JPH032066B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a pad printing method, and is intended to enable repeated and clear pad printing even when using ultraviolet curable ink.

By the way, in normal pad printing, as illustrated in FIG. 1, first, a highly elastic pad 1 attached to a pad support 2 and a printing plate 3, which is an intaglio plate equipped with an ink pocket 4, are prepared. After supplying the required amount of ink 5 to the ink pocket 4 of the printing plate 3 as shown in FIG. 1, press the pad 1 against the printing plate 3 as shown in FIG. The pad 1 is received as shown in FIG. 3, and then the pad 1 is pressed onto the printing surface of the target article 6 as shown in FIG. 4, and the ink 5 on the pad surface is transferred to the printing surface as shown in FIG. is executed.

Solvent-based ink is usually used in such pad printing. This type of ink has the property of increasing its viscosity as the solvent evaporates, increasing its adhesion to other objects, and eventually solidifying. Therefore, when using such ink for the above pad printing,
Even within the short time that the ink is attached to the pad surface until it is transferred from the printing plate 3 to the target article 6,
Since the viscosity of the ink is increased to some extent by evaporation of the solvent, the ink can be easily transferred from the pad surface to the printing surface without remaining on the surface of the pad, so that it can be continued for the next time. It is possible to make clear pad printing possible.

On the other hand, UV-curable inks can form a printed film that is hard and has good UV resistance, so they are used in applications where, for example, scratch resistance or fading due to UV rays is a problem.

However, unlike the above-mentioned solvent-based inks, this type of ink is a solvent-free type that does not contain a solvent, so it cannot be expected to have the effect of evaporation of the solvent, and therefore cannot be handled in the same way as solvent-based inks. That is, this ultraviolet curable ink is made by using a synthetic resin that polymerizes when exposed to ultraviolet light as a color vehicle, and hardens by the reaction, and the color vehicle is
Polymerization does not start under the weak ultraviolet light contained in indoor lighting, but polymerization starts only when exposed to strong ultraviolet rays from an ultraviolet lamp, so even if left in the air. Its viscosity does not change and therefore it does not harden naturally. Therefore, after printing, it is necessary for this ink to be irradiated with ultraviolet rays using the above-mentioned lamp to polymerize the color vehicle and forcibly harden it, so to speak.

Therefore, when attempting to use such ultraviolet curable ink for the above-mentioned pad printing, the following problems arise.

First, in the pad printing process shown in FIG. 1, if an ultraviolet curable ink is used instead of the usual solvent-based ink, this ink is transferred from the ink pocket 4 to the surface of the pad 1 at the stage shown in FIG. 3, and is then pressed onto the printing surface of the article 6 as shown in FIG. cannot be transferred to

That is, as shown in FIG. 2, which corresponds to the stage shown in FIG. Even when the pad 1 is pressed against the surface, the entire amount is not transferred to the surface, and when the pad 1 is pulled away from the article 6, it is approximately bisected from the vicinity of the line A-A in the figure, and is indicated by reference numerals 51 and 52 in the same figure. As such, only about half is transferred to the printing surface, and the rest remains attached to the pad surface.
Therefore, since the amount of transferred ink 51 on the printing surface is smaller than expected, the thickness of the printing film is thin, which tends to result in so-called blurred printing with poor ink transfer, and also the amount of ink 51 left on the pad surface is thin. ink 52
Even a slight misalignment with the new ink that the surface receives from the printing plate will destroy the outline of the printing pattern drawn with the new ink, making subsequent printing unclear. There are many.

Therefore, due to the above-mentioned circumstances, UV-curable inks are currently considered unsuitable for pad printing, and it is considered impossible to obtain a hard, UV-resistant printed film by pad printing. was.

The present invention has been developed in order to cope with the conventional situation and to easily and repeatedly print clear pads using ultraviolet curable ink. At this step, polymerization of the color vehicle is partially initiated to slightly increase the viscosity of the ink, which is then transferred to the printing surface. The details will be explained below based on the embodiment shown in FIG.

In FIG. 3, the same reference numerals as in FIGS. 1 and 2 indicate the same components, and 7 and 8 are ultraviolet lamps.

First, as shown in FIG. 3, a required amount of ultraviolet curable ink 50 is supplied to the ink pocket 4 of the printing plate 3 by known means, and then the pad 1 is pressed against the printing plate surface as shown in FIG. The ink 50 in 4 is received on the surface of the pad. The process up to this point is the same as before.

Ink 5 transferred to the pad surface in this way
Next, as shown in FIG. 3, the ink is irradiated with ultraviolet light using an ultraviolet lamp 7 until the ink is transferred onto the object 6 for the next process. Then, the viscosity of the ink 50 increases due to the initiation of polymerization of the synthetic resin used as a color vehicle. However, this ultraviolet irradiation is performed for the purpose of increasing the viscosity of the ink 50, and is not for the purpose of completely solidifying the ink. Therefore, the ultraviolet lamp 7 used in this step may have a small output, and its irradiation amount is set within a range that can increase the viscosity of the ink to the extent that it facilitates ink transfer in the next step. be done.

Thereafter, as shown in FIG. 3, the pad 1 with the ultraviolet irradiated ink 50' is pressed onto the printing surface of the article 6. Then this ink 5
0′ has increased viscosity as mentioned above, so
As shown in FIG. 5, it is easily transferred from the surface of the pad onto the surface to be printed, and does not remain on the surface of the pad.

In other words, the ink 50' that has been irradiated with ultraviolet rays can be handled in the same way as solvent-based ink when the solvent has partially evaporated, and the entire amount can be transferred onto the printing surface. The printing film has a large thickness, so it is possible to achieve so-called pad printing with good ink coverage, and since there is no ink left on the pad surface, it is possible to print clearly and without losing the outline of the printed pattern from next time onwards. becomes.

It should be noted that the ink 50' transferred onto the printing surface in this manner has only a higher viscosity than the initial one, and has not hardened yet. Therefore, after the transfer, as shown in FIG. 3, it is necessary to irradiate ultraviolet rays again with an ultraviolet lamp 8 to completely cure and solidify the color vehicle.

As described above, in pad printing using ultraviolet curable ink, the present invention irradiates ultraviolet rays to the ink transferred from printing to the pad surface before the ink is transferred in the next process. The printing method of the present invention increases the viscosity of the ink, and then transfers the ink to the printing surface of the article to be printed. Pad printing using ultraviolet curable ink, which had previously been used, can now be carried out relatively easily, and a clear printed film with a large film thickness without losing the outline of the printed pattern can be repeatedly and easily formed on the printing surface. can be done.

[Brief explanation of the drawing]

Figures 1 to 5 are front views showing the process order of normal pad printing using solvent-based ink, Figures 2 1 and 2
3 is a front view showing a conventional example in which an ultraviolet curable ink is used, and FIGS. 3 1 to 6 are front views showing embodiments of the present invention in the order of steps. 1... Pad, 3... Printing plate, 4... Ink pocket, 6... Article to be printed, 7... Ultraviolet lamp, 50, 50'... Ultraviolet curing ink.

Claims (1)

[Claims] 1. The ultraviolet curable ink supplied to the ink pocket of the printing plate is received by the surface of the pad pressed against the printing plate surface, and then the ink on the surface of the pad is transferred until the ink is transferred in the next process. irradiate with ultraviolet rays to increase the viscosity of the ink,
A pad printing method using an ultraviolet curable ink, characterized in that the ink is then transferred from the pad surface to the printing surface of an article to be printed.