DE3012946A1 - High speed recording equipment drop generator - has heating element producing bubbles near end of fine tube - Google Patents

Abstract

A drop generator uses a bubble (1B) source (4) in a fine tube (1) carrying the fluid (IK). The bubbles are produced and dissipated so as to cause drops of fluid to be forced out of an opening in the fine tube. It is more compact than conventional drop generators but is suitable for high speed recording and high density nozzle arrays. The bubbles cause a high pressure to develop which in turn causes the agitation of drops (7) of practically constant dia. The bubble generator is positioned so that the bubbles are not in contact with the surrounding air. It is a flat heating element lying along the fine tubes. The distance of the edge of the element from the tube outlet is between one and fifty times the opening dia.

Description

Droplet generator

The invention relates to a droplet generating device, which result in the ejection of a spray liquid commonly referred to as ink an opening and its flight in form of droplets by means of a thermal effect on the ink.

Among the various known recording systems is the so-called Ink jet recording process which is essentially a during recording Noiseless, non-stop recording method is and is on the ordinary Paper enables high-speed recording without fusing than recognized as an extremely useful recording method. For the ink jet recording method a wide variety of possibilities and improvements have been proposed so far. Some ink jet recording systems are already commercially available while efforts are still being made in other ink jet recording systems to make them usable in practice.

In the ink jet recording method, recording is made achieved by the fact that small droplets of the recording liquid called ink riac different propulsion principles are made to fly and the droplets appear adhere to a recording surface such as paper or the like.

In the ink jet recording method, usually a Uses an apparatus provided with a recording head having a discharge port, through which the ink is ejected and made to fly in the form of small droplets is, and has an inlet opening through which the ink can flow. The different Device types differ in the system by which the small ink droplets are created be generated.

For example, there is one type of device in which the ink is pressurized or under the given subsequent delivery conditions, for example through utilization the capillary effect, supplied from an ink supply tank into a specific chamber will. Applied between the ink in the chamber and one in front of the discharge port A voltage is applied to the electrode to electrostatically discharge the ink from the discharge port In another ink jet recording apparatus, the ejection is the Ink and the flight in the form of small droplets due to mechanical vibrations evoked. With this type of device, the volume of the chamber in which the Ink is due to the mechanical vibration of a piezoelectric vibration generating element varies according to a signal so that the ink is ejected as small droplets will.

The exact structure of this device is described in US Pat. No. 3,747,110 as well as in the IEEE Transactions on Industry Applications Vol. IA-13, o.1, January / February 1977, etc. described.

A specific example of a droplet generating device, those in the one described above Ink jet recording method can be used is described in U, -PS 3,878,519. From this patent specification the following droplet generation device is known: droplet generation device, in the case of droplets with a practically constant breakaway point and practically unidirectional Distance from each other can be formed from a stream of liquid, the droplet generating device a device for replenishing the fluid flow through an opening or something similar, as well as a device for selectively changing surface tension demarcated sections of the liquid stream having to droplets with practically uniform distance from each other and practically uniform porm to form, whereby the selective changing device on each of the delimited portions of the liquid flow acts when it passes a certain section of the fluid path to to reduce the surface tension of each of the demarcated sections before the Fluid flow dissolves by itself in 2 droplets after the fluid flow has emerged from the opening.

The device for selectively changing the surface tension delimited Sections of the liquid stream to form droplets with practically uniform Distance from one another and practically uniform in size is in this droplet generating device in particular, one "high intensity light source" and one near the discharge port located "ironing device".

This droplet generating device is not of the type that the entire ink supply device including the pressure generating device for ejecting the stream of ink, and the deflector for the droplet and uses the generated droplets. Therefore, it needs a drainage channel that collects unnecessary droplets. Thus there is a reduction in size the entire device difficult. As in this device, the droplet generating force is small, the uniformity of the droplet diameter is insufficient. liird Furthermore, in this device the pressure in the ink supply is not precisely set, so it is impossible to have a uniform droplet diameter, a constant ejection speed and to achieve a uniform ejection direction of the droplets.

The invention is based on the object on this technical Area to solve the technical problems that could not be solved so far. For this purpose, a droplet generation device is to be created which is excellent Properties related to the uniformity of the ejected ink droplets, the soot kick responsiveness or the ejection uniformity and the long term ejection stability Has. Perner is intended to use the device for high-speed recording despite its small dimensions be suitable. The droplet generation device should also be easy to manufacture and can be used in a practical, high-density multiple nozzle head.

According to the invention, this object is characterized by what is stated in claim 1 Features solved.

The invention is described below using exemplary embodiments Described in more detail with reference to the drawing. It shows: Fig. 1 schematically a Cross section through a droplet generation device according to the invention.

Figs. 2 to 8 are schematic plan views of examples of the invention used heating devices.

9A, 9B to 12 show an embodiment of the Invention.

In the case of the droplet generating device described, the signal Energy is used with high efficiency to eject the ink and as droplets to make it fly. This increases the ejection yield of the ink droplets, ejection responsiveness and long-term continuous recordability are essential elevated. Furthermore, in the device described, the size and the direction of ejection of the ink droplets ejected through the ejection opening largely from any Disturbances unaffected. Thus, the device has excellent uniformity of the ejected ink droplets and excellent ejection stability.

Nevertheless, the device described has a simple structure and requires a low manufacturing cost, so that the actual droplet generation head with much smaller dimensions than comparable droplet generation devices can be produced. The simplicity of construction and ease of manufacture enables a high-density multi-nozzle head suitable for high-speed recording is indispensable. Another essential property of the droplet generation device described is that the signal electrode can be laid very easily, so that during manufacture of a multiple head, the arrangement of the ejection orifices in the droplet generation head part can be arbitrary, and that the head section is extremely simple as a rod-shaped structure can be produced.

In the following an embodiment in connection with the drawing to be discribed. Fig. 1 generally shows an ink jet recording with the described droplet generating device. To simplify the description becomes an embodiment described by the nozzle type. It understands goes without saying that the droplet generating device described, of course, does not is limited to the injector type, and that just as easily a droplet generating device can be realized with a multiple nozzle arrangement.

Fig. 1 shows that of an unillustrated ink supply tank Inflowing ink 1K in the direction of arrow IP through an inlet 1 into a working chamber 2 flows in from an elongated bore in a recording head portion 3 exists to fill the working chamber. One on a section of the working chamber 2 attached Ileizelement 4 is in contact with the ink IK, which in the working chamber 2 has flowed in. When the heating element 4 is electrically energized to generate heat and the ink IK is heated above its evaporation temperature, it becomes a bubble IB instantaneously formed in the ink 1K. A sufficient thermal impulse to evaporate the ink IK generated the heating element 4 by electrical excitation via the electrodes 51 and which are connected to the heating element. The result generated heat acts on the ink IK and causes a phase change of the ink, namely the evaporation of the ink. As a result, a bubble IB is formed, by which the internal pressure in the working chamber 2 is increased. In response to that When the internal pressure is increased, the ink IK is ejected through an opening 6. the Ejected ink forms a droplet 7, which is a recording member 8 made of paper or something like that flies and sticks there, causing the recording process is carried out.

The heating element 4 is arranged on a base plate 9 and stands in contact with a section of the working chamber 2. There is a tension between the electrodes 51 and 52 in accordance with the input of a recording signal applied, the heating element generates heat in pulses. Thus, with the one shown Execution Example of recording by means of a singing signal corresponding ink droplet carried out by the ink droplet 7, the to the recording paper 8 has flown and adhered to it.

In the above-described ink jet recording method the quality of the ink droplet ejection depends largely on the effective heat generating one Area of the heating element 4 and the position at which the heating element 4 is relatively is attached to the working chamber 2. Therefore these points deserve increased attention be dedicated. In connection with the described droplet generating device various designs of droplet generating devices with a Basic principle according to FIG. 1, but with a different structure and arrangement manufactured and examined. It was found that the place where the heating element 4 is mounted in the working chamber 2, and above all the relative positional relationship between the heating element and the discharge opening 6 is a very important factor, which determines the quality of the ejection state of the ink droplets.

If the ileizelement 4 is attached too close to the discharge opening 6, so the bubble IB generated in the ink IK stands with the atmosphere through the opening 6 in connection. Therefore, the ink IK ejected through the opening 6 does not form Droplets of a certain size but will be in fog-like fine droplets with divided into random diameter. These fine droplets tend to splash. Extends If the heating element 4 enters the discharge opening 6 in an extreme pall, no Ink droplets ejected even if a bubble IB is formed. To such shortcomings to avoid, it is appropriate that the heating element 4 from the discharge opening one Distance in a certain area. Is the distance between the heating element 4 and the discharge opening 6 are not in this area, the diameter of the ejected ink droplets irregularly, while at the same time the initial speed of the ejected ink droplets is reduced until the end in the work shop 2 there is no longer sufficient pressure to eject ink droplets on the ink IK. Therefore, the distance between the heating element and the discharge port is limited. In the studies carried out on these conditions, it was found that if is the diameter of the discharge port d (the discharge port can be an arbitrary one Have shape, for example, it can be circular, rectangular, etc .; in this Palle is meant with the above diameter the maximum diameter), it is advantageous is to mount the heating element 4 in the working chamber 2 so that that of the discharge port 6 adjacent edge of the heating element from the discharge opening 6 a distance in the area between about d and about 50 d.

It has also been found that when looking at the ejection speed the ink droplets attaches importance, it is appropriate to place the heating element 4 in one area to be applied between approx. 10 d and approx. 30 d. On the other hand, if one measures the uniformity the ejected ink droplets and the long-term ejection stability importance at, it is expedient to keep the heating element 4 fresh in the region of about d and about 10 d to be attached. If a droplet generating device is manufactured that utilizes the the above conditions are met, the uniformity of the ink droplet size, the stability of the ejection direction, the ejection speed or the creep stability be kept at a usable value.

The embodiment shown in Fig. 1 is in one mode of operation in which recording is carried out by making the recording paper 8 is moved in the direction of the arrow. In the device according to the invention, the recording process is not limited to this mode of operation. The record tion paper 8 only has to be moved relative to the opening 6. Therefore, the most diverse Changes are made, for example, the recording paper 8 in in a direction opposite to the direction of the arrow, or the up drawing paper 8 can be moved forward and backward with respect to the plane of the drawing or the opening 6 can be moved in any direction, wherein the recording paper 8 is fixed.

Furthermore, it is possible and very easy to do at will, the described droplet generating device in a multi-orifice recorder to use.

In the case of the droplet generating device described, it is expedient to in order to efficiently transfer the heat generated by the heating element 4 to the ink IK, that the heating element 4 is attached to the inner wall of the working chamber 2; However it is not easy to determine the effective area for the heating element (the area leading to the Capable of generating the heat required to eject the ink) in the working chamber 2 to accommodate, which consists of a fine hole, the cross-sectional area has a diameter of the order of 30 to 250 µm.

In the case of the droplet generating device described, the heating element 4 in the axial direction of the working chamber 2 so that the effective tarpaulin is housed in the fine working chamber 2.

This is described in the following as an example.

Fig. 2 shows in a schematic plan view a for the described Droplet generating device suitable heating element 4. The heating element 4 is a flat heating resistor, the one in the area indicated by dashed lines Working chamber 2 is attached and a shorter side a (length 11), which is perpendicular to the axis of the working chamber 2 (dashed line) and a longer side b has a constraint of 2 x 11 or more in the axial direction the working chamber 2 has.

The planar shape of the sheet member 4 in the described ink jet recording system does not reproduce as a recording form (radio form due to the ink droplet) and can therefore, in contrast to the form of the so-called conventional thermal head, that for making the record in contact with thermosensitive paper is to be chosen with a considerable price. Accordingly, the described droplet generating device has various shapes for the Heating element 4 possible; schematic plan views are shown in FIGS. 3 to 8 as examples similar to that shown in FIG.

In the examples shown in FIGS. 2 through 8, similar components have the same reference numbers.

The heating element 4 is essentially in the examples shown similar to a thermal print head used in thermosensitive recording built up. These are commonly used in thick film heads, thin film heads, and semiconductor heads due to the manufacturing process and the differences in the heat generating Divided resistances. All of these resistances are in the device described usable. However, when j is high speed ink jet recording and With high resolution, the use of a thin film head is particularly desirable advantageous.

The one used in the droplet generating device described Ink IK is produced by making or dissolving a wetting agent, for example Ethylene glycol, a surface activating agent, and different Dyes in a main solvent, for example water, ethanol, toluene or something similar. To prevent the discharge opening from being clogged, it is appropriate to filter insoluble particles or the like beforehand to filter out.

Further details of the droplet generating device are given below described using an exemplary embodiment. The embodiment shown is in connection with a manufacturing process of a multi-nozzle recording head described. The fig.

9A and 9B schematically show two components in a perspective view PA and PB showing the working chamber block of a multi-nozzle recording head.

FIG. 9A shows the component PA and FIG. 913 the component PB.

The component PA is manufactured as follows: First, the both surfaces of a flat plate of photosensitive alkali metal fluoride glass (the glass contains SiO2, Li2O, Na2O, K2O, Al2O3, Au, AgCl and CeO2) polished. Afterward the burst is cut to a size of 100 mm x 100 mm (thickness 2 mm). Photosensitive glasses of this type are Photoceram and Photoform (trade names from the manufacturing company Corning Co., Inc.), which are commercially available. Each of these Glasses can be used. Next, the so treated photosensitive Glass plate IG with a coupling wave (frequency-doubled wave) of a dye laser with a wavelength of 310 nm, which with an N2 laser (not shown) with a Wavelength of 620 rim is generated, illuminated to thereby create interference fringes with a pitch of 100 µm and a width of 50 µm on the photosensitive Manufacture glass plate. These interference fringes are on a surface of 90mm x 90mm uniform, the electric power of the base light source is 10 W. Since the photosensitive glass plate has an absorption line of Ce ++ for has a wavelength of 310 nm, exposure to a laser light is whose Wavelength of this absorption line is carried out selectively. after the If interference fringes have been formed, the glass plate PG becomes one hour subjected to a heat treatment at 60,000 to crystallize them. The surface the glass plate PG is polished to a thickness of about 0.1 mm to the surface to smooth out further.

Then the surface of the glass plate is that of the polished The opposite surface is coated with a resin. The glass plate IG will then placed in a 5% aqueous HF solution and etched. Meanwhile, ultrasonic waves become created. In this etching process, the etching speed is that of the crystallized Parts of the glass plate PG significantly higher than the etching speed of the non-crystallized Parts. The difference in etch rate is on the order of 20: 1.

In the procedure described above, as in Fig. 9A shown a certain number of elongated grooves IV, each one Cross section of 50 µm x 50 µm and a pitch of 100 µm on the glass plate PG to have.

The grooves I.V are not on the dimensions of the described embodiment limited. Rather, the grooves can have a cross section of 10 μm × 10 μm to 150 μm for x 150 µm and a pitch ranging from 30 µm to 200 µm. A change is possible by one part len of the optical exposure system, etc.

With the technique described above, a total of six were corresponding Glass plates made of PG.

Next, an epoxy resin is used as the connecting material an immersion process applied to the surface of each glass plate PG, which is provided with the elongated grooves. Will the glass plate PG lifted in a direction parallel to the axes of the grooves LV, so can achieve a coating with epoxy resin that is substantially uniform along its length of the wall surfaces of the formed grooves is LV. Then this coating is applied in preparation, dried and semi-hardened at 100 ° C for about five minutes. Here then the glass plate is cut to the predetermined size in order to achieve the To receive component PA.

The joining material is not limited to epoxy resin. as Rather, connecting material materials can be used in which the adhesive effect occurs through heating. For example, organic adhesives such as epoxy resin adhesives, Phenolic resin adhesives, urethane resin adhesives, silicone resin adhesives, triazine resins, BT resin or something similar or inorganic adhesives such as molten silver salts, Low melting point glasses or something similar can be used as in the Japanese Patent Publication No. 20227/1963. The inorganic Adhesives are mostly not used in liquid form but in powder form. Separated From the component PA, the component is produced as shown in FIG. 913. That Component PB can be made by successive application of a heat-storing layer 12 (sprayed-on SiO2 film with a thickness of 2 to 3 µm), a heat-generating one I resistance layer 13 (sprayed on HfB2 film with a thickness of 50 to 100 rim), an electrode layer 14 (evaporated aluminum layer with a thickness of 70 to 80 nm), a protective layer 15 (sprayed-on SiO2 film with a thickness of 1 1im) and a stop layer 16 (parylene, silicone or sprayed-on Ta203 film) on a substrate with a thickness of about 0.6 mm made of alumina, monocrystalline Silicon or made from a metal such as aluminum, iron, or something similar will. Fig. 10 shows in a cross section at the line X-Y in Pig. 9B these layers.

The component is then cut to a specific size. A specific pattern is etched into the electrode layer 14. The electrode layer is divided into individual line electrodes PE and a common line electrode CE divided. Pig. 913 shows this in a perspective view. Be at the same time in the heat generating resistance layer 13 rectangular strips HT with the same Pitch as the elongated grooves LV generated in the component PA, with the size of t2 is 250 µm and the size of l3 is 50 µm. The one in Pig. 10 protective layer shown 15 and the stop layer 16 do not have to be applied in different balls.

A total of six substrates 11 are in a certain number of heat generating resistance patterns HT as described above. These substrates 11 were cut so that the width 14 of the common lead electrode CE 80 for is (component B-1), 150 µm (component B-2), 350 µm (component B-3), 800 µm (Component B-4), 1500 µm (component B-5) and 2500 µm (component B-6).

The six components PA and PB produced in this way are each aligned in such a way that that, as shown in Fig. 11, the grooves LV are the heat generating resistive strip IIT are opposite. Then they are connected with an adhesive. as next they are subjected to a ten-minute heat treatment at about 1000C, to half-cure the adhesive layer, not shown.

It is then examined whether there are any positional deviations between the two components are present or not, or whether the grooves LV are clogged. Is the result of this Examination "no", the components PA and PB are separated.

The component PB is cleaned for reuse, the component PA On the other hand, if no fault is found, the heat treatment is carried out at 1000C for fifty minutes and then continued at 1800C for two hours the adhesive layer completely closes harden. Then the Check again the absence or presence of clogging of the grooves LV, and if so no error is found, the completed working chamber block BC to the next Manufacturing step forwarded.

In a further manufacturing step, an intermediate chamber block BD for ink supply shown in Fig. 12 was prepared. First will an adhesive of the composition below on the side surfaces BE and BE ' applied. Then the intermediate chamber block BD, as indicated by the arrows in Pig.

12, aligned with the working chamber block 130.

A one minute heat treatment at about 6000 turns the adhesive half dried. Subsequently, the occurrence or non-occurrence of any Deviations in position between the two or the flow of glue into the other Component checked.

Adhesive: Epikoat 828 (manufacturer: Shell Chemical Co.) 100 parts by weight Epomate B-002 (Manufacturer: Aginomoto Co.) 40 parts by weight is the result of this Test "no", the components BE and BE 'are separated from the working chamber block BC and the two components cleaned for reuse. On the other hand, there is no mistake before, they are subjected to a 30-minute heat treatment at about 60 ° O, to dry out the glue.

Next, adhesive is applied to a rear end member bp and aligned this component.

In a one minute heat treatment at about 600C the adhesive will harden half dried, and a test similar to the previous steps was performed. If the result of the test is "no", component BF is cleans. If, on the other hand, there is no fault, the heat treatment at etera 600C is for thirty Continued for minutes to cure the adhesive. Then glue is applied a cover plate component BS is applied and this component is aligned. The cover plate component is heat treated at 600e for one minute to give the adhesive half harden, and perform a test similar to the previous steps.

If the result of this test is no ", the cover plate component will be cleaned in a similar way to the previous steps. On the other hand, there is no mistake before, it will be for thirty minutes at 600C and then for ten minutes at 1000C subjected to a heat treatment to fully cure the adhesive.

Subsequently, tubular members BH and BH 'are placed in the block used, the production of which is completed with this step. The columns are like with glue. In this case it is necessary to cure the adhesive slowly. Therefore, the assembly is left to stand at room temperature for thirty minutes. Next, it is checked whether there is glue in the components BH and BH 'or in the intermediate ink supply chamber has flowed in or not. If the result of this test is "no", the Arrange for reuse in the same way as in the previous steps cleaned. If, on the other hand, there is no error, it will be around for thirty minutes 60 ° C and subjected to a heat treatment for ten minutes at about 1000C in order to obtain the Cure adhesive completely.

In this way, the connection of the inter-chamber block BD with the rear end of the working chamber block BC completed. Then the end face OF of the working chamber block BC, on which the discharge openings OR are located, by means of A polishing compound (grit 1000 or more) is polished to a smooth surface to build. The component is then cleaned to protect the Polishing sand as well as to remove excess material that has got into the grooves LV through the openings OR penetrated during polishing. Whether the end face OF a completely has become smooth surface or not and whether the inside of the grooves LV completely has been cleaned or not 'is checked. If the polishing process is incomplete, so the end surface OF is polished again and then cleaned. In a similar way If a test is carried out, the result of this test is "no" repeating the step again; if, on the other hand, there is no error, the arrangement will be dried from the block BG and the block BD. Now the entire head is on one Aluminum plate put on and the lead electrodes with a flexible printed circuit board tied together.

The following is an example of the ink jet recording in conjunction with FIG using the recording head thus prepared. In Fig. 12, the various parts of the block are separated for the sake of illustration from each other. It goes without saying that the various parts and blocks are of course integrally bonded together by glue, as above has been described.

In the embodiment shown, the recording ink is first introduced into each of the elongated grooves LV by the components SH and BREI '. If an electrical pulse signal to the heat-generating resistor, not shown is applied, a thermal impulse is created and as a result the ink becomes instantly evaporates. The bubble created by evaporation creates a Pressure wave (acting force) that acts on the ink. As a result of this will Ink is ejected and flies in the form of substantially uniform droplets through the openings OR, which are in communication with the grooves LV. These droplets adhere to the recording paper, not shown, so that recording is carried out will.

Msn examines the ink ejection of the six recording heads that as described above using ink with the the following composition under the experimental conditions mentioned below, this results in a stable ejection of ink droplets over 109 processes and more in each of these recording heads. The resulting ink droplets have essentially the same porm. The ejection speed of the ink droplets is as below Table listed.

Water 70 percent by weight diethylene glycol 29 black dye 1 Ink Pulses applied to the recording head droplet Value of i4 exhaust Pulse- No. at the voltage frequency speed broad Component PB (m / sec.) 1 80 µm 1.3 2 150 µm 1.5 3 350 µm 2.0 4 800 µm .40 V 10 µs 10 kHz 3.2 5 1500 µm 3.6 6 2500 on | 1.9 As has been described in detail above, with the droplet generating device according to this embodiment, an ink jet recording apparatus can be produced in which the responsiveness of the ink droplet ejection to the input signal and the ejection state of the ink droplets are very good and the output level is so high that recording images of good quality with can be obtained at a high speed.

The invention described above in all details Droplet generating device can of course also be used as a recording head with a Multiple opening arrangement are formed. In this case, the ink is in each Working chamber supplied by a common ink supply chamber, which with the fluid inlet of each of the plurality of working chambers in communication stands.

L e r s e i t e

Claims (8)

Claims 1. Droplet generating device, in which in a Section of a fine bore a liquid passage is formed, a bubble generating device is arranged in the fluid that has flowed into the fine bore, and in the the creation and disappearance of the vesicles is brought about that the Fluid expelled from an orifice communicating with the fine bore is, characterized in that the bubbles generated in the liquid (IK) (IB) a sufficient pressure to build up droplets (7) with an essentially uniform diameter from to poke, and that the bubble generating device (4) Is arranged so that the bubbles do not communicate with the surrounding air stand. 2. Droplet generating device according to claim 1, characterized in that that the bubble generating device (4) is a heating device. 3. Droplet generating device according to claim 1 or 2, characterized characterized in that when the maximum diameter of the opening (6) is d, the next the edge of the bubble generating device (4) lying on the opening (6) from the opening (6) a distance between d and 50 d has. 4. Droplet generating device according to claim 1 or 2, characterized characterized in that when the maximum diameter of the opening (6) is d, the next the edge of the bubble generating device (4) lying on the opening (6) from the opening (6) a distance between 10 d and 30 d. 5. Droplet generating device according to one of the preceding claims, characterized in that the bubble generating device (4) is a flat heating device extending along the fine bore. 6. Droplet generating device according to one of the preceding claims, characterized in that the bubble generating device (4) on the inner wall the fine bore is attached. 7. Droplet generating device according to claim 1 or 2, characterized characterized in that when the maximum diameter of the opening (6) is d, the next the edge of the bubble generating device (4) lying on the opening (6) from the opening (6) has a distance between d and 10 d. 8. Droplet generating device according to one of the preceding claims, characterized in that the opening (6) has an area between 10 11111 x 10 µm up to 150 x 150 µm.