JPH0784058B2 - Inkjet head - Google Patents

Description

TECHNICAL FIELD The present invention relates to an inkjet head, and more particularly to an inkjet head in which a substrate that constitutes the head and a vibration plate are anodically bonded.

[Prior Art] FIG. 2 shows a structural cross-sectional view of an example of an on-demand type head already proposed.

As shown in the figure, the substrate 1 is provided with nozzles 5, pressure chambers 4, ink supply paths 7, and grooves corresponding to the ink reservoirs 6, and each function is obtained by joining the vibration plate 2 to the substrate 1. It becomes a flow path. In addition, the pressure chamber 4 of the diaphragm 2
The electromechanical conversion element 3 is joined to the portion corresponding to. The ink reservoir 6 is connected to an external ink supply system (not shown).

The operation principle of such an inkjet head will be briefly described. When a drive signal is applied to the electromechanical conversion element 3, the electromechanical conversion element 3 tends to deform in the lateral direction, but since the electromechanical conversion element 3 is constrained by the diaphragm, the pressure chamber 4 side, pressure chamber 4
Generate pressure on. This pressure causes the ink
The ink droplets 8 are further pushed out and fly as ink droplets 8. At this time, the drive signal of the electromechanical conversion element 3 is cut off, the original state is restored, the pressure chamber 4 temporarily becomes a negative pressure, and the ink from the ink reservoir 6 passes through the ink supply path 7 It flows into 4 and returns to the initial state.

By performing this series of operations as appropriate, the ink droplets are ejected and transferred to the paper to perform printing.

In such an inkjet head, the diameter is 50μ
Since it is necessary to fly very small ink droplets of m to 100 μm, the nozzle 5 has a width of 50 μm to 100 μm and a depth of 5
It is necessary to form a fine groove of 0 μm, and the pressure chamber 4, the ink supply path 7, and the ink reservoir 6 communicating with the nozzle 5 are also required to be precisely processed. Usually, the substrate 1 is made of glass or silicon, and the flow path is precisely formed by photoetching. Also, when the diaphragm 2 is bonded to the substrate 1, an adhesive or the like that may stick out may not be used to form the fine flow path, and a direct bonding method such as diffusion bonding or anodic bonding may be used. Is used.

Here, the series of flow path forming methods will be described in detail with reference to the drawings.

FIG. 2 shows a series of steps for forming a flow path on a substrate. First, as shown in FIG. 3 (a), a silicon substrate
A silicon nitride film 10a to be an etching mask is deposited on 1a by thermal nitridation or CVD. Next, as shown in FIG. 3 (b), the silicon nitride film in the portion to be the flow path is removed by photoetching to form 11a. Next, as shown in FIG. 3C, the silicon substrate 1a is etched using the silicon nitride film 10a left in the step of FIG. 3B as a mask to form the channel 5a.

Next, as shown in FIG. 3 (d), the flow path 5a formed as described above is corroded by an alkaline ink because the silicon is exposed, or the silicon itself is water repellent so that the ink is Since the flow of the liquid becomes worse and the air bubbles can be easily bitten, it is necessary to attach a protective film on the surface, and when the substrate 1a is thermally oxidized, the silicon oxide film 11a is formed only on the flow passage surface where the silicon is exposed. It becomes a protective film.

In the step of FIG. 3 (e), the silicon nitride film 10a which becomes an obstacle when the glass diaphragm 2 is finally anodically bonded is removed by hot phosphoric acid. At this time, since the silicon oxide film 11a cannot be removed by hot phosphoric acid, it remains on the inner wall of the flow path 5a as it is.
Finally, as shown in FIG. 3 (f), the silicon substrate 1a and the diaphragm 2 are joined and integrated by an anodic joining method. As a specific method of anodic bonding, the substrate 1a and the diaphragm 2 are stacked and heated to 450 ° C., and the silicon substrate 1 is left as it is.
When a voltage of 600 V is applied with a as an anode and the diaphragm 2 as a cathode, the bonding is completed within a few minutes. This method is extremely effective for inkjet heads such as those having precise and fine grooves because the joining surface is strong, no adhesive is used, and precise joining can be easily performed. There are combinations of materials that can be used. Generally, for the inorganic insulator, the other member is made of metal or semiconductor.

[Problems to be Solved by the Invention] However, even if silicon, which is easy to process, is used as the substrate, the silicon nitride film used as the mask material must be removed, and the process is complicated. Furthermore, if silicon is exposed in the flow path, the silicon will be corroded by the alkaline ink, and since the silicon is water repellent, it will hinder the ink flow. Therefore, after processing the flow path on the substrate, an oxide film, etc. It is necessary to add a process for attaching a mark, which further complicates the process. As a means for avoiding such an inconvenience, there is one in which the substrate side is made of glass and the diaphragm side is made of silicon, but a similar oxide film treatment is necessary for the portion corresponding to the flow passage on the diaphragm side, The process complexity was the same.

It is an object of the present invention to provide an ink jet head which solves the above-mentioned problems and which effectively uses more effective anodic bonding by a bonding method even though it is a simple process, and is precise and has good characteristics for ink. It is in.

[Means for Solving Problems] The present invention has been made to achieve the above-mentioned object,
A material with good wettability for ink is used for the substrate, and the mask for etching the groove corresponding to the flow path on the substrate or the diaphragm is made of a material that can be anodically bonded to the diaphragm or the substrate. It is a feature.

[Operation] The above means works as follows. When a material having good wettability with respect to the ink such as glass is used for the substrate, the wettability remains good even if the channel is formed in the substrate. In addition, although such a material having good wettability is generally an inorganic insulator, in order to etch such a material to a depth of several tens of microns for forming a flow channel, an organic resist mask is used for etching. Since it cannot withstand the liquid, a corrosion resistant film that can withstand the etching liquid of the substrate is applied to the substrate, the film of the portion corresponding to the flow path is etched and removed, and the substrate may be etched after forming a mask. .

At this time, if the anticorrosive film to be used as a mask is made of a material that can be anodically bonded to the diaphragm material, the mask used during etching will act as an anodically bonding material this time, and it will be possible to easily bond it to the diaphragm. Become.

[Example] An example will be described with reference to FIG. In FIG. 1 (a), a corrosion resistant coating 10b is applied to a substrate 1b in which a flow channel is formed. Borosilicate glass is used as the material of the substrate 1.
Polycrystalline silicon or amorphous silicon is suitable for the corrosion resistant film, and the former can be deposited by low pressure CVD and the latter by plasma CVD. The thickness of the anticorrosion coating is preferably 0.3μ to 1μ.

A photoresist method is used for this anticorrosion film 10b, the portions other than the portions corresponding to the flow paths are masked with photoresist, and the anticorrosion film 10b of the flow path corresponding portions 11b is formed by plasma etching.
To remove. Next, as shown in FIG. 1 (c), the substrate 1b is etched to form the channel 5b. The substrate material is
Since it is borosilicate glass, hydrofluoric acid is suitable as the etching solution. Since hydrofluoric acid alone does not substantially corrode polycrystalline silicon or amorphous silicon, only the flow path corresponding portion 11b not covered with the corrosion resistant film is etched to form the flow path 5b. Finally, as shown in FIG. 4, a borosilicate glass vibrating plate 2 is overlaid on the substrate 1b on which the corrosion resistant coating 10b has been applied, and heated to 450 ° C. to make the substrate 1 an anode,
When a DC voltage of 600 V to 1000 V is applied with the diaphragm 2 as a cathode, anodic bonding is completed in a few minutes.

At this point, all the flow paths of the inkjet head have been formed.In this state, an electrode is formed in the portion of the diaphragm that corresponds to the pressure chamber, and the electromechanical conversion element is adhered onto the electrode to form the inkjet. The head is completed.

The ink jet head created by such a method has good flowability of ink because the inner surface of the flow path is composed of a hydrophilic glass surface, and it is less likely to entrap air bubbles in the flow path, thus improving the accuracy of the flow path. Is maintained very well, so that good injection characteristics can be obtained.

In this example, borosilicate glass was used for the diaphragm and the substrate, and polycrystalline silicon or amorphous silicon was used for the corrosion resistant film, but there are various combinations of materials that can be used in the present invention, and the substrate is hydrophilic, Needless to say, the present invention is not limited to this embodiment as long as the anticorrosive film at the time of etching the substrate is a material that can be anodically bonded to the diaphragm material.

[Effects of the Invention] As described above, according to the present invention, while the groove processing of the substrate, which is a part of the manufacturing process of the inkjet head, and the bonding process are simplified, a precise and fine flow path is formed and the ink is formed. There is an effect that it is possible to provide a head with high reliability by realizing a head structure that does not hinder the flow of liquid.

[Brief description of drawings]

FIG. 1 is a sectional view showing a flow path manufacturing process of an ink jet head of the present invention, FIG. 2 is a sectional view showing an outline of an on-demand type ink jet head, and FIG. 3 is a flow path manufacturing process of a conventional ink jet head. It is sectional drawing shown. 1,1a, 1b …… Substrate 2 …… Vibration plate 5a, 5b …… Flow path 10a, 10b …… Corrosion resistant film

Claims (2)

[Claims] 1. An ink jet head comprising: a substrate having flow passage grooves; and a vibrating plate covering the substrate to form the flow passage grooves in a nozzle, an ink supply passage, and a pressure chamber.
An ink jet head, comprising an etching mask for forming the flow path groove on the substrate, and a thin film member capable of being anodically bonded to the diaphragm. 2. An ink jet head comprising: a substrate having a flow path groove formed therein; and a vibration plate covering the substrate to form the flow path groove in a nozzle, an ink supply path and a pressure chamber. An ink jet head characterized by being coated with a thin film member which is an etching mask for forming a flow path groove and which can be anodically bonded to the substrate.