JPH02270558A - Thermal ink jet recording device - Google Patents

Abstract

PURPOSE:To form recorded spots of high density and sharpness by providing the surface which is brought into contact with a perforated film on the thermal element of a thermal head, with very small protruding and recessed parts which could grow into the nuclei of generated vapor bubbles distributed uniformly. CONSTITUTION:Thermal elements 2 are energized and allowed to generate heat using a recording signal circuit of a control device 8 in accordance with a recording pattern. Evaporated ink forms vapor bubbles 9, and the ink is ejected from through holes 7 by the pressure of the vapor bubbles. The perforated film which has passed over a thermal head again passes through the ink, undergoing the same process. The vapor bubbles 9 generate and grow evenly in the gap between the surface of the elements 2 and also the through holes 7 because pits 3 which could grow into the nuclei of generated vapor bubbles are present evenly in the thermal elements 2. Consequently, ink droplets 10 ejected from the holes 7 of the perforated film 5 are sent flying to recording paper 11 almost stably and vertically. Then the ink permeates through the recording paper 11 to form recorded spots 12a of high density and sharpness without much splash.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a thermal inkjet image forming apparatus, and in particular, a thermal ink jet type image forming apparatus in which a thermal ink is provided oppositely to the back side of a perforated film having a large number of micropores, The present invention also relates to a thermal inkjet image forming apparatus in which a recording paper is opposed to the surface of the perforated film, and liquid ink that can be jetted onto the recording paper is held in the micropores.

[Conventional technology]

Conventionally, as a method of thermal inkjet recording, a perforated film having a large number of fine through-holes and holding liquid ink in the through-holes is run while in contact with a thermal head, and is printed onto an opposing recording paper. A method for recording images has been proposed. The recording principle is as follows.
A perforated film filled with liquid ink with many fine through-holes is run while in contact with a thermal head, and when the thermal head is energized to generate heat according to the recording pattern, the low boiling point components of the ink evaporate and become vapor. Bubbles are generated, and the pressure of the bubbles causes ink to be ejected from the through holes. The ejected ink reaches and adheres to the opposing recording paper across a small gap to form a recording spot.

In this recording method, the through holes through which ink is ejected to form a recording spot corresponding to one heating element are not fixed, and moreover, when the density of the through holes is fine compared to the recording density, Since one recording spot is made up of ink droplets ejected from multiple through holes, even if some of the through holes become clogged and ink cannot be ejected, the recording result will be affected. It has the characteristics of being able to perform highly reliable recording without causing any major problems and without missing any dots.

[Problem to be solved by the invention]

The vapor bubbles that cause ink to be ejected from the through-holes are generated from pits or cavities present on the surface of the thermal head heating element. However, pits and cavities on the thermal head do not exist uniformly on the surface of the element, so even though the surface temperature at the center of the element is the highest, the location where vapor bubbles are generated is on the surface of the element at that time. Depends on surface condition. As a result, the unevenly generated vapor bubbles deflect the ink inside the through holes and eject it, causing the ink droplets on the recording paper to deviate from the ideal recording position, resulting in the problem of not being able to form a recording spot with high density and clarity. there were. A conventional example will be explained with reference to the drawings. Steam bubbles are generated and grow unevenly within the through-hole, which is the distance between the surface on the heating element and the perforated film (Fig. 3(a)).
, (b)).

Therefore, the ink droplet 10 ejected from the through hole is deflected, and the recording spoiler 12b becomes indistinct with large scattering and low density (FIG. 3(d)).

(e)).

[Means to solve the problem]

In the present invention, a thermal head is provided opposite to the back surface of a perforated film having a large number of micropores, a recording paper is opposed to the surface of this perforated film, and furthermore, the micropores are capable of ejecting water onto the recording paper. A thermal inkjet recording device retaining liquid ink, characterized in that the surface in contact with the perforated film on the heating element of the thermal head has minute irregularities in a -like distribution that can become vapor bubble generation nuclei. do.

[Effect]

According to the present invention, when a perforated film having a large number of fine through holes filled with liquid ink is run while being in contact with a thermal head, and the thermal head is energized to generate heat according to a recording pattern, the A plurality of minute recesses on the surface serve as a generation nucleus for vapor bubbles, and a plurality of vapor bubbles grow around the point between the surface on the core element and the perforated film and inside the through-holes of the perforated film, The ink inside the through hole is pushed up by a -like pressure.

The pushed up ink is almost stably ejected perpendicularly toward the thermal head and the opposing recording paper through a small gap, penetrating the recording paper and forming a recording spot with high density and clarity.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 are diagrams showing the recording process and recording state according to the embodiment of the present invention, and are used in a thermal inkjet recording apparatus basically similar to that shown in FIG. 3, which shows the recording state of the conventional example. It will be done. The difference from the conventional example is the pits 3 on the surface of the heat generating element 2 of the thermal head l. The pits were generated by sandblasting. The ink adhering to the surface of the perforated film 5 that has passed through the ink 4 is scraped off by the doctor blade 6 and filled into the through holes 7 (FIG. 1). When the ink in the space between the surface of the element that has moved above the thermal head and the perforated film and inside the through-holes of the perforated film is heated by the heating element 2, its low boiling point components are vaporized. The heating element is energized to generate heat according to the recording pattern by the recording signal circuit of the control device 8. The vaporized ink creates vapor bubbles 9, and the pressure causes the ink to be jetted out from the through hole 7. The perforated film that has passed over the thermal head passes through the ink again and undergoes the same process. In this example, in particular, since there are pits 3 on average on the heat generating element 2 that can become the nucleus for generation of steam bubbles, the steam bubbles 9 are generated in the space between the surface on the element and the perforated film, and inside the through holes. Generates and grows on average (Figure 2 (
a).

(b)). Therefore, the ink droplets 10 ejected from the through-holes of the perforated film are almost stably ejected vertically toward the recording paper, penetrate into the recording paper, and create high-density, clear recording spora) 12a with little scattering. form (Fig. 2(c),
(d)).

〔Effect of the invention〕

In this way, in the present invention, a thermal head is disposed opposite to the back surface of a perforated film having a large number of micropores, a recording paper is opposed to the surface of this perforated film, and the recording paper is placed in the micropores. In a thermal inkjet recording device that holds liquid ink that can be ejected to the thermal head, if the surface in contact with the perforated film on the heating element of the thermal head has minute irregularities that can become vapor bubble generating nuclei uniformly distributed, This has the effect of forming recording spots with high density and clarity.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a recording process according to an embodiment of the present invention, FIG. 2 is a diagram showing a recording process according to the present invention, and FIG. 3 is a diagram showing a recording process according to a conventional example. 1... Thermal head, 2... Heat generating element, 3... Bit, 4... Ink, 5... Perforated film, 6 ...Doctor blade, 7...Through hole, 8...
Control device, 9... vapor bubble, 10... ink drop, 11... recording paper, 12... recording spot. Agent: Susumu Hara, Patent Attorney, M-1, 1, 1, 1, 7, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 3, 3, 3, 3, 3, 3, 4, 5, 5, 5, 7, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 100, 100, 100, 1000, 1000, 1000, 1000 1000's'100's'rows''rows' (b) (1000's)

Claims (1)

[Claims] A thermal head is disposed opposite to the back surface of a perforated film having a large number of micropores, a recording paper is opposed to the surface of the perforated film, and liquid ink that can be jetted onto the recording paper is placed in the micropores. A thermal ink jet recording device held in a thermal ink jet recording device, wherein a surface of the heat generating element of the thermal head in contact with the perforated film has a plurality of minute irregularities that can become bubble generation nuclei.