JP3467030B2 - Ink jet recording head and ink jet recording apparatus - Google Patents

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 for use in an ink jet printer, in particular, a bubble jet (registered trademark) recording system utilizing a bubbling phenomenon.

[0002]

2. Description of the Related Art Generally, a bubble jet recording type ink jet recording head is provided with a fine discharge port, a flow path, and a heating element provided in a part of this flow path. The bubble jet recording method uses a heating element to locally raise the temperature of the liquid in the flow channel to generate bubbles, and the high pressure at the time of foaming is used to push the liquid out from a fine ejection port. This is a recording method in which droplets are attached to recording paper or the like.

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

The heating element usually has a thickness of 0.05 μm.
A tantalum nitride thin film resistor of about a certain degree is used, and the liquid is foamed by Joule heat when energized. In order to prevent the resistance heating element surface from being damaged by cavitation, such a resistance heating element is usually made of a metal such as Ta having a thickness of about 0.2 μm through an insulating layer such as SiN having a thickness of about 0.8 μm. The anti-cavitation layer is provided.

Further, in Japanese Patent Laid-Open No. 64-20150, a plurality of vertical wirings and a plurality of horizontal wirings are provided on a substrate,
There is disclosed a multi-nozzle inkjet head 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. Further, Japanese Patent Laid-Open No. 57-36679 discloses a thermal head in which a plurality of diodes capable of generating heat by forward conduction 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 section 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 performed in a single process. However, for example, a full-line multi-head having a full width of paper requires a length of about 12 inches (about 30 cm), and it is difficult to use a normal silicon wafer, and the cost is increased if it is integrally formed. May invite.

Therefore, by using a non-linear element which can be produced 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, non-linear elements such as MIM elements have been used in liquid crystal devices. When this MIM element is used in a liquid crystal device, the normal power density is 1 W / m ²
It is a degree. 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 larger electric power to the resistance element connected in series with the MIM element as compared with the case of being used in the liquid crystal device. For 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
The heat generated by the M element itself may raise the temperature of the MIM element, resulting in destruction of the element itself. Such heat generation of the MIM element itself does not pose any problem in the conventional configuration in which the MIM element is a non-linear element for matrix driving, such as when used in a liquid crystal device.
When the IM element is used as a non-linear element for driving the matrix of the heating element of the bubble jet recording apparatus, a particular problem is that the MIM element itself may be destroyed by the heat generated by the MIM element.

Therefore, an object of the present invention is to use a non-linear element having MIM type electric characteristics to drive a heating element of a bubble jet recording system, and prevent the non-linear element itself from being destroyed by heat generation of the non-linear element. An object of the present invention is to provide an inkjet recording head and an inkjet recording device that can be elongated at low cost.

[0010]

The feature of the present invention is that the ink
And a pair of electrodes connected to the resistance heating element, the resistance heating element being provided in a flow path communicating with a discharge port for discharging the ink and generating thermal energy used for discharging the ink. And a heating means having a and a series connected to the resistance heating element for driving the resistance heating element, the resistance value when a low voltage is applied is higher than the resistance value when a high voltage is applied, regardless of polarity. And a non-linear element having a MIM type current-voltage characteristic exhibiting a high value, and at least a part of the non-linear element is in the flow path.
Alternatively, it is placed in a liquid chamber that communicates with the flow path and
The area of the element is SMIM, and the driving state of the nonlinear element
If the resistance value is RMIM, the area between a pair of electrodes forming the resistance heating element is SH, and the resistance value of the resistance heating element is RH.
3.7RMIM / SSIM is smaller than RH / SH
There is a place. With this configuration, it is possible to prevent the non-linear element itself from being destroyed by the heat generated by the non-linear element.

Further, it is preferable that the area of the non-linear element is 3.7 to 10 ⁸ times the area between the pair of electrodes of the resistance heating element. This prevents the nonlinear element itself from being destroyed due to the heat generated by the nonlinear element,
Does not hinder the miniaturization of the head. Further, the driving voltage can be kept low to the extent that the element driving cost does not increase while allowing a large current required for bubbling the ejection liquid to flow.

Further, it is preferable that the length of the non-linear element in the ejection port array direction is shorter than the length in the direction substantially orthogonal to the array direction. Thereby, the ejection port and the non-linear element can be arranged in high density.

Further , 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 has a flow path from the resistance heating element forming portion. , May extend mainly to the side where the non-linear element is disposed.
In that case, a large area non-linear element can be arranged so as not to interfere with the liquid ejection.

Further, when the cooling structure for the non-linear element is provided, it is possible to more reliably prevent the non-linear element itself from being broken due to heat generation of the non-linear element.

Further, 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 forming a matrix circuit for applying a voltage to the heating means.
The non-linear element may be located at the intersection of the matrix electrodes.

The ink jet recording head of the present invention may be one which ejects the ink by causing film boiling in the ink by thermal energy.

The ink jet recording apparatus of the present invention is provided in correspondence with the resistance heating element and has an ejection port for ejecting ink facing the surface to be recorded of the recording medium. At least a head and a recording medium conveying unit are provided.

[0019]

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

Reference Example FIG. 1 is a plan view of a main part showing a reference example , FIG. 2 is a graph showing its electric characteristics, FIG. 3 is a cross-sectional view of the main part, and FIG. 4 is a circuit diagram showing its electric circuit. It is a figure.

As shown in FIGS. 1 and 3, the ink jet recording head of this reference example has a lower layer (thin oxide insulating layer) 22.
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 formed on a substrate 23 having A striped upper electrode (lateral electrode) 6 is formed,
Further, a thin film resistance heating element (heating element) 2 is formed. The discharge port forming portion 5 is formed on the substrate 23 configured as described above.
2 are arranged.

The substrate 23 is formed by forming the lower layer 22 on a heat conductive material. The plurality of lower electrodes 5 are scanning electrodes forming 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 in parallel to the direction intersecting 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 to form a matrix circuit. Here, the discharge port forming portion 52 is connected to a plurality of flow paths 31 corresponding to the resistance heating elements 2. In addition, each flow path 31 has a plurality of discharge ports 8 that are open to the outside.

In this reference example , the lower electrode 5 and the upper electrode 6
And the insulating thin film 24 interposed therebetween, M
Non-linear element showing IM type current-voltage characteristics, that is, MIM
The element 1 is configured. The area of this MIM element 1 is larger than the area of the resistance heating element 2.

As shown in FIG. 2, the MIM type electric characteristic means 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. 2, like the current-voltage characteristics of the MIM element and the varistor. It is the current-voltage characteristic shown. What is MIM element?
Originally, it is a tunnel junction element having a structure of metal / insulator / metal, but normally, a junction element having a structure of conductor electrode / insulator / conductor electrode is also called MIM element. Here, as the conduction mechanism of the insulator, hopping type electric conduction in which multiple tunneling is repeated in the insulator such as pool Frenkel type conduction, and relatively simple tunnel conduction such as Fowler-Nordheim type conduction It has been known. In order for such a tunnel type current to flow and a current to flow to the junction element, the distance between the electrodes needs to be extremely small. The so-called varistor in which a sintered body layer obtained by adding a metal oxide such as Bi or Pr and Co to ZnO or a granular crystal layer of silicon carbide SiC is arranged between the electrodes instead of the insulating layer is also described above. Like the MIM element, it can be used as a non-linear element, and MIM type electric characteristics can be obtained.

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

Due to such a structure, as will be described later, the lower electrodes 5 and the information electrodes 7 forming the matrix circuit.
When a voltage is applied between and, the MIM element 1 is turned on, and power is supplied to the resistance heating element 2. Resistance heating element 2
When it receives heat and heats up, the ejection liquid supply port 5
The discharge liquid (ink) that is supplied from the nozzle 4 and is present in the flow path 31 is rapidly heated to generate bubbles, and the bubbling pressure causes the droplet 9 to be discharged from the discharge port 8 and the discharged droplet 9 to the outside. An image is formed by adhering to the recording medium (not shown). Of course, as described above, the heat generation of the resistance heating element 2 and the liquid ejection are performed only at the portion (selection point) where a sufficient voltage is applied to the lower electrode 5 and the information electrode 7.
The liquid is not ejected at a portion (non-selection point) where a sufficient voltage is not applied to both electrodes 5, 7.

Since the MIM element 1 is arranged at the intersection of both electrodes 5 and 7 forming a matrix with the extremely thin lower layer 22 interposed, it is a non-ejection point (non-selection point) due to the bias voltage during matrix driving. The unnecessary heat generation can be suppressed and the resistance heating element 2 can be matrix-driven. Further, since the driver (driving means) (not shown) can be easily provided separately from the resistance heating element 2 by matrix driving, it is not necessary to use an expensive Si substrate, and mass production can be performed at low cost.

In order to perform matrix driving, applied voltages V ₁ and − for generating currents having an equal absolute value I ₀ are used.
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 film thickness of the insulating thin film 24, that is, the limit value of the distance between the electrodes 5 and 6 at which a current can flow in the MIM element 1 greatly depends on the kind of the insulating material and the electrode material and the conduction structure. However, in order for a significant current to flow in the MIM element 1, it is preferable that the distance between the electrodes 5 and 6 be approximately 100 nm or less. Further, in order to obtain a large current required for matrix driving of the bubble jet recording head at a low voltage, it is preferable that this interval be 40 nm or less. On the other hand, if the interval is extremely narrow, the ions on the metal surface of the electrodes 5 and 6 may cause field emission, so it is preferably 1 nm or more. Further, in order to obtain a stable tunnel junction, the thickness is preferably 4 nm or more. That is, the distance between the electrodes 5 and 6 is preferably 1 to 100 nm, and in particular, in order to obtain a large current required for matrix driving of the bubble jet recording head at a low voltage, the distance between the electrodes 5 and 6 is It is preferably 4 to 40 nm.

However, in this reference example shown in FIGS.
A resistance heating element 2 is provided separately from the IM element 1, and the resistance heating element 2 heats the liquid. In this reference example , FIG.
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 as shown in FIG. Since the temperature rise of the element 1 itself is suppressed, the MIM
It is possible to prevent the element 1 from being destroyed.

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 scanning electrodes (lower electrodes) Y _j and Y _{j + 1} ,
The i-th and i + 1-th information electrodes X _i and X _{i + 1} are schematically shown, respectively. The scanning electrodes Y _j and Y _{j + 1} and the information electrodes X _i and X _{i + 1} form a matrix circuit, and the MIM element 1 which is a non-linear element is provided at the intersection of the matrix circuits.
And the resistance heating element 2 is arranged. In addition, the discharged droplet 9
Is schematically shown.

In FIG. 4, by inputting a selection potential waveform to the scanning electrode and an ejection or non-ejection information potential waveform to the information electrode according to the image signal, the MIM element 1
Can be controlled to an on state or an off state. That is, only the MIM element 1 located at the intersection of the scan 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. Electric 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 either the selection potential waveform is input to the scan electrode or the ejection information potential waveform is input to the information electrode. No electric power is supplied to the generated resistance heating element 2, and the droplet 9 is not ejected.

As described above, the area of the MIM element 1 is the area between the pair of electrodes of the resistance heating element connected in series to the MIM element 1 (hereinafter, also simply referred to as "area of resistance heating element").
Is larger than that of MIM, the MIM due to heat generation of the MIM element 1
The risk of destruction of the element 1 itself is avoided. But MIM
If the area of the element 1 becomes too large, it may be difficult to miniaturize the head. Conventionally, by analogy with the power density during operation when a 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 better. However, in the bubble jet recording head, in particular, the voltage applied to the MIM element 1 that supplies a large amount of electric power to the resistance heating element 2 is increased so that the large amount required for foaming the ejection liquid when the MIM element 1 is in the ON state. It is important to pass an electric current. In order to satisfy this requirement and to lower the drive voltage in order to avoid an increase in device drive cost, the MIM device 1 in the drive state is required.
It is necessary to substantially equalize the resistance value R _MIM of R _MIM and the resistance value R _H of the resistance heating element, and 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, a value of 3.7 as a coefficient means that the film boiling temperature of the discharge liquid containing water as a main component is about 3
The temperature is 00 ° C., and 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 preferably S _H. That is, the area of the non-linear element 1 is preferably 3.7 times to 10 ⁸ times larger than the area of the resistance heating element 2.

In this reference example , the ejection port 8 of the MIM element 1
Since the length of the MIM element 1 in the arrangement direction is shorter than the length of the MIM element 1 in a direction substantially perpendicular to the arrangement direction of the ejection openings 8, the ejection openings 8 and the MIM elements 1 can be arranged at high density. In addition, in this reference example , the MIM element 1 is formed on the same substrate 23 as the resistance heating element 2, the discharge port 5 is formed in a direction substantially perpendicular to the substrate 23, and the flow path 31 is formed. Since it extends mainly from the portion where the resistance heating element 2 is formed to the side substantially opposite to the position where the MIM element 1 is disposed, the large area MIM element 1 can be disposed so as not to disturb the liquid ejection. .

A method of manufacturing the MIM element 1 of the present reference example will be described. This MIM element 1 includes an insulating thin film (oxide insulating film) 24 obtained by anodizing a striped metal electrode (lower electrode) 5. A stripe-shaped metal electrode (upper electrode) 6 that intersects with the lower electrode 5 is provided on the top. 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. Is. At this time, the RF sputtering process is about 10
^-2 Performed in an Ar gas atmosphere of about Torr. The anodic oxidation process is performed in a 0.8% by weight aqueous citric acid solution using the mesh 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, and the substrate 23 has a crystal axis <111> having a thickness of 0.625 mm.
The lower layer 22 on the surface of the lower electrode 5 is a Si thermal oxide film having a thickness of 2.75 μm, and the resistance heating element 2 is
It is a tantalum nitride thin film having a thickness of 0.05 μm.

In this reference example , the resistance heating element 2 has a size of 25 μm × 25 μm and an area of 625 μm ² , and the element resistance thereof is 53Ω. In addition, the width of the flow path 31 is 30 μ
m, the spacing between the channels is 80 μm. The MIM element 1 has a size of 84.5 μm × 20000 μm and an area of 169.
It is 0000 μm ² and has a strip shape that extends long in the direction perpendicular to the arrangement direction of the ejection ports 8. The area of the MIM element 1 is 2704 times the area of the resistance heating element 2. Also, M
When the voltage applied between both ends of the IM 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,
A current of 126 mA flows. At this time, the power consumption converted into heat by the MIM element 1 and the resistance heating element 2 is 0.847.
W, and the power density of the MIM element 1 is 0.5 MW /
m ² , the power density of the resistance heating element 2 is 1.355 GW / m ²
Is. When power is supplied to the resistance heating element 2 under such conditions, sufficient heat is generated to heat and foam the discharge liquid. The heat generation amount per unit area of the MIM element 1 is 1/2704 of the heat generation amount per unit area of the resistance heating element 2.
Therefore, the temperature rise can be suppressed. In addition, in particular, heat escapes to the Si substrate 23 via the lower layer 22, so that the temperature rise of the MIM element 1 can be efficiently suppressed. Furthermore, since the resistance values of the MIM element 1 and the resistance heating element 2 are equal, a large amount of 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 the large current required for foaming.

[0038] (First Embodiment) FIG. 5, the main part of an ink jet recording head of the first embodiment of the present invention is shown. The same parts as those in the reference example are designated by the same reference numerals and the description thereof 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 ejection port 18 is formed in a direction substantially parallel to the substrate 23. Channel 19
Extends mainly from the portion where the resistance heating element 2 is formed to the side where the MIM element 1 is disposed. Therefore, the MIM element 1 having a large area does not interfere with the liquid ejection. Further, since a part of the MIM element 1 is in thermal contact with the ejection liquid, the 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. .

[0040] (Second Embodiment) FIG. 6 is a main part of an ink jet recording head of the second embodiment of the present invention is shown. The same parts as those in the reference example and the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

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

For example, 2 μ is provided between the lower electrode 5 and the upper electrode 6.
When the droplet 9 is ejected by applying the pulsed voltage of s, the thermal 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 discharging voltage is applied is quickly released to the discharging liquid, and the temperature rise of the MIM element 11 can be suppressed at the same time. The MIM element 11 can be protected.

In this embodiment as well, a method of manufacturing the MIM element 11 will be described in the same manner as in the reference example . The MIM element 11 is an insulating thin film obtained by anodizing the striped metal electrode (lower electrode) 5. On the (oxide insulating film) 24,
Striped metal electrode (upper electrode) intersecting lower electrode 5
6 is provided. Specifically, the lower electrode 5 is
After forming a Ta thin film with a thickness of about 300 nm by the RF sputtering method, the surface is oxidized by an anodic oxidation method and the thickness is about 32 nm.
Of the Ta ₂ O ₅ thin film. At this time, RF
The sputtering process is performed in an Ar gas atmosphere of about 10 ⁻² Torr. The anodic oxidation process is performed in a 0.8% by weight aqueous citric acid solution using the mesh 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, and the substrate 23 has a crystal axis <111>.
Is a 0.625 mm thick Si substrate, the lower layer 22 on the surface of the lower electrode 5 is a 2.75 μm thick Si thermal oxide film, and the resistance heating element 2 is a 0.05 μm thick tantalum nitride thin film. Is.

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 path 31 is 6
At 0 μm, the spacing between the channels is 80 μm. The size of the MIM element 11 is 42.25 μm × 40000 μm, the area is 1690000 μm ² , and it is a strip shape extending long in the direction perpendicular to the arrangement direction of the ejection ports 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.
It is 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 discharge 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, it is possible to suppress the temperature rise.

Further, since the condition of _{3.7R MIM / S MIM <R H} / S H is satisfied, not considered in the design of the MIM element 11, the water was to foam occurs mainly discharge There is no risk of instability.

In this embodiment, the MIM element 11 is arranged adjacent to the ejection liquid, and this acts as a heat dissipation 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 the pulse voltage of the period Δt is applied to the MIM element 11, the thickness of the protective film 505 is κΔt. Square root of 2
It is less than double. As a result, it is possible to prevent the MIM element 11 itself from being damaged by the heat generated by the MIM element 11.

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-mentioned embodiments.

This ink jet recording apparatus has a paper feed roller 405 whose drive is controlled by a drive circuit 403.
Is configured to convey the paper 406 which is a recording medium. Further, the inkjet recording head 407 controlled by the control unit 404 is provided so that each ejection port thereof faces the conveyed paper 406.
By controlling the non-linear element 1 to the ON state or the OFF state according to the signal from 04, the ejection and non-ejection of the ejection droplet 9 from the ejection port 8 is controlled. By rapidly heating the ink on the resistance heating element 2 to which electric power is supplied in this way, bubbles based on the film boiling phenomenon are generated all over the surface of the resistance heating element 2 with 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. Further, as the ejection droplet 9 is ejected, ink is supplied from the ink tank 402 to the inkjet recording head 407.

[0049]

According to the present invention, the area of the nonlinear element is
Since the resistance heating element connected in series with this is larger than the area between the pair of electrodes, it is possible to prevent the non-linear element itself from being destroyed by the heat generated by the non-linear element. Particularly, the area of the non-linear element is equal to the area of the resistance heating element between the pair of electrodes.
When it is 7 times to 10 ⁸ times, it is possible to prevent the non-linear element itself from being destroyed by heat generation of the non-linear element, and it does not hinder the miniaturization of the head. Further, the driving voltage can be kept low to the extent that the element driving cost does not increase while allowing a large current required for bubbling the ejection liquid to flow.

If the length of the non-linear element in the ejection port array direction is shorter than the length in the direction substantially orthogonal to the array direction, the ejection port and the non-linear element can be arranged in high density.

Further, when the cooling structure for the non-linear element is provided, it is possible to more reliably prevent the non-linear element itself from being broken due to heat generation of the non-linear element.

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

[Brief description of drawings]

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

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

FIG. 3 is a cross-sectional view of a main part of an inkjet recording head of a reference example .

FIG. 4 is an electric circuit diagram schematically showing an inkjet recording head of a reference example .

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

FIG. 6 is a plan view of a main part of an inkjet recording head according to a second embodiment of the present invention.

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

[Explanation of symbols]

1 MIM element (non-linear 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 outlets 9 droplets 11 MIM element (non-linear element) 18 outlets 19 channels 22 Lower layer (thin oxide insulation film) 23 board 24 Insulating thin film 31 channel 52 Discharge port forming part 54 Discharge liquid supply port 402 ink tank 403 drive circuit 404 control unit 405 Paper feed roller 406 paper 407 inkjet recording head 505 protective film

Continuation of front page (56) Reference JP-A-7-164632 (JP, A) JP-A-6-301060 (JP, A) JP-A-9-80486 (JP, A) JP-A-2-141246 (JP , A) JP 57-182452 (JP, A) JP 59-207262 (JP, A) JP 13-71500 (JP, A) JP 13-71499 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) B41J 2/05

Claims (8)

(57) [Claims] 1. A communication with an ejection port for ejecting ink
A resistance heating element that is provided in the flow path and that generates thermal energy used to eject ink, and a pair of electrodes that are connected to the resistance heating element; and the resistance heating element. It is connected in series to the resistance heating element for driving, and the resistance value when a low voltage is applied, regardless of the polarity,
M showing a higher value than the resistance value when a high voltage is applied
An inkjet recording head having a non-linear element having IM type current-voltage characteristics, wherein at least a part of the non-linear element is in the flow path or
The non-linear element is placed in the liquid chamber that communicates with the flow path.
Keep the area of the child in the SIMM and the driving state of the nonlinear element.
That the resistance value and RMIM, the area between the front <br/> Symbol pair of electrodes of the resistance heating element SH, the resistance of the resistance heating element
Is RH / 3.7RMIM / SMIM is RH /
An inkjet recording head characterized by being smaller than SH . 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 the resistance value of the non-linear element in the driven state is substantially equal to the resistance value of the resistance heating element. 4. The ink jet recording according to claim 1, wherein the length of the non-linear element in the ejection port array direction is shorter than the length in the direction substantially orthogonal to the array direction. head. 5. The non-linear element is formed on the same substrate as the resistance heating element, and in a flow path formed corresponding to the resistance heating element in a direction substantially parallel to the substrate. A discharge port for discharging ink is formed, and the flow path is
The extension from the position where the resistance heating element is formed mainly to the position where the non-linear element is provided.
4. The inkjet recording head according to any one of 4 above. 6. have a matrix electrode constituting a matrix circuit for applying a voltage to the resistance heating element, wherein
A non-linear element is placed at the intersection of the matrix electrodes.
An ink jet recording head according to any one of claims Koko 1-5 which are. 7. to rise to film boiling in ink by the thermal energy for ejecting ink, an ink jet recording head according to any one of claims 1-6. 8. provided corresponding to the resistance heating element having a discharge port for discharging ink onto a recording surface of the recording medium, and an ink jet recording head according to any one of claims 1-7 An inkjet recording apparatus comprising at least a transporting unit that transports a recording medium.