JP2007216669A - Liquid discharge head and manufacturing method thereof - Google Patents

Abstract

A diaphragm is prevented from cracking at an end portion of an individual liquid chamber.
A diaphragm 7 is deformed by a piezoelectric drive unit 6 to pressurize a liquid in an individual liquid chamber 5 formed on a base 3 and discharge the liquid from a discharge port 2. Since the deformation amount of the diaphragm 7 increases at both ends in the longitudinal direction of the individual liquid chamber 5 and cracks may occur, a convex portion 8 that protrudes in a step shape from the diaphragm 7 is formed, The rigidity of both ends of the diaphragm 7 is strengthened. Even when the thin diaphragm 7 is used corresponding to the individual liquid chamber 5 which is thinned for high definition, it is possible to prevent the deformation amount of the diaphragm 7 from locally increasing and cracking.
[Selection] Figure 1

Description

  The present invention includes an ejection port for ejecting liquid droplets and an individual liquid chamber communicating with the ejection port, and ejects liquid droplets by applying displacement to a vibration plate provided corresponding to the individual liquid chamber and constituting a part thereof. The present invention relates to a liquid discharge head and a manufacturing method thereof.

  2. Description of the Related Art Conventionally, liquid discharge heads have been widely incorporated in recording apparatuses such as printers and facsimiles for reasons such as low noise, low running cost, and easy size and colorization of the apparatus. In particular, liquid discharge heads using piezoelectric actuators are also being used as patterning apparatuses for device manufacturing because of the high degree of freedom in selecting the liquid to be discharged.

  In the liquid discharge head using a piezoelectric actuator, looking at the process of discharging liquid from the discharge port in detail, the displacement that changes with time is first applied to the diaphragm that forms part of the individual liquid chamber by the input of an electrical signal. By applying, the volume of the individual liquid chamber is contracted or expanded. By carrying out such volume control, the liquid extends to the outside in the liquid column state and begins to protrude. After that, for example, the gap between the recording head (liquid ejection head) and the recording material flies while being separated into a plurality of droplets by surface tension. On the other hand, for both uses of a recording apparatus and a patterning apparatus, higher resolution of nozzles and a smaller amount of ejected droplets are being promoted. At the same time, the accuracy of droplet landing has been improved. Among these, as the main method for increasing the resolution, it is considered to narrow the width of the individual liquid chamber.

When the resolution is increased by narrowing the width of the individual liquid chamber, it is necessary to improve the displacement efficiency in order to realize desired discharge performance such as discharge amount and discharge speed. Therefore, it is known to reduce the thickness of the diaphragm as a countermeasure (see Patent Document 1 and Patent Document 2).
JP 11-291495 A Japanese Patent Application Laid-Open No. 11-300971

  However, when the thickness of the diaphragm is made as thin as possible, the following technical problem has been clarified from the detailed examination of the inventor.

  The object of study is a unimorph type (bender type) piezo recording head in which a piezoelectric body as a piezoelectric drive unit and electrodes are formed on a diaphragm. Several types of piezoelectric recording heads having different diaphragm thicknesses were prepared, and the discharge lifetimes were compared. The criterion for judging the life here was the time of occurrence of liquid leakage at the diaphragm portion due to the cracking of the diaphragm, and the evaluation was made by the number of discharge operations up to that time. As expected easily, the thinner the diaphragm, the shorter the lifetime due to cracking of the diaphragm.

  Further, when the displacement amount of the diaphragm in the length direction of the individual liquid chamber of one element of the unimorph type piezo recording head was measured, the following tendency was observed.

  FIG. 8 is a sectional view of a unimorph type piezo recording head. The length of the individual liquid chamber 105 is 2.5 mm. The diaphragm 107 is deformed by applying a voltage to the piezoelectric element 106. FIG. 9 is a plot of the displacement of the diaphragm 107 with respect to the longitudinal direction of the individual liquid chamber at a certain time after voltage input.

Curves T ₁ , T ₂ , and T ₃ show how the diaphragm 107 is deformed as time t elapses from t1, t2, and t3. However, it can be seen that the displacement amount of the diaphragm 107 in the both end regions of the individual liquid chamber 105, that is, in the vicinity of the discharge port 102 and the end portion on the common liquid chamber side, is greatly displaced as compared with other places.

  In this way, if the displacement of the diaphragm at the end on the discharge port side and the common liquid chamber side is significantly larger than that in most other areas, the diaphragm is broken or cracked at that part. It tends to occur. In particular, when the diaphragm is made thin, it has been found that the diaphragm end portions on the discharge port side and the common liquid chamber side are more easily broken.

  The present invention has been made in view of the above-mentioned unsolved problems of the conventional technology, and prevents the cracking of the diaphragm to extend the life, and has a high discharge resolution and a sufficient discharge life, and a method of manufacturing the same Is intended to provide.

  The liquid discharge head according to the present invention includes a diaphragm provided with a piezoelectric drive unit, and a pressure generation chamber that supports the diaphragm and communicates with a discharge port that discharges liquid, corresponding to the piezoelectric drive unit. In the liquid discharge head having the substrate, a portion on the diaphragm side of the substrate in a region of an end portion in the longitudinal direction of the pressure generating chamber is stepped in the pressure generating chamber along the longitudinal direction. It is characterized by protruding.

  Since the base body supporting the diaphragm projects as convex portions at both ends in the longitudinal direction of the pressure generating chamber, it is possible to suppress the displacement of two horn-like peaks generated at both longitudinal ends of the diaphragm by the convex portions.

  In particular, in a configuration in which the width of the pressure generation chamber is narrowed in order to achieve high resolution, it is necessary to make the diaphragm thin in order to ensure sufficient diaphragm displacement. Even in such a case, the diaphragm can be prevented from cracking to extend its life, and a sufficient discharge life can be secured.

  In addition, by using the BOX layer of the SOI substrate as an etching stop layer, it is possible to make the diaphragm film thickness between adjacent elements uniform and flatten the diaphragm within one element. This can reduce variations in the amount of displacement between elements.

  The best mode for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 shows a liquid discharge head according to a first embodiment. A nozzle plate 1 has a discharge port (nozzle) 2 for discharging droplets, and a base 3 has a communication port 4 communicating with the discharge port 2 and An individual liquid chamber 5 which is a pressure generating chamber is provided. The piezoelectric drive unit 6 that generates a pressure for discharging a droplet includes an upper electrode 6 a, a piezoelectric film 6 b, and a lower electrode 6 c, and pressurizes the liquid in the individual liquid chamber 5 via the vibration plate 7.

  At both ends in the longitudinal direction of the individual liquid chamber 5, as shown in FIG. 1B, portions (hereinafter referred to as “convex portions”) 8 for suppressing the displacement of the diaphragm 7 are provided in steps. It is done. In other words, the diaphragm side portion of the base in the region of the end portion in the longitudinal direction of the pressure generating chamber protrudes stepwise into the pressure generating chamber along the longitudinal direction. As a result, the displacement of the diaphragm 7 in the both end regions in the longitudinal direction of the individual liquid chamber accompanying the increase in the amount of displacement of the piezoelectric drive unit 6 or the decrease in the drive voltage is controlled, and the specific displacement behavior of the diaphragm in this region is controlled. Can be suppressed. In the present invention, since the convex portions are displaced together while suppressing the displacement of the diaphragm, the thickness is preferably 5 μm or less, and more preferably 3 μm or less. In the present embodiment, the thickness of the convex portion is 3 μm.

  In this embodiment, as shown in FIG. 1A, convex portions 8a for suppressing the displacement of the diaphragm 7 are provided in steps at both ends of the individual liquid chamber 5 in the short direction. It is done. Thereby, the same effect can be produced also in the lateral direction of the individual liquid chamber 5.

  In this embodiment, since the convex portion protrudes stepwise from the pressure generating chamber, the space in the pressure generating chamber is larger than that in the case where the convex portion is not stepped. As a result, there is also an effect that bubbles do not easily stay in the pressure generation chamber.

  The liquid discharge head of this embodiment is manufactured by the following process. As shown in FIG. 2A, an SOI substrate 10 having an active layer 10a thickness of 6 .mu.m, a BOX (buried oxide) layer 10b thickness of 0.5 .mu.m, and a handle layer 10c thickness of 200 .mu.m is prepared. . The SOI substrate 10 may have an arbitrary film thickness, and an oxide film may be formed on the surfaces of the active layer 10a and the handle layer 10c.

A lower electrode 6c and a piezoelectric film 6b are formed on the active layer 10a of the SOI substrate 10 by sputtering. Although the Ti / Pt film is formed to 30/300 nm as the lower electrode 6c, the electrode material and the electrode film thickness are not limited thereto. As the piezoelectric film 6b, a Pb (Zr, Ti) O ₃ perovskite oxide (PZT) composed of lead, titanium, and zirconium is formed to a thickness of 3 μm by sputtering. In order to obtain good piezoelectricity, the composition of the PZT thin film is Pb (Zr _0.52 Ti _0.48 ) O ₃ . The composition of the PZT film is not necessarily limited to the above composition, and other compositions may be used. Further, the PZT film thickness may be arbitrarily determined to achieve a desired performance.

  Next, after removing the SOI substrate 10 on which the piezoelectric film 6b is formed from the sputtering apparatus, baking is performed at 700 ° C. in an oxygen atmosphere to crystallize the PZT film.

  Thereafter, as the upper electrode 6a, a film of Ti and a thickness of 30 nm and Pt are formed, respectively. Here, the electrode material and the electrode film thickness are not limited to the above, like the lower electrode.

  Subsequently, the piezoelectric film 6 b and the upper electrode 6 a are processed by etching so as to correspond to the individual liquid chambers 5. First, a photoresist is provided on the upper electrode 6a, and after patterning, the upper electrode 6a is processed by dry etching. Similarly, the piezoelectric film 6b is patterned and etched. Subsequently, a part of a liquid supply port (not shown) is formed by dry etching of the lower electrode 6c and Si dry etching of the active layer 10a in the same manner as the upper electrode 6a, thereby forming the piezoelectric driving unit 6 which is a piezoelectric element device.

  Next, using an ICP (Inductively Coupled Plasma) etching apparatus, a flow path such as the individual liquid chamber 5 is formed in the handle layer 10c. First, as shown in FIG. 2B, an oxide film 11 having a thickness of 2 μm for forming an etching mask is formed on the surface of the handle layer 10c, and further, corresponding to the convex portions 8 at both ends of the diaphragm 7. Thus, a resist pattern 12 is formed and the oxide film 11 is etched. Thereafter, as shown in FIG. 2C, Si of the handle layer 10c is processed by 3 μm by ICP etching.

  Next, after peeling off the resist pattern 12, as shown in FIG. 3, the resist pattern 13 is formed again so as to have an individual liquid chamber shape. After the oxide film 11 is etched, the Si of the handle layer 10c is processed by ICP etching to reach the BOX layer 10b except for the portions that become the convex portions 8 at both ends of the diaphragm.

Subsequently, the SiO ₂ film, which is the BOX layer 10b, is peeled off with buffered hydrofluoric acid to expose the diaphragm 7 made of the handle layer 10c and facing the individual liquid chamber 5, as shown in FIG. . Further, as shown in FIG. 4B, the resist pattern 13 is peeled off.

  Although the individual liquid chamber 5 has a width of 100 μm and a length of 2.5 mm, it goes without saying that the present invention is not limited to this.

  Finally, a 200 μm wafer serving as the nozzle plate 1 is ICP etched from both sides to form the communication port 4, the discharge port 2, and the like, and the nozzle plate 1 and the substrate 3 are joined to produce a piezo-type inkjet head. .

  At this time, the nozzle plate 1 may be processed by other methods, or may be a laminate of several plates.

  According to the present embodiment, as shown in FIG. 5, two horn-like ridges at both ends in the longitudinal direction of the individual liquid chamber in the displacement shape of the diaphragm 7 can be controlled.

In the process of manufacturing a liquid discharge head by bonding a nozzle plate having discharge ports formed in an Si substrate and an SOI substrate having a piezoelectric drive unit and individual liquid chambers, the BOX layer made of the SiO ₂ film of the SOI substrate vibrates. It becomes an etching stop layer when forming the convex part of a board. Accordingly, the convex portions at both ends of the diaphragm and the thickness of the diaphragm can be formed with high accuracy, and the amount of displacement between elements can be made uniform and the life of the diaphragm can be averaged. In addition, the displacement of the diaphragm can be arbitrarily controlled by changing the ratio of the thickness of the diaphragm and the thickness of the convex portion.

  As shown in FIGS. 6 and 7, in this embodiment, a rib-like member 8 b extending in the longitudinal direction of the individual liquid chamber 5 is added to the diaphragm 7 of Embodiment 1 to form a longitudinal groove. Is. The steps of forming an upper electrode, a piezoelectric body, and a lower electrode on an SOI substrate, patterning, and joining the nozzle plate are the same as in the first embodiment. Since the rib-like member is displaced together with the diaphragm, the thickness is preferably 5 μm or less, and more preferably 3 μm or less. In the present embodiment, the thickness of the rib-like member is 3 μm.

  The individual liquid chamber 5 is formed by the same process as described above using an SOI substrate having a handle layer thickness of 100 μm. Thereafter, an elastomer resin is poured into the grooves between the rib-like members 8 b and cured to form the protective layer 9 that covers the flat surface of the diaphragm 7.

  The material for forming the protective layer 9 is not particularly limited as long as the Young's modulus is sufficiently lower than that of the diaphragm 7. For example, a silicone resin, an epoxy resin, an acrylic resin, or the like can also be suitably used.

  In the present embodiment, it is possible to efficiently eliminate bubbles accumulated at the boundary between the diaphragm 7 and the convex portion 8 as the liquid discharge time elapses. This can suppress bubble discharge and a decrease in displacement. In addition, by using an SOI substrate with a thin handle layer to be the vibration plate 7, the depth of the individual liquid chamber 5 and the aspect ratio of the short width of the vibration plate 7 and the individual liquid chamber 5 are reduced, and the processing accuracy is increased. It is also possible to provide a liquid ejection head having a high height.

(Comparative example)
In each configuration according to the first and second embodiments, a liquid discharge head according to a comparative example in which convex portions and rib-like members are omitted was manufactured, and a rectangular voltage waveform was input to repeat the liquid discharge operation.

  As a result, the lifetimes of Examples 1 and 2 were improved compared to the comparative example. That is, as a result of taking time history data of the displacement of the surface of the piezoelectric drive unit using a non-contact displacement meter at several points in the longitudinal direction of the individual liquid chamber, two horn-like peaks generated at both ends in the longitudinal direction of the individual liquid chamber As a result, it is considered that severe bending is not added and the life is extended.

  The liquid discharge head of the present invention can be applied to a recording apparatus that prints on paper, cloth, leather, nonwoven fabric, an OHP sheet, or the like, a patterning apparatus that applies liquid to a solid material such as a substrate or a plate, and a coating apparatus.

1 shows a liquid discharge head according to a first embodiment, where (a) is a cross-sectional view of the individual liquid chamber in the short-side direction, and (b) is a cross-sectional view in the longitudinal direction. FIG. 4 is a diagram illustrating a part of the manufacturing process of the liquid ejection head in FIG. 1. FIG. 4 is a diagram illustrating a part of the manufacturing process of the liquid ejection head in FIG. 1. FIG. 4 is a diagram illustrating a part of the manufacturing process of the liquid ejection head in FIG. 1. 3 is a graph showing a deformation mode of a diaphragm of the liquid ejection head in FIG. 1. It is a figure which shows the convex part and rib-shaped member by Example 2. FIG. FIG. 3 shows a liquid discharge head according to a second embodiment, where (a) is a cross-sectional view of the individual liquid chamber in the short direction, and (b) is a cross-sectional view in the longitudinal direction. It is sectional drawing which shows one prior art example. It is a graph which shows the deformation mode of the diaphragm of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Nozzle plate 2 Ejection port 3 Base | substrate 4 Communication port 5 Individual liquid chamber 6 Piezoelectric drive part 7 Diaphragm 8a Protrusion part 8b Rib-shaped member 9 Protective layer

Claims (7)

A liquid discharger comprising: a diaphragm provided with a piezoelectric drive unit; and a base that supports the vibration plate and communicates with a discharge port that discharges liquid and is provided corresponding to the piezoelectric drive unit. In the head
The liquid ejection head, wherein a portion of the base on the diaphragm side in an end region in the longitudinal direction of the pressure generating chamber protrudes stepwise into the pressure generating chamber along the longitudinal direction. .   The liquid discharge head according to claim 1, wherein the portion has a thickness of 5 μm or less.   The liquid discharge head according to claim 1, wherein the portion is also provided in a region of an end portion of the pressure generation chamber with respect to a short direction.   The liquid ejection head according to claim 1, wherein the vibration plate includes an active layer of an SOI substrate, and the base includes a handle layer of the SOI substrate.   The liquid discharge head according to claim 4, wherein a rib-like member extending in a longitudinal direction of the pressure generating chamber is formed on the base.   The liquid discharge head according to claim 5, wherein a space between the rib-like members is filled with a material having a Young's modulus lower than that of the material constituting the diaphragm. It is a manufacturing method of the liquid discharge head according to claim 4,
A method of manufacturing a liquid discharge head, wherein a BOX layer of the SOI substrate is used as an etching stop layer when the pressure generating chamber is formed in the substrate by etching.

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