Display device

1. A display device comprising a substrate, a display portion formed on the substrate, an upper layer which covers the display portion, and a gas barrier layer provided between at least a part of the substrate and the display portion, wherein the improvement comprises that

the gas barrier layer is positioned near to a position which forms a neutral plane when bending moment in a direction in which the substrate is warped acts on the display device.

2. A display device as defined in claim 1 in which a distance between the neutral plane and the gas barrier layer is not larger than 30% of a distance between the neutral plane and a surface of the substrate on a side of the gas barrier layer.

3. A display device as defined in claim 2 in which the display portion is positioned near to the position which forms the neutral plane.

4. A display device as defined in claim 3 in which a distance between the neutral plane and the display portion is not larger than 30% of a distance between the neutral plane and a surface of the substrate on a side of the display portion.

5. A display device as defined in claim 1 in which the upper layer is formed of a same material as the substrate.

6. A display device as defined in claim 5 in which a distance between the neutral plane and the gas barrier layer is not larger than 30% of a distance between the neutral plane and a surface of the substrate on a side of the gas barrier layer.

7. A display device as defined in claim 6 in which the display portion is positioned near to the position which forms the neutral plane.

8. A display device as defined in claim 7 in which a distance between the neutral plane and the display portion is not larger than 30% of the distance between the neutral plane and the surface of the substrate on a side of the display portion.

9. A display device as defined in claim 5 in which the display portion is positioned near to the position which forms the neutral plane.

10. A display device as defined in claim 9 in which 5 a distance between the neutral plane and the display portion is not larger than 30% of a distance between the neutral plane and a surface of the substrate on a side of the display portion.

11. A display device as defined in claim 1 in which the display portion is positioned near to the position which forms the neutral plane.

12. A display device as defined in claim 11 in which a distance between the neutral plane and the display portion is not larger than 30% of a distance between the neutral plane and a surface of the substrate on a side of the display portion.

13. A display device as defined in claim 1 in which the gas barrier layer includes at least one of aluminum oxide (Al 2 0 3 ), silicon oxide (SiO 2 ) and silicon oxide nitride (SiO x N y ).

14. A display device as defined in claim 1 in which a second gas barrier layer is formed on a side of the display device opposite to the substrate, and the second gas barrier layer is positioned near to the position which forms the neutral plane.

15. A display device as defined in claim 14 in which the second gas barrier layer includes at least silicon nitride (SiN x ).

16. A display device as defined in claim 1 in which the substrate is a resin substrate formed of macromolecular material.

17. A display device as defined in claim 1 in which the display device comprises an organic EL element.

18. A display device as defined in claim 1 , wherein E 1 *Y 1 2 substantially equals to E 2 *Y 2 2 , where E 1 and E 2 are moduli of longitudinal elasticity of the upper layer and the substrate, respectively; Y 1 is a distances between the gas barrier layer and a surface of the upper layer on an opposite side of the gas barrier; and Y 2 is a distances between the gas barrier layer and a surface of the substrate on an opposite side of the gas barrier.

19. A display device as defined in claim 1 , wherein the display portion is positioned substantially close to the neutral plane without overlapping the neutral plane.