JP3509266B2 - Printing blanket - 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 blanket used in offset printing in which ink is transferred from a plate to a printing blanket and then transferred to an object to be printed.

[0002]

2. Description of the Related Art Silicone rubber transfer bodies have a rubber hardness of 1
It is frequently used as a transfer member in that it can be freely changed in a wide hardness range from ° to 80 ° and has extremely excellent solvent resistance. Especially in recent years in the electronics field, attention has been paid to the purpose of highly accurately transferring and reproducing fine patterns. This silicone rubber is roughly classified into a condensation type and an addition type. Since the transferability (ink release property) is good in conventional pad printing (general curved surface printing), the condensation type is mainly used. Has been.

However, in the electronics field, it is necessary to perform printing with a line width of 30 to 100 μm with high accuracy and no defect, and a large amount of filler (filler filler) is contained as a reinforcing material and a large amount of oil (mostly unreacted component) is contained. In terms of print reproducibility (quality), the condensation type that contains contains oil that oozes into the surface excessively, and the linear shape is disturbed depending on the component, and pinhole defects are likely to occur in the printed matter due to the secondary aggregation component of the filler that appears on the surface. It has become clear that the material is difficult to use. Therefore, it is considered to use an addition type silicone rubber in which the reaction proceeds to the end point in a short time by a vinyl addition reaction, and has been developed as a transfer material in various fields.

However, since the addition type silicone rubber has a too high affinity with ink, it is the current situation that an ink transfer property is finally realized by adding an appropriate amount of low molecular weight silicone oil or the like. Low molecular weight components such as silicone oil are originally designed to form a monomolecular layer on the rubber surface and function as an ink release layer).

Further, in terms of durability, silicone rubber has the drawbacks that it is basically low in mechanical strength and has good gas permeability so that it tends to be plasticized. Especially when used as a printing blanket for intaglio offset printing, there is always at least one step of applying a certain pressure to the intaglio plate with unevenness, mechanical damage due to the intaglio edge is large, and the blanket surface is extremely cracked. Is likely to occur. The swelling of the blanket due to the ink solvent or the like, which occurs when the ink is transferred from the intaglio plate to the blanket, not only accelerates the plasticization of the surface but also has the action of extracting the uncrosslinked low molecular weight molecules in the blanket.
Phenomenon of this action appears as a minute depression of the ink contact portion on the blanket surface.

It is conventionally known that there is a correlation between the surface deterioration (roughening and deformation) of a blanket and the deterioration of print quality in the general commercial printing world. In the electronics field, when characteristic values such as electrical characteristics such as electric wiring patterns, phosphor patterns, and plasma displays are emphasized, even if some surface deterioration of the blanket occurs, the influence on the product is relatively small, but the liquid crystal display device. When a product such as a color filter is directly visually observed, the quality of the printed matter (particularly the image edge shape and the image cross section shape) directly determines the product quality.

The first problem in terms of durability "mechanical deterioration"
In order to prevent this, the mechanical strength of the printing blanket should be set to a value that is stronger than the internal stress generated during printing. To suppress the second problem "swelling deterioration due to solvent etc." It is necessary to suppress the diffusion of the solvent in the above. These are usually solved by increasing the crosslink density of the rubber, but if the crosslink density of the rubber is simply increased, the uncrosslinked components are taken up and consumed in the rubber, so the oil stains It is suppressed and is not preferable as a printing blanket. Therefore, conventionally, mechanical strength is sacrificed to some extent, and crosslinking of the surface layer of the blanket is stopped in the middle to secure oil bleeding to the surface layer, thereby balancing mechanical strength and ink transferability.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a printing blanket made of silicone rubber, which has improved durability while maintaining printing characteristics (particularly ink transferability).

[0009]

In order to solve the above-mentioned problems, the present invention provides a printing blanket for printing and reproducing a fine pattern with high accuracy, wherein the surface of the blanket is
The layer is formed of an addition type silicone rubber containing dimethyl silicone oil, and the outermost surface of the surface layer is completely crosslinked.
It is a printing blanket in which the cross-linking density gradually decreases from the outermost surface toward the inside of the surface layer. Also,
In an embodiment of the present invention, the total content of dimethyl silicone oil and uncrosslinked low molecular weight in the surface layer is 5% by weight to
The printing blanket is 20% by weight, and the surface blank is the printing blanket formed on the substrate (or the base fabric) via the compression layer.

The details will be described below. FIG. 1 shows a schematic diagram of one embodiment of the present invention. The intermediate layer 2 and the surface layer 1 are laminated on the base material 3, and the shaded portion in the surface layer 1 is the outermost surface layer a. The surface layer 1 contains dimethyl silicone oil. The intermediate layer 2 may be used by appropriately combining a compression layer, an adhesive layer, a reinforcing layer, or the like, or may be omitted. Moreover, it does not specify the number of intermediate layers. The base material 3 is a blanket base layer, but may be a normal base cloth layer or other materials (plastic, metal) or the like.

The stress concentration value at the time of printing can be obtained by the following equation from the load value at the time of printing (printing pressure: modulus value 4 to 50) obtained from the experiment and the shape factor obtained from the sectional edge shape of the intaglio plate. Edge radius: ρ Rubber deformation amount: t Shape factor: α x% Modulus during deformation (stress during x% deformation): Mx, α = 1 + 2 (t / ρ) ^1/2 (stress concentration value) = Mx × α This stress concentration value is compared with the maximum load value of the rubber material used for the surface layer of the blanket. If (maximum load value)> (stress concentration value), no crack is generated in the surface rubber layer.

In the case of intaglio offset printing, since the shape of the intaglio edge is an acute angle and the shape factor α is about 30, a considerable amount of stress concentration occurs. Generally, the mechanical strength of silicone rubber is weak, and it is necessary to promote the crosslinking of the rubber material as much as possible in order to increase the maximum load value. Therefore, in order to resist the stress concentration that occurs during printing and at the same time obtain a stable ink transfer transfer capability, the strength of the outermost surface layer of the blanket that directly contacts the intaglio plate must be increased, and that outermost surface layer must be used for ink transfer. It is necessary to keep it always covered with a peelable component (dimethyl silicone oil or uncrosslinked low molecular weight component).

In order to realize this, the cross-linking density on the outermost surface is maximized, and the cross-linking density gradually decreases toward the inside, and a peelable oil or uncrosslinked component is filled inside. Specifically, in the case of a room temperature curable or heat curable silicone rubber, it is carried out by providing a temperature gradient from the outermost surface to the lowermost surface in order to control the crosslinking density.

For the temperature gradient, for example, when the blanket is crosslinked in an oven, a temperature control jacket (such as a constant temperature plate connected to a cooling circulator) is brought into close contact with the lowermost surface of the blanket, or in the mold. In the case of cross-linking with, the method can be obtained by a method in which a heater is installed in the upper mold (outermost surface side) and the above-mentioned cooler is set in the lower mold (base material side). Also, in the case of manufacturing on a coating line, the same effect can be obtained by controlling the heater on the outermost surface side and the cooling roll (or a support such as a surface plate) on the substrate side.

When a UV curable silicone rubber is used, it is not necessary to provide a temperature gradient for controlling the crosslink density, and the UV irradiation amount from the outermost surface side is controlled. . At this time, when the surface layer is thin and it is difficult to control the crosslink density only by controlling UV, a sensitizer is added to disperse an appropriate amount of UV-cut dye or the like in the silicone rubber to make it a resistance to UV transmission. It can be carried out by changing the amount and type, adjusting the type and addition amount of the antifoggant, and the like. In the case of the UV curing type, it is possible to use UV irradiation and heating together.

The total content of dimethyl silicone oil and uncrosslinked low molecular weight compounds in the surface layer is preferably 5% by weight to 20% by weight. If it is less than 5% by weight, the formation of the peeling layer on the surface becomes unstable, and the ink transfer ability is deteriorated.
If it is more than 0% by weight, the amount of oil as a peeling layer on the surface becomes excessive and the shape of the ink transfer to the blanket is disturbed. Further, it is preferable that the surface layer is formed on the base material (or the base cloth) via a compression layer or the like in order to obtain a uniform printing pressure on the entire printing effective surface.

[0017]

In the printing blanket of the present invention, the mechanical strength of the outermost surface layer is maximized and the peeling component (dimethyl silicone oil or unreacted low molecular weight component) is obtained by setting the above-mentioned conditions for the silicone rubber layer of the surface layer. ) Can be stored inside the surface layer and replenished to the outermost surface layer, it is possible to prevent the generation of cracks on the surface of the blanket and also to perform good ink transfer transfer. Further, by setting the total content of dimethyl silicone oil and uncrosslinked low molecule in the surface layer 5 wt% to 20 wt%, peeling component is supplied to moderately surface layer, excellent transfer properties obtained To be The surface
Since the layer is formed on the base material (or the base cloth) via the compression layer or the like, an appropriate elastic force can be obtained.

[0018]

EXAMPLES As examples, only a single-layer blanket was shown, but since the silicone rubber layer forming the surface layer is important, the comparison was made. The lower layer may be multi-layered with a commonly used substrate.

<Example 1> Room temperature curing (RTV) methyl vinyl silicone (KE160 manufactured by Shin-Etsu Chemical Co., Ltd.)
3) After mixing 95% by weight and 5% by weight of dimethyl silicone oil (TSF451-500 manufactured by Toshiba Silicone Co., Ltd.), 10% by weight of a curing agent was added to the methyl vinyl silicone from the outside and the mixture was mixed again with stirring. The RTV type silicone mixture was applied onto an aluminum plate having an anchor layer formed thereon with a thickness of 600 μm using an applicator, and the surface of the aluminum plate was set on a constant temperature platen controlled at 40 ° C. In this state, it was inserted into an oven at 60 ° C. and heat-cured for 60 minutes to prepare a blanket.

Comparative Example 1 A silicone mixture having the same composition as in Example 1 was coated on an aluminum plate having an anchor layer to a thickness of 600 μm with an applicator, and the coated mixture was placed in an oven at 60 ° C. and cured for 20 minutes. And made a blanket.

Comparative Example 2 A silicone mixture having the same composition as in Example 1 was coated on an aluminum plate having an anchor layer to a thickness of 600 μm with an applicator, and the coating was inserted into an oven at 60 ° C. for curing for 120 minutes. And made a blanket. The results of the above implementation are shown in (Table 1).

[0022]

[Table 1]

As a result of an actual printing test, Comparative Example 1 in which the curing was insufficient was good in the initial ink transfer property, but about 1
When 50 prints were made, uneven printing occurred due to deterioration of the blanket. Further, in Comparative Example 2 where the curing was excessive, streak-like unevenness caused by defective transfer occurred from the initial stage of printing. In addition, uneven printing occurred due to blanket deterioration at the time of passing 500 times. On the other hand, the blanket shown in Example 1 has good transferability from the initial stage, no print unevenness occurs at the time of 500 passes, and the evaluation is also abnormal at the time of printing about 500 passes thereafter. Was not found.

[0024]

The blanket of the present invention has a structure in which the outermost surface portion of the silicone rubber layer of the blanket surface layer is completely crosslinked, and the crosslink density inside the outermost surface layer gradually decreases toward the substrate. Even though the outermost surface portion of the surface layer is completely cross-linked, it has a structure in which a peelable component such as dimethyl silicone oil is stored inside, and is constantly replenished to the outermost surface portion. It is possible to provide a printing blanket having improved durability while maintaining the transferability). Further, when the total content of dimethyl silicone oil and uncrosslinked low molecular weight in the surface layer is 5% by weight to 20% by weight, the releasable component is appropriately on the outermost surface.
It is replenished to the layer to obtain a better transfer property. The table
Since the surface layer is formed on the base material (or the base cloth) via the compression layer and the like, an appropriate elastic force is obtained, and the transferability and durability are improved.

[0025]

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention.

[Explanation of symbols]

1 ... Surface layer 2 ... Intermediate layer 3 ... Base material a ... Outermost surface layer

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) B41N 10/00-10/04

Claims (3)

(57) [Claims] 1. A printing blanket formed by addition type silicone rubber in the surface layer comprises a dimethyl silicone oil on the surface layer, and the rubber from the outermost surface in the surface layer toward the interior of the surface layer A printing blanket characterized by a continuously lower crosslink density. 2. The total content of uncrosslinked low molecular weight compounds not crosslinked with dimethylsilicone oil in the surface layer is 5% by weight.
The printing blanket according to claim 1, wherein the content is about 20% by weight. 3. The printing blanket according to claim 1, wherein the surface layer is formed on a base material (or a base cloth) via a compression layer.