JPH11291604A - Printer and printing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide simply and easily the output of offset printing picture quality. SOLUTION: A toner image is formed on a plate 19 by using the electronic photograph method, and the toner image is fixed temporarily by heat to form a temporary plate provided with the high speed properties equivalent to that of an electronic photograph. Waterless lithographic ink is wall-formed on the plate 19, and the ink is transferred onto a material 11 to be printed to carry out the lithographic printing. The toner image fixed temporarily on the plate 19 as an object having an ink-repellent surface is removed together with an ink image remaining on the toner image after printing to form a rewritable plate 19.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a printing apparatus and a printing method using a rewritable plate that represents the gradation of an image by the size of a halftone dot.

[0002]

2. Description of the Related Art Conventionally, so-called electrophotographic printers such as laser printers and LED printers have been proposed, and these printers have been used to obtain a relatively small number of output of one or several sheets. Was. On the other hand, the lithographic printing method is used for obtaining a relatively large number of outputs.

[0003] Electrophotographic printers can be used with simple operations, but draw images one by one, requiring a certain amount of time for output, and are more expensive than general printing systems. Therefore, it is not suitable for outputting a large number of sheets. On the other hand, in the lithographic printing method, since the print data is only transferred once to the “media”, which is an intermediate medium, and then only transferred from the “media” to the paper, the time for outputting a large number of sheets is short, and
Since the ink is relatively inexpensive, the cost can be kept low.

[0004] In terms of image quality, there has been a remarkable improvement in the image quality of electrophotographic printers in recent years. At present, the image quality is high and the lithographic printing method still has a long day.

[0005] The thickness of the image contributes to such discomfort. That is, while the printed matter output by the electrophotographic method has a toner thickness of about 10 to 30 μm,
This is because the ink thickness of the printed matter output by lithographic printing is only about 0.5 to 2 μm, and the lithographic printed matter is finished as a printed matter that does not impair the feel of the printing material.

On the other hand, such a lithographic printing method requires time and cost for plate making, so that when the number of output sheets is small, the cost becomes higher and the time is longer than that of the electrophotographic method. Had become.

[0007]

Therefore, there is a need for a new printing system which can obtain the image quality of a lithographic printing system while maintaining the simplicity of an electrophotographic printer, and which does not require much cost and time even when outputting a small number of sheets. Have been.

In view of the simplicity of the electrophotographic printer, various plate making methods for the offset printing plate using the electrophotographic method have been devised. This is, for example, using a zinc oxide as a photoreceptor, forming an electrostatic latent image directly from an underlay document electrophotographically, developing with a wet toner and fixing on the zinc oxide surface as a lithographic plate, This is a printing method in which the surface is a hydrophilic portion and the toner image portion is a hydrophobic portion, and offset printing is performed using oil-based ink.

[0009] In order to simplify printing, various methods called waterless lithography have been devised and actually used. This is because in conventional offset printing, a hydrophilic portion and a lipophilic portion are formed on a plate surface by plate making, and water (fountain solution) and oil-based ink are supplied to the plate surface to cause the ink to adhere to the lipophilic portion. While this was transferred to plain paper via a blanket, a special photosensitive lithographic printing plate was used to form a lithographic printing plate that did not require dampening water at the time of printing. Instead, printing is performed by applying a lipophilic ink.

However, in this method, the photosensitive lithographic printing plate needs to be treated with a developing solution, which requires a preparation of a developing solution and a developing machine, which requires a large cost. Further, in these methods, it is necessary to switch the “plate” for each image, and when the number of prints is small, it is inevitable that the printing becomes expensive.

Various proposals have been made for a printing apparatus that reuses "plates" instead of disposable ones. In particular, JP-A-56-43646 describes a method of forming a toner image by an electrophotographic method, transferring the toner image to a reusable offset printing plate, and printing a large number of sheets. However, all of them have problems with printing durability, have not been put into practical use, and have not gone out of their research.

In the name of a printing machine without a “plate”,
In recent years, printing apparatuses called on-demand printing machines have appeared. This is an electrophotographic system itself or an extension thereof, and is inferior to the image quality of a general printing system in image quality.

Accordingly, the present invention is not limited to the conventional concept that "it is meaningless unless a large number of sheets can be printed because of the printing method", and "the printing durability is not required if only one sheet is printed. Rewritable by weakening the adhesion of the toner to the plate material to provide a printing device and a printing method based on a new concept of a simple printer capable of obtaining an output having image quality of offset printing. What you want to do.

[0014]

In order to solve the above-mentioned problems, a printing apparatus according to the present invention is a printing apparatus that performs printing in which the gradation of an image is represented by the size of halftone dots using a rewritable plate. A toner image forming means for forming a toner image having ink affinity on the photoreceptor; and a toner adhered at a temperature of 250 ° C. or less after the toner forming the toner image having ink repellency is adhered. A plate material to which a toner image is formed and transferred from a material that is not completely fixed, a heating means for heating the toner image transferred onto the plate material and temporarily fixing the toner image on the plate material, and an ultraviolet curable waterless offset Ink depositing means for forming an ink image by depositing ink for a toner image assumed on a plate material, transfer means for transferring the ink image to a printing material, and applying the ink image to the printing material. Remains on the plate after being transferred The toner image and a toner image removing means for removing with remaining ink image on the plate material.

In the printing apparatus, an ink image corresponding to the first toner image is transferred to a printing material, and the first toner image remaining on the printing material is removed from the printing material. By forming the second toner image on the photoconductor,
It is characterized in that different images are repeatedly printed.

That is, using an electrophotographic technique, a toner image is formed on an object having an ink repellent surface on which the toner is not completely fixed by heating at 250 ° C. or less with a toner having an ink affinity, and this is heated. By assuming that
By using a temporary plate, it achieves the same high speed as electrophotography. At the same time, the plate is coated with waterless lithographic ink, and this ink is transferred to a printing material (paper, etc.) to perform lithographic printing. Realize.

Further, after printing, a rewritable plate is realized by removing the toner image assumed on the object having the ink repellent surface together with the ink image remaining on the toner image.

Conventionally, there has been a pre-established concept that mass printing must be performed using this plate. Therefore, it has been attempted to prevent this image from peeling off, and the plate is made weak enough to be rewritable. There was no idea. In the present invention, the above-mentioned problem has been solved by aiming to obtain one output using such a plate.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, the printing apparatus according to the present invention has a casing 1 and an electrophotographic unit 2 on the casing 1. This electrophotographic unit 2
Is a cylindrical photosensitive member 3 driven by a motor (not shown) to be rotated in the direction of arrow A in FIG. 1, a charging charger 4 for charging the outer peripheral surface of the photosensitive member 3, and a laser on the photosensitive member 3. A laser beam irradiation device 5 for exposing a light beam, a developing device 6, a transfer charger 7 as a transfer portion, and a photoconductor 3
A first cleaning device 9 having a blade A8 in contact with the outer peripheral surface of the first cleaning device 9;

The laser beam irradiation device 5 includes a semiconductor laser oscillator, a polygon mirror 5a that is rotated, a lens 5b,
The laser beam emitted from the semiconductor laser oscillator is irradiated onto the outer peripheral surface of the photoconductor 3 while scanning the outer peripheral surface of the photoreceptor 3. The semiconductor laser oscillator is configured to irradiate the surface of the photoconductor 3 with laser light based on predetermined image data.

The housing 1 is located near the photoconductor 3 and
A charging charger 4 is provided. When the photoreceptor 3 is rotated, the charging charger 4 causes the photoreceptor 3 to rotate.
The portion of the outer peripheral surface to be irradiated with the laser beam is disposed at a position facing the laser beam prior to irradiation.

The housing 1 is provided with a developing device 6 located near the photoconductor 3. When the photoconductor 3 is rotated, the developing unit 6 is disposed at a position on the outer peripheral surface of the photoconductor 3 where the portion irradiated with the laser beam is next to the irradiation position of the laser beam. Have been. The developing device 6 supplies a toner, which is a colored charged fine particle, to the electrostatic latent image formed on the photoreceptor 3 by irradiating the laser beam and electrostatically adheres the toner to form a toner image.

The housing 1 is provided with a first cleaning device 9 having a first blade 8 located near the photoconductor 3 and in contact with the outer peripheral surface of the photoconductor 3. . When the photoconductor 3 is rotated, the first cleaning device 9 passes through a position corresponding to the developing device 6 on the outer peripheral surface of the photoconductor 3 and further faces a plate cylinder 19 described later. The portion that has passed the position is disposed at a position facing the plate cylinder 19 next. The first cleaning device 9 uses the first blade 8 to
The toner and other attached matter (paper powder, etc.) remaining on the outer peripheral surface portion of the unremoved portion and not transferred are removed.

Further, a static elimination lamp 10 is provided in the housing 1 in the vicinity of the photoconductor 3. When the photoreceptor 3 is rotated, the portion of the outer peripheral surface of the photoreceptor 3 that has passed a position corresponding to the first cleaning device 9 is located next to the first cleaning device 9. In addition, it is disposed at a position facing the charging charger 4 before facing the charging charger 4.

In the lower part of the housing 1, a paper feed cassette case 12 capable of holding a plurality of sheets 11 in a stacked state and keeping the height of the uppermost sheet 11 constant is provided.
It is provided detachably with respect to the housing 1. The topmost sheet of paper 11 in the paper cassette case 12
The paper cassette case 1 is rotated by a paper feed roller 13 provided in the housing 1 so as to be rotatable in contact with the paper 11.
2 to the outside. The sheet 11 sent out of the sheet cassette case 12 is transferred to a registration roller 14.
Is further operated.

Further, the paper 1 by the registration roller 14
An impression cylinder 16 that is rotated in the direction of arrow B in FIG. The impression cylinder 16 has a notch 16a on the outer peripheral surface, and has a clamper 15 in the notch 16a. Paper cassette case 12
The paper 11 sent out by the registration rollers 14 is held at the front end side by a clamper 15, and is wound around the outer peripheral surface of the impression cylinder 16 by rotating the impression cylinder 16.

A discharge roller 1 for discharging the paper 11 wound on the outer peripheral surface of the impression cylinder 16 is provided on the housing 1.
7 are provided. This paper discharge roller 17 is
The front end side of the paper 11 wound on the outer peripheral surface of the
To the outside of the box. The sheet 11 sent by the sheet discharge roller 17 is guided to a sheet discharge table 18 attached to the housing 1.

In the vicinity of the impression cylinder 16, an ultraviolet lamp 2 serving as an ink drying device for irradiating ultraviolet rays to the sheet 11 before being separated from the impression cylinder 16 by the paper ejection roller 17.
6 are provided.

Then, between the photoreceptor 3 and the impression cylinder 16,
A cylindrical plate cylinder 19 serving as a plate material is rotatably provided. The outer peripheral surface of the plate cylinder 19 is coated with a material having ink repellency, for example, silicone rubber, to form a plate material. The plate cylinder 19 is driven by a drive mechanism (not shown) as shown by an arrow C in FIG.
The photoreceptor 3 is rotated at the same peripheral speed in a rotational direction in which the outer peripheral surface moves in the same direction as the outer peripheral surface of the opposing photoreceptor 3.

The transfer charger 7 is provided inside the plate cylinder 19. The transfer charger 7 includes the plate cylinder 1
9, the position closest to the photoconductor 3 is set as
It is arranged fixed to the housing 1. The transfer charger 7 transfers the toner image formed on the photoreceptor 3 to the outer peripheral surface of the plate cylinder 19 when the photoreceptor 3 and the plate cylinder 19 are rotated by bringing the outer peripheral surfaces thereof into contact with each other.

The housing 1 is provided with a hypothetical wearing xenon flash hypothetical wearer 20 located near the plate cylinder 19. This Xenon flash hypothetical dresser 20
When the plate cylinder 19 is rotated, a portion of the outer peripheral surface of the plate cylinder 19 that has passed a position corresponding to the transfer charger 7 is disposed at a position facing the transfer charger 7 next. I have.

Further, the housing 1 is provided with an ink supply device 21 located near the plate cylinder 19. When the plate cylinder 19 is rotated, the ink supply device 21
The portion of the outer peripheral surface of the plate cylinder 19 which has passed through a position corresponding to the assumed xenon flash dresser 20 is disposed at a position sequentially facing the xenon flash assumed dresser 20 next. The ink supply device 21 includes a plurality of ink supply rollers 21a and 21b, and is provided with the ink supply rollers 21a and 21b.
An ultraviolet curing type waterless offset ink is supplied to the plate forming the outer peripheral surface of the plate cylinder 19 to perform the inking.

Further, the housing 1 is provided with a second cleaning device 23 having a second blade 22 which is located near the plate cylinder 19 and is in contact with the outer periphery of the plate cylinder 19.
When the plate cylinder 19 is rotated, the second cleaning device 23 passes through a position corresponding to the ink supply device 21 on the outer peripheral surface of the plate cylinder 19, and further moves the impression cylinder 16.
The portion that has passed through the position opposite to the impression cylinder is disposed at a position next to the impression cylinder. The second cleaning device 23 removes the toner image supposedly attached to the outer peripheral surface of the plate cylinder 19 together with the ultraviolet curable waterless offset ink attached to the toner image by the second blade 22.

Further, the housing 1 is provided with a third cleaning device 24 which is located near the plate cylinder 19 and has a roller body which comes into contact with the outer periphery of the plate cylinder 19. This third
When the plate cylinder 19 is rotated, the portion of the outer peripheral surface of the plate cylinder 19 that passes through a position corresponding to the second cleaning device 23 is the second cleaning device 24.
The cleaning device 23 is disposed at a position next to the cleaning device 23. The third cleaning device 24 is a plate cylinder 1 that cannot be removed by the second cleaning device 23.
9 to remove the toner image and the UV curable waterless offset ink.

The housing 1 is provided with a static elimination brush 25 located near the plate cylinder 19 and in contact with the outer periphery of the plate cylinder 19. When the plate cylinder 19 is rotated, the portion of the outer peripheral surface of the plate cylinder 19 that has passed through a position corresponding to the third cleaning device 24 is located next to the third cleaning device 24. In addition, prior to reaching the position corresponding to the transfer charger 7, it is disposed at a position facing the transfer charger 7. The static elimination brush 25 performs static elimination of the plate cylinder 19.

In the printing apparatus according to the present invention configured as described above, the printing method according to the present invention is executed.
That is, in this printing apparatus, first, a toner image is formed on the photoconductor 3 by the so-called electrophotographic process by the laser beam irradiation device 5 and the developing device 6. The toner image on the photosensitive member is transferred by the transfer charger 7 as shown in FIG.
As shown in the middle (a), the toner image is transferred to the plate cylinder 19 and becomes a toner image 30a on the plate cylinder 19. The surface of the plate cylinder 19 has ink repellency. As shown in FIG. 2B, the toner image 30a on the plate cylinder 19 becomes a toner image 30b that is heated and assumed by the xenon flash assumed attachment 20. This toner image 30b is ink-friendly.

Next, the assumed toner image 30b includes:
As shown in FIG. 2C, the ultraviolet curable waterless offset ink 27 is deposited by the ink supply rollers 21a and 21b of the ink supply device. At this time, the ultraviolet curable waterless offset ink 27 does not adhere to the outer peripheral surface of the plate cylinder 19 having ink repellency, but adheres only to the toner image 30b having ink affinity. That is, the ink image 30c is formed on the toner image 30b.

The outer peripheral surfaces of the ink supply rollers 21a and 21b of the ink supply device 21 are not in contact with the surface of the plate cylinder 19 except when the ink is applied to the plate cylinder 19, and the ink deposition is not performed. Only at this time, it is moved by a driving device (not shown) and comes into contact with the plate cylinder 19. In the ink supply device 21, an ink layer having an appropriate viscosity and an appropriate thickness can be supplied to the surfaces of the ink rollers 21a and 21b.

Then, as shown in FIG. 3A, the paper 11 fixed on the outer peripheral surface of the impression cylinder 16 is pressed against the plate cylinder 19 by the clamper of the impression cylinder 16 and the ink on the toner image 30b is pressed. The image is transferred to the sheet 11 as an ink image 30d, and printing is performed. The paper 11 on which printing has been performed in this manner is obtained by further rotating the impression cylinder 16.
Ultraviolet light is irradiated by an ultraviolet lamp to cure the transferred ink image 30d.

On the other hand, as shown in FIG.
9 and the ink image 30e remaining on the toner image 30b and the second blade 22
Is removed by What has not been completely removed by the second blade is wiped off with a cleaning sheet having an adhesive property in a third cleaning device and removed.
In this printing apparatus, the toner image 30b on the plate cylinder 19 is not firmly fixed to the surface of the plate cylinder 19, and can be easily removed.

Further, by rotating the plate cylinder 19,
The surface of the plate cylinder 19 is neutralized by a neutralization brush to prevent a toner image transfer failure due to unnecessary charging.

In other words, in this printing apparatus, a plate cylinder which is an ink-repellent toner having an ink-repellent surface and is not completely fixed by heating at 250 ° C. or less using a so-called electrophotographic method. A temporary image is formed on a toner image formed thereon, and the image is temporarily attached by heat, thereby realizing high-speed operation comparable to electrophotography.
Further, lithographic printing is realized by depositing waterless lithographic ink on the plate cylinder and transferring the ink to a printing material (paper or the like). After printing, the rewritable plate is realized by removing the toner image assumed on the plate cylinder together with the ink image remaining on the toner image.

In this embodiment, the ink image formed on the plate cylinder is directly transferred to the paper. However, the ink image on the plate cylinder is transferred to the offset cylinder as in normal offset printing. However, the ink image of the offset cylinder may be transferred to a sheet.

Further, in this embodiment, the case where printing is performed using only one color ink has been described. However, this printing apparatus uses four different colors of ink, for example, cyan, magenta, yellow, and black. By repeating plate making and printing, full-color printing can be performed. In this printing apparatus, when performing full-color printing, the mechanism of the present invention may be prepared for four colors of cyan, magenta, yellow, and black. If four colors of yellow and black are prepared, one photoconductor, one plate cylinder, and one impression cylinder may be provided. That is, full color printing can be performed by repeating the plate making and printing processes four times while replacing only the ink supply device while holding the paper by the clamper of the impression cylinder.

Further, in this embodiment, a cylindrical (cylindrical) photosensitive member is used as the photosensitive member, but a belt-like photosensitive member may be used.

In this embodiment, a toner image is formed on a photoreceptor, and then this toner image is transferred to a plate cylinder. The surface of the plate cylinder is made of a dielectric material having ink repulsion. After forming an electrostatic latent image on the photoreceptor, the latent image may be transferred to a plate cylinder, and the toner may be developed on the plate cylinder to form a toner image.

Further, the photosensitive drum and the plate cylinder are not separated from each other, but a transparent silicone rubber layer or the like is provided on the photosensitive drum to form a single unit, on which an electrostatic latent image is directly formed and developed. What was done may be used as a plate. Further, the plate cylinder is not limited to the drum-shaped one as described above, and may be a belt-shaped one.

When a colorless and transparent toner is used, even when a part of the toner forming the image is carried along with the ink when the ink is transferred to the printing material, the printed matter can be printed. The defect that the color of the toner can be seen at the same time can be avoided. However, in this case, since the heating cannot be performed by the assumed xenon flash dresser, another heating means is used. Similarly, the above defect can be avoided by using a color similar to the color of the ink used to print the color of the toner.

In this embodiment, a transfer charger is used to transfer a toner image from a photosensitive member to a plate cylinder. However, a bias transfer roller may be used.
Alternatively, pressure transfer may be used.

In the above embodiment, the two cleaning devices, the second cleaning device and the third cleaning device, are used as the cleaning device for the plate cylinder after the ink transfer.
This may be only one of them. Further, if there is no significant adverse effect even when the plate cylinder is charged, the charge removing brush may be omitted.

[0052]

As described above, in the printing apparatus according to the present invention, a toner image is formed by using an electrophotographic technique, and the toner image is temporarily put on by heat to form a temporary printing plate. Achieves high speed comparable to a photograph. Further, lithographic printing is realized by depositing a waterless lithographic ink on the plate and transferring the ink to a printing material. After printing, the plate is made rewritable by removing the toner image assumed on the object having the ink-repellent surface and the ink image remaining on the toner image. This version is intended to get one output.

In other words, the present invention is not restricted to the conventional concept that "it is meaningless unless a large number of sheets can be printed because of the printing method", and "the printing durability is not required if only one sheet is printed. Rewritable by weakening the adhesion of the toner to the plate material to provide a printing device and a printing method based on a new concept of a simple printer capable of obtaining an output having image quality of offset printing. Is what you can do.

[Brief description of the drawings]

FIG. 1 is a front view showing a configuration of a main part of a printing apparatus according to the present invention.

FIG. 2 is a side view showing first to third steps of plate making and printing executed in the printing apparatus.

FIG. 3 is a side view showing fourth to fifth steps of plate making and printing executed in the printing apparatus.

[Explanation of symbols]

Reference Signs List 3 photoreceptor, 5 laser beam irradiation device, 7 transfer charger, 9 first cleaning device, 15 clamper, 1
6 plate cylinder, 19 plate cylinder, 20 Xenon flash assumed dresser, 23 first cleaning device, 24 third cleaning device

Claims (2)

[Claims] 1. A printing apparatus for performing printing using a rewritable plate to represent the gradation of an image by the size of a halftone dot, wherein the toner image forming device forms a toner image having ink affinity on a photoreceptor. After the toner having the ink repellency and forming the toner image is attached, at a temperature of 250 ° C. or less, the attached toner is formed of a material that is not completely fixed, and the toner image is transferred. Plate material, a provisional application means for heating the toner image transferred onto the plate material and presumably applying the toner image onto the plate material, and an ultraviolet curable waterless offset ink is presumably applied on the plate material. An ink filling unit for forming an ink image on the toner image, a transfer unit for transferring the ink image to a printing material, and the plate material after the ink image is transferred to the printing material. The remaining toner image on this plate And a toner image removing means for removing the ink image corresponding to the first toner image on the printing material to form a single printed matter. A printing apparatus for printing different images repeatedly by forming a second toner image on a photoreceptor after removing a first toner image from the plate material. 2. A printing method for performing printing using a rewritable plate to represent the gradation of an image by the size of halftone dots, comprising forming a first toner image having ink affinity on a photoreceptor. When the toner which forms the toner image and has ink repellency is adhered, the first toner image is formed on a plate material formed of a material in which the adhered toner is not completely fixed at a temperature of 250 ° C. or less. The first toner image transferred and transferred onto the plate material is heated and assumed on the plate material, and the ultraviolet curable waterless offset ink is first assumed on the plate material. After the ink image is formed on the toner image to form an ink image, the ink image is transferred to a printing material, one printed matter is prepared, and the ink image is transferred to the printing material. The first toner image remaining on the plate is replaced with the ink remaining on the plate material. Was removed with, then, by forming a second toner image on the photoconductor, printing method and performing printing of repeated different images.