JPH07125203A - Ink jet head and production thereof - Google Patents

Abstract

PURPOSE:To enhance the pressure of ink by buckling deformation by constituting a pressure generator of a buckling structure driven by a temp. change and the substrate supporting the buckling structure through a spacer and having ink passages. CONSTITUTION:When a current is applied through electrodes 9a, 9b, a buckling structure 3 is heated by resistance heat tending to thermally expand. However, since the buckling structure 3 is fixed at both ends thereof in this case, it can not generate expansive deformation and compression force is generated in a predetermined direction. When this compression force exceeds buckling load, buckling deformation is generated and an unfixed buckling part is deformed toward a nozzle plate 1 and the pressure is transmitted to the ink in the space between the buckling structure 3 and the nozzle plate 1 and an ink droplet 6 is formed from a nozzle orifice 2 to be jetted to the outside. Since the buckling structure is extremely simple in its structure and can obtain large displacement quantity even if the shape thereof is small, a head can be miniaturized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved ink jet head having a mechanism for driving a pressure generator immersed in ink to increase the pressure in the ink and eject ink droplets from a nozzle orifice. .

[0002]

2. Description of the Related Art An ink jet method for recording by ejecting and flying a recording liquid has been conventionally known. This method has a number of advantages such as low noise, relatively high speed printing, compact size of the apparatus and easy color recording. In such an inkjet recording method, recording is performed using an inkjet recording head based on various droplet ejection principles. For example, an inkjet head that uses the pressure of a piezoelectric element as a liquid droplet ejecting means,
There is a bubble type ink jet head or the like in which an electric current is passed through a heating resistor to vaporize a liquid by the temperature rise of the heating element and the pressure during vaporization is used.

[0003]

However, the above-mentioned conventional techniques have the following problems, respectively.

That is, in an ink jet head using a piezoelectric element, a voltage is applied to the piezoelectric element to deform the piezoelectric element and the deformation causes ink droplets to be ejected for recording. Ink droplets are ejected by stacking elements or forming a bimorph type piezoelectric actuator having a large shape to increase the displacement amount. Therefore, a piezoelectric element and an ink chamber that are much larger than the nozzle pitch are required, which makes it difficult to manufacture a multi-nozzle head in which nozzles are integrated.

In the bubble type ink jet head, the ink is vaporized by the heat from the heating element to generate bubbles, and the volume expansion at that time is used to eject ink droplets. It is relatively easy to integrate small nozzles, and there is an advantage that the time required for recording is short. However, since the heating element is heated to near 1000 ° C. in a short time in order to obtain clean air bubbles, the heating element is apt to deteriorate and the life of the inkjet head is relatively short.

[0006]

An ink jet head according to the present invention comprises a nozzle plate having one or more nozzle orifices, and a pressure generator disposed corresponding to each nozzle orifice and immersed in ink. ,
The pressure generator is composed of a buckling structure that is driven by a temperature change and a substrate that supports the buckling structure.

Further, in the manufacturing method, a buckling structure body is formed on a sacrificial layer formed on a substrate by plating or the like, and the sacrificial layer is etched to form a spatial three-dimensional structure.

[0008]

According to the present invention, a buckling structure having a simple structure can be thermally driven, and the buckling deformation can increase the pressure of ink. The buckling structure can obtain a large amount of displacement even if it has a small shape, and can generate a large amount of displacement at a lower temperature than a bubble type inkjet head. Further, since the photolithography is used in the manufacturing, the pattern dimensional accuracy is high, the mass production effect is large, and high integration and cost reduction are possible.

[0009]

1 and 2 are cross-sectional views for explaining the recording principle of a recording head of the present invention, showing a standby state and an operating state, respectively.

The nozzle plate 1 has one or more nozzle orifices 2 formed in a conical shape or a funnel shape, buckling structures 3 are arranged corresponding to the respective nozzle orifices, and a housing 8 on the back side is provided. The structure is soaked in the ink in the ink chamber 4 formed between and. The buckling structure 3 is formed of a metal material such as nickel which is electrically conductive and elastically deforms. Both ends of the buckling structure body 3 are fixed to the substrate 5 by the insulating member 7 and serve as electrodes 9a and 9b for conducting electricity. Further, both ends of the surface of the buckling structure 3 are connected to the nozzle plate 1 via the spacers 10,
The back surface of the substrate 5 is fixed to the housing 8. The electrode may be provided with another conductor on the surface of the buckling structure.

When a current is applied through the electrodes 9a and 9b, the buckling structure 3 is heated by resistance heating and tends to cause thermal expansion. However, in this case, since both ends are fixed, it cannot be expanded and deformed, and as shown in FIG. 2, a compressive force P in the arrow direction is generated. When the compressive force P exceeds the buckling load, buckling deformation occurs, and the unfixed buckling portion deforms toward the nozzle plate 1 side, and the buckling structure 3
The pressure propagates to the ink filling the space between the nozzle plate 1 and the nozzle plate 1, and the ink droplet 6 is formed from the nozzle orifice 2 and ejected to the outside. For example, if the buckling structure pair 3 is made of nickel and the sizes of the buckling portions are 300 μm (length), 48 μm (width), and 6 μm (thickness), when the room temperature is 25 ° C., the temperature is 98 ° C. or higher. Buckling occurs. When the buckling structure 3 is further heated to 225 ° C., the buckling structure 3 is deformed toward the nozzle plate 1 side, and the ink droplet 6 is formed from the nozzle orifice 2 and can be ejected to the outside. The edge of the spacer 10 is slightly outward of the edge of the insulating member 7 so that the buckling structure 3 is bent toward the nozzle plate 1.

When the buckling structure 3 is cooled to 98 ° C. by cutting off the current flowing through the electrodes 9a and 9b, the standby state shown in FIG. 1 is restored.

Next, after applying a current to the electrodes 9a, 9b, the time when the buckling structure 3 is heated to 225 ° C. by resistance heating and thermal expansion occurs (rise response speed: Tr), and the current of the electrodes 9a, 9b. Time after which the buckling structure 3 is cooled to 98 ° C and returns to the standby state (rise response speed: Td)
Can be calculated by simulation using the heat conduction equation.

FIG. 3 is an exploded perspective view of an example of an ink jet head according to the present invention, FIG. 4 is a sectional view taken along the line XX 'when assembled in FIG. 3, and FIG.
It is a Y'sectional view. The material of the buckling structure is nickel, and the substrate is silicon single crystal.

The nozzle plate 1 has one or more nozzle orifices 2, 2 ... As described above. Spacer 1
0 is provided with cavities 10-1, 10-1 ... Corresponding to the back of the nozzle orifices 2, 2. On one surface of the substrate 5, a recess for forming the ink chamber 4 is formed and an ink flow path 5-1 corresponding to the noise orifice 2 is provided. The angle of this slope is 54.
It is set to 7 °. The buckling structure 3 is formed on the other surface of the substrate 5 by photolithography with the insulating member 7 interposed therebetween. Nozzle orifices 2, 2 ... Are provided in the buckling structure 3.
Are formed so as to correspond to, and electrodes 9a and 9b are provided at appropriate places. In the example of FIGS. 1 and 2, the electrodes 9a and 9b are provided on both sides of the row of nozzle orifices, but in the example of FIG. 3, they are provided on one side of the row of nozzle orifices. The housing 8 is fixed to the other side of the substrate 5, and the ink chamber 4
And the ink is supplied from the ink reservoir to the ink chamber 4.

Although not shown in FIG. 3, as shown in FIGS. 1, 4 and 5, the space at the peripheral portion of the buckling structure 3 is filled with an appropriate filler 11.

FIG. 6 is a diagram for explaining the flow of heat generated in the buckling structure body 3. As the boundary condition, first, when the buckling structure 3 is heated to 225 ° C., the buckling structure 3
Deforms 9 μm toward the nozzle plate. Therefore, the simulation was performed with a structure in which the buckling structure 3 was deformed by an average of 4.5 μm. Next, the buckling structure 3 and the substrate 5
Was placed in a container 14 larger by 20 μm than its outer dimension, and the inside thereof was filled with ink, and the gap between the surface of the buckling structure 3 and the liquid surface of the ink was set to 20 μm. The simulation was performed on the assumption that the inner surface of the container 14 and the bottom surface of the substrate 5 are kept at 25 ° C. Arrows indicate the main heat flow.

In FIG. 5, the thickness t (μm) of the buckling structure 3, the gap g (μm) between the buckling structure 3 and the substrate 5, the width w (μm) of the ink flow path outlet, the thickness of the substrate 5 FIG. 7 shows the results of simulating the changes in the rising response speed (Tr) and the falling response speed (Td) when h (μm) is changed appropriately by the device shown in FIG. , FIG. 8, FIG. 9 and FIG.

7 to 9, the buckling structure 3 has a total length of 900 μm, a buckling portion length L = 300 μm, and h = 500.
μm. The pulse height is 4.676W.

FIG. 7 is a graph showing the relationship between t and Tr (Δ mark) and Td (◯ mark) when g = 1 μm and w = 100 μm. The smaller the thickness t of the buckling structure, the faster the response speeds of both Tr and Td. However, if the thickness t of the buckling structure is less than 6 μm, sufficient energy cannot be obtained to eject the ink droplet 6 from the nozzle orifice, so the ink droplet 6 is ejected from the nozzle orifice. I can't. Therefore, the lower limit of the optimum thickness of the buckling structure is 6 μm.

FIG. 8 is a graph showing the relationship between g and Tr (Δ mark) and Td (◯ mark) when t = 6 μm and w = 100 μm. The distance g between the buckling structure and the substrate does not affect the rising response speed Tr so much, but the falling response speed Td is faster as the distance g is smaller. Therefore,
When the head is driven at 2.5 kHz, for example, the gap g needs to be set to 5 μm or less. Further, if the interval g is set to 1 μm or less, it is possible to drive at 3.8 kHz.

FIG. 9 shows the dependency of the rising response speed Tr (marked by Δ) and the falling response speed Td (marked by ◯) on the ink channel width w when t = 6 μm and the gap g is appropriately changed. It is a graph. Although the ink flow path width w has little influence on the rising response speed Tr, the falling response speed Td is
The smaller the ink flow path width w, the faster. This tendency is the same for any gap between the buckling structure and the substrate. Therefore, when the head is driven at 2.5 kHz, for example, when the ink flow path w is set to 40 μm or less, the gap g between the buckling structure and the substrate needs to be set to 10 μm or less, and the ink flow path width w is 100 μm or less. That is, when the buckling portion of the buckling structure is set to one-third or less of the length of 300 μm, the gap g between the buckling structure and the substrate needs to be set to 5 μm or less. Further, although not shown, if the ink flow path width w is set to 40 μm or less and the gap g between the buckling structure and the substrate is set to 10 μm or less, it is possible to drive at 3.8 kHz.

Next, FIG. 10 shows L = 300 μm and t = 6 μm.
6 is a graph showing the relationship between the substrate thickness h and the rising response speed Tr (Δ mark) and the falling response speed Td (◯ mark) when m, g = 2 μm and the pulse height is 4.676 W. When the substrate thickness h is 20 μm or more, the rising response speed T
The r and the falling response speed Td are not much affected. However, when glass, for example, is used instead of the silicon single crystal, the thermal conductivity is inferior to that of the silicon single crystal, so that the falling response speed Td becomes slow. Therefore, it is necessary to use a silicon single crystal having good heat conductivity for the substrate, and a silicon single crystal plate having a substrate thickness h of 525 μm can be used.

As a result, in order to increase the rising response speed Tr and the falling response speed Td, the gap g between the buckling structure 3 and the substrate 5 is reduced and the ink flow passage width w is narrowed.
A silicon single crystal may be used for the substrate.

FIG. 11A shows the structure of FIG. 5 in which the thickness t of the buckling structure is 6 μm and the distance g between the buckling structure and the substrate is 1 μm.
m, ink channel width w = 40 μm, substrate thickness h = 500
FIG. 11B is a temperature profile of the buckling structure in the case of μm, and FIG. 11B shows a drive waveform. From FIG. 11A, rising response speed Tr = 28 μsec, falling response speed Td =
123 μsec is obtained, and Tr + Td <167 μsec
Therefore, it is possible to drive at 6 kHz. From FIG. 11B, the effective value of the power consumption per nozzle is W = 4.676 (W) × 28 (μsec) / 167 (μ
sec) = 0.784 (w).

Next, an example of a manufacturing process of the buckling structure body which is the main member of the present invention and the substrate supporting the buckling structure body will be described with reference to FIG.

First, the thermal oxide films 110 are formed on the front and back surfaces of the silicon substrate 100 to have a predetermined thickness, for example, 1 μm (see FIG. 12A).

Photoresist is applied to the back surface, and patterning corresponding to the shape of the ink flow path to be formed is performed.
The thermal oxide film 110 is etched with CHF ₃ (see FIG. 12B). At this time, if a silicon single crystal having a plane orientation (100) is used, it is formed after etching (1
11) Since the inclined surface forms an angle of 54.7 ° with the (100) surface, its thickness is h = 525 μm and ink flow path width is w =
If the width is 40 μm, the width of the inlet side of the ink flow path is w ′ = w
From + 2h / tan 54.7 °, it may be designed to w ′ = 785 μm.

Next, a photoresist is applied to the surface, patterning corresponding to the shape of the buckling structure to be formed is performed, and the thermal oxide film 110 is etched with CHF ₃ (see FIG. 12C). .

Next, a polyimide film 120 having the same thickness as the thermal oxide film 110, for example, 1 μm, is applied on the surface by a spinner, patterning is performed corresponding to the shape of the insulating member 7 to be formed, and the pattern is formed at 350 ° C. for 1 hour. Bake (see FIG. 12D).

Next, nickel is deposited on the surface by, for example, a sputtering method, and this is used as an electrode to perform nickel plating with a predetermined thickness, for example, 6 μm by electrolytic plating to form a nickel film 130 (FIG. 12 (e)). )reference). For electrolytic plating, nickel plating with a nickel sulfamate bath can be used, for example.

Next, a photoresist is applied to the surface, patterning is performed corresponding to the shape of the buckling structure to be formed, and an aqueous solution of nitric acid and hydrogen peroxide (for example, HNO ₃ :
The nickel film 130 is etched with H ₂ O ₂ : H ₂ O = 22: 11: 67) (see FIG. 12F).

When the silicon substrate 100 in this state is dipped in a potassium hydroxide solution, the silicon in the portion without the thermal oxide film 110 and the polyimide 120 is removed, and an ink flow path is formed (see FIG. 12 (g)).

Further, when the silicon substrate 100 in this state is dipped in a hydrofluoric acid solution, the thermal oxide films 1 on both sides of the silicon substrate 100 are formed.
The buckling structure body 3 becomes a spatial three-dimensional structure in which the buckling structure body 3 is separated from the substrate 5 by removing the thermal oxidation film 110 which is the inner sacrifice layer at this time (see FIG. 12H).

As described above, the thickness t of the buckling structure is t =
A pressure generator having 6 μm, a gap g between the buckling structure and the substrate g = 1 μm, and an ink flow path width w = 40 μm is completed.

Finally, the nozzle plate 1, the spacer 2,
The substrate 4 on which the buckling structure 3 is arranged and the housing 8 are joined together to complete an inkjet head.

[0037]

As described above, according to the present invention, since the buckling deformation of the buckling structure by thermal driving is used as the mechanism for increasing the ink pressure, the structure of the buckling structure is very simple. Even if the shape is small, a large amount of displacement can be obtained, so the size of the head can be reduced, and large displacement can be generated at a lower temperature than that of a bubble type inkjet head. Very small, the amount of heat required is small and efficient. Further, since the structure is such that heat is easily released, high-speed response is possible, and the multi-orifice necessary for high-speed recording can be realized. In addition, since the photolithography technique is used in the manufacturing method, the dimensional accuracy of the pattern is high, the mass production effect is large, and high integration and cost reduction are possible.

[Brief description of drawings]

FIG. 1 is a sectional view of an inkjet head of the present invention in a standby state.

FIG. 2 is a sectional view of an operating state of the inkjet head of the present invention.

FIG. 3 is an exploded perspective view of the inkjet head of the present invention.

FIG. 4 is a sectional view taken along line XX ′ of FIG.

5 is a cross-sectional view taken along the line YY ′ of FIG.

FIG. 6 is a schematic diagram for explaining a flow of heat generated in a buckling structure body.

FIG. 7 is a graph showing the relationship between the thickness of the buckling structure and the response speed.

FIG. 8 is a graph showing a change in response speed depending on the distance between the buckling structure and the substrate.

FIG. 9 is a graph showing the relationship of the response speed depending on the ink channel width and the distance between the buckling structure and the substrate.

FIG. 10 is a graph showing the relationship between substrate thickness and response speed.

11A is a graph showing a temperature profile of a buckling structure body, and FIG. 11B is a graph of a drive waveform.

12A to 12H are cross-sectional views showing a manufacturing process of a buckling structure body and a substrate supporting the buckling structure body, respectively.

[Explanation of symbols]

 1 Nozzle Plate 2 Nozzle Orifice 3 Buckling Structure 4 Ink Chamber 5 Substrate 7 Insulation Member 8 Housing 9a, 9b Electrode 10 Spacer 100 Silicon Substrate 110 Thermal Oxidation Film 120 Polyimide 130 Nickel Film

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuya Inui 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Within Sharp Corporation (72) Kenji Ota 22-22 Nagaike-cho, Abeno-ku, Osaka, Osaka Incorporated (72) Inventor Shingo Abe 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka

Claims (6)

[Claims] 1. An ink chamber comprising a nozzle plate having a nozzle orifice and a casing behind the nozzle plate, and a pressure generator provided in the ink chamber. The pressure generator is a seat driven by a temperature change. An ink jet head comprising: a buckling structure; and a substrate that supports the buckling structure via a spacer and has an ink flow path. 2. The ink jet head according to claim 1, wherein the gap between the buckling structure and the substrate is 10 μm or less. 3. The ink jet head according to claim 1, wherein the ink flow path width of the buckling structure is 1/3 or less of the length of the buckling portion of the buckling structure. 4. The ink jet head according to claim 1, wherein the substrate supporting the buckling structure is a silicon single crystal. 5. A pressure of a three-dimensional structure including a step of forming a sacrificial layer on a substrate, a step of forming a nickel film to be a buckling structure body on the sacrificial layer, and a step of removing the sacrificial layer by etching. A method of manufacturing an ink jet head, comprising: a step of forming a generator; and a step of connecting a nozzle plate in front of the pressure generator and connecting a casing in the rear of the pressure generator to form an ink chamber. 6. The patterning of the nickel film of the buckling structure is carried out by etching with an aqueous solution of nitric acid and hydrogen peroxide, and the removal of the thermal oxide film which is the sacrificial layer is carried out by etching with a hydrofluoric acid solution. 5. The method for manufacturing an inkjet head described in 5.