JP2906537B2 - Hot melt type inkjet recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an ink jet recording apparatus using a so-called hot melt type ink, in which a solid phase ink is heated and melted at room temperature to be used as a liquid phase for ink jet recording. The present invention relates to an on-demand type ink jet recording apparatus that performs ejection according to a recording signal.

(Prior art and problems) Conventionally, in such an ink jet recording apparatus, in order to maintain a liquid phase for ejecting ink, see Japanese Patent Application Laid-Open No. 61-9854.
As shown in FIG. 7, all the constituent members of the ink jet head were made of a suitable heat conductive material, and were heated by a heating plate provided thereunder so as to keep the temperature of the entire ink passage constant.

However, in such a configuration, although the ink is heated to a sufficiently high temperature inside the ink ejection head, the temperature is easily reduced and solidified due to exposure to air near the nozzle, so it is necessary to always maintain a high temperature in preparation for ejection. Since the heating means has a large power capacity, there is a problem particularly in an on-demand type ink jet recording apparatus which is a recording apparatus which consumes low power. Also, in the multi-nozzle type in which a large number of nozzles are provided in an array for high-speed printing, the temperature of the head tends to be high at the center and low at both ends. However, there is a problem that the ink droplets ejected are not formed in a uniform size due to the non-uniformity of the nozzles, and printing unevenness occurs.

SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet recording apparatus which consumes low power and has no printing unevenness even when a multi-nozzle type is used.

(Means for Solving the Problems) For this reason, in the present invention, the nozzle holes are formed in a thermally conductive plate-like member, and heating means is provided near the nozzle holes on the outer surface of the plate-like member to indirectly supply the ink. Heat to

(Embodiment) FIGS. 1, 2 and 3 show an ink jet recording apparatus to which the present invention is applied. The ink chamber 5 of the head 1 has a truncated cone shape with a diameter of 5 mm on the piezo element 4 side and a diameter of 1.5 mm on the nozzle side.
The recording paper is heated and melted at 0 degrees, and pressure is generated in the ink chamber 5 when a pulse voltage is applied to the piezo element 4 provided on the back surface of the head 1. Ink droplets are ejected toward 7.
The nozzle plate 2 is formed of a stainless steel having a thickness of 20 μm, and a nozzle hole 6 having a diameter of 15 μm is formed by electric discharge machining. The nozzle plate 2 may be made of ceramic or glass other than metal as long as the material has high thermal conductivity. An annular resistor 8 having an inner diameter of 1 mm and an outer diameter of 2 mm is provided as a heating means on the surface of the nozzle plate 2 so as to surround the nozzle hole 6. The resistor 8 generates heat when energized, and is formed by applying a printing technique on a surface of the nozzle plate 2 after applying an insulating thin film thereon.

Since the nozzle plate 2 has high thermal conductivity and the heating means is close to the nozzle hole 6 in this manner, it is easy to efficiently heat the ink near the noise hole 6 with low power through the nozzle plate. Further, since the nozzle plate 2 is thin and the temperature of the ink in the ink chamber 5 is easily reduced, the effect of providing the heating means is high.

Also, as shown in FIG. 3, an electrode 10 is added to the front of the nozzle plate 2 and to the back of the recording paper 7 in opposition to the nozzle hole 6, and an electrostatic field between the ink in the head and the added electrode 10 is formed. In this case, the ink is always projected from the nozzle hole 6 irrespective of the recording signal, and the ink is easily ejected by the generation of pressure by the piezo element.
Since the surface area of the ink exposed from the surface is large and easy to cool, the effect of providing the heating means is high.

FIG. 4 shows a multi-nozzle type ink jet recording apparatus to which the present invention is applied. The heating resistor is formed so that the amount of heat generated at both ends is increased so that the temperature of the nozzle portion becomes uniform. In this ink jet recording apparatus, the nozzle holes 16a,
Pressure waves traveling in the arrangement direction such as 16b are generated by the piezo element 14, and recording is performed by applying a voltage to the back electrode according to the recording signal.

(Effects of the Invention) As described above, according to the present invention, it is possible to efficiently prevent the temperature of ink exposed to air near the nozzle hole from decreasing.

Therefore, there is no need to provide high-power heating means for heating and melting the ink, and the size of the ink droplets ejected is made uniform by making the temperature of the ink in contact with each nozzle hole of the multi-nozzle type ink jet recording apparatus uniform. Printing without density unevenness.

[Brief description of the drawings]

1 and 2 are schematic views of an ink jet recording apparatus to which the present invention is applied, FIG. 3 is a projection state of ink when an electrode for applying an electrostatic field is added to the apparatus of FIGS. 1 and 2, and FIG. FIG. 1 is a schematic view of a multi-nozzle type inkjet recording apparatus to which the present invention is applied. 1,11; Head, 2,12; Nozzle plate, 3,13; Head heater, 4; 1
4; Piezo element, 5; Ink chamber, 6, 16a, 16b; Nozzle hole, 7; Recording paper, 8, 8; Heating resistor, 10; Back electrode

Claims (1)

(57) [Claims] 1. An ink jet recording apparatus which uses an ink which is in a solid phase at room temperature and which is heated and melted to form a liquid phase for recording, and which ejects from a nozzle hole in accordance with a recording signal. An ink jet recording apparatus comprising: a conductive plate member; and heating means for indirectly heating ink near the nozzle hole on the outer surface of the plate member.