Transmissive and reflective type liquid crystal display

• US 7,929,082 B2
• Filed: 11/10/2004
• Issued: 04/19/2011
• Est. Priority Date: 12/18/2001
• Status: Expired due to Fees

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Kim, Hyung-Guel, Jang, Yong-Kyu
• Primary Examiner(s): Kim; Richard H
• Application Number:
  US10/985,780
• Publication Number:
  US 20050062914A1
• Time in Patent Office: 2,351 Days
• Field of Search: 349/114
• 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:

an array substrate;

a counter substrate having an inner surface facing the array substrate;

a liquid crystal layer formed between the array substrate and the counter substrate;

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

a second polarizing plate formed on an outer surface of the counter 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 in a first direction, and partially reflecting and transmitting a second polarization component of the incident light in a second direction,

wherein the transflective film is deposited or coated on a surface of the first polarizing plate, so that the transflective film is integrally formed with the first polarizing plate,

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 that satisfy the following relationships;

n1_x=n1_z≠

n1_y;

n2_x=n2_y=n2_z;

n1_x≠

n2_x;

n1_y≠

n2_y; and

|n1_x−

n2_x|<

|n1_y−

n2_y|

wherein the transflective film has a thickness direction of z-axis and a film plane of x-y plane, wherein n1x, n1y, n1z denotes a main refractive index of the first layer in an x-axis, y-axis, z-axis, respectively, and n2x, n2y, n2z denotes a main refractive index of the second layer in an x-axis, y-axis, z-axis, respectively.

2. The transmissive and reflective type LCD of claim 1, wherein the first and second layers are alternately stacked.

3. 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.

4. The transmissive and reflective type LCD of claim 1, further comprising a light scattering layer formed on the array substrate or the counter substrate, wherein the light scattering layer is formed between the array substrate and the first polarizing plate, between the counter substrate and the second polarizing plate, or between the first polarizing plate and the transflective film.

5. The transmissive and reflective type LCD of claim 1, further comprising a phase difference plate formed on the array substrate or the counter substrate wherein the phase difference plate is formed between the array substrate and the first polarizing plate, or between the counter substrate and the second polarizing plate.

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

nd of about 0.2-0.6 μ

m that is a product of a refractive anisotropy Δ

n and a thickness d of the liquid crystal layer.

7. 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.

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 at least two transflective films being disposed one on top of the other.

9. The transmissive and reflective type LCD of claim 8, wherein the transflective film comprises a first transflective film and a second transflective film, and 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 9, 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 9, further comprising a light scattering layer formed on the array substrate or the counter substrate, wherein the light scattering layer is formed between the array substrate and the first polarizing plate, between the counter substrate and the second polarizing plate, or between the first polarizing plate and the transflective film.

12. The transmissive and reflective type LCD of claim 9, further comprising a phase difference plate formed on the array substrate or the counter substrate wherein the phase difference plate is formed between the array substrate and the first polarizing plate, or between the counter substrate and the second polarizing plate.

13. The transmissive and reflective type LCD of claim 9, wherein the liquid crystal layer has a Δ

nd of about 0.2-0.6 μ

m that is a product of a refractive anisotropy Δ

n and a thickness d of the liquid crystal layer.

14. The transmissive and reflective type LCD of claim 9, 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.

15. A transmissive and reflective type LCD comprising:

an array substrate on which a switching element and a first transparent electrode is formed;

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

a liquid crystal layer formed between the array substrate and the counter substrate;

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

a second polarizing plate formed on an outer surface of the counter substrate, opposite the inner surface of the counter 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 in a first direction, and partially reflecting and transmitting a second polarization of the incident light in a second direction,

wherein the transflective film is deposited or coated on a surface of the first polarizing plate, so that the transflective film is integrally formed with the first polarizing plate,

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 , that satisfy the following relationships;

n1_x=n1_z≠

n1_y;

n2_x=n2_y=n2_z;

n1_x≠

n2_x;

n1_y≠

n2_y; and

|n1_x−

n2_x|<

|n1_y−

n2_y|

wherein the transflective film has a thickness direction of z-axis and a film plane of x-y plane, wherein n1x, n1y, n1z denotes a main refractive index of the first layer in an x-axis, y-axis, z-axis, respectively, and n2x, n2y, n2z denotes a main refractive index of the second layer in an x-axis, y-axis, z-axis, respectively.

16. The transmissive and reflective type LCD of claim 15, wherein the first transparent electrode is a signal electrode and the second transparent electrode is a scanning electrode.

17. The transmissive and reflective type LCD of claim 16, wherein the switching element is a thin film transistor.

18. The transmissive and reflective type LCD of claim 15, wherein the first and second layers are alternately stacked.

19. The transmissive and reflective type LCD of claim 15, 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.

20. The transmissive and reflective type LCD of claim 15, further comprising a light scattering layer formed on the array substrate or the counter substrate, wherein the light scattering layer is formed between the array substrate and the first polarizing plate, between the counter substrate and the second polarizing plate, or between the first polarizing plate and the transflective film.

21. The transmissive and reflective type LCD of claim 15, further comprising a phase difference plate formed on the array substrate or the counter substrate wherein the phase difference plate is formed between the array substrate and the first polarizing plate, or between the counter substrate and the second polarizing plate.

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

nd of about 0.2-0.6 μ

m that is a product of a refractive anisotropy Δ

n and a thickness d of the liquid crystal layer.

23. The transmissive and reflective type LCD of claim 15, 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.