Optical compensation apparatus and a method for manufacturing the same, and a liquid crystal device having the optical compensation apparatus

Abstract

An optical compensation structure and its fabricating process are disclosed. The optical compensation structure comprises an upper polarizer film, a transparent substrate, a first retarder film (C+ plate), and a second retarder film (A-plate). The upper polarizer film provides polarization function and possesses a top surface and a bottom surface. The transparent substrate is directly laminated onto the top surface of upper polarizer film. The first retarder film is coated with a bonding layer made of crosslinking agent on one side and the bonding layer is directly laminated onto the bottom surface of upper polarizer film. The second retarder film binds to the side of first retarder film away from the upper polarizer film. The optical compensation structure is coated with the bonding layer to address the drawback of prior art where the upper polarizer film and the first retarder film are not closely adhered to each other, thereby allowing the use of one less substrate and offering a thinner compensation structure. When applied to liquid crystal display (LCD), the optical compensation structure improves the contrast and color shift problems of LCD at oblique viewing angles.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The details of the present invention will be more readily understood from a detailed description of the preferred embodiments taken in conjunction with the following figures.

FIG. 1A shows the sectional view of a conventional LCD.

FIG. 1B shows the color distribution curve of conventional IPS LCD under completely dark screen.

FIG. 1C shows the contrast curve under the viewing range of a conventional IPS LCD.

FIG. 2A shows the flow process of adding a retarder film to a conventional LCD upper polarizer.

FIG. 2B shows the sectional view of a conventional LCD added with optical compensation structure.

FIG. 3 shows the sectional view of an optical compensation structure according to a first preferred embodiment of the present invention.

FIG. 4A shows the process flow for the first preferred embodiment of optical compensation structure in FIG. 3.

FIG. 4B shows a working diagram of the process for the first preferred embodiment of optical compensation structure in FIG. 3.

FIG. 5 shows the sectional view of an optical compensation structure according to a second preferred embodiment of the present invention.

FIG. 6A shows the process flow for the second preferred embodiment of optical compensation structure in FIG. 5.

FIG. 6B shows a working diagram of the process for the second preferred embodiment of optical compensation structure in FIG. 5.

FIG. 7 shows the sectional view of a LCD device with optical compensation structure according to a first embodiment of the invention.

FIG. 8 shows the contrast curve under the viewing range of a LCD device with optical compensation structure according to a first preferred embodiment of the invention.

FIG. 9 shows the sectional view of a LCD with optical compensation structure according to a second preferred embodiment of the invention.

FIG. 10 shows the contrast curve under the viewing range of a LCD with optical compensation structure according to a second embodiment of the invention.

Claims

1. An optical compensation structure, comprising: an upper polarizer film which provides polarization function and has a top surface and a bottom surface thereon;a transparent substrate directly laminated onto the top surface of upper polarizer film;a first retarder film coated with a bonding layer on one side which is directly adhered to the bottom surface of upper polarizer film; anda second retarder film which binds to the side of upper polarizer film away from the first retarder film.

2. The optical compensation structure according to claim 1, wherein a pressure sensitive adhesive layer is disposed between the first retarder film and the second retarder film.

3. The optical compensation structure according to claim 1, wherein an adhesive layer is further disposed between the bonding layer and the upper polarizer film.

4. The optical compensation structure according to claim 1, wherein the bonding layer is made of a coupling agent, a crosslinking agent or a primer.

5. The optical compensation structure according to claim 1, wherein said first retarder film satisfies the optical condition of nx=ny<nz; the second retarder film satisfies the optical condition of nx>ny=nz; where nx denotes the refractive index along x-axis of surface; ny denotes the refractive index along y-axis of surface; nz is thicknesswise refractive index along z-axis.

6. The optical compensation structure according to claim 5, wherein the first retarder film and the second retarder film further satisfy the optical conditions of: 0.1 nm<Ro(a)+Ro(b)<220 nm;−270 nm<Rth(a)+Rth(b)<60 nm; and−300 nm<Rth(a)<−10 nm;where Ro(a) and Rth(a) are respectively the in-plane retardation (Ro) and out-of-plane retardation (Rth) of first retarder film; Ro(b) and Rth(b) are respectively the Ro and Rth of second retarder film; and Ro=(nx−ny)*d; Rth={(nx+ny)/2−nz}*d; and d is film thickness.

7. A liquid crystal display device having optical compensation structure, comprising: a liquid crystal cell defined with a liquid crystal orientation and consisting of a upper side and a lower side;a lower polarizer disposed on the lower side of liquid crystal cell and defined with an extension direction which is the same as the liquid crystal orientation; andan upper polarizer with an optical compensation structure disposed on the upper side of liquid crystal cell and further comprising: an upper polarizer film which provides polarization function and is defined with an extension direction perpendicular to the extension direction of lower polarizer;a transparent substrate directly laminated onto the side of upper polarizer film away from the liquid crystal cell;a first retarder film coated with a bonding layer on one side which is directly adhered to the side of upper polarizer film closer to the liquid crystal cell; anda second retarder film which binds to the side of first retarder film closer to the liquid crystal cell and is defined with a direction of maximum refractivity perpendicular to the liquid crystal orientation.

8. The liquid crystal display device according to claim 7, wherein the lower polarizer further comprises: a lower polarizer film which provides polarization function;at least a transparent substrate directly laminated onto the side of lower polarizer film away from the liquid crystal cell; anda third retarder film adhered to the side of lower polarizer film closer to the liquid crystal cell and defined with a direction of maximum refractivity identical to the liquid crystal orientation.

9. The liquid crystal display device according to claim 8, wherein there are two transparent substrates with one of them disposed between the third retarder film and the lower polarizer film.

10. The liquid crystal display device according to claim 8, wherein said retarder film satisfies the optical condition of nx>ny=nz; where nx denotes the refractive index along x-axis of surface; ny denotes the refractive index along y-axis of surface; nz is thicknesswise refractive index along z-axis.

11. The liquid crystal display device according to claim 7, wherein a pressure sensitive adhesive layer is disposed between the first retarder film and the second retarder film.

12. The liquid crystal display device according to claim 7, wherein an adhesive layer is further disposed between the bonding layer and the upper polarizer film.

13. The liquid crystal display device according to claim 7, wherein the bonding layer is made of a coupling agent, a crosslinking agent or a primer.

14. The liquid crystal display device according to claim 7, wherein said first retarder film satisfies the optical condition of nx=ny<nz; the second retarder film satisfies the optical condition of nx>ny=nz; where nx denotes the refractive index along x-axis of surface; ny denotes the refractive index along y-axis of surface; nz is thicknesswise refractive index along z-axis.

15. The liquid crystal display device according to claim 14, wherein the first retarder film and the second retarder film further satisfy the optical conditions of: 0.1 nm<Ro(a)+Ro(b)<220 nm;−270 nm<Rth(a)+Rth(b)<60 nm; and−300 nm<Rth(a)<−10 mn;

16. A process for fabricating optical compensation structure, comprising the steps of: providing a second retarder film having a first surface and a second surface opposing each other;coating on the first surface in sequence an alignment layer and a liquid crystal layer; the combination of alignment layer and the liquid crystal layer forms essentially a first retarder film on the second retarder film;coating a bonding layer on the first retarder film; andbinding the bonding layer to an upper polarizer film and a transparent substrate such that the upper polarizer film is disposed on the first retarder film through the bonding layer to constitute the optical compensation structure.

17. The optical compensation structure according to claim 16, wherein the bonding layer is made of a coupling agent, a crosslinking agent or a primer.

18. The process according to claim 16, wherein said first retarder film satisfies the optical condition of nx=ny<nz; the second retarder film satisfies the optical condition of nx>ny=nz; where nx denotes the refractive index along x-axis of surface; ny denotes the refractive index along y-axis of surface; nz is thicknesswise refractive index along z-axis.

19. The process according to claim 17, wherein the first retarder film and the second retarder film further satisfy the optical conditions of: 0.1 nm<Ro(a)+Ro(b)<220 nm;−270 nm<Rth(a)+Rth(b)<60 nm; and−300 nm<Rth(a)<−10 nm;where Ro(a) and Rth(a) are respectively the in-plane retardation (Ro) and out-of-plane retardation (Rth) of first retarder film; Ro(b) and Rth(b) are respectively the Ro and Rth of second retarder film; and Ro=(nx−ny)*d; Rth={(nx+ny)/2−nz}*d; and d is film thickness.