LCD-cell

• US 20020171799A1
• Filed: 04/23/2002
• Published: 11/21/2002
• Est. Priority Date: 04/30/2001
• Status: Active Grant

• Current Assignee: AEG Gesellschaft
• Original Assignee: AEG Gesellschaft
• Inventors: Bader, Otto, Bitter, Thomas, Bayrle, Reiner
• Granted Patent: US 6,876,423 B2
• Time in Patent Office: Days
• US Class Current: 349/155
• CPC Class Codes: G02F 1/13392 spacers dispersed on the cell substrate, e.g. spherical particles, microfibres

Abstract

Cells in liquid crystal displays (hereinafter LCD) are comprised of two parallel plates (1, 2) between which a liquid crystal (4) is to be found. Between the plates (1, 2) are placed, in conventional cells, spacers (5), which determine the layer thickness d of the LCD cell. Because of the clearly higher heat expansion of the liquid crystal (4) as compared to that of the spacers (5), vacuum void formation can occur in the case of conventional LCD cells when subjected to excessively low operating temperatures, or a macroscopic layer thickness change can occur under conditions of high operating temperatures which can lead to nonuniform color effects.

In the case of a LCD cell in accord with the invention, the spacers (5) include a first spacer (5a) and a second spacer (5b), which differentiate themselves from one another by their material characteristics and their geometric dimensioning. By means of an appropriate local and quantitative apportionment of the spacers, over the entire cell a localized different structural strength and/or heat expansion can be made.

Claims

1. An LCD cell with a first transparent plate (1), a second parallel, transparent plate (2) parallel to and located behind the first transparent plate (1), a liquid crystal (4) placed between the first and the second plates (1, 2), a sealing means (3) peripherally sealing the first and the second plates (1, 2) to retain the liquid crystal (4), and spacers (5) placed between the two plates (1, 2), therein characterized, in that the spacers 5 comprise first spacers (5a) and second spacers (5b), which said second spacers (5b) differentiate themselves from the first spacers (5a) in their dimensions and in the properties of their materials of construction.

2. An LCD cell in accord with claim 1, therein characterized, in that the first spacers (5a), in a direction perpendicular to the two plates (1, 2), exhibit a dimensioning, which essentially corresponds to the difference in distance between the surfaces of the two plates (1, 2) which face one another.

3. An LCD cell in accord with claim 1, therein characterized, in that the compression module for the first spacer (5a) lies clearly above that of the liquid crystal (4).

4. An LCD cell in accord with claim 3, therein characterized, in that the first spacers (5a), in a direction perpendicular to the two plates, possess a structural strength in a general magnitude not less than that of glass.

5. An LCD cell in accord with claim 1, therein characterized, in that the first spacers (5a) possess a clearly lesser heat expansion coefficient than that of the liquid crystal (4).

6. An LCD cell in accord with claim 1, therein characterized, in that the first spacers (5a) are affixed by adhesive means on at least one of the surfaces of the plates (1, 2) which face one another.

7. An LCD cell in accord with claim 1, therein characterized, in that that the dimensioning of the second spacer (5b), in a direction perpendicular to the two plates, is so selected, that said dimensioning, in the undeformed condition, is greater than the distance between the facing surfaces of the plates (1, 2) even at the highest operating temperature of the LCD cell.

8. An LCD cell in accord with claim 1, therein characterized, in that the second spacers (5b) at least in a direction perpendicular to the two plates exhibits a lesser structural strength than the structural strength of the first spacers (5a).

9. An LCD cell in accord with claim 1, therein characterized, in that the second spacers (5b) show a higher heat expansion coefficient than that of the first spacers (5a).

10. An LCD cell in accord with claim 1, therein characterized, in that the apportionment of the spacers (5a, 5b) is so selected, that a defined elasticity exists between the first plate (1) and the second plate (2).

11. An LCD cell in accord with claim 1, therein characterized, in that the apportionment of the spacers (5a, 5b) is so selected, that a defined heat expansion capability between the first plate (1) and the second plate (2) exists.

12. An LCD cell in accord with claim 1, therein characterized, in that the expansion of the spacers (5a, 5b) in a direction perpendicular to the two plates is so selected, that the majority of the first spacers (5a) are smaller than the majority of the second spacers (5b).

13. An LCD cell in accord with claim 1, therein characterized, in that the sum of the average value of the expansion in a direction perpendicular to the two plates of the first spacers (5a) and the threefold variance of which is smaller than the difference of the average value of the expansion of the second spacers (5b) in a direction perpendicular to the two plates and the threefold variance thereof.

14. An LCD cell in accord with claim 1, therein characterized, in that the sum of the average values of the expansion of the first spacers (5a) in a direction perpendicular to the two plates and the variance thereof, is smaller than the difference of the average values of the expansion of the second spacers (5b) in a direction perpendicular to the two plates and the variance thereof.