Transmissive and reflective type liquid crystal display

• US 6,831,719 B2
• Filed: 06/26/2002
• Issued: 12/14/2004
• Est. Priority Date: 12/18/2001
• Status: Expired due to Fees

• Current Assignee: Samsung Display Company Limited (Samsung Group)
• Original Assignee: Samsung Electronics Co. Ltd. (Samsung Group)
• Inventors: Kim, Hyung-Guel, Jang, Yong-Kyu
• Primary Examiner(s): Kim, Robert H.
• Assistant Examiner(s): Kim, Richard H
• Application Number:
  US10/183,143
• Publication Number:
  US 20030112388A1
• Time in Patent Office: 902 Days
• Field of Search: 349/113-115
• US Class Current: 349/114
• CPC Class Codes: G02F 1/133536 Reflective polarizers G02F1/13362 takes precedence
• CPC Class Codes: G02F 1/133545 Dielectric stack polarisers
• CPC Class Codes: G02F 1/133555 Transflectors
• CPC Class Codes: G02F 1/133567 on the back side
• CPC Class Codes: G02F 1/133615 Edge-illuminating devices, i.e. illuminating from the side

Abstract

Disclosed is a transmissive and reflective type LCD. In the LCD, a second substrate faces a first substrate. A liquid crystal layer is formed between the first substrate and the second substrate. A first polarizing plate is formed on an outer surface of the first substrate. A second polarizing plate is formed on an outer surface of the second substrate. A backlight is arranged for irradiating incident light onto the polarizing plate. A transparent transflective film is arranged between the first polarizing plate and the backlight for partially reflecting and partially transmitting the incident light. The transparent transflective film includes at least a first layer and a second layer, the first and second layers having different refractivity indexes from each other and are alternatively stacked. By a restoring process occurring between the transflective film and the backlight, a predetermined amount of the incident light is transmitted through the transflective film repeatedly, so that transmissivity and light efficiency are enhanced.

Claims

1. A transmissive and reflective type LCD comprising:

a first substrate;

a second substrate having an inner surface facing the first substrate;

a liquid crystal layer formed between the first substrate and the second substrate;

a first polarizing plate formed on an outer surface of the first substrate;

a second polarizing plate formed on an outer surface of the second substrate;

a backlight for irradiating incident light onto the first polarizing plate; and

a transflective film arranged between the first polarizing plate and the backlight, the transflective film reflecting a first polarization component of the incident light polarized in a first direction, and partially reflecting and transmitting a second polarization component of the incident light polarized in a second direction orthogonal to the first direction.

2. The transmissive and reflective type LCD of claim 1, wherein the transflective film includes at least a first layer and a second layer, the first and second layers having different refractivity indexes from each other and are alternatively stacked.

3. The transmissive and reflective type LCD of claim 1, wherein the transflective film is integrally formed with the first polarizing plate.

4. The transmissive and reflective type LCD of claim 1, wherein the transflective film is separately formed from the first polarizing plate.

5. The transmssive and reflective type LCD of claim 1, wherein the transflective film includes at least a first layer and a second layer, and the first layer of the transflective film has a refractive anisotropy and the second layer of the transflective film does not have the refractive anisotropy within a plane thereof.

6. The transmissive and reflective type LCD of claim 1, wherein the transflective film has anisotropy characteristics with transmissivity and reflectivity depending on polarizing state and direction of the incident light.

7. The transmissive and reflective type LCD of claim 6, wherein the transflective film includes at least a first layer and a second layer, and each of the first layer and the second layer has three main refractive indexes of n_x, n_y, and n_z with the following relationships:

8. The transmissive and reflective type LCD of claim 1, wherein the transflective film comprises at least two transflective films having a varying transmissivity and reflectivity depending on polarizing state and direction of the incident light, the two transflective films being disposed one on top of the other.

9. The transmissive and reflective type LCD of claim 1, wherein the transflective film comprises a first transflective film and a second transflective film vertically aligned with each other, the first transflective film having a transmissivity and a reflectivity that vary according to polarizing state and direction of the incident light, and the second transflective film having isotropic transmission and reflection characteristics independent of the polarizing state and the direction of the incident light.

10. The transmissive and reflective type LCD of claim 1, wherein the transflective film has a reflectivity of no less than about 4% with respect to any direction of polarization components when the incident light is incident onto the transflective film with an angle perpendicular to a surface thereof.

11. The transmissive and reflective type LCD of claim 1, further comprising a light scattering layer formed on the first substrate or the second substrate.

12. The transmissive and reflective type LCD of claim 11, wherein the light scattering layer is formed between the first substrate and the first polarizing plate, between the second substrate and the second polarizing plate, or between the first polarizing plate and the transflective film.

13. The transmissive and reflective type LCD of claim 1, further comprising a phase difference plate formed on the first substrate or the second substrate.

14. The transmissive and reflective type LCD of claim 13, wherein the phase difference plate is formed between the first substrate and the first polarizing plate, or between the second substrate and the second polarizing plate.

15. The transmissive and reflective type LCD of claim 1, wherein the liquid crystal layer has a Δ

nd of about 0.2 μ

m to about 0.6 μ

m that is a product of a refractive anisotropy Δ

n and a thickness d of the liquid crystal layer.

16. The transmissive and reflective type LCD of claim 1, wherein a transmitting direction of the incident light at the first polarizing plate is the same direction as a partially reflecting and transmitting direction of the incident light at the transflective film.

17. A transmissive and reflective type LCD for partially reflecting and transmitting incident light, comprising:

an LC cell including a first substrate, a second substrate having an inner surface that is arranged to face the first substrate, and a liquid crystal layer formed between the first substrate and the second substrate;

a first polarizing plate formed on an outer surface of the first substrate;

a second polarizing plate formed on an outer surface of the second substrate;

a backlight arranged at a rear side of the first polarizing plate; and

a transparent transflective film arranged between the first polarizing plate and the backlight and having a plurality of layers in which a first layer and a second layer have different refractivity indexes from each other, the transflective film reflecting a first polarization component of the incident light polarized in a first direction, and partially reflecting and transmitting a second polarization component of the incident light polarized in a second direction orthogonal to the first direction,

wherein the transmissive and reflective type LCD has a reflection light path along which the incident light is incident onto the LC cell from a front side of the LC cell, is reflected by the transflective film, and is output through the front side of the LC cell, and a transmission light path along which the incident light is incident onto the LC cell from a rear side of the LC cell, is transmitted through the transflective film, and is output through the front side of the LC cell.

18. The transmissive and reflective type LCD of claim 17, wherein the first layer of the transflective film has refractive anisotropy and the second layer of the transflective film does not have refractive anisotropy.

19. The transmissive and reflective type LCD of claim 17, wherein the transflective film has anisotropy characteristics of varying transmissivity and reflectivity depending on polarizing state and direction of the incident light.

20. The transmissive and reflective type LCD of claim 19, wherein each of the first layer and the second layer has three main refractive indexes of n_x, n_y, and n_z with the following relationships:

21. The transmissive and reflective type LCD of claim 17, wherein the transflective film comprises two transflective films having a varying transmissivity and reflectivity depending on polarizing state and direction of incident light, the two transflective films being vertically aligned with each other.

22. The transmissive and reflective type LCD of claim 17, wherein the transflective film comprises a first transflective film and a second transflective film disposed to each other, the first transflective film having a transmissivity and a reflectivity that varies dependently upon polarizing state and direction of incident light, and the second transflective film having isotropic transmission and reflection characteristics independent of polarizing state and direction of incident light.

23. The transmissive and reflective type LCD of claim 17, when the incident light is incident onto the transflective film with an angle perpendicular to a plane thereof, wherein the transflective film has a reflectivity of no less than about 4% with respect to all directions of polarization components.

24. The transmissive and reflective type LCD of claim 17, further comprising a light scattering layer formed on the first substrate or the second substrate.

25. The transmissive and reflective type LCD of claim 17, wherein a transmitting direction of the incident light at the first polarizing plate is the same direction as a partially reflecting the transmitting direction of the incident light at the transflective film.

26. A transmissive and reflective type LCD comprising:

a first substrate on which a first transparent electrode is formed;

a second substrate of which an inner surface is arranged facing the first substrate, the inner surface of the second substrate having a second transparent electrode thereon;

a liquid crystal layer formed between the first substrate and the second substrate;

a first polarizing plate formed on an outer surface of the first substrate;

a second polarizing plate formed on an outer surface of the second substrate, opposite the inner surface of the second substrate;

a backlight arranged at a rear side of the first polarizing plate; and

a transparent transflective film arranged between the first polarizing plate and the backlight, the transflective film reflecting a first polarization component of incident light polarized in a first direction, and partially reflecting and transmitting a second polarization of the incident light polarized in a second direction orthogonal to the first direction.

27. The transmissive and reflective type LCD of claim 26, wherein the transparent transflective film includes at least a first layer and a second layer, the first and second layers having different refractivity indexes from each other and being alternatively stacked.

28. The transmissive and reflective type LCD of claim 26, wherein the first transparent electrode is a signal electrode and the second transparent electrode is a scanning electrode.

29. The transmissive and reflective type LCD of claim 26, wherein a transmitting direction of the incident light at the first polarizing plate is the same direction as a partially reflecting and transmitting direction of the incident light at the transflective film.

30. A transmissive and reflective type LCD comprising:

a first substrate on which a switching element and a transparent pixel electrode connected to the switching element are formed;

a second substrate of which an inner surface is arranged facing the first substrate, the inner surface of the second substrate having a transparent common electrode thereon;

a liquid crystal layer formed between the first substrate and the second substrate;

a first polarizing plate formed on an outer surface of the first substrate;

a second polarizing plate formed on an outer surface of the second substrate, opposite the inner surface of the second substrate;

a backlight arranged at a rear side of the first polarizing plate; and

a transparent transflective film arranged between the first polarizing plate and the backlight, said transparent transflective film having a plurality of layers in which a first layer and a second layer having different refractivity indexes from each other are alternatively stacked, the transparent transflective film reflecting a first polarization component of incident light polarized in a first direction, and partially reflecting and transmitting a second polarization component of the incident light polarized in a second direction orthogonal to the first direction.

31. The transmissive and reflective type LCD of claim 30, wherein the switching element is a thin film transistor.

32. The transmissive and reflective type LCD of claim 30, wherein a transmitting direction of the incident light at the first polarizing plate is the same direction as a partially reflecting and transmitting direction of the incident light at the transflective film.