JPH06218923A - Ink jet head - Google Patents

Abstract

PURPOSE:To obtain equalization of discharging ink speed by a method wherein a plurality of nondischarge passages are provided respectively to both ends of an ink passage arrangement. CONSTITUTION:In an ink jet head wherein arranged ink passages 4A, 4B, 4C and nozzles discharging ink which are arranged respectively in contact with the ink passages 4A, 4B, 4C are provided, and a part or all of the ink passage 4 is composed of piezoelectric materials, a plurality of nondischarging passages 13A-13E are provided respectively to both ends of the arrangement of the ink passages 4A, 4B, 4C.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to ink jet printers. More specifically, the present invention relates to an inkjet head of an inkjet printer that selectively deposits ink droplets on a recording medium to form an image.

[0002]

2. Description of the Related Art In recent years, ink jet printers have been rapidly developed due to advantages such as high speed printing, low noise and high printing quality. As a general method, there is a method in which a piezoelectric material is used to generate a pressure pulse in an ink chamber to eject an ink droplet from a nozzle.

However, in this method, since the efficiency of the piezoelectric material is low, the ink jet head itself becomes large.
In addition, the manufacturing process becomes complicated, it is not suitable for mass production, and as a result, it becomes expensive. Further, since it is difficult to increase the density of the nozzle array, it is difficult to obtain high print quality. Due to these issues, it has not been widely spread.

As a method for solving the problem of this system, Japanese Patent Laid-Open No. 63-247501 discloses a method of forming a plurality of parallel rectangular cross-section flow paths having intervals in the nozzle arrangement direction. An electrode is formed on a part or the entire surface of the side wall of the side wall, and the side wall is partly or entirely formed of a piezoelectric material, and the side wall is deformed parallel to the direction in which the flow paths are arranged,
There has been proposed an inkjet head that changes the pressure in the flow path to form an ink droplet at one end of the flow path and eject the ink drop.

The structure of the conventional ink jet head is
This will be described with reference to FIG.

FIG. 3 is a perspective view showing the structure of a conventional ink jet head. 1 is a piezoelectric substrate, 2 is a nozzle plate, 3 is a nozzle, 4 is an ink flow path, 5 is a side wall made of a piezoelectric material (hereinafter abbreviated as piezoelectric side wall), 6 is an upper substrate, 7 is an ink supply port, and 9 is ink. Discharge port, 10 is an electrode, 12 is a non-ejection channel, 13 is an adhesive, 15 is a channel end opening, 1
Reference numeral 6 is a mounting portion electrode.

In this ink jet head, a large number of ink flow paths 4 which are parallel to each other are formed. The ink flow path 4 is
Comprised of a groove formed in the piezoelectric substrate 1 and the upper substrate 6,
Its cross-sectional shape is rectangular. One end of the ink flow path 4 is
It is connected to the slit-shaped ink discharge port 9 and connected to the nozzle 3 formed on the nozzle plate 2. Further, the other end of the ink flow path 4 is connected to the ink supply port 7, and passes through the flow path end opening 15 and the ink supply port 7 corresponding to each ink flow path 4 to an ink storage tank (not shown). Connected.

The ink ejection operation of the conventional ink jet head will be described with reference to FIG.

In FIG. 5, the piezoelectric side wall 5 is formed of two piezoelectric ceramics having different polarization directions 11.

FIG. 5A shows a state in which a voltage pulse is not applied to the electrodes 10 formed on both surfaces of the piezoelectric side wall 5 by an electric driving means (not shown). Figure 5 (b)
At this time, when a voltage pulse is applied, the piezoelectric side wall 5 is deformed to the reversal plane of the polarization direction of the piezoelectric side wall, and the pressure generated by the volume of the ink flow path 4 is reduced.
A part of the ink that fills the ink is discharged to the ink storage tank side through the ink supply port 7, and the other part is ejected from the nozzle 3 as an ink droplet for printing.

The ink supply to the nozzle portion after the ink droplets are discharged is supplied from the ink storage tank to the nozzle 3 through the ink supply port 7 and the flow path 4 by the capillary force of the nozzle 3 in FIG.

A method of manufacturing a flow path portion of a conventional ink jet head will be described below. FIG. 6 is a sectional view of a conventional ink flow path.

As shown in FIG. 6A, the ink flow path 4
An electrode 10 is formed on the piezoelectric substrate 1 on which the electrodes have been formed.

As shown in FIG. 6 (b), unnecessary electrodes formed on the adhesive surface 20 of the piezoelectric substrate 1 are removed by plane polishing to form a flat adhesive surface 20. Then, the adhesive 13 is applied uniformly.

As shown in FIG. 6B, the upper substrate 6 is bonded. The upper substrate 6 is adhered and pressure is applied to the adhesive 13
To cure. The adhesive 13 flows into the ink flow path 4 as shown in the figure and is cured.

Hereinafter, the nozzle plate, the ink supply means, etc. were formed to have the structure shown in FIG.

[0017]

However, the conventional ink jet head has the following problems.

The problems of the prior art will be described below with reference to FIGS. 4 and 7.

FIG. 4 is a sectional view of the conventional ink jet head in which the ink flow path is viewed from the front.

An adhesive 13 is used to bond the piezoelectric substrate 1 and the upper substrate 6. In the ink jet head of this system, the piezoelectric side wall 5 is driven to serve as pressure generating means. In order to keep the loss with respect to the driving power low, the adhesive layer between the piezoelectric substrate 1 and the upper substrate 6 needs to be as thin as possible.

In order to prevent ink leakage between the adjacent ink flow paths 4, it is desirable that the contact surfaces of the piezoelectric substrate 1 and the upper substrate 6 be completely covered.

In order to obtain the adhesive layer as thin as possible, the piezoelectric substrate 1 and the upper substrate 6 are bonded together under pressure. Therefore, the adhesive 13 flows out into the ink flow path 4 and the non-ejection flow path 12, and is hardened on the upper substrate bonding surface 20 and a part of the surface of the piezoelectric side wall 5. The adhesive 13 that has flowed out suppresses the deformation of the piezoelectric side wall 5 and causes a loss in drive power.

As shown in FIG. 4, the flow of the adhesive into the ink flow path 4 is uniform, but only the non-ejection flow paths 12 on both outer sides of the array of the ink flow paths 4 are outside the flow path array. The adhesive 13 flows in from the side wall 14. Therefore, the amount of the adhesive that flows into the non-ejection channel 12 and cures becomes large.

As described above, since the deformation of the piezoelectric side walls 5A forming the ink flow paths 4A at both ends of the array is suppressed, the ejection speed of the ink ejected from the ink flow paths 4A becomes slow.

In this method, an image is formed on the recording medium by moving the inkjet head or the recording medium while ejecting ink. Therefore, the image is disturbed on the recording medium corresponding to both ends of the arrangement of the ink flow paths 4, and it is difficult to obtain a high-quality image. Moreover, it has been a major obstacle in attempting to further increase the printing speed.

Attempts have been made to reduce the amount of the adhesive 13 used for joining the upper substrate 6, but ink leakage has occurred at the upper substrate bonding surface 20 between the adjacent ink flow paths 4, resulting in a stable improvement. There wasn't.

Further, the conventional ink jet head has the following problems.

FIG. 7 is a view of a cross section of an ink flow path of a conventional ink jet as viewed from above.

Conventionally, one non-ejection channel 12 was provided on both outsides of the arrangement of the ink channels 4, but the nozzle 3 was not provided.

Therefore, the air accumulated in the non-ejection flow passage 12 is left in the flow passage, the ink filling amount is insufficient, and the state of the remaining air differs depending on the use environment, and the piezoelectric side wall 5A is not affected. The influence is large, and the ink ejected from the ink flow path 4A has a different speed from the ink ejected from the other ink flow paths 4B, 4C, 4D, ....

Alternatively, similarly, the ink in the non-ejection channel 12 is altered and solidified and adheres to the piezoelectric side wall 5A,
Similar adverse effects occur.

The present invention solves the above problems, and an object of the present invention is to provide at low cost an ink jet head having excellent printing quality and capable of high speed printing.

[0033]

The ink jet head of the present invention has an array of flow channels and a nozzle surface for ejecting ink disposed in the flow channels, and a part or the whole of the flow channels is piezoelectric. In an inkjet head made of a material, a plurality of flow paths that do not eject ink are provided at both ends of the flow path array, or the flow path that does not eject ink is provided outside the location other than where ink is supplied. It is characterized in that it has a hole leading to.

[0034]

EXAMPLES Examples of the present invention will be described below with reference to the drawings, but the present invention is not limited to the following examples.

First, FIG. 1 shows a first embodiment of an ink jet head of the present invention, and is a view of a cross section of an ink flow path as viewed from the front.

In FIG. 1, 1 is a piezoelectric substrate, 4 is an ink flow path, 5 is a piezoelectric side wall, 6 is an upper substrate, 10 is an electrode, and 11
Is a polarization direction, 12 is a non-ejection flow path, 13 is an adhesive, 14 is a piezoelectric side wall outside the flow path array, and 20 is an upper substrate bonding surface.

The ejection operation of the ink jet head is the same as that of the conventional ink jet head.

As shown in FIG. 1, the ink jet head of this embodiment has two non-ejection channels 12A and 12B on both outer sides of the array of the ink channels 4 at the same intervals as the array of the ink channels 4. Is provided (only one side of the arrangement of the ink flow path 4 is shown. The same applies hereinafter).

The amount of adhesive 13 flowing in is determined by the non-ejection flow path 1
In 2A, the amount is large compared to other flow paths. However, the amounts of the adhesive 13 that have flowed into the non-ejection channels 12B and the ink channels 4 are all uniform, and the ink channels 4A, 4B, and 4
Piezoelectric side wall 5 which forms C, 4D ... and participates in ink ejection
The amounts of the adhesives 13 of B, 5C, 5D ... All became uniform.

As a result, in all the ink flow paths 4 involved in the ink ejection, the ejection speed variation of the ejected ink can be kept within 10%.

Further, by the means described below, it is possible to further reduce the variation in the ink ejection speed of the ink flow paths 4A at both ends of the ink flow path array.

FIG. 2 is a second embodiment of the present invention and is a view of the cross section of the ink flow path of the ink jet head as seen from above.

In FIG. 2, 2 is a nozzle plate, 3 is a nozzle, 4 is an ink flow path, 5 is a piezoelectric side wall, 12 is a non-ejection flow path, 14 is a piezoelectric side wall outside the flow path array, and 17 is a non-ejection nozzle. .

The ejection operation is similar to that of the conventional ink jet head.

As shown in FIG. 2, the non-ejection nozzle 17 is provided in the non-ejection channel 12B so that a normal head cleaning operation is performed (ink is filled in the ink channel by suction from the nozzle side). It is possible to always fill with new ink.

This makes it possible to equalize the loads that suppress the deformation of the piezoelectric side wall 5 due to driving, of all the piezoelectric side walls 5B, 5C, 5D, ... Dispersion of discharge speed
It became possible to set it within 3%.

[0047]

According to the ink jet head of the present invention, ink is ejected from all ink flow paths at a uniform speed,
It is possible to provide an inkjet head that ensures excellent printing quality and enables high-speed printing.

[Brief description of drawings]

FIG. 1 is a front view showing a cross-sectional structure of an ink flow path of an inkjet head according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a cross-sectional structure of an ink flow path of an inkjet head according to a second embodiment of the present invention from above.

FIG. 3 is a perspective view showing a configuration of a conventional inkjet head.

FIG. 4 is a front view showing a cross-sectional structure of an ink flow path of a conventional inkjet head.

FIG. 5 is a view showing a principle of ink ejection of a conventional inkjet head in a cross section of an ink flow path.

FIG. 6 is a cross-sectional view of an ink flow path showing a conventional inkjet head manufacturing method.

FIG. 7 is a diagram showing a cross-sectional structure of an ink flow path of a conventional inkjet head from above.

[Explanation of symbols]

 1 Piezoelectric Substrate 2 Nozzle Plate 3 Nozzle 4 Ink Channel 5 Piezoelectric Sidewall 6 Upper Substrate 10 Electrode 11 Piezoelectric Sidewall Polarization Direction 12 Non-Ejection Channel 13 Adhesive 20 Upper Substrate Bonding Surface

Claims (3)

[Claims] 1. An ink jet head having an array of flow paths and a nozzle surface for ejecting ink, which is arranged in contact with the flow path, wherein a part or the whole of the flow path is made of a piezoelectric material. An ink jet head characterized in that a plurality of flow paths that do not eject ink are provided at both ends of the flow path array. 2. The ink jet head according to claim 1, wherein a hole that communicates with the outside of the flow path is provided in the flow path that does not eject the ink, in addition to the location where the ink is supplied. 3. An ink jet head having an array of flow paths and a nozzle surface for ejecting ink, which is disposed in contact with the flow paths, wherein a part or the whole of the flow path is made of a piezoelectric material. An ink jet head characterized in that a hole communicating with the outside of the flow path is provided in addition to a position where ink is supplied to the flow path that does not eject ink.