Brightness enhancement film, and methods of making and using the same

A brightness enhancement film, comprising:

• a diffusing film comprising a front surface and a back surface, wherein the diffusing film has a stress retardation gradient of less than or equal to 50 nm/in, wherein an interval for calculation of the stress retardation gradient is less than 1 inch;
• a coating on the front surface;
• and
• light redirecting structures disposed in the coating;
• wherein the brightness enhancement film is capable of collimating light.

A brightness enhancement film, comprising:

• a diffusing film comprising a front surface, a back surface, and a diffusing film refractive index, wherein the front surface comprises an average surface roughness (Ra) of greater than or equal to about 0.1 micrometers;
• a coating on the front surface, wherein the coating has a coating refractive index;
• and
• light redirecting structures disposed in the coating;
• wherein the brightness enhancement film is capable of collimating light;
• and
• wherein a difference in the diffusing film refractive index and the coating refractive index is less than or equal to about ±0.2.

A method of making a brightness enhancement film, comprising:

• melting a thermoplastic resin at a temperature greater than or equal to a glass transition temperature of the thermoplastic resin;
• extruding the thermoplastic resin into a gap between a first calendering roll and a second calendering roll;
• cooling the thermoplastic resin to a temperature below the glass transition temperature to produce a diffusing film;
• disposing a coating on a front surface of the diffusing film;
• disposing a light-redirecting structures into the coating;
• and
• curing the coating;
• wherein the brightness enhancement film is capable of collimating light, and wherein, prior to disposing the coating on the front of the diffusing film, the diffusing film was capable of spread light passing through a back surface.

A method of making a brightness enhancement film, comprising:

• melting a thermoplastic resin at a temperature greater than or equal to a glass transition temperature of the thermoplastic resin;
• extruding the thermoplastic resin into a gap between a first calendering roll and a second calendering roll;
• cooling the thermoplastic resin to a temperature below the glass transition temperature to produce a diffusing film, wherein a stress retardation gradient across the diffusing film is less than or equal to 50 nanometers per inch, wherein an interval for calculation of the stress retardation gradient is less than 1 inch;
• disposing a coating on a front surface of the diffusing film;
• disposing a light-redirecting structures into the coating;
• and
• curing the coating;
• wherein the brightness enhancement film is capable of collimating light.