EP0012921B1 - Flat gas discharge display device - Google Patents

Abstract

A luminescent screen for flat image display devices, having improved light efficiency comprises a perforated plate (5) positioned on the inside of a luminescent screen glass (1), with the plate holes (6) extending above the individual spaced-apart luminescent areas or phosphor dots and the hole walls (6a) being provided with a metallization layer (8) and/or an extension of the luminescent layer (7) on the glass screen (1). In preferred embodiments, the plate holes are etched so that each hole is enlarged toward the front of the screen and the walls thereof assumes at least an approximately parabolical shape opening toward the glass screen and such angular walls are at least partially coated with a metal layer and/or a luminescent material layer for further improved light efficiency (FIG. 4).

Description

The invention relates to a flat gas discharge display device according to the preamble of claim 1.

With flat image display devices, i.e. Image display devices with a flat screen, such as are known in particular according to the principle of gas discharge display as a plasma panel or plasma display and are described, for example, in DE-OS 24 12 869, require a luminescent screen with one or more colors and with a high luminous efficacy. A plasma serves as the actual cathode, from which an electron beam is drawn via a control perforated plate with matrix control for each illuminated spot to be excited. Compared to the classic cathode ray picture tube, where a single electron beam has to reach all the luminous points and can experience very high accelerations with the dimensions of the picture tube required as a result, the electron beams are low-energy in gas discharge display devices. Due to the flat design, high acceleration voltages are not possible. It is therefore extremely important to get a high luminous efficacy when converting the electron energy into light or when generating light in the luminous dots, for example through UV radiation.

For this purpose, it is already known in the classic cathode ray tube and described, for example, in US Pat. No. 3,858,083, to coat the phosphor dots on the inside with a reflective metal layer. The light emitted to the rear by the excited phosphor is largely reflected by this metal layer and added to the light emitted to the front. However, the exciting electrons are also weakened on this metal layer, which does not play a major role in the case of the high-energy cathode-ray electrons, but makes it difficult to use such metal mirrors in the case of the low-energy electrons of the flat gas discharge display devices.

From the above-mentioned US Pat. No. 3,858,083, it is also known to separate the luminous dots from one another by means of opaque borders. In connection with flat image display devices, this is also described in the older patent application P 28 06 436. FR-PS 22 78 152 shows a gas discharge display device in which a separate plasma space is assigned to each pixel. This plasma room has conical walls covered with fluorescent material. There is no post-acceleration of electrons there, the light yield is low, in particular because only the plasma particles generated in the very small space between the glass plate on the observer side and the phosphor layer can reach the phosphor and excite it.

The present invention has for its object to provide a luminescent screen with black-rimmed luminous dots high yield and color purity without the measures adversely affect the energy source causing the light.

• a) auf der Innenseite des Leuchtschirms trägt eine Schirmglasplatte über der Schwarzumrandungsschicht eine Lochplatte, die über jedem Leuchtpunkt ein Loch hat;
• b) die Wände der Plattenlöcher tragen zumindest auf einem der Schirmglasplatte zugewandten Wandteil eine Leuchtstoffschicht, die als Erweiterung der unter den Löchern auf der Schirmglasplatte aufgebrachten Leuchtstoffpunkte auf die Lochwände hochgezogen ist.

To achieve this object, the following features are proposed according to the invention in a fluorescent screen of the type mentioned at the outset:

• a) on the inside of the fluorescent screen, a screen glass plate carries a perforated plate over the black border layer, which has a hole above each luminous point;
• b) the walls of the plate holes carry, at least on a wall part facing the screen glass plate, a phosphor layer which is drawn up onto the hole walls as an extension of the phosphor points applied under the holes on the screen glass plate.

With the aid of a fluorescent screen according to the invention, the active fluorescent surface can be considerably enlarged or better utilized compared to the pure illuminated dot surface. More electrons reach fluorescent particles that emit their light in all directions, including forward. The amount of light emitted towards the front becomes significantly larger per luminous point than if only one fluorescent surface corresponding to the luminous point and only lying in the luminous point plane is used.

The perforated plate separates the illuminated dots from each other. No electrons scattered at one luminous point can reach an adjacent luminous point. This decoupling of the luminous dots considerably improves the contrast and color purity compared to purely flat screen arrangements. Reflected electrons also contribute to increasing the luminous efficiency when they hit additional phosphor layers of the same color.

A further increase in the luminous efficacy is achieved by metallizing the perforated walls, i.e. at the locations of the perforated walls where the additional layer of fluorescent material is attached, between the wall and the fluorescent layer. As a result, the proportion of light emitted by the phosphor in the direction of the perforated wall is at least partially reflected in the direction of the screen glass.

The holes advantageously widen toward the screen glass side and thereby form a mirror for the light component emitted towards the rear, ie into the holes, which largely reflects the light towards the front.

An advantageous embodiment is obtained if the expansion with the metallization results in a parabolic mirror.

It is also advantageous if the metallization of the perforated walls also extends to the connecting surfaces of the perforated plate with the black border layer, so that a coherent, electrically conductive layer arises. Then the entire metallization can be used as an electrode for the impinging electrons. The metallization takes place before the perforated plate is applied, for example by a cathode sputtering process, by vapor deposition, a defined metallization depth into the holes being achieved by a certain vapor deposition angle, by chemical vapor deposition or by electroless deposition in the liquid phase. In operation, the metallization of the perforated plate is set to a potential which firstly allows enough electrons to strike the wall and thus the fluorescent substance located there, secondly, to prevent charging effects, the electrons are discharged, and thirdly enough electrons for them leaves the phosphor layer sitting on the screen glass, ie does not impair the function of the acceleration anode lying between the phosphor layer and the screen glass.

The perforated plate is preferably made of glass and is melted onto the black border layer. An intermediate metallization does not affect this connection. The use of a suitable ceramic material is also possible.

According to a development of the fluorescent screen according to the invention, the perforated plate is so strong that it serves as a spacer between the screen glass plate and the control perforated plate used in a gas discharge display device. Even in the case where the perforated plate is only used as a base for any further plates or elements as a spacer between the screen glass plate and the control perforated plate, it enables an exact spacing in which the fluorescent layers are protected.

• Figur 1 eine perspektivische Darstellung einer Lochplatte,
• Figur 2 einen Schnitt durch einen erfindungsgemäßen Leuchtschirm mit parallelen metallisierten Lochwänden in der Lochplatte und zusätzlicher Leuchtstoffschicht,
• Figur 3 einen Schnitt mit annähernd parabelförmigen metallisierten Lochwänden und zusätzlicher Leuchtstoffschicht,
• Figur 4 einen Schnitt mit doppelkegligen metallisierten Lochwänden und zusätzlicher Leuchtstoffschicht.

The invention will be explained in more detail with reference to exemplary embodiments shown in the figures of the drawing. Show

• FIG. 1 shows a perspective illustration of a perforated plate,
• FIG. 2 shows a section through a fluorescent screen according to the invention with parallel metallized perforated walls in the perforated plate and additional phosphor layer,
• FIG. 3 shows a section with approximately parabolic metallized perforated walls and additional phosphor layer,
• Figure 4 shows a section with double-cone metallized perforated walls and additional phosphor layer.

In the perspective schematic representation of FIG. 1, 1 denotes a screen glass as the front pane of a flat gas discharge image display device. There is - in the interior of the image display device - an approximately 0.2 μm thick conductive layer 2 made of doped indium oxide as an acceleration anode for the electron beams drawn from the gas discharge (indicated by arrows). There is a black border layer 3 in the form of a grid, which leaves the surfaces 4 free for luminous dots. On the black border layer 3 there is a perforated plate 5, which has through-holes 6 above the grid openings 4 of the black border layer 3.

The further structure can be seen from the sectional view of FIG. 2. In the openings 4 of the black border layer 3 there are fluorescent layers as luminous dots, which extend further into the walls of the holes 6 up to approximately two thirds of the depth. Between the perforated plate 5 and the black border layer 3 there is a metallization layer 8, which also extends to the walls of the holes 6 and comes to rest there between the phosphor layers 7 and the perforated walls of the perforated plate 5.

This arrangement of a fluorescent screen according to the invention is produced, for example, as follows: A glass solder grating is applied as a black border 3 to the screen glass 1. For this purpose, glass solder is slurried with a so-called "black dye" additive made from various metal oxides with methyl glycol acetate, spray thinner and photo lacquer, sprayed over the entire surface and, after drying, exposed with masks of the appropriate three-color grid for color television, then developed and dried. A black border as a common expression means an opaque border.

A 1 mm thick glass pane is used as the perforated plate 5, the outer dimensions of which correspond to those of the screen glass 1. The holes have either been created using classic glass etching processes or by means of a photo process, as is used, for example, in the commercially available photo-shaped glass. The metallization is carried out by evaporating a 100 nm thick Al layer 8 in a high vacuum. The holes 6 are vapor-coated with aluminum to a depth of approximately 0.2 mm. With a perforated area of approx. 0.2 x 0.5 mm ^2, the «active» area is quadrupled. Screen glass 1 and perforated plate 5 are sintered together after adjustment, the pre-dried glass solder grid of black border 3 applied to screen glass 1 serving as solder.

Then sprayable slurries of a red (e.g. Y ₂ 0 ₂ S: Eu), green (e.g. (Zn, Cd) S: Cu) and blue (e.g. ZnS: Eu) phosphor are successively used for the phosphor coating through corresponding magnetically held steel masks or sprayed nickel on the illuminated dot areas corresponding to the colors. The masks lie on the perforated plate 5 and are mechanically adjusted. With the appropriate spray setting, the screen glass 1 and the glass plate walls are covered with phosphorus. The phosphor layer is then degassed by binders.

3 shows the embodiment in which the holes 6 of the glass plate 5 are widened toward the screen glass 1 and carry a metallization layer 8, the phosphor layer 7 is pulled up to the metallization 8 of the perforated walls and the expansion is approximately parabolic by appropriate etching, so that 8 parabolic mirrors can be removed with the metallization.

Fig. 4 shows a further modified hole shape, the holes 6 of the perforated plate 5 are formed by etching on both sides and are thus open on both sides. They are approximately double-cone-shaped, the cone open towards the screen glass 1 carrying the metallization 8 and the phosphor layer 7.

The two-sided expansion of the holes 6 has the advantage that the cone walls can be kept steeper without the electron-side opening of the holes 6 becoming too narrow. This is particularly advantageous if the perforated plate 5 is so thick that it serves as a spacer between the screen glass 1 and the control perforated plate of the gas discharge display device.

Claims (7)

1. A flat gas discharge display device having a plasma serving as cathode, a perforated control plate having a matrix control for each fluorescent dot on a fluorescent screen, which is to be excited, an acceleration anode to which an acceleration voltage adapted to the production of an electron beam is applied, and fluorescent dots which are separated from one another by a black border, characterised by the following features :

a) on the inner side of the fluorescent screen, above the black border layer (3), a shielding glass plate (1) supports a perforated plate (5) which has an aperture (6) above each fluorescent dot;

b) the walls of the plate apertures (6) on at least one of the wall sections facing the shielding glass plate (1), carry a layer (7) of a fluorescent material which is provided on the aperture walls as an upward extension of the dots of fluorescent material located below the plate apertures (6) on the shielding glass plate (1).

2. A gas discharge display device as claimed in Claim 1, characterised in that the plate apertures (6) widen towards the shielding glass plate.

3. A gas discharge display device as claimed in Claim 2, characterised in that on the widening portions of the plate apertures (6), there is first arranged a metallisation (8) and then a layer (7) of a fluorescent material.

4. A gas discharge display device as claimed in Claim 3, characterised in that the widening portion, together with the metallisation (8), approximately forms a parabolic mirror.

5. A gas discharge display device as claimed in one of Claims 3 or 4, characterised in that the metallisation (8) of the aperture walls also extends to the connection surface of the perforated plate (8) with the black border layer (3), so that a continuous electrically conductive layer is produced.

6. A gas discharge display device as claimed in one of Claims 1 to 5, characterised in that the perforated plate (5) consists of glass and is fused onto the black border layer (3).

7. A gas discharge display device as claimed in one of Claims 1 to 6, characterised in that the perforated plate (5) is so thick that it serves as a spacer between the shielding glass plate (1) and the control perforated plate used in a gas discharge display device.

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