Liquid crystal display device

1. A liquid crystal display device comprising:

a liquid crystal display panel; and

a backlight device for irradiating the liquid crystal display panel with a planar backlight beam from a back side of the liquid crystal display panel,

the backlight device including:

a light source;

a light guide which converts light from the light source to the planar light beam and emits the planar light beam;

an optical sheet disposed on a back side of the light guide; and

an optical sheet group which is disposed on an irradiation-surface side of the light guide emitting the planar light beam and includes a plurality of optical sheets arranged in stacked relation,

wherein out of the optical sheets disposed on the back side and the irradiation side of the light guide, at least one first optical sheet disposed on the back side of the light guide and at least one second optical sheet of the optical sheet group disposed on the surface side of the light guide are each formed to have a larger outside configuration than at least the light guide and the other optical sheets,

periphery parts of the first optical sheet and the second optical sheet are bonded together to form a bag shape, and the light guide and the other optical sheets are retained in the bag-like body formed of the first optical sheet and the second optical sheet, and

a bonded portion of periphery parts does not overlap the light guide in a plane view from the irradiation-surface side.

2. The liquid crystal display device according to claim 1 , wherein the first optical sheet is an optical sheet that is the outermost one of the optical sheets disposed on the back side of the light guide, and

the second optical sheet is an optical sheet that is the outermost one of the optical sheet group disposed on the surface side of the light guide.

3. The liquid crystal display device according to claim 1 , wherein the light source is disposed outside of the bag-like body and the light from the light source is made incident from a lateral side of the light guide via the first optical sheet or the second optical sheet.

4. The liquid crystal display device according to claim 3 , wherein the first optical sheet or the second optical sheet includes a light-transmitting window for the light from the light source to penetrate.

5. The liquid crystal display device according to claim 1 , wherein the light source is disposed in the bag-like body and a power line for power supply to the light source is connected to the light source via a through-hole formed in a lateral side of the first optical sheet or the second optical sheet, or a through-hole formed in a bond part between the first optical sheet and the second optical sheet.

6. The liquid crystal display device according to claim 2 , wherein the light source is disposed in the bag-like body and a power line for power supply to the light source is connected to the light source via a through-hole formed in a lateral side of the first optical sheet or the second optical sheet, or a through-hole formed in a bond part between the first optical sheet and the second optical sheet.

7. The liquid crystal display device according to claim 5 , wherein a clearance between the through-hole and the power line is sealed.

8. The liquid crystal display device according to claim 6 , wherein a clearance between the through-hole and the power line is sealed.

9. The liquid crystal display device according to claim 1 , wherein the first optical sheet and the second optical sheet are bonded together on respective opposed surfaces thereof.

10. The liquid crystal display device according to claim 2 , wherein the first optical sheet and the second optical sheet are bonded together on respective opposed surfaces thereof.

11. The liquid crystal display device according to claim 3 , wherein the first optical sheet and the second optical sheet are bonded together on respective opposed surfaces thereof.

12. The liquid crystal display device according to claim 7 , wherein the first optical sheet and the second optical sheet are bonded together by thermal compression bond.