Composite sheet, substrate for a display element including same, and display device including same

A composite sheet comprising:

• a matrix comprising at least one of a silicone resin, a styrene-butadiene rubber (SBR), a butadiene rubber, an isoprene rubber, a chloroprene rubber, a neoprene rubber, an ethylene-propylene-diene terpolymer, a styrene-ethylene-butylene-styrene (SEBS) block copolymer, a styrene-ethylene-propylene-styrene (SEPS) block copolymer, an acrylonitrile-butadiene rubber (NBR), a hydrogenated nitrile rubber (NBR), a fluorinated rubber, or a plasticized polyvinyl chloride;
• a reinforcement material impregnated into the matrix;
• a coating layer formed on at least one surface of the matrix;
• and
• a barrier layer formed on at least one surface of the coating layer, wherein the coating layer is formed between the matrix and the barrier layer,
• wherein, when the matrix has an elastic modulus at 25° C. of E2 and the coating layer has an elastic modulus at 25° C. of E3, a ratio of the elastic modulus E3/E2 is about 5×104 or less,
• wherein the coating layer comprises at least one of acrylic resins, epoxy resins, urethane resins, and unsaturated polyester resins.