Micro-optical element having high bonding strength between glass substrate and micro-structure layer

1. A micro-optical element comprising:

a glass substrate;

a microstructure layer of polymer imprinted on the glass substrate; and

a bonding strength between the microstructure layer and the glass substrate that is higher than 0.5 MPa,

wherein the glass substrate has a thickness less than or equal to 1500 μm, a Total Thickness Variation (TTV) less than or equal to 40 μm, and a thickness tolerance of less than or equal to 80 μm.

2. The micro-optical element of claim 1 , wherein the bonding strength is higher than 1.5 MPa, the thickness is less than or equal to 1100 μm, the TTV is less than or equal to 5 μm, and the thickness tolerance is less than or equal to 2 μm.

3. The micro-optical element of claim 1 , wherein the glass substrate has a special number of Non-Bridge Oxygen (NBO) greater than or equal to 0.3, wherein NBO=(R 2 O+R′O)/(P 2 O 5 +Al 2 O 3 +B 2 O 3 +TiO 2 +ZrO 2 ),

wherein R is alkali metal selected from a group consisting of Li, Na, and K; and

R′ is alkali earth metal selected from a group consisting of Mg, Ca, and Ba, and

wherein the glass substrate has a glue contact angle of less than 35°.

4. The micro-optical element of claim 3 , wherein the NBO is greater than or equal to 2 and/or wherein the glue contact angle is less than 15°.

5. The micro-optical element of claim 1 , wherein the glass substrate has a ratio X=(R 2 O+R′O−P 2 O 5 −Al 2 O 3 −B 2 O 3 )/(SiO 2 +P 2 O 5 +Al 2 O 3 +B 2 O 3 ) that is more than −0.2,

wherein R is alkali metal selected from a group consisting of Li, Na, and K; and

R′ is alkali earth metal selected from a group consisting of Mg, Ca, and Ba, and

wherein the glass substrate has a glue contact angle of less than 35°.

6. The micro-optical element of claim 5 , wherein the ratio X is more than 0.2 and/or wherein the glue contact angle is less than 15°.

7. The micro-optical element of claim 1 , wherein the glass substrate has a warp of less than or equal to 500 μm.

8. The micro-optical element of claim 1 , wherein the glass substrate exhibits a ratio of the TTV to the thickness of less than 10%.

9. The micro-optical element of claim 1 , wherein the glass substrate has a surface roughness (Ra) of less than or equal to 20 nm.

10. The micro-optical element of claim 1 , wherein the glass substrate has a composition, in mol % based on oxide, comprising:

Components

Proportion (mol %)

SiO2

60-83,

B2O3

 0-12,

Na2O

 0-13,

K2O

0-7,

MgO

0-7,

CaO

 0-10,

BaO

0-1,

TiO2

      0-4, and

ZnO

0-6.

11. The micro-optical element of claim 1 , wherein the glass substrate has a refractive index (n d ) in a range from 1.4 to 2.5.

12. The micro-optical element of claim 11 , wherein the refractive index (n d ) is in the range from 1.45 to 1.6.

13. The micro-optical element of claim 1 , wherein the glass substrate has a transmission index (T) greater than or equal to 90% and/or has a Coefficient of Thermal Expansion (CTE 20-300° C. ) less than or equal to 15×10 −6 /K.

14. The micro-optical element of claim 1 , further comprising a ratio of a Coefficient of Thermal Expansion of glass the glass substrate (CTE glass ) to a Coefficient of Thermal Expansion of polymer of the microstructure layer (CTE polymer ) that is less than or equal to 100.

15. The micro-optical element of claim 14 , wherein the ratio is less than or equal to 80.

16. The micro-optical element of claim 1 , further comprising a difference of a refractive index (n d ) between the glass substrate and the microstructure layer that is less than or equal to 0.5.

17. The micro-optical element of claim 1 , wherein the glass substrate comprises a glass selected from a group consisting of silicate glass, borosilicate glass, aluminosilicate glass, aluminum borosilicate glass, soda lime glass, and lithium aluminum silicate glass.

18. The micro-optical element of claim 1 , wherein the microstructure layer consists of a polymer of epoxy resins or acrylic resins.

19. The micro-optical element of claim 1 , wherein the glass substrate has a ratio X=(R 2 O+R′O−P 2 O 5 −Al 2 O 3 −B 2 O 3 )/(SiO 2 +P 2 O 5 +Al 2 O 3 +B 2 O 3 ) that is more than 0,

wherein R is alkali metal selected from a group consisting of Li, Na, and K; and

R′ is alkali earth metal selected from a group consisting of Mg, Ca, and Ba, and

wherein the glass substrate has a glue contact angle of less than 35°.

20. The micro-optical element of claim 1 , wherein the glass substrate has a ratio X=(R 2 O+R′O−P 2 O 5 −Al 2 O 3 −B 2 O 3 )/(SiO 2 +P 2 O 5 +Al 2 O 3 +B 2 O 3 ) that is more than 0.2,

wherein R is alkali metal selected from a group consisting of Li, Na, and K; and

R′ is alkali earth metal selected from a group consisting of Mg, Ca, and Ba, and

wherein the glass substrate has a glue contact angle of less than 35°.

21. A method for manufacturing a micro-optical element, comprising:

providing a glass substrate with a thickness less than or equal to 1500 μm, a Total Thickness Variation (TTV) less than or equal to 40 μm, and a thickness tolerance of less than or equal to 80 μm; and

applying a microstructured polymer layer to the glass substrate to form a microstructure layer such that a bonding strength between the microstructure layer and the glass substrate is higher than 0.5 MPa.

22. The method of claim 21 , wherein the step of applying the microstructured polymer layer comprises homogenously applying the microstructured polymer layer using a process selected from a group consisting of spin coating, spray coating, and deposition.

23. The method of claim 21 , wherein the step of applying the microstructured polymer layer comprises:

depositing a polymer layer onto a first side of the glass substrate positioning a template above the polymer;

pressing the template into the polymer layer;

curing the polymer layer to a cured polymer layer;

releasing the template from the cured polymer with features of the template imprinted therein.

24. The method of claim 23 , wherein the template is a UV-transparent template and the step of curing comprises UV curing.