JPH07186568A - Dampening roller for printer - Google Patents

Abstract

PURPOSE:To form a thin, uniform film of water an a distributing roller by covering a surface of the roller using a dampening device of an offset printer with a metal layer having hydrophilic nature, and eliminating pores. CONSTITUTION:A surface of a core bar made of soft iron is polished. The bar is degreased and cleaned, then sequentially copper-plated, and nickel-plated to be substrate-treated. A bearing of the treated bar is previously masked, and dipped in a bath to be gold-plated. As a result, a water distribution roller 4 having a gold layer which has hydrophilic property on a surface of the bar can be obtained. Accordingly, the surface of the roller 4 has high water wettability no pore, a water film becomes uniform, and a printed matter having high contrast can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a dampening water roller for a printing machine incorporated in a dampening water device of an offset printing machine.

[0002]

2. Description of the Related Art As is well known, offset printing is a printing method that utilizes the repulsive nature of oil (ink) and water, and is the current mainstream printing technology for printing newspapers, magazines, textbooks, leaflets, etc. It is used a lot.

In the above offset printing, an image portion (ink-philic resin layer) and a non-image portion (hydrophilic aluminum layer) are formed on a plate in advance, and water is first applied to the non-image portion by a dampening water device. After that, ink is applied to the image area by an inking device, and the ink image is transferred to a rubber blanket which rotates in contact with this plate. Further, an object to be printed such as paper is passed between an impression cylinder rotating in contact with the rubber blanket, and the ink image on the rubber blanket is transferred and printed.

FIG. 1 is a diagram showing a part of the configuration of a printing apparatus.

First, the dampening water 2 in the watercraft 1 is pumped up by a rubber-made water source roller 3 and transferred to a water leveling roller 4 having a surface which is contact-rotated and is chrome-plated. Here, the water leveling roller 4 reciprocates in the axial direction in order to uniformly spread the dampening water film.
Next, the dampening water is transferred to the watering roller 5 made of rubber, and is supplied to the non-image portion of the plate mounted on the plate copper 6 which is also rotating in contact with the dampening roller 5 to dampen the plate surface. After this, the inking device 7
Ink is supplied to the image area to form a basic printed image. After this step, the image is transferred from the rubber blanket to the paper and it is understood that accurate image formation on the plate is essential. If the ink adheres to the non-image area of the plate, it will be printed on the non-printed body and become dirty and become a defective product. Further, if the dampening water is excessive, the fountain solution will adhere to the image-receiving portion and the subsequent ink transfer will be insufficient, resulting in insufficient ink density in the printed matter.

The appropriate dampening water film thickness on the plate is 0.1 μm.
It is said that the degree. In fact, about 5 times this dampening water is used. Reducing the amount of dampening water has the effects of (1) increasing the density of printed matter, (2) improving the contrast (balance between solid density and halftone dots), and (3) reducing ghosting. Water is preferably uniform and thin. However, under the present circumstances, it is impossible to make the dampening water uniform and form a thin film, so that excessive dampening water is used and various troubles occur. The reason why the dampening water cannot be made uniform or thinned is that the water leveling roller 4 has poor hydrophilicity. Currently, chromium plating is applied on the core metal to improve hydrophilicity,
The contact angle of water is about 84 degrees, and wetting is not good. By the way, if the hydrophilicity is insufficient, the dampening water 2 pumped up from the water source roller 3 cannot evenly wet the water leveling roller 4, so that a uniform water film is not formed and partial unevenness or, in severe cases, It becomes a polka dot. As a result, the dampening water film supplied to the plate via the watering roller 5 becomes uneven, and ink adheres to the non-image area where water is insufficient, resulting in stains on the printed matter. Further, if the excessive dampening water transferred in the form of polka dots is supplied to the image area, the subsequent ink reception is hindered, and the ink density is partially insufficient.

In order to solve these problems, a method of adding about 5 to 25% of isopropyl alcohol to the fountain solution has been tried, and is widely practiced at present. In addition, isopropyl alcohol aims to lower the surface tension, improve the wetting of soaking water, and make the dampening water film on the roller uniform and thin.

[0008]

However, since isopropyl alcohol evaporates, there is a problem that the working environment of the printing plant is deteriorated and the health of the worker is impaired.
In addition, the use of isopropyl alcohol increases the cost of the product.

On the other hand, by improving the material of the water leveling roller 4,
There are also proposals to improve wetting and water retention of dampening water. For example, Japanese Utility Model Publication No. 55-14518 proposes a method of forming a porous layer by spraying ceramics on the core metal of a water leveling roller. However, because the rollers made by this method are porous, they tend to have too much water. Therefore, the acceptance of the ink to the plate is deteriorated as a whole, and there are problems that the ink density of the printed matter is lowered, the contrast is lowered, and a ghost is generated. Usually, since the rollers of the dampening water device rotate in contact with each other, a part of the ink on the plate returns to the dampening water of the fountain and exists as small ink particles. In the porous water leveling roller, the ink gets into the holes, and this time repels the dampening water, causing unevenness.

Japanese Unexamined Patent Publication (Kokai) No. 62-71649 proposes a method of mixing a large amount of hydrophilic inorganic powder in a resin, hardening and polishing the resin to prepare a water leveling roller. When this water leveling roller is used for a long period of time, it becomes easy to receive ink due to the oleophilicity of the resin, and as a result, dampening water is repelled and water unevenness is likely to occur.

The present invention has been made in view of the above circumstances, and has a very good wettability with dampening water, and a dampening water film for a printing machine capable of forming a uniform and thin film on the water leveling roller. The purpose is to provide a water roller.

[0012]

SUMMARY OF THE INVENTION The present invention relates to a roller used in a dampening water apparatus for offset printing, the surface of which is covered with a hydrophilic metal layer and has no pores. It is a dampening water roller.

The inventors of the present invention have made a material which has a very good wettability with dampening water in order to reduce the harmful addition of isopropyl alcohol in the dampening water and which can be made uniform and thin on the water leveling roller. As a result of intensive studies, it was invented that the hydrophilic metal perfectly meets this purpose.

In the present invention, the hydrophilic metal includes
Titanium (Ti), Nickel (Ni), Cadmium (C
d), zinc (Zn), aluminum (AI), gold (A
u), silver (Ag), lead (Pb), platinum (Pt) and the like. Here, the contact angle of Ti, Ni, Cd with respect to water at room temperature is 0 degree, that of Zn is 5 degrees 52 minutes, AI
It is 8 degrees and 11 minutes, that of Au is 4 degrees and 26 minutes, that of Ag is 11 degrees and 32 minutes, that of Pb is 2 degrees and 36 minutes, that of Pt is 10 degrees and 43 minutes ("Chemical Handbook", basic edition, revision 2).
Edition, published by Maruzen, p. 375, p. 625).

In the present invention, the most commonly used immersion water roller is a chrome-plated roll, which has a contact angle with water of 84 degrees. In addition, it is 43 degrees even with a ceramic-coated roller, which is considered to have a relatively good wettability ("Printing magazine", 1990.voI. 73, February issue).

The method for producing a water leveling roller for dampening water according to the present invention is an electroplating method, a hot dipping method, or
The hydrophilic metal layer is formed by a vacuum deposition method, a metal infiltration method, a xenon gold method, or the like. In addition, electroless plating method, ion vapor deposition method, CVD method and the like are also possible. These manufacturing methods are
The method suitable for the hydrophilic metal is selected.

In the present invention, the material of the core bar is
Examples include soft iron, cast iron, stainless steel, brass and the like. Further, in order to improve the wear resistance of the surface layer, for example, an alloy of nickel and gold may be used. In the method of the present invention, the surface condition of the core metal is important. Specifically, first, it is important that there be no voids such as "su". Also,
It is important to finish the surface of the core metal as finely as possible. The reason for this is as described in (a) and (b) below.

A. Since the hydrophilic metal layer formed on the surface of the cored bar is very thin (for example, several microns for gold or platinum), if the cored bar has cavities, the hydrophilic metal layer cannot be completely filled. Therefore, water enters the hydrophilic metal layer, corrodes the core metal, and separates the hydrophilic metal layer. B. If the surface roughness of the core metal is too rough, the formed hydrophilic metal layer becomes uneven,
The water film has uneven thickness.

In the present invention, when the hydrophilic metal is gold, gold or platinum is used as the anode. When a core metal is used as a cathode and direct current is used for gold plating in a gold cyanide bath, a dampening roller having a gold coating layer on its surface is obtained.
In this case, the liquid temperature is about 60 to 70 ° C and the electric density is 0.1.
~ 0.5 A / dm ² is preferable.

[0020]

The hydrophilic metal according to the present invention has a very good wettability with water, and when it is brought into contact with water, it spreads on the metal in an extremely short time to form a uniform thin film. Therefore, the leveling roll for the dampening water device in which the above-mentioned hydrophilic metal is formed on the cored bar has extremely good wettability with water. As a result, the use of harmful isopropyl alcohol can be completely stopped.

Further, since the water leveling roller according to the present invention has no pores, it is very smooth and there is no risk of ink penetration. Therefore, it is possible to make the dampening water uniform and thin.
Very effective in improving ink density, contrast, reducing ghosts, and reducing costs.

It has been found that the water leveling roll according to the present invention is also very effective in the dampening water apparatus 11 having the mechanism shown in FIG. That is, in the dampening water device of this mechanism, instead of pumping the dampening water 2 from the water boat 1, the brush roller
Water is applied to 12 and water droplets are splashed on the water leveling roller 4 by the blade 13. Therefore, the fountain solution is likely to be supplied to the plate as polka dots, and as a result, unevenness of the printed matter is likely to occur. By using the water leveling roller according to the present invention, harmful isopropyl alcohol can be completely removed, and print quality can be improved. In addition, in FIG. 2, 5a and 5b
Indicates a watering roller.

[0023]

Example First, the surface of a soft iron core bar having a diameter of 120 mm was rounded.
Polish to 0.06 μm. Subsequently, after degreasing and cleaning the core metal, copper plating and nickel plating are sequentially applied to complete the base treatment.

Using gold as the anode, a gold cyanide bath with 6
Adjust to 0 ° C. The bearing part of the prepared core metal is masked in advance and immersed in a bath, and the electric density is 0.5 A.
Gold plating at / dm ² . As a result, a fountain solution roller having a 0.03 μm thick gold layer on the surface of the core metal was obtained.

After thoroughly washing the roller with water and drying, the contact angle of direct water was measured with a P-type contact angle meter manufactured by Kyowa Chemical Co., Ltd., and it was 3 degrees.

This roller was attached to an offset printing machine as a water leveling roller 4 as shown in FIG. 1, and printing was performed on coated paper with zero addition of isopropyl alcohol. Immediately after printing, the surface of the water leveling roller was extremely wettable with water and the water film was uniform. In fact, continuous printing was performed at a speed of 13000 sheets / H for 8 hours, but since the dampening water film was uniform from the beginning to the end of printing, the rotation of the water source roller could be reduced to reduce the amount of water. Therefore, a thin film was obtained, the density of the printed matter was increased, and a printed matter with high contrast was obtained.

Further, since gold has excellent corrosion resistance, it is quite stable even to an acidic substance added in a small amount in dampening water, and is stably used without change even after two years.

[0028]

As described in detail above, according to the present invention, a highly reliable printing machine which has extremely good wetting with immersion water and which can be evenly and thinly formed by immersion on a water leveling roller. A soaking water roller can be provided.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an offset printing machine.

FIG. 2 is an explanatory diagram of a newspaper offset press.

[Explanation of symbols]

1 ... water boat, 2 ... soaking water,
3 ... Mizumoto roller, 4 ... Water leveling roller, 5, 5a,
5b ... Watering roller, 6 ... Plate cylinder, 7 ... Inking device,
8, 11 ... Immersion water device, 12 ... Brush roller,
13 ... Blade.

Claims (4)

[Claims] 1. A fountain solution roller for a printing press, characterized in that the roller is used in a dampening solution device for offset printing, the surface of which is covered with a hydrophilic metal layer and has no pores. 2. The dampening water roller for a printing machine according to claim 1, wherein a contact angle of the metal layer with respect to water is 10 degrees or less. 3. The dampening water roller for a printing machine according to claim 1, wherein at least the surface is a single layer of zinc, aluminum, gold, silver, platinum, titanium, nickel, cadmium, or a mixed layer of these metals. 4. The dampening water roller for a printing machine according to claim 1, wherein the metal layer is formed by any one of an electroplating method, a hot dipping method, a vacuum deposition method, a metal infiltration method, and a xenon gold method.