Reflective liquid crystal display device and reflective liquid crystal display device incorporating touch panel arranged therefrom

• US 6,922,220 B2
• Filed: 03/19/2004
• Issued: 07/26/2005
• Est. Priority Date: 04/23/1997
• 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: Satoh, Takashi, Okamoto, Masayuki, Mitsui, Seiichi
• Primary Examiner(s): Parker, Kenneth
• Assistant Examiner(s): CHUNG, DAVID Y
• Application Number:
  US10/804,109
• Publication Number:
  US 20040174477A1
• Time in Patent Office: 494 Days
• Field of Search: 349/113, 349/117, 349/119, 349/96, 349/97, 349/98
• US Class Current: 349/113
• CPC Class Codes: G02F 1/133528 Polarisers
• CPC Class Codes: G02F 1/133531 characterised by the arrangement of polariser or analyser axes
• CPC Class Codes: G02F 1/133553 Reflecting elements associated to illuminating devices G02F1/133605
• CPC Class Codes: G02F 1/133602 Direct backlight
• CPC Class Codes: G02F 1/13363 Birefringent elements, e.g. for optical compensation
• CPC Class Codes: 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
• CPC Class Codes: G02F 1/1396 the liquid crystal being selectively controlled between a twisted state and a non-twisted state, e.g. TN-LC cell G02F1/141 takes precedence
• CPC Class Codes: G02F 1/1398 the twist being below 90°
• CPC Class Codes: G02F 2202/40 Materials having a particular birefringence, retardation
• CPC Class Codes: G02F 2413/03 Number of plates being 3
• CPC Class Codes: G02F 2413/07 All plates on one side of the LC cell
• CPC Class Codes: G02F 2413/08 with a particular optical axis orientation
• CPC Class Codes: G02F 2413/10 with refractive index ellipsoid inclined, or tilted, relative to the LC-layer surface O plate

Abstract

A reflective color liquid crystal display device with a liquid crystal layer sandwiched between a first substrate having a light reflectibility and a second substrate having a light transmissibility. The liquid crystal layer being composed of twist-aligned nematic liquid crystal having a positive dielectric anisotropy. A circularly polarizing unit, including a single linear polarizer plate, selectively passes either right handed or left handed circularly polarized light out of natural light. The circularly polarizing unit is disposed so that a major surface of the circularly polarizing unit is on a liquid crystal layer side, the circularly polarized light exiting the circularly polarizing unit through the major surface when natural light enters the circularly polarizing unit. Various parameters of the liquid crystal layer are optimized for a liquid crystal layer having a twist angle in the range of 0° to 100°.

Claims

1. A liquid crystal display device, comprising:

a first substrate having a light reflectibility;

a second substrate having a light transmissibility;

a liquid crystal layer sandwiched between the first substrate and the second substrate, the liquid crystal layer being composed of twist-aligned nematic liquid crystal having,

a dielectric anisotropy,

a twist angle in a range of about 0°

to 10°

, and

a birefringence difference, which for twist angle in the range of about 0°

to 5°

if multiplied by a thickness of the liquid crystal layer produces a product in the range of not less than about 90 nm and not more than about 188 nm, or not less than about 382 nm and not more than about 451 nm, and which for twist angle in the range of about 5°

to 10°

if multiplied by a thickness of the liquid crystal layer produces a product in the range of not less than about 90 nm and not more than about 188 nm, or not less than about 380 nm and not more than about 451 nm; and

a circular polarizing unit that selectively passes either right handed or left handed substantially circularly polarized light out of a plurality of wavelengths of natural light in the visible spectrum,

wherein, the circular polarizing unit is disposed such that a major surface of the circular polarizing unit is on a liquid crystal layer side, the substantially circularly polarized light exiting the circular polarizing unit through the major surface when natural light enters the circular polarizing unit, and

wherein, said incoming substantially circularly polarized light being linearly polarized at a surface of said first substrate in a plurality of directions respectively representative of said plurality of wave lengths of said natural light to thereby create a display.

5. The liquid crystal display device as set forth in any one of claims 1, 2, 3 and 4, wherein

the first substrate having a light reflectibility includes a light reflective film, and

the light reflective film has smooth and continuously changing concavities and convexities, and is made of a conductive material.

6. The liquid crystal display device as set forth in any one of claims 1, 2, 3 and 4, further comprising:

one of an optical retardation compensator unit and a plurality of optical retardation compensator units provided between the circular polarizing unit and the liquid crystal layer to minimize influence from a residual phase difference of the liquid crystal layer.

7. The liquid crystal display device as set forth in any one of claims 1, 2, 3 and 4, wherein

the circular polarizing unit performs as an optical retardation compensator that minimizes influence from a residual phase difference of the liquid crystal layer during application of a voltage to the liquid crystal layer.

8. The liquid crystal display device as set forth in any one of claims 1, 2, 3 and 4, wherein the circular polarizing unit includes,

a first optical retardation compensator plate,

a second optical retardation compensator plate having a retardation in a substrate normal direction set to not less than 200 nm and not more than 360 nm, and

a linear polarizer plate, and

wherein, |2×

θ

2−

θ

1| has a value not less than 35° and

not more than 55°

, where θ

1 represents an angle formed by a slow axis of the first optical retardation compensator plate and either a transmission axis or an absorption axis of the linear polarizer plate, and θ

2 represents an angle formed by a slow axis of the second optical retardation compensator plate and either the transmission axis or the absorption axis of the linear polarizer plate,

a direction of the slow axis of the first optical retardation compensator plate is parallel to an alignment direction of a liquid crystal in a middle of the liquid crystal later in a thickness direction, and

a retardation in the substrate normal direction of the first optical retardation compensator plate is set to a retardation that is smaller, by 10 nm to 50 nm, than a retardation for not less than 100 nm and not more than 180 nm that provides, across an entire visible range, a phase difference equivalent to a quarter wavelength.

9. The liquid crystal display device as set forth in any one of claims 1, 2, 3 and 4, wherein the circular polarizing unit includes,

a first optical retardation compensator plate,

a second optical retardation compensator plate having a retardation in a substrate normal direction set to not less than 200 nm and not more than 360 nm, and

a linear polarizer plate, and

wherein, |2×

θ

2−

θ

1| has a value not less than 35° and

not more than 55°

, where θ

1 represents an angle formed by a slow axis of the first optical retardation compensator plate and either a transmission axis or an absorption axis of the linear polarizer plate, and θ

2 represents an angle formed by a slow axis of the second optical retardation compensator plate and either the transmission axis or the absorption axis of the linear polarizer plate,

the slow axis of the first optical retardation compensator plate is orthogonal to an alignment direction of a liquid crystal in a middle of the liquid crystal layer in a thickness direction, and

a retardation in the substrate normal direction of the first optical retardation compensator plate is set to a retardation that is greater, by 10 nm to 50 nm, than a retardation for not less than 100 nm and not more than 180 nm that provides, across an entire visible range, a phase difference equivalent to a quarter wavelength.

2. A liquid crystal display device, comprising:

a first substrate having a light reflectibility;

a second substrate having a light transmissibility;

a liquid crystal layer sandwiched between the first substrate and the second substrate, the liquid crystal layer being composed of twist-aligned nematic liquid crystal having,

a dielectric anisotropy,

a twist angle in a range of about 10°

to 20°

, and

a birefringence difference, which for a twist angle in a range of about 10°

to 15°

if multiplied by a thickness of the liquid crystal layer produces a product in the range of not less than about 90 nm and not more than about 190 nm, or not less than about 378 nm and not more than about 450 nm, and which for a twist angle in a range of about 15°

to 20°

if multiplied by a thickness of the liquid crystal layer produces a product in the range of not less than about 90 nm and not more than about 192 nm, or not less than about 372 nm and not more than about 448 nm; and

a circular polarizing unit that selectively passes either right handed or left handed substantially circularly polarized light out of a plurality of wavelengths of natural light in the visible spectrum,

wherein, the circular polarizing unit is disposed such that a major surface of the circular polarizing unit is on a liquid crystal layer side, the substantially circularly polarized light exiting the circular polarizing unit through the major surface when natural light enters the circular polarizing unit, and

wherein, said incoming substantially circularly polarized light being linearly polarized at a surface of said first substrate in a plurality of directions respectively representative of said plurality of wave lengths of said natural light to thereby create a display.

3. A liquid crystal display device, comprising:

a first substrate having a light reflectibility;

a second substrate having a light transmissibility;

a liquid crystal layer sandwiched between the first substrate and the second substrate, the liquid crystal layer being composed of twist-aligned nematic liquid crystal having,

a dielectric anisotropy,

a twist angle in a range of about 20°

to 30°

, and

a birefringence difference, which for a twist angle in a range of about 20°

to 25°

if multiplied by a thickness of the liquid crystal layer produces a product in the range of not less than about 92 nm and not more than about 195 nm, or not less than about 365 nm and not more than about 448 nm, and which for a twist angle in a range of about 25°

to 30°

if multiplied by a thickness of the liquid crystal layer produces a product in the range of not less than about 95 nm and not more than about 202 nm, or not less than about 356 nm and not more than about 445 nm; and

a circular polarizing unit that selectively passes either right handed or left handed substantially circularly polarized light out of a plurality of wavelengths of natural light in the visible spectrum,

wherein, the circular polarizing unit is disposed such that a major surface of the circular polarizing unit is on a liquid crystal layer side, the substantially circularly polarized light exiting the circular polarizing unit through the major surface when natural light enters the circular polarizing unit, and

wherein, said incoming substantially circularly polarized light being linearly polarized at a surface of said first substrate in a plurality of directions respectively representative of said plurality of wave lengths of said natural light to thereby create a display.

4. A liquid crystal display device, comprising:

a first substrate having a light reflectibility;

a second substrate having a light transmissibility;

a liquid crystal layer sandwiched between the first substrate and the second substrate, the liquid crystal layer being composed of twist-aligned nematic liquid crystal having,

a dielectric anisotropy,

a twist angle in a range of about 30°

to 45°

, and

a birefringence difference, which for a twist angle in a range of about 30°

to 35°

if multiplied by a thickness of the liquid crystal layer produces a product in the range of not less than about 98 nm and not more than about 210 nm, or not less than about 341 nm and not more than about 441 nm, which for a twist angle in a range of about 35°

to 40°

if multiplied by a thickness of the liquid crystal layer produces a product in the range of not less than about 98 nm and not more than about 220 nm, or not less than about 323 nm and not more than about 437 nm, and which for a twist angle in a range of about 40°

to 45°

if multiplied by a thickness of the liquid crystal layer produces a product in the range of not less than about 100 nm and not more than about 240 nm, or not less than about 300 nm and not more than about 432 nm

a circular polarizing unit that selectively passes either right handed or left handed substantially circularly polarized light out of a plurality of wavelengths of natural light in the visible spectrum,

wherein, the circular polarizing unit is disposed such that a major surface of the circular polarizing unit is on a liquid crystal layer side, the substantially circularly polarized light exiting the circular polarizing unit through the major surface when natural light enters the circular polarizing unit, and

wherein, said incoming substantially circularly polarized light being linearly polarized at a surface of said first substrate in a plurality of directions respectively representative of said plurality of wave lengths of said natural light to thereby create a display.

10. A liquid crystal display device, comprising:

a first substrate having a light reflectibility;

a second substrate having a light transmissibility;

a liquid crystal layer sandwiched between the first substrate and the second substrate, the liquid crystal layer being composed of twist-aligned nematic liquid crystal having,

a dielectric anisotropy,

a birefringence difference, which if multiplied by a thickness of the liquid crystal layer produces a product in the range of not less than 100 nm and not more than 185 nm, or not less than 385 nm and not more than 430 nm, and

a twist angle in a range of 0°

to 45°

; and

a circular polarizing unit, including a single linear polarizer plate, that selectively passes either right handed or left handed substantially circularly polarized light out of a plurality of wavelengths of natural light in the visible spectrum,

wherein, the circular polarizing unit is disposed such that a major surface of the circular polarizing unit is on a liquid crystal layer side, the substantially circularly polarized light exiting the circular polarizing unit through the major surface when natural light enters the circular polarizing unit, and

wherein, said incoming substantially circularly polarized light being linearly polarized at a surface of said first substrate in a plurality of directions respectively representative of said plurality of wave lengths of said natural light to thereby create a display.

11. A liquid crystal display device, comprising:

a first substrate having a light reflectibility;

a second substrate having a light transmissibility;

a liquid crystal layer sandwiched between the first substrate and the second substrate, the liquid crystal layer being composed of twist-aligned nematic liquid crystal having,

a dielectric anisotropy,

a birefringence difference, which if multiplied by a thickness of the liquid crystal layer produces a product in the range of not less than 95 nm and not more than 125 nm, and

a twist angle in a range of 0°

to 45°

; and

a circular polarizing unit, including a single linear polarizer plate, that selectively passes either right handed or left handed substantially circularly polarized light out of a plurality of wavelengths of natural light in the visible spectrum,

wherein, the circular polarizing unit is disposed such that a major surface of the circular polarizing unit is on a liquid crystal layer side, the substantially circularly polarized light exiting the circular polarizing unit through the major surface when natural light enters the circular polarizing unit, and

wherein, said incoming substantially circularly polarized light being linearly polarized at a surface of said first substrate in a plurality of directions respectively representative of said plurality of wave lengths of said natural light to thereby create a display.

12. A liquid crystal display device, comprising:

a first substrate having a light reflectibility;

a second substrate having a light transmissibility;

a liquid crystal layer sandwiched between the first substrate and the second substrate, the liquid crystal layer being composed of twist-aligned nematic liquid crystal having,

a dielectric anisotropy, and

a birefringence difference Δ

n, a thickness of the liquid crystal layer d, and a twist angle φ

_tw in the range of 0°

to 45°

, such that the value of the function $f_{\mathrm{vis}}=k<br><br>{\int <br><br>}_{380}^{780}<br><br>\stackrel{\_}{y}<br><br>\left(\mathrm{\lambda <br><br>}\right)<br><br>S_{\mathrm{D65}}<br><br>\left(\mathrm{\lambda <br><br>}\right)<br><br>f<br><br>\left(\mathrm{\lambda <br><br>}\right)<br><br>d<br><br>\mathrm{\lambda <br><br>}$

is 0.7 or higher, where $k=1/{\int <br><br>}_{380}^{780}<br><br>\stackrel{\_}{y}<br><br>\left(\mathrm{\lambda <br><br>}\right)<br><br>S_{\mathrm{D65}}<br><br>\left(\mathrm{\lambda <br><br>}\right)<br><br>d<br><br>\mathrm{\lambda <br><br>}$

{overscore (y)}(λ

) is the visual sensitivity curve of the color matching function of CIE1931,

S_D65(λ

) is the spectrum density of a D₆₅ standard light source,

f(λ

)=1−

{1−

2φ

_ref²(sin c√

{square root over (φ

_ref²+φ

_ref²))}²}²

${\mathrm{\varphi <br><br>}}_{\mathrm{ret}}=\mathrm{\pi <br><br>}<br><br>\frac{\mathrm{\Delta <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{nd}}{\mathrm{\lambda <br><br>}}$

and $\sin <br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{cX}=\frac{\sin <br><br>\text{\hspace{1em}<br><br>}<br><br>X}{X};<br><br>$

and

a circular polarizing unit, including a single linear polarizer plate, that selectively passes either right handed or left handed substantially circularly polarized light out of a plurality of wavelengths of natural light in the visible spectrum,

wherein, the circular polarizing unit is disposed such that a major surface of the circular polarizing unit is on a liquid crystal layer side, the substantially circularly polarized light exiting the circular polarizing unit through the major surface when natural light enters the circular polarizing unit, and

wherein, said incoming substantially circularly polarized light being linearly polarized at a surface of said first substrate in a plurality of directions respectively representative of said plurality of wave lengths of said natural light to thereby create a display.

13. A liquid crystal display device, comprising:

a first substrate having a light reflectibility;

a second substrate having a light transmissibility;

a liquid crystal layer sandwiched between the first substrate and the second substrate, the liquid crystal layer being composed of twist-aligned nematic liquid crystal having a dielectric anisotropy and a twist angle in a range of 0°

to 45°

; and

a circular polarizing unit that selectively passes either right handed or left handed substantially circularly polarized light out of a plurality of wavelengths of natural light in the visible spectrum,

wherein, the circular polarizing unit is disposed such that a major surface of the circular polarizing unit is on a liquid crystal layer side, the substantially circularly polarized light exiting the circular polarizing unit through the major surface when natural light enters the circular polarizing unit, and

wherein, said incoming substantially circularly polarized light being linearly polarized at a surface of said first substrate in a plurality of directions respectively representative of said plurality of wave lengths of said natural light to thereby create a display.