JPH058395A - Liquid jet recording head, production thereof, and liquid jet recording method - Google Patents

Abstract

PURPOSE:To obtain a liquid jet recording head superior in durability and capable of arranging delivery ports with a high density and conducting a gradation recording. CONSTITUTION:In a liquid fly recording head comprising heating element layers 17, 23; electrothermal energy conversion bodies 21, 27 which are respectively provided with heating parts 20, 26 formed by connecting a pair of electrodes 18, 19 (24, 25) to the heating element layers 17, 23; and delivery ports from which liquid subjected to the action of the bubbles generated in the liquid by heat from the heating parts 20, 26 is delivered as flying liquid drops, the two or more electrothermal energy conversion bodies 21, 27 are laminated through an insulating layer 22. In addition, the areas of the heating parts 20, 26 are made different from each other for each of the laminated electrothermal energy conversion bodies 21, 27. Alternatively, the positions of the heating parts 20, 26 are shifted to each other for each of the laminated electrothermal energy conversion bodies 21, 27.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid jet recording head,
More specifically, the present invention relates to a liquid jet recording head that enables gradation recording in a so-called thermal inkjet printer that uses heat to fly ink.

[0002]

2. Description of the Related Art The non-impact recording method has recently been attracting attention because noise generation during recording is extremely small so that it can be ignored. Among them, the so-called ink jet recording method, which is capable of high-speed recording and is capable of recording on so-called plain paper without requiring a special fixing process, is an extremely powerful recording method, and has been widely used so far. A method has been proposed, or already commercialized and put into practical use.

In such an ink jet recording method, small droplets of a recording liquid, so-called ink, are ejected and adhered to a recording medium for recording, and the generation method and the generation of the recording liquid droplets are performed. Depending on the control method for controlling the flight direction of the recording liquid droplets, it is roughly classified into several methods.

The first method is, for example, US Pat. No. 3060.
No. 429 is disclosed. this is,
It is called a Teletype method, in which the recording liquid droplets are electrostatically attracted, and the generated recording liquid droplets are subjected to an electric field control according to a recording signal to selectively eject the recording liquid droplets on a recording medium. The recording is performed by attaching them.

More specifically, an electric field is applied between the nozzle and the accelerating electrode to eject uniformly charged recording liquid droplets from the nozzle, and the ejected recording liquid droplets can be electrically controlled according to a recording signal. Recording is performed by flying between the xy deflection electrodes configured as described above and selectively adhering recording liquid droplets onto the recording medium according to a change in the strength of the electric field.

The second method is, for example, US Pat. No. 3,596.
No. 275, U.S. Pat. No. 3,298,030, and the like. This is called a Sweet method, and a recording liquid droplet whose charge amount is controlled is generated by a continuous vibration generating method, and this recording liquid droplet whose charge amount is controlled is applied with a uniform electric field. Recording is performed on the recording medium by flying between the deflection electrodes.

Specifically, a charging electrode configured so that a recording signal is applied before an orifice (ejection port) of a nozzle, which is a part of a recording head provided with a piezoelectric vibrating element, has a predetermined distance. The piezoelectric vibrating elements are mechanically vibrated by applying an electric signal having a constant frequency to the piezoelectric vibrating elements so as to eject recording liquid droplets from the orifices. At this time, electric charges are electrostatically induced in the recording liquid droplets ejected by the charging electrodes, and the recording liquid droplets are charged with a charge amount according to the recording signal. The recording liquid droplet whose charge amount is controlled is deflected according to the added charge amount when flying between the deflection electrodes to which a constant electric field is uniformly applied, and the recording liquid droplet bears a recording signal. Only the liquid is allowed to adhere onto the recording liquid.

The third method is, for example, US Pat. No. 3,416.
No. 153 is disclosed. this is,
The Hertz method is a method in which an electric field is applied between a nozzle and a ring-shaped charging electrode to generate and atomize recording liquid droplets by a continuous vibration generation method, and recording is performed. That is, the atomization state of the recording liquid droplets is controlled by modulating the electric field strength applied between the nozzle and the charging electrode according to the recording signal, and the gradation of the recorded image is produced and recording is performed.

The fourth method is, for example, US Pat. No. 3747.
No. 120 specification. this is,
It is called the Stemme system and has a fundamentally different principle from the first to third systems. That is, in any of the first to third methods, the recording liquid droplets ejected from the nozzles are electrically controlled while flying, and the recording liquid droplets carrying the recording signal are selectively covered. On the other hand, recording is performed by attaching the recording liquid onto a recording medium, whereas in the Stemme system, recording liquid droplets are ejected and ejected from an ejection port according to a recording signal to perform recording.

That is, in the Stemme system, an electric recording signal is applied to a piezoelectric vibrating element attached to a recording head having an ejection port for ejecting a recording liquid droplet, and this electric recording signal is applied to the piezoelectric vibrating element. The recording is performed by changing to the mechanical vibration of (1) and ejecting and ejecting the recording liquid droplets from the ejection port according to the mechanical vibration to adhere to the recording medium.

Each of these four methods has its own characteristics, but at the same time, it has problems to be solved.

First, in the first to third methods, the direct energy for generating the recording liquid droplets is electric energy, and the deflection control of the recording liquid droplets is also electric field control. Therefore, the first method has a simple structure, but requires high voltage to generate recording liquid droplets, and it is difficult to form the recording head with multiple nozzles, and is not suitable for high-speed recording.

The second method is capable of multi-nozzle recording heads and is suitable for high-speed recording, but it is complicated in structure, and the electrical control of recording liquid droplets is high and difficult. Satellite dots are easily generated on the recording medium.

The third method enables recording with excellent gradation by atomizing recording liquid droplets, but it is difficult to control the atomization state. Further, there are drawbacks such that fog occurs in a recorded image and it is not suitable for high-speed recording because it is difficult to form a recording head with multiple nozzles.

The fourth method has many advantages over the first to third methods. First, the structure is simple. Further, since the recording liquid droplets are ejected on demand from the ejection ports of the nozzles for recording, the recording liquid droplets ejected and ejected as in the first to third methods that are not necessary for image recording. Collecting liquid droplets is no longer necessary. Further, unlike the first and second methods, there is no need to use a conductive recording liquid, and there is an advantage that the degree of freedom in terms of the substance of the recording liquid is large. However, because of a problem in processing the recording head, and because it is extremely difficult to downsize the piezoelectric vibration element having a desired resonance frequency,
It is difficult to use multiple nozzles for the recording head. Further, since the recording liquid droplets are ejected and ejected by mechanical energy called mechanical vibration of the piezo-vibration element, it is unsuitable for high-speed recording in combination with the difficulty of forming multiple nozzles.

As described above, the conventional liquid jet recording method has advantages and disadvantages in terms of configuration, high-speed recording, multi-nozzle recording head, generation of satellite dots and fog of recorded image. However, there is a restriction that it can be applied only to the application in which its advantage is exerted.

However, such an inconvenience can be almost eliminated by adopting the ink jet recording system disclosed in Japanese Patent Publication No. 56-9429 proposed by the present applicant. In this method, the ink in the liquid chamber is heated to generate bubbles, thereby causing a pressure increase in the ink and ejecting the ink from a fine capillary nozzle to perform recording. Many inventions have been made using this principle. For example, Japanese Patent Publication No. 59-31943.
There is one disclosed in the publication. According to the present invention, gradation recording is performed by applying a signal having gradation information to an electrothermal converter having a heat generating portion having a heat generation amount adjusting structure and generating heat in the heat generating portion according to the signal. It is a feature. Specifically, the structure is such that the thickness of the protective layer, the heat storage layer or the heating element layer gradually changes, or the pattern width of the heating element layer gradually changes.

FIGS. 13 (a) to 13 (c) are sectional structural views showing examples of the electrothermal converters disclosed in FIGS. 4 to 6 of the above Japanese Patent Publication No. 59-31943, respectively. Reference numeral 1 is a substrate, 2 is a heat storage layer, 3 is a heating element layer, 4 and 5 are a pair of electrodes facing each other, and 6 is a protective film. In the example shown in FIG. 13 (a), the protective film 6 is provided with a thickness gradient from the electrode 4 side to the electrode 5 side, so that it acts on the liquid in contact with the surface of the heat generating portion 7. The amount of heat generated per unit time is gradually reduced from A to B. Moreover, the example shown in FIG.
Is gradually reduced from A to B in the heat generating portion 7 so that the amount of heat generated from the heat generating portion 7 to the substrate 1 is distributed and the liquid contacting the surface of the heat generating portion 7 is distributed. A gradient is provided in the amount of heat per unit time that acts on. In the example shown in FIG. 13C, the heat generating layer 3 having a thickness gradient in the range of the heat generating portion 7 is used as the heat storage layer 2.
It is formed on the above, and controls the amount of heat generation per unit time in each part of the heat generating part 7 by changing the resistance in each part of the heat generating part 7.

Further, FIGS. 14 (a) to 14 (e) are respectively shown in FIGS. 9 to 13 of Japanese Patent Publication No. 59-31943.
In the plan structure diagram showing an example of the electrothermal converter disclosed in the figure,
In the figure, 8 is a heat generating part, and 9 and 10 are a pair of electrodes facing each other. In the example shown in FIG. 14A, the heat generating portion 8 has a rectangular planar shape, and the connecting portion between the electrode 9 and the heat generating portion 8 is smaller than the connecting portion between the electrode 10 and the heat generating portion 8. 14
In the examples shown in (b) and (c), the central portion of the heat generating portion 8 has a planar shape that is thinner than both ends. Further, in the example shown in FIG. 14D, the planar shape of the heat generating portion 8 is a trapezoid, and the electrodes 9 and 10 are connected as shown in the opposite sides of the trapezoid that are not parallel to each other. Also, FIG.
4 (e) is a plan view in which the central portion of the heat generating portion 8 is wider than both ends. These examples are from A to B of the heating section 8.
Configured to give a negative slope to the current density towards
By changing the applied power level, the heating unit 8
By controlling the abrupt change in the state of the liquid above, the size of the ejected droplet is changed, and gradation recording is performed by this.

[0020]

However, as shown in FIG. 13 (a).
It is practically impossible to form a three-dimensional structure like the example shown in (c) by a thin film forming technique, and even if it can be formed, it has a disadvantage that the cost is very high. There is.

As shown in FIGS. 14 (a) to 14 (e), in which the pattern width of the heating portion 8 is changed, the variable diameter region of the dot formed by the liquid droplets adhering to the recording medium is formed. In addition to being narrow, it is difficult to control, and disconnection is likely to occur at the narrowest pattern width, and good results have not always been obtained in terms of durability.

On the other hand, Japanese Patent Laid-Open No. 63-42872 discloses a similar gradation recording technique. This is also a special public Sho 59
Similar to the technique of Japanese Patent Publication No. 31943, it is characterized in that the heating element layer has a three-dimensional structure, and has a drawback that it is extremely difficult to manufacture.

Other gradation recording techniques include Japanese Patent Publication Sho 6
Those described in JP-A-2-46358 and JP-B-62-46359 are known. They select a predetermined number of heat generating elements from a plurality of heat generating elements arranged in one flow path respectively, or select one of a plurality of heat generating elements having different heat generation amounts to generate bubbles. The discharge amount is changed by changing the size or variably controlling the deviation of the input timing of the drive signal to the plurality of heating elements.

However, in these techniques, for example, as shown in FIGS. 15 (a) and 15 (b), since a plurality of heating elements 11 and 12 correspond to one flow passage or discharge port, Since the individual electrodes 13 and 14 connected to the plurality of heating elements 11 and 12 are arranged side by side, it is impossible to arrange the discharge ports at a high density.

Further, Japanese Patent Laid-Open No. 59-124863,
Japanese Unexamined Patent Publication No. 59-124864 discloses a technique for controlling the ejection amount by using a heating element and a bubble generating part which are different from the heating element for ejecting droplets.
It has a drawback that high density arrangement is difficult due to the existence of the bubble generating part.

Further, Japanese Patent Laid-Open No. 63-42869 discloses a technique of controlling the discharge amount of liquid droplets by changing the number of times of generation of bubbles by changing the time for energizing the resistor. However, in a normal bubble jet, the energization time is limited to several to several tens of μs, and if the energization time is longer than that, the heating element is broken.
The technique of Japanese Patent Publication No. 69 is durable and practically unrealizable.

As described above, various attempts have been made in the prior art to perform gradation recording. However, in terms of manufacturing and durability, and from the viewpoint of high-density arrangement, a satisfactory result is not always obtained. Not obtained.

[0028]

According to another aspect of the invention, there is provided an electrothermal converter having a heating element layer and a heating element formed by connecting a pair of electrodes to the heating element layer.
In a liquid jet recording head having an ejection port for ejecting the liquid, which has been subjected to the action of bubbles generated in the liquid by the heat from the heat generating portion, as flying droplets, a plurality of electrothermal converters are provided via an insulating layer. Laminated.

According to a second aspect of the invention, in the first aspect of the invention, the area of the heat generating portion is different for each laminated electrothermal converter.

According to a third aspect of the invention, in the first aspect of the invention, the position of the heat generating portion is shifted for each laminated electrothermal converter.

According to a fourth aspect of the invention, in the first aspect of the invention, the area of the heat generating portion is made smaller as the electrothermal converter is closer to a liquid.

According to the invention of claim 5, claims 1, 2,
In the invention described in 3 or 4, at least two electrothermal converters are connected to each other at one electrode.

According to a sixth aspect of the present invention, in the fifth aspect of the present invention, the heating element layer and the electrode layer are formed on the substrate by photofabrication, and are patterned into a desired shape to form the first electrothermal conversion. A step of forming a body,
Forming an insulating layer on the first electrothermal converter, forming an opening by photoetching at a position in the insulating layer corresponding to one electrode of the first electrothermal converter; And a step of forming a second electrothermal converter by patterning into a desired shape while forming a heating element layer and an electrode layer on the layer by photofabrication, and one of the first electrothermal converters. The electrode and one electrode of the second electrothermal converter were connected through the opening.

According to a seventh aspect of the present invention, a plurality of electrothermal converters each having a heating element layer and a heating section formed by connecting a pair of electrodes to the heating element layer are laminated via an insulating layer. A liquid jet recording method for performing recording by ejecting the liquid, which is subjected to the action of bubbles generated in the liquid by the heat from the heat generating portion, as ejection liquid droplets from an ejection port,
Selecting the electrothermal converter for inputting a signal according to image information, or changing the number of the electrothermal converters for inputting a signal, or changing the input energy to the electrothermal converter Alternatively, the mass of the flying droplets to be ejected is changed by changing the timing of the signal input to each electrothermal converter.

[0035]

According to the first aspect of the present invention, by stacking a plurality of electrothermal converters with the insulating layer interposed therebetween, one discharge port can be provided without being restricted by the arrangement of the electrodes of each electrothermal converter. It is possible to provide a plurality of electrothermal converters, and by appropriately controlling the voltage applied to the electrodes of these electrothermal converters, the mass of flying droplets to be ejected changes, and gradation recording can be performed.

According to the second aspect of the present invention, the area of the heat generating portion is different for each electrothermal converter, so that the volume of bubbles generated changes depending on which electrode of the electrothermal converter the voltage is applied to. With this, the mass of the flying droplets discharged changes.

According to the third aspect of the invention, the heating area is changed and the heating area is changed by changing the number of the electrothermal converters to which a voltage is applied by shifting the position of the heating portion for each electrothermal converter. The volume of the bubbles that are formed changes, and the mass of the ejected flying droplets changes.

According to the fourth aspect of the present invention, the area of the heat generating portion is made smaller as the electrothermal converter is closer to the liquid, so that the spread of the temperature distribution due to the thermal diffusion at the contact surface with the liquid can be reduced. The mass can be suppressed as much as the mass is reduced, and the mass of the flying droplet can be further suppressed.

Further, in the invention according to claim 5, by connecting one electrode of at least two electrothermal converters, the extraction of these electrodes becomes one.

Further, in the invention according to claim 6, the first electrothermal converter and the second electrothermal converter are formed on the substrate by photofabrication, and further, one electrode of the first electrothermal converter is formed. Since the opening for connecting to one electrode of the second electrothermal converter is formed by photoetching, the liquid jet recording head having a fine structure has high accuracy.

According to the seventh aspect of the invention, the electrothermal converter for inputting a signal is selected according to the image information,
By changing the number of electrothermal converters that input signals, changing the input energy to the electrothermal converters, or changing the timing of the signals that are input to each electrothermal converter, the amount of heat generated from each heating unit and The size of the bubbles generated by the change in the heat generation timing changes, and the mass of the flying droplets discharged changes.

[0042]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. 1 shows the final stage of the manufacturing process of the liquid jet recording head, and FIGS. 2 and 3 show the final manufacturing process. First,
In the manufacturing process shown in FIG. 2, the substrate 15 is made of Si.
By thermally oxidizing the surface of the wafer, SiO 2 with a thickness of 2 μm
_Two layers (lower layer) 16 are formed. As the substrate material, it is also possible to use an alumina substrate with a glaze layer, which is often used in a technique such as a thermal head. The lower layer 16 and the glaze layer (composition is the same as that of glass) when the alumina substrate is used both work as a heat storage layer. In addition to thermal oxidation, this SiO ₂ layer may be formed by CVD or by a technique such as sputtering.

Next, the first heating element layer 17 is formed on the lower layer 16. As the useful material for forming the heat generating layer 17, for example, a mixture of tantalum -SiO _2, tantalum nitride, nichrome, silver - palladium alloy, silicon semiconductor or, hafnium, lanthanum, zirconium, titanium, tantalum, tungsten And boride of metals such as molybdenum, niobium, chromium, and vanadium. Among the materials forming these heating element layers 17,
In particular, metal borides can be mentioned as excellent ones, and among them, hafnium boride has the most excellent characteristics, and zirconium boride, lanthanum boride, tantalum boride, vanadium boride are next. , Followed by niobium boride. Further, the heating element layer 17 can be formed by using a method such as electron beam vapor deposition or sputtering using the above materials. The thickness of the heating element layer 17 depends on the area and material, the shape and size of the heating portion described later, and the actual power consumption so that the amount of heat generated per unit time is as desired. It is to be determined, but usually 0.001 to 5 μm, preferably 0.
It is set to 01 to 1 μm. Here, a 0.3 μm thick HfB ₂ layer was formed by sputtering.

Subsequently, an Al layer which is an electrode layer having a thickness of 0.5 μm is formed on the heating element layer 17 by sputtering, and an individual electrode 18 which is an electrode and a common electrode 19 which is an electrode are formed by a photolithography technique. To do. The electrodes 18,
As a material for forming 19, many of commonly used electrode materials are effectively used, and Ag, Au, Pt, Cu or the like may be used in addition to Al described above. A heat generating portion 20 is formed in a portion of the heat generating layer 17 sandwiched by the pair of electrodes 18, 19, and the first electrothermal converter comprises the heat generating layer 17, the electrodes 18, 19 and the heat generating portion 20. 21 is configured.

Next, in the manufacturing process shown in FIG. 3, the insulating layer 22 is formed on the first electrothermal converter 21, and the second heating element layer 23 and the individual electrode are formed on the insulating layer 22. The second electrothermal converter 27 is formed of 24, the common electrode 25, and the heat generating portion 26, and the first electrothermal converter 21 and the second electrothermal converter 27 are laminated with the insulating layer 22 interposed therebetween. It becomes a structure. Here, the insulating layer 22 has a thickness of 1 μm.
A thick SiO ₂ layer was formed by sputtering, and a 0.3 μm thick HfB ₂ layer was formed as the heating element layer 23 by sputtering. In addition, the electrodes 24 and 25
In the same manner as the formation of the electrodes 18 and 19, was formed by a photolithography technique on a 0.5 μm thick Al layer formed by sputtering. The heat generating portion 2 of the second heat conversion body 27
The area of 6 is set smaller than the area of the heat generating portion 20 of the first heat conversion body 21. Specifically, the heat generating parts 20, 26
Both have a width of 24 μm, but the length of the heating portion 20 (distance between the electrodes 18 and 19) is 120 μm, while the length of the heating portion 26 (distance between the electrodes 24 and 25) is 80 μm.
m.

Next, as shown in FIG. 1, a first upper protective layer 28, a second upper protective layer 29, and a third upper protective layer 30 are laminated on the second heat conversion body 27. Here, the first upper protective layer 28 is formed of SiO ₂ by a magnetron type high rate sputtering method, and the second upper protective layer 29 is formed of Ta (tantalum) by a magnetron type high rate sputtering method. . The second upper protective layer 29 is formed by the photolithography technique on the heat generating portion 2.
The pattern is formed so as to cover the upper portions of 0 and 26. Examples of useful materials for forming the upper protective layers 27 and 28 include silicon nitride, magnesium oxide, aluminum oxide, tantalum oxide, zirconium oxide, and the like, in addition to the above-described SiO ₂ and Ta. It can be formed using a technique such as electron beam evaporation or sputtering. Further, the film thickness of the upper protective layers 28 and 29 is usually 0.
01 to 10 μm, preferably 0.1 to 5 μm, optimally 0.1 to 3 μm, and here, the first upper protective layer 28.
Is formed to a thickness of 1.0 μm, and the second upper protective layer 29 is formed to a thickness of 0.5 μm. Next, as the third upper protective layer 30, a photosensitive polyimide (trade name, Photo Nice) is used as the upper protective layer 2.
It is formed by applying it on 8, 29 and then removing the upper parts of the heat generating parts 20, 26 by a photolithography technique.

As shown in FIG. 4, a photosensitive resin dry film 31 having a thickness of 25 .mu.m is laminated on the substrate 15 on which the first electrothermal converter 21 and the second electrothermal converter 27 are formed in this manner, and the predetermined film is formed. The liquid flow path 32 and the common liquid chamber region 33 are formed by performing exposure and development using the pattern mask of No. 3, and further, on the photosensitive resin dry film 31 is made of glass via an epoxy adhesive. A liquid jet recording head is created by stacking the ceiling plates 34. Note that 35
Is an ejection port for ejecting ink (liquid) as flying droplets, and 36 is an ink supply port.

Here, the above-mentioned liquid flow path 32 has a width of 25 μm,
It is formed to have a height of 25 μm and a length of 500 μm. Further, the discharge port 35 is formed to have a size of 25 μm × 25 μm,
The length from the discharge port 35 to the most front position of the heat generating part 20 is 1
It is formed to 50 μm.

In such a structure, FIG. 5 shows bubbles generated when a pulse voltage is applied to the electrodes 18 and 19 of the first electrothermal converter 21 or the electrodes 24 and 25 of the second electrothermal converter 27. It shows the volume and the ink ejection amount. FIG. 5A shows an electrode 24 of the second electrothermal converter 27,
25 shows a state in which a pulse voltage is applied to 25, and FIG. 5 (b) shows a state in which a pulse voltage is applied to the electrodes 18 and 19 of the first electrothermal converter 21, and the areas of the heat generating portions 20 and 26 are different. Therefore, the volume of the bubble (hatched portion) generated by the application of the pulse voltage is different, and the ink ejection amount is also changed.
Specifically, with a pulse width of 6 μs and a drive frequency of 1 kHz,
When a pulse voltage (18 V for the electrodes 24 and 25 and 30 V for the electrodes 18 and 19) at which film boiling stably occurs is applied, the ink ejection amount is about 2.2 × 1 each.
It was 0 to ⁸ g and about 3.5 × 10 to ⁸ g.

Therefore, by increasing the number of laminated electrothermal converters having different areas of the heat generating portion and selecting the electrothermal converters to which the pulse voltage is applied, the ink ejection amount can be changed in a wide range and surely. Can be made. But,
It is disadvantageous in terms of cost and yield to stack the electrothermal converters in multiple layers.

Therefore, the electrode 1 of the first electrothermal converter 21
When a voltage is applied to the electrodes 8 and 19 and the electrodes 24 and 25 of the second electrothermal converter 27, attention is paid to the fact that the positional relationship between the heat generating portions 20 and 26 causes a deviation in the amount of heat generation and a temperature distribution is formed. That is, by changing the voltage applied to the electrodes 18 and 19 and the electrodes 24 and 25, the area of the region above the critical temperature at which film boiling occurs is controlled and the ink ejection amount is changed.

6 (a) to 6 (c), a pulse voltage that stably causes film boiling is applied to the electrodes 24 and 25 of the second electrothermal converter 27, and the first electrothermal converter 21 is heated. Electrode 1
20 shows a change state of the ink ejection amount when the pulse voltage applied to 8 and 19 is changed. Figure 6
6A shows the case where no pulse voltage is applied to the electrodes 18 and 19, FIG. 6B shows the case where a small pulse voltage is applied to the electrodes 18 and 19, and FIG.
This is the case where a large pulse voltage is applied to 9. In this way, the pulse voltage applied to the electrodes 24 and 25 of the second electrothermal converter 27 is kept constant, and the pulse voltage applied to the electrodes 18 and 19 of the first electrothermal converter 21 is changed. By doing so, the area in which the bubbles are generated changes, the volume of the generated bubbles also changes, and the ink ejection amount also changes.

Next, in FIG. 7, a pulse voltage of 18 V is applied to the electrodes 24 and 25 of the second electrothermal converter 27,
7 is a graph showing a state in which the ink ejection amount changes when the voltage applied to the electrodes 18 and 19 of the first electrothermal converter 21 is changed from 0V to 30V. In addition,
The pulse voltages applied to the electrodes 24 and 25 and the electrodes 18 and 19 are synchronized with a pulse width of 6 μs and a frequency of 1 kHz. As is clear from the graph of FIG. 7, the electrodes 18, 1
Increasing the pulse voltage applied to 9 increases the ink ejection amount, and good gradation recording can be performed.

Here, since the first electrothermal converter 21 and the second electrothermal converter 27 have a laminated structure, the individual electrodes 18,
It is possible to provide a plurality of electrothermal converters for one discharge port 35 without being restricted by the arrangement of the common electrode 24 and the common electrodes 19 and 25, and to arrange the discharge ports 35 at a high density. it can. Further, since the pattern widths of the heat generating portions 20 and 26 are uniform, it is difficult to break the wire and the durability is improved.

Further, the second electrothermal converter 27 close to the ink
The area of the heat generating portion 26 of the heat generating portion 2 of the first electrothermal converter 21
Since the area is smaller than 0, when the mass of the flying droplets is to be reduced by the heat generated only from the heat generating portion 26, the spread of the temperature distribution due to the thermal diffusion on the contact surface with the ink can be suppressed. Therefore, it is possible to reliably form flying droplets having a small mass.

Next, a second embodiment of the present invention will be described with reference to FIGS. The same parts as those described with reference to FIGS. 1 to 7 are designated by the same reference numerals, and description thereof will be omitted (the same applies hereinafter). 8 to 10 show a manufacturing process of the liquid flying recording head in this embodiment. First, in the manufacturing process shown in FIG. 8, the lower part is formed on the substrate 15 similarly to the manufacturing process shown in FIG. Forming layer 16,
Further, the first heating element layer 17 and the pair of electrodes 18, 19 are formed, and the heating element 20 is formed in the portion of the heating element layer 17 sandwiched by the electrodes 18, 19. Then, the heating element layer 17, the electrodes 18 and 19, and the heating section 20 constitute a first electrothermal converter 21. The manufacturing process shown in FIG. 8 differs from the manufacturing process shown in FIG. 2 in that the area of the heat generating portion 20 in the manufacturing process shown in FIG. 8 is reduced.

Next, in the manufacturing process shown in FIG. 9, a 1 μm thick SiO ₂ layer is formed as an insulating layer 22 on the first electrothermal converter 21, and 0.3 μm is formed on this insulating layer 22.
An m-thick HfB ₂ layer is formed as the second heating element layer 23 by sputtering. Further, a contact hole 37, which is an opening, is formed in the insulating layer 22 and the heating element layer 23 above the common electrode 19 by photolithography.

Next, in the manufacturing process shown in FIG. 10, an Al layer having a thickness of 1 μm is formed on the heating element layer 23 by sputtering, and the individual electrode 24 and the common electrode 25 are formed by the photolithography technique. The heat generating portion 2 is provided in a portion of the heat generating layer 23 sandwiched by the electrodes 24 and 25.
6 is formed, and the heating element layer 23, the electrodes 24 and 25, and the heating section 26 form a second electrothermal converter 27. Here, the common electrode 19 of the first electrothermal converter 21 and the common electrode 25 of the second electrothermal converter 27 are electrically connected via the contact hole 37, and the heat generating parts 20, 26 are , The width is 24 μm, and the length (distance between electrodes) is 60 μm, but the positions are displaced in the ink ejection direction.

Next, a protective layer as shown in FIG. 1 is formed on the second electrothermal converter 27, and further, on the photosensitive resin dry film laminated on the substrate 15 as shown in FIG. A liquid jet recording head is prepared by laminating a glass ceiling plate on the above with an epoxy adhesive.

In such a structure, the heat generating parts 20, 2
Since 6 is formed by shifting the position, when the pulse voltage is applied to the electrodes 18 and 19 of the first electrothermal converter 21 and the electrodes 24 and 25 of the second electrothermal converter 27, When the pulse voltage is applied only to the electrodes 24 and 25 of the converter 27, the heating area changes, the volume of bubbles generated changes, and the ink ejection amount also changes. Therefore, gradation recording can be performed by changing the ink ejection amount by changing the number of electrothermal converters 21 and 27 that apply the pulse voltage.

Further, since the common electrodes 19 and 25 are electrically connected to each other through the contact hole 37, the common electrodes 19 and 25 only need to be drawn out, and the liquid jet recording head can be easily assembled. .

Next, a third embodiment of the present invention will be described with reference to FIGS. 11 and 12. In this embodiment, a pulse voltage applied to the electrodes 18 and 19 of the first electrothermal converter 21 and
By shifting the application timing of the pulse voltage applied to the electrodes 24 and 25 of the second electrothermal converter 27, the volume of the bubble (synthetic bubble) generated is changed and the ink ejection amount is changed, so that gradation recording is performed. It is the one.
FIG. 11 shows the pulse voltage (V
₁ schematically shows the relationship between ₁ ) and the pulse voltage (V ₂ ) applied to the electrodes 24 and 25, the volume of bubbles generated, and the size of ejected ink droplets. In addition,
The pulse voltage is shown by a solid line, and the size of the volume of bubbles generated due to heat generation is shown by a broken line. FIG. 11A shows the case where the application timings of the pulse voltages coincide with each other, and the volume of bubbles (coalescing bubbles) generated is maximum and the size of the ejected ink droplet is also maximum. In FIG. 11B, the application timing of the pulse voltage is shifted by the pulse width “τ”, the maximum volume of the coalesced bubble is reduced, and the size of the ejected ink droplet is also reduced. In FIG. 11C, the application timing of the pulse voltage is shifted by twice the pulse width “τ”, and the size of the ejected ink droplet is as shown in FIG.
As shown in (d), this is the same as when the pulse voltage is applied only to the electrodes 18 and 19. Specifically, the pulse width “τ” is 6 μs, the driving frequency is 1 kHz, and the pulse voltages V ₁ and V ₂ are both 25V.

Next, FIG. 12 is a graph showing the relationship between the deviation amount of the application timing of the pulse voltage V ₂ with respect to the pulse voltage V ₁ and the ink ejection amount. By shifting the application timing, the ink ejection amount is changed. It can be changed and gradation recording can be performed.

The heat generating parts 20, 26 in this embodiment are
Regarding the above, the area may be changed as described in FIG. 1, the position may be shifted without changing the area as described in FIG. 10, and a combination of both may be used. Good. Further, as the liquid flying recording method in the present invention, as described above, the electrothermal converter for applying the pulse voltage is selected, the number of electrothermal converters for applying the pulse voltage is changed, or the application is performed. The gradation is controlled by controlling the ink discharge amount by changing the pulse voltage to be applied or changing the application timing of the pulse voltage to be applied, but these may be performed independently. Moreover, you may implement in combination with each other.

[0065]

As described in the first aspect of the present invention, a plurality of electrothermal converters each having a heat generating portion are laminated with an insulating layer interposed therebetween, so that there is a restriction due to the arrangement of electrodes of each electrothermal converter. It is possible to provide a plurality of electrothermal converters for one ejection port without needing to obtain a liquid jet recording head in which the ejection ports are arranged in high density, and moreover, the heat generating portion of each electrothermal conversion unit. It is possible to perform gradation recording by changing the mass of the flying droplets ejected from the same ejection port by appropriately controlling the above, and in each electrothermal converter laminated as in the invention of claim 2. By changing the area of the heat generating portion, it is possible to change the mass of the flying droplets and to perform gradation recording by selecting the electrothermal converter to which a voltage is applied.
By shifting the position of the heat generating portion in each of the stacked electrothermal converters as in the described invention, the mass of the flying droplets can be changed by changing the number of electrothermal converters to which a voltage is applied. It is possible to perform gradation recording and to form flying droplets having a smaller mass by reducing the area of the heat generating portion for an electrothermal converter closer to a liquid as in the invention of claim 4. This makes it possible to perform gradation recording more clearly, and by electrically connecting one electrode of the electrothermal converters laminated as in the invention of claim 5, these It is possible to use only one electrode for the liquid ejection head and to simplify the assembly of the liquid jet recording head.
Further, as in the invention according to claim 6, the first and second electrothermal converters are formed on the substrate by photofabrication, and one electrode of the first electrothermal converter and the second electrothermal converter are formed. Since the opening for electrically connecting to one of the electrodes is formed by photoetching, the liquid flying recording head having a fine structure can be formed with high accuracy, and the invention according to claim 7 is also provided. Depending on the image information, select the electrothermal converter to input the signal, change the number of electrothermal converters to input the signal, change the input energy to the electrothermal converter, By changing the timing of the signal input to the heating element, it is possible to change the heat generation amount and heat generation timing from each heat generating portion and also to change the size of the bubbles that are generated. An effect such as can perform gradation recording it is possible to change the mass of the droplet.

[Brief description of drawings]

FIG. 1 shows a structure of a liquid jet recording head on a substrate side in a first embodiment of the present invention, in which (a) is a plan view,
(B) is the aa line sectional view.

2A and 2B show a state in which even a first electrothermal converter is formed in a manufacturing process of a liquid jet recording head, wherein FIG. 2A is a plan view and FIG. 2B is a sectional view taken along the line aa.

3A and 3B show a state in which even a second electrothermal converter is formed in a manufacturing process of a liquid jet recording head, FIG. 3A is a plan view, and FIG. 3B is a sectional view taken along the line aa.

FIG. 4 is a perspective view showing a liquid jet recording head completed by laminating a ceiling plate on a substrate.

FIG. 5 is an explanatory diagram illustrating a state in which the ink ejection amount changes when a pulse voltage is applied to the electrodes of the first electrothermal converter and when a pulse voltage is applied to the electrodes of the second electrothermal converter. is there.

FIG. 6 is an explanatory diagram illustrating a state in which the ink ejection amount changes when the magnitude of the pulse voltage applied to the electrothermal converter is changed.

FIG. 7 is a graph showing the relationship between the magnitude of the pulse voltage applied to the electrothermal converter and the ink ejection amount.

8A and 8B show a state in which even a first electrothermal converter is formed in a manufacturing process of a liquid jet recording head of a second embodiment of the present invention, FIG. 8A is a plan view, and FIG. FIG.

9A and 9B are views showing a state in which even a contact hole is formed in a manufacturing process of a liquid jet recording head, FIG. 9A is a plan view, and FIG.

FIG. 10 is a view showing a state in which even a second electrothermal converter is formed in the manufacturing process of the liquid jet recording head,
Is a plan view and (b) is a sectional view taken along line aa.

FIG. 11 is an explanatory diagram illustrating the application timing of the pulse voltage, the volume of bubbles generated, and the size of ink droplets to be ejected according to the third embodiment of the present invention.

FIG. 12 is a graph showing the relationship between the amount of deviation in the application timing of pulse voltage and the amount of ink ejection.

FIG. 13 is a vertical sectional front view showing a conventional example in which a thin film having a three-dimensional structure is formed for performing gradation recording.

FIG. 14 is a plan view showing a conventional example in which the pattern width of a heat generating portion is changed to perform gradation recording.

FIG. 15 is a plan view showing a conventional example in which a plurality of heating elements are provided for performing gradation recording.

[Explanation of symbols]

15 substrates 17,23 Heater layer 18, 19, 24, 25 electrodes 20,26 Heat generating part 21,27 electrothermal converter 22 Insulation layer 35 outlet 37 opening

Claims (7)

[Claims] 1. An electrothermal converter having a heating element layer and a heating element formed by connecting a pair of electrodes to the heating element layer, and the action of bubbles generated in the liquid by the heat from the heating element. A liquid jet recording head having a discharge port for discharging the received liquid as flying droplets, wherein a plurality of electrothermal converters are laminated with an insulating layer interposed therebetween. 2. The liquid jet recording head according to claim 1, wherein the area of the heat generating portion is different for each of the stacked electrothermal converters. 3. The liquid jet recording head according to claim 1, wherein the position of the heat generating portion is shifted for each of the laminated electrothermal converters. 4. The liquid jet recording head according to claim 1, wherein an electrothermal converter closer to a liquid has a smaller area of a heat generating portion. 5. The at least two electrothermal converters are connected to each other at one electrode.
2. A liquid jet recording head according to 2, 3, or 4. 6. A step of forming a heating element layer and an electrode layer on a substrate by photofabrication and patterning into a desired shape to form a first electrothermal converter.
Forming an insulating layer on the first electrothermal converter, forming an opening by photoetching at a position in the insulating layer corresponding to one electrode of the first electrothermal converter; And a step of forming a second electrothermal converter by patterning into a desired shape while forming a heating element layer and an electrode layer on the layer by photofabrication, and one of the first electrothermal converters. The method for manufacturing a liquid jet recording head according to claim 5, wherein the electrode and one electrode of the second electrothermal converter are connected through the opening. 7. A plurality of electrothermal converters having a heating element layer and a heating element formed by connecting a pair of electrodes to the heating element layer are laminated via an insulating layer, In a liquid jet recording method for recording by ejecting the liquid, which is subjected to the action of bubbles generated in the liquid by heat, as flying droplets from a discharge port, the electrothermal converter that inputs a signal according to image information is used. Choosing, or
Changing the number of the electrothermal converters for inputting a signal,
Alternatively, the mass of the flying droplets to be ejected is changed by changing the input energy to the electrothermal converter or by changing the timing of the signal input to each electrothermal converter. Liquid jet recording method.