An optical film comprising: a base layer comprising a base resin; a plurality of polymer particles disposed in the base layer; and a plurality of voids formed in the base layer and enclosing the respective polymer particles, wherein the polymer particles comprise a crosslinked polymer; wherein the content of the base resin is 60 to 90 wt% based on the total weight of the optical film, and the base layer is drawn in at least one direction, and the voids have a shape elongated in the direction parallel to the direction in which the base layer is drawn; wherein the polymer particles have a horizontal diameter in the direction parallel to the base layer and a vertical diameter in the direction perpendicular to the base layer, and the ratio of the horizontal diameter to the vertical diameter is 1.2:1 to 1:1.2; wherein the average polymer particle size is 0.5 to 0.8 μm and the particle size dispersity is 0.7 to 0.8; wherein each of the voids has an elliptical cross-sectional shape, the length of the minor axis of the ellipse being 0.1 to 10 μm; wherein the optical film has a reflectance of 97% or more at the wavelength of 550 nm; wherein the optical film further comprises a plurality of inorganic particles disposed in the base layer; and a plurality of second voids formed in the base layer and enclosing the respective inorganic particles; wherein the inorganic particles, and the polymer particles are 9 to 30 wt%, and 1 to 10 wt%, respectively, based on the total weight of the optical film; wherein the base layer comprises a polyester resin; and wherein the crosslinked polymer is incompatible with the polyester resin. a base layer comprising a base resin; a plurality of polymer particles disposed in the base layer; and a plurality of voids formed in the base layer and enclosing the respective polymer particles, wherein the polymer particles comprise a crosslinked polymer; wherein the content of the base resin is 60 to 90 wt% based on the total weight of the optical film, and the base layer is drawn in at least one direction, and the voids have a shape elongated in the direction parallel to the direction in which the base layer is drawn; wherein the polymer particles have a horizontal diameter in the direction parallel to the base layer and a vertical diameter in the direction perpendicular to the base layer, and the ratio of the horizontal diameter to the vertical diameter is 1.2:1 to 1:1.2; wherein the average polymer particle size is 0.5 to 0.8 μm and the particle size dispersity is 0.7 to 0.8; wherein each of the voids has an elliptical cross-sectional shape, the length of the minor axis of the ellipse being 0.1 to 10 μm; wherein the optical film has a reflectance of 97% or more at the wavelength of 550 nm; wherein the optical film further comprises a plurality of inorganic particles disposed in the base layer; and a plurality of second voids formed in the base layer and enclosing the respective inorganic particles; wherein the inorganic particles, and the polymer particles are 9 to 30 wt%, and 1 to 10 wt%, respectively, based on the total weight of the optical film; wherein the base layer comprises a polyester resin; and wherein the crosslinked polymer is incompatible with the polyester resin. wherein the polymer particles comprise a crosslinked polymer; wherein the content of the base resin is 60 to 90 wt% based on the total weight of the optical film, and the base layer is drawn in at least one direction, and the voids have a shape elongated in the direction parallel to the direction in which the base layer is drawn; wherein the polymer particles have a horizontal diameter in the direction parallel to the base layer and a vertical diameter in the direction perpendicular to the base layer, and the ratio of the horizontal diameter to the vertical diameter is 1.2:1 to 1:1.2; wherein the average polymer particle size is 0.5 to 0.8 μm and the particle size dispersity is 0.7 to 0.8; wherein each of the voids has an elliptical cross-sectional shape, the length of the minor axis of the ellipse being 0.1 to 10 μm; wherein the optical film has a reflectance of 97% or more at the wavelength of 550 nm; wherein the optical film further comprises a plurality of inorganic particles disposed in the base layer; and a plurality of second voids formed in the base layer and enclosing the respective inorganic particles; wherein the inorganic particles, and the polymer particles are 9 to 30 wt%, and 1 to 10 wt%, respectively, based on the total weight of the optical film; wherein the base layer comprises a polyester resin; and wherein the crosslinked polymer is incompatible with the polyester resin.