JPH02143863A - Ink-jet printer - Google Patents

Abstract

PURPOSE:To shorten an interval between jetted ink drops by providing in one of a pair of deflecting electrodes an electrode which is applied with a direct current voltage, a layer of a photo-conductive substance formed on the surface of said electrode and a light radiating means for selectively radiating a light to said layer of a photo-conductive substance depending on whether or not flying charged ink drops are necessary. CONSTITUTION:A deflecting electrodes 3A is formed in a layered structure of a glass substrate 3a, a transparent electrode 3b formed on the glass substrate 3a and a layer 3c of a photo-conductive substance formed on the electrode 3b. A laser driving circuit 8a constituting a laser light source 8 drives a laser diode 8b in accordance with a binary signal recorded by a recording signal generating source 5 and at a predetermined timing with a continuous pulse train supplied from a continuous pulse train generating circuit 6. Accordingly, a laser light is generated. The laser light is reflected by a reflecting mirror 9, passing the glass substrate 3a and transparent electrode 3b of the deflecting electrode 3A, and radiated to the layer 3c. Thus, it becomes not necessary to provide a high-speed high-pressure pulse generating mechanism and therefore, manufacturing cost of an ink-jet printer can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an inkjet printer used as a non-impact printer in the field of office equipment.

(Prior Art) In the field of office equipment, inkjet printers are widely used as non-impact printers with low operating noise.

There are two types of inkjet printers: continuous-jet printers that eject ink droplets from the head at predetermined time intervals and selectively deflect only the ink droplets necessary for printing to adhere to the printing paper; It is broadly divided into on-demand type, which selectively sprays only the desired amount from the head.

A typical continuous jet inkjet printer has an inkjet head 11 as shown in FIG.
, a charging circuit 12, a deflection electrode 13, a gutter 14, a recording signal source 15, a continuous pulse train generation circuit 16, and a high voltage pulse generation circuit 17.

The ink in the tank lla of the ink jet head 11 is stored in the ink chamber 1 in which an electric heating element tic is formed on the wall.
1b. The electric heating element (llc) is heated at predetermined time intervals based on voltage pulses supplied from the continuous pulse generating circuit 16 to generate bubbles in the ink chamber. The ink in the ink chamber displaced by the bubbles is ejected forward as ink droplets from a nozzle at the tip of the head. The ejected ink droplets are charged when they pass through a charging mechanism 12 that performs discharge in synchronization with the continuous pulse train. When the charged ink droplets pass between the deflection electrodes 13a and 13b, they are generated by high-voltage pulses generated by the high-voltage pulse generation circuit 17 in synchronization with the binary signal supplied from the recording signal source 15 and the continuous pulse train. Selectively deflected. That is, charged ink droplets necessary for printing are deflected and pass above the gutter and adhere to the printing paper P, while ink droplets unnecessary for printing go straight without being deflected and are collected by the gutter 14.

(Problems to be Solved by the Invention) The conventional continuous jet inkjet printer described above generates high-speed, high-pressure pulses to deflect charged ink droplets. Therefore, there are problems in that the manufacturing cost of the deflection pulse generation circuit increases and failures are more likely to occur.

In addition, in conventional continuous-jet ink shared printers, the length of the deflection electrode cannot be shortened sufficiently due to manufacturing accuracy, so the ejected ink droplets must be spaced to a certain extent, which reduces printing speed. There's a problem.

(Means for Solving the Problems) According to the continuous jet inkjet printer according to the present invention, at least one of the pair of deflection electrodes is an electrode to which a DC voltage is applied, and the electrode is formed on the surface of this electrode. By comprising a layer of photoconductive material and a light irradiation means that selectively irradiates the layer of photoconductive material with light depending on whether or not the charged ink droplets in flight are required for printing, high-speed, high-voltage pulses can be produced. It is configured to eliminate the need for a generation mechanism and to enable shortening of the interval between ejected ink droplets due to the fine irradiation beam width.

Hereinafter, the operation of the present invention will be explained in detail together with examples.

(Embodiment) FIG. 1 is a block diagram showing the configuration of an inkjet printer according to an embodiment of the present invention, in which 1 is an inkjet head, 2 is a charging mechanism, 3 is a polarizer 8 is a laser light source, and 9 is a reflective device. It's a mirror.

The ink in the tank la of the inkjet head 1 is
The ink is supplied to the ink chamber 1b. This inkjet head has an air chamber 1d formed in contact with the ink chamber 1b with an elastic diaphragm 1c in between, and an electric heating element 1e formed within this air chamber. This elastic diaphragm IC is
It is made of a material such as rubber that is highly elastic, heat resistant, and airtight, and keeps the air chamber 1d filled with air at approximately atmospheric pressure. The electric heating element 1e is heated at predetermined time intervals based on voltage pulses supplied from the continuous pulse generation circuit 6, and expands the air in the air chamber.

The ink in the ink chamber lb, which is pushed away by the expanded air through the diaphragm 1c, is ejected forward as ink droplets from a nozzle at the tip of the head.

The ejected ink droplets are charged when they pass through a charging mechanism 2 that performs discharge in synchronization with a continuous pulse train supplied from a continuous pulse train generation circuit 6.

The charged ink droplets are selectively deflected while passing between the pair of deflection electrodes 3A and 3B, and those necessary for printing pass above the gutter 4 and adhere to the printing paper P. Charged ink droplets unnecessary for printing collide with the gutter 4 and are collected.

The deflection electrode 3A has a laminated structure of a glass substrate 3a, a transparent electrode 3b formed thereon, and a layer 3C of photoconductive material further formed thereon. A laser drive circuit 8a constituting a laser light source 8 drives a laser diode 8b according to a binary signal recorded from a recording signal generation source 5 at a predetermined timing with a continuous pulse train supplied from a continuous pulse train generation circuit 6. and generates laser light.

This laser light is reflected by the reflecting mirror 9, passes through the glass substrate 3a of the deflection electrode 3A and the transparent electrode 3b, and is irradiated onto the photoconductive material layer 3C.

Figures 2 and 3 show the distribution of charges and the distribution of potential (V) and electric field strength (E) between the electrode pairs at the center of the deflection electrode pairs 3A and 3B. FIG. 4 is a conceptual diagram showing the cases before irradiation (FIG. 3) and immediately after irradiation (FIG. 4).

Before irradiation with laser light, as shown in FIG.
b and the other deflection electrode 3B, positive and negative charges are distributed almost equally, and a DC high voltage V is supplied from the DC high voltage generation circuit 7. is this transparent electrode 3b and the other deflection electrode 3B
is applied between.

This applies a uniform electric field strength E0 to the flight path of the charged ink droplet. On the other hand, immediately after the laser beam irradiation, as shown in FIG. move to the surface. As this charge moves, the DC high voltage v0 supplied from the DC high voltage generation circuit 7 is applied to the photoconductive material layer 3C and the deflection electrode 3B.
is applied between. Along with this, the electric field strength applied to the flight path of the charged ink droplet increases to the value E0 immediately before laser light irradiation.
It rises from E+ to E+.

Therefore, the charged ink droplets that fly between the pair of deflection electrodes before being irradiated with laser light are only slightly deflected, collide with the gutter, and are collected. On the other hand, the charged ink droplets that fly between the pair of deflection electrodes immediately after being irradiated with the laser beam are deflected by a large amount, pass over the gutter, and adhere to the printing paper.

By turning the laser light source 8 on and off in accordance with the binary signal recorded from the recording signal generation source 5 in this manner, high-speed deflection can be achieved without generating high-frequency, high-voltage pulses.

Above, a configuration in which one of the pair of deflection electrodes is held at a predetermined potential has been exemplified. However, a configuration may also be adopted in which both of the deflection electrode pair have a laminated structure of a transparent electrode and a photoconductive material, and both are irradiated with light at the same time.

Further, a configuration in which a laser light source with a narrow beam width is used as the light irradiation means is illustrated. However, if the purpose is to eliminate the need for a high-speed, high-voltage pulse generation circuit,
Other suitable light sources can also be used, such as wide beam width photodiodes.

Furthermore, an example has been described in which an ink shared head is configured to heat the air in the air chamber that contacts the ink chamber through the diaphragm with an electric heating element. however,
Instead of this head, a normal bubble jet head or piezoelectric head may be used.

(Effects of the Invention) As explained in detail above, the inkjet printer of the present invention
The printer is configured such that at least one of the pair of deflection electrodes has an electrode to which a direct current voltage is applied, a layer of photoconductive material formed on the surface of this electrode, and a layer of photoconductive material formed on the surface of the electrode, and whether or not charged ink droplets are required to be printed in flight. Since the structure includes a light irradiation means that selectively irradiates the photoconductive material layer with light according to the amount of light, a high-speed high-voltage pulse generation mechanism is not required, reducing manufacturing costs and improving reliability. .

Further, since a laser beam with a fine beam width can be realized, an electric field for deflection can be applied only to a very short section of the flight path of a charged ink droplet. As a result, it is possible to shorten the interval between ejected ink droplets.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a continuous jet inkjet printer according to an embodiment of the present invention, and FIGS. 2 and 3 show the distribution of charges on the deflection electrode pair shown in FIG. 1 and the distance between the deflection electrode pair. FIG. 4 is a conceptual diagram showing the potential and electric field strength distribution separately before and after laser beam irradiation. FIG. 4 is a block diagram showing the configuration of a typical conventional continuous jet inkjet printer. 1... Inkjet head, 2... Charging mechanism,
3A, 3B... Deflection electrode pair, 3a... Glass substrate,
3b...Transparent electrode, 3c...Layer of photoconductive material, 4
... Gutter, 5... Recording signal generation source, 6... Continuous pulse generation source, 8... Laser light source. Patent applicant: NEC Home Electronics Co., Ltd.

Claims (4)

[Claims] (1) An inkjet head that ejects ink droplets at predetermined time intervals, a charging means that charges the ejected ink droplets, and an electrical system that charges only those ejected and charged ink droplets that are necessary for printing. In a continuous jet inkjet printer, the continuous jet inkjet printer is provided with electrical deflection means for selectively directing the ink droplets toward the printing space by means of the deflection means, wherein the electrical deflection means are arranged opposite to each other on both sides of the flight path of the ink droplets to be deflected. At least one of the deflection electrode pairs includes an electrode to which a DC voltage is applied, a layer of photoconductive material formed on the surface of this electrode, and a layer of photoconductive material formed on the surface of the electrode, and an ink droplet in flight. an inkjet printer comprising a light irradiation means for selectively irradiating light to the layer of the photoconductive material depending on whether or not it is necessary for printing. (2) The inkjet printer according to claim 1, wherein the light irradiation means comprises a laser light irradiation means. (3) Claims characterized in that the electrode to which a DC voltage is applied constituting the one deflection electrode is made of a transparent electrode, and the layer of photoconductive material is irradiated with light through the transparent electrode. The inkjet printer according to item 1 or 3. (4) The inkjet head has an ink discharge port formed in front of the head, an ink chamber that supplies ink to the ink discharge port, and an ink chamber that is in contact with the ink chamber via an elastic diaphragm and is filled with gas. Claims 1 and 2 include a chamber, an electric heating element installed in the gas chamber, and an energizing circuit that supplies power to the electric heating element at the predetermined time intervals. Or the inkjet printer according to item 3.