JP4580203B2 - Inkjet head manufacturing method and inkjet head - Google Patents

Description

  The present invention relates to an inkjet head manufacturing method and an inkjet head.

  Ink jet heads are used in printers, fax machines, and the like, and are further used for manufacturing filters and the like provided in liquid crystal display devices, and are widely used in industrial applications. As an inkjet head, an inkjet head of a system that ejects ink droplets from a plurality of nozzles is generally used, and a piezoelectric inkjet head that uses a piezoelectric member as an ejection force generating member that generates the ejection force, or an ejection generating member As a thermal ink jet head using a heating element has been developed.

  In such an ink jet head, in order to prevent the image quality from being deteriorated, the ink discharge amount of the ink discharged from a plurality of nozzles is required to be uniform. Further, even when a plurality of inkjet heads are used for color printing, printing on a large sheet, or the like, in order to prevent deterioration in image quality, it is required to make the ink discharge amount uniform between these inkjet heads. There are many factors that cause the ink discharge amount of the inkjet head to be non-uniform, but it is possible to suppress variations in the ink discharge amount to some extent by inspection in the manufacturing process of the inkjet head, control of processing accuracy, and the like. However, there is a limit to this, and it is difficult to make the ink discharge amount uniform.

  When a piezoelectric ink jet head is used, the ink discharge amount may become non-uniform due to variations in characteristics of the piezoelectric member. In particular, when PZT (lead zirconate titanate), which is a sintered ceramic, is used as the piezoelectric member, it is difficult to keep the characteristics constant. This is because the characteristics of PZT differ depending on the location, or differ stepwise depending on the production lot. Usually, a large block of PZT is cut into several tens of micron sections and used as an inkjet head as a piezoelectric member. Therefore, sections with different characteristics are used in the sections, or sections with different characteristics among a plurality of inkjet heads. It will be used.

  Even when PZT is molded by screen printing or the like and sintered, there is an error in the PZT volume, mainly in the thickness direction, resulting in non-uniform ink discharge as in the case of using large PZT. End up. Even when a thermal ink jet head is used, the ink discharge amount may be non-uniform due to variations in resistance values of the heating elements. Since the heating element is mainly produced by the sputtering method, the resistance value of the heating element varies depending on the film thickness distribution.

  In order to make the ink discharge amount uniform, several methods have been proposed. For example, there is a method of changing conditions when ink is ejected from an inkjet head. This method is a method of making the ink discharge amount uniform by changing the voltage application condition for each nozzle of the inkjet head. Moreover, in patent document 1, the discharge chamber for discharging an ink is shaved with a laser processing machine, and discharge conditions are made uniform. In Patent Document 2, the variation of the ink discharge amount (discharge volume) is suppressed by adjusting the nozzle area and the nozzle volume. In Patent Document 3, the actuator units having piezoelectric elements are ranked by measuring the capacitance of the piezoelectric elements, and the ejection characteristics are made uniform by combining the actuator units of the same rank and mounting them on the inkjet head. Yes.

JP 2003-136708 A JP 2003-94666 A JP 2003-326723 A

  However, in the method in which the voltage application condition is changed for each nozzle, driving is performed according to each condition of several tens to several hundreds of nozzles, and thus drive control becomes difficult. In both Patent Document 1 and Patent Document 2, the ink discharge amount (discharge volume) of the completed inkjet head is measured. For this reason, after the completion of the inkjet head, the manufacturing process of ejection → measurement → cleaning → processing is performed, which is inefficient because the manufacturing process becomes longer.

  In Patent Document 1, the ink discharge amount can be adjusted only in one direction because a cutting process is performed to cut the diaphragm with a laser processing machine. Further, in Patent Document 2, since the nozzle is processed again after forming the nozzle, fine alignment is necessary to maintain the nozzle pitch during reprocessing, and the alignment operation is difficult. Furthermore, in Patent Document 3, the number of piezoelectric elements corresponding to the number of nozzles is measured, the actuator units are ranked, and the same rank actuator units are combined. However, this operation is not easy and inefficient. It is.

  An object of the present invention is to easily realize uniform ink discharge amount of an ink jet head and to efficiently manufacture the ink jet head.

The present invention provides a method of manufacturing an ink jet head to produce an ink jet head for discharging ink droplets from a plurality of nozzles by ejection force generating member for generating a discharge force, the electrical characteristics before Symbol ejection force generating member before Symbol each nozzle and measuring the change containers product before Symbol nozzle according to the electric characteristics of the ejection force generating member, before Symbol amounts Louis ink discharge amount is in a predetermined issue nozzle or al-discharge of the previous SL each nozzle measured , forming a pre-Symbol nozzle to be characterized in that it comprises a.

  Therefore, the nozzle volumes of the plurality of nozzles are changed according to the electrical characteristics of the ejection force generating member for each of the plurality of nozzles, and the respective ink ejection amounts become a predetermined ink ejection amount.

  According to the present invention, since the ink discharge amount is accurately and uniformly adjusted in a short manufacturing process, the ink discharge amount of the ink jet head can be easily made uniform, and the ink jet head can be manufactured efficiently.

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

<Inkjet head>
An inkjet head 1 according to the present embodiment will be described with reference to FIG. FIG. 1 is an exploded perspective view schematically showing an inkjet head 1 according to the present embodiment.

  As shown in FIG. 1, an inkjet head 1 includes a head body 3 having a plurality of ink chambers 2 that respectively store ink, and a nozzle plate 5 having nozzles 4 that are a plurality of through holes that respectively communicate with the plurality of ink chambers 2. And a top plate 7 having a common ink chamber 6 provided in the head body 3 and communicating with the ink chamber 2.

  The head body 3 is formed by laminating an upper substrate 8 and a lower substrate 9 at least one of which is made of a piezoelectric member. In the present embodiment, the head body 3 is formed by bonding the upper substrate 8 and the lower substrate 9 made of two piezoelectric members polarized in the plate thickness direction so that the polarization directions are opposite to each other. . For example, PZT (lead zirconate titanate) is used as the piezoelectric member. This piezoelectric member functions as a discharge force generating member.

  In the head body 3, the upper layer substrate 8 and the lower layer substrate 9 are shaved in the stacking direction with a diamond wheel or the like, and a plurality of grooves 10 reaching from the upper surface of the upper layer substrate 8 to the inside of the lower layer substrate 9 are formed. These grooves 10 are formed so as to reach from the upper surface of the upper substrate 8 to the inside of the lower substrate 9, and the front surface is opened and the rear portion is closed. That is, the plurality of grooves 10 extend substantially in parallel to the head main body 3 from the front surface toward the rear surface to the middle thereof.

  Electrodes (not shown) are formed on the inner surfaces of the plurality of grooves 10 by an electroless nickel plating method or the like. In addition, a wiring pattern 11 continuous with the electrodes is formed on the upper surface of the upper substrate 8. When water-based ink is used as the ink, an insulating film (not shown) is formed on a part of the electrode and wiring pattern 11, that is, a portion that contacts the ink. Here, the ink chamber 2 includes a bottom wall 12 of the groove 10, side walls 13 formed on both sides of the groove 10, and a part of the top plate 7, and functions as a pressure chamber.

  The nozzle plate 5 is formed with a plurality of nozzles 4 arranged in a substantially straight line. These nozzles 4 are through holes formed in a substantially cylindrical shape, but are not limited thereto, and may be through holes formed in, for example, a substantially conical shape. Each of the plurality of nozzles 4 discharges the volume (volume of the through hole) from each of the plurality of nozzles 4 according to the electrical characteristics of the piezoelectric member, for example, electrostatic capacity, which is a characteristic that varies the discharge force for each nozzle 4. Each ink discharge amount is changed so as to be a predetermined ink discharge amount. Thereby, since the ink discharge amount of the inkjet head 1 becomes uniform, it is possible to prevent the image quality from being deteriorated. Further, even when a plurality of inkjet heads 1 are used, it is possible to achieve a uniform ink discharge amount among these inkjet heads 1 and suppress density variations.

  The top plate 7 is formed with an ink inlet 14 through which ink supplied from an ink tank (not shown) or the like flows. The ink inlet 14 communicates with the common ink chamber 6. Such a top plate 7 is fixed to the head body 3 with, for example, a thermosetting adhesive (heat bonding) or the like. The ink is supplied from the ink inlet 14 to the common ink chamber 6.

  Such an ink jet head 1 is connected to a control circuit (not shown) for controlling the driving thereof. By control by this control circuit, the ink jet head 1 selectively changes the ink supplied to the ink chamber 2 from the plurality of nozzles 4 by changing the volume of the desired ink chamber 2 and applying pressure to the ink. It is made to discharge as. In order to change the volume of the ink chamber 2, the piezoelectric members of the upper layer substrate 8 and the lower layer substrate 9 are deformed.

  As the ink, for example, various inks such as water-based ink, oil-based ink, solvent ink, and UV ink (ultraviolet curable ink) are used. The UV ink is composed of, for example, a pigment, a monomer, an oligomer, a photopolymerization initiator, a dispersant, and other additives (for example, a surface tension adjusting agent).

  In the present embodiment, the piezoelectric inkjet head 1 using a piezoelectric member (for example, a piezo element) is used as the ejection force generating member. However, the present invention is not limited to this, and for example, as the ejection force generating member. A thermal ink jet head using a heating element may be used. In this case, the heating element is provided in the groove 10 communicating with the nozzle 4, that is, in the ink chamber 2. For example, the heating element is formed as the bottom wall 12 of the groove 10. In either method, the ink in the ink chamber 2 is ejected as ink droplets from the nozzle 4 by applying pressure (pressure due to volume change of the ink chamber 2 or pressure due to bubbles) to the ink in the ink chamber 2. .

<Inkjet head manufacturing method>
A method for manufacturing the inkjet head 1 of the present embodiment will be described with reference to FIG. FIG. 2 is a perspective view schematically showing a manufacturing process of the ink jet head 1 of the present embodiment.

  As shown in FIG. 2, the method of manufacturing the inkjet head 1 includes a step of laminating an upper layer substrate 8 and a lower layer substrate 9 made of piezoelectric members to form a head body 3 (lamination step: see FIG. 2A), A step of forming a plurality of grooves 10 in the head body 3 (groove forming step: see FIG. 2B) and a step of forming electrodes and wiring patterns 11 in the plurality of grooves 10 (electrode forming step: FIG. 2C). Reference), a step (measuring step) of measuring the electrostatic capacity of the piezoelectric members of the upper layer substrate 8 and the lower layer substrate 9 for each of the plurality of ink chambers 2, that is, the plurality of nozzles 4, and the top plate 7 A step (installation step) in which the common ink chamber 6 is provided in the head main body 3 so as to face the plurality of grooves 10, and the nozzle plate 5 in which the nozzles 4 are not formed is opposed to the plurality of grooves 10 in the head main body 3. (See Fig. 2 (d)) And a step of forming the plurality of nozzles 4 on the nozzle plate 5 provided in the head body 3 based on the capacitance of the piezoelectric member for each of the plurality of nozzles 4 (nozzle formation step: see FIG. 2E). Has been.

  In the step of forming the head body 3 (lamination step: see FIG. 2A), the upper layer substrate 8 and the lower layer substrate 9 are bonded together with an adhesive or the like. As the adhesive, for example, a thermosetting adhesive is used. For example, the adhesive is applied to the upper substrate 8 by screen printing or the like. In addition to screen printing, a method such as spin coater, spray coating, and brush coating can be selected as an adhesive coating method in accordance with the adhesive to be used. When a thermosetting adhesive is used, the bonded upper layer substrate 8 and lower layer substrate 9 are placed in an autoclave device (not shown) and heated under pressure to cure the adhesive (heat bonding). The bonded upper layer substrate 8 and lower layer substrate 9 may be mechanically pressed with a jig or the like and placed in an oven in the pressurized state to be cured by heating. Here, the adhesive may be cured in a later step without curing the adhesive.

  In the step of forming the plurality of grooves 10 (groove forming step: see FIG. 2B), the head main body 3 is processed to form a plurality of grooves 10 extending substantially in parallel from the front surface toward the rear surface. . This groove processing is performed using a diamond wheel of a dicing saw used for cutting an IC wafer or the like.

  In the step of forming the electrode and wiring pattern 11 (electrode forming step: see FIG. 2C), the electrode and wiring pattern 11 are respectively formed on the inner surfaces of the plurality of grooves 10 and the surface of the upper substrate 8 by an electroless nickel plating method or the like. Form. At this time, the electrode and the wiring pattern 11 are continuous. When water-based ink is used as the ink, an insulating film (not shown) is formed on a part of the electrode and wiring pattern 11, that is, a portion that comes into contact with the ink. This insulating film is formed of, for example, an electrodeposition paint. Since the electrodeposition paint solution reaches the inside of the groove 10, the insulating film is uniformly formed on the electrode.

  In the step of measuring the capacitance of the piezoelectric member (measurement step), the capacitance of the piezoelectric members of the upper layer substrate 8 and the lower layer substrate 9 is measured for each of the plurality of ink chambers 2, that is, for each of the plurality of nozzles 4. At this time, the capacitance of the piezoelectric member is measured, and inspections such as short circuit and open of the wiring are also performed.

  In the step of providing the top plate 7 and the nozzle plate 5 (installation step: see FIG. 2D), the nozzle plate 5 on which the top plate 7 and the nozzle 4 are not formed is bonded to the head body 3 with an adhesive or the like. As the adhesive, for example, a thermosetting adhesive is used. For example, the adhesive is applied to the top plate 7 and the nozzle plate 5 by screen printing or the like. As the method for applying the adhesive, in addition to screen printing, a method such as spray coating or brush coating can be selected in accordance with the adhesive to be used. When a thermosetting adhesive is used, the head body 3 to which the top plate 7 and the nozzle plate 5 are bonded is put in an autoclave device (not shown) and heated under pressure to cure the adhesive (heating) Glue). Note that the bonded top plate 7 and nozzle plate 5 may be mechanically pressed with a jig or the like and placed in an oven in the pressurized state to be cured by heating. If the adhesive is not cured in the step of forming the head body 3, the adhesive may be cured at the same time in this installation step.

  In the step of forming the plurality of nozzles 4 on the nozzle plate 5 (nozzle formation step: see FIG. 2E), for example, a laser processing machine or the like based on the measured electrostatic capacitance of the piezoelectric member for each of the plurality of nozzles 4 Thus, a plurality of nozzles 4 are formed on the nozzle plate 5 provided on the head body 3. That is, the nozzle volume of the plurality of nozzles 4 is changed according to the measured electrostatic capacity of the piezoelectric member for each of the plurality of nozzles 4, and each ink discharge amount of the ink discharged from each of the plurality of nozzles 4 is a predetermined ink discharge amount. A plurality of nozzles 4 are formed so that

  Specifically, the hole diameters of the plurality of nozzles 4 are determined based on the capacitance of the piezoelectric member for each of the plurality of nozzles 4, and a plurality of nozzles 4 are formed on the nozzle plate 5 one by one with these hole diameters. Is done. Thereby, each ink discharge amount of the ink discharged from each of the plurality of nozzles 4 is set to a predetermined ink discharge amount. The hole diameter varies depending on the resolution of the inkjet head 1, but the adjustment range is ± 10%. This adjustment range is a range for preventing the image quality from being deteriorated due to a large change in the discharge speed because the ink discharge speed changes with the ink discharge amount (discharge volume) due to the change in the hole diameter.

  As a method of adjusting by changing the hole diameter of the nozzle 4 by the laser processing machine, a method of preparing a plurality of masks used by the laser processing machine and switching them, a method of shifting the focal position of the laser beam, or the like is used. It is done. In this way, by changing the laser processing conditions of the laser processing machine for each of the plurality of nozzles 4, it is possible to form a plurality of nozzles 4 each having a desired hole diameter in the nozzle plate 5.

  As described above, according to the present embodiment, the nozzle volume of each nozzle 4 is changed according to the electrostatic capacity of the piezoelectric member for each of the plurality of nozzles 4, and each nozzle 4 has a predetermined ink discharge amount. The ink discharge amount is formed. Thereby, since the ink discharge amount is accurately and uniformly adjusted in a short manufacturing process, the ink discharge amount of the ink jet head 1 can be easily made uniform, and the ink jet head 1 can be manufactured efficiently. In particular, since the ink discharge amount of the inkjet head 1 becomes uniform, it is possible to prevent image quality deterioration. Further, even when a plurality of inkjet heads 1 are used, it is possible to achieve a uniform ink discharge amount among these inkjet heads 1 and suppress density variations.

  The step of measuring the capacitance of the piezoelectric member may be performed after the step of providing the top plate 7 and the nozzle plate 5 as shown in FIG. Further, the step of forming the plurality of nozzles 4 on the nozzle plate 5 as shown in FIG. 2E may be performed before the step of providing the top plate 7 and the nozzle plate 5 as shown in FIG. good. In this case, a plurality of nozzles 4 are formed on the nozzle plate 5 on which the nozzles 4 are not formed based on the measured capacitance of the piezoelectric member, and then the nozzle plate 5 on which the nozzles 4 are formed and the top of the nozzle plate 5 are formed. A plate 7 is provided on the head body 3. When a plurality of nozzles 4 are formed on the nozzle plate 5 before the nozzle plate 5 is provided on the head body 3 as described above, the nozzles 4 can be formed on the nozzle plate 5 by laser processing, pressing, electroforming, or the like. It is.

  Further, in the step of forming the plurality of nozzles 4 on the nozzle plate 5, the ink discharge amount is adjusted by changing the nozzle volume by changing the hole diameter of the nozzle 4. However, the present invention is not limited to this. The ink discharge amount may be adjusted by changing the nozzle volume by changing the taper angle of the nozzle 4.

  Here, adjustment of the nozzle volume will be described with reference to FIG. FIG. 3 schematically shows the shape of the nozzle 4, (a) a vertical side view when the taper angle is small, and (b) a vertical side view when the taper angle is large.

  In FIG. 3A, the nozzle diameter on the ink discharge side is a, the nozzle diameter on the ink side is b, and the taper angle is c. In FIG. 3, the taper angle c of the nozzle 4 is larger in the nozzle 4 shown in (b) than in the nozzle 4 shown in (a).

  For example, when the taper angle c is constant, the nozzle volume is adjusted by changing the nozzle diameter a on the ink ejection side (the mask used in the laser processing machine is changed). At this time, the nozzle diameter b on the ink side also changes. On the other hand, when the nozzle diameter a on the ink discharge side is made constant, the nozzle volume is adjusted (laser by changing the taper angle c (from FIG. 3A to FIG. 3B)). Adjustment of laser power and laser angle on the processing machine). At this time, the nozzle diameter b on the ink side also changes. The taper angle c of the nozzle 4 is changed by adjusting the laser beam by controlling the laser oscillation output of the laser processing machine, using an attenuator, adjusting the number of shots, and the like. Also, the hole diameter and the taper angle c can be adjusted by adjusting the optical system (for example, zoom).

  Further, in the step of forming the plurality of nozzles 4 on the nozzle plate 5, the hole diameters of the plurality of nozzles 4 are determined based on the electrostatic capacity of the piezoelectric member for each of the plurality of nozzles 4, and the plurality of nozzle diameters are determined by the hole diameters. The nozzles 4 are formed one by one on the nozzle plate 5, but the present invention is not limited to this. For example, a plurality of nozzles 4 may be divided into several blocks, and the nozzles 4 for each block may be formed simultaneously. . In this case, the nozzle 4 hole diameter for each block is determined based on the electrostatic capacity of the piezoelectric member for each of the plurality of nozzles 4 in consideration of the difference in ink discharge amount for each block. Further, if the hole diameter of each nozzle 4 changes in adjacent blocks, the density difference at the boundary between these blocks becomes conspicuous, so the change in the hole diameter of adjacent blocks is within ± 5%, especially ± 1%. It is desirable to be within. One block is set according to the number of nozzles 4 formed on the nozzle plate 5, but is configured in units of about 2 to 200 nozzles. In addition, as the inkjet head 1, there are an inkjet head 1 having about several tens of nozzles with a small number of nozzles 4 and an inkjet head 1 with several hundreds of nozzles having a large number of nozzles 4.

  In the present embodiment, nozzle processing is performed by changing the hole diameter of the nozzle 4 based on the electrostatic capacity after groove processing, but the present invention is not limited to this. For example, the density between the inkjet heads 1 is made uniform by changing the processing conditions of the entire nozzles 4 of the inkjet head 1 according to the electrical characteristics of the piezo element before embedding, such as mechanical coupling constants and piezoelectric constants. You can also

  Moreover, in this Embodiment, although the electrostatic capacitance of a piezoelectric member is measured for every some nozzle 4, it does not restrict to this. For example, in the case of using a thermal ink jet head that uses a heating element as the discharge force generating member, a resistance value that is an electrical characteristic of the heating element is measured for each of the plurality of nozzles 4, and a plurality of resistance values are determined according to the resistance value. By changing the nozzle volume of the nozzle 4 and forming the plurality of nozzles 4 so that each ink discharge amount of the plurality of nozzles 4 becomes a predetermined ink discharge amount, the ink discharge amount can be made uniform. . Specifically, the hole diameters of the plurality of nozzles 4 are determined based on the resistance values of the heating elements for the plurality of nozzles 4, and the nozzles 4 are formed with the hole diameters. Thereby, each ink discharge amount of the plurality of nozzles 4 is set to a predetermined ink discharge amount.

  In the present embodiment, in the step of forming the plurality of nozzles 4, the plurality of nozzles 4 are formed one by one, so that the ink discharge amount can be made uniform with high accuracy.

  In the present embodiment, the step of forming the plurality of nozzles 4 divides the plurality of nozzles 4 into several blocks and simultaneously forms the nozzles 4 for each block, thereby realizing uniform ink discharge amount. Manufacturing time can be shortened.

  In the present embodiment, in the inkjet head 1 that ejects ink droplets from a plurality of nozzles 4 by a piezoelectric member that is a discharge force generating member that generates a discharge force, the plurality of nozzles 4 are inks ejected from the nozzles 4 respectively. Each nozzle volume is formed in accordance with the electrical characteristics of the piezoelectric member, for example, the electrostatic capacity, which is a characteristic that varies the ejection force of each nozzle 4 so that the ink ejection amount of the ink becomes a predetermined ink ejection amount. Therefore, since the ink discharge amount of the inkjet head 1 is uniform, it is possible to prevent the image quality from being deteriorated.

1 is an exploded perspective view schematically showing an inkjet head according to an embodiment of the present invention. It is a perspective view which shows roughly the manufacturing process of the inkjet head of one Embodiment of this invention. The shape of a nozzle is shown roughly, (a) A longitudinal side view when a taper angle is small, (b) A longitudinal side view when a taper angle is large.

Explanation of symbols

1 Inkjet head 4 Nozzle 8, 9 Discharge force generating member (upper layer substrate, lower layer substrate)

Claims (4)

In an inkjet head manufacturing method for manufacturing an inkjet head that discharges ink droplets from a plurality of nozzles by an ejection force generating member that generates an ejection force,
And measuring the electrical characteristics before Symbol ejection force generating member before Symbol each nozzle,
By changing the contents product before Symbol nozzle according to the electric characteristics of the ink ejection force generating member before Symbol each nozzle measured before as prior SL Louis ink discharge amount issuing nozzle or we ejection reaches a predetermined amount Forming the nozzle,
An inkjet head manufacturing method comprising: Forming a plurality of said nozzles, one by one form the prior SL nozzle,
The method of manufacturing an ink jet head according to claim 1. The step of forming a plurality of the nozzles includes dividing the plurality of nozzles into several blocks and simultaneously forming nozzles for each block.
The method of manufacturing an ink jet head according to claim 1. A plurality of nozzles for ejecting Lee ink droplets, wherein provided for each nozzle, the ink jet head having a discharge force generating member for generating a discharge force for discharging ink droplets from the nozzle,
A plurality of said nozzles, a constant ink discharge amount, the ink jet head is characterized in that the nozzle volume varies depending on the electrical characteristics Ru varying the ejection output of the ejection force generating member for each Bruno nozzle.

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