JPH07132591A - Printing head - Google Patents

Abstract

PURPOSE:To obtain a printing head good in energe efficiency by reducing the electrostatic capacity in the side wall of an inclined part by eliminating a part of the side wall part of the inclined part. CONSTITUTION:A drive electric field is generated in a side wall 11a in the direction shown by an arrow 14a and a drive electric field is generated in a side wall 11b in the direction shown by an arrow 14b. Whereupon, since the directions 14a, 14b of the drive electric fields cross a polarizing direction 61 at a right angle, the side walls 11a, 11b are rapidly deformed in the outside direction of an ink chamber 12a by piezoelectric thickness sliding effect. The volume of the ink chamber 12a is increased by this deformation to generate negative pressure and ink is supplied to the channel groove part 17 of the ink chamber 12a from an ink supply source through an ink introducing port 21, a manifold 22 and the R-shaped groove part 19 of the ink chamber 12a. When the application of drive voltage V is stopped, the side walls 11a, 11b are returned to the positions before deformation and, therefore, the pressure of the ink in the channel groove part 17 of the ink chamber 12a is rapidly increased and a pressure wave is generated to eject an ink droplet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a print head for ejecting ink used in an ink jet printer or the like.

[0002]

2. Description of the Related Art Conventionally, a so-called bubble jet type print head using a heating element which is an electro-thermal conversion element as an on-demand type print head used in an ink jet printer or a piezoelectric element which is an electro-mechanical conversion element. A piezo type print head using an element has been put into practical use. A print head that uses a piezoelectric element does not generate heat compared to a print head that uses a heating element, so there are less restrictions on the liquid that is ejected, and the print head has excellent durability. have. On the other hand, there is a problem that it is inferior in terms of the degree of integration and miniaturization as compared with a print head using a heating element to which semiconductor manufacturing technology can be applied. However, in recent years, JP-A-2-15035
As disclosed in Japanese Patent Publication No. 5, the shear mode (thickness sliding mode) among the deformation modes of the piezoelectric material is used to generate pressure, so that it is higher than the conventional print head using a piezoelectric element. A print head configuration that has achieved integration and miniaturization has been proposed, and a schematic configuration thereof will be described below with reference to the drawings.

As shown in FIG. 8, 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 is made of a lead zirconate titanate (PZT) -based ceramic material having ferroelectricity. The piezoelectric ceramic plate 2 is polarized in the direction of arrow 5. Next, in the piezoelectric ceramic plate 2, as shown in FIG. 9, the groove 8 is cut by the rotation of the diamond cutter blade 30. During this cutting, the cutting direction of the diamond cutter blade 30 is 30
A, 30B, 30C are changed, the channel groove portion 17,
The groove 8 including the R-shaped groove portion 19 and the shallow groove portion 16 is formed.

The channel groove portion 17 is formed by the cutting direction 30A of the diamond cutter blade 30. Subsequently, the cutting direction is changed from 30A to 30B, and the depth of cutting is changed. At this time, the R-shaped groove portion 19 which is a curved surface having a radius of curvature of the diamond cutter blade 30 is formed. And the cutting direction is from 30B to 30
The shallow groove portion 16 is formed by changing to C.

As shown in FIG. 8, a plurality of grooves 8 are formed in the piezoelectric ceramic plate 2 cut in this way. The grooves 8 are of the same depth and are parallel. The shallow groove portion 16 is formed near the one end surface 15 of the piezoelectric ceramic plate 2. The dimensions of the channel groove portion 17 and the shallow groove portion 16 are determined by the thickness and the set depth of cut of the diamond cutter blade 30 to be used, and the pitch and the number of the grooves 8 control the feed pitch of the processing table and the number of times of groove processing when the grooves 8 are processed. The curvature of the curved surface of the R-shaped groove portion 19 is determined by the diameter of the diamond cutter blade 30. This method is used in the semiconductor manufacturing process. Since a very thin diamond cutter blade 30 having a thickness of about 0.02 mm is commercially available, it is a technology that can sufficiently support the high integration required for the print head. It can be said that there is. Further, the side wall 11 which is the side surface of the groove 8 is polarized in the direction of arrow 5 by the polarization treatment.

Further, the channel groove portion 17 and the R-shaped groove portion 1
9 and the inner surface of the shallow groove 16 have metal electrodes 13, 1
8 and 9 are formed by the vapor deposition method. As shown in FIG. 10, when the metal electrodes 13, 18 and 9 are formed, the piezoelectric ceramic plate 2 is inclined with respect to the direction of vapor emission from a vapor deposition source (not shown). When the vapor is discharged, the shadow effect of the side wall 11 causes the inner surface of the shallow groove portion 16 to reach the upper half of the side surface of the channel groove portion 17, the side surface of the R-shaped groove portion 19 to the half position of the side surface of the channel groove portion 17. Metal electrodes 13, 18, 9, 10 are formed on the upper surface of the side wall 11. Next, the piezoelectric ceramic plate 2 is
It is rotated by 0 degrees and the metal electrodes 13, 18, 9,
10 is formed. After that, the unnecessary metal electrode 10 formed on the upper surface of the side wall 11 is removed by lapping or the like. Thus, the metal electrodes 13 formed on both side surfaces of the channel groove portion 17 are electrically connected by the metal electrode 9 formed on the inner surface of the shallow groove portion 16 via the metal electrode 18 formed on the side surface of the R-shaped groove portion 19. Has been done.

Next, the cover plate 3 shown in FIG. 8 is made of a ceramic material, a resin material or the like.
The cover plate 3 has an ink inlet 21 and a manifold 22 formed by grinding or cutting. Then, the surface of the piezoelectric ceramic plate 2 on the groove 8 side and the manifold 22 of the cover plate 3
Adhesive 4 such as epoxy-based with the processed side (see Fig. 12)
Glued by. Therefore, in the ink jet printer head 1, the upper surfaces of the grooves 8 are covered, and a plurality of ink chambers 12 (FIG. 12) are formed which are laterally spaced from each other. Then, the ink is filled in all the ink chambers 12.

A nozzle plate 31 having nozzles 32 provided at positions corresponding to the positions of the ink chambers 12 is adhered to the end faces of the piezoelectric ceramic plate 2 and the cover plate 3. The nozzle plate 31 is made 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 chamber 12. Pattern 4 of the conductive layer
2 and the metal electrode 9 on the bottom surface of the shallow groove portion 16 are connected by a conductive wire 43 by known wire bonding or the like.

Next, the configuration of the control unit will be described with reference to FIG. 11 showing a block diagram of the control unit. The conductive layer patterns 42 formed on the substrate 41 are individually formed on the LSI chip 51.
It is connected to the. The clock line 52, the data line 53, the voltage line 54, and the ground line 55 are also L
It is connected to the SI chip 51. LSI chip 51
Determines which nozzle 32 should eject an ink droplet, according to the data appearing on the data line 53, based on the continuous clock pulses supplied from the clock line 52. Then, the LSI chip 51 applies the voltage V of the voltage line 54 to the pattern 42 of the conductive layer electrically connected to the metal electrode 13 of the ink chamber 12 to be driven, and the metal electrode 13 other than the ink chamber 12 to be driven. A voltage of 0 V on the ground line 55 is applied to the pattern 42 of the conductive layer connected to.

Next, the operation of the ink jet printer head 1 will be described with reference to FIGS.

The LSI chip 51 causes the ink chamber 12b of the ink jet printer head 1 to follow the required data.
It is determined that the ink is ejected from. Then, the positive drive voltage V is applied to the metal electrodes 13e and 13f through the conductive layer pattern 42 corresponding to the ink chamber 12b, the metal electrode 9 and the metal electrode 18, and the metal electrodes 13d and 13g.
And are grounded. As shown in FIG. 13, 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 5, the side walls 11b and 11c are rapidly deformed inward in the ink chamber 12b due to the piezoelectric thickness slip effect. Due to this deformation, the volume of the ink chamber 12b decreases, the ink pressure rapidly increases, and a pressure wave is generated,
Ink droplets are ejected from the nozzle 32 (FIG. 8) communicating with the ink chamber 12b.

When the application of the drive voltage V is stopped,
Since the side walls 11b and 11c return to the positions before deformation (see FIG. 12), the ink pressure in the ink chamber 12b decreases. Then, from the ink inlet 21 (FIG. 8) to the manifold 22.
Ink is supplied into the ink flow path 12b through (FIG. 8).

[0015]

In the ink jet printer head 1 described above, when a voltage is applied to deform the side wall 11 and eject ink from the inside of the ink chamber 12, the side wall 11 portion which is the side surface of the channel groove portion 17 is formed. Is deformed, and the portion of the side wall 11 on the side surface of the R-shaped groove portion 19 is hardly deformed. That is, the pressure generation that contributes to the injection is performed on the side wall 11 of the channel groove portion 17, and the side wall 11 of the R-shaped groove portion 19 and the shallow groove portion 16 does not contribute to the pressure generation. That is, the ink filled in the channel groove portion 17 receives a pressure, and the ink droplet of a predetermined volume is ejected from the nozzle 32 at a predetermined ejection speed.

Here, electrically, the piezoelectric material forming the side wall 11 acts as a kind of capacitor. Therefore, even the R-shaped groove portion 19 and the shallow groove portion 16 which do not substantially contribute to the pressure generation are made of the piezoelectric material, so that the capacitance as the capacitor is increased and the pressure generation against the electric input energy is generated. There was a problem that the efficiency of the energy consumed by the car was low.

The present invention has been made to solve the above-mentioned problems, and an object thereof is to provide a print head having high energy efficiency.

[0018]

In order to achieve this object, in claim 1 of the present invention, an inclined portion is formed at one end,
An ink chamber filled with ink; and a side wall that forms a part of the ink chamber, at least a portion of which is a piezoelectric portion, and an electrode for generating an electric field in the piezoelectric portion of the side wall, In a print head which deforms the side wall by generating an electric field from an electrode and ejects ink from the ink chamber, a part of the side wall portion in the inclined portion is deleted.

According to a second aspect, the deleted portion of the side wall is
It is characterized in that it also serves as a manifold for supplying ink to the plurality of ink chambers.

[0020]

In the print head of the present invention having the above structure,
By deleting a part of the side wall portion of the inclined portion, the capacitance on the side wall of the inclined portion is reduced.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. For the sake of convenience, the same parts and equivalent parts as in the conventional example are designated by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIG. 1, the ink jet printer head 20 of this embodiment comprises an actuator 24, a cover plate 3, a nozzle plate 31, and a substrate 41 (see FIG. 8).

Now, a method of manufacturing the actuator 24 will be described.

First, as in the case of the conventional example shown in FIG.
The piezoelectric ceramic material substrate 33 polarized in the 1 (FIG. 1) direction is removed by the diamond cutter blade 30.
A plurality of grooves 8 are formed. The groove 8 includes a channel groove portion 17, an R-shaped groove portion 19, and a shallow groove portion 16.

The channel groove portion 17 is formed in the piezoelectric ceramic material substrate 33 by the cutting direction 30A of the diamond cutter blade 30. Then the cutting direction is 30A
To 30B, the cutting depth is changed.
At this time, the R-shaped groove portion 19 which is a curved surface having a radius of curvature of the diamond cutter blade 30 is formed. Then, the cutting direction is changed from 30B to 30C, and the shallow groove portion 1
6 is formed.

In this way, a plurality of grooves 8 are formed.
The dimensions of the channel groove portion 17 and the shallow groove portion 16 are determined by the thickness and the set depth of cut of the diamond cutter blade 30 to be used, and the pitch and the number of the grooves 8 control the feed pitch of the processing table and the number of times of groove processing when the grooves 8 are processed The curvature of the curved surface of the R-shaped groove portion 19 is determined by the diameter of the diamond cutter blade 30.

Further, as shown in FIGS. 1 and 2, metal electrodes 13, 18 and 9 are formed on the side surfaces of the channel groove portion 17 and the R-shaped groove portion 19 and on the inner surface of the shallow groove portion 16 by the vapor deposition method as in the prior art. .

Next, as shown in FIGS. 1 and 3, the side wall 11 of the R-shaped groove portion 19 is deeply cut by cutting with a diamond cutter blade in a direction orthogonal to the groove 8, laser processing, ultrasonic processing, or the like. Saga channel groove 17
Side wall removing portions 34 that are shallower than half of the side surfaces of the
The actuator 24 is manufactured.

Next, as shown in FIG. 1, the surface of the actuator 24 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 together with an adhesive such as epoxy. Therefore, the inkjet printer head 20
, The upper surface of the groove 8 is covered to form a plurality of ink chambers 12 (FIG. 4) which are laterally spaced from each other. At this time, as shown in FIG. 3, since the side wall removing portions 34 are also formed on the both outer side walls 11, the side wall removing portions 34 of the outer both side walls 11 are closed by a member (not shown). It is also possible not to form the side wall removing portion 34 on the both outer side walls 11.

A nozzle plate 31 having nozzles 32 provided at positions corresponding to the positions of the ink chambers 12 is adhered to the end faces of the piezoelectric ceramic plate 2 and the cover plate 3. The substrate 41 (see FIG. 8) is provided on the surface of the piezoelectric ceramic plate 2 opposite to the processed side of the groove 8.
However, they are adhered by an epoxy adhesive or the like. A conductive layer pattern 42 (see FIG. 8) is formed on the substrate 41 at a position corresponding to the position of each ink chamber 12. The conductive layer pattern 42 and the metal electrode 9 on the bottom surface of the shallow groove portion 16 are connected to each other by a well-known wire bonding or the like to form a conductive wire 43.
(See FIG. 8).

Next, the operation of the ink jet printer head 20 will be described with reference to FIGS. 1, 4 and 5.

When ink is ejected from the ink chamber 12a of the ink jet printer head 20 in accordance with the required data, the conductive layer pattern 42 (FIG. 8) corresponding to the ink chamber 12a, the metal electrode 9 and the metal electrode 18 are interposed. A positive drive voltage V is applied to the metal electrodes 13b and 13c, and the metal electrodes 13a and 13d are grounded. Then, the driving electric field is generated only in the side wall 11 which is the side surface of the channel groove portion 17 formed of the piezoelectric material. As shown in FIG. 5, a driving electric field in the direction of arrow 14a is generated on the side wall 11a, and a driving electric field in the direction of arrow 14b is generated on the side wall 11b. Then, the driving electric field directions 14a and 1
4b is orthogonal to the polarization direction 61, the side wall 11a
And 11b, due to the piezoelectric thickness sliding effect, in this case,
It is rapidly deformed in the outer direction of the ink chamber 12a. Due to this deformation, the volume of the ink chamber 12a is increased, and a negative pressure is generated. Supplied.

When the application of the drive voltage V is stopped after a predetermined time, the side walls 11a and 11b return to the positions before the deformation (see FIG. 4), so that the ink pressure in the channel groove portion 17 of the ink chamber 12a is rapidly increased. , A pressure wave is generated, and an ink droplet is ejected from the nozzle 32 communicating with the ink chamber 12a.

Here, considering the driving of the ink jet printer head 20 as described above, in order to eject ink droplets, an input signal to the side wall 11 formed of the piezoelectric material which is the side surface of the channel groove portion 17 is accompanied. Therefore, it is necessary to apply a predetermined voltage from the driver. Electrically side wall 1
The piezoelectric material constituting 1 will act as a kind of capacitor. Here, the capacitance (C) as a capacitor is the width dimension (t) of the side wall 11 of the piezoelectric material, the electrode area (s) of the metal electrode 13 formed on the side surface, and the relative permittivity (ε ₁₁ ) of the piezoelectric material. ^T ), C = ε ₁₁ ^T · ε ₀ ·
It becomes s / t (here, ε ₀ : relative dielectric constant of vacuum).
In the ink jet head 20 of the present embodiment, the side wall 11 of the portion corresponding to the R-shaped groove portion 19 of the side wall 11 is partially removed.
As a result, the electrode area s becomes smaller and the capacitance C becomes smaller than in the conventional case.

It is known that when a capacitive load is driven as in the print head having the above-mentioned configuration, the input power from the driver is proportional to CV ² (V: voltage). Therefore, when driven with the same drive voltage, the capacitance C
The smaller is, the less input power is required. Therefore, as described above, the inkjet head 20 of the present embodiment has a capacitance C greater than that of the conventional inkjet head 1.
Therefore, the inkjet head 20 of the present embodiment may require less input power to obtain a predetermined ink ejection speed than the conventional inkjet head 1.

Therefore, the characteristics of the conventional inkjet printer head 1 and the inkjet printer head 20 of the present embodiment were compared. However, the polarization direction of the side wall 11 of the inkjet printer head 1 is set to the arrow 61 direction.

In this embodiment, the relative dielectric constant (ε ₁₁ ^T ) 2000
Inkjet printer heads 1 and 20 were manufactured using the piezoelectric ceramic material of. The groove 8 has a depth of 0.5 mm, a width of 0.1 mm, and a pitch of 0.2 mm. The channel groove portion 17 and the R-shaped groove portion 1 shown in FIGS.
9, the shallow groove portion 16 is set to 9, 5, and 5 mm, respectively, and the side wall removing portion 34 shown in FIG. 1 has a depth of 0.2 mm and a width of 3 mm.
And Further, the metal electrode 13 is 0.2 from the upper end of the side wall 11.
It was formed to a depth of 5 mm. Therefore, the side wall 11 of the piezoelectric material
The width dimension (t) of is necessarily 0.1 mm.

Each inkjet printer head 1,
As a comparative experiment of 20 droplet ejection characteristics, a droplet ejection experiment was performed using a commercially available ink as the ejection liquid and a rectangular wave with a driving voltage of 50V. As a result of performing the data sampling of the ejection velocity and the ink droplet volume of 100 ejected ink droplets, the conventional inkjet printer head 1
In the case of, the injection speed is 6.24 ± 0.35 m / sec,
The ink droplet volume is 50 ± 3 pl, and in the case of the inkjet printer head 20 which is one embodiment of the present invention, the ejection speed is 6.20 ± 0.45 m / sec and the ink droplet volume is 49.
It became ± 4 pl.

Comparing the ink jet printer head 20 according to one embodiment of the present invention with the ink jet printer head 1 according to the related art, when the driving voltage is the same, the ejection speed and the ink droplet volume show almost the same numerical values. This is because pressure generation for ink droplet ejection is performed only in the channel groove portion 17 shown in FIGS. 1 and 8, and the R-shaped groove portion 19 and the shallow groove portion 1 are formed.
This is because 6 does not contribute. Therefore, the R-shaped groove 1
Even if the side wall 11 of 9 is removed, the droplet ejection characteristics are not affected.

Here, as a result of measuring the capacitance of the side wall 11 of the conventional ink jet printer head 1 having the above-mentioned dimensions using an LCR meter under the conditions of a measurement voltage of 0.5 V and a measurement frequency of 1 kHz, It became 737 nF. On the other hand, the capacitance of the side wall 11 of the inkjet printer head 20 according to the embodiment of the present invention is 0.412.
It was nF. Therefore, since the ink jet characteristics of the ink jet printer heads 1 and 20 are similar to each other as described above, the ink jet head 20 of the present embodiment has a capacitance higher than that of the conventional ink jet head 1 in terms of capacitance. The input energy can be reduced by about 44%.

Although the cover plate 3 is provided with the manifold 22 in this embodiment, the cover plate 3 is not provided with the manifold as shown in FIG. Ink may be supplied.

Further, in this embodiment, the side wall removing portion 34 is one groove, but the side wall removing portion 35 may be constituted by a plurality of grooves as shown in FIG.

[0043]

As is apparent from the above description, according to the print head of the present invention, a part of the side wall portion of the inclined portion in the ink chamber is deleted, so that the inclination is increased. The sidewall has a small capacitance on the side wall. For this reason, the capacitance of the entire print head is lower than in the past, and the energy efficiency is better than in the past.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an inkjet printer head according to an embodiment of the present invention.

FIG. 2 is a perspective view showing an actuator in the manufacturing process of the embodiment.

FIG. 3 is a perspective view showing the actuator of the embodiment.

FIG. 4 is a cross-sectional view of the ink jet printer head of the above embodiment.

FIG. 5 is an explanatory diagram showing an operating state of the inkjet printer head of the embodiment.

FIG. 6 is an explanatory diagram showing an inkjet printer head of another example of the present invention.

FIG. 7 is an explanatory diagram showing an inkjet printer head of still another example of the present invention.

FIG. 8 is a perspective view showing a conventional inkjet printer head.

FIG. 9 is an explanatory diagram showing a conventional groove processing.

FIG. 10 is an explanatory view showing an electrode forming process of a conventional piezoelectric ceramic plate.

FIG. 11 is an explanatory diagram showing a control unit of a conventional inkjet printer head.

FIG. 12 is a cross-sectional view of a conventional inkjet printer head.

FIG. 13 is an explanatory diagram showing an operating state of a conventional inkjet printer head.

[Explanation of symbols]

 3 Cover Plate 8 Groove 9 Metal Electrode 11 Sidewall 12 Ink Chamber 13 Metal Electrode 16 Shallow Groove 17 Channel Groove 18 Metal Electrode 19 R-Shaped Groove 24 Actuator 31 Nozzle Plate 32 Nozzle 33 Piezoelectric Ceramic Material Substrate 34 Sidewall Deleted Section 35 Sidewall Removal Section

Claims (2)

[Claims] 1. An ink chamber in which an inclined portion is formed at one end and which is filled with ink, and at least a part of which is a piezoelectric portion,
Ink having a side wall forming a part of the ink chamber and an electrode for generating an electric field in the piezoelectric portion of the side wall, the side wall being deformed by the generation of the electric field from the electrode, In a print head for ejecting ink, a part of the side wall of the inclined portion is deleted. 2. The print head according to claim 1, wherein the deletion portion of the side wall also serves as a manifold for supplying ink to the plurality of ink chambers.