JP2700132B2 - Blanket for offset printing - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a printing blanket used for an offset printing press, and more particularly to an offset printing blanket suitable for multicolor printing.

(Prior Art) In offset printing, a special device is used for an offset printing press because it is once transferred from an ink image printing plate to a blanket and then printed on paper.

The printing unit in the offset printing press will be described. As shown in the drawing, a general printing unit is an ink installation 2 for supplying ink to a plate cylinder 1 on which a printing plate is mounted, and a water supply device 3 for supplying dampening water. Is arranged,
Furthermore, a blanket cylinder 4 and an impression cylinder 5 equipped with a blanket are provided. The current mainstream offset printing presses have a water supply for giving appropriate wetness to the plate.

That is, first, dampening water is supplied to the printing plate from the water supply device 3, and then sufficiently kneaded ink is supplied from the inking device 2, and the ink image on the printing plate is transferred to the blanket mounted on the blanket cylinder 4. This image is printed on a printing sheet passing between the impression cylinder 5 and the printing paper. The ink does not adhere to the non-image area due to the dampening solution, but adheres only to the image area. Offset printing requires skill in the operation of the dampening solution and blanket, and in particular, controlling the dampening solution is a significant factor that affects print quality. Control ".

For example, when printing three colors of cyan, magenta, and yellow in this order, each ink is supplied in each printing unit, a cyan image is first printed on printing paper, and the cyan ink adheres in a wet state. Magenta is immediately printed on the printing paper, and then yellow ink is printed immediately on the printing paper on which the cyan ink and the magenta ink are adhered in a wet state.

At this time, when the ink image on the printing paper printed by the previous printing unit is printed by the next printing unit, the ink image on the printing paper is transferred to the blanket because the ink adheres in a wet state. The so-called reverse trapping phenomenon often occurs. The reverse trapping phenomenon means that, for example, a cyan image is printed on the first printing unit, the cyan ink image on the printing paper is sent to the second printing unit in a wet state, and the magenta ink image is transferred from the blanket to the printing paper In this case, the cyan ink image on the printing paper is transferred to a blanket.

The use of fountain solution, which is a feature of offset printing, affects print quality.If too much fountain solution is used, it is difficult for ink to transfer to the image area. A so-called ink stain in which the ink adheres to the non-image portion where it does not adhere is generated.

(Problems to be Solved by the Invention) With respect to the reverse trapping phenomenon in which the ink image on the paper printed by the previous printing unit is transferred to the image portion of the blanket as described above, the printing order of each color is appropriately selected. To some extent, it can be prevented by taking measures such as adjusting the ink density.

In addition, when alcohol is added to dampening water against ink stains, a uniform water film can be formed even with a small amount of dampening water, and automatic water supply equipment for alcohol addition is widely used because of easy control. ing. However, in recent years, the method of adding the alcohol has been regulated in terms of environmental pollution. For this reason, development of dampening water having the same characteristics as the addition of alcohol by adding a surfactant or the like instead of alcohol has been promoted.

Thus, to date, research has been conducted on the dampening solution itself to prevent ink stains on the non-image area with a small amount of dampening solution supplied, but no proposal has been made on the blanket itself. Not done.

The present invention has been made in view of such a situation, and an object of the present invention is to make a surface printing layer of a blanket an oil-resistant material having hydrophilicity, thereby obviating a complicated adjustment operation of dampening solution. An object of the present invention is to provide a printing blanket in which a trapping phenomenon is unlikely to occur and an ink stain on a non-image area can be prevented even with a small supply amount of dampening water.

(Means for Solving the Problems) Therefore, the present invention has the following configuration to achieve the above object.

That is, in a blanket for offset printing obtained by laminating a surface printing layer and at least one support with or without a porous compressible layer below the surface printing layer, the surface printing layer may have a thickness of 35%. This is a hydrophilic surface printing layer formed of an oil-resistant material having a surface tension of up to 60 mN / m.

The surface tension of the surface printing layer of a conventionally known blanket is approximately 30 mN / m, and a small amount of dampening water cannot form a uniform water film to prevent ink stains. There has been a phenomenon that the ink is hardly transferred to the image area.

According to the present invention, by setting the surface tension of the surface printing layer to be between 35 and 60 mN / m, it is possible to prevent the reverse trapping phenomenon and the ink stain on the non-image portion. Surface tension is 35mN / m
Below, the ink stain is slightly generated and the surface tension is
Ink transfer from the printing plate to the blanket of 60 mN / m or more is not performed smoothly, making it difficult to perform normal printing.

Surface printing layer in the present invention, the polymer, acrylonitrile butadiene copolymer rubber, chloroprene rubber, chlorosulfonated polyethylene, chlorinated polyethylene, synthetic rubber such as ethylene propylene diene rubber, oil-resistant material such as polyurethane, It is adjusted from various compounding agents such as a crosslinking agent, a filler, and a plasticizer.

Then, to impart hydrophilicity having a surface tension of 35 to 60 mN / m to the surface printing layer, a polymer having a hydrophilic group such as an amino group, a hydroxyl group, a carboxyl group, an isocyanate group, a sulfone group, or a siloxane is coated on the surface printing layer. A method of using as a polymer component, a modifier having the hydrophilic group, for example, a titanate coupling agent, a reactive silicon modifier, a method of adding an activator to the polymer component during the curing reaction of the surface printing layer, Alternatively, there is a method of adding a hydrophilic filler, a plasticizer, and the like. These methods can be used alone or in combination.

Further, as another method for hydrophilizing, a method such as a grafting treatment, an ultraviolet irradiation treatment, or a plasma treatment of a surface printing layer manufactured in advance can be used.

(Operation) Since a certain hydrophilic property is previously given to the surface printing layer, a uniform water film is formed even with a small amount of dampening water.

(Examples) Hereinafter, the present invention will be described in detail based on examples.

Example 1 This example used a method of adding a modifier to impart hydrophilicity to the surface printing layer.

The blanket was formed by sequentially laminating a plurality of non-extensible supports and a compressible layer by a known production method, and forming a surface printing layer of a rubber composition having the following composition on the uppermost layer.

For the surface printing layer, the following rubber composition was applied and vulcanized. As a result of measuring the surface tension of the completed blanket, it was shown that the product of the example had a higher surface tension than that of the comparative example 1, which was a conventional product, and had a surface hydrophilized by a hydroxyl-terminated silicone.

Next, the blanket is mounted on a two-color offset printing machine, and the ink is imbalanced so that the reverse trapping phenomenon in which the ink is transferred to the blanket easily occurs. Magenta ink was printed.

As a result, the reverse trapping phenomenon and the ink stain on the non-image area when printing with a reduced amount of dampening solution were observed in the conventional product, but the reverse trapping phenomenon and the ink stain were observed in the example product. Did not.

The results of comparison with the conventional product are as follows.

The above-mentioned surface tension is the same. Label: W. Rabel: Ferbe und Lack, 77 (10), 997 (197
Measured based on 1).

Example 2 In this example, in order to impart hydrophilicity to the surface printing layer,
A method of adding a hydrophilic filler and a hydrophilic plasticizer was used.

A urethane solution having the following composition comprising urethane having hydrophilicity, hydrophilic metal powder, and glycol plasticizer was prepared.

A blanket is formed by successively laminating a support and a compressible layer by a known production method, applying a surface printing layer made of a rubber composition having the following composition to the uppermost layer, vulcanizing and then applying the following urethane solution, It was dried and thermally cured to complete the blanket.

The completed blanket was subjected to surface tension measurement and printing in the same manner as in Example 1. As a result, it was confirmed that the product of the Example had a higher surface tension than that of Comparative Example 1 as a conventional product, and that the surface printing layer was hydrophilic. In addition, no reverse trapping phenomenon occurred, and no printing stains were observed in the non-image area when printing was performed with the supply amount of dampening solution reduced.

The results of comparison with the conventional product are as follows.

Example 3 In this example, hydrophilicity was imparted to the surface printing layer.
A method of adding a hydrophilic organic compound was used.

In this example, acrylonitrile-butadiene copolymer rubber (NB
R) and polyvinylpyrrolidone (PVP) were heated and mixed with an internal mixer to react NBR and PVP.

Then, another compounding agent is added to the mixture of NBR and PVP to prepare a rubber composition having the following composition. As in Example 1, a surface printing layer made of the rubber composition having the above composition was applied to the uppermost layer, followed by vulcanization molding. As a result of measuring and printing the surface tension on the completed blanket in the same manner as in Example 1,
The product of the example had a higher surface tension than that of the comparative example 2, which was a conventional product, indicating that the surface printing layer was hydrophilic, and no reverse trapping phenomenon and no ink stain were observed.

The results of comparison with the conventional product are as follows.

Example 4 In this example, to impart hydrophilicity to the surface printing layer,
The method of ultraviolet irradiation treatment was used.

The blanket is formed by sequentially laminating a support, a compressible layer, and the like by a known production method, applying a surface printing layer made of the same rubber composition as in Comparative Example 2 to the uppermost layer, and then vulcanizing. Next, after applying and drying an acetone solution of acrylamide on the surface printing layer, ultraviolet rays having a main wavelength of 365 nm and an output of 2 KV are irradiated to cause a surface graft reaction. UV irradiation time is 1
Minutes, 2 minutes and 3 minutes. Next, the remaining acrylamide was removed by washing with water to complete a blanket.

The completed blanket was subjected to surface tension measurement and printing in the same manner as in Example 1. As a result, the product of this example had a higher surface tension than that of Comparative Example 2, which was a conventional product, and the surface printing layer was hydrophilic. That was shown.

In addition, when the surface tension of the blanket was 35 mN / m, the ink stain in the non-image area which occurred when printing was performed by reducing the supply amount of dampening solution slightly occurred. No trapping phenomenon occurred. In addition, when the surface tension was 53 mN / m, no ink stain on the non-image portion and no reverse trapping phenomenon occurred. In addition, the surface tension
At 60 mN / m, the transferability of the ink was slightly reduced, but no reverse trapping phenomenon occurred.

 The results of comparison with the conventional product are as follows.

(Effects of the Invention) As described above, since the present invention has a hydrophilic surface printing layer having a surface tension of 35 to 60 mN / m, a uniform water film can be formed with a small amount of dampening water supplied. Therefore, no skill is required for the operation of the offset printing machine, and high-quality printing can be obtained in which the workability is improved and the reverse trapping phenomenon and the ink stain on the non-image area are prevented.

[Brief description of the drawings]

 The drawing is an explanatory view of an offset printing press.

Claims (1)

(57) [Claims] 1. A blanket for offset printing comprising a surface printing layer and at least one support laminated with or without a porous compressible layer below the surface printing layer, wherein the surface printing is performed. A blanket for offset printing, wherein the layer is a hydrophilic surface printing layer formed of an oil-resistant material having a surface tension of 35 to 60 mN / m.