JPH0692056A - Offset blanket for printing - Google Patents

Abstract

PURPOSE:To make high speed printing of very minute pattern possible by a method wherein an offset blanket for printing is prepared by laminating surface printing layer made of silicone rubber onto support layer and the characteristics on the viscoelasticity of the silicone rubber are specified. CONSTITUTION:The offset blanket for printing concerned, which is suitable for printing minute pattern of lithographic offset printing, of gravure offset printing, especially of liquid crystal color film or the like, is prepared by laminating surface printing layer made of silicone rubber onto support layer. As the silicone rubber, one having a tandelta or the ratio E'/E'', in which E' is elastic term and E'' is viscous term, at 20 deg.C in the frequency of 1-100Hz of 0.1-0.5 is used. Thus, the dependence of pattern on speed is reduced, resulting in obtaining an offset blanket, with which pattern can be favorably transferred, even when printing speed is increased.

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 used for lithographic offset printing and gravure offset printing, and more particularly to a printing offset blanket suitable for printing fine patterns such as liquid crystal color filters.

[0002]

2. Description of the Related Art When an ink layer printed on a transparent glass surface such as a liquid crystal color filter consisting of three colors of red, green and blue is viewed by transmitted light, the ink layer If the film thickness varies, the transmitted light may have light and shade, which causes the image quality to vary. In order to prevent such variations in film thickness, it is necessary that the ink on the plate be completely transferred to the glass surface through the offset blanket when printing on the glass surface by lithographic offset printing or gravure printing. Is. However, in a conventional offset blanket that usually uses a rubber material such as acrylonitrile-butadiene copolymer rubber (NBR) as a surface printing layer, the ink remains on the surface of the blanket and separates on the glass and the blanket. Irregularities are inevitably generated on the surface of, and variations in film thickness occur.

Therefore, the inventors of the present invention tested various rubber materials and found that when silicone rubber was used as the surface printing layer of an offset blanket, the ink on the blanket could be almost completely transferred onto the glass. We have found that a flat ink layer can be obtained. However, since silicone rubber originally has a very low surface tension and is difficult to receive ink, the speed dependency is very large and the ink does not transfer to the blanket when the printing speed is increased, and as a result, the printing speed can be increased. Instead, it was a big obstacle in terms of productivity.

That is, at present, when a liquid crystal color filter is printed by a printing method, particularly a gravure offset method, the pattern shape greatly depends on the printing speed, and the tendency becomes more remarkable as the pattern becomes thinner. Specifically, for a pattern having a width of about 200 μm, when the printing speed is increased from 10 mm / sec to 50 mm / sec, the pattern width on the blanket is reduced by about 10%, but the pattern shape is not greatly affected. ., A fine pattern of about 50 .mu.m causes pattern disconnection and ink repelling, making it difficult to accurately transfer the pattern to the glass substrate.

Therefore, a main object of the present invention is to provide an offset blanket for printing, which is particularly suitable for multicolor printing of a fine pattern such as a liquid crystal color filter and enables high speed printing to improve productivity. Especially.

[0006]

Means and Actions for Solving the Problems The present inventors have conducted various experiments by gravure offset printing using an offset blanket having a surface printing layer made of silicone rubber, and as a result, the viscoelasticity of the silicone rubber used. Have a great influence on the pattern shape. In particular, a new fact was found that when a high Tan δ silicone rubber material having a large viscosity term is used, the dependence on the printing speed is reduced and the pattern can be transferred to the glass substrate very accurately in high speed printing. . Further, there are various types of silicone rubber materials, and in any of these types, a material having a high Tan δ shows good pattern reproducibility.

That is, in order to evaluate the pattern reproducibility by using various silicone rubber materials having different viscoelasticities, the complex elastic modulus E ^* , the elastic term E ',
The viscosity term E ″ and its ratio (E ′ / E ″) Tan δ
Was measured. As a result, focusing on Tan δ, when the value of Tan δ is in the range of 0.1 to 0.5 in the frequency range of 1 to 100 Hz at 20 ° C., the speed dependence of the pattern is small and the printing speed is increased. Also found a new fact that it is possible to transfer patterns well. Particularly, taking into consideration the compression permanent property and the like, Tan δ is more preferably in the range of 0.1 to 0.3.

On the other hand, when a silicone rubber material having a Tan δ smaller than 0.1 is used, the printing speed dependency of the pattern becomes extremely large. Considering the reason based on the printing mechanism in the gravure offset printing, the blanket pulls out the ink in the gravure cell (the cell depth is in the range of 5 to 10 μm in the case of a color filter) to print the pattern, Higher printing speeds reduce the time for the blanket to pass through the nip where the blanket and plate are in contact, which reduces contact time.
At this time, the material with small Tan δ recovers quickly against deformation, and the recovery of deformation within the nip is fast. Therefore, when the printing speed becomes fast, the cells do not sufficiently follow the deformation, and as a result, the ink is not transferred in the pattern. It is thought to be because it will end up.

On the other hand, when the value of Tan δ exceeds 0.5, the compression set characteristic of the rubber material is extremely deteriorated and the recovery against deformation is remarkably deteriorated. It is not preferable because the scratches remain without being recovered. Therefore, the offset blanket for printing of the present invention is one in which the surface printing layer made of silicone rubber is laminated on the support layer, and the Tan δ of the silicone rubber is 20 ° C. and the frequency is 1 to 100.
It is characterized by being in the range of 0.1 to 0.5 at Hz.

The silicone rubber used in the offset blanket of the present invention is, for example, one selected from the group consisting of methylvinyl silicone rubber, fluorosilicone rubber having a trifluoropropyl group and phenylsilicone rubber having a phenyl group, or Examples thereof include a mixture of two or more, but are not limited to these.

The silicone rubber can be used in various conventionally known forms, for example, a millable millable silicone rubber, a room temperature vulcanizing type silicone rubber (RTV rubber) that crosslinks at room temperature, and an LIM capable of injection molding. (Liquid I
njection Molding) Silicone rubber etc. can be used. The silicone rubber is an RTV silicone rubber based on a low polymerization degree liquid silicone rubber having a polymerization degree of 100 to 800 and a polymerization degree of 600.
A millable silicone rubber based on 0 to 10000 gel-like silicone raw rubber can be considered. In each case, the raw rubber is an anhydrous silica-based reinforcing filler such as Aerosil, an increasing filler such as talc and mica, and a dispersion accelerator. It is supplied as a rubber compound containing the above ingredients. RT
V silicone rubber is generally polydimethylsiloxane. As the millable silicone rubber, one having a methyl vinyl group introduced in an amount of about 0.1 to 0.5 mol% is used in order to balance the crosslinkability and the physical properties. Further, a fluorosilicone rubber having a trifluoropropyl group introduced therein, a phenylsilicone rubber having a phenyl group introduced therein, and the like can also be used, and a mixture thereof can also be similarly used.

The surface-printed layer in the present invention is formed by mixing the silicone rubber with a crosslinking agent (vulcanizing agent), molding the surface-printed layer, and then crosslinking. As the crosslinking agent contained in the compounded rubber, for example, an organic peroxide type crosslinking agent can be used. Examples of the organic peroxide-based cross-linking agent include benzoyl peroxide, bis2,4-dichlorobenzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide,
Examples thereof include p-monochlorobenzoyl peroxide, 2,5-dimethyl-2,5-bis (tert-butylperoxy) hexane and tert-butylcumyl peroxide.

Examples of the filler include inorganic fillers such as silicic acid anhydride, calcium carbonate, hard clay, barium sulfate, talc, mica, asbestos and graphite; regenerated rubber, powdered rubber, asphalt, styrene resin, and organic such as glue. Fillers may be mentioned. The surface rubber hardness of the surface printing layer is usually 20 to 90, preferably 40 according to JIS A.
If the hardness is lower than this, the one of about 70 is used.
The rubber changes during printing and the pattern cannot be transferred accurately. On the other hand, when the hardness exceeds this, it becomes difficult for the rubber to receive the ink, and the transfer to glass or the like becomes insufficient, which is not preferable.

Since the surface roughness of the surface printing layer has a great influence on the shape of the printing pattern, it is desirable that the surface printing layer be as fine as possible. Usually 10 points average roughness (R _Z ) 3
It is not more than μm, preferably not more than 1.5 μm. In the present invention, the surface printing layer is laminated on the support layer. As the support layer, for example, a plurality of layers of base cloth impregnated with a rubber material (rubber paste) (usually, three or four or more cotton cloths are laminated), and at least one compressible layer provided if necessary. An example is a product made by stacking and.

As the base cloth, woven cloth such as cotton, polyester and rayon is used. Examples of the rubber material to be impregnated include acrylonitrile-butadiene copolymer rubber and chloroprene rubber. These rubbers contain a predetermined amount of a cross-linking agent, a cross-linking accelerator and, if necessary, a thickener and the like. Then, the woven cloth is coated with the above 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 pressed at a predetermined pressure and temperature to be crosslinked to obtain an offset blanket. The compressible layer is provided on at least one intermediate fabric,
Applying a rubber paste in which a water-soluble powder such as salt is dissolved, drying and crosslinking it, and then immersing it in warm water at 60 to 100 ° C for 6 to 10 hours to elute and dry the water-soluble powder. Formed by.

As the above-mentioned base cloth, glass fiber or polyamide fiber having a small elongation (for example, Kepler (registered trademark manufactured by DuPont)) can be used. Further, instead of the laminated type support layer, polyethylene terephthalate (PE
T), polycarbonate (PC), polypropylene (P
Films or sheets such as P), polyimide, aluminum foil, and stainless steel sheets may be used as the support layer. These may have a compressible layer.

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.

[0018]

【Example】

Example 1 "KE5" manufactured by Shin-Etsu Chemical Co., Ltd., which is a millable silicone rubber
75 U "(high-strength methyl vinyl silicone rubber compound) 100 parts by weight as a cross-linking agent" C
8A "[containing 80% 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane] 0.6 part by weight. This compound is then added at 170 ° C for 20
Primary vulcanization is carried out for 4 minutes and then in an oven at 200 ° C
Second time secondary vulcanization was performed.

The above rubber was laminated on a polyethylene terephthalate film having a thickness of 350 μm to a thickness of 750 μm,
An offset blanket having a total thickness of 1.0 mm was produced.
Since the surface of the mold was very smooth, the roughness was R
_z = 1.0 μm, resulting in a very smooth finish. In each of Examples 2 to 3 and Comparative Examples 1 and 2, the silicone rubbers a to h shown in Table 1 which are RTV silicone rubbers were used and blended in the ratio shown in the same table.

[0020]

[Table 1]

The silicone rubbers ah used are as follows. a- "KE1204AL" manufactured by Shin-Etsu Chemical ^* b- "KE1204BL" manufactured by Shin-Etsu Chemical ^* c- "KE1603A" manufactured by Shin-Etsu Chemical d- "KE1603B" manufactured by Shin-Etsu Chemical e- "Made by Shin-Etsu Chemical" X-34-391A " ^* f-" X-34-391B "by Shin-Etsu Chemical Co., Ltd. ^* g-" TSE3402A "by Toshiba Silicone Co., Ltd." TSE3402B "by Toshiba Silicone Co., Ltd. where * is a low molecular weight siloxane. It means that it is a removed product, and has a low molecular weight siloxane component (degree of polymerization of 3 to 2).
0) is reduced to 1000 ppm or less.

Each of the resulting blended products was cured (crosslinked) by leaving it at room temperature for 24 hours. However, Comparative Example 2
Was further heated at 200 ° C. for 4 hours to cure. Using the obtained rubber, the surface roughness was R _{z in the same} manner as in Example 1.
= 1.0 μm and a total thickness of 1.0 mm was produced. Physical Property Test In order to evaluate the viscoelasticity of the rubbers obtained in the above Examples 1 to 3 and Comparative Examples 1 and 2, measurement was performed using a viscoelasticity spectrometer. The sample used is 10 cm in length x 1 in width
Rubber was poured into a mold of 0 cm x 2 mm in depth, left standing at room temperature for one day to cure, and then punched out with dumbbells to a size of 4 mm x 45 mm. Other measurement conditions are shown below.

Measuring instrument: Viscoelasticity spectrum meter "VES-III" type manufactured by Iwamoto Seisakusho Co., Ltd. Measuring frequency: 1, 3, 5, 10, 30, 50 and 10
0Hz Swing: 0.5%, 1.0% and 2.0% Measuring temperature: 20 ° C Distance between chucks: 30mm Measuring mode: Extension mode Initial load: 100g Here, the amplitude is 30mm at both ends of the sample. When the sample is gripped at intervals, the initial load 100 g is loaded in that state, the sample is extended in the longitudinal direction, and an amplitude is given in the longitudinal direction centering on the extended position, the length in the initial load loaded state The ratio of the length of the amplitude.

The measurement results are shown in Table 2, Table 3 and Table 4, respectively.

[0025]

[Table 2]

[0026]

[Table 3]

[0027]

[Table 4]

Printing Test Each of the blankets obtained in Examples 1 to 3 and Comparative Examples 1 and 2 was mounted on a flatbed printing machine (Ecter 600CL manufactured by Koyosha Co., Ltd.) and placed on soda lime glass (thickness 1.1 mm). Width 5 using blue ink (UV curing type) for color filters
A printing test of a fine pattern of 0 to 100 μm was performed. The printing method was a gravure offset method, and the plate used was an etching plate having a depth of 8 μm. As printing conditions,
A printing test was conducted by changing the printing speed in the range of 4 mm / sec to 40 mm / sec, and the shape of the stripe pattern on the blanket was observed with an electron microscope. The results are shown in Table 5 together with the value of Tan δ of each Example and Comparative Example. In the table, the pattern shape was evaluated according to the following criteria from the result of electron microscope observation.

◯: The pattern was not thin and the shape was sharp. Δ: The pattern is slightly narrowed. X: The pattern is broken and the width is extremely narrow.

[0030]

[Table 5]

From Table 5, in Comparative Examples 1 and 2 in which Tan δ is smaller than 0.1, the dependence on the printing speed is large, and as the printing speed is increased, the pattern becomes thinner, and eventually the pattern is broken or chipped, resulting in accurate patterning. It can be seen that can no longer be transferred. On the other hand, in Examples 1 to 3 in which Tan δ was larger than 0.1, the speed dependence was small, the pattern shape was extremely sharp, and the reproducibility was good. Example 4 and Comparative Examples 3 to 4 All of the millable silicone rubbers, i.e., silicone rubbers i to k shown in Table 6, were blended in the proportions shown in the same table.

[0032]

[Table 6]

The silicone rubbers i to k used are as follows. i— “KE5501BU” manufactured by Shin-Etsu Chemical Co., Ltd. “—KE5751” manufactured by Shin-Etsu Chemical Co., Ltd. “KE951” manufactured by Shin-Etsu Chemical Co., Ltd. The crosslinking agent used is “C8A” manufactured by Shin-Etsu Chemical Co., Ltd. (described above).

This compound was subjected to primary vulcanization at 170 ° C. for 20 minutes, and then secondary vulcanization at 200 ° C. for 4 hours in an oven. Using the obtained rubber, an offset blanket having a surface roughness R _z = 1.0 μm and a total thickness of 1.0 mm was prepared in the same manner as in Example 1. Physical Property Test In order to evaluate the viscoelasticity of the rubbers obtained in Example 4 and Comparative Examples 3 to 4 above, measurement was performed using a viscoelasticity spectrometer. The measurement conditions are the same as in Examples 1 to 3 and Comparative Examples 1 and 2 except that the amplitude was 0.5%. The measurement results are shown in Table 7.

[0035]

[Table 7]

Printing Test Printing was performed in the same manner as in Examples 1 to 3 and Comparative Examples 1 and 2, and the pattern shape on the blanket was observed. The results are shown in Table 8. The evaluation criteria for the stripe pattern are the same as above.

[0037]

[Table 8]

As can be seen from Table 8, Comparative Example 4 has a Tan δ smaller than 0.1, and thus has a large dependency on the printing speed and has a break or a chip in the pattern, as in Comparative Examples 1 and 2 described above. It was On the other hand, as in Example 4 and Comparative Example 3,
The higher Tan δ, the less the dependency on the printing speed and the better the pattern shape. However, when Tan δ exceeds 0.5 as in Comparative Example 3, the compression set characteristic of the rubber surface is deteriorated, and the plate Edge marks and scratches during cleaning tend to remain, which makes it impractical as a blanket.

From these test results, Tan δ is 0.1
Within the range of 0.5 to 0.5, it is favorable from the viewpoint of the dependency on the pattern shape and the printing speed. Further, considering the compression set characteristics of the rubber surface, Tan δ falls within the range of 0.1 to 0.3. It can be said that there is more.

[0040]

As described above, in the offset blanket for printing of the present invention, the Tan δ of the silicone rubber constituting the surface printing layer is set in the range of 0.1 to 0.5 at a frequency of 1 to 100 Hz at 20 ° C. By doing so, it becomes suitable for printing a very fine pattern, and in particular, according to the present invention, high-speed printing of a fine pattern is possible, so that a thermal head, an electronic component such as a printed circuit board, a color filter or an ITO film. In the present situation where the conventional photolithography method is being changed to a low-cost printing method in terms of manufacturing cost when manufacturing liquid crystal devices such as the above, the offset blanket of the present invention has a very wide range of applications and is useful.

Claims (1)

[Claims] 1. An offset blanket for printing, wherein a surface printing layer made of silicone rubber is laminated on a support layer, and the Tan δ of the silicone rubber is 0.1 to 0.5 at 20 ° C. and a frequency of 1 to 100 Hz. Offset blanket for printing characterized by being in the range of.