JPH04299148A - Ink jet head - Google Patents

Abstract

PURPOSE:To make excellent resolution compatible with excellent gradation by making liquid ink discharged in atomized form. CONSTITUTION:Driving electrodes 4 are formed over a piezoelectric body 3 and a common electrode 5 is formed on the underside of said body 3. Slit members 2 are attached, facing the piezoelectric body, through gap members 6 to places where the driving electrodes 4 are not mounted on the surface of the piezoelectric body 3. Then ink is selectivity discharged from ink discharge chambers 7 that are made up to parts where the driving electrodes 4 of the piezoelectric body 3 intersect the common electrode 5, the gap members 6 and the slit member 2, and is further discharged through ink discharge ports 11.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet head for a printing device, and more particularly to an inkjet head for a printing device that selectively ejects liquid ink to form a record on a recording medium.

0002

2. Description of the Related Art Conventional inkjet heads that eject liquid ink to obtain recordings are shown in FIGS.
There is an inkjet head as shown in (b). This type of inkjet head is
The bimorph type piezo element 21 is vibrated to eject ink. When the ink chamber 22 contracts as shown in FIG. 6(a), ink droplets 24 are ejected from the orifice 23, and when the ink chamber 22 expands as shown in FIG. 6(b),
Ink is replenished from an ink tank (not shown) to prepare for the next ink discharge. Using the configuration shown in Figure 6(a) or 6(b) as one element, a multi-head is constructed by arranging several to several dozen elements in line, and the ink is deposited on any position on the recording medium to record. can be obtained.

[0003] In addition, there is a type of head that generates air bubbles in an ink chamber and discharges ink by the pressure of the expanding air bubbles.

0004

[Problems to be Solved by the Invention] In the inkjet head of the printing device as described above, the size of ink particles ejected by one vibration of a piezo element or one expansion of a bubble is approximately 100 μm to 200 μm. It is. With this particle size, in the case of binary recording such as character information, high resolution recording of about 150 dpi to 300 dpi is possible. However, since image information such as photographs and paintings includes density information,
In order to express this on a recording medium, it is necessary to express it using area gradation such as a dither matrix. Therefore, one data must be expressed by a plurality of ink particles, and a problem arises in that resolution decreases when gradation is improved. For this reason, it has been difficult to achieve both high resolution and high gradation.

[0005] Also, a piezo element 2 is provided for each orifice 23.
1, high precision and high integration are required for the formation. Therefore, it has been extremely difficult to manufacture large linear inkjet heads and even high-resolution inkjet heads at low cost.

[0006]

[Means for Solving the Problems] An inkjet head of the present invention includes a resonator made of a piezoelectric material having electrodes formed on both sides, and a resonator parallel to the resonator such that a gap is created between the resonator and the resonator. a drive circuit connected to the formed slit member and the electrode to generate a signal that periodically varies the electric field in the piezoelectric body and vibrates the resonator, selectively spraying ink from the gap in the form of a mist. It is characterized by recording by ejecting it.

[0007]Furthermore, it is characterized in that a groove or a notch is formed between each of the electrodes from the ink ejection end face of the resonator.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings.

The principle of ink ejection by an inkjet head according to an embodiment of the present invention will be explained using FIGS. 1 and 2.

1 is a resonator, and as shown in FIG.
It has a structure in which a drive electrode 4 and a common electrode 5 are patterned on both surfaces, respectively. The drive electrode 4 and the common electrode 5 are each connected to a drive circuit (not shown). The drive circuit generates a drive signal with a frequency that causes the piezoelectric body 3 to resonate in the thickness direction. The piezoelectric body 3 is polarized in the thickness direction, and by applying an electric field between one of the drive electrodes 4 and the common electrode 5, the piezoelectric body 3 can be expanded and contracted in the thickness direction at 12 portions.

2 is a slit member with a distance of several μ between it and the resonator 1.
A gap of more than ten μm is formed from m to 100 μm, and this gap becomes the ink ejection chamber 7. The thickness of the ink discharge chamber 7 is less than ten-odd micrometers, and the ink in the ink supply chamber 9 is always filled up to the ink discharge holes 11 of the ink discharge chamber 7 due to capillary action. The ink filled in the ink discharge chamber 7 has a resonator 1
are in contact with each other. This resonator 1 is subjected to resonant vibration in the thickness direction by a drive circuit, and the vibration energy is transmitted to the ink.

The vibrational energy propagated to the ink finally forms a surface wave at the ink interface of the ink discharge hole 11,
When the electrical energy input to the resonator 1 increases beyond a certain value, ink particles separate from the surface waves. Then, ink particles having a particle size corresponding to the vibration frequency of the resonator 1 are ejected in the D direction.

As an inkjet head according to an embodiment of the present invention, a line type inkjet head with a recording density of 100 dpi (dot/inch) and 120 ink ejection holes was prepared.

In this embodiment, PZT ceramics was used for the resonator 1, and the drive electrode 4 and common electrode 5 were formed in accordance with the dot pitch by sputtering and photolithography. A gap member 6 for maintaining a constant distance between the resonator 1 and the slit member 2 is formed in the slit member 2 for each ink ejection hole. The formation method is to form an aluminum thin film layer with a thickness of several to several tens of micrometers on the slit member 2 by sputtering, and to form the ink discharge chambers 7 by etching the aluminum thin film layer at the pitch of the ink discharge holes by a photolithography process.

By bonding the slit member 2 provided with the gap member 6 to the resonator 1, an ink discharge chamber 3, an ink discharge hole 11, and an ink supply chamber 9 are formed, thereby forming an ink jet head.

In this example, an inkjet head manufactured by the above process was used for evaluation. In the PZT ceramics used as the resonator in this example, approximately 2.2M
Resonant vibration in the thickness direction occurred at Hz, and when the amplitude of the drive voltage input to the resonator 1 was 30 (v) or more, atomized ink particles with a particle size of 10 μm or less were ejected from the ink ejection holes 11.

When an ink image was actually formed, it was confirmed that the printing density changed extremely smoothly due to the change in the coverage of the ink on the recording medium due to the atomized ink. Unlike conventional inkjet heads, ink is ejected continuously while an electric field is applied between the drive electrode 4 and the common electrode 5, so by controlling this time, the amount of ink ejected can be controlled. This is because it is possible. Therefore, by using the inkjet head of the present invention, it is possible to modulate the density of each printed dot, and it is possible to record information including gradation information such as image information without reducing resolution.

[0018]Also, quick drying is a major factor in high-speed printing, and since the inkjet head of the present invention deposits the ink on the recording medium in the form of a mist with a particle size of several micrometers, it is quickly deposited on the paper. Compared to conventional inkjet heads, the surface area relative to the ink volume is larger, so the quick drying properties are greatly improved.

Further, another embodiment of the present invention will be explained using FIGS. 3 and 4. 3 and 4 schematically show the structure and shape of the resonator portion of the resonator with the cut 10 and the groove 13, respectively. Here, a dicing saw is used to make one cut between the electrodes with the same configuration as above.
0 and grooves 13 were inserted to form a resonator 1, and a slit member 2 (not shown) was bonded to form an inkjet head.

FIG. 5 shows the vibration amplitude of the end face of the ejection hole when an electric field is applied to the electrode in the center of the figure.
Curve b) and the one without any modification (curve c) are shown.

By providing the cuts or grooves, the interference of the non-vibrating portions with the vibrating portions is alleviated and a larger expansion/contraction amplitude is obtained. When a 0.6 mm PZT ceramic was used as the piezoelectric body, the amplitude when a voltage of 10 V was applied was 8 nm without any modification, 12 nm with grooves, and 15 nm with cuts. Also,
A significant improvement in crosstalk was also seen by providing a space between the electrodes. As a result of the above, the efficiency of ink atomization with respect to voltage was greatly improved compared to the case where no cuts were added.

[0022] The same effect as described above was also observed for a mechanism that selectively supplies ink to the gap between the resonator and the slit member and atomizes it.

[0023]

[Effects of the Invention] According to the present invention, by selectively supplying ink between the resonator and the slit member which are resonantly vibrating in the thickness edge mode, the ink can be ejected in the form of a mist. This has the effect that density modulation within one dot is possible, and an inkjet head that can print image information without reducing resolution can be realized. Furthermore, since each ink ejection chamber can be easily formed in the present invention, an inexpensive and high-density line-shaped head can also be realized.

Furthermore, by printing with the inkjet head of the present invention, there is also the effect that the drying properties of the ink are significantly improved compared to those printed with a conventional inkjet head.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the structure of an inkjet head according to an embodiment of the present invention.

FIG. 2 is a sectional view of the inkjet head of the present invention.

FIG. 3 is a schematic diagram of an inkjet head according to another embodiment of the present invention.

FIG. 4 is a schematic diagram of an inkjet head according to another embodiment of the present invention.

FIG. 5 is a diagram showing the vibration amplitude of the ejection end face of the inkjet head of this example.

FIG. 6 is a sectional view showing the principle of a conventional inkjet head.

[Explanation of symbols]

1 Resonator 2 Slit member 3 Piezoelectric body 4 Drive electrode 5 Common electrode 6 Gap member 7 Ink discharge chamber 8 Ink 9 Ink supply chamber 10 Notch 11 Ink discharge hole 13 Groove

Claims (2)

[Claims] 1. A resonator made of a piezoelectric material with electrodes formed on both sides; a slit member parallel to the resonator and formed so as to create a gap between the resonator; and a slit member connected to the electrode. and periodically varying the electric field within the piezoelectric body,
An inkjet head comprising a drive circuit that generates a signal to vibrate a resonator, and performs recording by selectively ejecting ink in the form of a mist from the gap. 2. The inkjet head according to claim 1, wherein a groove or notch is formed between each of the electrodes from an ink ejection end face of the resonator.