Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Including a second component containing structurally defined...
Reexamination Certificate
1998-09-29
2001-04-10
Thibodeau, Paul (Department: 1773)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Including a second component containing structurally defined...
C428S328000, C428S329000, C428S331000, C359S599000, C359S601000
Reexamination Certificate
active
06214457
ABSTRACT:
BACKGROUND OF THE INVENTION
A substrate with reduced glare, method for manufacturing a display window of a cathode ray tube and to a cathode ray tube having a display window.
Such methods are for instance used to reduce the glare of a display window of a display device such as a cathode ray tube or an LCD device.
The invention also relates to a method for manufacturing a display window of display device and to a display device having a display window with reduced glare.
Reflections on a substrate are often considered bothersome, especially when they occur on a surface of a display window of a display device, since such reflection reduce the contrast, clarity and/or colour reproduction of the displayed image. There are two ways in which the reflection on a surface can be suppressed; by randomly diffusing the reflected image (anti-glare, AG) or by preventing distinct optical interfaces (anti-reflex, AR). To reduce the glare several methods are known such as etching, wet-blasting and spraying of silica-like materials. These methods each have their short-comings. Etching requires the use of a strong etching fluid, which represent an environmental as well as a safety hazard and relatively expensive. Wet-blasting, which is a method in which hard particles suspended in a fluid are blasted against the surface to thereby change the surface structure of said surface, is a relatively expensive and time-consuming method and requires safety measures. Spraying of silica-like materials is a method which is time-consuming and in which relatively easily loose particles are generated and for which it is very difficult to achieve a even distribution of the silica particles over the surface and thus a evenly distributed reduction of the diffuse reflection.
SUMMARY OF THE INVENTION
The present invention has as its objective to provide a display device having a display window with a surface with reduced diffuse reflection.
To this end, according to the invention, a suspension comprising sub-micron transparent oxide particles and a binder is coated on the substrate e.g. on a surface of the display window to form a film, whereafter the film is dried in such manner that in situ flocculation of the particles takes place.
A display device according to the invention is characterized in that a coated film is provided on a surface of the display window which film comprises flocculated sub-micron transparent oxide particles.
Flocculation is a process wherein several particles flocculate (agglomerate) to form irregularly shaped larger flocs. Said flocs, preferably having an average size of approximately 1-5 &mgr;m, affect, namely strongly reduce, the diffuse reflection of visible light on said surface.
Flocculation of a suspension is normally considered a process which is to be prevented. Flocculation usually reduces the life-time of a suspension, the process itself, if it occurs, is very difficult to control, flocculation may notably prevent effective filtering of the suspension (because dust particles have approximately a size of 1-5 &mgr;m) and may lead to clogging up of suspension conduit pipes, spraying nozzles etc and reduces the homogenity of the applied layer leading to striations, patchiness etc of the dried layer.
The inventors have, however, realized that a film comprising flocculated sub-micron particles suppress diffuse reflection in a broad wavelength range, due to the fact that the size of the flocs is more or less randomly distributed in size. Therefor a very uniform suppression of diffuse reflection occurs. Furthermore it is realized that in situ, i.e. “on the surface of the substrate”, flocculation of the sub-micron particles is possible. By applying the suspension on the surface, and thereafter effecting flocculation of the sub-micron particles, distribution of the flocs is achieved which is on a centimeter scale evenly distributed, yet is, on a micron scale, truly random.
The layer could be applied by means of for instance flow-coating or spraying or other methods. Preferably, however, the film is applied by means of spin-coating. Spin coating allows in a simple manner to achieve a uniform thickness of the suspension over the surface. This increases the uniformity (on a large scale) of the distribution of the flocs over the display window.
Preferably the size of the sub-micron particles is between approximately 350 and 30 nm. In this size range the effect of each singular particle on the reflected light is small. Preferably the size of the particle is smaller than 200 nm. The effect of each particle on the light is then negligible.
The transparent oxide particles could consist of TiO
2
, SiO
2
, Al
2
O
3
etc.
Preferably the suspension is a colloidal suspension of the particles in water. Such suspensions do not require special health or environmental safety measures.
REFERENCES:
patent: 5296974 (1994-03-01), Tada et al.
patent: 5307438 (1994-04-01), Bilkadi et al.
patent: 5612128 (1997-03-01), Endo et al.
Compen Johannes M.A.A.
Cuppen Sebastianus N.G.
Meulendijks Gijsbertus H.W.M.
Vandijck Hendrikus L.
Faller F. Brice
Rickman Holly C.
Thibodeau Paul
U.S. Philips Corporation
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