Double-crosslinked cellulose nanofiber film with high strength and high transmittance and method for manufacturing the same

A method for manufacturing a cellulose nanofiber film, the method comprising:

• preparing a cellulose nanofiber dispersion having cellulose nanofibers;
• performing a chemical crosslinking by adding an epichlorohydrin-based material to the cellulose nanofiber dispersion to prepare a planar body;
• and
• performing a physical crosslinking after the chemical crosslinking in which a metal chloride is added to the planar body,
• wherein the epichlorohydrin-based material comprises epichlorohydrin,
• wherein the metal chloride comprises calcium chloride (CaCl2),
• wherein the epichlorohydrin-based material is added in an amount in a range of 0.4 parts by weight to 0.7 parts by weight based on 1 part by weight of the cellulose nanofibers,
• wherein the metal chloride is added in an amount in a range of 0.1 parts by weight to 0.5 parts by weight based on 1 part by weight of the cellulose nanofibers,
• wherein the chemical crosslinking is performed by adding the epichlorohydrin-based material to the cellulose nanofiber dispersion and by then mixing at a temperature in a range of 20° C. to 30° C. for 12 hours to 16 hours, and
• wherein the physical crosslinking is performed by contacting an aqueous solution comprising the metal chloride with the planar body at a temperature in a range of 20° C. to 30° C. for 6 hours to 12 hours.