JP2002059672A - Blanket for offset printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printing blanket which can be used under a waterless system of high-speed offset printing and shows outstanding properties in terms of ink coating paper unloading, cleaning or the like. SOLUTION: In the blanket for offset printing comprising a support layer having a compressible layer and a surface printing layer laminated on the support layer, the surface printing layer is formed of an oil-resistant rubber composition with 5-10 MPa modulus of elasticity E' when a dynamic change stress (10 Hz, 23 deg.C, 50 μm amplitude, 20 mm interchuck distance and 2 mm stretch, initial distortion) is applied to the surface printing layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blanket for offset printing, and more particularly, to a blanket for offset printing which has improved ink depositing property and paper discharging property in high-speed printing with an offset rotary printing press.

[0002]

2. Description of the Related Art Offset printing is a printing method in which an image from a printing plate is transferred to a blanket and then printed on paper. The offset printing press comprises a plate cylinder, a blanket cylinder, and an impression cylinder. As the blanket, a blanket conventionally provided with a surface printing layer made of synthetic rubber on a support layer made of a plurality of base fabrics is used. Conventionally, in offset printing, dampening water has been supplied to prevent ink from adhering to non-image portions on the surface of a plate. After supplying dampening water to the plate surface with the water supply roller, and then supplying ink with the ink roller,
This is for forming an image on the plate surface. The management and adjustment of the dampening solution supply is an important and skillful operation, and is a point that determines the printing quality. For example, if the amount of the dampening solution is too large, the dampening solution flows back into the ink fountain via the ink roller, causing emulsification of the ink and causing deterioration of the ink transfer.

[0003] In recent years, flat plates that do not require dampening solution have been put into practical use instead of conventional flat plates that require dampening solution. In this method, a layer of silicone rubber is provided in the non-image area,
It is intended to form an image by preventing ink adhesion. This method eliminates the need for skilled fountain solution adjustment and management, and reduces the time required for starting up the printing press (adjustment for obtaining a clear image close to the original when printing a new pattern). Along with this, the benefits of CR by reducing wasted paper, the ability to respond to high-mix small-lot printing, shorter delivery times, shorter working hours, prevention of quality differences in printed materials due to differences in operator proficiency and experience, and stable quality It has been highly evaluated for its effects such as conversion. The dampening solution is usually a few percent of isopropyl alcohol (I)
Since a solvent such as PA) is used, a printing waste liquid containing an organic solvent is generated, and there is also a problem of odor generation in a work place. There is also a merit that such environmental problems can be solved by replacing the waterless system, and it is being actively introduced in Europe, the United States and Japan.

On the other hand, since waterless printing does not use dampening water, heat is easily stored in the printing press, the temperature of the plate surface is increased, the ink viscosity is reduced, and background staining is more likely to occur. To prevent this, it is necessary to use a special ink with high viscosity, and as a result, when printing with a conventional blanket (a blanket generally used in printing with water), there is no fluidity of the ink Therefore, the ink inking property and paper release property are deteriorated, slurs are easily generated, the ink is easily piled on the blanket surface, the blanket cleaning property is poor,
There are problems such as.

[0005] Today, not only in waterless printing but also in printing with water, inks with a high drying speed tend to be used in order to increase the speed of the printing press. Since the solvent contained therein dries and the penetration speed into the blanket surface rubber is high, the viscosity increases during use, and the same problem as in the case of waterless printing as described above occurs. Further, even in the printing with water, the same may occur in a case where the amount of dampening water during printing is reduced as much as possible to take advantage of the printing without water.

In consideration of such circumstances, the following printing blankets have been proposed. Japanese Patent Application Laid-Open No. 8-300845 proposes a blanket in which the surface rubber layer is composed of two layers and the hardness of the outer rubber layer is made softer than that of the inner rubber layer so as to enhance the ink deposition property. Have been. However, using two surface rubber layers in this way complicates the structure and increases the cost.

[0007] Japanese Patent No. 3023907 discloses a blanket in which far-infrared ceramics is blended in a surface rubber layer. This blanket is a cluster state of dampening water due to far-infrared rays radiated from the surface. Is intended to print even with a small amount of fountain solution and to improve the paper releasability, which is deteriorated by reducing the fountain solution, by blending a far-infrared ceramic. Here, there is no mention of improving the solid inking property.

[0008]

As described above, in high-speed offset printing, it is not possible to practically prevent ink from adhering to a non-image portion on the surface of a plate and to improve solid filling properties and paper discharge properties. However, there are still problems to be solved in both printing with water and printing without water. Therefore, an object of the present invention is to solve the above problems and to provide a blanket for offset printing in which printing performance at the time of high-speed printing by an offset rotary printing press is improved.

[0009]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have proposed a method for offset printing comprising a support layer having a compressible layer and a surface print layer laminated on the support layer. In a blanket, as a result of studying focusing on the mechanical properties of the surface printing layer, the present invention has been completed. That is, the present invention relates to the following blanket for offset printing.

1) In a blanket for offset printing including a support layer having a compressible layer and a surface print layer laminated on the support layer, the surface print layer has a dynamic change stress (10 Hz, 23 ° C.). A blanket for offset printing, wherein the blanket is made of an oil-resistant rubber composition having an elastic modulus E ′ of 5 to 10 MPa when an amplitude of 50 μm, an inter-chuck distance of 20 mm, and an initial strain of 2 mm are applied. 2) The ratio of the oil-resistant rubber in the surface printing layer is 50 to 50%.
The blanket for offset printing according to the above item 1), which is 75% by weight.

3) The blanket for offset printing according to the above item 1) or 2), which is for waterless printing. Since the blanket for offset printing of the present invention has a surface printing layer having the above characteristics, even when a highly viscous ink is used, the blanket is squeezed and transferred to the paper surface to improve the solid inking property and discharge the paper. The performance is also improved. This printing blanket has a ratio of oil resistant rubber constituting the surface printing layer of 50%.
By setting the weight% or more, the solid inking property is improved,
Further, by setting this ratio to 75% by weight or less, the cleaning property is improved. Since ink has affinity for rubber, the inking property and detergency are in opposition to each other.
It is preferable that the ratio of the oil-resistant rubber in the surface printing layer is 50 to 75% by weight as in the blanket for offset printing described above.

[0012] The printing blanket of the present invention is the above 3).
As described above, even when a high-viscosity ink such as waterless printing is used, the solid inking property is excellent and the paper discharging property is improved. Even an ink with a high drying speed accompanying high-speed printing can be suitably used. Of course, it is also useful for printing with water. The elastic modulus E ′ in the present invention is, as described above, a test frequency of 10H.
z, the test temperature is 23 ° C., the test amplitude is 25 μm, the distance between the chucks is 24 mm, and the initial stress is 2 mm. As a measurement sample, only the surface printing layer (rubber layer) of the prepared blanket was sliced and taken out into a sheet form, which was used for measurement. In addition, a rheology viscoelastic spectrometer (model number "DV
E-V4 ") was used.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a blanket for offset printing according to the present invention will be described below with reference to FIG. The offset printing blanket 10 of the present invention has a surface printing layer 20 and a support layer 30 formed by laminating a plurality of base fabric layers (reinforcing layers) 34 and 35, and the inside of the support layer 30. It has at least one compressible layer 32 made of a porous elastic member.

A blanket 1 for offset printing according to the present invention.
0, the elastic modulus E ′ of the surface printing layer is 5 to 10 MPa.
And preferably 6 to 9 MPa. By setting the elastic modulus E ′ within the above range, solid inking property, paper discharge property,
The cleaning property is good, and the generation of slur is well suppressed. The solid inking property is not good when the elastic modulus E ′ exceeds the above range. When the elastic modulus E ′ falls below the above range,
Slurs are generated, resulting in poor cleaning performance.

In the printing blanket of the present invention, the surface printing layer 20 is formed by adding a predetermined amount of a vulcanizing agent to an oil-resistant rubber material.
Compounding a vulcanization accelerator and, if necessary, a filler, etc., dissolving the same in toluene, methyl ethyl ketone, etc., and performing blade coating on the support layer 30 described below to a predetermined thickness as the above-mentioned rubber paste. Produced by Examples of the oil-resistant rubber material used for the surface printing layer 20 include acrylonitrile-butadiene rubber (NBR), and synthetic rubbers such as chloroprene rubber (CR) and polyurethane rubber (U). Mixtures of rubber and polysulfide rubber can also be used.

The elastic modulus E 'of the surface printing layer is set in the above range by appropriately selecting the type of rubber material, the type and amount of filler, the degree of vulcanization, and the like. For example, a relatively large amount of hydrous silica as a filler,
Alternatively, the modulus of elasticity E 'can be set in the above range by a method such as supplementing with a small amount of hydrous silica with a thermosetting phenol resin. Although the surface roughness of the surface printing layer 20 is not particularly limited, the 10-point average roughness Rz is 1.0 μm.
m or less. If the surface roughness of the surface printing layer 20 exceeds the above range, a problem arises in that the shape of the printed halftone dot is disturbed and the print quality is reduced. The smaller the surface roughness is, the better from the viewpoint of print quality.

The thickness of the surface printing layer 20 is not particularly limited, but is usually 0.05 to 2.0 mm, preferably 0.1 to 0.6 mm, and more preferably 0.2 to 0.4 m.
It is appropriate to set in the range of m. If the thickness of the surface printing layer 20 is less than the above range, the pattern of the base fabric may appear on a printed image. Conversely, if the thickness exceeds the above range, the distortion during printing may become too large and the print quality may be degraded. The support layer 30 is formed by laminating a plurality of base fabric layers (reinforcing layers) 34 and 35 and at least one compressible layer 32.

The base fabric layers 34 and 35 are made of cotton, polyester,
A woven fabric such as rayon or a non-woven fabric is impregnated with rubber paste, and a woven fabric subjected to stretch processing is particularly preferable. The rubber glue for the base fabric layer includes, for example, a rubber material such as acrylonitrile-butadiene rubber (NBR), acrylic rubber (ACM), chloroprene rubber (CR), a predetermined amount of a vulcanizing agent, a vulcanization accelerator and, if necessary, What contains a thickener and the like is used.

The thickness of the base fabric layer is not particularly limited, but is usually 0.15 to 0.5 mm, preferably 0.25 to 0.5 mm.
It is appropriate to set within a range of 45 mm. The thickness of the entire support layer 30 is set in accordance with the thickness of the compressible layer 32 described later, and is usually 1.45 to 1.45.
It is set in the range of 85 mm, preferably 1.55 to 1.75 mm. The number of layers of the base fabric layer may be appropriately set according to the characteristics required for the product and the like, and is usually preferably 1 to 5 layers.

In the present invention, the support layer 3
In place of the base cloth at 0, a film made of a synthetic resin such as polyethylene terephthalate (PET), polycarbonate (PC), polyethersulfone (PES), or nylon, or a thin metal plate such as aluminum or stainless steel may be used. it can. Although the rubber constituting the compressible layer 32 is not particularly limited, for example, it has resistance to inks and cleaning liquids such as acrylonitrile-butadiene rubber (NBR), acrylic rubber (ACM), chloroprene rubber (CR), and urethane rubber (U). The oil-resistant rubber having is preferably used.

For the compressible layer 32, a predetermined amount of a vulcanizing agent, a vulcanization accelerator and the like are mixed with the above rubber material, and further, a filler such as a foaming agent or hollow fine particles to be described later is mixed as necessary. Things are used. Further, instead of the foaming agent and the hollow fine particles, a mixture containing salt may be used. Compressible layer 32
The hardness of the rubber used for JIS is not particularly limited.
It is appropriate to adjust the A hardness in the range of 40 to 80 °, preferably 45 to 75 °, more preferably 50 to 70 °. If the hardness of the compressible layer 32 is less than the above range, the resilience of the compressible layer 32 and eventually the offset printing blanket 10 itself may be reduced to cause settling, or the printing pressure required for printing may not be obtained. . Conversely, if the hardness exceeds the above range, the compressibility may be reduced and the adjustment of the printing pressure may be insufficient.

The thickness of the compressible layer 32 is not particularly limited, but is usually 0.1 to 0.8 mm, preferably 0.2 to 0.8 mm.
It is appropriate to set in the range of 0.5 mm. If the thickness of the compressible layer 32 is less than the above range, the compressibility may be reduced and the adjustment of the printing pressure may be insufficient. Conversely, if the thickness exceeds the above range, the distortion during printing may become too large and the print quality may be degraded. The compressible layer 32 is made of a porous elastic member as described above, and has a continuous pore structure in which each pore inside the layer has an independent pore structure and a pore structure in which each pore communicates with each other. There is. In the present invention, either structure may be used, or both structures may be used together.

Among the above, the compressible layer having an independent pore structure is formed by, for example, dispersing a foaming agent which generates a gas by thermal decomposition in unvulcanized rubber and foaming the rubber at the same time as vulcanization of the rubber.
Alternatively, it is formed by a method of dispersing hollow fine particles in rubber (micro balloon method). On the other hand, the compressible layer having a continuous pore structure disperses extractable particles such as salt in unvulcanized rubber, and after vulcanization, uses a solvent (water in the case of salt) that does not affect the properties of the rubber. The particles are formed by a method of extracting the particles (leaching method).

The proportion of pores in the compressible layer 32 (hereinafter referred to as "porosity") is not particularly limited, but is usually 30 to 7
0%, preferably 35-60%, more preferably 40-
It is appropriate to adjust to a range of 55%. Compressible layer 32
If the porosity is below the above range, the compressibility may be reduced and the adjustment of the printing pressure may be insufficient. Conversely, if the porosity exceeds the above range, resilience is reduced and settling occurs,
The printing pressure required for printing may not be obtained.

[0025]

The present invention will be described more specifically below with reference to examples and comparative examples. Examples 1 to 6, Comparative Examples 1 and 2 (Preparation of Offset Printing Blanket) Under the following conditions, the offset printing blanket shown in FIG. 1 was prepared. (i) Production of Surface Printing Layer 20 As shown in Table 1, the rubber paste for the surface printing layer is acrylonitrile-butadiene rubber (NB) which is an oil-resistant rubber.
R), hydrated silica, thermosetting phenolic resin, vulcanizing agent, vulcanization accelerator, filler and other components are mixed in the proportions shown in the same table, and this mixture is dissolved in toluene at a weight ratio of 1: 1. Was used.

[0026]

[Table 1]

The surface print layer rubber paste shown in Table 3 was coated on the support layer 30 by a blade coating method and dried to form a surface print layer 20 having a thickness of 0.3 mm. (ii) Preparation of Support Layer 30 As a base fabric, a blended fabric formed by combining fibers of cotton cloth, polyester, and rayon was used. As shown in Table 2, components such as vulcanizing agent, vulcanization accelerator and filler are added to acrylonitrile-butadiene rubber (NBR), which is an oil-resistant rubber, as shown in Table 2. The mixture was mixed at a ratio, and this mixture was dissolved in toluene at a weight ratio of 1: 1.

[0028]

[Table 2]

The base cloth layer rubber paste shown in Table 1 was paste-coated on the above-mentioned base cloth, and the thickness of the rubber by the rubber paste was reduced to 0.01 m.
m. The three base cloths thus obtained are pressed with a roll to form a base cloth layer 34 (the thickness of each base cloth layer is 0.3 mm).
I got Next, as shown in Table 3, a curing agent was added to the NBR,
Components such as a vulcanization accelerator and a filler are mixed in the ratio shown in the same table, and this mixture is dissolved in toluene at a weight ratio of 1: 1.
Further, acrylonitrile-based resin hollow fine particles (trade name “F-100D” manufactured by Matsumoto Yushi Seiyaku Co., Ltd., particle size 30 to 150 μm)
m) and / or salt particles (particle diameter: 1 to 50 μm) were mixed to obtain a compressible layer rubber paste.

Table 3 shows the porosity (continuous porosity, volume%) of the continuous pores obtained by the salt particles and the porosity (independent porosity, volume%) of the independent mechanism obtained by the hollow fine particles. Indicated. The porosity is obtained by vulcanizing the blanket including the compressible layer by the method described later, and then expressing the percentage of the volume of the pore portion in the total volume of the compressible layer in percentage.

[0031]

[Table 3]

The rubber paste for the compressible layer shown in Table 3 was coated on the base fabric layer 35 (one layer) prepared in the same manner as in (i) "Preparation of the support layer 30" and dried. I let it. The thickness of the obtained compressible layer 32 was 0.4 mm. Next, the compressible layer 32 and the base fabric layer 35 are combined with the base fabric layer 34 described above.
A support layer 30 was formed by bonding the layers so as to have a layer configuration shown in FIG. (iii) Vulcanization and molding The unvulcanized laminate obtained by the methods (i) and (ii) was vulcanized and molded at a pressure of 2 kg / cm ² and a temperature of 150 ° C. for 30 minutes. After vulcanization, the blanket thickness is 1.
Finish polishing was performed to 98 mm to obtain a blanket for offset printing. The printing blankets produced in the above Examples and Comparative Examples were subjected to a method described below to obtain an elastic modulus E ′.
Was measured and the solid inking property, slur, paper discharging property and washing property were evaluated. The results are as shown in Table 1 above.

As shown in Table 1 above, Examples 1 to
6. From the results of Comparative Examples 1 and 2, when the elastic modulus E ′ of the surface print layer is in the range of 5 to 10 MPa, the solid inking property and the paper discharge property are good. Further, from the results of Examples 2 to 5, the solid inking property is particularly good when the ratio of the oil-resistant rubber is 50 to 75% by weight. If this ratio is less than 50% by weight, the solid inking property tends to be slightly inferior, and if it exceeds 75% by weight, the detergency tends to be inferior.

<Evaluation Method> The printing test was conducted by winding a blanket around a transfer cylinder of an offset printing machine (Ryobi 560) and printing solid and halftone dots on coated paper. The printing conditions are as follows. Printing speed: 10,000 sheets / hour Ink: "Dryo Color Artis" (waterless printing ink) manufactured by Dainippon Ink and Chemicals, Inc. Plate: waterless flat plate manufactured by Toray Dampening solution: not used (1) Elasticity Measurement of Modulus E 'Only the surface printing layer was sliced from the blanket for offset printing prepared in each of the above Examples and Comparative Examples, taken out into a sheet, and the elastic modulus E' was measured. The measurement conditions are as described above. (2) Solid inking property The solid part density distribution was examined by image analysis, and the standard deviation was determined to evaluate the solid inking property. The smaller the standard deviation value, the better. (3) Slur The degree of flow of the halftone dots in the printing direction (ellipticity) was evaluated by determining the vertical / horizontal line width ratio (horizontal line width / vertical line width) using a slur gauge. The smaller the line width ratio, the better. (4) Paper Ejection The curl height was measured when 10 sheets of coated paper printed in total solid were stacked. The lower the curl height, the better the paper discharge property (paper separation property). (5) Washability After printing 5,000 sheets of the entire solid surface, the surface was washed using a cleaning liquid Dieclean manufactured by Dainippon Ink and Chemicals, and the washability was observed. 50μ width on blanket surface before printing
m and two depths of 100 μm and 200 μm were cut along the entire length of the blanket, and after the above printing and washing, the remaining ink was observed in the grooves.
It was evaluated on a scale.

○ Indicates the level of cleaning with no ink in grooves at all depths. Δ indicates a cleaning level at which ink residue is observed only in grooves of 200 μm or less. × Indicates a cleaning level at which ink residue is observed in both grooves.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of an offset printing blanket of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Blanket for offset printing 20 Surface printing layer 30 Support layer 32 Compressible layer

Claims (3)

[Claims] 1. A blanket for offset printing comprising a support layer having a compressible layer and a surface print layer laminated on the support layer, wherein the surface print layer has a dynamic change stress (10 Hz, 23 ° C.). , Amplitude 50μm, distance between chucks 2
A blanket for offset printing, comprising an oil-resistant rubber composition having an elastic modulus E 'of 5 to 10 MPa when an initial strain of 0 mm and an initial strain of 2 mm is applied. 2. The offset printing blanket according to claim 1, wherein the ratio of the oil-resistant rubber in the surface printing layer is 50 to 75% by weight. 3. The blanket for offset printing according to claim 1, which is for waterless printing.