JPH0976658A - Printing offset blanket - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the sheet deliverability and ink transferability of a surface print layer and to improve the ink solid adhesion by further providing a fine uneven part on the surface provided with the uneven part of an offset blanket. SOLUTION: An uneven part 2 is formed on the surface of a surface print layer 1, and bubbles 4 are formed in the layer 1. The parts of the bubbles 4 appear on the surface of the layer 1 to form fine recess parts 3. Even if the layer 1 has no uneven part on the surface, the uneven part is formed on the surface by a method for buffing the surface of the layer 1. The pitch (p) of the uneven part is 3 to 10μm, preferably 4 to 8μm, and the elevational height (h) between high and low parts is 2 to 16μm, preferably 6 to 9μm, and the maximum diameter W of the fine recess is preferably 0.6μm or less. The number of the fine recesses is 40 to 1,000 pieces per 0.01mm<2> of the surface of the layer 1, preferably 200 to 600 pieces. Accordingly, the roughness of the surface improves the ink transferability and the solid ink adhesion is not lowered, and hence excellent printing quality can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing offset blanket, and more particularly, it relates to a printing offset blanket having improved paper discharge properties and ink transfer properties.

[0002]

2. Description of the Related Art An offset blanket used for flat plate offset printing, gravure offset printing, etc. is generally shown in FIG.
It has the configuration shown in (b) or (c). That is, one layer or a plurality of layers of the base cloth 6 impregnated with a rubber material (rubber paste) may be laminated via the primer layer G [FIG.
(A)], a porous compressive layer 7 is interposed between the base fabrics 6 and 6 [Fig. 2 (b)], and the base fabric 6 and the compressible layer 7 are laminated on the sheet P [Fig. 2 (c)] and the like, and a surface printing layer 11 provided on the support layer 5.

However, the conventional offset blanket is acrylonitrile-butadiene rubber (NB
Since the surface printing layer 11 is made of a rubber material such as R) having a high elastic modulus and oil resistance, an adhesive force is generated between the surface printing layer and the printing paper during printing, and the printing paper curls. I have something to do. Further, when printing with an offset rotary press, so-called delamination may occur in which the printing paper is caught by the blanket and becomes dirty or broken. Further, the same problem occurs even when printing on a printing paper having a smooth surface such as coated paper. Therefore,
It is required for the offset blanket for printing to improve the paper discharge property (paper release property) of the surface printing layer.

In addition to the above-mentioned paper discharging property, the surface printing layer has
There is a problem that a considerable amount of the ink transferred from the printing plate to the surface of the offset blanket remains on the offset blanket and is not completely transferred to printing paper or the like. As a result, the surface of the ink layer transferred to the printing paper or the like becomes uneven, and the edges of the printed pattern cannot be clearly reproduced, and the solid inking property is deteriorated. Therefore, the offset blanket
It is also required to improve the ink transfer property of the surface printing layer.

Conventionally, as a method for solving the above-mentioned problems, for example, a method of transferring irregularities on the surface of vulcanized paper or buffing is used, as shown in FIG.
It has been attempted to form the unevenness 21 on the surface of the. However, when the height difference h of the unevenness 21 is large and the pitch p is narrow, the discharge property and the ink transfer property of the offset blanket can be improved, but the contact area between the blanket and the paper is reduced. As a result, the solid inking property becomes extremely poor, which causes a problem that a fine pattern cannot be accurately reproduced. On the other hand, when the height difference h of the unevenness is small or the pitch p is wide, the paper discharge property and the ink transfer property cannot be improved.

As a method of roughening the surface shape of the surface printing layer, in addition to the above method, the starch added to the surface printing layer is eluted to form pores having openings of 3 to 65 μm on the surface. (Japanese Patent Publication No. 3-239) is also disclosed. However, when using this method,
Although the paper ejection property is improved, the solid ink receptivity is deteriorated, and there is a problem that a fine pattern cannot be accurately reproduced.

An object of the present invention is to provide an offset blanket for printing, which has improved paper discharging property and ink transfer property of the surface printing layer and also improved solid inking property.

[0008]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that when a large number of minute concave portions are formed on a surface of a surface printing layer, the surface It is possible to obtain an offset blanket for printing that has good dischargeability because the surface of the printing layer has irregularities, and has improved ink transferability due to the provision of minute irregularities, and that also has improved solid inking property. The inventors have found a new fact that they can, and completed the present invention.

The unevenness has a pitch of 3 to 10 μm.
m, the difference in height is 2 to 16 μm, and the maximum diameter of the minute recesses is preferably 0.6 μm or less.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The offset blanket for printing of the present invention will be described in detail below. As shown in FIG. 1, the surface printing layer in the offset blanket for printing of the present invention has unevenness 2 formed on the surface of the surface printing layer 1,
Bubbles 4 are formed inside the surface printing layer 1. The minute recesses 3 are formed by exposing a part of the bubbles 4 on the surface of the surface printing layer 1.

As a method of forming the bubbles 4 in the surface printing layer 1, heat-meltable resin particles are compounded in a rubber material together with various compounding agents, and the particles are melted by heating at the time of vulcanization. A method of generating bubbles 4 can be mentioned. The heat-meltable resin particles used in the present invention preferably have a maximum particle size of 0.6 μm or less, and more preferably have a maximum particle size of 0.2 to 0.3 μm. When resin particles having a maximum particle size of more than 0.6 μm are used, it is not preferable because the offset blanket obtained has poor paper discharge properties and ink accumulation increases. Further, the resin particles may be filled with a resin inside, or may be hollow. The melting temperature of the resin particles is usually 80 to 160 ° C, preferably 80 to 120 ° C. Since the heat-fusible resin particles may remain on the surface of the surface printing layer after melting, it is preferable that the heat-fusible resin particles are a material that does not deteriorate the paper discharge property and the ink transfer property of the offset blanket. Specifically, for example, heat-meltable resin particles such as vinylidene chloride-acrylonitrile copolymer, polyethylene, polypropylene, nylon, acrylic resin can be used.

As another method for producing the bubbles 4, soluble particles such as salt particles are mixed with various compounding agents in a rubber material to form a surface printing layer, and then the particles are eluted with a solvent such as water. The method of making it possible can also be used. As the rubber material, various conventionally known rubbers used as a surface printing layer of an offset blanket can be used.
For example, natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (S
BR), butyl rubber (IIR), ethylene propylene rubber (EPM, EPDM), chloroprene rubber (CR),
Acrylonitrile-butadiene rubber (NBR), acrylic rubber (ACM, AEM), etc. can be used.

Examples of various compounding agents include vulcanizing agents, vulcanization accelerators, vulcanization accelerating aids, reinforcing agents, fillers, plasticizers and the like, each of which is conventionally known if necessary. can do. As a method for producing the surface printing layer,
Various conventionally known types can be used. As an example,
Examples include a method in which the above rubber composition is kneaded, dissolved in a solvent to form a paste, which is glued onto a support layer, and then vulcanized. Although the solvent varies depending on the rubber material used, for example, when the rubber material is NBR, halogenated hydrocarbons, aromatic hydrocarbons, ketones and the like can be used.

The surface-printed layer thus obtained has no irregularities on its surface, and irregularities are formed on the surface by a conventional method such as buffing the surface of the surface-printed layer. It The pitch p of the irregularities is 3 to 10 μm, preferably 4 to 8 μm, and the height difference h is 2 to 16 μm, preferably 6 to 9 μm. If the pitch p of the irregularities is narrower than the above range, or if the height difference h is deeper than the above range, the solid receptivity may decrease.

The maximum particle size of the heat-meltable resin particles used to form the bubbles is preferably 0.6 μm or less. Therefore, the maximum diameter of the bubbles is less than 0.6 μm,
The maximum diameter of the minute recess can be 0.6 μm or less. The number of minute recesses is 0.01 on the surface of the surface printing layer.
40 to 1000 pieces, preferably 200 to 60 pieces per mm ^2.
It is preferably 0.

If the maximum diameter of the fine recesses is larger than 0.6 μm, or if the number of the fine recesses is larger than the above range, the solid inking property may be deteriorated. on the other hand,
When the number of minute recesses is less than the above range, the effect of improving the paper discharge property and the ink transfer property is poor. To set the number of minute recesses within the above range, for example, a thickness of 0.3 m
When producing the surface-printed layer of m, the heat-fusible resin particles may be mixed in a ratio of 1 to 30 parts by weight with respect to 100 parts by weight of the rubber material.

[0017]

EXAMPLES The offset blanket for printing of the present invention will be described below with reference to examples and comparative examples. Examples 1 to 6 and Comparative Examples 1 and 2 Preparation of Support Layer A cotton cloth was used as a base cloth, and an NBR having a thickness of 0.08 m was used.
Four sheets were impregnated to have a thickness of m. However, one intermediate base fabric is formed by coating a rubber material in which salt is dispersed as a water-soluble powder to a predetermined thickness, vulcanizing and leaching to form a porous compressive layer. Preparation of surface-printed layer The composition shown in Table 1 was added to Matsumoto Yushi-Seiyaku Co., Ltd. under the trade name "Saran Micro Square" as heat-fusible resin particles.
(Vinylidene chloride-acrylonitrile copolymer) is shown in Table 2.
The mixture was added and kneaded at the ratio shown in, and toluene was added to prepare a coating liquid for the surface printing layer.

[0018]

[Table 1]

[0019]

[Table 2]

Next, the coating solution was applied onto the support layer using a doctor knife and dried to form a surface printing layer having a thickness of 0.3 mm on the support layer. The thickness of the surface printing layer formed on the support layer was 0.3 mm. Pressure of the obtained laminate is 4.2 kg
/ Cm ² , at a temperature of 150 ° C, pressurize and heat to vulcanize and mold,
An offset blanket for printing having a thickness of 1.90 mm was obtained.

When a cross section of the surface-printed layer of the offset blanket obtained in each of Examples and Comparative Examples was observed with a microscope, a large number of bubbles were formed. When the surface printing layer of the obtained offset blanket for printing was polished with sandpaper to form irregularities on the surface, in Example and Comparative Example 1, a large number of minute recesses based on the bubbles were formed. On the other hand, in Comparative Example 2, the presence of minute recesses was not recognized.

For each of the above Examples and Comparative Examples, the pitch p and the height difference h of the irregularities formed on the surface of the surface printing layer, and the maximum diameter w of the minute recesses were measured. The pitch p of the irregularities, the maximum diameter w of the minute concaves, and the height difference h of the irregularities
Was measured by a three-dimensional roughness measuring machine manufactured by Kosaka Seisakusho. The number of minute recesses generated on the surface of the surface printing layer is
Microscopic depressions existing in a 0.1 mm square on the surface of the offset blanket were counted using a micrograph.

Table 2 shows the respective measurement results. Evaluation of printing characteristics Each of the above offset blankets (thickness 1.90 mm) was wrapped around a transfer cylinder of an offset printing machine (type 560 manufactured by Ryobi Co., Ltd.) and coated paper (trade name “Utrilo Coat 110 kg” manufactured by Daio Paper Co., Ltd.) A black solid image was printed on and the following items were evaluated. For printing, 1000 inks from Toyo Ink Co., Ltd. (trade name "Mark V New") were used.
Printing was performed at a speed of 0 sheet / hour. (Solidness of inking) The density distribution of the solid part was examined by image analysis, and the standard deviation (n) was determined. The smaller the standard deviation is, the better the solid inking property is.

N ≦ 7 ─ ◎ excellent 7 <n ≦ 9 ─ good 9 <n ≦ 11 ─ △ yes n> 11 ─ × no (ink transfer) Ink thickness on offset blanket t ₁ and printing paper The thickness t ₂ of the transferred ink was measured with a laser microscope, and the ink transfer rate was calculated from the following equation.

Ink transfer rate = t ₂ / t ₁ The ink transfer rate of Example 3 thus obtained is 100.
The ink transfer property of each offset blanket was evaluated by the index. The evaluation results of the above printing characteristics are as shown in Table 2 above.

[0026]

According to the present invention, the surface of the surface printing layer is provided with irregularities for improving the sheet discharging property, and the surface of the irregularities is provided with minute recesses. An offset blanket having such a surface-printed layer can obtain good print quality because its surface roughness is sufficient to improve the ink transfer property and the solid ink receptivity is not deteriorated. .

The offset blanket for printing of the present invention is particularly suitable for use in reproducing a precise pattern such as printing of a liquid crystal color filter.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a surface printing layer in a printing offset blanket of the present invention.

FIG. 2 is a sectional view showing an example of a conventional offset blanket for printing.

FIG. 3 is a cross-sectional view showing a conventional surface printing layer having unevenness on the surface.

[Explanation of symbols]

 1 surface printing layer 2 unevenness 3 minute recesses p pitch h height difference w maximum diameter

Claims (2)

[Claims] 1. An offset blanket in which unevenness is provided on the surface of a surface printing layer, wherein a large number of minute recesses are provided on the uneven surface of the offset blanket. 2. The pitch of the irregularities is 3 to 10 μm, the height difference is 2 to 16 μm, and the maximum diameter of the minute recesses is 0.
The offset blanket for printing according to claim 1, which has a thickness of 6 μm or less.