Method of manufacturing display panel

1. A method of manufacturing a display panel in which a sealing material is placed in a position enclosing an internal space created between a pair of substrates spaced opposite to each other at a required distance, and the sealing material is heated to be softened at a predetermined temperature and fused to the substrates to seal the internal space between the pair of substrates, comprising:

a sealing process for sealing the internal space between the pair of substrates by use of the sealing material;

a primary evacuation process that is performed for evacuation of the internal space between the pair of substrates after a temperature for heating the sealing material reaches a starting temperature for softening the sealing material, and before the sealing process is performed; and

an introduction process that is performed for introducing replacement gas into the internal space undergoing the primary evacuation process, after the temperature for heating the sealing material reaches the starting temperature for softening the sealing material, and before the sealing process is performed.

2. A method of manufacturing a display panel according to claim 1 , wherein the primary evacuation process, the replacement gas introduction process and the sealing process are performed while the temperature for heating the sealing material is retained either at the starting temperature for softening the sealing material or at a temperature around and higher than the starting temperature for softening the sealing material.

3. A method of manufacturing a display panel according to claim 2 , further comprising a secondary evacuation process that is performed for evacuating the internal space sealed between the pair of substrates while the temperature for heating the sealing material is retained at a predetermined temperature lower than the starting temperature for softening the sealing material, after the primary evacuation process, the replacement gas introduction process and the sealing process are performed.

4. A method of manufacturing a display panel according to claim 2 , further comprising a secondary evacuation process that is performed for evacuating the internal space sealed between the pair of substrates while the temperature for heating the sealing material is retained at a temperature approximately equal to a temperature at which the primary evacuation process, the replacement gas introduction process and the sealing process are performed, after the primary evacuation process, the replacement gas introduction process and the sealing process have been performed.

5. A method of manufacturing a display panel according to claim 1 , wherein the primary evacuation process and the replacement gas introduction process are performed after the temperature for heating the sealing material has reached the starting temperature for softening the sealing material, while the temperature for heating the sealing material is retained at a predetermined temperature lower than the starting temperature for softening the sealing material.

6. A method of manufacturing a display panel according to claim 5 , whereinafter the primary evacuation process and the replacement gas introduction process have been performed, the sealing process is performed while the temperature for heating the sealing material is retained at a predetermined temperature higher than the starting temperature for softening the sealing material.

7. A method of manufacturing a display panel according to claim 6 , further comprising a secondary evacuation process that is performed while the temperature for heating the sealing material is retained at a predetermined temperature lower than the starting temperature for softening the sealing material, after the sealing process has been performed.

8. A method of manufacturing a display panel according to claim 5 , wherein after the primary evacuation process and the replacement gas introduction process have been performed, the sealing process is performed while the temperature for heating the sealing material is retained at a predetermined temperature lower than the starting temperature for softening the sealing material.

9. A method of manufacturing a display panel according to claim 8 , further comprising a secondary evacuation process that is performed while the temperature for heating the sealing material is retained at a predetermined temperature lower than the starting temperature for softening the sealing material, after the sealing process has been performed.

10. A method of manufacturing a display panel according to claim 6 , further comprising a secondary evacuation process that is performed after a decrease in the temperature of heating the sealing material has been started subsequent to the sealing process and then the decreasing temperature of heating the sealing material reaches a temperature lower than the starting temperature for softening the sealing material.

11. A method of manufacturing a display panel according to claim 1 , wherein the replacement gas includes hydrogen gas.

12. A method of manufacturing a display panel according to claim 11 , wherein a percentage of the hydrogen gas in the replacement gas is equal to or less than 3 percent.

13. A method of manufacturing a display panel according to claim 1 , wherein the replacement gas includes oxygen gas.

14. A method of manufacturing a display panel according to claim 13 , wherein a percentage of the oxygen gas in the replacement gas is equal to or less than 20 percent.

15. A method of manufacturing a display panel according to claim 1 , wherein an evacuation pressure in the primary evacuation process is equal to or lower than 1×10 −2 Pascal.

16. A method of manufacturing a display panel according to claim 1 , wherein in the replacement gas introduction process, the replacement gas of a 100 percent oxygen concentration is introduced.