JPH02270559A - Thermal ink jet recording device - Google Patents

Abstract

PURPOSE:To form recorded spots of high density and sharpness by positioning a high-thermal conductivity member on the thermal head side of a perforated film. CONSTITUTION:A perforated film 5 consists of a low-thermal conductivity member 3a and a high-thermal conductivity member 3b. Vapor bubbles 9 which generate in the gap between the surface of thermal elements 2 and the perforated film grow significantly through holes 7 as heat is absorbed from the bubbles by the high-thermal conductivity member 3b and subsequently, the growth rate of the bubbles in the gap becomes low. Ink droplets 10 ejected from the through holes of the perforated film are sent flying to recording paper 11 almost stably and vertically. Then the ink permeates through the recording paper, forming recorded spots 12a of high density and sharpness without much splash.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thermal inkjet image forming apparatus, in particular a thermal inkjet image forming apparatus in which a thermal head is disposed opposite to the back side of a perforated film having a large number of micropores. The present invention relates to a thermal inkjet image forming apparatus in which a recording paper is opposed to the surface of a 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 when the density of the through-holes is smaller than 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 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 bits 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 in the gap between the surface of the heating element and the perforated film, and inside the through-holes (Fig. 3(a)).

(b)). Therefore, the ink droplet 1 ejected from the through hole
0 is deflected, and recording spora) 12b becomes unclear at low density with large scattering (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. In the recording portion of the thermal inkjet recording device in which liquid ink is held, a high heat transfer coefficient member is located on the thermal head side of the perforated film.

[Effect]

According to the present invention, 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 when the thermal head is energized and generated according to a recording pattern, the thermal head is heated. Low boiling point components of the ink in the gaps between the perforated film on the element and inside the through holes of the perforated film are vaporized to generate vapor bubbles. The steam bubbles generated in the gap between the surface on the element and the perforated film are absorbed by the high thermal conductivity member on the thermal head side of the perforated film, which reduces the growth rate in the gap. . As a result, the growth of the vapor bubbles within the through-hole progresses on an average basis, regardless of the initial position of the vapor bubble, and the ink inside the through-hole is pushed up by a -like pressure for each through-hole. The pushed-up ink is almost stably jetted perpendicularly toward the recording paper facing the thermal head separated by a minute gap, permeates the recording paper, and forms a recording spot with a high density and sharpness.

〔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 of the embodiment of the present invention, and a third diagram showing the recording state of the conventional example.
It is used in a thermal inkjet recording device basically similar to the one shown in the figure. The difference from the conventional example is that the perforated film 5 is composed of a low thermal conductivity member 3a and a high thermal conductivity member 3b. The ink adhering to the surface of the perforated film 50 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 gap between the surface of the element that has moved above the thermal head and the perforated film, and in 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 and generates 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 particular, in this embodiment, the vapor bubbles generated in the gap between the surface of the heat generating element 2 and the perforated film are absorbed by the high thermal conductivity member, and the growth rate in the gap is reduced, so that the vapor bubbles 9 grows significantly only inside the through hole 7 (Fig. 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 the recording part of a thermal inkjet recording device that holds liquid ink that can be jetted to the surface, if a high thermal conductivity member is installed on the thermal head side of the perforated film, a recording spot with high density and clarity can be formed. has.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the recording process of an embodiment of the present invention;
FIG. 2 is a diagram showing the recording state of the present invention, and FIG. 3 is a diagram showing the recording state of the conventional example. 1...Thermal head, 2...Heating element, 3a...Low thermal conductivity member, 3b...
... High thermal conductivity member, 4 ... Ink, 5.
... Perforated film, 6 ... Doctor blade, 7 ... Through hole, 8 ... Control device, 9 ... Steam bubble, 10・・・・・・ink drops,
11... Recording paper, 12... Recording spot. Agent Patent Attorney Uchihara Uchihara Ongyo Hakumeitsu Ichika Loquat I 1 Haya 1 Figure Hanrei (VU's −≦1ρ child scolding itari's butten hiss <C)

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, characterized in that in a recording portion of the thermal ink jet recording device held, a high heat transfer coefficient member is located on the thermal head side of the perforated film.