JPH09226114A - Inkjet printer head - Google Patents

Abstract

An object of the present invention is to provide a compact inkjet printer head suitable for printing high resolution full color graphics. The present invention relates to an inkjet printer head that uses a piezoelectric element that is deformed by an electric signal and that can increase the nozzle density. It is composed of a piezoelectric element which is deformed by an electric signal and a pressure chamber having a surface made of a vibration plate in contact with the piezoelectric element. Then, ink is supplied from the reservoir to the pressure chamber via the ink supply path, and the pressure chamber is arranged in the horizontal direction with respect to the printing surface. The ink supply path is formed in the diaphragm, and the reservoir is formed on the back surface of the diaphragm. Further, the ink tank ports are arranged obliquely with respect to the nozzle row arrangement direction, and the ink tanks are arranged with respect to the nozzle row arrangement direction.
It is arranged vertically.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet printer head. More specifically, the present invention relates to an inkjet printer head that selectively adheres ink droplets to a recording medium by deforming a piezoelectric element.

[0002]

2. Description of the Related Art In recent years, printers have rapidly become popular along with the spread of personal computers. Among them, inkjet printers are rapidly developing by suppressing other printing methods due to their advantages such as high speed printing, low noise, high printing quality, good color printing, and low cost for the market. .

However, even in the ink jet printer, the problem that color printing requires a long time has become apparent. This is because the information handled by personal computers, etc. has changed from the conventional monochrome character base to a full color graphic base due to the development of the Internet and multimedia, and the display of graphics has evolved to higher resolution, and the amount of information has dramatically increased. Because it is increasing. Therefore, the time required to print full-color graphics of 1024 * 756 dots is 100 times or more that of the conventional monochrome character base. If a high resolution of 10,000 * 10000 dots or more is provided in the future, the printing time will be 10,000 times or more.

Here, an example of the structure of a conventional ink jet printer head, ink droplet ejection operation, and arrangement of ink tanks of an ink jet printer head having a plurality of nozzle rows will be described with reference to the drawings.

First, the structure of a conventional ink jet printer head will be described with reference to FIG. FIG. 4 is a partial perspective view of the inkjet printer head. In FIG. 4, 1 is a nozzle hole, 2 is a nozzle plate, 3 is a partition wall, 4 is a pressure chamber, 5 is a vibrating plate, 6 is a piezoelectric element, 7 is a supply port, 8 is a reservoir, and 9 is an ink tank port. Indicates. A plurality of pressure chambers 4 are arranged in parallel at regular intervals. A vibration plate 5 to which a piezoelectric element 6 is arranged is formed on one surface of the pressure chamber 4. An electric signal is sent to the piezoelectric element 6 from a signal circuit (not shown). The surface of the pressure chamber 4 opposite to the vibrating plate 5 is composed of a nozzle plate 2 having a nozzle hole 1 formed across a partition wall 3. A reservoir 8 is formed perpendicular to the arrangement direction of the pressure chambers 4. The individual pressure chambers 4 and the reservoirs 8 are connected by the elongated slit-shaped supply port 7. The reservoir 8 is
An ink tank (not shown) on the reservoir 8 is connected to the ink tank port 9. The ink in the ink tank is filled in the reservoir 8. Ink reservoir 8
Through the supply port 7 to fill the pressure chamber 4.

Next, the ink droplet ejection operation of the conventional ink jet printer head will be described with reference to FIG. Fifth
The figure is a sectional view of a pressure chamber of an inkjet printer head. In FIG. 5, 1 is a nozzle hole, 2 is a nozzle plate,
4 is a pressure chamber, 5 is a diaphragm, 6 is a piezoelectric element, 7 is a supply port,
Reference numeral 8 indicates a reservoir, and 9 indicates an ink tank port.

When an electric signal is sent to the piezoelectric element 6 from a signal circuit (not shown), the piezoelectric element 6 expands and contracts, and the diaphragm 5
Transforms. The volume change occurs in the pressure chamber 4, and the ink filled in the pressure chamber 4 tries to escape to the nozzle hole 1 and the supply port 7. Since there is ink from the ink tank on the supply port 7 side, more ink will try to escape to the nozzle hole 1 side. As a result, ink droplets are ejected from the nozzle holes 1.

Next, the arrangement of ink tanks of an ink jet printer head having a plurality of nozzle rows will be described with reference to FIG. FIG. 6 is a perspective view showing a state in which four ink tanks are arranged in an inkjet printer head in which the inkjet printer head of FIG. 4 is connected to four nozzle rows. In FIG. 6, 9 is an ink tank port, 10
Is a nozzle row A, 11 is a nozzle row B, 12 is a nozzle row C,
Reference numeral 13 is a nozzle row D, 14 is an ink tank A, 15 is an ink tank B, 16 is an ink tank C, 17 is an ink tank D, and 18 is a nozzle row arrangement direction. When color printing is performed with four colors of yellow, magenta, cyan, and black, four nozzle rows are required. The yellow nozzle row is nozzle row A10, and the magenta nozzle row is nozzle row B1.
1, the cyan nozzle row is a nozzle row C12, and the black nozzle row is a nozzle row D13. The yellow ink tank is the ink tank A14, the magenta ink tank is the ink tank B15, the cyan ink tank is the ink tank C16, and the black ink tank is the ink tank D1.
7 is assumed. Each nozzle row has an ink tank port 9 on which the respective ink tank is arranged. The ink tanks are arranged in the same direction as the arrangement direction 18 of the nozzle rows.

[0009]

As described above, the advent of an ink jet printer head capable of printing a drastically increased amount of information in a short time has been desired.

The method of shortening the printing time of the ink jet printer, that is, the method of increasing the printing speed will be specifically described below to clarify the problems of the prior art.

There are two methods described below for increasing the printing speed. The first method is to increase the driving frequency of the inkjet printer head. If the driving frequency is doubled, the printing speed can be doubled. The second method is to increase the number of nozzles in the head of an inkjet printer. If you double the number of nozzles, you can double the printing speed.

[0012] The first method is technically approaching its limit, and a dramatic improvement cannot be expected. Therefore, the second method, that is, the development in the direction of increasing the number of nozzles, has been made. In this case, it is not necessary to simply increase the number of nozzles, but it is necessary to increase the nozzle density as well. The reason will be described below. As described above, when printing a high-resolution graphic display, if the nozzle density is low, the nozzle row must be increased. When full-color printing is performed with four colors of yellow, magenta, cyan, and black, nozzles corresponding to the respective colors are required. As a result, the inkjet head becomes large, high precision is required for the alignment between the nozzle rows, and an expensive and large inkjet printer is obtained. 180D as an example
When an inkjet printer head with a nozzle density of PI (dots / inch) is used to perform full-color printing of 1440 DPI, eight nozzle rows are required for each color,
32 columns of 4 colors are required. If the distance between the nozzle rows is 5 mm, the total length of the nozzle rows needs to be 5 * 31 = 155 mm or more. Therefore, the inkjet printer head itself is large and expensive. In addition, the printer will grow accordingly.

Further, since the reservoir has a reservoir beside the pressure chamber, in an ink jet printer head having a plurality of nozzle rows, the nozzle rows must be provided with an extra space corresponding to the length of the reservoir. 180 DPI given earlier as an example
In order to perform full-color printing of 1440 DPI with an inkjet printer head having a (dot / inch) nozzle density, 32 nozzle rows are required. If 3 mm is required by providing a reservoir, the distance between nozzle rows becomes 8 mm, and the total length of nozzle rows is 8 * 31 = 248.
mm or more is required.

In order to increase the nozzle density, the pressure chamber of the ink jet printer head must be made minute. The same applies to the path from the ink tank to the pressure chamber. When the pressure chamber and the path are minute, the influence of the capillary force of the ink becomes large, and it becomes difficult to smoothly move the ink from the ink tank to the pressure chamber. In addition, it is difficult to eliminate bubbles generated in the ink. Due to these, there arises a problem that good ejection performance cannot be selected.

This problem will be specifically described below. The ink flow in the conventional inkjet printer head is as shown by the arrow in FIG. It flows to the reservoir just below the ink in the ink tank. The ink in the reservoir flows horizontally to the pressure chamber. The ink flow changes 90 degrees in the reservoir. In this part, the ink flow deteriorates,
Bubbles generated in the ink tend to stay. When air bubbles stay, it becomes difficult for the ink to flow, and the ejection performance deteriorates. To a great extent, the ink will not flow and will not be ejected. A conventional 180 DPI nozzle row has a pitch of 141 μm, and if the width of the flow passage is half that of 70 μm, then 1440 DPI has a pitch of 17.6 μm and a flow passage width of 8.8 μm. Ink will move in a micro tube of micron order. The influence of the capillary force becomes large, and the ink becomes difficult to move.

When the ink becomes hard to move, the driving frequency must be slowed down. The diaphragm 5 in FIG. 5 is deformed,
After the volume of the pressure chamber 4 changes and ink droplets are ejected from the nozzle hole, the pressure chamber 4 returns to its original state. Ink corresponding to the volume of the ink droplet moves from the supply port 7 to the pressure chamber 4 and is filled therein. If the ink does not move easily, it takes longer to fill the ink, resulting in a slower driving frequency. As a result, the printing speed becomes slow.

Therefore, it is desirable that the ink path from the ink tank to the pressure chamber be short and linear.

The present invention solves such a problem, and realizes an ink jet printer head which can achieve both high nozzle density and high driving frequency, and provides a compact ink jet printer suitable for printing high resolution full color graphics. The purpose is to

[0019]

In order to solve such a problem, an ink jet printer head of the present invention has a piezoelectric element which is deformed by an electric signal and an ink supply path formed on a vibration plate to which the piezoelectric element is arranged. A reservoir is formed on the back side of the diaphragm.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an example of an ink jet printer head of the present invention will be described with reference to FIG. FIG. 1 is a partial perspective view showing the structure of an inkjet printer head. In FIG. 1, 1 is a nozzle hole, 2 is a nozzle plate, 3 is a partition wall, 4 is a pressure chamber, 5 is a vibrating plate, 6 is a piezoelectric element, 7 is a supply port, 8 is a reservoir, and 9 is an ink tank port. Indicates. This drawing shows an inkjet printer head having four nozzle rows. The pressure chamber 4 sandwiches the opposing partition wall 3,
The nozzle plate 2 and the vibrating plate 5 are opposed to each other. The pressure chambers 4 are arranged at regular intervals. If it is a nozzle row of 1440 DPI, it is arranged at an interval of 17.6 mm. Nozzle holes 1 corresponding to the individual pressure chambers 4 are formed in the nozzle plate 2. A piezoelectric element 6 corresponding to the pressure chamber 4 is arranged on the diaphragm 5. A supply port 7 is formed in the diaphragm 5. The reservoir 8 faces the pressure chamber 4 with the diaphragm 5 interposed therebetween. The reservoir 8 is provided with an ink tank port 9 and is connected to an ink tank (not shown).

Next, the ink droplet ejection operation and ink flow of the ink jet printer head of the present invention will be described with reference to FIG. 2 is a sectional view of the ink jet printer head taken along the "section line in FIG. 2" in FIG.
In FIG. 2, 1 is a nozzle hole, 2 is a nozzle plate, 4 is a pressure chamber, 5 is a vibrating plate, 6 is a piezoelectric element, 7 is a supply port, 8 is a reservoir, and 9 is an ink tank port. There are three types of arrows,
The flow of ink, the expansion / contraction direction of the piezoelectric element 6, and the deformation direction of the vibration plate 5 are shown. Ink flows from an ink tank (not shown) to the ink tank port 9 as shown by an ink flow arrow.
After that, the reservoir 8 is filled. The ink in the reservoir 8 is filled in the pressure chamber 4 through the supply port 7. Next, the ink droplet ejection operation will be described. When an electric signal is sent to the piezoelectric element 6 from a signal circuit (not shown), the piezoelectric element 6 is transformed into the "expansion and contraction arrow" of the piezoelectric element. Then,
The diaphragm 5 is also deformed in the "vibration plate deformation direction 1". When the electric signal is released, the piezoelectric element 6 returns to the original state, and the diaphragm 5 also returns to the original state, but the piezoelectric element 6 is deformed in the “deformation direction 2 of the diaphragm” due to the mass and rigidity of the diaphragm 5 itself. The volume of the pressure chamber 4 becomes small and a pressure wave is generated. The pressure wave is transmitted to the nozzle port and the supply port. As a result, the ink is ejected as an ink droplet from the nozzle opening.

Next, the arrangement of the ink tanks of the ink jet printer head of the present invention will be described with reference to FIG. FIG. 3 is a perspective view showing a state in which an ink tank is arranged in the inkjet printer head of FIG. In FIG. 3, 9 is an ink tank port, 10 is a nozzle row A, 11
Is the nozzle row B, 12 is the nozzle row C, 13 is the nozzle row D,
Reference numeral 14 is an ink tank A, 15 is an ink tank B, 16 is an ink tank C, 17 is an ink tank D, and 18 is an arrangement direction of nozzle rows. Assuming that four colors of magenta, cyan, and black are printed, the nozzle row for yellow is nozzle row A
10, a magenta nozzle row is a nozzle row B11, a cyan nozzle row is a nozzle row C12, and a black nozzle row is a nozzle row D13. The yellow ink tank is ink tank A14 and the magenta ink tank is ink tank B.
15, a cyan ink tank is an ink tank C16, and a black ink tank is an ink tank D17. Each nozzle row has an ink tank port 9 on which the respective ink tank is arranged. The four ink tank ports 9 (two of which are hidden in the ink tank and not shown) are arranged obliquely with respect to the alignment direction 18 of the nozzle rows. The ink tank is arranged in the direction opposite to the arrangement direction of the nozzle rows. If the distance between the nozzle rows can be shortened as can be realized by the present invention, there is a problem described below in the case of the conventional ink tank arranged in the direction in which the nozzle rows are arranged. If the width of the inkjet printer head is 200 mm for printing A4 size, When the width of the nozzle row is 2 mm, the size of the ink tank is 200 * 2 mm. When a long and narrow ink tank is used, it becomes difficult for the ink in the end portion of the ink tank to move to the ink tank port 9, which adversely affects the ejection performance. Furthermore, the amount of ink that can be supplied to the inkjet printer head is reduced. Also, because of the elongated shape,
It becomes difficult to connect the ink tank to the inkjet printer head. The dimensions are 50 * 8mm by arranging the ink tanks in the direction opposite to the nozzle row arrangement direction.
Therefore, the above problem can be solved.

An example of the method of manufacturing the ink jet printer head of the present invention will be described below. Thickness 200μ
A platinum film having a thickness of 1 μm is formed on a silicon wafer having a size of m by sputtering. A piezoelectric film is formed thereon by the following method.

0.105 mol of lead acetate, 0.045 mol of zirconium acetylacetonate, 0.005 mol of magnesium acetate and 30 ml of acetic acid at 100 ° C.
To dissolve. After cooling to room temperature, 0.040 mol of titanium tetraisopropoxide and 0.010 mol of pentaethoxyniobium were dissolved in 50 ml of ethyl cerasolve and added. After 30 ml of acetylacetone was added to stabilize, 30% by weight of polyethylene glycol was added to the metal oxide in the sol, and the mixture was stirred well to obtain a homogeneous sol.

The prepared sol was applied on the platinum film by spin coating, and calcined at 400 ° C. An amorphous porous gel thin film having a thickness of 0.3 μm could be formed without cracks. Further, application of sol and calcination at 400 ° C. were repeated twice to form a porous gel thin film having a thickness of 0.9 μm. Next, using RTA (Rapid Thermal Annealing), in an oxygen atmosphere, it was heated to 650 ° C. for 5 seconds and held for 1 minute to perform pre-annealing to form a dense thin film having a thickness of 0.6 μm.

The sol is applied again by spin coating and 40
The step of calcination at 0 ° C. was repeated 3 times to laminate an amorphous porous gel thin film having a film thickness of 0.9 μm. Next, RTA was used to pre-anneal at 650 ° C. and holding for 1 minute to form a crystalline dense film having a thickness of 1.2 μm. After etching with borofluoric acid through the photoresist and peeling off the resist, RTA is used in an oxygen atmosphere for 900 times.
It was annealed by heating to ℃ and holding for 1 minute. A piezoelectric thin film having the same thickness of 1.2 μm was obtained. An aluminum electrode was formed on the piezoelectric thin film by a vapor deposition method, and after polarization, the physical properties were measured and the relative dielectric constant was 2000 and the piezoelectric strain constant was 1.
It showed excellent characteristics of 50 pC / N. This piezoelectric film was patterned by photoetching to have a width of 4 μm, a length of 0.9 mm, and a pitch of 17.6 μm (1440 DPI).
A plurality of piezoelectric elements were formed.

On the surface of the silicon wafer opposite to the surface on which the piezoelectric element is formed, a width of 8 μm and a length of 1 are formed by anisotropic etching.
Grooves having a pitch of 1 mm and a pitch of 17.6 μm were formed at positions corresponding to the respective piezoelectric elements. After forming the gold top electrode,
A supply port having a diameter of 3 μm was formed on the piezoelectric element by an excimer laser. Further, a SiO2 film serving as an insulating film was formed thereon by sputtering to a thickness of 0.2 .mu.m. An ink jet head was prepared by combining a nozzle plate having nozzle holes, a reservoir member, and a signal circuit with a silicon wafer having the piezoelectric element formed thereon. When ink was ejected, sufficient ejection force was obtained. When printing was performed by incorporating the ink jet recording apparatus in an ink jet recording apparatus, good printing quality was obtained.

[0028]

As described above, according to the ink jet printer head of the present invention, high resolution full color printing can be performed in a short time, the ink jet printer head itself can be made small, and a compact ink jet printer can be provided. There is an effect.

Further, a piezoelectric element and a pressure chamber having a high nozzle density can be easily formed by photoetching a silicon wafer. As a result, the higher the nozzle density, the more the number of silicon wafers taken from the silicon wafer can be increased, which is an excellent effect that an inexpensive inkjet printer head can be provided.

[0030]

[Brief description of drawings]

FIG. 1 is a partial perspective view illustrating the structure of an inkjet printer head of the present invention.

FIG. 2 is a cross-sectional view illustrating an ink droplet ejection operation and ink flow of the inkjet printer head of the present invention.

FIG. 3 is a perspective view showing a state in which an ink tank of the inkjet printer head of the present invention is arranged.

FIG. 4 is a partial perspective view illustrating the structure of a conventional inkjet printer head.

FIG. 5 is a cross-sectional view illustrating an ink droplet ejection operation and ink flow of a conventional inkjet printer head.

FIG. 6 is a perspective view showing a state in which ink tanks of a conventional inkjet printer head are arranged.

[Explanation of symbols]

 1 Nozzle Hole 2 Nozzle Plate 3 Partition 4 Pressure Chamber 5 Vibrating Plate 6 Piezoelectric Element 7 Supply Port 8 Reservoir 9 Ink Tank Port 10 Nozzle Row A 11 Nozzle Row B 12 Nozzle Row C 13 Nozzle Row D 14 Ink Tank A 15 Ink Tank B 16 Ink tank C 17 Ink tank D 18 Nozzle row alignment direction

Claims (3)

[Claims] 1. A piezoelectric element which is deformed by an electric signal, a pressure chamber having a surface composed of a vibrating plate in contact with the piezoelectric element, and an ink supply path for supplying ink to the pressure chamber,
An ink jet printer head in which the pressure chambers are arranged in a horizontal direction with respect to a printing surface, wherein the ink supply path is formed in the vibrating plate. 2. The inkjet printer head according to claim 1, wherein the ink supply path of the inkjet printer head is connected to the reservoir, wherein the reservoir is formed on the back surface of the diaphragm. And inkjet printer head. 3. The ink jet printer head according to claim 2, wherein a plurality of nozzle rows are formed, and a plurality of ink tanks corresponding to the nozzle rows and an ink tank in each of the individual nozzle rows are provided in the reservoir. An ink tank port to be connected is provided, a plurality of ink tank ports are arranged diagonally with respect to the nozzle row arrangement direction, and a plurality of ink tanks are arranged vertically with respect to the nozzle row arrangement direction. An inkjet printer head characterized by.