Liquid emission recording head, substrate therefor and liquid emission recording apparatus utilizing said head

Abstract: A substrate for a liquid emission recording head, comprises: a support member (15); plural electrothermal converting elements formed on said support member and each provided with a heat generating resistor layer (3), a common electrode wiring layer (4) and an individual electrode wiring layer (5) both connected to said heat generating resistor layer, and a protective layer (6a) for the above-mentioned layers; an insulating layer (6b) formed on said common electrode wiring layer; and a common electrode (10) connected in common to said plural common electrode wiring layers across said insulating layer by through-holes (9) provided in said insulating layer.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a liquid emission recording head for emitting recording liquid from a discharge opening to generate flying droplets, thereby effecting recording, a substrate for said head, and a liquid emission recording apparatus equipped with said recording head. Related Background Art In the conventional liquid emission recording head, the common electrode of wirings is constructed, for example, as disclosed in U.S. Patent No. 4,499,480. Fig. 1 is a schematic plan view of a substrate for the conventional liquid emission recording head, and Fig. 2 is a schematic cross sectional view along a line B - B' in Fig. 1, in which a substrate 11 for the liquid emission recording head is shown. There are also shown a heat-generating resistor layer 3 composed of HfB₂ and formed on a substrate 15; an aluminum wiring layer 4 for the common electrode; an aluminum layer 5 for the individual electrodes; an anti-oxidation protective layer 6 composed of SiO₂; an anti-cavitation protective layer 7 composed of Ta; and an ink-resistant protective layer 8 composed of photosensitive polyimide. The heat-generating resistor layer 3, wiring layers 4, 5 and protective layers 6, 7, 8 constitute an electrothermal converting element for generating thermal energy to be utilized in the emission of liquid from the discharge opening. After the principle portions of said substrate 11 for the liquid emission recording head are completed, a common electrode member 13 consisting of a copper-laminated glass-epoxy board is adhered to a broken-lined portion 12, and said common electrode member 13 and the common electrode wiring layer 4 are connected by wire bonding. This state is shown in Fig. 3 and Fig. 4. Fig. 4 is a schematic cross-sectional view along a line C - C' in Fig. 3; same components as those shown in Figs. 1 and 2 are represented by same numbers. In Fig. 4, there is shown a wire 14 connected by wire bonding. However, such conventional structure, requiring the preparation of wiring member (common electrode 13 etc.) separate from the liquid emitting part and the subsequent connection of said wiring member for example by wire bonding, is associated with the drawbacks of complex procedure and eventual disconnection of the wire bonding even after the completion of the procedure. Particularly in the liquid emission recording head of so-called full line type in which the discharge openings are provided corresponding to the full line width of the recording material, the wire bondings have to be conducted corresponding to the number of said discharge openings. Consequently the process is very complex and requires high precision and secure operations, and the head is still associated with the drawbacks of increased possibility of wire disconnection because of the increased number of bonding wires and cumbersome preparation of the common electrode member corresponding to the width of said recording head. Another substrate for an ink jet recording head is known from patent document DE 30 08 487 A1. This substrate which corresponds to the substrate according to the preamble of the claim 1 has a support member, plural electrothermal converting elements formed on said support member and each provided with a heat generating resistor layer, a common electrode wiring layer and an individual electrode wiring layer, both connected to said heat generating resistor layer and a protective layer for the above-mentioned layers, an insulating layer formed on said common electrode wiring layer, and a common electrode connected in common to said plural common electrode wiring layers by through-holes provided in said insulating layer and said protective layer. Also this structure has, however, the disadvantage that the manufacturing requires high precision and that nevertheless the electrical connections are not very reliable. SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide a substrate for an ink jet recording head which operates with high precision and reliability and which still can be produced at low cost by means of a very simple process. Another object of the present invention is to provide a substrate for liquid emission recording head, provided with a support member; plural electrothermal converting elements each having a heat-generating resistor layer, a common electrode wiring layer and an individual electrode wiring layer both connected to said heat-generating resistor layer, and a protective layer for the aforementioned layers; an insulating layer provided on said common electrode wiring layer; and a common electrode connected in common to said plural common electrode wiring layers across said insulating layer by through-holes provided therein. Still another object of the present invention is to provide a liquid emission recording head, having liquid paths formed on the above-mentioned substrate corresponding to the heat-generating areas formed between said common electrode wiring layer and said individual electrode wiring layers, wherein the liquid is emitted from discharge openings communicating with said liquid paths utilizing thermal energy generated in said heat-generating areas. Still another object of the present invention is to provide a liquid emission recording apparatus equipped with the above-mentioned liquid emission recording head, and switch means of a power source for driving said recording head. These and other objects are achieved by the features claimed in the characterizing portions of the claims 1, 2 and 7. According to the characterizing portion of claim 1 a substrate for an ink jet recording head is provided, wherein the insulating layer covers the protective layer and is in contact with the common electrode wiring layers in the through-holes. According to the characterizing portion of claim 2 an ink jet recording head is provided, wherein the substrate of the ink jet recording head is the substrate claimed in claim 1, ink paths formed on said substrate correspond to heat generating portions formed between the common electrode wiring layers and the individual electrode wiring layers, and a discharge opening communicating with each of said ink paths is adapted to discharge ink by means of the thermal energy generated by said heat generating portion. According to the characterizing portion of claim 7 an ink jet recording apparatus is provided, wherein the ink jet recording head of said apparatus is the ink jet recording head claimed in any one of the claims 2 to 6, and switch means for power supply for driving said ink jet recording head is provided. The invention will now be described in greater detail, thereby referring to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic plan view of the principle portion of a substrate for a conventional liquid emission recording head; Fig. 2 is a schematic cross-sectional view along a line B - B' in Fig. 1; Fig. 3 is a schematic plan view of the principle portion of the substrate for the liquid emission recording head shown in Fig. 1, with a common electrode member and with wire bonding; Fig. 4 is a schematic cross-sectional view along a line C - C' in Fig. 3; Fig. 5 is a schematic plan view of the principal portion of a substrate for a liquid emission recording head constituting an embodiment of the present invention; Fig. 6 is a schematic cross-sectional view along a line A - A' in Fig. 5, showing an embodiment of the peripheral structure of a common electrode 10; Fig. 7 is a schematic perspective view, in a partially disassembled state, of an embodiment of the liquid emission recording head of the present invention; Fig. 8 is a schematic perspective view of another embodiment of the liquid emission recording head of the present invention; and Fig. 9 is a schematic perspective view of a liquid emission recording apparatus equipped with the liquid emission recording head of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Now the present invention will be clarified in detail by embodiments thereof shown in the attached drawings. Fig. 5 is a schematic plan view of the principal portion of a substrate for the liquid emission recording head constituting an embodiment of the present invention, and Fig. 6 is a schematic cross-sectional view along lines A - A' in Fig. 5. In these drawings there are generally shown a liquid emitting portion 1, and a wiring portion 2. Referring to Fig. 6, an anti-oxidation protective layer 6a of the liquid emitting portion 1 and an inter-layer insulating layer 6b of the wiring portion 2, are both formed with SiO₂ and simultaneously prepared in a same step. An ink-resistant protective layer 8a of the liquid emitting portion 1 and an interlayer insulating layer 8b of the wiring portion 2 are both formed with photosensitive polyimide resin and simultaneously formed in a same step. In the following there will be explained the manufacturing process of the present embodiment. (1) At first a HfB₂ film of a thickness of 1,000 Å is prepared by sputtering as the heat-generating resistor layer 3, and is patterned with fluoric-nitric wet etch to obtain the pattern shown in Fig. 5; (2) Then an aluminum film of a thickness of 5,000 Å is prepared by sputtering as the common electrode wiring layer 4 and the individual electrode wiring layer 5, and is patterned with acetic-nitric-phosphoric wet etch to obtain the pattern shown in Fig. 5; (3) A SiO₂ film of a thickness of 2 microns is formed by sputtering as the anti-oxidation protective layer 6a and the inter-layer insulating layer 6b, and is patterned with reactive ion etching utilizing CF₄ gas to form through-holes 9; (4) A Ta film of a thickness of 5,000 Å is prepared by sputtering the anti-cavitation protective layer 7, and is patterned with fluoric-nitric wet etching so as to cover the heat-generating portion between the wiring layers 4 and 5; (5) Photosensitive polyimide resin (Photoeece, product and trademark of Toray Corp.) is applied with a thickness of 2 microns as the ink-resistant protective layer 8a and the inter-layer insulating layer 8b, and is patterned by photolithography to form through-holes 9; (6) A TiCu film of a thickness of 5,000 Å is prepared by sputtering as the common electrode 10, and is patterned by wet etching to obtain the pattern shown in Fig. 5, whereby the common electrode 10 is connected to the common electrode wiring layers 4 by the through-holes 9; and (7) Finally the common electrode 10 is plated with a Cu-Ni-Au alloy film of a thickness of 10 microns, in order to improve the conductivity of the common electrode 10. In this embodiment, the organic protective layers 8a, 8b are so formed as to cover the protective layers 6a, 6b, whereby the protective layers 8a, 8b of low pinhole frequency adhere strongly to the wiring layer 4, thus providing a mechanically strong substrate for the liquid emission recording head. Fig. 7 is a schematic perspective view, in a partially disassembled state, of a liquid emission recording head of the present invention, prepared with the substrate prepared in the above-explained manner. In Fig. 7, numeral 16 indicates heat generating parts of the thermal energy generating elements formed between the wiring layers 4, 5, and there are formed, corresponding to said heat generating parts, liquid paths communicating with discharge openings 17 and having a common liquid chamber 18. A cover plate 19 for forming said liquid paths is provided with a recess 20 corresponding to said common liquid chamber 18 and a supply aperture 21 for supplying said common liquid chamber 18 with the recording liquid. Numeral 10 schematically shows the common electrode shown in Figs. 5 and 6, and said common electrode 10 and individual electrode wiring layers 5 (not shown in Fig. 7) are connected to a driving circuit component 22. Fig. 8 is a schematic perspective view of another embodiment of the liquid emission recording head of the present invention, seen from a side opposite to the discharge openings. The liquid emission recording head of this embodiment is so called full-line type, provided with discharge openings over the entire line width of the recording material, wherein said components as those in Fig. 7 are represented by same numbers. Numeral 23 indicates collectively the member constituting the walls of the liquid paths shown in Fig. 7 and the cover plate 19. In the foregoing embodiments, the direction of liquid emission from the discharge openings is substantially the same as the direction of supply of the recording liquid in the liquid path to the heat generating part of the thermal energy generating element, but the present invention is not limited to such embodiments. For example it is likewise applicable to the liquid emission recording heads in which said two directions are mutually different, for example mutually perpendicular. Also the materials and method of preparation of the layers constituting the liquid emission recording head of the present invention are not limited to those described in the foregoing embodiments, but can be those commonly employed in the preparation of the liquid emission recording head. Fig. 9 is a schematic perspective view of a liquid emission recording apparatus equipped with a liquid emission recording head of the present invention, in which a main body 1000, a switch 1100 for the power supply for driving said recording head, and an operation panel 1200 are shown. As explained in the foregoing, the present invention allows to prepare the liquid emission portion and the wiring portion of the liquid emission recording head simultaneously in a same gaseous process, and to prevent the drawbacks in the prior technology such as the disconnection of bonding wires after the preparation of the recording head. Consequently the present invention allows to produce the liquid emission recording head with a very simple process and with a reduced cost and to still ensure high precision and reliability with respect, for example, to the electrical connections. The present invention is particularly effective in simplifying the process of producing the recording head, when the protective layer of the liquid emitting portion and the inter-layer insulating layer of the wiring portion are simultaneously prepared in a same process. A substrate for a liquid emission recording head comprises; a support member; plural electrothermal converting elements formed on said support member and each provided with a heat generating resistor layer, a common electrode wiring layer and an individual electrode wiring layer both connected to said heat generating resistor layer, and a protective layer for the above-mentioned layers; an insulating layer formed on said common electrode wiring layer; and a common electrode connected in common to said plural common electrode wiring layers across said insulating layer by through-holes provided in said insulating layer.

Claims: A substrate for an ink jet recording head, having a support member (15), plural electrothermal converting elements formed on said support member (15) and each provided with a heat generating resistor layer (3), a common electrode wiring layer (4) and an individual electrode wiring layer (5), both connected to said heat generating resistor layer (3), and a protective layer (6a, 6b) for the above-mentioned layers, an insulating layer (8a, 8b) formed on said common electrode wiring layer (4), and a common electrode (10) connected in common to said plural common electrode wiring layers (4) by through-holes (9) provided in said insulating layer (8a, 8b) and said protective layer (6a, 6b), characterized in that said insulating layer (8a, 8b) covers said protective layer (6a, 6b) and is in contact with said common electrode wiring layers (4) in said through-holes (9). An ink jet recording head characterized by ink paths formed on the substrate according to claim 1, corresponding to heat generating portions (16) formed between said common electrode wiring layers (4) and said individual electrode wiring layers (5), wherein a discharge opening (17) communicating with each of said ink paths is adapted to discharge ink by means of the thermal energy generated by said heat generating portion (16). An ink jet recording head according to claim 2, characterized in that said discharge opening (17) is provided in a plural number depending on the width of recording area of a record receiving material. An ink jet recording head according to claim 2 or 3, characterized in that the direction of ink discharge from said discharge opening (17) is generally the same as the direction of ink supply to said heat generating portion (16). An ink jet recording head according to claim 2 or 3, characterized in that the direction of ink discharge from said discharge opening (17) is different from the direction of ink supply to said heat generating portion (16). An ink jet recording head according to claim 5, characterized in that the two directions form generally a right angle. An ink jet recording apparatus characterized by an ink jet recording head according to any one of the claims 2 to 6 and switch means for power supply for driving said ink jet recording head.

Inventors: TAMURA HIDEO, TAMURA, HIDEO
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1989
Main classification: B41J2
IPC codes: B41J2