JPH0852955A - Offset blanket for printing - Google Patents

Abstract

PURPOSE:To provide an offset blanket markedly improved in solid deposition properties without bringing about the lowering of printing quality or the complication of a manufacturing process, enhanced in paper delivery properties, paper powder remaining properties and durability and made suitable for the use of high speed printing or mass printing due to an offset rotary press. CONSTITUTION:A surface printing layer is composed of a rubber material satisfying a region of formula (1); tandelta<0.005XHs+0.42showing the relation between rubber hardness Hs(IRHD) and tandelta at a time when dynamic change stress (23 deg.C, 10Hz, amplitude 50mum, chuck-to-chuck distance 20mm, initial strain 2 mm elongation) is applied.

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 to a printing offset blanket having a surface printing layer which has improved printability during high-speed printing, in particular, solid ink receptivity.

[0002]

2. Description of the Related Art An offset blanket used for lithographic offset printing or gravure offset printing usually has a surface printing layer 1 as shown in FIG. 2 and a porous compression layer 3 inside. And a support layer 2 which may have As the material of the surface printing layer 1, a rubber material having high oil resistance, mainly acrylonitrile butadiene rubber (NBR) is used.

However, the offset blanket using such a rubber for the surface printing layer 1 has a poor paper discharge property (paper release property). Therefore, in the case of high speed printing, an adhesive force is generated between the paper and the offset blanket, and the paper curls or breaks. Furthermore, when an offset blanket using such a rubber is used in an offset rotary press, the printing paper is taken up by the blanket, causing delamination such that it is out of register, dirty or broken.

Therefore, in order to improve the discharge property of the offset blanket, attempts have been made to roughen the surface of the surface printing layer and to increase the hardness of the rubber material used for the surface printing layer. There is. However, in the former case, the shape of the halftone dots on the offset blanket becomes poor, and the reproducibility of the halftone dots during printing is impaired. Further, in the latter case, the ink inking property in a solid part having a halftone dot area of 100%, that is, the so-called solid inking property is deteriorated. Therefore, the print quality deteriorates in both cases.

In addition to the above, (1) the surface printing layer is irradiated with ultraviolet rays (Japanese Patent Laid-Open No. 51-37706),
(2) The surface of the surface-printed layer may be treated with chlorine (Japanese Patent Laid-Open No. 47-47).
No. 51729), (3) coating of polyvinyl chloride, polyvinyl acetate, silicone rubber or the like on the surface of the surface printing layer has been attempted. They are,
By treating the surface of the surface printing layer, it is intended to improve the paper discharge property. However, (1) when irradiating with ultraviolet rays, the irradiation equipment is large-scale, and the process control becomes complicated, and (2) when chlorine treatment is performed, the working environment deteriorates, and (3) coating the surface. In this case, there are problems that print quality is deteriorated and the number of steps is increased. That is, it was very difficult to achieve both the paper ejection property and the solid ink receptivity.

On the other hand, in the offset blanket, in addition to the above-mentioned problem of paper discharge, paper dust is accumulated on the offset blanket by printing for a long time, and the paper dust mixes with the ink to deteriorate the print quality. have.
If paper dust builds up, the offset blanket must be cleaned. However, due to resource saving and recycling in recent years, the percentage of using recycled paper with deteriorated paper quality is increasing, and along with this, the amount of paper dust generated (paper dust residue)
Is also increasing. Therefore, the frequency of cleaning the offset blanket becomes frequent. Further, the increase in the number of times of cleaning also causes deterioration of the offset blanket.

Therefore, an object of the present invention is to solve the above-mentioned technical problems, improve solid inking property, improve paper discharge property and paper dust remaining property without complicating the manufacturing process, and It is an object of the present invention to provide an offset blanket for printing which can reduce the occurrence of printing troubles such as lamination.

[0008]

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a support layer which may have a porous compression layer and a support layer provided on the support layer. In the offset blanket for printing, the surface printing layer comprises a rubber hardness (IRHD, AHD).
The hardness when measured by STM D1415-83) Hs and the stress when dynamically changing stress (23 ° C., 10 Hz, amplitude 50 μm, chuck distance 20 mm, initial strain 2 mm extension) are applied.
Equation (1) showing the relationship with nδ:

[0009]

## EQU00002 ## When a rubber material satisfying the range of tan .delta. <-0.005.times.Hs + 0.42-(1) is used, the solid inking property is improved, and the paper discharge property and the paper dust remaining property are remarkably improved. The present invention has been completed by discovering a new fact that it is done.

The boundary line of the region represented by the above equation (1) is shown by (i) in FIG. The tan δ is a viscoelastic property that is observed when a dynamically changing stress such as sinusoidal vibration is applied to the rubber material used for the surface printing layer,
Complex elastic modulus E ^* is represented by the ratio of storage elastic modulus E ′ and loss elastic modulus E ″ in the following formula (2) [the following formula (3)].

[0011]

## EQU00003 ## E ^* = E '+ i.times.E "-(2) tan.delta. = E" / E'-(3) (where i represents an imaginary number, and the following equation:

[0012]

## EQU4 ## It is represented by i = (-1) ^1/2 . ) The measurement conditions of tan δ in the present invention are the test temperature 23
C, test frequency 10 Hz, amplitude 50 μm, chuck distance 20 mm, initial strain 2 mm extension.

On the other hand, the hardness Hs (IRHD) of the rubber
(Hereinafter, simply referred to as Hs.) Is a rubber material used for the surface printing layer, measured according to ASTM D1415-83. The Hs in the offset blanket for printing of the present invention is a value at a temperature of 23 ° C., and the preferable range of the Hs value under this condition is 40 to 80, more preferably 50 to 75. If the value of Hs exceeds this value, the solid ink receptivity deteriorates, and if it falls below this value, the paper ejection property deteriorates and the registration property also deteriorates.

In order to further improve the paper ejection property and the paper dust remaining property of the offset blanket for printing, the surface printing layer has a formula (4) showing the relationship between tan δ and Hs:

[0015]

## EQU5 ## It is preferable to use a rubber material that satisfies the region of tan δ <−0.0056 × Hs + 0.43− (4). still,
The boundary line of the area expressed by the equation (4) is (i) in FIG.
i). Hereinafter, the offset blanket for printing of the present invention will be described in more detail with reference to FIG. 2 showing an example thereof.

As the rubber material used for the surface printing layer 1,
Acrylonitrile butadiene rubber (NBR), hydrogenated N
BR, chloroprene rubber (CR), polyurethane rubber,
Examples thereof include synthetic rubber such as acrylic rubber, and further, a mixture of these synthetic rubbers, a mixture of the synthetic rubber and polysulfide rubber, and the like. The support layer 2 is made by laminating a plurality of layers of base fabrics 4a, 4b, 4c impregnated with a rubber agent (rubber paste) and at least one compression layer 5 provided as necessary. Is.

The base fabrics 4a, 4b and 4c are woven fabrics such as cotton, polyester and rayon. Examples of the rubber agent to be impregnated include acrylonitrile butadiene rubber and chloroprene rubber. These rubber agents contain a predetermined amount of a vulcanizing agent, a vulcanization accelerator and, if necessary, a thickener. Then, the woven cloth is coated with the above-mentioned rubber agent by a blade coating method or the like. Next, the surface printing layer-forming rubber agent made of the above-mentioned mixture is applied to the surface of the support layer 2 via the primer layer and dried to form the surface printing layer 1. The laminate thus obtained is heated and pressed at a predetermined pressure and temperature for vulcanization to obtain an offset blanket 1 having a compression layer 3 in a support layer 2.

For the compression layer 3, at least one intermediate base cloth is coated with a rubber paste in which a water-soluble powder such as salt is dissolved, dried and vulcanized, and then placed in warm water at 60 to 100 ° C. ~
It is formed by soaking for 10 hours, eluting the water-soluble powder and drying. The offset blanket 1 thus obtained is used by being adhered to the peripheral surface of the cylinder of the transfer cylinder directly or through an undercoating agent.

[0019]

[Function] Since the offset blanket having the above-described structure significantly improves solid ink receptivity and improves sheet discharge performance, occurrence of printing defects such as delamination during high-speed printing or printing by an offset rotary press is reduced. To be done. Further, the generation of the paper dust accumulated on the offset blanket is suppressed when the printing paper is quickly separated from the offset blanket, so that not only the paper discharging property but also the paper dust remaining property is improved.

[0020]

Examples of the present invention will be described below. Examples 1 to 5 and Comparative Examples 1 to 4 Production of Offset Blanket An offset blanket shown in FIG. 2 was produced under the following conditions. (1) Preparation of Support Layer 2 Four pieces of cotton cloth were used as the base cloths 4a, 4b, and 4c, and acrylonitrile butadiene rubber (NBR) was impregnated with the cloth to a thickness of 0.08 mm. Of these, the rubber material that is impregnated into the one base cloth located in the middle is
It was created by a leaching method using salt as the water-soluble powder. (2) Preparation of surface printing layer 1 The rubber compositions of Examples 1 to 5 and Comparative Examples 1 to 4 shown in Table 1 below were prepared and dissolved in toluene / methyl ethyl ketone to prepare the support layer 2 (not Vulcanization) with a thickness of 0.
It was applied to have a thickness of 30 mm and dried. (3) Vulcanization / molding After laminating the surface printing layers 1 of Examples 1 to 5 and Comparative Examples 1 to 4, pressure 1 kg / cm ² , temperature 150 ° C.
Heated and molded in. After vulcanization, the surface printing layer was ground to have a 10-point average roughness (Rz, JIS B 0601-1982) of 3 to 6 μm to obtain each offset blanket. The Hs and tan δ of the surface printing layer 1 were measured by taking out test pieces from the rubber compositions of Examples 1 to 5 and Comparative Examples 1 to 4 described above. For the measurement of Hs, five test pieces each having a width of 20 mm, a length of 20 mm and a thickness of 0.3 mm were stacked, and a micro hard nester manufactured by Wallace was used, and ASTM D1 was used.
It measured based on 415-83. On the other hand, for the measurement of tan δ, a test piece with a width of 4 mm, a length of 30 mm and a thickness of 0.3 mm was used, and dynamic change stress (23 ° C., 10 Hz, amplitude 50 μm, chuck distance 20 mm, initial strain 2 mm extension) was applied. Then, it was measured with DVE-V4 manufactured by Rheology.

The values of Hs and tan δ in Examples 1 to 5 and Comparative Examples 1 to 4 are shown in Table 1 below.

[0022]

[Table 1]

Printing Test Example A printing test was carried out in order to evaluate the paper discharge properties, paper dust remaining properties and printing characteristics of the offset blankets in Examples 1 to 5 and Comparative Examples 1 to 4. In the test, each of the obtained offset blankets (thickness 1.90 mm) was wound around a transfer cylinder of an offset printing machine (type 560 manufactured by Ryobi Co., Ltd.) and coated on coated paper ("Utrilo Coat 110 kg" manufactured by Daio Paper Co., Ltd.). I printed it. Incidentally, "Mark V New" manufactured by Toyo Ink Co., Ltd. was used as the printing ink, and the printing speed was 10,000 sheets / hour.

Table 2 shows the evaluation of the printing test in Examples 1 to 5 and Comparative Examples 1 to 4.

[0025]

[Table 2]

In the table, each evaluation was performed according to the following criteria. (A) Paper discharge property (delamination) 10 sheets of coated paper printed in full solid were stacked, and the height (h, unit mm) of the curled portion of the paper was measured. The lower the curl height, the less delamination occurs,
It shows that the paper ejection property is good.

◎ ─ 0 ≤ h <3 〇 ─ 3 ≤ h <5 △ ─ 5 ≤ h <7 × ─ h ≧ 7 (b) Solid inking property The density distribution of the solid part was examined by image analysis, and its standard deviation (N) was determined. The smaller the standard deviation is, the better the solid inking property is.

◎ ─n ≦ 7 ○ ─7 <n ≦ 9 △ ─ 9 ≦ n <11 × ─ n ≧ 11 (c) Paper dust residual property Paper dust adhered to the surface of the offset blanket after printing 100,000 sheets Was visually evaluated.

⊙—There is extremely little paper dust. 〇 ─ Almost no paper dust gets on it. △ ─ Paper dust collects near the edges. × ─ Paper dust collects on the entire surface. (D) Durability After printing 5 million sheets with an offset rotary press, the surface of the offset blanket was visually evaluated.

◯ —No breakage or wear was observed. B: Minor breakage and wear were observed. × ─ There was a lot of breakage and wear. The values of tan δ and Hs of each of the examples shown in Table 2 are represented by a graph in which ordinate tan δ and abscissa Hs are shown in FIG. In FIG. 1, (i) is a boundary line of the region represented by the formula (1), and (ii) is a boundary line of the region represented by the formula (4).

Example 1 within the range of formula (2) in FIG.
The offset blankets for printing of Nos. 5 to 5 are superior in all of the dischargeability, the residual paper dust, the solid sticking property and the durability as compared with Comparative Examples 1 to 4 which are out of the range of the formula (2). ing. Further, the printing offset blankets of Examples 4 and 5 which are within the range of the formula (4) in FIG. 1 were superior to Examples 1 to 3 in paper discharge property, paper dust remaining property, solid ink retentivity and durability. Is even better.

[0032]

As described above, according to the offset blanket of the present invention, the solid inking property is greatly improved, and the paper discharging property and the paper dust remaining property are excellent. Therefore, the printing characteristics are excellent during high-speed printing. In addition, the residual paper dust caused by printing for a long time is greatly reduced, so that the offset blanket is not frequently washed. Furthermore, durability is also improved.

Therefore, the offset blanket of the present invention is suitable for applications such as high speed printing and mass printing by an offset rotary press.

[Brief description of drawings]

FIG. 1 tan δ in Examples of the present invention and Comparative Examples
Is a graph showing the relationship between Hs and Hs, where (i) represents the boundary line of the region represented by formula (1), and (ii) represents the boundary line of the region represented by formula (4). Show.

FIG. 2 is a cross-sectional view showing an example of a printing offset blanket.

[Explanation of symbols]

 1-surface printed layer 2-support layer 3-compressed layer

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[Procedure amendment]

[Submission date] August 25, 1994

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 2

[Correction method] Change

[Correction content]

[Fig. 2]

Claims (1)

[Claims] 1. An offset blanket for printing comprising a support layer which may have a porous compression layer and a surface printing layer provided on the support layer, wherein the surface printing layer has a rubber hardness ( IRHD, ASTM D1415-8
3 hardness) Hs and dynamic change stress (23 ° C, 10H
z, amplitude 50 μm, chuck distance 20 mm, initial strain 2 mm) (1) tan δ <−0.005 × Hs + 0.42 ─ (1) ) An offset blanket for printing, characterized in that it is made of a rubber material that fills the area.