JP2000025239A - Ink-jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To discharge ink in the shape of ink drops smoothly from a nozzle by connecting the discharge nozzle with a leading end of a nozzle path tapered like a funnel and setting an inner diameter of the leading end of the nozzle path and an inner diameter of the discharge nozzle to a specific condition. SOLUTION: A pressure chamber 7 is formed to a substrate 2. A nozzle path 14 is connected under the pressure chamber 7. The nozzle path 14 forms a tapered flow path like a funnel from the pressure chamber 7. A nozzle plate 11 having a nozzle 15 formed beforehand is united and attached to a lower face of the substrate 2. An inner diameter DR of a leading end of the nozzle path 14 connected with the pressure chamber 7 and an inner diameter DN of the nozzle 15 are set to hold a size relationship of DR<=3DN. Air bubbles 21 are prevented from staying at beds 20 formed at a joint part of the nozzle path 14 and nozzle plate 11.

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 an ink jet printer.

[0002]

2. Description of the Related Art In a so-called on-demand type ink jet printer, an ink jet head used for discharging ink droplets is usually provided on a single substrate with a number of pressurizing chambers and a plurality of pressurizing chambers. A nozzle for ejecting ink droplets is provided. The pressure chamber is provided with a piezoelectric element, and the pressure chamber is pressurized by the piezoelectric element, so that an ink droplet is ejected from a nozzle.

[0003] Specifically, for example, as shown in FIG.
An independent piezoelectric element is provided for each of the pressure chambers 91a on a substrate 91 on which a plurality of pressure chambers 91a are arranged, directly above each of the pressure chambers 91a via a vibration plate 92 having at least an upper surface made conductive. The film 93 and the upper electrode 94 are stacked in this order. On the lower surface side of the substrate 91, a nozzle plate 95 in which a plurality of nozzles 95a corresponding to the respective pressure chambers 91a are formed is stacked.

In the ink jet head 9 having such a configuration, the conductive upper surface of the diaphragm 92 is used as a lower electrode, and printing data is printed between the lower electrode and an arbitrary upper electrode 94 among a plurality of electrodes. When the electric field is applied in accordance with the above, the piezoelectric film 93 between both electrodes is bent, and the pressurizing chamber 91 a immediately below is pressed via the vibration plate 92.

[0005] By this pressurization, the pressurizing chamber 91a
A predetermined amount of the ink previously filled in the nozzle flow path 96 connected to the nozzle flow path 96 is output as ink droplets from the nozzle 95a connected to the nozzle flow path 96, and printing is performed by repeating this process.

[0006]

Since the amount of ink droplets ejected from the nozzle 95a has a great influence on the quality of the resulting print, the inner diameter of the nozzle 95a is precisely machined to a desired inner diameter. For this reason, usually, as described above, the nozzle 95a is attached to the dedicated nozzle plate 95 having a predetermined thickness.
Is formed, the nozzle plate 95 is bonded to the lower surface side of the substrate 91.

On the other hand, a pressurizing chamber 91a formed in the substrate 91
The nozzle channel 96a is formed by etching using a photolithographic method or the like, and has a considerably larger capacity than the nozzle 95a. The reason for this is that it is necessary to fill the ink necessary for ejection with a sufficient amount.

For this reason, in the conventional ink jet head, when the nozzle 95a and the nozzle flow path 96 are bonded to each other, a shelf is formed at the joint, and bubbles remain on the shelf, which adversely affects ink filling and ejection. There was a problem that it was easy.

An object of the present invention is to provide an ink jet head which solves the above problem and ensures that the ink filled in the pressurizing chamber and the nozzle flow path is reliably and smoothly ejected from the nozzle as ink droplets. .

[0010]

According to the first aspect of the present invention,
An ink jet head for performing printing by repeating ejection of ink droplets, a pressurized chamber pressurized at the time of ejection of ink droplets, and a nozzle flow path connected to the pressurized chamber and tapered in a funnel shape. A discharge nozzle communicated with the tip of the nozzle flow path, and the inner diameter D _R of the tip of the nozzle flow path.
If, the inner diameter D _N of the ejection nozzle, and is characterized in that it is set to D _R ≦ 3D _N.

According to a second aspect of the present invention, in the ink jet head according to the first aspect, the discharge nozzle is formed on a thin nozzle plate prepared in advance, and the pressurizing chamber and the nozzle flow path are formed on the substrate. Wherein the nozzle plate and the substrate are formed by being bonded to each other.

According to the first aspect of the present invention, the inner diameter D _{R at} the tip of the nozzle flow path and the inner diameter D _{N of} the nozzle are D _R ≦ 3.
It is set to the relationship of _DN . Usually, the nozzle flow path has a funnel-shaped tapered shape, and the inner diameter at the tip is the smallest. However, the inner diameter of the nozzle is sufficiently smaller than the inner diameter of the nozzle flow path. Therefore, there is a dimensional difference between the inner diameter of the tip of the nozzle flow path and the inner diameter of the nozzle. This dimensional difference prevents the ink from flowing smoothly from the nozzle flow path to the nozzle, and causes a problem that air bubbles are likely to remain on a shelf generated at a joint between the tip of the nozzle flow path and the plate surface of the nozzle plate. The remaining air bubbles absorb the pressure generated by the piezoelectric element, and cause problems such as that a required amount of ink droplet is not ejected.

The inventor of the present application has studied this point, and as a result, has found that the inner diameter D _R of the tip of the nozzle flow path is equal to the inner diameter D _{N of} the nozzle.
It was experimentally confirmed that if it is less than three times, it is difficult for air bubbles to remain at the joint between the substrate and the nozzle plate.

According to the second aspect of the present invention, if the inner diameter D _R of the tip of the nozzle flow path and the inner diameter D _{N of the} nozzle are set to the above-mentioned sizes, the substrate and the nozzle plate can be formed. It was confirmed that the misalignment between the two can be absorbed when bonding the two, and that the bonding can be performed relatively easily.

[0015]

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

FIG. 1 is a sectional view showing a configuration which is a feature of one embodiment of the present invention. In FIG. 1, reference numeral 2 denotes a substrate, and reference numeral 7 denotes a pressurizing chamber formed on the substrate 2. Pressurizing chamber 7
The nozzle flow path 14 is connected to the lower part of the nozzle. The nozzle flow path 14 is a flow path that tapers in a funnel shape from the pressurizing chamber 7. The nozzle flow path 14 is also formed in the substrate 2.

A nozzle plate 11 is joined to the lower surface of the substrate 2. A nozzle 15 is formed in advance on the nozzle plate 11, and the nozzle plate 11 on which the nozzle 15 is formed is attached to the substrate 2.

The feature of this embodiment is that the dimensional relationship between the inner diameter D _R of the tip (lower end in FIG. 1) of the nozzle flow path 14 connected to the pressurizing chamber 7 and the inner diameter D _{N of the} nozzle 15 is D _R. ≦ is that it is set to 3D _N. Thereby, it is possible to suppress the bubbles 21 as indicated by the broken lines from remaining on the shelf 20 generated at the joint between the nozzle flow path 14 and the nozzle plate 11.

More specifically, the ink supplied to the pressurizing chamber 7 is initially supplied to the pressurizing chamber 7 and the nozzle flow path 14.
Accumulate in At the tip end of the nozzle flow path 14, the nozzle flow path 1
A nozzle 15 having a diameter smaller than 4 is communicated. Accordingly, a shelf 20 is formed at the joint between the tip of the nozzle flow path 14 and the nozzle plate 11. It is preferable that the ink that accumulates in the nozzle flow path 14 spreads evenly in the nozzle flow path 14. May remain. The remaining air bubbles 21 absorb the pressure generated by the piezoelectric element when the ink in the nozzle flow path 14 is ejected, causing an ejection failure, and the amount of ink ejected for one time during printing is reduced. It becomes defective and a defective pixel occurs.

Therefore, as in this embodiment, the area of the shelf 20 is reduced by setting the dimensional relationship between the inner diameter D _R of the tip of the nozzle flow path 14 and the inner diameter D _{N of the} nozzle 15 to D _R ≦ 3D _N. It becomes smaller, and it is possible to suppress bubbles and the like from remaining here.

FIG. 2 is a plan view showing the relationship between the tip of the nozzle flow path 14 and the nozzle 15. The dimensional relationship between the two
When set as described above, the maximum value L of the distance from the inlet edge of the nozzle 15 to the wall surface of the nozzle channel 14, does not exceed twice the inner diameter D _N of the nozzle 15. Then, the area of the shelf 20 formed by this distance L is small,
No air bubbles remain here.

Incidentally, in the plan view of FIG.
Are shifted from the center of the nozzle 15.
Preferably, the tip of the nozzle flow path 14 and the nozzle 15 are concentric in plan view. However, an error in forming the nozzle flow path 14 formed in the substrate 2, an error in forming the nozzle 15 formed in the nozzle plate 11, The nozzle flow path 14 and the nozzle 15 may not always be arranged concentrically due to a displacement of the substrate 2 and the nozzle plate 11 or the like.

In this embodiment, even in such a case,
The inner diameter D _R of the tip of the nozzle flow path 14 and the inner diameter D _{N of the} nozzle 15
Is determined as described above, the misalignment between the nozzle flow path 14 and the nozzle 15 can be absorbed, and the positioning at the time of bonding the substrate 2 and the nozzle plate 11 can be performed relatively easily. .

If the overall dimensions of the ink jet head to which this embodiment is applied are shown as an example, the substrate 2 is 50 mm in width and 19 mm in length in plan view, and has 252 pressure chambers 7 therein. Can be listed.

The present invention is not limited to being applied only to the pressurized chamber, the nozzle flow path and the nozzle having the shape described in the embodiment. The same applies to those that do.

That is, the nozzle flow path 14 according to the present invention
The dimensional relationship between the nozzle 15 and the nozzle 15 is not limited by the nozzle flow path and the shape of the nozzle, and may have the dimensional relationship described in the claims. By adopting such a dimensional configuration, it is possible to prevent bubbles from remaining in the nozzle flow path immediately before the nozzle.

[0027]

According to the present invention, it is possible to suppress bubbles from remaining in the ink supplied to the nozzles of the ink jet head, and to provide an ink jet head having good performance.

[Brief description of the drawings]

FIG. 1 is an illustrative sectional view for explaining a dimensional relationship among a pressurizing chamber, a nozzle flow path, and a nozzle according to an embodiment of the present invention.

FIG. 2 is a schematic plan view for explaining a dimensional relationship between a tip portion of a nozzle channel and a nozzle.

FIG. 3 is a cross-sectional view illustrating a configuration of a portion related to a pressure chamber and a nozzle of a conventional inkjet head.

[Explanation of symbols]

 2 Substrate 7 Pressure chamber 11 Nozzle plate 14 Nozzle channel 15 Nozzle 20 Shelf

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Koichi Baba 1-2-28 Tamazuki, Chuo-ku, Osaka-shi, Osaka Inside Mita Kogyo Co., Ltd. (72) Inventor Keisuke Sumita 1-2-2 Tamatsuzo, Chuo-ku, Osaka-shi, Osaka No. 28 Inside Mita Kogyo Co., Ltd. (72) Junko Yamada, Inventor Junko Yamada 1-2-2, Takumazo, Chuo-ku, Osaka, Osaka Prefecture Inside Mita Kogyo Co., Ltd. No. 28 Inside Mita Kogyo Co., Ltd. (72) Inventor Masatake Hayashi 1-2-2 Tamatsukuri, Chuo-ku, Osaka-shi, Osaka No. 28 Inside Mita Kogyo Co., Ltd. No. 28 Inside Mita Kogyo Co., Ltd. (72) Koji Kuramasu Inventor 1-2-2 Tamazo, Chuo-ku, Osaka-shi, Osaka F-term inside Mita Kogyo Co., Ltd. 2C057 AG01 AG12 AG31 AG44 BA04 BA14

Claims (2)

[Claims] An ink jet head for performing printing by repeating ejection of ink droplets, wherein the ink jet head is connected to a pressure chamber which is pressurized at the time of ejection of ink droplets, and which is tapered in a funnel shape. a nozzle channel has, and a discharge nozzle communicating with the tip of the nozzle passage, the inner diameter D _R of the tip of the nozzle channel, the inner diameter D of the discharge nozzles
_N is set so that D _R ≦ 3D _N. 2. The ink jet head according to claim 1, wherein the discharge nozzle is formed on a thin nozzle plate prepared in advance, and the pressurizing chamber and the nozzle flow path are formed on a substrate. An ink jet head, wherein a substrate is formed by bonding.