Transmissive and reflective type liquid crystal display

• US 6,937,303 B2
• Filed: 12/18/2002
• Issued: 08/30/2005
• 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: Lee, Dong-Ho, Kim, Hyung-Guel, Jang, Yong-Kyu, Yoon, Jong-Soo
• Primary Examiner(s): Chowdhury, Tarifur R.
• Assistant Examiner(s): KIM, RICHARD H
• Application Number:
  US10/322,812
• Publication Number:
  US 20030112391A1
• Time in Patent Office: 986 Days
• Field of Search: 349/114, 349/96
• US Class Current: 349/114
• 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. Liquid crystal layer is formed between the first and second substrate. A first polarizing plate is formed on outer surface of the first substrate. A second polarizing plate is formed on outer surface of the second substrate. A backlight is arranged at a rear side of the first polarizing plate. A transparent transflective film is arranged between the first polarizing plate and the backlight and has a plurality of layers where a first and a second layer each having different refractivity indexes are alternatively stacked. The transparent transflective film partially reflects and transmits incident light. 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 that is arranged so as to face 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, the outer surface being opposite to 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 specific directional polarization component of an incident light, and partially reflecting and transmitting a polarization component of the incident light that is polarized in a direction orthogonal to the specific direction.

2. The transmissive and reflective type LCD of claim 1, wherein 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.

3. The transmissive and reflective type LCD of claim 1, wherein the transflective film has an anisotropy characteristic having various transmissivity and reflectivity depending on a polarizing state and a direction of the incident light.

4. The transmissive and reflective type LCD of claim 3, wherein it is assumed that the transflective film has a thickness direction of z-axis and a film plane of x-y plane, wherein 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 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.

5. The transmissive and reflective type LCD of claim 1, wherein the transflective film comprises two transflective films having various transmissivity and reflectivity depending on a polarizing state and a direction of the incident light, the two transflective films being vertically attached to each other.

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

7. A transmissive and reflective type LCD 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 that oppositely faces 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 and 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 specific directional polarization component of an incident light, and partially reflecting and transmitting a polarization component of the incident light that is polarized in a direction orthogonal to the specific direction,

wherein the transmissive and reflective type LCD has a reflection light path along which a first incident light beam is incident into the LC cell from a front side of the cell, is reflected by the transflective film, and is outputted through the front side of the LC cell,

and a transmission light path along which a second incident light beam is incident into the LC cell from a rear side of the LC cell, is transmitted through the transflective film, and is outputted through the front side of the LC cell.

8. The transmissive and reflective type LCD of claim 7, wherein 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.

9. The transmissive and reflective type LCD of claim 7, wherein the transflective film has an anisotropy characteristic of various transmissivity and reflectivity depending on a polarizing state and a direction of the incident light.

10. The transmissive and reflective type LCD of claim 9, when it is assumed that the transflective film has a thickness direction of z-axis and a film plane of x-y plane, wherein 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 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.

11. The transmissive and reflective type LCD of claim 7, wherein the transflective film comprises two transflective films having various transmissivity and reflectivity depending on a polarizing state and a direction of the incident light, the two transflective films being vertically attached to each other.

12. The transmissive and reflective type LCD of claim 7, wherein the transflective film comprises a first transflective film and a second transflective film attached to each other, the first transflective film having a transmissivity and a reflectivity that varying with a polarizing state and a direction of the incident light, and the second transflective film having isotropic transmission and reflection characteristics regardless of the polarizing state and the direction of the incident light.

13. A transmissive and reflective type LCD comprising:

a first substrate including a gate line formed on an insulating substrate, a data line insulated from the gate line and arranged to intersect the gate line, and a pixel electrode electrically connected to the data line;

a second substrate of which an inner surface is arranged so as to face 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;

a backlight for irradiating incident light onto 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 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.

14. The transmissive and reflective type LCD of claim 13, wherein the transflective film has anisotropy characteristics with transmissivity and reflectivity depending on a polarizing state and a direction of the incident light.

15. The transmissive and reflective type LCD of claim 13, wherein the transflective film comprises at least two transflective films having a varying transmissivity and reflectivity depending on polarizing state and a direction of the incident light, the two transflective films being disposed one on top of the other.

16. The transmissive and reflective type LCD of claim 13, 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 a polarizing state and a 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.

17. The transmissive and reflective type LCD of claim 13, 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.

18. The transmissive and reflective type LCD of claim 13, 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.

19. A transmissive and reflective type LCD comprising:

a first substrate including i) a thin film transistor having a gate electrode formed on an insulating substrate, a gate insulating layer formed on the gate electrode and on the insulating substrate, an active pattern formed on the gate insulating layer to be disposed above the gate electrode, and a source electrode and a drain electrode separately formed on the active pattern apart from each other, and ii) a pixel electrode electrically connected to one of the source electrode and the drain electrode;

a second substate of which an inner surface is arranged so as to face 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;

a backlight for irradiating an 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 specific directional polarization component of the incident light, and partially reflecting and transmitting a polarization component of the incident light that is polarized in a direction orthogonal to the specific direction.

20. The transmissive and reflective type LCD of claim 19, wherein the active pattern is comprised of polycrystalline silicon.

21. The transmissive and reflective type LCD of claim 19, wherein the active pattern is comprised of amorphous silicon.

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

23. A transmissive and reflective type LCD comprising:

a first substrate including i) a thin film transistor having an active pattern formed on an insulating substrate, a gate insulating layer formed on the active pattern and on the insulating substrate, gate electrode formed on the gate insulating layer to be disposed above the active pattern, an interinsulation layer formed on the gate electrode and the gate insulating layer, and a source electrode and a drain electrode separately formed on the interinsulation layer apart from each other, and ii) a pixel electrode electrically connected to one of the source electrode and the drain electrode;

a second substrate of which an inner surface is arranged so as to face the first substrate, the inner surface of the second substrate having a transparent comment 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;

a backlight for irradiating an 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 specific directional polarization component of the incident light, and partially reflecting and transmitting a polarization component of the incident light that is polarized in a direction orthogonal to the specific direction.

24. The transmissive and reflective type LCD of claim 23, wherein the active pattern is comprised of polycrystalline silicon.

25. The transmissive and reflective type LCD of claim 23, wherein the active pattern is comprised of amorphous silicon.

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

27. A transmissive and reflective type LCD comprising:

a first substrate including i) a display cell array circuit formed on an insulating substrate, a plurality of data lines and a plurality of gate lines arranged in a matrix shape to intersect each other on the display cell array circuit, and ii) a gate driver circuit, formed adjacent to a first portion of the display cell array circuit, for driving the gate lines;

a second substrate of which an inner surface is arranged so as to face 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 an an outer surface of the first substrate;

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

a backlight for irradiating an 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 specific directional polarization component of the incident light, and partially reflecting and transmitting a polarization component of the incident light that is polarized in a direction orthogonal to the specific direction.

28. The transmissive and reflective type LCD of claim 27, further comprising a data driver circuit, formed adjacent to a second portion of the display cell array circuit, for driving the data lines.

29. The transmissive and reflective type LCD of claim 27, 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.