JPS5849267A - Ink jet printer - Google Patents

Abstract

PURPOSE:To provide a subject printer which provides a clear reproduced picture through combination of a conventional graduation recording means, by constituting the printer such that a distance between each nozzle and a needleform electrode differs from each, and the number of nozzles, which causes ink to fly, varies with a change in a potential apllied to the needleform electorde. CONSTITUTION:A single needleform electrode 9 is installed facing and opposite to a nozzle group consisting of a plural number of nozzles 8a, 8b.... A switching circuit 10 for changing an applied voltage corresponding to a graduation of a picture signal S0 is connected to the needleform electrode 9. A distance between each of the nozzles 8a, 8b... and the single needleform electrode 9 varies with each nozzle. In case low density is demanded, a low voltage V1 is applied to reduce the number of the nozzles which causes flying of ink, and in case a high density is demanded, a high voltage V3 is applied to increase the number of the nozzleswitch causes flying of ink.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inkjet printer equipped with a multi-nozzle head having several nozzles.

Conventional printing devices and information output terminals record various types of output information by colliding wire heads, type, etc. with recording paper via an ink ribbon, but the noise during recording is quite large, making it difficult to compare. When used in quiet offices, etc., it caused noise pollution. As an output device to solve these problems, a so-called inkjet type output device (inkjet printer) has been developed in recent years, which uses some means to eject liquid ink and attach it to recording paper to record various output information. and is beginning to be commonly used. Inkjet methods can be roughly divided into four methods: charge control method, ink on demand method, electric field control method, and ink mist method. The charging control method uses a vibrator to constantly eject ink in the form of droplets, and this ejected ink is electrically charged.
Thereafter, output information is recorded by deflecting the charged ink droplets using an electric field.

The ink-on-demand method is a method in which a piezoelectric element applies pressure to an ink reservoir according to output information, causing ink to fly, thereby recording on recording paper. The electric field control method is a method in which a potential is applied between a nozzle opening and a recording paper according to output information, and ink is drawn out from the nozzle opening and attached to the recording paper by electrostatic attraction to perform recording. The ink mist method uses a vibrator to atomize the ink held in the ink reservoir, selectively ionizes the atomized ink using electrical discharge according to the output information, and then uses electrostatic It is attached to the recording paper by gravity. The inkjet printer of the present invention is an electric field control type inkjet printer. Conventionally, the nozzle head in an electric field control type inkjet printer has a single nozzle opening. A method has been used in which recording is performed on the entire recording paper by scanning in the direction, that is, in the line direction. However, this method has the problem that recording is performed at a relatively low speed because the nozzle head is mechanically scanned. In order to solve this problem, we use a multi-nozzle head that has multiple nozzles lined up in a straight line in the line direction, and can print multiple nozzles according to the output information without mechanically scanning the nozzle head. A method has been proposed in which one line of information is recorded almost simultaneously by selectively ejecting ink from nozzles.

A schematic diagram of an inkjet printer equipped with such a multi-nozzle/rad having a plurality of nozzles is shown in FIG.

A multi-nozzle head 1 having a plurality of nozzles arranged in a straight line is installed so that the plurality of nozzles arranged in a straight line are perpendicular to an arrow 3 in the transport direction of the recording paper 2. A counter electrode 4 having a plurality of needle-shaped electrodes of the same number as the number of nozzles in the head 1 is arranged through the recording paper 2 so that the nozzles of the multi-nozzle head 1 and the needle-shaped electrodes of the counter electrode 4 correspond one-to-one. is set up. The liquid ink is pressurized by the pressure pump 5 or static ink pressure, thereby forming a hemispherical meniscus at the nozzle opening of each nozzle of the multi-nozzle head 1. By controlling and processing serially inputted output information by a control circuit, and applying a voltage corresponding to the output information processed by the control circuit between the voltage application terminal 6 and the counter electrode 4 by a drive circuit, that is, by controlling the counter electrode By applying a selective voltage to each of the needle electrodes 4 in accordance with the output information, the meniscus of ink formed at each nozzle opening is selectively ejected by electrostatic attraction and adheres to the recording paper 2. The output information is recorded. Since the recording paper 2 is being transported at a constant speed in the direction of the arrow 3 by the feed roller 7, after recording the output information for one line, the output information for the next line is recorded, thereby covering the entire recording paper 2. Output information can be recorded.

There is a strong demand for outputting images with halftones, such as photographs, using an inkjet printer having a multi-nozzle head configured as described above, but conventional inkjet printers have no method of producing gradations. There are known methods that adjust the number of ink droplets to be ejected, and a method called area gradation in which one pixel is composed of multiple matrices, but even if the above two are combined, the number of gradations that can be obtained is at most ten. The problem is that it is difficult to obtain clear and high-quality reproduced images.

An object of the present invention is to have a mechanism capable of creating new gradations different from conventional ones, and to perform output recording with high gradations when used in combination with conventional gradation recording means. Our goal is to provide an inkjet printer that can.

The inkjet printer of the present invention is an inkjet printer equipped with a multi-nozzle head having a plurality of nozzles. The distance between a needle electrode having an end face facing each nozzle of the nozzle group and the plurality of nozzles constituting the nozzle group is different for each nozzle.

Therefore, by changing the potential applied between the nozzle group and the acicular electrode according to the gradation of the image signal, the number of nozzles that eject ink can be varied, and gradation recording can be achieved. It can be done.

By using the inkjet printer of the present invention in combination with conventional gradation recording means, output recording with high gradation can be performed, and continuous gradation images such as photographs can be printed with clear and high quality. Output recording can be performed as a reproduced image.

Hereinafter, the inkjet printer of the present invention will be explained in detail with reference to the drawings.

FIGS. 2A and 2B are schematic diagrams showing the basic operating principle of gradation recording performed in the inkjet printer of the present invention.

Three nozzles 8a, 8b, and 8C constitute one nozzle group, and one needle electrode 9 faces the nozzle group.
is provided.

The needle-shaped electrode 9 has nozzles 8a and 8a, depending on the gradation of the image signal SO.
A switching circuit 10 is connected so that the voltage applied between 8b, 8c and the needle electrode 9 can be changed.

The distance between the three nozzles 8a, 8b, 8c and the end face of one needle electrode 9 is different for each nozzle.
The magnitude of the electric field formed between a, 8b, 8c and the needle electrode 9 differs for each nozzle.

Therefore, the voltage applied to the needle electrode 9 according to the gradation of the image signal SO is set in three stages (V+ (V2<V3
) to eject ink from only nozzle 8a, to eject ink from nozzles 8a and 8b, and to eject ink from all nozzles 8a, 8b, and 8c. .

Therefore, when a relatively low concentration is required as shown in FIG. 2A, the voltage applied to the needle electrode 9 is set to Vl by the switching circuit io, and the voltage applied to the needle electrode 9 is set to Vl. Only the electric field formed between them becomes an electric field sufficient to make the ink fly, and the ink can be made to fly from the nozzle 8a. In addition, when a high concentration is required as shown in FIG. 2B, the switching circuit 10 applies a voltage of All the nozzles 8a are made to have an electric field that is sufficient to cause the ink to fly.

Ink from 8b and 8c? It can be made to fly.

FIG. 3 is a schematic diagram illustrating a preferred embodiment of the inventive inkjet printer.

In this embodiment, one nozzle group lla is constituted by three nozzles 8a- and 8bs8c in the multi-nozzle head 1, and one pixel can be formed by one nozzle group. Each nozzle group 11a, l
Needle-like electrodes 9a, 9b, and 9c are provided on the lh and llc to face each other.

Between the nozzle and the needle electrode, flying ink is placed on the recording paper 2 so that area gradation in a 3x3 matrix is performed.
A deflection electrode 12 is provided for deflecting in the direction of transport. The end faces of the needle electrodes 9a, 9b, and 9c facing the nozzles have an inclination so that the distance between each nozzle of the nozzle group and the needle electrode is different for each nozzle. The conveyance means for the recording paper 2 and the ink pressure means (not shown) are the same as those shown in FIG. 1.

In the inkjet printer configured in this way, three nozzles 8a, 8b, 8c forming the nozzle group 11a are used as explained using FIGS. 2A and 2B.
The number of nozzles that eject ink is the image signal So
By changing the voltage applied to the needle-like electrode 9a according to the gradation, the voltage can be changed in three stages, so three gradations can be obtained.Also, by performing area gradation using the deflection electrode 12, Nine gradations can be obtained, and several gradations can be obtained by changing the number of ejected ink droplets, so approximately 30 to 60 gradations can be obtained with the configuration shown in FIG.

For example, FIG. 4 shows the state of one pixel recorded on the recording paper according to this embodiment.

One pixel 13 consists of nine small parts 14a, 14b, 14c
, 14d.

It consists of nozzles 14e, 14f, 14g, 14h, and 14i, and the small parts 14a, 14b, and 14c are nozzles 8a and 8b, respectively.

This is the part where recording is done with ink flying from 8c, and small parts 14d, 14e, 14f, and 14g.
, 14h, and 14i indicate areas actually recorded with ink by changing the number of ink droplets ejected from the nozzle 8a into three stages by the deflection electrode 17.

As described above, if the recording capacity is 30 to 60 gradations, a reproduced image that is almost as good as the original image can be obtained even when a continuous gradation photograph or the like is output and recorded.

The number of nozzles constituting the horn nozzle group is not limited to three as in the above embodiment, but may be any number as long as it is plural. Further, the number of nozzle groups constituting one pixel is not limited to one, and several nozzle groups may be arranged in parallel when the deflection electrode 12 as in the above embodiment is not used.

Furthermore, in addition to the method in which the distance between the plurality of nozzles constituting a nozzle group and the needle-like electrode is changed by tilting the end face facing the nozzle of the needle-like electrode as in the above embodiment, the nozzle of the needle-like electrode The end surface facing the multi-nozzle head 1 may be inclined.

As explained above in detail, the inkjet printer of the present invention can change the number of nozzles that eject ink by changing the voltage applied between the nozzles and the needle-like electrodes that make up the nozzle group. 1. When used in combination with conventional gradation recording means, continuous gradation images such as photographs can be output and recorded as clear and high quality images. Furthermore, since only one needle-like electrode is required for one nozzle group, there is no difficulty in microfabrication and the manufacturing process of the counter electrode is simplified.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an inkjet printer equipped with a multi-nozzle head, FIGS. 2A and 2B are schematic diagrams showing the basic operating principle of gradation recording performed in the inkjet printer of the present invention, and FIG. 3 is a diagram of the present invention. A schematic diagram showing a preferred embodiment of the inkjet printer of the invention. FIG. 4 is a diagram showing the state of one pixel obtained in the embodiment shown in FIG. 3. 1...Multi-nozzle head 2...Recording paper 4...
- Counter electrodes 8a, 8b, 8c... Nozzles 9, 9a, 9b, 9c... Needle electrodes 10...
Switching circuit 11a, llb, llc... Tuzzle group 1
2... Deflection electrode 13... One pixel

Claims (1)

[Claims] 1) A multi-nozzle head having a plurality of nozzles arranged in a straight line for ejecting ink, and a multi-nozzle head installed opposite to the nozzle for drawing ink from the nozzle by electrostatic attraction. a counter electrode, a transport means for transporting recording paper installed between the multi-nozzle head and the counter electrode, and a plurality of nozzles configured to selectively eject ink from the plurality of nozzles in accordance with an image signal. In an inkjet printer comprising a control means for selectively applying a voltage between each nozzle and the counter electrode according to the image signal, one pixel is selected from at least one nozzle group consisting of a plurality of nozzles. The counter electrode is provided for each nozzle group and includes a needle-shaped electrode having an end face facing each nozzle of the nozzle group, and the counter electrode is provided for each nozzle group and has an end face facing each nozzle of the nozzle group, and the opposite electrode is provided for each nozzle group. An inkjet printer characterized in that the distance between the needle electrode and the end surface is different for each nozzle. 2) Claims characterized in that the control means varies the voltage applied between the plurality of nozzles constituting the nozzle group and the needle electrode according to the gradation of the image signal. The inkjet printer according to item 1.