JP2504652B2 - Offset blanket for printing - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to lithographic offset printing,
The present invention relates to a printing offset blanket used for gravure offset printing and the like, and more particularly to a printing offset blanket suitable for printing a fine pattern such as a liquid crystal color filter.

[0002]

2. Description of the Related Art When an ink layer printed on the surface of a transparent glass plate such as a liquid crystal color filter is viewed with transmitted light, if the thickness of the ink layer varies, it causes This causes shading in transmitted light, which causes variations in image quality. Further, the color filter of the TFT liquid crystal device has a very complicated pattern, and the edge shape of the pattern is required to be sharp without beards or the like. In conventional lithographic offset printing and gravure offset printing, the ink on the plate is transferred onto the offset blanket, and when it is then printed on the glass plate, the ink remains on the surface of the offset blanket. Irregularities inevitably occur on the film surface. In addition, when the ink does not sufficiently transfer from the plate to the surface of the offset blanket, even if the ink on the offset blanket completely transfers to the glass plate, it may cause pinholes or disorder of the edge shape.

However, it is very difficult to simultaneously satisfy the two contradictory phenomena of completely transferring the ink from the plate to the offset blanket and completely transferring the ink from the offset blanket to the printing medium. It was difficult. That is, in order to completely transfer the ink on the surface of the offset blanket to the printing medium, it is sufficient to use a material having a surface tension as low as possible on the surface of the offset blanket. Transferability of the ink from the ink to the surface of the offset blanket becomes extremely poor,
As described above, it may cause pinholes and make the edge shape unclear.

Therefore, an object of the present invention is to solve the above-mentioned technical problems and to print an ink layer having a substantially uniform thickness and sharp edges on the surface of a printing medium such as a glass plate, An object of the present invention is to provide a printing offset blanket suitable for printing liquid crystal color filters and the like.

[0005]

SUMMARY OF THE INVENTION As described above, the present inventors have two contradictory requirements, that is, the ink transferability from the plate to the offset blanket and the ink transferability from the offset blanket to the printing medium. In order to provide an offset blanket that is almost completely satisfactory,
As a result of intensive studies, when a rubber material that swells with respect to the ink vehicle is used in the surface printing layer of the offset blanket, both the ink transferability from the plate to the blanket and the ink transferability from the blanket to the printing medium are achieved. At the same time, they found a new fact that they can be satisfied, and completed the present invention. That is, according to the present invention
The offset blanket for printing has a support layer and this support.
It consists of a surface printing layer laminated on the carrier layer.
The surface printing layer is a vehicle for printing ink.
24 hours at 40 ° C for 1- to 6-valent acrylate monomer
Methyl having a volume change rate after immersion of 3 to 15%
Vinyl silicone rubber (hereinafter referred to as VMQ), tri
Fluorosilane-based silicone resin having fluoropropyl group
Has a phenyl group (hereinafter referred to as FVMQ)
Phenyl silicone rubber (hereinafter referred to as PVMQ)
Specially consisting of at least one selected from the group consisting of
To collect.

[0006]

[0007]

When the volume change rate is smaller than the above range, the wettability of the ink to the surface printing layer of the offset blanket is extremely poor, so that pinholes and edge shapes become unclear, and no ink is left on the surface. Part occurs. Further, when the volume change rate is larger than the above range, first, the ink on the surface printing layer does not completely transfer to the material to be printed, and there is a part that remains on the surface of the surface printing layer, or during continuous printing. In addition, the rubber of the surface printing layer absorbs the acrylate monomer, causing swelling, softening, and breaking.

As the silicone rubber used in the present invention, various conventionally known silicone rubbers can be used. For example, a millable type silicone rubber which can be kneaded and a room temperature vulcanization type which cures at room temperature ( RTV) silicone rubber, LIM silicone rubber that can be injection-molded, and the like. Silicone rubber is polymethyl siloxane, such as RTV silicone rubber based on a low degree of polymerization liquid silicone gum having a degree of polymerization of about 100 to 800, and a millable silicone rubber based on a gel silicone gum having a degree of polymerization of about 6000 to 10,000. It is conceivable that all of them are supplied as a rubber compound in which a raw gum is mixed with an anhydrous silica-based reinforcing filler such as aerosil, an increasing filler such as talc and mica, and a dispersion accelerator. RTV silicone rubber generally contains polydimethylsiloxane, and millable silicone rubber contains methyl vinyl group of 0.1 to 0.1% in order to balance crosslinkability and physical properties.
What was introduced about 0.5 mol% is used. Further, trifluoropropyl group-introduced FVMQ, phenyl group-introduced PVMQ and the like can also be used, and a mixture thereof can also be used.

The surface printing layer is formed by mixing the above silicone rubber with a vulcanizing agent, molding the mixture, and then vulcanizing it by a conventional method. Examples of the vulcanizing agent include benzoyl peroxide, bis2,4-dichlorobenzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, p-monochlorobenzoyl peroxide and 2,5-dimethyl-2,5. Examples thereof include organic peroxide-based cross-linking agents such as -bis (t-butylperoxy) hexane and t-butylcumyl peroxide.

As the filler, silicic acid anhydride, hydrous silicic acid, calcium carbonate, hard clay, barium sulfate, talc,
Inorganic fillers such as asbestos and graphite and recycled rubber,
Examples include powder rubber, asphalt, styrene resin, and organic filler such as glue. The offset blanket of the present invention is formed by laminating the surface printing layer having the above structure on the support layer. Examples of the support layer include those prepared by laminating a plurality of base fabrics impregnated with a rubber material (rubber paste) and at least one compressible layer provided as necessary. .

The base fabric is a woven fabric of cotton, polyester, rayon or the like. Examples of the rubber material to be impregnated include acrylonitrile-butadiene copolymer rubber and chloroprene rubber. These rubber materials contain a predetermined amount of a vulcanizing agent, a vulcanization accelerator and, if necessary, a thickener and the like. Then, the woven cloth is coated with the rubber agent by an appropriate application means such as a blade coating method. Then, the surface printing layer forming rubber paste made of the above-mentioned specific rubber material is applied to the surface of the support layer through the primer layer and dried, or a sheet-like material formed by a calendar or the like is laminated. The obtained laminate is heated and pressurized at a predetermined pressure and temperature for vulcanization to obtain an offset blanket having a compressive layer in the support layer. The compressible layer is formed by applying a rubber paste obtained by dissolving a water-soluble powder such as salt to at least one intermediate base fabric, drying and vulcanizing the resultant, and then warming it to 60 to 100 ° C. in warm water at a temperature of 6 to 100 ° C. It is formed by immersing for a time, eluting and drying the water-soluble powder.

Further, instead of such a laminated type support layer, a film or sheet such as polyethylene terephthalate (PET), polycarbonate (PC), polypropylene (PP), aluminum foil, and stainless sheet is used as the support layer. Good. The obtained offset blanket is used by being adhered to the peripheral surface of the cylinder of the transfer cylinder either directly or through an undercoating material.

As a plate for transferring ink to the offset blanket of the present invention, a conventional PS plate, a waterless flat plate or the like is used. In particular, a waterless plate is preferably used for printing a liquid crystal color filter. That is, in a normal PS plate that forms an image by utilizing the repulsive property of water and ink, it is unavoidable that water and ink come into contact with each other and become an emulsified state, so that the alkaline component contained in water If they enter into, it will shorten the life of the liquid crystal.
On the other hand, in a waterless flat plate (strictly speaking, an intaglio plate), without using water, an ink repellent layer such as silicone rubber provided on a support such as aluminum foil is used as a non-image area, and Ink is placed in the voids (cells) between the non-image areas that are the line areas, and then transferred to the surface of the offset blanket for printing.

[0015]

Examples Examples 1 to 3 and Comparative Examples 1 to 3 (1) Preparation of Rubber Composition for Surface Printing Layer Based on VMQ (polydimethylsiloxane gum containing methyl vinyl group having a degree of polymerization of 8000) Reinforcing anhydrous silica, hydrous silica, non-reinforcing talc or mica as a filler is compounded in the compounding amounts shown in Table 1, and further a predetermined amount of a dispersion stabilizer and a cross-linking agent is added to the rubber for the surface printing layer. A composition was obtained. Also, phenyl modified PVM
Q was also compounded in the same manner to obtain a rubber composition for surface printing layer.

[0016]

[Table 1]

(2) Swelling test Each compounded rubber composition described above is molded and vulcanized to 1 mm × 2 cm ×
A 2 cm block was prepared and immersed in an acrylate monomer kept at 40 ° C. for 24 hours. After the immersion, the block was taken out, and the volume change rate ΔV shown in the following formula was calculated from the volume V ₁ before the immersion and the volume V ₂ after the immersion.

ΔV (%) = (V ₂ −V ₁ ) / V ₁ × 100 The results are shown in Table 2. The acrylate monomer used was a compound having a bifunctional group represented by the following formula (KAYARAD MANDA manufactured by Nippon Kayaku Co., Ltd., molecular weight 31).
2).

[0019]

Embedded image

(3) Preparation of offset blanket A rubber composition having the above composition was molded and vulcanized to have a thickness of 750.
A surface printing layer having a thickness of 350 μm is prepared and a P
It was laminated and adhered on an ET film to obtain an offset blanket having a thickness of 1.0 mm. Since a mold having a smooth surface was used for molding the surface printing layer, the rough surface RZ was 1.0 μm and the surface was very smooth. (4) Printing test Flatbed offset printing machine (Ector 600C manufactured by Koyosha)
L), a waterless flat plate having a line width of 100 μm and a space of 200 μm was produced, and this was used as a plate. Then, each blanket obtained in (3) above was used to print on the glass surface with an ultraviolet curable ink (manufactured by Dainippon Ink and Chemicals, Inc.). The surface shape of the printed glass was observed with a surface shape analyzer (SAS2010 manufactured by Meisho Machinery Co., Ltd.) and a laser microscope (1LM21W manufactured by Lasertec Corporation).

The results are shown in Table 2. The test methods and evaluation criteria shown in the table are as follows. (a) Plate-to-blanket transition rate The cell depth of the ink on a waterless plate (strictly speaking, an intaglio plate) was measured with a laser microscope. In general, when the ink is transferred from the plate to the surface of the blanket, it can be considered that the ink film thickness on the blanket is substantially the same as the cell depth of the ink. Therefore, the cell depth of the plate is t ₀ , and the ink on the blanket is When the film thickness is t ₁ , the transition rate is represented by the following equation.

Transfer rate = (t ₁ / t ₀ ) × 100 (%) Incidentally, the cell depth t ₀ of the plate is usually about 2 to 3 μm, and the ink film thickness t ₁ on the blanket is ₁ to 1.5 μm.
m. (b) Blanket → Glass Transition Rate Using a laser microscope, the thickness of the ink film on the surface of the blanket and the thickness of the ink film transferred to glass were measured. Similarly to (a), when the ink film thickness on the blanket is t ₁ and the ink thickness on the glass surface is t ₂ , the transition rate is expressed by the following equation.

Transfer rate = (t ₂ / t ₁ ) × 100 (%) (c) Pinhole rate on blanket A certain section is set, and the total area S _{0 of the} pattern is calculated by the image processing apparatus. Usually 100 μm as a pattern
Measure the width x length 100 mm section. Then, the total area S ₁ of the pinhole portion in the section is calculated by the image processing device, and the pinhole ratio is obtained from the following equation.

Pinhole rate = (S ₁ / S ₀ ) × 100
(%) (C) Shape of the printed pattern on the glass plate Observed with a laser microscope, pinhole by sensory inspection,
The shape, film thickness, etc. were evaluated comprehensively. Then, the best one was evaluated as ⊚, and the evaluation was performed in the order of ○, ×, and XX.

[0025]

[Table 2]

From Table 2, it can be seen that the ink transfer rate to the blanket surface and the print pattern shape change in relation to the volume change rate (swelling degree) with respect to the acrylate monomer, regardless of the type of silicone rubber or additive. Recognize. The surface printing layer, which exhibits a volume change rate of about 3 to 15%, especially 5 to 10%, with respect to the vehicle of the ink (acrylate monomer) has improved wettability of the ink, and as a result, a precise printed pattern is extremely clear. It turned out that it can be reproduced. Examples 4 to 6 and Comparative Examples 4 to 6 Millable type VMQ (KE951U manufactured by Shin-Etsu Chemical Co., Ltd., hardness 50 °) and millable type FVMQ (FE manufactured by Shin-Etsu Chemical Co., Ltd.)
251 U, hardness 50 °) was used to prepare a rubber composition for a surface printing layer having the composition shown in Table 3.

[0027]

[Table 3]

Using each rubber composition shown in Table 3, a swelling test and a printing test were conducted in the same manner as described above. The results are shown in Table 4. The acrylate monomer used in the swelling test is a compound having a bifunctional group represented by the following formula (KAYARADR604 manufactured by Nippon Kayaku Co., molecular weight 326).
Is.

[0029]

Embedded image

[0030]

[Table 4]

From Table 4, the VMQ used has a very low swelling rate with respect to the acrylate monomer.
In Comparative Example 4 (volume change rate 2%) using Q alone,
It can be seen that the ink transfer from the plate to the blanket is poor and it is difficult to get wet, so pinholes are easily generated in the pattern on the blanket, and because the amount of ink on the blanket is small, the thickness of the printed pattern is also thin. .
On the other hand, when the FVMQ, which is relatively swellable with respect to the acrylate monomer, is blended with the VMQ, the volume change rate is also increased, so that in Examples 4 to 6 in which the volume change rate is within the range of 3 to 15%. It can be seen that a very good pattern could be printed. On the other hand, in Comparative Examples 5 and 6 in which the volume change rate exceeded 15%, the surface printing layer swelled and softened during printing, resulting in breakage.

[0032]

As described above, according to the offset blanket of the present invention, since the surface printing layer is constituted by using the silicone rubber which swells at a predetermined volume change rate with respect to the ink viscosity, the ink of the plate is Is effectively transferred to the blanket, and the ink can be completely transferred from the blanket to the printing medium.
Therefore, the offset blanket for printing of the present invention is particularly suitable for printing on a mask pattern of a liquid crystal color filter, a transmissive liquid crystal display or the like, or on a high-density printed board, and its industrial significance is great.

Claims (1)

(57) [Claims] 1. A printing offset blanket comprising a support layer and a surface printing layer laminated on the support layer, wherein the surface printing layer is a vehicle of printing ink.
Methyl vinyl silicone rubber, fluorosilane silicone rubber having a trifluoropropyl group, and phenyl group having a phenyl group having a volume change rate of 3 to 15% after being immersed in a hexavalent acrylate monomer at 40 ° C. for 24 hours. An offset blanket for printing, comprising at least one selected from the group consisting of silicone rubber.