JP2636646B2 - Offset blanket for printing - Google Patents

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 a fine pattern such as a liquid crystal color filter.

[0002]

2. Description of the Related Art When an ink layer printed on a transparent glass surface is viewed by transmitted light, such as a liquid crystal color filter having three colors of red, green, and blue, the ink layer has If there is a variation in the film thickness, this causes shading in the transmitted light, which causes the image quality to vary. In order to prevent such variations in film thickness, when printing on the glass surface by lithographic offset printing or gravure printing, the ink on the plate must be completely transferred to the glass surface via the offset blanket. It is. However, in a conventional offset blanket having a surface printing layer made of a rubber material such as acrylonitrile-butadiene copolymer rubber (NBR), the ink usually remains on the surface of the blanket and separates on the glass and the blanket. Inevitably, irregularities are generated on the surface of the film, and the film thickness varies.

The inventors of the present invention have conducted tests on various rubber materials. As a result, when silicone rubber was used as the surface printing layer of the offset blanket, the ink on the blanket could be almost completely transferred onto the glass, and the use of the silicone rubber was extremely difficult. To obtain a flat ink layer. However, since silicone rubber is originally a material that has a very low surface tension and is difficult to receive ink, it has a very high speed dependency, and when the printing speed is increased, the ink does not transfer to the blanket, and as a result, the printing speed can be increased. And a major obstacle to productivity.

That is, when a liquid crystal color filter is currently printed by a printing method, particularly a gravure offset method, the pattern shape largely depends on the printing speed, and the tendency becomes more remarkable as the pattern becomes thinner. Specifically, when the printing speed is increased from 10 mm / sec to 50 mm / sec for a pattern having a width of about 200 μm, the pattern width on the blanket is reduced by about 10% and does not significantly affect the pattern shape. In the case of a fine pattern of about 50 μm, disconnection of the pattern and repelling of ink occur, and it is difficult to transfer the pattern accurately to the glass substrate.

Accordingly, a main object of the present invention is to provide a printing offset blanket which is particularly suitable for multicolor printing of a fine pattern such as a liquid crystal color filter and which can perform high-speed printing and improve productivity. It is in.

[0006]

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

That is, in order to evaluate the pattern reproducibility using various silicone rubber materials having different viscoelasticities, as described in the following Examples, the complex elastic modulus E ^* and the storage elastic modulus
( Elastic term ) E ′, loss elastic modulus ( viscous term ) E ″ and its ratio ( E ″ / E ′ ), Tanδ (dielectric tangent), were measured. Here, the complex elastic modulus E ^* is E ^* =
E ′ + iE ″ [where i is (−1) ⁻¹ and complex
Is a number]. 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. Have found a new fact that a pattern can be transferred well. In particular, Tan δ is more preferably in the range of 0.1 to 0.3 in consideration of permanent compression characteristics and the like.

On the other hand, when a silicone rubber material having Tan δ smaller than 0.1 is used, the printing speed dependence 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. As the printing speed increases, the time for the blanket to pass through the nip where the blanket and the plate are in contact is reduced, and the contact time is reduced.
At this time, since the material having a small Tan δ recovers quickly to deformation and recovers quickly in the nip, when the printing speed is increased, the material does not sufficiently follow the deformation in the cell, and as a result, the ink is not transferred according to the pattern. It is thought to be.

On the other hand, if the value of Tan δ exceeds 0.5, the compression set characteristic of the rubber material is extremely deteriorated, and the recovery from deformation is significantly deteriorated. It is not preferable because the wound remains without recovering. Therefore, the printing offset blanket of the present invention is obtained by laminating a surface printing layer made of silicone rubber on a support layer, wherein the silicone rubber has a Tanδ of 20 ° C and a frequency of 1 to 100.
It is characterized by being in the range of 0.1 to 0.5 in Hz.

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

The silicone rubber can be used in various conventionally known forms, for example, a kneadable millable silicone rubber, a room temperature vulcanizable silicone rubber (RTV rubber) which crosslinks at room temperature, and an injection moldable LIM. (Liquid I
njection Molding) Silicone rubber can be used. The silicone rubber may be an RTV silicone rubber based on polydimethylsiloxane and a low polymerization degree liquid silicone rubber having a polymerization degree of 100 to 800, or a polymerization degree of 600.
A millable silicone rubber based on a gel silicone raw rubber of 0 to 10,000 is conceivable, but in all cases, the raw rubber is an anhydrous silica-based reinforcing filler such as aerosil, an increasing filler such as talc or mica, and a dispersion accelerator. It is supplied as a rubber compound containing the same. RT
V silicone rubber is generally high in polydimethylsiloxane. As the millable silicone rubber, a rubber into which a methyl vinyl group is 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 phenyl silicone rubber having a phenyl group introduced therein, and the like can be used, and a mixture thereof can also be used.

The surface printing layer in the present invention is formed by mixing a crosslinking agent (vulcanizing agent) with the silicone rubber, forming the surface printing layer, and then crosslinking. As the cross-linking agent contained in the compounded rubber, for example, an organic peroxide-based cross-linking agent can be used. Examples of such organic peroxide-based crosslinking agents include benzoyl peroxide, bis 2,4-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 anhydride, calcium carbonate, hard clay, barium sulfate, talc, mica, asbestos, graphite, etc .; recycled rubber, powdered rubber, asphalts, styrene resin, glue, etc. Fillers. The surface rubber hardness of the surface printing layer is usually 20 to 90, preferably 40 in JIS A.
If the hardness is less than about 70 is used,
When the rubber changes during printing, 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 is not sufficient, which is not preferable.

Since the surface roughness of the surface printing layer has a great influence on the shape of the printed pattern, it is desirable that the surface roughness be as small as possible. Usually 10 points average roughness (R _Z ) is 3
μm or less, preferably 1.5 μm or less. 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 a base fabric impregnated with a rubber material (rubber glue) (generally, three or four or more cotton cloths are laminated) and at least one compressible layer provided as necessary And those formed by laminating the above.

As the base cloth, for example, a 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 crosslinking agent, a crosslinking accelerator, and if necessary, a thickener. Then, the rubber agent is coated on the woven fabric by an appropriate application means such as a blade coating method.
Then, a rubber paste for forming a surface print layer made of the above-mentioned specific rubber material is applied to the surface of the support layer via a primer layer and dried, or a sheet-like material formed by calendering or the like is laminated. The obtained laminate is cross-linked by heating and pressing at a predetermined pressure and temperature to obtain an offset blanket. The compressible layer is formed on at least one intermediate fabric.
After applying a rubber paste in which a water-soluble powder such as salt is dissolved, drying and cross-linking, 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 base cloth, glass fiber or polyamide fiber (for example, Kepler (registered trademark) manufactured by DuPont) having low elongation can be used. Further, instead of the laminated support layer, polyethylene terephthalate (PE)
T), polycarbonate (PC), polypropylene (P
A film or sheet such as P), polyimide, aluminum foil, and stainless sheet may be used as the support layer. These may have a compressible layer.

The obtained offset blanket is used by being adhered directly or through a lower adhesive material onto the peripheral surface of the cylinder of the transfer cylinder.

[0018]

【Example】

Example 1 "KE5" manufactured by Shin-Etsu Chemical Co., Ltd.
75U ”(high-strength methylvinyl-based silicone rubber compound) in 100 parts by weight as a crosslinking agent“ C
8A "[containing 80% of 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane]. Then, the compound was added at 170 ° C. for 20 minutes.
Primary vulcanization for 4 minutes and then oven
Time secondary vulcanization was performed.

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

[0020]

[Table 1]

The silicone rubbers a to h used are as follows. a─ Shin-Etsu Chemical Co., Ltd. of "KE1204AL" ^{* b─} Shin-Etsu Chemical Co., Ltd. of "KE1204BL" ^{* c─} Shin-Etsu Chemical Co., Ltd. of "KE1603A" d─ Shin-Etsu Chemical Co., Ltd. of "KE1603B" e─ Shin-Etsu Chemical Co., Ltd. of " X-34-391A ^{"* f─} Shin-Etsu chemical Co., Ltd. of the" X-34-391B ^{"* g─} Toshiba silicone Co., Ltd. of" TSE3402A "h─ Toshiba silicone Co., Ltd. of" TSE3402B "here, * a low molecular weight siloxane It means that the product is a low-molecular-weight siloxane component (polymerization degree 3 to 2).
0) was reduced to 1000 ppm or less.

Each of the obtained blends was cured (crosslinked) by leaving it at room temperature for 24 hours. However, Comparative Example 2
Was further cured by heating at 200 ° C. for 4 hours. Using the obtained rubber, the surface roughness was _{Rz in the same} manner as in Example 1.
= 1.0 μm and an offset blanket having a total thickness of 1.0 mm. Physical property test In order to evaluate the viscoelasticity of the rubber obtained in Examples 1 to 3 and Comparative Examples 1 and 2, measurement was performed using a viscoelasticity spectrum meter. The sample used is 10cm long x 1cm wide.
Rubber was poured into a mold having a size of 0 cm × 2 mm in depth, allowed to stand at room temperature for 24 hours, cured, and then punched out with a dumbbell to 4 mm × 45 mm to have a thickness of 2 mm. Other measurement conditions are shown below.

Measuring instrument: Viscoelastic spectrum meter "VES-III" manufactured by Iwamoto Seisakusho Measurement frequency: 1, 3, 5, 10, 30, 50 and 10
0 Hz amplitude: 0.5%, 1.0% and 2.0% Measurement temperature: 20 ° C. Distance between chucks: 30 mm Measurement mode: elongation mode Initial load: 100 g Here, the amplitude means that both ends of the sample are 30 mm. When the sample is stretched in the longitudinal direction by applying an initial load of 100 g in that state, and the sample is stretched in the longitudinal direction with the stretched position as the center, the length of the sample in the initial load state is determined. The ratio of the length of the amplitude.

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

[0025]

[Table 2]

[0026]

[Table 3]

[0027]

[Table 4]

Printing Test Each blanket obtained in each of Examples 1 to 3 and Comparative Examples 1 and 2 was mounted on a flatbed printing machine (Ector 600CL, manufactured by Koyo Co., Ltd.) and placed on soda lime glass (thickness: 1.1 mm). Width 5 using blue ink (UV curing type) for color filter
A printing test of a fine pattern of 0 to 100 μm was performed. The printing method used was a gravure offset method, and the plate used was an etching plate having a depth of 8 μm. As printing conditions,
Printing tests were performed while 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 values of Tan δ of the respective examples and comparative examples. In the table, the pattern shape was evaluated based on the following criteria based on the results of electron microscope observation.

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

[0030]

[Table 5]

According to Table 5, in Comparative Examples 1 and 2 in which Tan δ is smaller than 0.1, the dependence on the printing speed was large, and the pattern became thinner as the printing speed was increased. It can be seen that the transfer cannot be performed. On the other hand, in Examples 1 to 3 in which Tan δ was larger than 0.1, the pattern dependence was small, the pattern shape was extremely sharp, and the reproducibility was good. Example 4 and Comparative Examples 3 and 4 In all cases, silicone rubbers i to k shown in Table 6, which are millable silicone rubbers, were blended at the ratios 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. j─ “KE575” manufactured by Shin-Etsu Chemical Co., Ltd. k─ “KE951” manufactured by Shin-Etsu Chemical Co., Ltd. The cross-linking agent used is “C8A” manufactured by Shin-Etsu Chemical Co., Ltd. (supra).

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

[0035]

[Table 7]

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

[0037]

[Table 8]

From Table 8, it can be seen that in Comparative Example 4, since Tan δ was smaller than 0.1, as in Comparative Examples 1 and 2, the dependence on the printing speed was large, and disconnection and chipping occurred in the pattern. Was. On the other hand, as in Example 4 and Comparative Example 3,
The higher the Tan δ, the lower the dependence 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 characteristics of the rubber surface become worse, and Edge marks and scratch marks during cleaning are likely to remain, which is not practical as a blanket.

From these test results, Tan δ was 0.1
When it is in the range of 0.5 to 0.5, it is good in terms of the dependence on the pattern shape and the printing speed, and further considering the compression set characteristics of the rubber surface, Tan δ is in the range of 0.1 to 0.3. It can be said that there is more preferable.

[0040]

As described above, in the printing offset blanket of the present invention, the tan δ of the silicone rubber constituting the surface printing layer is set at 20 ° C. within the range of 0.1 to 0.5 at a frequency of 1 to 100 Hz. By doing so, it becomes suitable for printing very fine patterns, and in particular, according to the present invention, high-speed printing of fine patterns becomes possible. Therefore, electronic components such as thermal heads and printed boards, color filters and ITO films In the present situation where the conversion from the conventional photolithography method to the inexpensive printing method is being studied from the viewpoint of the manufacturing cost when manufacturing liquid crystal devices and the like, the offset blanket of the present invention has a very wide range of applications and is useful.

Claims (1)

(57) [Claims] 1. A printing offset blanket in which a surface printing layer made of silicone rubber is laminated on a support layer, wherein the silicone rubber has a Tan δ represented by the following formula:
Is 0.1 ° at a frequency of 1 to 100 Hz at 20 ° C.
An offset blanket for printing characterized by being in the range of 0.5. Tan δ = E ″ / E ′ (where E ″ indicates a loss modulus and E ′ indicates a storage modulus)
You. )