▎ 摘　　要

NOVELTY - Composite color film comprises 99-99.7 wt.% nano-crystalline cellulose and 0.3-1 wt.% graphene. The composite color film is prepared by subjecting nano-crystalline cellulose and graphene to vacuum filtration process. USE - The composite color film is useful in the preparation of thin film (claimed), photovoltaic field and anti-counterfeit labels, and preparation of advanced anti-counterfeiting ink of security paper. ADVANTAGE - The composite color film has water absorption capacity, good humidity effect, can change the color of the film containing water to composite color film (all claimed). DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for preparing the film, comprising (i) preparing nano-crystalline cellulose suspension stirring cellulose by adding 55-69 wt.% sulfuric acid at 40-60 degrees C to perform acid hydrolysis, terminating the reaction by adding deionized water, allowing the resulting solution to stand for certain period, centrifugally separating in a centrifuge to obtain a precipitate, washing, and repeatedly separating to obtain turbid supernatant, to obtain the product, and then subjecting the suspension to ultrasonic treatment in an ice-water bath for 10-40 minutes, and storing; (ii) preparing low-temperature thermal reduction graphene by dispersing graphene oxide powder in water, and performing ultrasonic treatment of graphene oxide powder in an ultrasonic device, to obtain graphene oxide solution, and then freeze-drying graphene oxide solution to obtain graphene oxide airgel, and carrying out low-temperature thermal annealing of graphene oxide airgel at 220-270 degrees C to obtain the product; and (iii) diluting nano-crystalline cellulose and graphene in 0.5-2 wt.% nano-crystalline cellulose suspension, performing ultrasonic treatment for 10-25 hours, uniformly dispersing graphene in the solution to obtain a composite solution; and (iv) carrying out vacuum filtration of the composite solution in a vacuum filtration to obtain the product.