JPH04216940A - Ink emitting head - Google Patents

Abstract

PURPOSE:To obtain an ink emitting head effectively re-dispersing the pigment in ink by the oscillation of ultrasonic waves and excellent in the emitting stability of ink by providing an ultrasonic actuator to the outer wall of the ink emitting head. CONSTITUTION:An ink emitting nozzle 11 receives ink wherein pigment 17 is dispersed in a dispersing medium 20 and has a structure emitting an ink droplet 18 from each of the nozzles 16 provided to a nozzle plate 15 by the vibration of a piezoelectric element 14. An ultrasonic actuator 12 capable of oscillating ultrasonic waves of 46kHz is arranged to the outer wall 13 of the ink emitting head 11. The whole of the container containing the ink is vibrated by ultrasonic waves generated from the ultrasonic actuator and the flocs of the pigment are re-dispersed by ultrasonic dispersing force and the ink can be stably emitted.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a non-impact printing method, and more particularly to an inkjet recording device that forms characters or images on a medium such as recording paper by ejecting ink droplets. Regarding the ejection head.

0002

2. Description of the Related Art Conventionally, ink jet recording apparatuses can be roughly divided into two types: continuous type and on-demand type.

Various inks have been reported for use in such inkjet recording apparatuses, in which pigments are dispersed in a dispersion medium. These advantages include excellent fixing properties, sharpness, color density, print bleeding, water resistance, and light resistance, and their future is attracting attention.

However, ink in which pigments are dispersed in a dispersion medium has the problem that the dispersed pigments become large particles over time, causing clogging in ink ejection nozzles, etc., and making it impossible to obtain stable ejection characteristics. . Several attempts to solve the above problems have also been reported. Such attempts are related to improvements in ink or recording devices.

For example, regarding the dispersion stability of ink, Japanese Patent Laid-Open No. 56-147861, Japanese Patent Laid-Open No. 147871
No. 1, JP-A-57-10661, etc. use a specific dispersant to improve the storage stability of the pigment in the ink. Furthermore, JP-A-57-12076 discloses a method for reducing the difference in specific gravity between a pigment and a dispersion medium to a specific value or less, and JP-A-61-55547 discloses a method for synthesizing pigments in a liquid medium in which a dispersant is present. Proposed.

[0006] Furthermore, as an example of redispersing pigment agglomerates due to improvements in recording devices, for example, Japanese Patent Publication No. 2-5588 describes a method for redispersing pigment aggregates when pigment supply ink supplied to a jet nozzle adheres to a filter medium. A method has been proposed in which an ultrasonic vibrating horn is used to crush pigment aggregates and supplied to a jet nozzle, and in JP-A-60-110458, a method is proposed in which a magnetic stirrer is used for the ink in an ink tank to prevent the pigment from settling. ing.

[0007]

[Problem to be solved by the invention] In the case of adding a specific dispersant or specific additive to the ink to impart dispersion stability to the dispersed pigment in the ink, the objective has been achieved in the short term. However, in the long term, pigment aggregation and sedimentation have not been completely eliminated.

[0008] Regarding the improvement of the recording device to re-disperse pigment aggregates, for example, the above-mentioned Japanese Patent Publication No. 2-55
In 88, it is true that the ink that has passed through the filter medium is redispersed and does not cause clogging of the ejection nozzle, etc., but this is an effective means when ejecting ink continuously, and it is not necessary to stop the operation of the recording device. However, if the recording apparatus is left still, the pigment in the ink around the ejection nozzle will aggregate again, making it impossible to stably eject the ink. Furthermore, although the method disclosed in JP-A-60-110458 has the effect of suppressing the sedimentation of the pigment in the ink, it does not have the ability to redisperse the pigment in the ink that has once aggregated.

Therefore, an object of the present invention is to effectively redisperse the pigment in the ink and improve the ink ejection stability in an inkjet recording device that performs print recording using ink in which pigment is dispersed in a dispersion medium. Our goal is to provide an excellent ink ejection head for

0010

[Means for Solving the Problems] The ink ejection head of the present invention is an ink ejection head that performs print recording by ejecting ink in which pigments are dispersed in a dispersion medium onto a transfer medium. The present invention is characterized in that it is comprised of a piezoelectric element that deforms and ejects ink according to the pressure, a nozzle plate having a nozzle arranged opposite to the piezoelectric element, and an ultrasonic actuator installed on the outer wall.

[0011]

[Operation] By vibrating the entire ink ejection head with ultrasonic waves generated from an ultrasonic actuator that is a component of the head, aggregates of pigment in the ink contained in the ink ejection head are redispersed. That is, by vibrating the entire container (ink ejection head) containing ink, pigment aggregates can be redispersed by ultrasonic dispersion force.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a sectional view of an ink ejection head according to the present invention.

The ink ejection head 11 contains ink in which a pigment 17 is dispersed in a dispersion medium 20, and the piezoelectric element 1
The structure is such that ink droplets 18 are ejected from nozzles 16 provided on a nozzle plate 15 by the vibration of 4. Further, an ultrasonic actuator 12 capable of transmitting ultrasonic waves of 46 kHz is installed on the outer wall 13 of the ink ejection head 11. Further, an ink supply port 19 is opened in the outer wall 13 so that ink can be supplied into the ink discharge head 11, and ink is supplied to the vicinity of the nozzle 16. Note that the ultrasonic actuator 12 may be installed at a position where the entire ink ejection head 11 vibrates, and can also be installed, for example, at a position C (outside the ink ejection head) shown by a dotted line.

A pulse signal was input to the piezoelectric element 14 so that it vibrated at 4 kHz. Outer wall 1 of ink ejection head 11
3 and the nozzle plate 15 are preferably made of a material having a high Young's modulus, for example, a metal such as iron or nickel. By adopting the structure described above, the ink ejection head of the present invention can apply ejection energy directly to the ink, so there is no escape of energy to other parts, and the voltage applied to the piezoelectric element for ink ejection is reduced. can be lowered.

FIG. 2 is a perspective view showing the main components of a printing apparatus (hereinafter referred to as a printing apparatus) equipped with the ink ejection head of the present invention. 21 is a transfer medium;
The paper is fed in the direction of arrow A shown in the figure by the platen 23, capstan roller 24, and paper holding roller 22. Carriage feed guides 26 and 27 are provided in a direction facing the platen 23, sandwiching the transfer medium therebetween. The ink ejection head 11 is mounted on a carriage 25 attached to carriage feed guides 26 and 27. The carriage 25 can be moved in the direction of arrow B parallel to the platen 23 shown in the figure by a motor and carriage moving wire (not shown). The configuration of a recording apparatus using the ink ejection head according to the present invention is not limited to the above configuration.

The printing test in the present invention was carried out as follows.

A printing test was carried out using the ink ejection head having the structure shown in FIG. 1 and mounted on a recording apparatus having the structure shown in FIG. As an ultrasonic actuator, 5ED-50-570 manufactured by Murata Manufacturing Co., Ltd. was installed in the head.
It was vibrated at kHz. Note that the actual ink discharge test was conducted after operating the ultrasonic actuator for 1 minute before printing on the entire ink discharge head. In addition, for the purpose of confirming the effects of the present invention, the ink ejection head used for the ink ejection test was pre-contained with ink in which pigments were dispersed in a dispersion medium, sealed to prevent the ink from drying, and kept in a high temperature tank at 40°C for 2 months. I used the one that had been left alone.

The following ink composition was used.

Carbon black 3wt% dispersant 0.3wt% insulating solvent 95wt% terpene resin 1.7wt% The ink was prepared by dispersing it for 10 hours using a paint shaker and filtering it with a filter to reduce the particle size of the pigment to 5 μm or less. And so.

A printing test for a comparative example of the present invention was conducted as follows.

Before the printing test, a test was conducted in the same manner as in the example except that the ultrasonic actuator was not activated.

As a result of observing whether the ink was stably ejected in the comparative example and the example, the ink was ejected in the present example immediately after a signal was sent to the piezoelectric element. Further, even after continuous printing for one hour, ink ejection was performed stably.

Regarding the comparative example, ink ejection could not be confirmed immediately after a signal was sent to the piezoelectric element, and after about 5 minutes, ink with a low pigment concentration was ejected, and printing with a low density was confirmed, but immediately Ink ejection has stopped.

[0024]

[Effects of the Invention] When the ink ejection head of the present invention is used,
It becomes possible to stably eject ink in which pigments, which have traditionally been expected to have excellent effects, are dispersed in a dispersion medium.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an ink ejection head according to the present invention.

FIG. 2 is a perspective view of a recording apparatus equipped with an ink ejection head according to the present invention.

[Explanation of symbols]

11 Ink discharge head 12 Ultrasonic actuator 13. External wall 14 Piezoelectric element 15 Ni film

Claims (1)

[Claims] 1. An ink ejection head that performs print recording by ejecting ink containing a pigment dispersed in a dispersion medium onto a transfer medium, comprising an outer wall and a piezoelectric element that is bonded to the outer wall and deforms in response to an input signal to eject ink. An ink ejection head comprising: a nozzle plate having a nozzle placed opposite to the piezoelectric element; and an ultrasonic actuator installed on the outer wall.