JP4736174B2 - Method for forming nozzle hole of inkjet head - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ink jet head, more particularly to a nozzle hole forming method of the ink jet heads having a nozzle hole shape capable of preventing air from entering the ink chamber.
[0002]
[Prior art]
Methods for forming nozzle holes in the nozzle plate of an inkjet head include electroforming, punching, drilling, etching, and laser ablation. However, among these methods, the electroforming method can only be applied to a conductive substrate, the plating operation is difficult and costly, and the punching method causes distortion and burrs in the nozzle plate due to processing. It is necessary to remove the burrs, and it is particularly troublesome to remove the burrs inside the nozzle holes. The drilling method has few drills suitable for drilling with a diameter of 100 μm or less, and the etching method has a decrease in drilling accuracy due to side etching.
[0003]
Therefore, many studies have been made on ablation methods using excimer lasers suitable for drilling polymer materials. The excimer laser ablation method can form holes and grooves without thermal distortion and burrs with micron-order accuracy in a short time at normal temperature and pressure. Moreover, if excimer laser light is irradiated to a workpiece (workpiece) through a mask, the mask pattern can be transferred to form holes and grooves of any shape. The excimer laser oscillates as a pulse, and the polymer material can be removed by about 0.1 to 0.5 μm by one pulse, so that the depth of removal can be accurately controlled by the number of pulses. The inkjet head is considered to be very advantageous for processing such as precision drilling of nozzle holes and precision formation of ink flow paths.
[0004]
However, there is a drawback that it is difficult to form an angle (taper) even though it is advantageous for straight-line machining. The taper angle of the hole can be controlled to some extent by changing the irradiation energy of the excimer laser, but has a limit. In order to uniformly process the nozzle holes of the nozzle plate of the inkjet head with an excimer laser with high accuracy, it is necessary to drill with a high irradiation energy density, and the holes to be drilled are linear with almost no taper. It becomes.
[0005]
The conditions required for the nozzle holes of the ink jet head are that the fluctuation of the hole diameter is small and the taper angle is large. A nozzle hole with a small taper angle has a small nozzle volume, so that when the volume of ink droplets to be ejected is large, bubbles enter the ink chamber after ejection. The ink meniscus formed inside the nozzle hole easily moves in the direction of a smaller nozzle diameter according to Laplace's law. Therefore, a nozzle hole with a larger taper angle is easier to eject and less likely to inhale air.
[0006]
Therefore, perforation using an excimer laser has a drawback that it is not possible to increase the taper angle while it is possible to form uniform nozzle holes with high accuracy. The taper angle of the nozzle hole of the ink jet head needs to be 10 to 20 ° on one side. However, when excimer laser drills with high accuracy and uniformity, the angle can only be 4 to 8 °.
[0007]
Under these circumstances, various methods for increasing the taper angle of the nozzle hole in the case of drilling the nozzle hole of the inkjet head using an excimer laser have been proposed. For example, Japanese Patent Application Laid-Open Nos. 5-77425 and 9-66606 describe a method in which laser irradiation is performed a plurality of times using a plurality of masks to taper the nozzle holes step by step. In the method, since the taper angle is increased to widen the inlet of the nozzle hole, there is a problem that the adhesive used for assembling the head easily flows into the nozzle hole. In JP-A-5-318744, JP-A-10-337876, JP-A-11-240159, and Japanese Patent No. 29985682, a plurality of masks are overlapped and moved to each other, and excimer laser is irradiated to taper the nozzle holes. Although it has been proposed to apply or eliminate the level difference at the inlet of the nozzle hole, there is a problem that a precise and complicated device for moving the mask is required. In JP-A-6-91833, 8-111111, 8-72250, and 11-170541, a bottomed recess is formed by a mechanical means at the nozzle formation position of the nozzle plate, and its bottom surface. Although a method of drilling with an excimer laser is described, the concave portion must be formed by mechanical means prior to drilling, which is a troublesome operation. Further, in JP-A-11-10891, JP-B-6-24874, and JP-A-6-506069, the nozzle plate is adhered to the end of the ink channel, the mask is brought into close contact with the nozzle plate, and the head and the mask are swung. Although a method of drilling with an excimer laser from the ink discharge side is described, there is a problem that the laser irradiation is performed while the workpiece is swung, which is very inefficient.
[0008]
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for easily obtaining an ink jet head capable of preventing air bubbles from entering an ink flow path.
[0009]
[Means for Solving the Problems]
The above object of the present invention is to
1. In forming the nozzle hole connected to the ink channel through the small diameter portion from the ink ejection side, the convex portion on the periphery of the small diameter portion and the large diameter portion continuous to the convex portion,
A first processing step of forming the small-diameter portion by irradiating an excimer laser through a first mask having a laser transmitting portion corresponding to the small-diameter portion;
Irradiating the excimer laser through a second mask having a laser opaque portion corresponding to the periphery of the small diameter portion and an annular pattern laser transparent portion formed outside the laser opaque portion and corresponding to the large diameter portion. The second processing step of forming an annular groove having the large-diameter portion and the convex portion protruding from the inner surface of the nozzle hole toward the second mask inside the annular groove is performed. A nozzle hole forming method for an inkjet head,
2. In forming the nozzle hole connected to the ink channel through the small diameter portion from the ink ejection side, the convex portion on the periphery of the small diameter portion and the large diameter portion continuous to the convex portion,
A first processing step of forming a groove having the large-diameter portion by irradiating an excimer laser through a third mask having a laser transmitting portion corresponding to the large-diameter portion;
A fourth mask having a laser transmitting portion corresponding to the small diameter portion, a laser nontransmitting portion corresponding to the periphery of the small diameter portion outside the laser transmitting portion, and a laser transmitting portion having an annular pattern outside the laser nontransmitting portion. The small-diameter portion, the annular groove, and the protrusion protruding from the inner surface of the nozzle hole to the fourth mask side are formed inside the annular groove by irradiating the excimer laser through A nozzle hole forming method for an inkjet head, characterized by undergoing a second processing step;
Is achieved.
[0010]
That is, the present inventor performs laser irradiation a plurality of times using a plurality of masks, and the method of tapering the nozzle holes in a stepwise manner is to form a step that can be formed at the junction between the ink chamber (ink channel) and the nozzle plate. Focusing on the fact that bubbles can be prevented from accumulating and the discharge is stable because it can be made smaller, and even if a simple combination of a large diameter part and a small diameter part, it protrudes from the ink discharge side of the nozzle hole to the periphery of the small diameter part It was found that the adhesive used for head assembly can be prevented from flowing into the small-diameter portion of the nozzle hole if the portion is provided.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to embodiments, but the present invention is not limited thereto.
[0012]
FIG. 1 is a perspective view showing a configuration of a shear mode type ink jet head as an example. In the figure, 1 is a piezoelectric ceramic substrate, 2 is a nozzle plate, 3 is a nozzle, 4 is an ink channel, 5 is a side wall, 6 is a cover plate, 7 is an ink supply section (also referred to as a manifold), and 8 is an ink inlet. It is.
[0013]
The piezoelectric ceramic substrate 1 is cut by a diamond blade or the like, and a plurality of grooves (ink channels) 4 are all formed in parallel with the same shape, and the side wall 5 which is the side surface of the groove 4 is divided in the direction of the arrow. . The depth of the groove 4 gradually becomes shallower as it approaches the one end face 12 of the piezoelectric ceramic substrate, and the shallow groove 10 is formed in the vicinity of the end face 12. On the inner surface of the groove 4, metal electrodes 9 are formed on the upper half of both side surfaces by vapor deposition or the like. A metal electrode 11 is formed on the inner surface of the ink channel 4 or the shallow groove 10 by vapor deposition or the like on the side surface and the bottom surface thereof, and the metal electrode 9 and the metal electrode 11 communicate with each other.
[0014]
The cover plate 6 is formed of a ceramic material or a resin material, and the ink introduction port 8 and the manifold 7 are formed by grinding or cutting. Then, the surface of the piezoelectric ceramic substrate 1 where the groove 4 is processed and the surface of the cover plate 6 where the manifold 7 is processed are bonded using an epoxy adhesive or the like, and the upper surface of the groove 4 is covered with the cover plate 6. It becomes an ink flow path.
[0015]
A nozzle plate 2 provided with a nozzle 3 at a position corresponding to the position of each ink flow path 4 is bonded to the end surfaces of the piezoelectric ceramic substrate 1 and the cover plate 6. The nozzle plate is made of a plastic such as polyalkylene terephthalate such as PET, polyimide, polyetherimide, polyetherketone, polyethersulfone, polycarbonate, or cellulose acetate.
[0016]
In the mask used in the present invention, for example, a pattern is made of aluminum on a quartz substrate, a total reflection film in which two types of dielectric films are alternately laminated is formed thereon, and then aluminum is melted. Thus, a desired pattern is formed. As shown in the image diagram of FIG. 2, the formed mask is inserted into the optical path of the excimer laser, and reduced to 1/4, for example, to irradiate the work. In the present embodiment, a first mask having a hole pattern with a diameter of 160 (40 by reduction) that transmits excimer laser light, an outer ring with a diameter of 240 (60) μm, and an inner ring with a diameter of 200 (50). A second mask having a pattern that transmits a μm ring-shaped excimer laser beam is used.
[0017]
An aqueous dispersion of tetrafluoroethylene / hexafluoropropylene copolymer (FEP) is applied to one side of a 75 μm thick polyimide plate so that the dry film thickness is 0.2 μm, and heat-treated at 380 ° C. for 30 minutes. To form a water repellent film. A protective sheet is attached to the water repellent film, and an excimer laser using KrF gas is passed through the first mask M1 from the back side of the water repellent film (not shown) of the plate P as shown in FIG. The through hole 21 is drilled by irradiating 300 pulses typically at 200 Hz at a processing speed of 0.3 μm per pulse. The shape of the through hole is not limited to a perfect circle, and may be an ellipse or an ellipse.
[0018]
Subsequently, 80 pulses of laser irradiation are performed using the second mask M2 or the like to form grooves 22 in an annular shape having a depth of 20 to 25 μm. The connecting portion between the bottom of the groove 22 and the through hole 21 hits the peripheral edge of the light shielding pattern of the inner ring of the second mask M2, and the laser light is blocked, but is slightly processed by diffracted light or the like, and eventually rises by about 10 μm from the surroundings. The protrusion 23 is formed (FIG. 3B).
[0019]
The nozzle plate in which the nozzle holes are perforated is peeled off from the protective film and adhered to the piezoelectric substrate having the ink channels. Adhesion is performed by applying, for example, an epoxy-based adhesive on the channel end portion side of the piezoelectric substrate and arranging the nozzle hole at the center of the channel. At this time, even if the adhesive enters the nozzle plate side by heating or pressurization, the protrusion 23 serves as a bank to prevent the inflow of the adhesive and does not block the nozzle hole. The bubble size that does not dissolve in the ink is about 30 μm or more in diameter, and it is desirable that the height of the protrusion does not exceed 30 μm from the viewpoint of preventing bubbles from remaining.
[0020]
Another embodiment of the present invention will be described.
Similarly, a substrate plate P on which a water-repellent film is formed and a protective sheet is attached is passed through a third mask M3 having an excimer laser light transmitting portion having a diameter of 240 (60) μm, as shown in FIG. The same excimer laser light is irradiated with 80 pulses to provide a groove 24 having a depth of 25 μm. Subsequently, a hole pattern that transmits excimer laser light having a diameter of 160 (40) μm and an annular pattern that transmits excimer laser light having an inner diameter of 200 (50) μm and an outer diameter of 220 (55) μm around the hole pattern are provided. Through the fourth mask M4, 200 pulses of excimer laser light are irradiated to penetrate the nozzle hole 21 having a diameter of 40 μm. Since the annular pattern has a narrow transmission part and the excimer laser beam spreads by diffraction, an annular groove 25 is formed as a result, and the protrusion 26 formed by this groove 25 similarly prevents the adhesive from flowing into the nozzle hole. it can. In this way, the processing depth can be adjusted by the width of the excimer laser light transmitting portion. In this embodiment, when the irradiation is about 300 pulses with a width of 10 to 30 μm, a groove that does not penetrate can be formed.
[0021]
【The invention's effect】
According to the present invention, an ink jet head capable of preventing bubbles from entering the ink flow path can be easily obtained.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an example of an inkjet head.
FIG. 2 is an image diagram showing processing using an excimer laser.
FIG. 3 is a model sectional view showing nozzle processing according to the present invention.
FIG. 4 is a model sectional view showing another nozzle processing according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Piezoelectric ceramic substrate 2 Nozzle plate 3 Nozzle 4 Ink channel 5 Side wall 6 Cover plate 7 Ink supply part 8 Ink introduction port 9, 11 Metal electrode 21 Through-hole 23, 26 Protrusion part

Claims (2)

In forming the nozzle hole connected to the ink channel through the small diameter portion from the ink ejection side, the convex portion on the periphery of the small diameter portion and the large diameter portion continuous to the convex portion,
A first processing step of forming the small-diameter portion by irradiating an excimer laser through a first mask having a laser transmitting portion corresponding to the small-diameter portion;
Irradiating the excimer laser through a second mask having a laser opaque portion corresponding to the periphery of the small diameter portion and an annular pattern laser transparent portion formed outside the laser opaque portion and corresponding to the large diameter portion. The second processing step of forming an annular groove having the large-diameter portion and the convex portion protruding from the inner surface of the nozzle hole toward the second mask inside the annular groove is performed. A method for forming a nozzle hole in an inkjet head. In forming the nozzle hole connected to the ink channel through the small diameter portion from the ink ejection side, the convex portion on the periphery of the small diameter portion and the large diameter portion continuous to the convex portion,
A first processing step of forming a groove having the large-diameter portion by irradiating an excimer laser through a third mask having a laser transmitting portion corresponding to the large-diameter portion;
A fourth mask having a laser transmitting portion corresponding to the small diameter portion, a laser nontransmitting portion corresponding to the periphery of the small diameter portion outside the laser transmitting portion, and a laser transmitting portion having an annular pattern outside the laser nontransmitting portion. The small-diameter portion, the annular groove, and the protrusion protruding from the inner surface of the nozzle hole to the fourth mask side are formed inside the annular groove by irradiating the excimer laser through A method for forming a nozzle hole of an ink jet head, wherein the second processing step is performed .

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