Display assembly and display apparatus

1. A display assembly, comprising a convex lens, a refractive index-adjustable layer, and a light-absorbing layer, wherein:

the refractive index-adjustable layer is disposed between a convex surface of the convex lens and the light-absorbing layer; and

the refractive index-adjustable layer is configured to have a refractive index adjustable between less than, and no less than, a critical value, configured such that a light incident into the convex lens from a side opposing to the refractive index-adjustable layer:

has a total reflection to thereby realize a bright state for the display assembly if the refractive index of the refractive index-adjustable layer is less than the critical value; and

transmits through the refractive index-adjustable layer and reaches the light-absorbing layer for absorption to thereby realize a dark state for the display assembly if the refractive index of the refractive index-adjustable layer is no less than the critical value.

2. The display assembly of claim 1 , wherein:

the convex lens is in direct contact with the refractive index-adjustable layer; and

the critical value is a refractive index of the convex lens.

3. The display assembly of claim 1 , further comprising a transparent film layer, disposed between the convex lens and the refractive index-adjustable layer, wherein:

the transparent film layer is in direct contact with the refractive index-adjustable layer; and

the critical value is a refractive index of the transparent film layer.

4. The display assembly of claim 1 , wherein the refractive index-adjustable layer comprises an electro-optic material layer or a piezoelectric material layer.

5. The display assembly of claim 4 , wherein the refractive index-adjustable layer comprises an electro-optic material layer, and the display assembly further comprises:

a first electrode layer, disposed between the convex lens and the electro-optic material layer, and comprising a transparent electrode material having a refractive index no less than the convex lens; and

a second electrode layer, disposed over a side surface of the electro-optic material layer opposing to the convex lens;

wherein:

the first electrode layer and the second electrode layer are configured to receive a voltage to form an electrical field therebetween, wherein the electrical field is configured to cause a change of the refractive index of the electro-optic material layer from an initial refractive index in an absence of the electrical field.

6. The display assembly of claim 5 , wherein a relationship between the change of the refractive index of the electro-optic material layer (Δn) and a strength of the electrical field between the first electrode layer and the second electrode layer (E) is described using a formula:

Δ n=n 0 3 rE/ 2= n 0 3 rU/ 2 d;

where n 0 is the initial refractive index of the electro-optic material layer in an absence of the electrical field, r is an electro-optic coefficient of the electro-optic material layer, U is the voltage applied to the electro-optic material layer, and d is a thickness of the electro-optic material layer.

7. The display assembly of claim 6 , wherein the initial refractive index of the electro-optic material layer is less than the critical value, and the voltage applied to the electro-optic material layer is configured to result in a second refractive index of the electro-optic material layer no less than the critical value.

8. The display assembly of claim 6 , wherein the initial refractive index of the electro-optic material layer is no less than the critical value, and the voltage applied to the electro-optic material layer is configured to result in a second refractive index of the electro-optic material layer less than the critical value.

9. The display assembly of claim 5 , wherein the critical value is the refractive index of the first electrode layer.

10. The display assembly of claim 5 , wherein the second electrode layer is the light-absorbing layer.

11. The display assembly of claim 5 , wherein the electro-optic material layer comprises an inorganic electro-optic material having an asymmetric center in a crystal structure thereof.

12. The display assembly of claim 11 , wherein the inorganic electro-optic material comprises at least one of potassium dihydrogen phosphate, ammonium dihydrogen phosphate, lithium niobate, or lithium iodate.

13. The display assembly of claim 5 , wherein the electro-optic material layer comprises an organic electro-optic material.

14. The display assembly of claim 13 , wherein the organic electro-optic material comprises polyurethane polymer.

15. The display assembly of claim 14 , wherein the polyurethane polymer comprises PMMA-AMA.

16. The display assembly of claim 5 , wherein the convex lens comprises resin.

17. The display assembly of claim 5 , wherein the first electrode layer comprises ITO.

18. The display assembly of claim 1 , wherein the convex surface of the convex lens is in a shape of a hemisphere or an ellipsoid.

19. A display apparatus, comprising at least one display assembly, wherein each of the at least one display assembly is a display assembly according to claim 1 .

20. The display apparatus according to claim 19 , comprising a plurality of display assemblies, arranged in an array.