JPH0480040A - Thermal ink jet recorder - Google Patents

Abstract

PURPOSE:To prevent scumming and tailing due to contact of recording paper with a perforated film from occurring by concentrating pressure solution to be generated by bubbles on a central vertical shaft of a heating element by a method wherein a heating element part of a thermal head is made depressed conically. CONSTITUTION:When a current is made to flow to a heating element 21 of a thermal head, heat is generated, and a low boiling point component in ink 2 reaches a boiling point to generate a bubble 22. The generated bubble 22 is developed by heating, which gradually pushes up the ink 2 stuck to a through hole 27 of a perforated film, and at last jets and ink drop from the through hole 27. Since a form of the heating element 21 is formed conically depressed at that time, pressure solution generated correrspondingly to this hollow place concentrates in a central line direction. Therefore, the ink drop is not dispersed. Then, a recording dot corresponding to the electrified heating element 21 is formed on recording paper 5. Further, the heating element 21 is hemispherically depressed, and effects similar thereto can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an inkjet image forming apparatus, and particularly to a thermal inkjet recording apparatus.

[Conventional technology]

Conventionally, the following recording method has been proposed as an inkjet recording method. The recording principle is, as shown in FIGS. 3(a) to 3(d), that a perforated film 1 having a large number of fine through holes 27 filled with ink 2 is
The thermal head 4a is run while being in contact with the thermal head 4a, and the thermal head 4a is energized according to the recording pattern, and the heating element 21
When a is made to generate heat, the low boiling point components of the ink 2 are vaporized and bubbles 22 are generated, and the pressure of the bubbles 22 causes the ink 2 to
is injected from the through hole 27. Sprayed ink droplets 25
reaches the opposite recording paper 5 across a small gap,
The recording dots 26 are formed by adhesion.

In this recording method, the number of through holes 27 through which ink 2 is ejected to form recording dots corresponding to one heating element is not fixed, and furthermore, the density of the through holes 27 is higher than the recording density. In the case of small prints, one recorded dot is composed of ink droplets 25 ejected from a plurality of through holes 27, so even if some of the through holes 27 become clogged, ink cannot be ejected. It has the characteristic that even in the case of a high-reliability recording without causing any major damage to the recording result and without any omission of I-...I.

[Problem to be solved by the invention]

The conventional thermal inkjet recording device described above uses ink or low viscosity liquid ink to fill the through holes,
Since the ejected ink flies while diverging, there is a drawback that increasing the distance from the opposing paper increases the diameter of the recording dots. Furthermore, if the distance between the sheet and the sheet facing the sheet is shortened, there is a drawback that stains and trailing dots occur when the sheet comes into contact with the perforated film.

[Means to solve the problem]

The thermal inkjet recording device of the present invention includes a perforated film having micropores and holding ink therein, a thermal head disposed opposite to the back surface of the perforated film, and a thermal head disposed opposite to the surface of the perforated film. A thermal inkjet recording apparatus that includes a recording paper and prints by jetting the ink onto the recording paper has a thermal head whose heating element is concave in the shape of a cone. Further, the conical shape may be a hemispherical shape.

[Example 1 Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a sectional view showing one embodiment of the present invention. In FIG. 1, the perforated film 1 is driven by a roller 7 in the direction of the arrow. The ink adhering to the perforated film 1 is regulated by the doctor blade, guided and driven by the roller 6.7, and reaches the recording area. The recording paper 5 faces the thermal head 4 with a fixed cap maintained, and recording is performed by ink 2 ejected from the perforated film 1.

FIGS. 2(a) to 2(d) are diagrams showing the process of recording on recording paper by the thermal inkjet recording apparatus of the present invention. First, when an electric current is passed through the heating element 21 of the thermal ink 4, heat is generated, and the low boiling point component in the ink 2 reaches its boiling point, generating bubbles 22 (FIG. 2(a)). The generated air bubbles 22 develop by heating and gradually become effective film 1.
push up the ink 2 adhering to the through hole 27 (see Fig. 2).
b)) Finally, the ink droplet 25 is ejected from the through hole 27 (FIG. 2(C)). At this time, since the shape of the heating element 21 is concave and concave, the pressure waves generated in response to this concave are concentrated in the direction of the center line, so that the ink droplets 25
does not radiate, and the energized heating element 2 is placed on the recording paper 5.
A recording dot 26 corresponding to 1 is formed (FIG. 2(d)
)).

Note that it is clear that the same effect can be obtained if the heating element 21 is concave in a hemispherical shape.

〔Effect of the invention〕

As explained above, in the present invention, by making the shape of the heating element concave, the pressure waves generated by the bubbles are concentrated on the central vertical axis of the heating element. It's hard to do.

Therefore, the cap between the perforated film and the recording paper can be widened, and there is an effect that scumming and trailing due to contact between the perforated film and the recording paper are prevented.

[Brief explanation of drawings]

Figure 1 is a sectional view showing one embodiment of the present invention, Figure 2 (a)
- Figure 3(d) is a diagram showing the process of printing on recording paper by the thermal inkjet recording apparatus of the present invention, Figure 3(a)
) to (d) of the same figure are diagrams showing the process of printing on recording paper by a conventional thermal inkjet recording device. DESCRIPTION OF SYMBOLS 1... Perforated film, 2... Ink, 3... Doctor blade, 4... Thermal head, 5... Recording paper, 6.7... Roller, 21... Heating element, 22...
・Air bubbles, 23 24.25...Ink droplets, 26...
Recording dot, 27... through hole.

Claims (1)

[Claims] 1. A perforated film having micropores and holding ink therein, a thermal head disposed opposite to the back surface of the perforated film, and a recording member facing the surface of the perforated film. 1. A thermal ink jet recording device comprising: a thermal ink jet recording device that prints by jetting the ink onto the recording paper, wherein the heating element portion of the thermal head is concave. 2. The thermal ink jet recording apparatus according to claim 1, wherein the conical shape is a hemispherical shape.