JPH10166592A - Electrostatic attraction type ink jet recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent air from being mixed in a nozzle owing to a reverse flow of ink by enabling ink to fly at high speed by quickening discharge of ink by a method wherein an exciting pulse of a specific frequency is applied to a nozzle, and a printing pulse is applied to print timing with a piezoelectric element. SOLUTION: A diaphragm 3 wherein a piezoelectric element 4 is respectively arranged by abutting against an opposed face of a nozzle 2 of a conductor of a nozzle head 1 is provided. Ink A filled in the nozzle head 1 is discharged from the nozzle 2 by vibration of print timing, made to fly to ward a rear face electrode 5 with a potential difference, and printed on recording paper B conveyed between the nozzle 2 and the rear face electrode 5. Further, a voltage pulse PI for excitation is collectively periodically applied irrespective of printing to all nozzles 2. Besides, at the print timing a voltage pulse for printing P2 is applied individually to both faces 4a, 4b of the piezo element 4, the diaphragm 3 is vibrated with generated distortion of both faces 4a, 4b, and vibromotive force thereby, and the ink A is excited to be discharged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for improving ink flying properties in an electrostatic suction type ink jet recording apparatus.

[0002]

2. Description of the Related Art Conventionally, in an electrostatic suction type ink jet recording apparatus, there is a type in which a print pulse is applied to a nozzle at a print timing to cause ink to fly toward a back electrode. as,
There are a type in which a pulse is applied directly to a nozzle and a type in which a pulse is applied via a piezo element (quartz oscillator).

[0003]

In order to obtain high printing accuracy, it is sufficient to increase the number of nozzles (that is, the number of dots). The ability to fly is required. In the conventional method of applying a print pulse of a charge enough to cause the ink to fly only in the print timing, the ink is retracted from the nozzle tip while the print pulse is not applied.
Even when a print pulse is applied, there is a problem that ink is not ejected from the nozzles well and printing accuracy is reduced. Also,
When the application means is a piezo element, a strong vibrating force can be obtained when the applied frequency and the natural frequency of the flat crystal plate are matched, but the swing back is also strong, so At the end of the application of the print pulse, there is a problem that a backflow phenomenon of the ink occurs, air is mixed into the nozzles, and it is impossible to fly the ink uniformly.

[0004]

The present invention uses the following means in order to solve the above problems. First of all, an electrostatic suction type ink jet recording apparatus for ejecting ink from a convex conductive nozzle toward a back electrode, in which the ink is ejected by a print pulse applied at a print timing, the ink is ejected to the nozzle. , An excitation pulse having a constant period is applied, and the printing pulse is applied by a piezo element.

Second, in the electrostatic suction type ink jet recording apparatus having the above-described configuration, a printing pulse by a piezo element is applied in synchronization with one of the excitation pulses.

Third, in any one of the above-mentioned electrostatic suction type ink jet recording apparatuses, an oil-based ink having a volume resistivity of 10 ⁵ to 10 ¹⁰ Ω is used as the ink.

[0007]

Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic diagram of a configuration of an electrostatic suction type inkjet recording apparatus of the present invention, and FIG. 2 is a sectional view of a nozzle tip showing a meniscus state of ink.

Referring to FIG. 1, the configuration of the present invention will be described. In the nozzle head 1, a plurality of conductive nozzles 2 projecting in a convex shape are provided on one surface, and further, the nozzle head 1 has individual nozzles 2, 2. A diaphragm 3 is disposed so as to face the nozzle 2 of each of the above, and a piezo element (quartz oscillator) 4 is arranged in contact with each of the diaphragms 3. Also, the nozzle 2 of the nozzle head 1
The back electrode 5 is provided so as to face the tip of 2.

In printing, the recording paper B is conveyed between the nozzles 2, 2... And the back electrode 5, and the ink A filled in the nozzle head 1 is vibrated at the printing timing to make each nozzle 2 The nozzle 2 side and the back electrode 5
With the voltage difference between the recording paper B and the recording paper B interposed in the middle, the ejected ink A is sucked toward the back electrode 5 and caused to fly.
Is printed.

.. For all the nozzles 2,..., Collectively and periodically, a voltage pulse for excitation (excitation pulse) P1
(For example, 500 to 2000 V).
The excitation pulse P1 is periodically applied to all the nozzles 2 regardless of printing.

When each nozzle 2 comes to a printing timing, 4a of the piezo element 4 facing the nozzle 2
A voltage pulse (print pulse) P2 (for example, 30 to 200 V) for printing is individually applied to both sides of 4b. Due to this application, a strain is generated between the two surfaces 4a and 4b of the piezo element 4, which becomes a vibrating force, and the vibration plate 3 in contact with the piezo element 4 vibrates. The ink A inside vibrates and is ejected from the tip of the nozzle 2.

FIG. 2 shows the effect of applying the excitation pulse P1.
A more detailed description will be given. In the case where the ink is caused to fly only by the print pulse as in the related art, when no ink is applied, the ink tends to retract inside the discharge port at the tip of the nozzle 2, and even if the ink protrudes from the discharge port, the amount of protrusion is small. Trace amount. When the excitation pulse P1 is periodically applied in a state where the print pulse P2 is not applied, the ink A protrudes from the discharge port of the nozzle 2 to a state in which the ink A rises to the longest value L1. This state is called meniscus. When the excitation pulse P1 is intermittent, the voltage becomes 0, and the ink A tries to retract inside the ejection port. However, until the ink P is completely retracted, the next excitation pulse P1 is applied again. The amount of retraction is suppressed to the projection length of the shortest value L2 shown in FIG.
The meniscus is retained. Further, in order to prevent the ink A from completely retracting, even when the next excitation pulse P1 is applied, the ink A protrudes again to the maximum value L1.

When the print pulse P2 is applied in a state where such a meniscus is held, the ink A is ejected very quickly, thereby enabling high-speed flying. Further, the print pulse P2
Is synchronized with the application timing, not the intermittent excitation pulse P1, so that the ink A has the protruding amount of the longest value L1 and is ejected and flies more quickly.

When the ink is flying only by applying the printing pulse by the piezo element 4, the vibration of the diaphragm 3 is large. 2 Nozzle 2 from the discharge port at the tip
In this case, the air is mixed into the nozzle head 1 and the ink cannot be jetted uniformly. However, by using the ink in combination with the excitation pulse P1, the harmful effects of air mixing can be avoided, and the piezo element 4 In addition, high-speed ink flying is effectively performed by the vibrating force generated by the diaphragm 3.

In order to obtain a meniscus state as shown in FIG. 2 by applying the excitation pulse P1, the volume resistivity of the ink A, which is a semiconductor, is preferably set to ^{10 5} Ω to 10 ¹⁰ Ω. is there. Generally, the oil-based ink has a volume resistivity, and the advantages such as the storability of the recording paper can be utilized by using the oil-based ink.

[0016]

According to the electrostatic suction type ink jet recording apparatus of the present invention, the following effects can be obtained by adopting the above configuration. First, by configuring as described in claim 1, the nozzle is constantly applied with an excitation pulse, so that a meniscus of ink is formed in a vibrating state at the nozzle tip,
When a printing pulse is applied to the ink and a vibrating force is applied to the ink, the ink is ejected very quickly, and high-speed flight is possible. Further, the problem that air is mixed into the nozzles due to the backflow of ink due to the application of the printing pulse of the piezo element is also eliminated, and an effective high-speed ink jet can be obtained by the strong vibrating force of the piezo element.

According to the second aspect of the present invention, by synchronizing the print pulse with any of the excitation pulses, the print pulse is applied in a state where the ink projects most from the nozzle tip. Discharge becomes quick, and ink flies at higher speed.

According to the third aspect of the present invention, by setting the volume resistivity of the ink, a meniscus of the vibration state of the ink at the nozzle tip is suitably formed, and the effects of the first and second aspects are reliably obtained. Can be In addition, an oil-based ink having good storability can be used effectively, and its advantages can be utilized, and the storability of recording paper can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a configuration of an electrostatic suction type inkjet recording apparatus of the present invention.

FIG. 2 is a sectional view of a nozzle tip showing a meniscus state of ink.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Nozzle head 2 Nozzle 3 Vibration plate 4 Piezo element (quartz oscillator) 5 Back electrode A Ink B Recording paper P1 Excitation pulse P2 Print pulse

Claims (3)

[Claims] 1. An electrostatic suction type ink jet recording apparatus for ejecting ink from a convex conductive nozzle toward a back electrode, wherein the ink is ejected by a print pulse applied at a print timing. An electrostatic suction type ink jet recording apparatus, wherein an excitation pulse having a constant period is applied, and the printing pulse is applied by a piezo element. 2. The electrostatic suction type ink jet recording apparatus according to claim 1, wherein a printing pulse by the piezo element is applied in synchronization with any one of the excitation pulses. 3. The electrostatic suction type ink jet recording apparatus according to claim 1, wherein an oily ink having a volume resistivity of 10 ⁵ to 10 ¹⁰ Ω is used as the ink. .