JP2004175038A - Ink discharge device and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink discharge device comprising ink discharge holes with the shape capable of achieving a desired size of liquid droplets to be ejected even when the ink discharge holes are arranged in extremely high density in an ink channel part. <P>SOLUTION: In the ink discharge device, ink discharge holes 4 to be used as ink-ejecting ports are formed facing the end opening of at least one or more ink channels 3 formed in a head part 2 for providing energy to ink in order to eject the same. The ink discharge hole 4 is formed in a tapered shape with the inner diameter of the ink outlet side opening being set smaller than that of the ink inlet side opening. In addition, the ink discharge hole 4 is formed in a closed loop wherein the shape of the ink outlet side opening has a major axis set in the same direction as the longitudinal direction of the end opening of the ink channel 3 and a minor axis orthogonal to the major axis. <P>COPYRIGHT: (C)2004,JPO

Description

【００５３】
また、出口側開口部の開口面積を同等にして、短軸長さａと長軸長さｂの比率を変化させた状態のインク吐出孔４も製作して、上記と同様の吐出実験を行った。その結果は前述と同様で、短軸長さａと長軸長さｂの比率が０．２５より小さい場合には、吐出状態が安定しなかった。
【００５４】
以上の実験を通じて、インク吐出孔４の出口側開口部の短軸長さａと長軸長さｂの比率は前記（１）式に示す範囲が良好であることを確認することができた。
【００５５】
【発明の効果】
以上の説明から明らかなように、本発明は、以下の効果を奏する。
【００５６】
（１）インク吐出孔の出口側開口部（及び入口側開口部）を、インク流路開口部の形状に合わせた長軸と短軸を有する閉ループ状に形成することで、狭いインク流路間においてもインク吐出孔がインク流路開口部内に収まりやすくなるため、インク吐出孔を高密度に配列しても、充分な開口面積を有するインク流路の出口側開口部の形成が容易となる。
【００５７】
また、インク吐出孔におけるインク出口側開口部の内径を、インク入口側開口部の内径よりも小さく設定しているため、インク吐出後のインク面のメニスカスが安定化して気泡の引き込みがなく、飛翔特性が安定化する。
【００５８】
（２）インク吐出孔の出口側開口部の形状が、短軸と長軸に対してそれぞれ軸対称に形成されているので、インク吐出孔を高密度に配置した場合においても、インク流路の狭い開口部に、所望のインク吐出孔出口側開口面積を有するインク吐出孔を容易かつ適切に収めることができる。
【００５９】
（３）インク吐出孔の出口側開口部の形状を、長円または楕円としたので、その短軸方向に、インク吐出孔列を高密度に配列することができ、かつ、その場合においても、インク流路の狭い開口部に、所望のインク吐出孔出口側開口面積を有するインク吐出孔を収めやすくなる。
【００６０】
（４）インク吐出孔の出口側開口部における内径の短軸長さをａ、長軸長さをｂとした場合に、０．２５≦ａ／ｂ＜１．０・・・・・・・・・（１）式が満たされるので、インク噴射の吐出安定化を実現できる。
【００６１】
（５）インク吐出孔の出口側開口部の短軸部のテーパー角度が長軸部よりも小さいので、インク吐出孔の入口側開口部においてインク吐出孔がインク流路開口部の壁面と交差せず、より大きく広いインク吐出孔出口側開口部を実現でき、ノズルプレート接合時の貼り合わせ精度に余裕が生じ、ノズルプレートの接合工程における歩留まりが向上する。
【００６２】
（６）インク吐出孔の加工にレーザ光を用いるので、高い加工精度を必要とするインク吐出孔の微細形状を安定的に精度良く作製でき、インク噴射の吐出安定化が達成できる。
【００６３】
（７）インク吐出孔を形成するノズルプレート基材として、紫外線を吸収する有機材料を用い、その基材厚をｔとすると、２０μｍ≦ｔ≦１００μｍ・・・・・・・・・（２）式が満たされるので、（レーザー加工により、）吐出状態が安定なインク吐出孔を形成することができる。
【００６４】
（８）マスクパターンを用いたレーザ加工により、高密度な配列が可能で、充分な開口面積を有するインク流路の出口側開口部の形成が容易なインク吐出孔を高精度に形成することができ、しかも接着剤等によりインク吐出に影響を及ぼすことのないように、ノズルプレートを接合することができ、インク吐出状態の安定したインク吐出装置を製造することができる。
【図面の簡単な説明】
【図１】本発明の実施の形態に係る楕円形状のインク吐出孔を有すインク吐出装置の説明図である。
【図２】同別の実施の形態に係る長円形状のインク吐出孔を有すインク吐出装置の説明図である。
【図３】同比較例としての真円形状のインク吐出孔を有すインク吐出装置の説明図である。
【図４】従来例のインク吐出装置の一例を示す一部破断斜視図である。
【図５】同インク吐出孔の一例を示すノズルプレートの斜視図である。
【符号の説明】
１−ノズルプレート
２−ヘッド部
３−インク流路
４−インク吐出孔
ａ−短軸長さ
ｂ−長軸長さ
ｔ１ −短軸部のテーパー角度
ｔ２ −長軸部のテーパー角度[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ink ejection apparatus capable of performing high-speed, high-density recording operation by ejecting ink from ink ejection holes formed in a nozzle plate, and a method of manufacturing the same.
[0002]
[Prior art]
2. Description of the Related Art In recent years, in printers, non-impact printing apparatuses, such as ink jet systems, which can easily cope with colorization and multi-gradation, have rapidly spread in place of impact printing apparatuses. As the ink ejection device used for this, a drop-on-demand type, which ejects only ink droplets necessary for printing, has been attracting attention because of its good ink ejection efficiency and ease of cost reduction.
[0003]
As the drop-on-demand type, the Kaiser method and the thermal jet method are mainly used. However, the Kaiser method is not suitable for increasing the density because it is difficult to reduce the size. Further, the thermal jet method is not preferable from the viewpoint of energy saving because the ink needs to be jetted at a high temperature, and thus heat resistance of the ink is required.
[0004]
Therefore, as a solution to the drawbacks in each of these methods, for example, an electrode film is formed on both side walls of an ink flow path made of a piezoelectric substrate material, and a potential difference is applied to the electrodes to form the ink flow path wall surface. There has been proposed an ink ejection method by piezoelectric driving in which the ink is deformed and the ink is ejected using the pressure wave fluctuation generated at that time (for example, see Patent Document 1). This method is suitable for increasing the density of the nozzle and saving energy.
[0005]
In an ink jet apparatus including the above method, as shown in a perspective view of FIG. 4, the nozzle plate 1 is joined to a position facing the ink flow path 3 of the head unit 2. The ink ejection hole 4 is formed in a tapered shape with a wide ink inlet side and a narrow outlet side. Then, the size of the ejected droplet changes depending on the opening area of the outlet side opening.
[0006]
If an attempt is made to increase the ejection density of ink ejection in order to realize higher density and higher speed printing, the interval between the ink ejection holes 4 is reduced, and a very narrow ink channel 3 is formed.
[0007]
On the other hand, the size of the opening on the outlet side of the ink ejection hole 4 can be changed by increasing the number of gradations. However, in order to fill the paper surface with a desired droplet size, the size of the ejection droplet having an appropriate size is determined. It is necessary to realize a size, and an opening on the outlet side of the ink ejection hole 4 having a desired area is required.
[0008]
In order to join the ink ejection holes 4 that fit in such a narrow ink channel 3, for example, by irradiating a laser beam passed through a plano-concave cylindrical lens to the inlet side of the nozzle plate 1, FIG. As shown in the drawings, a method of forming an ink ejection hole 4 in which the entrance side opening of the ink ejection hole 4 is elliptical and the exit side opening (shown by a dotted line) is a perfect circle has been proposed (for example, Patent Document 2). reference).
[0009]
[Patent Document 1]
JP-A-63-247051 (FIGS. 9 (a) and 9 (b), specification p11 upper right column, line 7 to p12 upper right column, three lines)
[Patent Document 2]
Japanese Patent No. 3285041 (FIG. 1, FIG. 2, FIG. 5, paragraphs “0017” to “0020”, “0030”, “0040”)
[0010]
[Problems to be solved by the invention]
As described above, the size of the ejected droplet varies depending on the opening area of the outlet opening of the ink ejection hole. Therefore, it is necessary to realize an appropriate minimum droplet size that does not cause a shortage of the droplet amount. In order to realize a droplet size of about 3 pl to 6 pl, an opening area of about 300 μm 2 to 800 μm 2 is required at the outlet side of the ink ejection hole, and a diameter of about 20 μm to 30 μm when converted to a perfect circular area. Therefore, it is necessary to form a relatively large ink ejection hole opening.
[0011]
However, since the cross-sectional shape of the ink ejection hole is formed in a tapered shape with a wide entrance and a small exit to reduce the ink ejection voltage value, if the entrance side of the ink ejection hole is formed so as to fit in the ink flow path, For example, even in the method of forming an ink ejection hole disclosed in Patent Document 2, since the shape on the outlet side is a perfect circle, the opening area is reduced, and as a result, the size of the ejected droplet may not be made to be a desired size.
[0012]
In other words, if the ink ejection holes are formed in a perfect circular shape in accordance with the surface area of the desired ink ejection hole outlet opening, the opening area of the entrance side opening of the ink ejection hole becomes large. A part of the opening on the inlet side of the hole overlaps with the wall of the ink flow path (the ellipse in the present invention is a rectangular or square pair of opposite sides, each having a semicircular diameter portion). Is circumscribed).
[0013]
As a result, at the time of nozzle plate bonding, there is a possibility that the adhesive used for nozzle plate bonding may cause the adhesive to enter the ink discharge hole tapered portion and further cause a problem that the ink discharge hole is blocked. In addition, the ink flow path wall overlapping with the ink discharge hole becomes an obstacle, which causes discharge instability such as entrapment of air bubbles and bending of the ink discharge direction.
[0014]
The present invention has been made in view of such circumstances, and has an ink ejection device having an ink ejection hole shape capable of obtaining a desired ejection droplet size even if ink ejection holes are arranged at high density, and manufacturing thereof. The aim is to provide a method.
[0015]
[Means for Solving the Problems]
According to the present invention, means for solving the above-described problem are configured as follows.
[0016]
(1) An ink ejection hole serving as an ink ejection port is formed facing an end opening of at least one or more ink flow paths formed in a head unit that applies energy to ink to eject ink. In the ink ejection device that has been
The ink ejection hole is formed in a tapered shape in which the inner diameter of the ink outlet side opening is set smaller than the inner diameter of the ink inlet side opening, and the shape of the ink outlet side opening is the ink flow path. Are formed in a closed loop shape having a major axis set in the same direction as the longitudinal direction of the end opening and a minor axis orthogonal to the major axis.
[0017]
In this configuration, the outlet side opening (and the inlet side opening) of the ink discharge hole is formed in a closed loop shape having a long axis and a short axis according to the shape of the ink flow path opening, so that a narrower ink can be obtained. Since the ink ejection holes are easily accommodated in the ink passage openings even between the flow passages, it is easy to form the outlet openings of the ink passages having a sufficient opening area even if the ink ejection holes are arranged at a high density. It becomes.
[0018]
Further, since the inner diameter of the ink outlet side opening in the ink discharge hole is set smaller than the inner diameter of the ink inlet side opening, the meniscus on the ink surface after ink discharge is stabilized, so that no bubbles are drawn and the ink flies. Characteristics are stabilized.
[0019]
(2) The shape of the outlet side opening of the ink ejection hole is formed to be axially symmetric with respect to the short axis and the long axis.
[0020]
In this configuration, the ink ejection holes are formed in the short axis direction, and each ink ejection hole is formed axially symmetric with respect to the short axis (and the long axis). Even in the case where the ink ejection holes are arranged, the ink ejection holes having a desired ink ejection hole exit side opening area can be easily and appropriately accommodated in the narrow openings of the ink flow paths.
[0021]
(3) The shape of the outlet side opening of the ink ejection hole is an ellipse or an ellipse.
[0022]
In this configuration, the shape of the outlet side opening of the ink ejection hole is an ellipse or an ellipse, so that the ink ejection hole array can be arranged at a high density in the short axis direction, and in that case, Also in this case, the ink discharge hole having a desired ink discharge hole exit side opening area can be easily accommodated in the narrow opening of the ink flow path.
[0023]
(4) When the short axis length of the inner diameter at the outlet side opening of the ink ejection hole is a and the long axis length is b,
0.25 ≦ a / b <1.0 Expression (1) The expression (1) is satisfied.
[0024]
In this configuration, the ratio between the major axis and the minor axis is set in the range of the above equation (1), so that the ink ejection can be stabilized.
[0025]
(5) The taper angle of the short axis portion of the opening on the outlet side of the ink ejection hole is smaller than the taper angle of the long axis portion.
[0026]
In this configuration, the ink discharge hole does not overlap the wall surface of the ink flow path opening at the inlet side opening of the ink discharge hole, and a larger and wider ink discharge hole outlet side opening can be formed. There is a margin in the bonding accuracy of the nozzle plates, and the yield in the nozzle plate bonding process is improved.
[0027]
(6) The method is characterized in that laser light is used for processing the ink ejection holes.
[0028]
With this configuration, the fine shape of the ink ejection hole that requires high processing accuracy can be stably and accurately manufactured, and the ejection stabilization of the ink ejection can be achieved. Note that the processing by the laser light is preferably processing by an excimer laser.
[0029]
(7) Assuming that a nozzle plate substrate for forming the ink ejection holes is made of an organic material that absorbs ultraviolet rays and the thickness of the substrate is t,
20 μm ≦ t ≦ 100 μm Expression (2) Expression (2) is satisfied.
[0030]
In this configuration, by using the nozzle plate base material having the above-described thickness, it is possible to form an ink ejection hole having a stable ejection state (by laser processing).
[0031]
(8) Using a mask pattern having a contour formed in a closed loop shape having a major axis and a minor axis orthogonal to the major axis, and having a shape axially symmetric with respect to the major axis and the minor axis. By processing a nozzle plate base made of an organic material that absorbs ultraviolet light by a laser processing device to form an ink discharge hole, the long axis direction of the ink discharge hole is set in the same direction as the longitudinal direction of the ink flow path opening. After setting, the nozzle plate in which the ink ejection holes are formed is joined to a head portion.
[0032]
In this manufacturing method, high-density arrangement is possible by laser processing using a mask pattern, and an ink discharge hole is formed with high accuracy in which it is easy to form an outlet opening of an ink flow path having a sufficient opening area. The nozzle plate can be joined so that the ink ejection is not affected by the adhesive or the like, and an ink ejection device with a stable ink ejection state can be manufactured.
[0033]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an ink ejection apparatus and a method of manufacturing the same according to an embodiment of the present invention will be described in detail with reference to the drawings.
[0034]
(Embodiments 1, 2)
FIG. 1 shows an ink ejection device according to the first embodiment having an elliptical ink ejection hole 4, and FIG. 2 shows an ink ejection device according to the second embodiment having an oval ink ejection hole 4. Hereinafter, an ink jet head operated by piezoelectric driving will be described as an example with reference to these drawings.
[0035]
The head portion 2 is formed by bonding and integrating a piezoelectric substrate 21 and a cover member 22. The piezoelectric substrate 21 is made of a material such as lead zirconate titanate (PZT) or lead titanate (PZ) that has been subjected to polarization treatment. Groove processing is performed on the piezoelectric ceramic substrate using a diamond blade to form a plurality of mutually parallel ink flow grooves having a groove depth of about 200 μm and a groove width of about 40 μm.
[0036]
Then, a conductive metal film such as Cu, Al, Ni, Cr, or Au is formed in the groove by using a vacuum deposition method or a plating method using a vapor deposition device, a sputtering device, a plasma CVD device, or the like, and then forming a cover. The ink channel 3 is formed by closing the upper part of the groove with the member 22.
[0037]
After forming a liquid-repellent layer having ink repellency on the surface of the nozzle plate 1, the ink ejection holes 4 are processed with high precision using a laser processing device such as an excimer laser. In the processing, a laser beam is made incident on the inner surface side of the nozzle plate, and the center of the ink flow path 3 is formed such that the inner diameter of the ink inlet side opening on the inner surface becomes larger than the inner diameter of the ink outlet side opening. The same number of ink ejection holes 4 as the ink flow paths 3 are formed in the portions corresponding to the above.
[0038]
That is, in the case of FIG. 1 (Embodiment 1), between the short axis a1 and the long axis b1 in the ink outlet side opening in the ink ejection hole 4 and the short axis a2 and the long axis b2 in the ink inlet side opening, The relations a1 <a2 and b1 <b2 hold. In the case of FIG. 2 (Embodiment 2), between the short axis a3 and the long axis b3 in the ink outlet side opening of the ink ejection hole 4 and the long axis a4 and the short axis b4 in the ink inlet side opening, The relations a3 <a4 and b3 <b4 hold.
[0039]
Further, between the minor axis length a and the major axis length b of the inner diameter at the outlet side opening of the ink ejection hole 4,
0.25 ≦ a / b <1.0 Expression (1) It is preferable that the relationship of Expression (1) is satisfied. By setting the ratio between the lengths of the major axis and the minor axis in such a range, the ejection state of ink ejection is stabilized.
[0040]
The base material of the nozzle plate 1 is preferably a material suitable for laser processing. For example, polyimide is used as an organic material that absorbs ultraviolet light having a wavelength range of 200 nm to 400 nm, and the base material thickness is, for example, 50 μm. . Regarding the base material thickness, as described above, since the ink ejection holes 4 are formed in a tapered shape in which the opening area differs between the laser light incident surface and the laser light emission surface, the base material thickness is represented by t.
20 μm ≦ t ≦ 100 μm (2) It is preferable that the above expression (2) is satisfied.
[0041]
With respect to this plate thickness, in the case of a base material having a base material thickness t smaller than 20 μm, when a negative pressure is applied to the ink filled in the ink discharge device, bubbles are easily entrapped through the ink discharge holes 4 into the device, Discharge is likely to be unstable.
[0042]
On the other hand, in the case of a base material having a thickness of more than 100 μm, if the ink inlet side opening of the ink discharge hole 4 at the laser beam incident portion is formed in accordance with the area of the ink outlet opening necessary for the droplet size due to the taper angle, the opening becomes When the ink ejection holes are arranged at a narrow pitch, the possibility that the periphery of the ink inlet side opening of the ink ejection holes 4 overlaps with the wall of the ink flow path 3 increases. Further, when the base material is thick, the variation in the processing accuracy by the laser becomes large, and it becomes impossible to stabilize the shape accuracy of the area of the outlet side opening of the ink ejection hole 4 which is a main factor that determines the size of the ejected droplet.
[0043]
(Comparative Example 1)
Incidentally, the pitch of the ink ejection holes 4 in the present embodiment is set to 300 dpi (dot per inch), that is, 85 μm. Therefore, when a groove having a groove depth of about 200 μm and a groove width of about 40 μm is formed in the above-described opening of the ink flow path 3, the ink ejection hole 4 is formed to realize a predetermined ejection droplet. For example, in Comparative Example 1 in which both the ink inlet side opening and the ink outlet opening as shown in FIGS. 3A and 3B are a perfect circle, the inner diameter of the outlet side opening is 28 μm and the surface area is about 615 μm 2. When the ink ejection hole 4 is formed, the opening at the inlet side of the ink ejection hole 4 has a perfect circular shape with an inner diameter of about 60 μm due to the taper angle. Therefore, as a result of being larger than the groove width of 40 μm, the peripheral edge of the inlet-side opening overlaps the wall of the ink flow path 3. In such a case, the ink flow path wall becomes an obstacle, which causes ejection instability such as entrapment of air bubbles and bending of the ink ejection direction.
[0044]
(Comparative Example 2)
Regarding this point, similarly, as described in Patent Document 2, even in a configuration in which the outlet side opening of the ink discharge hole 4 is a perfect circle and the inlet side opening is an ellipse, the base material thickness of the nozzle plate 1 Is set to 50 μm, when the taper angle of the ink discharge hole is taken into consideration, there is no margin in the groove width of the ink flow path 3 at the opening on the inlet side. The possibility that a part of the ink passage 4 overlaps the wall of the ink flow path 3 increases.
[0045]
When the inner diameter of the inlet opening of the ink ejection hole 4 is larger than the groove width as in Comparative Examples 1 and 2 described above, the inlet opening protrudes from the groove to form a wedge-shaped portion. As a result, the flow of ink is disturbed, so that the ink ejection state becomes unstable, and the flying characteristics also deteriorate. In addition, since the ink easily accumulates in the wedge-shaped portion, cleaning of the nozzle portion is troublesome.
[0046]
(Experimental examples 1, 2, 3)
On the other hand, in Experimental Example 1 (see FIG. 2), the short-axis length a4 of the inlet-side opening of the ink discharge hole 4 was 29.5 μm, the long-axis length b4 was 58 μm, and the short-side of the outlet side opening was short. The shaft length a3 was set to 17 μm and the long axis length b3 was set to 41 μm to form the oval ink ejection holes 4 on both the inlet side and the outlet side.
[0047]
At that time, in the laser processing, the ink ejection holes 4 having different taper angles in the major axis portion and the minor axis portion can be formed. At this time, the taper angle t1 of the minor axis portion is changed to the taper angle of the major axis portion. Since the angle is smaller than the angle t2, the short-axis portion on the inlet side of the ink ejection hole 4 does not become too large, and the margin of the size of the ink ejection hole 4 with respect to the ink flow path 3 increases. Thereby, even if there is a slight error in the position of the ink ejection hole 4, the error can be absorbed, which is advantageous in the step of joining the nozzle plate 1. That is, regarding the taper angle of the ink ejection hole 4,
The taper angle t1 of the short axis portion <the taper angle t2 of the long axis portion (3)
It is preferable that the above expression (3) is satisfied. This is the same in the case of FIG. 1 (not shown).
[0048]
In order to evaluate the stability of the ink ejection holes 4 formed as described above in the ink ejection direction, the ink ejection holes 4 having different ratios of the short axis length a and the long axis length b were manufactured, and ejection experiments were performed on each of them. Was done.
[0049]
In order to compare the experiment with the ink ejection hole 4 of the above-described experiment example 1, as a test piece of the experiment example 2, the outlet side long axis length b of the ink ejection hole 4 was 63 μm, and the short axis length a was 17 μm. An ink outlet 4 having an oval shape was formed at both the inlet and the outlet.
Further, as the test piece of Experimental Example 3, the outlet-side long axis length b of the ink ejection hole 4 was set to 69 μm and the short axis length a was set to 17 μm. Was made.
[0050]
Next, after transferring the epoxy liquid adhesive to each of the nozzle plates 1 of the above-described Experimental Examples 1, 2, and 3 onto the nozzle plate bonding surface of the head portion 2 with a thickness of about 2 μm, The nozzles are aligned so that the ink ejection holes 4 are located at the center of the ink flow path 3, and the long axis direction of the opening on the outlet side of the ink ejection holes 4 coincides with the longitudinal direction of the ink flow path opening. The plate 1 and the head section 2 were bonded under pressure.
[0051]
In the experiment, ink was introduced into the head unit 2 to which each nozzle plate 1 was joined, an electric field was applied, and the flying state was observed and compared. As a result, as shown in Table 1, in Experimental Example 3, the ratio of the short axis to the long axis was 0.25 or less, and the ejection state was unstable (ejection state was unstable).
[0052]
[Table 1]

[0053]
In addition, an ink ejection hole 4 in a state in which the ratio of the short axis length a to the long axis length b is changed by making the opening area of the outlet side opening equal, and performing the same ejection experiment as above. Was. The results were the same as described above. When the ratio of the minor axis length a to the major axis length b was smaller than 0.25, the ejection state was not stable.
[0054]
Through the above experiment, it was confirmed that the ratio of the minor axis length a to the major axis length b of the opening on the outlet side of the ink ejection hole 4 was good in the range shown in the above equation (1).
[0055]
【The invention's effect】
As is clear from the above description, the present invention has the following effects.
[0056]
(1) By forming the outlet-side opening (and the inlet-side opening) of the ink discharge hole in a closed loop shape having a long axis and a short axis according to the shape of the ink flow path opening, the narrow ink flow path In this case, since the ink discharge holes are easily accommodated in the ink flow path openings, even if the ink discharge holes are arranged at a high density, it is easy to form the outlet openings of the ink flow paths having a sufficient opening area.
[0057]
Further, since the inner diameter of the ink outlet side opening in the ink discharge hole is set smaller than the inner diameter of the ink inlet side opening, the meniscus on the ink surface after ink discharge is stabilized, so that no bubbles are drawn and the ink flies. Characteristics are stabilized.
[0058]
(2) Since the shape of the outlet side opening of the ink ejection hole is formed axially symmetric with respect to the short axis and the long axis, even when the ink ejection holes are arranged at high density, An ink ejection hole having a desired ink ejection hole outlet side opening area can be easily and appropriately accommodated in the narrow opening.
[0059]
(3) Since the shape of the outlet side opening of the ink ejection hole is an ellipse or an ellipse, the ink ejection hole array can be arranged at a high density in the short axis direction. It becomes easy to fit the ink discharge hole having a desired ink discharge hole outlet side opening area into the narrow opening of the ink flow path.
[0060]
(4) When the short axis length of the inner diameter at the outlet side opening of the ink ejection hole is a and the long axis length is b, 0.25 ≦ a / b <1.0... ... Since the expression (1) is satisfied, it is possible to stabilize the ejection of the ink jet.
[0061]
(5) Since the taper angle of the short axis portion of the outlet side opening of the ink ejection hole is smaller than that of the long axis portion, the ink ejection hole intersects the wall surface of the ink flow path opening at the entrance side opening of the ink ejection hole. In addition, a larger and wider opening portion on the outlet side of the ink discharge hole can be realized, and the bonding accuracy at the time of nozzle plate bonding has a margin, thereby improving the yield in the nozzle plate bonding process.
[0062]
(6) Since a laser beam is used for processing the ink discharge holes, a fine shape of the ink discharge holes requiring high processing accuracy can be stably and accurately produced, and the discharge stabilization of the ink discharge can be achieved.
[0063]
(7) Assuming that the nozzle plate base material for forming the ink discharge holes is made of an organic material that absorbs ultraviolet rays and the base material thickness is t, 20 μm ≦ t ≦ 100 μm (2) Since the expression is satisfied, it is possible to form an ink ejection hole having a stable ejection state (by laser processing).
[0064]
(8) By laser processing using a mask pattern, high-density arrangement is possible, and it is possible to form an ink discharge hole with high accuracy in which an outlet side opening of an ink flow path having a sufficient opening area can be easily formed. The nozzle plate can be joined so that the ink ejection is not affected by the adhesive or the like, and an ink ejection device with a stable ink ejection state can be manufactured.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of an ink ejection device having an elliptical ink ejection hole according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram of an ink ejection device having an oblong ink ejection hole according to another embodiment.
FIG. 3 is an explanatory diagram of an ink ejection device having a perfect circular ink ejection hole as the comparative example.
FIG. 4 is a partially cutaway perspective view showing an example of a conventional ink ejection device.
FIG. 5 is a perspective view of a nozzle plate showing an example of the ink ejection hole.
[Explanation of symbols]
1-Nozzle plate 2-Head part 3-Ink flow path 4-Ink ejection hole a-Short axis length b-Long axis length t1-Short axis taper angle t2-Long axis taper angle

Claims (8)

Ink formed with an ink ejection hole serving as an ink ejection port facing an end opening of at least one or more ink flow paths formed in a head unit that applies energy to the ink to eject the ink. In the discharge device,
The ink discharge hole is formed in a tapered shape, the inner diameter of the ink outlet side opening is set smaller than the inner diameter of the ink inlet side opening, and
The shape of the ink outlet side opening is formed in a closed loop shape having a long axis set in the same direction as the longitudinal direction of the end opening of the ink flow path, and a short axis orthogonal to the long axis. An ink ejection device, characterized in that: 2. The ink discharge device according to claim 1, wherein the shape of the outlet side opening of the ink discharge hole is formed to be axially symmetric with respect to the short axis and the long axis. 3. The ink discharge device according to claim 1, wherein the shape of the outlet side opening of the ink discharge hole is an ellipse or an ellipse. When the minor axis length of the inner diameter at the outlet side opening of the ink ejection hole is a and the major axis length is b,
0.25 ≦ a / b <1.0 (1) Expression (1) The expression (1) is satisfied, the ink ejection according to any one of claims 1 to 3, wherein apparatus. The ink ejection device according to claim 1, wherein a taper angle of a short axis portion of the outlet side opening of the ink ejection hole is smaller than a taper angle of a long axis portion. 6. The ink discharge device according to claim 1, wherein a laser beam is used for processing the ink discharge hole. As a nozzle plate base material for forming the ink ejection holes, an organic material that absorbs ultraviolet light is used, and the base material thickness is represented by t.
20 .mu.m.ltoreq.t.ltoreq.100 .mu.m (2) Equation (2) The ink ejection apparatus according to claim 1, wherein the equation (2) is satisfied. Laser processing is performed by using a mask pattern in which a contour is formed in a closed loop shape having a major axis and a minor axis orthogonal to the major axis, and has an axisymmetric shape with respect to the major axis and the minor axis. A nozzle plate substrate made of an organic material that absorbs ultraviolet light is processed by an apparatus to form ink ejection holes, and the long axis direction of the ink ejection holes is set to the same direction as the longitudinal direction of the ink flow path opening. 8. The method according to claim 1, wherein the nozzle plate having the ink discharge holes is joined to a head portion.

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