JPH05116291A - Ink jet recording head - Google Patents

Abstract

PURPOSE:To improve emitting characteristics without changing the density of recording grade by stabilizing foaming. CONSTITUTION:A heating resistor layer 102 generating heat energy by the supply of a current in order to apply heat energy to a liquid passage 107 for emitting a recording liquid and the recording liquid on a heat acting surface 106 to emit the recording liquid is provided to an ink jet recording head and a gap 110 containing air is provided to a part of a heat accumulation layer for conducting the heat generated from the heating resistor layer 102 to the heat acting part 106.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording head, and more particularly to an ink jet recording head capable of improving the thermal efficiency of the recording head.

[0002]

2. Description of the Related Art The ink jet recording method described in U.S. Pat. No. 4,723,129 or U.S. Pat. No. 4,740,796 is capable of high-speed, high-density, high-precision and high-quality recording. It is suitable for colorization and compactness, and has been attracting particular attention in recent years. In a typical example of an apparatus using this method, a recording liquid or the like (hereinafter referred to as ink)
Since the ink is ejected by using thermal energy, there is a heat acting portion that applies heat to the ink. That is, an electrothermal converter having a pair of wiring electrodes corresponding to the ink flow path and a heating resistor layer for generating heat in a region between the wiring electrodes, which is connected to the wiring electrodes, is provided. The ink on the heat-acting surface is rapidly heated and foamed by using the thermal energy generated from the heating resistor layer, and the ink is ejected by this foaming.

By the way, the thermal action surface of the ink jet recording head is exposed to mechanical impact caused by cavitation due to repeated foaming and defoaming of ink, and further to erosion.
Since it is exposed to a harsh environment such as being exposed to temperature rises and falls around 1000 ° C in an extremely short time of microseconds, a protective layer is provided to protect the heating resistor layer from the environment in which it is used. ing. The protective layer is required to have excellent heat resistance, liquid resistance, liquid permeation prevention property, oxidation stability, insulation property, puncture resistance, and thermal conductivity, and inorganic compounds such as SiO ₂ are generally used. It is used. In addition, a single protective layer may be insufficient in the protective performance of the heating resistor layer, and the outermost protective layer corresponding to the heat acting surface may be made of a metal such as Ta.

The protective performance of the protective layer is an important factor that determines the life of the ink jet recording head.

Further, in order to efficiently transfer the heat generated by the heating resistor layer to the heat acting surface side, a so-called heat storage layer having a low thermal conductivity is provided below the heating resistor layer. As a constituent factor of the material of the heat storage layer, it is necessary to have a characteristic that the heat is not sufficiently dissipated during the time until the foaming is started, that is, the heat is rapidly dissipated during the cooling. Further, in the ink jet recording head, as described above, it is exposed to extremely high temperature, and further, it receives a mechanical shock,
It must have high heat resistance and high mechanical strength. Conventionally, SiO ₂ (glass) is generally used as a material satisfying such conditions. Examples of the method for forming the heat storage layer include a thermal oxidation method of a Si substrate, a vacuum deposition method, a sputtering method, a CVD method, a spray baking method, a thick film coating baking method, and the like, and an inkjet recording head having desired performance and cost. In order to obtain the above, the above-mentioned forming method is appropriately selected and used.

[0006]

However, in the ink jet recording head having the conventional structure described above, since SiO ₂ is used for the heat storage layer, the thermal efficiency of the recording head (= heat quantity transferred to ink / heat generation) The power applied to the resistor layer) is as bad as 10 to 12%, and the heat generated except for heating the ink, that is, about 90% is transferred to the heat storage layer (supporting substrate) side. Due to this low thermal efficiency, the supporting substrate accumulates heat and the temperature of the entire recording head rises. The increase in the temperature of the recording head causes a small bubbling phenomenon, that is, thermal crosstalk, even at a timing other than bubbling and ejection, and the bubbling itself becomes unstable. When the foaming becomes unstable, the volume of the ink droplet changes, which causes a change in the density of the recorded image. Further, when the temperature of the recording head rises, the ink may boil at a portion other than the heat acting surface to block the liquid flow path and recording may not be possible.

As described above, the problem that the obtained recorded image has a change in density or that the image is partially missing is against the demand for high quality and high-speed recording of the recorded image, and is solved early. Is a problem that requires

Therefore, an object of the present invention is to reduce the efficiency with which the heat for heating the ink escapes to the heat storage layer, the thermal efficiency is good, the foaming is stable, the density variation of the recording quality does not occur so much, and the ejection characteristics are improved. It is to provide a good inkjet recording head.

[0009]

The inventors of the present invention have paid attention to the fact that sputtered gas is taken into the sputtered thin film as a result of repeated research to utilize gas as a heat storage layer.
It was found that the gas is positively mixed in the sputtered film and the mixed gas is released by heating. Further, as a means for enclosing the released gas, it was possible to form at least one thin film on the layer from which the gas is to be released, and then release the gas by heating to form the heat storage layer.

In the ink jet recording head of the present invention, a liquid flow path for ejecting the recording liquid and the recording liquid on the heat acting surface are provided with thermal energy to eject the recording liquid.
An ink jet recording head comprising: a heating resistor layer that generates the thermal energy by energization; and an electrothermal converter that has a heat storage layer that transfers heat generated from the heating resistor layer to the heat acting surface. A void containing a gas is provided in a part of the heat storage layer.

Ar is generally used as a sputtering gas, but other than Ar, any inert gas such as He, Ne or Kr can be used.

[0012]

According to the present invention, the void layer containing gas is provided in a part of the heat storage layer. In general, gas has a low thermal conductivity, poor heat dissipation during heating, and has a property of rapidly radiating heat during cooling due to its small heat capacity, so the efficiency of escaping to the heat storage layer is reduced, and the bubbling of the recording liquid is stable. ..

[0013]

Embodiments of the present invention will now be described in detail with reference to the drawings.

(Embodiment) FIG. 1 is a perspective view showing an outline of an ink jet recording head of the present invention. Further, FIG. 2 shows a cross-sectional configuration diagram on the XY line in FIG. Note that FIG.
In order to simplify the description, the layers on the heat acting surface 106 side above the heating resistor layer 102 and the electrode wiring layer 103 are omitted.

A Si (111) single crystal substrate 108 (p type, diameter 4 inches, 525 μm thickness) as a supporting substrate of an ink jet recording head is provided in a predetermined manner in an RF magnetron sputtering device (device name: SPF-730H manufactured by Nichiden Anelva). Place it in a position, and use a SiO ₂ target (purity: 99.9%) with a diameter of 8 inches and a thickness of 5 mm for 2.4 kW and an Ar pressure of 4
× 10 ^-3 Torr, the distance between the target and the substrate is 8
The first heat storage layer 100 was formed by sputtering at 8 mm for 24 minutes. Next, a substrate bias voltage of −100 V was continuously applied and sputtering was performed for 88 minutes to form a second heat storage layer 101.
The first heat storage layer 100 (see FIG. 2) obtained through the above steps had a thickness of SiO ₂ of 0.5 μm, and the second heat storage layer 101 had a thickness of 1.4 μm.

Next, the target in the above-mentioned RF magnetron sputtering apparatus was set to HfB ₂ (diameter 8 inches, thickness 5 m).
m, purity 99%), 1.5 kW, Ar pressure 5 ×
Sputtering was performed at 10 ⁻³ Torr for 10 minutes, and the heating resistor layer 1 was formed.
02 (see FIG. 2) was deposited to a thickness of 0.1 μm. When the specific resistance of the obtained heating resistor layer 102 was measured by an ordinary method, it was 240 μΩ · cm.

Further, an Al film having a thickness of 0.5 μm was laminated on the heating resistor layer 102 by an electron beam evaporation method, and an electrode wiring layer 103 having a wiring width of 22 μm was formed by a photolithography process.

Further, by a photolithography process,
The pattern of the heating resistor layer 102 was formed.

After that, the SiO ₂ target was set to 2.4 kW and the Ar pressure was set to 4 by the RF magnetron sputtering apparatus described above.
Sputtering was performed at × 10 ⁻³ Torr for 90 minutes to form a protective layer 104 of the heating resistor layer 102 with a thickness of 1.9 μm.

Then, the target in the above-mentioned RF magnetron sputtering apparatus was Ta (diameter 8 inch, thickness 5 mm,
Purity 99.9%), 1.5kW, Ar pressure 1x
Sputtering is performed at 10 ^-2 Torr for 10 minutes, and the heat acting surface 106
The outermost surface protective layer 105 corresponding to the above was deposited to a thickness of 0.5 μm.

The electrode wiring layer 103 was provided with a terminal (not shown) for receiving an electric signal from the outside. Through the above steps, the size of the heat acting surface in contact with the liquid is 20 × 100.
One element was formed by arranging 48 heat generating portions having a pitch of 62.5 μm and a pitch of 62.5 μm.

Next, a partition wall made of a polyimide resin is formed by a conventional method so that the liquid flow path 107 (see FIG. 2) communicating with the discharge port 112 (see FIG. 1) is located at a position corresponding to each heat generating portion. 111 (see FIG. 1) height 30 μm, width 52.
It is provided to have a thickness of 5 μm, and further covers 1 m of the partition wall 111.
An ink jet recording head was manufactured by bonding a glass flat plate 109 (see FIG. 1) having a thickness of m with an epoxy resin.

A DC (direct current) power supply was connected to one element thus obtained, and a current was applied for 5 minutes at DC15V. When the Ar gas in the heat storage layer was released, the layer above the heating resistor layer was released. Expanded and a smooth R-shaped heat acting surface was obtained. In FIG. 2, reference numeral 110 is a void layer containing Ar. The release of Ar was confirmed by the following method.

(Ar emission confirmation method) 1) A HfB ₂ heating resistor layer is formed on a Si substrate having a thermally oxidized SiO _{2 layer} having a thickness of 2.5 μm formed on the surface in exactly the same manner as the above-described manufacturing method, and then a heat storage layer. The SiO ₂ film is laminated under the same Ar-containing condition as that used for forming. Two such substrates were produced, and the outermost surface of one substrate A was left as SiO _{2 and} a Ta film was formed on the other substrate B to a thickness of 0.1 μm.

2) For the substrates A and B, the amount of Ar in the SiO ₂ film was measured using an electron beam microanalyzer (manufactured by Shimadzu Corporation: EPM-810). Characteristic X-ray A
The ratio was calculated as the ratio of the rKα ray count value and the SiKα ray count value, and the results are shown in the initial column of Table 1.

3) Next, regarding substrate A and substrate B, D
C heating was performed under conditions of 15 V and 5 min, and the amount of Ar was measured again by an electron beam microanalyzer. The results are shown in Table 1.
In the column after heating.

[0027]

[Table 1]

4) On the other hand, the unevenness of the surfaces of the substrates A and B before and after heating was measured in the direction of FIGS. 1a → b by a stylus meter, and the results are shown in FIG. The heights of the convex portions of the substrates A and B were exactly the same. From FIG. 3, it can be seen that the heating operation of 3) formed a convex portion having a height of 0.10 μm together with the substrates A and B in the heat generating portion.

5) Further, a part of the substrates A and B having convex portions formed by heating is taken, and the substrate A is made of a SiO ₂ film.
When the F-NH ₄ F aqueous solution was dissolved and removed, the heating resistor layer was flat. For the substrate B, a Ta film is HF-
When the film was dissolved in an HNO ₃ aqueous solution and the SiO ₂ film was dissolved and removed using an HF—NH ₄ F aqueous solution, it was flat like the substrate A.

6) From the results of 3), 4) and 5) above, the following has been found.

That is, Ar in the SiO ₂ film is released by heating and deforms the film. However, when the Sio ₂ film is sandwiched by dense metals or the like, Ar is not released outside the system and the SiO ₂ film is not released. It is considered that they remain at the interface between the film and the film that gives heat.

After confirming the discharge of Ar gas as described above, a tube for supplying ink to one of the ink jet recording heads of the present invention was attached so that recording was possible.

Next, the ejection performance and the printing performance of the ink jet recording head of this embodiment were tested. For the performance test, three elements were selected from one element cut out from the same substrate.

The ejection performance was evaluated by measuring the electric power (P _com ) required to eject an ink droplet having a predetermined volume at a predetermined speed. This evaluation is a test for estimating the power consumption of the ink jet recording head, and it can be determined that the smaller P _com is, the higher the thermal efficiency is, and as a result, the temperature rise of the recording head is less.

The printing performance was evaluated by continuously ejecting ink simultaneously from all the ejection ports in one element to continue printing on the recording paper, and it was possible to record until the printed matter was faint or could not be printed. The line length (L _max ) was used. This evaluation is a heat storage stability test of the recording head, and it can be judged that the larger L _max is, the higher the heat storage stability is.

The results of the above performance tests are shown in Table 2. In addition, Table 2 also shows a comparative example described later.

[0037]

[Table 2]

From Table 2, the ink jet recording head of this embodiment has a power consumption ratio = 28.0 / 41.4 = 67.6.
%, Power saving of about 32% was achieved. Then, when the heat storage stability L _max was compared as the effect of power saving, a performance improvement of 35/18 = 1.94 times was observed.

In this embodiment, the ink jet recording head has a configuration in which the ink ejection direction and the ink supply direction to the thermal action surface are substantially the same. The same effect was seen even in the form in which the direction in which was supplied was at a right angle.

(Comparative Example) FIG. 4 shows a partial sectional view of an ink jet recording head having a conventional structure as a comparative example.

Thermally oxidized SiO ₂ which is the heat storage layer 200 on the surface
Si (111) single crystal supporting substrate 207 (p type, diameter 4 inches, 525 μm thickness) in which the layer was formed to a thickness of 1.90 μm.
Was placed at a predetermined position in the RF magnetron sputtering apparatus, the input power at discharge was 1.5 kW, and the Ar pressure at discharge was 5 × 10 ⁻³ To with the same HfB ₂ target as in the example.
The heating resistor layer 20 is set to rr and sputtered for 10 minutes.
1 was formed.

Next, an Al film having a thickness of 0.5 μm was laminated on the heating resistor layer 201 by an electron beam evaporation method, and an electrode wiring layer 202 was formed by a photolithography process.

Further, a pattern of the heating resistor layer 201 was formed by patterning a wiring width of 30 μm by a photolithography process, and further removing a portion corresponding to a heat generating portion (20 × 100 μm) of the electrode wiring.

Thereafter, SiO ₂ covering the heating resistor layer 201 is formed by the same RF magnetron sputtering apparatus as in the embodiment.
The layers were stacked to have a thickness of 1.9 μm to form an electric insulating layer 203.

Subsequently, Ta as the outermost surface protective layer 204 corresponding to the heat acting surface 206 was formed in a thickness of 0.5 μm by the RF magnetron sputtering device under the same conditions as in the example.

A terminal (not shown) for receiving a signal from the outside was provided on each electrode wiring. Through the above steps, the size of the heat acting portion in contact with the liquid is 20 × 100 μm, the pitch is 62.5 μm, and 48 heat generating portions are arranged side by side.
There are two elements.

Next, a partition wall (height: 30 μm) made of a polyimide resin is provided by a conventional method so that the liquid flow path 205 communicating with the discharge port is located at a position corresponding to each heat generating portion, and the partition wall is further formed. A 1 mm glass flat plate 208 that covers was bonded using an epoxy resin, and each 4-inch substrate was cut into individual discharge elements each having a size of 10 mm × 10 mm, to manufacture an inkjet recording head. The structural dimensions of the liquid flow path were exactly the same as those of the inkjet recording head of the example.

The performance test of the ink jet recording head manufactured by the above steps was performed in exactly the same manner as in the example, and the results are shown in Table 2. As described above, the ink jet recording head of the conventional example had insufficient power consumption and heat storage stability.

(Others) The present invention is particularly provided with means for generating thermal energy as energy used for ejecting ink (for example, an electrothermal converter or a laser beam) even in the ink jet recording system. The present invention provides excellent effects in a recording head and a recording apparatus of the type in which the thermal energy causes a change in ink state. This is because such a system can achieve high density recording and high definition recording.

Regarding the typical structure and principle thereof, see, for example, US Pat. No. 4,723,129 and US Pat. No. 4,740.
What is done using the basic principles disclosed in 796 is preferred. This method is a so-called on-demand type,
It can be applied to any of the continuous type, but especially in the case of the on-demand type, it can be applied to the sheet holding the liquid (ink) or the electrothermal converter arranged corresponding to the liquid path. By applying at least one drive signal corresponding to the recorded information and giving a rapid temperature rise exceeding nucleate boiling, heat energy is generated in the electrothermal converter, and film boiling is caused on the heat acting surface of the recording head. Liquid (ink) corresponding to this drive signal as a result
This is effective because bubbles can be formed inside. Due to the growth and contraction of the bubbles, liquid (ink) is ejected through the ejection openings to form at least one droplet. It is more preferable to make this drive signal into a pulse shape, because the bubble growth and contraction are immediately and appropriately performed, so that the ejection of the liquid (ink) with excellent responsiveness can be achieved. As the pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. If the conditions described in US Pat. No. 4,313,124 of the invention relating to the rate of temperature rise on the heat acting surface are adopted, more excellent recording can be performed.

As the constitution of the recording head, in addition to the combination constitution of the discharge port, the liquid passage, and the electrothermal converter (the straight liquid passage or the right-angled liquid passage) as disclosed in the above-mentioned specifications, U.S. Pat. No. 4,558,333, U.S. Pat. No. 44, which discloses a configuration in which a heat acting portion is arranged in a bending region.
The configuration using the specification of No. 59600 is also included in the present invention. In addition, Japanese Unexamined Patent Publication No. 59-123670 discloses a configuration in which a common slit is used as a discharge portion of the electrothermal converter for a plurality of electrothermal converters, and an opening for absorbing a pressure wave of thermal energy is provided. The effect of the present invention is effective even if the configuration corresponding to the ejection portion is disclosed in Japanese Patent Laid-Open No. 59-138461. That is, according to the present invention, recording can be surely and efficiently performed regardless of the form of the recording head.

Further, 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 which can be recorded by the recording apparatus. Such a recording head may have a configuration that satisfies the length by a combination of a plurality of recording heads or a configuration as one recording head integrally formed.

In addition, even in the case of the serial type as in the above example, the recording head fixed to the main body of the apparatus or the electrical connection to the main body of the apparatus or the ink from the main body of the apparatus by being attached to the main body of the apparatus. The present invention is also effective when a replaceable chip-type recording head that can be supplied or a cartridge-type recording head in which an ink tank is integrally provided in the recording head itself is used.

Further, as the constitution of the recording apparatus of the present invention, it is preferable to add ejection recovery means of the recording head, preliminary auxiliary means and the like because the effects of the present invention can be further stabilized. Specifically, heating is performed by using a capping means, a cleaning means, a pressure or suction means for the recording head, an electrothermal converter or a heating element other than this, or a combination thereof. Examples thereof include a preliminary heating unit for performing the discharge and a preliminary discharge unit for performing discharge different from the recording.

Regarding the type and number of recording heads to be mounted, for example, only one is provided corresponding to a single color ink, or a plurality of inks having different recording colors and densities are supported. A plurality of pieces may be provided. That is, for example, the recording mode of the recording apparatus is not limited to the recording mode of only the mainstream color such as black, but may be either integrally formed of the recording heads or a combination of a plurality of them. The present invention is also very effective for an apparatus provided with at least one of full-color recording modes by color mixing.

In addition, in the above-described embodiments of the present invention, the ink is described as a liquid, but an ink that solidifies at room temperature or lower and that softens or liquefies at room temperature may be used. Or, in the inkjet method, it is common to adjust the temperature of the ink itself within the range of 30 ° C. or higher and 70 ° C. or lower to control the temperature so that the viscosity of the ink is within the stable ejection range. At times, a liquid ink may be used. In addition, the temperature rise due to thermal energy is positively prevented by using it as the energy for changing the state of the ink from the solid state to the liquid state, or in order to prevent the evaporation of the ink, it is solidified and heated in a standing state. You may use the ink liquefied by. In any case, by applying heat energy such as ink that is liquefied by applying heat energy according to the recording signal and liquid ink is ejected, or that begins to solidify when it reaches the recording medium. The present invention can be applied to the case where an ink having a property of being liquefied for the first time is used. In this case, the ink is
JP 54-56847 A or JP 60-7.
As described in Japanese Patent No. 1260, it may be configured to face the electrothermal converter in a state of being held as a liquid or a solid in the concave portion or the through hole of the porous sheet. In the present invention, the most effective one for each of the above-mentioned inks is to execute the above-mentioned film boiling method.

In addition, as the form of the ink jet recording apparatus of the present invention, besides the one used as an image output terminal of information processing equipment such as a computer, a copying apparatus combined with a reader or the like, and a facsimile apparatus having a transmission / reception function It may be a form or the like.

[0058]

As described above, the void layer containing gas is provided in a part of the heat storage layer. In general, gas has a low thermal conductivity, poor heat dissipation during heating, and has a property of rapidly radiating heat during cooling due to its small heat capacity, so the efficiency of escaping to the heat storage layer is reduced, and the bubbling of the recording liquid is stable. ..

Further, according to the present invention, since the efficiency for the heat for heating the ink to escape to the heat storage layer is reduced, the power consumption is achieved, the heat storage stability is improved, and the recording quality is increased. ..

[Brief description of drawings]

FIG. 1 is a perspective view showing an outline of an inkjet recording head of the present invention.

FIG. 2 is a sectional view taken along the line XY shown in the perspective view of FIG.

FIG. 3 is a characteristic diagram showing the results of measuring the cross-sectional shape of the heat storage layer of the inkjet recording head of the present invention using a stylus meter.

FIG. 4 is a cross-sectional configuration diagram of an inkjet recording head having a conventional configuration.

[Explanation of symbols]

 100 First heat storage layer 101 Second heat storage layer 102 Heating resistor layer 103 Electrode wiring layer 104 Protective layer 105 Outermost surface protective layer 106 Thermal action surface 107 Liquid flow path 108 Support substrate 109 Glass flat plate 110 Void layer 111 Partition wall 112 Discharge Outlet 200 Heat storage layer 201 Heating resistor layer 202 Electrode wiring layer 203 Electrical insulating layer 204 Outermost surface protective layer 205 Liquid flow path 206 Thermal action surface 207 Si single crystal support substrate 208 Glass flat plate

Claims (6)

[Claims] 1. A liquid flow path for discharging a recording liquid, and a heating resistor generated by energizing the thermal energy in order to apply thermal energy to the recording liquid on a heat-acting surface to discharge the recording liquid. In an ink jet recording head including a body layer, and an electrothermal converter having a heat storage layer for transferring heat generated from the heating resistor layer to the heat acting surface, a gas is provided in a part of the heat storage layer. An ink jet recording head, characterized in that it is provided with a void containing the same. 2. The ink jet recording head according to claim 1, wherein the gas is Ar. 3. The ink jet recording head according to claim 1, wherein the heat acting surface is formed by a protective layer on the heating resistor layer. 4. The ink jet recording head according to claim 1, wherein the heat acting surface is formed of the heat generating resistor layer. 5. The ink jet recording according to claim 1, wherein a direction in which the recording liquid is ejected and a direction in which the ink is supplied to the heat acting surface are substantially the same. head. 6. The method according to claim 1, wherein a direction in which the recording liquid is discharged and a direction in which the recording liquid is supplied to the heat acting surface are substantially perpendicular to each other.
The inkjet recording head according to any one of 1.