JPH0412861A - Base body for inkjet recording head, inkjet recording head having the base body and inkjet recording apparatus having the recording head - Google Patents

Abstract

PURPOSE:To obtain a heat generating body to constitute a bubble jet printer head having a high pressure when bubbles are generated and accordingly a high discharging speed when liquid drops are discharged by using a heat generating element having the average value of the contact angle between the surface of a heat operating part and ink and the difference between the maximum and minimum contact angles specified. CONSTITUTION:A surface-oxidized SiO2 layer 22 is formed on the surface of a substrate 21, onto which an HfB2 resistance layer 23, an Al electrode 24, an SiO2 insulating layer (working also as a protecting film) 25 and a Ta-Si-B protecting layer 26 are sequentially formed respectively through sputtering, EB deposition, sputtering and sputtering. When the state of the surface oxidization of the protecting layer 26 is changed by aging the heat generating resistance body with heat, wetting characteristics are changed. In this case, supposing that the contact angle between a point (r) at the surface of the heat operating part and ink is thetar, the average value of thetar is theta, and the difference of the maximum and minimum contact angles thetar is DELTAtheta, the contact angle at the surface should be theta<=120 deg. and DELTA<=90 deg..

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a substrate for an inkjet recording head for recording by ejecting liquid using thermal energy, an inkjet recording head having the substrate, and the inkjet recording. The present invention relates to an inkjet recording device having a head.

[Prior Art] The inkjet recording method, which performs recording by ejecting (discharging) liquid using thermal energy, is capable of high-resolution, high-speed printing, high recording quality, low noise, and color image recording. It has excellent features such as being able to easily perform printing, printing on plain paper, etc., and making it easy to downsize the printing head and the entire device.

Among them, bubble jet recording utilizes a film boiling phenomenon that occurs by rapidly heating a heating element that is in contact with ink. Therefore, since the properties of the surface of the heating element for bubble jet printers have a great influence on the performance of the printer, various efforts have been made to date. In JP-A-5610471, the surface of the heating element is roughened (J
A configuration is disclosed in which recording can be performed with low energy consumption by forming bubble nuclei on the irregularities on the surface and causing boiling at a lower temperature by setting the IS roughness to 0.05S to 2S. There is. JP-A-56-19771 discloses a method of setting an energy level for good recording using a heating element with a rough surface (JIS roughness of 0.05S to 2S). Japanese Unexamined Patent Publication 1986-20
No. 1254 discloses a structure in which the gradation can be controlled by making the surface of the heating element rough and by making the heat generation amount of the heating element larger at the center than at the ends.

Furthermore, since the surface condition of the heating resistor depends on the surface condition of the substrate on which the heating element is formed, improvements have also been made to the substrate. In JP-A No. 56-10470, the surface of the substrate is roughened (JIS roughness 0.1S to 5S) to create irregularities on the surface of the heating element, and similar to JP-A No. 56-10471, A configuration is disclosed that achieves the effect. On the other hand, from the perspective of the durability of the heating element,
Since coverage of the protective layer on the surface of the heating element is important, a smooth substrate is preferable. Japanese Patent Publication No. 60-203452
No. and JP-A No. 60-206655, the surface of the heating element formed thereon is made smooth (JIS center line average roughness R, <0.1 μm) by making the surface of the substrate on which the heating element is provided smooth. Structures have been developed to improve the coverage of the protective layer.

Various efforts have been made to improve the properties of the flow channel wall surface, which is not limited to the surface of the heating element, from a hydrodynamic viewpoint. JP-A No. 55-128470 discloses a configuration in which smoothing treatment is performed on the inner walls of the flow channels to improve the affinity of the ink to the walls in the flow channels and realize smooth ink flow. . Japanese Unexamined Patent Publication No. 58-1.11
No. 73 discloses a configuration in which the flow path is formed with a cured film of photosensitive resin and the inner wall of the flow path has a finely roughened surface, thereby facilitating production and speeding up the dispensing of ink. .

[Problems to be Solved by the Invention] However, the conventional example described above has a problem in that it lacks a measure to increase the pressure when the liquid boils. That is, in JP-A-56-10471, JP-A-56-19771, JP-A-62-2 (11254), and JP-A-56-10470, since the liquid boils at a low temperature, the The vapor pressure is small (in some cases, sufficient droplet ejection speed cannot be obtained. JP-A-60-2
03452 and JP-A-60-206655, although the surface coverage is taken into consideration,
It does not give any suggestion as to what should be done to increase the pressure when the liquid boils. JP-A-55-128470 and JP-A-58-11173
Although the surface condition as a channel wall is considered in this issue, the properties of the heating element surface as a heat transfer surface (heat acting surface) are not considered, so the pressure when the liquid boils is It does not give any suggestions as to what should be done to improve it. For this reason, the pressure at the time of bubbling becomes small, and there are cases where it is not possible to obtain a sufficient droplet ejection speed to perform high-quality recording.

The internal pressure of the bubble during foaming is approximately equal to the vapor pressure of the ink at the temperature when the bubble is generated. Therefore, in order to increase the pressure during foaming, it is necessary to suppress the generation of bubbles at low temperatures and to generate bubbles only when the surface of the heating element reaches a high temperature.

SUMMARY OF THE INVENTION An object of the present invention is to provide a heating element for configuring a bubble jet printer head that has a high pressure during foaming and therefore a high droplet ejection speed.

[Means for Solving the Problems] In order to achieve such an object, the inkjet recording head substrate according to the present invention has the following characteristics: the maximum value of (γ) between the surface of the heat-acting part and the ink at a point γ on the surface of the heat-acting part; When the difference between the minimum value and the minimum value is Δθ, the contact angle on the surface is θ≦1
The inkjet recording head of the present invention, characterized in that it has a heating element in which 20' is Δθ<90°, has at least the following: When the average value of θ (γ) and θ (γ) is ■, and the difference between the maximum and minimum values of θ (γ) is Δθ, the contact angle on the surface is θ≦120° and Δθ≦90°. It is characterized by having a base body having a heating element, a discharge port provided corresponding to the heating element, and a liquid path communicating with the discharge port.

The inkjet recording apparatus of the present invention adjusts the contact angle between the ink and the surface of the heat-acting section at least at point γ to θ(γ
), the average value of θ (γ) is ■, and the difference between the maximum and minimum values of θ (γ) is Δθ, the heating element has a contact angle on the surface of θ≦120° and Δθ≦90゛. an inkjet recording head having an ejection port provided corresponding to the heating element, and a liquid path communicating with the ejection opening, and a drive circuit that generates an electric signal for driving the heating element; The apparatus is characterized by comprising a platen provided at a position that can face the ejection port.

In the present invention, when the contact angle of the ink at point γ on the surface of the heating element is θ(?), the average value of θ(7) is Δθ, and the difference between the maximum and minimum values of θ(γ) is Δθ, θ ≦120° Δθ〈
The angle is set to 90°. Since the ink has good wettability with respect to the surface of the heating element, the generation of bubble nuclei at low temperatures is suppressed, and bubbles are generated when the temperature of the surface of the heating element becomes sufficiently high. Therefore, the pressure during foaming is increased,
A sufficient ejection speed can be obtained, and at the same time, there is little variation in ejection speed, and good printing can be achieved. As a result, it is possible to record high-quality images, and since the pressure during foaming is high (and the acting force for ejecting the liquid is strong), so-called clogging is less likely to occur.

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

FIG. 1 shows a schematic configuration example of a liquid jet recording apparatus (inkjet recording apparatus) equipped with a recording head to which the present invention is applied, and FIG. 2 shows an example configuration of the recording head.

First, in FIG. 1, numeral 1 denotes a head cartridge, which integrates a recording head and an ink tank serving as an ink supply source. This head cartridge 1 is fixed on a carriage 3 by a holding member 2, which can reciprocate along a shaft 4 in the longitudinal direction. The ink ejected from the recording head reaches the recording medium 6 whose recording surface is regulated by the platen 5 at a slight distance from the recording head, and forms an image on the recording medium 6.

The recording head is connected to a drive circuit via a cable 7 and a terminal (not shown) connected thereto, and is supplied with an earth discharging signal corresponding to image data from an appropriate data supply source.

The number of head cartridges can be one or more (two in the figure) depending on the ink color used.

In addition, in FIG. 1, 8 connects the carriage 3 to the shaft 4.
9 is a wire that transmits the driving force of the motor 8 to the carriage 3.

Further, 1o is a feed motor coupled to the platen roller 5 for conveying the recording medium 6. Further, reference numeral 11 is a reference temperature sensor provided at an appropriate location on the main body of the apparatus. This reference temperature sensor 11 is placed at an appropriate location that is not affected by temperature rise inside the machine, and monitors the ambient temperature.

FIG. 2 shows an example of the structure of a recording head to which the present invention is applied. Here, 12 is a heater board (substrate), and an electrothermal converter (discharge heating element) 13 according to the present invention and wiring 14 such as A for supplying electric power to this are formed by film-forming technology. Become. Then, for this heater board 12,
A liquid jet recording head is constructed by adhering a top plate 16 provided with a partition wall for forming a liquid path (nozzle) 15 for recording liquid. Note that this partition wall does not need to be provided on the top plate 16, and a partition wall may be provided on the heater board 12, and a top plate without a partition wall may be provided on the partition wall.

The recording liquid (ink) is supplied through the supply port 1 provided on the top plate 16.
7 to the common liquid chamber 18, and from here to each nozzle 15.
Guided within. Then, when the heating element 13 generates heat due to energization, the ink filled in the nozzle 15 bubbles, and ink droplets are ejected from the ejection port 19.

FIG. 3 shows a cross-sectional view of an embodiment of a heating resistor according to the present invention. In this example, a 2.5 μm thick surface oxidized SiO□ layer 22 is formed on the surface of a 525 μm thick Si substrate 21, and a 0.1 μm thick layer 22 is formed on the surface by sputtering.
m of HfB2 resistance layer 23 to a thickness of 0 by EB evaporation method.
．． A 5 μm thick β electrode 24 is formed with a 1.5 μm thick SiO□ insulating layer (also serves as a protective film) 2 by sputtering.
5 was made of Ta with a thickness of 0.5 μm by sputtering method.
-3L-B protective layers 26 are formed in sequence. The area of the heating part of the heating resistor is 30μm x 50μ
It was set as m.

The heating resistor is aged by heating to form a protective layer 26.
By changing the surface oxidation state, the wettability changed. Ink was dropped onto the surface of the heating element to form ink droplets, and a photograph was taken from the side to measure the contact angle of the ink to the surface of the heating element. As for the relationship between aging conditions and contact angle, a quantitative relational expression has not yet been obtained, so it was determined by trial and error.

Using the heating resistor of this example and using water-based ink as the ink,? When night temperature was discharged, the average value θ of the ink contact angle θ (γ) at point γ on the heating element surface was 120
A sufficient droplet ejection speed was obtained when the temperature was below . However, when the contact angle exceeded 120°, a sufficient droplet ejection speed could not be obtained. Furthermore, when the difference between the maximum value and the minimum value of θ(γ), Δθ, was 90° or less, there was little variation in the MA discharge specific speed, but when it exceeded 90°, there was a large variation in the droplet discharge speed.

Similar results were obtained when inks other than water-based, such as ethanol-based, were used.

FIG. 4 shows a sectional view of another embodiment of the heating resistor according to the present invention. In this embodiment, a Si substrate 21 with a thickness of 525 μm is used.
A surface oxidized SiO□ layer 22 with a thickness of 2.5 μm is formed on the surface of
The HfB2 resistive layer 23 of 0.0 mm is deposited to a thickness of 0.5 mm using the EB evaporation method.
A 5 μm/l electrode 24 is formed by sequentially forming a 15 μm thick 5i02 insulating layer 25 by sputtering, and a 05 μm thick Ta-3i electrode is further formed by sputtering.
A C protective layer 27 is formed.

The area of the heating portion of the heating resistor was 30 gm x 50 μm.

The heating resistor is aged by heating to form a protective layer 27.
Changing the surface oxidation state of the material changed the wettability and the contact angle. In this case as well, the average contact angle is 120°
Hereinafter, a sufficient droplet ejection speed was obtained only when the variation was 90° or less.

(Others) The present invention brings about excellent effects particularly in a bubble jet type recording head and recording apparatus among inkjet recording types.

This is because such a system can achieve higher recording density and higher definition.

As for typical configurations and principles thereof, it is preferable to use the basic principles disclosed in, for example, US Pat. No. 4,723,129 and US Pat. No. 4,740,796. This method can be applied to both the so-called on-demand type and continuous type, but especially in the case of the on-demand type, it is necessary to arrange the liquid (ink) in accordance with the sheet and liquid path that hold it. The electrothermal converter that is
By applying at least one drive signal corresponding to recorded information and providing a rapid temperature rise above nucleate boiling, - causing the electrothermal transducer to generate thermal energy and causing a film to form on the thermally active surface of the recording head; This is effective because it causes boiling, resulting in the formation of bubbles in the liquid (ink) that correspond in pairs to this drive signal. The growth and contraction of these bubbles causes liquid (ink) to be discharged through the soil discharge opening.
Forming at least one drop. It is more preferable to use this drive signal in a pulse form, since the growth and contraction of bubbles can be carried out immediately and appropriately, making it possible to eject liquid (ink) with particularly excellent responsiveness. This pulse-shaped drive signal is described in U.S. Pat. No. 4,463,359 and U.S. Pat.
Suitable are those described in No. 62 specification. Furthermore, if the conditions described in US Pat. No. 4,313,124 concerning the invention regarding the temperature increase rate of the heat acting surface are adopted, even more excellent recording can be performed.

The configuration of the recording head includes, in addition to the combination configuration of ejection ports, liquid paths, and electrothermal converters (straight liquid flow path or right-angled liquid flow path) as disclosed in the above-mentioned specifications, a heat acting section. The present invention also includes configurations using US Pat. No. 4,558,333 and US Pat. No. 4,459,600, which disclose configurations in which the wafer is placed in a bending region. In addition, Japanese Patent Application Laid-Open No. 1989-5 discloses a configuration in which a common slit is used as a discharge part of a plurality of electrothermal converters.
No. 9-123670 and Japanese Patent Application Laid-Open No. 59/1989 which discloses a configuration in which a discharge portion is made to correspond to an opening that absorbs pressure waves of thermal energy.
The effects of the present invention are also effective even if the structure is based on the publication No.-138461. That is, regardless of the form of the recording head, according to the present invention, recording can be performed reliably and efficiently.

Furthermore, the present invention can be effectively applied to a full-line type recording head having a length corresponding to the maximum width of a recording medium that can be recorded by a recording apparatus.

Such a recording head may have either a configuration in which the length is satisfied by a combination of a plurality of recording heads, or a configuration as a single recording head formed integrally.

In addition, even with the serial type shown above, the recording head is fixed to the device body, or by being attached to the device body, electrical connection to the device body and ink supply from the device body are possible. The present invention is also effective when using a replaceable chip type recording head or a cartridge type recording head in which an ink tank is integrally provided in the recording head itself.

Further, it is preferable to add recovery means for the recording head, preliminary auxiliary means, etc., which are provided as a configuration of the recording apparatus, to the present invention, because the effects of the present invention can be further stabilized. Specifically, these include capping means for the recording head, cleaning means, pressure or suction means, preheating means using an electrothermal transducer or another heating element, or a combination thereof; It is also effective to perform a preliminary ejection mode in which ejection is performed separately from recording in order to perform stable recording.

In addition, regarding the type and number of recording heads installed, for example, in addition to one type that corresponds to single-color ink, there is also a plurality of recording heads that correspond to multiple inks with different recording colors and densities. It may be something that can be done. In other words, for example, the recording mode of the recording device is not only a recording mode for only the mainstream color such as black (although the recording head may be configured integrally or by a combination of multiple heads, it can also be used for multiple colors of different colors). The present invention is also extremely effective for devices equipped with at least one of full colors, or mixed colors.

Additionally, in the embodiments of the present invention described above,
Although ink is described as a liquid, it is an ink that solidifies at room temperature or below, but softens or liquefies at room temperature, or in an inkjet method, the ink itself is
Generally, the temperature is adjusted within the range of 0°C or more and 70°C or less so that the viscosity of the ink is within the stable ejection range, so even if the ink is in a liquid state when the recording signal is applied. Bye. In addition, the temperature increase caused by thermal energy can be actively prevented by using the energy to change the state of the ink from a solid state to a liquid state, or an ink that solidifies when left standing is used to prevent ink evaporation. In any case, the ink is liquefied by applying thermal energy in accordance with the recording signal, and the liquid ink is ejected, or the ink has already begun to solidify by the time it reaches the recording medium. The present invention is also applicable when using ink that is liquefied only by energy. The ink used in this case is
Publication No. 4-56847 or JP-A-60-71260
As described in the above publication, the material may be held in a liquid or solid state in the recesses or through holes of a porous sheet and face the electrothermal converter. In the present invention, the most effective method for each of the above-mentioned inks is to implement the above-mentioned film boiling method.

In addition, in addition to being used as an image output terminal for information processing equipment such as a computer, the inkjet recording apparatus of the present invention may also take the form of a copying machine combined with a league, etc., or a facsimile machine having a transmission/reception function. It may also be something.

[Effects of the Invention] As described above, according to the present invention, high-quality recording can be performed by reducing the average value of the contact angle on the surface of the heating resistor and at the same time reducing the variation.

Furthermore, since the pressure at the time of foaming increases and the acting force for discharging the liquid becomes stronger, so-called clogging is less likely to occur.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the configuration of an inkjet recording apparatus equipped with a recording head to which the present invention is applied, FIG. 4 is a sectional view of a heating resistor in another embodiment of the invention. FIG. 4 is a sectional view of a heating resistor in another embodiment of the invention. DESCRIPTION OF SYMBOLS 1... Head cartridge, 2... Holding part, 3... Carriage, 4... Shaft, 5... Platen, 6... Recording medium, 7... Cable, 8... Carriage Motor, 9... Wire, 10... Feed motor, 11... Reference temperature sensor, 12... Heater board, 13... Heating element, 14... Wiring, 15... Nozzle, 16 ...Top plate, 17... Supply port, 18... Common liquid chamber, 19... Discharge port, 21... SL substrate, 22... Surface oxidation layer, 23... HfB2 resistance layer , 24...A°C electrode, 25...SiO□ insulating layer, 26=-Ta-3i-B protective layer, 27-4a-3i-C protective layer. Figure 1 Figure

Claims (1)

[Claims] 1) The contact angle between the surface and the ink at the point ■ on the surface of the heat acting part is θ (■), the average value of θ (■) is @θ@, the above θ
An inkjet recording head substrate characterized by having a heating element having a contact angle on the surface of @θ≦120° and Δθ≦90°, where Δθ is the difference between the maximum value and the minimum value of (■). . 2) The substrate for an inkjet recording head according to claim 1, wherein the heating element has a heating resistor layer and at least one pair of electrodes electrically connected to the heating resistor layer. 3) The substrate for an inkjet recording head according to claim 2, wherein the heating element further includes a protective layer covering the heating resistor and the at least one pair of electrodes. 4) The substrate for an inkjet recording head according to claim 3, wherein the protective layer has a plurality of layers. 5) The substrate for an inkjet recording head according to claim 3, wherein the protective layer contains Ta. 6) The substrate for an inkjet recording head according to claim 5, wherein the protective layer further contains at least one of Si, B, and C. 7) The substrate for an inkjet recording head according to claim 1, wherein the ink is a water-based ink. 8) At least the contact angle between the surface and the ink at point ■ on the surface of the heat acting part is θ (■), and the average value of θ (■) is @θ
@, when the difference between the maximum and minimum values of θ (■) is Δθ, the contact angle on the surface is @θ@≦120° and Δ
An inkjet recording head comprising: a base body having a heat generating element where θ≦90°; an ejection port provided corresponding to the heat generating element; and a liquid path communicating with the ejection port. 9) The inkjet recording head according to claim 8, wherein the heating element has a heating resistor layer and at least one pair of electrodes electrically connected to the heating resistor layer. 10) The inkjet recording head according to claim 9, wherein the heating element further includes a protective layer covering the heating resistor and the at least one pair of electrodes. 11) The inkjet recording head according to claim 10, wherein the protective layer has a plurality of layers. 12) The inkjet recording head according to claim 10, wherein the protective layer contains Ta. 13) The inkjet recording head according to claim 12, wherein the protective layer further contains at least one of Si, B, and C. 14) At least the contact angle between the surface and the ink at the point (■) on the surface of the heat acting part is θ (■), and the average value of θ (■) is ■
, when the difference between the maximum and minimum values of θ (■) is Δθ, the contact angle on the surface is @θ@≦120° and Δθ
≦90°, an inkjet recording head having a base body having a heat generating element, an ejection port provided corresponding to the heat generating element, and a liquid path communicating with the ejection port, and an electric signal for driving the heat generating element. What is claimed is: 1. An ink jet recording apparatus comprising: a drive circuit that generates an ink jet; and a platen provided at a position facing the ejection port. 15) The inkjet recording apparatus according to claim 14, wherein the heating element has a heating resistor layer and at least one pair of electrodes electrically connected to the heating resistor layer. 16) The inkjet recording apparatus according to claim 15, wherein the heating element further includes a protective layer covering the heating resistor and the at least one pair of electrodes. 17) The inkjet recording apparatus according to claim 16, wherein the protective layer has a plurality of layers. 18) The inkjet recording apparatus according to claim 16, wherein the protective layer contains Ta. 19) The inkjet recording apparatus according to claim 18, wherein the protective layer further contains at least one of Si, B, and C.