Recording apparatus with a recording head having a wiring substrate

Abstract: In the wiring portion in the wiring substrate constituting the recording head of a liquid spray type recording apparatus, the electroconductive layers (30, 141) comprises at least two layers, the protective layer of the electroconductive layer includes at least two unit layers (35, 36, 142, 144), one of them being formed so that it has a shape and size different has a size and shape different from those of the through hole(s) (35a, 36a) in remaining unit protective layer(s) (35, 36, 142, 144), thereby assuring the formation of electric connection portion and improving durability of the electric connection portion.

Description: The present invention relates to a recording system applicable to copying machines, facsimile apparatuses, word processors, printers as an output terminal for a computer or the like which system performs recording by discharging a recording ink through a discharge portion, a recording head used for the above-described recording system and a wiring substrate suitable for the recording head. Conventionally, full-line type ink jet recording heads having structures as illustrated, for example, in Fig. 1 have been known as a recording head. In the head 1 illustrated in Fig. 1, an insulated substrate 3 on which there are arranged a plurality of semiconductor devices 2 such as electro-thermal converting elements and their wire bondings and an IC for driving them is placed in a row together with a flexible cable 4 on a support plate 5. The substrate 3 and the cable 4 are pressed onto the support plate 5 by a rigid holding member 6 for holding the flexible cable and five screws 7 through a rubber holder 8 so that a wiring portion of the substrate 3 and the flexible cable 4 can be fixed mechanically and connected electrically to each other. Reference numeral 9 denotes an ink feed pipe for feeding ink from both sides into a common liquid chamber 10. The ink feed pipe is composed of an elastic tube. A part of the common liquid chamber 10 is formed by providing a member or top plate 11 composed of a resin or the like with depressions, and a part of an ink discharge portion or orifice 12 is similarly formed thereby. By bonding these on the substrate 3 a space for flowing ink therein and openings for discharging ink therethrough are formed, thus constructing the ink jet head 1. On the other hand, Fig. 2 is a schematic perspective view illustrating a serial scanning type ink jet recording apparatus. In Fig. 2, the head 1 having, for example, 16 to 256 discharge portions is detachably mounted on a carriage 21 which is guided on a guide shaft 20, and in this state is scanned in a direction perpendicular to the direction in which recording paper 22 is conveyed. Reference numeral 23 denotes a belt conveyor for scanning the carriage 21. Reference numeral 24 denotes a conveyor roll and reference numeral 25 denotes a platen. These convey the recording paper 22 to a desired position. Further, reference numeral 26 denotes a discharge recovering apparatus for maintaining the discharge portions in good conditions, which includes an elastic cap, an aspirator and the like. The system of the above-described example is constructed such that signal outputs for driving the recording paper conveying means, head scanning means and discharge recovering means as well as those for driving the recording head can be controlled by controlling means based on instruction put out from CPU of the main body of the ink jet recording apparatus. The present invention is suitable for an apparatus of a type which discharges ink by utilizing thermal energy. The typical structure and operational principle of this type are preferably the one disclosed in U.S. Patent Nos. 4,723,129 and 4,740,796. On the wiring substrate 3 of the above-described conventional recording head 1 are formed an electro-thermal converting element which generates thermal energy utilized for discharging ink and a wiring portion for connecting the electro-thermal converting element to the semiconductor device 2 such as IC for driving. In the wiring portion is provided a bump electrode to be connected to a solder bump provided in the semiconductor device. Referring to Figs. 3A to 3E, an example of the structure of the bump electrode in the conventional film wiring substrate will be explained according to its production procedures. Firstly, as shown in Fig. 3A, there are formed on the insulated substrate 3 an Al electrode 30 and also a protective layer 31 composed of an inorganic insulating layer such as a SiO₂ or SiN layer or an organic insulating layer such as a polyimide layer and having a circular through hole 31a. Subsequently, as shown in Fig. 3B, on the substrate 1 are deposited by sputtering a barrier metal layer 32 made of, for example, Cr, Ti, Ni or the like and a solder connecting layer 33 made of, for example, Cu, Au, Cu-Au alloy or the like. Over the entire surface of the substrate 3 provided with the electrode 30, the protective layer 31, the barrier metal layer 32 and the solder connecting layer 33 is coated a photoresist layer 34 by a spin coating method, a roll coating method, a dipping method, a printing method or the like, and then exposure treatment and development treatment are performed. Thereafter, as shown Fig. 3D, the solder connecting layer 31 and the metal layer 32 are etched using the photoresist layer 34 as a mask. Finally, as shown in Fig. 3E, the photoresist layer 34 is peeled off to complete the procedures. In the production of the above-described conventional film wiring substrate, it is generally the case that a roll coating method is selected in the step of photoresist coating in view of the fact that the substrate is of a polygon (usually quadrilateral) and has a large area and of productivity. However, in the above-described conventional film wiring substrate, as shown in Fig. 3B, a circular concave portion 33a of, for example, several centimeters or more in depth exists in the solder connecting layer 33 above the through hole 31a of the protective layer 31. Thus, it tends to become more difficult at every pitch of a groove of a grooved coating roll (especially, at thread portions of the roll) to carry out coating of the photoresist layer 34, resulting in that there has been a possibility that in a subsequent etching step the through hole portions of the metal layer (i.e., the solder connecting layer 33 and in addition the barrier metal layer 32) of the concave portion 34a could be etched out where coating has been carried out incompletely. On the other hand, electro-thermal converting elements in conventional thin film wiring substrates are constructed as follows. Electro-thermal converting elements have heating units which convert electric energy to thermal energy to be used for discharging ink. As shown in Figs. 4A and 4B, in order to construct an electro-thermal converting element, at first an HfB₂ film 40 serving as a heat generating resistor layer and an Al film serving as an electrode 41 are formed on the substrate plate 3, for example, by sputtering or the like, followed by patterning to form an electro-thermal converting element. Next, an SiO₂ film serving as an antioxidation film 42 and a Ta film serving as anti-cavitation film 43 for the electro-thermal converting element are formed, for example, by sputtering or the like, followed by patterning. Thereafter, a photosensitive polyimide as an ink-resistant protective film 44.is coated thereon and patterning is carried out. Further, the second layer, i.e., Al conductive layer 41, is partially exposed and on this exposed portion is formed a common electrode 45 which is Cu-plated. In this case, the SiO₂ layer 42 and the photosensitive polyimide layer 44 underlying the common electrode 45 function as an interlayer insulator layer. Thereafter, a plate 11 having a concave portion for forming a common liquid chamber 10 as a passage for a recording liquid and individual liquid paths 46 is bonded, and a wiring to be connected to a driving circuit which generates driving signals for driving the electro-thermal converting element is electrically connected, thus producing a liquid spray recording head.(not shown). In Fig. 4A, the heat generating resistor layer 40, the electrode 41 and the common electrode 45 are illustrated but the protective layers 42, 43 and 44 and the plate 11 are omitted. On one end of the electrode 41 opposite to the common electrode, i.e., segment electrode, is usually formed the above-described bump electrode through which the electrode 41 is connected to a semiconductor device. It should be noted that the same is true in the case where the semiconductor device is connected to the end on the side of the common electrode 45. In the conventional technique as described above, the common electrode 45 is placed outside the plate 11, more specifically outside the liquid paths of the recording head and therefore the part of the electrode 41 on the side of the common electrode 45 must have a length of M₂ as shown in Figs. 4A and 4B which is considerably larger than the length M₁ of the part of the electrode 41 within the plate 11 and thus a considerably long high density wiring is necessary. This makes severer disadvantages involved in production such as low yield due to short circuit, disconnection or the like. That is, repeated driving of the conventional device under application of a large amount of electric current which can generate heat enough to discharge liquid causes short circuit or disconnection, resulting in that the durability of the recording head decreases unacceptably. EP-A-0344809 discloses a recording head for recording by liquid emission in which a wiring pattern for connecting to a heat-generating resistor portion, comprises a conductive electrode covered by an anti-oxidation protective insulating layer and an ink-resistant protective insulating layer. For connecting a common electrode to the conductive layer, holes are formed in the protective insulating layers and the common electrode is formed to contact the conductive layer through the holes. Arrangements are disclosed in which the hole in one of the insulating protective layers is larger than the hole in the other insulating protective layer, so that the edge of the hole is stepped. EP-A-0352142 discloses a wiring substrate for an ink jet recording unit, in which bump-shaped electrodes are formed in contact with an underlying conductive layer through holes in upper and lower insulating layers. In some embodiments, the upper insulating layer lines the inside of the hole in the lower insulating layer. The relative positions of the edges of the holes in the insulating layers and the edges of the conductive layers is not discussed, and is not shown precisely. JP-A-56-19639 proposes a square electrode pad provided by two aluminium films and holes in two insulating films. A wiring line in the lower aluminium film is expanded into a square at the pad. The upper aluminium film is a larger square extending over and beyond the square pad in the lower aluminium film. A square opening in the lower insulating film is larger than both aluminium film squares, so that the lower insulating film does not overlap either aluminium film square. The upper insulating film has a square opening which is smaller than the square of the upper aluminium film but larger than the square of the lower aluminium film, so that the upper insulating layer overlaps the edges of the upper aluminium film but does not overlap the square of the lower aluminium film. This construction is intended to flatten the edge of the pad in order to allow good contact between the exposed part of the upper aluminium film and a metal part which is to be bonded to it. According to the present invention there is provided an electrical wiring pattern according to claim 1. Claims 2 to 8 disclose optional features. The invention also provides a recording head using the wiring pattern as set out in claims 9 to 13, and the invention also provides a recording apparatus having the recording head. Embodiments of the present invention, given by way of non-limiting example, will now be described with reference to the accompanying drawings. Fig. 1 is a perspective view of a conventional ink jet recording head; Fig. 2 is a perspective view of a conventional ink jet recording apparatus; Figs. 3A to 3E are cross sections illustrating the production procedures of a bump electrode in the conventional thin film wiring substrate; Fig 4A is a schematic plan view illustrating the conventional recording head; Fig. 4B is a cross section of the conventional recording head along the line B-B′ in Fig. 4A; Figs. 5A to 5G are cross sections of the wiring substrate illustrating the production method for producing a bump electrode embodying the present invention; Fig. 6 is a top view of the wiring substrate shown in Fig. 5D;. Figs. 7A and 7B illustrate the wiring substrate according to another embodiment of the present invention, Fig. 7A showing a top view of the laminated substrate and Fig. 7B being cross section along the line A-A′ in Fig. 7A; Fig. 8 is a top view of the wiring substrate according to still another embodiment of the present invention; and Fig. 9 is a cross section of the ink jet recording head embodying the present invention. Embodiment 1 This embodiment relates to a wiring substrate having an improved bump electrode portion. Hereafter, this embodiment will be explained in detail with reference to the attached drawings. In the drawings, the same components as those shown in Figs. 3A to 3E are indicated with the same reference numerals as used therein and their explanation are simplified herein. Figs. 5A to 5G are intended to illustrate the thin film wiring substrate according to one embodiment of the present invention and are each a cross section showing the production procedure of the bump electrode of the wiring substrate. Firstly, as shown in Fig. 5A, the Al electrode 30 is formed on the insulated substrate 3. Thereafter, as shown in Fig. 5B, a protective layer 35 is formed which is provided with a through hole 35a of a quadrilateral shape and having a size larger than the outer size of the Al electrode 30. Then, as shown in Fig. 5C, a protective layer 36 is formed. The protective layer 36 is provided with a through hole 36a of a circular shape and having a size smaller than the outer size of the Al electrode 30. On this occasion, the thicknesses of the protective layers 35 and 36 may be enough to protect portions excepting the through hole portion of the Al electrode 30 when they are several micrometers (mm) in total, and the thickness of the protective layer 36 can be made considerably smaller than that of the protective layer 35. Therefore, the thickness of the protective layer to be formed on the Al electrode 30 can naturally be made small enough. Next, as shown in Fig. 5D, the barrier metal layer 32 and the solder connecting layer 33 are deposited by a known method. Subsequently, as shown in Fig. 5C, the photoresist layer 34 is coated by a roll coating method, exposed to light and developed. Upon coating the photoresist, as shown in Fig. 5D and Fig. 6, the protective layer on the Al electrode 30 can be made formed to a small thickness even when it has a construction such that the thickness of the through hole portion (the thickness of the laminate within the through hole, i.e., the thicknesses of the barrier metal layer 32 + the solder connecting layer 33 + the photoresist layer 34) is the same in total as that of the conventional ones, resulting in that the circular concave portion 33a of the solder connecting layer 33 positioned within the through hole portion where it has hitherto been difficult to coat photoresists can be made extremely small in depth. Therefore, coating performance can be improved greatly by reducing the difference in height, or depth, of the concave portion 33a of the solder connecting layer 33. Use of the protective layer of a two-layer structure makes it possible to design the shape of through holes freely; through holes may have different shapes one from another. Accordingly, the through hole in the lower layer may be of a shape corresponding to the contour of the electrode and the one in the upper layer may be of a shape suitable for the bump electrode portion. This construction increases the area of the through hole in the upper layer and further the area of the concave portion 33a in the solder connecting layer 33, thus making it possible to increase coating area of the photoresist and solving the problem that coating of photoresist is impossible in the conventional circular through hole portion. As described above, because the protective layer for the Al electrode is laminated in at least two layers, number of defects such as pin-holes in the protective layer is negligibly small and it is now unnecessary to increase the thickness of the coating film excessively as has been required in protective layers of a single layer construction conventionally used, resulting in that the film thickness can be made smaller than ever, which decreases cost of materials and prevents curling or other undesirable phenomena of the substrate which could otherwise occur due to lamination of the substrate material with different kinds of materials. After the above-described step, as shown in Fig. 5F, etching of the metal layer 32 is carried out, and finally, as shown in Fig. 5G, the photoresist layer 34 is peeled off to complete the procedure. While in the above description, the through hole in the upper protective layer 36 is made of a circular form and the through hole in the lower protective layer 35 is made of a quadrilateral form as shown in Fig. 6, they may be made in reverse relation, that is, the through hole in the protective layer 36 is quadrilateral and the through hole in the protective layer 35 is circular as shown in Figs. 7A and 7B. Further, the quadrilateral shape of the through hole may be selected freely; for example, it may be constructed such that the hole in one of the protective layers (the protective layer 36) is formed continuously for a plurality of electrodes 30 (Fig. 8). While in the above description, the through hole in either one of the protective layers 35 and 36 is made of a size larger than the outer size of the Al electrode 30, basically no problem will occur if it has the same size as the outer size of the Al electrode 30. What is important is to make the thickness of the protective layer on the electrode 30 small enough, and for this purpose, the protective layer is made of a multilayer construction, thus maintaining as a whole a film thickness sufficient for protecting the electrode while at least one among plural layers covers the electrode around the periphery of the through hole portion. There is no limitation on the kind of materials for the protective layers 35 and 36 and any type of inorganic or organic insulating film may be used. Embodiment 2 In the case where the wired electrode substrate 3 according to Embodiment 1 is applied to a substrate for an ink jet recording head, the substrate is constructed as follows. Firstly, as shown in Fig. 9, the protective layer 35 is formed of the same material and has the same film thickness as the antioxidation layer such as SiO₂, SiN, SiC or the like on the heat generating resistor layer 40, and at the same time the protective layer 36 is formed of the same material and has the same film thickness as the ink resistant layer made of polyimide resin, epoxy resin or the like. This construction makes it easy to form the bump electrode 37 for efficiently connecting the substrate to the electrode (not shown) of a semiconductor device 2 in the same step, and also makes it possible to form an ink jet recording head having such bump electrode. Using the substrate as described above, a recording head as shown in Fig. 1 can be constructed. Further, a recording apparatus as shown in Fig. 2 can be constructed using such recording head. According to above embodiments, upon coating the photoresist for patterning of the bump electrode, even if the photoresist layer is coated by roll coating method having a high-productivity but not a better coating performance, there is no coating area being impossible to coat. In these embodiments, because the protective layer for the Al electrode is laminated in at least two layers, number of defects such as pin-holes in the protective layer is negligibly small and it is now unnecessary to increase the thickness of the coating film excessively as has been required in protective layer of a single construction conventionally used, resulting in that the film thickness can be made smaller than ever, which decreases cost of materials and prevents curling or other undesirable phenomena of the substrate which could otherwise occur due to lamination of the substrate material with different kinds of materials In these embodiments, further more, as shown in Fig. 9, one layer out of the two protective layers may be formed from layer having low-pattern density and low-accuracy of pattern. Thus, in this case, one layer out of the two protective layers may be formed by low-cost patterning method such as screen printing method. Based on Embodiments 1 and 2 and with reference mainly to Fig. 9, concrete examples will be described hereafter. Example On the substrate plate 3 made of a single crystal of Si having on its surface an SiO₂ film (film thickness: 2.75 mm) formed by thermal oxidation was formed an HfB₂ layer (layer thickness: 1,000 Å) functioning as the heat generating resistor layer 4 by sputtering in a vacuum chamber using HfB₂ (purity: 99.9% or higher) as a target. Conditions for the sputtering were as follows. Sputtering Conditions Target area: 8 inch f High frequency power: 1,500 W. Temperature at which substrate plate is set: 100°C Film forming time: 20 minutes Base pressure: 1 X 10⁻⁵ Pa or lower Sputtering gas: argon Sputtering gas pressure: 0.5 Pa Then, the target was changed to Ti (purity: 99.9% or higher) and sputtering was carried out under the same conditions as above excepting the following: Film forming time: 1 hour to form a Ti layer (layer thickness: 50 Å, not shown) serving as a contact layer. Further, the target was changed to Al (purity: 99.9% or higher) and sputtering was carried out under the same conditions as above excepting the following: High frequency power: 5,000 W Film forming time: 6 minutes to form an Al layer (layer thickness: 4,500 Å) serving as the electrode 30. Subsequently, patterning was performed by lithography as described below relative to the lamination of the HfB₂ layer with the Ti layer and to the Al layer. Firstly, a photoresist (trade name: OFPR800, produced by Tokyo Oka Co., Ltd.) was coated as a layer (layer thickness: 1.3 mm) on the Al layer, which was exposed to light, developed and baked by conventional methods. Then, etching of the Al layer was carried out using a mixture of acetic acid, phosphoric acid and nitric acid (acetic acid: 9%, phosphoric acid: 73% and nitric acid: 2%) as an etching solution. Thereafter, etching of the lamination of the HfB₂ layer and the Ti layer was carried out by reactive etching in a vacuum chamber to remove the photoresist, thus completing the patterning. The reactive etching was performed under the following conditions: Conditions of reactive etching Etching power: 450 W Etching time: 5 minutes Base pressure : 1 X 10⁻³ Pa Gas species: BCl₃ Gas pressure: 3 Pa Then, an SiO₂ layer (layer thickness: 1.3 mm) serving as the protective layer 35 having mainly an antioxidation function was formed by sputtering in a vacuum chamber using SiO₂ (purity: 99.9% or higher) as a target. Conditions of the sputtering were as follows:. Sputtering Conditions Target area: 8 inch f High frequency power: 2,000 W. Temperature at which substrate plate is set: 100°C Film forming time: 90 minutes Base pressure: 8 X 10⁻⁴ Pa or lower Sputtering gas: argon Sputtering gas pressure: 0.5 Pa Further, the target was changed to Ta (purity 99.9% or higher) and sputtering was carried out under the same conditions as SiO₂ excepting the following: High frequency power: 1,500 W Film forming time: 30 minutes to form a Ta layer (layer thickness: 0.5 mm) serving as the protective layer 37a having mainly an anti-cavitation function. Subsequently, patterning was performed by lithography as described below relative to the SiO₂ layer and the Ta layer. Firstly, the same photoresist as described above was coated as a layer (layer thickness: 1.3 mm) on the Al layer, which was exposed to light, developed and baked by conventional methods. Then, chemical etching of the Ta layer was carried out to form a pattern of the protective layer 37a, followed by removal of the photoresist. Conditions of the chemical etching were as follows: Conditions of chemical etching Etching power: 600 W Etching time: 8 minutes Base pressure : 1 Pa Gas species: CF₄ (flow rate: 200 sccm) Gas species: O₂ (flow rate: 100 sccm) Gas pressure: 15 Pa Thereafter, the same photoresist as described above was coated as a layer (layer thickness: 2.6 mm), which was exposed to light, developed and baked by conventional methods. Then, reactive etching of the SiO₂ layer was carried out to form a pattern of the protective layer 35 including a through hole, followed by removal of the photoresist. Conditions of the reactive etching were as follows: Conditions of reactive etching Etching power: 950 W Etching time: 33 minutes Base pressure : 5 X 10⁻³ Pa Gas species: CHF₃ (flow rate: 16 sccm) C₂F₅ (flow rate: 24 sccm) O₂ (flow rate: 5 sccm) Gas pressure: 2 Pa Next, a polyimide (trade name: UR3100, produced by Toray Corporation) was coated by a roll coating method to form a pattern of 2.5 mm in thickness, which was pre-baked, exposed to light, developed and post-cured by conventional methods to complete formation of the protective layer 36. Subsequently, the target was changed to Ti (purity: 99.9% or higher) and sputtering was carried out under the same conditions as described above excepting the following: Film forming time: 10 minutes to form a Ti layer (layer thickness: 500 Å) serving as the barrier metal layer.32. Further, the target was changed to Cu (purity: 99.9% or higher) and sputtering was carried out under the same conditions as the Ti formation excepting the following: High frequency power: 5,000 W Film forming time: 4 minutes to form a Cu layer (layer thickness: 3,000 Å) serving as the solder connecting layer 33. Subsequently, patterning of lamination between the Ti layer and the Cu layer was carried out by lithography as described below. Firstly, the same photoresist as described above was coated as a layer (layer thickness: 1.3 mm) by a roll coating method, which layer was exposed to light, developed and baked by conventional methods. Then, etching of the Cu layer was carried out for 30 seconds using 10% by weight ammonium persulfate solution as an etching solution to form the solder connecting layer 33. Next, etching of the Ti layer was carried out for 20 seconds using 2% by weight hydrofluoric acid solution as an etching solution to form the barrier metal layer 32, and thereafter the photoresist was removed. On the thus-formed substrate for an ink jet head was arranged the plate 11 made of glass and provided with a concave portion serving as a wall of the passage for ink communicated to discharge portions. On the other hand, a wiring electrode (not shown) provided on the surface of the driving substrate 2 with a semiconductor cable was connected to the solder connecting layer 33 through the bump electrode 37 to form an ink jet head as shown in Fig. 9. The ink jet head had several thousands of discharge portions each corresponding to a plurality of heat generating portions. The ink jet head was fitted to the main body of an ink jet apparatus and recording was performed with actually discharging ink. As a result, it was confirmed that the ink jet head obtained in this example was very excellent both from a point of view of recording quality and of durability. Embodiment 3 The laminate structure including a bump electrode as described in Embodiment 1 is formed so that the bump electrode is positioned on the corresponding substrate plate in the common ink chamber. Thereafter, a protective layer is formed on the bump electrode using an organic material such as photosensitive polyimide to make a substrate for the ink jet head according to this embodiment. On the substrate for ink jet head thus prepared are formed walls of ink paths communicated to discharge portions using a photosensitive resin, and a glass plate is provided thereon to make an ink jet recording head. As described earlier, the above-described wiring substrate, recording head and recording apparatus of the present invention are desirably applied to apparatuses of types utilizing basic operational principle disclosed, for example, in U.S. Patents Nos. 4,723129 and 4,749,796 The principle is applicable to a so-called on-demand type recording system and a continuous type recording system, particularly it is suitable for the on-demand type because the principle is such that at least one driving signal is applied to an electro-thermal converting element disposed on liquid (ink) retaining sheet or ink passage, the driving signal being enough to provide such a quick temperature rise beyond a departure from nucleation boiling point, by which the thermal energy is provided by the electro-thermal converting element to produce film boiling on the heating portion of the recording head, whereby a bubble can be formed in the liquid (ink) corresponding to each of the driving signals. By the development and collapse of the bubble, the liquid (ink) is discharged through an discharge portion to produce at least one droplet. The driving signal is preferably in the form of a pulse because the development and collapse of the bubble can be effected instantaneously, and therefore, the liquid (ink) is discharged with quick response. the driving signal in the form of the pulse is preferably such as disclosed in U.S. Patent Nos. 4,463,359 and 4,345,262. In addition, the temperature increasing rate of the heating surface is preferably such as disclosed in U.S. Patent No. 4,313,124. The structure of the recording head may be as shown in U.S. Patent Nos. 4,558,333 and 4,459,600 wherein the heating portion is disposed at a bent portion in addition to the structure of the combination of the discharging portion, liquid passage and the above-described patents. In addition, the present invention is applicable to the structure disclosed in Japanese Patent Application Laying-Open No. 123670/1984 wherein a common slit is used a discharge portion for plural electro-thermal converting elements, and to the structure disclosed in Japanese Patent Application Laying-Open No. 138461/1984 wherein an opening for absorbing pressure wave of the thermal energy is formed corresponding to the discharge portion. Further, the present invention is effectively applicable to a so-called full-line type recording head having a length corresponding to the maximum recording width and having a thousand of discharging portions or over. Such a recording head may comprise a single recording head integrally formed and a plurality recording heads combined to cover the entire width. In addition, the present invention is applicable to a serial type recording head wherein the recording head is fixed on the main assembly, to a replaceable chip type recording head which is connected electrically with the main apparatus and can be supplied with the ink by being mounted in the main assembly, or to a cartridge type recording head having an integral ink container. The provision of the recovery means and the auxiliary means for the preliminary operation are preferred because they can further stabilize the effect of the present invention. As for such means, there are capping means for the recording head, cleaning means therefor, pressing or sucking means, preliminary heating means by the discharging electro-thermal converting element and additional heating element and means for preliminary discharge not for the recording operation, which can stabilize the recording operation. As regards the kind and the number of the recording heads mounted, a single head corresponding to a single color ink may be equipped, or a plurality of heads corresponding, respectively, to a plurality of ink materials having different recording color or density may be equipped. The present invention is effectively applicable to an apparatus having at least one of a monochromatic mode solely with main color such as black and a multi-color mode with different color ink materials or a full-color mode by color mixture. The multi-color or full-color mode may be realized by a single recording head unit having a plurality of head formed integrally or by a combination of a plurality of recording heads. Furthermore, the form of the ink jet recording apparatus to which the present invention is applicable may be the one which can be used as an image output terminal for information processor such as computers and the like and in addition thereto a copying apparatus combined with a reader or the like as well as a facsimile apparatus having transmission and receiving functions. Still further, in the foregoing embodiment,the ink has been liquid. It may, however, be an ink material solidified at room temperature or below and liquefied at room temperature. Since in the ink jet recording system, the ink is controlled within the temperature not less than 30°C and not more than 70°C to stabilize the viscosity of the ink to provide the stabilized discharging, in usual recording apparatus of this type, the ink is such that it is liquid within the temperature range when the recording signal is applied. In addition, the temperature rise due to the thermal energy is positively prevented by consuming it for the state change of the ink from the solid state to the liquid state, or the ink material is solidified when it is left is used to prevent the evaporation of the ink. In either of the cases, the application of the recording signal producing thermal energy, the ink may be liquefied, and the liquefied ink may be discharged. The ink may start to be solidified at the time when it reaches the recording material. The present invention is applicable to such an ink material as is liquefied by the application of the thermal energy. Such an ink material may be retained as a liquid or solid material on through holes or recesses formed in a porous sheet as disclosed in Japanese Patent Application Laying-Open No. 56847/1979 and Japanese Patent Application Laying-Open No. 71260/1985. The sheet is faced to the electro-thermal converting elements. The most effective one for the ink materials described above is the film boiling system. The invention has been described in detail with respect to 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 as claimed.

Claims: An electrical wiring pattern for an ink jet recording head in which a first electrically conductive portion (30) is provided on a substrate (3) and an insulating layer, comprising first and second sub-layers (35, 36), is formed over the first electrically conductive portion (30), the first and second sub-layers (35, 36) having respective through-holes (35a, 36a) through them, overlapping with each other, so as to allow the first electrically conductive portion (30) to be connected to a second electrically conductive portion (32, 33, 37) through the through-holes, and along a part of the edge of the through-hole in the first sub-layer, the first sub-layer does not reach the first electrically conductive portion (30) or reaches the first electrically conductive portion (30) but does not overlap it, so that there is a part of the first electrically conductive portion (30) extending from the edge of the first electrically conductive portion to the edge of the through-hole in the second sub-layer which portion is overlapped by the second sub-layer but not by the first sub-layer, characterised in that the second electrically conductive portion (32, 33, 37) extends over the whole of the through-hole in the second sub-layer but does not overlap the first sub-layer. An electrical wiring pattern according to claim 1 in which the second sub-layer is thinner than the first sub-layer. An electrical wiring pattern according to claim 1 or claim 2 in which the first sub-layer overlies the second sub-layer. An electrical wiring pattern according to claim 1 or claim 2 in which the second sub-layer overlies the first sub-layer. An electrical wiring pattern according to any one of claims 1 to 4 in which the through-hole in the first sub-layer has a shape different from the through-hole in the second sub-layer. An electrical wiring pattern according to any one of the preceding claims in which the second electrically conductive portion (32, 33, 37) provides a bump electrode for connection to a semiconductor device (2). An electrical wiring pattern according to any one of the preceding claims in which one of the first and second sub-layers (35, 36) comprises an inorganic material and the other comprises an organic material. An electrical wiring pattern according to any one of the preceding claims in which an electrothermal converting element is provided on the substrate, the first electrically conductive portion (30) providing an electrode for the electrothermal converting element. A recording head comprising an electrical wiring pattern according to any one of the preceding claims. A recording head comprising a plurality of electrical wiring patterns according to claim 8, the recording head comprising: a plurality of liquid discharging portions for discharging liquid using thermal energy generated by the electrothermal converting elements; a plurality of liquid paths communicating with the liquid discharging portions; and a liquid chamber (10) communicating with the plurality of liquid paths. A recording head according to claim 10 in which the through-holes in the first and second sub-layers (35, 36) of the wiring patterns are in the liquid chamber (10). A recording head according to claim 10 in which the through-holes in the first and second sub-layers (35, 36) of the wiring patterns are outside the liquid chamber (10) and on the side of the liquid chamber (10) remote from the liquid discharging portions. A recording head according to any one of claims 10 to 12 in which a single through-hole in the first sub-layer is common to a plurality of said wiring patterns each of which has a respective through-hole in the second sub-layer. A recording apparatus having a recording head according to any one of claims 9 to 13.

Inventors: TAMURA HIDEO CANON KABUSHIKI K, WATANABE YASUTOMO CANON KABUSH, WATANABE, YASUTOMO, CANON KABUSHIKI KAISHA, TAMURA, HIDEO, CANON KABUSHIKI KAISHA
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1991
Main classification: B41J2
IPC codes: B41J2