

FIG. 9 is a sectional view showing Embodiment 5 of the inkjet head of the present invention.

FIG. 10 is a sixth embodiment of the inkjet head of the present invention.
FIG.

[Explanation of symbols]

1 nozzle plate 2 substrates 3 spacers 4 heating element 5 cavities 6 nozzles 7 Void 11 Protective film 12 heater 13 Insulating film 14 wiring

Claims (6)

(57) [Claims] By 1. A causing the heating element originating heated, in
In the inkjet head that ejects click, a nozzle plate in which the nozzles for ejecting ink is provided
And ink through the spacer facing the nozzle plate.
The heating element is inserted between the head substrate for enclosing
And a space portion covered by the heating element is formed on the head substrate.
And a communication hole through which the space communicates with the external atmosphere in the substrate.
An inkjet head , wherein the heating element is configured to buckle in the void due to thermal expansion due to temperature rise. 2. The heating element protects the heater and the heater.
Install the protective film on the nozzle side and the heater from the head substrate.
Ri is composed of an insulating insulating film, ink jet head according to claim 1, characterized in that formed at substantially equal material from each other linear expansion coefficient of each component. 3. The ink jet head according to claim 1, wherein the heating element is configured to come into contact with the head substrate when buckled in the void. 4. The ink jet head according to claim 1, wherein the heating element has a bimetal structure made of a plurality of metal materials so as to be deformed into the voids due to a temperature rise. 5. A shape memory alloy layer is formed on the space side so that the heating element is deformed to the void side when the temperature exceeds a predetermined temperature.
The ink jet head according to claim 1, wherein the ink jet heads are laminated . By 6.] be a heating element originating heated, Inn
In the inkjet head that ejects click, a nozzle plate in which the nozzles for ejecting ink is provided
And ink through the spacer corresponding to the nozzle plate
The heating element is inserted between the head substrate for enclosing
Zaisa allowed, in the head substrate, space so as to correspond with the nozzle
A piezoelectric element that forms a concave portion that presses the heating element and deforms it toward the void portion is fixed at one end to the nozzle plate side, and the other end is raised.
An ink jet head, which is arranged so as to face the storage space .