Backlight unit, liquid-crystal display apparatus, and stacked structure

1. A backlight unit that supplies light exiting from an exit surface of a light guide plate to a liquid-crystal display panel via a reflective polarizing plate after correcting directivity of the exiting light using a prism sheet, the backlight unit comprising:

a reflective sheet disposed on a rear surface, a surface opposite the liquid-crystal display panel, of the light guide plate,

the light guide plate which first receives the light supplied from a light source,

the prism sheet having a repeated polygonal cross-sectional shape which receives the light before the reflective polarizing plate,

a light-diffusing sheet between the prism sheet and a ¼ wavelength plate,

the ¼ wavelength plate, and

the reflective polarizing plate which receives the light after the prism sheet,

wherein the prism sheet and the light diffusing sheet are formed of a material having refractive-index isotropy,

whereby light which has been reflected from the reflective polarizing plate and has passed through the ¼-wavelength plate and the light which has been output from the light guide plate and enters the ¼-wavelength plate are suppressed from experiencing a retardation in the in-plane direction of the ¼-wavelength plate.

2. The backlight unit according to claim 1 , wherein a base of the prism sheet has a retardation value Re of 20 nm or smaller.

3. The backlight unit according to claim 1 , wherein the ¼-wavelength plate and the reflective polarizing plate are integrated with each other.

4. The backlight unit according to claim 1 , wherein the prism sheet, the ¼-wavelength plate, and the reflective polarizing plate are integrated with each other.

5. The backlight unit according to claim 1 , wherein the ¼-wavelength plate and the reflective sheet are integrated with each other.

6. A liquid-crystal display apparatus comprising: a liquid-crystal display panel stacked on the backlight unit according to claim 1 .

7. The backlight unit according to claim 1 , wherein the polygonal cross-sectional shape of the convex structure of the prism sheet is triangular.

8. A liquid-crystal display apparatus comprising: a liquid-crystal display panel, a reflective polarizing plate, a ¼-wavelength plate that applies a retardation of ¼ wavelength to transmission light, a light-diffusing sheet, a light control sheet that controls directivity of transmission light, and a light guide plate, which are sequentially stacked,

wherein the ¼-wavelength plate exhibits reverse wavelength dispersion characteristics with respect to light reflected from the reflective polarizing plate so that a retardation applied to transmission light increases as the wavelength of the transmission light increases,

the light control sheet is a prism sheet formed of a material having refractive-index isotropy,

wherein the prism sheet and the ¼-wavelength plate are integrated with each other

wherein the light control sheet is a prism sheet in which a convex structure having a polygonal cross-sectional shape is repeatedly formed on a light entrance surface or a light exit surface,

wherein the prism sheet and the light diffusing sheet are formed of a material having refractive-index isotropy,

whereby light which has been reflected from the reflective polarizing plate and has passed through the ¼-wavelength plate and the light which has been output from the light guide plate and enters the ¼-wavelength plate are suppressed from experiencing a retardation in the in-plane direction of the ¼-wavelength plate.

9. The liquid-crystal display apparatus according to claim 8 ,

wherein the ¼-wavelength plate includes:

a transparent base;

an alignment film formed on the transparent base; and

a retardation layer formed of a liquid crystal material having reverse wavelength dispersion characteristics and cured in a state in which the liquid crystal material is aligned by alignment restricting force of the alignment film.

10. The liquid-crystal display apparatus according to claim 8 ,

wherein the ¼-wavelength plate is a stacked structure including:

a ½-wavelength retardation layer that applies a retardation of ½ wavelength to transmission light; and

a ¼-wavelength retardation layer that applies a retardation of ¼ wavelength to transmission light.

11. A liquid-crystal display apparatus comprising: a liquid-crystal display panel, a reflective polarizing plate, a ¼-wavelength plate that applies a retardation of ¼ wavelength to transmission light, a light-diffusing sheet, a light control sheet that controls directivity of transmission light, and a light guide plate which are sequentially stacked,

wherein the ¼-wavelength plate exhibits reverse wavelength dispersion characteristics with respect to light reflected from the reflective polarizing plate so that a retardation applied to transmission light increases as the wavelength of the transmission light increases,

the light control sheet is formed of a material having refractive-index isotropy, and

wherein the light control sheet is a prism sheet in which a convex structure having a polygonal cross-sectional shape is repeatedly formed on a light entrance surface,

wherein the prism sheet and the light diffusing sheet are formed of a material having refractive-index isotropy,

whereby light which has been reflected from the reflective polarizing plate and has passed through the ¼-wavelength plate and the light which has been output from the light guide plate and enters the ¼-wavelength plate are suppressed from experiencing a retardation in the in-plane direction of the ¼-wavelength plate.