JPH06246918A - Ink jet device - Google Patents

Abstract

PURPOSE:To provide an ink jet device excellent in printing quality and mass productivity. CONSTITUTION:Within a region wherein a taper angle being a ratio reducing and changing the diameter of a nozzle from the cross-sectional part of the nozzle on an ink passage side to that of the nozzle on an ink injection side is 5-30 deg., it is cleared that the flying speed of an ink droplet is fast and relatively stable. Therefore, even when the taper angles of the respective nozzles are different, the nozzle may be produced in the ratio within the region. As a result, the number of inferior products can be lowered when an ink jet printing head is produced and an ink jet device is excellent in printing quality and mass productivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention deforms the wall of an ink flow path by changing the shape of a piezoelectric ceramic to change the volume of the ink flow path and arranges the ink filled in the ink flow path in correspondence with the ink flow path. The present invention relates to an ink ejecting device that ejects from a nozzle that is ejected.

[0002]

2. Description of the Related Art Conventionally, this type of ink ejecting apparatus has been used in, for example, an inkjet printer. A first conventional example of such an ink ejecting apparatus will be described with reference to FIG. A piezoelectric ceramic element 76 is provided on a side wall 74 of the housing 72 forming the ink chamber 70. The electrodes 7 are formed on both surfaces of the piezoelectric ceramic element 76.
7 is formed, and the drive circuit 79 is connected to the electrode 77.

When a driving voltage is applied to the electrode 77 by the driving circuit 79, the piezoelectric ceramic element 76 is deformed. At this time, along with the deformation of the piezoelectric ceramic element 76, the side wall 74 is deformed as shown by the alternate long and short dash line to reduce the volume of the ink chamber 70, and the ink as the ejection liquid filled in the ink chamber 70 is reduced. 80 ink drops
And is ejected from the nozzle 82.

After that, when the application of the drive voltage is stopped,
The piezoelectric ceramic element 76 returns to the shape before the deformation, the volume of the ink chamber 70 increases, and the ink flows from the ink supply passage 84 into the ink chamber 70. When used as an inkjet printer, such an ink chamber 70
It is configured with many.

Next, a second conventional example of an ink jet device using a piezoelectric ceramic element will be described.

As shown in FIG. 7, the ink jet printer head 1 is composed of a piezoelectric ceramic plate 2, a cover plate 3, a nozzle plate 31, and a substrate 41.

The piezoelectric ceramic plate 2 has a plurality of grooves 8 formed therein. Further, the side wall 11 which is the side surface of the groove 8 is polarized in the direction of arrow 5. The grooves 8 have the same depth and are parallel. The depths of the grooves 8 gradually become shallower as they approach the one end face 15 of the piezoelectric ceramic plate 2, and a shallow groove 16 is formed near the one end face 15. Then, on the inner surface of the groove 8, metal electrodes 13 are formed on the upper half of both side surfaces by sputtering or the like. The metal electrode 9 is formed on the inner surface of the shallow groove 16 on the side surface and the bottom surface by sputtering or the like. As a result, the metal electrodes 13 formed on both sides of the groove 8 are electrically connected by the metal electrodes 9 formed in the shallow groove 16.

Next, the cover plate 3 is made of a ceramic material, a resin material, or the like. Then, the cover plate 3 is formed by grinding or cutting.
An ink inlet 21 and a manifold 22 are formed. Then, the surface of the piezoelectric ceramic plate 2 on the side where the groove 8 is processed and the surface of the cover plate 3 on the side where the manifold 22 is processed are bonded by an epoxy adhesive or the like. Therefore,
The ink jet printer head 1 has a plurality of ink flow paths 1 which are covered with the upper surfaces of the grooves 8 and are laterally spaced from each other.
2 (FIG. 9) is constructed. The ink flow path 12 has an elongated shape with a rectangular cross section, and ink is filled in all the ink flow paths 12.

To the end faces of the piezoelectric ceramic plate 2 and the cover plate 3, a nozzle plate 31 having a nozzle 32 provided at a position corresponding to the position of each ink flow path 12 is adhered. The nozzle plate 31 is formed of a plastic such as polyalkylene (for example, ethylene), terephthalate, polyimide, polyetherimide, polyetherketone, polyethersulfone, polycarbonate, or cellulose acetate.

A substrate 41 is adhered to the surface of the piezoelectric ceramic plate 2 opposite to the processed side of the groove 8 with an epoxy adhesive or the like. Its substrate 41
A conductive layer pattern 42 is formed at a position corresponding to the position of each ink flow path 12. The pattern 42 of the conductive layer and the metal electrode 9 on the bottom surface of the shallow groove 16 are connected by a conductive wire 43 by wire bonding.

Next, the structure of the control unit will be described with reference to FIG. 8 which is a block diagram of the control unit. The conductive layer patterns 42 formed on the substrate 41 are individually connected to the LSI chip 51. The clock line 52, the data line 53, the voltage line 54, and the ground line 55 are also LS.
It is connected to the I-chip 51. The LSI chip 51 is
Based on the continuous clock pulse supplied from the clock line 52, it is determined from which nozzle 32 the ink droplet should be ejected according to the data appearing on the data line 53. Then, the voltage V of the voltage line 54 is applied to the pattern 42 of the conductive layer that is electrically connected to the metal electrode 13 in the driven ink flow path 12. Further, the voltage 0V of the ground line 55 is applied to the pattern 42 of the conductive layer electrically connected to the metal electrode 13 other than the driven ink flow path 12.

Next, the operation of the ink jet printer head 1 will be described with reference to FIGS. It is determined that the LSI chip 51 ejects ink droplets from the ink flow path 12b of the inkjet printer head 1 according to the required data. Then, the positive drive voltage V is applied to the metal electrodes 13e and 13f, and the metal electrodes 13d and 13g are grounded. As shown in FIG. 10, a driving electric field in the direction of arrow 14b is generated on the side wall 11b, and a driving electric field in the direction of arrow 14c is generated on the side wall 11c. Then, since the driving electric field directions 14b and 14c are orthogonal to the polarization direction 4, the side walls 11b and 11c are rapidly deformed inward in the ink flow path 12b due to the piezoelectric thickness sliding effect. Due to this deformation, the volume of the ink flow path 12b is decreased, the ink pressure is rapidly increased, a pressure wave is generated, and an ink droplet is ejected from the nozzle 32 (FIG. 7) communicating with the ink flow path 12b.

When the application of the driving voltage V is stopped,
Since the side walls 11b and 11c gradually return to the positions before the deformation (see FIG. 9), the ink pressure in the ink flow path 12b gradually decreases. Then, ink is supplied from the ink supply port 21 (FIG. 7) through the manifold 22 (FIG. 7) into the ink flow path 12b.

[0014]

However, as described above, as the shape of the nozzle 32 in the conventional ink ejecting apparatus, it is generally preferable that the ink flow path 12 side has a taper having a hole diameter larger than the ink ejecting side. Channel 12
When the side has a taper that is smaller than the ink jetting side, or when the hole diameters of the ink flow path 12 side and the ink jetting side are the same, that is, the amount of ink droplets and the jetting speed are higher than those of a straight nozzle hole without a taper. Is believed to be stable. However, the taper angle θ, which is the rate at which the nozzle diameter decreases from the cross section of the nozzle 32 on the ink flow path 12 side to the cross section of the ink ejection side, has not been clearly determined. Therefore, if the taper angle θ is extremely large or small, the flying speed of the ink droplet may be different, and the printing speed may be different for each inkjet printer head 1. Therefore, the print quality was poor and the mass productivity of the inkjet printer head 1 was not excellent.

If there is a nozzle 32 having a large taper angle in one inkjet printer head 1 as well, the flying speed of the ink droplets may vary from nozzle to nozzle 32, so the printing quality in the inkjet printer head 1 may be different. Is significantly reduced,
There was a problem that it did not function as a head. Therefore, the number of defective products produced during mass production of the inkjet printer head 1 was large.

The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to provide an ink ejecting apparatus having good printing quality and excellent mass productivity.

[0017]

In order to achieve this object, according to the present invention, the wall of the ink flow path is deformed by the deformation of the piezoelectric ceramic to change the volume thereof, and the ink filled in the ink flow path is changed. In an ink ejecting apparatus that ejects from a nozzle arranged corresponding to an ink flow path, a taper angle θ, which is a ratio of the nozzle diameter decreasing and changing from the ink flow path side cross section of the nozzle to the ink injection side cross section, 5
It is in the range between ° and 30 °.

[0018]

In the present invention having the above structure, the wall of the ink flow path is deformed by the deformation of the piezoelectric ceramics to change the volume thereof, and the ink filled in the ink flow path is made to correspond to the ink flow path. In the ink ejecting apparatus that ejects from the arranged nozzles, the rate at which the nozzle diameter decreases from the ink flow passage side cross section of the nozzle to the ink ejection side cross section, that is, the taper angle θ is between 5 ° and 30 ° Since the area is set, the flight speed of the ink droplet is increased.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The basic structure and operation of an embodiment embodying the present invention is the same as the structure and operation of the second example of the prior art, and the description thereof will be omitted.

First, the nozzle 32 for the ink flow path 12
The center position of will be described.

The center position of the nozzle 32 with respect to the ink flow path 12 was changed, and the flying speed of the ink droplet at that time was measured. The flight speed of the ink droplets is determined by changing the light emission interval of the strobes using a strobe that emits light at regular intervals and measuring the issuance interval when the ink drops are synchronized with the strobe, and the flight speed of the ink drops. I asked. FIG. 2 shows the relationship between the flying speed of the ink droplet thus measured and the center position of the nozzle 32 with respect to the ink flow path 12.

In FIG. 2, the diameter D _{1 of the} nozzle 32 is 3
A case of 0 μm and a case of the diameter D ₂ of 45 μm are shown. At this time, the length L between the side walls 11, which is the width of the ink flow path 12, is 90 μm, and the height is 300 μm. The height of the center position of the nozzle 32 is set to 300 μm, and the center position of the nozzle 32 is set to the side wall 11 of the ink flow path 12.
From the one side wall 11 to the other side wall 11 in the direction in which the side wall 11 and the side wall 11 face each other is 1/12 of the side wall length 7.5.
It was changed by μm.

As is apparent from FIG. 2, when the diameter D _{1 of the} nozzle 32 is 30 μm, 15.0 μm to 75.0 μm.
When the center position of the nozzle 32 is located within μm, the flight speed of the ink droplet is fast and relatively stable. When the diameter D _{2 of the} nozzle 32 is 45 μm, 2
When the center position of the nozzle 32 is located within the range of 2.5 μm to 67.5 μm, the flight speed of the ink droplet is fast and relatively stable.

As described above, the side wall 1 is closer to the center of the nozzle 32 than the center between the side walls 11 with respect to the facing direction.
1 1/2 of the length L to 1 / the diameter D of the nozzle 32
When it exists within the distance other than the length of 2, the flying speed of the ink droplet is high and it is relatively stable.

Although not shown, the nozzle 32 is used to measure the flying speed of the ink droplet when the center position of the nozzle 32 is changed from the one side wall 11 to the other side wall 7.5 by 7.5 μm in the opposite direction. When the height of the central position of 32 was changed, the same tendency result was obtained. Therefore,
The center position of the nozzle 32 with respect to the ink flow path 12 is not affected in the height direction of the ink flow path 12.

Furthermore, by changing the diameter D of the nozzle 32, although the center position of the nozzle 32 as described above was measured jet speeds of ink droplets while varying the opposite direction and the height direction, the diameter D ₁ Is 30 μm and the diameter D ₂ is 45 μ
The result of the tendency similar to the case of m was obtained.

That is, with respect to the direction in which the center position of the nozzle 32 faces the side wall 11 from the center between the side walls 11.
1/2 of the length L to 1/2 of the diameter D of the nozzle 32
Area 90 excluding the length of (dotted line area shown in FIG. 1)
When it exists in, the flying speed of the ink droplet is fast and it is relatively stable.

The amount of deformation of the side wall 11 having the above-mentioned size is 3
The amount of deformation of the side wall 11 is very small with respect to the size of the nozzle 32. Therefore, even if the deformation amount of the side wall 11 changes, the size is negligible with respect to the size of the nozzle 32. Therefore, even if the deformation amount of the side wall 11 changes, the same tendency as in FIG.

Therefore, if the nozzle 32 is formed on the nozzle plate 31 so that the center position of the nozzle 31 is located in the area, the flying speed of the ink droplet is high,
Since it is relatively stable, the central position accuracy of the nozzle 32 does not need to be high when the nozzle 32 is formed. Further, if the nozzle plate 31 is adhered so that the center position of the nozzle 31 is located within the area, the flying speed of the ink droplet is fast and relatively stable, so that the center position of the nozzle 32 with respect to the ink flow path 12 is relatively stable. The alignment accuracy does not have to be high. In this way, the nozzle 32 is provided for each ink flow path 12.
Even if the center positions of the ink jet printers 1 are different, as long as they are arranged in the above area, the number of defective products at the time of manufacturing the inkjet printer head 1 is reduced. Therefore, the print quality and mass productivity are excellent.

Next, the shape of the nozzle 32 will be described. As for the nozzle shape, it is generally the case that the ink flow path side has a taper with a hole diameter larger than the ink ejection side, the ink flow path side has a taper with a hole diameter smaller than the ink ejection side, or the ink flow path side and the ink ejection side. When the hole diameter of and is the same, that is, rather than a straight nozzle hole without taper,
It is believed that the amount of ink drops and the ejection speed can be stably obtained.

Therefore, the flying speed of the ink droplet was measured by changing the ratio of the areas of the ink jet side cross-sectional area of the nozzle 32 and the ink flow path 12 side cross-sectional area. The measuring method is the method described above. The measurement result is shown in FIG.

FIG. 3 shows a case where the diameter of the nozzle 32 on the ink ejection side is fixed to 30 μm and the diameter of the nozzle 32 on the ink flow path 12 side is changed. At this time, the central position of the nozzle 32 is arranged substantially in the center with respect to the ink flow path 12. The width of the ink flow path 12 is 90 μm and the height is 300 μm.

As is apparent from FIG. 3, when the ratio of the cross-sectional area of the ink jet side of the nozzle 32 to the cross-sectional area of the ink flow path 12 is between 1: 2 and 1:50, the ink flying speed is relatively fast and stable. ing. Also, more preferably 1 to 2 to 1
The range is 15 pairs.

The same result was obtained when the center position of the nozzle 32 was moved within the above-mentioned region and the same measurement was carried out.

Further, the same measurement was carried out by changing the diameter of the nozzle 32 on the ink ejection side, and the same tendency result was obtained.

As described above, the ratio of the cross-sectional area of the ink jet side of the nozzle 32 to the cross-sectional area of the ink flow path 12 is 1: 2 to 1: 5.
Between 0, the flight speed of the ink droplet is stable and fast, so that the degree of freedom in designing the nozzle 32 is expanded. Even if the nozzle 32 has a different shape due to a manufacturing error, if the ratio of the cross-sectional area of the ink ejection side to the cross-sectional area of the ink flow path 12 is between 1: 2 and 1:50, the ink ejected from each nozzle Since the flight speed of the droplets is stable, the number of defective products at the time of manufacturing the ink jet flying inkjet printer head 1 is reduced. Therefore, the print quality and mass productivity are excellent.

Next, the taper angle θ of the nozzle 32 shown in FIG. 4A was changed and the flight speed of the ink droplet was measured.
The measuring method is the method described above. Figure 4 shows the measurement results.
It shows in (b).

FIG. 4B shows a case where the diameter of the nozzle 32 on the ink ejection side is fixed to 30 μm and the taper angle θ of the nozzle 32 is changed. However, the measurement was performed in the range where the ratio of the cross-sectional area of the nozzle 32 on the ink ejection side to the cross-sectional area of the ink flow path 12 was 1: 1.5 to 1:15. At this time, the center position of the nozzle 32 is located at the ink flow path 12
It is located almost in the center. The width of the ink flow path 12 is 90 μm and the height is 300 μm.

As is clear from FIG. 4B, the nozzle 3
When the taper angle θ of 2 is 5 ° to 30 °, the flying speed of the ink droplet is relatively fast and stable. Further, more preferably, the taper angle θ is in the range of 5 ° to 20 °.

Further, the same measurement was carried out by changing the diameter of the nozzle 32 on the ink jet side, and the same result was obtained.

Further, the center position of the nozzle 32 was moved within the above-mentioned region and the same measurement was carried out, but the same result was obtained.

Thus, the taper angle θ of the nozzle 32 is 5
Between 0 ° and 30 °, the flight speed of the ink droplet is stable and fast, so that the degree of freedom in designing the nozzle 32 is expanded.
Even if the shape of the nozzle 32 is different due to manufacturing error, the flight speed of ink droplets ejected from each nozzle is stable if the taper angle θ of the nozzle 32 is between 5 ° and 30 °. Flying Ink Drops The number of defective products at the time of manufacturing the inkjet printer head 1 is reduced. Therefore, the print quality and mass productivity are excellent.

Here, the maximum projected area of the solid content in the ink component and the area of the minimum cross section of the nozzle 32 will be described. Ink having different solid contents contained in various ink components was prepared, and the flight speed of the ink droplet was measured. The result is shown in FIG.

FIG. 5 shows the case where the diameter of the nozzle 32 on the ink ejection side is fixed to 30 μm and the size of the solid content contained in the ink component is changed. However, the ink jet side cross-sectional area of the nozzle 32 and the ink flow path 12
The measurement was performed on the nozzle 32 having a ratio of the side cross-sectional area of 1: 1.5 to 1:15 and a taper angle of 5 ° to 20 °. At this time, the central position of the nozzle 32 is arranged substantially in the center with respect to the ink flow path 12. The width of the ink flow path 12 is 90 μm, and the height is 300 μm.
Is.

As is clear from FIG. 5, when the cross-sectional area of the nozzle 32 on the ink ejection side is 4 times or more the maximum projected area of the solid content in the ink component, the ink flying speed is fast and stable. More preferably, it is 16 times or more. This is because the solid content in the ink component comes into contact with the nozzle 32 at the time of ejecting the ink droplet, and thus resistance is generated in the ink droplet, and the ink ejection cross-sectional area of the nozzle 32 is the maximum projected area of the solid content in the ink component. If it is 4 times or less, it is considered that the flight speed of the ink droplet is reduced.

Further, the same measurement was carried out by moving the center position of the nozzle 32 within the above-mentioned area and performing the same measurement, but the same result was obtained.

Further, the same measurement was carried out by changing the diameter of the nozzle 32 on the ink ejection side, but the same tendency result was obtained.

The smallest cross section of the nozzle 32 is the nozzle 3.
Although the area is 2 on the ink ejection side, the tendency is the same as in FIG. 5 regardless of which portion of the nozzle 32 has the smallest cross section.

As described above, when the area of the minimum cross-sectional portion of the nozzle 32 is four times or more of the maximum projected area of the solid content in the ink component, the flying speed of the ink droplet is stable, so that one ink jet printer is used. The head 1 can eject a plurality of types of ink. Further, the nozzles 32 having the same shape can be used for the plurality of inkjet printer heads 1 corresponding to the plurality of inks used for color printing, which is excellent in productivity. Further, if the area of the minimum cross-sectional portion of the nozzle 32 is 4 times or more of the maximum projected area of the solid content in the ink component, the flight speed of the ink droplet is stable and fast, so that the design freedom of the nozzle 32 is widened. .
Even if the shape of the nozzle 32 is different due to manufacturing error, if the area of the minimum cross-sectional portion of the nozzle 32 is four times or more the maximum projected area of the solid content in the ink component, the ink droplets ejected from each nozzle Since the flying speed is stable, the number of defective products during the production of the ink jet flying inkjet printer head 1 is reduced. Therefore, the print quality and mass productivity are excellent.

The flight speed of the ink droplet described above was measured with the same structure and operation as the first example of the prior art. The results were similar to those in FIGS. 2, 3, 4 (b) and 5.

Further, the same measurement was carried out by changing the width and height of the ink flow path 12, but the same tendency results as in FIGS. 2, 3, 4 (b) and 5 were obtained.

Although the nozzle 32 has a circular shape, it may have a rectangular shape or an elliptical shape as shown in FIG. 2, FIG. 3, FIG. 4 (b) and FIG.
The result of the same tendency was obtained.

[0053]

As is apparent from the above description, according to the ink ejecting apparatus of the present invention, the nozzle diameter decreases and changes from the ink flow passage side cross section of the nozzle to the ink ejection side cross section. Since the taper angle θ is in the range of 5 ° to 30 °, the flight speed of the ink droplets ejected from the nozzles is uniform in all nozzles, and the printing quality is excellent. In addition, special adjustment for each nozzle is not required, which is advantageous in mass productivity.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a region in which a nozzle center position is arranged in an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a relationship between a nozzle center position and an ink flying speed in the embodiment.

FIG. 3 is an explanatory diagram showing a relationship between a ratio of a cross-sectional area of an ink ejection side of a nozzle to a cross-sectional area of an ink flow path side and an ink flying speed in the embodiment.

FIG. 4A is an explanatory diagram showing a taper angle of a nozzle in the embodiment. FIG. 6B is an explanatory diagram showing the relationship between the nozzle taper angle and the ink flying speed in the above embodiment.

FIG. 5 is an explanatory diagram showing the relationship between the ratio of the cross-sectional area of the nozzle on the ink ejection side to the maximum projected area of the solid content in the ink component, and the ink flying speed in the embodiment.

FIG. 6 is a cross-sectional view showing a configuration of an ink ejecting apparatus of a first conventional example of the present invention.

FIG. 7 is a perspective view showing a configuration of an inkjet printer head of a second conventional example of the present invention.

FIG. 8 is an explanatory diagram showing a control unit of the inkjet printer head of the second conventional example.

FIG. 9 is a cross-sectional view showing a configuration of the inkjet printer head of the second conventional example.

FIG. 10 is an explanatory diagram showing an operating state of the inkjet printer head of the second conventional example.

[Explanation of symbols]

 2 Piezoelectric ceramic plate 12 Ink channel 11 Side wall 32 Nozzle 31 Nozzle plate 90 Nozzle center position area

Claims (2)

[Claims] 1. A wall of an ink flow path is deformed by deformation of piezoelectric ceramics to change its volume, and ink filled in the ink flow path is ejected from nozzles arranged corresponding to the ink flow path. In the ink ejecting apparatus, a taper angle θ that is a rate at which the nozzle diameter decreases from the ink flow passage side cross section of the nozzle to the ink ejection side cross section
Is in the range between 5 ° and 30 °. 2. The center position of the nozzle is ½ of the length between the wall of the ink flow path and the center of the opposing wall with respect to the wall and the distance between both walls in the direction in which the wall faces the opposing wall. 1 / the length of the nozzle in the opposite direction from the length
The ink ejecting apparatus according to claim 1, wherein the ink ejecting apparatus is in a region having a length excluding the length of 2.