JPS63188047A - Gravure press - Google Patents

Abstract

PURPOSE:To make a high-viscosity ink, a quick-drying ink or solvent serviceable without occurrence of clogging in printing to enable a continuous printing of fine characters and images with a sharp printing quality, by a method wherein a brush for scraping an ink remaining in the recessed portions of a plate surface is disposed close to a rotating plate cylinder. CONSTITUTION:A brush 8 for scraping an ink remaining the recessed portions of a plate surface is disposed close to a plate cylinder 6. Even after a plate surface 7 comes into contact with an elastic rubber 9 of a transfer cylinder, an ink remaining in cells is scraped by the brush 8. This brush 8 is so provided that it can approach to or separate from the plate surface and the tip end of the brush is pressed into the cells. The material of brush 8 for use is not particularly limited, but generally a bristle of a natural fiber, such as animal hair and hemp-palm, or a synthetic fiber, such as polypropylene, polyamide, and polyester, is especially preferable because of its resistance to solvent and appropriate rigidity. A material with a fiber diameter of the order of 10mum-1mm is preferable, and particularly that of 50-500mum is desirable.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a gravure printing machine.

[Conventional technology]

Gravure printing involves supplying ink onto a plate cylinder that has recesses (cells) on its surface, then removing unnecessary ink from the plate surface with a doctor blade for ink scraping, filling only the cells with ink, and then printing. The ink is transferred directly or indirectly onto the printing material.

Direct printing machines, which directly print ink on the printing plate onto a printing medium, are widely used for printing packaging films and laminated paper for building materials. Offset printing, which prints indirectly, is also known. In other words, the ink is once offset from the plate cylinder due to its low surface hardness.

There are known printing machines that transfer the material to a rubber cylinder (transfer cylinder) and then use a rubber cushion to transfer it to the printing material, and conventionally, acrylonitrile/butadiene rubber etc. have been used for continuous printing on plywood and metal plates. A printing method using a rubber cylinder as the transfer cylinder is used. Recently, printing machines that use silicone rubber cylinders as transfer cylinders have been used for continuous printing of non-planar objects such as vibrators and hoses.

In this type of printing press, special attention must be paid to maintaining a constant state of ink transfer from the plate cylinder to the printing material, from the printing cylinder to the transfer cylinder, and from the transfer cylinder to the printing material. Due to the difference in transferability, not only the hue but also the reproducibility of the image differs markedly.

The excess ink supplied to the plate is scraped off with a doctor blade, and only the cells are filled with ink. This ink is transferred by contacting the printing medium or the transfer cylinder, but at this time not all of the ink in the cells is transferred. The ratio varies depending on the cell depth, the type and viscosity of the ink, the material of the printing medium or transfer cylinder, the printing speed, etc., but in any case, it is at most about 1/2, and always about 1/2 of the ink is remain inside. This remaining ink is usually mixed and homogenized with fresh ink supplied to the printing plate.

However, if the ink remaining in the cell dries out due to inappropriate printing conditions, even if new ink is supplied to the plate, it will be doctored before it can dissolve and mix, leaving only the surface layer with a low viscosity. Contact the transfer cylinder with fresh ink.

For this reason, the transfer rate gradually decreases, resulting in plate jam. In other words, fine characters and line drawings become blurred, making it impossible to print with beautiful quality. Such a phenomenon is particularly likely to occur in offset printing using high viscosity ink. To avoid this, add a solvent to lower the ink concentration, or
Countermeasures are taken such as using solvents with slow drying speeds and increasing printing speeds, but these adjustments are not easy.
Trial and error based on experience is required.

Moreover, even if this method solves the plate jam, many other problems will occur. When the ink concentration is lowered, the ink film thickness on the printing substrate becomes thinner, that is, thick build-up cannot be achieved. Furthermore, not only the hiding power decreases, but also the swimming of the solid area (mottling) occurs, which lowers the print quality.If a slow-drying solvent is used or the printing speed is increased, the drying time of the print will be burdensome, making it less economical. Particularly when the transfer cylinder is made of silicone rubber, lowering the ink viscosity too much will cause frequent splatter on the surface of the transfer cylinder, and using a slow-drying agent to slow down the drying process will cause problems with the transfer. There was a problem in that the ink transfer on the cylinder was incomplete, resulting in poor print quality.

The phenomenon of plate clogging occurs not only due to the above-mentioned causes, but also due to foreign substances in the ink as well as pigments used. In particular, white ink contains a large amount of inorganic particles such as titanium oxide in order to increase its hiding power, so it is difficult to replace the remaining ink in the cells, and there is a problem that pigments tend to accumulate at the bottom of the cells.

[Problem that the invention seeks to solve]

The present invention was invented in view of the drawbacks of the prior art, and it eliminates plate jams during printing, allows the use of high viscosity ink, quick-drying ink, or solvent, and allows for beautiful printing. The objective is to provide a gravure printing machine that enables continuous printing of fine characters and line drawings with high quality, and also helps save energy during drying.

[Means for solving problems]

The object of the present invention is to provide an apparatus in which a rotating plate cylinder contacts a printing material directly or via a transfer cylinder to transfer and print ink in concave portions of the plate surface, in which a rotating plate cylinder is provided in the vicinity of the plate cylinder,
This is achieved by a gravure printing machine characterized by being equipped with a brush for scraping off residual ink in the concave portions of the printing plate.

The present invention will be described in detail below with reference to a gravure offset printing machine illustrated in the drawings. In the figure, 1 is a doctor blade, 2 is an ink nozzle, 3 is a tray, 4 is a pump,
5 is a tank, 6 is a plate cylinder, 7 is a plate material that is attached to the plate cylinder and has recesses (cells) of a predetermined shape on its surface (i.e., plate surface), and 8 is a plate surface provided close to the plate cylinder 6. A brush is used to scrape off the ink in the recesses, 9 is an elastic rubber, 10 is a transfer cylinder, 11 is a printing medium, and 12 is an impression cylinder.

The ink supplied onto the printing plate by the ink nozzle 2 is scraped off by the doctor blade 1, and the ink is filled only into the cells. Then, by coming into contact with the elastic rubber 9 of the transfer cylinder, some of the ink is transferred onto the elastic rubber. The doctor blade used is a known one made of metal or ceramic.The scraped off excess ink is collected in a tank 6 through a tray 3, and is supplied to the printing plate again from a nozzle by a pump 5 to be reused. Ru. Other known ink supply methods include a method in which a part of the copper plate is directly immersed in an ink pan, and a method in which ink is supplied from an ink pan via a roller. The inks that can be used are commonly used inks such as oil-based, water-based, evaporative drying type, UV cure type, etc., and are not particularly limited. They are selected and used as appropriate depending on the required characteristics.

Even after the plate surface 7 comes into contact with the elastic rubber 9 of the transfer cylinder, the ink remaining in the cells is scraped off by the brush. This brush can be moved toward and away from the printing plate, and is mounted so that the tip of the brush can be pressed into the cells.

The material of the brush to be used is not particularly limited, but when the plate material is a photosensitive resin intaglio plate, a rigid metal brush that easily damages the plate surface is not preferred. Usually, natural fibers such as animal hair and palmetto, and synthetic fibers, such as bristles of polypropylene, polyamide, polyester (polyethylene terephthalate, polybutylene terephthalate, etc.), are particularly preferred because they are solvent resistant and have appropriate rigidity. The diameter of the fibers is appropriately selected; however, if the fibers are too thin, they will not be stiff and will not enter the cells and will simply slide on the surface, resulting in no effect. If it is too thick, it may not fit into the fine cells or may damage the surface of the printing plate. It is preferably about 10μ to 1mm, particularly preferably 50μ to 500μ.

The shape of the brush may be flat or roll-shaped, and is not particularly limited. For example, a flat brush has a cross section of U.
It is manufactured by implanting fibers into a grooved metal plate, caulking it, and then cutting it to the same fiber length. You can also use a wooden square rod with many holes drilled in it and holes planted in it. If necessary, the tip of the brush can be processed to make it rounded or thin.

A rolled brush is manufactured, for example, by wrapping a brush embedded in a U-shaped metal plate in a helical pattern around a metal round bar to make the fiber lengths uniform. You can also use a round rod with many holes drilled, fibers planted in it, and the tips cut and aligned. The rolled brush can be configured to be rotatable, preferably forward and reverse rotation. In order to obtain good effects, it is preferable that both the flat brush and the roll brush be configured to be slidable in the axial direction of the plate cylinder.

The plate cylinder is no different from that used in conventional gravure printing machines, and the surface of the plate material attached to its circumferential surface (plate surface) has recesses (cells) filled with ink. . This printing plate material may be a cylindrical metal intaglio plate or a flat plate-shaped intaglio plate rolled up onto a cylinder. Alternatively, an intaglio plate made of photosensitive resin may be wound into a cylindrical shape.

The surface layer of the transfer cylinder that receives the ink is made of elastic rubber, which allows the ink image on the printing plate to be faithfully transferred onto the surface of the transfer cylinder. Beautiful printing is possible even on objects that are not printed on paper. As the elastic rubber, known elastic rubbers having a Shore A hardness of 10 to 90° can be used. It is selected in consideration of ink resistance, ink receptivity, transferability, etc. Specific examples include acrylonitrile/butadiene rubber, chloroprene rubber, ethylene/propylene rubber, and polyurethane. Particularly preferred is silicone rubber. This rubber has better ink transfer properties than other rubbers, making it possible to print with a thick ink film. It also has the advantage of being less prone to scumming even if the ink on the printing plate is slightly incompletely collected. Each of these rubbers is continuously or partially mounted and fixed at a constant thickness on a transfer cylinder, which is usually made of metal, by a conventional method. If the thickness of the rubber is too thin, the above-mentioned effects will not be achieved. There is no particular restriction on the thickness, and when the printing medium is non-planar, a thick one is preferable. Usually 0.1m
m or more, preferably 1 mm or more.

The ink image on the transfer cylinder is printed onto a printing medium that is pressed by an impression cylinder, and is fixed by heating or UV pre-irradiation, if necessary. The operations from supplying ink to the printing plate to printing are normally performed continuously, but they are repeated as one pile, either continuously or discontinuously.

〔Effect of the invention〕

According to the gravure printing machine of the present invention, residual ink in the plate cells can be reliably scraped off and the cells can always be filled with new ink, resulting in the following remarkable effects compared to conventional printing machines. It will be done.

(1) Since plate clogging does not occur even with ink with a high pigment concentration, fine letters and line drawings can be printed continuously with beautiful quality.

(2) Since plate clogging does not occur, ink or solvent that dries quickly can be used. In an offset printing machine using a silicone rubber transfer cylinder, it is required that the ink image on the transfer cylinder be completely transferred onto the printing material.
An important requirement is the ability to use quick-drying inks and solvents, and the printing machine of the present invention allows the use of quick-drying inks and solvents, making it possible to print with high quality.

In addition, the energy and equipment burden required for drying after printing is reduced, making it economically advantageous.

(3) Even when high-viscosity ink is used, the ink within the cell is always uniform, so high-quality thick printing can be performed continuously. In particular, gravure offset printing machines whose transfer cylinders are made of silicone rubber require the use of high-viscosity ink to prevent repelling on the transfer cylinders, whereas conventional printing machines are prone to plate jams. The printing machine of the present invention does not have such drawbacks.

(4) Even when a plate with a deep cell depth is used, ink receptivity can be expected to improve.

"Example" Example 1 Viscosity 75 mainly composed of nitrocellulose/maleic acid resin, titanium oxide and ethyl acetate/cellosolve acetate
Using ink with a drying time of 4 minutes (the drying standard is the drying time to the touch when applied on the film with a #6 bar coater and air-dried at room temperature), use a character pattern (size 6 to
For Grade 16 Mincho typeface and Gothic), the following printing materials,
Continuous printing was performed using a gravure offset printing machine (manufactured by Mobetsu Sangyo) under the printing conditions.

■ Film with a plate thickness of 350μ (Lumirror manufactured by Toshi Co., Ltd.)
The above character pattern was printed using a conventional method on a plate material (RG plate manufactured by Toshi Co., Ltd.) on which a polyamide photosensitive resin with a thickness of 25μ was laminated, and developed to create an intaglio plate with a cell depth of 25μ, followed by drying and carving. I did it.

(2) The above intaglio plate was attached to an aluminum cylinder with a diameter of 99 mm and a width of 100 mm using adhesive tape, the joint was filled with a curable resin and fixed, and the surface was finished by cutting.

■ The brush for scraping off the residual ink in the brush cell has a fiber diameter of 100μ.
A flat brush with a width of 110 mm and a bristles length of 5 mm is made by caulking the end of polybutylene terephthalate with a U-shaped metal plate, and it is attached below the ink nozzle and applied to the printing plate by 0.1 mm.
I attached it by pressing it down.

■ Use an ink supply pump to supply ink from the nozzle to the printing plate, and the thickness is Q, 5m.
The ink was scraped off with a ceramic doctor blade, and the excess ink was collected in a tray and recycled.

(2) Transfer cylinder An aluminum cylinder with a diameter of 100 mm and covered with silicone rubber having a shore A hardness of 35 and a thickness of 1 Q mm was used.

(2) A printing material "Lumirror"#100x43 was used and was continuously conveyed at a speed of 5 m/min while being pressed with a polyacetal impression cylinder having a diameter of 60 mm.

After about 15 minutes of continuous operation (equivalent to 250 printed sheets), I compared the quality of the first and last printed materials, but there was no particular difference, and there was no blurring in the fine horizontal lines of the Mincho typeface, and neither character It was also beautifully printed.

Comparative Example Printing was carried out under conditions different from Example 1 only in that no brush was used. At the beginning of printing, the printout was clean, but after 5 minutes, the fine horizontal lines of Mincho fonts of Grade 8 or lower began to fade, and by the time 10 minutes had passed, the fine print was almost unreadable. became.

[Brief explanation of the drawing]

The figure is a schematic side view showing one example of a gravure printing machine according to the present invention. 1: Doctor blade 2: Ink nozzle 6: Plate cylinder
7: Plate material 8: Brush 10: Transfer cylinder 11: Impression cylinder

Claims (1)

[Claims] In an apparatus in which a rotating plate cylinder contacts the printing material directly or via a transfer cylinder to transfer and print ink in the recesses on the plate surface, a brush for scraping off residual ink in the recesses on the plate surface is provided in close proximity to the plate cylinder. A gravure printing machine characterized by being equipped with.