JPH08300845A - Rubber blanket for offset printing - Google Patents

Abstract

PURPOSE: To obtain printed matter preventing a dot gain, enhanced in the adhesion of printing ink to printing paper and excellent in gradation by constituting a rubber layer of two layers and making the hardness of a surface rubber layer lower than that of an inner surface rubber layer and making the surface rubber layer soft. CONSTITUTION: The rubber layer of a rubber blanket 10 is constituted of an inner surface rubber layer 1 high in compression force and a surface rubber layer 2 low in compression force and attached to the blanket cylinder 11 of a printing press. The hardness of the surface rubber layer 2 is set to 76-81 deg. and that of the inner surface rubber layer 1 is set to 80-85 deg.. The printing ink 14 built on the surface rubber layer 2 of the rubber blanket 10 comes into contact with printing paper 13 to be transferred (printed) thereto. At this time, since the printing ink 14 is pressed to the printing paper 13 by the high compression force of the inner surface rubber layer 1, the adhesion of the printing ink 14 to the printing paper 13 is enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a rubber blanket mounted on a blanket cylinder of an offset printing machine, and more particularly to a rubber blanket for offset printing suitable for waterless offset printing.

[0002]

2. Description of the Related Art Conventionally, an offset printing machine used for commercial printing, publication printing, etc. transfers the printing ink on the printing plate to a rubber blanket mounted on a blanket cylinder for further printing. It is well known that printing is performed by transferring to paper. This rubber blanket is
Low rubber hardness (soft) is desired to prevent dot gain (thickness of halftone dots), but high rubber hardness (hard) to improve ink receptivity to printing paper. Therefore, the rubber hardness is determined in consideration of the balance between the dot gain and the inking property.

However, in waterless offset printing, which has been introduced in recent years, the ink is harder than water-based (fountain solution) printing and there is no emulsification of the ink.
In order to obtain the required ink receptivity, it is necessary to use a rubber blanket having a higher rubber hardness than printing with water.

[0004]

However, in the conventional rubber blanket for offset printing, if the rubber layer hardness is lowered (softened) in order to improve the inking property, dot print is generated due to generation of dot gain. Since the crushing occurs and the film thickness of the printing ink becomes thin, the gradation of the printed pattern becomes poor, which causes a problem that the print quality deteriorates.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a rubber blanket for osset printing which prevents dot gain and is excellent in inking property.

[0006]

In order to achieve the above object, the rubber blanket for offset printing of the present invention comprises two rubber layers, and the surface side rubber layer hardness of this rubber blanket is the inner surface side rubber layer. It is characterized in that it is made lower than the layer hardness to soften the surface side rubber layer.

The surface rubber layer hardness is in the range of 76 to 81 degrees (according to JIS-A type hardness tester), and the inner surface side rubber layer hardness is in the range of 80 to 85 degree (JIS-A type hardness tester). According to)).

[0008]

As described above, according to the offset printing blanket of the present invention, the rubber layer is composed of two layers, the front side rubber layer is made softer than the inner side rubber layer, and the ink is wrapped with the soft rubber layer to form dots. It is possible to prevent the gain and increase the printing pressure with the hard inner rubber layer to improve the ink receptivity to the printing paper.

[0009]

Embodiments Embodiments will be described in detail below with reference to the drawings.
FIG. 1 is a schematic view showing the structure of a rubber blanket for offset printing according to the present invention. As shown in the figure, the rubber layer of the blanket (10) is composed of a high compression inner surface side rubber layer (1) and a low compression force front surface rubber layer (2). It is attached to the torso (11). Here, the thickness of the surface side rubber layer (2) is a number 1
It is set to 0 to several hundreds of μm, and rubber is applied to the inner rubber layer (1) to form the front rubber layer (2).

FIG. 2 shows that the ink (14) on the printing plate (12) is transferred to the rubber blanket (10). As shown in FIG. 2, the printing plate (1
The printing ink (14) inked in 2) comes into contact with the rubber blanket (10), so that the printing ink comes into contact with the surface side rubber layer (2) of the rubber blanket and is transferred. At this time, the surface rubber layer (2) has a low compression force,
Wrap the printing ink (14) to prevent dot gain.

FIG. 3 shows that the printing ink (14) transferred to the rubber blanket (10) is transferred to the printing paper (13). As shown in the figure, the printing ink (14) deposited on the surface side rubber layer (2) of the rubber blanket (10) is transferred (printed) to the printing paper (13) by contacting the printing paper (13). To) At this time, the printing ink (14) is pressed against the printing paper (13) due to the high compression force of the inner rubber layer (1), and the printing ink (14) is pressed against the printing paper (1).
3) The inking property is improved.

[0012]

Since the present invention has the above-mentioned constitution, it has the following effects. That is, according to the rubber blanket for offset printing of the present invention, it is possible to provide a printed matter having excellent gradation by preventing dot gain and improving the inking property of the printing ink on the printing paper. .

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a laminated structure of a rubber blanket for offset printing in an example of the present invention.

FIG. 2 is an explanatory diagram showing transfer of printing ink to a rubber blanket for offset printing of the present invention.

FIG. 3 is an explanatory diagram showing the transfer of printing ink from the rubber blanket for osset printing of the present invention to printing paper.

[Explanation of reference symbols] 1 ... inner rubber layer 2 ... front rubber layer 10 ... rubber blanket 11 ... blanket cylinder 12 ... plate cylinder 13 ... printing paper 14 ... printing ink

Claims (2)

[Claims] 1. A rubber blanket for printing, which is mounted on a blanket cylinder of an offset printing machine and used for printing a printed pattern layer, wherein the rubber layer of the rubber blanket is composed of two layers, and the surface side of the rubber blanket is formed. A rubber blanket for offset printing, wherein the rubber layer hardness is softer than the inner rubber layer hardness. 2. The offset printing according to claim 1, wherein the surface side rubber layer hardness is in the range of 76 to 81 degrees and the inner surface side rubber layer hardness is in the range of 80 to 85 degrees. Rubber blanket.