The antigen detection kit purchased by the public belongs to light industry. Light industry includes printed matter. In daily life, people come into contact with newspapers, books and magazines, maps, posters, advertisements, envelopes, stationery, file bags, trademarks, labels, business cards, invitations, banknotes, greeting cards, desk calendars, picture books, various identification cards, packaging boxes, gift boxes, circuit boards and so on, all of which belong to the category of printed matter.