JPH02158346A - liquid jet recording head - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid jet recording head, and more specifically,
Related to recording heads of inkjet printers.

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,
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 and improvements have been made to improve the quality of products. Some have been developed, and efforts are still being made to put them into practical use.

In this inkjet recording method, droplets of a liquid called ink are ejected.

Recording is performed by attaching the recording liquid to a recording member, and it is roughly divided into several methods depending on the method of generating recording liquid droplets and the control method for controlling the flight direction of the generated recording liquid droplets. Ru.

First, the first method is disclosed in, for example, US Pat. No. 3,060,429 (Tele type method), in which the generation of recording liquid droplets is electrostatically absorbed, k, =
3, and the generated recording liquid droplets are controlled in an electric field according to a recording signal 7, and recording is performed by selectively making the recording liquid droplets unique 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 the method (Sweet method) disclosed in, for example, U.S. Pat. No. 3,596,275, U.S. Pat. Recording is performed on a recording member by generating small droplets of recording liquid with a controlled amount of charge and flying the generated droplets between deflection electrodes to which a negative electric field is applied. It is something.

Specifically, a charging electrode configured such that a recording signal is applied in front of the nozzle orifice (ejection opening), which is a part of the recording head to which the piezo vibrating element is attached, is used. The piezoelectric vibrating elements are arranged at a predetermined distance apart, and by applying an electric signal of a constant frequency to the piezoelectric vibrating elements, the piezoelectric vibrating elements are mechanically vibrated, and small droplets of recording liquid are ejected from the ejection ports. 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 added, and the droplet carries the recording signal. only can be deposited on the recording member.

The third method is, for example, the method disclosed in U.S. Pat. No. 3,416,153 (Hertz method),
In this method, an electric field is applied between a nozzle and a ring-shaped charged electrode, and small droplets of recording liquid are generated and atomized using a continuous vibration generation method to perform recording. 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 US Pat. 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, 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.

Each of these four conventional methods has its own advantages, but there is also a weak point that can be solved in the other method.

That is, in the first to third methods, the direct energy of generation of one drop of recording liquid is electrical energy, and
Deflection control of droplets is also controlled by electric field, )),,:,.

Therefore, although the first method is simple in structure, it requires a high voltage to generate droplets2, 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 the recording liquid droplets is sophisticated and difficult. There are problems such as the tendency for 1-dot 1- to occur.

The third method has the advantage of being able to record images with excellent gradation by atomizing recording liquid droplets, but on the other hand, it is difficult to control the atomization state and fog occurs in the recorded image. In addition, it is difficult to create a multi-nozzle recording head.
There are various problems such as being unsuitable for high-speed recording.

The fourth method has relatively more advantages than the first to third methods. In other words, the structure is simple, and in order to perform recording by ejecting the recording liquid from the ejection opening of the nozzle on-demand, small droplets that fly are ejected as in the first and third methods. Among them, there is no need to collect droplets that are not needed for recording 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 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. The disadvantages of this method include 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 (corresponding to the above-mentioned US Pat. No. 3,747,120) discloses, as a modification,
It is described that thermal energy is used instead of using mechanical vibration energy by means such as the piezo vibrating element described above.

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 the liquid ink can enter and exit, 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, in Japanese Patent Laid-Open No. 54-51837, the applicant of the present invention has proposed a so-called bubble jet inkjet system that utilizes thermal energy. This is an excellent method in which the area where energy is applied to the ink can be made small and a high-density arrangement can be achieved. As an example of implementing this method, for example, Japanese Patent Laid-Open No. 55-27281 is known.

Although this document describes a method of manufacturing a bubble jet inkjet head using ultrafine processing technology, there is no concept of variations in individual ejection elements.

On the other hand, in Japanese Patent Application Laid-Open No. 63-4955, bubble diene 1
~Inkjet 1-The size of the electrothermal conversion element in the head is
In order to solve the problem caused by variations caused by etching, it has been disclosed that the variation area, that is, both ends of a plurality of arranged electrothermal total ventilation elements are treated as dummy heaters and are not actually used.

This was the first time that the concept of how to manufacture a head for mass production was demonstrated, and compared to previous inventions that only contained theoretical descriptions at the laboratory level, It can be said that this has shown significant progress.

However, JP-A No. 63-4955 merely presents the concept of providing dummy heaters on both sides of the heater that will actually be used, and does not clarify how many dummy heaters should be provided. This has not been considered, and if this continues, it will not be possible to manufacture truly mass-produced heads with consistent high yields.

Purpose The present invention was made in order to solve the drawbacks such as "double series", and to specifically show the range in which variations in ejection performance are allowed, and to provide a method for manufacturing heads for true mass production with a high yield. The purpose of the present invention is to propose a liquid jet recording head that is capable of producing high-quality prints by suppressing variations in the electrothermal converter of the head within an allowable range for variations in ejection performance. It was made with the purpose of providing.

In order to achieve the above object, the present invention provides an ejection port for ejecting a recording liquid to form flying droplets, and a method for guiding the recording liquid to the ejection port. In a liquid jet recording head having a liquid path and an energy application section for applying energy to the recording liquid, a plurality of the energy application sections are arranged, and one of the plurality of energy application sections is actually used for ejecting the recording liquid. This is a liquid jet recording head that has an energy application section near the center, excluding several to several dozen pieces at both ends, and the length in the arrangement direction of the area of the energy application section near the center is expressed as Du, When the length in the arrangement direction of only one side of the energy acting part region not used for ejection is Dd, the following is satisfied: Dd≧0.0279Du+0.548, and the energy acting part is formed by photofabrication; Alternatively, an ejection port for ejecting the recording liquid to form flying droplets, a liquid path for guiding the recording liquid to the ejection port, and an energy applying section for applying energy to the recording liquid. In the liquid jet recording head, a plurality of the energy applying portions are formed in an array by photofabrication, and at least a part of the energy applying portions is the same as the previous energy applying portion by the photofabrication at both ends of the energy applying portions formed in the array. , the length of the region of the energy acting portion in the arrangement direction is Du, and the length of the energy acting portion of only one side of the region having at least a portion of the same layer in the arrangement direction. It is characterized by satisfying the following conditions: Dd≧0, 0279 D u + 0, and 548, where Dd is the distance.

First, the principle of ink ejection using a bubble jet will be explained based on FIG. In the figure, 21 is a lid substrate, 22
27 is a heating element substrate, 27 is a selection (independent) electrode, 28 is a common electrode, 29 is a heating element (heater), 3o is ink, 31 is a bubble, and 32 is a flying ink droplet.

(a) is a steady state, in which the surface tension of the ink 30 and the external pressure are in equilibrium on the orifice surface.

In (b), the heater 29 is heated until the surface temperature of the heater 29 rises rapidly and boiling B development occurs in the adjacent ink layer, and microbubbles 31 are scattered.

(c) shows a state in which the adjacent ink layer that is rapidly heated on the entire surface of the heater 29 is instantaneously vaporized to form a boiling film, and the bubbles 31 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 30 corresponding to the volume of the bubble is pushed out from the orifice surface. At this time, no current is flowing through the heater 29, and the surface temperature of the heater 29 is decreasing. The maximum value of the volume of the bubble 31 is slightly delayed from the timing of electric pulse application.

(e) shows a state in which the bubbles 31 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 31 are further contracted, the ink comes into contact with the heater surface, and the heater surface is 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/sec.

(g) is a process in which ink is again supplied to the orifice by capillary action (refilling) and returns to the state of (a).
The bubbles have completely disappeared. 32 is a flying ink droplet.

Figure 3 is a perspective view of the bubble jet recording spatula I;
The figure is an exploded configuration diagram of the recording head. (,) is the lid substrate, (b)
) is a diagram showing the heating element substrate, and FIG. 5 is a back view of the lid substrate shown in FIG. 4(a).

In the figure, 23 is a recording liquid inlet, 24 is an orifice, and 25
2 is a flow path, and 26 is a region for forming a liquid chamber.

Figures 3 to 5 are simplified diagrams to show the concept of a bubble jet, and the number of orifices (= number of heating elements) is shown as four, but in reality, this is the purpose of the printer. Depending on the situation, 20 to 1000 or more are used. A suitable method for forming these heat generating elements on the plurality of substrates is photofabrication, which is used in a so-called semiconductor manufacturing process. Photofabrication refers to techniques for forming thin films such as vapor deposition and sputtering, and techniques for forming fine patterns from them using techniques such as photolithography, etching, and lift-off. It will be used to form the heating element substrate of the bubble jet head that is being developed. Next, a method for forming a heating element substrate of a bubble jet head to which the present invention is applied will be explained.

First, 5μm thick 5J was deposited on the surface of the Si wafer by thermal oxidation.
-02 film is formed. Furthermore, HfB2 is sputtered to a thickness of 1,500 layers as a heating resistor layer using a sputtering method, and then a layer of 5,000 layers is integrated by electron beam evaporation.

Next, a pattern is formed by a follin graphier process so that desired shapes of the heating element and electrodes are obtained. Next, the 5i02 layer was formed by high-rate sputtering.
．． Accumulate 5 μm.

Thereafter, as a resist for Ta lift-off, a polyimide film such as PIQ manufactured by Hitachi Chemical is patterned to a thickness of 3 μm, and a Ta film of 1.5 μm is patterned by DC sputtering. otLrn. After this Ta film is formed, the PIQ film is peeled off to obtain a desired Ta film pattern, and the substrate fabrication is completed.

In the photofabrication process for producing this heating element substrate, poor circulation of the developer when developing the photoresist or slow development speed may result in many patterns (for example, multiple patterns in the present invention). (the central area where individual heating elements are arranged) and where the pattern is only on one side (for example, in the present invention, both ends where multiple heating elements are arranged)
Then, due to the difference, the width of the photoresist pattern becomes non-uniform, and by masking the non-uniform photoresist and etching it afterwards, the non-uniformity of the photoresist pattern width becomes the pattern of the underlying thin film. As reflected in this, for example, there is a problem in that the size of the heating element formed of a thin film is different between the heating element in the central region of the plurality of arranged heating elements and the heating element at both ends. Furthermore, if some means were used (for example, it is possible to slightly change the photomask pattern d1 at the center and both ends to compensate for variations during development), one pattern after development of the photoresist could be Even if it is possible to form a uniform pattern, there may be problems with poor circulation of the etching solution, or the speed at which the etching progresses. There is a problem that, for example, the pattern lJ of the heating element becomes non-uniform due to the difference in the area where there is only one side. In view of these problems, Japanese Patent Laid-Open No. 63-4955, which presents a concept for solving the problems, can be said to be an excellent invention. However, since there is no description as to how many dummy heaters should be provided in more detail, it is not possible to actually supply heads for mass production without variation as is. In view of this, the inventors of the present invention have repeatedly carried out a huge amount of experiments and prototypes, quantitatively clarified the optimum conditions, and made it possible to manufacture a head for mass production without variation. Hereinafter, the present invention will be explained based on examples.

FIG. 1 is a configuration diagram for explaining one embodiment of a liquid jet recording head according to the present invention. In the figure, numeral 11 indicates an area of an energy applying part (here, a heat generating part) used for ejecting ink droplets; Let Du be the length in the arrangement direction. Reference numeral 12 denotes a region of an energy application portion that is not used for ejecting ink droplets, in other words, a region of a dummy heater provided to compensate for variations in pattern size due to photoetching, and its length in the arrangement direction is designated as Dd. IIA is a heating element, and IIB is an electrode. Note that Dd is on both sides, and their lengths are generally equal, but they do not necessarily have to be equal. If they are not equal due to some design reasons, the shorter Dd can be used in the present invention. It is better to apply it to Note that the definition of Du and D'd is not strictly a value measured from the edge of the pattern of the heating element 11A, but is a unit of one ejection element (including the replaced electrode 11B), and therefore a number This includes an error of μm to several tens of μm.

Table 1 shows the evaluation results for the prototype.

Next, other embodiments of the present invention are shown in FIGS. 6 to 8. Here, 10 is a region of an energy acting portion used for ejecting ink droplets, and its length in the arrangement direction is Du. 11A is a heating element, 13 is an electrode, 41.51.61 is different from the case in FIG. 1, and does not take the form of a dummy heater; This is a region having the same layer, for example, the same layer as the heating element 11, and its length (here, the length in the direction in which the energy acting parts are arranged) is set as Dd.

Table 2 shows the results of trial production and evaluation with such patterns provided at both ends of the energy application section. The prototype actually manufactured here is of the type shown in FIG. 6, and FIGS. 7 and 8 are shown to show that such examples are also possible.

Based on the above prototype production, evaluation, and study results, the present inventors found that in order to form such an energy acting part by photofabrication and keep the variation in ejection performance of the inkjet head within an allowable range, We found that it would be sufficient to provide a dummy heater or an equivalent area.

However, if the number of dummy heaters or an equivalent area is too small, it will not be effective, and even if an unlimited number of dummy heaters are provided, the cost will only increase. Based on the above results, the present inventors determined that the length Du in the arrangement direction of the region of the energy action part used for ejection, the length in the arrangement direction of only one side of the region of the energy action part not used for ejection, or the length in the arrangement direction of the region of the energy action part not used for ejection At least a part of the area forms a region having the same layer. Length D in the arrangement direction of the energy acting area
If the energy application section and the dummy heater or the dummy heater equivalent section are laid out so that d satisfies the following conditions, the completed head will have small variations in ink droplet ejection speed and high image quality. It was discovered that printing could be obtained. That is, by designing the head so as to satisfy Dd≧0.0279Du+0.548, a head with little variation and suitable for high-quality mass production can be obtained.

It should be noted that this empirical formula is suitably applied when the area of the energy acting part used for ejection is 3.3 mm to 4.3 mm, and when the arrangement density force of the element is 200 to 800 dpj. As is clear from the above explanation, according to the present invention, by optimizing the conditions for providing the dummy heater, it is possible to mass-produce high-performance heads with the highest production efficiency and less variation. became. Furthermore, by using this head, it has become possible to print with extremely high image quality (corresponding to claim 1).

Further, since it is not necessarily necessary to have the same shape as the energy acting part used for ejection, the photomask can be simplified and can be made at low cost. The production efficiency effect of providing a region equivalent to a dummy heater under certain conditions (experimental formula of the present invention), or the fact that high-performance heads can now be mass-produced and that high-quality printing can be performed using them. The above points are the same as the effects corresponding to claim 1 (corresponding to claim 2).

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram for explaining an embodiment of a liquid jet recording head according to the present invention, and FIG. 2 is a principle diagram for explaining the generation and disappearance of bubbles in the ejection of bubble jet ink from the recording head. FIG. 3 is a perspective view of the recording head, and FIG. 4 is an exploded view of the recording head.
) is a diagram showing the heating element substrate, FIG. 5 is a back view of the lid substrate of the recording head, and FIGS. 6 to 8 are diagrams showing other embodiments of the liquid jet recording head according to the present invention. . 10... Energy acting part, 11... Area of energy acting part used for ejecting ink droplets, LA... Heat generating element (heater), 12... Area of energy acting part not used for ejecting ink droplets, IIB, 13...electrode, 4.1,
51.61...Energy action part. Patent applicant Rico Co., Ltd.

Claims (1)

[Scope of Claims] 1. An ejection port for ejecting recording liquid to form flying droplets, a liquid path for guiding the recording liquid to the ejection port, and for applying energy to the recording liquid. In a liquid jet recording head having an energy application section, a plurality of energy application sections are arranged, and among the plurality of energy application sections, only a few at both ends to several 1 are actually used for ejecting the recording liquid.
In a liquid jet recording head that is an energy application section near the center excluding 0 pieces, the length in the arrangement direction of the area of the energy application section near the center is Du, and only one side of the energy application section area is not used for ejection. The length in the array direction is D
A liquid jet recording head, wherein Dd≧0.0279Du+0.548 is satisfied, and the energy application portion is formed by photofabrication. 2. An ejection port for ejecting recording liquid to form flying droplets, a liquid path for guiding the recording liquid to the ejection port, and an energy applying section for applying energy to the recording liquid. In the liquid jet recording head, a plurality of the energy application parts are formed in an array by photofabrication, and a plurality of energy application parts are arranged at both ends of the arrayed energy application parts by the photofabrication.
A region having at least a part of the same layer as the front energy acting part is formed, and the length of the region of the energy acting part in the arrangement direction is Du, and the at least part of the region has the same layer only on one side. A liquid jet recording head characterized in that, where Dd is the length of the energy application portions in the arrangement direction, Dd≧0.0279Du+0.548 is satisfied.