Method of manufacturing a lens presenting a graded tint

A method of manufacturing a lens presenting a graded tint lens comprising first and second layers each of which is made of a thermoplastic material, with only one of the layers being colored in the tint concerned, the method comprising the steps of:

• injecting the thermoplastic material of the first layer into a first mold cavity in order to form the first layer, wherein:
• the first layer is the layer colored in the tint concerned and occupies a front face of the lens,
• said first layer being of varying thickness along a vertical direction and presenting on a top edge a thickness which is greater or equal to about 1.5 mm and on a bottom edge a thickness which is at least less than or equal to about 0.8 mm;
• said variation of the thickness of the first layer from the top to the bottom of the lens providing a graded vertical tinting effect to the lens, which presents a major variation of transmission (Tv), along a vertical direction, into a space comprised from about 20 to 25 mm above and below a geometric centre of said lens along a horizontal direction,
• said first layer being of constant thickness as measured along a horizontal direction to provide along this horizontal direction a constant horizontal tinting effect to the lens;
• and
• placing the first layer in a second mold cavity and injecting therein the thermoplastic of the second layer so as to form the second layer on the first layer,
• the second layer occupying a rear face of the lens,
• said second layer being of varying thickness along a vertical direction from a top edge of the lens to a bottom edge of the lens, in a substantially complementary manner with the first layer to provide a lens which presents on the top edge and on the bottom edge a thickness at least greater than 1.5 mm
• said second layer being of varying thickness as measured along a horizontal direction to provide an optical property to the lens.