JP2001063038A - Ink jet recording head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the structure of an ink jet recording head enhanced in nozzle density and almost free from mutual interference. SOLUTION: Vibration plates 23 constituting a part of a plurality of the pressure liquid chambers connected to a plurality of nozzles are displaced by a plurality of the piezoelectric elements provided corresponding to the numbers of vibration plates 23, and ink drops are emitted from the nozzles 27 by the rise in pressure generated in the pressure liquid chambers 31. The laminated piezoelectric element provided on a fixed substrate 11 and having an inert region at the central part thereof is divided into two parts by the groove dividing the inert region, and also divided in the nozzle arranging direction right- angled to the direction of the groove by a plurality of grooves to form individual piezoelectric elements. The grooves are filled with a conductive adhesive 42 and the cut electrodes are integrated as a common electrode. The individual electrodes are electrically connected to end surface electrodes in the same way by the conductive adhesive.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording head, and more particularly, to a structure of an ink jet recording head using a laminated piezoelectric element.

[0002]

2. Description of the Related Art FIG. 7 is an exploded perspective view showing an example of an ink jet recording head to which the present invention is applied, and FIG.
9 is an enlarged sectional view of a main part in a direction orthogonal to the nozzle arrangement direction, and FIG. 9 is an enlarged sectional view of a main part in the nozzle arrangement direction of FIG.
The inkjet recording head includes a driving unit 1 and
A liquid chamber unit 2 and a head cover 3 are provided.

The drive unit 1 has a laminated piezoelectric element 12 bonded and arranged in two rows on an insulating substrate 11 made of ceramic, glass epoxy resin or the like, and cut by a dicing saw, a wire saw or the like. Further, a common electrode pattern 14 and an individual electrode pattern 15 are provided on the substrate 11, and the common electrode pattern 14 and the individual electrode pattern 15 are respectively connected to the piezoelectric element 1 via a conductive adhesive 16.
2 are connected to end electrodes 17 and 18 in which respective internal electrodes are alternately connected. The common electrode pattern 14 is electrically connected to each other by filling a conductive adhesive in a hole 19 provided in the frame member 13. Further, a frame member 13 serving as a liquid chamber supporting unit is joined so as to surround the periphery of the multilayer piezoelectric element 12. The substrate 11 is a spacer member (head holder) 21 serving as a head support member.
An FPC cable 22 in which a PCB substrate having a head driving IC and the like disposed and held in the spacer member 21 and each piezoelectric element 12 of the driving unit 1 are joined to each of the electrode patterns 14 and 15 is supported. Connected through.

The liquid chamber unit 2 includes a vibration plate 23 made of a thin film of metal or resin, and a photosensitive resin layer 2 made of a three-layer photoresist film constituting a liquid chamber partition member.
No. 4, 25, 26 and a nozzle plate 28 formed of metal, resin or the like in which the nozzle holes 27 are formed are sequentially laminated and formed by heat fusion. On the surface of the nozzle plate 28, a water-repellent film 29, which is a water-repellent surface treatment film, is formed.
Non-water-repellent treated surface 30 not subjected to water-repellent treatment around 9
Is provided. The pressurized liquid chamber 31 through which the nozzle holes 27 communicate with each other, common ink chambers 32, 32 located on both sides of the pressurized liquid chamber 31, and the common ink chamber 32 to the pressurized liquid chamber 31. Ink supply paths 33, 33 serving as fluid resistance portions for supplying ink are formed.

The nozzle cover (head cover) 3 is formed in a box shape to cover the periphery of the nozzle plate 28 and the side surface of the head, and has an opening corresponding to the water-repellent film 29 of the nozzle plate 28. The non-water-repellent surface 30 of the plate 28 is adhesively bonded with an adhesive. The ink jet head is provided with ink supply holes 35 to 38 in the spacer member 21, the substrate 11, the frame member 13, and the vibration plate 23 to supply ink from an ink cartridge (not shown) to the liquid chamber.

[0006] In the ink jet recording head utilizing the mechanical displacement of the piezoelectric element 12 as described above, the drop velocity when each piezoelectric element is driven independently and the drop velocity when the adjacent piezoelectric elements are driven at the same time. A problem is that a drop in the ratio, i.e. the drop velocity due to mutual interference, leads to a deterioration of the image quality. In the case of the configuration shown in FIGS. 7 to 9, when the piezoelectric elements are driven, non-driven piezoelectric elements are arranged adjacent to each driving piezoelectric element, which prevents mechanical mutual interference. Since it acts as a support, there is almost no mutual interference, and good printing quality can be obtained.

[0007]

On the other hand, there is a strong demand for an ink jet recording apparatus to improve the recording speed, and in order to cope with this, it is necessary to increase the number of nozzles. Increasing the number of nozzles inevitably increases the size of the head. Therefore, it is necessary to improve the nozzle array density and reduce the increase in head size. In the case of the configuration shown in FIGS. 7 to 9, the nozzle density in one row of the piezoelectric element is 100 dpi (25 dpi).
At this time, the width of the groove and the width of the piezoelectric element are 40 μm and 87 μm, respectively.

[0008] The first way to increase the nozzle density is
The purpose is to reduce the width of the groove and the piezoelectric element. Fifteen
When achieving 0 dpi, the width of the groove and the width of the piezoelectric element are 30 to 40 μm and 44.5 to 54.5 μm, respectively. Also,
When achieving 180 dpi, the width of the piezoelectric element is 35.5 μm, even as the groove width. Such groove formation has a problem that the piezoelectric element falls down when the piezoelectric element is cut by a dicing saw, a wire saw, or the like, and is difficult to realize from the viewpoint of mass productivity.

A second method is to remove the support columns of the piezoelectric element shown in FIGS. In the case of 150 dpi, the groove and the piezoelectric element width are, for example, 69 μm each.
m, 100 μm, which results in almost no processing restrictions. However, since the effect of preventing the mutual interference by the above-mentioned columns is lost, the image quality is degraded due to the change in the ink droplet speed during single driving and the simultaneous driving of a plurality of columns. For this reason,
At the same time as making the thickness of the diaphragm extremely thin, it becomes necessary to increase the voltage applied to the piezoelectric elements, increase the number of stacked piezoelectric elements, and so on, resulting in an increase in cost.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a structure of an ink jet recording head which has an improved nozzle density and almost no mutual interference.

[0011]

It has been confirmed that the above-mentioned mutual interference is almost entirely caused by mechanical coupling due to the configuration of the head. Therefore, a head configuration with little mutual interference is achieved by mechanically fixing and supporting the periphery of the driving piezoelectric element. Specifically, the laminated piezoelectric element having an inactive region is divided into two by cutting the inactive layer portion and divided into a plurality of piezoelectric elements in the nozzle row direction, and is divided by the inactive region. The piezoelectric elements of each row are alternately arranged as a driving section and a non-driving section in the nozzle arrangement direction, and the driving sections of each row are arranged in a staggered state, and a diaphragm section corresponding to the non-driving section is provided. By fixing to the non-driven diaphragm, a head configuration with little mutual interference can be obtained. Further, in order to further improve the nozzle density and the recording speed, by using a plurality (N) of laminated piezoelectric elements having an inactive region, the nozzle density Mdp in one row can be increased.
For i, a compact head configuration with a nozzle density of M × 2N is obtained.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a plan view and a front view for explaining the structure of a drive unit used in an ink jet recording head according to the present invention. As shown in FIG. A common electrode 14 and an individual electrode pattern 15 are formed thereon. As shown in FIG. 1B, a laminated piezoelectric element 12 is bonded to the insulating substrate 11 with an adhesive or the like. This laminated piezoelectric element 12 has the structure shown in FIG.
Unlike the above case, the structure has an inactive region in the center. As shown in FIG. 1C, the inactive region at the center of the laminated piezoelectric element 12 is divided into two by a groove processing 40 using a dicing saw or a wire saw, and is divided into individual piezoelectric elements by a groove 41. . A conductive adhesive 42 is provided in the groove 40.
And the cut electrodes are integrated as a common electrode 14. The individual electrodes 15 are also made of a conductive adhesive 16.
, And is electrically connected to the end face electrodes 17 and 18. The frame member 13 is bonded to the insulating substrate 11 thus formed with an adhesive to complete the drive unit 1.

FIG. 2 shows the driving unit 1 shown in FIG.
FIG. 10 is a diagram showing a cross-sectional configuration when the liquid chamber units 2 described in FIGS. 7 to 9 are joined (an enlarged cross-sectional view taken along line II-II in FIG. 3).
Throughout the drawings, parts having similar functions are denoted by the same reference numerals.

FIG. 3 schematically shows the positional relationship between the individual piezoelectric elements of the ink jet recording head according to the present invention, the pressurized liquid chamber 31, and the nozzle 27. The grooves 40 are divided into even rows and odd rows. The laminated piezoelectric elements 12 are alternately used for the drive unit and the non-drive unit, and the pressurized liquid chambers 31 and the nozzles 27 corresponding to the drive units in the odd and even rows are arranged in a staggered arrangement. Have been. The diaphragm has two projections corresponding to the even and odd rows, one of which is fixed to the driven laminated piezoelectric element 12 with an adhesive or the like, and the other of which is fixed to the non-driven laminated piezoelectric element 12. ing. Therefore,
When one odd-numbered laminated piezoelectric element 12 is driven, two odd-numbered adjacent laminated piezoelectric elements 12 and one even-numbered laminated piezoelectric element 12 adjacent to the laminated piezoelectric element 12 of interest
The three laminated piezoelectric elements 12 in total become non-driven and function as columns.

In this head configuration, a piezoelectric element having substantially the same length as that of FIGS. 7 to 9 is used. The length of the active part is about half as cut by the inactive layer part, but the pitch in the column direction is about twice as large, so the volume change in the pressurized liquid chamber by the entire piezoelectric element is almost the same Becomes Further, since the pitch of the pressurized liquid chamber is doubled as compared with the case of FIGS. 7 to 9, there is an advantage that the processing accuracy in forming the liquid chamber and the alignment accuracy in assembling are reduced.

(Embodiment 1) A single layer piezoelectric element is 30 μm thick.
And 14 layers were used. The length of the laminated piezoelectric element 12 is 2.7 mm, the length of the active portion is 1 mm each, and the length of the inactive portions at the end and the center is 0.2 mm and 0.3 m, respectively.
m. The central groove 40 has a width of 10 with a dicing saw.
Cut at 0 μm. In addition, width 69 by dicing saw
By forming 91 grooves 41 with a pitch of 169 μm, 92 laminated piezoelectric elements 12 having a width of 100 μm were formed. The liquid chamber unit was formed in the same manner as in FIGS. At this time, the width of the joint of the drive plate 23 and the laminated piezoelectric element 12 was 60 μm, and the length was 1.0 mm. The length and width of the pressurized liquid chamber 31 were 1.2 mm and 260 μm, respectively. The vibration displacement of the nozzle surface when there was no ink in the pressurized liquid chamber 31 was measured using a laser Doppler vibrometer to measure 92 laminated piezoelectric elements 12 by 22 Vol.
When the voltage t was simultaneously driven and measured, a very small displacement of 0.01 μm was observed as compared with the displacement of 0.16 μm of the driving element, and it was confirmed that the mechanical mutual interference was small. In addition, a viscosity of 2.4 c. In a state where the ink of p was filled and the ink was ejected from all the nozzles, the vibration displacement of the nozzle surface was measured in the same manner, and the displacement amount was 0.0.
It was found to be as small as 2 μm. At this time, when one element is driven independently, the ink droplet speed is 7 m / s,
The drop speed in the case of full driving was 6.7 m / s, and it was confirmed that the drop speed reduction rate due to mutual interference was as good as 95%.

FIGS. 4 to 6 are diagrams for explaining another configuration of the ink jet recording head of the present invention.
On the upper side, two laminated piezoelectric elements 12 similar to those in FIG. 1 are joined in parallel. Further, a through hole 43 is formed in the insulating substrate 11. At this time, the through holes 43 are provided corresponding to the arrangement of the piezoelectric elements of the driving units in each row and corresponding to the common electrode. The inactive portions at the center of the two piezoelectric elements 12 are cut by the grooves 40. Further, by avoiding the through hole 43 and simultaneously processing two laminated piezoelectric elements, individual laminated piezoelectric elements 12 are obtained. The groove 40 is filled with a conductive adhesive 42, and the cut electrode is integrated as the common electrode 14, and the electrode reaches the back surface through the through hole 43 at the end of the common electrode 14. Similarly, the individual electrodes reach the back surface through the through holes 43. Insulating substrate 1 thus obtained
1, the frame member 13 is joined to the substrate to form the drive unit 1. A liquid chamber unit 2 formed in the same manner as in FIGS. 7 to 9 is joined to the drive unit 1.

FIG. 6 shows an individual piezoelectric element and a pressurized liquid chamber 31,
And a diagram schematically showing the relationship between the nozzle 27 and the groove 40.
The multi-layer piezoelectric element 12 divided into even rows and odd rows has a configuration in which the pressurized liquid chamber 31 and the nozzles 27 are arranged in a staggered arrangement. As in the case of FIG. A total of three laminated piezoelectric elements 12 adjacent to 12 are not driven and function as columns. Further, by shifting the position of the nozzle 27 with respect to the pressurized liquid chamber, a nozzle density four times the nozzle density in one row is achieved.

Such a nozzle arrangement is particularly effective for black printing. In the case of color printing, since the ink supply paths are provided separately, for example, it is possible to use the left odd and even columns for yellow and the right odd and even columns for magenta. Must have the same nozzle arrangement for yellow and magenta.
On the other hand, there is a strong demand for an increase in the speed of black printing centering on text, and in such a case, the number of nozzles needs to be increased, so the configuration shown in FIG. 6 is required.

One of the piezoelectric elements at the end of each row is supported by the frame member 13. For this reason, it was found that the rigidity of the frame member 13 itself was lower than that of the piezoelectric element, and that the distance to the frame member 13 was larger than the pitch in the nozzle row direction, and the effect as a support was small. For this reason, it is necessary to make the ends of the piezoelectric elements in each row a non-driving part, and to prevent a decrease in the injection efficiency at the ends.

Example 2 Al ₂ O ₃ having a thickness of 1 mm was used as an insulating substrate 11, and a through hole having a hole diameter of 1.0 mm was formed in the substrate. The same laminated piezoelectric element as in Example 1 was arranged 1 mm apart. The central groove 40 was cut with a dicing saw to a width of 100 μm. In addition, width 50μ
By forming the grooves 41 at a pitch of 169 μm and avoiding the through holes 43, 92 laminated piezoelectric elements 12 having a width of 119 μm were formed. A PC on which a driver IC is mounted is mounted on the insulating substrate using an FPC (not shown).
It was connected to the B substrate.

The liquid chamber unit was formed in the same manner as in the first embodiment. However, the position of the nozzle 27 with respect to the pressurized liquid chamber 31 is
The arrangement was such that one row had 75 dpi and four rows had 300 dpi. Further, a projection was provided on the diaphragm 23, and three peripheral elements around the driving element of interest were joined so as not to be driven. As a result of measuring the mutual interference with and without the ink, the same result as in Example 1 was obtained, and it was confirmed that the drop speed reduction rate due to the mutual interference was as good as 95%.

[0023]

According to the present invention, a laminated piezoelectric element having an inactive layer in the center portion is used, divided into two by the inactive layer portion, and individual piezoelectric elements in the column direction. And the driving of each row is alternately arranged as a driving part and a non-driving part, and the driving of each row is arranged in a staggered manner.
A high-density head with little mutual interference can be realized. Also,
By joining the piezoelectric element portion corresponding to the non-drive portion to the projection provided on the corresponding diaphragm portion, a head with less mutual interference can be realized. Further, since both ends of the drive elements in each row are non-drive sections, mutual interference deterioration at the ends can be prevented.

By arranging a plurality of laminated piezoelectric elements each having an inactive layer in the center, a high-density, low-interference head that can cope with high-speed recording can be realized. Further, by making the insulating substrate for fixing the piezoelectric element into a through hole, a reduction in head size can be achieved.

[Brief description of the drawings]

FIG. 1 is a plan view and a front view for explaining the configuration of a drive unit used in an ink jet recording head according to the present invention.

FIG. 2 is a diagram showing a cross-sectional configuration when the liquid chamber unit described in FIGS. 7 to 9 is joined to the drive unit shown in FIG.

FIG. 3 is a diagram schematically showing a positional relationship between individual piezoelectric elements, a pressurized liquid chamber, and nozzles of an ink jet recording head according to the present invention.

FIG. 4 is a diagram illustrating a configuration of another inkjet recording head of the present invention.

FIG. 5 is a diagram illustrating a configuration of another inkjet recording head of the present invention.

FIG. 6 is a view for explaining the configuration of another ink jet recording head of the present invention, in which an individual piezoelectric element and a pressurized liquid chamber;
FIG. 4 is a diagram schematically showing a relationship between nozzles.

FIG. 7 is an exploded perspective view showing an example of an inkjet recording head to which the present invention is applied.

8 is an enlarged sectional view of a main part in a direction orthogonal to the nozzle arrangement direction in FIG.

9 is an enlarged sectional view of a main part in the nozzle arrangement direction of FIG. 7;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Drive unit, 2 ... Liquid chamber unit, 3 ... Head cover, 11 ... Insulating substrate, 12 ... Piezoelectric element, 13 ... Frame member, 14 ... Common electrode pattern, 15 ... Individual electrode pattern, 16 ... Conductive adhesive, 17, 18 ... end face electrodes, 1
9 ... hole, 21 ... spacer, 22 ... FPC cable, 23
... vibrating plates, 24, 25, 26 ... photosensitive resin layers, 27 ... nozzle holes, 28 ... nozzle plates, 29 ... water-repellent films, 30 ...
Non-water-repellent surface, 31: pressurized liquid chamber, 32: common liquid chamber, 33
... Ink supply paths, 35, 36, 37, 38. Ink supply holes, 40, 41. Grooves, 42. Conductive adhesive, 43.

Claims (7)

[Claims] 1. A vibration plate constituting a part of a plurality of pressurized liquid chambers connected to a plurality of nozzles is displaced by a plurality of piezoelectric elements provided corresponding to each of the vibratory plates to generate a pressure in the pressurized liquid chamber. In an ink jet recording head that ejects ink droplets from nozzles due to a rise in pressure, a laminated piezoelectric element that is provided on a fixed substrate and has an inactive region in the center is divided into two by grooves that divide the inactive region. An ink jet recording head characterized in that individual piezoelectric elements are formed by dividing a plurality of grooves in a nozzle array direction at right angles to the above. 2. The piezoelectric elements of each row divided by the inactive area are alternately arranged as a driving section and a non-driving section in a nozzle arrangement direction, and the driving sections of each row are arranged in a staggered state. The ink jet recording head according to claim 1, wherein: 3. The ink jet recording head according to claim 1, wherein the piezoelectric element corresponding to the non-driving section is joined to the piezoelectric element by a projection provided on a diaphragm. 4. The ink jet recording head according to claim 1, wherein a plurality of laminated piezoelectric elements having an inactive region in the central portion are arranged such that a plurality of the fixed members are arranged close to each other on a substrate. 5. The number of laminated piezoelectric elements having an inactive region is N
5. The ink jet recording head according to claim 4, wherein when the nozzle density of each row is Mdpi, the nozzle density of the entire head is M × 2N. 6. The ink jet recording head according to claim 1, wherein the fixed substrate has a through hole. 7. The ink jet recording head according to claim 1, wherein both ends of the driving elements in each row are non-driving parts.