JP2010253765A - Inkjet head and method for manufacturing same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet head having the configuration in which the shapes and the volumes of members attached to sandwich a piezoelectric substrate are different, the inkjet head having stable jetting characteristics by reducing residual stress difference generated between the members when the members are cooled after being cured with heat. <P>SOLUTION: The inkjet head is of share mode type, and jets an ink by bonding together the piezoelectric substrate wherein a plurality of parallel grooves having electrodes provided on the inner walls are formed, and a nozzle plate provided with nozzle holes corresponding to the plurality of grooves of the piezoelectric substrate. The share mode type inkjet head is provided with: the piezoelectric substrate; the nozzle plate; and a first manifold wherein a common ink chamber and an ink channel for supplying the ink to the piezoelectric substrate are formed. The piezoelectric substrate, the nozzle plate and the first manifold are bonded to each other, and in the first manifold, a fine gap is formed in the vicinity of the bonded portion. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an inkjet head and a method for manufacturing the same. Ink jet heads are used, for example, for industrial applications or special applications having a landing accuracy at a specified address.

  In recent years, an inkjet method using a shear mode deformation of a piezoelectric material has been proposed for a printer. This method uses an electrode formed on both sides of an ink channel wall made of piezoelectric material (hereinafter referred to as “channel wall”) to generate an electric field in a direction perpendicular to the polarization direction of the piezoelectric material. The channel wall is deformed in the share mode, and ink droplets are ejected by utilizing the pressure wave fluctuation generated at that time, which is suitable for increasing the density of the nozzles, reducing the power consumption, and increasing the driving frequency.

  Recently, the use of ink jet heads utilizing this shear mode deformation for industrial purposes has become active. For example, wiring is drawn by discharging a conductive material as ink, a color filter is manufactured by discharging inks of R, G, and B colors, or thermosetting or ultraviolet (UV) curable ink. The application of producing a three-dimensional structure such as a microlens or a spacer by discharging the liquid is being promoted.

  As an application form of an inkjet device for industrial use, it is often used for application to a substrate, and there is a strong demand for increasing the area, speeding up, and increasing the definition.

  Therefore, it is conceivable to use a long inkjet head as a means for solving an increase in area and speed. In addition, the requirement of an inkjet head for higher definition is required to achieve high reproducibility and positional deviation.

  As a related art related to these, in Patent Document 1, a support substrate having substantially the same dimensions is bonded to both planes of a plate-like base member at symmetrical positions, and the support substrate is bonded to the base member. The support substrate is cut so as to be divided to prevent deformation of the piezoelectric actuator due to a difference in linear expansion coefficient between the base member and the support substrate.

  Also, in Patent Document 2, a slit is formed in the central portion of the FPC in the electrode pattern arrangement direction for the problem that the piezoelectric element collapses due to thermal contraction of the piezoelectric element when the FPC is thermocompression-bonded to the inkjet head. The residual stress due to heat shrinkage is reduced.

JP 2003-25572 A JP 2005-153321 A

  Comparing the use of an inkjet head for industrial use with the use of an inkjet head as a consumer printer, a consumer inkjet head ejects water-soluble ink onto a recording medium such as paper multiple times with multiple nozzles. Then, characters and image information are recorded by landing. In addition, since consumer ink jet heads use water-based ink or the like as the ink used, inexpensive plastic materials that do not require high chemical resistance are used. On the other hand, an inkjet head for industrial use is required to be used under much severer conditions and to operate with higher accuracy than consumer use. In industrial applications, it is required to land a specified amount of droplets at a specified address, and control of landing accuracy and droplet amount is strictly required. Therefore, in an ink jet head, an ink channel that should be able to be ejected cannot be ejected due to some trouble, even if the occurrence rate is not a problem for consumer use. When an inkjet head is used as an application, it becomes a serious problem. In addition, with the development of such a wide variety of inkjet application fields, a variety of inks are used. For example, highly volatile ink containing an organic solvent, strongly acidic / strongly alkaline ink, ink containing pigments and resin components, ink containing fine particles such as beads, and ink combining these. It is done. A member used for an ink jet head, particularly a member in contact with ink, is required to have ink resistance, and a material selection is required so that swelling and dissolution by ink do not occur.

On the other hand, due to the demand for cost reduction, there is an increasing demand for materials with high ink resistance and low cost, and the appearance of members using engineering plastics is remarkable.
There is an increasing demand for an increase in printing speed for industrial inkjet heads, and in order to meet this demand, an increase in the length of the inkjet head is being studied. Long inkjet heads may have a head length that is 4 to 5 times longer than that of consumer inkjet heads of about 20 mm, making it difficult to achieve uniform discharge characteristics by increasing the length. there were.

When materials having different coefficients of thermal expansion are bonded to the piezoelectric substrate, the longer the bonding length, the greater the influence of the difference in thermal expansion, and problems such as warping, distortion, and peeling occur with respect to temperature changes. Here, the piezoelectric substrate usually has a thermal expansion coefficient of about 2 to 8 × 10 ⁻⁶ / ° C., whereas the engineering plastic has a thermal expansion coefficient of about 20 to 60 × 10 ⁻⁶ / ° C. have. Therefore, there has been a problem that the landing accuracy is poor in the production of the long inkjet head.

  Specifically, an engineering plastic is selected as a material that does not swell or dissolve due to ink, and a material to which a low thermal expansion filler is added is used, and members are bonded so as to sandwich the piezoelectric substrate. As a result of confirming the landing accuracy with an ink jet head having a configuration in which the members bonded so as to sandwich the shape are different, it was about ± 20 μm, and the droplet could not be landed at the designated address. This landing variation is caused by the bending of the nozzle hole position, and is caused by the difference in thermal expansion and the heat capacity.

  First, in order to produce a member at low cost using an engineering plastic, it is preferable to perform molding. Regarding the variation in the coefficient of thermal expansion, it is possible to suppress the variation in the coefficient of thermal expansion by stabilizing the filling state of the filler. I was able to confirm that it was possible. However, in order to make the members bonded so as to sandwich the piezoelectric substrate into the same shape, unifying them into a large shape increases unnecessary material cost. Therefore, in the long inkjet head, the member bonded so as to sandwich the piezoelectric substrate. There is a demand for an ink jet head in which the nozzle hole position is not bent even when the shape of the nozzle hole is irregular.

In order to achieve the above object, an ink jet head according to claim 1 based on the present invention comprises:
In the share mode type inkjet head that discharges ink by bonding a piezoelectric substrate having a plurality of parallel grooves with electrodes on the inner wall and a nozzle plate having nozzle holes corresponding to the plurality of grooves of the piezoelectric substrate, The piezoelectric substrate, the nozzle plate, and a first manifold in which a common ink chamber for supplying ink to the piezoelectric substrate and an ink flow path are formed, the piezoelectric substrate, the nozzle plate, and the first manifold The first manifold is characterized in that a slit portion is formed in the vicinity of the bonded portion. According to this configuration, due to the difference in heat capacity between the first and second manifolds, the effect of distortion such as warpage and deformation caused by heating and cooling caused by heating and cooling is provided by providing the slit portion. It is possible to suppress the transmission to the area. Therefore, by adjusting the heat capacity difference in the bonded area of the manifold, it is possible to produce an ink jet head that does not warp or deform the piezoelectric substrate, and droplets can be landed at specified addresses. In addition, the piezoelectric substrate constituting the ink jet head can be constituted only by a drive portion that ejects ink, and the region that does not contribute to ink ejection can be made of an inexpensive engineering plastic or the like. Thereby, the cost of the inkjet head can be reduced.

  The common ink chamber of the ink jet head according to claim 2 is formed in the vicinity of a contact portion of the piezoelectric substrate, the nozzle plate, and the first manifold. According to this configuration, in addition to the above-described effects, the ink is circulated by the manifold in which the common ink chamber is formed. It does not occur and the number of fine particles in the discharged droplet can be stabilized.

  The first manifold of the ink jet head according to claim 3 is separated into a supply portion in contact with the piezoelectric substrate and a filter portion in contact with the filter unit by the narrow gap portion formed in the vicinity of the adhesion portion. The connecting portion is provided with a communication hole through which ink flows. According to this configuration, the slit portion that suppresses the warping of the non-adhesion region and the effect of distortion such as deformation to the adhesion region is provided, and the adhesion region and the non-adhesion region are separated from the piezoelectric substrate. If it is necessary to communicate the common ink chamber formed on the non-adhesive region with the ink flow path, the ink supply and discharge can be performed by arranging the ink flow path at the joint portion between the adhesive portion and the non-adhesive portion. Enable circulation. By circulating the ink, even if the ink contains high viscosity ink and fine particles such as beads, precipitation and floating do not occur, and the number of fine particles in the discharged droplet can be stabilized.

  The filter portion of the first manifold of the ink jet head according to claim 4 is characterized in that a filter portion for removing foreign matters in the ink is formed. According to this configuration, it is possible to eliminate the problem that foreign matter such as dust adheres to the nozzle holes during ink ejection or ink circulation and causes non-ejection. In addition, even if the heat capacity of the non-adhesive region is increased by forming the filter portion, the slit portion is provided with the effect of warping due to thermal stress, distortion such as deformation, which occurs when heating and cooling are performed. Therefore, it is possible to suppress transmission to the adhesion region, and the landing accuracy is not deteriorated.

  The inkjet head according to claim 5, wherein a second manifold in which a common ink chamber and a drain for discharging ink from the piezoelectric substrate are further formed is formed in the inkjet configuration, and the piezoelectric substrate and It is characterized by being bonded to the nozzle plate. According to this configuration, the piezoelectric substrate that constitutes the ink jet head can be configured only by the drive portion that ejects ink, and the region that does not contribute to ink ejection can be made of inexpensive engineering plastics or the like. is there. Thereby, the cost of the inkjet head can be reduced. In addition, by circulating ink through a manifold with a common ink chamber, even if the ink contains fine particles such as beads, precipitation and floating do not occur, and the number of fine particles in the discharged droplets can be stabilized. Is possible.

The first and second manifolds of the ink jet head according to claim 6 are characterized in that they are formed of an engineering plastic to which a filler is added. According to this configuration, the engineering plastic has good mechanical properties and excellent heat resistance. Moreover, even if it is excellent in chemical resistance and used as a member that comes into direct contact with ink, it is not affected by the ink and there are no problems such as swelling and dissolution. In addition, it is possible to reduce the thermal expansion coefficient of engineering plastics to about 10 × 10 ⁻⁶ / ° C., and it is possible to reduce warpage, distortion, peeling, and the like due to differences in thermal expansion from the piezoelectric substrate. .

  The supply portion of the first manifold and the second manifold of the ink jet head according to claim 7 have substantially the same shape and are formed with substantially the same heat capacity. According to this configuration, by manufacturing the manifold by molding, not only cost reduction but also thermal expansion variation among members can be suppressed, and warpage, distortion, peeling due to difference in thermal expansion between members can be suppressed. Etc. can be reduced. In addition, the degree of freedom of design can be improved by attaching a filter and drain to a manifold with a filter, and various shapes with different heat capacities can be created. For this reason, the shape of the manifold can be made substantially the same, and it is easy to form a slit portion in the vicinity of the adhesion region. As a result, it is possible to suppress the effects of distortion such as warpage and deformation caused by thermal stress that occurs when the adhesive is heated and cooled, so that the thermal stress caused by the difference in heat capacity can be suppressed. It is possible to eliminate the influence.

  The piezoelectric substrate of the ink jet head according to claim 8, the nozzle plate, and the first and second manifolds are bonded by a thermosetting adhesive. According to this configuration, in order to use a member with excellent chemical resistance, it is necessary to use an adhesive with excellent chemical resistance. By performing heat curing on the ink, it is possible to bond the ink without problems such as swelling and dissolution.

  In the present invention, a shear mode type in which ink is ejected by bonding a piezoelectric substrate having a plurality of parallel grooves provided with electrodes on the inner wall and a nozzle plate having nozzle holes corresponding to the plurality of grooves of the piezoelectric substrate. The inkjet head includes the piezoelectric substrate, the nozzle plate, a first manifold in which a common ink chamber for supplying ink to the piezoelectric substrate and an ink flow path are formed, and the piezoelectric substrate and the nozzle plate And the first manifold are bonded to each other, and a slit portion is formed in the vicinity of the bonded portion of the first manifold. According to this configuration, due to the difference in heat capacity between the first and second manifolds, the effect of distortion such as warpage and deformation caused by heating and cooling caused by heating and cooling is provided by providing the slit portion. It is possible to suppress the transmission to the area. Therefore, by adjusting the heat capacity difference in the bonded area of the manifold, it is possible to produce an ink jet head that does not warp or deform the piezoelectric substrate, and droplets can be landed at specified addresses. In addition, the piezoelectric substrate constituting the ink jet head can be constituted only by a drive portion that ejects ink, and the region that does not contribute to ink ejection can be made of an inexpensive engineering plastic or the like. Thereby, the cost of the inkjet head can be reduced.

  Therefore, it can be used for the use of an inkjet device for industrial use, that is, for application to a substrate, and can cope with large area, high speed and high definition. In addition, it is possible to manufacture an elongated inkjet head, and it is possible to achieve high reliability and positional deviation.

It is a perspective view of the ink jet head in an embodiment based on the present invention. It is a perspective view in the state where a nozzle plate of an ink jet head in an embodiment based on the present invention was removed. FIG. 3 is a perspective view showing a state in which the manifold in FIG. 2 is removed. FIG. 3 is an exploded perspective view of a member on which an ink supply side manifold and a filter unit are formed according to the present invention. It is a result which shows the landing deviation of the inkjet head which has a slit part in embodiment based on this invention. As a comparative example in FIG. 5, it is the result which shows the landing deviation of the inkjet head which does not have a slit part in embodiment based on this invention.

(Embodiment 1)
With reference to FIGS. 1-4, the inkjet head in embodiment based on this invention is demonstrated.
(Constitution)
FIG. 1 shows an ink jet head 25 in the present embodiment. The place where the nozzle plate 21 of the inkjet head 25 is removed is shown in FIG. FIG. 3 is a perspective view showing a state in which the first manifolds 11 and 12 in FIG. 2 are removed. FIG. 4 is an exploded perspective view of the first manifold 18 in which the ink supply side manifold 11 is formed.

  As shown in FIGS. 2 and 3, the ink jet head 25 includes a base 15, a piezoelectric substrate 1 attached on the base 15, a nozzle plate 21 having nozzle holes 20, and ink attached so as to sandwich the piezoelectric substrate 1. A first manifold 18 having a supply-side manifold 11 and a second manifold 12 having an ink discharge-side drain 7b are provided.

  The base 15 extends in the back and front direction (longitudinal direction) in FIGS. 1, 2, and 3. Flange portions 15e and 15f are integrally formed at both ends of the base 15 in the longitudinal direction. A fixing hole 14 is formed through the flange portions 15e and 15f in the vertical direction. The fixing hole 14 can be used to fix the ink ejection device 50 to the production device with screws when the ink ejection device 50 is mounted on a production device (not shown), for example. In this example, the piezoelectric substrate 1 is attached on the base 15 by bonding.

  The piezoelectric substrate 1 is made of a piezoelectric material having a plurality of groove-shaped ink chambers 2 formed in parallel to each other by groove processing, and is formed such that the ink chambers 2 are opened on the side surfaces of the piezoelectric substrate 1. The ink chambers 2 are separated from each other by a partition wall 3. An electrode 4 is formed on the inner wall of the ink chamber 2.

The electrode 4 is formed of a metal material such as Al or Cu by film formation such as vapor deposition or sputtering. The electrode 4 is extended to the side surface of the piezoelectric substrate 1 to form an external extraction electrode 4a.
A wiring substrate 10 is connected to the external lead electrode 4a through an anisotropic conductive film (hereinafter referred to as “ACF”).

  The manifolds 11 and 12 have dimensions comparable to the longitudinal dimensions of the piezoelectric substrate 1 (the back and front directions in FIGS. 1 and 2), and are bonded to both side surfaces of the piezoelectric substrate 1 where the ink chambers 2 are open. Attached. Position adjustment is performed so that the upper surfaces of the manifolds 11 and 12 are substantially flush with the upper surface of the partition wall 3 of the piezoelectric substrate 1 or are flush with the upper surface. On the tops of the manifolds 11 and 12, steps 5 a and 5 b that are recessed in a substantially arc shape are formed so as to communicate with the ink chamber 2 of the piezoelectric substrate 1. A space surrounded by the side surface of the piezoelectric substrate 1, the steps 5 a and 5 b of the manifolds 11 and 12, and the lower surface of the nozzle plate 21 is called a common ink chamber as a manifold (referred to by the same reference numerals 5 a and 5 b as the steps for simplicity). ) Is formed. A common ink chamber is not formed in the piezoelectric substrate 1.

  The first manifold 11 includes an ink supply unit 11a having a common ink chamber 5a and a filter unit 11b. The manifold 11 bonded to the side surface of the piezoelectric substrate 1 where the ink chamber 2 is opened is connected to the supply unit 11a and the filter. The part to which the unit 80 is added is called a filter unit 11b.

  The supply part 11a and the filter part 11b of the manifold 11 are mostly separated by a slit 90, which is a narrow gap part, and a communication hole serving as an ink flow path for connecting the common ink chamber 5a and the filter unit 80 to the joint part. 7a part is formed.

  The second manifold 12 having a connecting hole that becomes the drain 7b on the ink discharge side is formed with a drain 7b that communicates the common ink chamber 5b with the back surface of the second manifold 12, and the drain 7b of the member 12 is connected to the drain 7b. Is connected to one end of an ink tube (not shown) from below.

  The nozzle plate 21 is attached by being bonded so as to straddle the partition wall 3 of the piezoelectric substrate 1 and the manifolds 11 and 12. The nozzle plate 21 has a plurality of nozzle holes 20 arranged so as to correspond to the respective ink chambers 2 on the piezoelectric substrate 1.

  Next, the first manifold 11 will be described with reference to FIG. In the filter unit 80, the housing portion into which the ink supplied from the ink tank flows is joined to the housing portion of the filter portion 11b of the first manifold. The ink supply part 11a and the filter part 11b of the first manifold are formed with slits 90, which are slits, leaving a communication part as an ink flow path. The ink supply part 11a and the filter part 11b of the first manifold are formed. Are separated. Thus, the first manifold 11 separated by the slit 90 has a configuration and volume substantially the same as the second manifold 12 having the ink discharge side drain 7b opposed to each other with the piezoelectric substrate 1 interposed therebetween. Yes. A filter plate 81 is installed inside the housing of the filter unit 80 to remove foreign matters (solid matter) in the ink supplied to the housing 80a, and the ink flows into the filter portion 11b of the first manifold. The filter plate 81 is not limited to the inside of the housing of the filter unit, and may be a position where foreign matter (solid matter) can be prevented from entering the first manifold 11.

  The ink flow will be described with reference to FIGS. Ink supplied from a first ink tank (not shown) is supplied from the nipple opening 19 to the inside of the filter unit 80 through an ink tube (not shown), and a filter plate 81 installed inside the filter unit 80. Is supplied to the filter portion 11b of the first manifold. Subsequently, it passes through the communication hole 7a and flows into the first common ink chamber 5a. The ink that has reached the first common ink chamber 5a continues to pass through one of the plurality of individual ink chambers 2 formed on the piezoelectric substrate 1 and flows into the second common ink chamber 5b. Further, the ink that has reached the second common ink chamber 5b passes through an ink tube (not shown) from the drain 7b and is discharged to a second ink tank (not shown).

  Therefore, according to the configuration of the inkjet head 25 in the present embodiment, the ink supplied from the first ink tank (not shown) first passes through the ink tube to the filter portion 11b of the first manifold from the nipple opening 19. Since the ink is supplied, it is removed by the filter plate 81 even when foreign matter is mixed in the supplied ink. For this reason, in the ink supplied to the ink chamber 2 from the first common ink chamber 5a through the filter portion 11b of the first manifold, non-discharge due to foreign matter clogging to the nozzle due to ejection is prevented, and ink in the ink flow path is used. The flow can be performed smoothly. Accordingly, it is possible to positively form an ink flow that passes through the interior of the ink chamber 2, which is the space immediately adjacent to the nozzle hole 20. As a result, even if the fine particles that have not been removed by the filter plate 81 are contained in the ink, the fine particles are suppressed from being settled or floated, and the fine particles contained in the droplets at the time of ejection. The number can be stabilized.

Next, characteristics of the inkjet head 25 when the embodiment of the present invention is used will be described.
As shown in FIG. 1, in the present embodiment, first manifolds 11 and 12 are attached so as to sandwich both side surfaces of the piezoelectric substrate 1 where the ink chambers 2 are opened, and a nozzle plate 21 is disposed on the piezoelectric substrate 1. Glued.

  In the first manifold 11, an ink supply part 11a and a filter part 11b are integrally formed. By molding, not only cost reduction but also thermal expansion variation between members can be suppressed, and it is possible to reduce warpage, distortion, peeling, etc. due to thermal expansion difference between members. is there. Further, there is an effect that foreign matters contained in the ink at the time of ink supply or foreign matters generated from the supply tube can be removed in the vicinity of the ink chamber, and the ejection stability of the inkjet head 25 can be improved.

  In addition, the ink supply part 11a of the first manifold 11 and the second manifold 12 are made of substantially the same shape using the same material, so that the heat capacity of the filter part 11b on the first manifold 11 is affected. The residual stress difference when the heated and bonded first manifold 11 and second manifold 12 are cooled to room temperature is eliminated, and the undulation of the nozzle plate 21 bonded to the upper portion of the piezoelectric substrate 1 is eliminated. And the bending of the nozzle hole 20 can be reduced.

  Further, the piezoelectric substrate 1, the nozzle plate 21, and the first manifold 11 and the second manifold 12 are attached by bonding with an adhesive and using heat curing.

  In this embodiment, an epoxy adhesive is used and heat curing is performed at 80 ° C. In order to use a member with excellent chemical resistance, it is necessary to use an adhesive with excellent chemical resistance. As a result of investigation, use an epoxy adhesive and heat cure to 80 ° C or higher. As a result, it was possible to find an adhesion condition free from problems such as swelling and dissolution with respect to the ink.

  The first manifold 11 and the second manifold 12 use engineering plastics of the same material, and the heat capacity of the ink supply part 11a of the first manifold 11 and the second manifold 12 is substantially the same volume. By using the same material, it is preferable to set so as to be adjusted to the same degree.

  When the first manifold 11 and the second manifold 12 are heated and cured at 80 ° C. with respect to the piezoelectric substrate 1, the residual stress generated during cooling increases on the first manifold 11 side. Is generated by the heat capacity of the filter portion 11b of the first manifold, and the residual stress of the filter portion 11b of the first manifold does not affect the manifold 11a due to the slit 90 which is a narrow gap portion, and the nozzle hole It does not cause 20 bends.

  In the present embodiment, it is preferable to use engineering plastics as materials for the manifolds 11 and 12 and the filter unit 80. Engineer plastics have good mechanical properties and excellent heat resistance. Moreover, even if it is excellent in chemical resistance and used as a member that comes into direct contact with ink, it is not affected by the ink and there are no problems such as swelling and dissolution. Further, by appropriately mixing the filler with the engineer plastic, the thermal conductivity can be increased and brought close to the thermal conductivity of the piezoelectric substrate 1, so that the deformation of the nozzle plate is reduced and the landing accuracy is improved.

  The discharge landing accuracy was evaluated in the apparatus configuration of the ink jet head shown in the above embodiment. The result is shown in FIG. The evaluation results show the landing results in the nozzle orthogonal direction (Y direction shown in FIG. 1).

  FIG. 5 shows a slit 90, which is a slit portion, formed between the ink supply portion 11a and the filter portion 11b of the first manifold shown in the embodiment of the present invention, and the first manifold 11 is integrally molded. 3 shows the result of the discharge and landing accuracy of the inkjet head 25 manufactured as described above.

As shown in FIG. 5, a slit 90 which is a slit portion is formed between the ink supply portion 11a and the filter portion 11b of the first manifold according to the embodiment of the present invention, and the first manifold 11 is integrated. The ink jet head 25 produced by molding had a landing accuracy of ± 5 μm or less. When the positions of the nozzle holes 20 of the ink jet head were confirmed, the arrangement was as if curved by 3 μm.
(Comparative Example 1)

  FIG. 6 shows an embodiment of the present invention, in which the first manifold 11 is integrated without forming a slit 90 that is a slit portion between the ink supply portion 11a and the filter portion 11b of the first manifold. The result of the discharge landing accuracy of the inkjet head 25 produced by molding is shown.

  As shown in FIG. 6, the ejection landing accuracy of the inkjet head 25 manufactured without forming the slit 90 which is the narrow gap portion is as large as about ± 20 μm, resulting in a large variation in landing.

  When the position of the nozzle hole 20 of this inkjet head was confirmed, it was an array that was curved by 30 μm. This is caused by the difference in residual stress caused by the difference in heat capacity between the members 11 and 12 as described above.

  This is because the member 11 formed by the separation communicates with the housing 80b by separating the ink supply part 11a and the filter part 11b of the first manifold, leaving a part that becomes an ink flow path at the slit 90. It can be said that it is the effect which has the heat capacity comparable as the member 12 which opposes so that the piezoelectric substrate 1 may be inserted | pinched.

  In other words, it was confirmed that the residual stress caused by the difference in heat capacity does not affect the manifold portion by forming the slit 90.

  Comparing Example 1 and Comparative Example 1, when the nozzle ch is 64 ch or less, the ink landing accuracy is within the required accuracy of ± 5 μm even in the case of a manifold having no slit portion. However, in the case of a long inkjet head having a head length of about 4 to 5 times or more, the landing deviation is ± 15 μm or more. According to the configuration shown in the present embodiment, the result is that the landing deviation is ± 5 μm or less, a head that can be sufficiently adapted to high speed can be created, and the landing position deviation accuracy is sufficient.

From the above, in the configuration of the present invention, it is possible to eliminate variations in the coefficient of thermal expansion and the bending of the nozzle hole position due to the difference in residual stress. An ink jet head having excellent chemical resistance such as ink of about 10 CP, toluene and xylene, and high rigidity and reliability is possible.
(Embodiment 2)
In addition, the following experiment was conducted in order to clarify the mechanism of the variation in landing and the bending of the nozzle hole position.

In the ink jet head shown in the first embodiment, zircon zinc titanate (PZT) is used for the piezoelectric substrate 1, and the thermal expansion coefficient is about 8 × 10 ⁻⁶ / ° C. In addition, polyether ether ketone (PEEK) low thermal expansion filler was added to the first manifold 11, the second manifold 12 and the filter unit 80 to reduce the thermal expansion coefficient to about 20 × 10 ⁻⁶ / ° C. The nozzle hole was bent by the presence or absence of thermal expansion variation between the members bonded so as to sandwich the piezoelectric substrate.

  In this experiment, an adhesive that cured at 80 ° C. (having cleared ink resistance) was used. The results are shown in Table 1.

  According to the second embodiment, since the support substrate having substantially the same size and shape is bonded to a position symmetrical with respect to both planes of the base substrate, it is considered that the bending of the nozzle hole position due to the residual stress difference hardly occurs. Also in the experiment, as a result of using the same shape member, the nozzle hole position is not bent.

  According to Example 3, when the film-like FPC was bonded to one side of the piezoelectric substrate at 80 ° C., it was confirmed in the experiment that the nozzle hole position was bent, but the nozzle hole position was not bent. The FPC is in the form of a film, has low rigidity, and has a small heat capacity. Therefore, it is considered that curing shrinkage that causes bending of the nozzle hole position does not occur.

  In general, consumer inkjet heads manufactured using FPC have a short head length of about 20 mm, so that the variation in thermal expansion coefficient and the difference in residual stress between members are small. Bending is unlikely to occur. However, since the thermal expansion coefficient is too different from that of the piezoelectric element, it cannot be bonded by heat, so that a highly accurate long inkjet head cannot be manufactured. In addition, there is a problem that swelling and dissolution with ink are likely to occur.

  According to Comparative Examples 2 and 3, the bending of the nozzle hole position was caused when the member that was bonded so as to sandwich the piezoelectric substrate and the variation in the coefficient of thermal expansion of the member were irregular. If there is variation in thermal expansion, it is considered that the nozzle hole position is bent because the contracted state of the member when the member heated and bonded so as to sandwich the piezoelectric substrate is cooled to room temperature is different. Even if there is no variation in the coefficient of thermal expansion, if the member bonded to sandwich the piezoelectric substrate has an irregular shape, the residual stress of the member when the bonded and heated member is cooled to room temperature to sandwich the piezoelectric substrate As a result, the nozzle hole was bent due to the difference.

  Specifically, when the landing accuracy was confirmed with the ink jet head of Comparative Example 2, it was about ± 20 μm, and the droplet could not be landed at the designated address.

  From the comparative study of the above examples and comparative examples, it has been found that the landing accuracy is improved when the variation in thermal expansion is suppressed and the manifolds are formed in substantially the same shape.

  When manufacturing a long inkjet head for industrial use, engineering plastic is selected as a material that does not swell and dissolve due to ink in the manifold, and a material added with a low thermal expansion filler is used. It turned out to be preferable.

  In addition, the said embodiment disclosed this time is an illustration in all the points, Comprising: It is not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and includes all modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Piezoelectric substrate 2 Individual ink chamber 3 Partition 4 Electrode 4a Electrode extraction part 5a First common ink chamber 5b Second common ink chamber 7a Communication hole 7b Drain communication hole 11 First manifold 11a Ink supply part 11b of first manifold Filter portion 12 of one manifold Second manifold 14 Fixing hole 15 Base 15e, 15f Flange portion 19 Nipple opening portion 20 Nozzle hole 21 Nozzle plate 25 Inkjet head 80 Filter unit 90 Slit

Claims (8)

In the share mode type inkjet head that discharges ink by bonding a piezoelectric substrate having a plurality of parallel grooves with electrodes on the inner wall and a nozzle plate having nozzle holes corresponding to the plurality of grooves of the piezoelectric substrate,
The piezoelectric substrate, the nozzle plate, and a first manifold in which a common ink chamber and an ink flow path for supplying ink to the piezoelectric substrate are formed,
The piezoelectric substrate, the nozzle plate and the first manifold are respectively bonded,
The inkjet head according to claim 1, wherein a slit portion is formed in the vicinity of the bonding portion in the first manifold.   2. The inkjet head according to claim 1, wherein the common ink chamber is formed in the vicinity of a contact portion of the piezoelectric substrate, the nozzle plate, and the first manifold.   The first manifold is separated into a supply part that is in contact with the piezoelectric substrate and a filter part that is in contact with the filter unit by the slit part formed in the vicinity of the adhesive part, and an ink is connected to the joint part between them. The ink-jet head according to claim 1, further comprising a communication hole through which the gas flows.   4. The ink jet head according to claim 3, wherein a filter portion for removing foreign matters in the ink is formed in the filter portion of the first manifold.   5. The ink jet head according to claim 1, further comprising a second manifold in which a common ink chamber and a drain for discharging ink from the piezoelectric substrate are formed, and the piezoelectric substrate and the nozzle plate. An ink jet head which is adhered to the ink jet head.   6. The ink jet head according to claim 1, wherein the first and second manifolds are formed of an engineering plastic to which a filler is added.   The inkjet head according to claim 1, wherein the supply portion of the first manifold and the second manifold have substantially the same shape and are formed with substantially the same heat capacity.   8. The ink jet head according to claim 1, wherein the piezoelectric substrate, the nozzle plate, and the first and second manifolds are bonded by a thermosetting adhesive.