Liquid crystal display with edge-lit backlight which uses ambient light injected between reflector and cholesteric polarizer

• US 6,160,595 A
• Filed: 06/09/1997
• Issued: 12/12/2000
• Est. Priority Date: 06/11/1996
• Status: Expired due to Term

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Kishimoto, Keiko
• Primary Examiner(s): Parker, Kenneth
• Application Number:
  US08/871,616
• Time in Patent Office: 1,282 Days
• Field of Search: 349/115, 349/104, 349/106, 349/194, 349/176, 349/98, 349/65, 349/62, 349/61
• US Class Current: 349/61
• CPC Class Codes: G02F 1/133536 Reflective polarizers G02F1/13362 takes precedence
• CPC Class Codes: G02F 1/133543 Cholesteric polarisers
• CPC Class Codes: G02F 1/133553 Reflecting elements associated to illuminating devices G02F1/133605
• CPC Class Codes: G02F 1/133638 Waveplates, i.e. plates with a retardation value of lambda/n
• CPC Class Codes: G02F 2413/15 with twisted orientation, e.g. comprising helically oriented LC-molecules or a plurality of twisted birefringent sublayers

Abstract

An object of the invention is to obtain brighter display in a liquid crystal display apparatus. Light of all the wavelengths in the visible range is converted into circularly polarized light by a first polarization condition converting member, converted into linearly polarized light by a second polarization condition converting member and is modulated by a liquid crystal display device. Then, transmission and block of the light is controlled by a polarizer. Specifically, one of the dextrorotatory circularly polarized light and the levorotatory circularly polarized light is reflected by a spectral member included in the first polarization condition converting member, converted into the other circularly polarized light by a reflecting member included in the first polarization condition converting member and supplied again to the spectral member. The other circularly polarized light is transmitted by the spectral member. Thus, by converting light of all the wavelengths in the visible range into circularly polarized light and then converting the circularly polarized light into linearly polarized light, in principle, 100% of the light is incident on a liquid crystal display device, so that brighter display is achieved.

Claims

1. A transmission, reflection-type liquid crystal display apparatus comprising in the following order:

first means for converting all of the light of all wavelengths in a visible range into circularly polarized light;

second means for converting the circularly polarized light obtained through conversion by the first converting means into linearly polarized light;

a liquid crystal display device for modulating the linearly polarized light obtained through conversion by the second converting means; and

a polarizer for controlling transmission and blocking of the light which has exited from the liquid crystal display device,

wherein the first conversion means includes;

spectral means for reflecting one of dextrorotary circularly polarized light and levorotary circularly polarized light of the circularly polarized light, the spectral means being composed of a polymer liquid crystal film formed of cholesteric liquid crystal whose liquid crystal molecules are twisted along a thickness;

reflecting means disposed at a distance from the spectral means for converting the one circularly polarized light reflected by the spectral means into the other circularly polarized light to supply the other circularly polarized light again to the spectral means; and

ambient light introducing means for effectively introducing ambient light into a gap between the spectral means and the reflecting means,

wherein the second converting means is composed of a 1/4 wave plate formed of a uniaxially drawn polymer film;

wherein a portion of the light used to illuminate the liquid crystal display device passes through the liquid crystal display device only once.

2. The reflection-type liquid crystal display apparatus of claim 1, wherein said spectral means and said reflection means are disposed at an angle to each other to provide an opening through which light can be directed between said spectral means and said reflection means to reflect from said reflection means through said spectral means and said liquid crystal display device.

3. A transmission, reflecting-type liquid crystal display apparatus consisting essentially of and in the following order:

first means for converting all of the light of all wavelengths in a visible range into circularly polarized light;

second means for converting the circularly polarized light obtained through conversion by the first converting means into linearly polarized light;

a liquid crystal display device for modulating the linearly polarized light obtained through conversion by the second converting means;

optical compensation means for compensating coloration of light having exited from the liquid crystal display device; and

a polarizer for controlling transmission and blocking of the light which has exited from the liquid crystal display device,

wherein the first conversion means includes;

spectral means for reflecting one of dextrorotary circularly polarized light and levorotary circularly polarized light of the circularly polarized light, the spectral means being composed of a polymer liquid crystal film formed of cholesteric liquid crystal whose liquid crystal molecules are twisted along a thickness;

reflecting means disposed at a distance from the spectral means for converting the one circularly polarized light reflected by the spectral means into the other circularly polarized light to supply the other circularly polarized light again to the spectral means; and

ambient light introducing means for effectively introducing ambient light into a gap between the spectral means and the reflecting means,

wherein the second converting means is composed of a 1/4 wave plate formed of a uniaxially drawn polymer film, and

wherein the polarizer controls transmission and blocking of the light whose compensation has been conducted by the optical compensation means;

wherein a portion of the light used to illuminate the liquid crystal display device passes through the liquid crystal display device only once.

4. The reflection-type liquid crystal display apparatus of claim 3, wherein said spectral means and said reflection means are disposed at an angle to each other to provide an opening through which light can be directed between said spectral means and said reflection means to reflect from said reflection means through said spectral means and said liquid crystal display device.

5. A terminal apparatus comprising a reflecting-type liquid crystal display apparatus having a spectral means and a reflecting means, and

ambient light introducing means for effectively introducing ambient light into a gap between the spectral means and the reflecting means of the liquid display apparatus:

the reflecting-type liquid crystal display apparatus comprising in the following order;

first means for converting all of the light of all wavelengths in a visible range into circularly polarized light;

second means for converting the circularly polarized light obtained through conversion by the first converting means into linearly polarized light;

a liquid crystal display device for modulating the linearly polarized light obtained through conversion by the second converting means; and

a polarizer for controlling transmission and blocking of the light which has exited from the liquid crystal display device,

wherein the first conversion means includes;

spectral means for reflecting one of dextrorotary circularly polarized light and levorotary circularly polarized light of the circularly polarized light, the spectral means being composed of a polymer liquid crystal film formed of cholesteric liquid crystal whose liquid crystal molecules are twisted along a thickness; and

reflecting means disposed at a distance from the spectral means for converting the one circularly polarized light reflected by the spectral means into the other circularly polarized light to supply the other circularly polarized light again to the spectral means, and

wherein the second converting means is composed of a 1/4 wave plate formed of a uniaxially drawn polymer film.

6. The terminal apparatus of claim 5, wherein a light incident plane of the spectral means and a light reflecting plane of the reflecting means are disposed opposite to each other to form a predetermined angle.

7. The terminal apparatus of claim 5, further comprising a light source, wherein the first converting means further includes means disposed between the spectral means and the reflecting means for directing the incident light from the light source.

8. The terminal apparatus of claim 5, further comprising optical compensation means for compensating coloration of light having exited from the liquid crystal display device,

wherein the polarizer controls transmission and block of the light whose coloration compensation has been conducted by the optical compensation means.

9. The terminal apparatus of claim 8,

wherein a product d·

Δ

n of a thickness d of a liquid crystal layer of the liquid crystal display device and a refractive index anisotropy Δ

n is selected to be in a range between 0.77 μ

m and 0.90 μ

m,

the optical compensation means has two phase difference plates each having a retardation value which is selected to be in a range between 0.39 μ

m and 0.46 μ

m, and

an angle between axes of retardation of the phase difference plates is selected to be in a range between 20° and

40°

.

11. The terminal apparatus of claim 5, wherein said spectral means and said reflection means are disposed at an angle to each other to provide an opening through which light can be directed between said spectral means and said reflection means to reflect from said reflection means through said spectral means and said liquid crystal display device.

10. The terminal apparatus of claim 18,

wherein a product d·

Δ

n of a thickness d of a liquid crystal layer of the liquid crystal display device and a refractive index anisotropy Δ

n is selected to be in a range between 0.77 μ

m and 0.90 μ

m, and

the optical compensation means has a retardation value which is selected to be in a range between 0.89 and 0.95 times the product d·

Δ

n of the thickness d of the liquid crystal layer of the liquid crystal display device and the refractive index anisotropy Δ

n and rotates light in an opposite direction but by the same angle as in the liquid crystal display device.