Liquid injector, method of manufacturing the injector, and ink-jet spray using the injector

[0002] The present invention relates to a small-sized liquid injector in a printing head in an ink-jet printer for delivering liquid such as ink, an ink-jet spray employing the liquid injector, and a method of manufacturing the liquid injector.

[0003] A conventional liquid injector includes a pressurizing-chamber-forming layer having pressurizing chambers provided therein, a pressurizing element on one side of the pressurizing-chamber-forming layer, and a substrate on the other side of the pressurizing-chamber-forming layer. Each the pressurizing chamber has a first opening provided directly on the substrate, a second opening provided directly on the pressurizing element, a liquid eject outlet which is opening to the outside, and a liquid feed inlet provided therein for feeding liquid into the pressurizing chamber. A pressure, upon being applied from the second opening by the pressurizing element, can be transmitted into the pressurizing chamber and eject the liquid from the liquid eject outlet to the outside of the pressurizing chamber.

[0004] In the conventional liquid injector, the pressurizing chamber, liquid eject outlet, and liquid feed inlet are formed in 3-dimensional shape with components made of ceramic material or stainless steel bonded one another. Since including the components element together, the liquid injector has a liquid eject outlet side thereof increased in area and can thus be hardly reduced in overall size.

[0005] A liquid injector which has a liquid eject outlet side thereof reduced in area is provided, thus contributing to a small-dimension ink-jet printer. The liquid injector includes: a head block including a first pressurizing-chamber-forming layer having a first pressurizing chamber formed therein for being filled with liquid, a first liquid eject outlet and a first liquid feed inlet through which the liquid is passed from the first pressurizing chamber; and a first actuator on the first pressurizing-chamber-forming layer for expanding and contracting an internal volume of the first pressurizing chamber. The first pressurizing chamber, the first liquid eject outlet, and the first liquid feed inlet are linearly aligned.

[0006] FIG. 1 is an exploded perspective view of a liquid injector according to Embodiment 1 of the present invention;

[0007] FIG. 2 is a cross sectional view of pressurizing chambers as a primary part in the liquid injector according to Embodiment 1;

[0008] FIG. 3 is a cross sectional view illustrating a process of manufacturing the liquid injector according to Embodiment 1;

[0009] FIG. 4 is a cross sectional view illustrating a process of manufacturing the liquid injector according to Embodiment 1;

[0010] FIG. 5 is a cross sectional view illustrating a process of manufacturing the liquid injector according to Embodiment 1;

[0011] FIG. 6 is a cross sectional view illustrating a process of manufacturing the liquid injector according to Embodiment 1;

[0012] FIG. 7 is a cross sectional view illustrating a process of manufacturing the liquid injector according to Embodiment 1;

[0013] FIG. 8 is a cross sectional view illustrating a process of manufacturing the liquid injector according to Embodiment 1;

[0014] FIG. 9 is a cross sectional view illustrating a process of manufacturing the liquid injector according to Embodiment 1;

[0015] FIG. 10 is a cross sectional view illustrating a process of manufacturing the liquid injector according to Embodiment 1;

[0016] FIG. 11 is a cross sectional view illustrating a process of manufacturing the liquid injector according to Embodiment 1;

[0017] FIG. 12 is a perspective view illustrating a process of manufacturing the liquid injector according to Embodiment 1;

[0018] FIG. 13 is a perspective view illustrating a process of manufacturing the liquid injector according to Embodiment 1;

[0019] FIG. 14 is a perspective view illustrating a process of manufacturing the liquid injector according to Embodiment 1;

[0020] FIG. 15 is a perspective view of an ink-jet pen using the liquid injector according to Embodiment 1;

[0021] FIG. 16 is a perspective view of a head block as a primary part in a liquid injector according to Embodiment 2 of the present invention;

[0022] FIG. 17 is a cross sectional view illustrating a process of manufacturing the liquid injector according to Embodiment 2;

[0023] FIG. 18 is a cross sectional view illustrating a process of manufacturing the liquid injector according to Embodiment 2;

[0024] FIG. 19 is a cross sectional view illustrating a process of manufacturing the liquid injector according to Embodiment 2; and

[0025] FIG. 20 is a cross sectional view illustrating a process of manufacturing the liquid injector according to Embodiment 2.

[0026] FIG. 1 is an exploded perspective view of a liquid injector according to Embodiment 1 of the present invention. A head block 4 includes a pressurizing-chamber-forming layer 1 made of silicon single-crystal material, a pressurizing element 2 mounted to one side of the pressurizing-chamber-forming layer 1, and a substrate 3 made of glass mounted to the other side of the pressurizing-chamber-forming layer 1. The head block 4 is bonded at its rear end to a liquid feed reservoir 5 for feeding liquid. First lead-out electrodes 15 are provided on the head block 4 and connected to respective second lead-out electrodes 16 mounted on a flexible substrate 17. The liquid feed reservoir 5 has a liquid supply inlet 6 at the rear end, a liquid passage 7 communicated to the liquid supply inlet 6, and an opening at the other end thereof.

[0027] FIG. 2 is a cross sectional view taken vertically to a longitudinal direction of pressurizing chambers 8, a primary part in the liquid injector. The pressurizing chambers 8 fully extend from one end to the other end of the pressurizing-chamber-forming layer 1. The forming layer 1 is bonded at one side to the pressurizing element 2 with by an adhesive layer 9 and bonded at the other end directly to the glass substrate 3 without adhesive. This allows the pressurizing chambers 8 to have both, upper and lower, opening sides are isolated from the outside. As a result, the assembly of them can 4 can be fabricated to any desired, intricate three-dimensional shape easily.

[0028] As shown in FIG. 1, each pressurizing chamber 8 has a liquid eject outlet 10 and a liquid feed inlet 11 (not shown) provided at both ends thereof The pressurizing chamber 8 is communicated to the liquid feed passage 7 through the liquid feed inlet 11. This allows the liquid such as printing ink to flow from the liquid feed inlet 6 to the liquid feed passage 7, the liquid feed inlet 11, the pressurizing chamber 8, and the liquid eject output 10. The liquid feed passage, since being constantly filled with the liquid or ink, can readily deliver the liquid to each pressurizing chamber.

[0029] The pressurizing element 2 incorporates a layer structure including second electrode strips 12, piezoelectric strips 13 made of lead titanate/zirconate, and a pressing-force-generating layer 14 made of conductive material such as chrome or titanium from above in this order. The lead titanate/zirconate strip, since expanding or contracting vertically in an electric field along its thickness direction, functions as an actuator for increasing the pressure in the pressurizing chamber 8. The pressurizing-force-generating layer 14 in this embodiment, upon being electrically conductive, may function as the first electrode layer. If the pressing-force-generating layer 14 is not conductive, the first electrode layer may be provided between the piezoelectric strip 13 and the pressing-force-generating layer 14. The pressurizing element 2 is bonded to the pressurizing-chamber-forming layer 1 with the adhesive layer 9 on the side to the pressurizing-chamber-forming layer 1 of the pressing-force-generating layer 14. The second electrode strips 12 and the piezoelectric strips 13 are provided for the pressurizing chambers 8 provided below. Each pressurizing chamber 8 has the liquid eject output 10 and the liquid feed inlet 11 provided linearly at both ends thereof.

[0030] In this liquid injector, when the second lead-out electrodes 16 connected to the respective second electrode strips 12 on the respective pressurizing chambers 8 are provided with a voltage, the pressurizing element 2 pressurizes the pressurizing chambers 8. As a result, the ink is pressed and moved to the liquid eject outlet 10 of each pressurizing chamber 8. Upon being ejected, droplets of the ink are patterned on a recording medium such as a sheet of paper for printing. Since the liquid feed inlet 11 and the liquid eject outlet 10 of the pressurizing chamber 8 are linearly aligned to each other, their installation area on the head block is reduced even having the plural pressurizing chambers 8. This allows the liquid feed reservoir 5 to be connected linearly to the liquid feed inlets 11, thus having a linear structure of the liquid injector. Accordingly, the liquid injector of the embodiment can has a reduced overall size. The liquid injector having such a linear construction may preferably be applied to a long, narrow product such as a pen, thus providing a portable ink-jet pen.

[0031] The head block 4 includes the liquid eject outlet 10, the pressurizing chamber 8, and the liquid feed inlet 11 which are linearly aligned. This allows the pressurizing-chamber-forming layer 1 to have a simple structure thus contributing to efficient mass production of the liquid injector. If the pressurizing-chamber-forming layer 1 is made of a silicon single-crystal sheet, the pressurizing chambers 8 can be formed easily by etching. Further, the pressurizing-chamber-forming layer 1 of a silicon single-crystal sheet can be mirror-like-finished and easily bonded at its mirror-like-finished side with a corresponding mirror-like-finished side of the glass substrate 3 to be unified. Since the cross section of the liquid passage 7 of the liquid feed reservoir 5 is greater than that of the liquid feed inlets 11 of the pressurizing-chamber-forming layer 1, the liquid is distributed to the liquid feed inlets 11 uniformly. Moreover, the head block and the liquid feed reservoir can easily be bonded to each other without misalignment. When the liquid feed reservoir 5 is made of plastic material at its opening 18 and arranged integral with the flexible substrate 17, the reservoir 5 can be bonded to the head block 4 at once by thermal bonding. Furthermore, when the liquid feed reservoir 5 is flexible, the liquid injector can apply the liquid to any curved object, e.g. an inner wall of a curved conduit.

[0032] A method of manufacturing the liquid injector will now be described.

[0033] FIG. 3 to FIG. 8 are cross sectional views illustrating processes of manufacturing the liquid injector according to Embodiment 1.

[0034] As shown in FIG. 3, a pressurizing element base 2A is formed on a pressurizing-element-forming layer 19 made of magnesium oxide single-crystal material. The pressurizing element base 2A is converted to the pressurizing element 2 by patterning. Similarly, a second electrode strip layer 12A, a piezoelectric strip layer 13A, and a pressing force generating layer 14 are formed.

[0035] Then, as shown in FIG. 4, plural pressurizing-element-forming layers 19 having the pressurizing element bases 2A provided thereon are bonded at its side to pressurizing element base 2A with an adhesive, which is softer than the silicon single-crystal material, to the pressurizing chamber-forming layer 1 of the silicon single-crystal material as shown in FIG. 4.

[0036] Then, other side of the side to the pressurizing element base 2A of the pressurizing-chamber-forming layer 1 is dry-etched with dry-etching gas containing fluorine, e.g. sulfur hexafluoride, to form the liquid eject outlets 10 and the liquid feed inlets 11, as shown in FIG. 5 and FIG. 6. The pressurizing-chamber-forming layer 1 is etched at two steps to modify the depth at the liquid eject outlets 10 and the liquid feed inlets 11 shown in FIGS. 5 and 6, however, the layer 1 may be subjected to a single etching process if the depth is not modified.

[0037] Then, as shown in FIG. 7, the pressurizing-chamber-forming layer 1 is again dry-etched with sulfur hexafluoride to shape the pressurizing chambers 8 until the layer 1 is perforated. For forming the pressurizing chambers 8, the pressurizing-chamber-forming layer 1 is etched from the other side than the side bonded to the pressurizing element bases 2A with the adhesive. The etching of the pressurizing chamber forming layer 1 is terminated upon reaching the adhesive layer. This allows the pressurizing chambers 8 to be simply fabricated by etching from one side to the other side of the pressurizing-chamber-forming layer 1. The pressurizing element bases 2A are unified with the pressurizing-element-forming layers 19, and then, bonded to one side of the pressurizing chamber forming layer 1 with the adhesive. Thereby, the pressurizing element bases 2A can first be developed on the pressurizing element forming layers 19 easily. Since the pressurizing element bases 2A with the pressurizing element forming layers 19 are then bonded by the adhesive to the pressurizing chamber forming layer 1, the liquid injector can be finished efficiently. 40 mm square or greater of a magnesium oxide single-crystal material which is commonly used as the pressurizing element forming layer can be hardly be formed. On the contrary, the silicon single-crystal material can be shaped to a greater size. The pressurizing chamber forming layer 1 of the silicon single-crystal material bonded with the pressurizing element forming layers can be processed. Therefore, more head block can be fabricated at once without difficulty. The head block, upon having the size equal to a fraction of the pressurizing-element-forming layer divided by an integer, can be fabricated efficiently.

[0038] In another method of forming the pressurizing chambers 8, as shown in FIG. 8, a metal layer 23 consisting mainly of gold is developed on the other side than the side to the pressurizing element base 2A of the pressurizing-element-forming layer 19 before the pressurizing chamber forming layer 1 is dry-etched. This allows the pressurizing-element-forming layers 19 to be made of a magnesium oxide single-crystal material which can thus be removed easily. The pressurizing-element-forming layer 19, upon being made of magnesium oxide single-crystal material, does not have a so high thermal conductivity. This may cause accumulation of heat in the magnesium oxide single-crystal material during the dry-etching process, and thus making the process unstable. As a result, a rate of the etching process is hardly consistent. Since the pressurizing-element-forming layer 19 of the magnetic oxide single-crystal material is coated with the metal or heat-radiating layer which has a thermal conductivity than magnesium oxide at the other side than the side to the pressurizing element base 2A, the heat accumulation during the dry etching process can successfully be avoided. Accordingly, the etching rate may be consistent thus contributing to the manufacturing of the pressurizing chambers 8 appropriately.

[0039] Then, the pressurizing chamber forming layer 1, after being provided with the pressurizing chambers 8, is rinsed together with the pressurizing-element-forming layers 19 with rinsing agent of acid type. As described previously, the metal layer 23 consisting mainly of gold can prevent the magnesium oxide single-crystal material of the pressurizing-element-forming layers 19 from being removed by the acid type rinsing agent during the rinsing process.

[0040] After being rinsed with the acid type rinsing agent, the pressurizing-chamber-forming layer 1 is bonded to the glass substrate 3 at the other side than the side to the pressurizing-element-forming layer 19 by direct bonding process, as shown in FIG. 9. The pressurizing-chamber-forming layer 1, since having been rinsed with the acid type rinsing agent, can directly be bonded to the glass substrate 3 easily. Further, the glass substrate 3 and the pressurizing-chamber-forming layer 1, upon being mirror-like-finished at the bonding side, can be bonded tightly to each other easily.

[0041] After the bonding, the metal layer 23 consisting mainly of gold (not shown in FIG. 9) is removed with neutral or like etching liquid such as iodine/potassium iodide solution.

[0042] Then, the pressurizing-element-forming layers 19 of the magnesium oxide single-crystal material is removed with phosphate solution, as shown in FIG. 10, and a second electrode layer 9A and a piezoelectric layer 10A are patterned to form the second electrode strip 12 and the piezoelectric strip 13 over each pressurizing chamber 8, respectively.

[0043] Then, the element is divided by dicing into the head blocks 4, as shown in FIG. 11. Since the neutral or like solution removes the heat radiating layer 23 consisting mainly of gold, the pressurizing-element-forming layers 19 of the magnesium oxide provided below the layers 23 is hardly corroded. The pressurizing-element-forming layers 19 remain intact and can thus be removed with the phosphate solution. The electrode layers provided below, since not being corroded with the phosphate solution, are properly patterned to form the pressurizing element 2. The head block 4, since being devided by dicing, has the liquid eject outlets 10 and liquid feed inlets 11 aligned along the line of the dicing and thus exposed evenly to the outside.

[0044] Then, the head block 4 is bonded to the liquid feed reservoir 5 to complete the liquid injector, as shown in FIG. 12. As shown in FIG. 1, the opening 18 of the liquid feed reservoir 5 is greater than the cross section of the head block 4 at the side to the liquid feed inlet 11. The liquid feed reservoir 5, upon being made of plastic material at the opening 18, can simply be inserted into and joined to the head block 4 by thermal bonding.

[0045] The flexible substrate 17 may be coupled to the liquid feed reservoir 5 in advance, as shown in FIG. 13. This allows the flexible substrate 17 to be connected to the first lead-out electrodes 15 of the head block 4 when the liquid feed reservoir 5 and the head block 4 are bonded to each other, as shown in FIG. 14.

[0046] The finished liquid injector 20 may be mounted as an ink-jet spray to the tip of a pen, as shown in FIG. 15. The pen may include a knob 21 provided thereon for controlling the amount of the ink to be ejected. The ink-jet spray may be turned on by pressing a switch 22, and can spray an amount of the link determined with the knob 21. Three or more of the liquid injectors of this embodiment, upon being mounted in a pen, can eject corresponding color inks at once at different gradations to develop a desired color for printing. The ejected inks are sprayed out in a larger area. Since the gradations of the color inks are modified by movement of the pen, a resultant color may range infinitely. The spray can create a full color print. The color of print may not be anticipated by the operator, and then the spray may be used as a toy or an artistic painting tool.

[0047] FIG. 16 is a perspective view of a head block of a liquid injector according to Embodiment 2 of the present invention.

[0048] As shown, a head block 30 includes a glass substrate 26, pressurizing-chamber-forming layers 25 of silicon single-crystal material on both sides of the glass substrate 26, and a pressurizing element 27 on one of the pressurizing-chamber-forming layers 25. The head block 30 is connected at the rear end to a liquid feed reservoir 5 (not shown) for supply of liquid. First lead-out electrodes 15 (not shown) provided on the head block 30 are connected to respective second lead-out electrodes 16 (not shown) provided on a flexible substrate 17 (not shown) (See FIG. 1).

[0049] Each pressurizing chamber extends between a liquid eject outlet 31 and a liquid feed inlet 32 (not shown). Similarly to Embodiment 1, the liquid feed reservoir 5, since being connected to the liquid feed inlets 32, can drive the liquid such as ink to flow to a liquid passage, i.e., the liquid feed inlets 32, the pressurizing chambers, and the liquid eject outlets 31. The liquid feed reservoir 5, upon having an opening greater than the cross section of the head block 30 at a side to the liquid feed inlet 32, can be bonded to the head block 30 easily. Plural pressurizing chamber forming layers 25, upon being bonded to both sides of the glass substrate 26 at the other side than the side to the pressurizing element 27, can increase liquid eject outlets 31 and liquid feed inlets 32 and locate them more closely to each other. This provides the liquid injector with more pressurizing chambers. When two, upper and lower, liquid eject outlets 31 and the liquid feed inlets 32 are vertically dislocated from each other about the glass substrate 26, the liquid injector can have the liquid eject outlets 31 positioned at high density.

[0050] A method of manufacturing the liquid injector according to Embodiment 2 will now be described.

[0051] FIG. 17 to FIG. 20 illustrate a procedure of fabricating the head block of the liquid injector according to Embodiment 2. The steps prior to a step shown in FIG. 17 are identical to those of Embodiment 1 shown in FIG. 3 to FIG. 7.

[0052] Assemblies including the respective pressurizing-chamber-forming layers 25 and pressure-element-forming layer base 32 are bonded directly to both respective sides of the glass substrate 26 at the other side than the side to the pressurizing element 27 to provide an assembly shown in FIG. 18. It may preferably be arranged to have two groups of the liquid eject outlets 31 and the liquid feed inlets 32 dislocated vertically from each other about the glass substrate 26. This permits the head block 30 to have more liquid eject outlets 31 and liquid feed inlets 32. Alternating the liquid eject outlets 31 and the liquid feed inlets 32 allows the head block 30 to be obtained easily.

[0053] Then, after the pressurizing-chamber-forming layers 25 have been bonded directly to the glass substrate 26, the pressurizing-element-forming layers of magnesium oxide are immersed in solution such as phosphate and etched until the pressurizing element 27 is exposed as shown in FIG. 19. Then, a common photo etching process to develop a pattern of second electrodes 28 and piezoelectric strips 29 is performed.

[0054] Then, as shown in FIG. 20, the element is divided along predetermined cutting lines into the head blocks 30. Thereby, the liquid eject outlets 31 and the liquid feed inlets 32 are formed by the final dividing process and can thus be aligned linearly being exposed to the outside.

[0055] The head block 30 is bonded to the liquid feed reservoir at the end to the liquid feed inlet 27, and then the liquid injector of Embodiment 2 is completed similarly to Embodiment 1.