JPH0356664B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to an inkjet recording head that uses electrostatic force to eject ink liquid to draw images such as characters and figures on a recording medium. BACKGROUND OF THE INVENTION The present applicant previously provided an inkjet recording head using airflow and electrostatic force, as shown in Japanese Patent Application Laid-open No. 120452/1983. To explain the principle of ejecting this ink liquid, as shown in FIG. 2, air ejection ports 101 are perforated in an insulating air nozzle plate 102 attached to a body member 113, and are approximately parallel to the air nozzle plate 102. An insulating ink nozzle plate 103 is arranged, and an ink discharge port 104 is perforated in the ink nozzle plate 103 facing the air discharge port 101 .
Air flows into the air supply path 108 from an air supply source 120, is made uniform in an annular air chamber 109, and flows from around the air layer 107 created by the air nozzle plate 102 and ink nozzle plate 103. , is flowing out from the air outlet 101. On the other hand, the ink chamber 110 adjacent to the ink discharge port 104 has an ink reservoir 111 and an ink supply path 106.
A constant pressure is applied to the ink in the ink reservoir 111 by air from an air supply source 120. This constant pressure is optionally regulated by a pressure regulating machine 121. This is because when the ink jet recording head is not driven, the air pressure near the ink ejection ports 104 and the ink pressure in the ink ejection ports 104 or the ink chamber 110 are approximately equal, and the meniscus of ink in the ink ejection ports 104 is kept stationary. This is to make adjustments so that the The signal source 105 is connected to the air outlet 10
1 and an electrode 115 provided around the back surface of the ink ejection port 104 to generate a potential difference between the electrode 112 and the electrode 115. Due to the electrostatic force caused by this potential difference, the meniscus of ink liquid generated at the ink ejection port 104 is stretched in the direction of the air ejection port 101 . Furthermore, since a constant air flow flows out from the air outlet 101 via the air layer 107, when the meniscus is stretched beyond a certain length, it is accelerated by the air flow, and the air outlet 101
Fly more. In order to increase the recording speed of an inkjet recording head having such a configuration, a multi-structure in which a plurality of air discharge ports 101 and ink discharge ports 104 are arranged side by side is used, as shown in Japanese Patent Laid-Open No. 58-220758. Bye. The multi-nozzle head also ejects ink using the same principle as the single nozzle head. Problems to be Solved by the Invention When the ink ejection ports 104 have a multi-head structure, an ink chamber 110 having a plurality of ink ejection ports 104 has an electrode 115 arranged near each ink ejection port 104 and an electrode 115 arranged outside the ink chamber 110. A potential difference is generated between the electrode 112 provided at the electrode 112, and the electrostatic force causes discharge. In this case, it is rare that ink is ejected from all the ink ejection ports 104 at the same time, and therefore, the plurality of electrodes 115 in the ink chamber 110 simultaneously apply the same potential difference to the electrode 11.
It is rarely added between 2 and 2, and it is added randomly to each electrode in the electrodes 115. In other words, if we focus on the individual electrodes among the electrodes 115, some of the electrodes 115 have a potential difference between them and the electrode 112 that allows ink to be ejected, while other electrodes 115 maintain a potential difference that does not allow ink to be ejected. Become. In such a case, a potential difference occurs between the individual electrodes 115, and this potential difference may reach several hundred volts. When such a high voltage is generated between the individual electrodes 115, a current flows through the ink between the electrodes 115, causing an electrochemical reaction between the electrodes 115 and shortening the life of the electrodes themselves. . SUMMARY OF THE INVENTION Therefore, the present invention provides an inkjet recording head that can prevent electrochemical reactions between the electrodes in the multi-structured head, thereby increasing the service life of the head. Means for Solving the Problems Technical means of the present invention for solving the problems described above include an ink chamber, a plurality of ink discharge ports communicating with the ink chamber, and an ink chamber provided outside the ink chamber. a plurality of air ejection ports corresponding to each ink ejection port; a plurality of first electrodes provided around each ink ejection port in the ink chamber; A potential difference is generated between a second electrode provided in the ink chamber, a third electrode provided around the air discharge port, and the first and third electrodes, and the first and second electrodes are and means for generating a potential difference between the electrodes. Function The present invention generates a potential difference between the first and third electrodes with the above configuration. The electrostatic force caused by this potential difference stretches the ink meniscus generated at the ink ejection port toward the air ejection port. During this time, an air stream is flowing out from the air outlet, so when the meniscus is extended beyond a certain length, it is accelerated by the air stream, flies out of the air outlet, reaches the recorded object, and prints characters, figures, etc. It is possible to draw an image of At this time, since there is no potential difference between the first electrode in the non-ejection state and the third electrode that enables ejection, there is no potential difference between the first electrode in the non-ejection state and the first electrode in the ejection state. However, by applying a potential equal to or less than the potential difference between the non-ejection state and the ejection state using the second electrode, the potential difference between the two electrodes is substantially lowered, and the electrochemical effect between the two electrodes is reduced. Reactions can be prevented. Embodiment Hereinafter, an embodiment of the present invention will be described in detail based on the drawings. An enlarged view of a nozzle portion in an embodiment of the present invention is shown. Other parts are similar to the conventional example shown in FIG. As shown in FIG. 1, an insulating air nozzle plate 2 is attached to an insulating body member 13,
A plurality of air discharge ports 1 are formed in this air nozzle plate 2. An insulating ink nozzle plate 3 is attached to the body member 13 substantially parallel to the air nozzle plate 2, and a plurality of ink discharge ports 4 are formed in this ink nozzle plate 3 in correspondence with the air discharge ports 1. ing. An ink chamber 10 is formed inside the ink nozzle plate 3 in the body member 13, and the ink supply path 6 is communicated with the ink chamber 10.
A first electrode 15 is provided on the back surface of the ink nozzle plate 3 around each ink discharge port 4 .
A second electrode 22 is provided on the inner wall of the ink chamber 10 facing the ink nozzle plate 3 . That is, the first and second electrodes 15 and 2 are provided in the ink chamber 10.
2 are provided facing each other. A third electrode 12 is provided on the surface of the air nozzle plate 2 around the air outlet 1 . In addition, an air chamber, an air supply path, an indoor supply source, an ink reservoir, a pressure adjustment mechanism, a signal source, etc. are provided in the same manner as in the prior art. Next, the operation of the above embodiment will be explained. A potential difference is generated between the desired first electrode 15 and the third electrode 12 by a power source, and the meniscus of the ink liquid generated at the ink discharge port 4 is stretched in the direction of the air discharge port 1 by the electrostatic force caused by this potential difference. . Further, since a constant air flow flows out from the air outlet 1, when the meniscus is stretched beyond a certain length, it is accelerated by the air flow, and the air outlet 1
Fly more. At this time, the first electrode 1 in the discharge state
5 and the first electrode 15 in the non-ejection state. Therefore, by using the second electrode 22, a potential difference equal to or less than the potential difference between the first electrode 15 in the ejecting state and the first electrode 15 in the non-ejecting state is used, regardless of the potential difference for ejecting ink. By applying a potential, the first
The potential difference between the electrodes 15 can be lowered.
Therefore, an electrochemical reaction between the first electrodes 15 can be prevented. Next, test examples will be explained. As a comparative test example of the present invention, copper was used for the first electrode 15 and the third electrode 12, and ink having a specific resistance of 3×10 ⁵ Ωcm was used. Therefore, the potential difference (bias voltage) between the first electrode 15 and the third electrode 12 during non-ejection
is set to 500 V, and when ejecting ink, 700 V is further added to this potential difference, so that a part of the first electrode 15 is in the ejecting state, and the other first electrode 15 is in the non-ejecting state,
A potential difference of 700V was created between the individual electrodes of the first electrode 15. On the other hand, as a test example of the present invention, the second
Copper was used for the electrode 22, and under the same conditions as above, the potential difference between the second electrode 22 and the non-ejection electrode of the first electrode 15 was set to 350V. Changes in the first electrode 15 were compared between this comparative test example and the present invention test example over a test time of 200 hours and with the voltage conditions fixed. (Note that the area of the second electrode 22 is three times that of the first electrode 15.) As a result, the area of the second electrode 15
In the case of the comparative test example in which the second electrode 22 was not used, the wear of the first electrode 15 was 1.6 times greater than in the test example of the present invention in which the second electrode 22 was used.
The effect of using the second electrode 22 was observed. As another test example, changes in the first electrode 15 by changing the electrode voltage of the second electrode were tested under the same conditions as the test example of the present invention, and the results are shown in Table 1. , the consumption amount of the first electrode 15 when the second electrode 22 is set to 550V is set to 1.)

[Table] From the above test results, the consumption of the first electrode 15 is reduced by increasing the voltage of the second electrode 22,
It is clear that the electrode life is increased. Also, from this test result, if the voltage is increased above 550V,
Since the second electrode 22 will be consumed and the power supply current required for the head will increase, in practice, it may be less than 550V, and if it is less than 250V, the effect of the second electrode 22 will be low, so if it is more than 150V, It turned out that it was actually necessary. In addition, although the case where a copper electrode was used as an electrode was explained in the said Example, it is clear that the effect of the said 2nd electrode will be produced even if an electrode of other materials is used. Effects of the Invention As is clear from the above description, according to the present invention, first electrodes are respectively provided in the periphery of a plurality of ink discharge ports in an ink chamber, and
A second electrode is provided opposite to the electrode of A potential difference is created between them.
Therefore, the potential difference between the first electrode in the ejection state and the non-ejection state can be reduced, electrochemical reactions between these electrodes can be prevented, and the service life can be extended.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the main parts of an embodiment of an in-jet recording head according to the present invention, and FIG. 2 is a schematic diagram of a conventional in-jet recording apparatus. 1...Air discharge port, 2...Air nozzle plate, 3...
...Ink nozzle plate, 4...Ink discharge port, 6...
Ink supply path, 10... ink chamber, 12... third
13...body member, 15...first electrode, 22...second electrode.

Claims (1)

[Scope of Claims] 1. An ink chamber, a plurality of ink ejection ports communicating with the ink chamber, a plurality of air ejection ports provided outside the ink chamber and corresponding to each ink ejection port, and an ink chamber. a plurality of first electrodes provided in the room around each ink ejection port, a second electrode provided in the ink chamber facing the first electrodes, and a periphery of the air ejection port. An ink jet characterized by comprising: a third electrode provided in the part; and means for generating a potential difference between the first and third electrodes, and generating a potential difference between the first and second electrodes. Record head. 2 The potential difference between the first and second electrodes is 150 to 550V
An inkjet recording head according to claim 1, which falls within the scope of claim 1.