JP2013248762A - Inkjet recording head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized and readily integrated thermal actuator type inkjet recording head increased in degree of freedom in liquid selection, having no problem of kogation, large in drive volume, large in drive energy, and high in reliability.SOLUTION: An inkjet recording head of one embodiment includes a pressure generation chamber having a nozzle plate provided with a nozzle opening for discharging ink, a sidewall part, and a movable plate facing the nozzle plate with the sidewall part interposed. The movable plate includes a first elastic film having a fixed end whose peripheral part is fixed to the sidewall part, and a second elastic film laminated on the first elastic film extending from the fixed end of the first elastic film toward a central part, not laminated on the central part of the first elastic film, and different from the first elastic film in thermal expansion coefficient.

Description

  Embodiments described herein relate generally to an ink jet recording head.

  In an ink jet recording apparatus used as an image recording apparatus (image forming apparatus) such as a printer, a facsimile machine, a copying apparatus, or a plotter, an ink jet recording head that is a droplet discharge head including a microactuator is used. An ink jet recording head includes a nozzle that ejects ink droplets, a liquid chamber (also referred to as a pressure chamber, a pressure chamber, a pressurized liquid chamber, an ink flow path, and a discharge chamber) that communicates with the nozzle, Pressure generating means (actuator means) for pressurizing the ink in the chamber. Then, the actuator means is driven to pressurize the ink in the liquid chamber and eject ink droplets from the nozzles.

  A conventional ink jet recording head is a piezoelectric type that discharges ink droplets by deforming and displacing a diaphragm that forms the wall surface of a liquid chamber using a piezoelectric element in terms of the type of actuator means. Bubble type that generates bubbles by ink film boiling using a heating resistor installed to eject ink droplets, thermal actuator type that generates actuator effect due to mechanical deformation accompanying thermal expansion, liquid chamber It is roughly classified into an electrostatic type that ejects ink droplets by deforming and displacing the diaphragm with an electrostatic force using a diaphragm (or an electrode integrated with the diaphragm) forming a wall surface and a counter electrode.

JP-A-2-030543

  Among the ink jet recording heads described above, the piezoelectric type has an advantage that there is no restriction on the type of ink to be used because the piezoelectric element does not directly contact the ink and the heat generation of the piezoelectric element can be ignored. On the other hand, high heat treatment (PZT firing) of piezoelectric elements, and when using stacked piezoelectric elements, mechanical and thermal technical issues such as segmentation and alignment of individual piezoelectric elements are significant, and complicated processes and equipment are used. Cost increases.

  In the bubble type, since the heater can be made very small by application of semiconductor technology, it has the advantage of easy integration and miniaturization of the head. It becomes as high as 400 to 450 ° C. For this reason, since an extremely high heat is applied to the ink, the ink composition changes, and kogation occurs at the ink contact portion of the heater. For this reason, it is important to select ink dyes, it is difficult to use pigment ink, and there is a limit to improving the quality of color images. In addition, the generation of bubbles due to deterioration of heaters caused by kogation becomes poor, and heat is high. Defects such as heater breakage due to deterioration of the heater due to cracks are likely to occur.

  In addition, the thermal actuator type can be divided into those using a cantilever bimetal and those using a cantilever buckling deformation, but those using a cantilever bimetal are driven energy ( There is a problem that the driving pressure is small and there is a liquid leak at the free end, and the one using the buckling deformation of the double-supported beam has a small driving volume.

  Further, in the case of the electrostatic type, the microfabrication process is difficult as in the piezo type, the material selectivity is low, the process steps are long, and the cost is high.

  In an ink jet recording head, in order to increase the ability to eject ink droplets, it is important to increase the driving volume and the driving energy applied to the ink during driving. The drive energy is generally proportional to the product of the drive volume and the pressure applied to the ink.

  In view of such circumstances, the present invention is a thermal actuator type in which the degree of freedom in selecting a liquid is improved, there is no problem of kogation, the driving volume is large, the driving energy is large, the reliability is small, and the integration is easy. It is an object of the present invention to provide an ink jet recording head.

  One ink jet recording head according to an embodiment includes a nozzle plate provided with a nozzle opening for ejecting ink, a side wall, and a movable plate facing the nozzle plate with the side wall interposed therebetween. The movable plate includes a first elastic film having a fixed end whose peripheral part is fixed to the side wall part, and extends from the fixed end of the first elastic film toward a central part, and The first elastic film is laminated, and is not laminated at the center of the first elastic film, and includes the first elastic film and a second elastic film having a different thermal expansion coefficient.

FIG. 2 is a top view of the ink jet recording head according to the first embodiment. It is AA sectional drawing of FIG. FIG. 5 is a diagram illustrating an operation of the ink jet recording head according to the first embodiment. It is a figure which shows the manufacturing method of the ink jet type recording head of 1st Embodiment. FIG. 6 is a top view of an ink jet recording head according to a second embodiment. It is AA sectional drawing of FIG. It is a figure which shows operation | movement of the ink jet type recording head of 2nd Embodiment. It is a figure which shows operation | movement of the modification of the ink jet type recording head of 1st thru | or 2nd Embodiment. It is a figure which shows operation | movement of the modification of the ink jet type recording head of 1st thru | or 2nd Embodiment. FIG. 6 is a top view of an ink jet recording head according to a third embodiment. It is AA sectional drawing of FIG. It is a top view of an ink jet recording head according to a fourth embodiment. FIG. 3 is a schematic diagram showing deformation behavior of the piezoelectric film and the elastic film of Example 1. It is a figure which shows the rigidity ratio of the elastic film of Example 1, and the relationship of a drive volume and drive energy. It is a figure which shows the ratio of the edge part length of the elastic film of Example 1, and the relationship of a drive volume and drive energy. It is a figure which shows the rigidity ratio of the elastic film of Example 2, and the relationship of a drive volume and drive energy. It is a figure which shows the ratio of the edge part length of the elastic film of Example 2, and the relationship of a drive volume and drive energy. 6 is a cross-sectional view of an ink jet recording head of Comparative Example 1. FIG. 6 is a cross-sectional view of an ink jet recording head of Comparative Example 2. FIG. It is a comparison figure of the simulation result of an Example and a comparative example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
The ink jet recording head of the present embodiment includes a pressure generating chamber having a nozzle plate provided with a nozzle opening for ejecting ink, a side wall, and a movable plate facing the nozzle plate with the side wall interposed therebetween. The movable plate has a first elastic film having a fixed end whose peripheral part is fixed to the side wall, and a first elastic film extending from the fixed end of the first elastic film toward the central part. The first elastic film is laminated and is not laminated at the central portion of the first elastic film, and includes a first elastic film and a second elastic film having a different thermal expansion coefficient.

  The ink jet recording head according to the present embodiment has the above-described configuration, so that the end portion of the movable plate formed by laminating the first elastic film and the second elastic film is greatly bent and deformed when heated. Further, the central portion of the movable plate made only of the first elastic film causes a large buckling deformation opposite to the end portion. As a result of the combination of the bending deformation and the buckling deformation, it becomes possible to provide an ink jet recording head having a large driving volume and a large driving energy by causing a large deformation as a whole of the movable plate.

  FIG. 1 is a top view of the ink jet recording head according to the first embodiment. The ink jet recording head 100 according to the present embodiment is a thermal actuator ink jet recording head.

  2 is a cross-sectional view taken along the line AA in FIG. The ink jet recording head 100 includes a plurality of pressure generation chambers 11. The inside of the pressure generation chamber 11 is hollow to be filled with ink. FIG. 2 shows a cross-sectional structure in the transverse direction of one pressure generation chamber among the plurality of pressure generation chambers 11 included in the ink jet recording head 100.

  The ink flow path and the pressure generation chamber 11 of the ink jet recording head 100 are formed using the flow path forming substrate 10. As the flow path forming substrate 10, for example, a silicon substrate having a thickness of about 100 to 300 μm is used. The thickness of the silicon substrate is desirably about 150 to 250 μm, more desirably about 200 μm. This is because the arrangement density of the pressure generating chambers 11 can be increased while maintaining the rigidity of the partition between the adjacent pressure generating chambers 11.

  A nozzle plate 20 made of a silicon substrate is connected to one surface of the flow path forming substrate 10. The nozzle plate 20 has a nozzle opening 21 for discharging ink, for example, by etching.

  A movable plate 30 is provided on the other surface of the flow path forming substrate 10. The pressure generating chamber 11 is configured by the nozzle plate 20, the side wall 10a, and the movable plate 30 facing the nozzle plate 20 with the side wall 10a interposed therebetween.

  The movable plate 30 is composed of a first elastic film 30a and a second elastic film 30b. The first elastic film 30a and the second elastic film 30b have different thermal expansion coefficients.

  As for the 1st elastic film 30a, the side wall part 10a, 10b side of the flow-path formation board | substrate 10 becomes a fixed end. And the 2nd elastic film 30b is laminated | stacked on the edge part 31 of the 1st elastic film 30a, and is not laminated | stacked on the center part 32 of the 1st elastic film 30a. That is, the second elastic film 30b extends from the fixed end of the first elastic film 30a toward the central portion and is laminated, but is not laminated on the central portion 32.

  When viewed from the cross-section of FIG. 2, when the free portion of the movable plate, that is, the distance between the side wall 10 a and the side wall 10 b (equal to the width inside the pressure generating chamber 11) is 1, the end 31 The ratio of the second elastic film 30b laminated on the first elastic film 30a is in the range of 0.3 to 0.4 on one side, that is, 0.6 to 0.8 on both sides. It is desirable to be. This is because the drive volume and drive energy of the ink jet recording head 100 can take the maximum values by being in this range.

The thermal expansion coefficients of the first elastic film 30a and the second elastic film 30b are desirably different by 5 × 10 ⁻⁶ / ° C. or more. This is because if it is less than this value, sufficient drive volume and drive energy for ejecting ink may not be obtained.

  Moreover, it is desirable that the rigidity ratio of the first elastic film 30a and the second elastic film 30c is 0.3 or more and 1.8 or less. If this range is exceeded, sufficient drive volume and drive energy may not be obtained for ejecting ink.

  The first elastic film 30a is formed of, for example, a silicon oxide film (silicon dioxide) having a thickness of 1 to 2 μm formed in advance by thermal oxidation. The first elastic film 30 a constitutes a part of the pressure generation chamber 11 that communicates with the nozzle opening 21.

  It is desirable that the silicon oxide film be amorphous from the viewpoint that uniform deformation can be realized. It is also desirable from the viewpoint of easy production of a film having a stable composition and characteristics. Furthermore, it is desirable from the viewpoint of good consistency with conventional semiconductor processes. From the same viewpoint, it is also desirable to apply an amorphous silicon nitride film. Note that a film other than the silicon oxide film or the silicon nitride film can be applied to the first elastic film 30a as long as it has elasticity.

  The second elastic film 30b is made of copper having a thickness of about 2 μm, for example. The second elastic film 30b is not formed in the central portion 32 of the first elastic film 30a.

  For example, a nozzle plate 20 made of a silicon substrate is connected to the side wall portions 10 a and 10 b of the flow path forming substrate 10. The nozzle plate 20 constitutes a part of the pressure generation chamber 11. A nozzle opening 21 is formed in the nozzle plate 20 by etching, for example.

  Here, the size of the pressure generation chamber 11 that applies ink droplet ejection pressure to the ink and the size of the nozzle opening 21 that ejects ink droplets are optimized according to the amount of ink droplets to be ejected, the ejection speed, and the ejection frequency. The For example, when recording 360 ink droplets per inch, the nozzle opening 11 needs to be accurately formed with a groove width of several tens of μm.

  The pressure generation chambers 11 and the common ink chamber 60 are communicated with each other via ink supply paths 61 formed at positions corresponding to one end portions of the pressure generation chambers 11 of the nozzle plate 20. Ink is supplied from the common ink chamber 60 through the ink supply path 61 and is distributed to the pressure generating chambers 11.

  The ink jet recording head 100 shown in FIGS. 1 and 2 takes in ink from an ink introduction port 62 connected to an external ink supply means (not shown), and the inside from the common ink chamber 60 to the nozzle openings 21 of the pressure generating chambers 11. Fill with ink.

  The ink jet recording head 100 includes an energization electrode that is connected to the second elastic film 30b and causes the second elastic film 30b to generate resistance heat. The energization electrodes are individual electrodes 72 and common electrodes 74 provided in each pressure generation chamber 11.

  In accordance with a recording signal from an external drive circuit (not shown), a voltage is applied to the second elastic film 30b via a lead 71 connected to the individual electrode 72 of each pressure generating chamber 11 and a lead 73 connected to the common electrode 74. The second elastic film 30b generates heat. Thereby, the second elastic film 30b is heated.

  The end portion 31 of the first elastic film 30a is bent and deformed in a convex shape due to the difference in thermal expansion coefficient between the first elastic film 30a and the second elastic film 30b, and the central portion 32 of the first elastic film 30b is It is buckled and deformed into a concave shape by compressive stress. As the movable plate 30 is greatly deformed in this manner, the pressure in the pressure generating chamber 11 is increased and ink droplets are ejected from the nozzle openings 21.

  In the ink jet recording head 100 of the present embodiment, the second elastic film 30b has a zigzag shape in order to increase the heat generation amount by increasing the resistance of the second elastic film 30b. A resistance heating element such as copper having a small specific resistance value can be used.

  In the ink jet recording head 100 of the present embodiment, the second elastic film 30b is laminated on the movable plate 30 only on the end 31 of the first elastic film 30a. For this reason, since the movable plate 30 is easily deformed only by the first elastic film 30a at the central portion 32 of the first elastic film 30a, the end 31 can be largely deformed by the bimetal effect. Further, the movable plate 30 undergoes a large buckling deformation at the central portion 32 due to compressive stress. Therefore, the displacement amount of the movable plate 30 can be improved, and an ink jet recording head having a large driving volume and a large driving energy and high driving efficiency is realized.

  In addition, the ink jet recording head 100 according to the present embodiment can realize an environment-friendly ink jet recording head that does not contain harmful substances such as lead used in the piezoelectric ink jet recording head. In addition, the first elastic film 30a and the second elastic film 30b can easily produce a stable composition and have good compatibility with the semiconductor process. Therefore, an ink jet recording head having stable characteristics can be manufactured at low cost.

  FIG. 3 is a diagram illustrating the operation of the ink jet recording head according to the first embodiment. FIG. 3 shows a case where the thermal expansion coefficient of the second elastic film 30b is larger than the thermal expansion coefficient of the first elastic film 30b. When a voltage is applied to the second elastic film 30b, the second elastic film 30b generates heat, and the movable plate 30 is deformed downward as a whole.

  4A to 4D are views showing a method for manufacturing the ink jet recording head of the present embodiment. Hereinafter, a process of forming the first elastic film 30a, the second elastic film 30b, and the like on the flow path forming substrate 10 made of a silicon single crystal substrate will be described with reference to FIGS. 4 (a) to 4 (d). To do.

  As shown in FIG. 4A, first, a silicon single crystal substrate wafer to be a flow path forming substrate 10 is thermally oxidized in a diffusion furnace at about 1100 ° C. to form a first elastic film 30a made of silicon dioxide. To do. Then, patterning is performed by photolithography and reactive ion etching.

  Next, as shown in FIG. 4B, a second elastic film 30b made of copper is formed on the first elastic film 30a by sputtering. Then, patterning is performed by photolithography and reactive ion etching.

  Next, as shown in FIG. 4C, the pattern of the pressure generation chamber 11 is patterned from the back side facing the first elastic film 30a of the flow path forming substrate 10 by back side photolithography and reactive ion etching. To form. Sidewall portions 10a and 10b are formed by this patterning.

  Next, as shown in FIG. 4D, the flow path forming substrate 10 and the nozzle plate 20 made of a silicon single crystal substrate in which the nozzle openings 21 are previously formed by photolithography and reactive ion etching are bonded. As the bonding method, for example, a silicon direct bonding method in which both substrate surfaces are brought into close contact with each other in a vacuum atmosphere and adhered by pressing may be used, or an organic adhesive may be used.

  In the series of film formation and etching described above, a large number of chips are simultaneously formed on a single wafer, and are divided into one chip as shown in FIG.

  The ink jet recording head 100 of this embodiment can be manufactured by the above manufacturing method.

  As described above, according to the present embodiment, the degree of freedom in selecting a liquid is improved, there is no problem of kogation, the driving volume is large, the driving energy is large, the reliability is small, and the thermal actuator type is easy to integrate. It is possible to provide an ink jet recording head.

(Second Embodiment)
The ink jet recording head according to the present embodiment further includes a resistance heating film formed in contact with the first elastic film or the second elastic film, and an energization electrode for causing the resistance heating film to generate resistance heat. The second elastic film is the same as the first embodiment except that the second elastic film is not a zigzag shape but a rectangular shape. Therefore, the description overlapping the first embodiment is omitted.

  FIG. 5 is a top view of the ink jet recording head according to the second embodiment. The ink jet recording head 200 of the present embodiment is a thermal actuator type ink jet recording head.

  6 is a cross-sectional view taken along the line AA in FIG. 2 shows a cross-sectional structure in the transverse direction of one pressure generation chamber 11 among a plurality of pressure generation chambers 11 included in the ink jet recording head 200.

  The ink jet recording head 200 according to the present embodiment includes a resistance heating film 30c formed in contact with the first elastic film 30a or the second elastic film 30b, and an energization electrode for causing the resistance heating film 30c to generate resistance heat. It has. As the resistance heating film 30c, a titanium / aluminum alloy or an iron / chromium alloy having a relatively large specific resistance can be used.

  Then, an energization electrode is provided that is connected to the resistance heating film 30c and causes the resistance heating film 30c to generate resistance heat. The energization electrodes are individual electrodes 72 and common electrodes 74 provided in each pressure generation chamber 11.

  The ink jet recording head 200 according to the present embodiment includes a resistance heating film 30c. As a result, unlike the first embodiment, the second elastic film 30b does not need to consider resistance as a heating element. Accordingly, the shape, thickness, etc. of the second elastic film 30b can be selected to be optimal for the deformation of the movable plate 30. Here, the case where the second elastic film 30b has a rectangular shape is illustrated.

  FIG. 7 is a diagram illustrating the operation of the ink jet recording head according to the second embodiment. FIG. 7 shows a case where the thermal expansion coefficient of the second elastic film 30b is larger than the thermal expansion coefficient of the first elastic film 30a. When a voltage is applied to the resistance heating film 30c, the resistance heating film 30c generates heat, and the movable plate 30 is deformed downward as a whole.

  The resistance heating film 30c is preferably thinner than the first elastic film 30a and the second elastic film 30b so that the resistance heating film 30c does not hinder the deformation of the movable plate 30 as much as possible. In addition, the elastic heating coefficient of the resistive heating film 30c is one of the thermal expansion coefficients of the first elastic film 30a and the second elastic film 30b so that the resistive heating film 30c does not hinder the deformation of the movable plate 30 as much as possible. It is desirable to be equal to or in the range between.

  For example, in the first embodiment, it is assumed that the thermal expansion coefficient of the second elastic film 30b is larger than the thermal expansion coefficient of the first elastic film 30a, the first elastic film 30a is an insulator, Although the example in which the elastic film 30b is a conductor and the second elastic film 30b is energized and heated has been described, many other modifications are possible.

  FIGS. 8A to 8E are views showing the operation of a modified example of the ink jet recording head according to the first or second embodiment. FIGS. 8A to 8E show modifications in the case where the thermal expansion coefficient of the first elastic film 30a is smaller than the thermal expansion coefficient of the second elastic film 30b.

  FIG. 8A shows an example in which the second elastic film 30b is energized and heated as a conductor, as in the first embodiment. For example, an inorganic insulating film such as silicon oxide or silicon nitride can be used as the first elastic film 30a, and a metal resistance film can be used as the second elastic film 30b.

  FIG. 8B shows an example in which the first elastic film 30a is energized and heated using a conductor. For example, a metal resistive film can be used as the first elastic film 30a, and an organic insulating film such as a polyimide film or an epoxy film having a large thermal expansion coefficient can be used as the second elastic film 30b.

  8C to 8E show an example in which a thin resistance heating film 30c is provided in addition to the first elastic film 30a and the second elastic film 30b. By making the resistance heating film 30c thin, the mechanical contribution to the deformation of the actuator is reduced, and the selection range of the material is expanded.

  FIG. 8C shows an example in which a resistance heating film 30c is provided between the first elastic film 30a and the second elastic film 30b. This is the same as in the second embodiment. A wide range of materials can be used for the resistance heating film 30c. Preferably, the thermal expansion coefficient is equal to one of the thermal expansion coefficients of the first elastic film 30a and the second elastic film 30b, or between them. It is desirable to be in range. For example, a semiconductor resistance such as polysilicon doped with an inorganic insulating film such as silicon oxide as the first elastic film 30a, an organic insulating film such as a polyimide film or an epoxy film as the second elastic film 30b, and the resistance heating film 30c. A membrane can be used.

  FIG. 8D shows an example in which a resistance heating film 30c is provided below the first elastic film 30a. Although a wide range of materials can be used for the resistance heating film 30c, it is desirable that the coefficient of thermal expansion be similar to that of the first elastic film 30a. For example, a semiconductor resistance such as polysilicon doped with an inorganic insulating film such as silicon nitride as the first elastic film 30a, an organic insulating film such as a polyimide film or an epoxy film as the second elastic film 30b, and the resistance heating film 30c. A membrane can be used.

  FIG. 8E shows an example in which a resistance heating film 30c is provided on the upper side of the second elastic film 30b. A wide range of materials can be used for the resistance heating film 30c. For example, polysilicon doped with an inorganic insulating film such as silicon oxide or silicon nitride as the first elastic film 30a, an organic insulating film such as a polyimide film or an epoxy film as the second elastic film 30b, and the like as the resistance heating film 30c The semiconductor resistance film can be used.

  FIGS. 9A to 9E are views showing the operation of a modified example of the ink jet recording head according to the first or second embodiment. FIGS. 9A to 9E show a modification in which the thermal expansion coefficient of the first elastic film 30a is larger than the thermal expansion coefficient of the second elastic film 30b.

  FIG. 9A shows an example in which the second elastic film 30b is energized and heated using a conductor. For example, an organic insulating film such as a polyimide film or an epoxy film can be used as the first elastic film 30a, and a metal resistance film can be used as the second elastic film 30b.

  FIG. 9B is an example in which the first elastic film 30a is energized and heated using a conductor. For example, a metal resistive film can be used as the first elastic film 30a, and an inorganic insulating film such as silicon oxide or silicon nitride can be used as the second elastic film 30b.

  FIGS. 9C to 9E show an example in which a thin resistance heating film 30c is provided in addition to the first elastic film 30a and the second elastic film 30b. By making the resistance heating film 30c thin, the mechanical contribution to the deformation of the actuator is reduced, and the selection range of the material is expanded.

  FIG. 9C shows an example in which a resistance heating film 30c is provided between the first elastic film 30a and the second elastic film 30b. A wide range of materials can be used for the resistance heating film 30c. For example, a semiconductor such as polysilicon doped with an organic insulating film such as a polyimide film or an epoxy film as the first elastic film 30a and an inorganic insulating film such as silicon oxide as the second elastic film 30b as the resistance heating film 30c. Resistive films can be used.

  FIG. 9D shows an example in which a resistance heating film 30c is provided below the first elastic film 30a. A wide range of materials can be used for the resistance heating film 30c. For example, a semiconductor resistance such as polysilicon doped with an organic insulating film such as a polyimide film or an epoxy film as the first elastic film 30a, an inorganic insulating film such as silicon nitride as the second elastic film 30b, and the resistance heating film 30c. A membrane can be used.

  FIG. 9E shows an example in which a resistance heating film 30c is provided on the upper side of the second elastic film 30b. A wide range of materials can be used for the resistance heating film 30c. For example, polysilicon doped with an organic insulating film such as a polyimide film or an epoxy film as the first elastic film 30a, an inorganic insulating film such as silicon oxide or silicon nitride as the second elastic film 30b, and the like as the resistance heating film 30c The semiconductor resistance film can be used.

  As shown in FIGS. 9A to 9E, when the second elastic film 30b side is convex upward when a voltage is applied, for example, the second insulating film 30b side is placed inside the pressure generation chamber 11. By doing so, it becomes possible to eject ink when a voltage is applied. Alternatively, the first elastic film 30a side may be the inside of the pressure generating chamber 11 and ink may be ejected by interrupting voltage application.

(Third embodiment)
The ink jet recording head of this embodiment is different from that of the first embodiment in that a third elastic film is formed at the lower center of the first elastic film. Except for this point, the second embodiment is basically the same as the first embodiment, and therefore, the description overlapping with the first embodiment is omitted.

  FIG. 10 is a top view of the ink jet recording head according to the third embodiment. The ink jet recording head 300 of the present embodiment is a thermal actuator type ink jet recording head.

  FIG. 11 is a cross-sectional view taken along the line AA in FIG. 2 shows a cross-sectional structure in the transverse direction of one pressure generation chamber 11 of a plurality of pressure generation chambers 11 included in the ink jet recording head 300. FIG.

  In the present embodiment, the movable plate 30 is formed with a third elastic film 30d. That is, in addition to the second elastic film 30b formed on the upper surface end 31 of the first elastic film 30a, the third elastic film 30d is laminated on the lower surface of the central portion 32 of the first elastic film 30a. Yes.

  From the viewpoint of improving the bending rigidity of the movable plate 30, it is desirable that the second elastic film 30b or the third elastic film 30d is laminated over the entire surface of the first elastic film 30a. In other words, it is desirable that the position of the end of the second elastic film 30b sandwiching the first elastic film 30a and the position of the end of the third elastic film 30d coincide or overlap.

  Further, from the viewpoint of increasing the drive volume and drive energy of the movable plate 30, it is desirable that the positions of the end portions of the second elastic film 30b and the third elastic film 30d are substantially the same. The term “substantially coincides” means that the end of the second elastic film 30b is obtained when the free part of the movable plate, that is, when the distance between the side wall 10a and the side wall 10b is normalized as 1, when viewed in the cross section of FIG. The distance between the portion and the end of the third elastic film 30d is preferably 0.05 or less.

  Then, an energization electrode is provided which is connected to the second elastic film 30a and causes the second elastic film 30b to generate resistance heat. The energization electrodes are individual electrodes 72 and common electrodes 74 provided in each pressure generation chamber 11. Further, since the third elastic film 30c is energized through the second elastic film 30a to generate heat, the second elastic film 30a and the third insulating film 30c are connected by the through holes 80 and 82. Yes.

  Here, the thermal expansion coefficient of the third elastic film 30d is larger than the thermal expansion coefficient of the first elastic film 30a in order to increase the deformation amount of the movable plate 30 by providing the third elastic film 30d. In particular, it is desirable that the third elastic film 30d and the second elastic film 30b are made of the same material so that the thermal expansion coefficients are made the same. This is because the amount of deformation of the movable plate 30 is increased and manufacturing is facilitated by using the same material.

  Hereinafter, the thermal expansion coefficient of the second elastic film 30b is larger than the thermal expansion coefficient of the first elastic film 30a, and the second elastic film 30b and the third elastic film 30d are the same material and have the same thermal expansion coefficient. A case will be described as an example. For example, the first elastic film 30a is a silicon oxide film, and the second and third elastic films 30b and 30d are copper (Cu).

  In the ink jet recording head 100 of the present embodiment, the second elastic film 30b has a zigzag shape in order to increase the resistance of the second elastic film 30b and increase the amount of heat generation.

  By energizing the second and third elastic films 30b and 30d, the first elastic film 30a, the second elastic film 30b, and the third elastic film 30d are heated. Then, the end portion 31 of the first elastic film 30a is bent and deformed into a convex shape (convex upward) by the difference in thermal expansion coefficient between the first elastic film 30a and the second elastic film 30b, and further the first elasticity. Due to the difference in thermal expansion coefficient between the film 30a and the third elastic film 30d, the central portion 32 of the first elastic film 30a is bent and deformed toward the inside of the pressure generating chamber 11 in a concave shape (convex downward). As a result, the pressure in the pressure generating chamber 11 is increased and ink droplets are ejected from the nozzle openings 21.

  In the ink jet recording head 300 of the present embodiment, the second elastic film 30b is laminated on the end 31 of the first elastic film 30a, and the surface opposite to the central part 32 of the first elastic film 30a. The third elastic film 30d is laminated. Therefore, the end portion 31 and the center portion 32 can be greatly deformed due to deformation in the opposite direction due to the bimetal effect. Therefore, it is possible to improve the amount of discharged liquid due to the displacement of the first elastic film 30d (or the movable plate 30), and an ink jet recording head with high driving efficiency is realized.

  Further, since the second elastic film 30b or the third elastic film 30d is formed over the entire surface of the first elastic film 30a, the bending rigidity of the first elastic film 30a is increased and the discharge pressure is increased. In addition, the driving energy proportional to the product of the discharge volume and the discharge pressure is also increased.

(Fourth embodiment)
The ink jet recording head of this embodiment is the same as that of the third embodiment, except that the shape of the second elastic film is not a zigzag shape but a rectangular shape. Therefore, the description overlapping with the third embodiment is omitted.

  FIG. 12 is a top view of the ink jet recording head according to the fourth embodiment. As shown in FIG. 12, the second elastic film 10b has a rectangular shape. That is, the end is not a zigzag but a straight line.

  As the second elastic film 30b used as the resistance heating film, for example, a metal film such as a titanium / aluminum alloy or an iron / chromium alloy having a relatively large specific resistance value is used. Instead of taking the zigzag shape as in the embodiment, it is possible to take a rectangular shape as in this embodiment.

  According to the present embodiment, restrictions on heat generation are eased with respect to the shape of the second elastic film 30b. Therefore, a shape that further considers the displacement of the movable plate 30 can be selected. Therefore, it is possible to realize an ink jet recording head having a larger driving volume and driving energy.

  The embodiments of the present invention have been described above with reference to specific examples. The above embodiment is merely given as an example, and does not limit the present invention. In the description of the embodiment, the description of the ink jet recording head and its manufacturing method, etc., which is not directly necessary for the description of the present invention is omitted. Elements relating to the manufacturing method and the like can be appropriately selected and used.

  For example, in addition to the silicon single crystal substrate, other semiconductor single crystal substrates or the like may be applied as the flow path forming substrate 10.

  In addition, all inkjet recording heads that include the elements of the present invention and that can be appropriately modified by those skilled in the art are included in the scope of the present invention. The scope of the present invention is defined by the appended claims and equivalents thereof.

  Hereinafter, examples and comparative examples will be described.

Example 1
A simulation was performed on an ink jet recording head having the same structure as that of the first embodiment shown in FIGS. The bending that occurs in the first elastic film 30a when the second elastic film 30b is energized and heated will be described in more detail based on the simulation results.

Table 1 shows the dimensions of the main part of the present example used in the simulation. Silicon dioxide (SiO ₂ ) was used as the first elastic film 30a, and copper was used as the second elastic film 30b.

  In this embodiment, the rigidity ratio of the first and second elastic membranes is about 0.73, and the ratio of the width of the end portion of the first elastic membrane to the width of the pressure generating chamber is 0.33. The stiffness ratio was calculated by equation (1). Here, E1 and V1 are the Young's modulus and cross-sectional area of the first elastic film, and E2 and V2 are the Young's modulus and cross-sectional area of the second elastic film.

  Rigidity ratio = E2 / V2 / (E1 / V1) Formula (1)

  FIG. 13 is calculated by the recording head simulator of this example when a current of 0.30 A was passed through the second elastic film 30b for 5 μs and the maximum temperature of the second elastic film 30b reached 200 ° C. It is a figure which shows the deformation | transformation of the movable plate. However, the deflection of the deformation is enlarged and displayed twice.

  It can be seen that the end 31 of the first elastic film 30a laminated with the second elastic film 30b is deformed into a convex shape due to a difference in thermal expansion, and the central portion 32 is deformed into a concave shape. The vertical displacement at the center of the central portion 32 is 0.44 μm, and the driving volume of the entire first elastic film 30 a having a length of 500 μm is 6 pl (picoliter). The driving pressure for deforming the center of the first elastic film 30a by 0.44 μm was 1.06 MPa, and the total driving energy of the ink jet driving head of this example was calculated to be 3.2 nJ.

  For example, the sum of surface energy and kinetic energy when ejecting ink droplets made of an organic solvent or aqueous solution with a volume of 5 pl (picoliter) at a speed of 10 m / s is about 0.1 to 0.3 nJ. In general, it is said that the driving energy required for the recording head is about 10 times the energy of the ink droplets. Therefore, the ink jet recording head of this embodiment ejects ink droplets having a volume of about 5 pl (picoliter). You can see that you have the ability.

  Next, the behavior when each parameter shown in Table 1 is changed in this embodiment will be examined in detail using the simulation result.

  First, the performance when the thicknesses of the first and second elastic films 30a and 30b were changed was examined. FIG. 14A shows the influence of the rigidity ratio of the first elastic film 30a and the second elastic film 30b on the driving volume, and FIG. 14B shows the influence of the rigidity ratio on the driving energy. .

  The drive volume shows the maximum value in the range where the rigidity ratio is 0.5 or more and 0.6 or less. On the other hand, the drive energy has a maximum value in the range where the rigidity ratio is 1 or more and 1.1 or less. In order to eject ink droplets, it is necessary that both the drive volume and drive energy are large. Therefore, the stiffness ratio is most preferably in the range of 0.5 to 1.1. In addition, since it is considered necessary to have a performance of ½ or more of each maximum value, it is desirable that the rigidity ratio is at least 0.3 to 1.8.

  Next, the width of the end 31 where the first elastic film 30a and the second elastic film 30b are stacked occupies the width of the pressure generating chamber 11 (equal to the distance between the side wall 10a and the side wall 10b). The ratio was examined. FIG. 15A shows the influence of the ratio of the width of the end 31 (end length) on the driving volume, and FIG. 15B shows the ratio of the width of the end 31 (end length) on the driving energy. Show the impact.

  The drive volume and drive energy both show maximum values when the ratio of the width of the end portion 31 (end portion length) is 0.3 to 0.4. Therefore, the ratio of the width of the end portion 31 is most preferably 0.3 or more and 0.4 or less. In addition, since it is considered necessary to have a performance of 1/2 or more of each maximum value, it is desirable that the ratio of the width of the end portion 31 is 0.2 or more and 0.45 or less.

(Example 2)
A simulation was performed on an ink jet recording head having the same structure as that of the third embodiment shown in FIGS. The bending that occurs in the first elastic film 30a when the second elastic film 30b and the third elastic film 30d are energized and heated will be described in more detail based on simulation results.

Table 2 shows the main dimensions of the present embodiment used in the simulation. Silicon dioxide (SiO ₂ ) was used as the first elastic film 30a, and copper was used as the second elastic film 30b and the third elastic film 30d.

  The rigidity ratio of the first and second to third elastic membranes in this embodiment is about 0.73, and the ratio of the width of the end portion of the first elastic membrane to the pressure generating chamber width is 0.25. is there. The rigidity ratio was calculated by the above formula (1).

  When a current of 0.28 A is passed through the second and third elastic membranes 30a and 30d for 5 μs and the maximum temperature of the second and third elastic membranes 30a and 30d reaches 200 ° C., the center of the central portion 32 is vertical. The displacement in the direction is 0.36 μm, and the driving volume of the entire first elastic film 30 having a length of 500 μm is 5.6 pl (picoliter). The driving pressure for deforming the center of the first elastic film 30a by 0.36 μm was 1.8 MPa, and the total driving energy of the ink jet driving head of this example was calculated to be 5.2 nJ.

  For example, the sum of surface energy and kinetic energy when an ink droplet made of an organic solvent or aqueous solution having a volume of 5 pl (picoliter) is ejected at a speed of 10 m / s is about 0.1 to 0.3 nJ. In general, it is said that the driving energy required for the recording head is about 10 times the energy of the ink droplets. Therefore, the ink jet recording head of this embodiment ejects ink droplets having a volume of about 5 pl (picoliter). You can see that you have the ability.

  Next, the behavior when each parameter shown in Table 2 in this embodiment is changed will be similarly examined in detail using the simulation result.

  First, the performance when the thicknesses of the second and third elastic films 30a and 30d were changed with respect to the first elastic film 30 was examined. FIG. 16A shows the influence of the rigidity ratio of the first elastic film and the second to third elastic films on the driving volume, and FIG. 16B shows the influence of the rigidity ratio on the driving energy. . The rigidity ratio was calculated in the same manner as the above formula (1).

  The driving volume increases as the rigidity ratio is smaller, while the driving energy shows a maximum value when the rigidity ratio is 1 or more and 1.1 or less. In order to eject ink droplets, it is necessary that both the drive volume and drive energy are large. Therefore, it is most desirable that the rigidity ratio be 0.5 or more and 1.1 or less. In addition, since it is considered necessary to have a performance of ½ or more of each maximum value, it is desirable that the rigidity ratio is at least 0.3 to 1.8.

  Next, the ratio of the width of the end portion 31 (length of the end portion) to the width of the pressure generating chamber 11 where the first elastic film 30a and the second elastic film 30b are stacked was examined. FIG. 17A shows the influence of the ratio of the width of the end 31 on the driving volume, and FIG. 17B shows the influence of the ratio of the end 31 on the driving energy.

  Both the driving volume and the driving energy show maximum values when the ratio of the width of the end portion 31 (end portion length) is 0.2 or more and 0.3 or less. Therefore, it is most desirable that the ratio of the width of the end portion 31 is 0.2 or more and 0.3 or less. In addition, since it is considered necessary to have a performance of 1/2 or more of each maximum value, it is desirable that the ratio of the width of the end portion 31 is 0.05 or more and 0.4 or less.

(Comparative Example 1)
Next, as Comparative Example 1, simulation results are similarly shown for an ink jet recording head having a conventional cantilever structure, and are compared in detail with Examples 1 and 2.

  FIG. 18 is a cross-sectional view of the ink jet recording head of Comparative Example 1. 6 is a view showing a cross-sectional structure in the transverse direction of one pressure generating chamber in Comparative Example 1. FIG. The same members as those in the first embodiment are denoted by the same reference numerals.

  In the ink jet recording head 500 of Comparative Example 1, the movable plate 330 includes a first elastic film 330a and a second elastic film 330b. The movable plate 330 has a cantilever-type first elastic film 330 a divided into left and right, and a second elastic film 330 b is directly laminated on the first elastic film 330, so-called A bimetal structure is formed.

  In this comparative example, the ejection performance considering the drive volume and drive energy is maximized when the stiffness ratio between the first elastic film 330a and the second elastic film 330b is approximately 1, so the stiffness ratio is 1. The thickness of the second elastic film 330b was determined so that

  Other shapes, dimensions, and materials are the same as those in the first embodiment. Table 3 shows the main dimensions of the comparative example used in the simulation.

  As a result of calculating the drive volume when the maximum temperature of the second elastic film 330b is 200 ° C. by simulation, a relatively large value of about 5 pl (picoliter) was obtained. However, the driving energy was as small as 1.7 nJ.

(Comparative Example 2)
Next, as Comparative Example 2, a simulation result is similarly shown for a buckled drive type ink jet recording head of a doubly supported beam and is compared in detail with Example 1.

  FIG. 19 is a cross-sectional view of the ink jet recording head of Comparative Example 2. 6 is a view showing a cross-sectional structure in the transverse direction of one pressure generating chamber in Comparative Example 2. FIG. The same members as those in the first embodiment are denoted by the same reference numerals.

  In the ink jet recording head 600 of Comparative Example 2, the movable plate 430 is composed of a first elastic film 430a and a second elastic film 430b. The first elastic film 430 a and the second elastic film 430 b are formed on the entire upper surface of the pressure generating chamber 11. When the second elastic film 430b and the first elastic film 430a are heated, compressive stress is applied to cause buckling deformation.

  In this comparative example, the ejection performance considering the drive volume and drive energy is maximized when the rigidity ratio of the first elastic film 330a and the second elastic film 330b is about 0.4, so the rigidity ratio The thickness of the second elastic film 330b was determined so as to be 0.4.

  Other shapes, dimensions, and materials are the same as those in the first embodiment. Table 3 shows the main dimensions of the comparative example used in the simulation.

  FIG. 20 is a comparison diagram of simulation results of the example and the comparative example. The result of comparing Comparative Example 1 and Comparative Example 2 with Examples 1 and 2 is shown. When Example 1 and Comparative Example 1 are compared, although the drive volume is almost the same, Example 1 is about twice as large as Drive Example in terms of drive energy, and the superiority of Example 1 is clear. Further, when Example 1 and Comparative Example 2 are compared, the driving energy is about an order of magnitude smaller than Example 1, and the superiority of Example 1 is clear.

DESCRIPTION OF SYMBOLS 10 Flow path formation board | substrate 10a Side wall part 10b Side wall part 11 Pressure generation chamber 20 Nozzle plate 21 Nozzle opening part 30 Movable plate 30a 1st elastic film 30b 2nd elastic film 30c Resistance heating film 30d 3rd elastic film 31 End part 32 Central portion 60 Common ink chamber 61 Ink supply path 62 Ink introduction port 71 Lead 72 Individual electrode 73 Lead 74 Common electrode 80 Through hole 82 Through hole 100 Inkjet recording head 200 Inkjet recording head 300 Inkjet recording head 400 Inkjet recording head

Claims (6)

A pressure generating chamber having a nozzle plate provided with a nozzle opening for discharging ink, a side wall, and a movable plate facing the nozzle plate across the side wall;
The movable plate has a first elastic film having a fixed end whose peripheral part is fixed to the side wall part, and extends from the fixed end of the first elastic film toward a central part, and An ink jet recording head comprising: a second elastic film which is laminated on an elastic film and is not laminated on a central portion of the first elastic film, and has a second elastic film having a thermal expansion coefficient different from that of the first elastic film. . The first elastic film and the second elastic film have different thermal expansion coefficients of 5 × 10 ⁻⁶ / ° C. or more, and the rigidity ratio of the first elastic film and the second elastic film is 0.3 or more. 2. The ink jet recording head according to claim 1, wherein the recording head is 1.8 or less.   Laminated on the center of the first elastic film on the opposite side of the second elastic film across the first elastic film, and has a thermal expansion coefficient equal to that of the second elastic film, or 3. The ink jet recording head according to claim 1, further comprising a third elastic film located between the thermal expansion coefficients of the first elastic film and the second elastic film.   4. The ink jet recording according to claim 1, further comprising a current-carrying electrode connected to the second elastic film and causing the second elastic film to generate resistance heat. 5. head.   4. The ink jet recording according to claim 1, further comprising a current-carrying electrode connected to the first elastic film for causing the first elastic film to generate resistance heat. 5. head.   2. A resistance heating film formed in contact with the first elastic film or the second elastic film, and a current-carrying electrode for causing the resistance heating film to generate resistance heat. The ink jet recording head according to claim 3.