JPH0557889A - Inkjet recording head - Google Patents

Abstract

(57) [Summary] [Purpose] The ink jet recording head has multiple nozzles, which enables uniform ink velocity, high-speed printing, and high-quality printing. [Structure] First ink passages 33A, 33B having curved and meandering portions on a substrate 30, ink pressurizing chambers 34A, 34B arranged in a zigzag pattern, and second ink passages 35A, 35B of two types, short and long. And a plurality of ink nozzles 37 communicating with them are formed. Ink pressurizing chamber 34A, 3
4B, a piezoelectric element is arranged above the second ink passage 35
Two types of voltage waveforms are applied to the piezoelectric element according to the lengths of A and 35B.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording head. More specifically, the arrangement, shape and structure of ink pressurizing chambers and ink passages as well as driving voltage waveforms are improved to realize high resolution and multiple nozzles. And an on-demand type ink jet recording head capable of high-speed printing.

[0002]

2. Description of the Related Art Conventionally, there are various types of ink jet recording heads and driving devices therefor, which are roughly classified into a continuous jet type, an on-demand type (impulse type), and an electrostatic attraction type. Among them, the on-demand type ink jet recording head has a relatively simple structure and can be manufactured at low cost.
It is widely used as a recording head for printers and facsimiles.

FIG. 5 schematically shows the main part of this type of recording head. In the figure, 1 is an ink tank, 2 is an ink passage, 3 is an ink pressurizing chamber, 4 is an ink nozzle, 5 Is an ink passage communicating with the ink nozzle 4, 6 is a vibrating plate (lid plate) attached to the outside of the ink pressurizing chamber 3, and 7 is a piezoelectric element as an electromechanical conversion element attached to the vibrating plate 6. Yes, the vibrating plate 6 and the piezoelectric element 7
The bimorph is composed of. In such a configuration, when a pulsed voltage is applied to the piezoelectric element 7,
Since the piezoelectric element 7 expands in the thickness direction and contracts in the length direction, the vibrating plate 6 bends inside the ink pressurizing chamber 3.
As a result, the volume of the ink pressurizing chamber 3 decreases slightly, and the pressure wave generated by the deformation of the vibrating plate 6 causes ink to be ejected as ink droplets from the ink nozzle 4 in the direction of arrow a in the figure.

Next, FIG. 6 shows a concrete example of a conventional on-demand type ink jet recording head. In the figure, a plurality of ink nozzles 12, an ink passage 13a communicating with these ink nozzles 12, an ink pressurizing chamber 14, an ink passage 13b, and an ink reservoir 15 are etched on a substrate 11 made of stainless steel glass or silicon. It is formed by means of machining or the like. And
A vibrating plate 16 is attached above the substrate 11 to form an ink flow path, and a plurality of piezoelectric elements 17 are attached to a position corresponding to the ink pressurizing chamber 14 on the upper surface of the substrate 11. Reference numeral 18 is an ink supply hole for supplying ink from an external ink tank to the ink reservoir 15.

The principle of ink ejection in this recording head is the same as in the case of FIG. Although not shown,
Normally, the back surface of the substrate 11 is also provided with ink nozzles, ink passages, groove portions such as ink pressurizing chambers, a vibration plate, piezoelectric elements, etc., like the front surface. By arranging the front and back ink nozzles in a zigzag pattern. Multi-nozzle (higher density) has been achieved.

[0006]

In recent years, there has been a strong demand for high resolution and multi-nozzle ink jet recording heads in response to the trend of high quality printing and high speed printing. The resolution is 180d in the past.
Although pi (nozzle pitch 0.141 mm) is the mainstream, recently, in printers, it is shifting to 240 dpi (nozzle pitch 0.105 mm) or 300 dpi (nozzle pitch 0.085 mm). The resolution required in the field of facsimile is 200 dp.
i (nozzle pitch 0.127 mm).

On the other hand, in order to increase the printing speed of the ink jet recording head, it is necessary to increase the number of ink nozzles of the recording head or increase the frequency of ink ejection for each nozzle. For the latter,
Since the upper limit is 4 to 5 KHz at a practical level, it is necessary to increase the number of ink nozzles, that is, to increase the number of ink nozzles in order to speed up printing.

FIG. 7 shows another conventional example of Japanese Patent Publication No. 61-61.
The recording head is disclosed in Japanese Patent Publication No. 45951. This recording head has a resolution of 180 dpi, and has 24 ink nozzles (12 ink nozzles are arranged on the front and back sides of the substrate). It's advanced.

In FIG. 7, 20 is an ink reservoir communicating with an external ink tank, 22 is an ink passage, and 21 is an end of the ink passage 22 on the ink reservoir 20 side, which functions as a filter for preventing dust from entering. A three-pronged portion that serves to prevent the pressure wave from returning, 24 is an ink pressurizing chamber, and 23 is an island arranged at the inlet and outlet of the ink pressurizing chamber 24 to make the ink flow in the pressurizing chamber 24 uniform. And 25 are ink nozzles 2
6 is an ink passage, 27 is a disk-shaped piezoelectric element (outline is shown by a broken line for convenience) arranged on a vibration plate (not shown) so as to correspond to the ink pressurizing chamber 24, and 28 is a substrate Is. In this recording head, it is said that the deformation efficiency is highest when the piezoelectric element 27 has a disk shape as shown in the figure.

In this recording head, each ink passage 22,
By changing the width, length, depth, etc. of 25, the flow path resistance as a head, the ink mass, etc. are adjusted, and the ink nozzle 2
The speed and the amount of the ink droplets ejected from 6 are made uniform. However, even this recording head has a resolution of at most 180 dpi and the number of ink nozzles is 24, and it cannot fully meet the demands for high-quality printing and high-speed printing required of the recent recording heads. The present invention has been made to solve the above problems, and an object of the present invention is to provide an ink jet recording head capable of realizing high resolution and multi-nozzle in order to realize high quality printing and high speed printing. Especially.

[0011]

In order to achieve the above object, a first aspect of the present invention applies a pressure to an ink pressurizing chamber provided corresponding to a piezoelectric element by the deformation of the piezoelectric element so that the ink inside the ink pressurizes the ink. An ink jet recording head for ejecting from a nozzle, an ink reservoir to which ink is supplied from the outside, a plurality of ink pressurizing chambers communicating with the ink reservoir via first ink passages, and these ink pressurizing chambers In an ink jet recording head in which a plurality of ink nozzles that communicate with each other via second ink passages are formed on a substrate, the second ink passages having two types of length, short and long, are alternately arranged on the substrate. Ink pressurizing chambers that communicate with the short second ink passages are respectively disposed between the long second ink passages, and the first ink communicating chambers that communicate with these ink pressurizing chambers are provided. Between each other passages, in which an ink pressure chamber communicating with the second ink passage long, which are located respectively.

A second invention is the same as the first invention,
A piezoelectric element corresponding to the ink pressurizing chamber communicating with the long second ink passage and a piezoelectric element corresponding to the ink pressurizing chamber communicating with the short second ink passage are driven by voltages having different waveforms. It is a thing.

A third invention is the same as the first or second invention, wherein the first ink passage has a curved or meandering portion.

A fourth invention is the above-mentioned first, second or third invention.
In the invention, the planar shape of the ink pressurizing chamber is substantially rectangular, and the ratio of the long side to the short side is 1.5 to 3.

In a fifth aspect based on the first, second, third or fourth aspect, the ink passages, the ink pressurizing chambers and the ink nozzles are formed on both sides of the substrate, and the ink on the front and back sides is formed. The pressurizing chambers are arranged so as to be displaced from each other by a predetermined distance when viewed in plan.

[0016]

According to the first aspect of the invention, the plurality of ink pressurizing chambers are arranged in a zigzag pattern on the substrate, increasing the number of ink pressurizing chambers per unit area, and consequently increasing the number of ink nozzles. increase. Further, since the ink pressurizing chambers are arranged not directly adjacent to each other through the ink passages,
This ink passage serves as a buffer zone to prevent the pressure applied by the piezoelectric element from one ink pressurizing chamber from adversely affecting another ink pressurizing chamber. Furthermore, by making the length of the second ink passages to be only two types, the influence on the ink ejection characteristics such as the ink speed due to the difference in the length of the ink passages is minimized.

According to the second aspect of the present invention, the drive voltage waveform of the piezoelectric element is changed in accordance with the difference in the length of the second ink passage, thereby canceling the difference in the length and the ink in all the ink nozzles. Uniform discharge characteristics.

According to the third aspect of the invention, by increasing the flow path resistance of the first ink passage, it is possible to prevent the pressure applied to the ink pressurizing chamber from acting in the ink reservoir direction, and to prevent the ink from the ink reservoir. The ink can be continuously and smoothly supplied to the pressure chamber.

According to the fourth aspect of the invention, by making the planar shape of the ink pressurizing chamber substantially rectangular, a large number of ink pressurizing chambers can be disposed on the substrate without waste, and the number of ink nozzles can be increased. ..

According to the fifth aspect, pressure transmission and interference between the ink pressurizing chambers on the front and back surfaces of the substrate are prevented, and the independence of the ink pressurizing operation is maintained.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view of a main portion of a 200 dpi recording head according to a first embodiment of the present invention. In the figure, ink passages, ink pressurizing chambers, ink nozzles and other groove portions formed on a substrate are shown. The vibrating plate made of glass, the piezoelectric element, and the like, which are shown in the center and mounted on the center, are not shown for convenience. Note that FIG. 1 shows only the surface of the substrate,
Actually, a groove portion or the like is also formed on the back surface. Figure 1
In the above, reference numeral 30 is a substrate made of silicon, and an ink reservoir 31 is formed at an end portion of the substrate 30. The ink reservoir 31 is for dividing the ink supplied from the external ink tank into the ink passages described later and supplying the ink, and the depth thereof is approximately 120 μm.

A plurality of island portions 32 are formed on the substrate 30 so as to be bilaterally symmetric when viewed from above. The first ink passages 33A and 33B and the ink pressurizing chamber are provided between these island portions 32. 34A, 34B and second ink passages 35A, 3
5B is formed. Here, the first ink passage 33
A, the ink pressurizing chamber 34A, and the second ink passage 35A communicate with each other, and the first ink passage 33A includes the three-pronged portion 36.
The second ink passage 35 </ b> A communicates with the ink nozzle 37. Similarly, the first ink passage 33B, the ink pressurizing chamber 34B, and the second ink passage 35B are in communication with each other, the first ink passage 33B is in communication with the ink reservoir 31 via the three-pronged portion 36, and The two-ink passage 35B communicates with the ink nozzle 37.

The first ink passages 33A and 33B have curved and meandering portions, and the bending increases the flow passage resistance in the ink passages 33A and 33B, which are generated in the ink pressurizing chambers 34A and 34B. The pressure wave is damped,
It is possible to continuously and smoothly supply the ink from the ink reservoir 31 to the first ink passages 33A and 33B. In addition,
It has been confirmed that the above effect can be sufficiently exhibited if the bending angle of the ink passages 33A and 33B is 90 degrees or less. Further, the second ink passages 35A, 35B do not have a remarkable curve or meandering portion unlike the first ink passages 33A, 33B, but are formed by a substantially straight portion or a gently curved portion. Further, the width of the three-pronged portion 36 formed between the first ink passages 33A and 33B and the ink reservoir 31 is about half the width of the ink passages 33A and 33B.

The first of the ink pressurizing chambers 34A and 34B
One ink pressurizing chamber 34A communicating with the ink passage 33A
Is communicated with the ink nozzle 37 through the relatively long second ink passage 35A, and the other ink pressurizing chamber 34B communicated with the first ink passage 33B is the relatively short second ink passage.
It communicates with the ink nozzle 37 through the ink passage 35B. That is, the ink pressurizing chambers 34A and 34B are in communication with the ink nozzle 37 via two types of second ink passages 35A and 35B, which are long and short.
When viewed from the 7 side, the ink pressurizing chamber 34B is disposed at a position relatively close to the ink nozzle 37, and the ink pressurizing chamber 34A is disposed slightly farther from the ink pressurizing chamber 34B. Further, a second ink passage 35A communicating with the ink pressurizing chamber 34A is provided between the ink pressurizing chambers 34B, and a first ink communicating with the ink pressurizing chamber 34B is provided between the ink pressurizing chambers 34A. Ink pressurization chambers 34A and 34B are arranged so that passages 33B are respectively arranged, and the ink nozzles 37 are located in the center and are adjacent to each other from one end of the substrate toward the other end.
If you follow, you will find that they are arranged in a zigzag pattern.

As described above, the ink pressurizing chambers 34A and 34B are arranged radially and in a zigzag manner by the second ink passages 35A and 35B of two types, long and short, with the ink nozzle 37 as the center, so that the substrate 30 having the same plane area is disposed. It is possible to arrange a large number of ink pressurizing chambers, and consequently to form a large number of ink nozzles 37. Further, by arranging the first ink passage 33B between the adjacent ink pressurizing chambers 34A and similarly arranging the second ink passage 35A between the adjacent ink pressurizing chambers 34B, each ink pressurizing chamber It is possible to prevent the vibration or the like generated by the applied pressure from being directly transmitted to and interfering with the adjacent ink pressurizing chamber.

Here, the ink pressurizing chamber 34 shown in FIG.
A and 34B have the same planar shape and the width is 1.5 m.
It has a substantially rectangular shape of m and a length of 3 mm. As the plane area of the ink pressurizing chamber is made smaller, the plane area of the entire recording head can be made smaller and its size can be reduced. However, as the plane area of the ink pressurizing chamber becomes smaller, the plane area of the piezoelectric element having a size corresponding to this becomes smaller, and the deforming force required for ink ejection cannot be obtained. Therefore, in the experiments conducted by the inventors, the planar shape of the ink pressurizing chamber has a width of 1 to 2 mm and a length of 1.5 to 3 mm (that is, the ratio of the long side to the short side is 1.5 to 3). We confirm that the range is reasonable.

If the ink pressurizing chambers 34A and 34B have a substantially rectangular plan shape, the ink pressurizing chambers can be disposed on the substrate 30 without waste, and the ink pressurizing chambers and hence the number of ink nozzles can be reduced. Effective to increase. Further, the reason why the lengths of the second ink passages 35A and 35B are two types, that is, long and short, has been found out that the length of the ink passage has a great influence on the resistance of the ink ejection, so this influence is minimized. This is because. Further, as the ink nozzle 37, the width of 40 to 60 μm and the depth of 30 to 45 μm were the best. In the embodiment of FIG. 1, the total number of ink nozzles on the front and back sides is 48, and the distance (nozzle pitch) between the ink nozzles on one side is 0.26 mm.

The ink reservoir 31, the first ink passages 33A and 33B, the second ink passage 35A, which are arranged as described above, are arranged.
35B, ink pressurizing chambers 34A and 34B, ink nozzle 3
7 and the like are processed and formed on a silicon substrate 30 by plasma etching, and glass as a vibration plate is integrated with this by an anodic bonding method. Then, at the positions corresponding to the ink pressurizing chambers 34A and 34B on the vibrating plate,
The piezoelectric element is adhered with an organic adhesive to form a bimorph.

Although not shown, it is preferable that the ink pressurizing chambers formed on the front and back surfaces of the substrate 30 are displaced by, for example, 0.5 to 1.5 mm so as not to overlap in plan view. .. This prevents a part of the pressure applied to the ink pressurizing chamber on one surface from being transmitted to the ink pressurizing chamber on the back surface when the substrate 30 is thin (for example, 1.5 mm or less). This is because.

Next, in the ink jet recording head, if the speed of the ink ejected from each nozzle and the amount of the ink droplet are not uniform, the landing position of the ink droplet will be displaced and the print quality will be degraded. To do. In order to prevent this, it is necessary to make the ink speed of each nozzle as constant as possible. On the other hand, when the deformation amount of the piezoelectric element is the same, if the distance from the ink pressurizing chamber to the ink nozzle (distance of the ink passage) is different, the movement time of the ink is displaced and the print quality is deteriorated. .. Therefore, in this embodiment, the length of the second ink passages 35A, 35B is limited to two types, short and long, and the piezoelectric elements corresponding to the ink pressurizing chambers 34A, 34B communicating with these ink passages 35A, 35B are compared. By applying different voltage waveforms as shown in FIGS. 2 and 3, the ink velocity and the ink droplet amount are made uniform.

FIG. 2 shows a drive voltage waveform applied to the piezoelectric element of the ink pressurizing chamber 34B corresponding to the short second ink passage 35B, and FIG. 3 shows the ink pressurizing chamber 34A corresponding to the long second ink passage 35A. 3 is a drive voltage waveform applied to the piezoelectric element of FIG. The optimum conditions of each waveform for making the ink velocity uniform with respect to the times T ₁ , T ₂ , T ₃ and the voltages V _A , V _B in these figures are as shown in Table 1 below. Note that T ₁
The condition is that + T ₂ is 40 to 60 μs.

[0032]

[Table 1]

The specifications and characteristics of the recording head in this embodiment are as follows. 1. Trifurcation 36: width 0.1 mm, length 1.2 mm, depth 0.04 mm 2. First ink passages 33A, 33B: width 0.48 mm,
Depth 0.12 mm 3. 3. Ink pressurizing chambers 34A and 34B: width 1.5 mm, length 3 mm, depth 0.12 mm 4. Second ink passage 35A: width 0.48 mm, length 12
mm, depth 0.12 mm 5. Second ink passage 35B: width 0.48 mm, length 8.
8 mm, depth 0.12 mm 6. Ink nozzle 37: width 0.055 mm, length 0.7
mm, depth 0.04 mm 7. Planar displacement of the ink pressurizing chamber on the front and back surfaces of the substrate: 1.
2 mm 8. Thickness of silicon substrate 30: 1 mm 9. Glass diaphragm thickness: 0.2 mm 10. Piezoelectric element: width 1.5 mm, length 2.6 mm, depth 0.15 mm 11. Overall shape of recording head: width 44.3 mm, height 2
9.5 mm, thickness 1.8 mm 12. Driving Voltage Waveform Waveform of FIG. 2: V _A = 100V, V _B = 40V, T ₁ = 2
0 μs, T ₂ = 30 μs, T ₃ = 10 μs Waveform of FIG. 3: V _A = 100 V, T ₁ = 20 μs, T ₂ =
30 μs, T ₃ = 10 μs 13. Ink velocity: Variation in ink velocity among 48 ink nozzles was within the range of 11 to 13 m / s. 14. Bending of vertical line: Max. 38 μm or less.

On the other hand, as a comparative example, the first ink passage 33 is provided.
When the A and 33B are linear without forming a curved or meandering portion and driven under the same conditions as described above, the ink velocity is reduced (5 to 8 m / s) as a whole, and the inside of the ink nozzle is reduced. There was a nozzle that made it impossible to eject ink due to the invasion of bubbles. In addition, the ink pressurizing chambers 34A, 34
The drive voltage waveform is not used properly according to the piezoelectric element corresponding to B, and all the piezoelectric elements have one of the waveforms in FIG. 2 or FIG.
If only the type of ink is used for driving, the variation in ink speed becomes large, and it was not possible to obtain practical print quality.

FIG. 4 shows a main part of another embodiment of the present invention. In this example, a recording head having a resolution of 300 dpi and ink nozzles of 50 is used. This is the same as the previous embodiment. It has been confirmed that even in this recording head, characteristics satisfying the ink speed and the like can be obtained under the same conditions as described above.

[0036]

As described above, according to the first aspect of the invention, since the plurality of ink pressurizing chambers are arranged in a zigzag pattern on the substrate, the ink pressurizing chambers per unit area and hence the number of ink nozzles are increased. The resolution is 20
It is possible to realize a high-density, high-definition multi-nozzle recording head having a number of nozzles of about 48 to 50 at 0 dpi or more. And, even though it is a multi-nozzle recording head, it is possible to make the overall shape small and lightweight. Further, since the ink pressurizing chambers are arranged not directly adjacent to each other through the ink passages, the ink passages serve as a buffer zone to prevent pressure transmission and interference between the ink pressurizing chambers. it can. Furthermore, the length of the second ink passage is set to 2
By using only the types, it is possible to minimize the influence on the ink ejection characteristics.

According to the second aspect of the invention, the difference in the length of the second ink passage can be canceled by the drive voltage waveform, so that the ink ejection characteristics such as the ink speed in all the ink nozzles can be made uniform. This enables high-speed printing and high-quality printing.

According to the third aspect of the invention, by increasing the flow path resistance of the first ink passage, it is possible to prevent the pressure applied to the ink pressurizing chamber from acting in the ink reservoir direction, and to prevent the ink from the ink reservoir. Ink can be continuously and smoothly supplied to the pressurizing chamber. In addition, this also facilitates the flow of ink from the ink pressurizing chamber toward the ink nozzles.

According to the fourth aspect of the invention, by making the planar shape of the ink pressurizing chamber substantially rectangular, it is possible to arrange a large number of ink pressurizing chambers on the substrate without waste, and as a result, it contributes to the formation of multiple nozzles. be able to.

According to the fifth invention, pressure transmission and interference between the ink pressurizing chambers on the front and back surfaces of the substrate are prevented, and the independence of the pressurizing operation in each ink pressurizing chamber can be maintained. ..

[Brief description of drawings]

FIG. 1 is a plan view showing a main part of an embodiment of the present invention.

FIG. 2 is a diagram showing an example of drive voltage waveforms of some piezoelectric elements.

FIG. 3 is a diagram showing an example of a drive voltage waveform of another piezoelectric element.

FIG. 4 is a plan view showing a main part of another embodiment of the present invention.

FIG. 5 is a diagram showing a schematic configuration of a main part of an on-demand type ink jet recording head.

FIG. 6 is an exploded perspective view showing a conventional technique.

FIG. 7 is a plan view of a main part showing another conventional technique.

[Explanation of symbols]

 30 Substrate 31 Ink Pond 32 Island 33A, 33B First Ink Passage 34A, 34B Ink Pressurizing Chamber 35A, 35B Second Ink Passage 36 Trifurcation 37 Ink Nozzle

Claims (5)

[Claims] 1. An ink jet recording head which presses an ink pressurizing chamber provided corresponding to a piezoelectric element by deformation of the piezoelectric element and ejects ink inside the ink nozzle from an ink nozzle, the ink being supplied from the outside. Ink pond,
A plurality of ink pressurizing chambers that communicate with the ink reservoir via the first ink passages and a second ink pressurizing chamber
In an ink jet recording head in which a plurality of ink nozzles that communicate with each other via ink passages are formed on a substrate, second ink passages having two types of length, short and long, are alternately arranged on the substrate, Ink pressurizing chambers that communicate with the short second ink passages are arranged between the second ink passages, and the first ink communicating chambers communicate with these ink pressurizing chambers.
An ink jet recording head, wherein ink pressurizing chambers communicating with the elongated second ink passages are arranged between the ink passages. 2. The ink jet recording head according to claim 1, wherein a piezoelectric element corresponding to the ink pressurizing chamber communicating with the long second ink passage and an ink pressurizing chamber communicating with the short second ink passage. An inkjet recording head characterized in that a corresponding piezoelectric element is driven by voltages having different waveforms. 3. The ink jet recording head according to claim 1, wherein the first ink passage has a curved or meandering portion. 4. The ink jet recording head according to claim 1, 2 or 3, wherein the planar shape of the ink pressurizing chamber is substantially rectangular, and the ratio of the long side to the short side is 1.5 to 3. Characteristic inkjet recording head. 5. The ink jet recording head according to claim 1, 2, 3 or 4, wherein each ink passage, an ink pressurizing chamber and an ink nozzle are formed on both front and back surfaces of a substrate and the front and back ink pressurizing chambers are formed. ,
An inkjet recording head, wherein the inkjet recording heads are arranged so as to be displaced from each other by a predetermined distance when seen in a plan view.