JPH06246897A - Printer - Google Patents

Abstract

PURPOSE:To prevent the generation of scumming of a press plate because of the remaining ink on blankets and the thickening of an image and increase of slippage and provide a good printing matter by using inks of wide range. CONSTITUTION:Ink 4 applied selectively on a press plate 5 is transferred to blankets 10, and further transferred to a body 12 to be transferred in a printer. A means 16 is provided for drying the ink 4 remaining on the blankets 10 after the ink has been transferred to the body 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing apparatus for selectively depositing ink for printing, and more particularly to a printing apparatus used in the field of light printing such as office printing.

[0002]

2. Description of the Related Art In a printing apparatus, an ink supply roll for supplying viscous ink to a plate cylinder, a plate cylinder for mounting a printing plate, and an ink that is selectively deposited on a plate according to an image are transferred. It consists of a blanket cylinder and an impression cylinder wrapped with a blanket, and between the blanket and the impression cylinder,
When a transfer target such as paper, synthetic paper, or a plastic film passes through, the ink on the blanket is transferred to the transfer target, and a printed matter can be obtained.

[0003]

However, in the above-mentioned conventional printing apparatus, the ink adhered to the area where the ink should not adhere, such as the background stain on the printing plate, is transferred to the blanket, and Unnecessary residual ink may be retransferred from the blanket to the printing plate, resulting in increased background stains. In particular, in the case of a small office offset printing apparatus, the mechanical accuracy is not so high as compared with a commercial printing apparatus, and it is difficult to maintain the rotational position accuracy of the plate cylinder and the blanket cylinder accurately and uniformly during printing. Adjust the pressure settings of the plate cylinder and blanket cylinder, and the blanket cylinder and impression cylinder according to the thickness of the printed image and the thickness of the transfer target,
It is also difficult to print accurately and consistently.

For the above reasons, background stains on the printing plate, image thickening and image shift on the blanket are likely to occur, and the ink remaining on the blanket after transfer is retransferred to the printing plate.
It is transferred to the blanket again, and by repeating this process, background stains, image thickening and misregistration increase, and defective prints occur.

In the case of lithographic printing, such residual ink can be removed by increasing the dampening water supply amount or decreasing the ink supply amount, but during the removal process,
It is necessary to stop the transfer of ink to the transfer target.
At this time, even if printing is continued without stopping, only defective printed matter is obtained, resulting in poor efficiency.

As a means for preventing the retransfer of the residual ink from the blanket to the printing plate, there is a method of using the quick-drying ink to quickly dry the surface of the residual ink after the blanket ink is transferred to the transfer target. However, when the quick-drying ink is used, the ink is clogged in a short time, and it is necessary to frequently clean and clean the ink fountain and the ink supply roll. In order to prevent this, it is conceivable to use an ink whose surface is dried quickly enough to prevent retransfer and which can be used without cleaning the ink fountain and the ink supply roll for a necessary period of time. It is very difficult to get.

Therefore, an object of the present invention is to provide a printing apparatus capable of preventing the ink remaining on the blanket after transfer from being retransferred onto the printing plate.

[0008]

SUMMARY OF THE INVENTION The present invention is a printing apparatus comprising an ink supply body, an ink supply roll, a plate cylinder, a blanket cylinder having a blanket, and an impression cylinder, wherein the means for drying the ink remaining on the blanket is the blanket. And a printing apparatus characterized by being installed facing the surface not coated with the transfer ink.

That is, in the printing apparatus of the present invention, the above-mentioned drying means dries the ink remaining on the blanket after the ink has been transferred to the transfer medium, thereby re-transferring the ink remaining on the blanket to the printing plate. And give good prints.

[0010]

The present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic sectional view of a printing apparatus for carrying out lithographic printing, which is an example of the printing apparatus of the present invention.

The ink supply body 1 comprises an ink fountain 2 and a plurality of ink supply rollers 3, and the ink 4 in the ink fountain is supplied onto the printing plate 5 by these ink supply rollers 3. The number of the ink supply rollers 3 is not particularly limited, but it is preferably about 4 to 20 in consideration of the kneading condition of the ink and the thickness of the ink layer.

The plate 5 attached to the plate cylinder 6 may be any plate as long as it is formed with a portion that is easily wetted by dampening water and a portion that is not easily wetted by dampening water, for example, a PS plate. The electrophotographic printing plate (so-called pink master), the printing plate described in Japanese Patent Application No. 3-220009, and the like are used.

An oleophilic ink as the ink 4 is supplied to the printing plate 5 by the ink supply body 1.
Prior to this ink supply, dampening water 7 is supplied. That is, by the rotation of the plate cylinder 6 in the direction of arrow A, the dampening water 7 is first supplied to the printing plate 5, and then the ink 4 is supplied.

By doing so, the dampening water 7 is retained and the ink 4 does not adhere to the wettable portion of the printing plate 5, and the dampening water 7 is repelled at the hard to wet portion of the printing plate 5. The ink adheres, and the ink 4 selectively adheres to the printing plate 5 according to the wettability. The dampening water 7 is supplied from the dampening water reservoir 9 to the printing plate 5 by a plurality of dampening water supply rollers 8. The number of dampening water supply rollers is not particularly limited, but is preferably about 2 to 10.

The printing plate 5 has a blanket 10 wound around a blanket cylinder 17 which rotates in the opposite direction to the plate cylinder 6.
Is in contact with the blanket 10 and the impression cylinder 11 is in contact with the blanket 10. The impression cylinder 11 rotates in the opposite direction to the blanket cylinder 17. In this way, the ink on the printing plate first comes in the blanket 10.
Then, the image is transferred onto the transfer target 12 such as paper or plastic that passes between the blanket 10 and the impression cylinder 11, and the printing is completed.

It is preferable that the plate cylinder, the blanket cylinder around which the blanket is wound, and the impression cylinder all have the same diameter, and they are driven by gears (not shown) in conjunction with each other so that the peripheral speeds are equal to each other.

Further, the blanket serves as a bridge for transferring ink from the printing plate to the transferred material, and if the ink is well transferred from the printing plate to the transferred material, Any material may be used, but it is common to use a rubber that is soft and can contact the transferred body smoothly, and also contacts the transferred body having irregularities well. As the rubber, nitrile rubber, natural rubber,
Urethane rubber, nylon, acrylic rubber, thiocol,
Butter rubber or the like is preferable, and usually, a reinforcing fiber or the like is provided inside or under the layer to reduce deformation.

The above-mentioned rubber blanket is usually wound around a metal cylinder roll for use, but it may be molded around the metal cylinder roll and integrated with the blanket cylinder. It is also possible to use a blanket of metal, but the transfer target and the printing plate are likely to be damaged and do not move elastically according to the unevenness of the transfer target, so that the ink can be transferred well. It is difficult and unsuitable for obtaining good printed matter.

The transfer-receiving member 12 is housed in a cassette 13 in FIG. 1, and is sent out of the cassette 13 by a feed stop 14. The transferred material 12 for which printing has been completed is discharged to the tray 15.

The drying means 16, which is a feature of the present invention, is located at a position where the ink remaining on the blanket after transferring the ink from the blanket to the transfer medium, that is, FIG.
The blanket from the position B to the position C in the rotation direction of the blanket cylinder is attached at a position where the blanket can be dried.

As the drying means, it is necessary to select a suitable one according to the ink to be used, but at least the surface of the ink should be dried (so-called set) and not retransferred to the printing plate. Examples of such methods include air blowing, steam blowing, microwave heating, infrared heating, ultraviolet irradiation, and electron beam irradiation. Of these, drying means such as an air blow method and an infrared heating method are usually preferable, and when an ultraviolet curable ink is used, an ultraviolet irradiation method is preferable.

Various forms of drying means are conceivable. For example, in the case of an air blow type drying means, FIG.
(A) is a schematic view and FIG. 2 (b) is a cross-sectional view. Those provided with slit-shaped openings, those provided with small-diameter hole-shaped openings, those blown with air from a nozzle, etc. Can be mentioned. Furthermore, a plurality of such drying means may be used. The air pressure introduced is preferably 0.
1 to 20 kgf / cm ² , more preferably 0.3 to 15
It is kgf / cm ² . The air temperature is preferably -15 to 100 ° C, more preferably -5 to 80 ° C.
It is a degree. At temperatures below this, water condensation is likely to occur, and the production of such low-temperature air leads to a significant cost increase. On the other hand, at a temperature higher than that, the blanket accumulates heat, which also heats the printing plate, the plate cylinder, and the ink supply member, and the viscosity of the ink changes with time, making it difficult to perform stable printing.

Further, when the air blow type means is used, in addition to drying, it is possible to remove paper dust, dust and the like adhering to the blanket.

In FIG. 1, the ink supply roller 3 and the dampening water supply roller 8 are provided independently, but the dampening water 7 is dampened on the ink supply roller 3 by the dampening water supply roller 8.
It is also possible to supply the ink 4 and the dampening water 7 onto the printing plate 5 at the same time by supplying the ink 4 and the dampening water 7 via This makes it possible to reduce the size of the printing apparatus, and is therefore suitable for a desktop lithographic printing apparatus.

Although FIG. 1 illustrates an apparatus using a printing plate having a difference in wettability, a so-called waterless planographic plate having a difference in ink adhesion can also be used as a printing plate. No need for dampening water supply.

Further, as described in, for example, Japanese Patent Laid-Open No. 3-240580, when light and / or heat energy of a specific wavelength is applied, a change in molecular structure or the like occurs, and the energy applying section and non-applying section. Plate cylinder coated with a material that causes a difference in wettability between the parts and returns to the original state by re-application of light and / or heat energy, or a plate cylinder made of such a material, that is, the plate cylinder itself. May be used as a printing plate for reuse. In that case, it is not necessary to mount the printing plate on the plate cylinder, but plate making means (not shown) such as an optical unit and a heating unit is required.

Further, the printing plate is not limited to a planographic plate, but may be a relief plate or an intaglio plate.

In FIG. 1, the ink supply body supplies ink from the ink fountain to the printing plate through rollers.
The ink supply means is not limited to this, and for example, ink may be supplied onto the printing plate using an ink ribbon in which a thin ink layer is formed on a plastic film support.

[0030]

The present invention will be described in more detail with reference to the following examples.

Example 1 A drying means, shown in FIGS. 2 (a) and 2 (b), consisting of two tubes having slit-like openings and separated from each other by about 40 mm, was placed at a distance of about 10 mm from the blanket. Using the printing apparatus shown in FIG. 1 installed at the position, Japanese Patent Application No. 3-2
A printing plate described in 200009 or a so-called pink master printing plate on which a toner image is formed by an electrophotographic method is attached to the plate cylinder, and an oil-based ink (trade name: BSD New Rubber Ink Silver, manufactured by Bunshodo) is used as the ink and dampened. When water was used and printing was performed at a printing speed of 120 sheets / min while performing air blowing, no retransfer of the ink to the printing plate was observed, and a good printed matter could be obtained. The diameter of the tube of the drying means is about 20 mm, and the introduced air pressure is 5 kgf /
The cm ² and air temperature were set to 27 ° C.

[0032]

As described above, the printing apparatus of the present invention can prevent the ink remaining on the blanket from being retransferred to the printing plate after the transfer to the transfer object, thereby causing the background stain and the image formation. It is possible to prevent an increase in thickness and misalignment, and it is possible to efficiently obtain a good printed matter.

Further, in the apparatus of the present invention, since it is not always necessary to use the quick-drying ink, the selection range of the ink is widened, and even when the relatively slow-drying ink is used, the blanket of the residual ink is changed to the printing plate. Retransfer can be prevented, and a slow drying ink can be used.
Therefore, a good printed matter can be obtained when printing is performed for a long time, or when printing is restarted after being left for a long time.

The printing apparatus of the present invention is particularly useful as a small-sized printing apparatus for office work in which scumming, image thickening and misalignment easily occur due to mechanical precision.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an embodiment of a printing apparatus of the present invention.

2A and 2B are views showing an air-blow type drying means having a slit-shaped opening, FIG. 2A is a schematic view thereof, and FIG. 2B is a schematic sectional view thereof.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ink supply body 2 Inkwell 3 Ink supply roller 4 Ink 5 Printing plate 6 Plate cylinder 7 Dampening water 8 Dampening water supply roller 9 Damping water reservoir 10 Blanket 11 Impressing drum 12 Transferred material 13 Cassette 14 Feeding tray 15 Tray 16 Drying device 17 Blanket cylinder

Claims (2)

[Claims] 1. A printing apparatus comprising an ink supply body, an ink supply roll, a plate cylinder, a blanket cylinder having a blanket, and an impression cylinder, wherein a means for drying the ink remaining on the blanket is coated with transfer ink for the blanket. A printing device characterized by being installed facing the non-exposed surface. 2. The printing apparatus according to claim 1, wherein the drying means is an air blow type, a steam blowing type, a microwave heating type, an infrared heating type, an ultraviolet irradiation type and / or an electron beam irradiation type.