JPH10181008A - Ink jet recording head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To discharge ink drops of a desired size by a method wherein the width of a piezoelectric member in the arranging direction of ink cavities, is formed so as to be narrower than that of the ink cavity, and a recessed part is provided on the surface of a partitioning wall which is located between the side wall of the ink cavity and the side surface of the piezoelectric member, regarding the arranging direction. SOLUTION: A width (c) of a piezoelectric member 42 in the arrangement of a plurality of ink cavities 26, is foamed so as to be narrower than a width (a) of the ink cavity 26 in the same direction, and on the surface of a partitioning wall 18 which is located between a side wall 27 of the ink cavity 26 and a side surface 48 of the piezoelectric member 42 regarding the arranging direction, a groove-form recessed part 50, of which the cross section forms an arc, is provided in the longitudinal direction, on both sides of the piezoelectric member 42. When a voltage is applied to the piezoelectric member 42, a considerable tension and impact are instantly applied to the partitioning wall 18 which is pushed in the ink cavity 26, but the groove-form recessed part 50 being formed on both sides of the piezoelectric member 42 on the partitioning wall 18, works as a damper, and the tension, etc., being applied to the partitioning wall 18 are softened by the groove-form recessed part 50, and a vibration which is propagated is alleviated as well.

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 for recording an image by ejecting ink droplets from a plurality of nozzles in accordance with an image signal and attaching the ink droplets to a recording medium such as recording paper.

[0002]

2. Description of the Related Art FIG. 7 shows an example of an ink jet head using a piezoelectric member. The head 12 includes an ink cavity 26 for accommodating ink, a partition wall that covers the ink cavity 26 so as to form one wall of the ink cavity 26, and a substrate 22 that faces the ink cavity 26 via the partition wall 38.
And a piezoelectric member 42 disposed thereon. FIG. 7 is an enlarged cross-sectional view of one of the ink cavities 26 arranged in the horizontal direction in FIG.

In the head 12, when a voltage is applied to the piezoelectric member 42 in accordance with an image signal, the piezoelectric member 42 is instantaneously deformed, and the partition 38 is pushed into the ink cavity 26 as shown by a dashed line in FIG. . As a result, the ink contained in the ink cavity 26 is pressurized and ejected from the nozzles 28 as ink droplets. The ink droplets adhere to a recording medium (not shown) passing near the head to form dots, and an image is printed by a group of the dots.

[0004]

However, when the ink droplets are ejected, considerable tension and impact force instantaneously act on the partition wall 38 as the piezoelectric member 42 is deformed. At this time, not only the side wall 27 of the ink cavity 26 may be deformed by the dashed line due to the tension or the like of the partition, but also the partition corresponding to the adjacent ink cavity 26 may be deformed.
Therefore, it is not possible to eject ink droplets of the intended size, or the amount of ink ejected from the adjacent ink cavity 26 changes depending on the voltage application pattern based on the image signal, or the ink droplet ejection may be stopped. There has been a problem that vibrations between the ink cavities, such as ejection of ink droplets from the unintended ink cavities 26, cause a phenomenon called crosstalk, in which the vibrations affect each other. The effect of the crosstalk does not appear so much when printing text that simply prints characters, but when printing a high-definition gradation image, particularly a color gradation image, there is a serious problem of deterioration in image quality.

[0005]

SUMMARY OF THE INVENTION Therefore, in order to suppress crosstalk, the present invention forms a plurality of ink cavities arranged in a predetermined direction for accommodating ink therein and one wall of these ink cavities. And a piezoelectric member opposed to each ink cavity through the partition, and pressurizes the ink in the ink cavity through the partition based on the deformation of the piezoelectric member at the time of applying a voltage. In the ink jet recording head that discharges ink droplets from nozzles communicating with the ink cavity, the width of the piezoelectric member in the arrangement direction of the ink cavities is formed to be narrower than that of the ink cavity, and the side wall of the piezoelectric member and the side wall of the piezoelectric member in the arrangement direction And a concave portion is provided on the surface of the partition wall located between them.

According to the present invention, there is provided an ink jet recording head for discharging ink from a nozzle communicating with the ink cavity by pressurizing the ink in the ink cavity through a partition by a piezoelectric member. Is provided.

[0007]

According to the ink jet recording head of the present invention, the groove-shaped recess formed in the partition functions as a damper, and the tension and impact of the partition caused by the deformation of the piezoelectric member are reduced. Therefore, the deformation of the side wall of the ink cab and the deformation of the partition wall portion of the adjacent ink cab can be made smaller than in the conventional case. In addition, the deformation of the piezoelectric member can be efficiently applied to the ink. Therefore, ink droplets of a desired size can be ejected, and crosstalk can be suppressed. As a result, the problem of image quality deterioration when printing a high-resolution gradation image can be solved.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 to 4 show an ink jet recording head 10 of the present embodiment. The head 10 is configured by integrally combining a top plate 16, a partition 18, a vibration plate 20, and a substrate 22.

The top plate 16 is made of a flat plate such as a metal, a synthetic resin, or a ceramic, and its back surface is finely processed by a conventionally known method such as photolithography.
A plurality of recesses are formed symmetrically with respect to. A partition 18 made of a thin film of a metal, a synthetic resin, or the like is adhered to the recess forming surface of the top plate 16 so as to cover them so as to form one wall of each recess. Each of the recesses covered by the partition wall 18 has an ink cavity 26 for storing ink 24 and an ink supply chamber 3 for storing replenishment ink.
0 and an ink inlet 32 for connecting each ink cavity 26 to the ink supply chamber 30 are formed.

The ink cavities 26 are elongated grooves extending in parallel with each other in a direction perpendicular to the center line 34, and are arranged in a direction along the center line 34. Further, the nozzles 28 communicating with the vicinity of the ends of the ink cavities 26 on the center line 34 side are formed at equal pitches on a straight line along the center line 34 by a method such as excimer laser processing on the top plate 16. . The ink supply chamber 30 is formed on the opposite side of the center line 34 across the ink cavity 26, and is connected to an ink tank (not shown).

The vibrating plate 20 is made of a well-known piezoelectric material, and has a conductive metal layer (not shown) functioning as a common electrode and an individual electrode on its upper and lower surfaces, respectively.
And the substrate 22. Further, the diaphragm 20
As shown in FIGS. 2 and 3, the piezoelectric member 42 is formed by dicing to form a vertical groove 58 and a horizontal groove 60, which are separated from each other.
And a partition wall 44 located between the adjacent piezoelectric members 42
And a surrounding wall 46 surrounding them. Each piezoelectric member 42 is polarized by applying a high voltage between the upper and lower common electrodes and the individual electrodes at a high temperature. The common electrode of each piezoelectric member 42 is connected to the ground, and the individual electrodes are connected to an image signal control circuit (not shown). The drive voltage applied to each piezoelectric member 42 can be changed by this image signal control circuit. Here, the piezoelectric member 42 is not limited to a single-layer type, and a laminated piezoelectric member formed by laminating a plurality of thin film piezoelectric sheets so as to alternately sandwich metal electrode layers may be used.

FIG. 4 is an enlarged view of the vicinity of one ink cavity 26 in FIG. 3, and the width c of the piezoelectric member 42 in the arrangement direction of the plurality of ink cavities 26 (the left-right direction in FIG. 4) is It is formed narrower than the width a of the cavity 26 in the same direction. Further, the side wall 27 of the ink cavity 26 and the piezoelectric member 4
On the surface of the partition wall 18 located between the second side surface 48 and the surface of the partition wall 18, groove-shaped concave portions 50 having an arc-shaped cross section are provided on both sides of the piezoelectric member 42 along the longitudinal direction by etching, press working, or the like. . The portion of the groove-shaped recess 50 has a lower elastic modulus than the other portions of the partition wall 18,
It plays a role of a damper against the tension and the impact force acting on the member.

The substrate 22 is made of ceramic, metal, synthetic resin, or the like, and is fixed to the diaphragm 20.

Next, the operation of ejecting ink droplets from the ink jet recording head 10 having the above configuration will be described. In the head 10, ink is supplied from an ink tank (not shown) to the ink supply chamber 30, and an ink inlet 32 is provided.
The ink is accommodated in each ink cavity 26 via the. In this state, the image signal control circuit sends the piezoelectric member 42
When a voltage is applied to, as shown by a dashed line in FIG.
The piezoelectric member 42 is instantaneously deformed and pushes the partition wall 18 toward the ink cavity 26. Accordingly, the ink in the ink cavity 26 is pressurized, and the ink droplet 40 is ejected from the nozzle 28. The ink droplets 40 adhere to the recording medium to form dots, and an image is formed by a collection of the dots. It should be noted that the piezoelectric member 4
2 returns to the original shape, and at this time, the ink cavity 26
The ink is supplied from the ink inlet 32 by the negative pressure generated in the inside, and is prepared for the next ink ejection.

As described above, considerable tension and impact act instantaneously on the partition wall 18 pushed into the ink cavity 26. However, since the groove-shaped concave portions 50 formed on both sides of the piezoelectric member 42 with respect to the partition wall 18 serve as a damper, the tension and the like acting on the partition wall 18 are alleviated by the groove-shaped concave portions 50. Further, the vibration propagating from the adjacent ink cavity 26 through the partition 18 is also mitigated by the in-groove recess 50. Therefore, the side wall 27 of the ink cavity 26 and the adjacent ink cavity 26
Of the partition 18 corresponding to the above can be made smaller than before. As a result, crosstalk can be suppressed, and a decrease in image quality when forming a high-definition gradation image can be prevented.

Here, the width b of the groove-shaped concave portion 50 in the arrangement direction of the ink cavities 26 is
And the respective widths a and c of the piezoelectric member 42,
It is preferable to set so as to satisfy the expression of (ac) / 2>b> 5 [μm]. If the width b is smaller than 5 μm, the effect of suppressing crosstalk is reduced, while (ac) / 2.
This is because, if it becomes larger, there is a concern that the responsiveness of the piezoelectric member 42 to the high-period vibration is reduced.

The above-groove recess 50 is formed on the surface of the partition wall 18 on the side of the piezoelectric member 42 or the ink cavity 26.
It may be provided on any of the sides, and may be provided on both sides. As in the above embodiment, it is effective to provide at least the side pressing the partition wall 18, that is, the piezoelectric member 42 side. Further, the cross-sectional shape is not limited to the arc shape, and may be, for example, a rectangular shape as shown in FIGS. 5 (a) and 5 (b) or a bulging shape. Further, the concave portion does not necessarily have to be extended in a groove shape. For example, a plurality of dot-shaped concave portions may be arranged along the piezoelectric member.

In the embodiment described above, the piezoelectric member 42 is fixed on the substrate 22 in a state where the piezoelectric member 42 is in contact with the partition wall 18. However, as in the head 11 shown in FIG. Then, the substrate 22 may be in a non-contact state. The other configuration is the same as that of the head 10. In the head 11, the piezoelectric member 42 and the partition 18 constitute a bimorph, and when a voltage is applied to the piezoelectric member 42, the piezoelectric member 42 deforms together with the partition 18 toward the ink cavity 26 in a “<” shape. Then, the ink in the ink cavity is pressurized to eject ink droplets. Also in this head 11, the groove-shaped concave portion 50 is provided in the partition wall 18, and the same effect as that of the head 10 can be achieved.

The present invention can be applied not only to a monochromatic print head but also to a color print head having a plurality of heads corresponding to inks of respective colors.

[Brief description of the drawings]

FIG. 1 is a front view partially showing a recording medium facing portion of an ink jet recording head according to an embodiment.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a sectional view taken along line III-III in FIG. 2;

FIG. 4 is an enlarged view of the vicinity of one ink cavity in FIG.

FIGS. 5A and 5B are diagrams showing a modification of the cross-sectional shape of the groove-shaped recess formed in the partition.

FIG. 6 is a partial cross-sectional view showing another embodiment in which the method of fixing the piezoelectric member is different.

FIG. 7 is a partial cross-sectional view illustrating an example of a conventional inkjet head.

[Explanation of symbols]

10: inkjet recording head, 18: partition wall, 26 ...
Ink cavity, 42: piezoelectric member, 50: groove-shaped recess.

Claims (2)

[Claims] A plurality of ink cavities arranged in a predetermined direction for accommodating ink therein, partition walls covering the ink cavities so as to form one wall of the ink cavities, and opposing the respective ink cavities via the partition walls. An ink jet recording head that pressurizes ink in an ink cavity through a partition based on deformation of the piezoelectric member when a voltage is applied, and discharges ink droplets from a nozzle communicating with the ink cavity. The width of the piezoelectric member in the direction in which the cavities are arranged is formed narrower than that of the ink cavity, and a recess is provided on the surface of the partition wall located between the side wall of the ink cavity and the side surface of the piezoelectric member in the direction of the arrangement. Inkjet recording head. 2. An ink jet recording head for discharging ink from a nozzle communicating with said ink cavity by pressurizing ink in said ink cavity by means of a piezoelectric member through a partition, wherein said partition has a recess for preventing deformation. An ink jet recording head characterized by the following.