JPH07256880A - Ink jet head and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve the ink discharge speed of an ink jet head using a buckling structure by making a part opposing the orifice of a nozzle of a buckling structure that drives by a temperature change deform locally. CONSTITUTION:When voltage is applied through electrodes 9a, 9b, a buckling structure 3 is heated by resistance heat and will expand. However, since the both ends are fixed, the buckling structure fails to expand and deform, and a compressive force P occurs. If the compressive force P exceeds a buckling load, buckling deformation occurs. At this time, if the cross-sectional area of the part of the buckling structure 3 opposite to the nozzle is smaller than other parts, stress concentration occurs. Therefore, the part opposite to the nozzle deforms toward the side of the nozzle plate 1 in response to the form of the nozzle orifice 2. In consequence, pressure is conveyed to ink filling a space between the buckling structure 3 and the nozzle plate 1, and an ink drop 6 is formed and jets out from the nozzle orifice.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, an ink jet method is known in which a recording liquid is discharged and ejected to perform recording. This method has various advantages such as low noise and relatively high-speed printing, downsizing 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 ink jet head utilizing the pressure of a bimetal generated by the deformation of a piezoelectric element as the liquid droplet ejecting means, for example, Japanese Patent Laid-Open No. 63-63.
-297052 is available.

Further, in Japanese Patent Application No. 5-278271 "Inkjet head and its manufacturing method" filed by the applicant on November 8, 1993, pressure generation by a pressure generator provided in the ink chamber is made. An invention using a buckling structure driven by temperature change as a source is disclosed.

[0004]

However, the above-mentioned JP-A-63-297052 has the following problems.

FIGS. 10 (a) and 10 (b) show Japanese Patent Laid-Open No. 63-29.
This corresponds to FIGS. 3 (a) and 3 (b) of No. 7052. In FIG. 10A, in the ink chamber 4 formed by the nozzle plate 1 having the nozzle orifice 2 and the housing 8, the piezoelectric element 23 is formed on the surface of the metal plate 25 supported by the spacers 27. Is attached, and the piezoelectric element 23 is deformed by the voltage supplied from the power source V. The figure (a) is a standby state, and the figure (b) is a state in which the ink droplets 6 are ejected.

When a voltage is applied to the piezoelectric element 23, the piezoelectric element 23 contracts in the lengthwise direction to form a bimetal structure with the metal plate 25, thereby changing the displacement in the thickness direction as shown in (b). Due to this displacement, pressure propagates to the ink filling the space between the piezoelectric element 23 and the nozzle orifice 2, and the ink droplet 6 is ejected from the nozzle orifice 2 for recording. However, in an ink jet head using a piezoelectric element, the bimetal is deformed in an arc shape when the piezoelectric element is driven, so that pressure is not concentrated on the nozzle orifice portion, which causes a drop in ink droplet ejection speed. .

Further, since the deformation of the piezoelectric element is small, a large area piezoelectric element is used and the thickness is increased due to the bimetal structure. Therefore, it is difficult to manufacture a multi-nozzle head in which nozzles are integrated.

Therefore, an ink jet head using a buckling structure was invented as in Japanese Patent Application No. 5-27871. In this application, the spacing between the buckling structure and the substrate,
Optimum conditions for the ink flow path width of the buckling structure were obtained, but the buckling structure had the same width and thickness throughout.

An object of the present invention is to further improve the ink ejection speed of an ink jet head using a buckling structure.

[0010]

An ink jet head according to the present invention comprises a nozzle plate having a plurality of nozzle orifices, a pressure generator disposed corresponding to each nozzle orifice, and immersed in ink. The pressure generator is composed of a buckling structure body driven by a temperature change and a substrate supporting the buckling structure body, and the buckling structure body is locally deformed. Therefore, in this buckling structure, the cross-sectional area of the portion facing the nozzle orifice is smaller than that of the other portions, and for example, the width of this portion is reduced or the thickness thereof is reduced.

In this buckling structure manufacturing method, a photoresist is formed on a portion of the substrate facing the nozzle orifice, and a nickel layer is electroplated on the metal film formed on the substrate including the photoresist. To form a buckling structure body, and etching is performed so that the cross-sectional area of the buckling structure body of the portion facing the nozzle orifice is smaller than that of the other portion.

[0012]

According to the above configuration of the present invention, when the buckling deformation of the buckling structure by thermal driving is used as the mechanism for increasing the ink pressure, the deformation of the portion facing the nozzle orifice is large and the shape is small. Since a large amount of displacement can be obtained,
The head can be miniaturized. Further, since the amount of deformation of the buckling structure at the position facing the nozzle orifice is large, the ejection speed of ink droplets is improved.

Further, 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.

[0014]

1 is a sectional view of an embodiment of the present invention in a standby state, FIG. 2 is a sectional view taken along the line X ₁ -X ₁ ′, FIG. 3 is a sectional view of the apparatus of FIG. 1 during ink ejection, FIG. 4 shows X ₂ of the apparatus of FIG.
-X ₂ 'is a cross-sectional view.

First, FIG. 1 will be described. The nozzle plate 1 has a plurality of nozzle orifices 2 formed in a conical shape or a funnel shape.
The buckling structure 3 is arranged corresponding to the above, and has a structure in which it is immersed in the ink in the ink chamber 4. Nozzle plate 1
For example, glass having a thickness of 0.2 mm can be used. The buckling structure 3 has a comb-teeth shape and is made of a metallic material such as nickel which is conductive and elastically deforms. Both ends of the buckling structure 3 are insulating members 7 such as silicon oxide, which are fixed to a substrate 5 such as silicon or glass, and electrodes 9a and 9b for conducting electricity are provided at their ends. There is. Buckling structure 3
The cross-sectional area of the portion of the central portion facing the nozzle orifice 2 is smaller than that of the other portions. The front surface of the substrate 5 is fixed to the nozzle plate 1 via an insulating spacer 10 such as polyimide, and the back surface of the substrate 5 is fixed to the housing 8.

Next, FIG. 3 will be described. Electrodes 9a, 9
When a voltage is applied through b, the buckling structure body 3 is heated by resistance heat generation and tends to cause thermal expansion. However, in this case, since both ends are fixed, it cannot be expanded and deformed, and the compressive force P is generated. When this compressive force P exceeds the buckling load, buckling deformation occurs. At this time, if the cross-sectional area of the portion of the buckling structure 3 facing the nozzle is made smaller than that of the other portion, stress concentration occurs, so that as shown in FIGS. From the state shown in FIGS. 1 and 2, the nozzle plate 1 is deformed corresponding to the shape of the nozzle orifice 2. Therefore, the pressure propagates to the ink filling the space between the buckling structure 3 and the nozzle plate 1, and the ink droplet 6 is formed from the nozzle orifice 2 and ejected to the outside.

Here, for example, the main material of the buckling structure 3 is nickel, the length is 300 μm, the width is 50 μm, and the thickness is about 6 μm, and the thickness of the central portion of the buckling structure 3 facing the nozzle orifice 2 is set. By applying a voltage of 0.59 V to the electrodes 9a and 9b,
The buckling structure 3 is deformed to the nozzle plate 1 side by 9 μm.
Further, it is known that the thickness of the spacer 10 has a great influence on the pressure propagation from the buckling structure 3 to the nozzle orifice 2, and it is desirable to set it to 2 to 5 μm.

The buckling structure 3 is bent so that the buckling structure 3 bends toward the nozzle plate 1 side due to the difference in linear expansion coefficient.
Has a two-layer structure of 0.01 μm thick tantalum on the substrate side and about 6 μm thick nickel on the nozzle plate side. When the buckling structure body 3 is cooled by cutting off the current flowing through the electrodes 9a and 9b, the standby state shown in FIGS. 1 and 2 is restored.

This series of operations is not limited to the case where the thickness of the central portion of the buckling structure 3 facing the nozzle orifice is thin, and the width is narrowed even if the thickness is the same as the other portions. This produces the same effect. For example, the buckling structure 3 to be described later has a length of 300 μm, a width of 50 μm, and a thickness of about 6 μm, and the width of the central portion of the buckling structure facing the nozzle orifice is 100 μm. The same operation is performed when the width is 25 μm.

FIG. 5 is an exploded perspective view of the apparatus of FIG.
6 is its XX 'sectional view, and FIG. 7 is its YY' sectional view. The nozzle plate 1 is provided with a large number of nozzle orifices 2, 2, ... The spacer 10 has a rectangular window 10-1, at a portion facing the nozzle orifices 2, 2 ...
10-1 ... are provided. The buckling structure 3 has a comb shape and is fixed to the substrate 5 having the ink flow path 5-1 via the insulating member 7. The ink flow channel 5-1 is formed in a slender funnel shape in the direction of the nozzle orifices 2, 2. Buckling structure 3 facing the window 10-1 of the spacer 10
The central portion 3-1 of the teeth of the comb has a thin thickness or a narrow width to facilitate deformation. In the case of FIG. 5, the width is narrow. The ends 9a and 9b of the buckling structure 3 serve as electrodes. The substrate 5 is attached to a housing 8 having a space 8-1 and an ink supply hole 8-2. The void 8-1 and the ink flow path 5-1 form the ink chamber 4. Reference numeral 11 is a filler that fills the space between the insulating member 7 and the spacer 10 of the buckling structure body 3. The insulating member 7 serves as a spacer that regulates the distance between the buckling structure 3 and the substrate 5.

Next, as an example of a manufacturing method, a manufacturing process of a buckling structure having a thinned portion facing the nozzle orifice and a substrate supporting the buckling structure will be described. 8 (a)-
(I) is sectional drawing of each process of the manufacturing method.

First, as shown in FIG. 8A, a thermal oxide film 110 having a predetermined thickness (for example, 1 μm) is formed on both front and back surfaces of a silicon substrate 100.

Next, as shown in FIG. 8B, a photoresist is applied to the back surface, patterning is performed corresponding to the shape of the ink flow path to be formed, and the thermal oxide film 1 is formed with CHF ₃ .
10 etching is performed.

Next, as shown in FIG. 8C, a photoresist is applied to the surface and etching is performed while leaving the photoresist 150 only in the portion facing the nozzle orifice. This is to reduce the thickness of the buckling structure.

Next, as shown in FIG. 8D, a tantalum film having a thickness of 0.01 μm is formed on the surface, and a nickel film having a thickness of 0.1 μm is formed thereon by, for example, a sputtering method. , Tantalum and nickel film 120 is formed. A photoresist 130 is applied on this, and patterning is performed in a comb tooth shape corresponding to the shape of the structure of the buckling structure to be formed. At this time, the length of the buckling structure of the photomask for photoresist patterning is 300.
A device designed to have a width of 50 μm and a width of 50 μm is used. The distance between the teeth of the comb is determined according to the distance between the nozzle orifices.

Next, as shown in FIG. 8E, the nickel plating layer 14 having a predetermined thickness, for example 6 μm, is formed by electrolytic plating using the tantalum and nickel films 120 as electrodes.
Form 0. Buckling structure body 3 is formed by tantalum / nickel film 120 and nickel plating layer 140.
For the electrolytic plating, for example, nickel plating using a nickel sulfamate bath can be used.

Next, as shown in FIG. 8F, the photoresist 130 is peeled off, and unnecessary tantalum by sputtering and both ends of the nickel film 120 are removed by dry etching such as ion milling.

Next, as shown in FIG. 8 (g), a photoresist is applied to the surface, and the portion of the buckling structure 3 facing the nozzle orifice is half-etched to a thickness of 3 μm, for example, and then the photoresist is removed. .

Next, as shown in FIG. 8H, when the silicon substrate 100 in the above state is immersed in a potassium hydroxide solution,
Silicon in the portion without the thermal oxide film 110 is removed, and the ink flow path 5-1 is formed.

Next, as shown in FIG. 8 (i), the silicon substrate 100 in the above state is dipped in a hydrofluoric acid solution to remove an unnecessary thermal oxide film. Next, the silicon substrate 10 in this state
When 0 is immersed in acetone, the photoresist 150 is removed, and only both ends of the buckling structure 3 are fixed to the substrate. This completes the pressure generator.

Finally, as shown in FIG. 5, the ink jet head is completed by joining the nozzle plate 1, the spacer 10, the substrate 5 on which the buckling structure 3 is arranged, and the housing 8.

Next, as a second example of the manufacturing method, a manufacturing process of a buckling structure body in which a portion facing the nozzle orifice is thin and a substrate supporting the buckling structure body will be described. FIG. 9 (a)
(G) is sectional drawing of each process of the manufacturing method.

First, as shown in FIG. 9A, thermal oxide films 10 are formed on both the front and back surfaces of the silicon substrate 100 to have a thickness of 1 μm, for example.

Next, as shown in FIG. 9B, a photoresist is applied to the back surface, patterning is performed corresponding to the shape of the flow path to be formed, and the thermal oxide film 110 is etched with CHF ₃ .

Next, as shown in FIG. 9C, a tantalum film having a thickness of 0.01 μm and a tantalum and nickel film 120 made of a nickel film having a thickness of 0.1 μm, for example, are formed on the surface by sputtering, for example. A film is formed, a photoresist 130 is applied thereon, and comb-shaped patterning corresponding to the shape of the buckling structure to be formed is performed. At this time, in the photomask for photoresist patterning, the buckling structure has a length of 300 μm and the width thereof is 50 μm, and the width of the buckling structure at the portion facing the nozzle orifice is 100 μm. 25μ over
The one designed in advance to be m is used.

Next, as shown in FIG. 9D, a nickel plating layer 140 having a predetermined thickness (for example, 6 μm) is formed by electrolytic plating using the nickel film as an electrode. The buckling structure 3 is formed by the nickel plating layer 140 and the tantalum / nickel film 120. For electrolytic plating,
For example, nickel plating with a nickel sulfamate bath can be used.

Next, as shown in FIG. 9E, the photoresist is peeled off, and the unnecessary tantalum and nickel films 120 by sputtering on both ends are removed by dry etching such as ion milling.

Next, 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 is removed, and the ink channel 5-1 is formed.

Next, as shown in FIG. 9G, when the silicon substrate 100 in the above-mentioned state is dipped in a hydrofluoric acid solution, unnecessary thermal oxide film is removed, and only the both ends of the buckling structure 3 are left as the substrate. It will be fixed. This completes the pressure generator.

Finally, as shown in FIG. 5, the substrate 5 on which the nozzle plate 1, the spacer 10 and the buckling structure 3 are arranged,
The housing 8 is joined to complete the inkjet head.

[0041]

As described above, according to the present invention, since the buckling deformation of the buckling structure body by thermal driving is used as a mechanism for increasing the pressure of ink, the structure of the pressure generator is very simple. Since a large amount of displacement can be obtained even if the shape is small, the head can be downsized. Further, since the buckling structure at the position facing the nozzle orifice is largely deformed, the ink droplet ejection speed is improved.

The flow rate can be controlled by changing the pulse cycle applied to the buckling structure. Further, since the photolithography technique is used in the manufacturing method, the pattern dimensional accuracy 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.

2 is a sectional view taken along line X ₁ -X ₁ ′ of FIG.

FIG. 3 is a cross-sectional view of an operating state of the inkjet head of the present invention.

4 is a sectional view taken along line X ₂ -X ₂ ′ of FIG.

FIG. 5 is an exploded perspective view of the inkjet head of the present invention.

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

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

8 (a) to (i) are cross-sectional views of respective steps of an example of the production method of the present invention.

9A to 9G are cross-sectional views of steps of another example of the production method of the present invention.

10A and 10B are cross-sectional views of a conventional inkjet head in a standby state and an operating state, respectively.

[Explanation of symbols]

 1 Nozzle 2 Nozzle Orifice 3 Buckling Structure 4 Ink Output 5 Substrate 6 Ink Drop 7 Insulating Member 8 Housing 9a, 9b Electrode 10 Spacer 100 Silicon Substrate 110 Thermal Oxide Film 120 Tantalum and Nickel Film 130 Photoresist 140 Nickel Plating Layer 150 photoresist

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

Claims (4)

[Claims] 1. An ink chamber comprising a nozzle plate having a nozzle orifice and a housing behind the nozzle plate, and a pressure generator provided in the ink chamber, the pressure generator being a seat driven by a temperature change. An inkjet characterized by comprising a buckling structure and a substrate supporting the buckling structure via a spacer and having an ink flow path, and a portion of the buckling structure facing the nozzle orifice is locally deformed. head. 2. The ink jet head according to claim 1, wherein a cross-sectional area of a portion of the buckling structure facing the nozzle orifice is smaller than that of the other portion. 3. The ink jet head according to claim 1, wherein the buckling structure comprises a nickel film formed on the tantalum film and a nickel layer formed on the nickel film. 4. A step of forming a photoresist on a portion of the substrate facing the nozzle orifice, a step of forming a nickel film to be a buckling structure body on the substrate containing the photoresist by electrolytic plating, The step of etching the nickel film so that the cross-sectional area of the nickel film facing the nozzle orifice is smaller than the cross-sectional area of the other area, the nozzle plate having the nozzle orifice is connected in front of the pressure generator, and the housing is installed in the rear. And a step of forming an ink chamber by combining them with each other.