Reflective type liquid crystal display device with phase compensator and reflector with undulating surface

• US 5,684,551 A
• Filed: 09/11/1995
• Issued: 11/04/1997
• Est. Priority Date: 06/26/1992
• Status: Expired due to Term

• Current Assignee: Sharp Electronics Corporation (Hon Hai Precision Industry Co., Ltd.), Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Nakamura, Kozo, Uchida, Tatsuo, Mitsui, Seiichi, Kimura, Naofumi, Seki, Hidehiro
• Primary Examiner(s): GROSS, ANITA P
• Application Number:
  US08/526,275
• Time in Patent Office: 785 Days
• Field of Search: 359/53, 359/73, 359/70, 349/113, 349/117, 349/76, 349/99
• US Class Current: 349/99
• 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 1/13363 Birefringent elements, e.g. for optical compensation
• CPC Class Codes: G02F 1/133637 characterised by the wavelength dispersion
• CPC Class Codes: G02F 1/1347 Arrangement of liquid crystal layers or cells in which the final condition of one light beam is achieved by the addition of the effects of two or more layers or cells
• CPC Class Codes: G02F 2203/02 reflective
• CPC Class Codes: G02F 2413/01 Number of plates being 1
• CPC Class Codes: G02F 2413/08 with a particular optical axis orientation

Abstract

A liquid crystal display device of high display quality and superior sharpness is presented. Large bumps and small bumps made of synthetic resin material are formed on a glass substrate. The bottom diameters of the large bumps and small bumps are defined, for example, at 5 μm and 3 μm, respectively, and their interval is at least, for example, 2 μm or more. Covering these bumps and filling the recesses among the bumps, a smoothing film is formed. On the smoothing film, a reflective metal film made of metal material such as aluminum is formed. This reflective a metal film is formed in plural rows in a longitudinal band form. On the glass substrate, the bumps, smoothing film, and reflective metal film are combined to compose a reflector. An orientation film is formed on the reflective metal film. By the electric field applied in the liquid crystal layer so as to be in the light shielding state when the retardation Δn₁ d₁ of the liquid crystal cell and the retardation Δn₂ d₂ of the substrate possessing optical phase compensating function satisfy |Δn₁ d₁ -Δn₂ d₂ |/λ=0.25+m/2±0.1 (m=0, 1, 2, . . . ), and in the light transmitting state when satisfying |Δn₁ d₁ -Δn₂ d₂ |λ=m/2±0.1 (m=0, 1, 2, . . . ), by crossing the director direction of the liquid crystal molecules of the liquid crystal cell and the slow direction of the substrate possessing optical phase compensating function almost orthogonally, the value of |Δn₁ d₁ -Δn₂ d₂ |/λ is varied, and these two states are used to present a display. Further, the absorption axis or transmission axis of the polarizer is set at 30° to 60° to the director direction of the liquid crystal molecule of the liquid crystal cell to produce a reflective type liquid crystal display device with no parallax, high contrast, high sharpness, and high display quality.

Claims

1. A reflective type liquid crystal display device comprising:

a polarizer at a light incident side of a liquid crystal cell, the liquid crystal cell including,

a first insulating substrate, including at least one transparent electrode,

a second insulating substrate,

a light reflecting member, including a first layer with smooth undulations formed on the second insulating substrate, and a light reflecting surface formed on the smooth undulations of the first layer, the light reflecting surface further forming at least one second electrode for display driving in connection with the at least one transparent electrode, and

a liquid crystal layer including liquid crystal molecules of a parallel orientation sealed between the first insulating substrate and the light reflecting member; and

an optical phase compensating member disposed between the polarizer and the liquid crystal cell, wherein a light transmission state is selected when a retardation Δ

n₁ d₁, wherein Δ

n₁ is an optical anisotropy of the liquid crystal layer and d₁ is a thickness of the liquid crystal layer, of the liquid crystal cell and a retardation Δ

n₂ d₂, wherein Δ

n₂ is an optical anisotropy of the optical phase compensating member and d₂ is a thickness of the optical phase compensating member, are in a relation of

space="preserve" listing-type="equation">|Δ

n.sub.1 d.sub.1 -Δ

n.sub.2 d.sub.2 |/λ

=m/2+0.1 (1)

, wherein m is an integer and λ

is a wavelength in a range of 400 to 700 nm, upon application of a voltage V1, and a light shielding state is selected when the retardation of the liquid crystal cell and the optical phase compensating member are in the relation of

space="preserve" listing-type="equation">|Δ

n.sub.1 d.sub.1 -Δ

n.sub.2 d.sub.2 |/λ

=0.25+m/2+0.1 (2)

upon application of a voltage V2, wherein a numerical value of |Δ

n₁ d₁ -Δ

n₂ d₂ |/λ

is varied depending on an electric field applied to the liquid crystal layer, wherein the retardation Δ

n₁ d₁ of the liquid crystal cell and the retardation Δ

n₂ d₂ of the optical phase compensating member are selected so as to satisfy formula (2) in terms of the wavelength λ

of the light in a range of 400 to 700 nm upon non-application of voltage, and the numerical value of |Δ

n₁ d₁ -Δ

n₂ d₂ |/λ

is varied depending on the electric field applied to the liquid crystal layer.

2. The reflective type liquid crystal display device of claim 1, wherein the light reflecting surface of the light reflecting member confronts the liquid crystal layer.

3. The reflective type liquid crystal display device of claim 1, wherein a transparent flattened layer is disposed on the light reflecting surface to flatten said surface with the smooth undulations, and a transparent electrode is formed on the transparent flattened layer, functioning as at least one second electrode confronting the at least one transparent electrode formed on the first insulating substrate.

4. The reflective type liquid crystal display device of claim 1, wherein a color filter layer is formed on one of the first insulating substrate and the at least one transparent electrode formed on the first insulating substrate.

20. The reflective type liquid crystal display device of any one of claims 1 and 13, wherein the light reflecting member is mirror finished.

22. The reflective type liquid crystal display device of any one of claims 1 and 13, wherein the light reflecting surface includes a metal.

23. The reflective type liquid crystal display device of claim 22, wherein the metal of the light reflecting surface is selected from the group consisting of aluminum, nickel, chromium and silver.

5. A reflective type liquid crystal display device comprising:

a light transmittable substrate, including at least one transparent electrode;

a reflector, including a first layer with smoothly and continuously changing undulations and a thin reflecting film formed on the first layer;

a liquid crystal cell including a liquid crystal layer, including liquid crystal molecules of a parallel orientation, inserted between the light transmittable substrate and the reflector;

a polarizer disposed at a light incident side; and

an optical phase compensating substrate disposed between the polarizer and the liquid crystal cell, wherein

the director direction of the liquid crystal molecules of the liquid crystal cell is almost orthogonal to a slow direction of the optical phase compensating substrate,

a value of |Δ

n₁ d₁ -Δ

n₂ d₂ |/λ

, wherein Δ

n₁ is an optical anisotropy of the liquid crystal layer and d₁ is a thickness of the liquid crystal layer, Δ

n₂ is an optical anisotropy of the optical phase compensating substrate and d₂ is a thickness of the optical phase compensating substrate and λ

is a wavelength 400 to 700 nm, is varied by an electric field applied to the liquid crystal layer so as to establish a light transmission state when a retardation Δ

n₁ d₁ of the liquid crystal layer and a retardation Δ

n₂ d₂ of the optical phase compensating substrate satisfy the formula,

space="preserve" listing-type="equation">|Δ

n.sub.1 d.sub.1 -Δ

n.sub.2 d.sub.2 |/λ

=m/2±

0.1, (1)

wherein m is an integer and a light shielding state when the retardations Δ

n₁ d₁ of the liquid crystal layer and Δ

n₂ d₂ of the optical phase compensating substrate satisfy the formula,

space="preserve" listing-type="equation">|Δ

n.sub.1 d.sub.1 -Δ

n.sub.2 d.sub.2 |/λ

=0.25+m/2±

0.1 (2),

and wherein one of an absorption axis and a transmission axis of the polarizer is set in a range of 30°

to 60°

to the director direction of the liquid crystal molecules of the liquid crystal cell.

6. The reflective type liquid crystal display device of claim 5, wherein a light shielding state is selected when the retardation Δ

n₁ d₁ of the liquid crystal cell and the retardation Δ

n₂ d₂ of the optical phase compensating substrate satisfy the formula (2) for a wavelength λ

in a range at 400 to 700 nm when voltage V₁ (V₁ ≧

0) is applied, and a light transmitting state is selected when Δ

n₁ d₁ and Δ

n₂ d₂ satisfy the formula (1) for a wavelength λ

in a range of 400 to 700 nm when voltage V₂ (V₂ >

V₁) is applied,

the relation (Δ

nλ

)F>

(Δ

nλ

)Lc is satisfied when Δ

n₁ d₁ >

Δ

n₂ d₂ is met in the light shielding state, wherein (Δ

nλ

)F is a magnitude of wavelength dispersion of the optical phase compensating substrate and (Δ

nλ

)Lc is a magnitude of wavelength dispersion of the liquid crystal cell, and the relation (Δ

nλ

)F<

(Δ

nλ

)Lc is satisfied when Δ

n₁ d₁ <

n₂ d₂ is met in the light shielding state.

7. The reflective type liquid crystal display device of claim 5, wherein a light transmitting state is selected when the retardation Δ

n₁ d₁ of the liquid crystal cell and the retardation Δ

n₂ d₂ of the optical phase compensating substrate satisfy the formula (1) for a wavelength λ

in a range of 400 to 700 nm when voltage V_l (V₁ ≧

0) is applied and a light shielding state is selected when Δ

n₁ d₁ and Δ

n₂ d₂ satisfy the formula (2) for a wavelength λ

in a range of 400 to 700 nm when voltage V₂ (V₂ >

V₁) is applied, the relation (Δ

nλ

)F>

(Δ

nλ

)Lc is satisfied when Δ

n₁ d₁ >

n₂ d₂ is met in the light shielding state, wherein (Δ

nλ

)F is a magnitude of wavelength dispersion of the optical phase compensating substrate and (Δ

nλ

)Lc is a magnitude of wavelength dispersion of the liquid crystal cell, and the relation (Δ

nλ

)F<

(Δ

nλ

)Lc is satisfied when Δ

n₁ d₁ <

n₂ d₂ is met in the light shielding state.

8. The reflective type liquid crystal display device of any one of claims 5 to 7, wherein the thin reflecting film confronts the liquid crystal layer.

9. The reflective type liquid crystal display device of any one of claims 5 to 7, wherein the thin reflecting film also functions as at least one second electrode confronting the at least one transparent electrode formed on the light transmittable substrate.

10. The reflective type crystal display device of any one of claims 5 to 7, wherein a transparent flattened layer is disposed on the thin reflecting film to flatten said film, and a transparent electrode is formed on the transparent flattened layer, functioning as at least one second electrode confronting the at least one transparent electrode formed on the light transmittable substrate.

11. The reflective type liquid crystal display device of any one of claims 5 to 7, wherein a color filter layer is formed on one of the surface and the at least one transparent electrode of the light transmittable substrate.

12. The reflective type liquid crystal display device of claim 8, wherein the thin reflecting film also functions as at least one second electrode confronting the at least one transparent electrode formed on the light transmittable substrate.

21. The reflective type liquid crystal display device of any one of claims 5-7, wherein the reflector is mirror finished.

24. The reflective type liquid crystal display device of any one of claims 5-7, wherein the thin reflecting film includes a metal.

25. The reflective type liquid crystal display device of claim 24, wherein the metal of the thin reflecting film is selected tom the group consisting of aluminum, nickel, chromium and silver.

13. A reflective type liquid crystal display device comprising:

a polarizer at a light incident side of a liquid crystal cell, the liquid crystal cell including,

a first insulating substrate, including at least one transparent electrode,

a second insulating substrate,

a light reflecting member, including a first layer with smooth undulations formed on the second insulating substrate, and a light reflecting surface formed on the smooth undulations of the first layer, the light reflecting surface further forming at least one second electrode for display driving in connection with the at least one transparent electrode, and

a liquid crystal layer including liquid crystal molecules of a parallel orientation sealed between the first insulating substrate and the light reflecting member; and

an optical phase compensating member disposed between the polarizer and the liquid crystal cell, wherein a light transmission state is selected when a retardation Δ

n₁ d₁, wherein Δ

n₁ is an optical anisotropy of the liquid crystal layer and d₁ is a thickness of the liquid crystal layer, of the liquid crystal cell and a retardation Δ

n₂ d₂, wherein Δ

n₂ is an optical anisotropy of the optical phase compensating member and d₂ is a thickness of the optical phase compensating member, are in a relation of

space="preserve" listing-type="equation">|Δ

n.sub.1 d.sub.1 -Δ

n.sub.2 d.sub.2 |/λ

=m/2±

0.1 (1)

, wherein m is an integer and λ

is a wavelength in a range of 400 to 700 nm, upon application of a voltage V1, and a light shielding state is selected when the retardation of the liquid crystal cell and the optical phase compensating member are in the relation of

space="preserve" listing-type="equation">|Δ

n.sub.1 d.sub.1 -Δ

n.sub.2 d.sub.2 |/λ

=0.35+m/2±

0.1 (2)

upon application of a voltage V2, wherein a numerical value of |Δ

n₁ d₁ -Δ

n₂ d₂ |/λ

is varied depending on an electric field applied to the liquid crystal layer,

wherein the first layer includes protruding portions of at least two different heights formed on the substrate and a smoothing film forming the smooth undulations on the protruding portions.

14. The reflective type liquid crystal display device of claim 13, wherein the protruding portions include a photosensitive resin.

15. The reflective type liquid crystal display device of claim 14, wherein the smoothing film includes a photosensitive resin.

16. The reflective type liquid crystal display device of claim 13, wherein the protruding portions are of at least two varying diameters.

17. The reflective type liquid crystal display device of claim 16, wherein at least two of the protruding portions are 5 μ

m and 3 μ

m in diameter, respectively.

18. The reflective type liquid crystal display device of claim 13, wherein the protruding portions are at least a predetermined distance apart on the substrate.

19. The reflective type liquid crystal display device of claim 18, wherein the protruding portions are at least 2 μ

m apart on the substrate.