JPH0431056A - Ink jet head - Google Patents

Abstract

PURPOSE:To make an ink jet head adaptable to the use of a wax ink by a method wherein a magnetic passage enclosed with a magnetic body outside an ink chamber and a highly magnetic body of a diaphragm is formed and the temperature of an exothermic body on the diaphragm is so controlled as to change the magnetic permeability of the highly magnetic body, a member of the diaphragm, to excite the diaphragm into vibrations. CONSTITUTION:A permanent magnet is provided at a horizontal part 11 and a magnetic passage is formed by being enclosed with the Ni alloy part of a highly magnetic plate 8 and a diaphragm 9. Ink discharge is effected by energizing an electrode 18 to activate an exothermic body 17 to generate heat. Concerning the magnetic body of the diaphragm 9, its Curie temperature reaches near 150 deg.C due to the component ratio of the materials constituting a magnetic passage part 15 mounted by electrolytic process. When the exothermic body is energized, therefore, the magnetic permeability of the part heated by the exothermic body is reduced considerably, resulting the failure to retain the conventional balance of the magnetic suction force. For this reason, the magnetic suction force acts mainly upon the end part of the magnetic passage part 15 of the diaphragm having a still high magnetic permeability. At this time, the balance position is changed to produce about 6mum displacement near the center of the diaphragm 9.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a print head of an inkjet type printing device among donmatrix printing devices, which are one of the peripheral devices of personal computers and the like.

[Prior Art] A conventional technique similar to the present invention uses a piezo plate as a diaphragm, deforms the member by applying a voltage, and generates vibrations of the diaphragm in an ink chamber to generate ink droplets. There is a method of ejecting and causing it to fly. There is also a method in which a heating element is installed in the ink chamber, and the ink is ejected by the change in volume that occurs when the ink heated by the heating element becomes a gas.

[Problems to be Solved by the Invention] Among the above-mentioned conventional techniques, in the method using piezo diaphragms, when attempting to create a print head with a high-density nozzle configuration by reducing the distance between adjacent diaphragms, It is necessary to cut out a diaphragm with a minute width from a piezo plate, which requires advanced manufacturing technology, which poses an issue in manufacturing at a low cost. Furthermore, the method of heating the ink to generate gas has the problem that it cannot be used with ink having an extremely high boiling point, such as wax ink.

On the other hand, it has been pointed out that uniform printing quality should be ensured regardless of the paper surface condition or paper quality, and wax ink can be said to be suitable for this purpose. In consideration of this point, the present invention aims to improve a conventional method that can also be applied to wax ink, and to provide a method that can be manufactured more easily.

[Means for Solving the Problem] The present invention has one nozzle for generating one printing pixel, has a diaphragm paired with the nozzle, and has an ink chamber for each nozzle, or This is an inkjet head that has multiple nozzles and has an ink chamber for each nozzle.It uses a ferromagnetic material for part or all of the diaphragm, has a heating element on the diaphragm, and has a magnetic material outside the ink chamber. By forming a closed magnetic path with the ferromagnetic material of the diaphragm and controlling the temperature of the heating element on the diaphragm, the magnetic permeability of the ferromagnetic material, which is a member of the diaphragm, is changed to generate vibrations. It is characterized by being configured in such a way that it causes

[Function] In the above configuration, the diaphragm made of ferromagnetic material forms a closed magnetic path with the magnetic circuit provided outside the ink chamber, and the ferromagnetic material layer in the diaphragm portion is thin. For,
The saturation magnetic flux is almost reached near the diaphragm. In such a configuration, when the heating element installed on the surface of the diaphragm is energized to generate heat, the magnetic permeability of a part of the ferromagnetic material forming the diaphragm decreases. When this happens, the balance of the mutual magnetic attraction forces is lost in the closed magnetic path portion described above, and the diaphragm moves to a position where a new balance occurs.

This movement causes movement of the ink liquid within the ink chamber, and ink droplets are ejected from the nozzle portion.

[Example] FIG. 2 shows a configuration diagram of a printing apparatus using the inkjet head of the present invention. The inkjet head 1 is mounted on a helad carriage 2 and moves in the direction of arrow B along a guide shaft 3.4. The printing paper 6 is moved by the frictional force with the paper feed roller 5 when the paper feed roller 5 rotates in the direction of arrow A. Ink droplets are ejected from the inkjet head 1 in the direction of arrow C, and print pixels are generated on the printing paper. The ink jet head of the present invention controls the ejection of ink droplets by ejecting the ink droplets only when the electrodes are energized at the positions where printing pixels are desired, and belongs to the so-called drop-on-demand ink jet method. FIG. 1 shows a configuration diagram of an inkjet head of the present invention. The nozzle plate 7 is made of a polyimide film with a thickness of 200 μm, and the nozzle 14 is formed with a diameter of 50 μm between the outside air surface.
It was formed by an etching process so that it became as follows. A 250 m thick ferromagnetic plate 8 made of 20% Co and 80% Ni is arranged on the upper surface of the nozzle plate 7, and a diaphragm 9 made of a thin Ni plate 50 μm thick is placed via a spacer.
has been established. The configuration of the diaphragm will be explained below with reference to FIG. FIG. 3 is a cross-sectional view of a portion of the diaphragm. The overall structure of the diaphragm 9 is that a plurality of slits are made in a thin plate, and a 250mm thick diaphragm is formed in the remaining portion at a position facing the nozzle 14.
The portion 15 that will become pm was attached by electrolytic plating so that the Cu content was 45% and the Ni content was 55%. In FIG. 3, the lower side of the drawing is the side facing the nozzle Z. On the Ni plate opposite to the nozzle 14, an insulating layer 16 made of 5102 film is provided with a thickness of 0.5 μm, and TaSi
A heating element 17 of 02 layers was deposited. For the heating element 17, electrodes 18 made of AI vapor deposition were installed separately for each nozzle.

FIG. 4 is a sectional view taken along line d-d' in FIG. Horizontal line part 11
A permanent magnet is installed at 12, 13 and 10 to form a magnetic path part made of iron, and the structure is such that it forms a closed magnetic path including the N1 alloy part of the ferromagnetic plate 8 and the diaphragm 9. .

Next, the operation of this embodiment will be explained.

Ink ejection according to the present invention is performed by energizing the electrode 18 to cause the heating element 17 to generate heat. In this example, the heating element portion was formed into a rectangle with a radius of 250 μm and a length of 50 μm.

This raises the temperature to 200° C. or higher up to a depth of 50 □m with a heat amount of 0.5 m Joule. Regarding the magnetic material of the diaphragm 9, the Curie temperature is around 150°C due to the component ratio of the material forming the magnetic path portion 15, which is attached by electrolytic method. The magnetic permeability of the part decreases significantly, and the conventional balance of magnetic attractive forces cannot be maintained. Therefore, the magnetic attraction force on the diaphragm mainly acts on the tip of the magnetic path portion 15, which still maintains high magnetic permeability. This is indicated by arrows E and E' in FIG. At this time, the balance position changes and a displacement of approximately 6 μm occurs near the center of the diaphragm 9. In this example, wax ink with a melting point of 60°C was used, and the temperature of the head and ink supply system was maintained at 80°C. Therefore, the time required for the minute portion heated by the heating element on the diaphragm to rise in temperature to 200° C. was 0.6 m5ec. Also, the heated part returns from 200°C to the same temperature as the surrounding ink 8
The time required for cooling to 0°C was 1.7 msec. However, the "heated minute part" mentioned above is 200
Cooling time from ℃ to 150℃ is only 0,1m5
ec, and at temperatures below this, the magnetic permeability increases rapidly. Therefore, when the heating element 17 located on the surface of the magnetic path portion 15 is energized with a pulse width of approximately 5°Oμsec, the temperature of the shaded area in FIG. 5 rises to about 0.0μsec. After 6 m5 ec, the temperature reaches around 200°C, and then it is further cooled to 150°C or less at about 1 m5 ec. Accordingly, the diaphragm 9 is 0.6m near its center.
5ec rose by about 6μm, and further increased by about 0.1m5ec
The nozzle will return to its original position in about 10 minutes, and at this time, an ink droplet of approximately 0.1 μg will be ejected from the front surface of the nozzle.

The formation of characters and images during printing is performed by repeating the above steps. That is, the method of the present invention energizes the electrodes at positions where it is desired to generate print pixels, ejects ink droplets, and generates ink dots on the printing paper.
The arrangement of dots (dot matrix) represents the shape and forms characters/images.

[Effects of the Invention] Due to the above structure, the present invention has an advantage in that, unlike a valve jet type inkjet print head, so-called "hot melt ink" which is solid at room temperature such as wax ink can be used. In the bubble jet method, which generates air bubbles by heating the ink and ejects ink droplets by increasing the volume at that time, waxes with too high boiling points cannot be used, so the inks that can be used are mainly water-based or solvent-based. However, hot melt inks have disadvantages such as being susceptible to dirt from oil and fat on the surface of the printing paper, smearing easily, and the color reproducibility of color inks differing significantly depending on the printing paper. It is excellent in both of these respects.

On the other hand, in comparison with other printing methods, such as thermal printers, this method is an inkjet method, so there is no contact with the printing paper, and therefore stable print quality is achieved even on sheets with low smoothness. It has the advantage of being able to maintain

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an inkjet head of the present invention. Second
The figure is a configuration diagram of a serial printer using the inkjet head of the present invention. Figure 3 is an enlarged view of the diaphragm. FIG. 4 is a sectional view taken from FIG. 1. Figure 5 is an enlarged view of a part of Figure 4. 1... Inkjet head 2... Head carriage 3... Guide shaft 4... Guide shaft 5... Paper feed roller 6... Printing paper 7... Nozzle plate 8... Magnetism Path forming member 9...Vibration plate 10...Magnetic path forming member 11...Permanent magnet 12...Magnetic path forming member 13...Magnetic path forming member 4...Nozzle 7...Heating element that's all

Claims (1)

[Claims] Having one nozzle for generating one printing pixel,
It is an inkjet head that has a diaphragm paired with the nozzle, and has an ink chamber for each nozzle, or has an ink chamber for multiple nozzles or all nozzles, and has a diaphragm in part or all of the diaphragm. Using a ferromagnetic material and having a heating element on a diaphragm, a closed magnetic path is formed by the magnetic material outside the ink chamber and the ferromagnetic material on the diaphragm, and the temperature of the heating element on the diaphragm is controlled. An inkjet head characterized in that the magnetic permeability of a ferromagnetic material, which is a member of a diaphragm, is changed to generate vibrations.