JPS5840509B2 - inkjet gun - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inkjet gun used in a device that performs desired recording on recording paper or the like by ejecting ink from a nozzle, and particularly to the structure of its nozzle and pressurizing chamber.

2. Description of the Related Art As a non-impact recording device, a device that records characters such as letters on recording paper by ejecting minute ink droplets from an inkjet gun is already known.

An inkjet gun used in a conventional device of this type generates an array of ink droplets by ejecting ink pressurized by a pressure pump from a nozzle while applying ultrasonic vibrations.

Ink droplets continuously ejected from a nozzle are allowed to reach the recording paper as they are when recording is being performed, but when not recording, an electrostatic field is applied to deflect the ink droplets so that they do not reach the recording paper.

In such devices, of the ink ejected from the nozzles, the amount of ink that is not involved in recording is 3 to 10 times the amount of ink that is involved in recording, so ink that is not involved in recording must be collected and recycled. I'm trying to use it.

However, if the ink is collected and reused, the ink may be exposed to air and deteriorate in quality, or dust may be mixed into the ink, making the nozzle easily clogged, making it difficult to improve the reliability of the device.

Recently, a pressure pulse control type inkjet gun has been proposed as an inkjet gun that overcomes these drawbacks.

This inkjet gun has a nozzle, an ink pressurizing chamber that communicates with the nozzle, and an electrostrictive vibrator attached to the outside of the wall of the ink pressurizing chamber, and a pulse voltage is applied to the electrostrictive vibrator. Then, the wall of the ink pressurizing chamber in that area deforms and the ink inside is pressurized in an impulse-like manner, and the traveling pressure wave generated in the ink at this time causes ink droplets to be ejected from the nozzle. ing.

Therefore, this type of inkjet gun can eject ink only during recording by controlling the pulse voltage applied to the electrostrictive vibrator. Since ink can be sucked into the pressurizing chamber from the ink reservoir during the process of recovery from the deformation of the wall of the pressurizing chamber, there is no need for an ink pressurizing pump, and there is an advantage that the apparatus can be made smaller.

Furthermore, the shape of the nozzle of the inkjet gun must be determined appropriately (this allows the ink droplets to fly in a fixed direction, so if a large number of such nozzles are arranged, the ink droplets can be deflected by an electrostatic field, etc.). It is also possible to perform the necessary recording without having to do so.

The pressure pulse control type inkjet gun has various advantages as described above, but according to research by the present inventors, it is necessary to finish the nozzle shape with extremely high precision for the following reasons. It became clear that this was not the case.

(1) In general, the pressure traveling waves in the ink inside the tube are easily affected by the stickiness of the ink on the tube wall, and when a vortex is generated on the tube wall, separation of the sticky flow occurs, and the flow of ink inside the tube is The direction of ink flight is not constant because the ink meanders.

Therefore, the inner wall surface of the nozzle is required to be extremely smooth.

(2) The flow of ink that adheres to the tube wall becomes unstable under a specific condition I determined by the relationship between the traveling speed of the pressure traveling wave and the cross-sectional area of the flow path of the nozzle.

In particular, when the cross-sectional area of the flow path is not constant with respect to the direction in which the ink flows, a flow tends to occur along a part of the inner wall of the nozzle, and the direction of flight of the ink is also not constant.

For this reason, the nozzle must be formed so that the cross-sectional area of the flow path is constant and is in a straight line.

(3) Since the ink droplets ejected from the nozzle tip are ejected against the surface tension of the ink at the nozzle tip,
The size of the ink droplet largely depends on the cross-sectional area of the nozzle tip.

Therefore, in order to equalize the area of each point recorded by ink droplets within a predetermined range, the deviation in the cross-sectional area of the tip of each nozzle must be made as small as possible.

(4) The pressure traveling wave generated in the ink in the pressurizing chamber by driving the electrostrictive vibrator propagates to both the nozzle side and the ink supply side, so the fluid impedance from the pressurizing chamber to the nozzle tip and the pressurizing chamber The size of the ink droplet ejected from the nozzle also depends on the ratio of the fluid impedance from the ink to the ink reservoir.

Therefore, in order to reduce the deviation in the size of ink droplets ejected from each nozzle, it is necessary to make the fluid impedance of each nozzle constant, that is, to make the cross-sectional area and length of the nozzle constant. .

An object of the present invention is to solve the above-mentioned problems and provide an inkjet gun in which the inner wall surface of the nozzle is highly smooth, has high linearity, has a constant cross-sectional area in the longitudinal direction, and is easy to manufacture. be.

To achieve this objective, the present invention proposes that the surface is (100)
On the surface of the substrate made of a single crystal which is a plane, there is a ■-shaped groove for a nozzle, the two side walls of which are made of (111) planes parallel to the ink ejection direction, and one end of which is opened as an ink ejection port on the side surface of the substrate; The side wall is tilted towards the center of the groove bottom (
111) forming a pressurizing chamber groove by etching, which is made of a surface, has a groove opening width wider than the groove opening width of the ■-shaped groove for the nozzle, and has a groove depth deeper than the groove depth of the ■-shaped groove for the nozzle; The present invention is characterized in that a cover plate is attached to the surface of the substrate so as to cover the groove openings of the square-shaped groove for the nozzle and the groove for the pressurizing chamber, thereby forming the nozzle and the pressurizing chamber.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an inkjet gun according to an embodiment of the present invention.

1 is a substrate, 2 is a cover plate, and 3 is an electrostrictive vibrator.

A substrate 1 (in which a groove of a predetermined shape is formed, and by covering this with a cover plate 2, an ink reservoir 4, a throttle passage 5,
A pressurizing chamber 6 and a nozzle 7 are formed.

An electrostrictive vibrator 3 is installed on the surface of the portion of the cover plate 2 corresponding to each pressurizing chamber 6, and each electrostrictive vibrator 3 and the cover plate 2 are connected to a common electrode 8 made of a conductive film. are connected via.

Individual electrodes 9 are fixed to the surface of each electrostrictive vibrator 3, respectively.

Further, a pipe for introducing ink into the ink reservoir 4 is attached to a portion of the cover plate 2 corresponding to the ink reservoir 4.

Ink supplied to the ink reservoir 4 through the pipe 10 enters the pressurizing chamber 6 through the throttle passage 5 and fills the inside thereof.

On the other hand, the common electrode 8 is held at a constant potential, and a selective pulse voltage is applied to the individual electrodes 9 in response to a recording command.

Then, the electrostrictive vibrator 3 corresponding to the individual electrode 9 to which the pulse voltage was applied is deformed, and this deformation is transmitted to the lid plate 2 in that part, applying impulse-like pressure to the ink in the corresponding pressurizing chamber 6. Add.

As a result, a pressure traveling wave is generated in the ink in the pressurizing chamber 6, and one of the pressure traveling waves is weakened by the impedance of the throttle passage 5 and reaches the ink reservoir 4, while the other one passes through the nozzle 7 and reaches the ink reservoir 4. It works by ejecting ink from the tip.

The inkjet gun is as described above,
In this embodiment, the substrate 1 is made of single crystal silicon.

This silicon single crystal is selected so that the X and Y axes in the figure are <110> axes that are orthogonal to each other, and
The axial planes (upper and lower surfaces) are selected to be the (100) plane of the single crystal.

In this way, the (111) plane of the single crystal is parallel to the Y axis and intersects the XY axis at an angle of about 54°.

A V-shaped groove for the nozzle 7 formed in the substrate 1 and a pressurizing chamber 6
The two sides of the trapezoidal groove used for this purpose are each crossed by (111) planes.

The etching speed of the (111) plane with an alkaline solution such as I-IJ hydroxide, potassium hydroxide, or hydrazine is extremely slow compared to other crystal planes, and when the (100) plane is etched with an alkaline solution, the (111 ) It is possible to obtain a ■-shaped groove regulated by the surface.

The width of the upper end of this V-shaped groove is determined by the gap between the photoresists during photoetching, and is extremely accurate.

Further, since the depth of the V-shaped groove is determined by the angle (approximately 54°) formed by the (100) plane and the (111) plane and the width of the upper end, this is also extremely accurate.

Furthermore, the (111) plane revealed by etching is extremely smooth and has high linearity.

Furthermore, in order to make the length of each nozzle 7 the same, it is sufficient to cut the X-2 plane of the nozzle tip using a dicing device used for cutting ordinary semiconductor devices. Since the predetermined portion can be cut with an accuracy of approximately ±0.03 mm, the deviation in the length of the nozzle 7 can also be extremely small.

As described above, in this embodiment, the V-shaped groove for the nozzle 7 formed in the substrate 1 is intercepted by the two (111) planes exposed by etching, so the nozzle accuracy is higher than that of the normal cutting process. Alternatively, the desired purpose can be achieved with a dramatic improvement over those formed by etching or the like without dependence on crystal orientation.

In addition, the intake reservoir 4 and the throttle passage 5 formed on the substrate 1 &
The grooves for the nozzle 7 and the pressurizing chamber 6 can also be formed by etching at the same time.

Further, in order to ensure the accuracy of the nozzle 7, it is preferable that the substrate 1 and the cover plate 2 be integrated by anodic bonding (electrostatic bonding) without using an adhesive.

In that case, it is preferable to use borosilicate glass, which can be anodically bonded to silicon, as the cover plate 2.

Further, in the above embodiment, an arrangement in which four nozzles are arranged has been described, but this number can be arbitrarily selected, and of course, it may be one nozzle.

Further, although the nozzles, pressurizing chambers, etc. are formed only on one side of the substrate, they can also be formed on both sides of the substrate, and by doing so, it becomes possible to increase the density of the nozzles.

Further, when a nozzle, a pressurizing chamber, etc. are formed only on one side of the substrate, the electrostrictive vibrator can be attached to the back side of the substrate instead of the cover plate.

In this case, if one electrode of the electrostrictive vibrator is gold,
The electrostrictive vibrator is heated to approximately 400℃ using gold-silicon eutectic solder.
It has the advantage that it can be bonded to a substrate at a relatively low temperature, and since the silicon 71 body is a conductor, there is no need to provide a common electrode.

Next, a method of forming a V-shaped groove for the nozzle 7 and a trapezoidal groove for the pressurizing chamber 6 in the substrate 1 will be explained with reference to FIG.

First, a substrate 1 made of silicon single crystal with the crystal orientation as described above is prepared.

In this figure, the direction perpendicular to the plane of the paper is the <110> axis, and the top and bottom surfaces of this substrate are the (ioo) planes.

This substrate 1 is placed in a steam atmosphere at, for example, about 800 to 1200° C., and a thermal oxide film 11 is formed on the surface (state A).

It is sufficient that the thickness of the thermal oxide film 11 is approximately 0.3% of the etching depth.

Next, a photoresist is applied to the entire upper surface of the thermal oxide film 11 by a well-known method, exposed through a photographic plate, and developed to obtain a photoresist pattern 12.

(State B). Next, the thermal oxide film 11 exposed between the photoresist patterns 12 is removed using a hydrofluoric acid aqueous solution or the like to obtain exposed silicon portions 1a and 1d, and then the photoresist 12 is removed (state C).

The substrate 1 in such a state is, for example, 5 to 40%, 8
Etch in potassium hydroxide solution at 0°C.

As a result, the etching of the exposed portions 1a and Id progresses, but the etching progress speed of the (111) plane increases (100
) surface (7)(-t'L(7)) Since the surface (-t'L(7)) is about 0.3 to 0.4%, the upper surface of the substrate 1 (which is 100) plane) which makes an angle of tan −' V/T (approximately 54°)
111) surfaces appear, and eventually grooves 1b, 1e'l! are formed by etching. ') The shape becomes trapezoidal (state D).

As the etching progresses further, the narrower groove 1b becomes a V-shaped groove 1c regulated by two (1'll) planes.
Therefore, the wider groove 1e becomes a trapezoidal groove 1f (or V-shaped groove) deeper than the ■-shaped groove 1c (state E).

Considering the accuracy of this V-shaped groove 1c, firstly, the so-called undercut on the lower side of the end of the thermal oxide film 11 is extremely small, and when high-purity potassium hydroxide is used, the etching depth of the (100) plane The diameter is only about 0.2φ.

Therefore, the width W of the ■-shaped groove 1c can be made accurate to about ±5 μm even if the error of the photomask dry plate is taken into consideration.

Further, the angle formed by the bottom of the ■-shaped groove 1c is determined by the angle (approximately 72°) formed by the (111) planes.

The depth d of the ■-shaped groove 1c is 1/JVw.

As described above, the precision of the ■-shaped groove 1c is extremely high, and it is extremely preferable as a groove for a nozzle formed on the substrate of an inkjet gun.

Furthermore, the V-shaped groove for the nozzle 7, which is narrow and shallow, and the trapezoidal groove for the pressurizing chamber 6, which is wide and deep, that is, has a large volume, can be formed at the same time by etching. It is also easy to manufacture.

Note that the trapezoidal groove 1f is suitable not only for the pressurizing chamber but also as a groove for a throttle passage and an ink reservoir.

In the above embodiment, a silicon single crystal is used as the substrate, but other materials such as germanium single crystal having the same crystal structure as silicon single crystal may also be used as the substrate material.

As explained above, according to the present invention, a groove for a nozzle is formed on the surface of a single crystal substrate having a (100) surface, and two side walls are formed in a (111) plane parallel to the ink jetting direction.
Since the nozzle is formed as a V-shaped groove with one end opening as an ink ejection port on the side surface of the substrate, a highly accurate nozzle with high linearity and smoothness and a uniform cross-sectional area in the longitudinal direction can be obtained.

Therefore, the size and flight direction of the ink droplets ejected from the nozzle become uniform, making it possible to perform accurate recording.

In addition, the V-shaped groove for the narrow and shallow nozzle and the trapezoidal groove (or V-shaped groove) for the wide and deep pressure chamber can be formed at the same time by etching. It becomes easier.

Furthermore, since the groove for the pressurization chamber is wide and deep, the volume of the pressurization chamber can be increased, and therefore the volume change of the pressurization chamber can be made large to increase the flow velocity at the nozzle. It becomes possible.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view showing an inkjet gun according to a first embodiment of the present invention, and FIGS. 2A to 2E are sectional views showing each step of the manufacturing process of the inkjet gun according to the present invention. 1...Substrate, 2...Lid plate, 3...
...Electrostrictive vibrator, 4...Ink reservoir, 5...
... Throttle passage, 6... Pressure chamber, 7...
·nozzle.

Claims (1)

[Claims] 1 In an inkjet gun equipped with a nozzle for ejecting ink, a pressurizing chamber communicating with this nozzle, and an electrostrictive vibrator placed outside the pressurizing chamber, the surface is (1
On the surface of a single crystal substrate having a 00) plane, a ■-shaped groove for a nozzle having two side walls formed of a (111) plane parallel to the ink ejection direction and one end opening as an ink ejection port on the side surface of the substrate; The two side walls are composed of (111) planes inclined toward the center of the groove bottom, and the groove opening width is wider than the groove opening width of the ■-shaped groove for the nozzle, and the groove depth is greater than the groove depth of the ■-shaped groove for the nozzle. A deep pressurizing chamber groove is formed by etching, and a nozzle and a pressurizing chamber are formed on the surface of the substrate by covering the groove openings of the nozzle square groove and the pressurizing chamber groove. , an inkjet gun characterized by having a lid plate attached.