Ink-jet type recording head

Abstract: Described is an ink-jet type recording head including a nozzle plate (2) provided with nozzle openings (2a), a spacer (1) provided with partitions for partitioning pressure generating chambers, ink supply ports and reservoirs, and a plate member (3) which are sandwiched and fixed together. Displacement of the plate member (3) is produced by piezoelectric vibrators (4) to thereby generate ink droplets. The spacer (1) is formed by anisotropic etching of a silicon single crystal substrate so that the pressure generating chambers, the ink supply ports and the reservoirs are formed as through-holes communicating with each other. Accordingly, etching conditions for the respective through-holes are made equal to each other. Particularly, through-holes small in sectional area such as the pressure generating chambers and the ink supply ports can be formed with a high accuracy.

Description: The present invention relates to an ink-jet type recording head. In an ink-jet type recording head in which dots on a recording medium are formed from ink droplets, printing with very high resolution can be made by reducing the ink droplet size, but it is necessary to increase the number of nozzle openings for the purpose of performing printing efficiently. Particularly in the case of an ink-jet recording head using piezoelectric vibrators as ink droplet jetting sources, it is necessary to increase the size of pressure generating chambers as to use the energy of the piezoelectric vibrators efficiently. However, this is contrary to the requirement of reducing the size of the recording head. To resolve the aforementioned problems, there is generally used a method of setting wills partitioning adjacent pressure chambers in such a manner as to be as thin as possible and of making the shape of the pressure generating chambers larger in the direction of the length thereof to thereby increase the volume thereof. Such pressure generating chambers or reservoirs are formed by making through-holes in a spacer, i.e ., a member for keeping the distance between a plate member and a nozzle plate it a predetermined value. So as to form through-holes coincident with pressure generating chambers having the required very small and complex shape, an etching technique is used generally. A laminate of photosensitive resin films is used generally as a material constituting the aforementioned spacer. When such a photosensitive resin film laminate is used, there arises an advantage in that a desired pattern can be formed extremely accurately due to the fact that such materials are well suitable for photolithography, and due to the fact that the adhesive property thereof can be used so that no adhesive agent is required for fixing the laminate to the plate member and the nozzle plate. On the other hand, there is a disadvantage in that crosstalk, distortion, etc ., can occur because of the low mechanical strength of the material, so that the quality in printing is lowered when this material is applied to a recording head with high resolution. Moreover, since a plurality of resin films are laminated in use, there is a risk of separation, so that the thickness of the spacer in limited by the characteristics of the material. There also arises a problem in that it is difficult to make the volume of each of the pressure generating chambers suitable for an ink-jet type recording head. To solve the aforementioned problems, a proposal has been made in which a silicon single crystal substrate of crystal orientation (110) is used, and pressure generating chambers in the form of through-holes and ink supply ports and nozzle openings in the form of grooves of a depth providing a fluid resistance required for these openings are formed by anisotropic etching of a silicon single crystal substrate (see U.S. Patent No. 4,312,008). There, however, arises a problem in that not only is controlling of the producing process complicated because it is necessary to precisely control the etching depth, but it is difficult to control the volume in positions necessary for securing fluid resistance to a precise degree, for instance in the ink supply ports, because the etched sectional shape is inherently a V-shape or a trapezoidal shape. It is therefore the object of the present invention to provide an in-jet type recording head which avoids the above-mentioned drawbacks. This object is solved by the ink-jet type recording head according to independent claim 1. Further advantageous features, aspects and details of the invention are evident from the dependent claims, the description and the drawings. The claims are to be understood as a first non-limiting approach to define the invention in general terms. The present invention relates to an ink-jet type recording head for generating pressure in pressure generating chambers substantially instantaneously by expansion/contraction of piezoelectric vibrators or by heat elements to thereby jet ink droplets from nozzle openings in response to the change in pressure. According to an aspect there is provided a novel ink-jet type recording head in which pressure generating chambers, ink supply ports and reservoirs can be formed with a high accuracy by etching of a crystalline substrate. To solve the aforementioned problems, according to the present invention, there is provided an ink-jet type recording head comprising: a nozzle plate provided with nozzle openings for jetting ink droplets; a spacer provided with partitions for partitioning pressure generating chambers, ink supply port and reservoirs; a plate member fixed to the other surface of the spacer so as to be opposite to the nozzle plate, the nozzle plate, the spacer and the plate member being sandwiched and fixed to each other; and pressure generating means for exerting a change of pressure suitable for forming ink droplets on the pressure generating chambers; characterized in that the spacer is formed by etching a silicon crystalline substrate or a silicon oxide crystalline substrate from its opposite surfaces so that the pressure generating chambers, the ink supply ports and the reservoirs are formed in the form of through-holes communicating with each other; said spacer (1; 60; 90) is formed such that its partitions (62) for partitioning said pressure generating chambers (1a, 10, 71, 95) and said ink supply ports (1b, 11, 72, 96) are in the form of cantilevers which have their free ends adjacent the reservoir (1c, 12, 97) and which are connected to a body on the nozzle opening side. Because the reservoirs, the pressure generating chambers and the ink supply ports partitioned by the spacer are formed in the form of through-holes from one surface to the other surface, accuracy is provided simply and without the necessity of controlling the etching depth strictly. Fig. 1 is a perspective view of in apparatus constructed according to a preferred embodiment of the present invention, showing the structure of a spacer, partly cut away in a nozzle plate; Fig. 2 is an enlarged sectional view showing the vicinity of pressure generating chambers in the apparatus; Figs. 3(a) and 3(b) are enlarged views respectively showing the arrangement of through-holes formed in the spacer and the vicinity of the through-holes; Figs. 4(a) and 4(b) are enlarged views respectively showing the arrangement of through-holes formed in the spacer and the vicinity of the through-holes; Fig. 5 is a view showing an embodiment in the case where the present invention is applied to a bubble jet type recording head; Figs. 6(a) to 6(e) are explanatory views showing a method of forming a spacer by anisotropic etching of a silicon single crystal substrate; Figs. 7(a) and 7(b) are explanatory views showing an etching process in the case where a silicon single crystal substrate of crystal orientation (110) is subjected to anisotropic etching; Figs. 8(a) to 8(e) are explanatory views showing a producing process in the case where a synthetic crystal substrate is used as a substrate constituting a spacer; Figs. 9(a) and 9(b) are views showing formation of surfaces and overhanging accompanying therewith in an etching process in the case where a synthetic crystal is used as a substrate; Fig. 10 is a view showing another embodiment of a spacer using a synthetic crystal; Figs. 11(a) and 11(b) are a sectional view showing a further embodiment of a spacer used in an ink-jet type recording head of the present invention and an enlarged view showing surfaces of adhesion; Fig. 12 is an enlarged view showing surfaces of adhesion in a further embodiment of spacer used in an ink-jet type jet recording head of the present invention; Fig. 13 is an enlarged view showing the vicinity of through-holes constituting pressure generating chambers and ink supply ports in a further embodiment of spacer used in an ink-jet type recording head of the present invention; Figs. 14(a) to 14(d) are views showing the behavior of an adhesive agent in the case where a nozzle plate and a plate member are joined with the spacer by the adhesive agent; Fig. 15 is a perspective view showing a further embodiment of a spacer used in an ink-jet recording head of the present invention; Fig. 16 is a view showing another embodiment of an ink-jet recording head of the present invention; Fig. 17 is a perspective view of a further embodiment of an ink-jet recording head of the present invention, partly cut away in a nozzle plate; and Fig. 18 is a view showing an embodiment of a spacer used in the apparatus. The present invention now will be further described on the basis of preferred embodiments shown in the drawings. Fig. 1 shows a first preferred embodiment of the present invention. In the drawing, reference numeral 1 designates a spacer constituting a feature of the present invention. In this embodiment, the spacer is constituted by a silicon single crystal substrate of crystal orientation (110) having a thickness suitable for securing the optimum volume as a pressure generating chamber. In this substrate, through-holes 1a, 1a, 1a... to form pressure generating chambers communicating with nozzle openings 2a, 2a, 2a... of a nozzle plate 2 at one end, a through-hole 1c to form a reservoir supplied with ink from an ink tank not shown and through-holes 1b, 1b, 1b... to form ink supply ports for communicating the respective through-holes 1a, 1a, 1a... with the through-hole 1c are formed by anisotropic etching (which will be described later), and are disposed between the nozzle plate 2 and a plate member 3 (which also will be described later). In the driving, reference numeral 2 designates the nozzle plate as described above. The nozzle plate is provided with the nozzle openings 2a, 2a, 2a... formed at intervals of a predetermined pitch, for example, 180 DPI, and is airtightly fixed to one surface of the spacer 1. Reference numeral 3 designates the plate member which is airtightly fixed to the other surface of the spacer 1 and cooperates with the nozzle plate 2 to form pressure generating chambers. Piezoelectric vibrators 4, 4, 4... are fixed to regions of the plate member 3 facing the pressure generating chambers. The piezoelectric vibrators 4, 4, 4... are formed as vertical vibration type piezoelectric vibrators which vibrate in the directions of the arrows B in the drawing, that is, in the directions perpendicular to the surface of the plate member 3. While one end of each of the piezoelectric vibrators abuts the plate member 3 as described above, the other end (the region represented by the wavy line A in the drawing) is fixed to a pedestal 5 by an adhesive agent. In the pedestal 5, there is formed a through-hole 7 having one end communicating with an ink tank (not shown) through a tube 6 and the other, opposite end connected to an ink flow-in port 8 and to the through-hole 1c to form a reservoir as described above The reservoir side containing the through-holes 1b, 1b, 1b... to form ink flow passages is fixed so that a region (represented by the wave line D in the drawing) shaped like a cantilever by the through-holes 1a, 1a, 1a... and 1b, 1b, 1b... in supported without inhibition of vibration by the piezoelectric vibrators of the plate member. Fig. 2 is an enlarged view of the vicinity of the pressure generating chambers in the aforementioned ink-jet type recording head. In this embodiment, for use of the displacement of, the plate member 3 due to the piezoelectric vibrators, the plate member 3 which cooperates with the through-holes 1a of the spacer 1 and the nozzle plate 2 to form pressure generating chambers has island portions 3a formed as thick portions for transmitting the expansion/-contraction of the piezoelectric vibrators 4 to the whole of the pressure generating chambers, and thin portions 3b formed to surround the island portions. When the piezoelectric vibrators 4 in the aforementioned structure expand/contract in the directions of the arrows B in the drawing (Fig. 1), a range as wide as possible, of the pressure generating chambers expands/contracts through the plate member 3. In the case of contraction, ink in the pressure generating chambers is jetted in the form of ink droplets from the nozzle openings. In the case of expansion, ink in the reservoir flows into the pressure generating chambers through the ink supply ports constituted by the through-holes 1b. Fig. 3(a) shows an embodiment of the aforementioned spacer. In this embodiment, the case where the spacer is applied to a recording head of the type in which the nozzle openings are arranged at intervals of a predetermined pitch, for example 141 µm, will be described as an example. In the drawing, reference numerals 1a, 1a, 1a... and 1a', 1a', 1a'... designate through-holes which form respective pressure generating chambers. The through-holes are arranged so as to be substantially symmetrical to each other with respect to a center line in accordance with the arrangement of nozzle trains. The sides facing each other of the through-holes are communicating with nozzle openings of a nozzle plate (not shown). In the opposite sides of the through-holes, there are formed through-holes 1b, 1b... and 1b', 1b'... to form ink supply ports communicating with reservoirs and through-holes 1c and 1c' to form reservoirs connected to the through-holes 1b, 1b,... and 1b', 1b'... These through-holes 1a, 1b, 1c, 1a', 1b' and 1c' are formed by anisotropic etching of a silicon single crystal substrate having crystal orientation (110), as will be described in more detail later. Accordingly, each of the through-holes 1a forming pressure generating chambers as shown in Fig. 3(b) is substantially shaped like a parallelogram constituted by wall surfaces 1a-a, 1a-b, 1a-c and 1a-d perpendicular to a surface. Of the two wall surfaces 1a-a and 1a-b extending in the direction of length of the through-hole 1a to form a pressure generating chamber, one wall surface side 1a-a abutting an extension line of the wall surface 1a-d at an acute angle  in the reservoir side is provided with a through-hole 1b to form an ink supply port partitioned by a wall surface 1b-a to form the same plane as the wall surface 1a-a, so that fluid resistance suitable to jetting of ink droplets and supplying of ink to the pressure generating chamber is obtained in accordance with the width and length of the through-hole 1b. The wall surface 1c-a forming a through-hole 1c as a reservoir is formed to have the optimum shape as a reservoir by zigzag repetition of fine planes for correction of the orientation due to anisotropic etching. These through-holes 1a, 1a, 1a..., 1b, 1b, 1b... and 1c are formed as through-holes each passing through a wall from one side to the other side. The wall surfaces partitioning the through-holes are perpendicular to a surface of the substrate formed as spacer 1. Fig. 4 shows another form of arrangement of the pressure generating chambers. In the drawing, reference numeral 9 designates a silicon single crystal substrate of crystal orientation (110) having the same structure as described above. This embodiment relates to the case where the silicon single substrate is applied to a recording head having 4 nozzle opening trains. In the drawing, reference numerals 10, 10, 10... designate through-holes forming respective pressure generating chamber. These are formed as through-holes by anisotropic etching of the two sides of the silicon single crystal substrate in the same inner as described above. In one end of each of the through-holes 10, 10, 10..., that is, in a side opposite to the nozzle opening side, there are formed through-holes 11, 11, 11... to form ink supply ports. Unlike the aforementioned embodiment, these through-holes 11, 11, 11... are arranged so as to be parallel to each other to form an angle of 35° with respect to an axial line of the through-holes as pressure generating chambers. Through-holes 12, 12, 12... as reservoirs are connected to the through-holes 11, 11, 11... as the respective groups of ink supply ports. Further, ink flow-in ports 13, 13, 13... being in communication with an ink tank are connected to respective ones of the through-holes 12, 12,... The through-holes 10, 10, 10... forming pressure generating chambers and the through-holes 11, 11, 11... forming ink supply ports are connected to each other at an angle of about 110°, as shown in Fig. 4(b). Because they are accordingly arranged so that discontinuous portions are reduced as much as possible, points of connection between pressure generating chambers and ink supply ports are smoothed so that bubbles and the like can be prevented from stagnation. Although the aforementioned embodiment concerns the case where pressure for jetting ink droplets is generated by changing the shape of each of the pressure generating chambers through the piezoelectric vibrators of the plate member, the same effect can be achieved in the case where electric resistance elements 19, 19, 19... are fixed to the plate member 3 and mounted in the through-holes 1a, 1a, 1a... constituting pressure generating chambers, as shown in Fig. 5. In the latter embodiment, pressure sufficient to jet ink droplets can be generated through instantaneous evaporation of a very small amount of ink due to Joule heating by supplying electric currents to the electric resistance elements 19, 19, 19... in accordance with printing signals. Fig. 6 shows the process of producing the aforementioned spacer. In the drawing, reference numeral 20 designates a silicon single crystal substrate of crystal orientation (110) having a thickness of, for example, 220 µm, necessary for functioning as a spacer. A silicon dioxide film 21 having a thickness of, for example, about 1 µm, necessary for functioning as a protective film in anisotropic etching is formed on the whole surface of the silicon single crystal substrate by the method of heat oxidation (Fig. 6(a)). Hydrogen fluoride resisting protective films 22 and 23 having windows 24 and 25 coincident with the aforementioned through-holes 1a, 1b and 1c are formed on front and rear surfaces of the substrate 20 coated with the silicon dioxide film 21 by photolithography (Fig. 6(b)). When etching is carried out with hydrogen fluoride in this condition, the silicon dioxide film 21 is partly removed in accordance with the windows 24 and 25 to form through-holes 1a, 1b and 1c. As a result, silicon dioxide films 28 and 29 having windows 26 and 27 for silicon single crystal etching are formed (Fig. 6(c)). When etching is carried out with an aqueous solution of about 17% potassium hydroxide kept at a constant temperature, for example, 80°C, in the stage in which silicon dioxide patterning is finished as described above, portions of the windows 26 and 27 are selectively subjected to etching in parallel to the plane of crystal orientation (111) from the front and rear surfaces at a speed of about 2 µm per minute with use of the silicon dioxide patterns 28 and 29 as protective films (Fig. 6(d)). In the stage in which a through-hole 30 is formed by anisotropic etching from the front and rear surfaces in the aforementioned manner, the silicon dioxide films 28 and 29 used as masks are removed with hydrogen fluoride and then heat oxidation is carried out again to form a silicon dioxide film 31 having a sufficient thickness, for example, about 1 µm, as a protective film on the whole exposed surface. As a result, the silicon dioxide film 31 is used as a protective film against ink (Fig. 6(e)). In execution of anisotropic etching of such a silicon single crystal substrate having the plane of crystal orientation (110) as a surface, (111) planes inclined with respect to the crystal orientation (110) as shown in Fig. 7 are formed using a target pattern. Accordingly, when the flow passage resistance is to be adjusted in accordance with the depth or when the spacer and the nozzle plate are to be constituted by one substrate, the configuration of flow passages in complicated because etching is stopped at the stage in which planes inclined with respect to the surface of the substrate are formed. On the contrary, when etching is carried out so that the substrate is pierced thoroughly, such inclined planes are eliminated so that respective surfaces partitioning a through-hole are formed perpendicular to the surface of the substrate. As a result, a flow passage of the size defined by the etching pattern can be formed. Fig. 8 shows a producing process in the case where a silicon oxide crystalline substrate, for example, Z-cut synthetic crystal, is used as a substrate constituting a spacer. In the drawing, reference numeral 40 designates a Z-cut synthetic crystal substrate having a thickness, for example, of 220 µm, necessary for functioning as a spacer. A metal film 41, for example, a 50 nm (500 angstrom) chromium and 100 nm (1000 angstrom) gold film, is formed on the whole surface of the substrate by sputtering (Fig. 8(a)). Films 44 and 45 having windows 42 and 43 coincident with the aforementioned through-holes 1a, 1b and 1c are formed on front and rear surfaces of the substrate 40 coated with the metal protective film 41 by photolithography (Fig. 8(b)). Then, the gold film and the chromium film are etched with an aqueous solution of potassium iodide and iodine and in ammoniated cerium nitrate etching solution, respectively, and then the resist film is removed with a solution of nitric acid and hydrogen peroxide (Fig. 8(c)). When etching is started from the two surfaces of the substrate with an ammonium bifluoride saturation aqueous solution or a mixture solution of hydrofluoric acid and ammonium fluoride kept at a predetermined temperature, for example, 80°C, in the stage in which a predetermined etching pattern is formed in the aforementioned manner, etching progresses at a speed of 70 µm per hour (Fig. 8(d)). When the etching of the substrate is finished, the metal film 41 is removed with an aqueous solution of potassium iodide and iodine and an ammoniated cerium nitrate etching solution (Fig. 8(e)). In the case where a silicon single crystal substrate is used, it is preferable that a silicon dioxide film be formed as a protective film. It is, however, unnecessary to form a specific protective film, because the crystal has an inherent resistance to chemical corrosion. On the other hand, in the case where through-holes are formed by etching of the synthetic crystal substrate 40, overhanging portions 50, 50 as shown in Fig. 9(a) are produced from the point of view of the characteristic of the material. By carrying out over-etching in this condition, however, nothing but overhanging portions 51 with a small projecting length ΔL is produced though the area of an opening of the through-hole is increased slightly (Fig. 9(b)). Because over-etching is, however, limited, a through-hole in which overhanging portions 54, 54 having a projecting length ΔL' as small as possible remain can be formed by etching a plurality of thin synthetic crystal substrates 53, 53 in the aforementioned manner, and then laminating the plurality of substrates into a predetermined thickness, as shown in Fig. 10. In the case where one spacer is formed by laminating a plurality of substrates, means of softening the substrates while applying pressure thereto or means of adhering the substrates by a general adhesive agent may be used. The spacer formed in the aforementioned manner is fixed to as to be inserted between the nozzle plate and the plate member to thereby define a flow passage constituent member. In doing so, respective joint surfaces may be welded under pressure after applying an adhesive agent onto the respective joint surfaces. Because such assembly using an adhesive agent can be performed at ordinary temperatures with respect to the spacer, the nozzle plate and the plate member, there arises an advantage in that not only is the assembly work simple, but residual heat distortion caused by the difference between the expansion coefficients of the respective members as in the case of on alloy joining method is prevented. When an adhesive agent is used at the time of joining, there is, however, a problem in that the adhesive agent overflows from the surfaces of adhesion to the through-holes defining the pressure generating chambers and ink supply ports to thereby reduce the volume of each of the through-holes and to thereby change the ink discharge quantity, even in the case where the quantity of adhesive agent applied is carefully controlled. Fig. 11 shows an embodiment of a spacer improved to cope with this problem. In the drawing, reference numeral 60 designates a spacer member constituted by a silicon single crystal substrate or a synthetic crystal. The spacer member is formed so that chamfered portions 62a, 62a, 62a... having an angle  with respect to other surfaces of adhesion are provided in edges of partitions 62 partitioning through-holes 61 constituting pressure generating chambers and ink supply ports so as to extend in the direction of length of the partitions 62. The spacer 60 formed in the aforementioned manner is joined with pressure to the plate member 67 abutting the piezoelectric vibrators 66 and the nozzle plate 65 with the nozzle openings 65a after the adhesive agent 63 (Fig. 11(b)) is applied onto the surface thereof. Thus, an ink-jet type recording head is assembled. The adhesive agent 63 overflows from the gap between the spacer 60 and the nozzle plate 65 and the gap between the spacer 60 and the plate member 67 by pressure bonding after application thereof. The overflowing adhesive agent 63a enters into sectionally V-shaped spaces 68 formed between the chamfered portions 62a and the surface of the plate member 67 or the nozzle plate 65, is received in these spaces and spreads along the chamfered portions. Accordingly, the formation of spherical projections in specific points is prevented, as well as the change of compliance of the plate member 67, the increase of, fluid resistance of the ink supply ports to a larger value than a set value, and the reduction of the volume of each of the pressure generating chambers to a smaller value than a set value. Fig. 12 shows an embodiment in which a spacer is formed by anisotropic etching of a silicon single crystal substrate. In this embodiment, isotropic etching with hydrofluoric acid is applied at the stage in which anisotropic etching is finished. When such isotropic etching is applied, the speed of etching of acute regions such as edge lines formed by the partitions 62 partitioning the through-holes formed by anisotropic etching and the surface becomes larger than the speed of etching of flat portions so that the edge portions are substantially selectively subjected to etching. In such chamfering using etching, each section is shaped like a circular arc, but sectionally V-shaped concave spaces are formed between the nozzle plate and the plane of the plate member so that the adhesive agent overflowing from the surfaces of adhesion can be absorbed by the spaces. An adhesive agent having a high viscosity such as an epoxy adhesive agent, etc ., is used for joining of these members. Because the adhesive agent is applied by a screen printing method, a pad transferring method, a roll coating method, etc ., the quantity of the adhesive agent applied can be controlled with a high accuracy. As a result, the function of the chamfered portions 62a and 62b is not affected as long as spaces capable of absorbing the adhesive agent overflowing from the surfaces of adhesion are available. It has accordingly been confirmed that a volume capable of absorbing the adhesive agent can be secured without reduction of the strength of the wall surfaces as long as the width Δw or radius R of each of the spaces is in a range of from about 1/12 to about 1/6 the thickness of each of the partitions 62. Fig. 13 shows another embodiment of an ink-jet type recording head according to the present invention. In the drawing, reference numeral 70 designates a silicon single crystal substrate or a crystal substrate having crystal orientation (110) and having a thickness sufficient to form a spacer. As described above, through-holes 71, 71, 71... to form pressure generating chambers, through-holes 72, 72, 72... to form ink supply ports, and a through-hole to form a reservoir (not shown) are formed by etching. In this embodiment, wall surfaces 71a , 71a of the through-holes 71, 71 to form pressure generating chambers and wall surfaces 72a, 72a of the through-holes 72, 72 to form ink supply ports are arranged sectionally rectangularly so that one surface thereof has a plurality of fine planes 71a-a, 71a-a, 71a- a... and 72a-a, 72a-a, 72a-a... and predetermined steps 71a-b, 71a-b, 71a-b... and 72a-b, 72a-b, 72-a-b... Grooves 73a and 74a extending in the direction of thickness are formed in surfaces 73, 73, 73..., 74, 74, 74, ... which do not substantially contribute to forming the aforementioned fine planes. When an adhesive agent 76 such as an epoxy adhesive agent is applied onto surfaces of the thus-formed spacer 70 by a screen printing method, a pad transferring method, a roll coating method or the like to form a predetermined thickness (Fig. 14(a)) and then the nozzle plate or plate member 77 is pressed by a predetermined amount of pressure F, the adhesive agent surplus 76a overflows to the wall surface side of the spacer 70 (Fig. 14(b)). The adhesive agent spreads along the fine planes 71a-a and 72a-a due to its surface tension (Fig. 14(c)), and then the rectangular spaces constituted by the fine planes 71a-a and 72a-a and the steps 71a-b and 72a-b are filled with the adhesive agent (Fig. 14(d)). The adhesive agent, overflowing to relatively narrow wall surfaces 73 and 74, is brought into the grooves 73a and 74a by capillary force so that the adhesive agent cannot overflow to the surface. Although the aforementioned embodiment relates to the case where fine planes are provided only in wall surfaces to form pressure generating chambers and ink supply ports in which sectional areas must be controlled relatively strictly, it is apparent that the same effect in achieved in the case where a wall surface 81 of a through-hole 80 to form a reservoir and a wall surface 82 for limiting an ink supply port 83 are formed sectionally rectangularly so that the wall surfaces 81 and 82 have fine planes 81a, 81a, 81a... and 82a, 82a, 82a... and predetermined steps 81b, 81b, 81b... and 82b, 82b, 82b..., shown in Fig. 15, in the same manner as described above. When sectionally rectangular planes are formed with respect to a reservoir, the overflowing of the adhesive agent to the through-holes is prevented so that an ink-jet type recording head higher in quality can be realized. Fig. 16 shows a further embodiment of an ink-jet type recording head according to the present invention. In the drawing, reference numeral 85 designates a silicon single crystal substrate or a synthetic crystal substrate having a thickness suitable for forming a spacer. Through-holes to form pressure generating chambers 86, ink supply ports and reservoirs are formed by etching. Further, the surface of the spacer joined with the nozzle plate 88 having the nozzle openings 88a and the plate meter 89 by the adhesive agent is roughed by an abrasive material or grinding stone of mean particle size such that concave-convex portions 85a and 85b with surface roughnesses of the order of micrometers are formed. According to this embodiment, the applied adhesive agent flows into the concave-convex portions of the surfaces. When the nozzle plate and the plate member are welded with pressure in this condition, the adhesive agent surplus tending to flow out of the regions of adhesion is kept back by the capillary force of the concave-convex portions or the rough surfaces so that the adhesive agent surplus is prevented from overflowing. As a result, the choking of the nozzle openings and the change of the volume of each of the pressure generating chambers and the ink supply ports is prevented. Fig. 17 shows a further embodiment of the present invention. In the drawing, reference numeral 90 designates a spacer constituted by a silicon single crystal substrate or a synthetic crystal substrate. A nozzle plate 91 having nozzle openings 91a and a plate member 92 are fixed to one surface of the spacer and the other surface of the spacer respectively by an adhesive agent. The spacer and pressure generating devices such as piezoelectric vibrators 93 in this embodiment are fixed to a pedestal 94 so that a pressure change is induced in the pressure generating chambers by the displacements of the piezoelectric vibrators 93 to thereby discharge ink droplets. In the spacer 90, through-holes 95 to form pressure generating chambers, through-holes 96 to form ink supply ports and a through-hole 97 to form a reservoir are formed by etching in the aforementioned manner. A plurality of partition portions 98a, 98a, 98a... for limiting fluid resistance of the ink supply ports are arranged as shown in Fig 18. In this embodiment, the partition portions extend toward the through-hole 97 side, that is, toward the reservoir side, so that the length of a partition portion increases as the partition portion is arranged every four through-holes so as to be far from an ink flow-in port 99 communicating with an ink tank. In this embodiment, the flow of ink from the ink supply port 99 is partly inhibited by the partition portions 98b, 98b... extending toward the reservoir so that the ink flow is converted into an ink flow toward the through-holes 96, 96, 96... to form ink supply ports in the vicinity of the partition portions. On the other hand, a part of the ink flow not inhibited by the partition portions 98b, 98b... enters the deeper side so that the other partition portions 98b, 98b... extending thereto convert the ink flow into an ink flow toward the through-holes 96, 96, 96... to form ink supply ports placed in the vicinity of the partition portions. Accordingly, with this arrangement not only can the volume and fluid resistance be controlled with high accuracy because the spaces partitioning the pressure generating chambers, the ink supply ports and the reservoirs can be formed by etching under the same conditions, but the ink can flow without stagnation while the wasteful action of surface tension is eliminated because the wall surfaces partitioning the through-holes are perpendicular to the surface of the substrate.

Claims: An ink-jet type recording head comprising: a nozzle plate (2; 65; 77; 88; 91) provided with nozzle openings (2a; 65a; 88a; 91a) for jetting ink droplets; a spacer (1; 60; 90) provided with partitions (62) defining pressure generating chambers, ink supply ports and reservoirs; said nozzle plate (2; 65; 77; 88; 91) being fixed to one surface of said spacer (1; 60; 90), a plate member (3; 67; 89; 92) fixed to the other surface of said spacer (1; 60; 90) so as to be opposite to said nozzle plate (2; 65; 77; 88; 91), said nozzle plate (2; 65; 77; 88; 91), said spacer (1; 60; 90) and said plate member (3; 67; 89; 92) being sandwiched and fixed to each other; and a pressure generating means for applying a change of pressure for forming ink droplets to said pressure generating chambers; characterized in that: said spacer (1; 60; 90) is formed by etching one of a silicon crystalline substrate and a silicon oxide crystalline substrate from its opposite surfaces so that said pressure generating chambers, said ink supply ports and said reservoirs are formed in the form of through-holes (1a,b,c; 10, 11, 12; 71, 72; 95, 96, 97) communicating with each other; and said spacer (1; 60; 90) is formed such that its partitions (62) for partitioning said pressure generating chambers (1a; 10; 71; 95) and said ink supply ports (1b; 11; 72; 96) are in the form of cantilevers which have their free ends adjacent the reservoir (1c; 2; 97) and which are connected to a body on the nozzle opening side. An ink-jet type recording head according to Claim 1, wherein said silicon crystalline substrate is a silicon single crystal substrate having a crystal orientation (110), and wherein wall surfaces (71a, 72a) partitioning said through-holes (71, 72) are formed as surfaces perpendicular to that (110) surface of said substrate which is fixed to said nozzle plate. An ink-jet type recording head according to Claim 1 or 2, wherein one surface (1b-a) of said walls partitioning said ink supply ports (1b) is formed in the same plane as one surface (1a-a) of the walls partitioning said pressure generating chambers (1a). An ink-jet type recording head according to one of the preceding Claims, wherein one surface of the walls partitioning said ink supply ports is formed so as to be in the same plane as that of one of the wall surfaces partitioning said pressure generating chambers at a side where two of said wall surfaces intersect at an acute angle. An ink-jet type recording head according to one of the preceding Claims, wherein said silicon oxide crystalline substrate is a synthetic crystal substrate. An ink-jet type recording head according to one of the preceding Claims, wherein said partitions (62) of said spacer (60) have chamfered portions (62a) with a width of from about 1/12 to about 1/6 as much as the width of said partitions (62), in lengthwise edge lines opposite to said nozzle plate (65) and said plate member (67), and wherein said spacer (60) is fixed to said nozzle plate (65) and said plate member (67) by an adhesive agent (63) so that spaces defined by said chamfered portions (62a), said nozzle plate (65) and said plate member (67) function as adhesive agent (63) absorbing spaces. An ink-jet type recording head according to one of Claims 1 to 5, wherein said spacer is formed so as to be rectangular in section so that each of the partitions thereof is constituted by a plurality of planes (71a-a, 72a-a) and predetermined steps (71a-b, 72a-b), and wherein said spacer is fixed to said nozzle plate and said plate member by an adhesive agent (76) so that said steps (71a-b, 72a-b) function as adhesive agent (76) absorbing spaces. An ink-jet type recording head according to one of the preceding Claims, wherein surfaces of said spacer (1; 60; 90) are roughened. An ink-jet type recording head according to one of the preceding Claims, wherein said pressure generating means are constituted by piezoelectric vibrators (4; 93) which vibrate in an axial direction, said piezoelectric vibrators (4; 93) being fixed at one end to a pedestal (5; 94) so that their one end abut respective diaphragms opposite to said pressure generating chambers, and wherein predetermined regions of said ink supply ports and said reservoirs are fixed to said pedestal (5; 94). An ink-jet type recording head according to one of the preceding Claims, wherein said pressure generating means comprise heaters for generating Joule heat fixed to the plate member partitioning said pressure generating chambers. An ink-jet type recording head according to one of the preceding Claims, wherein said partitions partitioning said ink supply ports extend toward the reservoir side in a manner so that said partitions increase in length at every plural ones of said partitions in a direction away from an ink supply port for an ink tank.

Inventors: FURUTA TATSUO, HOSOKAWA HIROSHI, KANAI FUMIYUKI, KOBAYASHI ATSUSHI, SAKAI SHINRI, FURUTA, TATSUO, HOSOKAWA, HIROSHI, KANAI, FUMIYUKI, KOBAYASHI, ATSUSHI, SAKAI, SHINRI
Applicants: SEIKO EPSON CORP, SEIKO EPSON CORPORATION
Application year: 1993
Main classification: B41J2
IPC codes: B41J2