JPH11216861A - Ink-jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve accuracy in position where ink drops land in an ink-jet head discharging a plurality of colors of ink drops by arranging on one substrate an energy generation means for generating energy to discharge the plurality of colors of ink drops. SOLUTION: An actuator unit 1 has a plurality of layer type piezoelectric elements 5 arranged in arrays for each of head parts 3k, 3y, 3m, 3c on an insulating ceramics substrate 4. The piezoelectric element is an energy generation means for generating energy to discharge ink drops of each color. A diaphragm 15 of a liquid chamber unit 2, and the piezoelectric elements 5 and frame members 6 of the actuator unit 1 are united by an adhesive 27. A driving waveform (pulse voltage of 10-50 V) is applied from a driving IC 10 to the piezoelectric element 5 in accordance with a record signal. The piezoelectric elements 5 are shifted in a layer direction, and the interior of pressure liquid chambers 17 is pressured via the diaphragm 15 to increase a pressure. As a result, ink drops are discharged from nozzles 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet head, and more particularly, to an ink jet head for discharging ink droplets of a plurality of colors.

[0002]

2. Description of the Related Art An ink jet recording apparatus used for a printer, a facsimile, a copying machine, etc. discharges ink droplets from nozzles of an ink jet head which is a recording head to record a recording medium (images are recorded. The image is not limited to “paper” such as glossy film paper and coated paper, but also includes OHP sheets and the like.) In particular, ink jet recording apparatuses have come to be frequently used because they are easy to colorize.

In this ink jet recording apparatus, for example, a recording head having one or a plurality of nozzles arranged in a sub-scanning direction is moved in a main scanning direction, and a recording medium is orthogonal to the main scanning direction. While moving in the sub-scanning direction, ink droplets of four colors of yellow (Y), magenta (M), cyan (C), and black (K) are selectively ejected from each nozzle, and color ink is ejected onto a recording medium. 2. Description of the Related Art There has been known a serial type color ink jet printing apparatus which prints an image while moving the printing medium in a sub-scanning direction with a head having a length corresponding to the width of the printing medium.

[0004]

As described above, when a color image is recorded by ejecting ink droplets of a plurality of colors, the ink droplets of each color ejected from a nozzle may land on a recording medium with high accuracy. This is important for recording high-quality images. The factors that determine the landing position accuracy of the ink droplets are roughly classified into the following four factors.

First, since a plurality of nozzles are provided for one color, it is necessary to arrange the nozzles on a nozzle forming member (nozzle plate) with high pitch accuracy. In this case, naturally, not only the pitch direction but also the straightness of the nozzle row is required. Second, the accuracy of the nozzle itself is a factor, not the physical positional accuracy of the nozzle. That is,
The roundness of the nozzle and the wettability of the nozzle outlet. If these are dispersed among the nozzles, the ejection direction varies, resulting in poor dot position accuracy. Among them, dust and the like in the nozzle are also included in a kind of roundness defect.

Thirdly, in the case of a serial printer, there are respective feeding accuracies in the feeding direction of the carriage (main scanning direction) and the feeding direction of the recording medium (sub-scanning direction). Fourth,
When printing multiple colors, the positional relationship between the heads of each color is an important factor. That is, the pitch in the arrangement direction and the shift or inclination in the longitudinal direction on the basis of a certain color are major factors that disturb the image, which is called color shift. Positioning with high accuracy

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to improve the accuracy of the ink droplet landing position in an ink jet head that discharges ink droplets of a plurality of colors.

[0008]

In order to solve the above-mentioned problems, an ink jet head according to a first aspect of the present invention generates an energy for discharging a plurality of color ink droplets in an ink jet head for discharging a plurality of color ink droplets. Energy generating means is arranged on a single substrate.

According to a second aspect of the present invention, in the inkjet head of the first aspect, an electrode pattern is formed on the substrate, and a through-hole for electrically connecting the electrode pattern to a back surface of the substrate is formed. Configuration.

According to a third aspect of the present invention, in the ink jet head of the first or second aspect, a nozzle forming member having a nozzle formed therein corresponding to the energy generating means on the substrate, and an ink liquid chamber communicating with the nozzle. And a liquid chamber unit integrally formed with a vibration plate for transmitting the energy of the energy generating means to the ink liquid chamber.

According to a fourth aspect of the present invention, in the ink jet head of the third aspect, an alignment mark for alignment is provided on a nozzle forming member and / or a diaphragm of the liquid chamber unit, and the alignment mark is provided on the substrate. The slit groove is provided.

According to a fifth aspect of the present invention, in the ink jet head according to any one of the first to fourth aspects, a region or a groove having different water repellency is provided on a boundary portion of each color on an ink droplet ejection surface. .

According to a sixth aspect of the present invention, in the ink jet head according to any one of the first to sixth aspects, the energy generating means includes an electromechanical transducer.

[0014]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 is a sectional view showing an example of an ink jet head to which the present invention is applied, FIG. 2 is a plan view of an actuator unit of the head, FIG. 3 is a rear view of the actuator unit, and FIG. 4 is an enlarged view of a liquid chamber unit of the head. FIG. 5 and FIG. 5 are plan views of the liquid chamber unit.

This ink-jet head includes an actuator unit 1 and a liquid chamber unit 2, and a head unit 3 for ejecting black (Bk) ink droplets from the actuator unit 1 and the liquid chamber unit 2.
k, a head unit 3y for ejecting ink droplets of yellow (Y) ink, a head unit 3m for ejecting ink droplets of magenta (M) ink, and a head for ejecting ink droplets of cyan (C) ink Part 3c is integrally formed,

The actuator unit 1 is a plurality of energy generating means for generating energy for discharging ink droplets of each color onto a single insulating substrate 4 such as barium titanate, alumina, forsterite or the like. Of each of the head units 3
They are arranged in rows for each of k, 3y, 3m, and 3c. Also,
On the substrate 4, a frame member 6 serving as a head interval wall portion and an outer peripheral partition portion between the respective head portions 3k, 3y, 3m, 3c.
Is arranged.

As the piezoelectric element 5, for example, a laminated piezoelectric element having ten or more layers is used. This laminated piezoelectric element has a lead zirconate titanate (PZ) having a thickness of 10 to 50 μm / 1 layer.
T) and silver / palladium (AgP) with a thickness of several μm / 1 layer
and the internal electrodes of d) are alternately laminated.
Further, the plurality of piezoelectric elements 5 are formed by forming slit grooves 7 cut into the substrate 4 by performing slit processing as shown in FIG. The piezoelectric element 5 is divided and formed. Note that lead zirconate titanate (PZT) having a large piezoelectric constant
When slitting is performed using the piezoelectric element 5, the slit processing is relatively easy by using a barium titanate-based ceramic material of the same material as the piezoelectric element also for the substrate 4 to which the piezoelectric element 5 is bonded.

On the substrate 4, a common electrode pattern 8 and an individual electrode pattern 9 for connecting to the end face electrodes of each piezoelectric element 5 are formed by Ni / Au evaporation, Au plating, AgPt paste printing,
It is formed by AgPd paste printing or the like. These common electrode patterns 8 and individual electrode patterns 9 are connected to end electrodes of each piezoelectric element 5 via a conductive adhesive or the like. A drive IC for giving a drive waveform to each piezoelectric element 5 of each of the heads 3k, 3y, 3m, 3c is provided on the back side of the substrate 4.
10 is attached.

The substrate 4 is provided with a through-hole 11 for establishing conduction between the individual electrode pattern 9 for each piezoelectric element and the back surface of the substrate, and the through-hole 11 and the individual electrode pattern 9B on the back surface of the substrate are provided. And is electrically connected to the drive IC 10 on the rear surface side of the substrate. The common electrode pattern 8 is also provided with a through-hole 12 with the back surface side, and the drive IC is driven through the common electrode pattern 8B on the back surface side of the substrate.
It is electrically connected to C10. The common electrode pattern 8 divided by the slit processing can be formed by forming a conductive film to connect the piezoelectric elements 5 to each other.

On the other hand, the liquid chamber unit 2 includes a diaphragm 15
Ink is supplied to the pressurized liquid chambers 17 corresponding to the piezoelectric elements 5 and ink to the pressurized liquid chambers 17 corresponding to the piezoelectric elements 5, and the frame member 16 serving as a head spacing wall and an outer peripheral partition between the heads 3 k, 3 y, 3 m, 3 c. Common liquid chamber 18 and common liquid chamber 18 and pressurized liquid chamber 17
A liquid chamber partition member 20 that forms an ink supply path 19 also serving as a fluid resistance section that communicates with the pressure chambers, and a single nozzle plate 22 that communicates with each pressurized liquid chamber 17 and forms a nozzle 21 that discharges ink droplets. Are laminated and joined.

As shown in FIG. 4, the liquid chamber unit 2 is formed of a photosensitive resin layer which forms a part of the liquid chamber partition member 20 on the vibration plate 15 and has a high precision fine liquid chamber pattern formed by a photolithography process. The photosensitive resin layer which forms the remainder of the liquid chamber partition member 20 on the nozzle plate 22 also forms a high-precision fine predetermined liquid chamber pattern by a photolithographic process, and the photosensitive resin layers are thermocompression-bonded to each other. And unitized. Since the main component of the photosensitive resin material is methacrylic resin, fusion bonding can be easily performed by heating both at a temperature of 150 to 200 ° C. and applying a pressure of 1 to 2 kgf / cm 2. .

The diaphragm 15 can be formed with a diaphragm portion in which a portion corresponding to the pressurized liquid chamber 17 is thinned. By having the diaphragm portion, the displacement of the piezoelectric element 5 can be efficiently transferred to the pressurized liquid chamber 17. You can propagate. As shown in FIG. 5, a water-repellent film 2 is formed on the ink ejection surface of the nozzle plate 22.
At the same time, a water-repellent film 25 having a different water-repellency from the water-repellent film 24 is formed at the boundary between the colors, that is, at the boundary between the heads 3k, 3y, 3m, and 3c. In this case, the wettability P of the water-repellent film 24 and the wettability Q of the water-repellent film 25 are P>
It may be Q or P <Q. Also, instead of forming two water repellent films 24 and 25 having different water repellency,
A slit groove 26 may be formed at the boundary as shown in FIG.

The vibration plate 15 and the nozzle plate 22 can be formed by a Ni electroforming method or the like and can be manufactured by a metal plating film or a resin plate. Further, the water repellent films 24, 2
5 is, for example, PTFE-Ni eutectoid plating, electrodeposition coating of fluororesin, vapor-deposited coating of evaporable fluororesin (for example, pitch fluoride), or silicon-based resin / fluororesin after solvent coating. The film can be formed by baking or the like.

Then, the vibration plate 15 of the liquid chamber unit 2 and the piezoelectric element 5 and the frame member 6 of the actuator unit 1 are joined with an adhesive 27 to constitute an ink jet head.

In the ink jet head configured as described above, the driving IC 1 is attached to the piezoelectric element 5 in accordance with the recording signal.
By applying a drive waveform (pulse voltage of 10 to 50 V) from 0, displacement in the laminating direction occurs in the piezoelectric element 5, and the inside of the pressurized liquid chamber 17 is pressurized via the vibration plate 15 and the pressure increases. Then, an ink droplet is ejected from the nozzle 21.

Then, with the end of the ink droplet ejection, the ink pressure in the pressurized liquid chamber 17 is reduced, and a negative pressure is generated in the pressurized liquid chamber 17 by the inertia of the ink flow and the discharge process of the drive pulse. To the ink filling process. At this time, the ink supplied from the ink tank flows into the common liquid chambers 18, 18, and from the common liquid chambers 18, 18 to the ink supply paths 19, 1.
Through 9, the pressurized liquid chamber 17 is filled. Then, the vibration of the ink meniscus surface near the outlet of the nozzle 21 is attenuated,
When the ink is returned to the vicinity of the outlet of the nozzle 21 by the surface tension (refill) and reaches a stable state, the operation shifts to the next ink droplet ejection operation.

Here, in this ink jet head, since the piezoelectric elements 5, 5,... For generating energy for ejecting ink droplets of each color are arranged on one substrate 4, the head portions 3k, 3k, The alignment of 3y, 3m, and 3c becomes unnecessary, and the pitch L in the arrangement direction of the head units (see FIG. 1), the inclination in the nozzle arrangement direction, and the like can be made the same for each head unit. And the image quality can be improved.

Further, by forming electrode patterns 8 and 9 on the substrate 4 and forming through holes 11 and 12 for electrically connecting the electrode patterns 8 and 9 to the back surface of the substrate 4, a plurality of colors are formed. The head having the liquid chamber 17 can be configured on one substrate 4, and the head can be reduced in size.

Further, corresponding to the energy generating means (piezoelectric element 5) on the substrate 4, a nozzle plate 22 having a nozzle 21 formed therein, an ink liquid chamber (pressurized liquid chamber 17) to which the nozzle 21 communicates, an energy generating means By joining the liquid chamber unit 2 integrally formed with the vibration plate 15 that transmits the energy of the ink to the ink liquid chamber, the assemblability is improved, and the liquid chamber unit can be inspected before assembling the entire head. And the cost can be reduced.

Further, the nozzles 21 for ejecting ink droplets of each color are formed on one nozzle plate 22, and regions having different water repellency (water repellent films 25 or slit grooves 26) are provided at the boundary portions, so that adjacent nozzles are provided. It is possible to prevent a color mixture in which ink dripping from the intermediate nozzle is mixed with ink of another color. Alternatively, in an inkjet head, wiping is performed to remove residual ink and the like on an ink ejection surface. However, when a nozzle for ejecting ink droplets of each color is formed on one nozzle plate, when wiping is performed, adhesion to the wiping blade occurs. When the mixed ink enters the nozzle of another color, the mixed color of the ink occurs and the image lacks sharpness until the mixed ink disappears.However, since there is an area with different water repellency at the boundary, wiping is performed. This can prevent ink between adjacent nozzles from being mixed.

Next, another embodiment of the present invention will be described with reference to FIGS. Here, positioning alignment marks (holes) 27a to 27d penetrating from the nozzle plate 22 to the vibration plate 15 of the liquid chamber unit 7 are formed, and the slit 4 of the piezoelectric element 5 is also formed on the substrate 4 of the actuator unit 1. Positioning slit groove 28,
28 to form alignment marks 29a-
29d are provided.

The alignment marks 27a to 27d on the liquid chamber unit 2 side can also serve as alignment marks used when assembling the liquid chamber unit 2 itself (joining the nozzle plate 22 and the diaphragm 15). Further, the alignment marks 27a to 27d may be patterned at the same time when the nozzle plate 22 and the vibration plate 15 are formed by electroforming, or may be formed by using a laser or the like to form holes later. . On the other hand, the alignment marks 29a to 29d on the actuator unit 1 side are formed as slit grooves, so that the mechanical accuracy of a dicing saw or the like for performing slit processing is about ± 5 μm, and the accuracy when marking by screen printing is ± 20 μm. It can be formed with a high positional accuracy even in comparison with certain cases.

When the liquid chamber unit 2 is joined to the actuator unit 1, the alignment mark 27
The liquid chamber unit 2 and the actuator unit 1 can be joined with high positional accuracy by detecting and matching the alignment marks a to 27d and the alignment marks 29a to 29d by optical mark recognition.

As a result, the displacement of the piezoelectric element 5 of the actuator 1 is efficiently transmitted to the pressurized liquid chamber 17 of the liquid chamber unit 2, so that the driving of the piezoelectric element is performed as compared with the case where the displacement is not efficiently transmitted. The voltage can be relatively low. That is, when the transmission efficiency of the displacement of the piezoelectric element is low, it is necessary to increase the drive voltage of the piezoelectric element to increase the displacement. However, such a high drive voltage is not required. Further, it is possible to prevent mutual interference between adjacent channels that occurs when the diaphragm is provided on the diaphragm.

[0035]

As described above, according to the ink-jet head of the first aspect, in the ink-jet head for discharging ink droplets of a plurality of colors, energy generating means for generating energy for discharging ink droplets of a plurality of colors. Are arranged on one substrate, the ink droplet landing position accuracy of each color is improved, and the image quality can be improved.

According to a second aspect of the present invention, there is provided the ink jet head of the first aspect, wherein an electrode pattern is formed on the substrate, and the through hole electrically connects the electrode pattern to the back surface of the substrate. Is formed, a head having liquid chambers of a plurality of colors can be formed on one substrate, and the size of the head can be reduced.

According to a third aspect of the present invention, in the inkjet head of the first or second aspect, a nozzle forming member having a nozzle formed therein corresponding to the energy generating means on the substrate, and an ink communicating with the nozzle. Since the liquid chamber unit, which integrally forms the liquid chamber and the vibration plate for transmitting the energy of the energy generating means to the ink liquid chamber, is joined, the assemblability is improved and the cost can be reduced.

According to the ink jet head of the fourth aspect, in the ink jet head of the third aspect, an alignment mark for positioning is provided on the nozzle forming member and / or the diaphragm of the liquid chamber unit, and the alignment mark is provided on the substrate. Since the alignment slit groove is provided, the liquid chamber unit can be joined to the piezoelectric element with high accuracy.

According to the ink jet head of the fifth aspect, in the ink jet head of any one of the first to fourth aspects, regions or grooves having different water repellency are provided at the boundary of each color on the ink droplet ejection surface. Color mixing of ink can be prevented.

According to the ink jet head of the sixth aspect, in the ink jet head of any one of the first to sixth aspects, since the energy generating means comprises an electromechanical transducer, the position of the ink droplet landing position of each color is high. An inkjet head using a mechanical conversion element can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of an inkjet head to which the present invention is applied.

FIG. 2 is a plan view of an actuator unit of the head.

FIG. 3 is a rear view of the actuator unit.

FIG. 4 is an enlarged view of a liquid chamber unit of the head.

FIG. 5 is a plan view of the liquid chamber unit.

FIG. 6 is a sectional view of another nozzle plate of the liquid chamber unit.

FIG. 7 is a plan view of a liquid chamber unit illustrating another embodiment of the present invention.

FIG. 8 is a plan view of the same actuator unit.

[Explanation of symbols]

1 ... actuator unit, 2 ... liquid chamber unit, 3
k, 3y, 3m, 3c head section, 4 substrate, 5 piezoelectric element, 6 frame member, 7 slit groove, 8 common electrode pattern, 9 individual electrode pattern, 10 drive IC,
11, 12: through hole, 15: diaphragm, 17: pressurized liquid chamber, 20: liquid chamber partition member, 21: nozzle, 22: nozzle plate, 24, 25: water repellent film, 26: slit groove, 27a
To 27d, 29a to 29d ... alignment marks.

Continued on the front page (72) Inventor Noboru Nakane 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Inventor Masayuki Iwase 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Inventor Hideyuki Makita 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Tsutomu Sasaki 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company

Claims (6)

[Claims] 1. An ink jet head for discharging ink droplets of a plurality of colors, wherein each energy generating means for generating energy for discharging the ink droplets of a plurality of colors is provided on a single substrate. Ink jet head. 2. The ink jet head according to claim 1, wherein an electrode pattern is formed on the substrate, and a through hole is formed to electrically connect the electrode pattern to a back side of the substrate. Inkjet head. 3. The ink jet head according to claim 1, wherein a nozzle forming member having a nozzle formed therein, an ink liquid chamber communicating with the nozzle, and the energy generating means correspond to the energy generating means on the substrate. An ink jet head, wherein a liquid chamber unit integrally formed with a vibration plate for transmitting the energy of the ink to the ink liquid chamber is joined. 4. The ink jet head according to claim 3, wherein a positioning alignment mark is provided on a nozzle forming member and / or a diaphragm of the liquid chamber unit, and a positioning slit groove is provided on the substrate. An ink jet head, characterized in that: 5. The ink-jet head according to claim 1, wherein regions or grooves having different water repellency are provided on a boundary portion of each color on an ink droplet ejection surface. 6. An ink jet head according to claim 1, wherein said energy generating means comprises an electromechanical transducer.