Display device and method for manufacturing display device

1. A display device, comprising:

a first substrate;

a display unit on the first substrate, the display unit displaying an image; and

a second substrate facing the first substrate with the display unit interposed therebetween, wherein a first portion of the first substrate and a second portion of the second substrate are in contact with each other and are bonded to each other by an optical contact bond, the first and second portions being made of amorphous glass.

2. The display device as claimed in claim 1 , wherein the optical contact bond between the first portion and the second portion is formed by Van der Waal's forces between first molecules of the first portion and second molecules of the second portion.

3. The display device as claimed in claim 1 , wherein the first portion-and the second portion are optical surfaces.

4. The display device as claimed in claim 3 , wherein the first and second portions have a surface flatness of about 0.1λ to about 0.25λ(λ is substantially 632.8 nm).

5. The display device as claimed in claim 4 , wherein the first and second portions have a maximum peak-to-valley roughness of about 100 to about 500 Å or a root-mean-square roughness (RMS value) of about 1 to about 10 Å.

6. The display device as claimed in claim 5 , wherein the first and second portions have a scratch and dig of about 60-40.

7. The display device as claimed in claim 1 , wherein the display unit includes an organic light emitting diode for emitting light.

8. The display device as claimed in claim 1 , wherein the first substrate includes a second protrusion protruding in the direction of the second substrate, the second protrusion contacting the second substrate.

9. The display device as claimed in claim 1 , wherein the second substrate includes a first protrusion protruding in the direction of the first substrate, the first protrusion contacting the first substrate.

10. A display device, comprising:

a first substrate;

a display unit on the first substrate, the display unit displaying an image; and

a second substrate facing the first substrate with the display unit interposed therebetween, wherein:

the first substrate and the second substrate are optical contact bonded to each other,

the second substrate includes a first protrusion protruding in the direction of the first substrate and contacting the first substrate, and

the first substrate includes a second protrusion protruding in the direction of the second substrate contacting the second substrate, the second protrusion contacting the first protrusion.

11. A method for manufacturing a display device, the method comprising:

preparing a first substrate such that the first substrate has a display unit thereon;

preparing a second substrate such that the second substrate faces the first substrate and is in contact therewith the display unit interposed therebetween; and

optical contact bonding a first portion of the first substrate and a second portion of the second substrate together, the first and second portions being made of amorphous glass.

12. The method as claimed in claim 11 , wherein the first and second portions have a surface flatness of about 0.1λ to about 0.25λ (λ is substantially 632.8 nm), a maximum peak-to-valley roughness of about 100 to about 500 Å or a root-mean-square roughness (RMS value) of about 1 to about 10 Å, and a scratch and dig of about 60-40.

13. The method of claim 12 , wherein preparing the first substrate and the second substrate includes washing the first and second portions, wherein washing the first and second portions includes:

removing inorganic materials from the first and second portions;

removing organic materials from the first and second portions with hydrochloric acid (HCl);

firstly washing the first and second portions with acetone; and

secondly washing the first and second portions with alcohol.

14. The method as claimed in claim 12 , wherein the optical contact bonding of the first substrate and the second substrate includes pressing the first and second substrates together with a pressure of about 0.2 to about 1.2 kg/cm 2 .

15. The method as claimed in claim 14 , wherein the optical contact bonding of the first substrate and the second substrate includes heating the first substrate and the second substrate, and the first and second substrates are heated to a temperature of about 30 to about 520° C.

16. The method as claimed in claim 13 , further comprising optically polishing the first portion of the first substrate and the second portion of the second substrate before washing the first portion of the first substrate and the second portion of the second substrate,

wherein the polishing and washing are performed prior to the optical contact bonding.

17. The method as claimed in claim 11 , wherein the optical contact bonding forms an optical contact bond between the first portion and the second portion, the optical contact bond being formed by Van der Waal's forces between first molecules of the first portion and second molecules of the second substrate.

18. The method as claimed in claim 11 , wherein the first and second substrates are prepared such that each of the first and second substrates includes a protrusion protruding in the direction of and contacting a protrusion of the other of the first and second substrates.