JPH05338168A - Ink jet recording head - Google Patents

Abstract

PURPOSE:To provide an ink jet recording head having a structure wherein an air bubble is easy to vent from an ink reservoir part. CONSTITUTION:An ink jet recording head is constituted by bonding a heater substrate 1 having a thick resin layer 3 and a channel substrate 3. The ink reservoir part 5 formed to the channel substrate 1 has a paralleloprogrammatic cross-sectional shape. Therefore, the air bubble 11 mixed with the ink in the ink reservoir part 5 rises by buoyancy to be discharged into an ink sub-tank 12. The air bubble discharged into the ink sub-tank 12 exercises no effect on the supply and emitting capacity of ink and stable printing becomes possible.

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 more particularly to an ink jet recording head in consideration of the structure of an ink reservoir section.

[0002]

2. Description of the Related Art Conventionally, as a structure of an ink jet recording head, for example, as described in JP-A-1-148560 and JP-A-2-1114696,
There is known a so-called thermal inkjet head that heats a heating resistor and ejects ink by using a pressure at which the ink vaporizes.

FIG. 6 is a perspective view showing the outline of a conventional thermal ink jet head. In the figure, 1 is a heater substrate, 2 is a channel substrate, 3 is a thick film resin layer, 4 is a nozzle,
Reference numeral 5 is an ink reservoir section. Although four nozzles 4 are shown in the figure, in reality, there are many nozzles, for example, 8 nozzles.
256 pieces are provided at a pitch of 4.7 μm.

FIG. 7 is a cross-sectional view taken along the plane indicated by the dotted line in FIG. In the figure, parts corresponding to those in FIG. 6 is a heating resistor, 7 is a pit (recess), 8 is a connecting groove, 9 is an unetched portion, 10
Is an ink drop.

On the heater substrate 1, a heating resistor 6 and a current-carrying electrode (not shown) for the heating resistor 6 and a protective layer are formed, and a thick resin layer 3 is formed thereon. Pits 7 and connection grooves 8 are patterned on the thick resin layer. As will be described later, the connecting groove 8 is formed at a position facing the unetched portion 9 of the channel substrate 2 and constitutes a flow path connecting the channel groove and the ink reservoir portion.

Instead of providing the connecting groove 8, the unetched portion 9 is cut with a dicing saw to connect the channel groove and the ink reservoir portion.

As the channel substrate 2, a silicon substrate is used,
The channel groove 4 and the ink reservoir portion of the through hole through which the ink flows are formed by the anisotropic etching method. In the anisotropic etching method, since the (111) plane exists at an angle of 54.7 ° on the (100) plane silicon substrate, the etching rate difference between the (100) plane and the (111) plane is used. Etching is performed in the depth direction. By anisotropic etching, V-shaped grooves and through holes are formed depending on the opening size of the mask. The reason is due to the above-mentioned difference in etching rate. In FIG. 10, assuming that the opening width of the etching mask is W and the side etching width is neglected, the depth T of the apex of the V-shaped groove is T = (W / 2) tan 54.7 ° due to the above-described etching rate difference. Become. If this T is smaller than the wafer thickness, a V-shaped groove is formed, and if it is larger, a through hole is formed.

The channel substrate 2 shown in FIG.
The groove and the ink reservoir are formed in the through hole.
The channel substrate 2 is attached to the heater substrate 1 and cut into individual heads to manufacture a thermal inkjet head.

As a method of forming the ink reservoir portion,
When anisotropic etching is performed from both sides of the silicon substrate, the ink reservoir portion is formed in a trapezoidal shape as shown in FIG. Note that, in FIG. 8, portions corresponding to those in FIG.

The ink supplied to the ink reservoir 5 is supplied to the nozzle 4 through the connecting groove 8 as shown by the arrows in FIGS. 7 and 8 and is generated in the pit 7 by heating the heating resistor 6. 10 drops of ink due to bubble pressure
Is discharged.

However, in the conventional structure, when the ink ejection direction is downward, as shown in FIG. 9, when air bubbles are mixed in the ink, the ink flows on the ink supply side to the nozzle. Since the bubbles are not discharged to the outside of the ink reservoir even if they are good in the initial stage, they are accumulated in the upper corner portion of the ink reservoir unit 5 in the vertical direction, and the accumulated bubbles 11 change the ejection characteristics, which deteriorates the print quality. There was a problem to do. Further, when the bubble 11 grows and becomes large, the ink supply port may be blocked, and as a result, ink may not be ejected. Although these bubbles are recovered to some extent by sucking them from the nozzle surface, it is difficult to completely remove them.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an ink jet recording head having a structure in which bubbles easily escape from an ink reservoir portion.

[0013]

According to the present invention, a first silicon substrate having a heating resistor is bonded to a second silicon substrate having a channel portion and an ink reservoir portion formed by anisotropic etching. In the ink jet recording head according to the first aspect of the invention, the second
The ink reservoir portion of the substrate is a through hole for allowing the ink to flow in from the outside, and the shape thereof is a parallelogram. In the invention according to claim 2, The ink reservoir portion of the substrate is a through hole for allowing the ink to flow in from the outside, and its shape is a trapezoid with a widened ink inlet side.

[0014]

According to the present invention, the shape of the ink reservoir portion manufactured by using the anisotropic etching method of silicon is set to be a parallelogram or a trapezoid with a widened ink inlet side, so that the head direction and the combination can be improved. By combining the bubbles, the bubbles mixed inside are discharged to the outside of the ink reservoir portion by the buoyancy, and the ink supply property to the nozzle portion can be stabilized.

[0015]

1 is a sectional view of a first embodiment of an ink jet recording head of the present invention. In the figure, 1 is a heater substrate, 2 is a channel substrate, 3 is a thick film resin layer, 4 is a nozzle,
Reference numeral 5 is an ink reservoir portion, 6 is a heating resistor, 7 is a pit (recess), 8 is a connecting groove, 9 is an unetched portion, 10 is an ink drop, 11 is a bubble, 12 is a sub ink tank, 13 is a recording medium. is there.

The ink is a large-capacity sub-ink tank 12 mounted outside the ink jet recording head.
As a result, the ink is supplied to the ink reservoir portion 5 and is supplied to the nozzle 4 through the connecting groove 8 as shown by an arrow, and the ink droplet 10 is ejected by the pressure of the bubble generated in the pit 7 by heating the heating resistor 6. Printing is performed on the recording medium 13.

As can be seen, the ink reservoir portion 5
The bubbles 11 mixed inside rise up due to buoyancy and are discharged into the sub ink tank 12. The bubbles discharged into the sub ink tank 12 do not have any influence on the ink supply and ejection performance. Therefore,
The ink supply to the nozzle due to air bubbles did not go wrong, and very stable printing became possible.

As described above, by setting the printing direction downward, the effect is great and air bubbles are easily discharged from the ink reservoir.

FIG. 2 is a schematic view showing a method of manufacturing a channel substrate in the first embodiment of the present invention. In the figure, 2 is a channel substrate, 5 is an ink reservoir portion, 14 is a thermal oxide film, 15 is a Si ₃ N ₄ film, 16 is a channel opening portion, 1
Reference numerals 7 and 18 denote ink reservoir openings. First, an etching mask is manufactured. As shown in FIG. 2A, (1
The thermal oxide film 14 is formed as a second etching mask on the silicon wafer having 00) on the surface. After the photolithography process and the etching process, patterning is performed so as to remove the ink reservoir openings 17 and 18 and the channel part 16.

The pattern at this time is on both sides of the substrate,
The pattern of the ink reservoir openings 18 on the back surface (upper side in the figure) needs to be aligned with the pattern on the front surface. As a means therefor, there are a method of performing alignment using infrared rays that pass through silicon, a method of using a substrate in which a through hole has been previously opened by etching, and performing alignment of patterns on the front and back sides based on the through hole ..

Next, Si is used as a first etching mask.
₃ N ₄ film 15 is deposited on the surface of the ink reservoir opening 1
7 is patterned. The back surface is entirely covered with the Si ₃ N ₄ film 15.

The channel substrate 2 manufactured as described above is
The first etching is performed using the heated KOH aqueous solution with the first etching mask. As a result,
As shown in (B), the ink reservoir portion 5 surrounded by the {111} plane is formed. This etching process is etching from one side, and the etched {111}
Since the etching rate in the crystal plane direction of the plane is very slow, the precision of the etched portion is good and the cross section becomes trapezoidal. Further, the {111} plane formed by etching has an angle of 54.7 ° with respect to the crystal orientation (100) plane of the wafer surface.

After completion of the first etching, the Si ₃ N ₄ film 15 used as the first etching mask is entirely stripped with heated phosphoric acid. This state is shown in FIG. Next, using the thermal oxide film 12 as a second etching mask,
Etch twice. Here, the ink reservoir opening 18 and the channel opening 16 on the back surface are simultaneously etched. By etching from the back surface, the portion shown by cross-hatching in FIG. 2D is etched, and the sectional shape of the completed ink reservoir portion becomes a parallelogram.

This is the ink reservoir opening 17 on the surface.
And the pattern of the ink reservoir opening 18 on the back surface can be realized by accurately providing a positional difference by a distance corresponding to an angle of 54.7 °. That is, assuming that the thickness of the silicon wafer is T, the position of the opening pattern corresponding to the ink reservoir portion on the front surface and the back surface is (W / 2) = T / tan 54.7, as is apparent from the description in FIG. The cross-sectional shape of the ink reservoir portion can be made to be a parallelogram by shifting by only °.

After completion of the second etching, the remaining thermal oxide film 14 is entirely removed by using hydrofluoric acid. This state is shown in FIG.

FIG. 3 is a schematic view showing another manufacturing method of the channel substrate in the first embodiment of the present invention. In the figure,
2 is a channel substrate, 5 is an ink reservoir, and 15 is Si
₃ N ₄ film, 16 are channel openings, and 17 and 18 are ink reservoir openings. In this method, a silicon wafer is provided with a channel opening 16 and an ink reservoir opening 1.
Using the etching mask in which 7 and 18 are patterned in advance, etching is performed from the front and back sides simultaneously from the beginning. That is, as shown in FIG.
The i ₃ N ₄ film 15 is deposited and then patterned. The patterns of the ink reservoir openings 17 and 18 on the front and back sides need to be aligned on the front and back sides in the same manner as described with reference to FIGS. 2 and 10.

The silicon wafer manufactured as described above is
Etching is performed using a heated KOH aqueous solution. As shown by cross-hatching in FIG. 3B, etching progresses from both surfaces of the ink reservoir openings 17 and 18 on the front and back, penetrates at the center, and then progresses until surrounded by the crystal plane of {111} plane. ..

After the etching is completed, the entire surface of the Si ₃ N ₄ film 15 used as the etching mask is stripped with heated phosphoric acid. Even in the case of being manufactured by this method, the ink reservoir portion 5 is finally formed in the same manner as that described in FIG.
The cross-sectional shape of the parallelogram as shown in (C) is completed.

FIG. 4 is a sectional view of a second embodiment of the ink jet recording head of the present invention. In the figure, parts corresponding to those in FIG. In this embodiment, the ink reservoir 5 has a trapezoidal cross section, but is characterized in that the ink inlet side is widened. As is clear from FIG. 4, the ink jet recording head of this embodiment has a structure in which the bubbles 11 are easily discharged from the ink reservoir portion 5 to the sub ink tank 12 when the ejection direction of the ink is horizontal. Of course, even when the ink ejection direction is downward, the same effect can be obtained, and ink ejection failure due to insufficient ink supply does not occur.

FIG. 5 is a schematic view showing a method of manufacturing a channel substrate in the second embodiment of the present invention. Figure 3
The parts corresponding to are given the same reference numerals and the description thereof will be omitted.
The manufacturing method and procedure are almost the same as the method described in FIG. 3, but the ink reservoir portion is etched only from the back surface of the substrate.

That is, as shown in FIG.
The i ₃ N ₄ film 15 is used to form a channel opening 16 from the front surface and an ink reservoir opening 18 from the back surface as mask patterns. As a method for aligning the ink reservoir opening 18, the patterning is accurately performed at a position in consideration of the thickness of the substrate, as in the above-described manufacturing method. Figure 5
(B) shows a cross-sectional shape after etching. Further, FIG. 5C shows a state in which the etching mask is removed. In this way, by etching the ink reservoir portion from the back surface, it is possible to form a broad trapezoidal shape on the ink inlet side.

[0032]

As is apparent from the above description, the ink jet recording head of the present invention can discharge bubbles generated at the time of initial filling of the ink or inside the ink to the outside of the ink reservoir portion, and stable printing is possible. There is an effect that there is.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a first embodiment of an inkjet recording head of the present invention.

FIG. 2 is a schematic view showing a method of manufacturing a channel substrate in the first embodiment of the present invention.

FIG. 3 is a schematic view showing another manufacturing method of the channel substrate in the first embodiment of the present invention.

FIG. 4 is a cross-sectional view of a second embodiment of the inkjet recording head of the present invention.

FIG. 5 is a schematic view showing a method of manufacturing a channel substrate in the second embodiment of the present invention.

FIG. 6 is a perspective view showing an outline of a conventional inkjet recording head.

[Figure 7]

FIG. 8 is a cross-sectional view of a conventional inkjet recording head.

FIG. 9 is an explanatory diagram of a usage state of a conventional inkjet recording head.

FIG. 10 is an explanatory diagram of an anisotropic etching method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 heater substrate, 2 channel substrate, 3 thick film resin layer, 4 nozzles, 5 ink reservoir part, 6 heating resistor, 7 pit, 8 connecting groove, 9 unetched part, 1
0 ink drops, 11 bubbles, 12 sub ink tanks,
13 recording medium, 14 thermal oxide film, 15 Si ₃ N
₄ membranes, 16 channel openings, 17, 18 ink reservoir openings.

Claims (2)

[Claims] 1. An ink jet recording head comprising a first silicon substrate having a heating resistor and a second silicon substrate having a channel portion and an ink reservoir portion formed by anisotropic etching, which are bonded to each other. The ink reservoir portion of the substrate is a through hole for allowing ink to flow in from the outside, and the shape thereof is a parallelogram. 2. An ink jet recording head comprising a first silicon substrate having a heating resistor and a second silicon substrate having a channel portion and an ink reservoir portion formed by anisotropic etching, which are bonded to each other. The ink jet recording head is characterized in that the ink reservoir portion of the substrate is a through hole for inflowing ink from the outside, and its shape is a trapezoid with a widened ink inflow side.