Ink-jet head, ink-jet cartridge and ink-jet apparatus

Abstract: The present invention provides an ink-jet head, an ink-jet cartridge and an ink-jet apparatus, which can provide certain and stable electrical connection in a separable manner between an energy generation element unit and a driving element unit. The ink-jet head includes the energy generation element unit U E having signal wires for supplying electric signals for heat generating resistors, and connecting electrodes (13a, 13b) projectingly provided at the ends of the signal wires positioned on the mating surface F E , and the driving element unit U D having signal wires for feeding electric signals from the driving elements for driving head generating resistors, and connecting electrodes (20) projectingly provided at the ends of the signal wires positioned on the mating surface F D. The connecting electrodes (13a, 13b, 20) are connected to each other by mutually mating the mating surfaces F E and F D of the energy generation element unit U E and the driving element unit U D . Projecting portion (14) is formed on at least one of the mating surfaces F E for maintaining mating interval between two units U E and U D .

Description: The present invention relates to an ink-jet head having an energy generation element unit including an energy generation element for ejecting a liquid to perform printing on a printing medium and a driving element unit including a driving element for driving the energy generation element, an ink-jet cartridge loaded the ink-jet head, and an ink-jet apparatus employing the ink-jet head. An ink-jet printing method is a method for performing printing by ejecting ink and/or treatment liquid for adjusting characteristics of the ink through ejection openings of an ink-jet head and by depositing the ink and/or the treatment liquid on a printing medium, such as paper or the like, and is advantageous because of its quite low noise characteristics and the capability of high speed printing. In one type of ink-jet head, thermal energy is used to abruptly heat liquid to generate a bubble to cause ejection of a liquid droplet from an ejection opening of a liquid passage by expansion of the bubble, and liquid is introduced into the liquid passage from a liquid chamber upon quenching of the bubble. This type of ink-jet head has the advantages of high response characteristics to a printing signal and ease of manufacture of an ink-jet head having many more ejection openings. The external appearance of the energy generation element unit of the ink-jet head is shown in Fig. 11, and a partially cut-away view thereof is shown in Fig. 12. As shown, heat generating resistors 102 serving electrothermal transducers as energy generation elements are provided on an insulation layer formed on the surface of a substrate 101. Also, electrodes (not shown) are provided for supplying a power to the heat generating resistor 102. Each liquid passage 103 with the associated heat generating resistor 102 on the substrate opens to a respective ejection opening 104 at one end and communicates with a common liquid chamber 105 at the other end. In the common liquid chamber 105, a liquid tank (not shown) separately provided from the ink-jet head is connected via a coupling member 106. It is necessary to control ON and OFF of power supply independently for the individual heat generating resistors 102. For performing control, the driving element may be integrally assembled with the energy generation element unit 107 as set forth above or, in the alternative, as shown in Fig. 13 and Fig. 14 (which shows a sectional structure along line XIV - XIV), may be electrically connected to the energy generation element unit 107 via the bonding wire 108. However, when the energy generation element unit 107 is fixedly connected with the driving element 109 and the bonding wire 108, one of the heat generation resistors 102 and the driving elements 109 fails, the overall ink-jet head can become inoperative. In order to solve such problems using the driving element unit having the driving elements shown in Fig. 15, there has been proposed an ink-jet head and an ink-jet apparatus employing the ink-jet head wherein the driving element unit 110 and the energy generation element unit 107 are separable, and electrical connection is made by tightly stacking connecting electrodes 111 and 112 on one another as shown in Fig. 16. As shown in Fig. 16, in an ink-jet head in which the energy generation element unit 107 and the driving element unit 110 are separable and tightly stacked, the number of connecting electrodes 111 and 112 corresponds to the number of heat generating resistors 102 actually used for ejecting ink. In order to completely achieve the required functions and perform as an ink-jet head, all of these connecting electrodes 111 and 112 are required to be securely connected. However, conventionally, it is possible for non-uniformity in the height and shape of the connecting electrodes 111 and 112 projecting from mating surfaces 113 and 114 of respective units 107 and 110 to occur, and for connection failure to occur between the connection electrodes 111 and 112 with the occurrence of offset of acting point of compression force upon connection of the units 107 and 110 as shown in Fig. 17 which causes moment between the units 107 and 110 about the centers of the connection electrodes 111 and 112. EP-A-0611653 and US-A-5243363 describe ink-jet recording heads of the type described above having an energy generation element unit with a plurality of energy generation elements for ejecting liquid, and a plurality of connecting electrodes projecting from a mating surface of said energy generation element unit with each energy generation element being connected to a respective different one of said connecting electrodes by a respective different one of a plurality of signal lines; and a driving element unit having a plurality of driving elements for driving to said energy generation elements, a plurality of connecting electrodes projecting from a mating surface of said driving element unit with each driving element being connected to a respective different one of connecting electrodes by a respective different one of a plurality of signal lines, and said connecting electrodes of said energy generation element unit and said driving element unit being connected to one another by mating of said mating surfaces of said energy generation element unit and said driving element unit. Therefore, it is an object of the present invention to provide an ink-jet head, an ink-jet cartridge loaded the ink-jet head, and an ink-jet apparatus employing the ink-jet head, which can certainly and stably establish electrical connection in a separable manner between the energy generation element unit and the driving element unit. According to the first aspect of the invention, there is provided an ink-jet head in accordance with claim 1. In an ink-jet head embodying the present invention, when the connecting electrodes of the energy generation element unit and the driving element unit are connected to each other by mating together the mating surfaces of the energy generation element unit and the driving element unit, a projecting portion separate from the connecting electrodes for maintaining a mating interval between the mating surfaces of the energy generation element unit and the driving element unit, is formed on at least one of the energy generation element unit and the driving element unit. These mating surfaces are correctly mated to correctly contact all of the connecting electrodes. In use of an ink-jet head embodying the invention, electric signals fed from the driving element of the driving element unit via the signal lines or wires is supplied to the energy generation elements from the signal wire of the energy generation element units via the connection electrodes. Thus, the energy generation elements are energized for ejecting the liquid. Here, the projecting portion may have a region arranged in alignment with the connecting electrodes, or a region aligned on an extension of the ends of the signal lines along the direction in which the connecting electrodes are arranged. In the alternative, the projecting portion may have a region aligned with the connecting electrodes and a region aligned on an extension of the ends of the signal lines along the direction in which the connecting electrodes are arranged. On the other hand, the projecting portion may be a dummy electrode in a shape corresponding to the connecting electrode. The energy generation element may be an electrothermal transducer generating a thermal energy for causing film boiling in the liquid. According to the second aspect of the present invention there is provided an ink-jet cartridge comprising an ink-jet head in accordance with the first aspect and a liquid tank for storing the liquid to be supplied to the ink-jet head. Here, the liquid may be desirably an ink or a treatment liquid for adjusting property of the ink to be ejected on a printing medium, or the ink and the treatment liquid. According to the third aspect of the present invention, there is provided an ink-jet apparatus employing an ink-jet head in accordance with the first aspect. Here, the projecting portion may have a region arranged in alignment with the connecting electrodes, or a region lying on an extension of a line extending through the ends of said signal lines connected to the connecting electrodes. In the alternative, the projecting portion may have a region aligned with the connecting electrodes and a region aligned on an extension of the other end sides of the signal lines along arranging direction of the connecting electrodes. On the other hand, the projecting portion may be a dummy electrode in a shape corresponding to the connecting electrode. Also, the ejection openings may be arranged over the entire width of the printing region of the printing medium. With the ink-jet head according to the present invention, since the projecting portion for maintaining the mating interval of mating surfaces of the energy generation element unit and the driving element unit. Thus, tight fitting condition of the connecting electrodes of two units can be unified to enable easy, certain and reliable electrical connection. On the other hand, position of acting point of pressurizing force upon coupling the energy generation element unit and the driving element unit may be rough in comparison with that required in the prior art. Thus, connection can be certainly established with simpler mechanism to achieve lowering of cost. The present invention will be understood more fully from the detailed description given herebelow and from the accompanying drawings of the preferred embodiment of the invention, which, however, should not be taken to be limitative to the present invention, but are for explanation and understanding only. In the drawings: Fig. 1 is a plan view showing a configuration of the first embodiment of a portion of a substrate forming an energy generation element unit of an ink-jet head according to the present invention; Fig. 2 is a section taken along line II - II of Fig. 1; Fig. 3 is a section showing a production process of the substrate shown in Fig. 2, together with Figs. 4 and 5; Fig. 4 is a section showing a production process of the substrate shown in Fig. 2, together with Figs. 3 and 5; Fig. 5 is a section showing a production process of the substrate shown in Fig. 2, together with Figs. 3 and 4; Fig. 6 is a conceptual illustration showing a coupled condition of the energy generating element unit and the driving element unit according to the present invention; Fig. 7 is a plan view showing a configuration of the second embodiment of a portion of a substrate forming an energy generation element unit of an ink-jet head according to the present invention; Fig. 8 is a plan view showing a configuration of the third embodiment of a substrate forming an energy generation element unit of an ink-jet head according to the present invention; Fig. 9 is a perspective view showing external appearance of the first embodiment of an ink-jet cartridge according to the present invention; Fig. 10 is a conceptual illustration showing an external appearance of the first embodiment of the ink-jet apparatus according to the present invention; Fig. 11 is a perspective view showing external appearance of an energy generation element unit of the ink-jet head, to which the present invention is directed to; Fig. 12 is a perspective view showing a partly cut-out energy generation element unit shown in Fig. 11; Fig. 13 is a plan view showing an electrical circuit of the conventional ink-jet head; Fig. 14 is a section taken along line XIV - XIV of Fig. 13; Fig. 15 is a perspective view showing an external appearance of the conventional driving element unit; Fig. 16 is a conceptual illustration showing a coupled condition of the conventional energy generation element unit and the driving element unit; and Fig. 17 is a conceptual illustration showing a condition of occurrence of connection failure of connection electrodes in Fig. 16. Several embodiments of an ink-jet head according to the present invention will be discussed hereinafter in detail with reference to Figs. 1 to 8. It should be noted that the basic construction of a portion of connecting electrode provided for each of the energy generation element unit and the driving element unit constructing the ink-jet head, can be identical in both of two units. Accordingly, while the following discussion will be concentrated to the energy generation element unit as one of the units, the driving element unit may employ the structure in a portion of the connection electrode identical to that in the energy generation element unit. As shown in Fig. 1 showing external appearance of a surface of a substrate of the first embodiment of an energy generation element unit and in Fig. 2 showing a sectional structure along line II - II of Fig. 1, on the surface of a quadrangular substrate 11, an insulative layer 12 having a head accumulation ability, such as silicon dioxide (SiO 2 ) is formed. On the insulative layer 12, a plurality of pairs of connection electrodes 13a, 13b and a dummy electrode 14 are arranged in alignment with given intervals along longitudinal direction. A portion of the surface of the substrate 11 around the connection electrodes 13a, 13b and the dummy electrode 14 serves as mating surface F E of the present invention. Respective pairs of the connection electrodes 13a and 13b are formed at one end portion of signal lines 15, such as aluminum or so forth, extending in back and forth direction (left and right direction in Fig. 2) of the substrate 11. The other ends of respective pairs of the signal lines 15 are mutually connected via heat generation elements, such as hafnium diboride (HfB 2 ) or so forth, which serves as the energy generation elements to form U-shaped configurations as a whole. These connection electrodes 13a and 13b are stacked on a resistor layers 16' and the signal lines 15. Except for these connection electrodes 13a and 13b, the resistor layers 16 and the signal lines 15 are covered with an oxidation resistive insulation layer 17 of silicon dioxide or so forth. Furthermore, an anti-cavitation layer 18 of tantalum or so forth is stacked on the heat generation resistor 16 via the insulation layer 17. The dummy electrode 14 as projecting portions of the present invention are arranged along the direction of alignment of the connection electrodes 13a and 13b in parallel relationship thereto at the position inclined to one end in the back and forth direction of the substrate 11 than the connection electrodes 13a and 13b. Similarly to the connection electrodes 13a and 13b, the dummy electrodes 14 are stacked on the resistor layer 16' and a conductive layer 15'. These resistor layer 16' and the conductive layer 15' are covered with the insulation layer 17 except for the dummy electrodes 14. Now, discussion will be given for fabrication process of the substrate 11 having the construction as set forth above. At first, on the surface of the substrate 11, the insulative layer 12, the resistor layer 16' and the conductive layer 15' are deposited in stacking manner respective at thicknesses of 2 µm, 0.2 µm and 0.6 µm (see Fig. 3). Then, by employing a photolithographic technology, respective of the resistor layer 16' and the conductive layer 16 are etched by way of photolithographic technology to pattern the head respective the heat generation resistor 16 and the signal lines 15, and the resistor layer 16' and the conductive layer 15' (see Fig. 4). Thereafter, on the surfaces of these layers, insulation layer and the anti-cavitation layer respectively having thicknesses of 0.9 µm and 0.5 µm are formed by way of sputtering. Then, by way of photolithographic technology, the insulation layer 17 and the anti-cavitation layer 18 are patterned. At this time, on the surface of the signal lines 15 and the surfaces corresponding to the dummy electrodes 14 and mating with the surface of the conductive layer 15', a part of the insulation layer 17 is etched to form through holes 19 (see Fig. 5). As an undercoating layer of electroplating, titanium and copper are respectively deposited in order at thicknesses of 0.05 µm and 0.3 µm. Then, after forming a pattern employing a resist for forming plated layer, several micrometers to several tens micrometers of layers of gold, nickel, copper, white gold or so forth is deposited. Thereafter, the resist is peeled off and etching for the undercoating layer is performed to form the connection electrodes 13a and 13b and the dummy electrodes 14 in the portion of the through holes 19 in a manner shown in Fig. 2. With respect to the substrate 11 thus obtained, ejection openings 104, ink passages 103 and common ink chamber 105 and so forth, shown in Fig. 12 are formed. Also, a coupling member 106 is further coupled to form the energy generation element unit, as shown in Fig. 11. As shown in Fig. 6, in which is shown the external appearance of the ink-jet head, in which the energy generation element unit and the driving element unit are assembled, the mating surface F E of the energy generation element unit U E projecting the connecting electrodes 13a and 13b and the dummy electrodes 14 is mated with a mating surface F D of the driving element unit U D projecting connection electrodes 20 and dummy electrodes 21. When the connecting electrodes 13a, 13b and 20 are mutually connected, if acting point of connecting force is present between the connection electrodes 13a, 13b and 20 and the dummy electrodes 14 and 21, the mating surfaces F E and F D are maintained in parallel relationship to each other, and thus, the connecting electrodes 13a, 13b and 20 can be maintained in good connecting condition. In this case, it is preferred that the projecting heights of the connecting electrodes 13a and 13b and the dummy electrodes 14 from the surface of the substrate 11 are set to be equal to each other. As long as such condition is satisfied, other projecting portions may be employed in place of the dummy electrodes 14. By thus forming the dummy electrodes 14 and 21, allowable range of position error of the acting point of the connecting force upon mating the energy generation element unit U E and the driving element unit U D can be expanded in comparison with that in the prior art shown in Figs. 16 and 17. Thus, positioning mechanism for the energy generation element unit U E and the driving element unit U D can be simplified to achieve lowering of cost. While the dummy electrodes 14 are formed along the alignment direction of the connecting electrodes 13a and 13b inclined to one end side in the back and forth direction of the substrate than the connection electrodes 13a and 13b in the foregoing embodiment, it is possible to arrange dummy electrodes 14a and 14b at both longitudinal ends of the substrate 11, namely at both ends along the aligning direction of the connecting electrodes 13a and 13b in alignment with the latter, as shown in Fig. 7, in which the external appearance of the surface of the substrate in the second embodiment of the present invention is illustrated. Also, as shown in Fig. 8, in which the external appearance of the surface of the substrate in the third embodiment of the present invention is illustrated, it is possible to form the dummy electrode along the alignment direction of the connecting electrodes 13a and 13b inclined to one end side in the back and forth direction of the substrate than the connection electrodes 13a and 13b, and form the dummy electrodes 14a and 14b at both longitudinal ends in alignment with the connecting electrodes 13a and 13b, by combining the foregoing two embodiments. It should be noted that in Figs. 7 and 8, the elements performing the same function to those in the former embodiment shown in Fig. 1 are represented by the same reference numerals. Next, one embodiment of an ink-jet cartridge according to the present invention, in which the foregoing ink-jet head is loaded will be discussed with reference to Fig. 9 illustrating the external appearance. Namely, the shown embodiment of an ink-jet cartridge 31 is positioned on a carriage of a not shown serial type ink-jet apparatus transmitting and receiving electrical signal with the ink-jet apparatus. The ink-jet cartridge 31 which is detachably mounted on the carriage is mainly constructed with the ink-jet head 10, a head holder 32 for holding the ink-jet head 10, a pushing block 33 for pushing ink-jet head 10 toward the head holder 32, an ink tank 34 storing an ink and a lid member 35 for sealingly closing the ink tank 34. In the ink tank 34 which occupies most part of volume of the ink-jet cartridge 31, an atmosphere communication aperture 36 for maintaining internal pressure of the ink tank 34 at the atmospheric pressure. The ink-jet head formed with a large number of ejection openings for ejecting ink, has a construction corresponding to the previously discussed embodiment of Figs. 1 to 8. The ink-jet head 10 is pushed to the head holder 32 by the pushing block 33 and thus held therein. The ink is introduced from the ink tank 34 to the common ink chamber 105 and respective ink passages 103 via not shown ink supply tubes and communication passages of the ink-jet head 10 (see Fig. 12, respectively). The shown embodiment of the ink-jet cartridge 31 is integrally formed with the ink-jet head 10 and the ink tank 34. However, the ink-jet cartridge 31 may have a construction, in which the ink-tank 34 is exchangeably coupled with the ink-jet head 10. Also, an external appearance of one embodiment of an ink-jet apparatus according to the present invention loaded the ink-jet head according to the invention is shown in Fig. 10. The shown embodiment of the ink-jet apparatus is a full-line type color printer which has four ink tanks 37Y, 37M, 37C and 37B (hereinafter generally referred to as ink tanks 37) respectively storing yellow color ink, magenta color ink, cyan color ink and black color ink, and four ink-jet heads 10Y, 10M, 10C and 10B (hereinafter generally referred to as ink-jet heads 10) having ink supply tubes connected to the ink tanks 37 via connection piping 38. Respective ink tanks 37 are exchangeably connected with the connection piping 38. The ink-jet head 10 which is switched power supply for respective head generating resistors 16 between ON and OFF by a head driver 40 which is connected to a control unit 39, has basically the identical construction to that in the embodiment shown in Figs. 1 to 8. The ink-jet heads 10 are arranged in opposition to a platen 42 across an endless transporting belt 41 with a given interval along a transporting direction of the transporting belt 41. By means of a head shifting means 43 for recovery process, operation of which is controlled by the control unit 39, the ink-jet heads 10 can be shifted toward and aft with respect to the platen 42 in the opposing direction. At the side of each ink-jet head 10, a head cap 45 for performing recovery process of the ink-jet head 10 by ejecting the old ink in the ink passage 103 through ink ejection openings 24, is arranged with an offset for a half pitch relative to arrangement interval of the ink-jet heads 10. By cap moving means 46, operation of which is controlled by the control unit 39, the head caps 45 are shifted immediately below the corresponding ink-jet head 10 to receive the waste ink ejected from the ink ejection openings 24. The transporting belt 41 for transporting a printing paper 44 is wound around a driving roller 48 which is, in turn, connected to a belt driving motor 47. Operation of the belt driving motor 47 is switched by a motor driver 49 connected to the control unit 39. On the other hand, at upstream side of the transporting belt 41, an electrostatic charger 50 for tightly fitting the printing paper 44 onto the transporting belt 41 by charging the transporting belt, is provided. Power supply for the electrostatic charger 50 is switched between ON and OFF by a electrostatic charger driver 51 connected to the control unit 39. To a pair of feeder rollers 52 for feeding the printing paper 44 onto the transporting belt 41, a feeder motor 53 is connected for rotatingly driving the pair of feeder rollers 52. Operation of the feeder motor 53 is switched by a motor driver 54 connected to the control unit 39. Accordingly, in advance of printing operation for the printing paper 44, the ink-jet head 10 is lifted away from the platen 42. Then, the head cap 45 is moved immediately below the ink-jet head 10 to perform recovery process. Thereafter, the head cap 45 is moved to the initial position, and the ink-jet head 10 is shifted toward the platen 42 to be placed at a printing position. Then, the electrostatic charger 50 is actuated, and, in conjunction therewith the transporting belt 41 is driven to mount the printing paper on the transporting belt 41 by the feeder rollers 52. Thereafter, predetermined color image is printed on the printing paper by respective ink-jet head. It should be noted that while the foregoing embodiments has been discussed in terms of the ink-jet head employing the electrothermal transducer element for generating the heat energy as the energy generation element for achieving high printing density and high precision, the invention should be applicable for the ink-jet head employing an electromechanical transducer, such as piezoelectric element or so forth. A typical structure and operational principle of the ink-jet head using above electothermal transducers on laser light is disclosed in U.S. patent Nos. 4,723,129 and 4,740,796, and it is preferable to use this basic principle to implement such a system. Although this system can be applied either to on-demand type or continuous type ink jet recording systems, it is particularly suitable for the on-demand type apparatus. This is because the on-demand type apparatus has electrothermal transducers, each disposed on a sheet or liquid passage that retains liquid (ink), and operates as follows: first, one or more drive signals are applied to the electrothermal transducers to cause thermal energy corresponding to recording information; second, the thermal energy induces sudden temperature rise that exceeds the nucleate boiling so as to cause the film boiling on heating portions of the recording head; and third, bubbles are grown in the liquid (ink) corresponding to the drive signals. By using the growth and collapse of the bubbles, the ink is expelled from at least one of the ink ejection orifices of the head to form one or more ink drops. The drive signal in the form of a pulse is preferable because the growth and collapse of the bubbles can be achieved instantaneously and suitably by this form of drive signal. As a drive signal in the form of a pulse, those described in U.S. patent Nos. 4,463,359 and 4,345,262 are preferable. In addition, it is preferable that the rate of temperature rise of the heating portions described in U.S. patent No. 4,313,124 be adopted to achieve better recording. U.S. patent Nos. 4,558,333 and 4,459,600 disclose the following structure of a recording head, which is relevant to the present invention: this structure includes heating portions disposed on bent portions in addition to a combination of the ejection orifices, liquid passages and the electrothermal transducers disclosed in the above patents. Moreover, the present invention can be applied to structures disclosed in Japanese Patent Application Laid-open Nos. 123670/1984 and 138461/1984 in order to achieve similar effects. The former discloses a structure in which a slit common to all the electrothermal transducers is used as ejection orifices of the electrothermal transducers, and the latter discloses a structure in which openings for absorbing pressure waves caused by thermal energy are formed corresponding to the ejection orifices. Thus, irrespective of the type of the recording head, the present invention can achieve recording positively and effectively. The present invention can be also applied to a so-called full-line type recording head whose length equals the maximum length across a recording medium. Such a recording head may consists of a plurality of recording heads combined together, or one integrally arranged recording head. In addition, the present invention can be applied to various serial type recording heads: a recording head fixed to the main assembly of a recording apparatus; a conveniently replaceable chip type recording head which, when loaded on the main assembly of a recording apparatus, is electrically connected to the main assembly, and is supplied with ink therefrom; and a cartridge type recording head integrally including an ink reservoir. It is further preferable to add a recovery system, or a preliminary auxiliary system for a recording head as a constituent of the recording apparatus because they serve to make the effect of the present invention more reliable. As examples of the recovery system, are a capping means and a cleaning means for the recording head, and a pressure or suction means for the recording head. As examples of the preliminary auxiliary system, are a preliminary heating means utilizing electrothermal transducers or a combination of other heater elements and the electrothermal transducers, and a means for carrying out preliminary ejection of ink independently of the ejection for recording. These systems are effective for reliable recording. The number and type of recording heads to be mounted on a recording apparatus can be also changed. For example, only one recording head corresponding to a single color ink, or a plurality of recording heads corresponding to a plurality of inks different in color or concentration can be used. In other words, the present invention can be effectively applied to an apparatus having at least one of the monochromatic, multi-color and full-color modes. Here, the monochromatic mode performs recording by using only one major color such as black. The multi-color mode carries out recording by using different color inks, and the full-color mode performs recording by color mixing. Furthermore, although the above-described embodiments use liquid ink, inks that are liquid when the recording signal is applied can be used: for example, inks can be employed that solidify at a temperature lower than the room temperature and are softened or liquefied in the room temperature. This is because in the ink jet system, the ink is generally temperature adjusted in a range of 30°C - 70°C so that the viscosity of the ink is maintained at such a value that the ink can be ejected reliably. In addition, the present invention can be applied to such apparatus where the ink is liquefied just before the ejection by the thermal energy as follows so that the ink is expelled from the orifices in the liquid state, and then begins to solidify on hitting the recording medium, thereby preventing the ink evaporation: the ink is transformed from solid to liquid state by positively utilizing the thermal energy which would otherwise cause the temperature rise; or the ink, which is dry when left in air, is liquefied in response to the thermal energy of the recording signal. In such cases, the ink may be retained in recesses or through holes formed in a porous sheet as liquid or solid substances so that the ink faces the electrothermal transducers as described in Japanese Patent Application Laid-open Nos. 56847/1979 or 71260/1985. The present invention is most effective when it uses the film boiling phenomenon to expel the ink. Furthermore, the ink jet recording apparatus of the present invention can be employed not only as an image output terminal of an information processing device such as a computer, but also as an output device of a copying machine including a reader, and as an output device of a facsimile apparatus having a transmission and receiving function. The present invention has been described in detail with respect to various embodiments, and it will now be apparent from the foregoing to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and it is the intention, therefore, in the appended claims to cover all such changes and modifications.

Claims: An ink-jet head comprising: an energy generation element unit having a plurality of energy generation elements (16) for ejecting liquid, and a plurality of connecting electrodes (13a, 13b) projecting from a mating surface of said energy generation element unit with each energy generation element being connected to a respective different one of said connecting electrodes by a respective different one of a plurality of signal lines; and a driving element unit having a plurality of driving elements for driving to said energy generation elements, and a plurality of connecting electrodes (20) projecting from a mating surface of said driving element unit with each driving element being connected to a respective different one of connecting electrodes by a respective different one of a plurality of signal lines, said connecting electrodes (13a, 13b and 20) of said energy generation element unit and said driving element unit being connected to one another by mating of said mating surfaces of said energy generation element unit and said driving element unit, characterised in that a projecting portion (14; 21) separate from the connecting electrodes is provided on at least one of said energy generation element unit and said driving element unit to maintain a mating distance between said mating surfaces of said energy generation element unit and said driving element unit. An ink-jet head as claimed in claim 1, wherein said projecting portion (14; 21) has a region aligned with said connecting electrodes (13a, 13b and 20). An ink-jet head as claimed in claim 1 or 2, wherein said projecting portion (14; 21) has a region lying on an extension of a line extending through the ends of said signal lines connected to said connecting electrodes (13a, 13b). An ink-jet head as claimed in any one of claims 1 to 3, wherein said projecting portion (14; 21) is a dummy electrode in a shape corresponding to that of a connecting electrode. An ink-jet head as claimed in any one of claims 1 to 4, wherein said energy generation elements are electrothermal transducers for generating thermal energy to cause the film boiling in the liquid. An ink-jet cartridge comprising an ink-jet head in accordance with any one of the preceding claims and a liquid tank for storing liquid to be supplied to said ink-jet head. An ink-jet cartridge as claimed in claim 6, wherein said liquid is an ink and/or a treatment liquid for adjusting a property of ink. An ink-jet apparatus comprising an ink-jet head according to any one of claims 1 to 5 or an ink-jet cartridge according to claim 6 or 7. An ink-jet apparatus as claimed in claim 8, wherein said ejection openings are arranged to provide an ejection opening array extending over the entire width of a printing region of a printing medium.

Inventors: HIROSAWA TOSHIAKI, SUEOKA MANABU, YAMANE TORU, HIROSAWA, TOSHIAKI, C/O CANON K.K., SUEOKA, MANABU, C/O CANON K.K., YAMANE, TORU, C/O CANON K.K.
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1996
Main classification: B41J2
IPC codes: B41J2