JPH042440B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a rubber (hereinafter referred to as a pad) used as an offset blanket used in intaglio offset printing, etc., commonly known as pad printing, tacho printing, and pad printing. It is something.

[Conventional technology]

In pad printing, the ink placed on an intaglio plate is transferred once to the surface of rubber-like pads of various shapes, and then the pads are pressed against the printing material and the ink printed on the pads is transferred once again to the printing material. This is an offset printing method in which printing is performed by
This pad printing method transfers ink through a soft pad, so the pad deforms, making it possible to print not only on flat surfaces but also on curved surfaces, and is used to print the eyes and noses of dolls with uneven surfaces. It is used in

The pads used used to be made of gelatin, but now silicone rubber is commonly used. This silicone rubber is soft and easy to get ink on by itself, but in order to adjust its hardness and ink attachment and detachment (receiving ink from the plate and transferring ink to the printing substrate), non-volatile liquid silicone oil ( (Also called diluent or thinner)
A method of adding .

In other words, liquid silicone oil is mixed into solid silicone rubber, and as the silicone oil gradually seeps out of the silicone resin, the composition ratio of silicone resin and silicone oil on the printed surface remains unchanged over time. is retained to some extent.

[Problem that the invention seeks to solve]

However, this silicone oil is eluted into the ink used during printing, or the silicone oil on the surface is transferred when it comes into contact with the printing material, and in particular, the surface of the pad is wiped with an organic solvent to clean the printed surface. As the work is repeated, more of the silicone oil mixed in the silicone rubber is leached to the outside, and the composition of the resin and silicone oil on the printing surface of the pad changes, resulting in a change in printability. However, there was a problem in that it was difficult to use the same pad for a long period of time.

Pads in which the silicone oil on the surface has been reduced due to elution to the outside are difficult to reuse and have to be disposed of as is, which is costly.

[Means for solving problems]

The present invention has improved this drawback, and has a structure in which the inside of the pad has a part containing more silicone oil than the printing part of the pad (where ink is attached and removed), and furthermore, the pad has a part that contains more silicone oil than the printing part of the pad (where ink is attached and removed). The feature is that the ratio of silicone rubber to silicone oil on the printed surface of the pad is changed by appropriately setting the distance from the pad surface to the part with a high silicone oil content depending on the pattern.

[Effect]

The present invention has the above-described structure, and since the amount of silicone oil eluted is small in the surface area of the pad (the area on which the ink is applied) which is located a long distance from the area with a high silicone oil content, the part of the pad where the ink is applied is The composition of resin and silicone oil is kept constant. On the other hand, since a large amount of silicone oil is eluted on the surface of the pad where ink does not need to be applied, it becomes difficult for the ink to be applied, and the amount of ink applied is adjusted depending on the form and position of the printing pattern provided on the printing material.

〔Example〕

Examples of the present invention will be described below.

Example 1 First, a female mold 1 with an inverted outer shape including the printed surface of the pad is prepared (FIG. 1). Inside this female mold 1, a male mold 2 is placed, which has a shape where the silicone oil content is high. Additives such as silicone rubber, silicone oil, and silicone rubber crosslinking agent, reversal agent, chain extender, etc. are mixed in the space 3 of the female mold 1 and the male mold 2 at a ratio that provides good printing suitability, and after defoaming. Pour the material 8 to obtain the outer pad 9. Among silicone rubbers, two-component RTV rubber, which is cured by adding and mixing a curing catalyst at room temperature, is superior in terms of workability.

Although it is possible to use one-component types such as acetic acid-free, acetone-free, and oxime-free types that cure with moisture in the air, they take time to harden to the inside, have poor release properties from the mold, and are difficult to cure. This is not appropriate as it will result in non-uniformity.

A good silicone oil is liquid silicone oil with a strength of 5 to 100 poise, which is sold as a diluent or thinner. This silicone oil has the effect of lowering the hardness of the rubber and improving the ink attachment and detachment. If the amount added is too large, there will be too much migration (bleed) to the printed surface of the prepared pad, and the surface will always be oily. Since the pad is covered with a film, it becomes difficult for ink to get on the pad, so the amount added must be adjusted.

If the amount of silicone oil is small, the hardness of the rubber will increase and the ink will transfer better, but on the other hand, when applying the ink to the printing substrate, the ink will not be completely transferred to the printing substrate, and the ink will remain on the pad, making it difficult to print. You will not be able to print properly.

The ratio of silicone rubber to silicone oil varies greatly depending on the ink and solvent used, but the ratio of silicone oil is 0.01% to 10%.

Once the injected silicone rubber has hardened, the male mold 2
, and create a composition in which the proportion of silicone oil is higher than that of material 8 in the part to be printed.
The inner pad 4 is made by curing in the same manner as the outer pad 9, and then the female mold 1 is removed and the third
Obtain the product as shown in the figure.

When a predetermined amount of silicone oil is added to silicone rubber before hardening and stirred well, it becomes uniformly dispersed. This is poured into a mold and left at room temperature, and hardening is completed in 1 to 2 days. When curing is complete, the silicone oil becomes a liquid dispersed state (solid solution) in the hardened silicone rubber.

Silicone rubber is compatible with silicone rubber because it is not crystallized as a resin molecular structure, and silicone resin has a high gas permeability (does not inhibit the permeation of foreign molecules). It migrates and oozes out at a slow speed that is invisible to the naked eye (property of moving through the resin from higher concentration to lower concentration).

Example 2 A female mold 5 is made for the part with a high content of silicone oil, an inner pad 4 is made with a composition with a high proportion of silicone oil, it is removed from the female mold 5, and the inner pad 4 is shaped into a pad. is placed into the inverted female mold 1', the position within the mold is determined and fixed, and silicone, which will become the outer pad 11, is injected into the space 10 created by the female mold 1' and the inner pad 4. The product is taken out from the mold 1' to obtain a product.

The thickness of the material for the outer pad varies depending on the size of the pad, but a suitable thickness is 2 to 5 mm.

Furthermore, if the distance 1 from the inner pad 4 to the portion 6 of the outer pad 11 in contact with the ink 7 is uniform, printing will generally be stable (FIG. 6).

This is because if there is a thin or thick part of the outer pad 11, the amount of silicone oil seeping out from that part will be different from other parts, making it difficult for the ink to get on the thin part. Therefore, printability differs locally, making it difficult to print stably over the entire surface. Therefore, it is necessary to set and manufacture the outer pad 11 and the inner pad 4 so that they are in the correct position.

If this fact is used inversely, it becomes possible to partially adjust the printability. For example, it would be better if the surface of the pad, which corresponds to the plain area where ink does not stick to the pad as a pattern, had properties that would prevent ink from adhering to the pad.During actual printing, scratches would occur on the plate or doctor, and the ink would actually be on the plate. Even if the ink remains on the pad, the ink will not get on the pad and will not print.

For example, as shown in FIG. 7, when the ink 7 is applied only to a certain part of the pad, the part of the pad other than the part where the ink 7 is applied does not need to have the property of being ink applied. In this case, adjustment can be made by reducing the thickness from the surface of the part where the ink 7 does not need to be applied to the part with a high silicon concentration.

〔Effect of the invention〕

Since the present invention has the above configuration, it has the following excellent practical effects.

(b) The silicone oil content of the inner pad is higher than that of the outer pad, so even if you print repeatedly, the composition of the resin content and silicone oil on the part of the outer pad surface where the ink is applied will remain the same. The printability remains constant without any change, and it can be used for a long period of time.

(b) Distance from the boundary between the inner and outer pads to the surface of the outer pad (thickness of the outer pad)
By appropriately setting l, it is possible to change the ratio of silicone rubber to silicone oil on the printed surface of the pad.

[Brief explanation of drawings]

1 and 2 are explanatory diagrams showing the manufacturing process of the pad of the present invention, FIG. 3 is a sectional view of the present invention, and FIG.
Fig. 5 is an explanatory diagram showing another manufacturing process of the pad of the present invention, Fig. 6 is an explanatory diagram showing a cross section of the pad of the present invention with ink applied to its surface, and Fig. 7 is an explanatory diagram showing another manufacturing process of the pad of the present invention. It is an explanatory view showing a cross section of a state in which ink is applied to the surface in an example. 1,1'...female type, 2...male type, 3...space,
4...Inner pad, 5...Female mold, 6...Part in contact with ink, 7...Ink, 8...Material, 9...
Outer pad, 10... Space, 11... Outer pad.

Claims (1)

[Claims] 1. Consists of an outer pad and an inner pad made of silicone resin and silicone oil, characterized in that the content of silicone oil in the inner pad is greater than the content of silicone oil in the outer pad. A pad for printing. 2. The printing pad according to claim 1, wherein the distance from the interface between the outer pad and the inner pad to the surface of the outer pad varies.