US 12,168,723 B2
Stretched polyester film and method for preparing the same
Da-Young Hwang, Seongnam-si (KR); Sangwoo Kim, Seongnam-si (KR); Jiyeon Eom, Seongnam-si (KR); and Boo-Youn Lee, Seongnam-si (KR)
Assigned to SK CHEMICALS CO., LTD., Seongnam-si (KR)
Filed by SK CHEMICALS CO., LTD., Seongnam-si (KR)
Filed on Aug. 14, 2023, as Appl. No. 18/233,566.
Application 18/233,566 is a continuation of application No. PCT/KR2023/007889, filed on Jun. 8, 2023.
Claims priority of application No. 10-2023-0048462 (KR), filed on Apr. 12, 2023.
Prior Publication US 2024/0343870 A1, Oct. 17, 2024
Int. Cl. C08J 5/18 (2006.01); B29C 48/00 (2019.01); B29C 48/305 (2019.01); B29C 55/04 (2006.01); B29K 67/00 (2006.01); C08G 63/183 (2006.01); C08G 63/199 (2006.01); C08G 63/86 (2006.01)
CPC C08J 5/18 (2013.01) [B29C 48/022 (2019.02); B29C 48/305 (2019.02); B29C 55/045 (2013.01); C08G 63/183 (2013.01); C08G 63/199 (2013.01); C08G 63/863 (2013.01); B29C 2948/92704 (2019.02); B29K 2067/003 (2013.01); B29K 2995/0051 (2013.01); B29K 2995/0097 (2013.01); C08J 2367/02 (2013.01)] 10 Claims
 
1. A stretched polyester film, which comprises a single crystalline polyester resin in which a diol component and a dicarboxylic acid component are polymerized,
wherein the single crystalline polyester resin consists of a single polyester material,
wherein a heat shrinkage rate of the stretched polyester film at 80° C. in main shrinkage direction is 40% or more, and, upon a first thermal treatment and a second thermal treatment, a first melting temperature (Tm1) and a second melting temperature (Tm2) appear when the stretched polyester film is analyzed by differential scanning calorimetry (DSC),
wherein the first melting temperature (Tm1) is 150 to 230° C., the second melting temperature (Tm2) is 150 to 230° C., and the first melting temperature (Tm1) and the second melting temperature (Tm2) are different from each other,
wherein a difference (|Tm1−Tm2|) between the first melting temperature (Tm1) and the second melting temperature (Tm2) is in a range of 10 to 60° C.,
wherein the first thermal treatment temperature is 60 to 105° C.,
wherein the second thermal treatment temperature is 140 to 220° C., and
wherein a ratio (H1/H2) of a first heat of fusion (H1) at the first melting temperature (Tm1) to a second heat of fusion (H2) at the second melting temperature (Tm2) is 0.1 to 10.