Ink jet recording head and apparatus

Abstract: An ink jet recording head includes a top plate having recesses for forming ink paths connected to a plurality of ejection outlets from which ink is ejected; a substrate for forming the ink paths by joining it with the top plate, with the recesses facing inward; wherein the top plate overhangs from an edge of the substrate in the direction of a plane of the joint between the top plate and substrate.

Description: The present invention relates to an ink jet recording head according to the preamble of Claim 1. Such a recording head records images by means of ejecting ink onto a piece of recording medium, and also to an ink jet recording apparatus comprising such an ink jet recording head. In this case, the terminology "record" means to "apply" the ink or the like to any ink receptive medium which includes fabric, yarn, paper, sheet material of various types, and the "recording apparatus" means an information processing apparatus itself inclusive of printer, or the printer itself as the output device, to which the present invention is applicable. Among various types of presently known recording systems, the ink jet recording system has been recognized as an extremely effective recording system, since it is a non-impact recording system which generates little noise during recording; it is capable of recording at a high speed; and in addition, it is capable of recording on plain paper without requiring a special fixing process. Figures 15 and 16 illustrate the essential portions of a typical ink jet recording head employed in such an ink jet recording system. Figure 15 is a schematic perspective view thereof, and Figure 16 is an exploded perspective view thereof. Figure 17 is a schematic sectional view of the internal structure of the ink jet recording head, at sectional plane X-X. Reference numeral 100 designates a base plate, on which various components (which will be described later) are constructed. On this base plate 100, a piece of substrate 200 (hereinafter, a heater board) is disposed, which comprises a plurality of electrothermal transducers (heaters) 201 as elements for ejection energy. On this heater board 200, an ink path (not illustrated) leading to a plurality of ink ejecting orifices 301 is located, and also, to a predetermined point thereof, a top plate 300 is joined. The top plate 300 comprises: an orifice plate 304 with the ink ejection orifices 301; a common liquid chamber 302 for storing the ink to be supplied through the aforementioned ink path; and a cylindrical ink inlet pipe for supplying the ink to this common liquid chamber 302. The top plate 300 is joined with the heater board 200 in the following manner. First, the top plate 300 is temporarily glued onto the heater board 200, in such a manner that the plurality of heaters 201 of the heater board 200 become aligned with the correspondent ink ejection orifices 301 of the top plate 300, and then, a mechanical pressure is applied, from above, to the top plate 300, with the use of a spring (unillustrated), so that two components can be satisfactorily joined in an airtight manner. Thereafter, the peripheries of the top plate 300 and heater board 200 are sealed with sealant 400 as shown in Figure 17, whereby the ink path and common liquid chamber 302 are airtightly sealed. It is well-known that liquid chamber partitioning walls 303 are disposed on the heater board 200 so as to form the common liquid chamber 302 on the inward facing surface of the heater board 200 (JP-A-3-101,958, or the like). Recently, however, the size of the heater board has been progressively reduced in order to reduce the size of the ink jet recording head as well as the heater board cost. As the results of this size reduction, there have been cases in which it is difficult, in terms of space, to form the liquid chamber walls on the inward facing surface of the heater board in a conventional manner. In addition, the reduced size of the heater board results in a reduced distance between the heater board edge and the outermost ink ejection orifice, and as a result, the sealant for sealing the common liquid chamber is liable to flow sometimes into the ink ejection orifices, creating thereby such a problem that the ink cannot be ejected. Accordingly, the primary object of the present invention is to provide a highly reliable ink jet recording head, which is even smaller in size and cost, and in which the sealant does not flow into the ink path, and also to provide an ink jet recording apparatus comprising such an ink jet recording head. A generic ink jet recording head is known from the DE-A-4 039 525. This document discloses an ink jet recording head having a top plate which is formed with recesses and sealingly joined to a substrate for providing ink paths connected to a plurality of ejection outlets, The top plate overhangs from an edge of the substrate in the direction of a plane of the joint between the top plate and the substrate. JP-A-3 101 958 relates to an ink jet recording head whose top plate is not provided with overhanging portions. It is an object of the present invention to further develop an ink jet recording head according to the preamble of claim 1 such that sealant is prevented from flowing into the ink path. This object is achieved by the features of claim 1. Advantageous further developments are set out in the dependent claims. An ink jet recording apparatus comprising the above ink jet recording head is subject matter of claim 11. Since the top plate overhangs from the edges of the substrate in the direction of the joint between the top plate and substrate, the size of the substrate is small. In addition, the joint becomes smaller than the conventional one; therefore, it is less probable that gaps will occur between the top plate and substrate due to the microscopic surface irregularities that are present in the joint. Consequently, the airtightness of the joint between the top plate and substrate is improved, preventing the sealant from flowing into the ink path. Further, since the top plate is disposed in such a manner as to overhang from the joint, the thickness of the top plate wall members that form the ink path is allowed to be substantially the same as those of the conventional design; therefore, their strength can be maintained at substantially the same level as the conventional one. According to the present invention, the extended overhanging portions of the liquid chamber wall are provided with an opening; therefore, the adhesive used to join temporarily the top plate and element substrate can be reliably prevented from flowing into the ink path. Preferably, the overhanging portions of the top plate are extended in the thickness direction of the substrate, and the substrate is disposed between the two extended overhanging portions; therefore, the sealant can be more reliably prevented from flowing into the ink path. Further, the extended portions of the top plate embrace the substrate; therefore, the strength, or reliability, of the ink jet recording head itself is improved. Advantageously, a portion of one of the common chamber walls projects toward the element substrate, the wall being the one that opposes the orifice plate. This projecting portion causes the mechanical pressure, which is applied to the top plate as the top plate and element substrate are joined, to be concentrated toward the ink path wall side of the element substrate; therefore, the ink path walls of the top plate, and substrate, can be airtightly joined with more reliability. Consequently, the sealant for sealing the joint between the element substrate and top plate can be reliably prevented from flowing into the common liquid chamber and/or ink ejection orifices. According to the present invention, notches are cut in the extended overhanging portion of the liquid chamber wall; therefore, the surface area, which comes in contact with the adhesive used for joining temporarily the top plate and element substrate, can be increased, whereby the adhesive strength is improved. The above object as well as features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention, taken in conjunction with the accompanying drawings. Figure 1 is a schematic perspective view of essential portions of a first comparative example of an ink jet recording head. Figure 2 is an exploded perspective view of Figure 1. Figure 3 is a schematic perspective view of the internal structure of a top plate of the first comparative example of the ink jet recording head. Figure 4 is the sectional view of Figure 1, at sectional plane X-X. Figure 5 is a schematic perspective view of the essential portions of a second comparative example of the ink jet recording head. Figure 6 is an exploded perspective view of Figure 5. Figure 7 is a schematic perspective view of the internal structure of the top plate in the second comparative example of the ink jet recording head. Figure 8 is a sectional view of Figure 5, at sectional plane X-X. Figure 9 is a schematic perspective view of the essential portions of third comparative example of the ink jet recording head. Figure 10 is a schematic perspective view of the internal structure of the top plate in the third comparative example of the ink jet recording head. Figure 11 is a sectional view of Figure 9, at sectional plane X-X. Figure 12 is a schematic perspective view of essential portions of an embodiment of the ink jet recording head in accordance with the present invention. Figure 13 is a schematic perspective view of the internal structure of the top plate in the embodiment of the ink jet recording head in accordance with the present invention. Figure 14 is a schematic perspective view of an embodiment of the ink jet recording apparatus in accordance with the present invention. Figure 15 is a schematic perspective view of the essential portions of a typical, conventional ink jet recording head. Figure 16 is an exploded perspective view of the essential portions of the typical, conventional ink jet recording head. Figure 17 is a schematic sectional view of the internal structure of the ink jet recording head of Figure 15, at sectional plane X-X. Hereinafter, preferred embodiments of the present invention will be described in detail referring to the drawings. Comparative example 1 Figures 1 - 4 depict the first comparative example of the ink jet recording head, wherein Figure 1 is a schematic perspective view of the essential portions thereof; Figure 2, an exploded perspective view of Figure 1; Figure 3, a schematic perspective view of the internal structure of the top plate; and Figure 4 is a sectional view of Figure 1, at sectional plane X-X. Among the structural components in this comparative example, those common to the conventional ink jet recording head illustrated in Figures 15 - 17 will be designated with the same references, and their descriptions will be omitted. This comparative example shows that the common liquid chamber wall 303 overhangs from the heater board 200, at both edges in the direction in which the plurality of heaters 201 are aligned on the heater board 200 as the element substrate, that is, in the direction in which the ejection orifices are aligned. This arrangement makes it possible to minimize the space occupied on the upward facing surface of the heater board 200 by the liquid chamber wall 303, that is, the portions involved to join the liquid chamber wall 303 and heater board 200; therefore, it is possible to reduce the heater board 200 size. Referring to Figure 4, it is preferable that the relationship between width m, which is the width of the heater board 200 in the direction in which the plurality of heaters 201 are aligned, and width l, which is the width of the common liquid chamber 302 in the same direction, satisfies the following formula: m > l. More specifically, the difference between m and l in this comparative example was set at 0.1 mm. Parenthetically, when the head was constructed with the relationship being: m < l, there was a problem in that the sealant flowed onto the upward facing surface of the heater board, and also into the ink ejection orifices 301. Also, this comparative example shows that a projection 306 is provided on the top plate 300, behind the common liquid chamber 302, relative to the ejection orifice plate 304, as shown in Figure 3. The common liquid chamber 302 is constituted of a recess formed in a surface of the top plate 300. In one of the lateral walls of the common liquid chamber 302, a plurality of ink passages 308 are formed in such a manner that each passage is correspondent to one of the plurality of ink ejection orifices 301 formed in the orifice plate 304, connecting thereby the common liquid chamber 302 and the ink ejection orifices 301. The aforementioned projection 306 is at the center portion of the opposite common chamber wall of this same common liquid chamber wall, in which the ink passages 308 are formed. The upward facing surfaces of the walls 303 of the common liquid chamber 302 constitute the surfaces to be joined with the heater board 200 of the top plate 300, but since the projection 306 is on one of these upward facing surfaces, the joint is actually constituted of the top surface of this projection 306, and the top surfaces of the plurality of the ink passage walls 307 that form the aforementioned plurality of ink passages 308. Therefore, the mechanical pressure applied to the top plate 300 by the leaf spring 401 is concentrated toward the ink passage walls 307. After the spring 401 is fitted, the peripheries of the top plate 300 and heater board 200 are sealed with the sealant 400 as shown in Figure 4, and at this time, the sealant 400 invades into slight gaps formed by the projection 306, between the heater board 200 and common liquid chamber walls 303, and seals them airtightly. Since no gap is formed between the ink passage walls 307 and heater board 200, the sealant 400 externally seals the joint between the top plate 300 and heater board 200. In this comparative example, the height of the projection 306 from the top surface of the common liquid chamber wall 303 is within a range of 5 - 20 µm. When it is no more than 5 µm, the satisfactory adhesion cannot be effected between the heater board 200 and ink passage walls 307, and when it is no less than 20 µm, the gap between the liquid chamber wall 303 and heater board 200 becomes excessively large, creating thereby a problem occasionally in that the sealant 400 flows onto the top surface of the heater board 200, and also into the ink ejection orifices. Comparative Example 2 Figures 5 - 7 illustrate the second comparative example of the ink jet recording head. Figure 5 is a schematic perspective view of the essential portions thereof; Figure 6, a schematic perspective view of the internal structure of the top plate; and Figure 7 is a sectional view of Figure 5, at sectional plane X-X. Also in this embodiment, the structural components common to the conventional ink jet recording head illustrated in Figures 15 - 17, and also to preceding comparative example, are designated with the same references, and their descriptions will be omitted. This comparative example shows that the heater board 200 is disposed between the opposing two walls 303a of the common liquid chamber 303 of the top plate 300, which extend in the direction perpendicular to the alignment direction of the plurality of ink ejection orifices 301 of the orifice plate 304. The liquid chamber walls 303a extend far beyond the top surfaces of the liquid chamber walls 303 as shown in Figure 7, and function, like a dam, to prevent the invasion of the sealant 400 used to seal externally the common liquid chamber 302 of the top plate 300. As for the amount of the projection of the liquid chamber wall 303a in this comparative example, it is set to be less than the thickness of the heater board 200. This is because, if the amount of the projection is set to be more than the thickness of the heater board 200, the sealant 400 cannot be successfully prevented from flowing into the common liquid chamber 302, and also, in some cases, the interface between the ink passage walls 307 and heater board 200 cannot be satisfactorily sealed. Thus, this comparative example enjoys the following effects in addition to those of the preceding comparative example. That is, the sealant 400 is reliably prevented from flowing into the common liquid chamber 302, so that the ink ejection orifices 301 do not become plugged up with the sealant 400; therefore, the ink can be reliably ejected to record high quality images. Comparative Example 3 Figures 9 - 11 depict the third of the ink jet recording head, wherein Figure 9 is a schematic perspective view of the essential portions thereof; Figure 10, a schematic perspective view of the internal structure of the top plate; and Figure 11 is a sectional view of Figure 9, at sectional plane X-X. Also in this comparative example, the structural components common to the conventional ink jet recording head illustrated in Figures 15 - 17, and also to the preceding comparative examples, are designated with the same references, and their description will be omitted. This comparative example shows that not only the projection 306 described in the preceding first embodiment is provided, but also, the heater board 200 is disposed between the opposing two walls 303a of the common liquid chamber 303 of the top plate 300, which extend in the direction perpendicular to the alignment direction of the plurality of ink ejection orifices 301 of the orifice plate 304. The liquid chamber walls 303a extends far beyond the top surfaces of the other liquid chamber walls 303 as shown in Figure 11, and function, like a dam, to prevent the invasion of the sealant 400 used to seal externally the common liquid chamber 302 of the top plate 300. As for the amount of the projection of the liquid chamber wall 303a in this comparative example, it is set to be less than the thickness of the heater board 200. This is because, if the amount of the projection is set to be more than the thickness of the heater board 200, the sealant 400 cannot be successfully prevented from flowing into the common liquid chamber 302, and also, in some cases, the interface between the ink passage walls 307 and heater board 200 cannot be satisfactorily sealed. Thus, this comparative example enjoys the following effects in addition to those of the preceding comparative examples. That is, the sealant 400 is reliably prevented from flowing into the common liquid chamber 302, so that the ink ejection orifices 301 do not become plugged up with the sealant 400; therefore, the ink can be reliably ejected to record high quality images. Embodiment Figures 12 and 13 depict an embodiment of the ink jet recording head in accordance with the present invention, wherein Figure 12 is a schematic perspective view of the essential portions thereof, and Figure 13 is a schematic perspective view of the internal structure of the top plate. Also in this embodiment, the structural components common to the conventional ink jet recording head illustrated in Figures 15 - 17, and also to the preceding comparative examples, are designated with the same alphanumeric references, and their descriptions will be omitted. This embodiment is characterized in that a pair of notches 309, and opening 310 (cutaway portion), are cut into both of the liquid chamber walls 303a described in the preceding third comparative example. The notched portion 309 is positioned away from the orifice plate 304, that is, closer to the liquid chamber wall 303 opposing the ink ejection orifices 301. This notched portion 309 functions to fix temporarily the positional relationship between the heater board 200 and top plate 300, when the two components are joined with adhesive (normally, UV-curing adhesive). The provision of this type of notched portion 309 increases the area of adhesion; therefore, adhesive strength is increased. As for the cutaway portion 310, it is formed by means of cutting away a portion of the liquid chamber wall 303a from the top surface of the liquid chamber wall 303a to the top surface of the liquid chamber wall 303. The purpose of this type of cutaway portion 310 is to prevent effectively the adhesive applied to the notched portion 309 for the temporary fixation, from flowing toward the ink ejection orifices 301, and plugging them, while the adhesive hardens. Therefore, it is important that this cutaway portion 310 is positioned at the end portion of ink path 308, that is, at the end portion away from the ink ejection orifices 301. Thus, this embodiment enjoys the following effects in addition to those of the preceding comparative examples. That is, not only can the temporary fixation between the heater board 200 and top plate 300 reliably occur with the presence of the notched portion 309 that is cut, as a barrier for preventing the sealant 400 from flowing into the common liquid chamber 302, in the liquid chamber wall 303a, but also, the adhesive used for the temporary fixation can be prevented from flowing into the area of ink ejection orifices 301, by the cutaway portion 310; therefore, the ink ejection orifice 301 is prevented from being plugged up with the adhesive, allowing thereby the ink to be reliably ejected to record high quality images. Those ink jet recording heads described in the preceding comparative examples and the embodiment of the present invention are mountable in such an ink jet recording apparatus as the one illustrated in Figure 14. Figure 14 is a schematic perspective view of an embodiment of the ink jet recording apparatus in accordance with the present invention. Referring to Figure 14, reference numeral 80 designates a cartridge, which is fixed on carriage 15 with the use of retaining member 81. These are reciprocative in the longitudinal direction of shaft 21 (primary scanning direction). The position of the cartridge 80 on the carriage 15 is fixed by a hole provided in the lid, and a dowel or the like provided on the carriage 15. As for the electrical connection, it is established when a contact pad provided on a wiring substrate is placed in contact with a connector provided on the carriage 15. Recording medium 18 is put through a minute gap between the recording head and platen 19, and its recording surface is regulated by the platen 19. The ink ejected from a recording head reaches the surface of the recording medium 18, where it forms an image. To the recording head, ejection signals reflecting image data are sent from an appropriate data source through cable 16 and a terminal connected thereto. The number of cartridge 80 may be one, or two or more, depending on the number of inks, or the colors of the image (two in this drawing). Also referring to Figure 14, reference numeral 17 designates a carriage motor, which moves the carriage 15 along the shaft 21; 22, a wire for transmitting the driving force of the motor 17 to the carriage 15; and 20 designates a feeder motor, which is connected to the platen 19 to feed the recording medium 18. As for the form of the ink jet recording apparatus to which the present invention is applicable, it may be in the form of an image outputting peripheral device of an information processing apparatus such as a computer. Also, it may be in the form of a copying machine that integrally comprises a reader or the like, and also in the form of a facsimile with both the transmitting and receiving capacities.

Claims: An ink jet recording head comprising: a top plate (300) having recesses for forming laterally adjacent ink paths (308) connected to a plurality of ejection outlets (301) from which ink is ejected; a substrate (200) for forming the ink paths (308) by joining it with said top plate (300), with the recesses facing inward; wherein said top plate (300) comprises lateral overhanging portions (303a) which overhang from an edge of said substrate (200) in the direction of a thickness of said substrate (200), the joint between said top plate (300) and said substrate (200) being sealed with a sealant, characterized in that the lateral overhanging portions (303a) of said top plate (300) are provided with an opening (310). An ink jet recording apparatus according to claim 1, characterized in that said top plate (300) has two such overhanging portions (303a) extended in the thickness direction of said substrate (200), and said substrate (200) is disposed between the lateral overhanging portions (303a). An ink jet recording apparatus according no claim 1, characterized in that the ink paths (308) comprise a plurality of ink passages connected between said ink ejection outlets (301) and a common ink chamber (302) for storing the ink to be supplied to the plurality of ink passages. An ink jet recording head according to claim 3, characterized in that a projection (306) is provided at said top plate (300) on a portion of the walls forming the common ink chamber (302) opposite to said plurality of ejection outlets (301). An ink jet recording head according to claim 1, characterized in that said top plate (300) integrally comprises an orifice plate (304) in which said plurality of ejection outlets (301) are aligned. An ink jet recording head according to claim 3, characterized in that energy generating means (201) for generating the energy to be used for ejecting the ink from said plurality of ejection outlets (301) are disposed along said ink passages (308). An ink jet recording head according to claim 6, characterized in that said energy generating means (201) comprise thermal energy generating members for generating thermal energy to create film-boiling of the ink. An ink jet recording head according to claim 7, characterized in that said thermal energy generating members (201) include electrothermal transducers. An ink jet recording head according to claim 1, characterized in that said top plate (300) and said substrate (200) are joined with a mechanical pressure before the sealant is applied. An ink jet recording head according to claim 1, characterized by a base plate (100) for mounting said substrate. An ink jet recording apparatus comprising: an ink jet recording head according to any of the preceding claims and a mounting member (15; 81) for mounting said ink jet recording head.

Inventors: SHIMIZU EIICHIRO, SHIMIZU, EIICHIRO
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1995
Main classification: B41J2
IPC codes: B41J2