JPS58107357A - Ink jet head - Google Patents

Abstract

PURPOSE:To enable to expand the region capable of obtaining adequate ink particles by providing a nozzle which satisfies the special relationship between the diameter of the nozzle and the length of the nozzle at an ink jet head. CONSTITUTION:In an ink jet head which granulates ink by injecting the ink from an ink injecting nozzle 3 and varying the pressure by providing electro- mechanical converting means 4 which applies vibration energy through a liquid chamber 2, the ink injecting nozzle 3 which communicates with the chamber 2 and a vibrator provided at the wall of the chamber 2 to the ink in the chamber, the nozzle 3 which satisfies the relationship of ls/d<1, where (d) represents the diameter of the nozzle 3 and ls represents the length of the nozzle is provided. It is preferred to provide means for heating the ink in the chamber 2, in the chamber 2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ink jet head for an ink jet printer having stable atomization characteristics.

In an inkjet head, pressurized ink is introduced into a liquid chamber, the ink is ejected from a nozzle communicating with the liquid chamber, and an electro-mechanical conversion element applies vibrational energy to the ink to continuously turn the ejected ink into particles. ,
It has been experimentally confirmed that the shape of the nozzle greatly affects the particle formation characteristics.

For example, in Japanese Patent Publication No. 55-18625, if the through trade length of the nozzle is set to be less than IA of the wavelength λ determined by the inkjet flow velocity and the nozzle excitation frequency, the ink particle state will be affected by the inkjet printer's printing. It is said that it is possible to obtain a stable and wide area that is suitable for so-called high-speed satellites and no satellites.

For example, if Totoro uses a nozzle with a diameter (d) = 30 μmφ and sets the particleization wavelength to around λ/d = 5.5, that is, λ = 165 μm, then λ/2 =
However, actual experiments show that a stable particle formation region cannot necessarily be obtained with a nozzle length of λ/2 = 82.5 μm, and the nozzle length in this case must be limited to a narrower range. It turned out that this was not the case. In other words, the nozzle length (same as the straight length of the nozzle) is required for particle formation characteristics.
Not only that, but also the nozzle length and nozzle diameter have a correlated effect.

The present invention was made based on the results of an experiment in which the nozzle length and atomization wavelength were varied with respect to the nozzle diameter to find an appropriate atomization region, and the present invention was developed based on the results of an experiment in which the appropriate atomization region was determined by changing the nozzle length and atomization wavelength with respect to the nozzle diameter. It provides a head. A detailed explanation will be given below according to the drawings.

FIG. 1 shows the structure of an inkjet device to which the present invention is applied. In the figure, 1 is a head block that constitutes a liquid chamber 2 inside, 3 is an ink jet nozzle that communicates with the liquid chamber 2, and 4 is an electro-mechanical conversion element that vibrates when driven by an external AC power source. Examples include piezoelectric vibrators. 5 is a diaphragm that vibrates integrally with the electro-mechanical conversion element 4, and 6 is an ink supply port. As shown in Fig. 2, the nozzle 3 has a diameter of d1 and a nozzle length of 1. It shall be represented by -. The nozzle part has a good head protrusion, and its material can be various metals, semiconductor crystals, glass, etc.

In the ink jet head constructed in this way, pressurized ink is supplied from the ink supply port 6 into the liquid chamber 2 and is ejected from the nozzle 3. On the other hand, the vibration of the electro-mechanical transducer 4 imparts vibrational energy to the ink via the diaphragm 5, and the ejected ink undergoes pressure modulation, so that it is continuously turned into particles. These ink droplets are usually selectively charged, and the charged ink droplets are deflected and printed on recording paper or the like.

By the way, when the ejected ink is turned into particles, very small particles may be generated as the main particles are separated, and these very small particles are usually called satellites. Furthermore, among the particle states in which satellites are generated, there are those in which the flying speed of the satellite is faster than the main particle, and therefore it catches up with the main particle flying ahead and merges with it, and vice versa, the satellite's flying speed is slower than the main particle, and therefore The particles that coalesce into the subsequent main particles are called dust, and the former are generally called fast satellites and the latter slow satellites. The particle state suitable for printing is in the case of no satellites, where no satellites occur.
It is well known that this is the case with high-speed satellites.

Figure 3 shows the usable particulate region at an ink temperature of 15°C to 45°C, that is, the region of no satellites and high-speed satellites) Ml (catch up within one wavelength). Wavelength λ (or wavelength to nozzle diameter ratio λ/
d), and the vibration amplitude (represented by the voltage Vp applied to the electro-mechanical transducer 4) is plotted on the vertical axis, and the nozzle diameter d is 30 μm and the nozzle length 1 m is 20 μm and 33 μm.
This is the case of m.

As is clear from Figure 3, 1s = 20μm is 7
! @ = 33 μm, the region extends to the higher side of λ (or λ/a ), and λ/a = 5.5 (λ = 16
The stability of particle formation (marnon) is greatest when it is set around 5 μm). For nozzles with No. 13 between 20 and 30 μm, an intermediate particulate area is given, and it has been confirmed that the closer to 20 μm, the wider the area. In addition, the ink physical property values used experimentally are viscosity 1.5 to 3.1 cp (T = 15
~45°C), surface tension 55~62 dynes, 4(T
= 15~45℃), density 1.04~1.05 E//C
m3 (T=15-45°C).

Figure 4 is a particulate area diagram for a nozzle diameter d of 32 μm. Similar to the one in Figure 3, the ratio of nozzle length ls to nozzle diameter d is larger than 1 and smaller than 1, and the area is The results show that there is a clear difference in width.

As explained above, according to the present invention, the atomization characteristics of ink are greatly influenced by the shape of the nozzle, especially the correlation between the nozzle length and the nozzle diameter, and the relationship between the nozzle length ls and the nozzle diameter d. By setting 1B/d<1 between the two, it is possible to expand the appropriate particle formation area and to perform stable printing.

By providing a means for controlling the temperature of the ink in a part of the liquid chamber, it is possible to eliminate one of the external disturbances that affect the atomization characteristics, and more stable printing can be performed.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of an ink jet head to which the present invention is applied, Fig. 2 is an enlarged view of the nozzle section in Fig. 1, and Figs. FIG. 2... Liquid chamber, 3... Nozzle, 4... Electro-mechanical conversion element, 5... Vibration plate, d... Nozzle diameter, ls
...Nozzle length O Figure 1 Figure 2 Figure 3 Figure 4! S・2 5μ

Claims (2)

[Claims] (1) A liquid chamber, an ink ejecting nozzle communicating with the liquid chamber, and an electro-mechanical conversion means that applies vibrational energy to the ink in the liquid chamber via a vibrating section provided on the wall of the liquid chamber. In the inkjet head, which ejects ink from the nozzle and modulates the pressure of the ink to form particles, the diameter of the nozzle is d1 and the nozzle length is A'a.
, an inkjet head 0 characterized by setting h4<1. (2) The liquid chamber has a means for heating the ink in the liquid chamber in a part thereof.
Ink jet head described in ).