JP2002113868A - Ink jet recording head and ink jet recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a nonlinear element itself from being broken by heating of the nonlinear element. SOLUTION: A plurality of striped lower electrodes 5 where an insulating thin film 24 is set, and a plurality of information electrodes 7 are formed on a substrate 23 having a lower layer (thin film oxidation insulating layer) 22, on which a plurality of striped upper electrodes 6 are formed, and moreover a resistance heating unit 2 is formed. The lower electrodes 5 and the information electrodes 7 constitute a matrix circuit, and at the same time the lower electrodes 5, the upper electrodes 6 and the insulating thin film 24 constitute an MIM element 1. The resistance heating unit 2 is connected in series to the MIM element 1. The MIM element 1 is turned on when a voltage is impressed between the lower electrodes 5 and the information electrodes 7, whereby an electricity is supplied to the resistance heating unit 2 to make the unit heat. Liquid drops 9 are accordingly discharged from a discharge opening 8. An area of the MIM element 1 is made larger than an area of the resistance heating unit 2.

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 and an ink jet recording apparatus of a bubble jet (registered trademark) recording system utilizing a foaming phenomenon, which is used for an ink jet printer.

[0002]

2. Description of the Related Art In general, an ink jet recording head of a bubble jet recording type is provided with a fine discharge port, a flow path, and a heating element provided in a part of the flow path. With the bubble jet recording method, bubbles are generated by locally raising the temperature of the liquid in the flow path using a heating element, and the liquid is extruded from a fine discharge port using high pressure at the time of foaming, This is a recording method in which droplets are attached to recording paper or the like.

In order to increase the definition of an image recorded by the bubble jet recording method, a technique for ejecting minute droplets at a high density is required. Therefore, it is particularly important to form a fine flow path and a fine heating element. Therefore, there has been proposed a method of manufacturing a head capable of achieving high density by making full use of photolithography technology, taking advantage of the simplicity of the structure of the bubble jet recording system (for example, Japanese Patent Application Laid-Open No. 08-15629). Further, in order to adjust the discharge amount of the droplet, a heating element having a larger heat generation amount at the center portion than at the end portion has been proposed (Japanese Patent Application Laid-Open No. 62-201254).

The heating element is usually 0.05 μm thick.
Using a thin tantalum nitride thin film resistor, liquid is bubbled by Joule heat when electricity is supplied to the thin film resistor. Such a resistance heating element is usually made of a metal such as Ta having a thickness of about 0.2 μm via an insulating layer such as SiN having a thickness of about 0.8 μm in order to prevent damage to the surface of the resistance heating element due to cavitation. The anti-cavitation layer is provided.

In Japanese Patent Application Laid-Open No. 64-20150, a plurality of vertical wirings and a plurality of horizontal wirings are provided on a substrate.
A multi-nozzle inkjet head is disclosed in which a rectifying element through which only a forward current flows and a heating element connected to the rectifying element are provided at the intersection of the two. Japanese Patent Application Laid-Open No. 57-36679 discloses a thermal head in which a plurality of diodes capable of generating heat by forward energization are arranged in an array on a substrate.

[0006]

In many conventional ink jet recording heads, a heating element, a diode, and a logic circuit portion are simultaneously formed on a silicon substrate by a semiconductor process (method such as ion implantation). Therefore, there is an advantage that a head having a relatively small number of nozzles can be made compact and can be made in a single process. However, for example, a full line multi-head having a length equal to the entire width of the paper requires a length of about 12 inches (about 30 cm). May be invited.

Therefore, by using a non-linear element which can be formed without relying on a conventional semiconductor process such as an ion implantation method,
If the heating elements for bubble jet recording arranged in a matrix can be selectively driven, there is a possibility that a long inkjet recording head can be provided at low cost.

Conventionally, a non-linear element such as an MIM element has been used for a liquid crystal device or the like. When this MIM element is used in a liquid crystal device, the usual power density is 1 W / m ²
It is about. On the other hand, the heating element of the bubble jet recording head needs to handle a power density of about 0.1 GW / m ² or more. Therefore, when an MIM element is used as a heating element of a bubble jet recording head,
It is necessary to supply much higher power to the resistance element connected in series to the MIM element than in the case where the liquid crystal device is used. To solve this problem, it is possible to increase the power that can be supplied to the MIM element to some extent by increasing the voltage applied to the MIM element. However, MI
There is a possibility that the temperature of the MIM element rises due to the heat generated by the M element itself, leading to destruction of the element itself. Such heat generation of the MIM element itself did not cause any problem in the conventional configuration in which the MIM element was used as a non-linear element for driving a matrix, such as when used in a liquid crystal device.
When the IM element is used as a non-linear element for driving a matrix of a heating element of a bubble jet recording apparatus, a specific problem is that the MIM element itself may be destroyed by heat generated by the MIM element.

An object of the present invention is to use a non-linear element having MIM-type electrical characteristics to drive a heating element of a bubble jet recording system, and to prevent the non-linear element itself from being destroyed by heat generated by the non-linear element. It is an object of the present invention to provide an ink jet recording head and an ink jet recording apparatus which can be lengthened at low cost.

[0010]

SUMMARY OF THE INVENTION The present invention is characterized in that a heating element having a resistance heating element for generating thermal energy used for ejecting ink, and a pair of electrodes connected to the resistance heating element. A MIM that is connected in series to the resistance heating element to drive the resistance heating element, and the resistance value when a low voltage is applied is higher than the resistance value when a high voltage is applied, regardless of the polarity. And a non-linear element having a current-voltage characteristic of the type, wherein the area of the non-linear element is larger than the area between the pair of electrodes of the resistance heating element. With this configuration, it is possible to prevent the nonlinear element itself from being destroyed by the heat generated by the nonlinear element.

Furthermore, the area of the non-linear element, the resistance heating element is preferably 3.7 times ^{to 108} times the area between the pair of electrodes. This prevents the nonlinear element itself from being destroyed by the heat generated by the nonlinear element,
It does not hinder downsizing of the head. Furthermore, while a large current necessary for bubbling of the ejection liquid flows, the drive voltage can be suppressed to a level that does not increase the element drive cost.

It is preferable that the length of the non-linear element in the ejection port arrangement direction is shorter than the length in the direction substantially orthogonal to the arrangement direction. Thus, the ejection ports and the non-linear elements can be arranged at a high density.

The non-linear element is formed on the same substrate as the resistance heating element, has a discharge port formed in a direction substantially perpendicular to the substrate, and has a flow path extending from the resistance heating element formation portion. , May extend mainly on the side opposite to the disposition position of the nonlinear element. Alternatively, the non-linear element is formed on the same substrate as the resistance heating element, has a discharge port formed in a direction substantially parallel to the substrate, and the flow path, from the resistance heating element forming portion,
It may extend mainly to the position where the nonlinear element is provided. In any case, the large-area nonlinear element can be arranged so as not to hinder the liquid ejection.

Further, if a cooling structure for the nonlinear element is provided, it is possible to more reliably prevent the nonlinear element itself from being destroyed by the heat generated by the nonlinear element.

It is preferable that the resistance value of the non-linear element in the driving state is substantially equal to the resistance value of the resistance heating element.

Further, it may have a matrix electrode constituting a matrix circuit for applying a voltage to the heating means.
Then, the nonlinear element may be located at the intersection of the matrix electrodes.

Further, the ink jet recording head of the present invention may be of a type which causes film boiling in the ink by thermal energy to discharge the ink.

An ink jet recording apparatus according to any one of the above-mentioned constitutions, wherein the ink jet recording apparatus of the present invention is provided corresponding to the resistance heating element and has an ejection port for ejecting ink so as to face a recording surface of a recording medium. It is characterized by comprising at least a head and a recording medium conveying means.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a plan view of an essential part showing a first embodiment of the present invention, FIG. 2 is a graph showing its electric characteristics, FIG. 3 is a sectional view of the essential part, and FIG. FIG. 3 is a circuit diagram schematically showing the electric circuit.

As shown in FIGS. 1 and 3, the ink jet recording head of this embodiment has a lower layer (thin oxide insulating layer) 2.
2, a plurality of stripe-shaped lower electrodes (vertical electrodes) 5 provided with an insulating thin film 24 and a plurality of signal electrodes (information electrodes) 7 are further formed thereon.
A plurality of stripe-shaped upper electrodes (horizontal electrodes) 6 are formed, and a thin-film resistance heating element (heating element) 2 is further formed. The discharge port forming part 52 is disposed on the substrate 23 configured as described above.

The substrate 23 has a lower layer 22 formed of a heat conductive material. The plurality of lower electrodes 5 are scanning electrodes constituting a matrix circuit, and are covered with an extremely thin insulating thin film 24. On the other hand, the plurality of upper electrodes 6 are arranged substantially parallel to a direction intersecting with the lower electrode 5, and are connected to one end of the resistance heating element 2. The information electrode 7 is connected to the other end of the resistance heating element 2 and forms a matrix circuit. Here, a plurality of flow paths 31 corresponding to each resistance heating element 2 are connected to the discharge port forming section 52. In addition, each flow path 31 has a plurality of discharge ports 8 that are open to the outside.

In this embodiment, the lower electrode 5 and the upper electrode 6
And the insulating thin film 24 interposed between them,
Nonlinear element showing IM type current-voltage characteristics, ie, MIM
Element 1 is configured. The area of the MIM element 1 is larger than the area of the resistance heating element 2.

As shown in FIG. 2, the MIM type electric characteristics indicate a low resistance value on the high voltage side and a high resistance value on the low voltage side, regardless of the polarity, as shown in FIG. It is a current-voltage characteristic shown. What is an MIM element?
Although a tunnel junction element having a structure of metal / insulator / metal is originally used, a junction element having a structure of conductor electrode / insulator / conductor electrode is usually also called an MIM element. Here, as the conduction mechanism of the insulator, there are hopping-type electric conduction that repeats multiple tunneling in the insulator such as Pool Frenkel type conduction, and relatively simple tunnel conduction such as Fowler-Nordheim conduction. It has been known. In order for such a tunnel-type current to flow and to flow through the junction element, the distance between the electrodes must be extremely small. A so-called varistor in which a sintered body layer obtained by adding a metal oxide such as Bi, Pr and Co to ZnO, or a granular crystal layer of silicon carbide SiC is arranged between electrodes instead of an insulating layer is also described above. Like the MIM element, it can be used as a non-linear element, and MIM-type electrical characteristics can be obtained.

The ink jet recording head of this embodiment has a matrix circuit composed of a lower electrode 5 and an information electrode 7, an MIM element 1 located at the intersection of the matrix circuit, and a resistance heating element connected in series to the MIM element 1. And the body 2.

With such a configuration, as will be described later, the lower electrode 5 and the information electrode 7 constituting the matrix circuit
When a voltage is applied between these two, the MIM element 1 is turned on, and power is supplied to the resistance heating element 2. Resistance heating element 2
Generates heat when supplied with electric power, the ejection liquid supply port 5
The liquid (ink) for ejection present in the flow path 31 supplied from the nozzle 4 is rapidly heated to generate bubbles, and the bubbling pressure causes the droplets 9 to be ejected from the ejection openings 8, and the ejected droplets 9 to be discharged to the outside. And an image is formed on the recording medium (not shown). Of course, as described above, the heating of the resistance heating element 2 and the liquid ejection are performed only at locations (selection points) where a sufficient voltage is applied to the lower electrode 5 and the information electrode 7.
At locations where a sufficient voltage is not applied to both electrodes 5 and 7 (non-selected points), liquid ejection is not performed.

Since the MIM element 1 is disposed at the intersection of the two electrodes 5 and 7 forming the matrix with the extremely thin lower layer 22 interposed therebetween, the MIM element 1 is at a non-discharge point (non-selection point) due to a bias voltage during matrix driving. Unnecessary heat generation can be suppressed, and the resistance heating element 2 can be driven in a matrix. In addition, a driver (driving means) (not shown) can be easily provided separately from the resistance heating element 2 by matrix driving, so that it is not necessary to use an expensive Si substrate, and mass production can be performed at low cost.

In order to perform the matrix driving, the applied voltage V ₁ for generating a current having a certain absolute value I ₀ and −
V _{2 is, 0.5 <(V 1 / V} 2) < satisfies the two relationships, and the absolute value of the applied voltage + V _1/2 and -V _2/2 corresponding to the current in the I _0/10 or less Preferably, there is.

The limit value of the thickness of the insulating thin film 24 at which a current can flow through the MIM element 1, that is, the limit value of the interval between the electrodes 5 and 6 greatly depends on the type of the insulating material and the electrode material and the conductive structure. However, in order for a significant current to flow as the MIM element 1, the distance between the electrodes 5 and 6 is preferably set to about 100 nm or less. Further, in order to obtain a large current required for matrix drive of the bubble jet recording head at a low voltage, it is preferable that this interval is 40 nm or less. On the other hand, if the interval is extremely narrow, ions on the metal surfaces of the electrodes 5 and 6 may cause electric field emission. In order to obtain a stable tunnel junction, the thickness is preferably 4 nm or more. That is, the interval between the electrodes 5 and 6 is preferably 1 to 100 nm. In particular, in order to obtain a large current required for driving the matrix of the bubble jet recording head at a low voltage, the interval between the electrodes 5 and 6 is preferably The thickness is preferably 4 to 40 nm.

However, in the present embodiment shown in FIGS.
A resistance heating element 2 is provided separately from the MIM element 1, and the resistance heating element 2 performs liquid heating. In this embodiment,
As shown in FIG. 1, since the area of the MIM element 1 is larger than the area of the resistance heating element 2 connected in series to the MIM element 1, even if the resistance heating element 2 supplies power having a power density that foams within a certain period of time. , Since the temperature rise of the MIM element 1 itself is suppressed,
Destruction of the M element 1 can be prevented.

Next, the matrix circuit of the present invention will be described again with reference to FIG. In FIG. 4, j-th and j + 1-th scan electrodes (lower electrodes) Y _j and Y _{j + 1} are shown.
The i-th and (i + 1) -th information electrodes X _i and X _{i + 1} are schematically shown, respectively. The scanning electrodes Y _j , Y _{j + 1} and the information electrodes X _i , X _{i + 1} constitute a matrix circuit. At the intersection of the matrix circuits, a non-linear MIM element 1
And a resistance heating element 2. In addition, the ejection droplet 9
Is schematically shown.

In FIG. 4, a MIM element 1 is obtained by inputting a selection potential waveform to a scanning electrode and inputting an ejection or non-ejection information potential waveform to an information electrode according to an image signal.
Can be controlled to an on state or an off state. That is, only the MIM element 1 located at the intersection of the scanning electrode to which the selection potential waveform is input and the information electrode to which the ejection information potential waveform is input is turned on, and the resistance heating element 2 connected in series to this is turned on. When power is supplied, thermal energy is generated between the pair of electrodes of the resistance heating element 2 and the droplet 9 is ejected. The other MIM elements 1 are turned off and connected in series even if only one of the input of the selected potential waveform to the scan electrode and the input of the ejection information potential waveform to the information electrode is performed. No power is supplied to the resistive heating element 2 that has been set, and the droplet 9 is not ejected.

As described above, the area of the MIM element 1 is equal to the area between a pair of electrodes of the resistance heating element connected in series to the MIM element 1 (hereinafter, also simply referred to as “area of the resistance heating element”).
The MIM due to the heat generated by the MIM element 1
The risk of destruction of the element 1 itself is avoided. But MIM
If the area of the element 1 is too large, miniaturization of the head may be difficult. Conventionally, by analogy with the power density during operation when the MIM element is used in a liquid crystal device, MI
The size of the M element 1 is one of the resistance heating elements 2 connected in series.
0 is preferably set to ⁸ times or less.

From the viewpoint of miniaturizing the head, the smaller the area of the MIM element 1, the more preferable. However, in the bubble jet recording head, in particular, by increasing the voltage applied to the MIM element 1 that supplies a large amount of power to the resistance heating element 2, the large amount of liquid necessary for foaming the ejection liquid when the MIM element 1 is in the ON state is set. It is important to pass current. In order to satisfy this requirement and to lower the driving voltage in order to avoid an increase in element driving cost, the MIM element 1 in the driving state is required.
There the resistance value R _H of the resistance value R _MIM and the resistance heating element needs to be substantially equal, it is preferable that R _MIM = R _H.
Further, a resistance heating element 2 in the area S _MIM of the MIM element 1 and the area S _H, considering that juxtaposition in ejection liquid containing water as a main component, resulting boiling by MIM element 1 connected in series without, to produce film boiling by the resistance heating element 2 is preferably _{3.7R MIM / S MIM <R H} / S H. Here, the numerical value of 3.7 as the coefficient indicates that the film boiling temperature of the ejection liquid containing water as a main component is about 3 times.
The temperature is calculated assuming that the normal boiling temperature is about 100 ° C. and the room temperature is about 25 ° C. Thus, from the above two conditional expressions, S _MIM > 3.7
It is preferable that the S _H. That is, it is preferable area of the non-linear element 1 is 3.7 times ^{to 108} times larger than the area of the resistance heating element 2.

In this embodiment, since the length of the MIM element 1 in the arrangement direction of the discharge ports 8 is shorter than the length of the MIM element 1 in the direction substantially perpendicular to the arrangement direction of the discharge ports 8, the discharge The outlet 8 and the MIM element 1 can be arranged at high density.
Further, in the present embodiment, the MIM element 1 is formed on the same substrate 23 as the resistance heating element 2, and the discharge port 5 is formed in a direction substantially perpendicular to the substrate 23.
Extend from the formation portion of the resistance heating element 2 mainly toward the side substantially opposite to the position where the MIM element 1 is provided.
The large-area MIM element 1 can be arranged so as not to hinder the liquid ejection.

The method of manufacturing the MIM element 1 according to the present embodiment will be described. The MIM element 1 is formed of an insulating thin film (oxide insulating film) 24 obtained by anodizing a striped metal electrode (lower electrode) 5. In this configuration, a striped metal electrode (upper electrode) 6 intersecting with the lower electrode 5 is provided on the upper side. Specifically, the lower electrode 5 is formed by forming a Ta thin film having a thickness of about 300 nm by an RF sputtering method, and then oxidizing the surface thereof by an anodizing method to form a Ta ₂ O ₅ thin film having a thickness of about 32 nm. It is. At this time, the RF sputtering process is performed at about 10 ⁻² T.
This is performed in an Ar gas atmosphere of about orr. The anodic oxidation step is performed in a 0.8% by weight aqueous citric acid solution using a mesh-shaped platinum electrode as a cathode. The upper electrode 6 and the information electrode 7 are tantalum thin film electrodes having a thickness of 23 nm, the substrate 23 is a Si substrate having a crystal axis <111> and a thickness of 0.625 mm, and the lower layer 22 on the surface of the lower electrode 5 is 2.75 thickness
The resistance heating element 2 has a thickness of 0.1 μm.
It is a 05 μm tantalum nitride thin film.

In this embodiment, the resistance heating element 2 has a size of 25 μm × 25 μm, an area of 625 μm ² , and an element resistance of 53Ω. The width of the channel 31 is 30
μm and the spacing between the channels is 80 μm. MIM element 1
Has a size of 84.5 μm × 20,000 μm and an area of 16
It is 90000 μm ² , and has a band shape extending long in a direction perpendicular to the direction in which the ejection openings 8 are arranged. The area of the MIM element 1 is 2704 times the area of the resistance heating element 2. Also,
When the voltage applied between both ends of the MIM element 1, that is, between the lower electrode 5 and the upper electrode 6 is 6.7 V, the element resistance of the MIM is 53Ω. Therefore, when a voltage of 13.4 V is applied between the lower electrode 5 and the information electrode 7, a voltage of 6.7 V is applied to each of the MIM element 1 and the resistance heating element 2, and a current of 126 mA flows. At this time, the MIM element 1
And the power consumption converted into heat by the resistance heating element 2 is 0.8
47 W, and the power density of the MIM element 1 is 0.5 MW /
m ² , and the power density of the resistance heating element 2 is 1.355 GW / m ² . When power is supplied to the resistance heating element 2 under such conditions, sufficient heat is generated to heat and foam the ejection liquid. Further, since the heat generation per unit area of the MIM element 1 is 1/2704 of the heat generation per unit area of the resistance heating element 2, the temperature rise can be suppressed. In particular, since heat escapes to the Si substrate 23 via the lower layer 22, the temperature rise of the MIM element 1 can be efficiently suppressed. Further, since the resistance values of the MIM element 1 and the resistance heating element 2 are equal, a large power is supplied to the resistance heating element 2 and the operating voltage of the MIM element 1 is high. It is possible to pass a large current required for foaming.

(Second Embodiment) FIG. 5 shows a main part of an ink jet recording head according to a second embodiment of the present invention. The same reference numerals are given to the same parts as in the first embodiment, and the description will be omitted.

In this embodiment, the MIM element 1 is formed on the same substrate 23 as the resistance heating element 2, and the discharge port 18 is formed in a direction substantially parallel to the substrate 23. Channel 19
Extends from the formation portion of the resistance heating element 2 mainly to the position where the MIM element 1 is provided. Therefore, the MIM element 1 having a large area does not hinder the liquid ejection. Further, since a part of the MIM element 1 is in thermal contact with the ejection liquid, heat generated in the MIM element 1 can be released to the ejection liquid, and the temperature rise of the MIM element can be effectively prevented. .

(Third Embodiment) FIG. 6 shows a third embodiment of the present invention.
2 shows a main part of the inkjet recording head of the embodiment. The same parts as those in the first and second embodiments are denoted by the same reference numerals, and description thereof is omitted.

In the present embodiment, the MIM element 11 which is entirely in contact with the discharge liquid via the thin film layer is provided. A thickness of 0.6 μm and a thermal diffusivity κ = 0.47 m are formed on the MIM element 11 and the resistance heating element 2 by sputtering deposition.
m ² / and SiO ₂ thin film is laminated in s, the SiO ₂
The thin film is a protective film 5 for the MIM element 11 and the resistance heating element 2.
05. By being protected by the protective film 505, the MIM element 11 can be disposed inside the liquid chamber 4 and the flow path 31 or adjacent thereto. Thus, the area of the MIM element 11 can be increased without increasing the size of the inkjet recording head.

For example, 2 μm between the lower electrode 5 and the upper electrode 6
When the droplet 9 is ejected by applying a pulse voltage of s, the heat conduction distance of the protective film 505, that is, twice the square root of κΔt is 1.94 μm. Since the thickness of the protective film 505 is smaller than the heat conduction distance, the heat generated by the MIM element 11 when the discharge voltage is applied is quickly released to the discharge liquid, and the temperature rise of the MIM element 11 can be suppressed. The MIM element 11 can be protected.

In this embodiment, as in the first embodiment,
A method of manufacturing the MIM element 11 will be described.
The IM element 11 has a striped metal electrode (lower electrode) 5
Insulating thin film (oxide insulating film) 24 obtained by anodizing aluminum
And a stripe-shaped metal electrode (upper electrode) 6 intersecting with the lower electrode 5. Specifically, the lower electrode 5 is formed by forming a Ta thin film having a thickness of about 300 nm by an RF sputtering method, and then oxidizing the surface thereof by an anodizing method to form a Ta ₂ O ₅ thin film having a thickness of about 32 nm. It is. At this time, the RF sputtering process is performed in an Ar gas atmosphere of about 10 ⁻² Torr. The anodic oxidation step is performed in a 0.8% by weight aqueous citric acid solution using a mesh-shaped platinum electrode as a cathode. The upper electrode 6 and the information electrode 7 have a thickness of 23 n.
m, and the substrate 23 has a crystal axis <11
1> a Si substrate having a thickness of 0.625 mm and a lower electrode 5
Is a Si thermal oxide film having a thickness of 2.75 μm, and the resistance heating element 2 is a tantalum nitride thin film having a thickness of 0.05 μm.

In this embodiment, the resistance heating element 2 has a size of 40 μm × 40 μm and an area of 1600 μm ² ,
The element resistance is 53Ω. The width of the flow channel 31 is 6
At 0 μm, the spacing between the channels is 80 μm. The MIM element 11 has a size of 42.25 μm × 40000 μm and an area of 1690000 μm ² , and has a band shape extending long in a direction perpendicular to the arrangement direction of the ejection openings 8. The area of the MIM element 11 is 1056 times the area of the resistance heating element 2. When the voltage applied between both ends of the MIM element 11, that is, between the lower electrode 5 and the upper electrode 6 is 6.7 V, the element resistance of the MIM is 53Ω. Therefore, when a voltage of 13.4 V is applied between the lower electrode 5 and the information electrode 7, a voltage of 6.7 V is applied to each of the MIM element 11 and the resistance heating element 2, and a current of 126 mA flows. At this time, MIM
The power consumption converted into heat by the element 11 and the resistance heating element 2 is 0.847 W, the power density of the MIM element 11 is 0.5 MW / m ² , and the power density of the resistance heating element 2 is 0.52
9 GW / m ² . When power is supplied to the resistance heating element 2 under such conditions, sufficient heat is generated to heat and foam the ejection liquid. Further, since the heat generation amount per unit area of the MIM element 11 is 1/1056 of the heat generation amount per unit area of the resistance heating element 2, the temperature rise can be suppressed.

Further, since the condition of 3.7 R _MIM / S _MIM <R _H / S _H is satisfied, bubbles mainly composed of water, which are not taken into consideration when designing the MIM element 11, are generated and discharge occurs. There is no risk of becoming unstable.

In the present embodiment, the MIM element 11 is arranged adjacent to the ejection liquid, and this functions as a heat radiation structure, that is, a cooling structure. Specifically, the MIM element 11 has a protective film 505 having a thermal diffusivity κ in contact with its electrode, and when a pulse voltage for a period Δt is applied to the MIM element 11, the thickness of the protective film 505 becomes κΔt Square root of 2
It is less than double. Thereby, destruction of the MIM element 11 itself due to heat generation of the MIM element 11 can be prevented.

Next, FIG. 7 shows a schematic view of an example of an ink jet recording apparatus equipped with the ink jet recording head shown in each of the above embodiments.

This ink jet recording apparatus has a paper feed roller 405 whose drive is controlled by a drive circuit 403.
And transports the paper 406 as a recording medium. In addition, the inkjet recording head 407 controlled by the control unit 404 is provided such that each ejection port faces the paper 406 to be conveyed.
By controlling the nonlinear element 1 to be in an on state or an off state in accordance with a signal from 04, the ejection and non-ejection of the ejection droplet 9 from the ejection port 8 are controlled. In this way, the ink on the resistance heating element 2 to which the power is supplied is rapidly heated, so that air bubbles based on the film boiling phenomenon are generated all over the surface of the resistance heating element 2 with an extremely high pressure. .
Due to this pressure, the ejection droplet 9 is ejected from the ejection port 8 as described above, and an image is formed on the recording medium. In addition, ink is supplied from the ink tank 402 to the inkjet recording head 407 with the ejection of the ejection droplets 9.

[0049]

According to the present invention, the area of the nonlinear element is
Since the area of the resistance heating element connected in series with the resistance heating element is larger than the area between the pair of electrodes, it is possible to prevent the nonlinear element itself from being destroyed by the heat generated by the nonlinear element. In particular, the area of the nonlinear element is equal to the area between the pair of electrodes of the resistance heating element.
If it is 7 times ^{to 108} times, it is non-linear element itself with prevented be destroyed by the heat generation of the nonlinear element, does not interfere with the miniaturization of the head. Furthermore, while a large current necessary for bubbling of the ejection liquid flows, the drive voltage can be suppressed to a level that does not increase the element drive cost.

If the length of the non-linear element in the direction of arrangement of the discharge ports is shorter than the length in a direction substantially orthogonal to the arrangement direction, the discharge ports and the non-linear elements can be arranged with high density.

Further, when a cooling structure for the nonlinear element is provided, it is possible to more reliably prevent the nonlinear element itself from being destroyed by the heat generated by the nonlinear element.

As a result, it is possible to provide an ink jet recording head and an ink jet recording apparatus which can be lengthened at low cost.

[Brief description of the drawings]

FIG. 1 is a plan view of a main part of an inkjet recording head according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of MIM type electric characteristics.

FIG. 3 is a sectional view of a main part of the inkjet recording head according to the first embodiment.

FIG. 4 is an electric circuit diagram schematically showing the ink jet recording head of the first embodiment.

FIG. 5 is a plan view of a main part of an inkjet recording head according to a second embodiment of the present invention.

FIG. 6 is a main part plan view of an ink jet recording head according to a third embodiment of the present invention.

FIG. 7 is a schematic view showing an example of the ink jet recording apparatus of the present invention equipped with the ink jet recording head of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 MIM element (nonlinear element) 2 Thin film resistance heating element (heating element) 5 Lower electrode (vertical electrode) 6 Upper electrode (horizontal electrode) 7 Signal electrode (information electrode) 8 Discharge port 9 Droplet 11 MIM element (nonlinear element) ) 18 discharge port 19 flow path 22 lower layer (thin oxide insulating film) 23 substrate 24 insulating thin film 31 flow path 52 discharge port forming section 54 discharge liquid supply port 402 ink tank 403 drive circuit 404 control section 405 paper feed roller 406 Paper 407 Inkjet recording head 505 Protective film

Claims (11)

[Claims] 1. A heating means having a resistance heating element for generating thermal energy used for discharging ink, a pair of electrodes connected to the resistance heating element, and driving the resistance heating element. Connected in series with the resistance heating element,
MIM showing that the resistance value when a low voltage is applied is higher than the resistance value when a high voltage is applied irrespective of the polarity
And a non-linear element having a current-voltage characteristic of a type, wherein an area of the non-linear element is larger than an area between the pair of electrodes of the resistance heating element. head. Area wherein said non-linear element, the resistance heating element, which is 3.7 times ^{to 108} times the area between the pair of electrodes, an ink jet recording head according to claim 1. 3. The ink jet recording head according to claim 1, wherein a resistance value of the non-linear element in a driving state is substantially equal to a resistance value of the resistance heating element. 4. The ink jet recording according to claim 1, wherein a length of the non-linear element in a discharge port arrangement direction is shorter than a length in a direction substantially orthogonal to the arrangement direction. head. 5. The non-linear element is formed on the same substrate as the resistance heating element, and in a direction substantially perpendicular to the substrate, a flow path formed in the flow path corresponding to the resistance heating element. An ejection port for ejecting ink is formed, and the flow path includes:
The ink jet recording head according to claim 1, wherein the ink jet recording head extends from a position where the resistance heating element is formed, mainly to a side opposite to a position where the nonlinear element is provided. 6. The non-linear element is formed on the same substrate as the resistance heating element, and is provided in a direction substantially parallel to the substrate in a flow path formed corresponding to the resistance heating element. An ejection port for ejecting ink is formed, and the flow path includes:
The position extending from the position where the resistance heating element is formed to a position where the nonlinear element is disposed.
5. The ink jet recording head according to any one of 4. 7. The ink jet recording head according to claim 1, having a cooling structure for said nonlinear element. 8. The ink jet recording head according to claim 1, further comprising a matrix electrode forming a matrix circuit for applying a voltage to said heat generating means. 9. The ink jet recording head according to claim 8, wherein said non-linear element is arranged at an intersection of said matrix electrodes. 10. The ink jet recording head according to claim 1, wherein the ink is ejected by causing film boiling of the ink by the thermal energy. 11. A device provided corresponding to the resistance heating element,
An ink jet recording head according to any one of claims 1 to 10, having an ejection port for ejecting ink on a recording surface of the recording medium, and a transport unit that transports the recording medium,
An ink jet recording apparatus comprising at least: