JP2735475B2 - Printing offset blanket and manufacturing method thereof - 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 a method of manufacturing the same, and more particularly, to a printing suitable for printing a fine pattern such as a liquid crystal color filter. The present invention relates to an offset blanket for use and a method for manufacturing the same.

[0002]

2. Description of the Related Art There are various techniques for forming a very delicate pattern, typically the photolithography method, but the printing method is considered the most promising in terms of cost. However, the printing method is
There are quality problems such as poor pattern accuracy and shape, and unstable printing accuracy. Among various printing methods, intaglio offset (gravure offset) printing using an intaglio transfers the intaglio ink to an offset blanket, and then completely transfers the ink pattern on the blanket to a glass substrate that is a 100% work. Therefore, the ink is split only once from the intaglio, which is half that in the normal offset printing. Therefore, both the pattern accuracy and the shape are better than the normal offset.

At this time, the present inventors examined a rubber material used for a surface printing layer of an offset blanket for printing in order to transfer an ink pattern to a glass substrate which is a 100% work. As a result, ordinary acrylonitrile- Silicone rubber was found to be more suitable than butadiene rubber.

[0004]

However, since silicone rubber is obtained by adding a filler, a cross-linking agent and the like based on cyclic siloxane and crosslinking the silicone rubber, low-molecular-weight cyclic siloxane remains in the silicone rubber, There is a problem of bleeding on the surface side. That is, the low molecular weight siloxane having a degree of polymerization of 3 to 20 contained in the silicone rubber bleeds from the rubber surface after the crosslinking reaction. Such a low-molecular-weight siloxane is extremely rich in water repellency and electrical insulation, and thus causes contact failure when used as a rubber component such as a touch panel.

On the other hand, in a liquid crystal color filter and the like,
In order to form a pattern by the three-color printing method of red, green, and blue, it is necessary to perform printing three times. However, when a surface printing layer of silicone rubber is used, the silicone rubber and glass adhere to each other, and It was found that water-repellent components such as siloxane were transferred from the inside to the glass, and the ink was repelled on the glass in the second and third printings, resulting in poor printing. That is, when red is printed for the first time and then green is printed, a water-repellent substance such as a low molecular weight siloxane component is applied to a non-line drawing portion (a portion where green and blue are to be printed) at the time of printing red. Is transferred, the ink is repelled on the glass at the time of the second printing and the third printing.

Further, after printing three colors, when depositing an ITO film (transparent electrode film) on a pattern of each color, the pattern is exposed to a high temperature of about 200 ° C. A protective film (for example, Optmer SS manufactured by Nippon Synthetic Rubber Co., Ltd.) is coated with a spin coater or a roll coater. At this time, if the surface of the printed pattern is water-repellent, a uniform film cannot be coated, which causes pinholes. Therefore, since the surface of the printing pattern also comes into contact with the rubber on the blanket surface during printing, it is necessary to reduce the water-repellent substance on the rubber surface as much as possible.

[0007] Usually, as a method for removing the low-molecular-weight siloxane component, a method of skipping the low-molecular-weight siloxane component in secondary vulcanization is generally performed. Silicone rubber from which low molecular weight components have been forcibly removed by suction at the stage of raw rubber is commercially available as low molecular weight siloxane-removed products. Therefore, the present inventors carried out secondary vulcanization of silicone rubber under various conditions at 200 ° C. for a maximum of 24 hours, and also obtained various silicone rubbers from which low-molecular-weight siloxane had been removed and performed printing tests. The water repellency of the glass surface was evaluated. The evaluation was performed by bringing a blanket into contact with a washing glass (a soda lime glass manufactured by Asahi Glass Co., Ltd., thickness: 1.1 mm) without using ink, and rolling, and then measuring the contact angle of the glass surface with pure water. It was judged.

As a result, when the conditions of the secondary vulcanization were changed, the amount of the low molecular weight siloxane was reduced, but the result was not so much improved as judged from the value of the contact angle. Also,
With respect to the low-molecular-weight siloxane-removed product, the contact angle was slightly reduced, but was not yet sufficient. Therefore, 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 prevents ink from being repelled on the surface of a printing medium, and a method of manufacturing the same. It is in.

Another object of the present invention is to prevent the formation of pinholes in the protective film coating the pattern surface due to the contact of the surface printing layer with the printed pattern surface in the multicolor printing as described above. An object of the present invention is to provide a printing offset blanket and a method of manufacturing the same.

[0010]

The present inventors have found that the results of the water repellency test performed when the secondary vulcanization conditions of the silicone rubber were changed and when the silicone rubber that had been removed from low-molecular-weight siloxane were subjected to the above-mentioned water repellency test. We thought that the low-molecular-weight siloxane was not the only water-repellent contaminant contaminating the glass surface, and analyzed the contaminants on the glass surface. It turned out that it was considerably included.

The inventors of the present invention have studied a method for efficiently removing low to medium molecular weight siloxanes that cause water repellency. As a result, the surface printing layer was subjected to ultrasonic cleaning in a solvent other than water to offset. By setting the contact angle of pure glass on the glass surface after pressing the blanket in the range of 0 to 30 °, siloxane of low to medium molecular weight, which is a water-repellent component, can be almost removed. It was found that the repelling of the ink and the formation of pinholes in the protective film coating the pattern surface could be prevented. The surface printing layer of silicone rubber having a contact angle in the above-mentioned range is a novel one that has never been seen before.

Accordingly, the printing offset blanket of the present invention is obtained by laminating a surface printing layer made of silicone rubber on a support layer, and the surface printing layer has a surface printing layer of 10 kg on the glass surface. The contact angle of pure water on the glass plate surface after pressure bonding at 1 minute / cm ² is 0 to 30.
°. In the method for producing an offset blanket for printing according to the present invention, a surface printing layer made of silicone rubber is laminated and crosslinked on a support layer, and then the surface printing layer is ultrasonically cleaned with a solvent (excluding water). It is characterized by the following.

The above-mentioned contact angle is used as a measure of the surface cleanability of the surface print layer of silicone rubber, in particular, the amount of siloxane on the surface. When the contact angle and the conditions in which the three colors (red, green, and blue) were overprinted and the overcoat repelled were examined in detail, when the contact angle of the glass surface with pure water exceeded 30 °, the ink or overcoat agent was rejected. Is repelled on the glass surface, and good printing cannot be performed. On the other hand, it has been found that when silicone rubber having a contact angle of 30 ° or less is used, repelling or the like is not caused and printing can be performed well. On the other hand, the cleaned glass surface usually has a contact angle with pure water of almost zero. Therefore, it is desirable to use a silicone rubber having a contact angle of 0 to 30 ° as described above.

As the silicone rubber in the present invention,
Examples include, but are not limited to, one or a mixture of two or more selected from the group consisting of a methylvinyl-based silicone rubber, a fluorosilicone rubber having a trifluoropropyl group, and a phenyl silicone rubber having a phenyl group. is not. Further, 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) that is crosslinked at room temperature, and an injection moldable LIM (Liquid Injection). Molding) Silicone rubber etc. can be used. The silicone rubber may be an RTV silicone rubber based on a low-polymerization liquid silicone rubber having a polymerization degree of 100 to 800 and a millable silicone rubber based on a gel silicone raw rubber having a polymerization degree of 6000 to 10000. However, all are supplied as rubber compounds in which raw rubber is blended 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 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. Also, FVMQ having a trifluoropropyl group introduced thereinto
And PVMQ into which a phenyl group has been introduced, all of which can be used, and mixtures 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 and graphite; recycled rubber, powdered rubber, asphalts, styrene resin, and glue. 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,
If the rubber is deformed during printing and the pattern cannot be transferred accurately, on the other hand, if 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 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. The support layer is formed, for example, by laminating a plurality of (three or more) base fabrics impregnated with a rubber material (rubber paste) and at least one compressible layer provided as necessary. What was done.

As the base fabric, for example, a woven fabric such as cotton, polyester, rayon or the like is used, but glass fibers or aromatic polyamide fibers having low elongation (registered trademark “Kevlar” manufactured by DuPont) can also be used. It is. Examples of the rubber material impregnated in the base fabric 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. Crosslinking is usually performed by heating at 140 to 170 ° C. for 1 to 5 hours.

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 cloth, drying and crosslinking, and then heating the paste in hot water at 60 to 100 ° C. ~
It is formed by immersing for 10 hours, eluting and drying the water-soluble powder. After crosslinking, the surface printing layer is subjected to ultrasonic cleaning in a solvent. Usable solvents include various solvents other than water, for example, N-methyl-2-pyrrolidone (N
MP), n-hexane, carbon tetrachloride, chloroform, tetrahydrofuran, dimethylformamide, dimethylsulfoxide and the like, and it is particularly preferable to use N-methyl-2-pyrrolidone (NMP) or n-hexane. The solvents may be used alone or as a mixture of two or more.

The ultrasonic cleaning is performed under such conditions that the contact angle of the glass surface with pure water after the offset blanket is pressed against the glass surface is within the above-mentioned range. Usually, a frequency of 20 to 100 kHz is used. For about 1 minute to 2 hours. Further, if necessary, it may be performed at a high frequency of about 1 MHz. Further, in addition to ultrasonic cleaning using a single frequency, ultrasonic cleaning may be performed by simultaneously or alternately switching two frequencies. The ultrasonic cleaning device to be used is, for example, a spray-type surface printing while ultrasonically oscillating the solvent from below while moving the surface printing layer downward in a certain direction so that only the surface printing layer can be cleaned. A so-called line type ultrasonic cleaning device that sprays the layer may be used, or a solvent is placed in a cleaning tank having an ultrasonic oscillator attached to the bottom, and an offset blanket is immersed in the solvent to perform vibration cleaning. There may be. In the latter case, the entire surface, including the surface printing layer and the support layer, will be washed.

The ultrasonic cleaning may be performed at room temperature.
It may be heated as needed. After ultrasonic cleaning, drying is performed to obtain the offset blanket of the present invention. 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. In addition, instead of the above-mentioned laminated type support layer, polyethylene terephthalate (PET), polycarbonate (PC), polypropylene (PP), polyimide, aluminum foil,
A film or sheet such as a stainless sheet may be used as the support layer. These may have a compressible layer.

[0022]

【Example】

Example 1 As a material of a surface printing layer, a dimethylsiloxane type silicone rubber of millable type [“KE5” manufactured by Shin-Etsu Chemical Co., Ltd.]
55U ”, hardness (JIS A): 50 °].
Cross-linking agent [C8A manufactured by Shin-Etsu Chemical Co.,
Containing 80% of 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane] at a ratio of 0.6 parts by weight.

Next, a silicone rubber having a thickness of 350 μm
750 μm on polyethylene terephthalate film
And sandwiched between molds with a smooth surface.
It was crosslinked by heating at 0 ° C. for 20 minutes to produce an offset blanket having a total thickness of 1.0 mm. Next, the offset blanket is immersed in N-methyl-2-pyrrolidone (NMP) in an ultrasonic cleaning tank (stainless steel tank) provided with an ultrasonic oscillator at the bottom, and is 38 kHz at room temperature for 30 minutes.
Was subjected to ultrasonic cleaning.

This offset blanket was mounted on a flatbed printing machine (Ector 600CL, manufactured by Koyo Co., Ltd.), and was placed on a soda-lime glass (thickness: 1.1 mm) without ink.
Crimping was performed at 0 kg / cm ² for 1 minute. The soda lime glass used was ultrasonically washed in isopropyl alcohol and hot water for 30 minutes each and dried. Then
The contact angle of a droplet formed by pure water on the glass surface was measured using a contact angle measuring device (CA-A type machine) manufactured by Kyowa Interface Science Co., Ltd. Table 1 shows the results. In addition, the contact angle of the glass surface immediately after washing was as very low as 3 °, and the glass surface was hardly contaminated by the water-repellent component. Example 2 An offset blanket was obtained in the same manner as in Example 1 except that n-hexane was used as a solvent in the ultrasonic cleaning and the ultrasonic cleaning was performed for 60 minutes, and after the surface printing layer was pressure-bonded to soda lime glass. The contact angle of the glass surface was measured. Table 1 shows the results. Example 3 As a material for the surface printing layer, a silicone rubber based on a room temperature curing type (RTV) dimethylsiloxane type silicone rubber [“KE1604” manufactured by Shin-Etsu Chemical Co., Ltd., hardness (JIS A): 40 °] was used. Example 1
An offset blanket was obtained in the same manner as described above, and the contact angle of the glass surface after the surface printing layer was pressed against soda lime glass was measured. Table 1 shows the results.

Since the surface of the offset blanket obtained in each of the examples was formed by using a very smooth mold, the roughness was R
_z = 1.0 μm and a very smooth finish was obtained. Comparative Example 1 An offset blanket was obtained in the same manner as in Example 1 except that ultrasonic cleaning was not performed, and the contact angle of the glass surface after the surface printing layer was pressed against soda lime glass was measured. Table 2 shows the results. Comparative Example 2 An offset blanket was obtained in the same manner as in Example 1 except that heat treatment was performed at 200 ° C. for 4 hours as secondary vulcanization in place of ultrasonic cleaning, and a soda of the surface printing layer was obtained. The contact angle of the glass surface after pressure bonding to lime glass was measured. Table 2 shows the results. Comparative Example 3 In Example 1, NMP was used as a solvent for ultrasonic cleaning.
The offset blanket was obtained in the same manner as in Example 1 except that ultrasonic cleaning was performed at room temperature for 30 minutes using pure water instead of pure water, and the surface of the glass surface after pressure bonding of the surface printing layer to soda lime glass was performed. The contact angle was measured. Table 2 shows the results. Comparative Example 4 The same room temperature curing type (RTV) as in Example 3 was used, but a dimethylsiloxane-type silicone rubber was used, and pure water was used instead of NMP as a solvent for ultrasonic cleaning. An offset blanket was obtained in the same manner as in Example 1 except for performing sonic cleaning, and the contact angle of the glass surface after the surface printing layer was pressed against soda lime glass was measured. Table 2 shows the results.

Printing Test Using the offset blanket obtained in each of the examples and comparative examples, the same flat table printing machine (Ector 6 manufactured by Koyo Co., Ltd.) was used.
(00CL), printing was performed in the order of red, green, and blue, and whether or not ink repelling occurred during printing of green and blue was visually observed to evaluate ink repellency. The results are shown in Table 1. Here, "printing failure" means that the ink was repelled during printing of green and blue and printing was not successfully performed, and "no printing failure", contrary to the above, there was no ink repelling. This means that printing was successfully performed.

[0027]

[Table 1]

[0028]

[Table 2]

From Tables 1 and 2, it can be seen that to reduce the water repellency repelling the ink, the contact angle of pure water on the glass surface must be zero.
Is very effective when the contact angle is 30 °.
It can be seen that in Comparative Examples 1 to 4 in which exceeds, printing failure due to ink repelling occurs. In addition, the contact angle is 0 to 30 °
It can be seen that ultrasonic cleaning of the surface printing layer with a solvent other than water is very effective in making the surface printing. This is presumably because ultrasonic cleaning removed from the low molecular weight siloxane component to the siloxane and silicone oil component having a considerably high molecular weight from the surface of the surface printing layer.

[0030]

As described above, the offset blanket for printing of the present invention can be used for multicolor printing of a fine pattern by setting the contact angle of the glass surface after pressing the surface printing layer to 0 to 30 °. Ink can be prevented from being repelled on the surface of the printing substrate, and even after printing, pinholes can be formed in the protective film that coats the pattern surface by contacting the surface printing layer with the printed pattern surface. Can be prevented.

Accordingly, it is possible to manufacture electronic components and liquid crystal color filters by a printing method with high throughput.
According to the method for producing an offset blanket for printing of the present invention, the water-repellent component is removed from the surface printing layer by ultrasonically cleaning the surface printing layer in a solvent (excluding water). An offset blanket having a surface printing layer having a contact angle of 0 to 30 ° can be easily produced.

Claims (2)

(57) [Claims] 1. A printing offset blanket comprising a support layer and a surface printing layer made of silicone rubber laminated on the substrate layer, wherein the surface printing layer is applied to the glass surface at 10 kg / cm ² for 1 minute. An offset blanket for printing, wherein the contact angle of pure water on the surface of the glass plate after pressure bonding is in the range of 0 to 30 °. 2. An offset blanket for printing, characterized in that a surface printing layer made of silicone rubber is laminated and crosslinked on a support layer, and the surface printing layer is ultrasonically washed with a solvent (excluding water). Manufacturing method.