Diffusion lens and display device having same

A diffusion lens comprising:

• a first lens surface having a concave curved shape such that light generated from a light source is incident on the first lens surface;
• a second lens surface having a convex curved shape such that part of the light incident on the first lens surface is output from the second lens surface;
• a side surface extending from a periphery of the second lens surface in a vertical direction of the diffusion lens such that part of a remainder of the light incident on the first lens surface is output from the side surface by passing through the side surface;
• and
• a bottom surface extending from a periphery of the first lens surface in a horizontal direction of the diffusion lens to meet a periphery of the side surface,
• wherein a sign of a rate of change of curvature of the first lens surface is the same as a sign of rate of change of curvature of the second lens surface,
• wherein a pattern in which arbitrary shapes are irregularly disposed or a pattern in which specified shapes are regularly or irregularly disposed is formed on the side surface and the bottom surface to diffuse the light passing through the side surface and diffuse the light reflected by the bottom surface,
• wherein in the pattern formed on the side surface, the arbitrary shapes or the specified shapes extend from the periphery of the second lens surface to the periphery of the side surface that meets bottom surface,
• wherein the pattern on the bottom surface is formed on part of the bottom surface, and
• wherein a diameter ratio (d/D) between a diameter “d” of a region where the pattern of the bottom surface is formed and a diameter “D” of the bottom surface ranges from 0.90 to 0.94.