# US 2014/0192304 A1 · Optical Compensation Film Group and Method for Reducing Light Leakage of Vertical Alignment LCD Using the Same

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- Number: US 2014/0192304 A1
- Document ID: US20140192304A1
- Status: Published application
- Kind: A1
- Application number: 13/697,854
- Filed: 2012-09-28
- Published: 2014-07-10
- Earliest claimed: 2012-09-24
- Assignees: Shenzhen China Star Optoelectronics Technology Co., Ltd.
- Applicants: Shenzhen China Star Optoelectronics Technology Co. Ltd.
- Inventors: Chih-Tsung Kang; Bo Hai
- Web page: https://patentgrep.com/patent/US20140192304A1

## CPC

- G02F 1/133362: {Optically addressed liquid crystal cells (G02F1/135 takes precedence)}
- G02F 1/133634: {the refractive index Nz perpendicular to the element surface being different from in-plane refractive indices Nx and Ny, e.g. biaxial or with normal optical axis}
- G02F 1/133742: {for homeotropic alignment}
- G02F 2413/04: Number of plates greater than or equal to 4
- G02F 2413/05: Single plate on one side of the LC cell
- G02F 2413/06: Two plates on one side of the LC cell
- G02F 2413/12: Biaxial compensators
- G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS

## Abstract

The present invention provides an optical compensation film group and a method for reducing light leakage of a vertical alignment LCD using the same. For the vertical alignment LCD at a wavelength of 550 nm, an LCΔnd in the range of [305.8 nm, 324.3 nm], and a pretilt angle in the range of [85°, 90°), a compensation value Ro of an in-plane optical path difference of the biaxial compensation film is in the range of 48 nm≦Ro≦84 nm, and a compensation value Rth of an out-of-plane optical path difference of the biaxial compensation film is in the range of 160 nm≦Rth≦280 nm, and a TAC compensation film having a compensation value Rth is in the range of Y1≦Rth≦Y2. The present invention can effectively improve the serious light leakage caused by the conventional compensation structure with a single biaxial compensation film, the contrast and sharpness at the large viewing angles, and the costs.

## Claims

### Claim 1

An optical compensation film group for a vertical alignment LCD, and for the vertical alignment LCD at a wavelength of 550 nm, an LC Δnd in the range of [305.8 nm, 324.3 nm], and a pretilt angle in the range of [85°, 90°), the optical compensation film group comprising:
a biaxial compensation film having a compensation value Ro of an in-plane optical path difference in the range of 48 nm≦Ro≦84 nm and a compensation value Rth of an out-of-plane optical path difference in the range of 160 nm≦Rth≦280 nm; and
a TAC compensation film having a compensation value Rth in the range of Y1≦Rth≦Y2, wherein:
Y1=0.005505x2−3.25016x+477.1;
Y2=−0.00625119x2+1.762274x+32; and
x representing the compensation value Rth of the out-of-plane optical path difference of the biaxial compensation film.

### Claim 2

A method for reducing light leakage of a vertical alignment LCD using optical compensation film group, wherein the optical compensation film group comprises a biaxial compensation film and a TAC compensation film, and for the vertical alignment LCD at a wavelength of 550 nm, an LC Δnd in the range of [305.8 nm, 324.3 nm], and a pretilt angle in range of [85°, 90°], the method comprising steps of:
adjusting a compensation value Ro of an in-plane optical path difference of the biaxial compensation film in the range of 48 nm≦Ro≦84 nm;
adjusting a compensation value Rth of an out-of-plane optical path difference of the biaxial compensation film in the range of 160 nm≦Rth≦280 nm; and
adjusting a compensation value Rth of the TAC compensation film in the range of Y1≦Rth≦Y2, wherein:
Y1=0.005505x2−3.25016x+477.1;
Y2=−0.00625119x2+1.762274x+32; and
x representing the compensation value Rth of the out-of-plane optical path difference of the biaxial compensation film.

### Claim 3 (depends on 2)

The method according to claim 2, wherein, the step of adjusting the compensation value Ro of the in-plane optical path difference of the biaxial compensation film in the range of 48 nm≦Ro≦84 nm and the step of adjusting the compensation value Rth of the out-of-plane optical path difference of the biaxial compensation film in the range of 160 nm≦Rth≦280 nm comprises:
when refractive index values Nx, Ny, Nz of the biaxial compensation film are known, adjusting a thickness d of the biaxial compensation film according to a following formula to produce the compensation value Ro of the in-plane optical path difference of the biaxial compensation film in the range of 48 nm≦Ro≦84 nm and the compensation value Rth of the out-of-plane optical path difference of the biaxial compensation film in the range of 160 nm≦Rth≦280 nm, the formula:
Ro=(Nx−Ny)*d
Rth=[(Nx+Ny)/2−Nz]*d
wherein, Nx representing the refractive index value in a X direction which gives a maximum refractive index value in the plane of the biaxial compensation film, Ny representing the refractive index value in a Y direction which is orthogonal to the X direction in the plane of the biaxial compensation film, and Nz representing the refractive index value in a thickness direction of the biaxial compensation film.

### Claim 4 (depends on 2)

The method according to claim 2, wherein, the step of adjusting the compensation value Rth of the TAC compensation film in the range of Y1≦Rth≦Y2 comprises:
when refractive index values Nx, Ny, Nz of the TAC compensation film are known, adjusting a thickness d of the TAC compensation film according to a following formula to produce the compensation value Rth of the TAC compensation film in the range of Y1≦Rth≦Y2, the formula:
Rth=[(Nx+Ny)/2−Nz]*d
wherein, Nx representing the refractive index value in a X direction which gives a maximum refractive index value in the plane of the TAC compensation film, Ny representing the refractive index value in a Y direction which is orthogonal to the X direction in the plane of the TAC compensation film, and Nz representing the refractive index in a thickness direction of the TAC compensation film.

### Claim 5 (depends on 2)

The method according to claim 2, wherein, the step of adjusting the compensation value Ro of the in-plane optical path difference of the biaxial compensation film in the range of 48 nm≦Ro≦84 nm and adjusting the compensation value Rth of the out-of-plane optical path difference in the range of 160 nm≦Rth≦280 nm comprises:
when a thickness d of the biaxial compensation film is known, adjusting refractive index value Nx, Ny, Nz of the biaxial compensation film according to a following formula to produce the compensation value Ro of the in-plane optical path difference of the biaxial compensation film in the range of 48 nm≦Ro≦84 nm, and the compensation value Rth of the out-of-plane optical path difference of the biaxial compensation film in the range of 160 nm≦Rth≦280 nm, the formula:
Ro=(Nx−Ny)*d
Rth=[(Nx+Ny)/2−Nz]*d
wherein, Nx representing the refractive index value in a X direction which gives a maximum refractive index in the plane of the biaxial compensation film, Ny representing the refractive index value in a Y direction which is orthogonal to the X direction in the plane of the biaxial compensation film, and Nz representing the refractive index value in a thickness direction of the biaxial compensation film.

### Claim 6 (depends on 2)

The method according to claim 2, wherein, the step of adjusting the compensation value Rth of the TAC compensation film in the range of Y1≦Rth≦Y2 comprises:
when a thickness d of the TAC compensation film is known, adjusting refractive index values Nx, Ny, Nz of the TAC compensation film according to a following formula to produce the compensation value Rth of the TAC compensation film in the range of Y1≦Rth≦Y2, the formula:
Rth=[(Nx+Ny)/2−Nz]*d
wherein, Nx representing the refractive index value in a X direction which gives a maximum refractive index value in the plane of the TAC compensation film, Ny representing the refractive index value in a Y direction which is orthogonal to the X direction in the plane of the TAC compensation film, and Nz representing the refractive index value in a thickness direction of the TAC compensation film.

### Claim 7 (depends on 2)

The method according to claim 2, wherein, the step of adjusting the compensation value Ro of the in-plane optical path difference of the biaxial compensation film in the range of 48 nm≦Ro≦84 nm and adjusting the compensation value Rth of the out-of-plane optical path difference of the biaxial compensation film in the range of 160 nm≦Rth≦280 nm comprises:
adjusting refractive index values Nx, Ny, Nz, and a thickness d of the biaxial compensation film at the same time according to a following formula to produce the compensation value Ro of the in-plane optical path difference of the biaxial compensation film in the range of 48 nm≦Ro≦84 nm and the compensation value Rth of the out-of-plane optical path difference of the biaxial compensation film in the range of 160 nm≦Rth≦280 nm, the formula:
Ro=(Nx−Ny)*d
Rth=[(Nx+Ny)/2−Nz]*d
wherein, Nx representing the refractive index value in a X direction which gives a maximum refractive index in the plane of the biaxial compensation film, Ny representing the refractive index value in a Y direction which is orthogonal to the X direction in the plane of the biaxial compensation film, and Nz representing the refractive index value in a thickness direction of the biaxial compensation film.

### Claim 8 (depends on 2)

The method according to claim 2, wherein, the step of adjusting the compensation value Rth of the TAC compensation film in the range of Y1≦Rth≦Y2 comprises:
adjusting refractive index values Nx, Ny, Nz, and a thickness d of the TAC compensation film at the same time according to a following formula to produce the compensation value Rth of the TAC compensation film in the range of Y1≦Rth≦Y2, the formula:
Rth=[(Nx+Ny)/2−Nz]*d
wherein, Nx representing the refractive index value in a X direction which gives a maximum refractive index value in the plane of the TAC compensation film, Ny representing the refractive index value in a Y direction which is orthogonal to the X direction in the plane of the TAC compensation film, and Nz representing the refractive index value in a thickness direction of the TAC compensation film.