JP2002234165A - Electrostatic ink jet recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an image quality deterioration of printing images resulting from variations of recording electrodes in an electrostatic ink jet recorder. SOLUTION: There are provided a slit-shaped ink discharge part for discharging ink including charged color material particles, a plurality of recording electrodes arranged at predetermined intervals in a widthwise direction of the ink discharge part for providing discharge positions where ink is discharged, counter electrodes disposed opposite to the recording electrodes for discharging ink by an electrostatic suction force from the recording electrodes, and a control unit for controlling a voltage to be impressed to the recording electrodes and the counter electrodes. Gradation level printing is carried out by applying recording electrode signals of a duty ratio pattern among a plurality of duty ratio patterns of recording electrode signals corresponding to gradation levels.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic ink jet recording apparatus and, more particularly, to a technique which is effective when applied to a reduction in image quality of a printed image.

[0002]

2. Description of the Related Art Ink jet technology is widely used in office automation and personal information recording devices, such as copiers, facsimile machines, printers, and word processors, as a printing technology capable of obtaining high quality images at low cost and at high speed.

[0003] Ink-jet recording principles include those using a heating resistor such as an electrothermal conversion element as an energy generating means for flying a color material, those using a piezo element such as an electromechanical conversion element, There is an electrostatic type that uses electric energy as it is.

[0004] Among them, in the electrostatic ink jet, the production of the recording head is simpler than other methods, and
There is an advantage that area gradation recording can be performed by controlling an electric signal applied to the recording electrode. Further, the amount of current consumed at the time of recording is remarkably small, and it can be said that this is a recording technology that is useful in the future as an energy-saving device. Furthermore, by using an oil-based pigment ink, printing with excellent water resistance can be performed, and the utility value is particularly high for office automation applications.

Here, the principle of the electrostatic ink jet will be briefly described. When a recording voltage of several kV is applied between a recording electrode filled with ink and a counter electrode holding a recording medium, when a recording voltage exceeds a certain threshold, an electrostatic force acting on the ink is generated. The ink droplets are ejected from the recording electrode to the counter electrode, overcoming the surface tension of the ink.

The configuration of an electrostatic ink jet recording apparatus based on this principle is described, for example, in US Pat.
No. 6 discloses a "slit type ink recording apparatus", and Japanese Patent Application Laid-Open No. 56-4467 discloses that "an ink ejection port is formed in a slit shape, and a number of electrodes are arranged on the inner surface of the slit. Ink recording head "which is disclosed. In this technique, a nozzle hole is not necessarily required for each recording electrode, and a so-called slit type common to a plurality of recording electrodes can be used for an ink discharge unit.
A feature of such a configuration is that clogging due to drying of ink is reduced by not providing a nozzle. Therefore, this configuration is not only a so-called serial type head which has several hundred recording electrodes and scans in the width direction of the recording medium, but also a so-called line type head having recording electrodes for the width of the recording medium. It is also very effective.

In the case of a configuration having a plurality of recording electrodes,
In order to operate each recording electrode independently, it is necessary to prevent a leak of electric charge due to forming a closed loop with an adjacent electrode. For this purpose, an oily solvent having a high electric resistance is usually used as a solvent for the ink. As a coloring material, an oil-based pigment or an oil-based dye can be used. However, an oil-based pigment is mainly used because of its variety.

However, in a usual electrostatic ink jet recording apparatus, since both the color material particles and the solvent receive an electrostatic force, a relatively large amount of solvent is discharged together with the color material particles, and the print density is reduced. There was a problem that.

In order to solve this problem, for example, Japanese Patent Application Laid-Open No. H8-295023 (hereinafter referred to as “A”) discloses a technique of “discharging only toner particles in ink from a discharge unit and controlling the discharge. By applying alternating current to the electrodes according to the toner consumption of the recorded image, regardless of the recorded image,
An electrostatic ink-jet recording apparatus capable of stabilizing the amount of discharged toner and obtaining recording of high print quality without unevenness is disclosed.

Japanese Patent Application Laid-Open No. 9-193389 (hereinafter referred to as “B”) discloses that “ink containing a dielectric carrier liquid having high electric resistivity as a constituent component is used. An ink jet recording apparatus characterized in that a force is applied only to the solid component charged toner particles dispersed in the toner to cause the toner to fly.

Here, the operation of the recording apparatus described in the publications A and B will be briefly described below.
It is assumed that the coloring material particles are positively charged.

FIGS. 5A and 5B are explanatory views showing the configuration of a recording head of a conventional electrostatic ink jet recording apparatus described in Japanese Patent Application Publication Nos. A and B, where FIG. ) Is a perspective view from the top of the head.

As shown in FIG. 5, the recording head has an upper head block 8 and a lower head block 9.
The head blocks 8 and 9 form an ink discharge section 5 that is a slit-shaped opening through which ink is discharged, and an ink flow path 7 that is a flow path of ink toward the ink discharge section 5. .

A recording electrode 1 whose tip protrudes from the ink discharge section 5 to discharge ink from the ink discharge section 5, and an aggregation electrode 2 that selectively aggregates color material particles on the recording electrode 1.
Are formed on a thin electrode substrate 10 having an insulating property.

Further, in the vicinity of the ink ejection section 5, an electrophoretic electrode 3 for concentrating color material particles on the ink ejection section 5 by an electrophoresis phenomenon is arranged. In addition, the migration electrode 3 may be provided in the ink flow path 7.

A counter electrode 4 is provided at a position facing the recording electrode 1.
A recording medium 6 on which ink ejected from the recording electrode 1 toward the opposing electrode 4 adheres by electrostatic attraction to perform printing is set on the front surface of the opposing electrode 4.

FIG. 6 is an explanatory diagram showing an example of a voltage waveform applied to each electrode provided in the recording head of FIG.

In one printing cycle T, a negative potential is applied to the counter electrode 4 disposed opposite to the recording electrode 1 via the recording medium 6, and a positive potential higher than the recording electrode 1 is applied to the aggregation electrode 2 and the migration electrode 3. After the coloring material particles contained in the ink are concentrated on the recording electrode 1, a potential equal to or higher than the aggregation electrode 2 and the migration electrode 3 is applied to the recording electrode 1. To separate and eject the ink to perform printing. This is because the ink creates a critical state of ink ejection by the electric field of the counter electrode 4. If the voltage is not applied to the counter electrode 4, the critical state of ink ejection cannot be exceeded, and therefore even if a recording voltage is applied to the recording electrode 1 in this state, ink ejection does not occur. Note that a direct current voltage is constantly applied to the aggregation electrode 2 and the migration electrode 3. Further, the aggregation electrodes G1 to G in FIG.
The same aggregated electrode signal is applied to all nine.

With respect to the recording electrode 1, if the on-time of the recording voltage is increased, the amount of ink ejected becomes relatively large, and accordingly, the dot diameter of the ink formed on the recording medium 6 becomes large. Therefore, in order to form an image having three or more gradation levels on the recording medium 6, the on-time of the recording voltage applied to the recording electrode 1 is changed in proportion to the gradation level. What is necessary is just to change the amount of ink ejected from No. 1.

FIG. 6 shows a control method of the recording electrode signal when expressing four gradations from gradation levels 0 to 3. In FIG. 6, the recording electrodes S1 to S in FIG.
8 is applied to the recording electrode signals of the same gradation level as an example, but when an actual image is printed, the recording electrodes S1 to S8 have different gradation levels. A recording electrode signal may be applied.

In order to continuously print on the recording medium 1, while moving the recording medium 1 at a constant speed in a direction perpendicular to the recording electrode row, for example, in a direction indicated by an arrow in FIG. The control of the voltage applied to each electrode in the cycle is repeatedly performed. As the recording electrode signal, a recording electrode signal corresponding to a gradation level designated for each printing cycle is applied.

[0022]

However, in the above-mentioned conventional technique, when there are a plurality of recording electrodes,
Due to variations in the recording electrodes that occur in the manufacture of the head, such as variations in the width and length of each recording electrode and variations in the tip shape,
The distance between the recording electrodes is different, whereby the electric field strength applied to each recording electrode is slightly different.

Due to such variations in electric field intensity and changes over time, the amount of ink ejected corresponding to the same gradation level differs for each recording electrode, and the dot diameter of the ink formed on the recording medium accordingly changes. It differs for each recording electrode.

Therefore, in the image formed on the recording medium, streaks or stripes are generated in the paper feed direction,
There is a problem that the image quality is significantly reduced.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electrostatic ink jet recording apparatus capable of reducing deterioration of the quality of a printed image due to variations in recording electrodes.

[0026]

In order to solve this problem, an electrostatic ink jet recording apparatus according to the present invention comprises a slit-shaped ink discharge section for discharging ink containing charged coloring material particles, A plurality of recording electrodes, which are arranged at predetermined intervals in the width direction of the ejection unit and provide ejection positions at which ink is ejected, are arranged to face the recording electrodes, and eject ink from the recording electrodes by electrostatic attraction. A recording electrode having one duty ratio pattern among a plurality of duty ratio patterns of a recording electrode signal corresponding to a gradation level, comprising: a counter electrode to be discharged; and a control unit for controlling a voltage applied to the recording electrode and the counter electrode. A signal is applied to a recording electrode to perform gradation level printing.

According to another aspect of the present invention, there is provided an electrostatic ink jet recording apparatus, comprising: a slit-shaped ink discharge portion from which ink containing charged coloring material particles is discharged; and a width of the ink discharge portion. A plurality of recording electrodes that are arranged at predetermined intervals in the direction and provide an ejection position at which ink is ejected, and a counter electrode that is arranged to face the recording electrode and ejects ink from the recording electrode by electrostatic attraction And a control unit for controlling a voltage applied to the recording electrode and the counter electrode, each of which controls a recording signal of any one of a plurality of duty ratio patterns of the recording electrode signal corresponding to the gradation level. And printing at the gradation level by applying to the recording electrodes.

Further, in order to solve this problem, an electrostatic ink jet recording apparatus according to the present invention comprises a slit-shaped ink discharge section from which ink containing charged coloring material particles is discharged, and a width of the ink discharge section. A plurality of recording electrodes that are arranged at predetermined intervals in the direction and provide an ejection position at which ink is ejected, and a counter electrode that is arranged to face the recording electrode and ejects ink from the recording electrode by electrostatic attraction And a control unit that controls the voltage applied to the recording electrode and the counter electrode, and from among a plurality of duty ratio patterns of the recording electrode signal corresponding to the gradation level, a duty ratio pattern specific to each recording electrode is previously determined. A plurality of selections are made, and a recording electrode signal of one of the duty ratio patterns is applied to the recording electrodes to perform gradation level printing.

As a result, it is possible to reduce the deterioration of the quality of the printed image due to the variation of the recording electrodes.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is characterized in that a slit-shaped ink discharge portion from which ink containing charged color material particles is discharged, and a predetermined interval in the width direction of the ink discharge portion. A plurality of recording electrodes that provide an ejection position at which ink is ejected, a counter electrode that is arranged to face the recording electrode, and that ejects ink from the recording electrode by electrostatic attraction, a recording electrode, and A control unit for controlling a voltage to be applied to the common electrode, and applying a recording electrode signal of one duty ratio pattern among a plurality of duty ratio patterns of the recording electrode signal corresponding to the gradation level to the recording electrode. This is an electrostatic ink jet recording apparatus that performs printing at a tone level, and has an effect that it is possible to reduce a decrease in image quality of a printed image due to variations in recording electrodes.

According to a second aspect of the present invention, there is provided a slit-shaped ink discharge portion from which ink containing charged coloring material particles is discharged, and a predetermined interval in the width direction of the ink discharge portion. A plurality of recording electrodes for providing an ejection position at which ink is ejected, a counter electrode disposed opposite to the recording electrode, for discharging ink by electrostatic attraction from the recording electrode, and a recording electrode and a counter electrode. A control unit for controlling a voltage to be applied to the recording electrode, and applying a recording signal of any one of a plurality of duty ratio patterns of the recording electrode signal corresponding to the gradation level to each of the recording electrodes. This is an electrostatic ink jet recording apparatus that performs level printing, and has an effect that it is possible to reduce deterioration in the quality of a printed image due to variations in recording electrodes.

According to a third aspect of the present invention, a slit-shaped ink discharge section from which ink containing charged color material particles is discharged is arranged at a predetermined interval in the width direction of the ink discharge section. A plurality of recording electrodes for providing an ejection position at which ink is ejected, a counter electrode disposed opposite to the recording electrode, for discharging ink by electrostatic attraction from the recording electrode, and a recording electrode and a counter electrode. A plurality of duty ratio patterns unique to each recording electrode are selected in advance from a plurality of duty ratio patterns of the recording electrode signal corresponding to the gradation level. This is an electrostatic ink jet recording device that applies a recording electrode signal of a duty ratio pattern to the recording electrodes and performs printing at a gradation level. It has the effect that it is possible to reduce the quality reduction.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG.

(Embodiment 1) FIG. 1 is an explanatory view showing an example of a voltage waveform applied to a recording electrode in an electrostatic ink jet recording apparatus according to Embodiment 1 of the present invention, and FIG. FIG. 4 is an explanatory diagram showing an example of a voltage waveform applied to each electrode when continuously printing ink dots of gradation level 2 on a plurality of recording electrodes in the electrostatic inkjet recording apparatus according to the first embodiment.

It should be noted that, including the embodiments described below,
Since the structure of the electrostatic ink jet recording apparatus is the same as that shown in FIG. 5, duplicate illustration and description are omitted here. In addition, the above-described four gradations will be described as an example, including the embodiment described below.

In FIG. 1, for gradation level 2,
Although the case where five duty ratio patterns from 2a to 2e are provided is illustrated, a plurality of duty ratio patterns can be provided for gradation levels other than gradation level 0. Note that the number of gradations and the duty ratio pattern shown here are merely examples, and the number of gradations and the number of duty ratio patterns can be freely set.
Further, the number of duty ratio patterns may be different for each gradation level.

In the electrostatic ink jet recording apparatus of the present embodiment, these duty ratio patterns corresponding to the gradation level 2 are stored in advance, and when the printing cycle for printing the gradation level 2 comes, Only one of the five duty ratio patterns shown in FIG. 1 is selected, for example, using a method such as random number generation, and is applied to the recording electrode. Note that the duty ratio pattern can be selected by various methods.

FIG. 2 shows a waveform of a voltage applied to each electrode when ink dots of gradation level 2 are continuously printed on a plurality of recording electrodes.

As shown in the figure, the pattern selection from the five duty ratio patterns is performed for each recording electrode and each printing cycle. Note that it is desirable that mutually different duty ratio patterns be selected between adjacent recording electrodes and before and after printing cycles on the same recording electrode.

As described above, according to the present embodiment, a plurality of duty ratio patterns of recording electrode signals corresponding to gradation levels are held in advance, and when printing at a predetermined gradation level, the Since one of the duty ratio patterns is selected and the recording electrode signal of this pattern is applied to the recording electrodes, it is possible to reduce the deterioration of the quality of the printed image due to the variation of the recording electrodes. Will be possible.

This makes it possible to make inconsistencies in the ink dot diameter between the recording electrodes which occur at the time of simultaneous printing with a plurality of recording electrodes inconspicuous, and to obtain a good printing result particularly in an image in which the same gradation level is spread over a wide range. Can be

(Embodiment 2) FIG. 3 shows a case where ink dots of gradation level 2 are continuously printed on a plurality of recording electrodes in an electrostatic ink jet recording apparatus according to Embodiment 2 of the present invention. FIG. 4 is an explanatory diagram showing an example of a voltage waveform applied to each electrode of FIG.

In FIG. 3, in printing of gradation level 2, for each of the recording electrodes S1 to S8,
This indicates that one of the duty ratio patterns 2a to 2e is always assigned.

Also in FIG. 3, for gradation level 2,
Although a case where five duty ratio patterns 2a to 2e are provided is illustrated, a plurality of duty ratio patterns can be provided for gradation levels other than gradation level 0. Note that the number of gradations and the duty ratio pattern shown here are merely examples, and the number of gradations and the number of duty ratio patterns can be freely set.
Further, the number of duty ratio patterns may be different for each gradation level.

As described above, according to the present embodiment, a plurality of duty ratio patterns of the recording electrode signals corresponding to the gradation levels are held in advance, and one duty ratio pattern is stored in advance for each recording electrode. Since the recording electrode signal having the duty ratio of this pattern is selected and applied to the recording electrodes, it is possible to reduce the deterioration of the image quality of the printed image due to the variation of the recording electrodes.

As a result, it is possible to reduce the variation of the ink dot diameter between the recording electrodes which occurs at the time of simultaneous printing by a plurality of recording electrodes, and to obtain a good printing result especially in an image in which the same gradation level is spread over a wide range. .

(Embodiment 3) FIG. 4 is an explanatory diagram showing an example of a voltage waveform applied to a recording electrode in an electrostatic ink jet recording apparatus according to Embodiment 3 of the present invention.

In FIG. 4, in the printing of the gradation level 2, for each of the recording electrodes S1 to S8,
It shows that any three of the duty ratio patterns 2a to 2e are assigned as duty ratio patterns unique to each electrode.

In the actual printing, for example, at the recording electrode S1, when a printing cycle for performing the printing of the gradation level 2 comes at a certain time, the recording electrode S1 corresponding to the gradation level 2 is set to 3
Out of the two duty ratio patterns 2a, 2b, 2c,
For example, using a method such as random number generation, only one is selected and applied to the recording electrodes. Note that the duty ratio pattern can be selected by various methods.

In the figure, for gradation level 2, 2
It has five duty ratio patterns from a to 2e,
Among them, the case where three patterns are provided for each recording electrode is illustrated. However, a plurality of duty ratio patterns can be provided for gradation levels other than gradation level 0. Note that the number of gradations and the duty ratio pattern shown here are merely examples, and the number of gradations and the number of duty ratio patterns can be freely set. Further, the number of duty ratio patterns may be different for each gradation level.

As described above, according to the present embodiment, a plurality of duty ratio patterns of recording electrode signals corresponding to gradation levels are held in advance, and a plurality of duty ratio patterns unique to each recording electrode are previously stored. Since one of the duty ratio patterns is selected and the recording electrode signal of this pattern is applied to the recording electrodes, the deterioration of the quality of the printed image due to the variation of the recording electrodes is reduced. It becomes possible.

This not only reduces the variation in the ink dot diameter between the recording electrodes that occurs during simultaneous printing by a plurality of recording electrodes, but also allows one recording electrode to print a plurality of different prints of the same gradation level. Variations in the ink dot diameter that occur when the printing is performed at the printing cycle can be reduced, and a good printing result can be obtained particularly in an image in which the same gradation level is spread over a wide range.

Although the above embodiment has been described with four gradations, it goes without saying that the present invention can be applied to cases other than four gradations.

[0054]

As described above, according to the present invention, it is possible to obtain an effective effect that it is possible to reduce the deterioration of the quality of a printed image due to the variation of the recording electrodes.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an example of a voltage waveform applied to a recording electrode in an electrostatic ink jet recording apparatus according to a first embodiment of the present invention.

FIG. 2 shows a waveform of a voltage applied to each electrode when continuously printing ink dots of a gradation level on a plurality of recording electrodes in the electrostatic ink jet recording apparatus according to the first embodiment of the present invention. Explanatory diagram showing an example

FIG. 3 shows a waveform of a voltage waveform applied to each electrode when an ink dot of a gradation level is continuously printed on a plurality of recording electrodes in the electrostatic ink jet recording apparatus according to the second embodiment of the present invention. Explanatory diagram showing an example

FIG. 4 is an explanatory diagram showing an example of a voltage waveform applied to a recording electrode in the electrostatic inkjet recording apparatus according to the third embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a configuration of a recording head of a conventional electrostatic ink jet recording apparatus.

FIG. 6 is an explanatory diagram showing an example of a voltage waveform applied to each electrode provided in the recording head of FIG. 5;

[Explanation of symbols]

 S1 to S16 Recording electrode 4 Counter electrode 5 Ink ejection unit

Claims (3)

[Claims] 1. A slit-shaped ink discharge section from which ink containing charged color material particles is discharged, and a predetermined distance in the width direction of the ink discharge section, the discharge being configured to discharge the ink. A plurality of recording electrodes for providing a position; a counter electrode disposed opposite to the recording electrode, for discharging ink from the recording electrode by electrostatic attraction; and controlling a voltage applied to the recording electrode and the counter electrode. And a control unit for applying a recording electrode signal of one duty ratio pattern among a plurality of duty ratio patterns of the recording electrode signal corresponding to the gradation level to the recording electrode to perform gradation level printing. An electrostatic ink jet recording apparatus characterized by the above-mentioned. 2. A slit-shaped ink discharge section from which ink containing charged color material particles is discharged, and a predetermined distance in the width direction of the ink discharge section, wherein the discharge is such that the ink is discharged. A plurality of recording electrodes for providing a position; a counter electrode disposed opposite to the recording electrode, for discharging ink from the recording electrode by electrostatic attraction; and controlling a voltage applied to the recording electrode and the counter electrode. And a control unit for applying a recording signal of any one of a plurality of duty ratio patterns of the recording electrode signal corresponding to the gradation level to each of the recording electrodes, thereby printing the gradation level. And an electrostatic ink jet recording apparatus. 3. A slit-shaped ink discharge portion from which ink containing charged color material particles is discharged, and a predetermined distance in the width direction of the ink discharge portion, wherein the discharge is such that the ink is discharged. A plurality of recording electrodes for providing a position; a counter electrode disposed opposite to the recording electrode, for discharging ink from the recording electrode by electrostatic attraction; and controlling a voltage applied to the recording electrode and the counter electrode. A plurality of duty ratio patterns unique to each of the recording electrodes are selected in advance from a plurality of duty ratio patterns of the recording electrode signals corresponding to the gradation levels, and one of the duty ratio patterns is selected from the plurality of duty ratio patterns. Wherein the recording electrode signal is applied to a recording electrode to perform printing at a gradation level.