JPH01234255A - Liquid jet recording head - Google Patents

Abstract

PURPOSE:To uniformize the emitting capacities of respective colors in such a case that a bubble jet type liquid jet head is used in color recording, by making all of the lengths from the parts communicating with liquid chambers of flow passages to heat energy acting parts not equal necessarily. CONSTITUTION:For example, heads are provided with respect to four colors Y(yellow), M(magnet), C(cyan), B(black) so as to obtain uniform emitting capacity even when the physical properties of plural inks having respective colors or densities are not constant necessarily. The lengths l from the parts communicating with liquid chambers 6 of flow passages 5 to heat energy acting parts 9 are changed or heads each having plural orifices are independently provided at every colors or the lengths l are made constant but the distances from the heat energy acting parts 9 to orifices 4 are changed. By this method, even when the physical properties of ink are different at every colors (or densities), by changing the lengths of the flow passages corresponding thereto, the irregularity of a supply speed can be corrected. The emitting capacities from the respective orifices of the respective inks can be also made uniform.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid jet recording head, and more particularly to a bubble jet type liquid jet color recording head.

Dead rice skin 4 Non-impact recording methods have recently attracted attention because the noise generated during recording is so small that it can be ignored. Among them, high-speed recording is possible,
However, the so-called inkjet recording method, which allows recording on plain paper without the need for special fixing treatment, is an extremely powerful recording method, and various methods have been proposed, improved, and commercialized. Some have been developed, and efforts are still being made 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. There are several types of methods depending on the control method used to control the flight direction of the generated recording liquid droplets.

First, the first method is the one disclosed in USP 3060429 (Tele type method), in which droplets of recording liquid are generated electrostatically, and the generated recording liquid droplets are used as a recording signal. Recording is performed by controlling the electric field in accordance with the temperature and selectively depositing recording liquid droplets on the 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 ejected recording liquid droplet is converted into a recording signal. Accordingly, the droplet is caused to fly between x and y deflection electrodes configured to be electrically controllable, and the droplet is selectively deposited on the recording member by changing the intensity of the electric field to perform recording.

The second method is described, for example, in USP 3596275, U
The method disclosed in SP 3298030 etc. (Swe
et method), in which droplets of recording liquid with a controlled amount of charge are generated by a continuous vibration generation method, and a --like electric field is applied to the generated droplets with a controlled amount of charge. Recording is performed on a recording member by flying between deflection electrodes.

Specifically, the orifice (discharge d) of the 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, charges are electrostatically induced in the recording liquid droplet discharged by the charging electrode, and the droplet is charged with an amount of charge corresponding to the recording signal. When a droplet of recording liquid with a controlled amount of charge flies between deflection electrodes to which a constant electric field is uniformly applied, it is deflected according to the amount of charge applied.
Only the droplets carrying the recording signal are allowed to deposit on the recording member.

The third method is, for example, the method disclosed in U.S.P. 3416153 (Hertz method), in which an electric field is applied between a nozzle and a ring-shaped charged electrode, and small droplets of recording liquid are generated by a continuous vibration generation method. This method records by atomizing it. That is, in this method, the atomization state of droplets is controlled by modulating the electric field intensity applied between the nozzle and the charging electrode in accordance with the recording signal, and the gradation of the recorded image is produced.

The fourth method is, for example, the method disclosed in USP 3747120 (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, the Stemme method applies an electrical recording signal to a piezo vibrating element attached to a recording head that has an ejection port for discharging recording liquid, and converts this electrical recording signal into mechanical vibration of the piezo vibrating element. In this method, recording is performed by ejecting small droplets of recording liquid from the ejection opening according to the mechanical vibrations and adhering them to the recording member.

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 the droplets 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 of being able to record images with excellent gradation by atomizing small droplets of recording liquid, but on the other hand, it is difficult to control the atomization state and the recorded image may be foggy. There are various problems such as the occurrence of the problem, the difficulty in making the recording head multi-nozzle, and the fact that it is 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 to record an image, and unlike the first and second methods, there is no need to use a conductive recording liquid, and the material of the recording liquid is It has great advantages such as a high degree of freedom. On the other hand, on the other hand, it is difficult to make a recording head with multiple nozzles due to problems in processing the recording head, and it is extremely difficult to miniaturize a piezoelectric vibrating element having a desired resonance number. This method has disadvantages such as that it is not suitable for high-speed recording because the recording liquid droplets are ejected into 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. 3,747,120) describes, as a modification, the use of thermal energy instead of the mechanical vibration energy provided by means such as the piezo vibration 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 important in practice.

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. There was a restriction that it could only be applied.

Furthermore, Japanese Patent Laid-Open No. 57-12659 discloses a recording head in which the distance between the orifice of each color of a color inkjet and a common ink chamber is the same, but since the physical properties of the ink differ depending on the color, It is not necessarily a good idea to make the distance between the orifice and the common ink chamber the same. If all the distances are made the same, the physical properties of the ink of each color must also be made the same, which causes considerable difficulty in ink production.

Purpose The present invention was made in view of the above-mentioned circumstances.
In particular, this was done with the aim of equalizing the ejection performance for each color when a bubble jet liquid ejecting head is used for color recording.

Structure In order to achieve the above object, the present invention contains a recording liquid to be introduced, generates bubbles in the recording liquid by heat, and generates an action force as the volume of the bubbles increases. a flow path provided with an energy acting section; an orifice connected to the flow path for causing the recording liquid to be ejected as droplets by the acting force; In a liquid jet recording head comprising a liquid chamber for introducing the recording liquid and a means for introducing the recording liquid into the liquid chamber, the orifice, the flow path, and the thermal energy applying portion each have a different color or a different color. The recording liquids are arranged according to the number of concentration recording liquids, and the lengths from the portions of the flow paths communicating with the liquid chambers to the thermal energy application portions are not necessarily all equal. Hereinafter, the present invention will be explained based on examples.

FIGS. 1(a) to (c) are main part configuration diagrams for explaining embodiments of the present invention, and FIG. 2 is an operation of a bubble jet head as an example of an inkjet head to which the present invention is applied. 3 is a perspective view showing an example of a bubble jet head, and FIG. 4 is a diagram showing a lid substrate (FIG. 4(a)) and a heating element constituting the head shown in FIG. 3. A perspective view of the substrate (FIG. 4(b)) when it is disassembled, and FIG. 5 is a perspective view of the lid substrate shown in FIG. 4(a) seen from the back side. 2 is a heating element substrate, 3 is a recording liquid inlet, 4 is an orifice, 5 is a channel, 6 is a region for forming a liquid chamber, 7 is an individual (independent) electrode, 8 is a common electrode,
9 is a heating element (heater), 10 is ink, 11 is a bubble, 1
2 is a flying ink droplet, and the present invention is applied to such a bubble jet type liquid jet recording head.

First, ink ejection by a bubble jet will be described with reference to FIG. 2. (a) is a steady state, in which the surface tension of the ink 10 and the external pressure are in equilibrium on the orifice surface.

In (b), the heater 9 is heated until the surface temperature of the heater 9 rises rapidly and boiling development occurs in the adjacent ink layer, and microbubbles 11 are scattered.

(Q) shows a state in which adjacent ink layers that are rapidly heated over the entire surface of the heater 9 are instantaneously vaporized to form a boiling film, and the bubbles 11 grow. At this time, the pressure inside the nozzle increases by the amount of bubble growth, and the balance with the external pressure on the orifice surface is lost, causing an ink column to begin to grow from the orifice.

(d) shows a state in which the bubble has grown to its maximum, and ink 10 corresponding to the volume of the bubble is pushed out from the orifice surface. At this time, no current is flowing through the heater 9, and the surface temperature of the heater 9 is decreasing. bubble 11
The maximum value of the volume of is slightly delayed from the timing of electric pulse application.

(e) shows a state in which the bubbles 11 are cooled by ink or the like and begin to contract. At the tip of the ink column, it moves forward while maintaining the extruded speed, and at the rear end, the ink flows backward from the orifice surface into the nozzle due to the decrease in nozzle internal pressure as the bubbles contract, creating a constriction in the ink column. .

In (f), the air bubbles 11 are further contracted, and the ink comes into contact with the heater surface, causing the heater surface to be cooled even more rapidly. At the orifice surface, the external pressure is higher than the nozzle internal pressure, so the meniscus is largely moving into the nozzle. The tip of the ink column becomes a droplet and drops 5 to 1 droplets toward the recording paper.
It is flying at a speed of 0 m/see.

In (g), the air bubbles have completely disappeared in the process of refilling the orifice with ink by capillary action and returning to the state of (a).

The present invention was made in view of the drawbacks of the invention described in JP-A No. 57-12659, and provides uniform ejection performance even if the physical properties of a plurality of inks of each color or density are not necessarily constant. The embodiment shown in FIG. 1(a) has one head for each of the four colors Y (yellow), M (magenta), C (cyan), and B (black). They are provided one by one. Here, in order to simplify the explanation, the lid substrate 1 and the heating element substrate 2 are omitted, and only the flow path and the liquid chamber are shown. This embodiment shows a case where the length Q from the part of the flow path 5 communicating with the liquid chamber 6 to the thermal energy application part 9 is not the same. Recording liquid (ink) is supplied from the liquid chamber 6 to each channel 5 by capillary action, and the supply speed varies depending on the physical properties of the ink. If the physical properties of all color inks could be made exactly the same, there would be no problem since they would all be supplied at the same speed, but it is difficult to make such inks. Therefore, as in the present invention, even if the ink physical properties are different for each color (or each density), variations in supply speed can be corrected by changing the length of the flow path accordingly.

Differences in ink physical properties cause not only variations in the speed at which ink is supplied to the thermal energy application area, but also variations in ejection performance for each color. Therefore, changing the length of the flow path for each color of ink not only corrects variations in supply speed, but also equalizes the ejection performance of each ink from each orifice.

The embodiment shown in FIG. 1(b) shows an example of a multi-array having a plurality of (three in this case) orifices (channels) 5 for each color. This is an example and does not necessarily require all orifices of all colors to be on the same substrate.
A head having a plurality of orifices may be provided independently for each color.

FIG. 1(c) shows another embodiment, in which the flooding is kept constant and the thermal energy acting part 9 is connected to the orifice 4.
It is designed to change the distance.

Note that the above explanation takes four colors, Y, M, C, and H, as an example, but it also applies to other colors or when the density of these colors is changed.

FIG. 6 is a diagram for explaining another means for generating bubbles in the recording liquid, in which 21 is a laser oscillator, 22 is a light modulation active circuit, 23 is a light modulator, 24 is a scanner, and 25 is a condensing lens, and the laser beam generated by the laser oscillator 21 is pulse-modulated in the optical modulator 23 according to the image information signal that is input to the optical modulator active circuit 22, electrically processed, and output. . The pulse-modulated laser beam passes through the scanner 24 and is focused by the condenser lens 25 on the outer wall of the thermal energy application section, heating the outer wall 26 of the recording head and causing the inner recording liquid 27 to be heated. to generate air bubbles. Or the wall 26 of the thermal energy acting part.
is made of a material that is transparent to laser light, and the light is focused on the recording liquid 27 inside by a condenser lens 25, and bubbles may be generated by directly heating the recording liquid. .

FIG. 7 is a diagram for explaining an example of a printer using laser light as described above. This example shows an example in which the entire area (width) is covered.

Laser light emitted from the laser oscillator 21 is guided to the entrance opening of the optical modulator 23. In the optical modulator 23, the laser beam is modulated in intensity according to the image information input signal to the optical modulator 23. The modulated laser beam passes through the reflecting mirror 2
8 bends the optical path toward the beam expander 29.

The beam enters the beam expander 29. The beam expander 29 expands the beam diameter while remaining parallel light.

Next, the laser light whose beam diameter has been expanded is incident on a rotating polygon mirror 30 that rotates at a constant high speed. The laser beam swept by the rotating polygon mirror 30 is focused by the condensing lens 25.
The image is formed on the outer wall 26 of the thermal energy acting part of the drop generator or on the recording liquid inside. As a result, bubbles are generated in each thermal energy applying portion, and recording droplets are ejected to perform recording on the recording paper 32.

FIG. 8 is a diagram showing still another bubble generating means. In this example, a pair of discharge electrodes 40 arranged on the inner wall side of the thermal energy application section receive a high voltage pulse from a discharge device 41. This device generates an electrical discharge in water, and the heat generated by the electrical discharge instantly forms bubbles.

9 to 16 are diagrams showing specific examples of the discharge electrode shown in FIG. 8, respectively. In the example shown in FIG. 9, the electrode 40 is shaped like a needle to concentrate the electric field and efficiently It is designed to cause a discharge (with low energy).

In the example shown in FIG. 10, two flat plate electrodes are used to stably generate bubbles between the electrodes. The position of the needle-shaped electrode and the generated bubbles is stable.

The example shown in FIG. 11 is one in which the electrode has a substantially coaxial hole. The holes in the two electrodes serve as guides, making the position of the bubbles even more stable.

The example shown in FIG.

This is a ring-shaped electrode, which is basically the same as the example shown in FIG. 11, and is a modified example thereof.

In the example shown in FIG. 13, one is a ring-shaped electrode and the other is a needle-shaped electrode. The ring-shaped electrode aims to stabilize the generated bubbles, and the needle-shaped electrode aims to improve efficiency by concentrating the electric field.

In the example shown in FIG. 14, one ring-shaped electrode is formed on the wall surface of the thermal energy application section. In addition to the effects of the example shown in FIG. 13, this is aimed at ease of manufacturing by forming electrodes in a two-dimensional manner on the substrate. A plurality of such planar electrodes can be easily manufactured with high density by vapor deposition (or sputtering) or photoetching techniques. Particularly effective for multi-arrays.

In the example shown in FIG. 15, the ring-shaped electrode forming portion of the example shown in FIG. 14 is shaped along the outer periphery of the electrode and is raised one step higher than the surroundings. Again, the aim is to stabilize the generated bubbles, and the stability is greater than that shown in FIG. 13 by adding a three-dimensional guide.

The example shown in FIG. 16, contrary to the example shown in FIG. 15, has a structure in which the ring-shaped electrode forming part is sunk downward from the periphery.
The generated bubbles are stably formed.

As is clear from the above description, according to the present invention, even if the physical properties of each color ink are different.

Uniform discharge performance can be achieved.

[Brief explanation of the drawing]

FIGS. 1(a) to (c) are main part configuration diagrams for explaining the present invention in detail, and FIG. 2 is an explanation of the operation of a bubble jet head as an example of an inkjet head to which the present invention is applied. 3 is a perspective view showing an example of a bubble jet head, FIG. 4 is an exploded perspective view, and FIG. 5 is a perspective view showing an example of a bubble jet head. FIG. 6 is a diagram illustrating an example of a bubble generating means using a laser beam, and FIG. 7 is a diagram illustrating an example of a printer. FIG. 8 is a diagram for explaining an example of a bubble generating means using discharge, and FIGS. 9 to 16 are diagrams showing specific examples of the discharge electrode shown in FIG. 8, respectively. DESCRIPTION OF SYMBOLS 1...Lid board, 2...Heating element board, 3...Ink supply port. 4... Orifice, 5... Channel, 6... Liquid chamber, 7
, 8... Electrode, 9... Heating element. Figure 1 (b) (C) ,! 2 Figure (d) Bow == Figure 3:5 Figure 4 Figure 5 Figure 6 Figure 8 Figure 9 Figure 11 Figure 13 Figure 15 Figure 1 (J Figure 12 Figure 14 Figure 16

Claims (1)

[Claims] 1. A flow path that accommodates the recording liquid to be introduced and is provided with a thermal energy acting section that generates bubbles in the recording liquid by heat and generates an acting force as the volume of the bubbles increases; an orifice that communicates with the flow path to eject the recording liquid as droplets by the acting force; a liquid chamber that communicates with the flow path and introduces the recording liquid into the flow path; In a liquid jet recording head comprising a means for introducing a liquid, the orifice, the flow path, and the thermal energy application section are respectively arranged according to the number of recording liquids of different colors or different concentrations, and the A liquid jet recording head characterized in that the lengths from the portions of the channels communicating with the liquid chambers to the thermal energy acting portions are not necessarily all equal.