Testing device for liquid crystal display base plate

• US 5,459,409 A
• Filed: 09/10/1991
• Issued: 10/17/1995
• Est. Priority Date: 09/10/1991
• Status: Expired due to Term

• Current Assignee: Photon Dynamics Incorporated (KLA Corporation)
• Original Assignee: Photon Dynamics Incorporated (KLA Corporation)
• Inventors: Henley, Francois J.
• Primary Examiner(s): Wieder, Kenneth A.
• Assistant Examiner(s): Bowser, Barry C.
• Application Number:
  US07/757,458
• Time in Patent Office: 1,498 Days
• Field of Search: 324/73 R, 324/770, 324/751-753
• US Class Current: 324/750.24
• CPC Class Codes: G01N 2021/9513 Liquid crystal panels
• CPC Class Codes: G02F 1/1309 Repairing; Testing
• CPC Class Codes: G09G 3/006 Electronic inspection or testing of displays and display drivers, e.g. of LED or LCD displays testing individual LED's G01R31/2635; testing lamps G01R31/44; testing of optical features of LCD displays G02F1/1309

Abstract

The present invention provides an electro-optical element arranged to face a liquid crystal base plate, an electric source to impress an electric voltage between them, a source of light for irradiating light on the electro-optical element, a light detector to receive the reflected light from the electro-optical element, and a mounting device for fixing the liquid crystal base plate in a fixed position. The mounting device has a highly flat surface, groove thereon and vacuum attaches the liquid crystal base plate on the surface of the base platform. Light irradiates a reflective layer located on the lower surface of an electro-optical element which is in close proximity to the liquid crystal display base plate. A voltage is applied across the electro-optical element and the light reflected by the electro-optical element are measured. The optical characteristics of the electro-optical element is measured. The optical characteristics of the electro-optical element change in proportion to the electric field across it. The electric field is supplied in part by the liquid crystal display base plate being tested. Thus, by measuring the reflected light, the integrity of the liquid crystal display base plate is evaluated.

Claims

1. A device for testing defects in a liquid crystal display base plate comprising:

a liquid crystal display base plate testing device placed facing the surface side of a liquid crystal display base plate;

an electro-optical element which changes its optical characteristics when an electric field from said liquid crystal display base plate is applied across it;

a power source to apply an electric voltage between said electro-optical element and each pixel element terminal of said liquid crystal display base plate;

irradiating light from a light source against the back side of said electro-optical element;

observing the reflected light received with a light detector;

a mounting device for fixing said liquid crystal display base plate during testing;

said mounting device having a flat surface and a base platform arranged so that the liquid crystal display base plate adheres to the surface of the mounting device;

a groove formed on the surface of the base platform; and

a device for vacuum attachment of the liquid crystal display base plate to the surface of the base platform by applying a vacuum to said groove.

9. The device of claim 1 wherein said electro-optical element includes a first and a second side, said first side of said electro-optical element being coated with a transparent electrical conductor.

10. The device of claim 1 wherein said electro-optical element includes a first and a second side, said second side of said electro-optical element being coated with a non-conductive, optically reflective coating.

11. The device of claim 1 wherein said electro-optical element comprises NCAP material.

12. The device of claim 1 wherein said electro-optical element comprises Pockell'"'"'s crystals.

13. The device of claim 1 wherein said base platform is rust-proof.

14. The device of claim 1 wherein said base platform includes a degree of flatness of about 0.1 microns.

15. The device of claim 1 wherein said base platform comprises stainless steel.

16. The device of claim 1 in which said groves are oriented such that by application of a vacuum of sufficient strength, said liquid crystal display base plate being tested can be held essentially flat against said base platform, temporarily curing any warping or sinuosity which may be present in said liquid crystal display base plate being tested.

17. The device of claim 9 in which said light source is located at an angle substantially perpendicular to said second side of said electro-optical element.

18. The device of claim 9 wherein said light detector is oriented at an angle substantially perpendicular to said second side of said electro-optical element.

19. The device of claim 1 wherein said light source is a tungsten lamp.

2. An apparatus for testing defects in liquid crystal display baseplates comprising:

a liquid crystal display baseplate to be tested;

an electro-optical element;

a voltage source;

a light source;

a mounting device; and

a light detector;

said electro-optical element comprising a first and second side, said first side of said electro-optical element being coated with a transparent electrical conductor, said second side of said electro-optical element being coated with a non-conductive, optically reflective coating;

said liquid crystal display baseplate having a circuit side, and a second side;

said electro-optical element being placed adjacent to said liquid crystal display baseplate to be tested such that said second side of said electro-optical element is facing, and slightly spaced apart from said circuit side of said liquid crystal display baseplate;

said light source illuminating said first side of said said electro-optical element;

said voltage source electrically connected to said electrically conductive layer on said first side of said electro-optical element, and said circuitry on said liquid crystal display baseplate to be tested;

said voltage source applying a voltage between said electro-optical element, and said liquid crystal display baseplate such that an electric field is generated across said electro-optical element; and

said light detector oriented such that it detects light reflected from said second side of said electro-optical element, such that defective circuitry on said circuit side of said liquid crystal display baseplate being testing will cause a variation in the electric field generated, and thus a variation in the light reflected by the electro-optical element.

3. The apparatus for testing defects in liquid crystal display baseplates as described in claim 2 which further includes a base platform;

and

a groove formed on the surface of said base platform, and a vacuum applied to said groove such that said liquid crystal display baseplate being tested is firmly attached to said base platform by application of said vacuum.

4. The apparatus for testing defects in liquid crystal display baseplates as described in claim 3 in which said base platform is formed of stainless steel.

5. The apparatus for testing defects in liquid crystal display baseplates as described in claim 3 in which said grooves are oriented such that by application of a vacuum of sufficient strength, said liquid crystal display base plate being tested can be held essentially flat against said base platform, temporarily curing any warping or sinuosity which may be present in said liquid crystal display base plate being tested.

6. The apparatus for testing defects in liquid crystal display baseplates as described in claim 2 in which said light source is located at an angle substantially perpendicular to said second surface of said electro-optical element.

7. The apparatus for testing defects in liquid crystal display baseplates as described in claim 2 in which said light detector is oriented at an angle substantially perpendicular to said second side of said electro-optical element.

8. The apparatus for testing defects in liquid crystal display baseplates as described in claim 2 in which said light source is a Tungsten lamp.