Inkjet head

Abstract

To provide an inkjet head improved in corrosion resistance of a diaphragm and stabilizing discharge characteristics of ink.SOLUTION: An inkjet head includes: a substrate having a flow passage communicating with a nozzle hole; a diaphragm which is mounted on the substrate so as to come in contact with ink in the flow passage and on both surfaces of which protection layers are formed; and a piezoelectric element mounted on the diaphragm so as to sandwich the diaphragm together with the substrate.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an inkjet head. [Background technology]

[0002] One known example of a conventional inkjet head is that disclosed in Patent Document 1. The inkjet head of Patent Document 1 includes a diaphragm that vibrates to pressurize ink in an ink chamber. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-202490 A Summary of the Invention [Problem to be solved by the invention]

[0004] Inkjet heads are increasingly being used in the production of semiconductor devices. However, some inks used in the production of semiconductor devices corrode the components that make up inkjet heads. Among the components of inkjet heads that come into contact with ink, the vibration plate is formed in a thin plate shape, so it is particularly susceptible to corrosion.

[0005] Furthermore, if the diaphragm is warped or otherwise deformed, this affects the vibration characteristics of the diaphragm and, ultimately, the ink ejection characteristics.

[0006] An object of the present disclosure is to improve the corrosion resistance of a diaphragm and stabilize the ink ejection characteristics in an inkjet head. [Means for solving the problem]

[0007] In order to achieve the above object, the inkjet head of the present disclosure includes a substrate having a flow path communicating with a nozzle hole, and a nozzle hole is attached to the substrate so as to be in contact with ink in the flow path, Made from aluminum, titanium or chromium The protective layer On both sides the piezoelectric element is attached to the vibration plate so as to sandwich the vibration plate together with the substrate, and the protective layers formed on both sides of the vibration plate are made of the same material. Effect of the Invention

[0008] According to the inkjet head of the present disclosure, it is possible to improve the corrosion resistance of the diaphragm and stabilize the ink ejection characteristics in the inkjet head. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view showing an outline of an inkjet head according to an embodiment of the present disclosure. [Diagram 2] Cross-sectional view showing the state before the diaphragm is attached to the substrate [Diagram 3] Cross-sectional view showing the state after the diaphragm is bonded to the substrate [Figure 4] An enlarged cross-sectional view showing the state of the adhesive layer after the diaphragm is bonded to the substrate. [Diagram 5] A plan view showing the state of the adhesive layer after the diaphragm is bonded to the substrate. [Figure 6] FIG. 1 is a cross-sectional view showing an outline of an inkjet head according to a comparative example. [Figure 7] FIG. 1 is a cross-sectional view showing a state before a diaphragm according to a comparative example is bonded to a substrate. [Figure 8] FIG. 11 is a cross-sectional view showing a state after a diaphragm according to a comparative example is bonded to a substrate. [Figure 9] FIG. 13 is an enlarged cross-sectional view showing a state of an adhesive layer after a diaphragm according to a comparative example is adhered to a substrate; [Figure 10] FIG. 13 is an enlarged cross-sectional view showing a state of an adhesive layer after a diaphragm according to a comparative example is adhered to a substrate; [Figure 11] FIG. 11 is a plan view showing a state of an adhesive layer after a diaphragm according to a comparative example is adhered to a substrate; [Figure 12] FIG. 11 is a cross-sectional view showing an outline of an inkjet head according to a modified example of an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Inkjet heads according to embodiments of the present disclosure will be described below with reference to the drawings. In the following description, the up-down direction in FIG. 1 is the up-down direction of the inkjet head 1, the left-right direction is the left-right direction of the inkjet head 1, and the direction perpendicular to the paper surface is the front-rear direction of the inkjet head 1.

[0011] The inkjet head 1 ejects ink to print an object. The ink is printing ink. In addition to printing ink, the ink may be, for example, solder paste, silver paste, imprinting paste, phosphor paste, or a cell suspension.

[0012] The inkjet head 1 ejects ink by controlling a piezoelectric element, which will be described later, with a control device (not shown). The inkjet head 1 is configured so that ink circulates between the inkjet head 1 and a liquid delivery device (not shown). In other words, the liquid delivery device supplies ink to the inkjet head 1 and collects ink from the inkjet head 1 that has not been ejected.

[0013] As shown in FIG. 1, the inkjet head 1 includes a head body 10 and a piezoelectric element unit 20.

[0014] The head body 10 is configured by stacking a nozzle plate 11, a substrate 12, and a diaphragm 13 in the vertical direction. The nozzle plate 11, the substrate 12, and the diaphragm 13 are bonded together by, for example, an adhesive.

[0015] The nozzle plate 11 is formed in a plate shape from alloy steel such as stainless steel, etc. The nozzle plate 11 has a plurality of nozzle holes 11a for ejecting ink formed in the plate and aligned in the left-right direction.

[0016] The substrate 12 is formed by, for example, bonding stainless steel plates formed by etching or pressing with an adhesive. A plurality of ink chambers 12a are formed in the substrate 12 so as to be aligned in the left-right direction. The ink chambers 12a are formed in a rectangular parallelepiped shape.

[0017] The nozzle plate 11 is attached to the substrate 12 so as to cover the ink chambers 12a and so that the nozzle holes 11a correspond to the ink chambers 12a. That is, the ink chambers 12a communicate with the nozzle holes 11a. In addition, ink flows in the ink chambers 12a in the front-rear direction. That is, the ink chambers 12a form part of a flow path that communicates with the nozzle holes 11a.

[0018] The diaphragm 13 is formed in a thin plate shape using metal. The material of the diaphragm 13 is specifically, but needless to say, not limited to, stainless steel. The diaphragm 13 is formed by photolithography using a stainless steel plate of a desired thickness. The material of the diaphragm 13 may also be a resin such as polyimide.

[0019] The vibration plate 13 is attached to the substrate 12 so as to cover the ink chambers 12a. The vibration plate 13 comes into contact with the ink in the ink chambers 12a. The vibration plate 13 vibrates to pressurize the ink in the ink chambers 12a. When the ink in the ink chambers 12a is pressurized, the ink is ejected from the nozzle holes 11a. In addition, a protective layer 13a is formed on both sides of the vibration plate 13.

[0020] The protective layer 13a provides the diaphragm 13 with corrosion resistance against ink. The protective layer 13a is a thin metal film having a passivation film formed on its surface. The protective layer 13a is, for example, a thin metal film of aluminum. The protective layer 13a is formed by sputtering the base material of the diaphragm 13. The protective layer 13a may also be an inorganic film such as silicon oxide or silicon nitride formed by using a CVD method.

[0021] The protective layers 13a formed on both sides of the diaphragm 13 are made of the same material. Note that the protective layers 13a formed on both sides of the diaphragm 13 may be made of different materials.

[0022] In addition, the protective layer 13a is formed by performing film formation multiple times on the base material of the diaphragm 13. When the protective layer 13a is formed by performing film formation multiple times, the thickness of the film formed at one time can be made thinner than when the protective layer 13a is formed by performing film formation once. Therefore, the variation in the thickness of the protective layer 13a can be suppressed.

[0023] Furthermore, the protective layer 13a is formed by alternately depositing a film on one side and a film on the other side of the diaphragm 13 once each. When depositing a film on one side and a film on the other side of the diaphragm 13 once each, the difference in film thickness between the one side and the other side during the formation of the protective layer 13a can be made smaller than when depositing a film on the one side multiple times and then depositing a film on the other side. Therefore, the variation in the residual stress of the protective layer 13a caused by the difference in film thickness between the one side and the other side, and further the deformation of the diaphragm 13, such as warping, caused by the residual stress of the protective layer 13a, can be suppressed.

[0024] Furthermore, by forming protective layers 13a on both sides of diaphragm 13, the corrosion resistance of diaphragm 13 can be improved. For example, if one protective layer 13a has a pinhole, ink may come into contact with the area where the pinhole occurs, causing corrosion. However, the position of a pinhole that occurs in one protective layer 13a does not match the position of a pinhole that occurs in the other protective layer 13a. Therefore, even if corrosion occurs at a pinhole in one protective layer 13a, the other protective layer 13a can prevent ink leakage.

[0025] The piezoelectric element unit 20 includes a base 21 and a piezoelectric element 22. The base 21 supports the piezoelectric element 22.

[0026] The piezoelectric element 22 is attached to the vibration plate 13 so as to sandwich the vibration plate 13 together with the substrate 12. The piezoelectric element 22 is formed in a comb shape such that a plurality of drive sections 22a and a plurality of support sections 22b are alternately arranged in the left-right direction. The plurality of drive sections 22a are arranged to correspond to the plurality of ink chambers 12a. The plurality of support sections 22b are arranged to correspond to portions of the substrate 12 where no flow paths are formed.

[0027] The driving section 22a is deformed when a voltage is applied thereto, and vibrates the diaphragm 13. The piezoelectric element unit 20 is configured to include electrodes (not shown) that apply a voltage to the driving section 22a.

[0028] Furthermore, the substrate 12 and the diaphragm 13, and the diaphragm 13 and the piezoelectric element 22 are bonded together with an adhesive 32 containing beads 31.

[0029] The adhesive 32 is, for example, an epoxy resin-based thermosetting adhesive. The adhesive 32 may be a two-liquid mixture adhesive, an ultraviolet-curing adhesive, or an anaerobic adhesive. The adhesive 32 hardens to form an adhesive layer 33. When the adhesive 32 is a thermosetting adhesive, the adhesive layer 33 can have a high hardness, and the responsiveness of the diaphragm 13 can be improved.

[0030] The beads 31 stabilize the thickness of the adhesive layer 33. The material of the beads 31 is ceramic, such as zirconia, alumina, or silica. The material of the beads 31 may be glass, metal, or the like. The particle size of the beads 31 is determined based on the desired thickness of the adhesive layer 33. The beads 31 do not have to be contained in the adhesive 32. In this case, the beads 31 are not disposed in the adhesive layer 33.

[0031] Next, the process of bonding diaphragm 13 to substrate 12 will be described with reference to Figures 2 and 3. As shown in Figure 2, adhesive 32 is applied to the portion of substrate 12 that will come into contact with diaphragm 13. The application of adhesive 32 is performed by, for example, screen printing. Note that adhesive 32 may be applied to diaphragm 13 instead of substrate 12.

[0032] On the other hand, the diaphragm 13 has the protective layer 13a formed on both sides as described above. Stress generated during film formation exists as residual stress in the protective layer 13a. This residual stress causes deformation such as warping of the diaphragm 13. However, since the protective layer 13a is formed on both sides of the diaphragm 13, the residual stress of one protective layer 13a is offset by the residual stress of the other protective layer 13a. Therefore, deformation such as warping of the diaphragm 13 is suppressed.

[0033] Next, the diaphragm 13 is aligned with the substrate 12, and the substrate 12 and the diaphragm 13 come into contact with each other as shown in Fig. 3, and the diaphragm 13 is pressed against the substrate 12. Since deformation such as warping of the diaphragm 13 is suppressed, deformation such as wrinkles is suppressed in the diaphragm 13 after pressing.

[0034] 4, when the substrate 12 and the diaphragm 13 are bonded together, a gap G is generated between the end face of the adhesive layer 33 and the end face of the substrate 12 in the left-right direction. The end face of the substrate 12 is the right or left side face of the ink chamber 12a. The gap G is generated due to variations in the alignment between the substrate 12 and the diaphragm 13, variations in the amount of adhesive 32 applied, and the like.

[0035] However, as described above, deformation of diaphragm 13 is suppressed. In addition, since substrate 12 and diaphragm 13 are in contact with each other via beads 31, the thickness of adhesive layer 33 and gap S between diaphragm 13 and substrate 12 are approximately constant depending on the particle size of beads 31.

[0036] Therefore, the size of the gap G is approximately constant in the front-rear direction. Therefore, as shown in Fig. 5, the end faces of the adhesive layers 33 extend approximately straight along the front-rear direction. In other words, the widths D in the left-right direction between the end faces of the adhesive layers 33 adjacent to each other are approximately equal in the front-rear direction.

[0037] The area between the adjacent end faces of the adhesive layer 33 is the area where the diaphragm 13 vibrates (hereinafter referred to as the vibration area). The width D in the left-right direction between the adjacent end faces of the adhesive layer 33 corresponds to the width D in the left-right direction of the vibration area. In other words, the width D in the left-right direction of the vibration area is approximately constant over the front-rear direction.

[0038] Further, there are a plurality of vibration parts corresponding to the plurality of ink chambers 12a. As described above, the width D of the vibration parts in the left-right direction is approximately equal across the front-rear direction. Therefore, the variation in the width D among the plurality of vibration parts is suppressed. Therefore, the variation in vibration characteristics among the plurality of vibration parts corresponding to the plurality of ink chambers 12a can be suppressed. Therefore, the ink ejection characteristics between the plurality of nozzle holes 11a can be stabilized.

[0039] Next, an inkjet head 2 according to a comparative example will be described with reference to Fig. 6 to Fig. 11. The configuration of the inkjet head 2 according to the comparative example differs from the configuration of the inkjet head 1 according to the present disclosure only in that a protective layer 113a is formed only on one side of the vibration plate 113, as shown in Fig. 6. Note that the reference numerals of the components of the inkjet head 2 according to the comparative example have a "1" added to the beginning of the reference numerals of the corresponding components of the inkjet head 1 according to the present disclosure.

[0040] When protective layer 113a is formed on one side of diaphragm 113, residual stress in protective layer 113a causes diaphragm 113 to warp convexly from the other side toward one side along the up-down direction, as shown in Fig. 7. The dashed line shown in Fig. 7 is an imaginary straight line L perpendicular to the up-down direction. When diaphragm 113 is bonded to substrate 112 in a warped state, diaphragm 113 deforms in a wavy shape along the left-right direction, as shown in Fig. 8. In this case, diaphragm 113 is also deformed in a wavy shape along the front-rear direction.

[0041] Since diaphragm 113 is deformed in a wavy shape in the front-rear direction, gap G between the end face of adhesive layer 133 and the end face of substrate 112 varies in the front-rear direction. Specifically, as shown in Fig. 9, there are areas where gap S between diaphragm 113 and substrate 112 is relatively narrow, and as shown in Fig. 10, there are areas where gap S is relatively wide. In the areas where gap S is relatively narrow (Fig. 9), adhesive 132 flows relatively close to the end face of substrate 112 due to capillary action.

[0042] Furthermore, in a portion where the gap S is relatively wide (FIG. 10), capillary action is less likely to occur than in a portion where the gap S is relatively narrow. As described above, in a portion where the gap S is relatively narrow, the adhesive 132 flows relatively close to the edge surface of the substrate 112. Therefore, in a portion where the gap S is relatively wide, the adhesive 132 moves away from the edge surface of the substrate 112. Therefore, the gap G is not approximately constant in the front-rear direction.

[0043] 11, the end face of the adhesive layer 133 becomes wavy, for example, in the front-rear direction. Therefore, the width D between the end faces of the adhesive layer 133 adjacent to each other, i.e., the width D of the vibrating part, is not approximately constant in the front-rear direction. In other words, the inkjet head 2 of the comparative example has a larger variation in vibration characteristics than the inkjet head 1 of the present disclosure. Therefore, the inkjet head 1 of the present disclosure can stabilize the ink ejection characteristics between the multiple nozzle holes 11a compared to the inkjet head 2 of the comparative example.

[0044] The present disclosure is not limited to the embodiments described above. As long as the modifications do not deviate from the gist of the present disclosure, they are also included in the scope of the present disclosure.

[0045] For example, the diaphragm 13 may be formed using nickel or a nickel alloy. This can improve the dimensional accuracy and durability of the diaphragm 13. In addition, the thickness of the diaphragm 13 can be further reduced, thereby improving the responsiveness of the diaphragm 13. When nickel or a nickel alloy is used as the material of the diaphragm 13, the diaphragm 13 is formed using, for example, an electroforming method. The nickel alloy is, for example, a nickel-cobalt alloy or a nickel-palladium alloy. The nickel-palladium alloy can particularly improve the durability of the diaphragm 13.

[0046] Also, as shown in FIG. 12, a plurality of plate members 13b may be arranged on the vibration plate 13. The plurality of plate members 13b are arranged on the vibration plate 13 at positions corresponding to the plurality of driving units 22a and the plurality of support units 22b. The plurality of plate members 13b are formed by forming a resist pattern corresponding to the shape of the plate members 13b on the plate surface of the vibration plate 13 by photolithography, and then performing electroforming. The plurality of plate members 13b can suppress the variation in the contact area between the vibration plate 13 and the piezoelectric element 22. Therefore, the variation in the vibration characteristics of each of the plurality of parts of the vibration plate 13 vibrated by the plurality of driving units 22a can be suppressed. Therefore, the ink ejection characteristics between the plurality of nozzle holes 11a can be stabilized.

[0047] The protective layer 13a may be made of titanium or chromium, which increases the strength of the protective layer 13a. A passivation film made of titanium or chromium has a relatively high corrosion resistance against ink. [Industrial Applicability]

[0048] The present invention is widely applicable to inkjet heads. [Explanation of symbols]

[0049] 1 Inkjet head 10 Head body 11 Nozzle plate 11a Nozzle hole 12 Substrate 12a Ink chamber 13 Diaphragm 13a Protective layer 13b Plate member 20 Piezoelectric element unit 22 Piezoelectric element 31 Beads 32 Adhesive 33 Adhesive layer

Claims

1. A substrate having a flow path communicating with the nozzle hole; a vibration plate attached to the substrate so as to be in contact with the ink in the flow path, the vibration plate having a protective layer formed on both sides thereof and made of aluminum, titanium or chromium; a piezoelectric element attached to the vibration plate so as to sandwich the vibration plate together with the substrate, The protective layers formed on both sides of the diaphragm are made of the same material. Inkjet head.

2. A substrate having a flow path communicating with the nozzle hole; a vibration plate attached to the substrate so as to be in contact with the ink in the flow path, the vibration plate having a protective layer formed on both sides thereof by a sputtering or CVD method; a piezoelectric element attached to the vibration plate so as to sandwich the vibration plate together with the substrate, The protective layers formed on both sides of the diaphragm are made of the same material. Inkjet head.

3. A substrate having a flow path communicating with the nozzle hole; a vibration plate attached to the substrate so as to be in contact with the ink in the flow path, the vibration plate having a metallic thin film formed as a protective layer on both sides of which a passivation film is formed; a piezoelectric element attached to the vibration plate so as to sandwich the vibration plate together with the substrate, Inkjet head.

4. A substrate having a flow path communicating with the nozzle hole; a vibration plate attached to the substrate so as to be in contact with the ink in the flow path, the vibration plate having a protective layer formed on both sides thereof for imparting corrosion resistance to the ink; a piezoelectric element attached to the vibration plate so as to sandwich the vibration plate together with the substrate, Inkjet head.

5. The protective layers formed on both sides of the diaphragm are formed by multiple film formations. The ink-jet head according to claim 1 .

6. The substrate and the vibration plate, and the vibration plate and the piezoelectric element are bonded with an adhesive containing beads. The ink-jet head according to claim 1 .

7. The diaphragm is made of nickel or a nickel alloy. The ink-jet head according to claim 1 .

8. A method for manufacturing the inkjet head according to claim 4, comprising the steps of: The protective layer is alternately formed on one side and the protective layer is alternately formed on the other side. Manufacturing method.

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