Liquid crystal display device having particular electrodes in transmission region and in reflection region

• US 7,538,845 B2
• Filed: 10/21/2005
• Issued: 05/26/2009
• Est. Priority Date: 10/29/2004
• Status: Expired due to Fees

• Current Assignee: Panasonic Liquid Crystal Display Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Hitachi Displays Limited (Japan Display Incorporated)
• Inventors: Hasegawa, Atsushi, Miyazawa, Toshio
• Primary Examiner(s): QI, ZHI QIANG
• Application Number:
  US11/255,107
• Publication Number:
  US 20060092363A1
• Time in Patent Office: 1,313 Days
• Field of Search: 349113-115, 349/141, 349/143, 349/149, 349/146
• US Class Current: 349/141
• CPC Class Codes: G02F 1/133555 Transflectors
• CPC Class Codes: G02F 1/134363 for applying an electric field parallel to the substrate, i.e. in-plane switching [IPS]

Abstract

The present invention provides a liquid crystal display device which can reduce the difference in brightness between an image obtained from a reflection region and an image obtained from a transmission region. The liquid crystal display device includes a pixel electrode and a counter electrode in each pixel region on a liquid-crystal-side surface of one substrate out of respective substrates which are arranged to face each other with liquid crystal therebetween. The pixel region includes a transmission region and a reflection region. A gap between the pixel electrode and the counter electrode in the reflection region is set larger than the gap between the pixel electrode and the counter electrode in the transmission region.

Claims

1. A liquid crystal display device comprising:

a first substrate;

a second substrate; and

liquid crystal sandwiched between the first substrate and the second substrate, wherein

the first substrate includes a first electrode having a plurality of linear portions and a second electrode having a planar portion in the inside of a pixel region,

the liquid crystal is driven by an electric field generated between the first electrode and the second electrode,

the linear portions of the first electrode are arranged above the planar portion of the second electrode in an overlapped manner by way of an insulation film,

the pixel region includes a transmission region which performs a display by allowing light from a back surface side to pass therethrough and a reflection region which performs a display by reflecting light from a front surface side, and

as viewed in a plan view, a gap between the neighboring linear portions of the first electrode in the reflection region is larger than a gap of the neighboring linear portions of the first electrode in the transmission region.

2. A liquid crystal display device according to claim 1, wherein as viewed in a plan view, a width of the linear portion of the first electrode in the reflection region is smaller than a width of the linear portion of the first electrode in the transmission region.

3. A liquid crystal display device comprising:

a first substrate;

a second substrate; and

liquid crystal sandwiched between the first substrate and the second substrate, wherein

the first substrate includes a first electrode having a plurality of linear portions and a second electrode having a planar portion in the inside of a pixel region,

the liquid crystal is driven by an electric field generated between the first electrode and the second electrode,

the linear portions of the first electrode are arranged above the planar portion of the second electrode in an overlapped manner by way of an insulation film,

the pixel region includes a transmission region which performs a display by allowing light from a back surface side to pass therethrough and a reflection region which performs a display by reflecting light from a front surface side,

assuming a layer thickness of the liquid crystal in the transmission region as dt and a layer thickness of the liquid crystal in the reflection region as dr, a relationship 0.75dt≦

dr≦

1.1dt is established, and

as viewed in a plan view, a gap between the neighboring linear portions of the first electrode in the reflection region is larger than a gap of the neighboring linear portions of the first electrode in the transmission region.

4. A liquid crystal display device comprising:

a first substrate;

a second substrate; and

liquid crystal sandwiched between the first substrate and the second substrate, wherein

the first substrate includes a pixel electrode to which a video signal is applied and a counter electrode to which a signal which is common with at least one of neighboring pixel regions and becomes the reference with respect to the video signal is applied in the inside of a pixel region,

the liquid crystal is driven by an electric field generated between the pixel electrode and the counter electrode,

the pixel region includes a reflector which performs a reflection display by reflecting light from the front surface side on at least a portion of the pixel region,

the reflector has at least a portion thereof overlapped to the pixel electrode and the counter electrode by way of an insulation film, and

the reflector is formed independently for every pixel region and a signal which is equal to a signal applied to the pixel electrode is applied to the reflector.

5. A liquid crystal display device according to claim 4, wherein the first substrate includes gate signal lines to which a scanning signal is applied, drain signal lines to which the video signal is applied, thin film transistors which are connected with the gate signal lines and are driven in response to the scanning signal, and source electrodes to which the video signal is applied by way of the thin film transistors, and

the reflector is formed by extending the source electrode.

6. A liquid crystal display device according to claim 5, wherein the liquid crystal display device includes a capacitance signal line which is formed at a position below the source electrode in an overlapped manner by way of a second insulation film.

7. A liquid crystal display device according to claim 4, wherein the pixel region includes a transmission region which performs a transmission display by allowing light from a back surface side to pass therethrough in at least a portion of the pixel region.

8. A liquid crystal display device comprising:

a first substrate;

a second substrate; and

liquid crystal sandwiched between the first substrate and the second substrate, wherein

the first substrate includes a pixel electrode to which a video signal is applied and a counter electrode to which a signal which is common with at least one of neighboring pixel regions and becomes the reference with respect to the video signal is applied in the inside of a pixel region,

the pixel region includes a reflector which performs a reflection display by reflecting light from the front surface side on at least a portion of the pixel region,

the pixel electrode and the reflector are formed below the counter electrode and have at least portions thereof overlapped to the counter electrode by way of an insulation film,

the reflector is independently formed for every pixel region and a signal equal to the signal applied to the pixel electrode is applied to the reflector,

the pixel region includes a transmission region which performs a transmission display by allowing light from a back surface side to pass therethrough in at least a portion of the pixel region;

the pixel electrode includes a light-transmitting conductive layer formed in the transmission region;

the light-transmitting conductive layer of the pixel electrode is formed below the counter electrode and has at least a portion thereof overlapped to the counter electrode by way of the insulation film in the transmission region, and

the liquid crystal is driven by an electric field which is generated between the pixel electrode which also functions as the reflector and the counter electrode in a reflection region, and is driven by an electric field which is generated between the light-transmitting conductive layer of the pixel electrode and the counter electrode in the transmission region.

9. A liquid crystal display device according to claim 8, wherein the first substrate includes gate signal lines to which a scanning signal is applied, drain signal lines to which the video signal is applied, thin film transistors which are connected with the gate signal lines and are driven in response to the scanning signal, and source electrodes to which the video signal is applied by way of the thin film transistors, and

the reflector is formed by extending the source electrode.

10. A liquid crystal display device according to claim 9, wherein the liquid crystal display device includes a capacitance signal line which is formed at a position below the source electrode in an overlapped manner by way of a second insulation film.