Transmission type liquid crystal display device having capacitance ratio of 10% or less and charging rate difference of 0.6% or less

• US 5,953,084 A
• Filed: 07/06/1998
• Issued: 09/14/1999
• Est. Priority Date: 08/11/1995
• Status: Expired due to Term

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Okamoto, Masaya, Shimada, Takayuki, Yamamoto, Akihiro, Katayama, Mikio, Shimada, Yoshinori, Kajitani, Masaru, Nishiki, Hirohiko, Nakata, Yukinobu, Kondo, Naofumi, Sakuhana, Yoshikazu
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): CHOWDHURY, TARIFUR RASHID
• Application Number:
  US09/110,151
• Time in Patent Office: 435 Days
• Field of Search: 349/38, 349/39, 349/42
• US Class Current: 349/38
• CPC Class Codes: G02F 1/133345 Insulating layers G02F1/1335, G02F1/1337, G02F1/135, G02F1/136 take precedence
• CPC Class Codes: G02F 1/13606 having means for reducing parasitic capacitance
• CPC Class Codes: G02F 1/136209 Light shielding layers, e.g. black matrix, incorporated in the active matrix substrate, e.g. structurally associated with the switching element
• CPC Class Codes: G02F 1/136213 Storage capacitors associated with the pixel electrode
• CPC Class Codes: G02F 1/136227 Through-hole connection of the pixel electrode to the active element through an insulation layer
• CPC Class Codes: G02F 2201/40 Arrangements for improving the aperture ratio

Abstract

The transmission type liquid crystal display device of this invention includes: gate lines; source lines; and switching elements each arranged near a crossing of each gate line and each source line, a gate electrode of each switching element being connected to the gate line, a source electrode of the switching element being connected to the source line, and a drain electrode of the switching element being connected to a pixel electrode for applying a voltage to a liquid crystal layer, wherein an interlayer insulating film formed of an organic film with high transparency is provided above the switching element, the gate line, and the source line, and wherein the pixel electrode formed of a transparent conductive film is provided on the interlayer insulating film.

Claims

1. A liquid crystal display device, comprising:

gate lines;

source lines; and

switching elements each arranged near a crossing of each gate line and each source line, a gate electrode of each switching element being connected to the gate line, a source electrode of the switching element being connected to the source line, a drain electrode of the switching element being connected to a pixel electrode for applying a voltage to a liquid crystal layer, wherein

an interlayer insulating film is above the switching element, the gate line, and the source line,

the pixel electrode is on the interlayer insulating film,

wherein a capacitance ratio is represented by expression;

space="preserve" listing-type="equation">Capacitance ratio=C.sub.sd /(C.sub.sd +C.sub.ls), and

the ratio is 10% or less, wherein C_sd denotes a capacitance value between the pixel electrode and the source line, and C_ls denotes a capacitance value of a liquid crystal portion corresponding to each pixel in an intermediate display state.

2. A liquid crystal display device according to claim 1, further comprising:

a storage capacitor for holding a voltage applied to the liquid crystal layer, the storage capacitor including;

a storage capacitor electrode;

a storage capacitor counter electrode; and

an insulating film therebetween;

wherein a capacitance ratio is represented by expression;

space="preserve" listing-type="equation">Capacitance ratio=C.sub.sd /(C.sub.sd +C.sub.ls +C.sub.s), and

the ratio is 10% or less, wherein C_sd denotes a capacitance value between the pixel electrode and the source line, C_ls denotes a capacitance value of a liquid crystal portion corresponding to each pixel in an intermediate display state, and C_s denotes a capacitance value of the storage capacitor of each pixel.

3. A liquid crystal display device according to claim 1, wherein the pixel electrode and the interlayer insulating film are transparent.

4. A liquid crystal display device according to claim 1, wherein the pixel electrode and at least one of the source line and the gate line overlap each other by 1 μ

m or more in a line width direction.

5. A liquid crystal display device according to claim 1, wherein the interlayer insulating film is made of organic material and the thickness of the interlayer insulating film is about 1.5 μ

m or more.

6. A liquid crystal display device according to claim 1, wherein the shape of the pixel electrode is rectangular with a side parallel to the gate line being shorter than a side parallel to the source line.

7. A liquid crystal display device according to claim 1, further comprising a driving circuit for supplying to the source line a data signal of which polarity is inverted for every horizontal scanning period, and the data signal is supplied to the pixel electrode via the switching element.

8. A liquid crystal display device according to claim 2, wherein the storage capacitor electrode is formed in the same layer as the source line.

9. A liquid crystal display device according to claim 2, wherein the storage capacitor counter electrode is formed of a part of the gate line.

10. A liquid crystal display device according to claim 2, wherein the pixel electrode and the storage capacitor electrode are connected via a contact hole formed through the interlayer insulating film above the storage capacitor electrode.

11. A liquid crystal display device according to claim 7, wherein signals of opposite polarities are input into pixel electrodes adjacent each other in the transverse direction and each of the polarities of the signals is inverted every horizontal scanning period.

12. A liquid crystal display device according to claim 7, wherein the liquid crystal display device further comprises a counter electrode opposing to the pixel electrode and the counter electrode is AC driven.

13. A liquid crystal display device comprising:

gate lines;

source lines; and

switching elements each arranged near a crossing of each gate line and each source line, a gate electrode of each switching element being connected to the gate line, a source electrode of the switching element being connected to the source line, a drain electrode of the switching element being connected to a pixel electrode for applying a voltage to a liquid crystal layer, wherein

an interlayer insulating film is above the switching element, the gate line, and the source line,

the pixel electrode is on the interlayer insulating film, and

a charging rate difference of 0.6% or less, wherein the charge rate difference indicates a ratio of an effective value of a voltage applied to the liquid crystal layer in a gray scale display portion when the gray scale is uniformly displayed to that when a black window pattern is displayed in the gray scale display at a vertical occupation of 33%.

14. A liquid crystal display device according to claim 13, wherein the pixel electrode and the interlayer insulating film are transparent.

15. A liquid crystal display device according to claim 13, wherein the pixel electrode and at least one of the source line and the gate line overlap each other by 1 μ

m or more in a line width direction.

16. A liquid crystal display device according to claim 13, wherein the interlayer insulating film is made of organic material and the thickness of the interlayer insulating film is about 1.5 μ

m or more.

17. A liquid crystal display device according to claim 13, wherein the shape of the pixel electrode is rectangular with a side parallel to the gate line being shorter than a side parallel to the source line.

18. A liquid crystal display device according to claim 13, further comprising a driving circuit for supplying to the source line a data signal of which polarity is inverted for every horizontal scanning period, and the data signal is supplied to the pixel electrode via the switching element.

19. A liquid crystal display device according to claim 18, wherein signals of opposite polarities are input into pixel electrodes adjacent each other in the transverse direction and each of the polarities of the signals is inverted every horizontal scanning period.

20. A liquid crystal display device according to claim 18, wherein the liquid crystal display device further comprises a counter electrode opposing to the pixel electrode and the counter electrode is AC driven.

21. An active matrix substrate, comprising:

gate lines;

source lines; and

switching elements each arranged near a crossing of each gate line and each source line, a gate electrode of each switching element being connected to the gate line, a source electrode of the switching element being connected to the source line, a drain electrode of the switching element being connected to an electrode for forming a capacitance, wherein

an interlayer insulating film is above the switching element, the gate line, and the source line,

the electrode for forming a capacitance is on the interlayer insulating film, wherein a capacitance ratio is represented by expression;

space="preserve" listing-type="equation">Capacitance ratio=C.sub.sd /(C.sub.sd +C.sub.ls), and

the ratio is 10% or less, wherein C_sd denotes a capacitance value between the electrode for forming a capacitance and the source line, and C_ls denotes a capacitance value of the capacitance corresponding to the electrode for forming a capacitance.

22. An active matrix substrate comprising:

gate lines;

source lines; and

switching elements each arranged near a crossing of each gate line and each source line, a gate electrode of each switching element being connected to the gate line, a source electrode of the switching element being connected to the source line, a drain electrode of the switching element being connected to an electrode for forming a capacitance, wherein

an interlayer insulating film is above the switching element, the gate line, and the source line,

the electrode for forming a capacitance is on the interlayer insulating film, and

a charging rate difference of 0.6% or less, wherein the charge rate difference indicates a ratio of an effective value of a voltage applied to the electrode for forming a capacitance.