JP2959052B2 - Inkjet print head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention, when print data is received, causes ink to fly as droplets or mist, and forms dots on recording paper using the ink droplets or mist. The present invention relates to an on-demand type ink jet print head to be operated. As a specific field, it is widely used as an output terminal of a computer or a color printer.

[Conventional technology]

The on-demand type ink jet print heads are roughly classified into three types. The first type is provided with a heater for instantaneously vaporizing the ink immediately below the nozzle or on the wall surface. The second type is a so-called bubble jet type for generating and flying, and the second type is provided with a piezoelectric element which is deformed by a signal in a container forming an ink reservoir, and causes the ink to fly as droplets by pressure generated at the time of deformation. In the third type, a piezoelectric element is provided in the ink reservoir so as to face the nozzle, and a dynamic pressure is generated in the nozzle region by the expansion and contraction of the piezoelectric element to cause the ink droplet to fly.

The on-demand type ink jet print head of the third type has a plurality of nozzle openings formed on a wall surface of a container constituting an ink tank, as shown in Japanese Patent Publication No. 60-8933. The piezoelectric elements are arranged so that the directions of expansion and contraction coincide with each other so as to face each nozzle opening. This print head expands a piezoelectric element by applying a print signal and a piezoelectric element, and ejects ink droplets from nozzles by a dynamic pressure of ink generated at this time to form dots on printing paper.

In a print head of this type, it is desirable that the droplet formation efficiency and the flying force be large. However,
Since the unit length of the piezoelectric element and the expansion and contraction rate per unit are extremely small, in order to obtain the droplet formation efficiency and flying force required for printing, a structure in which the dynamic pressure of the ink is concentrated at the nozzle opening is further required. It is necessary to apply a high voltage, and there is a problem that a structure, a driving circuit, and measures for electrical insulation are complicated.

The following proposals have been proposed to solve the above problems. First, as a structure in which the dynamic pressure of the ink for obtaining the droplet formation efficiency and the flying force required for printing is concentrated at the nozzle opening, the nozzle opening on the ink reservoir side is generally larger than the ink outlet opening. How to Specifically, a method of providing a step and a horn-shaped shape in the thickness direction of a member having a nozzle opening, a conical shape shown in Japanese Patent Publication No. 63-8953, and further, an ink reservoir side Various proposals, such as a method of projecting the above shape, have been proposed. However, in realizing such a method, since a complicated shape is formed in the nozzle opening on the ink reservoir side, that is, the inner wall of the container, it is necessary to use a separate member from the container in terms of processing method and manufacturing cost. I had no choice. Therefore, by coupling the separate member having the above-mentioned shape to the container, the center of the dynamic pressure and the center of the above-mentioned shape of the nozzle opening are shifted or tilted due to accumulation or deformation of dimensional accuracy. There is a problem that the effect is reduced, and in connection such as bonding, there is a problem that peeling occurs due to environmental conditions and time lapse conditions, and the reliability is extremely poor.

As a method of not applying a high voltage to obtain a flying force required for printing, Japanese Patent Application Laid-Open No. 63-295269 discloses a method.
As disclosed in Japanese Patent Application Laid-Open Publication No. H11-207, there has been proposed a piezoelectric element for an ink jet print head in which electrodes and piezoelectric materials are alternately stacked in a sandwich shape. According to this piezoelectric element, the distance between the electrodes can be made as small as possible, so that the voltage of the drive signal can be reduced.

[Problems to be solved by the invention]

However, since it is difficult to form such a piezoelectric element into a small size, there is a problem that its use is limited.

An object of the present invention is to provide an ink jet print head having a novel structure that can be miniaturized, can have a high density, and can stably eject ink droplets having a sufficient flying force at a voltage as low as possible. Aim.

[Means for solving the problem]

The ink jet print head of the present invention has a plurality of piezoelectric elements formed of a piezoelectric material and a conductive material, a base having the other end fixed such that one end of the plurality of piezoelectric elements is a free end, and the free end. An opposing partitioning member opposingly arranged via a space serving as an ink reservoir, a nozzle member formed with a nozzle opening communicating with the ink reservoir, and a row partitioning member disposed between the piezoelectric elements, The piezoelectric element, the nozzle member, and the inter-row partition member are similarly formed with the opposed partition member interposed therebetween.

Further, the opposed partition member and the inter-row partition member are integrally formed.

Further, the opposing partition member, the inter-row partition member, and the nozzle member are integrally formed.

Further, the invention is characterized in that the inter-row partition member is formed so as to partition the space forming the ink reservoir for each piezoelectric element.

Further, the piezoelectric element is formed by alternately laminating a plurality of piezoelectric materials and conductive materials in layers.

[Action]

The on-demand type ink jet print head of the present invention configured as described above has an opposing partition member provided with a space for forming an ink reservoir facing the free end of the piezoelectric element row, and a space for forming the ink reservoir. Since the nozzle member having the nozzle opening facing the nozzle and the row partitioning member arranged between the piezoelectric element rows are integrally formed, displacement, deformation, peeling, and the like due to the pasting also occur. Disappears. In particular, since the vicinity of the nozzle opening is surrounded as close as possible by the opposing partitioning member and the inter-row partitioning member, the nozzle opening is more firmly supported, and no deformation or peeling can occur.

In addition, the above-described effect is further increased by extending and independently extending the space forming the ink reservoir by the inter-row partition member so as to partition the space for each piezoelectric element row, and the nozzle of the dynamic pressure to the ink due to the expansion and contraction of the piezoelectric element. By eliminating the escape and interference in the direction adjacent to the opening, the efficiency of ion droplet formation can be increased and the flying force can be increased.

Further, since the piezoelectric element row is formed by cutting a predetermined width of a baked piezoelectric plate obtained by laminating a paste-like piezoelectric material and a conductive material alternately in layers, a sufficient flying force can be obtained at a low voltage. Can be.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings by way of examples.

1 to 5 show the configuration of a first type of on-demand type ink jet print head of the present invention. FIG. 1 is an external perspective view, FIG. 2 is a plan view, and FIG. FIG. 4 is a cross-sectional view of the drive section centered on the nozzle section in the AA 'section in FIG. 2, FIG. 4 is a cross-sectional view of the drive section in the BB' cross section in FIG. 2, and FIG. FIG. 3 is a plan view in which a nozzle forming section 7 provided with a nozzle 8 in FIG. 2 is removed. In FIGS. 3, 4 and 5, the piezoelectric element 4 is fixed to the substrate 1 and the housing 2 by a strong adhesive 15 or the like. The internal electrodes of the piezoelectric element 4 are alternately formed in the direction facing the cavity 11 so as to vibrate longitudinally in the direction of the piezoelectric constant d33. The external electrodes of the piezoelectric element 4 are formed over the entire upper and lower surfaces, and are electrically connected to the lead electrodes 14 formed on the substrate 1 via an adhesive or a conductive material 9. Further, the gap between the rows of the piezoelectric elements 4 is filled with a resin material such as an adhesive or a filler having a Young's modulus of 20% or less of the Young's modulus of the piezoelectric elements 4 and is hardened to form a partition b5 which is a row separating member. Has formed. In addition, the cavity part also
Are separated from each other by the same material as that of the piezoelectric element 4 to form an independent cavity 11 for each piezoelectric element 4. The side surface of the cavity 11 facing the piezoelectric element 4 forms a partition portion a3, which is a facing partition member, of the same material as the partition portion b5, and is closely adhered to the substrate 1. The nozzle forming portion 7 having the nozzle 8 facing the cavity 11 is formed of a material equivalent to the partition b5 on the end faces of the cavity 11, the partition b5, and the piezoelectric element 4 and the housing 2 opposite to the substrate 1 side. It is formed in a predetermined thickness and size.

The on-demand type ink jet print head according to the present invention having the above-described configuration will be described in detail while following the manufacturing process.

FIG. 6 is a detailed view of the substrate 1. The broken line a in the figure is designed to be a unit line, that is, one head, so that the substrate 1 is designed so that multiple chips can be simultaneously formed. The number of sheets to be taken is determined by the number of nozzles of each head and the capacity of the manufacturing apparatus. The substrate 1 is made of an insulating material, and a ceramic such as alumina or a glass substrate is used. Reference numeral 21 denotes a through hole for introducing ink, which penetrates the back surface by laser or molding. Reference numeral 22 denotes a conductive paste for a conductive electrode made by firing the surface electrode, and is generally an Ag / Pd-based, Au /
Pd type and Pt / Pd type are used. Of course, other conductive pastes can also be used, and the thickness is preferably from 3 μm to 20 μm. On this, 30 partition blocks a and piezoelectric element blocks 34 are bonded with 15 adhesives. As the adhesive, an epoxy-based or silicone-based resin-based adhesive is used.

FIG. 7 is a view in which 30 partition blocks a and piezoelectric element blocks 34 are adhered on the substrate 1. The 30 partition blocks a may be formed into a predetermined block shape with a soluble resin that can be removed later, and may be sandwiched by the piezoelectric element block 34, or a photolithographic resist may be poured and solidified. Next, the thirty partition blocks a are connected to 31 in FIG.
Is removed by a predetermined thickness, and the portion of the partition space 3 'is removed. As for the removing method, a slit having a width of the partition space 3 'is formed by using a dicing saw or a wire saw to remove. At this time, cutting is performed until the surface of the substrate 1 is exposed. The 31 partition block b is a portion where the cavity 11 will be formed in the future, and has a predetermined thickness necessary for forming the cavity. Further, at this point in FIG. 7, the piezoelectric element block 34 is not divided into the respective arrays, and is a block state diagram. External electrodes on the upper and lower surfaces of the piezoelectric element block 34 are respectively covered over the entire surface.

When the piezoelectric element block 34 is fixed to the substrate 1, the end opposite to the cavity 11 is fixed by a member having a Young's modulus equivalent to that of the high-strength piezoelectric element 4, so that the amount of expansion and contraction of the piezoelectric element 4 is increased. Can effectively act on the free end side of the cavity 11 side. Therefore, in this embodiment, the housing 2 is made of a high Young's modulus material such as ceramics, and the piezoelectric element 4
Were arranged in close contact with the fixed end of the. In order to further secure the fixing, it is possible to use a high Young's modulus adhesive between the substrate 1 and the piezoelectric element 4 and between the housing 2 and the piezoelectric element 4 at portions 6 and 9 in FIG. For example, it is a glass frit material, a ceramic paste material, or the like, and can be fixed by firing or the like in a process before forming the 30 partition blocks a.

 Further, the piezoelectric element 4 will be described in detail.

FIG. 8 (a) shows a piezoelectric element block 34, in which reference numerals 40, 40, 40,... Indicate conductive layers constituting one electrode, respectively, and 42, 42, 42,. , Each of which is alternately arranged in parallel with the piezoelectric material 44, 44,... So as to be parallel to each other, and has a conductive shape of one of the electrodes 40, 40,. The layer is exposed on one side surface (lower surface in the drawing), and the conductive layer to be the other electrodes 42, 42,... Is exposed on the other side surface (upper surface in the drawing). Such a layer structure may be made of a suitable piezoelectric element material,
For example, a titanate / lead zirconate-based composite perovskite ceramic material is formed into a green sheet, and an internal electrode material is printed on the surface of the green sheet by a printing method. In this way, a predetermined number of sheets are formed, and pre-drying and sintering are performed to obtain a sintered body. This state is shown in FIG. Conductive materials 47 and 48 are applied to the surfaces of the rectangular parallelepiped, on which the internal electrodes 42 and 40 are exposed, and dried or fired, respectively, to obtain FIG. 8B. This is the piezoelectric element block 34, which is finally divided into arrays with slits 46 and used.

An independent lead member is connected to the conductive layer 47 connecting one electrode of each element thus configured,
A common lead member is connected to the conductive layer 48 connecting the other electrode. Accordingly, when an electric signal is applied between the independent lead member and the common lead member, the piezoelectric element to which the signal is selectively applied by the independent lead member has the same voltage between the electrodes via the conductive layer. Are applied at the same time, so that the piezoelectric material between the electrodes expands at the same time,
The displacement of each layer is added to displace the free end side in the axial direction. Needless to say, since each conductive layer is formed to be extremely thin, the voltage for performing the maximum elongation requires an extremely small value.

The piezoelectric element block 34 is electrically connected to the electrodes on the substrate 1 by the conductive agent. There are various conduction methods, but in general,
Ag brazing material, conductive paste or conductive adhesive is used. or,
In some cases, a metal bowl is used by being crushed between a substrate and a piezoelectric element. The conductive space does not need to be the entire surface of the electrode, and it is sufficient if a certain portion is electrically connected. However, since the piezoelectric element block 34 is used after being cut as described above, it is necessary to take care that each of the arrays is conductive.

Next, a slit having a predetermined width is formed in this state using a dicing saw or a wire saw in the direction of dashed line cc 'in FIG. At this time, cutting is performed to a depth of 10 to 50 μm from the surface of the substrate 1 so that the surface electrode 22 of the substrate 1 is also divided. At this time, with the same slit width
The 31 partition blocks b are also cut similarly to each array of the piezoelectric elements 4. Needless to say, the pitch may be a desired value. For example, to make a 300 DPI head, 150 DPI on one side
The pitch becomes 169.3 μm. The housing 2 is installed so as to surround the piezoelectric element 4 thus cut. The housing 2 is strongly contacted or fixed to the opposite end face of the array of the substrate 1 and the piezoelectric element 4 on the cavity 11 side. It is desirable that the adhesive used here has as large a Young's modulus as possible.

Next, the electrodes formed on the upper surface of the array of each piezoelectric element 4 are made conductive to take out the common electrode. The electrodes on the substrate 1 side and the lower surface of the array of each piezoelectric element 4 are already configured as individual lead electrodes, and the upper surface is electrically connected to the substrate 1 side common electrode terminal 13 by using, for example, the outer wall of the housing 2. FIG. 10 shows an example of this, in which a conductive path is formed on the surface of the housing 2 with a conductive paste. In the figure, reference numeral 61 denotes a conductive path on the surface of the housing, which is electrically connected to the upper surface electrode of the array of the piezoelectric elements 4 by the conductive paste 62. The conductive path 61 is also electrically connected to the common electrode 13 on the substrate by the conductive paste 63. There are various types of this electrical bonding method, and for example, a flexible cable can be used or wire bonding can be performed.

Next, a slit having a predetermined width, a partition space 3 ', and the nozzle forming portion 7 between the arrays of the piezoelectric elements 4 formed by cutting with a dicing saw or a wire saw are integrally formed. FIG. 11 shows an example of this, in which a frame 16 higher than the predetermined position D of the thickness of the nozzle forming portion 7 by E dimension is temporarily bonded to the substrate 1 so as to surround the outside of the housing 2. The resin material 5 is injected and filled into the slits and the partition spaces 3 'having a predetermined width between the arrays of the piezoelectric elements 4 up to the height of the upper surface (D + E) of the frame 16 and hardened. The resin-based material 5 is suitably an epoxy-based or silicon-based material. However, if the cured film has appropriate hardness, adhesion, and strength, there is no need to stick to this. Next, the frame 16 is removed and ground to a predetermined position D of the thickness of the nozzle forming section 7 to make it smooth. Grinding is performed using a surface grinder, a lapping device, or a dicing saw. Thereafter, the nozzle forming portion 7 is formed at a predetermined position in a space facing each array of the piezoelectric elements 4 of the 31 partition blocks b filled with a soluble resin to form the cavity 11 by laser or drill.
Nozzle 8, which is a hole that passes through the thickness of the nozzle, is accurately drilled.
The drilling accuracy may be determined, for example, by a reference at the time of cutting the piezoelectric element 4 into each array and at the time of cutting the partition space 3 ′, for example, a reference hole provided on the substrate 1 or an XY end face of the piezoelectric element block 34. Needless to say, it can be reduced to several μm or less by drilling in the same manner as described above. In addition, the thickness after nozzle formation 7 is
The partition space 3 ′ is made of a resin material of a transparent grade having a thickness of about 0.05 to 0.5 mm, and is formed by coloring the soluble resin of the 31 partition blocks b filled to form the cavity 11. A3
The partition b5 hardened by injecting and filling into a slit of a predetermined width corresponding to each array of the piezoelectric elements 4 and the piezoelectric element 4 can be easily identified by the image processing technique or the like. Therefore, it is possible to make a hole at an accurate position without inclination. Also, the frame
16 may be ground at the same time without being removed, in which case it is necessary to securely adhere to the substrate 1. In this way, the nozzle forming section 7, the partition section a3, and each partition section b5 are made of the same resin-based material 5.
The nozzle opening is very strongly supported without being deformed or peeled off since the vicinity of the nozzle opening is surrounded by the nozzle opening, and is hardened. Also, it can be very easily integrated with high precision.

In addition, in the above-described cutting, the portion of the substrate 1 corresponding to the partition portion a3 and each partition portion is cut to a position where the substrate material is exposed. Will be increased.

Next, the soluble resin in the partition block b of FIG. 9 which is filled to form the cavity 11 is removed. In the case of a positive photoresist, it is preferable to remove it with acetone or aqueous ammonia. In the case of a negative photoresist, a strong acid aqueous solution is heated and sprayed to remove. As a result, a cavity as shown in FIG. 12 can be formed. FIG. 12 is a view showing a state in which the 31 partition block b is also cut at the same time as the piezoelectric element 4, and the resin material 5 is injected and filled into the space and cured to form the cavity 11, and the nozzle forming section 7 and the nozzle 8 are formed. This is an example of a state in which is deleted.

In the present embodiment, the method in which the cavities 11 are opposed to each other with the partition portion a3 interposed therebetween has been described.

When an electric signal is applied to the piezoelectric element 4 via the cable 12, the print head configured as described above receives the piezoelectric elements 4, 4, and 4.
Since... Extend in the electrode stacking direction, the free end of the piezoelectric element pushes the ink on the front surface toward the third partition a. As a result, the ink enters the nozzle opening 8 under the dynamic pressure, flies as an ink droplet in the external space, and forms dots on the printing paper.

When the application of the electric signal is stopped, the piezoelectric element is reduced to the original state, and the ink flows into the gap between the third partition part a and the piezoelectric element 4 to prepare for the next ink droplet generation.

By the way, the ink for an ink jet printer may be insulative or conductive. Particularly when using conductive ink, the electrodes of the piezoelectric element must be completely sealed from the ink. In order to clear these points, it is desirable to form a layer that does not participate in the piezoelectric action at both free ends with a piezoelectric material, such as the layer b in FIG. Further, it is also a good method that the entire piezoelectric array is dipped in an insulating resin solution, for example, a polyimide solution before the partition b5 is poured between the slits, and a thin insulating film is coated on the surface of the piezoelectric element.

In the above-described embodiments, the common electrode is taken out first, and thereafter, the nozzle forming part 7, the partition part a3, and the partition part b5 corresponding to each array of the piezoelectric elements 4 are simultaneously injected with a resin material. Although the method of filling, curing and integrally forming has been described, the present invention is not limited to this method.
For example, a method may be employed in which the partitioning part a3 and the partitioning part b5 are first formed integrally, then the common electrode is taken out, and then the nozzle forming part 7 is formed and integrated.

FIG. 14 shows a second embodiment in which a resin material as a partition member of each cavity does not extend to the partition portion a3. Since the first embodiment is a high-density head, there is a problem of crosstalk. This embodiment is relatively effective when the density of adjacent nozzle openings is not high, and is sufficiently practical. The figure sees through the nozzle forming part 7,
The space between the piezoelectric elements is filled with a partition b5. In the figure, reference numeral 3 denotes a partition a for partitioning the piezoelectric element row. In the case of this embodiment, there is no need to provide 31 partition blocks b in FIG.
Each piezoelectric block body 34 is bonded at a predetermined distance, and after filling the resin between the piezoelectric element rows and the partition, a space corresponding to 31 is cut with a dicing saw or the like, and a soluble resist is injected and solidified to form a cavity. A part can be formed.
FIG. 14 shows a gap formed in this manner.

〔The invention's effect〕

As described above, according to the ink jet print head of the present invention, a plurality of piezoelectric elements formed of a piezoelectric material and a conductive material, and the other ends are fixed such that one end of each of the plurality of piezoelectric elements is a free end. A base, and an opposing partition member opposingly arranged via a space serving as an ink reservoir with the free end,
By providing a nozzle member having a nozzle opening communicating with the ink reservoir and a row partitioning member provided between the piezoelectric elements, miniaturization and high density can be achieved, and as low as possible. It is possible to provide a print head capable of ejecting ink droplets having a sufficient flying force with a voltage. further,
Since the piezoelectric element, the nozzle member, and the inter-row partition member are similarly formed with the opposed partition member interposed therebetween, an ink jet print head having a plurality of rows of nozzles can be easily manufactured with high precision.

Further, by forming at least the opposing partitioning member and the row partitioning member integrally, it is possible to reduce displacement and deformation at the time of manufacturing the print head, and in particular, the vicinity of the nozzle opening is supported by a member made of the same material. Temperature,
It is stable against deformation due to time conditions and the like, and can fly ink droplets stably.

Further, since the inter-row partition member is formed so as to partition the space forming the ink reservoir for each piezoelectric element, it is possible to prevent unintended ink droplets from flying from adjacent nozzles.

In addition, since the piezoelectric element is formed by alternately laminating a plurality of piezoelectric materials and conductive materials in layers, it is possible to fly ink droplets having a sufficient flying force at a lower voltage.

[Brief description of the drawings]

1 to 5 show the configuration of a first type of on-demand type ink jet print head of the present invention, and FIG. 1 is an external perspective view. FIG. 2 is a plan view. FIG. 3 is a cross-sectional view of the driving section centering on the nozzle section in the AA 'cross section in FIG. FIG. 4 is a cross-sectional view of the BB ′ cross-section in FIG. FIG. 5 is a plan view of FIG. 2 from which a nozzle forming portion 7 provided with a nozzle 8 is removed. 6 to 11 are diagrams showing a manufacturing process in the present invention, and FIG. 6 is a detailed view of a substrate. FIG. 7 is a view in which a partition block and a piezoelectric element block are bonded on a substrate. FIG. 8A is a state diagram of a sintered body of the piezoelectric element block. FIG. 8 (b) is a state diagram of the piezoelectric element block with external electrodes. FIG. 9 is a state diagram of the split cutting of the piezoelectric element block. FIG. 10 is a diagram showing an example of a state in which a common electrode is taken out. FIG. 11 is a diagram showing an example of a state of being formed integrally with a nozzle forming portion. FIG. 12 is a diagram showing an example of a cavity formation state. FIG. 13 is a diagram showing an example of the structure of a piezoelectric element for insulating sealing. FIG. 14 is a view showing another embodiment in which the partition member of the cavity does not extend to the partition portion. DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Housing 3 ... Partition part a4 ... Piezoelectric element 5 ... Partition part b 7 ... Nozzle formation part 8 ... Nozzle 11 ... Cavity 12 ... Cable

Claims (5)

(57) [Claims] 1. A plurality of piezoelectric elements formed of a piezoelectric material and a conductive material, a base having the other end fixed so that one end of each of the plurality of piezoelectric elements is a free end, and the free end and an ink reservoir. An opposing partition member opposingly arranged via a space, a nozzle member formed with a nozzle opening communicating with the ink reservoir, and an inter-row partition member disposed between the piezoelectric elements, wherein the piezoelectric element The nozzle member and the row partition member are
An ink jet print head, which is similarly formed with the opposing partition member interposed therebetween. 2. An ink jet print head, wherein said opposing partition member and said inter-row partition member are formed integrally. 3. An ink jet print head according to claim 1, wherein said opposing partition member, said row partition member, and a nozzle member are integrally formed. 4. An ink jet print head according to claim 1, wherein said inter-column partition member is formed so as to partition a space forming said ink reservoir for each piezoelectric element. 5. An ink jet print head according to claim 1, wherein said piezoelectric element is formed by alternately laminating a plurality of piezoelectric materials and conductive materials in layers.