Sorry to get your question that late, Belen 13.
I guess the EN for "carton" in a film can be either "dialog card", "title card" or insert - depends on the type of "carton" and the film (a silent film or a creative one like Godard's for example).
Or wasn't your sentence referring to FR typographical convention, which then would be : "sont en italiques [dans?] les cartons ou inserts, les titres d’œuvres...", since italics is to be used for titles and can also be used for quotations.
But you probably found the proper word since then ;0)