JP2660000B2 - UV curable ink for stencil printing - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ultraviolet curable ink for stencil printing, and more particularly to an ultraviolet curable ink used for stencil printing and having a high curing speed.

[Conventional technology]

Conventionally, emulsion ink has been used as stencil printing ink for rotary transfer printing, but this emulsion ink is slow to dry, and when there are many solid parts in the printed matter, set-off, that is, overlapping the printed matter just printed In such a case, there is a problem in that the ink of the adjacent printed matter adheres to the printed matter and stains the printed matter. Therefore, instead of emulsion inks, ultraviolet curable inks that are immediately cured by ultraviolet irradiation have been used. However, even when printing with this UV-curable ink, in order to eliminate set-off, the printing speed must be slowed to extend the UV irradiation time, or the UV irradiation energy density must be increased, When the printing speed is reduced, the printing work efficiency is reduced, and when the ultraviolet irradiation intensity is increased, the printing paper itself is disadvantageously discolored. Recently, in order to eliminate the above problem and further increase the curing speed of the ultraviolet curable ink, improvement of the reactivity of the resin contained in the ink and improvement of the photoinitiator have been studied.

However, when trying to improve the reactivity of the resin, the toxicity increases, the irritation to the human body becomes strong, and the storage stability of the ink decreases, and the problem that gelation occurs in storage in a dark place occurs. . On the other hand, by improving the photoinitiator, an unpleasant odor may be generated when the ink is used, which causes a new problem.

[Problems to be solved by the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an ultraviolet curable ink for stencil printing, which solves the above-mentioned problems of the prior art and can obtain good printed matter without set-off, and has a high curing speed.

[Means for solving the problem]

The present inventors have conducted intensive studies to improve only the curability without deteriorating the toxicity and storage stability of the UV-curable ink, and as a result, by adding fine acrylic resin powder to the UV-curable ink, The inventors have found that the speed is significantly increased and arrived at the present invention.

That is, the present invention is characterized in that in an ultraviolet curable ink for stencil printing containing an ultraviolet curable resin and a pigment, 100 parts by weight of the ultraviolet curable ink contains 2 to 5% by weight of acrylic resin fine powder.

It is not clear why the addition of fine acrylic resin powder to UV-curable ink improves the curability of the ink, but this is due to the fact that the addition of fine powder of the same material and the same degree of Since no improvement is observed, it is considered that the improvement is not caused by the optical action of the fine powder, but rather is caused by the chemical property of the acrylic resin fine powder.

The acrylic resin powder used in the present invention does not contain a surfactant prepared by a soap-free emulsion polymerization method, unlike the conventional polymerization method.

The soap-free emulsion polymerization method is an emulsion polymerization method that does not use a surfactant such as soap, in which a monomer is dissolved or dispersed in water in the presence of a dispersion stabilizer, and a polymerization initiator is added thereto to polymerize. It is. The particle size distribution of the polymer produced by this method depends on the stirring conditions in the polymer particle producing step, and generally 0.2 to 0.5 μm particles are produced. Regarding such a soap-free emulsion polymerization method, for example, "New development and problems of synthetic polymer latex" Shinsuke Yamazaki, Tokyo Engineering News: Chemical Data Vol3, No.4
Is referred to.

The particle size of the acrylic resin powder used in the present invention is from 2 to
A range of 0.15 microns is preferred. The smaller the particle size of the acrylic resin powder, the higher the curing speed of the ink. First
The table shows the relationship between the average particle size of the acrylic resin fine powder and the fixability of the ink.

The above-mentioned adhesiveness is determined by adding 3% of each of the acrylic resins shown in the table to an ultraviolet-curable ink to prepare an ultraviolet-curable stencil printing ink. Product)
UV light is applied to the printed matter by a UV irradiator (300W).
This is an evaluation of the strength against kosle when irradiated for 2 seconds.

The amount of fine acrylic resin powder added is
2 to 5% by weight, preferably 3 to 4% by weight in 100 parts by weight
It is. If the amount is less than 2% by weight, the effect of increasing the curing speed is not seen, and if the amount exceeds 5% by weight, only the cost increases but the curability does not improve much.

In the present invention, known UV-curable inks can be used, and the UV-curable resin and pigment in the ink are not particularly limited. For example, as the ultraviolet curable resin, an epoxy resin, a polyester resin, or the like is used. Further, a known photoinitiator may be contained in the ink.

〔Example〕

 Next, the present invention will be described in more detail with reference to examples.

In the examples, the curability test of the ink was performed according to the method described below.

Ink curability test Put the test ink in a jig (aluminum, width 10mm, thickness 50μm) for forming an ink film, use a small UV irradiator with 300W output, and move the shutter in the horizontal direction of the UV irradiator By changing the irradiation time of the ultraviolet light having an irradiation intensity of 40 W / cm to the ink stretched in layers on the jig in steps of 1 second, the time until the test ink became a film and peeled off from the jig was measured.

In Examples, parts and% representing the components of the ink are:
Parts by weight and% by weight respectively.

Example 1 3.1 parts of an epoxy UV curable resin UV-22C (manufactured by Harima Kasei Co., Ltd.), 4 parts of a photoinitiator (Irgar Cure 651, manufactured by Ciba Geigy), and a polyester UV curable resin
63.1 parts of SA-2006 (Mitsubishi Yuka Co., Ltd.) and SA-4100 of polyester UV curable resin (Mitsubishi Yuka Co., Ltd.) 6.
2 parts and organic bentonite powder (trade name: Thixogel V
Z, manufactured by Nissan Gardler Catalyst Co., Ltd.) and 100 parts of ultraviolet curable stencil printing ink consisting of 8.0 parts of carbon black # 10 (manufactured by Mitsubishi Kasei) in 2.5 parts of ink, and 100 parts of soap-free emulsifying weight 3% of acrylic resin MP-3100 (particle size: 0.4 μm, manufactured by Soken Chemical Co., Ltd.) manufactured by a legal method is blended, and the mixture is preliminarily stirred by a three-one motor (manufactured by Shinto Kagaku) for 1 hour and 40 minutes. The mixture was passed twice to obtain an ultraviolet curable stencil printing ink containing acrylic resin fine powder. Next, a curability test was performed using this ink, and printing was performed at a maximum printing speed (120 sheets / min) using a rotary printing press RISOGRAPH 007 (manufactured by Riso Kagaku). A good print without discoloration was obtained.

Comparative Example 1 An ultraviolet-curable stencil printing ink was prepared in the same manner as in Example 1 except that no acrylic resin was added, and the same test was performed.

Table 2 summarizes the results of Example 1 and Comparative Example 1.

The ultraviolet-curable stencil printing ink to which the acrylic resin fine powder of Example 1 was added was more excellent in curability, and the obtained printed matter was good without set-off.

Example 2 Using the ultraviolet-curable stencil printing ink of Example 1,
When printing at a printing atmosphere temperature of 5 ° C and 35 ° C, 35 ° C
Although a slight increase in print density was observed at this time, a good print without blurring or bleeding was obtained under both conditions, and there was no problem that the viscosity of the ink was too high and the printing paper was stuck to the stencil.

〔The invention's effect〕

According to the present invention, since the curability of the ink is improved by adding the fine powder of the acrylic resin to the ultraviolet curable ink, it is not necessary to increase the irradiation intensity and time of the ultraviolet light at the time of printing. Good printed matter without discoloration of itself is obtained.

By using the ultraviolet curable ink of the present invention, the printing speed can be increased, so that the printing operation efficiency is improved.

Claims (2)

(57) [Claims] An ultraviolet curable ink for stencil printing containing an ultraviolet curable resin and a pigment, wherein 100 parts by weight of the ultraviolet curable ink contains 2 to 5% by weight of acrylic resin fine powder. UV curable ink. 2. The ultraviolet curable ink for stencil printing according to claim 1, wherein said acrylic resin fine powder is produced by a soap-free emulsion polymerization method.