Optical sheet and display device having the optical sheet

An optical sheet comprising:

• a transparent base material;
• a fine lens array constituted by a plurality of fine unit lenses formed on a front surface of said transparent base material;
• a diffusing layer formed on a rear surface of said transparent base material opposite to said surface on which said fine lens array is formed;
• and
• a light absorbing layer formed on said diffusing layer and including fine opening portions substantially located at focal points of said unit lenses;
• wherein said diffusing layer is made of a transparent medium containing transparent fine particles different in refractive index from said transparent medium, and
• said transparent fine particles have a mean particle size in one range selected from a particle size range for maximizing a value of Q/R at each of wavelengths in a visible region and a range which is near said particle size range and in which variation in the value of Q/R due to the wavelengths in the visible region is reduced, when Q is a scattering sectional area per transparent fine particle, and R is a radius of each of said transparent fine particles.

An optical sheet comprising:

• a transparent base material;
• a fine lens array constituted by a plurality of fine unit lenses formed on a front surface of said transparent base material;
• and
• a light absorbing layer formed on a rear surface of said transparent base material opposite to said surface on which said fine lens array is formed, said light absorbing layer including fine opening portions substantially located at focal points of said unit lenses;
• wherein each of bottom surfaces of said unit lenses constituting said fine lens array is basically shaped like a hexagon so that said unit lenses are arranged so as to be closest packed.

A back projection type display device comprising:

• a projector including a light source, a two-dimensional optical switching element for modulating light emitted from said light source in accordance with image information to form an optical image, and a projection lens for projecting said optical image while magnifying said optical image;
• and
• a transmission type screen having a back surface for receiving light projected from said projector, and a front surface for displaying said light, said transmission type screen including an optical sheet, and a Fresnel lens sheet provided on a projection light incidence side of said optical sheet, said optical sheet having a transparent base material, a fine lens array constituted by a plurality of fine unit lenses formed on a front surface of said transparent base material, a diffusing layer formed on a rear surface of said transparent base material opposite to said surface on which said fine lens array is formed, and a light absorbing layer formed on said diffusing layer and having fine opening portions substantially located at focal points of said unit lenses;
• wherein said diffusing layer of said optical sheet is made of a transparent medium containing transparent fine particles different in refractive index from said transparent medium, and said transparent fine particles have a mean particle size in one range selected from a particle size range for maximizing a value of Q/R at each of wavelengths in a visible region and a range which is near said particle size range and in which variation in the value of Q/R due to the wavelengths in the visible region is reduced, when Q is a scattering sectional area per transparent fine particle, and R is a radius of each of said transparent fine particles.

A liquid-crystal display device comprising:

• a pair of transparent substrates each of which is constituted by a laminate of a transparent electrode and an oriented film and which are bonded to each other through a predetermined gap so that surfaces on which said oriented films are formed are opposite to each other;
• a liquid-crystal layer held between said pair of transparent substrates;
• a unit for applying a voltage corresponding to an image signal between said transparent electrodes;
• and
• polarizers arranged on a light incidence surface side and a light emitting surface side of said pair of transparent substrates respectively;
• wherein said liquid-crystal display device further comprises a backlight unit disposed on a back surface side of said pair of transparent substrates for outputting substantially parallel light rays, and an optical sheet disposed on a light emitting surface side of said pair of transparent substrates, said optical sheet including a transparent base material, a fine lens array constituted by a plurality of fine unit lenses formed on a front surface of said transparent base material, a diffusing layer formed on a rear surface of said transparent base material opposite to said surface on which said fine lens array is formed, and a light absorbing layer formed on said diffusing layer and having fine opening portions substantially located at focal points of said unit lenses;
• said diffusing layer of said optical sheet is made of a transparent medium containing transparent fine particles different in refractive index from said transparent medium;
• and
• said transparent fine particles have a mean particle size in one range selected from a particle size range for maximizing a value of Q/R at each of wavelengths in a visible region and a range which is near said particle size range and in which variation in the value of Q/R due to the wavelengths in the visible region is reduced, when Q is a scattering sectional area per transparent fine particle, and R is a radius of each of said transparent fine particles.