Liquid crystal display device

1. A method of fabricating a liquid crystal display device comprising a pair of opposed and spaced substrates, an alignment layer formed on one of said substrates, an alignment layer formed on the other substrate, and a liquid crystal inserted between said pair of substrates, said method comprising the steps of:

forming an alignment layer on each of said substrates; and

irradiating the surface of at least one of said alignment layers with ultraviolet light in the oblique direction, using a mask having a body portion and a plurality of light path changing portions arranged in said body portion corresponding to pixel pitches and having a refractive index different from that of said body portion, and

wherein said body portion has a light incident surface, and said light path changing portions have oblique surfaces inclined with respect to said light incident surface.

2. A method of fabricating a liquid crystal display device as described in claim 1 , characterized in that each of said light path changing portions has a saw-toothed shape having an equilateral triangular cross-section with a bottom side, the length of the bottom side being equal to the length of a pixel pitch, and a shielding layer is formed on a portion of said light path changing portion corresponding to the apex of said equilateral triangle.

3. A method of fabricating a liquid crystal display device as described in claim 2 , characterized in that the following equation (1) is satisfied in the case where θ1≦60,

n 1 cos (3θ1/2)= n 2 sin (θ2−θ1/2)  (1)

and the following equation (2) is satisfied in the case where θ1>60,

n 1 cos (3θ1/2)= n 2 sin (θ2/2−θ2)  (2)

where n1 is the refractive index of said body portion, n2 is the refractive index of said light path changing portions,

θ1 is the apex angle of the saw-toothed section, and

θ2 is the incident angle of the ultraviolet light irradiated on the alignment layer through said light path changing portions.

4. A method of fabricating a liquid crystal display device as described in claim 3 , characterized in that the refractive index n1 of the body portion, the refractive index n2 of the light path changing portions and the apex angle θ1 of the saw-toothed section have the following relationship,

cos θ1>n2/n1.  (5)

5. A method of fabricating a liquid crystal display device as described in claim 4 , characterized in that said light path changing portions are formed of air.

6. A method of fabricating a liquid crystal display device as described in claim 1 , characterized in that each of said light path changing portions is a saw-toothed shape having a trapezoidal cross-section with a bottom side the length of the bottom side being equal to the length of a pixel pitch, and a shielding film is formed on a portion of said light path changing portion corresponding to the upper side of said trapezoid.

7. A method of fabricating a liquid crystal display device as described in claim 6 , characterized in that the following equation (1) is satisfied in the case where θ1≦60,

n 1 cos (3θ1/2)= n 2 sin (θ2−θ1/2)  (1)

and the following equation (2) is satisfied in the case where θ1>60,

n 1 cos (3θ1/2)= n 2 sin (θ2/2−θ2)  (2)

where n1 is the refractive index of said body portion, n2 is the refractive index of said light path changing portions,

θ1 is the apex angle of the saw-toothed section, and θ2 is the incident angle of the ultraviolet light irradiated on the alignment layer through said light path changing portions.

8. A method of fabricating a liquid crystal display device as described in claim 7 , characterized in that the refractive index n1 of the body portion, the refractive index n2 of the light path changing portions and the apex angle θ1 of the saw-toothed section have the following relationship,

cos θ1 >n 2 /n 1.  (5)

9. A method of fabricating a liquid crystal display device as described in claim 8 , characterized in that said light path changing portions are formed of air.

10. A method of fabricating a liquid crystal display device as described in claim 1 , characterized in that said body portion of said mask has a first flat surface, a second surface on the opposite side from said first surface, and a plurality of cavities provided in said second surface, each cavity having first and second oblique surfaces arranged to diverge in the direction from said first surface toward said second surface, and a central line between said first and second oblique surfaces, said light path changing portions being formed by said cavities and a material contained in said cavities,

whereby the ultraviolet light, which is made incident to said body portion from said first surface and passing through said first oblique surface, is applied to said alignment layer in a first oblique direction, and the ultraviolet light, which is made incident to said body portion from said first surface and passing through said second oblique surface, is applied to said alignment layer in a second oblique direction opposite to said first oblique direction.

11. A method of fabricating a liquid crystal display device comprising a pair of opposed and spaced substrates, an alignment layer formed on one of said substrates, an alignment layer formed on the other substrate, a plurality of bus lines provided on one of said substrates, and a liquid crystal inserted between said pair of substrates, said method comprising the steps of:

forming an alignment layer on each of said substrates;

preparing a mask having a body portion and a plurality of light path changing portions arranged in said body portion corresponding to pixel pitches, said body portion of said mask has a first flat surface, a second surface on the opposite side from said first surface, and a plurality of cavities provided in said second surface, each cavity having first and second oblique surfaces arranged on either side of a vertical plane perpendicular to said first surface to diverge in the direction from said first surface toward said second surface, said light path changing portions being formed by said cavities and a material contained in said cavities;

regarding the substrate having said bus lines, putting said mask on said substrate so that said vertical plane between said first and second oblique surfaces is located at a position corresponding to said bus line; and

irradiating the surface of said alignment layer of said substrate with ultraviolet light in the oblique direction, using said mask.

12. A method of fabricating a liquid crystal display device as described in claim 11 , characterized in that said cavity has a saw-toothed shape having an equilateral triangular cross-section, and a shielding layer is formed at a position corresponding to an apex portion of the equilateral triangle.

13. A method of fabricating a liquid crystal display device as described in claim 11 , characterized in that said cavity has a saw-toothed shape having a trapezoidal cross-section, and a shielding layer is formed at a position corresponding to an upper side of the trapezoid.

14. A method of fabricating a liquid crystal display device as described in claim 11 , characterized in that said alignment layer has a vertical aligning property by which the liquid crystal molecules align perpendicular to the surface of the substrate.

15. A method of fabricating a liquid crystal display device as described in claim 11 , characterized in that said liquid crystal has birefringence of cΔε<0.

16. A method of fabricating a liquid crystal display device comprising a pair of opposed and spaced substrates, an alignment layer formed on one of said substrates, an alignment layer formed on the other substrate, a plurality of bus lines provided on one of said substrates, and a liquid crystal inserted between said pair of substrates, said method comprising the steps of:

forming an alignment layer on each of said substrates;

preparing a mask having a body portion and a plurality of light path changing portions arranged in said body portion corresponding to pixel pitches, said body portion of said mask has a first flat surface, a second flat surface on the opposite side from said first surface, and a plurality of cavities provided in said second surface, each cavity having first and second oblique surfaces arranged on either side of a vertical plane perpendicular to said first surface to diverge in the direction from said first surface toward said second surface, said light path changing portions being formed by said cavities and a material contained in said cavities;

regarding the substrate having no such bus lines, putting said mask on said substrate so that an end of said first oblique surface on said second surface and an end of said second oblique surface on said second surface are located at positions corresponding to said bus lines; and

irradiating the surface of said alignment layer of said substrate with the ultraviolet light in the oblique direction, using said mask.

17. A method of fabricating a liquid crystal display device as described in claim 16 , characterized in that said cavity has a saw-toothed shape having an equilateral triangular cross-section, and a shielding layer is formed at a position corresponding to an apex portion of the equilateral triangle.

18. A method of fabricating a liquid crystal display device as described in claim 16 , characterized in that said cavity has a saw-toothed shape having a trapezoidal cross-section, and a shielding layer is formed at a position corresponding to an upper side of the trapezoid.

19. A method of fabricating a liquid crystal display device as described in claim 16 , characterized in that said alignment layer has a vertical aligning property by which the liquid crystal molecules align perpendicular to the surface of the substrate.

20. A method of fabricating a liquid crystal display device as described in claim 16 , characterized in that said liquid crystal has birefringence of cΔε<0.