JP3046456B2 - Inkjet head - Google Patents

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 performing recording by ejecting ink droplets toward a recording medium.

There are several types of ink jet heads. A so-called drop-on-demand type in which a voltage is applied to a piezoelectric element to deform it to generate a pressure wave in an ink liquid in a pressure chamber to eject ink droplets. Inkjet heads are highly practical.

[0003]

2. Description of the Related Art In a conventional drop-on-demand type ink jet head, electrodes of a piezoelectric element are provided one by one on both sides of the piezoelectric element. It was necessary to change the voltage and pulse width.

However, when the voltage or pulse width applied to the piezoelectric element is changed, the ejection speed of the ink droplet changes greatly, so that the volume of the ink droplet cannot be sufficiently changed. .

Conventionally, as shown in FIG. 5, a surface electrode 90 provided as a whole on the front side of a piezoelectric element is divided into a center electrode 91, a peripheral electrode 92, and an intermediate electrode 93 in between. The number of electrodes to be applied is changed according to the required ink droplet diameter (Japanese Patent Application Laid-Open No. 1-237151).

[0006]

However, when the rectangular electrode 90 is divided concentrically as described above, it is not easy to divide the electrode into a large number, and the area occupied by the gap between the electrodes is very small. It becomes big. For this reason, conventionally, the electrodes cannot be divided into a large number, and multi-gradation recording cannot be performed.

Accordingly, an object of the present invention is to provide an ink jet head capable of easily performing multi-tone printing without changing the voltage applied to the piezoelectric element or the pulse width.

[0008]

In order to achieve the above object, an ink jet head according to the present invention is provided with an ink supply path 5 for supplying an ink liquid as shown in FIG. And a pressure chamber 4 formed between the nozzle and the nozzle 3 for ejecting ink droplets, and a pressure wave is generated in the ink liquid in the pressure chamber 4 by being deformed by applying a voltage. The piezoelectric element 6 is arranged along the outer wall surface of the pressure chamber 4 so that ink droplets are ejected from the nozzle 3, and the piezoelectric element 6 is sandwiched between the piezoelectric element 6 to apply a voltage to the piezoelectric element 6. Back electrode 7 arranged on the outer wall side of pressure chamber 4 and ink supply path 5
And a surface electrode 8 that is divided by a plurality of division lines for sequentially dividing the surface electrode and the nozzle 3 side and that is disposed on the surface side of the piezoelectric element 6. It may be equally divided into a plurality.

[0009]

Since the surface electrode 8 is divided into a plurality of division lines for sequentially dividing the surface electrode 8 into the ink supply path 5 and the nozzle 3, the surface electrode 8 can be easily divided into a large number. The area occupied by the gap between the divided electrodes can be small.

[0010]

An embodiment will be described with reference to the drawings. 1 and 2 schematically show an ink jet head.

First and second substrates 1 and 2 joined together
Are formed of photosensitive glass, and the first substrate 1 has a pressure chamber 4 for applying pressure to the ink liquid,
An ink supply path 5 for supplying an ink liquid to the pressure chamber 4 is formed in a concave shape, and a nozzle 3 for ejecting an ink droplet is formed in the second substrate 2 perpendicularly to the plate surface. .

Then, the first and second substrates 1 and 2 are joined so that the nozzle 3 is located at the upper end of the pressure chamber 4, and a thin silver paste is applied to the outer wall surface of the first substrate 1. Sintered. Thus, the ink passage and the silver electrode 11 that pass from the ink supply passage 5 to the nozzle 3 through the pressure chamber 4 are formed.
Are formed.

The piezoelectric element 6 includes a back electrode 7 which is a negative electrode,
It is sandwiched between a surface electrode 8 serving as a positive electrode and a sandwich. Then, the piezoelectric element 6 is positioned in accordance with the position of the pressure chamber 4, and the back electrode 7 is adhered to the silver electrode 11 in close contact.

The surface electrode 8 provided in close contact with the front surface of the piezoelectric element 6 is divided by a plurality of division lines for sequentially dividing the ink into the ink supply path 5 and the nozzle 3. In FIG. 1, the surface electrode 8 is schematically shown as being divided into five parts, but in actuality, in this embodiment, it is divided into ten parts as shown in FIG.

FIG. 3 shows a divided state of the surface electrode 8. The pressure chamber 4 has a length of slightly more than 5 mm and a width of 1.2 mm.
The surface electrode 8 is formed as a whole with a length of 5 mm and a width of 1 mm, and nine 0.05 electrodes orthogonal to the long side of the pressure chamber 4.
By a linear division line having a width of mm, the ink is divided into ten equal parts on the ink supply path 5 side and the nozzle 3 side at a pitch of 0.5 mm.

The division of the surface electrode 8 can be performed by cutting the surface electrode 8 joined to the piezoelectric element 6 from the front side with a diamond cutter or the like.

Referring back to FIG. 1, a positive electrode of a drive power supply 10 is connected to each of the equally divided surface electrodes 8 via a voltage application area changeover switch 9. The negative electrode of the driving power supply 10 is connected to the silver electrode 11 that is in contact with the back electrode 7 and is grounded.

In the ink jet head configured as described above, the total length of the surface electrode 8 to which the voltage is applied is changed by switching the voltage application range changeover switch 9, thereby reducing the driving length of the piezoelectric element 6. Alternatively, the ink droplets can be ejected.

FIG. 4 shows the result of measuring the diameter of the recording dot printed by the ink droplet ejected from the nozzle 3 while changing the driving length of the piezoelectric element 6. In addition,
The drive length of the piezoelectric element 6 is sequentially increased from the nozzle 3 side to the ink supply path 5 side, and the applied voltage and the pulse width are constant.

From these results, it was confirmed that the recording dot diameter changed in the range of 38 to 100% depending on the driving length of the piezoelectric element 6.

[0021]

According to the ink jet head of the present invention, the surface electrodes of the piezoelectric element are divided by the plurality of division lines for sequentially dividing the surface electrodes into the ink supply path side and the nozzle side. And the gap between the electrodes is not large and the loss is small. Therefore, the surface electrodes can be divided into a large number and multi-tone recording without changing the applied voltage or pulse width to the piezoelectric element. To perform high-quality gradation recording.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of an embodiment.

FIG. 2 is a side sectional view of the embodiment.

FIG. 3 is a front view of the embodiment.

FIG. 4 is a diagram showing experimental results of an example.

FIG. 5 is a front view of a conventional example.

[Explanation of symbols]

 3 Nozzle 4 Pressure chamber 5 Ink supply path 6 Piezoelectric element 7 Back electrode 8 Front electrode

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-237151 (JP, A) JP-A-59-39556 (JP, A) JP-A-57-113943 (JP, U) (58) Survey Field (Int.Cl. ⁷ , DB name) B41J 2/045 B41J 2/055 B41J 2/205

Claims (1)

(57) [Claims] A pressure chamber having a fixed width formed between an ink supply path for supplying an ink liquid and a nozzle for ejecting ink droplets, the pressure chamber being formed in communication therewith; A flat-plate-shaped piezoelectric element having a constant width arranged along the outer wall surface of the pressure chamber so as to deform and generate a pressure wave in the ink liquid in the pressure chamber to eject an ink droplet from the nozzle; In order to apply a voltage to the piezoelectric element, a back electrode disposed on the outer wall surface side of the pressure chamber with the piezoelectric element interposed therebetween, and traverses a direction from the ink supply path side to the nozzle.
An ink jet head, comprising: a flat surface electrode which is divided at equal intervals by a plurality of division lines in a width direction and which is disposed on the surface side of the piezoelectric element.