JP3551603B2 - Ink jet printer head and ink jet recording apparatus - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ink jet printer head. More specifically, the present invention relates to an ink jet printer head for selectively applying ink droplets to a recording medium by deforming a piezoelectric element.
[0002]
[Prior art]
2. Description of the Related Art In recent years, printers have rapidly spread in step with the spread of personal computers. Above all, inkjet printers are rapidly developing with the advantages of high-speed printing, low noise, high printing quality, good color printing, low cost printing, and other advantages. .
[0003]
However, the problem that a long time is required for color printing has also become apparent in an ink jet printer. This is because the information handled by personal computers changes 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 also evolved to higher resolution, dramatically increasing the amount of information Due to the increase. Therefore, the time required for printing 1024 * 756-dot full-color graphics is more than 100 times that of a conventional monochrome character base. If the resolution becomes 10,000 × 10000 dots or more in the future, the printing time will need to be 10,000 times or more.
[0004]
Here, an example of the structure of a conventional ink jet printer head, an ink droplet ejection operation, and an arrangement of ink tanks of an ink jet printer head having a plurality of nozzle rows will be described with reference to the drawings.
[0005]
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 ink jet printer head. In FIG. 4, 1 is a nozzle hole, 2 is a nozzle plate, 3 is a partition, 4 is a pressure chamber, 5 is a vibration plate, 6 is a piezoelectric element, 7 is a supply port, 8 is a reservoir, and 9 is an ink tank port. Is shown. A plurality of pressure chambers 4 are arranged in parallel at regular intervals. On one surface of the pressure chamber 4, a vibration plate 5 on which a piezoelectric element 6 is disposed is formed. 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 vibration plate 5 is composed of a nozzle plate 2 having a nozzle hole 1 formed with a partition wall 3 interposed therebetween. A reservoir 8 is formed perpendicular to the direction in which the pressure chambers 4 are arranged. Each of the pressure chambers 4 and the reservoir 8 are connected by an elongated slit-shaped supply port 7. The reservoir 8 is connected to an ink tank (not shown) on the reservoir 8 by an ink tank port 9. The ink in the ink tank is filled in the reservoir 8. The ink passes through the supply port 7 from the reservoir 8 and fills the pressure chamber 4.
[0006]
Next, the operation of ejecting ink droplets of a conventional ink jet printer head will be described with reference to FIG. FIG. 5 is a sectional view of a pressure chamber of the ink jet printer head. In FIG. 5, 1 is a nozzle hole, 2 is a nozzle plate, 4 is a pressure chamber, 5 is a vibration plate, 6 is a piezoelectric element, 7 is a supply port, 8 is a reservoir, and 9 is an ink tank port.
[0007]
When an electric signal is sent from a signal circuit (not shown) to the piezoelectric element 6, the piezoelectric element 6 expands and contracts, and the diaphragm 5 deforms. A 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 the ink from the ink tank exists on the supply port 7 side, the ink tends to escape to the nozzle hole 1 side. As a result, ink droplets are ejected from the nozzle holes 1.
[0008]
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 ink jet printer head in which the ink jet 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, 13 is a nozzle row D, 14 is an ink tank A, 15 is an ink tank B, 16 Indicates the ink tank C, 17 indicates the ink tank D, and 18 indicates the direction in which the nozzle rows are arranged. When color printing is performed in four colors of yellow, magenta, cyan, and black, four nozzle rows are required. The yellow nozzle row is referred to as a nozzle row A10, the magenta nozzle row is referred to as a nozzle row B11, the cyan nozzle row is referred to as a nozzle row C12, and the black nozzle row is referred to as a nozzle row D13. The yellow ink tank is ink tank A14, the magenta ink tank is ink tank B15, the cyan ink tank is ink tank C16, and the black ink tank is ink tank D17. Each nozzle row has an ink tank opening 9 on which each ink tank is arranged. The ink tanks are arranged in the same direction as the arrangement direction 18 of the nozzle rows.
[0009]
[Problems to be solved by the invention]
As described above, the emergence of an ink jet printer head capable of printing dramatically increased information in a short time has been awaited.
[0010]
Hereinafter, a method of shortening the printing time of the ink jet printer, that is, a method of increasing the printing speed will be specifically described, and the problems of the related art will be clarified.
[0011]
There are two methods described below to increase the printing speed. The first method is to increase the driving frequency of the ink jet printer head. If the driving frequency is doubled, the printing speed can be doubled. A second method is to increase the number of nozzles of the ink jet printer head. If the number of nozzles is doubled, the printing speed can be doubled.
[0012]
The first method is technically approaching its limit, and no dramatic improvement can be expected. Then, the second method, that is, development in the direction of increasing the number of nozzles, has been performed. In this case, it is not only necessary to simply increase the number of nozzles, but also to increase the nozzle density. The reason will be described below. As described above, when printing a high-resolution graphics display, if the nozzle density is low, the number of nozzle rows must be increased. Further, when full-color printing is performed in four colors of yellow, magenta, cyan, and black, nozzles corresponding to each color are required. As a result, the size of the ink jet head becomes large, and high precision is required for positioning between nozzle rows, resulting in an expensive and large ink jet printer. As an example, when performing full-color printing at 1440 DPI with an inkjet printer head having a nozzle density of 180 DPI (dots / inch), eight nozzle rows are required for each color, and 32 nozzles are required for four colors. If the interval 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 ink jet printer head itself is large and expensive. In addition, the printer becomes larger accordingly.
[0013]
In addition, since a reservoir is provided beside the pressure chamber, in an ink jet printer head having a plurality of nozzle rows, the interval between the nozzle rows must be longer than the length of the reservoir. When performing the full-color printing of 1440 DPI with the ink jet printer head having the nozzle density of 180 DPI (dot / inch) described above as an example, 32 nozzle rows are required. If 3 mm is required by providing a reservoir, the interval between the nozzle rows becomes 8 mm, and the total length of the nozzle rows needs to be 8 * 31 = 248 mm or more.
[0014]
In order to increase the nozzle density, the pressure chamber of the ink jet printer head must be minute. The same goes for the path from the ink tank to the pressure chamber. When the pressure chamber and the path are small, the influence of the capillary force of the ink becomes large, and it becomes difficult for the ink to smoothly move from the ink tank to the pressure chamber. Also, it is difficult to eliminate bubbles generated in the ink. Due to these, the problem that good ejection performance cannot be selected appears.
[0015]
The following specifically describes this problem. The flow of ink in the conventional ink jet printer head is as shown by the arrow in FIG. It flows to the reservoir just below the ink in the ink tank. The reservoir ink flows horizontally into the pressure chamber. The ink flow changes 90 degrees in the reservoir. In this portion, the ink flow becomes worse, and bubbles generated in the ink tend to stay. When the bubbles stay, the ink becomes difficult to flow, and the ejection performance deteriorates. Severely, the ink does not flow and does not discharge. The conventional 180 DPI nozzle array has a 141 micron pitch, and if the width of the flow path is half that of 70 microns, then the 1440 DPI has a 17.6 micron pitch and the flow path width is 8.8 microns. Ink moves in a microscopic tube on the order of microns. The effect of the capillary force increases, making it difficult for the ink to move.
[0016]
When the ink becomes difficult to move, the driving frequency must be reduced. After the diaphragm 5 in FIG. 5 is deformed, the volume of the pressure chamber 4 changes, and after the ink droplet is ejected from the nozzle hole, the pressure chamber 4 returns to its original state. The ink corresponding to the volume of the ink droplet moves from the supply port 7 to the pressure chamber 4 and is filled. If the ink is difficult to move, the filling time becomes longer, and as a result, the driving frequency becomes slower. As a result, the printing speed also decreases.
[0017]
Therefore, it is desirable that the path of the ink from the ink tank to the pressure chamber is short and straight.
[0018]
SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an ink jet printer head capable of achieving both a high nozzle density and a high driving frequency, and to provide a compact ink jet printer suitable for printing high-resolution full-color graphics. And
[0019]
[Means for Solving the Problems]
The ink jet printer head of the present invention has a plurality of nozzles , a plurality of nozzle rows having a pressure chamber formed with a diaphragm ,
In an ink jet printer head comprising an ink supply path for supplying ink to the pressure chamber,
The ink supply path is formed in the diaphragm,
The plurality of nozzle rows are each connected to an ink tank by an ink tank opening formed corresponding to the plurality of nozzle rows,
The plurality of ink tank openings are arranged obliquely to the arrangement direction of the nozzle rows, and the plurality of ink tanks are arranged so as to intersect and overlap with the nozzle rows. This is an inkjet printer head.
The ink jet printer head according to the present invention is characterized in that the ink supply path is formed in a reservoir formed in a nozzle row, and the reservoir is formed to face the pressure chamber with the diaphragm interposed therebetween. This is an ink-jet printer head.
An ink jet printer head according to the present invention is characterized in that the reservoir is provided with an ink tank port connected to an ink tank.
An inkjet recording apparatus according to the present invention is an inkjet recording apparatus including the inkjet printer head.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
First, an example of the 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 the ink jet printer head. In FIG. 1, 1 is a nozzle hole, 2 is a nozzle plate, 3 is a partition, 4 is a pressure chamber, 5 is a vibration plate, 6 is a piezoelectric element, 7 is a supply port, 8 is a reservoir, and 9 is an ink tank port. Is shown. This figure shows an ink jet printer head having four nozzle arrays. The pressure chamber 4 is formed by the opposed nozzle plate 2 and the diaphragm 5 with the opposed partition wall 3 interposed therebetween. The pressure chambers 4 are arranged at regular intervals. In the case of a 1440 DPI nozzle array, they are arranged at an interval of 17.6 mm. Nozzle holes 1 corresponding to individual pressure chambers 4 are formed in the nozzle plate 2. A piezoelectric element 6 corresponding to the pressure chamber 4 is connected to the vibration plate 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).
[0021]
Next, the ink droplet ejection operation and the ink flow of the ink jet printer head of the present invention will be described with reference to FIG. FIG. 2 is a cross-sectional view of the ink jet printer head taken along a "cross-sectional 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 vibration 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, indicating the flow of ink, the direction in which the piezoelectric element 6 expands and contracts, and the direction in which the diaphragm 5 deforms. The ink is filled in the reservoir 8 from the ink tank (not shown) through the ink tank opening 9 as shown by the ink flow arrow. The ink in the reservoir 8 is filled in the pressure chamber 4 through the supply port 7. Next, the operation of ejecting ink droplets will be described. When an electric signal is sent from a signal circuit (not shown) to the piezoelectric element 6, the piezoelectric element 6 is deformed into an "arrow in the expansion and contraction direction" of the piezoelectric element. Then, the diaphragm 5 is also deformed in the “deformation direction 1 of the diaphragm”. When the electric signal is released, the piezoelectric element 6 returns to its original state, and the diaphragm 5 also returns to its original state. However, due to the mass and rigidity of the diaphragm 5, the diaphragm 5 is deformed in the "deformation direction 2 of the diaphragm". The volume of the pressure chamber 4 is reduced, 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 from the nozzle openings as ink droplets.
[0022]
Next, the arrangement of the ink tank 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 ink jet printer head of FIG. In FIG. 3, 9 is an ink tank port, 10 is a nozzle row A, 11 is a nozzle row B, 12 is a nozzle row C, 13 is a nozzle row D, 14 is an ink tank A, 15 is an ink tank B, 16 Indicates the ink tank C, 17 indicates the ink tank D, and 18 indicates the direction in which the nozzle rows are arranged. Assuming that four colors of magenta, cyan, and black are to be printed, the nozzle row of yellow is nozzle row A10, the nozzle row of magenta is nozzle row B11, the nozzle row of cyan is nozzle row C12, and the nozzle row of black is nozzle row D13. . The yellow ink tank is ink tank A14, the magenta ink tank is ink tank B15, the cyan ink tank is ink tank C16, and the black ink tank is ink tank D17. Each nozzle row has an ink tank opening 9 on which each ink tank is arranged. The four ink tank openings 9 (two are hidden by the ink tanks and not shown) are arranged obliquely with respect to the direction 18 in which the nozzle rows are arranged. The ink tank is arranged in a direction opposite to the direction in which the nozzle rows are arranged. If the interval between the nozzle rows can be shortened as can be realized by the present invention, the following problem occurs if the conventional ink tanks are arranged in the direction in which the nozzle rows are arranged. If the width of the nozzle row is 2 mm, the size of the ink tank is 200 * 2 mm. When the ink tank is elongated, it becomes difficult for the ink at the end of the ink tank to move to the ink tank port 9, and this has an adverse effect on the ejection performance. Further, the amount of ink that can be supplied to the ink jet printer head is reduced. In addition, because of the elongated shape, it is difficult to connect the ink tank to the ink jet printer head. By arranging the ink tanks in the direction opposite to the direction in which the nozzle rows are arranged, the size becomes 50 * 8 mm, and the above-described problem can be solved.
[0023]
An example of the method for manufacturing the ink jet printer head of the present invention will be described below. A 1 μm-thick platinum film is formed on a 200 μm-thick silicon wafer by a sputtering method. A piezoelectric film is formed thereon by the following method.
[0024]
0.105 mol of lead acetate, 0.045 mol of zirconium acetylacetonate, 0.005 mol of magnesium acetate and 30 ml of acetic acid were dissolved by heating to 100 ° C. 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.
[0025]
The sol prepared on the platinum film was applied 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 generating cracks. Further, the application of the sol and the preliminary baking at 400 ° C. were repeated twice to form a porous gel thin film having a thickness of 0.9 μm. Next, it was heated to 650 ° C. for 5 seconds in an oxygen atmosphere using RTA (Rapid Thermal Annealing) and held for 1 minute to perform pre-annealing, thereby forming a dense thin film having a thickness of 0.6 μm.
[0026]
The step of applying the sol again by spin coating and pre-baking at 400 ° C. was repeated three times, and an amorphous porous gel thin film having a thickness of 0.9 μm was laminated. Next, by pre-annealing at 650 ° C. using RTA and holding for 1 minute, a crystalline dense thin film having a thickness of 1.2 μm was obtained. After etching with borofluoric acid through the photoresist and stripping the resist, the substrate was annealed by heating to 900 ° C. in an oxygen atmosphere using RTA for 1 minute. A piezoelectric thin film whose thickness did not change from that of 1.2 μm was obtained. An aluminum electrode was formed on the piezoelectric thin film by a vapor deposition method, and after polarization, physical properties were measured. As a result, it was found that the dielectric constant was 2000, and the piezoelectric strain constant was 150 pC / N. This piezoelectric film was patterned by photoetching into a width of 4 μm, a length of 0.9 mm, and a pitch of 17.6 μm (1440 DPI) to form a plurality of piezoelectric elements.
[0027]
Grooves having a width of 8 μm, a length of 1 mm, and a pitch of 17.6 μm were formed on the surface of the silicon wafer opposite to the surface on which the piezoelectric elements were formed by anisotropic etching at positions corresponding to the respective piezoelectric elements. After forming the gold upper electrode, a supply port having a diameter of 3 μm was formed on the piezoelectric element by using an excimer laser. Further, an SiO2 film serving as an insulating film was formed thereon by a thickness of 0.2 μm by a sputtering method. A nozzle plate having a nozzle hole formed therein, a reservoir member, and a signal circuit were combined on the silicon wafer on which the piezoelectric element was formed to prepare an ink jet head. When the ink was ejected, a sufficient ejection force was obtained. When printing was performed by incorporating the ink jet recording apparatus into an ink jet recording apparatus, good printing quality was obtained.
[0028]
【The invention's effect】
As described above, according to the inkjet printer head of the present invention, there is an excellent effect that high-resolution full-color printing can be performed in a short time, the inkjet printer head itself can be reduced in size, and a compact inkjet printer can be provided.
[0029]
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 is, the more the number of pieces taken from a silicon wafer can be increased, and there is an excellent effect that an inexpensive inkjet printer head can be provided.
[0030]
[Brief description of the drawings]
FIG. 1 is a partial perspective view illustrating the structure of an ink jet printer head according to the present invention.
FIG. 2 is a cross-sectional view illustrating an ink droplet ejection operation and ink flow of the ink jet printer head of the present invention.
FIG. 3 is a perspective view showing a state in which ink tanks of the ink jet printer head of the present invention are 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 the operation of ejecting ink droplets and the flow of ink in a conventional inkjet printer head.
FIG. 6 is a perspective view showing a state in which ink tanks of a conventional ink jet printer head are arranged.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Nozzle hole 2 Nozzle plate 3 Partition wall 4 Pressure chamber 5 Vibration 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 arrangement direction

Claims (4)

A plurality of nozzle rows having a plurality of nozzles and having a pressure chamber formed with a diaphragm ,
In an ink jet printer head comprising an ink supply path for supplying ink to the pressure chamber,
The ink supply path is formed in the diaphragm,
The plurality of nozzle rows are each connected to an ink tank by an ink tank opening formed corresponding to the plurality of nozzle rows,
The plurality of ink tank openings are arranged obliquely to the arrangement direction of the nozzle rows, and the plurality of ink tanks are arranged so as to intersect and overlap with the nozzle rows. Inkjet printer head. 2. The ink jet printer head according to claim 1, wherein the ink supply path is formed in a reservoir formed in a nozzle row, and the reservoir is formed to face the pressure chamber with the vibration plate interposed therebetween. Characteristic inkjet printer head. 3. An ink jet printer head according to claim 2, wherein said reservoir is provided with an ink tank port connected to an ink tank. An inkjet recording apparatus comprising the inkjet printer head according to claim 1.

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