JP2001232805A - Method and apparatus for ink jet printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet printing method for printing different images clearly on a print medium inexpensively at high speed in which digital image data can be dealt with. SOLUTION: In the ink jet printing method for forming an image directly on a print medium by ink jet system where oil ink is ejected based on an image data signal utilizing an electrostatic field and producing a printed matter by fixing that image, an ink jet recording head is cleaned by immersing it into cleaning liquid and applying a voltage thereto.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a printing method for forming a print image directly on a print medium, and more particularly, to printing quality of an electrostatic ink jet recording using an oil-based ink by cleaning a recording head. The present invention relates to an ink-jet printing method and a printing apparatus which have good printing performance and can perform high-speed printing.

[0002]

2. Description of the Related Art As a printing method for forming a print image on a print medium based on an image data signal, there are an electrophotographic system, a sublimation type and a fusion type thermal transfer system, an ink jet system, and the like. The electrophotographic method requires a process of forming an electrostatic latent image on a photosensitive drum by charging and exposure, and the system becomes complicated and becomes an expensive apparatus. In the thermal transfer system, the apparatus is inexpensive, but the use of an ink ribbon causes a high running cost and waste materials are generated. On the other hand, the ink jet system is an inexpensive device and discharges ink only to a required image portion to perform printing directly on a print medium. Therefore, the colorant can be used efficiently and the running cost is low.

As a method of applying the ink jet technology to a printing system, for example, Japanese Patent Application Laid-Open No. Hei 10-286939 discloses a method in which an ink jet printing device is attached to a rotary printing press and variable numbers and marks are added on the same printing paper. A method for printing with an inkjet system is disclosed. However, it is more preferable to be able to print advanced image information such as a photographic image. However, with the conventional ink technology in which a water-based or organic solvent-based ink containing a dye or pigment as a colorant is ejected by using pressure, droplets containing a large amount of solvent are ejected, so printing without using expensive special paper is required. There is a drawback that the image blurs. Therefore, when printing is performed on ordinary printing paper or a plastic sheet that is a non-absorbable medium, a high-quality printed image cannot be obtained.

[0004] As one of the ink-jet technologies,
There is a method in which an ink in a solid state is heated and melted at room temperature to eject a liquid ink to form an image. When this ink is used, the bleeding of the printed image is reduced, but since the ink viscosity at the time of ejection is high, it is difficult to eject fine droplets,
The obtained individual dot images have a large area and a large thickness, and it is difficult to form a high-definition image.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to print a clear, high-quality image by using an inexpensive apparatus and a simple method. It is an object of the present invention to provide an ink jet printing method that enables printing of a clear and high-quality image at all times by cleaning a recording head used at that time with an inexpensive device and a simple method. is there.

[0006]

[MEANS FOR SOLVING THE PROBLEMS] To achieve the above object
Next, the invention will be described with reference to the accompanying drawings.
According to Ming, use of electrostatic field based on image data signal
Printing by inkjet method to discharge oily ink
By forming an image directly on a medium and fixing the image,
Ink-jet printing method to create printed materials
Dipping the inkjet recording head in the cleaning liquid
Immersion, and recording by applying a voltage to the recording head
The head is cleaned.
Further, according to the invention of claim 2, the oil-based ink
Has a specific electric resistance of 10 ⁹Ωcm or more and dielectric constant of 3.5
In the following non-aqueous solvent, at least the colored particles are dispersed
It is characterized by the fact that Further, according to claim 3
According to the invention of the printing apparatus, based on the signal of the image data,
Image forming means for forming an image directly on a print medium;
An image obtained by fixing an image formed by the image forming means to obtain a printed matter.
Image fixing means, wherein the image forming means utilizes an electrostatic field.
Ink jetting the oil-based ink from the recording head
In a printing apparatus which is a jet drawing apparatus, the recording head is used.
With the recording head immersed in the cleaning liquid.
Cleaning by applying voltage to the
It is characterized by. Further, according to the invention of claim 4,
If the oil-based ink has a specific electric resistance of 10⁹Ωcm
At least in a non-aqueous solvent having a dielectric constant of 3.5 or less,
It is characterized by being a dispersion of colored particles.
According to the fifth aspect of the present invention, the printing medium
Before and / or during printing on the surface of the print medium
Characterized by having dust removing means for removing dust
I have. According to the invention described in claim 6, the printing medium
When drawing on the body, the recording head is connected via the print medium.
The rotation of the opposing drum located at the position facing the
By moving the print medium, drawing can be performed.
It is characterized by. Further, according to the invention described in claim 7,
If the recording head is a single channel head or
Consists of a multi-channel head, with the head facing the drum
It is characterized by drawing by moving in the axial direction of
And Further, according to the invention described in claim 8,
When drawing on a print medium, at least one pair of caps
The printing medium can be run while sandwiched between
Thus, drawing is performed. Soshi
According to the ninth aspect, the recording head includes:
Single channel head or multi channel head
And a front direction perpendicular to the running direction of the print medium.
Drawing by moving the recording head
Features. Further, according to the tenth aspect of the present invention,
If the recording head has a length substantially equal to the width of the print medium,
A full line head with
You. According to the eleventh aspect of the present invention, the ink
A jet drawing apparatus is provided with the oil-based ink on the recording head.
Characterized by having an ink supply means for supplying
You. According to the twelfth aspect of the present invention, the recording
An ink collecting means for collecting the oil-based ink from the ink cartridge.
In addition, ink circulation is performed. Further
According to the thirteenth aspect of the present invention,
An ink tank for storing the oil-based ink
Having a stirring means for stirring the oil-based ink in the
Features. And according to the invention of claim 14,
If, for example, the inkjet drawing apparatus converts the oil-based ink
Manages the temperature of the oil-based ink in the stored ink tank
Characterized by having ink temperature management means
You. According to a fifteenth aspect of the present invention, the ink
A jet drawing apparatus for controlling the concentration of the oil-based ink
It is characterized by having ink density control means.

[0007]

Embodiments of the present invention will be described below in detail. The present invention is characterized in that the recording head is cleaned by an ink jet method in which an oil-based ink is discharged by an electrostatic field onto a print medium supplied to a printing apparatus.

The ink-jet method according to the present invention uses a PC
T publication WO93 / 11866, and in this ink jet method, an insulating solvent contains
An ink having a high resistance in which at least colored particles are dispersed is used, and a strong electric field is applied to the ink at the ejection position to form an aggregate of the colored particles at the ejection position. An object is discharged from the discharge position. Thus, the colored particles are ejected as agglomerates with a high concentration, and the ink droplets contain only a small amount of solvent. As a result, there is no bleeding on printing paper or a printing plastic film used as a recording medium,
A clear image is formed at a high density. In the present inkjet method, the size of the ejected ink droplet is determined by the size of the tip of the ejection electrode or the electric field forming condition. Therefore, if a small ejection electrode and appropriate electric field forming conditions are used, a small ink droplet can be obtained without reducing the ejection nozzle diameter or slit width. Therefore, fine images can be controlled without the problem of ink clogging of the head, and the present invention provides an inkjet printing method capable of printing a clear and high-quality image print.

An example of the configuration of a printing apparatus used for carrying out the ink jet printing method of the present invention will be described below. However, the present invention is not limited to the following configuration examples.

FIG. 1 to FIG. 6 are diagrams showing an example of a schematic configuration of a printing apparatus according to the present invention for drawing by moving a print medium by rotation of an opposite drum. FIG. 1 to FIG. 4 are views showing a schematic configuration example of a Web-type printing apparatus in which a roll-shaped print medium is stretched by an opposed drum, a print medium supply roll, and a print medium take-up roll or a guide roll. FIG.
FIG. 2 shows a Web-type apparatus for printing one-sided single color, and FIG. 2 shows a Web-type apparatus for printing one-sided four-color. FIGS. FIG. 5 is a diagram showing an example of a schematic configuration of a single-sided four-color printing apparatus that cuts a roll-shaped printing medium and performs winding printing on an opposite drum, and FIG. 6 is a schematic view of a printing apparatus using a sheet-shaped recording medium. It is a figure showing the example of composition. FIGS. 7 and 8 are schematic diagrams showing an example of a schematic configuration of a printing apparatus that performs drawing by sandwiching and running a print medium with a cap stun roller according to the present invention. FIG. FIG. 8 is a view showing a schematic configuration example of a printing apparatus using a print medium, and FIG. Each of the printing apparatuses shown in FIGS.
In common, a head cleaning means 60 is provided according to the present invention. As will be described later, the head cleaning unit 60 cleans the recording head by applying a voltage to the recording head while the recording head is immersed in the cleaning liquid. FIG. 9 is a schematic configuration example of a drawing apparatus including a control unit, an ink supply unit, and a head separation mechanism of the drawing apparatus. 10 to FIG.
Reference numeral 6 denotes an ink jet recording apparatus provided in the drawing apparatus of FIG. FIG. 17 is an explanatory view for explaining the printhead cleaning means according to the present invention, and FIG. 18 is a flowchart for explaining the operation of the printhead cleaning means in FIG.

First, a printing process according to the present invention will be described with reference to an overall configuration diagram of an apparatus for performing one-sided one-color printing on a roll-shaped printing medium shown in FIG. An inkjet printing apparatus (hereinafter also referred to as “printing apparatus”) shown in FIG. 1 includes a supply roll 1 for a roll-shaped printing medium, a dust / paper dust removing apparatus 2,
The image forming apparatus includes a drawing device 3, a facing (drawing) drum 4, a fixing device 5, and a print medium take-up roll 6, which are arranged at positions facing the drawing device 3 via a print medium. After the dust and the like on the printing medium sent from the supply roll are removed by the dust / paper dust removing device 2, the ink is discharged from the ink discharge unit (described later) of the drawing device 3 to the printing medium on the drawing drum 4 on the printing medium. The ink is ejected in an imagewise direction, and a printed image is recorded.
After fixing the image on the print medium using the fixing device 5, the printed print medium is taken up by the print medium take-up roll 6.

The opposing (drawing) drum 4 is a metal roll or a roll having a conductive rubber layer on the surface thereof, or an insulating drum of plastic, glass, ceramic or the like, for use as a counter electrode with respect to the discharge electrode of the ink discharge section. For example, a metal layer provided on the surface by vapor deposition, plating, or the like is used. Thereby, an effective electric field can be formed between the discharge unit of the drawing apparatus 3. Providing a heating means on the drawing drum 4 to increase the drum temperature is also effective for improving the drawing quality. Bleeding is further suppressed in order to promote quick fixing of the ejected ink droplets on the print medium. Further, by keeping the drum temperature constant, the physical property values of the ink droplets ejected on the print medium are controlled, and stable and uniform dot formation becomes possible. In order to stabilize the temperature of the drum, it is more preferable to have a cooling unit.

As a means for removing dust, paper dust and the like, there can be used a contact method using a brush or a roller, in addition to a known non-contact method such as suction removal, blow-off removal and electrostatic removal. In the present invention, it is desirable to use either air suction or air blowing, or a combination thereof.

Further, the drawing device 3 has an ink jet recording device 20 as shown in FIG. In the ink jet recording apparatus 20, oily ink is ejected onto a print medium by an electrostatic field formed between the recording head 22 and the opposing drum 4 in accordance with the image data sent from the image data arithmetic control unit 21. To form a drawing image.

An image data arithmetic control unit 21 receives image data from an image scanner, a magnetic disk device, an image data transmission device, etc., performs color separation, and has an appropriate number of pixels and gradation for the separated data. Divide into numbers and distribute to each head. Further, the inkjet recording device 2
In order to convert the oil-based ink image into a halftone dot using the ink jet recording head 22 (see FIG. 10, which will be described later) of 0, a dot area ratio is also calculated.

As will be described later, the image data calculation control unit 21 controls the movement of the ink jet head 22, the ejection timing of the oil-based ink, and also controls the print medium operation timing as needed.

The printing process by the printing apparatus will be described in detail below with reference to FIGS.

The print medium sent out from the print medium supply roll is given tension by driving the print medium take-up roll, and abuts on the drawing (opposite) drum. Thus, it is possible to prevent the print medium web from vibrating and contacting the ink jet recording apparatus at the time of drawing to damage the print medium web. In addition, means for adhering the printing medium to the drawing (opposite) drum only around the drawing position of the ink jet recording apparatus is provided, and this is acted upon at least when drawing is performed, so that the printing medium contacts the ink jet recording apparatus. It can also be prevented. Specifically, for example, a pressing roller is arranged upstream and downstream of the drawing position of the drawing drum,
It is effective to use a guide or electrostatic attraction.

Image data from a magnetic disk device or the like
The image data arithmetic control unit 21 calculates the discharge position of the oil-based ink and the halftone dot area ratio at that position in accordance with the input image data. These calculation data are temporarily stored in the buffer. The image data calculation control unit 21 causes the recording head 22 to move closer to a position where the recording head 22 is brought close to the printing medium in contact with the drawing drum by the head separation / contact device 31. The distance between the recording head 22 and the surface of the drawing drum is controlled by mechanical distance control such as a contact roller.
Alternatively, the head is kept at a predetermined distance during writing by controlling the head separation / contact device based on a signal from the optical distance detector. As the recording head 22, a single channel head, a multi-channel head, or a full line head can be used. When a single-channel head or multi-channel head is used as a recording head,
The direction of arrangement of the ejection units is set substantially parallel to the running direction of the print medium, and printing is performed by performing main scanning by moving the recording head in the axial direction of the opposing drum and performing sub-scanning by rotating the opposing drum. The above-described movement control of the opposing drum and the recording head is performed by the image data calculation control unit 21, and the recording head discharges the oil-based ink onto the print medium at the discharge position and the dot area ratio obtained by the above calculation. This allows
On the print medium, a halftone image corresponding to the density of the print document is drawn with oil-based ink. This operation continues until a predetermined ink image is formed on the print medium. On the other hand, recording head 2
In the case where 2 is a full line head having a length substantially equal to the width of the drum, the arrangement direction of the discharge units is set substantially perpendicular to the running direction of the print medium, and the rotation of the opposing drum causes the print medium to move the drawing unit. By passing the ink, an oil-based ink image is formed and a printed matter is completed.

After printing, if necessary, the recording head 22 is retracted away from a position close to the drawing drum to protect the recording head 22. At this time, only the recording head 22 may be separated and connected, or the recording head 22 and the ink supply unit 24 may be separated and connected together.

This separation / contact means operates so as to separate the recording head from the drawing drum by at least 500 μm except during drawing. The detachment operation may be a sliding type, or the head may be fixed by an arm fixed to a certain axis, and the arm may be moved around the axis to move like a pendulum. By retracting the head during non-drawing in this manner, the head can be protected from physical damage or contamination, and a long life can be achieved.

Further, the formed oil-based ink image is reinforced by the fixing device 5. As a means of fixing ink,
Known means such as heat fixing and solvent fixing can be used. In the heat fixing, an infrared lamp, a halogen lamp, a xenon flash lamp irradiation, hot air fixing using a heater, and heat roll fixing are generally used. Flash fixing using a xenon lamp or the like is known as a method for fixing electrophotographic toner, and has an advantage that fixing can be performed in a short time. Also, when using laminated paper, a rapid rise in temperature causes the water inside the paper to evaporate rapidly, causing development called blisters, which cause irregularities on the paper surface. It is preferable to change the power supply and / or the distance from the fixing device to the recording medium so as to gradually increase the temperature in order to prevent blisters.

In solvent fixing, a solvent capable of dissolving the resin component in the ink, such as methanol or ethyl acetate, is sprayed or exposed to vapor, and excess solvent vapor is recovered. In addition, at least in the process from the formation of the oil-based ink image by the recording head 22 to the fixing by the fixing device 5, it is preferable that nothing is kept in contact with the image on the print medium.

FIGS. 2 to 4 show examples of the configuration of the single-sided and double-sided four-color printing apparatus. The operation principle and the like can be easily inferred from the above description of the single-sided single-color printing apparatus, and therefore the description thereof will be omitted. Although the configuration example of the four-color printing apparatus has been described here, the present invention is not limited to this, and the number of colors is arbitrarily determined as needed.

FIGS. 5 and 6 show another configuration example according to the present invention, and are explanatory views of a printing apparatus having an automatic discharge device 7 and using a printing medium wound around an opposite drum. FIG.
Is a device configuration example using a sheet-shaped print medium having an automatic feeding device 9. Here, a description will be given using an example of an apparatus configuration using a roll-shaped print medium in FIG.

First, the print medium supply roll 1 is
And the print medium cut into an arbitrary size by the cutter 8 is mounted. At this time, a known seat head /
The printing medium is tightly fixed on the drum by a mechanical method such as a tail holding device, an air suction device, or an electrostatic method, so that the paper flutters and comes into contact with the ink discharge drawing device 3 at the time of drawing and is damaged. Can be prevented. In addition, means for adhering the print medium to the drum only around the drawing position of the ink discharge drawing apparatus is provided, and at least at the time of drawing, the print medium is operated to prevent the print medium from contacting the ink jet recording apparatus. Can also. Specifically, for example, there is a method of arranging a pressing roller upstream and downstream of the drawing position of the opposing drum. Further, when no drawing is performed, it is desirable to keep the head away from the print medium, and thereby it is possible to effectively prevent the occurrence of problems such as contact damage in the ink discharge drawing device.

As the recording head 22, a single-channel head, a multi-channel head, or a full-line head can be used. In the case of a multi-channel head or a full line head having a plurality of discharge units, the arrangement direction of the discharge units is set in the axial direction of the opposed drum 4. Further, in the case of a single-channel head or a multi-channel head, the head 22 is continuously or sequentially moved in the axial direction of the opposing drum by the image data arithmetic control unit 21 and is obtained by the arithmetic operation of the image data arithmetic control unit 21. The oil-based ink is discharged onto the print medium mounted on the drum 11 at the specified discharge position and the dot area ratio. As a result, a halftone image corresponding to the density of the print document is drawn on the print medium with the oil-based ink. This operation continues until a predetermined oil-based ink image is formed on the print medium. On the other hand, when the recording head 22 is a full-line head having a length substantially equal to the width of the drum, one rotation of the drum forms an oil-based ink image on a print medium to produce a printed matter. By performing the main scanning by rotating the drum in this manner, the positional accuracy in the main scanning direction can be improved, and high-speed drawing can be performed. The printed print medium is fixed by the fixing device 5 and discharged by the automatic discharge device 7.

Here, an example of the configuration of a single-sided four-color printing machine has been described, but the present invention is not limited to this, and the number of colors and single-sided / double-sided printing can be arbitrarily determined as necessary. .

FIGS. 7 and 8 are schematic diagrams each showing an example of a schematic configuration of a printing apparatus which performs drawing by nipping and running a print medium with a cap stun roller according to the present invention. FIG. FIG. 8 is a diagram showing a schematic configuration example of a printing apparatus using a sheet-shaped printing medium, and FIG.

Here, a description will be given with reference to an overall configuration diagram of an apparatus for performing single-sided four-color printing on a roll-shaped print medium shown in FIG. The print medium M is nipped and conveyed by two pairs of capstan rollers 10, and is subjected to ink ejection drawing using data divided and processed into an appropriate number of pixels and an appropriate number of gradations by an image data calculation control unit (21 in FIG. 9). The image is drawn by the device 3.
In a part where drawing is performed by the ink discharge drawing device 3,
In the electrostatic field ejection, it is preferable to provide a grounding means 11 to be a counter electrode of the recording head electrode, thereby facilitating drawing.

In FIG. 7, a sheet cutter 8 is provided upstream of the automatic discharge device 7 for cutting the roll-shaped print medium. However, the sheet cutter can be arranged at any desired position.

Next, referring to FIG. 7, the process of producing a printed matter by the printing apparatus of the present invention will be described in more detail below.

First, the print medium is transported using the cap stun roller 10. At this time, by providing a print medium guide unit (not shown) as necessary, it is possible to prevent the head / tail of the print medium from fluttering and coming into contact with the ink ejection drawing device 3 and being damaged. In addition, means for preventing the print medium from sagging only around the drawing position of the ink discharge drawing apparatus is provided, and at least when drawing is performed, it is operated to prevent the print medium from contacting the ink discharge drawing apparatus. Can also. Specifically, for example, there is a method of arranging a pressing roller upstream and downstream of the drawing position. Further, when no drawing is performed, it is desirable to keep the head away from the print medium, and thereby it is possible to effectively prevent the occurrence of problems such as contact damage in the ink discharge drawing device.

Image data from a magnetic disk device or the like
The image data calculation control unit 21 shown in FIG. 9 calculates the ejection position of the oil-based ink and the dot area ratio at that position in accordance with the input image data. These calculation data are temporarily stored in the buffer.
The image data calculation control unit 21
2, the timing of discharging the oil-based ink, and the timing of the operation of the capstan roller are controlled, and the recording head 22 is moved closer to the print medium by the head separating device 31 as needed. The distance between the recording head 22 and the surface of the print medium is maintained at a predetermined distance during drawing by mechanical distance control such as a contact roller or control of a head separation device by a signal from an optical distance detector. . By this distance control, good printing can be performed without the dot diameter becoming non-uniform due to the floating of the printing medium or the dot diameter not changing even when vibration is applied to the printing apparatus.

As the recording head 22, a single-channel head, a multi-channel head, or a full-line head can be used, and the sub-scan is performed by transporting the print medium. In the case of a multi-channel head having a plurality of discharge units, the arrangement direction of the discharge units is set substantially parallel to the running direction of the print medium. Further, in the case of a single-channel head or a multi-channel head, the head 22 is moved in a direction perpendicular to the running direction of the print medium by the image data calculation control unit 21, and the ejection position and the dot area ratio obtained by the above calculation are calculated. Discharges oil-based ink. As a result, a halftone image corresponding to the density of the print document is drawn on the print medium with the oil-based ink. This operation continues until a predetermined oil-based ink image is formed on the print medium. On the other hand, when the recording head 22 is a full line head having substantially the same length as the width of the drum, the arrangement direction of the ejection units is set substantially perpendicular to the traveling direction of the printing medium, and the printing medium passes through the drawing unit. This forms an oil-based ink image on the print medium. The printed print medium is fixed by the fixing device 5 and discharged by the automatic discharge device.

Here, an example of the configuration of the single-sided four-color printing machine has been described, but the present invention is not limited to this, and the number of colors and single-sided / double-sided printing are arbitrarily determined as needed.

Next, FIG.
This will be described in detail with reference to FIG.

As shown in FIG. 9, the drawing apparatus used in the present ink jet printing method includes a recording head 22 and an ink supply unit 24. The ink supply unit 24 further includes:
An ink tank 25, an ink supply device 26, and an ink concentration control unit 29 are provided.
Ink temperature management means 28 is included. The ink may be circulated in the head, and in this case, the ink supply unit also has a recovery circulation function. The stirring means 27 is used to settle the solid components of the ink.
Suppress aggregation. As the stirring means, a rotary blade, an ultrasonic vibrator, and a circulation pump can be used, and these are used or in combination. Ink temperature management means 28
Are arranged such that the physical properties of the ink change due to a change in the surrounding temperature, and a high-quality image can be stably formed without changing the dot diameter. As the ink temperature management means, a heating element or a cooling element such as a heater or a Peltier element is arranged in an ink tank together with a stirring means so as to keep the temperature distribution in the tank constant, and controlled by a temperature sensor such as a thermostat. A publicly known method such as the above method can be used. The ink temperature in the ink tank was 15 ° C.
The temperature is desirably at least 60 ° C and preferably at most 20 ° C and at most 50 ° C. Further, the stirring means for keeping the temperature distribution in the tank constant may be shared with the stirring means for suppressing the precipitation and aggregation of the solid components of the ink. The drawing printing apparatus further includes an ink density control unit 29 for performing high-quality drawing. The ink density is measured by optical detection, physical property measurement such as conductivity measurement, viscosity measurement, or the like, or management based on the number of drawn images. When managing by physical property measurement, an optical detector, conductivity meter, and viscosity meter are provided alone or in combination in the ink tank or ink flow path, and drawing is performed by the output signal of the optical detector, conductivity meter, and viscosity meter. When performing management based on the number of prints, the supply of liquid from a replenishment concentrated ink tank or a dilution ink carrier tank (not shown) to the ink tank is controlled based on the number of prints and the frequency.

As described above, the image data calculation control section 21 calculates the input image data, and controls the head separation / contact device 31,
The timing pulse from the encoder 30 installed on the opposing drum or the capstan roller is taken in, and the head is driven according to the timing pulse. When drawing is performed by the ink jet recording apparatus, the drawing drum is driven by a high-precision driving unit. Specifically, for example, the output from a high-precision motor is converted to a high-precision gear,
Alternatively, there is a method of driving the drawing drum at a reduced speed by a steel belt or the like. By using such means alone or in combination of two or more, higher-quality drawing can be performed.

Next, the recording head will be described with reference to FIGS.
This will be described using. However, the contents of the present invention are not limited to the following examples.

FIGS. 10 and 11 show an example of a head provided in an ink jet recording apparatus. Head 22
Has a slit sandwiched between an upper unit 221 and a lower unit 222 made of an insulating base material, the tip of which is a discharge slit 22a, and a discharge electrode 22b is arranged in the slit. Is supplied to the inside of the slit.
Examples of the insulating substrate include plastic, glass,
Ceramics and the like can be applied. Also, the ejection electrode 22b
Is vacuum-evaporated, sputtered, or electrolessly plated with a conductive material such as aluminum, nickel, chromium, gold, and platinum on the lower unit 222 made of an insulating base material.
A photoresist is applied thereon, the photoresist is exposed through a mask having a predetermined electrode pattern, and the photoresist is exposed and developed to form a photoresist pattern of the discharge electrode 22b. Then, the photoresist pattern is etched or removed mechanically. It is formed by a known method such as a method or a method combining them.

In the head 22, a voltage is applied to the ejection electrode 22b according to a digital signal of image pattern information. As shown in FIG. 10, a drawing drum serving as a counter electrode is provided so as to face the discharge electrode 22b, and a printing medium is provided on the drawing drum. By applying a voltage, a circuit was formed between the discharge electrode 22b and the drawing drum serving as the counter electrode, and the oil-based ink 23 was discharged from the discharge slit 22a of the head 22 and provided on the drawing drum serving as the counter electrode. An image is formed on the print medium.

The width of the discharge electrode 22b is preferably as narrow as possible in order to form a high quality image. Specific numerical values vary depending on conditions such as applied voltage and ink physical properties, but are usually used in a range of a tip width of 5 to 100 μm.

For example, the discharge electrode 22b having a tip of 20 μm width
And the drawing drum 4 serving as the counter electrode and the discharge electrode 22b
Is set to 1.0 mm, a dot of 40 μm can be formed on the print medium 9 by applying a voltage of 3 KV between the electrodes for 0.1 millisecond.

FIGS. 12 and 13 are a schematic sectional view and a schematic front view, respectively, showing the vicinity of the ink discharge portion of another example of the recording head. In the figure, reference numeral 22 denotes a recording head.
The recording head 22 has a first insulating substrate 33 having a gradually decreasing shape. The first insulating substrate 33 has a second
The insulating base material 34 is provided so as to be spaced apart and opposed, and a slope portion 35 is formed at the tip end of the second insulating base material 34. The first and second insulating substrates are made of, for example, plastic, glass, ceramics, or the like. Upper surface 3 forming an acute angle with slope 35 of second insulating substrate 34
6 is provided with a plurality of ejection electrodes 22b as electrostatic field forming means for forming an electrostatic field in the ejection section. The tips of the plurality of ejection electrodes 22b extend to near the tips of the upper surface portion 36, and the tips protrude forward of the first insulating base material 33 to form ejection portions.
The ink inflow path 3 is provided between the first and second insulating bases 33 and 34 as a means for supplying the ink 23 to the discharge section.
7 is formed, and an ink recovery path 38 is formed below the second insulating base material 34. The ejection electrode 22
b is formed by using a conductive material such as aluminum, nickel, chromium, gold, or platinum on the second insulating base material 34 by a known method as described above. Individual electrode 22b
Are electrically insulated from each other. The amount by which the tip of the discharge electrode 22b projects from the tip of the insulating substrate 33 is preferably 2 mm or less. The reason why the amount of protrusion is limited to the above range is that if the amount of protrusion is too large, the ink meniscus does not reach the tip of the discharge portion, making it difficult to discharge or lowering the recording frequency. Also,
The space between the first and second insulating substrates 33 and 34 is preferably in the range of 0.1 to 3 mm. The reason for limiting this space to the above range is that if the space is too narrow, it becomes difficult to supply ink and it becomes difficult to discharge, or the recording frequency is lowered, and if the space is too wide, the meniscus is not stable. This is because the ejection becomes unstable.
The ejection electrode 22b is connected to the image data calculation control unit 21, and when recording is performed, a voltage is applied to the ejection electrode based on image information to eject ink on the ejection electrode, and the ejection electrode 22b is arranged to face the ejection unit. Is drawn on a print medium (not shown). The direction opposite to the ink droplet ejection direction of the ink inflow path 37 is connected to an ink feeding unit of an ink supply device (not shown). A backing 39 is provided on the surface of the second insulating substrate 34 opposite to the surface on which the ejection electrodes are formed, facing away from each other, and an ink recovery path 38 is provided between the two. The space of the ink recovery path 38 is desirably 0.1 mm or more. The reason for limiting this space to the above range is that if the space is too narrow, it becomes difficult to collect the ink, which may cause ink leakage. The ink recovery path 38 is connected to an ink recovery means of an ink supply device (not shown). When a uniform ink flow on the ejection section is required, a groove 40 may be provided between the ejection section and the ink recovery path. FIG. 13 is a schematic front view showing the vicinity of the ink ejection portion of the recording head. The inclined surface of the second insulating base 34 has a plurality of grooves extending from the vicinity of the boundary with the ejection electrode 22 b toward the ink recovery path 38. 40 are provided. A plurality of the grooves 40 are arranged in the arrangement direction of the ejection electrodes 22b, and a certain amount of ink near the tip of the ejection electrode is guided from the opening on the ejection electrode 22b side by a capillary force according to the opening diameter. Ink collection path 3
8 has the function of discharging. Therefore, it has a function of forming an ink flow having a constant liquid thickness near the tip of the discharge electrode. The shape of the groove 40 may be any range as long as the capillary force acts, and particularly preferably, the width is 10 to 200 μm and the depth is 10 to 300 μm. The necessary number of grooves 40 are provided so that a uniform ink flow can be formed over the entire surface of the head.

The width of the discharge electrode 22b is preferably as narrow as possible in order to form a high quality image. The specific numerical value varies depending on the applied voltage, the physical properties of the ink, and the like, but is usually used in the range of the tip width of 5 to 100 μm.

FIGS. 14 and 15 show another example of the recording head used to carry out the present invention. FIG.
Is a schematic diagram showing only a part of the head for explanation. As shown in FIG. 14, the recording head 22 includes a head main body 41 made of an insulating material such as plastic, ceramic, and glass, and meniscus regulating plates 42 and 42 '. In the drawing, reference numeral 22b denotes an ejection electrode for applying a voltage to form an electrostatic field in the ejection portion. Further, the head main body will be described in detail with reference to FIG. 15 in which the regulating plates 42 and 42 'have been removed from the head. The head body 41 is provided with a plurality of ink grooves 43 for circulating ink perpendicular to the edge of the head body. The shape of the ink groove 43 may be set in a range where the capillary force acts so that a uniform ink flow can be formed, and particularly preferably, the width is 10 to 200 μm.
m, the depth is 10 to 300 μm. The ejection electrode 22b is provided inside the ink groove 43. The discharge electrode 22b is formed on a head body 40 made of an insulating material by using a conductive material such as aluminum, nickel, chromium, gold, or platinum by a known method similar to that of the above-described apparatus embodiment. It may be arranged on the entire surface in the groove 43 or may be formed only on a part thereof. The discharge electrodes are electrically isolated. Two adjacent ink grooves form one cell, and ejection parts 45 and 45 'are provided at the end of the partition wall 44 at the center. In the ejection portions 45 and 45 ', the partition walls are thinner than the other partition portions 44 and are sharpened. Such a head body is manufactured by a known method such as machining, etching, or molding of an insulating material block. The thickness of the partition wall at the discharge portion is preferably 5 to 100 μm, and the radius of curvature of the sharpened tip is preferably 5 to 50 μm. The tip of the discharge section may be slightly chamfered, such as 45 '. Although only two cells are shown in the figure,
The cells are partitioned by a partition wall 46, and a tip end portion 47 is chamfered so as to be retracted from the discharge portions 45 and 45 '. Ink is supplied to the head from an I direction through an ink groove by an ink feeding means of an ink supply device (not shown) to supply ink to a discharge unit. Further, surplus ink is collected in the O direction by an ink collecting means (not shown), and as a result, fresh ink is always supplied to the ejection unit. In this state, a voltage is applied to the discharge electrode according to image information to a drawing drum (opposite drum) (not shown), which is provided so as to face the discharge section and has a print medium in contact with the surface thereof. The ink is ejected from the section to form an image on the print medium.

Another embodiment of the recording head will be described with reference to FIG. As shown in FIG. 16, the recording head 22 has a pair of substantially rectangular plate-shaped support members 50 and 50 '. These support members 50, 50 'are made of a plate-like plastic, glass, ceramic or the like having a thickness of 1 to 10 mm having an insulating property, and one surface of each is parallel to each other according to the recording resolution. A plurality of elongated rectangular grooves 51, 51 'are formed. Each groove 51, 5
1 'is preferably in the range of 10 to 200 μm in width and 10 to 300 μm in depth, and the discharge electrode 22b is formed entirely or partially inside. As described above, by forming the plurality of grooves 51, 51 'on one surface of the support members 50, 50', a plurality of rectangular partition walls 52 are inevitably provided between the grooves 51. Each support member 50, 50 '
Are combined so that the surfaces on which the grooves 51 and 51 'are not formed face each other. That is, the recording head 22 has a plurality of grooves on the outer peripheral surface for flowing ink.
Grooves 51, 51 'formed in each support member 50, 50'
Are connected in a one-to-one correspondence via a rectangular portion 54 of the recording head 22, and the rectangular portion 54 to which each groove is connected is a predetermined distance (50 to 500 μm) from the upper end 53 of the recording head 22.
m) has receded. That is, on both sides of each rectangular portion 54, the upper end 55 of each partition 52 of each support member 50, 50 '.
Are provided so as to protrude from the rectangular portion 54. A guide protrusion 56 made of an insulating material as described above is provided so as to protrude from each rectangular portion 54 to form a discharge portion. Recording head 22 configured as described above
When the ink is circulated to each of the rectangular portions 54 via the respective grooves 51 formed on the outer peripheral surface of one of the support members 50, the ink is supplied to the respective rectangular portions 54, and the respective grooves 51 'formed on the opposite support member 50'. Drain through. In this case, the recording head 22 is inclined at a predetermined angle in order to enable smooth ink distribution. That is, the ink supply side (support member 50)
The recording head 22 is tilted such that is positioned above and the ink discharge side (support member 50 ') is positioned below. In this way, when the ink is circulated through the recording head 22, the ink passing through each rectangular portion 54 gets wet along each projection 56, and an ink meniscus is formed near the rectangular portion 54 and the projection 56. Then, in a state in which an independent ink meniscus is formed in each rectangular portion 54, the ink meniscus is provided so as to face the discharge unit, and the discharge electrode 22b is applied to a drawing drum (not shown) having a surface in contact with a print medium. By applying voltage based on image information,
Ink is ejected from the ejection unit to form an image on a print medium. By providing a cover for covering the groove on the outer peripheral surface of each support member 50, 50 ', each support member 50, 50' is provided.
Forming a pipe-like ink flow path along the outer peripheral surface of 0 ';
The ink may be forcibly circulated through the ink flow path. In this case, it is not necessary to tilt the recording head 22.

The recording head 22 described above with reference to FIGS.
In order to maintain a good drawing state, cleaning or the like is performed. For example, when the hibernation state continues or when there is a problem with the image quality, the print head tip is wiped with a flexible brush, brush, cloth, or the like, circulating only the ink solvent, supplying only the ink solvent or Suction the ejection part while circulating, and also keep the recording head in a cover filled with ink solvent vapor to prevent ink sticking, cool the head part, suppress evaporation of the ink solvent, and further remove dirt. In severe cases, forcibly suck the ink from the ejection section, forcibly insert air, ink or ink solvent jet from the ink flow path, or apply ultrasonic waves with the head immersed in the ink solvent, Are used alone or in combination. However, it has been found that the use of the following cleaning means makes it possible to keep the recording head simpler and more clean than these cleaning methods.

Next, the cleaning means according to the present invention will be described with reference to FIG. Cleaning means 6
It is indicated by 0. The cleaning unit 60 is configured such that, after a transport mechanism (not shown) transports the recording head 22 to the cleaning unit 60, at least the discharge tip of the recording head 22 is immersed in the cleaning liquid 57, and the discharge electrode of the recording head 22 is A voltage having the same polarity as that of the solid charged component in the ink is applied from a power source 59 via a conducting wire 591 to a power source 5.
9 is connected to a metal chassis of the cleaning liquid reservoir 58. With this connection, the solid charged component is repelled by the discharge electrode and is strongly removed. In this case, the applied voltage may be an AC voltage, or the AC voltage may be superimposed on a voltage having the same polarity as the solid charged component. In particular, when an AC voltage is superimposed, the solid charged component vibrates, and the cleaning effect is enhanced. The effect is further enhanced by applying ultrasonic waves together with voltage application. Any cleaning liquid may be used as long as it does not damage the recording head, but alcohol, an ink solvent, or the ink itself is preferably used as such a liquid.

FIG. 18 is a flow chart for explaining the operation of the recording head cleaning means of FIG.
The cleaning unit 60 operates when the printing apparatus is in a halt state for a long time and when there is a problem with an image or image quality. The period is counted, and when a predetermined period (for example, one month) has passed (step 1), the cleaning unit 60 operates (step 3). Further, the image and the image quality are always detected by a known method, for example, by a CCD camera, and the reference image and the image
U compares. Then, as a result of the comparison, if there is a problem with the image or the image quality (step 2), the cleaning unit 60 operates even if the suspension period of the printing apparatus is within the predetermined period (step 3). When the cleaning means 60 operates,
As shown in FIG. 17 described above, cleaning is performed by immersing at least the ejection tip of the recording head 22 in the cleaning liquid 57. After the cleaning is completed, the pause period counter for counting the pause state of the printing apparatus is reset, and counting of the pause state of the printing apparatus is started again.

Next, the printing medium used in the present invention will be described. Examples of the print medium include high quality paper, finely coated paper, and coated paper that are commonly used printing papers.
Further, for example, a polyolefin laminated paper having a resin film layer on the surface, and a plastic film such as a polyester film, a polystyrene film, a vinyl chloride film, a polyolefin film, and the like can also be used. Further, a plastic film or processed paper on which a metal is vapor-deposited on the surface or a metal foil is laminated can also be used. Of course, a special paper and a special film for inkjet can also be used.

The oil-based ink used in the present invention will be described below.

The oil-based ink used in the present invention is obtained by dispersing at least colored particles in a non-aqueous solvent having a specific electric resistance of 10 ⁹ Ωcm or more and a dielectric constant of 3.5 or less.

The specific electric resistance used in the present invention is 10 ⁹ Ωcm.
As the non-aqueous solvent having a dielectric constant of 3.5 or less, preferably a linear or branched aliphatic hydrocarbon, alicyclic hydrocarbon, or aromatic hydrocarbon, and a halogen-substituted product of these hydrocarbons are used. is there. For example, hexane, heptane, octane, isooctane, decane, isodecane, decalin,
Nonane, dodecane, isododecane, cyclohexane, cyclooctane, cyclodecane, benzene, toluene, xylene, mesitylene, isoper C, isoper E, isoper G, isoper H, isoper L (Isoper; trade name of Exxon), Shellsol 70, shell Sol 71 (Shellsol; trade name of Shell Oil Co.), Amsco OMS, Amsco 460 solvent (Amsco; trade name of Spirits Co., Ltd.), silicone oil and the like are used alone or in combination. The upper limit of the specific electric resistance of such a non-aqueous solvent is about 10 ¹⁶ Ωcm, and the lower limit of the dielectric constant is about 1.9.

The reason why the electric resistance of the non-aqueous solvent used is within the above range is that when the electric resistance is low, the concentration of the colored particles and the like hardly occurs, and the color of the formed dot becomes light or bleeds. The reason why the dielectric constant is set in the above range is that when the dielectric constant is increased, the electric field is relaxed due to the polarization of the solvent, whereby the ejection of the ink tends to be deteriorated.

The colored particles dispersed in the above non-aqueous solvent may be dispersed in the non-aqueous solvent as the coloring material itself as dispersed particles, or may be contained in the dispersed resin particles for improving fixability. May be. When it is contained, pigments and the like are generally coated with the resin material of the dispersed resin particles to obtain resin-coated particles, and dyes and the like are generally obtained by coloring the dispersed resin particles into colored particles. is there.

As the coloring material, any pigments and dyes conventionally used in oil-based ink compositions or liquid developers for electrophotography can be used.

As the pigment, those generally used in the technical field of printing can be used irrespective of inorganic pigments and organic pigments. Specifically, for example, carbon black, cadmium red, molybdenum red, chrome yellow, cadmium yellow, titanium yellow, chromium oxide, viridian, cobalt green, ultramarine blue, Prussian blue, cobalt blue, azo pigment, phthalocyanine pigment , Quinacridone-based pigments, isoindolinone-based pigments, dioxazine-based pigments, threne-based pigments, perylene-based pigments, perinone-based pigments, thioindigo-based pigments, quinophthalone-based pigments, metal complex pigments, and other known pigments. It can be used without.

As dyes, azo dyes, metal complex dyes,
Naphthol dye, anthraquinone dye, indigo dye,
Oil-soluble dyes such as carbonium dyes, quinone imine dyes, xanthene dyes, aniline dyes, quinoline dyes, nitro dyes, nitroso dyes, benzoquinone dyes, naphthoquinone dyes, phthalocyanine dyes and metal phthalocyanine dyes are preferred.

These pigments and dyes may be used alone or in combination as appropriate, but may be contained in the range of 0.5 to 5% by weight based on the whole ink. desirable.

The oil-based ink used in the present invention preferably contains, in addition to the colored particles, dispersed resin particles for improving the fixability of an image after printing.

The resin particles dispersed in the non-aqueous solvent may be any particles of a hydrophobic resin which is solid at a temperature of 35 ° C. or lower and has a good affinity for the non-aqueous solvent. Glass transition point is -5 ° C to 110 ° C or softening point 33 ° C
The resin (P) having a glass transition point of 10 to 100 ° C or a softening point of 38 to 1 ° C is more preferable.
20 ° C., more preferably 15 ° C.
80 ° C or a softening point of 38 ° C to 100 ° C.

By using such a resin having a glass transition point or a softening point, the affinity between the surface of the printing medium and the resin particles is increased, and the bonding between the resin particles on the printing medium is strengthened. The adhesion between the image area and the surface of the print medium is improved, and the anti-scratch property is improved. On the other hand, regardless of whether the glass transition point or the softening point is low or high, the affinity between the printing medium surface and the resin particles is reduced, or the bonding between the resin particles is weakened.

The weight average molecular weight Mw of the resin (P) is 1 ×
10 ³ to 1 × 10 ⁶ , preferably 5 × 10 ³ to 8 ×
10 ⁵ , more preferably 1 × 10 ^{4 to} 5 × 10 ⁵ .

As such a resin (P), specifically,
Olefin polymers and copolymers (eg, polyethylene,
Polypropylene, polyisobutylene, ethylene-vinyl acetate copolymer, ethylene-acrylate copolymer, ethylene-methacrylate copolymer, ethylene-methacrylic acid copolymer, etc.), vinyl chloride polymer and copolymer (for example, polychlorinated Vinyl, vinyl chloride-vinyl acetate copolymer, etc.), vinylidene chloride copolymer, vinyl alkanoate polymer and copolymer, allyl alkanoate polymer and copolymer, polymer and copolymer of styrene and its derivatives (For example, butadiene-styrene copolymer, isoprene-
Styrene copolymer, styrene-methacrylate copolymer, styrene-acrylate copolymer, etc.), acrylonitrile copolymer, methacrylonitrile copolymer, alkyl vinyl ether copolymer, acrylic ester polymer and copolymer, methacryl Acid ester polymer and copolymer, itaconic acid diester polymer and copolymer, maleic anhydride copolymer, acrylamide copolymer, methacrylamide copolymer, phenol resin, alkyd resin, polycarbonate resin, ketone resin, polyester resin,
Silicon resin, amide resin, hydroxyl and carboxyl group modified polyester resin, butyral resin, polyvinyl acetal resin, urethane resin, rosin resin, hydrogenated rosin resin, petroleum resin, hydrogenated petroleum resin, maleic acid resin, terpene resin, hydrogenated Terpene resin, coumarone-indene resin, cyclized rubber-methacrylic acid ester copolymer, cyclized rubber-acrylic acid ester copolymer, copolymer containing a nitrogen-free heterocycle (for example, furan Ring, tetrahydrofuran ring, thiophene ring, dioxane ring, dioxofuran ring, lactone ring,
Benzofuran ring, benzothiophene ring, 1,3-dioxetane ring, etc.), epoxy resin and the like.

The total content of the dispersed colored particles and resin particles in the oil-based ink of the present invention is preferably 0.5 to 20% by weight of the whole ink. If the content is low, the density of the printed image becomes insufficient, or the affinity between the ink and the printing medium surface becomes difficult to obtain, so that a problem such as that a strong image cannot be obtained tends to occur. When the number of inks increases, it becomes difficult to obtain a uniform dispersion liquid, the ink flow in the recording head tends to be uneven, and it is difficult to obtain stable ink ejection.

The colored particles dispersed in the non-aqueous solvent of the present invention, further including resin particles and the like, preferably have an average particle diameter of 0.05 μm to 5 μm. More preferably 0.1 μm to 1.5 μm, even more preferably 0.4 μm
The range is from μm to 1.0 μm. This particle size is CAPA-
500 (trade name, manufactured by Horiba, Ltd.).

The non-aqueous dispersion colored particles used in the present invention can be produced by a conventionally known mechanical pulverization method or polymerization granulation method. As a mechanical pulverization method, if necessary, a colorant and a resin are mixed, melted, kneaded, and then directly pulverized with a conventionally known pulverizer to obtain fine particles, and a dispersed polymer is used in combination. (For example, ball mill
A method of dispersing with a paint shaker, a caddy mill, a dyno mill, etc.), a colorant material to be a colored particle component, and a dispersing auxiliary polymer (or a coating polymer) are kneaded in advance to form a kneaded material, and then pulverized, and then the coexistence of the dispersed polymer And dispersion. Specifically, a method for producing a paint or a liquid developer for electrostatography can be used. For example, these are described in Kenji Ueki, “Flow of paint and pigment dispersion”, Kyoritsu Shuppan (1971), Solomon “ Paint Science "
Hirokawa Shoten (1969), Yuji Harasaki "Coating Engineering"
It is described in such books as Asakura Shoten (1971) and Yuji Harasaki "Basic Science of Coating" Maki Shoten (1977).

There is also a method in which resin particles granulated by polymerization granulation are colored by dyeing to produce colored particles.
As the polymerization granulation method, a conventionally known non-aqueous dispersion polymerization method can be mentioned, and specifically, the latest technology of ultrafine polymer supervised by Soichi Muroi, Chapter 2, CMC Publishing (1991), edited by Koichi Nakamura, ed. Recent Electrophotographic Development System and Development and Practical Use of Toner Materials ", Chapter 3, (Nippon Kagaku Kagaku Co., Ltd. 1985), KEJ Barrett," Dispersion Polymerization
in Organic Media "and written books such as John Wiley (1975).

Usually, a dispersion polymer is used in combination to stabilize the dispersion of the dispersed particles in a non-aqueous solvent. The dispersed polymer contains a repeating unit soluble in a non-aqueous solvent as a main component, and has an average molecular weight of 1 × 10 in weight average molecular weight Mw.
^It is preferably ³ to 1 × 10 ⁶ , more preferably 5 × 10 ³
５5 × 10 ⁵ .

Preferred examples of the soluble repeating unit of the dispersion polymer used in the present invention include a polymerization component represented by the following general formula (1).

[0073]

Embedded image

In the general formula (I), X ₁ is —COO
Represents-, -OCO- or -O-.

R represents an alkyl or alkenyl group having 10 to 32 carbon atoms, preferably an alkyl or alkenyl group having 10 to 22 carbon atoms, which may be linear or branched, and unsubstituted. Those are preferable, but may have a substituent.

Specifically, decyl, dodecyl, tridecyl, tetradecyl, hexadecyl, octadecyl, eicosanyl, docosanyl, decenyl,
A dodecenyl group, a tridecenyl group, a hexadecenyl group, an octadecenyl group, a linolenyl group and the like.

A ₁ and a ₂ may be the same or different from each other and include a hydrogen atom, a halogen atom (eg, a chlorine atom or a bromine atom), a cyano group, an alkyl group having 1 to 3 carbon atoms (eg, methyl Group, ethyl group, propyl group, etc.),-
COO-Z ₁ or —CH ₂ COO-Z ₁ [Z ₁ is an optionally substituted hydrocarbon group having a carbon number of 22 or less (eg, an alkyl group, an alkenyl group, an aralkyl group, an alicyclic group, an aryl group Etc.).

Among the hydrocarbon groups represented by Z ₁ , preferred hydrocarbon groups include alkyl groups having 1 to 22 carbon atoms which may be substituted (for example, methyl group, ethyl group, propyl group, butyl group, Hexyl group, heptyl group, octyl group, nonyl group, decyl group, dodecyl group, tridecyl group,
Tetradecyl group, hexadecyl group, octadecyl group, eicosanyl group, docosanyl group, 2-chloroethyl group, 2
-Bromoethyl group, 2-cyanoethyl group, 2-methoxycarbonylethyl group, 2-methoxyethyl group, 3-bromopropyl group and the like, and an optionally substituted alkenyl group having 4 to 18 carbon atoms (for example, 2-methyl- 1-propenyl group, 2-butenyl group, 2-pentenyl group, 3-methyl-
2-pentenyl group, 1-pentenyl group, 1-hexenyl group, 2-hexenyl group, 4-methyl-2-hexenyl group, decenyl group, dodecenyl group, tridecenyl group, hexadecenyl group, octadecenyl group, linolenyl group, etc.),
An aralkyl group having 7 to 12 carbon atoms which may be substituted (for example, benzyl group, phenethyl group, 3-phenylpropyl group, naphthylmethyl group, 2-naphthylethyl group, chlorobenzyl group, bromobenzyl group, methylbenzyl group, An ethylbenzyl group, a methoxybenzyl group, a dimethylbenzyl group, a dimethoxybenzyl group, etc., an alicyclic group having 5 to 8 carbon atoms which may be substituted (for example, cyclohexyl group,
-Cyclohexylethyl group, 2-cyclopentylethyl group, etc.) and an optionally substituted aromatic group having 6 to 12 carbon atoms (for example, phenyl group, naphthyl group, tolyl group, xylyl group, propylphenyl group, butylphenyl group) Octylphenyl, dodecylphenyl, methoxyphenyl, ethoxyphenyl, butoxyphenyl, decyloxyphenyl, chlorophenyl, dichlorophenyl, bromophenyl, cyanophenyl, acetylphenyl, methoxycarbonylphenyl, ethoxy Carbonylphenyl group, butoxycarbonylphenyl group, acetamidophenyl group, propionamidophenyl group, dodecyloylamidophenyl group, etc.).

The dispersing polymer may contain another repeating unit as a copolymer component together with the repeating unit represented by the general formula (I). Other copolymer components include:
Any compound may be used as long as it is composed of a monomer copolymerizable with a monomer corresponding to the repeating unit of the general formula (I).

The proportion of the polymer component represented by the general formula (I) in the dispersion polymer is preferably at least 50% by weight, more preferably at least 60% by weight.

Specific examples of these dispersion polymers include:
Examples include the dispersion stabilizing resin (Q-1) used in Examples, and a commercially available product (Solprene 1205, manufactured by Asahi Kasei Corporation) can also be used.

When the resin (P) particles are prepared as a dispersion (latex) or the like, the dispersion polymer is preferably added in advance during polymerization.

The amount of the dispersing polymer to be added depends on the resin for particles (P)
About 1 to 50% by weight.

The colored particles (or coloring material particles) and the dispersed resin particles in the oil-based ink of the present invention are preferably positively or negatively chargeable particles.

In order to impart an electric detecting property to these particles, it can be achieved by appropriately utilizing a technique of a wet type electrophotographic developer. Specifically, the above-mentioned “Recent development and practical use of electrophotographic development systems and toner materials”, pp. 139-148,
The Society of Electrophotography, "Basics and Application of Electrophotographic Technology," 497-
505 (Corona Publishing Co., 1988), Yuji Harazaki "Electrophotography" 16 (No. 2), page 44 (1977), etc., by using a charge detecting material such as a charge control agent and other additives. Done.

Specifically, for example, British Patent No. 8934
No. 29, No. 934038, No. 11222397,
U.S. Patent Nos. 3,900,412 and 4,606,899,
JP-A-60-179751, JP-A-60-185963
And JP-A-2-13965.

The charge control agent described above is preferably used in an amount of 0.001 to 1.0 part by weight based on 1000 parts by weight of the dispersion medium as the carrier liquid. If desired, various additives may be added. The upper limit of the total amount of these additives is regulated by the electrical resistance of the oil-based ink. That is, if the specific electric resistance of the ink from which the dispersed particles have been removed is lower than 10 ⁹ Ωcm, it becomes difficult to obtain a high-quality continuous tone image. desirable.

[0088]

The present invention will be described in detail with reference to the following examples, but the present invention is not limited to these examples. First, a production example of the resin particles for ink (PL-1) will be described.

Production Example 1 Production of Resin Particles (PL-1) A mixed solution of 10 g of a dispersion stabilizing resin (Q-1) having the following structure, 100 g of vinyl acetate and 384 g of Isopar H was heated to 70 ° C. while stirring under a nitrogen stream. Warmed. 0.8 g of 2,2'-azobis (isovaleronitrile) (abbreviated AIVN) was added as a polymerization initiator and reacted for 3 hours. Twenty minutes after addition of the initiator, cloudiness occurred and the reaction temperature rose to 88 ° C. Further, 0.5 g of this initiator was added, and after reacting for 2 hours, the temperature was raised to 100 ° C., and the mixture was stirred for 2 hours to distill off unreacted vinyl acetate. After cooling, the mixture was passed through a 200-mesh nylon cloth, and the resulting white dispersion was a latex having a degree of polymerization of 90% and an average particle size of 0.23 μm and having good monodispersity. The particle size was measured with CAPA-500 (manufactured by Horiba, Ltd.).

[0090]

Embedded image

A part of the white dispersion was centrifuged (rotation speed: 1 × 10 ⁴ rpm, rotation time: 60 minutes), and the precipitated resin particles were collected and dried. The weight average molecular weight (Mw: GPC value in terms of polystyrene) of the resin particles is 2
× 10 ⁵ , and the glass transition point (Tg) was 38 ° C.

Example 1 First, an oil-based ink was prepared. <Oil-based ink (IK-1)> dodecyl methacrylate /
Acrylic acid copolymer (copolymerization ratio; 95/5 weight ratio)
0 g, Nigrosine 10 g and Shersol 71 30 g
Was placed in a paint shaker (manufactured by Toyo Seiki Co., Ltd.) together with the glass beads, and dispersed for 4 hours to obtain a fine dispersion of nigrosine.

Preparation of Resin Particles for Ink 30 g of resin particles (PL-1) of Example 1 (as solid content), 20 g of the above nigrosine dispersion, FOC-1400 (Nissan Chemical Co., Ltd.)
G), and octadecene-half-maleic acid octadecylamide copolymer 0.08
g was diluted to 1 liter of Isopar G to prepare a black oil-based ink.

Next, 2 liters of the oil-based ink (IK-1) prepared as described above was filled in an ink tank of the ink jet recording apparatus of the drawing apparatus of the printing apparatus shown in FIG.
Here, a recording head 900 of the type shown in FIG.
dpi, full line head was used. A throwing heater and a stirring blade are provided in the ink tank as ink temperature management means, the ink temperature is set at 30 ° C., and the stirring blade is set at 30 rpm.
The temperature was controlled with a thermostat while rotating at m. Here, the stirring blade was also used as a stirring means for preventing sedimentation and aggregation. Further, the ink flow path is partially transparent, and an LED light emitting element and a light detecting element are disposed with the ink flow path interposed therebetween. The density was adjusted by a factor of 2). A rolled fine coated paper as a print medium was provided on a counter drum and transported. After removing dust on the print medium surface by suction of the air pump, move the recording head close to the print medium to the drawing position, transmit the image data to be printed to the image data calculation control unit, and transport the print medium by rotating the opposing drum. An oil-based ink was ejected from the full-line multi-channel head while forming the image to form an image. At this time, the tip width of the ejection electrode of the ink jet head is 10 μm, and the distance between the head and the print medium is 1 according to the output from the optical gap detection device.
mm. A voltage of 2.5 KV is constantly applied as a bias voltage, and when performing ejection, a pulse voltage of 500 V is further superimposed, and the pulse voltage is 256 steps within a range of 0.2 ms to 0.05 ms. The drawing was performed while changing the area of the dot by changing. No drawing failure due to dust or the like was observed at all, and no image deterioration due to a change in dot diameter or the like was observed even when the outside air temperature was changed or the printing time was increased, and good printing was possible.

Further, the image was strengthened by heating with a xenon flash fixing device (light emission intensity 200 J / pulse, manufactured by Ushio Inc.). After printing, the ink jet recording apparatus was retracted 50 mm from a position close to the drawing drum in order to protect the ink jet head.

The obtained printed matter was an extremely clear image without any skipping or blurring in the printed image. After the printing is completed, the tip of the recording head is immersed in Isopar G, and 1 kV
By applying the positive direct-current voltage of 30 seconds for 30 seconds, a good printed matter could be produced for three months without any maintenance work.

Example 2 Using the printing apparatus shown in FIGS. 2 and 3, a circulating pump as a stirring means (27 in FIG. 9), and four 150 dpi 64-channel multi-channel heads of the type shown in FIG. The heads were arranged such that the ejection units for 64 channels were arranged in a direction perpendicular to the axial direction of the drum. As oil-based inks, black ink IK-1 and cyan ink IK-2 produced in the same manner as IK-1 ink except that nigrosine used as a coloring material of IK-1 ink was replaced with phthalocyanine blue, and IK- A magenta ink IK-3 prepared in the same manner as the IK-1 ink except that the nigrosine used as the coloring material of one ink was replaced with CI Pigment Red 57: 1, and nigrosine used as the coloring material of the IK-1 ink were used. Except for replacing with CI Pigment Yellow 14, inks of four colors of yellow ink IK-4 produced in the same manner as IK-1 ink were used to fill four heads respectively. Here, a pump is used, and ink reservoirs are respectively provided between the pump and the ink inflow path of the recording head, and between the ink recovery path of the recording head and the ink tank. As a means, use a heater and the above-mentioned pump,
The ink temperature was set at 35 ° C. and controlled with a thermostat. Here, the circulation pump was also used as a stirring means for preventing precipitation and aggregation. In addition, a conductivity measuring device was arranged in the ink flow path, and the density was controlled by diluting the ink or feeding the concentrated ink based on the output signal. After removing the dust on the print medium surface with a rotating brush made of nylon, the image data to be printed is transmitted to the image data calculation control unit, the head is moved in the axial direction of the drum, the main scanning is performed, and the drawing drum is rotated. By performing sub-scanning while drawing, ink was ejected onto the rolled fine coated paper to form an image. No defective drawing due to dust is observed at all, and no image deterioration due to a change in dot diameter or the like is observed even when the outside air temperature changes or the number of printed sheets increases, and the head of either type shown in FIGS. 12 and 14 is used. If you have
Good single-sided and double-sided full-color printing was possible. Further, after the printing, the tip of the recording head was immersed in Isopar G, and cleaning was performed by applying an AC voltage of 0.5 kV / 1 kHz for 40 seconds. Good printed matter was produced. Further, instead of the ink jet head of the type shown in FIG. 12, 150 dpi 6 of the type shown in FIG.
When a similar operation was performed using a four-channel multi-channel head, good results were obtained as described above.

Example 3 Using the printing apparatus shown in FIG. 5, full-color printing of four colors on one side was performed. As the oil-based ink, the four color inks described in the second embodiment are used for each of four sets of ink jet drawing apparatuses, and four 100 dpi 256-channel multi-channel heads of the type shown in FIG. 16 are used. It is arranged in parallel with the axis, performs main scanning by rotating the opposing drum, and draws a 900 dpi image on coated paper by moving the head sequentially in each rotation in the axial direction of the drum, clear, high-quality full-color printed matter I got
After printing, the tip of the recording head was immersed in isopropanol, and cleaning was performed by applying an AC voltage of 0.5 kV / 1 kHz for 20 seconds. Could be produced.

Example 4 Using the printing apparatus shown in FIGS. 7 and 8, full-color printing of four colors on one side was performed. As the oil-based ink, the same four-color inks as in Example 3 were used. Here, a 600 dpi, 64 channel multi-channel head of the type shown in FIG. 12 was used as the recording head, and the ejection portions were arranged at an angle of about 60 degrees with the running direction of the print medium. The image data to be printed is transmitted to the image data arithmetic control unit,
While moving the channel multi-channel head in a direction perpendicular to the print medium, the print medium was conveyed by rotating the cap stun roller, thereby forming an image of 700 dpi on the ink jet exclusive paper. Otherwise, the same operation as in Example 1 was performed, and good printing of four full colors was possible. After printing, the leading end of the recording head was immersed in the used oil-based ink, and cleaned by applying a positive DC voltage of 1 kV and an AC voltage of 0.5 kV / 5 kHz for 30 seconds. Good prints could be produced without the need for maintenance work.

[0100]

According to the present invention, an image is formed directly on a print medium based on a signal of image data by an ink jet method in which an oil-based ink is discharged by utilizing an electrostatic field, and the image is fixed by fixing the image. In the ink-jet printing method for producing a print head, the print head is cleaned by immersing the ink-jet print head in a cleaning liquid and applying a voltage to the print head, so that the print head is always kept clean. Therefore, even if printing is performed on ordinary printing paper or a plastic sheet which is a non-absorbing medium without using expensive paper, bleeding does not occur in the image, and discharge of fine droplets is always possible. Accordingly, the obtained dot images have a small area and a small area, and it is possible to print high-quality image information such as a photographic image at low cost and at high speed.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram schematically illustrating a Web-type apparatus that performs single-sided, single-color printing, which is an example of an inkjet printing apparatus according to the present invention.

FIG. 2 is an overall configuration diagram schematically illustrating a Web-type apparatus that performs four-color printing on one side, which is another example of the inkjet printing apparatus of the present invention.

FIG. 3 is an overall configuration diagram schematically showing a two-sided four-color printing apparatus which is another example of the inkjet printing apparatus of the present invention.

FIG. 4 is an overall configuration diagram schematically showing a two-sided four-color printing apparatus which is another example of the inkjet printing apparatus of the present invention.

FIG. 5 is an overall configuration diagram schematically showing a single-sided, four-color printing apparatus that cuts a roll-shaped printing medium and winds it around an opposing drum, which is another example of the inkjet printing apparatus of the present invention.

FIG. 6 is an overall configuration diagram schematically illustrating a printing apparatus using a sheet-shaped recording medium, which is another example of the inkjet printing apparatus of the present invention.

FIG. 7 is an overall configuration diagram schematically illustrating a printing apparatus that performs drawing by nipping and running a roll-shaped printing medium with a cap stun roller, which is another example of the inkjet printing apparatus of the present invention.

FIG. 8 is an overall configuration diagram schematically showing a printing apparatus that performs drawing by nipping and running a sheet-shaped recording medium with a cap stun roller, which is another example of the inkjet printing apparatus of the present invention.

FIG. 9 is a schematic configuration example of a drawing apparatus including a control unit, an ink supply unit, and a head separation / attachment mechanism of the drawing apparatus of the inkjet printing apparatus of the present invention.

FIG. 10 is a diagram illustrating an ink jet recording apparatus included in the drawing apparatus of FIG.

11 is a diagram for explaining an enlarged cross section of the ink jet recording apparatus of FIG.

FIG. 12 is a diagram schematically illustrating a cross section near an ink ejection unit of another example of a recording head.

FIG. 13 is a schematic front view showing the vicinity of an ink ejection unit of another example of a recording head.

FIG. 14 is a schematic diagram showing only a part of a recording head of another example.

FIG. 15 shows a state in which the recording head shown in FIG.
FIG.

FIG. 16 is a schematic view showing another embodiment of the recording head.

FIG. 17 is an explanatory diagram for explaining a recording head cleaning unit according to the present invention.

18 is a flowchart for explaining the operation of the recording head cleaning means of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Print medium supply roll 2 Dust removal device 3 Ink discharge drawing device 4 Opposing (drawing) drum 5 Fixing device 6 Print medium take-up roll 7 Automatic discharge device 8 Cutter 9 Automatic supply device 10 Cap stun roller 11 Grounding means 20 Ink jet recording device DESCRIPTION OF SYMBOLS 21 Image data calculation control part 22 Recording head 221 Upper unit 222 Lower unit 22a Discharge slit 22b Discharge electrode 23 Oil-based ink 24 Ink supply part 25 Ink tank 26 Ink supply device 27 Stirring means 28 Ink temperature management means 29 Ink temperature control means 30 Encoder DESCRIPTION OF SYMBOLS 31 Head separation / attachment device 32 Head sub-scanning means 33 First insulating base material 34 Second insulating base material 35 Slope portion of second insulating base material 36 Upper surface portion of second insulating base material 37 Ink Inflow path 38 Ink recovery path 39 Locking 40 Groove 41 Head body 42, 42 ′ Meniscus regulating plate 43 Ink groove 44 Partition wall 45, 45 ′ Ejecting section 46 Partition wall 47 Partition tip 48, 50 ′ Support member 49, 51 Groove 50 Partition wall 51 Upper end section 52 Rectangular section 53 Partition wall Upper end 54 Guide protrusion 57 Cleaning liquid 58 Cleaning liquid reservoir 59 Power supply 60 Recording head cleaning means M Print medium

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kazuo Ishii 4,000 Kawajiri, Yoshida-cho, Haibara-gun, Shizuoka Prefecture Inside Fujisha Shin Film Co., Ltd. Incorporated F term (reference) 2C056 EA16 EA28 EB20 EB30 EC21 EC43 FA07 FA13 HA33 JB15 JB18 2C057 AF01 AG22 BD05

Claims (15)

[Claims] 1. An ink-jet printing method in which an image is formed directly on a print medium by an ink-jet method in which an oil-based ink is discharged using an electrostatic field based on a signal of image data, and the image is fixed to form a printed matter. A method of immersing an ink jet recording head in a cleaning liquid, and cleaning the recording head by applying a voltage to the recording head. 2. The method according to claim 1, wherein the oil-based ink has a specific electric resistance value of 10.
^2. The ink-jet printing method according to claim 1, wherein at least colored particles are dispersed in a non-aqueous solvent having a resistivity of not less than ⁹ Ωcm and not more than 3.5. 3. An image forming means for forming an image directly on a print medium based on a signal of image data, and an image fixing means for fixing an image formed by the image forming means to obtain a printed matter, In a printing apparatus, which is an inkjet drawing apparatus in which the image forming unit discharges oil-based ink from a recording head using an electrostatic field, in a state where the recording head is immersed in a cleaning liquid,
An ink jet printing apparatus comprising: a recording head cleaning unit that performs cleaning by applying a voltage to the recording head. 4. The oil-based ink has a specific electric resistance of 10
4. The printing apparatus according to claim 3, wherein at least colored particles are dispersed in a non-aqueous solvent having a resistivity of not less than ⁹ Ωcm and not more than 3.5. 5. The printing apparatus according to claim 3, further comprising dust removing means for removing dust existing on the surface of the print medium before and / or during printing on the print medium. 6. When drawing on the print medium, drawing is performed by rotating an opposing drum disposed at a position facing the recording head through the print medium to move the print medium. The printing apparatus according to any one of claims 3 to 5, wherein the printing apparatus is a printing apparatus. 7. The printing apparatus according to claim 6, wherein the recording head is a single-channel head or a multi-channel head, and performs drawing by moving the head in the axial direction of the opposing drum. 8. The image forming apparatus according to claim 3, wherein at the time of drawing on said print medium, drawing is performed by nipping and running said print medium by at least a pair of cap stun rollers. The printing device according to the above. 9. The image forming apparatus according to claim 8, wherein the recording head comprises a single-channel head or a multi-channel head, and performs drawing by moving the recording head in a direction perpendicular to a running direction of the print medium. Printing equipment. 10. The printing apparatus according to claim 6, wherein the recording head comprises a full line head having a length substantially equal to a width of the print medium. 11. The ink-jet drawing apparatus according to claim 3, further comprising an ink supply unit for supplying the oil-based ink to the recording head.
A printing device according to any one of the preceding claims. 12. The printing apparatus according to claim 11, further comprising an ink collecting means for collecting the oil-based ink from the recording head, and performing ink circulation. 13. The ink jet drawing apparatus according to claim 3, further comprising a stirring unit for stirring the oil-based ink in an ink tank storing the oil-based ink.
13. The printing apparatus according to any one of claims 12 to 12. 14. The ink-jet drawing apparatus according to claim 3, further comprising an ink temperature management unit for managing a temperature of the oil-based ink in an ink tank storing the oil-based ink. The printing device according to the above. 15. The printing apparatus according to claim 3, wherein the inkjet drawing apparatus has an ink density control unit that controls the density of the oil-based ink.