JPH0623985A - Ink jet head and its manufacture - Google Patents

Abstract

PURPOSE:To reconcile a highly precise nozzle formation of a high yield having ensured stability for discharge of ink which is worked with ultraviolet light from a pressure chamber side and ink flying normal to a medium to be printed in parallel with a reference face of a passage substrate. CONSTITUTION:1 is a nozzle, 2 is a pressure chamber, 3 is a nozzle forming part, and 4 is a passage substrate which forms the pressure chamber. 4A is a reference face of the passage substrate 4, which is a reference for assembling other parts and an upper face of the pressure chamber 2 also. The nozzle 1 is formed aslant the reference face 4A side by irradiating the nozzle forming member 3 with ultraviolet light from the pressure chamber 2 side. Then, a shape of the spearhead of the nozzle 1 is formed so that a peripheral length on the reference face 4A side becomes larger than that for an anti-reference face.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet head for ejecting ink droplets for recording on a recording medium and a method for manufacturing the ink jet head.

[0002]

2. Description of the Related Art Recently, due to the demand for higher performance and lower cost of ink jet heads, the nozzles that determine the characteristics of the ink jet heads are formed with high precision and high yield of ultraviolet light (for example, excimer laser). (Light) processing methods are being used. Among them, as disclosed in Japanese Patent Laid-Open No. 2-187346, a shape in which the cross-sectional area of the nozzle is reduced in the ink ejection direction in order to irradiate the excimer laser light from the pressure chamber side and stabilize the ink ejection. The method of forming the same is widely used.

[0003]

However, the above method has the following problems (see FIG. 16). Ultraviolet light 11 (eg excimer laser light, dotted arrow)
To irradiate the light from the pressure chamber 2 side, a member (not shown) behind the pressure chamber 2 of the flow channel substrate 4 forming the pressure chamber 2 (on the right side in the drawing) or the flow channel substrate 4 is formed. Side walls (not shown) between the pressure chambers 2 and the pressure chambers 2 as shown in FIG.
There is no choice but to inject with a certain inclination with respect to the reference surface 4A of the flow path substrate 4, which is the upper surface. In FIG. 16, 1 is a nozzle, 2 is a pressure chamber, 3 is a nozzle forming member, 4 is a flow path substrate that forms the pressure chamber, and 5 is the front face of the nozzle.

In this structure, the reference surface 4 of the flow path substrate 4 is
Since the nozzle 1 is arranged so as to be inclined with respect to A, the ejected ink droplets are directed to the reference surface 4A by the solid arrow 12 in FIG.
It flies diagonally (in the direction of ink droplet ejection). Normal,
As shown in FIG. 17, the reference surface 4A is arranged perpendicular to the print media 21, 22 (the reason will be described later), so that the ejected ink droplets land obliquely on the print media. If the platen gap (distance between the nozzle front surface 5 and the print media 21, 22) does not change and the discharge ink drops are strictly constant, the print directions 13, 14 are reversed (reciprocal print compatible). However, by controlling the print timing, there is no problem regarding the print position accuracy. But,
It is difficult to ensure that the platen gap is strictly constant and invariable due to the accumulation of the precision of multiple parts that determine the platen gap and the variation in the thickness of the print medium (for example, paper). Is. Therefore, as shown in FIG. 17, by changing the platen gap (the print medium position is changed in the figure), the extension line (two-dot chain line in the figure) of the ink droplet ejection direction 12 and the print medium 2 are changed.
D1 is set at the landing position of the ejected ink drop indicated by the intersection with Nos. 1 and 22.
Misalignment (along print directions 13, 14) occurs.
This misalignment causes two print quality deteriorations. One is the variation in dot position accuracy when the platen gap changes at each printing location, and the other is the variation in the printing area between individuals when the average platen gap varies among individuals. appear.

Here, the reference surface 4A is the print medium 21,2.
The reason why they are arranged perpendicular to 2 will be described (see FIG. 17). Normally, in manufacturing all parts, or molds and tools for making the parts, it is much more difficult to manufacture them with a certain inclination than those having parallel or right angles. . Of course, assembling while ensuring the inclination also raises the manufacturing difficulty significantly, which leads to an increase in manufacturing cost and deterioration of angular accuracy. In order to avoid this, the components and the inter-component configuration are formed in a combination of right angles and parallels with respect to the reference surface (here, the reference surface 4A of the flow path substrate 4). For example, the upper surface (upper side in the drawing) of the canopy 6 having the pressure chamber 2 of the flow path substrate 4 as a closed groove is set to be parallel to the reference surface 4A. As described above, the respective components are connected not only inside the inkjet head but also as a system as a whole at a right angle and a parallel angle. Finally, the reference surface 4A of the flow path substrate 4 is connected to the print media 21, 22. Will be arranged perpendicular to. The condition of the configuration between the components is not indispensable, but it is the most important requirement for constructing a highly reliable inkjet head at the lowest cost (due to reduction in manufacturing difficulty, improvement in yield, etc.).

Next, a case where the above-mentioned conventional example (nozzle formation by irradiation of ultraviolet light from the pressure chamber 2 side) is applied to a double-sided channel forming substrate will be described.

Recent ink jet heads have high density,
There is a demand for higher speeds, and in order to meet this demand, increasing the number of nozzles is a very effective means. Among them, as shown in FIG. 18, a plurality of pressure chambers 2 are formed on both surfaces of the flow path substrate 4B (the pressure chambers 2 on the back surface are not shown in the figure), and the number of nozzles communicating with the pressure chambers 2 is increased. Is generally doubled. However, in order to achieve both high nozzle count and high precision and high yield nozzle formation, the double-sided flow channel forming substrate is used for the multi-nozzle method, and ultraviolet light (for example, excimer laser light) is irradiated from the pressure chamber 2 side. If the methods for forming a nozzle according to the above are combined, the problem shown in FIG. 19 occurs.

In FIG. 19, the reference planes 4A are parallel to each other and are arranged perpendicular to the printing directions 13 and 14 and the print media 21 and 22. The relationship between each nozzle 1 and the reference surface 4A and the oblique ink flight are shown in FIG.
The same as in the case of one side of
As indicated by the ink droplet ejection direction 12 in FIG. 9, the ink droplet flies in a direction in which the distance is narrowed. As a result, when the platen gap fluctuates, a dot position deviation of (D3-D2) occurs, and this deviation cannot be coped with by the control of the print timing unless the fluctuation of the platen gap is clearly expected.

Further, even if the platen gap is not changed and is strictly constant, in the above configuration, when the vertical relationship between the reference surface 4A and the print media 21, 22 is slightly broken, both ejected ink droplets land. The position and its distance fluctuate, leading to deterioration of print quality.

Therefore, the present invention is intended to solve such a problem, and its object is to form a high-precision, high-yield nozzle in which ink ejection stability is secured and ink flight perpendicular to a print medium. It is an object of the present invention to provide a highly reliable inkjet head that does not deteriorate the print quality even when a disturbance such as a change in the platen gap is satisfied. In addition, it is also an object of the present invention to apply the present invention to a double-sided flow path forming substrate to provide a high-density, high-speed inkjet head with a large number of nozzles.

[0011]

In order to solve the above-mentioned problems, according to the present invention, a nozzle for ejecting an ink droplet communicates with a pressure chamber, and is a top surface of the pressure chamber of a flow path substrate forming the pressure chamber. In the ink jet head in which the nozzle is arranged to be inclined with respect to the surface, the end surface shape of the nozzle is characterized in that the circumferential length of the flow path substrate on the reference surface side is larger than the anti-reference surface.

Further, a plurality of the pressure chambers are formed on both sides of the flow path substrate forming the pressure chambers, and the nozzle is communicated with the end surface of the flow path substrate. The end surface shape of the nozzle is the same as that of the flow path substrate. The peripheral length on the side of the reference surface is larger than that of the anti-reference surface.

[0013]

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

FIG. 1 is a main schematic sectional view of the first embodiment. 1 is a nozzle, 2 is a pressure chamber, 3 is a nozzle forming member, 4
Is a flow path substrate that forms a pressure chamber. Reference numeral 4A is a reference surface of the flow path substrate 4 which serves as an assembly reference with other components, and is also an upper surface of the pressure chamber 2. Further, the flow path substrate 4 and the nozzle forming member 3 may be joined together as separate members or may be integrally formed. Ultraviolet light 11 (for example, excimer laser light) is irradiated from the pressure chamber 2 side to the nozzle forming member 3 and the flow path substrate 4 that are integrated to form the nozzle 1. The ultraviolet light 11 is applied to a member (not shown) behind the pressure chamber 2 (on the right side in the drawing) of the flow path substrate 4 forming the pressure chamber 2 and the flow path substrate 4.
In order to irradiate the nozzle forming member 3 while avoiding the side wall (not shown) between the pressure chambers 2 formed on the upper surface of the pressure chamber 2, as shown in FIG. There is no choice but to inject with a certain inclination. Of course, as shown in FIG. 1, the nozzle 1 to be formed is also formed obliquely with a certain inclination with respect to the reference surface 4A.

The nozzle tip 9 which is the end face of the nozzle 1.
2 is, as shown in FIG. 2 (viewed from the front surface 5 of the nozzle), symmetrical with respect to the line AA drawn perpendicular to the reference surface 4A, and the circumferential length of the flow path substrate 4 on the reference surface 4A side. Is longer than the anti-reference plane.

In this structure (after completed as an ink jet head), the ink droplets ejected from the nozzle 1 are formed at the tip of the nozzle 1 as shown in FIG. 3 (enlarged view of the vicinity of the nozzle of FIG. 1). Ink meniscus (nozzle 1
Reference surface 4A of the liquid surface of the ink formed on the most advanced portion 9 of the
Velocity component 15 caused by the difference in holding force between the side and the opposite side
Due to the balance between A and the velocity component 15B generated in the nozzle direction due to the inertia of the ink at the time of ink ejection, it flies parallel to the reference surface 4A (indicated by the ink droplet ejection direction 15).

The velocity component 15A is also greatly affected by the ink tension on the nozzle surface. In particular, when the nozzle front surface 5 gets wet with ink, the velocity component 15A becomes larger.

The nozzle 1 on the reference surface 4A side of the flow path substrate 4
The optimum shape including the peripheral length difference of the most tip 9 is greatly affected by the speed of the ejected ink droplets and the characteristics of the ink (viscosity, surface tension, etc.), and has a considerable influence on other dimensions and required characteristics. To be done. Therefore, the leading edge circumference of the nozzle 1 on the reference surface 4A side may be calculated or experimentally found depending on the balance between the design required quality and the manufacturing required dimension.

By the way, in the prototype, in the case where the leading edge of the nozzle 1 has a shape in which an ellipse having a major axis of 60 μm and a single axis of 45 μm is divided into two parts by a minor axis, and the nozzle length is 100 μm, discharge is performed. Ink drop speed is 8-10m / s
Then, the straightness of ± 2 degrees with respect to the reference surface 4A was confirmed.

On the other hand, in the flying state of the ink droplet when the nozzle tip 9 is circular, the ink droplet flew at an angle of 6 to 8 degrees in the direction opposite to the reference plane 4A.

In the embodiment of the present invention, the nozzle 1
Although the elliptical shape of the ellipse is a shape obtained by dividing an ellipse into two with a short axis, the difference in meniscus force acting on the most distal end portion 9 of the nozzle 1 is closer to the reference surface 4A side than to the opposite side of the reference surface 4A. Any shape may be used as long as it is large, and the shapes shown in FIGS. 4, 5, 6, 7, and 8 (each of which is a view as seen from the front surface of the nozzle) can be applied. Enter the range.

By the way, the flow path substrate 4 (nozzle forming member 3
Are included by injection molding of a polymer resin, a photolithography method of a photosensitive composition, or the like. In addition, the flow path substrate can be formed by laminating thin metal plates having an open shape pattern of the pressure chamber 2 or by die casting a metal material.
UV light (for example, excimer laser light) for nozzle formation
It is not suitable for the above (in the above case, the nozzle can be formed by YAG laser processing or the like).

FIG. 9 is a main schematic sectional view of the second embodiment of the present invention. The basic configuration and effects are the same as those of the first embodiment, but the cross-sectional shape of the nozzle 1 along the nozzle direction is greatly reduced toward the tip 9 of the nozzle (the nozzle direction of the nozzle 1). Has a shape in which the vertical cross-sectional area thereof decreases in the ink ejection direction). Also in the first embodiment, the taper angle is set to 2 to 3 degrees on one side, but in the second embodiment, the taper angle is set to be larger. The taper angle is set to 15 degrees on one side. With this structure, ink ejection stability and ink droplet ejection efficiency with respect to input energy are improved, reliability is improved, and energy saving is achieved. In our prototype, the applied voltage could be reduced by 25-30% compared to that of the first embodiment.

FIG. 10 is a main schematic sectional view of the third embodiment of the present invention. The basic configuration and effect are the same as those of the first embodiment, but the incident surface 7 (nozzle forming member 3) of the ultraviolet light 11 is inclined so as to be substantially perpendicular to the ultraviolet light 11. With this structure, the material removal (nozzle 1 formation) rate with respect to the irradiation ultraviolet light is improved, which leads to inexpensive nozzle 1 formation. Further, it is possible to reduce the fluid loss in the communicating portion between the pressure chamber 2 and the nozzle 1.

As described above, in the first, second, and third embodiments of the present invention, even if the nozzle 1 is formed obliquely with a certain inclination with respect to the reference surface 4A, it is parallel to the reference surface 4A. Since various ink ejections are achieved, ink flight perpendicular to the print medium can be realized at low cost and with high reliability. Therefore, it is possible to provide a highly reliable inkjet head in which the print quality does not deteriorate even with disturbance such as a change in the platen gap.

In addition, as shown in FIGS. 11 and 12, craters 8A, 8B are provided on the nozzle front face 5 for each nozzle 1.
Disposing the (recessed portion that protects the most distal end portion 9 of the nozzle 1) also belongs to the present invention. The craters 8A and 8B are arranged such that the tip of the nozzle 1 is moved further than the front surface 5 of the nozzle 1 at the time of collision or contact (for example, paper jam or paper rubbing) between the tip end portion 5 of the nozzle and the print medium, which occurs as a trouble during printing. Since the print medium is pulled in, it is possible to directly prevent the print medium from colliding with the tip of the nozzle 1. The craters 8A and 8B have a degree of freedom in setting their shapes, and may be any as long as they surround the tip of the nozzle 1. Also, the nozzle 1 and the crater 8A are not always required.
(8B) does not have to correspond one-to-one, and one crater may correspond to a plurality of nozzles 1. (Not shown) The crater 8A shown in FIG. 11 is formed by irradiating ultraviolet light from the nozzle front surface 5 side, and its incident direction must be perpendicular to the nozzle front surface 5. If this crater 8A is formed after the nozzle 1 is formed, it is possible to simultaneously remove dross (such as burrs that occurs when ultraviolet light penetrates) that occurs when the nozzle 1 is formed. The crater 8B shown in FIG. 12 is formed at the same time when the nozzle forming member 3 (flow channel substrate 4) is formed, and is used as a reference surface 4A for forming the pressure chamber 2 of the flow channel substrate 4 as a closed groove. The canopy 6 joined to is used to substitute that one tomb. This method has an advantage in manufacturing cost because it is not necessary to perform post-processing for forming the crater 8B.

Next, a fourth embodiment of the present invention will be described with reference to FIG. This is one in which the first, second and third embodiments are applied to a double-sided channel forming substrate for the purpose of increasing the number of nozzles.

The structure on one side (upper or lower in the figure) is basically the same as that of the above-mentioned embodiment, and the reference surfaces 4A on the front and back sides (upper and lower in the figure) of the flow path substrate 4B are made parallel to each other. The ejected ink droplets are set to be parallel, and the ejected ink droplets are also made to fly in parallel (15 in the figure) to both reference surfaces 4A. The flow path substrates 4B on both surfaces may be integrally formed on the back surface, or may be integrated by combining two ones so that the reference surface 4A is on the outside.

In this structure, the nozzles 1A and 1B have the reference surface 4
Even if the nozzles 1A and 1B are formed so as to be oblique to A and have an inclination such that they face each other, the ink droplets ejected from both nozzles 1A and 1B are parallel and are also parallel to both reference surfaces 4A. Therefore, it is possible to realize ink flight perpendicular to the print medium and in parallel, at low cost and with high reliability. Therefore, it is possible to increase the number of nozzles in the highly reliable inkjet head that does not deteriorate the print quality even when the platen gap changes or the like.

14 and 15 show an embodiment relating to the nozzle arrangement of the head corresponding to both sides. FIG. 14 shows an example in which a plurality of nozzles 1A row and 1B row on both sides are arranged at the same pitch without any deviation in the printing height direction (vertical direction in the drawing), which corresponds to speeding up. FIG. 15 shows an example in which a plurality of nozzles 1A and 1B on both sides are arranged at the same pitch and are shifted by a half pitch in the print height direction (vertical direction in the drawing), which corresponds to high density. The amount of shift can be variously set according to the purpose, but all belong to the scope of application of the present invention.

In all of the above-described embodiments of the present invention, as the active element (not shown) for generating the pressure fluctuation in the pressure chamber 2, the heat generating element for converting the electric energy into the heat energy or the electric energy is used. A piezoelectric element that is converted into mechanical energy and bends the canopy 6 (installed on the canopy 6 and outside the pressure chamber 2) or the like can be used.

[0032]

As described above, the present invention achieves both high precision and high yield nozzle formation that secures ink ejection stability, and ink flight perpendicular to the print medium.
It is possible to provide a highly reliable inkjet head in which the print quality does not deteriorate even with a disturbance such as a change in the platen gap. In addition, the present invention can be applied to a double-sided channel forming substrate to provide a high-density, high-speed inkjet head that also has the above effects.

[Brief description of drawings]

FIG. 1 is a main schematic cross-sectional view of a first embodiment of the present invention.

FIG. 2 is a front view of the nozzle according to the first embodiment of the present invention.

FIG. 3 is an enlarged view of the vicinity of the nozzle of FIG.

FIG. 4 is a front view of the nozzle according to the embodiment of the present invention.

FIG. 5 is a front view of the nozzle according to the embodiment of the present invention.

FIG. 6 is a front view of the nozzle according to the embodiment of the present invention.

FIG. 7 is a front view of the nozzle according to the embodiment of the present invention.

FIG. 8 is a front view of the nozzle according to the embodiment of the present invention.

FIG. 9 is a main schematic cross-sectional view of the second embodiment of the present invention.

FIG. 10 is a main schematic cross-sectional view of a third embodiment of the present invention.

FIG. 11 is a sectional perspective view from the front surface of the nozzle according to the embodiment of the present invention.

FIG. 12 is a sectional perspective view from the front surface of the nozzle according to the embodiment of the present invention.

FIG. 13 is a main schematic cross-sectional view of a fourth embodiment of the present invention.

FIG. 14 is a perspective view of a double-sided channel forming plate according to a fourth embodiment of the present invention.

FIG. 15 is a perspective view of a double-sided channel forming plate according to a fourth embodiment of the present invention.

FIG. 16 is a main schematic cross-sectional view of a conventional example.

FIG. 17 is a correlation diagram between a conventional example and a print medium.

FIG. 18 is a main schematic cross-sectional view of a conventional example.

FIG. 19 is a correlation diagram between a conventional example and a print medium.

[Explanation of symbols]

1 Nozzle 1A Nozzle 1B Nozzle 2 Pressure Chamber 3 Nozzle Forming Member 4 Flow Path Substrate 4A Reference Surface 4B Flow Path Substrate 5 Nozzle Front Surface 6 Canopy 7 UV Light Incident Surface 8A Crater 8B Crater 9 Nozzle Leading Edge 11 UV Light 12 Ink Droplet ejection direction 13 Printing direction 14 Printing direction 15 Ink droplet ejection direction 15A Velocity component of ejected ink droplet due to nozzle meniscus 15B Velocity component of ejected ink droplet in nozzle direction 21 Print medium 22 Print medium D1 Displacement of ejected ink droplet D2 Distance between landing positions of ejected ink drops on both sides D3 Distance between landing positions of ejected ink drops on both sides

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B41J 2/135

Claims (4)

[Claims] 1. An ink jet head in which a nozzle for ejecting an ink droplet communicates with a pressure chamber, and the nozzle is arranged to be inclined with respect to a reference surface which is an upper surface of the pressure chamber of a flow path substrate forming the pressure chamber. In the ink jet head, the end surface shape of the nozzle is such that the circumferential length of the flow path substrate on the reference surface side is larger than that on the anti-reference surface side. 2. The pressure chamber according to claim 1, wherein a plurality of the pressure chambers are formed on both sides of the flow path substrate forming the pressure chamber, and the nozzle communicates with an end surface of the flow path substrate. Inkjet head. 3. The method of manufacturing an inkjet head according to claim 1, wherein the nozzle is formed by using ultraviolet light. 4. The method for manufacturing an ink jet head according to claim 1, wherein the nozzle is formed by irradiating ultraviolet light from the pressure chamber side.