The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements.
Embodiments of the invention will be described. A droplet discharge head to which the invention is applied is described as a first embodiment. Here, a face-discharge type ink-jet head which discharges ink droplets from nozzle openings provided on the surface of a nozzle substrate is described as an example of the droplet discharge head of the embodiment. The invention is obviously not limited to the structures and the elements shown in the accompanying drawings, but also encompasses any variations that may be considered by any person skilled in the art, within the general scope of the invention. For example, the invention can also be applied to an edge-discharge type droplet discharge head which discharges ink droplets through nozzle openings provided on the edge of a substrate. Moreover, though the actuator described hereunder is an electrostatic driving type, the actuator can be any driving types.
Unlike a typical electrostatic driving type ink-jet head that has a three-layered structure including a nozzle substrate, a cavity substrate and an electrode substrate which are adhered together, an ink-jet head 10 (an example of the droplet discharge head) shown in
The nozzle substrate 1 is for example about 50 μm thick and made of silicon. A nozzle opening 11 is provided in the plural number in a predetermined pitch in the nozzle substrate 1. Though only five nozzle openings 11 arranged in a row are shown in
Each nozzle opening 11 has an injection tip 11a which is a small opening part provided coaxially and vertically to the substrate face and an introduction part 11b whose diameter is larger than that of the injection tip 11a.
The reservoir substrate 2 has a thickness of for example about 180 μm and is made of for example a (100)-silicon which has a plane direction of (100). A nozzle communicating opening 21 is provided in the plural number in the reservoir substrate 2. Each nozzle communicating opening 21 vertically penetrates the reservoir substrate 2 and communicates with the nozzle opening 11 respectively. The diameter of the nozzle communicating opening 21 is relatively large (equal or larger than the diameter of the introduction part 11b). A reservoir concave portion 23a which is a common reservoir 23 (common ink chamber) communicating with the nozzle communicating openings 21 and the nozzle openings 11 through feed openings 22 is provided in the reservoir substrate 2.
The reservoir concave portion 23a opens wider toward a bonding plane (hereinafter also called as an “N-plane”) with the nozzle substrate 1 and its cross-sectional shape is a substantially inverted trapezoid. Under a bottom wall 23b of the reservoir concave portion 23a toward the cavity substrate 3, a void part 110 reaching a bonding plane (hereinafter also called as “C-plane”) of the reservoir substrate 2 and the cavity substrate 3 is provided in the reservoir substrate 2.
Furthermore, a shallow concave portion 23c (second concave portion) whose depth is much smaller than that of the reservoir concave portion 23a is provided on the periphery of the opening of the reservoir concave portion 23a in the reservoir substrate 2. A resin thin film 111 is provided on the whole face of the reservoir substrate 2 (provided on the whole inner face of the reservoir concave portion 23a and the bottom face of the shallow concave portion 23c) where the reservoir concave portion is formed, but the film is not formed in the area of the bonding face with the cavity substrate 3 and on the inner face of the nozzle communicating opening 21. The shallow concave portion 23c is formed so as to have a smaller depth than the thickness of the resin thin film 111 and such that the top face of the thin film 111 will not protrude from the top face of the reservoir substrate 2. The resin thin film 111 is hereunder described in detail.
A part of the resin thin film 111 where opposes the void part 110 forms a part of the bottom face of the reservoir concave portion 23a and also serves as a diaphragm 100 which buffers the pressure variation. In other words, the part of the resin thin film 111 which faces the void part 110 floats in the space between the void part 110 and the reservoir concave portion 23a. The void part 110 allows the resin thin film 111 to be deflected.
The resin thin film 111 is formed in the fabrication process of the reservoir substrate 2 and is made of for example parylene.
The feed openings 22 and an ink feed opening 27 though which ink is supplied to the reservoir 23 from an outside source are formed in the bottom wall 23b of the reservoir concave portion 23a so as to avoid the diaphragm 100.
A second concave portion 28 which is a long narrow groove consisting a part of a discharge chamber 31 is formed in the C-plane of the reservoir substrate 2. The second concave portion 28 is provided in order to prevent the resistance in the flow channel of the discharge chamber 31 from being increased especially when the cavity substrate 3 is made thin. The second concave portion 28 is provided if needed and it is not necessarily formed.
The nozzle communicating opening 21 which penetrates the reservoir substrate 2 is formed so as to be coaxial to the nozzle opening 11 in the nozzle substrate 1 so that ink droplets can be discharged straight. In this way, the discharge characteristic is significantly improved. This means that an infinitesimal amount of the ink droplet can be discharged and provided at a desired position and it is possible to precisely reproduce a subtle change in tone of an image without causing a color drift and the like. Therefore it is possible to realize a fine and high image quality.
The cavity substrate 3 is made of for example silicon and has a thickness of for example about 30 μm. A first concave portion 33 which serves as the discharge chamber 31 is provided in the plural number in the cavity substrate 3. Each first concave portion 33 communicates with the corresponding nozzle communicating opening 21. The first concave portion 33 and the second concave portion 28 together forms the discharge chamber 31. The bottom wall of the discharge chamber 31 (first concave portion 33) forms a vibrating plate 32. The vibrating plate 32 can be made of a boron diffused layer which is formed by diffusing highly-concentrated boron into silicon. When the vibrating plate 32 is made of the boron diffused layer, etching stop works well in a wet-etching process. Thereby it is possible to precisely control the thickness of the vibrating plate 32 and the roughness of the plate surface.
An insulating film (not shown in the drawings) having a thickness of for example 0.1 μm and made of for example an SiO2 film which is formed by plasma chemical vapor deposition (CVD) using Tetraethyl-orthosilicate Tetra-ethoxysilane (TEOS) is formed at least on the lower face of the cavity substrate 3. This insulating film is provided in order to prevent breakdown or shot-circuit when the ink-jet head 10 is driven. An ink protection film (not shown in the drawings) which is same as that of the reservoir substrate 2 is formed on the upper face of the cavity substrate 3. An ink feed opening 35 that communicates with the ink feed opening 27 in the reservoir substrate 2 is formed in the cavity substrate 3.
The electrode substrate 4 is for example a glass substrate having a thickness of about 1 mm. More specifically, it is preferable that a heat resistance and hard borosilicate glass whose thermal expansion coefficient is close to that of the silicon material of the cavity substrate 3 be used. If such heat resistance and hard borosilicate glass is adopted, it is possible to reduce the stress between the electrode substrate 4 and the cavity substrate 3 generated at the time when these substrates are anionically bonded because the thermal expansion coefficients of these substrates are close. Thereby it is possible to firmly bond the electrode substrate 4 with the cavity substrate 3 without causing any problems such as detachment.
A concave portion 42 is formed in the face of the electrode substrate 4 and provided in the plural number such that each concave portion 42 is situated correspondingly to the opposing vibrating plate 32 which is provided in the cavity substrate 3. The concave portion 42 is formed in about 0.3 μm deep by etching. At the bottom face of each concave portion 42, an individual electrode 41 which is typically made of indium tin oxide (ITO) and has a thickness of for example 0.1 μm is formed by sputtering. The size of an air gap G formed between the vibrating plate 32 and the individual electrode 41 is decided by the depth of the concave portion 42 and the thicknesses of the insulating films that cover the individual electrode 41 and the vibrating plate 32. The discharge characteristic of the ink-jet head 10 is largely affected by the size of the air gap G. In this embodiment, the size of the air gap G is 0.2 μm. An open edge of the air gap G is air-tightly sealed by a sealing member 43 which is made of an epoxy adhesive and the like. With this sealing member, it is possible to prevent foreign matter, moisture and the like from getting into the air gap G. In this way, it is possible to secure the reliability of the ink-jet head 10.
The individual electrode 41 can be made of other metals such as indium zinc oxide (IZO), gold and copper in addition to the ITO. The ITO is generally used because the ITO is transparent and the contacting state of the vibrating plate can be easily checked with eyes.
A terminal part 41a of the individual electrode 41 is exposed on an electrode extraction part 44 which is formed by removing the edges of the reservoir substrate 2 and the cavity substrate 3. In the electrode extraction part 44, a flexible wiring substrate (not shown in the drawings) for example on which a driving control circuit 5 such as a driver IC is mounted is coupled with the terminal parts 41a of the individual electrodes 41 and with a common electrode 36 which is provided on the peripheral of the cavity substrate 3.
An ink feed opening 45 which is coupled to an ink cartridge (not shown in the drawings) is provided in the electrode substrate 4. The ink feed opening 45 communicates with the reservoir 23 through the ink feed opening 35 provided in the cavity substrate 3 and the ink feed opening 27 provided in the reservoir substrate 2.
Operation of the ink-jet head 10 is now described.
Ink is firstly supplied from an external ink cartridge (not shown in the drawings) into the reservoir 23 through the ink feed openings 45, 35, 27. The supplied ink flows through the feed openings 22 and fills each discharge chamber 31 and each nozzle communicating opening 21 to the tips of the nozzle openings 11. The driving control circuit 5 such as a driver IC that controls the operation of the ink-jet head 10 is provided and coupled between the individual electrodes 41 and the common electrode 36 in the cavity substrate 3.
When the driving control circuit 5 supplies a driving signal (pulse voltage) to the individual electrode 41 and the pulse voltage is applied to the individual electrode 41, the individual electrode 41 is positively charged whereas the corresponding vibrating plate 32 is negatively charged. In this state, an electrostatic force (Coulomb force) is generated between the individual electrode 41 and the vibrating plate 32, and the vibrating plate 32 is deflected toward the individual electrode 41 by the electrostatic force. This increases the volume of the discharge chamber 31. Subsequently when the pulse voltage is turned off, the electrostatic force disappears and the vibrating plate 32 gets back to the original position by its elastic force and the volume of the discharge chamber 31 is drastically decreased. This action generates a pressure. A part of the ink in the discharge chamber 31 is pushed toward the nozzle communicating opening 21 by the pressure, and the ink is discharged from the nozzle opening 11 in a form of droplet. When the pulse voltage is applied again, the vibrating plate 32 is deflected toward the individual electrode 41, and the discharge chamber 31 is supplied with the ink from the reservoir 23 through the feed opening 22.
According to the embodiment, the pressure in the discharge chamber 31 is transmitted to the reservoir 23 when the ink-jet head 10 is driven. The diaphragm 100 having the resin thin film 111 is provided on the bottom wall 23b of the reservoir 23 as described above. Thereby the resin thin film 111 is deflected downward into the void part 110 when the pressure in the reservoir 23 is positive, whereas the resin thin film 111 is deflected upward from the void part 110 when the pressure in the reservoir 23 is negative. This buffers the pressure variation in the reservoir 23, and it is possible to prevent the pressure interference among the nozzle openings 11. Consequently, it is possible to eliminate the troubles such that the ink is leaked from other nozzles than the driven nozzle, the amount of the ink discharged from the driven nozzle falls short of the required amount, and the like.
Moreover, the resin thin film 111 is provided on the bottom wall 23b of the reservoir 23 according to the embodiment so that it is possible to increase the area of the diaphragm 100 so as to increase the pressure buffering effect.
Furthermore, according to the embodiment, the resin thin film 111 is formed throughout the inner face of the reservoir concave portion 23a and on the bottom face of the shallow concave portion 23c. And the resin thin film 111 which serves as the diaphragm 100 is uniformly formed on the surface of the bottom wall 23b of the reservoir 23, a part of the peripheral wall of the feed opening 22, and a part of the peripheral wall of the ink feed opening 27. Therefore the contact area of the resin thin film 111 and the reservoir substrate 2 becomes relatively large compared with the case shown in
Furthermore, according to the embodiment, the diaphragm 100 is provided in the reservoir substrate 2, and the C-plane side is not exposed to the outside since it is covered by the cavity substrate 3. Thereby it is possible to protect the diaphragm 100 having the resin thin film 111 from external force, and it is not necessary to provide a protection member such as a protection cover. Accordingly, it is possible to downsize the ink-jet head 10 and to cut the cost.
According to the embodiment, the diaphragm 100 is formed to have a relatively large area so that it is possible to steadily deflect (vibrate) in the void part 110. A small vent (not shown in the drawings) which couples the void part 110 with the outside can be provided in the cavity substrate 3 or the electrode substrate 4 if needed.
A method for manufacturing the ink-jet head 10 according to the embodiment will be now described with reference to
A method for manufacturing the reservoir substrate 2 is described with reference to
a) A reservoir base substrate 200 which is made of the (100)-silicon and has a thickness of 180 μm is provided. Both faces of the reservoir base substrate 200 is coated with a resist 200a and a part 200b where the shallow concave portion 23c is going to be formed is patterned on a nozzle substrate bonding face (hereinafter called a “N-plane”) as shown in
b) Referring to
c) Referring to
d) Referring now to
e) Referring to
f) Referring to
g) Referring now to
h) Referring to
i) The thermally-oxidized film 201 is removed and a thermally-oxidized film 201a having a thickness of 0.2 μm is then formed as shown in
j) Referring to
k) Referring to
l) Referring now to
As described above, the resin thin film 111 is formed in the manufacturing process of the reservoir substrate 2.
m) Referring to
n) Referring to
o) Referring to
Through the above-described process, the reservoir substrate 2 is fabricated.
Manufacturing processes of the electrode substrate 4 and the cavity substrate 3 are now described with reference to
The electrode substrate 4 is fabricated in the following manner.
a) Referring now to
The individual electrodes 41 made of indium tin oxide (ITO) are formed inside the concave portion 42 by sputtering and patterning. Subsequently, a part 45a where the ink feed opening 45 is going to be formed is formed by performing blast or the like. In this way, the electrode substrate 4 is fabricated.
b) A cavity base substrate 300 made of silicon and having a thickness of about 220 μm is prepared. A boron-doped layer (not shown in the drawings) having a predetermined thickness is formed on the face where is bonded with the electrode substrate 4, this face is referred as an E-plane. Referring now to
c) Referring now to
d) Referring to
e) Referring to now
f) The surface of the TEOS oxide film 301 is coated with a resist (not shown in the drawings). The resist is then patterned by photolithography. The TEOS oxide film 301 is subsequently etched so as to form parts 33a, 35a, 44a where respectively the first concave portion 33 of the discharge chamber 31, the ink feed opening 35 and the electrode extraction part 44 are formed as shown in
g) Referring to
In this etching process, a potassium hydroxide solution of 35 wt % concentration is firstly used to etch the cavity base substrate 300 till its thickness becomes for example 5 μm. A potassium hydroxide solution of 3 wt % concentration is then used in order to generate an effect of etching stop and to prevent the surface of the part 32a where the vibrating plate 32 is going to be formed from becoming rough. In this way, it is possible to obtain a desired thickness as fine as 0.80±0.05 μm. Here the etching stop is defined as the state where bubbles are not generated anymore from the etching face. In case of the practical wet-etching, the etching stop is judged by whether bubble generation is stopped or not.
h) After the etching of the cavity base substrate 300 is finished, the TEOS oxide film 301 which is formed on the upper face of the cavity base substrate 300 is remove by etching using a hydrofluoric acid solution as shown in
i) Referring now to
j) Referring now to
Through the above-described process, the cavity substrate 3 is fabricated from the cavity base substrate 300 to which the electrode substrate 4 is bonded.
k) Referring now to
l) Referring to
m) Referring to
As described above, the ink-jet head according to the embodiment has a structure in which the diaphragm 100 is formed separately from the discharge chamber 31 in the substrate (the reservoir substrate 2) other than the substrate of the discharge chamber 31 (the cavity substrate 3). Thereby it is possible to secure a sufficient volume of the reservoir 23. Accordingly, the nozzles 11 can be arranged densely. In addition, the compliance of the reservoir 23 can be reduced and this decreases the pressure variation in the reservoir 23. Consequently, it is possible to prevent the pressure interference among the nozzles which occurs when the ink is discharged. In other words, it is possible to obtain a fine discharge characteristic.
Moreover, according to the embodiment, the diaphragm 100 is provided in the reservoir substrate 2 and the diaphragm 100 is included in a head chip. Thereby an external force will not be applied to the diaphragm 100 and the diaphragm 100 can be made thinner. It is possible to enhance the strength against the external force of the head unit without providing a protection member such as a protection cover for the diaphragm 100.
Furthermore, according to the embodiment, the diaphragm 100 in the reservoir substrate 2 is situated at the bottom face of the reservoir 23. Thereby it is possible to make the area of the diaphragm 100 large because the whole bottom face of the reservoir 23 serves as the diaphragm 100. Consequently, the pressure buffering effect of the diaphragm 100 can be increased.
The diaphragm 100 is formed by forming the resin thin film 111 so that the diaphragm 100 and other component can be simultaneously fabricated on the wafer and it improves the production efficiency.
Moreover, according to the embodiment, the void part 110 into which the diaphragm 100 is deflected is formed by etching the face opposite to the face on which the reservoir 23 is formed. This means that it is not necessary to process the cavity substrate 3 and the nozzle substrate 1 in order to form the void part 110. Therefore the design or processing of the cavity substrate 3 and the nozzle substrate 1 will not be affected.
Furthermore, according to the embodiment, the shallow concave portion 23c has a depth which is larger than the thickness of the resin thin film 111. Therefore, the surface of the resin thin film 111 will not protrude out from the surface of the shallow concave portion 23c. Accordingly, deterioration of the adhesiveness caused by the resin thin film 111 contacting with the nozzle substrate 1 will not happen.
The resin thin film 111 is formed only on the inner face of the reservoir 23 and the bottom face of the shallow concave portion 23c. The resin thin film 111 is not formed the bonding faces of the reservoir substrate 2 with the nozzle substrate 1 and with the cavity substrate 3. Thereby the deterioration of the adhesiveness at the bonding faces will not occur since the resin thin film 111 is not interposed therebetween.
Furthermore, according to the embodiment, a part of the resin thin film 111 is cut in the shallow concave portion 23c, and the unnecessary part of the resin thin film 111 is removed when the protection film 204 is removed. This simplifies the manufacturing process.
Furthermore, according to the embodiment, the resin thin film 111 is formed of the parylene. Thereby it is possible to form a defect-free resin thin film which has a fine coatability and is highly resistant against heat, chemicals and vapor. In addition, the thin film of the diaphragm 100 which is made of the parylene can exert the pressure absorption effect 100-1000 times greater than that of the case where it is made of for example a silicon thin film.
In the embodiment, the leaser is used to cut the resin thin film 111 so that it can be cut along the desired line.
Moreover, according to the embodiment, the protection film 204 which protects the N-plane when the resin thin film 111 is formed has the opening 204a which is larger than the size of the reservoir concave portion 23a. Thereby even if the protection film 204 is not well aligned with the reservoir substrate 2, the resin thin film 111 is securely formed on the reservoir concave portion 23a. Accordingly it is possible to secure the cutting region of the resin thin film 111.
Moreover, according to the embodiment, the C-pane of the reservoir substrate 2 is also protected by the protection film 203 so that it is possible to prevent the resin thin film 111 from being formed on the boding face of the reservoir substrate 2 with the cavity substrate 3. Consequently, the deterioration of the adhesiveness at the bonding face between the reservoir substrate 2 and the cavity substrate 3 will not occur since the resin thin film 111 is not interposed therebetween.
Furthermore, according to the embodiment, hydrophilicity is imparted to the surface of the resin thin film 111 through the oxide plasma treatment. Therefore, it is easy to secure the hydrophilicity for the droplet flow channels.
Moreover, according to the embodiment, the SF6 plasma is used in the dry-etching for forming the diaphragm 100. Therefore, it is possible to minimize the damage given to the resin thin film 111 when the silicon is dry-etched.
Furthermore, according to the embodiment, the void part 110 is provided on the side of the bonding face of the reservoir substrate 2 with the cavity substrate 3. In other words, the discharge chamber 3 is formed on the opposite side to the side where the reservoir 23 is formed in the reservoir substrate 2. Thereby, the reservoir 23 can be placed such that it overlaps the discharge chamber 31 of the cavity substrate 3, and it is possible to minimize the area of the ink-jet head.
Though the parylene is used for forming the resin thin film 111 in the above-described embodiment, the resin thin film 111 can be formed of other material such as Cytop© transparent fluoropolymers (product by Asahi Glass Co. LTD).
Though the electrostatic driving type ink-jet head and the manufacturing method thereof have been described in the above embodiment, the invention is obviously not limited to the specific embodiments herein, but also encompasses any variations that may be considered by any person skilled in the art, within the general scope of the invention. For example, the invention can be also applied to other driving type ink-jet head in addition to the electrostatic driving type. In the case of a piezoelectric type, a piezoelectric element is adhered to the bottom face of each discharge chamber instead of the electrode substrate. In the case of a bubble type, a heat element is provided on the bottom face of each discharge chamber. The ink-jet head 10 according to the embodiment can be used for fabrication of various parts components of various devices by changing the kinds of droplets discharged from the head. In addition to the ink-jet printer shown in
Number | Date | Country | Kind |
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2006-274068 | Oct 2006 | JP | national |