DURABLE AND FLEXIBLE INK COMPOSITION FOR HIGH-QUALITY/HIGH-DEFINI TION SCREEN PRINTING, PRINTED PRODUCT OBTAINED BY SCREEN PRINTING SAID INK COMPOSITION, AND MANUFACTURING METHOD FOR SAID PRINTED PRODUCT.

摘要

Provided is an ink composition for screen printing, with which it is possible to produce a printed product, wherein when the printed product is produced by screen printing the ink composition on a thermoplastic resin substrate using a 360-mesh screen printing plate made of a high-strength, non-deformable stainless mesh having a wire diameter of 25 µm, the sag width at an edge of any portion of a printed print image, including an outline portion, with respect to the image design dimensions of the printing plate in which both a solid image pattern and a fine image pattern are present, does not exceed 10 µm. This ink composition for screen printing on a thermoplastic resin substrate is characterized as follows. The flow radius measurement value of the ink composition, as measured 1 minute after the start of measurement by a flowability measurement method using a parallel-plate viscometer (spread meter) at 25°C in accordance with JIS K5701-1:2000, is 13.0-24.0 mm. If F60 is defined as the flow radius measurement value 1 minute after the start of measurement by a flowability measurement method using the parallel-plate viscometer, and F45 is defined as the flow radius measurement value 45 seconds after, then F60-F45=1.0 mm. The viscosity of the ink composition, as measured by a BH-type rotational viscometer at 25°C, is 5-180 Pa and has a thixotropic index (TI) value of 2.0-8.0. The ink composition contains, in a proportion of at least 70 mass% of the total solvents, a solvent having a boiling point of at least 170°C. The ink composition contains, in a proportion of at least 10 mass% with respect to the total amount of the ink composition, a thermoplastic polymer having a weight-average molecular weight of at least 4000 and a Tg of 20-95°C. With the ink composition, it is possible to produce a printed product such that, after being vacuum formed or pressure formed, a print image coating film has an elongation ratio of at least 250%.