JPH021320A - Ink jet recording head - Google Patents

Abstract

PURPOSE:To prevent interference such as thread-forming of ink at a peripheral part or the like by a method wherein an aperture size (d) of a plurality of discharge orifices and an interval (l) between adjacent orifice fringes are taken as a relation of 4d>l, and an outer surface of the discharge orifice is processed by water repellency (oil repellency). CONSTITUTION:In a multi-orifice head wherein orifices are formed by lining a heating element base plate 11 in which a heater layer 12 and an electrode layer 13 are laminated to be enclosed and a cover base plate 14 having a passage groove 15 together, an aperture size of the orifices 16 is taken as (d) and an interval between adjacent orifice finges as (l), and the orifices are so arranged as to meet a relation of 4d>l. Further, an outer surface of the orifice is processed by water repellent treatment (toluene solution of silicone resin and others) or by oil repellent treatment (gum arabic phosphoric acid aqueous solution and others). It is thereby prevented that an ink drop discharged and scattered between the adjacent orifices wets an orifice surface and the ink is drawn out to generate a satellite drop.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid jet recording head, and more particularly to a structure of an orifice in a bubble jet liquid jet recording head.

The recording method has recently attracted attention because the noise generated during recording is so small that it can be ignored. Among these, the so-called Infusiera 1 recording method, which enables high-speed recording and can record on so-called plain paper without the need for special fixing processing, is an extremely powerful recording method, and has been used in various ways until now. Several methods have been proposed, some have been improved and commercialized, and others are still being worked on to put them into practical use.

In this type of inkjet recording method, recording is performed by causing droplets of a recording liquid called ink to fly and adhere to a recording member, and the method of generating these recording liquid droplets is The method is roughly divided into several methods depending on the control method for controlling the flying direction of the generated recording liquid droplets.

The first method is, for example, the one disclosed in USP No. 3,060,429 (Teletype method), in which droplets of recording liquid are generated by electrostatic attraction, and the generated droplets of recording liquid are used for recording. Recording is performed by controlling an electric field in accordance with a signal to selectively attach recording liquid droplets onto a recording member.

To explain this in more detail, an electric field is applied between the nozzle and the accelerating electrode to eject a negatively charged recording liquid droplet from the nozzle, and the droplets of the ejected recording liquid are adjusted according to the recording signal. The droplet is caused to fly between x and y deflection electrodes configured to be electrically controllable, and the droplet is selectively attached to the recording member by changing the intensity of the electric field to perform recording.

The second method is a method (Sweat method) disclosed in, for example, USP No. 3,596,275, USP No. 3,298,030, etc., in which the 4'+F electric charge is controlled by a connected 52 vibration generation method. The controlled droplets of the generated recording liquid are caused to fly between the deflection electrodes to which a −-like electric field is applied, onto the recording member. It is for recording.

Specifically, the orifice (discharge port) of a nozzle, which is a part of the recording head to which the piezo vibrating element is attached.
A charged electrode configured to have a recording signal applied thereto is arranged at a predetermined distance in front of the piezo vibrating element, and an electric signal of a constant frequency is applied to the piezo vibrating element to mechanically vibrate the piezo vibrating element, A small droplet of recording liquid is ejected from the ejection port. At this time, a charge is electrostatically induced in the recording liquid droplet ejected by the 4'+F electrode, and the droplet is charged with an amount of charge equal to the recording signal. band? When a droplet of recording liquid with a controlled ttJf flies between deflection electrodes to which a constant electric field is uniformly applied, an applied 'ftF
It is deflected according to the amount of electric charge so that only the droplet carrying the recording signal can be deposited on the recording member.

The third method is, for example, the method disclosed in USP No. 34]6153 (Hertz method), in which an electric field is applied between a nozzle and a ring-shaped charging electrode, and a continuous vibration generation method is used to generate recording liquid. This method records by generating small droplets and atomizing them. In other words, in this method, the nozzle and the charging ゛1'I?
By modulating the electric field strength applied between the electrodes according to the recording signal, the atomization state of the droplets is controlled, and the gradation of the recorded image is produced and recorded.

The fourth method is, for example, the method disclosed in USP No. 3,747,120 (Stemme method), and this method is fundamentally different in principle from the above three methods.

That is, in all three methods, the droplets of recording liquid ejected from the nozzle are electrically controlled while they are in flight, and the droplets carrying the recording signal are selectively attached to the recording member. In contrast, this Stemme method
Recording is performed by ejecting small droplets of recording liquid from an ejection port in response to a recording signal.

In other words, in the St, emme method, an electric recording signal is applied to a piezoelectric vibrating element attached to a recording head having an ejection port for ejecting recording liquid, and this electric recording signal is transmitted to the piezoelectric vibrating element mechanically. According to the mechanical vibration, small droplets of recording liquid are ejected from the ejection port and attached to the recording member, thereby performing recording.

These four conventional methods each have their own advantages, but there are also points that can be solved in the other method.

That is, in the first to third methods, the direct energy for generating droplets of the recording liquid is electrical energy, and the deflection control of Komitsu is also electric field control.

Therefore, although the first method is simple in structure, it requires a high voltage to generate droplets, and it is difficult to use a multi-nozzle recording head, making it unsuitable for high-speed recording.

The second method allows the recording head to have multiple nozzles and is suitable for high-speed recording, but it has a complicated structure, and the electrical control of recording liquid droplets is sophisticated and difficult, and satellite dots are placed on the recording member. There are problems such as easy occurrence of.

The third method has the advantage that an image with excellent gradation can be recorded by atomizing a small amount of recording liquid, but on the other hand, it is difficult to control the atomization state and fog occurs on the recorded image. And it is difficult to make the recording head multi-nozzle.
There are various problems such as being unsuitable for high-speed recording.

The fourth method has relatively many advantages compared to the first to third methods. In other words, the structure is simple, and since recording is performed by ejecting recording liquid from the ejection opening of the nozzle on-demand, it is possible to reduce the number of small droplets that fly as in the first to third methods. Second, it is not necessary to collect droplets that are not needed for recording an image, and unlike the first and second methods, there is no need to use H1 conductive recording liquid, and the material of the recording liquid is It has great advantages such as a large degree of freedom. On the other hand, it is difficult to make the recording head multi-nozzle because there are problems in processing the recording head, and it is extremely difficult to miniaturize the piezoelectric vibrating element having the desired resonance number. This method has drawbacks such as that it is not suitable for high-speed recording because the recording liquid droplets are ejected and ejected in flight using the mechanical energy of the mechanical vibration of the piezoelectric vibrating element.

Furthermore, Japanese Patent Application Laid-Open No. 48-9622 (the above-mentioned USP No. 3)
No. 747120 (corresponding to the specification) discloses, as a modification, the use of thermal energy instead of the mechanical vibration energy provided by means such as the piezo vibrating element.

That is, the above-mentioned publication describes a so-called bubble jet liquid jet recording device that uses a heating coil that directly heats liquid as a pressure increasing means instead of a piezo vibrating element to generate steam that causes a pressure increase. There is.

However, in the above publication, the liquid ink in the bag-shaped ink chamber (liquid chamber), which has only one opening through which liquid ink can go in and out, is directly heated and vaporized by energizing the heating coil as a pressure increasing means. However, when discharging liquid continuously and repeatedly, it is not clear how to heat it.
There is nothing to suggest. In addition, the heating coil is located at the deepest part of the bag-shaped liquid chamber far from the liquid ink supply path, which makes the head structure complicated and requires continuous high-speed printing. For repeated use,
It is not suitable.

Moreover, with the technical content described in the above-mentioned publication, it is not possible to quickly prepare for the next liquid discharge after discharging the liquid using the generated heat, which is of paramount importance in practical use.

As described above, conventional methods have advantages and disadvantages in terms of structure, high-speed recording, multi-nozzle recording heads, generation of satellite dots, and fogging of recorded images, etc., and there are applications that take advantage of these advantages. There was a restriction that it could only be applied to

Furthermore, Japanese Patent Application Laid-Open No. 55-107481 discloses that the recording liquid introduced into the liquid chamber is ejected as small droplets from an orifice communicating with the liquid chamber, and the droplets are caused to adhere to the surface of the recording paper. In a liquid jet recording device that performs recording,
A recording head has been proposed in which at least the peripheral edge of the orifice is treated to have an affinity for the liquid.

However, if the peripheral edge of the orifice is made alkaline, in the case of a head with a high density arrangement, when ink droplets are ejected, they will also drag (eject) ink from adjacent orifices, causing There is a drawback that the ejecting direction may be bent due to the influence of time, or the ink may become droplets when rubbed, disturbing the image quality.

The present invention was made in view of the above-mentioned circumstances,
Particularly, in an inkjet that can be arranged in high density (4 orifices/mn+) such as a bubble jet inkjet, the purpose is to prevent mutual interference between adjacent orifices during ejection.

Structure 1. In order to achieve the above object, the present invention has a plurality of ejection orifices arranged close to each other, and utilizes thermal energy for the recording liquid introduced into a chamber communicating with each orifice. In a liquid jet recording head which performs recording by ejecting and flying small droplets from each orifice and attaching the droplets to the recording surface, the orifice opening size of the plurality of ejection orifices is d, and the interval between adjacent orifice edges is When Q is 4d>l, and the outer surface of the discharge orifice is treated to be water or oil repellent.

Hereinafter, the present invention will be explained based on examples.

The present invention relates to a multi-orifice type inkjet, and particularly to a bubble-jet type multi-orifice head capable of high-density arrangement (4 orifices/mtn or more). Conventionally, inkjet heads have been known in which the peripheral edge of the orifice has affinity as described above. However, in such a head, the peripheral edge of the orifice is wetted by the ink due to affinity, so when an ink droplet is ejected from one orifice, the ink around it is dragged along with it, causing it to fly out. In the case of a head with a high density arrangement, ink droplets ejected from adjacent orifices at the same time may They have the disadvantage of merging during flight or during ejection.

The present invention has been made in view of the above points, and proposes a head that does not cause ink dragging on the periphery, instability in the ejection direction, or merging of droplets during ejection/B or during flight. .

Here, the present invention will be explained in more detail by giving examples.

First, the ink printing method 1 to the recording method to which the present invention is applied will be outlined with reference to FIG. For convenience of explanation, 2.
Hereinafter, a single orifice recording device will be explained as an example. In FIG. 4, a recording liquid 3, generally called ink, introduced into a liquid chamber 2 through an introduction pipe 1, is heated by electricity generated by an electric/thermal converter 4 attached to the liquid chamber 2. Causes instantaneous state changes. The converter 4 generates a thermal pulse signal by applying current through electrodes 5□, 5□ connected thereto. In this way, due to the change in the state of the recording liquid 3, an acting force is applied to said liquid 3, and as a result, the liquid 3 is moved from the orifice 6 to the small droplet 7.
Recording is performed by ejecting and flying the recording material and adhering to the recording material 10, such as paper.

The converter 4 is provided on the substrate 8, and the voltage rX9 is applied according to the recording input, and the converter 4 according to the human input signal is applied.
Heat is generated, and a record corresponding to the human input signal is formed by the small droplets 7 flying and adhering to the recording member 10.

Note that the size (diameter) of the droplet 7 ejected from the orifice 6 and flying is the amount of electrical energy input to the electric/thermal converter 4 as information, and the transfer of the thermal energy converted there to the recording liquid 3. Efficiency, conversion efficiency of electrical/thermal converters,
The diameter of the orifice 6, the inner diameter of the liquid chamber 2, the distance from the position of the orifice 6 to the converter 4, the acting force applied to the recording liquid 3, the amount of the liquid 3 subjected to the action, the specific heat of the recording liquid 3, the thermal conductivity, Determined depending on boiling point, latent heat of vaporization, etc.

Therefore, by changing any one or two or more of these factors, the size of the droplet 7 can be easily controlled, and the size of the droplet 7 can be easily controlled, and the size of the droplet 7 can be adjusted to any desired diameter on the recording member. A record can be made on 10.

Incidentally, as the electric/thermal converter 4 shown in No. 4, a thermal print head (that is, a thermal head) widely used in the field of thermal recording is applied. They are classified into JIX film heads, thin film heads, and semiconductor heads depending on the manufacturing method, heating resistor, etc., but all of them can be used in the present invention. However, it is currently preferable to use a thin film head, especially when performing high-speed, high-resolution recording.

Further, the recording liquid used in the present invention includes water, ethanol,
It is prepared by dissolving or dispersing a wetting agent such as ethylene glycol, a surfactant, various dyes, etc. in a main solvent such as toluene.

Note that in order to prevent clogging of the orifice, it is effective to filter the liquid with a filter after preparation or to provide a filter in the liquid chamber, as in the case of existing inkjet recording methods.

FIG. 1 is an exploded view of the main parts explaining the configuration of a multi-orifice array device to which the present invention is applied.
On the Q203 substrate 11, 5in2 which is 7ζ thermal n, HfB which is the heater layer 12, and AQ which is the electrode layer 3 were sequentially laminated by thin film formation technology, and then a pattern as shown in the figure was made by selective etching. .

The present invention exhibits its effects in the case of a high-density arrangement, and now, when the opening size of the orifice 16 is d (if the orifice is circular, it refers to the diameter), and the interval between adjacent orifice edges is Q. , 4 satisfies d>l, that is, it is applied to heads arranged in high density. In the head as described above, in the present invention, as shown in FIG. 2, the outer surface (shaded area) of the orifice is treated to be water or oil repellent.

For the above-mentioned water or oil repellent treatment, a prefabricated head is immersed in a treatment solution (for example, a toluene solution of silicone resin for water repellent treatment, a gum arabic-phosphoric acid aqueous solution for oil repellent treatment, etc.), or This can be easily done by spraying with a Teflon dispersion or the like.

The experimental results are shown in Table 1 below. Table 1 is for the case where an orifice plate as in FIG. 3 is used. Note that the ink is a water-based ink, and the surface treatment is water repellent treatment. Further, the nozzle shape is round.

Table 1: From this, when 4d-Q<O, good results are obtained in all cases without the jets connecting, but when 4d-fl<O, good results are not always obtained. It turns out that this is not the case. However, 4d-
Even when Q>O, if water repellent treatment is applied, very good results can be obtained, and the results shown in Table 2 are practical for producing heads with a high yield.

Next, Table 2 shows the results of an experiment conducted using a so-called edge shooter type head in which the tip of the flow path directly serves as an orifice, as in the case of FIG. The major difference from Table 1 is that the spatula 1-1, especially the orifice part (nozzle part), depends on the manufacturing method, but adjacent orifices communicate with each other by a line on the edge of the end. be. In other respects, water-based ink was used in the same manner as in Table 1, and the water-repellent treatment was also the same.

From this, in a head like the case in FIG.

It can be seen that good results cannot be obtained unless water repellent treatment is performed regardless of whether 4d-fl is positive or negative.

This is because adjacent orifices communicate with each other by the edge lines at their ends, making it easier for jets to connect to each other. Therefore, it goes without saying that the present invention is effective for orifices as shown in FIG. 3, and is particularly effective for orifices as shown in FIG.

The present invention provides an orifice plate 17 as shown in FIG.
It can also be applied to a structure in which the head is attached to the front surface of the head as shown in FIG. In the case of FIG. 2, a rectangular orifice is formed by gluing a lid substrate 14 having a channel groove 15 and a heating element substrate 11 together. Therefore, a part of the contour forming the orifice edge is connected to each other by the edge line of the end of the heating element substrate 11, and ink flows along the line on the outer surface of the orifice to each orifice. It became wet all over, and the 33rd
It is less preferable to the orifice spray 1 as shown in the figure. Therefore, it goes without saying that the present invention is effective in the case shown in FIG. 3, but as shown in FIG. This is particularly effective if the person is easy to contact.

As is clear from the above description, according to the present invention, in the bubble jet 1~ with crystal density array, ink droplets ejected and flying from between adjacent orifices are ejected due to ink wetting on the orifice surface. High image quality can be obtained without the occurrence of merging due to directional deviations, or satellite droplets caused by dragging ink due to wetting.

[Brief explanation of the drawing]

1 to 3 are main part configuration diagrams for explaining the present invention in detail, and FIG. 4 is a configuration diagram for explaining an example of an inkjet recording apparatus to which the present invention is applied. 11.14...Substrate, 12...Heating element, 13...
electrode. 15. Flow path, 16. Orifice. Patent applicant Ricoh Co., Ltd. Figure 1 Figure 4 Figure 2 Figure 3

Claims (1)

[Claims] 1. Having a plurality of ejection orifices arranged close to each other, the recording liquid introduced into a chamber communicating with each orifice is ejected and made to fly as small droplets from each of the orifices by using thermal energy; In a liquid jet recording head that performs recording by adhering small droplets to a recording surface, when the orifice opening size of the plurality of ejection orifices is d, and the interval between adjacent orifice edges is l,
4d>l, and the outer surface of the ejection orifice is treated to be water-repellent or oil-repellent.