JPS6334144A - Liquid jet recording head - Google Patents

Abstract

PURPOSE:To improve the accuracy of landing liquid droplets on a recording medium and thereby enable high-quality recording by providing a recessed part in parallel with the ejection direction of liquid droplets on a contact surface with a recording liquid in a thermal action part, thus preventing a deflection of the liquid droplets in an ejection direction. CONSTITUTION:A protective layer 10 is provided on a thermal resistor 5, and a plurality of recessed parts are provided in parallel with a liquid bubble ejection direction. Thermal energy is supplied to a recording liquid through the protective layer 10 by energization and heating of the thermal resistor 5. At that time, the protective layer 10 becomes thin in a part in which the recessed part is created and thick in the other part. Consequently the surface of the protective layer in which the recessed part is created becomes hotter, than the other part which generates bubbles in a recording liquid centered around a hot part and prompts the growth of the bubbles in the recessed part direction. That is, the bubble generating direction of the recording liquid can be controlled so that it may be in parallel with a liquid droplets ejection direction. In this manner, a pressure to be brought to the recording paper by the formation of bubbles can be controlled so that it may processed stably in the ejection direction, thus preventing a deflection of the liquid droplets in the ejection direction.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to liquid jet recording in which a recording liquid is ejected in the form of droplets and is attached to a recording medium such as paper to record characters, images, etc. The present invention relates to heads, and particularly to liquid jet recording heads that eject droplets by utilizing the bubbling phenomenon of recording liquid due to thermal action as a method of ejecting droplets.

[Prior Art] Liquid jet recording heads that utilize thermal energy have been known, for example, as disclosed in Japanese Patent Application Laid-Open No. 55-27828.

Such a liquid jet recording head generally includes a liquid ejection port for ejecting recording liquid, a liquid flow path (nozzle) that communicates with the liquid ejection port, and a liquid droplet formation device for the recording liquid in the liquid flow path. It is constructed as having a heat acting part that provides thermal energy for. Recording is performed by heating and foaming the recording liquid that comes into contact with the heat acting part by the thermal action of the heat acting part, and by ejecting the recording liquid from the liquid ejection port by the pressure generated by the bubbling.

Various types of heat acting parts have been proposed for such liquid jet recording heads. Usually, a heating resistor is connected to at least one pair of electrodes and has a heat generating area between these electrodes. However, in some cases, for example, as disclosed in Japanese Patent Application Laid-Open No. 56-10471, the surface roughness of the contact interface with the recording liquid in the heat acting part is 0.05 to 2. There are proposals for foaming and discharging with low energy as a rough surface of about O8, and for example, as in Japanese Patent Application Laid-Open No. 60-236758, a protective layer is provided on the heat acting part and the thickness of the protective layer of the heat acting part is reduced. Proposals have also been made to make the foam thinner than other parts to achieve both a protective function and a reduction in the energy required for foaming.

However, since such liquid jet recording heads basically utilize the phenomenon of bubbling of the recording liquid caused by thermal action, it was inevitable that there would be statistical fluctuations in this bubbling phenomenon. . For this reason, there is a drawback that the pressure vector of the recording liquid that is generated due to bubbling also fluctuates, resulting in fluctuations in the ejection direction of the droplets. Such fluctuations in the droplet ejection direction make the landing positions of the droplets on the recording medium inaccurate, and are a major factor in poor image quality and other deterioration in recording quality.

FIGS. 7(a) and 7(b) are diagrams for explaining the fluctuation in the droplet ejection direction as described above.

That is, FIG. 7(a) shows a case where bubbles are growing along the droplet ejection direction A. Here, the reference numeral 7 in the figure collects bubbles grown by the thermal energy supplied from the heating resistor 5, 8 collects flying droplets, and 6 indicates that the heating resistor 5 is heated by electricity. This is the electrode.

However, as described above, in the conventional liquid jet recording head, as illustrated in FIG. This is unavoidable, and this causes a phenomenon in which the ejection direction C of the droplet 8 deviates from the original ejection direction A. Here, the symbol 01 in the figure is the deviation angle of the bubble growth direction B with respect to the original ejection direction A, and θ2 is the deviation angle of the droplet 8 from the original ejection direction A due to the deviation in the bubble growth direction. It is.

[Problems to be Solved by the Invention] The present invention has been made in view of the problems of the conventional example described above, and improves the landing accuracy of droplets to be deposited on a recording medium by preventing fluctuations in the droplet ejection direction. An object of the present invention is to provide a new liquid jet recording head that enables high-quality recording.

[Means for Solving the Problems] The above objects of the present invention are achieved by the present invention below.

a liquid ejection port for ejecting recording liquid to form droplets;
In a single shot recording head, the liquid n'° single-shot recording head is provided with a heat acting part, which is a part where thermal energy for forming droplets acts on the recording liquid, at least at the contact interface of the heat acting part with the recording liquid. . A liquid jet recording head, characterized in that a concave portion is provided parallel to the ejection direction of the droplets.

[Function] In the present invention, the growth direction of bubbles in the recording liquid is controlled in a direction parallel to the recess by the recess provided in the contact interface of the heat acting part with the recording liquid parallel to the ejection direction of droplets. Therefore, fluctuations in the direction of bubble growth as described above do not occur. Therefore, fluctuations in the droplet ejection direction are prevented, the droplets can be deposited on the recording medium with high accuracy, and high-quality recording can be performed.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a perspective view of a single-nozzle recording head having one liquid flow path (nozzle) as an example of the liquid jet recording head of the present invention. It goes without saying that the present invention is applicable not only to a recording head having a single nozzle, but also to a recording head having a plurality of nozzles. Further, in order to simplify the explanation, the recessed portion is omitted in FIG. 1.

This liquid jet/jet recording head is formed by providing a channel wall 2 and the like on a substrate 1 using well-known integrated circuit technology, and bonding a top plate 3 to this. Here, 4 is a liquid flow path consisting of a substrate 1, a flow path wall 2, and a top plate 3,
20 is a liquid discharge port communicating with the liquid flow path 4. Reference numeral 5 denotes a heat generating resistor as a heat acting portion, and 6 indicates an electrode for heating the heat generating resistor 5 with electricity.

In the above configuration, electrical energy supplied through the electrode 6 is converted into thermal energy by the heating resistor 5, and the thermal energy is transmitted to the recording liquid in the liquid flow path 4. The recording liquid heated in this way vaporizes and foams to generate pressure.
The recording liquid in the liquid flow path 4 is forced to the liquid ejection port 20, and the liquid J is ejected as droplets from the liquid ejection port 4, thereby performing printing.

Next, examples of the heat acting portion included in the liquid jet recording head of the present invention are shown in FIGS. 2 to 6. In addition, FIGS. 2 to 6 each show (a) a plan view of the vicinity of the heat acting part of the liquid jet recording head of the present invention, and (b) each show an X-Y cross section in (a). A diagram is shown. In addition, these X-Y cross-sectional views (b) are
2 is a cross-sectional view when cut at a position corresponding to a line, and the plan view (a) is seen from the Z direction in FIG. 1. FIG.

In these figures, 1 is a substrate, 5 is a heating resistor as a heat generating section, and 9 is a concave portion provided in parallel to the droplet ejection direction according to the present invention. In addition, Figures 2 to 4
What is indicated by the symbol 10 only in the figure is a protective layer that blocks the heating resistor 5 from contact with the recording liquid. The protective layer 10 may be provided as necessary, and is not necessarily required in the present invention.

In the liquid jet recording head illustrated in FIG. 2, a protective layer 10 is provided on the heat generating resistor 5, and the protective layer 10 serves as a contact interface between the recording liquid and the heat acting part, and the liquid droplet is ejected onto the protective layer IO in the direction of ejection. A plurality of recesses 9 are provided parallel to the . Thermal energy is supplied to the recording liquid through the protective layer IO by heating the heating resistor 5 with electricity, but at this time, the thickness of the protective layer 10 is thinner in the area where the recess 9 is provided and thicker in other areas. Therefore, the surface of the protective layer provided with the recesses 9 becomes hotter than other parts. Foaming of the recording liquid occurs using this high temperature portion as a core, and the bubbles grow toward the recessed portion. In other words, the bubbling direction of the recording liquid can be controlled in a direction parallel to the droplet ejection direction, and the pressure effect on the recording liquid due to the bubbling is controlled to be stably directed in the droplet ejection direction. This makes it possible to prevent fluctuations.

The method for forming the recess 9 is not particularly limited, and may be formed by, for example, an etching technique using a photoresist or the like, or mechanical cutting using a dicing saw or the like.

Although the example in FIG. 3 has one recess 9 in FIG. 2, it is possible to obtain the same effect as described above with such a recess.

In the example shown in FIG. 4, the recess 9 is shaped like a sushi, and the protective layer 10 is arranged so that the longitudinal direction of the recess 9 is parallel to the droplet ejection direction.
They are randomly placed on the top.

If such a sushi-shaped recess is desired, the recess may be formed by mechanical polishing or the like.

In the examples shown in FIGS. 5 and 6, a recess 9 is provided directly on the heating resistor 5 without providing a protective layer, but in FIG. In FIG. 6, the same square shape as in FIG. 2 is used.

Although not specifically explained above, it is not always necessary to provide the heat acting portion on the substrate, and it may be provided on the channel wall or the top plate. In particular, by arranging heat acting parts on both the substrate and the channel wall, and providing recesses parallel to the droplet ejection direction in both heat acting parts, fluctuations in the droplet ejection direction can be suppressed in two directions: horizontal and vertical. This is preferable because it can be prevented. Alternatively, the heating resistor may be rectangular, and the recess may be formed by arranging a plurality of rectangular heating resistors in parallel to the droplet ejection direction.

[Effects of the Invention] The effects brought about by the present invention include the following.

l) The bubbling direction of the recording liquid can be aligned with the droplet ejection direction, the droplet ejection direction is stabilized, the droplet landing accuracy is improved, and high-quality recording can be performed.

2) By providing the concave portion, the energy required for ejecting droplets can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an example of a liquid jet recording head of the present invention;
2 to 6 are schematic diagrams of the vicinity of the heat-acting section of the liquid jet recording head of the present invention, and FIGS. 7(a) and 7(b) show the state of droplet ejection by the conventional liquid jet recording head. FIG.

Claims (2)

[Claims] (1) Liquid jet recording equipped with a liquid ejection port for ejecting recording liquid to form droplets, and a heat acting part that is a part where thermal energy for forming the droplets acts on the recording liquid. 1. A liquid jet recording head, characterized in that the head is provided with a concave portion parallel to the ejection direction of the droplets, at least at a contact interface of the heat acting portion with the recording liquid. (2) The liquid jet recording head according to claim 1, wherein the longitudinal direction of the recess is parallel to the ejection direction of the droplet.