JP3972932B2 - INK JET HEAD MANUFACTURING METHOD AND INK JET DEVICE - Google Patents

Description

  The present invention relates to an inkjet head of an inkjet printer. More particularly, the present invention relates to a structure of an ink jet head suitable for preventing pressure interference between ink nozzles.

  Various types of inkjet heads are known depending on the mechanism for generating (discharging) ink droplets. For example, there is an ink jet head of a type that heats a heater to boil ink and ejects ink droplets with a bubble pressure generated thereby. In addition, there is an ink jet head that ejects ink droplets by expanding and contracting the volume of a pressure chamber by applying a voltage to a piezoelectric element attached to a pressure chamber that stores ink. Further, there is a type in which ink droplets are ejected by changing the volume of a pressure chamber storing ink using electrostatic force. In any type of ink jet head, ink droplets are ejected only when necessary for recording by utilizing the pressure fluctuation in the pressure chamber.

  These types of inkjet heads are generally arranged corresponding to each of a plurality of ink nozzles, and pressure chambers for ejecting ink droplets from the corresponding ink nozzles by pressure fluctuations, and supplying ink to each pressure chamber Each of the pressure chambers and an ink supply port communicating with the ink reservoir. The pressure chamber, the ink reservoir, and the ink supply port are partitioned and formed in a state of being arranged in a plane direction between the substrates by overlapping the flat substrates.

  When pressure fluctuation is generated in the pressure chamber to eject ink droplets, the pressure (ejection pressure) is transmitted to the ink reservoir. When pressure fluctuations occur in the ink reservoir, pressure interference occurs between the ink nozzles via the ink reservoir, and the ink droplet ejection amount changes or ink nozzles other than the ink nozzle (drive nozzle) that you want to eject There is a problem that ink droplets leak from the (non-driven nozzle). For example, when a positive pressure is generated in the ink reservoir, ink droplets leak from the non-driving nozzle, and when a negative pressure is generated in the ink reservoir, the ink discharge amount from the driving nozzle is reduced.

  In order to avoid such an adverse effect, Japanese Patent Publication No. 2-59769 discloses a unit called an ink distribution plate provided with a diaphragm that relieves pressure shock. When this unit is assembled to a member on which ink nozzles are formed, pressure fluctuations generated in the ink reservoir by the diaphragm are suppressed. As a result, desired ink ejection characteristics can be obtained.

  Ink jet heads are required to be smaller and thinner with the miniaturization of printers. However, if the ink distribution plate disclosed in Japanese Patent Publication No. 2-59769 is separately assembled, the ink jet head cannot be reduced in size and thickness.

  An object of the present invention is to propose an ink jet head that can prevent pressure interference between ink nozzles without increasing the size of the ink jet head.

  Another object of the present invention is to propose an ink jet head that can easily form a diaphragm for preventing pressure interference having a target characteristic.

In order to solve the above problems, in the method of manufacturing an ink jet head according to the present invention, a first substrate on which ink nozzles are formed, and a second substrate on which a recess serving as a first substrate and a pressure chamber is formed. By superimposing each other, a pressure chamber that is disposed corresponding to each of the plurality of ink nozzles that eject ink, and that ejects ink droplets from the corresponding ink nozzle by pressure fluctuation, and each pressure chamber An ink jet head manufacturing method in which an ink reservoir that supplies ink to an ink supply port and an ink supply port that communicates each pressure chamber with the ink reservoir are partitioned and formed in a planar direction,
A first etching step of etching one surface of the first substrate to form a recess for forming an ink nozzle portion and a pressure fluctuation buffer portion;
A second etching step of etching the other surface of the first substrate, penetrating the nozzle, and forming a flexible pressure fluctuation buffer portion having a thickness;
And a step of bonding the first substrate and the second substrate.

In the method for manufacturing an inkjet head of the present invention, the first substrate and the second substrate are silicon. Therefore, since it is not necessary to assemble another member such as an ink distribution plate, an ink jet head that can prevent pressure interference between ink nozzles without increasing the size can be realized.

Furthermore, in the method of manufacturing an ink jet head according to the present invention, before the first etching step, an oxide film is formed on the surface of the first substrate, the oxide film is half-etched, Forming a pattern for forming an ink supply port and a pressure fluctuation buffer portion;
Forming a pattern for forming a small cross-section nozzle portion by etching in a half etching region corresponding to the large cross-section nozzle portion of the ink nozzle.

Note that the first etching is anisotropic dry etching, and the second etching is anisotropic wet etching.

(overall structure)
FIG. 1 is a perspective view showing the external shape of an inkjet head to which the present invention is applied. 2 is an exploded perspective view of a part of the ink jet head, and FIG. 3 is a partial cross-sectional view thereof.

  As shown in these drawings, the inkjet head 1 is a face inkjet type that ejects ink droplets from an ink nozzle provided on the upper surface of a substrate, and is of an electrostatic drive type. The inkjet head 1 has a laminated structure in which a nozzle plate (first substrate) 2, a cavity plate (second substrate) 3, and a glass substrate 4 are bonded together in this order.

  The cavity plate 3 is, for example, a silicon substrate, and a recess 7 that forms a pressure chamber 6 whose bottom wall functions as the diaphragm 5 on the surface of the plate, and an ink supply port provided at the rear of the recess 7. 8 are formed by etching, and a recess 11 that forms an ink reservoir 10 for supplying ink to each pressure chamber 6 is formed by etching. The lower surface of the cavity plate 3 is smoothed by mirror polishing and serves as a mounting portion for the glass substrate 4.

  In the nozzle plate 2 joined to the upper surface of the cavity plate 3 (the substrate surface on the groove forming side), a plurality of ink nozzles 21 communicating with each pressure chamber 6 are formed on the wall portion defining the upper surface of the pressure chamber 6. Has been. The ink nozzle 21 has a stepped cross section, and a circular small section nozzle portion 21a is formed on the front side in the ink droplet ejection direction, and a circular large section nozzle portion 21b is formed on the rear side.

  When the nozzle plate 2 and the cavity plate 3 are overlapped with each other, the pressure chamber 6, the ink supply port 8, and the ink reservoir 10 are arranged in the plane direction H between the plates 2 and 3. It is divided into sections.

  In the glass substrate 4 bonded to the lower surface of the cavity plate 3, an ink supply hole 19 is formed in a wall portion corresponding to the bottom surface of the ink reservoir 10. The ink supply hole 19 extends to the ink reservoir 10. An external ink supply source such as an ink tank is connected to the ink supply hole 19 via a connection pipe. Ink can be supplied from the ink supply source to the ink reservoir 10 through the ink supply hole 19.

  In the glass substrate 4, concave portions 13 that constitute the vibration chambers 12 are formed in portions facing the respective vibration plates 5. An individual electrode 14 that faces the diaphragm 5 is disposed on the bottom surface of the recess 13. The individual electrode 14 is connected to the terminal portion 16 via the lead portion 15. The individual electrodes 14 and the lead portions 15 except for the terminal portions 16 are covered with an insulating film 17. A lead wire 18 is bonded to each terminal portion 16.

  The diaphragm 5 that defines the bottom surface of each pressure chamber 6 formed in the cavity plate 2 functions as a common electrode, and a driver 20 is connected between the common electrode and the terminal portion 16 of each individual electrode 14. Has been. When applied to the individual electrode 14 by the driver 20, the diaphragm 5 facing the individual electrode 14 to which a voltage is applied vibrates due to electrostatic force, and the pressure in the pressure chamber 6 fluctuates accordingly, and the ink nozzle 21 Ink droplets 23 are ejected.

  For example, when a positive voltage pulse is applied to charge the surface of the individual electrode 14 to a positive potential, the corresponding lower surface of the diaphragm 5 is charged to a negative potential. Therefore, the diaphragm 5 is attracted by the electrostatic force and bent downward. Next, when the voltage pulse applied to the individual electrode 14 is turned off, the diaphragm 5 returns to the original position. By this returning operation, the internal pressure of the pressure chamber 6 rapidly increases, and the ink droplets 23 are ejected from the ink nozzles 21. Then, when the vibration plate 5 is bent downward, ink is supplied from the ink reservoir 10 to the pressure chamber 6 via the ink supply port 8.

  The ink used in the inkjet head 1 is prepared by dissolving or dispersing a surfactant such as ethylene glycol and a dye or pigment in a main solvent such as water, alcohol or toluene. Furthermore, if a heater is provided in the ink jet head, hot melt ink can also be used.

  Here, the partition wall portion 10a made up of the nozzle plate 2 and the cavity plate 3 that define the ink reservoir 10 is opposed to each other and extends in the plane direction H, and the first partition wall portion 10b and the second partition wall portion 10a. Partition wall portion 10c. Among these partition wall portions 10b and 10c, the first partition wall portion 10b on the side close to the ink supply port 8 has a thin pressure fluctuation buffer portion 22 in order to buffer the pressure fluctuation of the ink reservoir 10. Are formed in total.

FIG. 4 shows the correlation between the compliance Cr of the pressure fluctuation buffer portion 22 and the weight change rate of the ink discharge amount. As can be seen from this figure, if the compliance Cr of the pressure fluctuation buffer portion 22 is 1 × 10 ⁻¹⁷ [N / m ⁵ ], the weight change rate of the ink discharge amount can be maintained at about 75%, and the ink It can fully satisfy the requirements of discharge characteristics For this reason, in the inkjet head 1, the thickness and area of the pressure fluctuation buffer portion 22 are adjusted so that the compliance Cr of the pressure fluctuation buffer portion 22 is 1 × 10 ⁻¹⁷ [N / m ⁵ ] or more. is there. Therefore, even if the pressure fluctuation occurs in the ink reservoir 10, the pressure fluctuation is sufficiently reduced by the pressure fluctuation buffer portion 22, and the mutual pressure interference between the ink nozzles can be suppressed. In order to eliminate the mutual pressure buffer between the ink nozzles so that the ink discharge amount has almost no change in weight, the compliance Cr of the pressure fluctuation buffer portion 22 is set to 3 × 10 ⁻¹⁷ [N / m ⁵ ]. The above is most preferable.

  As described above, in the inkjet head 1, the pressure fluctuation buffering portion 22 is formed in the first partition wall portion 10 b extending in the plane direction H that defines the ink reservoir 10. Accordingly, it is not necessary to assemble another member such as an ink distribution plate disclosed in Japanese Patent Publication No. 2-59769, and pressure interference between ink nozzles can be prevented without increasing the size. In addition, since the pressure fluctuation buffer portion 22 having a large area can be formed, the pressure fluctuation buffer portion 22 for preventing pressure interference having a target characteristic can be easily formed.

  In the inkjet head 1, the first partition wall portion 10 b in which the pressure fluctuation buffering portion 22 is formed is a partition wall portion on the side close to the ink supply port 8. Therefore, the discharge pressure transmitted from the pressure chamber 6 via the ink supply port 8 can be absorbed by the pressure fluctuation buffer portion 22 when entering the ink reservoir 10. For this reason, since the pressure can be relieved in the stage before transmission to the ink reservoir 11, pressure interference between the ink nozzles can be effectively prevented.

  5 to 8 show an example of the manufacturing process of the nozzle plate 2. The manufacturing procedure of the nozzle plate 2 will be described with reference to these drawings.

(Step 1: first thermal oxide film forming step)
First, as shown in FIG. 5A, a silicon wafer 30 having a thickness of 180 microns is prepared, the silicon wafer 30 is thermally oxidized, and the thickness of the resist film on the surface is 1.2 microns or more. The SiO2 film 31 is formed.

(Step 2: First patterning step of SiO2 film)
Next, as shown in FIG. 5B, half-etching is performed on the portion of the SiO2 film 31 that covers the surface 30a of the silicon wafer 30, so that the large-section nozzle portion 21b of the ink nozzle 21 and the ink supply port 8 are formed. And patterns 32b and 33 for forming the first partition wall portion 10b of the ink reservoir 10 are formed. As an etchant, ammonium fluoride (HF: NH4F = 880 ml: 5610 ml) can be used.

(Step 3: Second patterning step of SiO2 film)
Thereafter, as shown in FIG. 5C, a pattern 32a for forming the small section nozzle portion 21a of the ink nozzle 21 is formed in a portion of the pattern 32b which is a half etching region of the SiO2 film 31. That is, these half-etched regions are etched to form a pattern 32a that exposes the silicon wafer surface. The etching liquid used in this case can also use the same ammonium fluoride as described above.

(Step 4: first dry etching step)
After the SiO2 film 210 is patterned twice in this way, anisotropic dry etching by ICP discharge is performed on the silicon wafer 30 as shown in FIG. As a result, the surface of the silicon wafer 30 is vertically etched in a shape corresponding to the pattern 32a formed in the above Step 3, and a groove 34 having a predetermined depth is formed. For example, CF4 and SF6 may be used as the etching gas in this case, and these etching gases may be used alternately. Here, CF4 is used to protect the groove side face so that the etching does not proceed to the side face of the groove to be formed, and SF6 is used to promote the vertical etching of the silicon wafer.

  After the grooves 34 are formed in this way, the SiO2 film 31 is etched away at an appropriate etching rate so that the patterns 32b and 33 are completely removed with an aqueous hydrofluoric acid solution. As a result, as shown in FIG. 6B, the portions of the patterns 32b and 33 formed in Step 2 are completely removed, and the surface of the silicon wafer 30 is exposed.

(Step 5: second dry etching step)
Next, as shown in FIG. 6C, anisotropic dry etching by ICP discharge is performed again. As a result, the surface portion of the exposed silicon wafer is vertically etched in the thickness direction while maintaining its cross-sectional shape. The etching gas in this case is also the same as in Step 4 above. As a result, a cross-sectional nozzle groove 36 corresponding to the stepped ink nozzle 21, a cross-sectional groove 37 corresponding to the ink supply port 8 and the first partition wall portion 10 b of the ink reservoir 10 are formed.

  Thereafter, the SiO2 film 31 is completely peeled off with a hydrofluoric acid aqueous solution (for example, HF: H2 O = 1: 5 vol, 25 [deg.] C.). FIG. 6D shows this state.

(Step 6: second thermal oxide film forming step)
Thereafter, as shown in FIG. 7A, the surface of the silicon wafer 30 is again thermally oxidized to form a SiO2 film 38 as a resist film. Even in this case, the thickness of the SiO2 film 38 may be 1.2 microns, for example.

(Step 7: Third patterning step of SiO2 film)
Next, as shown in FIG. 7B, a portion of the SiO2 film 38 that covers the surface 30b on the opposite side of the silicon wafer 30 is etched, and a pattern 40 corresponding to the recess in which the ink nozzles 21 are opened. , And a pattern 41 corresponding to the pressure fluctuation buffer portion 22 is formed. In this case, the etching solution used in Step 2 can be used.

(Step 8: Wet etching process)
Next, as shown in FIG. 7C, the silicon wafer 30 is immersed in an etching solution and anisotropic wet etching is performed on the exposed portion of the silicon wafer 30 to form a groove 42 and penetrate the nozzle 21. . Moreover, the groove | channel 43 is formed and the pressure fluctuation buffer part 22 of predetermined thickness is formed. The etching solution used in this case is an aqueous potassium hydroxide solution having a concentration of 2 wt% and a solution temperature of 80 ° C. After the etching is completed, as shown in FIG. 7D, the SiO2 film 38 is completely removed with a hydrofluoric acid aqueous solution. As a result, the surface of the silicon wafer 30 is exposed.

  Finally, as shown in FIG. 8, in order to ensure the ink resistance of the silicon wafer and the adhesion of the water repellent treatment of the nozzle surface, the silicon wafer is again thermally oxidized to form a SiO2 film. Thus, the nozzle plate 2 is obtained. By joining the cavity plate 3 to the nozzle plate 2 obtained in this manner, the pressure chamber 6, the ink supply port 8, and the ink reservoir 10 are partitioned and formed in the plane direction H.

[Other embodiments]
The shape of the nozzle plate 2 is not limited to the above example, and may be a shape as shown in FIGS. 9A to 9D. The determination may be made in consideration of the volume of the ink reservoir 2 and the like.

  In order to protect the pressure fluctuation buffer portion 22 from the outside, it is desirable to cover the portion with a protective cover 25 as shown in FIG. However, as shown in FIG. 10 (A), if it is completely covered by the protective cover 25, it may become airtight and may adversely affect the vibration of the pressure fluctuation buffer portion 22. For this reason, as shown in FIG. 10 (B), it is more desirable to provide a vent 25a in the protective cover 25.

The inkjet head 1 described above is a face inkjet type that ejects ink droplets 23 from the upper surface of the nozzle plate 2, but the present invention is also applied to an edge inkjet type that ejects ink droplets 23 from the side of the nozzle plate 2. it can.

It is a perspective view which shows the external appearance shape of the inkjet head to which this invention is applied. It is a disassembled perspective view which shows a part of inkjet head shown in FIG. It is a fragmentary sectional view which shows a part of inkjet head shown in FIG. It is a graph which shows the correlation of the change of the weight of the variation of a pressure fluctuation buffer part, and the ink discharge amount. (A) is an explanatory view showing the first thermal oxide film forming step in the manufacturing process of the nozzle plate of the inkjet head of FIG. 1, (B) is an explanatory view showing the first patterning step of the SiO2 film, (C) is It is explanatory drawing which shows the 2nd patterning process of a SiO2 film. (A) is explanatory drawing which shows the 1st dry etching process with respect to the silicon wafer in the manufacturing process of the nozzle plate of the inkjet head of FIG. 1, (B) is explanatory drawing which shows the state after removing a half etching part, (C ) Is an explanatory view showing a second dry etching process for the silicon wafer, and (D) is an explanatory view showing a state after the SiO2 film is removed. (A) is an explanatory view showing a second thermal oxide film forming step in the manufacturing process of the nozzle plate of the ink jet head of FIG. 1, (B) is an explanatory view showing a third patterning step of the SiO2 film, and (C) is an explanatory view. FIG. 4D is an explanatory view showing a wet etching process for a silicon wafer, and FIG. 4D is an explanatory view showing a state after removing the SiO2 film. It is explanatory drawing which shows the last thermal oxide film formation process in the manufacturing process of the nozzle plate of the inkjet head of FIG. It is sectional drawing which shows the example of the nozzle plate different from the nozzle plate of the inkjet head of FIG. It is sectional drawing which shows the example in which the protective cover which protects a pressure fluctuation buffer part is attached to the nozzle plate.

Explanation of symbols

1 Inkjet head 2 Nozzle plate (first substrate)
3 Cavity plate (second substrate)
4 Glass substrate 5 Vibrating plate 6 Pressure chamber 8 Ink supply port 10 Ink reservoir 10a Partition wall portion 10b First partition wall portion 10c Second partition wall portion 12 Individual electrode 21 Ink nozzle 22 Pressure fluctuation buffer portion 25 Protective cover 25a through Pore H Plane direction

Claims (6)

A plurality of the first substrate on which the ink nozzles are formed and the second substrate on which the first substrate and the recesses that form the pressure chambers are overlapped with each other, thereby ejecting ink therebetween. A pressure chamber that is disposed corresponding to each of the ink nozzles and discharges ink droplets from the corresponding ink nozzles by pressure fluctuations, an ink reservoir that supplies ink to each pressure chamber, and each pressure chamber is connected to the ink reservoir A method of manufacturing an ink jet head, wherein the ink supply ports communicated with each other are partitioned and formed in a state of being arranged in a plane direction,
A first etching step of etching one surface of the first substrate to form a recess for forming the ink nozzle portion and the pressure fluctuation buffer portion;
Etching the opposite surface of the first surface of the first substrate, penetrating the nozzle, and forming the pressure fluctuation buffer portion to a flexible thickness; and
A method of manufacturing an ink jet head, comprising the step of bonding the first substrate and the second substrate.   2. The method of manufacturing an ink jet head according to claim 1, wherein the first substrate and the second substrate are silicon. The ink nozzle has a two-stage structure in which a large cross-section nozzle portion and a small cross-section nozzle portion smaller than the cross-sectional area of the large cross-section nozzle portion overlap,
Before the first etching step, an oxide film is formed on the surface of the first substrate, the oxide film is half-etched, the large-section nozzle portion of the ink nozzle, the ink supply port, and the pressure fluctuation buffer. Forming a pattern for forming a portion;
3. The method of manufacturing an ink jet head according to claim 1, further comprising a step of forming a pattern for forming the small section nozzle portion on the first substrate by etching.   The method of manufacturing an ink jet head according to claim 1, wherein the first etching is anisotropic dry etching.   The method of manufacturing an ink jet head according to claim 1, wherein the second etching is anisotropic wet etching.   An inkjet apparatus having an inkjet head manufactured by the inkjet manufacturing method according to claim 1.

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