Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
1995-04-10
2001-02-13
Shingleton, Michael B (Department: 2817)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C315S012100, C313S422000, C313S495000
Reexamination Certificate
active
06188178
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a color picture display device having a vacuum envelope, and including a front wall a, luminescent screen, and a rear wall, and particularly relates to a flat-panel picture display device (i.e. a picture display device having a small “front-to-back dimension”) which is clearly distinguished from state-of-the-art display devices.
Many research efforts in the field of picture display devices of the flat-panel type relate to devices having a transparent face plate and a rear plate which are interconnected by means of side walls and in which the inner side of the face plate is provided with a phosphor pattern, one side of which is provided with an electrically conducting coating (the combination generally being referred to as luminescent screen). A large number of electron-beam-producing means is generally arranged on the rear plate and a large number of deflection means is provided to cause each electron beam produced to scan a part of the luminescent screen. If video-information-controlled electron beams impinge upon the luminescent screen, a visual image is formed which is visible via the front side of the face plate. (The expression electron beam is understood to mean that the paths of the electrons in the beam are substantially parallel, or extend only at a small angle to one another, and that there is a main direction in which the electrons move.) The electron-beam controlled devices hitherto known require, inter alia, complicated electron-beam producing, focusing, and/or amplifying means and complicated deflection means.
In the case of a thin CRT display device having a flat face plate and rear plate the atmospheric pressure exerts a great force on the face plate and on the rear plate. The larger the dimensions of the display screen, the thicker the face plate and the rear plate must be, if no internal support means are provided.
SUMMARY OF THE INVENTION
In view of the foregoing, it is an object of the invention to provide a flat-panel picture display device which substantially does not have the drawbacks of the above-mentioned devices.
According to the invention, a color picture display device having a vacuum envelope including a front wall with a luminescent screen and a rear wall therefore comprises a plurality of juxtaposed sources for emitting electrons, electron ducts in the rear of the device and cooperating with the sources and having walls of substantially electrically insulating material having a secondary emission coefficient suitable for electron transport for transporting, through vacuum, electrons in the form of electron currents, means for withdrawing each electron current at predetermined (particularly successive) locations from its duct and means for directing said current toward a desired location on the luminescent screen, said luminescent screen having a repetitive pattern of triplets of phosphor elements luminescing in different colors (for example, red, green and blue), a flu-spacer structure of electrically insulating material being arranged adjacent to the luminescent screen. A flu-spacer structure is herein understood to mean a spacer which is adjacent to the luminescent screen.
The inventive approach of providing a flat-panel picture display device is based on the discovery that electron transport is possible when electrons impinge on a wall of an elongate evacuated cavity (referred to as compartment) defined by walls of high-ohmic, substantially electrically insulating material (for example, glass) if an electric field of sufficient power is realised in the longitudinal direction of the compartment (by, for example, applying an electric potential difference across the ends of the compartment). The impinging electrons then generate secondary electrons by wall interaction which are attracted to a further wall section and in their turn generate secondary electrons by wall interaction. As will be further described, the circumstances (field strength, electrical resistance of the walls, secondary emission coefficient &dgr; of the walls) may be chosen to be such that a constant vacuum current will flow in the compartment.
By withdrawing electrons at desired locations (via apertures) from the compartments and directing them towards a luminescent screen, for example, by means of an accelerating field, a picture can then be formed on the luminescent screen.
The maximal landing reserve is obtained by forming the color pattern on the luminescent screen as a delta configuration (triplets arranged in a triangular form). This landing reserve may be, for example, larger than in the case of a screen with color lines. Moreover, in the case of matrix-oriented displays with a screen of color lines, artifacts may occur in the picture (for example, a striped structure), which artifacts are now avoided.
A first embodiment is characterized in that the means for directing each electron current to a desired location on the luminescent screen comprises an apertured selection plate of electrically insulating material separated from the luminescent screen by the flu-spacer structure, each aperture of the selection plate being associated with one of the phosphor elements via an aperture in the flu-spacer structure which may be plate-shaped or honeycomb-shaped, for example. The desired vacuum support is now obtained by the combination: side walls of the electron duct-selection plate-flu-spacer structure.
The flu-spacer structure may be, for example, a system of mutually parallel walls extending at an angle (of approximately 60°) to the side walls of the electron ducts. This is possible because of the delta configuration of the phosphor elements and leads to a stabler construction than in the case where the side walls and the spacer walls would be parallel.
A preferred embodiment is, however, characterized in that the flu-spacer structure comprises a plate-shaped or honeycomb-shaped structure having apertures which correspond to the phosphor elements. These apertures associate each phosphor element with one aperture in the adjacent selection plate. In addition to a greater stability, the use of these structures has the extra advantage that electrons backscattered from the luminescent screen cannot land on other phosphor elements, which leads to a better contrast and a better color purity.
A selection means is provided by providing the apertures in the selection plate row by row with electrodes which are energizable by means of a first (positive) electric voltage (pulse) so as to withdraw electron currents from the ducts via the apertures of a row, or they are energizable by means of a second (lower) electric voltage if no electrons should be locally withdrawn from the ducts. The electrons extracted by this selection means can be directed towards the screen by applying an acceleration voltage.
All electron currents generated by the electron sources should be guided in the electron ducts across at least a part of the height towards the upper edge or the lower edge of the luminescent screen. For this purpose one row of electron sources or a plurality of parallel rows of electron sources may be provided.
Each of these electron sources may be placed within the electron duct with which it cooperates, or they are alternatively located at the outer side, opposite an entrance portion, of the electron duct with which they cooperate.
By applying a sufficiently large positive voltage difference between an electron source and the entrance portion of an electron duct cooperating therewith, the emitted electrons are accelerated towards the electron duct, whereafter they generate secondary electrons in the electron duct by means of wall interaction.
Electrons which are line-sequentially withdrawn from the electron ducts can be accelerated (as beams) towards the luminescent screen by a applying a sufficiently large voltage difference between the electron ducts and the screen, for example, a difference of 3 kV. One picture line at a time can thus be written. The video information (grey scales) can be presented, for example, in the form of puls
De Zwart Siebe T.
Lambert Nicolaas
Trompenaars Petrus H. F.
Van Gorkom Gerardus G. P.
Shingleton Michael B
U.S. Philips Corporation
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