To solve a problem wherein confidential documents and a plurality of documents enclosed in window envelopes or direct mails are frequently sent to specific customers to fill the customers' mailboxes daily with lots of mails and deliveries, from which the customers usually select only what they need by checking senders or windows on the mails, open only the selected mails and deliveries and discard the other mails and deliveries without even opening them.
A Lippman hologram sheet is stuck to the window portion of the window envelope to differentiate the envelope from other mails and deliveries. Moreover, its opening is large and provided at a portion corresponding to an address or the like which is surely confirmed by an addressee to provide the window envelope attaining further positive improvement in opening efficiency.
DANJO KOTARO
Keiko Fukamachi
Hideo Ito
Hiromi Fujimasu
Naoki Goto
Yusuke Ito