LCD having particular dielectric constant relationship between orientation film and LC layer

• US 6,384,892 B1
• Filed: 01/13/2000
• Issued: 05/07/2002
• Est. Priority Date: 01/13/1999
• Status: Expired due to Fees

• Current Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: Johnson, Mark T., Van Der Put, Adrianus A.
• Primary Examiner(s): TON, MINH TOAN T
• Application Number:
  US09/482,930
• Time in Patent Office: 845 Days
• Field of Search: 349/123, 349/177, 349/171, 399/123, 399/171, 399/177
• US Class Current: 349/177
• CPC Class Codes: G02F 1/13306 Circuit arrangements or driving methods for the control of single liquid crystal cells G02F1/132, G02F1/133382 take precedence
• CPC Class Codes: G02F 1/1337 Surface-induced orientation of the liquid crystal molecules, e.g. by alignment layers
• CPC Class Codes: G02F 1/139 based on orientation effects in which the liquid crystal remains transparent

Abstract

In a liquid crystal display device, the dielectric constants (∈) and resistivities (ρ) of the liquid crystal material and the layers of orienting material have such values that the liquid crystal display device can be driven by means of a DC voltage.

Claims

1. A liquid crystal display device comprising pixels and electrodes for driving the pixels, each pixel comprising a display element defined by picture electrodes, which display element comprises layers of orienting material and a layer of liquid crystal material between the picture electrodes, characterized in that, for the quotient Q of a dielectric constant ∈

_LC of the liquid crystal material and the dielectric constant of the layers of orienting material ∈

_ol it holds that Q=∈

_LC/∈

_ol>

0.7ρ

_ol/ρ

_LC, in which, for a liquid crystal material having a negative dielectric anisotropy (Δ

∈

<

0)∈

_LC, the dielectric constant perpendicular to the directors of the liquid crystal material is (∈

_⊥

), and for a liquid crystal material having a positive dielectric anisotropy (Δ

∈

>

0)∈

_LC, the dielectric constant parallel to the directors of the liquid crystal material is (∈

_∥

) and ρ

_ol and ρ

_LC are the resistivities of the liquid crystal material and the layers of orienting material, respectively, and wherein the display device is DC driven.

2. A liquid crystal display device as claimed in claim 1, characterized in that Q=∈

_LC/∈

_ol≧

ρ

_ol/ρ

_LC.

3. A liquid crystal display device as claimed in claim 1, characterized in that Q=∈

_LC/∈

_ol has a value of between 1 and 4.

4. A liquid crystal display device as claimed in claim 3, characterized in that 1≦

Q≦

1.8.

5. A liquid crystal display device as claimed in claim 1, characterized in that ρ

_ol/ρ

_LC<

10 (T=25°

C.).

6. A liquid crystal display device as claimed in claim 1, characterized in that ρ

_ol is at least 10⁷ ohmmeter (T=25°

C.).

7. A liquid crystal display device as claimed in claim 1, characterized in that the display device comprises means for presenting drive voltages in one polarity across the pixels.

8. A liquid crystal display device as claimed in claim 7, characterized in that the display device comprises drive means for presenting row selection signals to the row electrodes and drive means for presenting data signals to the column electrodes.

9. A liquid crystal display device as claimed in claim 8, characterized in that the drive means for presenting data signals comprise correction means for adapting the voltage of the data signals in dependence upon presented data.

10. A liquid crystal display device as claimed in claim 7, characterized in that the display device is provided with an illumination unit comprising means for sequentially presenting light in at least two wavelength ranges, and the drive means are provided with means for presenting, to the display device, the data signals of a wavelength range-associated sub-image of an image to be displayed.

11. A liquid crystal display device as claimed in claim 1, characterized in that the display device comprises driving means for inverting the voltages over the display elements at switching on the display device or after a period of one minute.