▎ 摘　　要

NOVELTY - Preparing bulk graphene film based on polymer necking process comprises (i) loading single-layer flake graphene on polyetherimide substrate and thermal curing at 120-160 degrees C for 40-70 minutes; (ii) stretching polyetherimide substrate in one direction, with a tensile force of 30-60 MPa and breaking to form graphene strips with a width of 1-2 mu m; (iii) stretching again in a direction perpendicular to step (ii), with a tensile force of 30-60 Mpa to break to form massive graphene, where the size of the strip or block graphene obtained by stretching is controllable, the relationship between the interface shear strength tc and the width of the tensile graphene fracture zone satisfies the formula as given in the specification. USE - The bulk graphene film is useful in blue LED device (claimed). ADVANTAGE - The method uses polymer necking process to prepare bulk graphene film, which can realize the control between the interface shear strength and the width of the stretched graphene fracture band, and can further adjust the size of the bulk graphene by reheating, has simple and easy operation, is money saving, time saving and high precision, adopts the polymer necking process to realize the patterning of the nano-film material graphene, used as the transparent conductive layer of blue LED, the process flow is simple, and the single-layer polycrystalline graphene material has high transmittance and high conductivity, and realizes the simple process, and excellent characteristics e.g. economical and high precision. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for: a used method of the bulk graphene film in blue LED device, where the blue LED device includes a silicon substrate, an adhesive layer, a highly reflective mirror layer, and an LED epitaxial layer (p-gallium nitride layer, p-aluminum gallium nitride layer, quantum well layer, n-gallium nitride layer), transparent conductive layer and chromium/gold electrode layer stacked in sequence from bottom to top, and the bulk graphene film is used as a transparent conductive layer of a blue LED device.