JP2000006543A - Printing blanket - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress occurrence of a dirt on a print image because of an ink deposited on a groove of a plate cylinder in a double-size transfer cylinder type offset printer. SOLUTION: The printing blanket 10 of a flat plate state comprises a support layer having a porous compressive layer and a surface print layer provided on the support layer. A recess 11 along an axial direction (x) of a blanket cylinder 20 is provided at a position opposed to a groove 22 of the cylinder 20 via a central axis 21 of the cylinder 20 in the state that the blanket is mounted on the cylinder 20 having a double-size cylinder diameter of a plate cylinder. Further, a coating film made of a silicone rubber or the like having low affinity with an ink is formed on a surface of the recess 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing blanket used for a so-called double cylinder type offset printing press.

[0002]

2. Description of the Related Art Offset rotary printing presses include a so-called single cylinder (single cylinder) type in which the plate cylinder and blanket cylinder have the same cylinder diameter, and a so-called blank cylinder in which the cylinder diameter is twice that of the plate cylinder. Double body type is known.

[0003] Among them, the double-cylinder offset printing press can secure a sufficient working space between the printing units and, when the rotation speed is the same, doubles the number of prints per rotation as compared with the single cylinder. There are advantages such as becoming.

[0004] On the other hand, when ink is accumulated in the groove portion of the plate cylinder (groove for mounting the printing plate) by repeating printing, this ink is transferred to the printed matter via the blanket, and as a result, the printed image becomes dirty. There is a problem that such a problem occurs.

That is, in a single-cylinder printing press, as shown in FIG. 4, the cylinder diameter ratio between the blanket cylinder 30 and the plate cylinder 40 is 1: 1. 30 also makes one revolution. Accordingly, as shown on the left side of FIG. 4, printing is started after the positions of the groove 41 of the plate cylinder (gap of the printing plate 42) and the groove 31 of the blanket cylinder (gap of the blanket 32) are adjusted in advance. This prevents the groove 41 of the plate cylinder from contacting the surface of the blanket 32.

On the other hand, in a double cylinder type offset printing press,
As shown in FIG. 5, since the diameter ratio between the blanket cylinder 20 and the plate cylinder 40 is 2: 1, even if the plate cylinder 40 makes one rotation, the blanket cylinder 20 rotates only half. Therefore, FIG.
As shown on the left side of FIG. 5, even if printing is started by previously aligning the position of the groove portion 22 of the blanket cylinder (gap portion of the blanket 24) with the groove portion 41 of the plate cylinder (gap portion of the printing plate 42). When the plate cylinder 40 makes one rotation as shown on the right side of the figure, the groove 41 of the plate cylinder comes into contact with the groove 22 of the blanket cylinder via the central axis 21 of the blanket cylinder. At the time of this contact, the ink 25 deposited in the groove 41 of the plate cylinder adheres to the surface of the blanket 24 (a place facing the groove 22 of the blanket cylinder). This ink 25 is further transferred to the printed matter, causing stains on the printed image.

[0007]

Therefore, in order to prevent the blanket surface from contacting with the groove of the plate cylinder in printing with a double cylinder type offset printing press, the blanket surface may contact the groove of the plate cylinder. Attempts have been made to use blankets with recesses at the locations. Such a blanket is provided with a recess along the axial direction of the blanket cylinder in the groove by reducing the thickness of a portion facing a groove (a groove for attaching a blanket) of the blanket cylinder via the central axis of the blanket cylinder. It is a thing.

However, the ink accumulated in the groove of the plate cylinder is scattered from the groove of the plate cylinder to the printing blanket by centrifugal force when the plate cylinder rotates. Therefore, even if the above-mentioned concave portion is provided on the surface of the blanket, it is not possible to solve the problem that the printed image is frequently stained when printing is repeated.

On the other hand, a method for solving the above problem by increasing the frequency of cleaning the printing plate is considered. However, the phenomenon that a printed image is stained with the accumulation of ink in the groove of the plate cylinder may occur by repeating printing, for example, about 1000 times, although it varies depending on printing conditions and the like. Therefore, in order to solve the above problem by such a method, the cleaning frequency of the printing plate becomes too high,
A new problem arises in that the productivity of printing is reduced.

Accordingly, an object of the present invention is to prevent the ink scattered from the groove of the plate cylinder from adhering when used in a double cylinder type offset printing machine in which the cylinder diameter of the blanket cylinder is twice the cylinder diameter of the plate cylinder. It is to provide a printing blanket that can be suppressed.

[0011]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have found that a support layer having a porous compressible layer, In a flat printing blanket comprising a surface printing layer provided on the blanket cylinder, the blanket cylinder is mounted on a blanket cylinder having a cylinder diameter twice as large as the plate cylinder, and the blanket cylinder is mounted via a central axis of the blanket cylinder. When a concave portion is provided along the axial direction of the blanket cylinder at a position facing the groove portion, and a coating film having low affinity with ink is formed on the surface of the concave portion, the concave portion is deposited on the groove portion of the plate cylinder. The present inventors have found a new fact that it is possible to sufficiently suppress the occurrence of a problem that a printed image is stained due to the ink, and have completed the present invention.

In the printing blanket of the present invention, at least one selected from the group consisting of silicone rubber, silicone resin, fluororesin, and fluororubber is used for the coating film having low affinity with ink.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a printing blanket of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a perspective view showing a printing blanket 10 according to an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along the line AA in which the vicinity of the concave portion 11 is enlarged, and FIG. FIG. 3 is a schematic diagram showing a state in which is mounted on a blanket cylinder 20.

The printing blanket 10 of the present invention is shown in FIG.
As shown in FIG. 2 and FIG. 2, a support layer 13 including a plurality of base fabric layers 12 and a surface printing layer 1 provided on the support layer 13 are provided.
4 A compressible layer 15 made of a porous elastic member may be provided inside the support layer 13.

As shown in FIGS. 1 and 3, when the printing blanket 10 is mounted on the blanket cylinder 20, the concave portion 11 provided on the surface of the printing blanket 10 is connected to the blanket via the central axis 21 of the blanket cylinder. A groove is formed at a position facing the groove portion 22 (gap portion of the blanket) of the cylinder in a direction along the axial direction x of the blanket cylinder. Reference numeral 23 in FIG. 3 denotes a fixing member for winding and fixing the printing blanket 10 in the groove 22 of the blanket cylinder.

The depth d of the concave portion 11 is, as shown in FIG.
Is the length up to the surface. The depth d of the concave portion is not particularly limited, but is 0.1 mm or more, preferably 0.2 to 0.5 m.
m, more preferably in the range of 0.3 to 0.4 mm. If the depth d of the concave portion is less than 0.1 mm, the effect of preventing the adhesion of the ink deposited on the groove of the plate cylinder may not be obtained.

The width w of the recess 11 is suitably set according to the width of the groove of the plate cylinder. That is, if the width w of the concave portion is too small compared to the width of the groove of the plate cylinder, the ink deposited in the groove may adhere to the surface of the blanket 10. Conversely, even if the width w of the concave portion is made larger than the width of the groove portion of the plate cylinder, the effect of preventing the adhesion of the ink remains unchanged, and disadvantageously, the printable area of the blanket 10 is unnecessarily narrowed. There is a risk.

On the surface of the concave portion 11, a coating film 16 having low affinity with ink is formed. By forming the coating film 16, it is possible to effectively prevent the ink accumulated in the groove of the plate cylinder from scattering and adhering to the concave portion 11.

Examples of the coating film having low affinity with ink include silicone rubber, silicone resin, fluorine resin, fluorine rubber and the like. These materials may be used alone or in combination of two or more.

The thickness t of the coating film 16 formed on the surface of the concave portion 11 is not particularly limited, but is 0.1 mm or more, preferably 0.2 to 0.5 mm, more preferably 0.3 to 0.4 mm. It is appropriate to set with.
When the thickness t of the coating film 16 is less than 0.1 mm,
There is a possibility that the effect of preventing ink from adhering to the plate gap may not be obtained.

Next, the surface printing layer 14, the support layer 13, and the like constituting the printing blanket of the present invention will be described.

[Surface Printed Layer 14] As the rubber material used for the surface printed layer 14, acrylonitrile-butadiene rubber (NBR), hydrogenated NBR, chloroprene rubber (C
R), synthetic rubbers such as polyurethane rubbers and acrylic rubbers, and mixtures thereof, and mixtures of the synthetic rubbers with polysulfide rubbers are also suitably used. When the surface printing layer 14 is formed, this rubber material is dissolved in a solvent such as toluene or methyl ethyl ketone together with a predetermined amount of a vulcanizing agent, a vulcanization accelerator and, if necessary, a filler, and the like. Used as

The thickness of the surface printing layer 14 is not particularly limited, but is usually 0.05 to 2.0 mm, preferably 0.1 to 2.0 mm.
It is appropriate to set the distance in the range of 0.6 mm, more preferably in the range of 0.2 to 0.4 mm. If the thickness of the surface printing layer 14 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 thickness of the surface printing layer in the portion where the recess 11 is formed is not particularly limited.
In one part, the surface print layer may not be present at all.

Although the hardness of the surface printing layer 14 is not particularly limited, it is 50 to 70 ° in JIS A hardness, preferably 55 to 70 °.
It is appropriate to adjust to a range of 65 °. Surface printing layer 1
If the hardness of No. 4 is lower than the above range, the distortion during printing becomes too large, so that the paper discharging property is reduced and the registration accuracy may be reduced. Conversely, if the hardness of the surface printing layer 14 exceeds the above range, the flexibility of the surface printing layer becomes insufficient, and the solid inking property may be reduced.

Although the surface roughness of the surface printing layer 14 is not particularly limited, it is preferable that the ten-point average roughness Rz is 1.0 μm or less. If the surface roughness of the surface printing layer 14 exceeds the above range, there is a problem that the quality of the printed halftone dots is disturbed and the print quality is reduced. The smaller the surface roughness is, the better from the viewpoint of print quality. [Support layer 13] The support layer 13 is formed by laminating a plurality of (four in FIG. 2) base cloth layers (reinforcing layers) 12 and at least one compressible layer 15 provided as necessary. It is.

The base fabric layer 12 is formed by impregnating a base fabric made of a woven or non-woven fabric of cotton, polyester, rayon, or the like with a rubber paste, and is preferably a woven fabric that has been stretched. 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.

Although the thickness of the base fabric layer 12 is not particularly limited,
Usually 0.15 to 0.5 mm, preferably 0.25 to
It is appropriate to set within the range of 0.45 mm. Also,
The thickness of the entire support layer 13 is set in accordance with the thickness of the compressible layer 15 described later and the like.
It is set in the range of 1.85 mm, preferably 1.55 to 1.75 mm. In addition, the number of the base fabric layers 12 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 1
Instead of the base fabric in 3, 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.

The rubber constituting the compressible layer 15 is not particularly limited, but may be an ink or a cleaning liquid such as acrylonitrile-butadiene rubber (NBR), acrylic rubber (ACM), chloroprene rubber (CR), urethane rubber (U), or the like. An oil-resistant rubber having resistance to the oil is preferably used. The compressible layer 15 is obtained by mixing a predetermined amount of a vulcanizing agent, a vulcanization accelerator, and the like with the rubber material, and further mixing a filler such as a foaming agent or hollow fine particles described below as necessary. Can be Further, instead of the foaming agent and the hollow fine particles, a mixture containing salt may be used.

The thickness of the compressible layer 15 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 15 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.

Although the hardness of the rubber used for the compressible layer 15 is not particularly limited, it is suitably adjusted to a JIS A hardness of 40 to 80 °, preferably 45 to 75 °, more preferably 50 to 70 °. It is. If the hardness of the compressible layer 15 is less than the above range, the resilience of the compressible layer 15 and, consequently, the 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.

As described above, the compressible layer 15 is made of a porous elastic member. The compressible layer 15 has a closed cell structure in which each cell in the layer is independent and an open cell structure in which each cell communicates with each other. There are things. In the present invention, either structure may be used, or both structures may be used together.

Among the above, the compressible layer having a closed-cell structure can be formed, for example, by dispersing a foaming agent which generates a gas upon thermal decomposition in unvulcanized rubber and foaming the rubber simultaneously with 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 an open-cell 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 (porosity) of the bubbles in the compressible layer 15 is not particularly limited, but is usually adjusted to 30 to 70%, preferably 35 to 60%, more preferably 40 to 55%. Appropriate. If the porosity of the compressible layer 15 falls 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,
There is a possibility that the restoring property is reduced and settling occurs, or a printing pressure required for printing cannot be obtained.

Next, a method for manufacturing the printing blanket 10 of the present invention will be described.

In order to manufacture the printing blanket 10 of the present invention, first, a predetermined number of the base fabric layers 12 are laminated, or the base fabric layers 12 are laminated via a compressible layer 15 as necessary. Layer 13 is created. Next, the surface print layer 14 is formed on the support layer 13 by blade coating the rubber paste for the surface print layer described above. Further, a blanket is obtained by heating and vulcanizing the thus obtained laminate at a predetermined pressure and temperature.

Next, a predetermined portion of the surface printing layer 14, that is, a portion facing the groove portion 22 of the blanket cylinder through the central axis 21 of the blanket cylinder while the printing blanket 10 is mounted on the blanket cylinder 20 (FIG. 3). reference)
In order to form the concave portion 11, the surface print layer 14 at that location is removed by means such as polishing or cutting. Further, by forming the above-mentioned coating film 16 on the surface of the groove thus obtained, the printing blanket 10 having the concave portion 11 of the present invention can be obtained.

As a method of producing the coating film 16, for example, when the coating film 16 is made of silicone rubber, a method of applying a liquid silicone rubber and drying by heating is used. When the coating film 16 is made of a silicone resin or a fluororesin, a method of dissolving the resin in an appropriate solvent, applying the solution, and drying by heating is used.

The silicone rubber, silicone resin, fluororesin and fluororubber used for the coating film 16 have a low affinity for ink and can form a film to which the ink does not easily adhere. Not limited. That is, for example, the liquid silicone rubber is not limited to a one-pack type and a two-pack type, a condensation type and an addition type, and various conventionally known types can be used. As the silicone oil, various conventionally known types such as dimethyl silicone oil, methylphenyl silicone oil, methyl hydrogen silicone oil, and modified silicone oil can be used.

[0042]

The present invention will be described below with reference to examples and comparative examples.

Example 1 A printing blanket 10 shown in FIGS. 1 and 2 was prepared as follows.

(I) Preparation of the support layer 13 A mixed fabric made of a combination of cotton fabric, polyester and rayon fibers was used as a base fabric. The base fabric layer rubber paste to be impregnated into this base fabric includes acrylonitrile-butadiene rubber (NBR) 100 parts by weight, precipitated calcium carbonate 30 parts by weight, dioctyl adipate 10 parts by weight,
Titanium oxide 5 parts by weight, zinc white 3 parts by weight, stearic acid 1
1 part by weight of sulfur, 1 part by weight of sulfur and 2 parts by weight of a vulcanization accelerator (thiazoles) were mixed and dissolved in toluene and methyl ethyl ketone. Further, the rubber paste for the compressible layer contains 45 parts by weight of carbon black, 5 parts by weight of zinc white, 1 part by weight of stearic acid, 5 parts by weight of dioctyl adipate, 1 part by weight of sulfur, and 1 part by weight of vulcanizate with respect to 100 parts by weight of NBR. 2 parts by weight of an accelerator (thiazoles) were mixed, dissolved in toluene and methyl ethyl ketone, and a mixture of salt particles (particle size: 1 to 50 μm) was used.

The rubber paste for the base cloth layer was coated on the base cloth to adjust the thickness of the rubber to 0.05 mm, and the three base cloth layers 12 thus obtained were pressed with a roll. Then
The above-mentioned rubber paste for a compressible layer is applied to the outer surface of the obtained laminate, and the thickness is 0.5 mm and the porosity is 50 by a leaching method.
A compressible layer 15 of volume% was formed.

Next, one base fabric layer obtained in the same manner as described above was bonded to the surface of the compressible layer 15 to obtain a support layer 13 having the layer structure shown in FIG.

(Ii) Preparation of Surface Printing Layer 14 The rubber paste for the surface printing layer includes 35 parts by weight of hard clay, 3 parts by weight of zinc white, 1 part by weight of stearic acid, and 5 parts by weight of dioctyl adipate based on 100 parts by weight of NBR. Parts, 1 part by weight of sulfur and 2 parts by weight of a vulcanization accelerator (thiazoles) were dissolved in toluene and methyl ethyl ketone.

The above-mentioned rubber paste for the surface printing layer is coated on the support layer 13 obtained in (i) by a blade coating method and dried to form a surface printing layer 14 having a thickness of 0.4 mm. did.

(Iii) Vulcanization and molding The unvulcanized laminate obtained by the above (i) and (ii) was vulcanized and molded at a pressure of 1 kg / cm ² and a temperature of 150 ° C. After vulcanization, the 10-point average roughness (Rz, JIS B0601-1982) of the surface of the surface printing layer 14 is 3 to 6 μm.
m. Thus, the length (L ₁ ) = 1
A laminate having a size of 310 mm and a width (L ₂ ) of 1,060 mm was obtained.

(Iv) Formation of the recess 11 As shown in FIG.
The surface print layer 14 was polished at a position of ６646 mm to form a groove having a depth of 0.2 mm and a width w of 10 mm. Further, a liquid silicone rubber (trade name “S Coat Gray” manufactured by Shin-Etsu Silicone Co., Ltd.) is applied to the surface of the groove and dried by heating at 50 ° C. for 20 hours to have a thickness of 0.1%.
A coating film 16 (silicone rubber layer) having a thickness of 1 mm was formed to obtain a printing blanket 10 shown in FIGS. The depth d of the recess 11 in the blanket 10 is 0.1 mm.

(Printing Test) In the printing test, the printing blanket 10 was mounted on a cylinder of a double-cylinder offset rotary printing press (model number "Narrow Gap Neo") manufactured by Mitsubishi Heavy Industries, Ltd., and the printing speed was 1000 rpm. A test chart consisting of a set of halftone dots provided with gradation was continuously printed on high-quality paper.

Then, the number of prints when stains caused by the ink deposited on the plate gap portion in the print image were confirmed.

Examples 2 to 4 and Comparative Examples 1 and 2 A printing blanket 10 was prepared in the same manner as in Example 1 except that the depth d of the recess 11 and the thickness t of the film 16 were different, and the printing test was performed. Was done.

In Comparative Example 1, no recess 11 was formed. Further, in Comparative Example 2, although the grooves were formed in the surface printing layer 14, the film 16 was not formed on the surface.

Table 1 shows the above results.

[0056]

As is clear from Table 1, when printing was performed using the printing blankets of Examples 1 to 4, stains caused by the ink accumulated in the gaps of the plate cylinder caused printing of 10,000 or more copies. Occurs after repeating. On the other hand, Comparative Example 1
When printing was performed with the printing blankets of Nos. 2 and 3, the number of prints until stains occurred was extremely small as compared with the examples.

[0057]

As described above in detail, according to the printing blanket of the present invention, even when printing is performed by a double-cylinder offset printing press, a printed image caused by ink accumulated in a gap portion of a plate cylinder can be obtained. Is sufficiently suppressed. Therefore, the cleaning frequency of the printing plate is low, and the printing productivity is not impaired.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of a printing blanket of the present invention.

FIG. 2 is an enlarged sectional view taken along the line AA of FIG. 1;

FIG. 3 is an explanatory view showing a state in which the printing blanket of the present invention is mounted on a blanket cylinder.

FIG. 4 is an explanatory view showing movement of a printing plate and a blanket in a single-body offset printing press.

FIG. 5 is an explanatory diagram showing that ink deposited in a groove portion of a plate cylinder adheres to a surface of a blanket in a conventional double-cylinder offset printing press.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Printing blanket 11 Concavity 13 Support layer 14 Surface printing layer 15 Compressible layer 16 Film 20 Blanket cylinder 21 Center axis 22 Blanket cylinder groove x-axis direction

Claims (2)

[Claims] 1. A flat printing blanket comprising a support layer which may have a porous compressible layer and a surface printing layer provided on the support layer, wherein the printing blanket is twice as large as the plate cylinder. A recess along the axial direction of the blanket cylinder is provided at a location facing the groove of the blanket cylinder via the central axis of the blanket cylinder, with the blanket attached to the blanket cylinder having the barrel diameter, and A printing blanket, characterized in that a coating film having low affinity with ink is formed on the surface of the printing blanket. 2. The method according to claim 1, wherein the coating film is a silicone rubber,
2. The printing blanket according to claim 1, wherein the blanket is at least one selected from the group consisting of a silicone resin, a fluororesin, and a fluororubber.