JP2003291350A - Ink jet recording head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an ink jet recording head for ejecting liquid by bubbling with heat generated from a heat generating means in which the heat generating means is prevented from having an excessively high temperature by controlling unnecessary heat generation of the heat generating means. <P>SOLUTION: The heat generating means comprises a heating resistor, especially a PTC thermistor heater, having a positive temperature coefficient of resistance where the resistance R increases abruptly when a specified temperature T0 is exceeded. The temperature T0 is preferably set substantially equal to the bubbling point Tb of the liquid. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet printer, and more particularly, to an inkjet recording head applied to a bubble jet (registered trademark) printer that utilizes a foaming phenomenon.

[0002]

2. Description of the Related Art A recording head applied to a bubble jet recording system generally has a fine ejection hole for ejecting a liquid,
It is provided with a flow path for guiding the liquid to the discharge hole and a heat generating means provided in a part of the flow path. What is bubble jet recording method?
By locally raising the temperature of the liquid in the flow path using a heat generating means, the liquid is foamed to generate bubbles, and the high pressure generated at the time of foaming is used to extrude the liquid from the minute discharge holes. This is a recording method in which liquid is attached to recording paper or the like.

In order to enhance the quality of an image recorded by this type of recording technique, there is required a technique for ejecting minute liquid droplets from ejection holes arranged at high density. Therefore, it is basically important to form fine flow paths and fine heat generating means. Therefore, in the bubble jet recording method, a method of making a recording head in which ejection holes, flow paths, and heating elements are arranged at high density is proposed by taking advantage of the simplicity of the structure and making full use of photolithography process technology ( See, for example, Japanese Patent Laid-Open No. 08-15629). Further, in order to adjust the discharge amount of droplets so that minute droplets can be discharged, it has been proposed to use a heating element that generates a larger amount of heat in the central portion than in the end portions (Japanese Patent Laid-Open No. 62-201254). (See Japanese Patent Publication).

The heat generating means usually has a thickness of 0.05 μm.
A resistance heating element composed of a thin film of tantalum nitride having a thickness of about m is used, and the liquid is foamed by Joule heat when energized. On such a resistance heating element, in order to prevent the surface of the resistance heating element from being damaged by cavitation, a thickness of about 0.2 μm is usually provided through an insulator such as SiN of about 0.8 μm. An anti-cavitation layer made of a metal such as Ta is arranged.

In the recording head of the bubble jet recording system as described above, the resistance heating element for ink bubbling usually has some variation in the finish resistance of itself and the resistance of the wiring to be connected. Therefore, even if the voltage is applied under a constant condition, the voltage drop due to the resistance varies, and thus the heat generation amount of the heater configured by the resistance heating element varies. Therefore, the drive voltage for driving the heater array composed of a plurality of heaters is normally set to the liquid of the individual resistance heating elements for the reason such as avoiding that the image quality is affected by the variation in the heat generation amount. Is set to a voltage value higher than a voltage value required to stably generate foaming on the entire surface facing the surface, in particular, a voltage value about 1.2 times the required voltage value.

[0006]

However, when the driving voltage is set to a high value as described above, the effect of variations in finish resistance, wiring resistance, etc. is small, and an average heater that does not cause a very large voltage drop is used. In principle, unnecessary heating is continued after foaming because an excessive voltage is applied to the entire surface.

Specifically, for example, when a heater is driven by applying a pulse voltage of 1 μs, typically, the entire surface is foamed in about 0.6 μs after the application of the pulse voltage is started. Then, even after the entire surface is foamed, unnecessary heating (excessive heating) is continued by applying a voltage to the heater. As a result, the heater surface typically reaches a high temperature of about 600 to 700 ° C. with respect to a foaming temperature of about 300 ° C., and there is a possibility that the heater surface may reach a higher temperature depending on conditions.

That is, the fact that the excessive heating is continued in principle in this way has the following disadvantages. Since energy is supplied even after the entire surface is foamed, the energy is wasted accordingly. Since the heater temperature may theoretically become excessively high, it is necessary to increase the heat resistance of the heater material more than necessary. Also, in some cases, there is a danger that the heater will be thermally destroyed. Further, rapid temperature changes are repeatedly generated, which may cause deterioration of durability performance.

Therefore, if it is possible to suppress excessive heat generation of the heater after foaming, it is possible to provide a preferable ink jet recording head from the viewpoints of energy saving, improvement of durability, prevention of thermal destruction, reduction of manufacturing cost and the like. is there.

In view of the above problems in the prior art, it is an object of the present invention to provide an ink jet recording head provided with a heater (heat generating means) capable of suppressing excessive heat generation after foaming.

[0011]

In order to achieve the above object, an ink jet recording head of the present invention has a heat generating means, and the liquid is foamed by the heat generating means, and the liquid is ejected by the pressure generated at the time of foaming. In the head, the heat generating means is composed of a resistance heating element having a positive resistance temperature coefficient in which the resistance value sharply increases when the temperature of the surface of the heat generating means in contact with the liquid rises above a predetermined temperature. Is characterized by.

As the resistance heating element having the above-mentioned characteristics, for example, Japanese Patent Application Laid-Open No. 5-47457 proposes an organic sheet heating element having a positive temperature coefficient (PTC) characteristic. Further, JP-A-5-258840 proposes a PTC heating device in which a plurality of PTC elements are connected in parallel. Further, in Japanese Patent Laid-Open No. 4-97927, an ink ejecting device for ejecting a liquid by using piezoelectric ceramics, an ink in which a temperature of ink in a nozzle is kept within a required temperature range by using a PTC thermistor heating element An injection device is disclosed. The resistance heating element in the present invention can be formed by appropriately applying the techniques described in these documents, that is, in particular, a PTC thermistor heating element can be used.

According to the structure of the present invention, when the temperature of the surface of the heat generating means that is in contact with the liquid rises above a predetermined temperature, the resistance value of the resistance heating element rapidly increases, so that the resistance heating element is substantially formed. No longer fever. Therefore, it is possible to prevent the temperature of the heat generating means from becoming higher than necessary.

It is preferable that the temperature at which the resistance value of the resistance heating element rises sharply is such that the temperature of the surface of the heat generating means in contact with the liquid becomes substantially the same as the foaming temperature of the liquid to be foamed. In other words, as the resistance heating element, when a predetermined voltage is applied, heat is generated in a state where the temperature of the surface of the heat generating means in contact with the liquid is equal to or lower than the foaming temperature of the liquid to be foamed,
In a state where the temperature is higher than the foaming temperature, it is preferable that the resistance value is significantly increased as compared with the case where the temperature is lower than the foaming temperature, and substantially no heat is generated. As a result, the liquid can be satisfactorily foamed by the heat generating means, and the resistance heating element hardly generates heat after the foaming, whereby unnecessary heat generation of the heat generating means can be prevented. The temperature at which the resistance value of the resistance heating element suddenly rises is, in particular, 250 ° C. or higher in consideration of the bubbling temperature of general ink.
It is preferably 90 ° C. or lower.

More specifically, the heat generating means can be composed of two electrodes laminated on the substrate and a resistance heating element laminated between the two electrodes. Alternatively, it may be composed of a resistance heating element formed on the substrate and two electrodes formed respectively in contact with opposing ends of the resistance heating element.

In the above structure, the liquid to be foamed is
Usually, it is guided over the substrate and onto the heating means. The resistance heating element is configured so as not to come into contact with the liquid in order to prevent the resistance heating element from being adversely affected by a chemical change or the like by flowing an electric current in contact with the liquid or in the state of being in contact with the liquid. Preferably.

Specifically, in the case of a structure in which both electrodes and a resistance heating element are laminated, an insulator is further laminated on the laminated lower electrode and the resistance heating element. A contact hole for exposing the upper surface of the resistance heating element is provided in the electrode, and the upper electrode is laminated so as to cover the resistance heating element exposed from the contact hole so that the resistance heating element does not come into contact with the liquid. In this case, if the upper electrode that comes into contact with the liquid is made of a chemically stable material such as platinum, it is possible to prevent the electrode from being deteriorated by coming into contact with the liquid, which is more preferable.

Further, in the case where the electrodes are formed in contact with the opposite ends of the resistance heating element, the resistance heating element does not come into contact with the liquid by forming an insulating layer on the resistance heating element. You can

Further, in the case of the structure in which the electrodes are formed in contact with the opposite ends of the resistance heating element, the electrodes having a comb-like planar shape may be arranged so that the comb teeth are engaged with each other. According to this configuration, it is possible to prevent the portions of the resistance heating element through which the current flows from concentrating in the areas on the line, and to disperse the areas where heat is generated and to properly foam the liquid.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIGS. 1 and 2 are schematic views of an ink jet recording head according to the first embodiment. FIG. 1 is a sectional view and FIG. 2 is a plan view. 1 and 2 show one foaming heater portion, and the entire inkjet recording head may have a configuration in which a plurality of foaming heater portions shown in FIGS.

This ink jet recording head has a substrate 6 in which an ink supply port 8 is opened as a through hole. A heat storage layer 4 is formed on the upper surface of the substrate 6, and two metal layers to be the metal electrodes 2 and 3 and a layer to be the resistance heating element 1 disposed between them are laminated on the heat storage layer 4. . In the example shown in FIG. 2, the two metal electrodes 2 and 3 have a striped planar shape that intersects each other, and the resistance heating element 1 is arranged at a position where the two metal electrodes 2 and 3 intersect. . With these configurations, the two metal electrodes 2,
A foaming heater is formed in a region where 3 intersects.

Further, on the substrate 6, the flow path 9 and the discharge hole 5 are provided.
The nozzle forming member 7 that forms the nozzle is arranged. The discharge hole 5 is opened at a position facing the bubbling heater. Although not shown in detail in FIGS. 1 and 2, the ink flow path 9 leads from the supply port 8 to the foaming heater,
A plurality of ink flow paths 9 that communicate with the plurality of foaming heaters are formed.

In this ink jet recording head, when a voltage is applied between the two metal electrodes 2 and 3 by the driving voltage application source 10, a current flows through the resistance heating element 1 and Joule heat is generated. By this Joule heat,
The liquid (ink) filled in the flow path 9 foams to form bubbles 1
1 is generated, and the discharge droplet 12 is discharged from the discharge hole 5 by the pressure at the time of bubbling.

The driving voltage application source 10 is usually provided in the main body of the ink jet recording apparatus, and the voltage is selectively applied to a plurality of foaming heaters at a predetermined timing. 1 and 2, these components are not shown, and only the driving voltage application source 10 is schematically shown. Also,
The ink supply port 8 is connected to an ink supply source (not shown), and after the ejection droplets 12 are ejected, liquid is discharged from the ink supply source through the ink supply port 8 into the flow path 9 in accordance with defoaming. Is introduced and filled.

In the present embodiment, for example, a Si substrate having a crystal axis <111> and a thickness of 0.625 mm can be used as the substrate 1. In this case, the ink supply port 8 is formed by anisotropic etching of Si. Can be formed. Further, as the electrodes 2 and 3, for example, a platinum thin film having a thickness of 0.2 μm can be used. In addition, the nozzle forming material 7
Can be formed of, for example, a resin.

In the ink jet recording apparatus of this embodiment, a PTC thermistor heating element is used as the resistance heating element 1. The PTC thermistor heating element is
A positive temperature coefficient of resistance, which reaches a characteristic temperature (Curie temperature or Curie point) Tc as a PTC thermistor material when the temperature of the surface in contact with the liquid becomes higher than a predetermined temperature and the resistance value sharply increases. Is a resistance heating element.

FIG. 3 shows a resistance heating element 1 according to this embodiment.
3 is a graph schematically showing a resistance value (R) -temperature characteristic of a PTC thermistor heating element that can be preferably used as the above. In the figure, Tb represents the foaming temperature. That is, in this example, ink that foams at about 300 ° C. is used as the liquid. When the resistance value of the PTC thermistor heating element changes abruptly, the temperature of the surface of the foaming heater that contacts the liquid is usually 250 to 250 in view of the general foaming temperature of the ink and the durability of the heater constituent material. 490 ° C
Is preferred.

On the other hand, Tc indicates the Curie point of the PTC thermistor heating element. Since the temperature of the surface of the foaming heater that contacts the liquid is slightly lower than the internal temperature of the PTC thermistor heating element, the Curie temperature of the PTC thermistor heating element used as the resistance heating element 1 is slightly higher than the foaming temperature Tb. It is preferable that in the example shown in FIG.
It is 50 ° C. As described above, the Curie temperature may be appropriately set according to the foaming temperature of the liquid, but the Curie temperature of the PTC thermistor used as the foaming heater of the ink jet recording head is generally the foaming temperature of ink and the durability of the heater constituent materials. In consideration of the property, the temperature is preferably 250 to 490 ° C., which is the same as the temperature of the surface of the foaming heater that contacts the liquid when the resistance value of the PTC thermistor heating element suddenly changes.

Such a PTC thermistor heating element is, for example, barium titanate doped with lead (Ba _0.5 P).
It can be constituted by a thin film of b _0.5 TiO _{3 having} a thickness of 0.8 μm. In this case, the PTC thermistor heating element has a specific resistance at room temperature of about 10 Ω · cm, a Curie point of about 350 ° C., and a specific resistance at 400 ° C. of about 1000 Ω ·
cm. When this PTC thermistor is used as the resistance heating element 1 to form a foaming heater and the effective size of the heater is 20 μm × 20 μm, the element resistance of this foaming heater at room temperature is about 200Ω.
The element resistance at 0 ° C. is about 20 KΩ. This foaming heater has, for example, a pulse width of about 1.0 μs and a pulse height of about 10 μm.
When a voltage of V is applied, a current of 0.05 A flows at a temperature lower than the Curie point, and the Joule heat generated thereby heat-foams the liquid to eject the ejected droplet 12 at a speed of about 15 m / s. .

Next, the liquid bubbling process using this ink jet recording head will be described with reference to FIG. FIG. 4 shows, in order from the top, three graphs showing temporal changes in the resistance value R of the resistance heating element 1, the power consumption, and the surface temperature of the foaming heater in the same period. In the graph of the power consumption and the heater surface temperature of FIG. 4, the broken line shows the change in the case of using a general resistance heating element whose resistance value does not change much even if the temperature changes within the operating temperature range.

As described above as the prior art, in the ink jet recording head, even if there is some variation in the finishing resistance and the wiring resistance of the resistance heating element forming the foaming heater, the liquid is surely foamed sufficiently. In order to stably and stably discharge the liquid, the drive voltage of the heater is usually set to a voltage higher than the voltage that can cause the entire surface bubbling by the average heater, which is not significantly affected by the resistance variation. ing. In the present embodiment as well, this is the same, and specifically, the drive voltage is set to about 1.2 times the voltage required to cause the entire surface foaming. The graph shown in FIG. 4 shows the change in the average resistance heating element, which is not significantly affected by the resistance variation.

When the application of the voltage pulse is started, the heater surface temperature first rises to the foaming temperature of the liquid, and the liquid begins to foam. At this time, since the heat energy of the heater is consumed due to the phase change of the liquid, the surface temperature of the heater remains at a constant foaming temperature until the foaming is completed, that is, until the entire surface is foamed. When a high voltage is applied with a predetermined applied pulse width as described above, the liquid on the heater surface is
After a certain amount of time has passed since the application of the voltage pulse was started, the entire surface is foamed before the application of the voltage pulse is completed. In the present embodiment, the drive voltage is about 1.2 times the voltage required to cause the foaming on the entire surface, that is, 40% more energy is input, so that a predetermined applied pulse width, for example, With respect to 1 μs, about 60% thereof, that is, about 0.6 μs, the liquid foams on the entire surface.

When a general resistance heating element whose resistance value does not change much even when the temperature changes after the entire surface is foamed,
The heater surface temperature further rises from the foaming temperature as shown by the broken line. Specifically, for example, the heater surface temperature is typically 600 to about 300 ° C. for the foaming temperature.
A high temperature of about 700 ° C. is reached. At this time, energy is consumed for such unnecessary heating (excessive heating). That is, as described above, when a drive voltage that is 1.2 times higher is used, in principle, about 40% of energy is wasted.

On the other hand, in the structure of this embodiment, as the resistance heating element 1, a PTC thermistor heating element having a Curie point slightly higher than the foaming temperature is used. in this case,
After the foaming is completed, if the temperature of the resistance heating element 1 further rises,
The resistance R of the resistance heating element 1 rapidly increases to a resistance R2 which is usually 10 times or more larger than the resistance R1 at room temperature, and almost no current flows through the resistance heating element 1. Therefore, according to the present embodiment, the heater surface temperature hardly rises even after the bubbling is completed. Specifically, in the example of the present embodiment, the heater surface temperature becomes about 300 ° C., and as the internal temperature of the PTC thermistor heating element approaches the Curie point of about 350 ° C., the element resistance of the foaming heater becomes room temperature. The resistance at 200 ° C. rapidly increases to about 20 KΩ at 400 ° C. As a result, when a general resistance heating element is used, the heater surface temperature is 600 to
In contrast to the high temperature of about 700 ° C., according to the present embodiment, the heater surface temperature is about the same as the foaming temperature of about 300
It can be suppressed to a dramatically low temperature of about ℃.

Further, after the completion of foaming, almost no current flows, so even if a voltage is continuously applied, almost no power is consumed. That is, it is possible to save the amount of power indicated by diagonal lines in the power consumption graph of FIG. 4, that is, about 40% in the example of the present embodiment.

As described above, according to the present embodiment, by using the PTC thermistor heating element as the resistance heating element 1, it is possible to suppress unnecessary heat generation after foaming of the foaming heater. As a result, the foaming heater can be prevented from having an excessively high temperature, and the durability of the heater can be improved. Further, after the foaming, the resistance heating element 1 can be prevented from substantially consuming electric power, and energy can be saved.

The structure of the resistance heating element 1 in this embodiment is not limited to the illustrated one. That is, generally, by using the resistance heating element 1 having a positive resistance temperature coefficient in which the resistance value rapidly increases when the temperature becomes higher than a predetermined temperature, the above-described effects of the present embodiment can be obtained. You can

(Second Embodiment) FIG. 5 shows a second embodiment of the present invention.
FIG. 3 is a schematic cross-sectional view of the inkjet recording head of the embodiment. FIG. 5 shows one bubbling heater portion, and the entire inkjet recording head can be configured by arranging a plurality of bubbling heater portions shown in FIG. In the figure, the same parts as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

In the ink jet recording head of this embodiment, the lower electrode 3b is laminated between the heat storage layer 4 and the adhesion layer 51. A layer of an insulator 52 is formed on the lower electrode 3b and the layer of the resistance heating element 1 laminated thereon. A contact hole that partially exposes the upper surface of the resistance heating element 1 is formed in the layer of the insulator 52. The upper electrode 2b is formed on the insulator 52 so as to pass through the contact hole. That is, the electrode 2b is in contact with the resistance heating element 1 at the contact hole portion.

The layer of the insulator 52 is, for example, a SiN thin film having a thickness of 1 μm, the electrodes 2b and 3b are platinum electrodes having a thickness of 0.2 μm, and the adhesion layer 51 is made of Ti having a thickness of 0.05 μm.
It is an adhesion layer. Further, the resistance heating element 1 can have the same configuration as that of the first embodiment, which can prevent the heater temperature from becoming excessively high, as in the first embodiment. Power consumption can be reduced.

In the present embodiment, the resistance heating element 1 is covered with the insulator 52, and the portion of the insulator 52 exposed from the contact hole is covered with the electrode 2b.
No contact with liquid. The electrode 2b that contacts the liquid is made of a chemically stable material, platinum in the above example. Therefore, the foaming heater can be prevented from being chemically damaged, and the durability of the foaming heater can be improved.

(Third Embodiment) FIG. 6 shows a third embodiment of the present invention.
FIG. 3 is a schematic cross-sectional view of the inkjet recording head of the embodiment. FIG. 6 shows one bubbling heater portion, and the entire inkjet recording head can be configured by arranging a plurality of bubbling heater portions shown in FIG. In the figure, the same parts as those in the first and second embodiments are designated by the same reference numerals, and the description thereof will be omitted.

In the present embodiment, the resistance heating element 61 is formed directly on the substrate 6, not on the electrodes. The two electrodes 62, 63 are in contact with the opposite ends of the resistance heating element 61, and extend from the ends of the substrate 6
Formed on. Each of the electrodes 62 and 63 is formed on the heat storage layer 4 via adhesion layers 64 and 65, respectively. A layer of an insulator 66 is formed on the resistance heating element 61, and a cavitation-resistant protective film 67 made of a material having strong resistance to cavitation is further formed thereon.

The adhesion layers 64 and 65 are, for example, Ti adhesion layers, the electrodes 62 and 63 are platinum electrodes, and the insulator 66.
Is a SiN film having a thickness of 0.3 μm, and the cavitation-resistant protective film 67 is a Ta film having a thickness of 0.2 μm.
The gap between the electrodes 62 and 63 is, for example, 1 μm, and the width of the electrodes 62 and 63 is 100 μm. In this case, the size of the foaming heater is 1 μm × 100 μm. As the resistance heating element 1, a PTC thermistor having the same structure as that shown in the first embodiment can be used, and in this case, the element resistance is about 200Ω at room temperature and about 20KΩ at 400 ° C. .

Also in this embodiment, by using the resistance heating element 61 having a positive temperature coefficient of resistance, it is possible to prevent the foaming heater from reaching an unnecessarily high temperature and to reduce power consumption. Further, by providing a layer of the insulator 66 that covers the resistance heating element 1, it is possible to prevent the heater from being chemically damaged, and by providing the cavitation-resistant protective film 67, damage due to cavitation can be prevented. Can be prevented. The synergistic effect of these makes it possible to construct a foaming heater having extremely high durability.

(Fourth Embodiment) FIG. 7 shows a fourth embodiment of the present invention.
FIG. 3 is a schematic plan view of the ink jet recording head of the embodiment. FIG. 7 shows one foaming heater portion, and the entire ink jet recording head can be configured by arranging a plurality of foaming heater portions shown in FIG. 7. In the figure, the same parts as those in the first to third embodiments are designated by the same reference numerals, and the description thereof will be omitted.

In this embodiment, the resistance heating element 7 is provided on the substrate 6.
3 and electrodes 71, 72 which are in contact with and are arranged facing each other. Also in this embodiment, as the resistance heating element 73, a PCT thermistor having a positive resistance temperature coefficient and having the same configuration as that of the first to third embodiments can be used, whereby the heater becomes excessively high in temperature. Can be prevented, and energy can be saved.

The opposite ends of the electrodes 71 and 72 have a comb-like shape, and the electrodes 71 and 72 are arranged so as to mesh with the comb teeth. Generally, when a voltage is applied between the opposing electrodes, a current flows between the two electrodes in a linear region, and heat is likely to be generated in the linear region. On the other hand, in the configuration of the present embodiment liquid, the electrode 7
It is possible to disperse the region in which the current flows between 1 and 72 and generate heat in the more dispersed region. Thereby, there is an effect that the liquid can be more favorably foamed and ejected.

[0050]

As described above, according to the present invention,
By using a PTC thermistor heating element having a positive temperature coefficient of resistance for the foaming heater that generates thermal energy used for foaming and discharging the droplets, the foaming heater generates unnecessary heat after foaming. Can be suppressed, and an excessively high temperature can be prevented. Therefore, according to the present invention, it is possible to provide an inkjet recording head with high durability and reduce the power consumption thereof.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an inkjet recording head according to a first embodiment.

FIG. 2 is a plan view of a heater unit of the inkjet recording head of FIG.

3 is a graph showing the temperature dependence of the resistance value in the resistance heating element used in the inkjet recording head of FIG.

4 is a graph showing changes with time of resistance of a resistance heating element, power consumption, and heater surface temperature in a liquid foaming process using the inkjet recording head of FIG.

FIG. 5 is a schematic cross-sectional view of an inkjet recording head according to a second embodiment.

FIG. 6 is a schematic cross-sectional view of an inkjet recording head of a third embodiment.

FIG. 7 is a schematic plan view of a heater unit of an inkjet recording head according to a fourth embodiment.

[Explanation of symbols]

1,61,73 Resistance heating element 2,2b, 3,3b, 62,63,71,72 electrodes 4 Heat storage layer 5 discharge holes 6 substrate 7 Nozzle forming member 8 ink supply port 9 channels 10 Driving voltage application source 11 bubbles 12 ejected droplets 51, 64, 65 Adhesion layer 52,66 insulator 67 Anti-cavitation protective film

Claims (13)

[Claims] 1. An ink jet recording head having a heat generating means for bubbling a liquid by the heat generating means and ejecting the liquid by a pressure generated at the time of bubbling, wherein the heat generating means is provided on a surface of the heat generating means in contact with the liquid. An ink jet recording head, comprising a resistance heating element having a positive resistance temperature coefficient in which a resistance value rapidly rises when the temperature rises above a predetermined temperature. 2. The ink jet recording head according to claim 1, wherein the resistance heating element is a PTC thermistor heating element. 3. The ink jet recording head according to claim 1, wherein the predetermined temperature at which the resistance value of the resistance heating element rapidly rises is substantially the same as the foaming temperature of the liquid to be foamed. . 4. The resistance heating element is such that, when a predetermined voltage is applied, the temperature of the surface of the heating means in contact with the liquid is
In the state below the foaming temperature of the liquid to be foamed, heat is generated,
The inkjet according to any one of claims 1 to 3, wherein, in a state of a temperature higher than the foaming temperature, a resistance value is significantly larger than that in a state of being lower than the foaming temperature and substantially no heat is generated. Recording head. 5. The predetermined temperature at which the resistance value of the resistance heating element rapidly rises is 250 ° C. or higher and 490 ° C. or lower,
The inkjet recording head according to any one of claims 1 to 4. 6. The Curie temperature of the resistance heating element is 25.
The inkjet recording head according to any one of claims 1 to 4, which has a temperature of 0 ° C or higher and 490 ° C or lower. 7. The heat generating means is laminated on a substrate.
7. The ink jet recording head according to claim 1, comprising one electrode and the resistance heating element laminated between the two electrodes. 8. An insulator is further laminated on the laminated lower electrode and the resistance heating element, and the insulation layer has a contact hole exposing the upper surface of the resistance heating element. The upper electrode is laminated to cover the resistance heating element exposed from the contact hole,
The inkjet recording head according to claim 7. 9. The ink jet recording head according to claim 8, wherein the upper electrode is made of a chemically stable material. 10. The ink jet recording head according to claim 9, wherein the upper electrode is made of platinum. 11. The heat generating means is composed of the resistance heating element formed on a substrate and two electrodes formed in contact with opposite ends of the resistance heating element, respectively.
The inkjet recording head according to any one of claims 1 to 6. 12. The ink jet recording head according to claim 11, wherein an insulating layer is formed to cover the resistance heating element. 13. The ink jet recording head according to claim 11, wherein each of the electrodes has a comb-like planar shape, and the electrodes are arranged so that the comb teeth are engaged with each other.