JP3185434B2 - Inkjet print head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a print head used for an ink jet printer and a method for manufacturing the same.

[0002]

2. Description of the Related Art A conventional ink jet print head is:
As shown in Japanese Patent Publication No. 60-8953, a plurality of nozzle openings are formed on the wall surface of a container constituting an ink tank, and a piezoelectric element is arranged in such a manner that the direction of expansion and contraction is matched to each nozzle opening. It is configured to be installed. In this print head, a drive signal is applied to a piezoelectric element to expand and contract the piezoelectric element, and ink droplets are ejected from nozzle openings by dynamic pressure of ink generated at this time to form dots on printing paper.

[0003] In a print head of this type,
It is desirable that the droplet formation efficiency and the flying force be large. However, since the piezoelectric element has a very small unit length and expansion / contraction ratio per unit voltage, it is necessary to apply a high voltage to obtain the flying force required for printing, which complicates the drive circuit and measures for electrical insulation. There is a problem of becoming.

To solve such a problem, Japanese Patent Laid-Open Publication No.
As disclosed in Japanese Patent Application Laid-Open No. 3-295269, a piezoelectric element for an ink jet print head in which electrodes and piezoelectric materials are alternately stacked in a sandwich shape has been proposed. According to this piezoelectric element, the distance between the electrodes can be reduced as much as possible, so that the voltage of the drive signal can be reduced.

However, any piezoelectric element is a fired body, and in consideration of characteristic variations and deformation such as warpage or undulation of the bulk piezoelectric body during firing, the length of the bulk piezoelectric body that can be fired is 30 to a maximum. The limit is 50 mm, and it has been difficult to increase the size of the print head (to a line head) with one bulk piezoelectric body.

As a structure that can avoid such a problem, Japanese Patent Publication No. 3-58917 discloses a print head structure in which a line head is composed of a plurality of head units.

[0007]

However, if it is attempted to form a line head by arranging a plurality of head units, it is difficult to ensure the nozzle position accuracy between the head units. This is a cause of unevenness such as streaks.

SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet print head of high print quality, in which piezoelectric elements can be easily arranged at a high density, and there is little characteristic variation, at a low cost.

[0009]

According to the present invention, there is provided an ink chamber having a nozzle plate provided with a plurality of nozzle openings for discharging ink droplets, and an ink chamber communicating with the nozzle openings. An ink jet apparatus comprising: a flow path forming member that forms an ink flow path communicating with an ink chamber; and a base plate unit in which a plurality of piezoelectric elements that generate pressure in the ink chamber are arranged on a base plate so as to correspond to the ink chamber. The type print head further includes a case-shaped base that determines the positions of the flow path constituent members and the plurality of base plate units, and surrounds the base plate units. And a piezoelectric element driving IC.

In the ink jet print head, the displacement characteristics of the piezoelectric elements are classified by unit, and a plurality of base plate units having equivalent displacement characteristics are arranged in the base plate unit. .

In the ink jet print head, the piezoelectric element is a laminated piezoelectric element, and the outermost layer of the piezoelectric material on the nozzle opening side or the outermost layer on both the nozzle opening side and the piezoelectric element fixing section side. The thickness of the piezoelectric material is greater than the thickness of the internal piezoelectric material layer.

In the ink jet print head, the thickness of the outermost piezoelectric material of the laminated piezoelectric element is an integral multiple of the thickness of the inner piezoelectric material layer.

In the ink jet print head, the ink jet print head is a line head having a length substantially equal to a recording width of a recording medium.

[0014]

FIG. 1 is a top view of an ink jet print head according to the present invention, FIG. 2 is a sectional view taken along line AA in FIG. 1, FIG. 3 is an enlarged view of a portion C in FIG. FIG. 4 is a sectional view taken along the line BB in FIG.

In FIG. 1 to FIG.
6, the vibration plate 103, the partition plate 104, and the nozzle plate 105 constitute a flow path constituting member, and the piezoelectric element 101 and the base plate 107 constitute a base plate unit. In the above-mentioned flow path constituting member, the ink is supplied from the ink supply holes 113 formed in the ink flow path plate 106 to the respective ink chambers 302 formed by the partition plate 104, the nozzle plate 105 and the vibration plate 103 through the ink flow path 110. You.

The piezoelectric elements 10 corresponding to each ink chamber 302
1 and an ink opening 102 are arranged, and the piezoelectric element 101 is arranged on a base plate 107 and repeatedly expands and contracts by an electric signal from the printer main body via the FPC 108 to eject ink from the nozzle opening 102.

First, a method for manufacturing a piezoelectric element will be described.

In FIG. 5, a piezoelectric material 50 such as a lead zirconate titanate-based composite perovskite ceramic prepared in the form of a green sheet or a paste is placed on a plate 501.
6, a first internal electrode material 601 serving as one electrode is formed on the surface of the first internal electrode material 601 by using a thick film printing method using a conductive paste in which Ag, Pd, and the like are adjusted. Further, in FIG. 7, a piezoelectric material 502 is applied to the surface of the internal electrode material layer 601 and an internal electrode material 701 to be the other electrode is applied to the upper surface by the above-described method as shown in FIG.
Thereafter, the internal electrode material layer and the piezoelectric material are repeatedly applied by the required number of layers by the above-described method, and the layers are dried to have a desired thickness and dried in FIG.

This is baked under pressure, and the external electrodes 1001 are formed on the surfaces where the conductive layers 601 and 701 are exposed as shown in FIG. A body 1101 is formed. The method for forming the external electrodes may be a thick film process or a thin film process, but the thin film process is more suitable in terms of uniformity of film thickness and adhesion strength. Further, since the thickness dimension at the time of printing shrinks at the time of firing, each layer must be printed thicker than the desired dimension in consideration of the shrinkage rate in advance. The shrinkage rate varies depending on the selected internal electrode material, piezoelectric material, and firing conditions, but is about 10 to 50%.

Here, the bulk piezoelectric body 1101 is deformed such as warpage or undulation due to shrinkage variation during firing or the like, and causes cracks and cracks when pressed and bonded to the base plate 107 in the next step. Becomes Therefore, the length of the bulk piezoelectric body 1101 is limited to 30 to 50 mm. The present invention is characterized in that a line head is constituted by arranging a plurality of base plate units on which a bulk piezoelectric body 1101 of 30 to 50 mm is arranged.

Hereinafter, the manufacturing process of the line head will be described. First, as shown in FIG. 11 and FIG. 12 which is a cross-sectional view of FIG. 11, a piezoelectric element driving wiring pattern 1102 for providing a driving signal from the driver IC to the piezoelectric element 101 formed at the same pitch as the nozzle opening pitch. FIG. 13 is a sectional view of FIG. 13 and FIG. 14 is a cross-sectional view of FIG. 13 and FIG. Driver IC as shown
After mounting the wire 202 by a wire bonding method, a flip chip method or the like, it is protected by a molding material 1401.

Thereafter, as shown in FIG. 15 and FIG. 16 which is a cross-sectional view of FIG. 15, a bulk piezoelectric body 1101 is disposed on a base plate 107, and is fixed by bonding.
A conductive material 1502 is applied in order to electrically connect 1 to the wiring pattern on the base plate. Here, the base plate 10
The material No. 7 does not deteriorate the vibration characteristics of the piezoelectric element 101, that is, the specific acoustic impedance (ρ × E) ＾ 1 expressed by the square of the product of the Young's modulus E of the material and the density ρ of the material. / 2 is preferably larger than the specific acoustic impedance of the piezoelectric element.

At this time, the length L of the bulk piezoelectric body 1101 in the nozzle array direction is the number of output bits n of one driver IC, the number m of driver ICs, and the number of piezoelectric elements 1
Assuming that the arrangement pitch is 01, it is preferable that L = P × n × m.

This is because if the number n of driver IC output bits on one base plate and the number of piezoelectric elements are different, it is necessary to ensure electrical continuity between the base plates and each piezoelectric element. Electrical continuity between them becomes difficult because the wiring becomes dense.

For this reason, in this embodiment, the nozzle pitch 8 /
Eight line heads of 300 inches and 512 nozzles are arranged in 64 bits by one driver IC.

Here, in consideration of the bonding accuracy between the base plate 107 and the bulk piezoelectric body 1101, the length L of one bulk piezoelectric body is L> 8/300 × 25.4 × 64 = 43.349 (mm) In the subsequent step, as shown in FIG. 19, both ends of the base plate 107 and the bulk piezoelectric body 1101 are simultaneously cut when forming the piezoelectric element rows, so that the base plate 10
7, the positional accuracy of the piezoelectric element 101 from the end face is ensured. That is, the length L after cutting is L = 43.349 mm.
It has become.

The bulk piezoelectric members 1101 on the base plate 107 are bonded obliquely due to variations in the thickness of the adhesive layer at the time of bonding, the initial shape of the bulk piezoelectric members 1101, and the like. There is a risk of height variations (steps). This height variation is caused by the nozzle opening 102 and the piezoelectric element 1 that affect the ink flying characteristics.
This causes the gap with 01 to vary.

In order to avoid this problem, in the present embodiment, the upper surface of the bulk piezoelectric element 1101 is ground with a dicing saw using a diamond blade to make the height uniform. In addition, as a method of making the height uniform, top lapping is effective in addition to top grinding.

Here, since the displacement of the laminated piezoelectric element is proportional to the electric field strength applied to one internal electrode layer, it is effective to reduce the thickness of the internal piezoelectric material layer in order to obtain a large displacement at a low voltage. is there. However, if the outermost layer is also made thinner like the internal electrode layer, the internal electrode is exposed during grinding of the upper surface unless the height variation of each bulk piezoelectric element is kept below the thickness of the outermost layer. For this reason, the bulk piezoelectric element 1101 at this time is adjusted to a bulk shape as shown in FIG. 17 by taking into account the height variation in advance so that the internal electrodes 601 and 701 are not exposed at the time of grinding or lapping. Nozzle opening side (uppermost outer layer) 17 of piezoelectric body 1101
01 or, as shown in FIG.
01 and the piezoelectric element fixing portion side 1801
1 (the lowermost outer layer) is desirably thicker than the inner piezoelectric material layer.

In this embodiment, the inner piezoelectric material 502 has a thickness of 35 μm and the outermost upper layer 1701 and the outermost lower layer 1
The thickness of 801 was 105 μm by stacking three 35 μm green sheets. In order to simplify the manufacturing process of the green sheet, the thickness of the outermost layers 1701 and 1801 is set to an integral multiple of the thickness of the inner piezoelectric material layer so that the inner piezoelectric material 502 can be laminated. Things are desirable.

Thereafter, as shown in FIG. 19 and FIG. 20, which is an enlarged view of a portion D in FIG. 19, the bulk piezoelectric body is processed in accordance with the wiring pattern 1102 to form the piezoelectric element 101 and the dummy piezoelectric element 115. By the base plate unit 1901
Get. Also, by cutting the base plate 107 by 50 to 100 μm, the conductive material 1502 could be completely electrically separated. Here, in this embodiment, as described above, in order to secure the positional accuracy of each piezoelectric element 101 from the end face of the base plate 107, the base plate end face and the bulk piezoelectric The body end face was simultaneously processed to provide a reference plane 1902. Here, since there is a limit to the depth L2 that can be cut by dicing, both ends of the base plate forming the reference plane 1902 are formed in a convex shape as shown in FIG.

In this embodiment, a line head having a nozzle pitch of 8/300 inches and 512 nozzles is connected to one driver IC.
, 64 bits, that is, eight base plate units are arranged. Here, in order to secure the positional accuracy between the vibration plate 103, the partition plate 104, the nozzle plate 105 and each of the piezoelectric elements 101 in the post-process, the units which come to both ends of the base plate unit arranged as shown in FIG. 2101,
As shown in FIGS. 21 and 22, a reference column 114 was formed by simultaneously processing the bulk piezoelectric material and the reference column material at the time of processing the base plate.

The base plate units 1901, 2101 and 2201 obtained as described above are inserted into the ink flow path plate 106 while the reference surfaces formed on the respective units are brought into contact with each other as shown in FIG. Thereafter, as shown in FIG. 24, the substrate is pressed against the base 2401 and adhered so that the upper surface of the ink flow path plate 106 and the upper surface of the piezoelectric element 101 become uniform.
A flow path plate unit 2402 as shown in FIG. 25 is obtained.

Here, as described above, since the piezoelectric element 101 is a fired body in which the internal electrodes are printed with a thick film, the characteristics vary depending on the internal electrode printing accuracy, firing state, and manufacturing lot. For this reason, for each base plate unit, the displacement characteristics of each piezoelectric element 101 after processing the bulk-shaped piezoelectric body were measured, and the piezoelectric elements 101 were classified according to the displacement characteristics into several preset classes. Thereafter, one head was formed by arranging base plate units of the same class. As a result, the prior inspection, which was conventionally performed using a substitute value such as capacitance, could be managed by the displacement of the piezoelectric element fixed to the base plate, which is a direct factor that affects the ink ejection characteristics.

As a result, since the displacement characteristics between the units could be precisely adjusted, the ink ejection characteristics were stabilized in one head, and an ink jet print head having excellent print quality could be obtained.

Next, as shown in FIG. 26, a flow path plate unit 2102 having an adhesive applied to the upper surface thereof is fixed to the base 2601 and a reference hole provided in the diaphragm 103 is inserted into the reference column 114 to align the position. I do. Thereafter, pressure is applied with a weight 2602 and, if necessary, adhesively fixed in a high-temperature atmosphere. Here, the dummy piezoelectric element 115 is left as a receiver for the partition plate 104. This operation is performed by repeatedly laminating and bonding the partition plate 104 and the nozzle plate 101 having the nozzle openings 102 formed therein, thereby determining the flow path constituent member, the base plate unit, the positions of both, and surrounding the base plate unit. An ink jet print head having a base is obtained.

In this embodiment, the nozzle rows 2701 are arranged in a single row as shown in FIG. 27 in order to reduce the size of the head and simplify the electric circuit (no need for a delay circuit or the like). As shown in FIG. 28, the first nozzle row 2801 and the second nozzle row 2802 can be arranged in a staggered arrangement for each base plate unit. Even with this structure, the present invention uses a single nozzle plate, so that the nozzle position accuracy at the boundary of the base plate unit is guaranteed at the time of manufacturing the nozzle plate. An inkjet head can be obtained.

In this embodiment, an example is shown in which one driver IC is mounted on one base plate. However, depending on the number of output bits of the driver IC and the length of the bulk piezoelectric body that can be manufactured, it is possible to mount a plurality of driver ICs on a single base plate as long as characteristic variations can be tolerated.

In this embodiment, a wire bonding method and a flip chip method are introduced as a method of mounting an IC on a base plate. However, as shown in FIGS.
(Tape Automated Bonding) type TAB unit 2901 is mounted on the base plate 107.
May be connected. Since the inspection at the time of mounting the IC is easy in the TAB method, an improvement in manufacturing yield can be expected.

In this embodiment, an example is shown in which the piezoelectric element 101 is a laminated piezoelectric element in the d33 direction utilizing displacement in the same direction as the electric field direction. However, as shown in FIG. D31 direction piezoelectric element 31 using displacement
01 may be used.

[0041]

As described above, a nozzle plate having a plurality of nozzle openings for ejecting ink droplets is provided, and an ink chamber communicating with the nozzle openings and an ink flow path communicating with the ink chamber are formed. In an ink jet print head comprising a flow path component, and a base plate unit in which a plurality of piezoelectric elements for generating pressure in an ink chamber are arranged on a base plate so as to correspond to the ink chambers, the flow path component and the plurality of Further comprising a case-shaped base for determining the position of the base plate unit and surrounding the base plate unit, and each base plate is provided with a piezoelectric element driving IC for driving a piezoelectric element. Thereby, not only can a long head having little characteristic variation be obtained, but also it is easy to align the flow path constituent member and the base plate unit,
Further, the piezoelectric element driving IC, which is a precise driving circuit, can be protected from disturbance by the base.

Therefore, even with a line type head having a large number of nozzles, there is an effect that an ink jet print head of high print quality, which has high reliability over a long period of time and little characteristic variation, can be provided at low cost.

[Brief description of the drawings]

FIG. 1 is a top view showing the structure of an ink jet print head of the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG. 1 showing the structure of the ink jet print head of the present invention.

FIG. 3 is an enlarged view of a portion C in FIG. 2 showing the structure of the ink jet print head of the present invention.

FIG. 4 is a sectional view taken along line BB of FIG. 1 showing the structure of the ink jet print head of the present invention.

FIG. 5 is a cross-sectional view illustrating a manufacturing process of the ink jet print head of the present invention.

FIG. 6 is a cross-sectional view illustrating a manufacturing process of the ink jet print head of the present invention.

FIG. 7 is a cross-sectional view illustrating a manufacturing process of the ink jet print head of the present invention.

FIG. 8 is a cross-sectional view illustrating a manufacturing process of the ink jet print head of the present invention.

FIG. 9 is a cross-sectional view showing a manufacturing process of the ink jet print head of the present invention.

FIG. 10 is a cross-sectional view illustrating a manufacturing process of the ink jet print head of the present invention.

FIG. 11 is a diagram showing a manufacturing process of the ink jet print head of the present invention.

FIG. 12 is a cross-sectional view illustrating a manufacturing process of the ink jet print head of the present invention.

FIG. 13 is a cross-sectional view illustrating a manufacturing process of the ink jet print head of the present invention.

FIG. 14 is a cross-sectional view illustrating a manufacturing process of the ink jet print head of the present invention.

FIG. 15 is a diagram showing a manufacturing process of the ink jet print head of the present invention.

FIG. 16 is a sectional view showing a manufacturing process of the ink jet print head of the present invention.

FIG. 17 is a sectional view showing an embodiment of the ink jet print head of the present invention.

FIG. 18 is a sectional view showing an embodiment of the ink jet print head of the present invention.

FIG. 19 is a diagram showing a manufacturing process of the ink jet print head of the present invention.

FIG. 20 is a diagram showing a manufacturing process of the ink jet print head of the present invention.

FIG. 21 is a diagram showing a manufacturing process of the ink jet print head of the present invention.

FIG. 22 is a diagram showing a manufacturing process of the ink jet print head of the present invention.

FIG. 23 is a perspective view illustrating a manufacturing process of the ink jet print head of the present invention.

FIG. 24 is a cross-sectional view illustrating a manufacturing process of the ink jet print head of the present invention.

FIG. 25 is a diagram showing a manufacturing process of the ink jet print head of the present invention.

FIG. 26 is a cross-sectional view illustrating a manufacturing process of the ink jet print head of the present invention.

FIG. 27 is a diagram showing an embodiment of the ink jet print head of the present invention.

FIG. 28 is a diagram showing an embodiment of the ink jet print head of the present invention.

FIG. 29 is a diagram showing an embodiment of the ink jet print head of the present invention.

FIG. 30 is a sectional view showing an embodiment of the ink jet print head of the present invention.

FIG. 31 is a sectional view showing an embodiment of the ink jet print head of the present invention.

[Explanation of symbols]

 Reference Signs List 101 piezoelectric element 102 nozzle opening 103 diaphragm 104 partition plate 105 nozzle plate 106 ink flow plate 107 base plate 108 FPC 109 electrode 110 ink flow passage

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B41J 2/045 B41J 2/055 B41J 2/16

Claims (5)

(57) [Claims] A plurality of nozzle openings for discharging ink droplets are provided.
A nozzle plate provided and communicates with the nozzle opening
And an ink passage communicating with the ink chamber.
A flow path constituting member, and a pressure generated in the ink chamber.
The piezoelectric element to be moved is placed on the base plate corresponding to the ink chamber.
With a plurality of base plate units
In a jet type print head, the positions of the flow path constituting member and the plurality of base plate units are determined.
And a case-shaped base for surrounding the base plate unit
A piezoelectric element for driving the piezoelectric element on each of the base plates.
An ink jet device comprising a driving IC.
Print head. 2. The base plate unit according to claim 1, wherein the displacement characteristics of the piezoelectric elements are classified for each unit, and a plurality of base plate units having equivalent displacement characteristics are arranged. Ink jet print head. 3. The piezoelectric element is a laminated piezoelectric element,
The thickness of the outermost layer piezoelectric material on the nozzle opening side, or the thickness of the outermost layer piezoelectric material on both the nozzle opening side and the piezoelectric element fixing section side is larger than the thickness of the internal piezoelectric material layer. 2. The ink jet print head according to 1. 4. The ink jet print head according to claim 3, wherein the thickness of the outermost piezoelectric material of the multilayer piezoelectric element is an integral multiple of the thickness of the internal piezoelectric material layer. 5. The ink jet print head according to claim 1, wherein the ink jet print head is a line head having a length substantially equal to a recording width of a recording medium.