Radiant energy – Invisible radiant energy responsive electric signalling – Infrared responsive
Reexamination Certificate
1998-10-14
2001-12-25
Hannaher, Constantine (Department: 2878)
Radiant energy
Invisible radiant energy responsive electric signalling
Infrared responsive
C356S632000, C356S051000
Reexamination Certificate
active
06333500
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a method of determining a property of a layer of a phosphor screen on a substrate. Said layer may be applied, for example, to the inner surface of a display window of a display device, for example the inner surface of a display window of a cathode ray tube, or to a lamp.
Cathode ray tubes are used, inter alia, in television receivers and computer monitors. Lamps are used in lighting devices.
Display devices, such as cathode ray tubes and plasma display apparatuses, comprise a phosphor screen on an inner surface of a display window. A phosphor screen comprises a number of layers, for example three phosphor layers (red, green and blue), a so-called black matrix layer and, sometimes, color filter layers. The quality of the image displayed by the display device is determined to a substantial degree by the properties of these layers. A method of determining a number of properties of phosphor layers in a cathode ray tube is disclosed, for example, in the English-language abstract of Japanese patent application 08-162023. The position of the phosphor layers is determined by means of optical measurements.
Phosphor layers are also applied to the inner surface of lamps. The quality of the lamps depends on the quality of the applied phosphor layer.
However, a number of properties and, in particular, the thickness of a layer cannot be measured by means of the known method. Hitherto, the thickness is customarily measured by making an incision in a phosphor layer whereafter the thickness is measured. However, this measuring method is destructive, which leads to higher costs and which also means that it is impossible to test a product which is to be sold.
It is an object of the invention to provide a method which enables properties of a layer of a phosphor screen on a substrate, for example the inner surface of a display window of a display device or a lamp, to be determined in a non-destructive manner.
SUMMARY OF THE INVENTION
To achieve this, the method in accordance with the invention is characterized in that the substrate and the layer are exposed to infrared radiation and, after passage through the layer and the substrate, the intensity of the beam is measured in a number of spots.
The invention is based on the recognition that the infrared light transmission of a layer of a phosphor screen is governed by the thickness and porosity of the layer, not, or only to a small degree, by other properties of the substrate and/or the phosphor layer. Other radiation (visible light or UV radiation) is largely absorbed by the material of the substrate (mostly a type of glass) or the material of the layer. Phosphor layers as well as color filter layers and black matrix layers exhibit a high degree of absorption in the visible-light spectrum. As a result, the transmission of visible light or UV radiation is much lower and subject to all kinds of disturbing variations. However, by using infrared light it becomes possible to measure the thickness of the layer (and/or other properties, as will be described hereinbelow) in a simple and non-destructive manner.
The method in accordance with the invention can particularly advantageously be used to determine the layer thickness of the phosphor layer, in which operation, preferably, also the porosity of the phosphor layer is determined.
Preferably, a substantially parallel beam of infra-red radiation is sent through the substrate and the phosphor layer.
The use of a substantially parallel beam enables the thickness of the phosphor layer to be determined more accurately.
The invention also relates to a device for determining a property of a layer of a phosphor screen on a substrate.
The device in accordance with the invention is characterized in that the device comprises a means for holding the substrate, an infrared source for emitting infrared radiation and a recording means for recording or measuring infrared radiation emitted by the source and passed by the substrate and the phosphor layer. Said recording means may be, for example, an infrared camera.
These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.
REFERENCES:
patent: 3764555 (1973-10-01), Vincent et al.
patent: 3773420 (1973-11-01), Conroy
patent: 4243882 (1981-01-01), Yasujima et al.
patent: 4680503 (1987-07-01), Spierings et al.
patent: 5619330 (1997-04-01), Ehemann, Jr. et al.
patent: 5644193 (1997-07-01), Matsuda et al.
patent: 08162023A (1996-06-01), None
Gehring Frederik C.
Scholten Pieter
Uitterhoeve Petrus J.
van Rijsewijk Lambertus J. J.
Hannaher Constantine
Lee Shun
Spain Norman N.
U.S. Philips Corporation
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