DE2903735A1 - Conductive cathode ray tube layer - applied after coating bare areas with lacquer film - Google Patents

Abstract

A magnetically and/or electrically conductive layer is applied to parts of the inside of a cathode ray tube, with sharp boundaries between coated and uncoated areas. The uncoated areas are first covered by a film of lacquer. The conductive layer is then applied and the film of lacquer is finally washed off together with any conductive layer on it. This ensures a uniform layer thickness and sharp boundaries where it adjoins uncoated areas.

Description

Method for applying a layer in cathode ray tubes.

The invention relates to the application of a magnetic and / or electrically conductive layer inside the bulb of a cathode ray tube.

Layers inside the picture tube are either called electrical Conductive layers, such as described in DE-AS 22 57 497, or as magnetic field. Shielding layers, e.g.

described in DE-OS-2050 841, used.

The acceleration voltages are on these layers, in the case of color picture tubes e.g. 25 kV. If the layers are also still on the part of the neck of a cathode ray tube extend where the electron gun is located, so flashovers can occur between the layers at high electrical potential and the electron gun appear. Also so-called throat punctures through the thin neck glass, e.g. to the deflection system are more common then.

Therefore there are areas inside the tube that correspond to those described Layers are covered and areas are left uncovered. The areas to remain vacant are part of the red neck and, in the case of color picture tubes, also the upper edge of the funnel-shaped Cone on which this is connected to a screen trough by means of a frit.

The layer thickness must be very uniform and, in particular, the The border between covered and uncovered areas must be very smooth, otherwise it will become bead-like transitions slightly Material of the layer crumbles, especially when the centering springs and contact springs of an electron gun be pushed across the border.

To avoid this crumbling, DE-OS 26 37 754 gives a method on, in which the layer, in this case an electrically conductive layer, on a Cone is applied, in which while the layer dries the neck up to the desired limit is kept moist by immersion e.g. in water and the part kept moist is washed off afterwards.

It has been shown that the usefulness of this process is strong depends on the type of layer applied. Many layers show capillary action, so that areas that have not been immersed remain moist while drying and washed off in the final step. This is how the border runs very unevenly contrary to the required work result.

So there is the task of a method for applying a layer indicate inside a picture tube which allows it, regardless of the nature the layer with a uniform layer thickness a smooth, sharp transition between coated and uncoated areas.

The solution to the problem can be found in the first claim.

Advantageous embodiments of the applied lacquer are in the Specified below. The solution according to the invention has the considerable The advantage of having several sharp, smooth dividing lines at the same time when using a any method for applying the Layer can be made can. By successively dipping in a quick-drying film former For example, first the neck and then the frit surface of a BilA tube cone with the protective varnish are provided. Then channel the actual layer through any one Verfahrerl, but in particular can be applied by spraying.

In the previously known method must during the slow drying a vessel with water must be permanently attached to the neck of the tube for the inner conductive layer, to keep the part of the layer to be removed moist. A simultaneous moisturizing the fritting surface that then stands up is excluded. A sharp one smooth edge between coated and uncoated areas on this upper one Place must be achieved through a special process.

The efficient spray-on process is therefore practically impossible.

pie invention is illustrated below with reference to the figure Implementation examples illustrated.

The figure shows a color picture tube cone coated according to the invention 1 with its neck part 2 and the frying area 3. The coated area 4 is area-dotted drawn. 5 is the boundary between coated and in-coated area in the neck part and 6 is the corresponding limit at the upper end of the cone.

After the method according to the invention, the well-cleaned cone first dipped with the neck in a film former, up to the point at which the transition between coated and uncoated area should lie. After the film former has dried on, the cone can be rotated and the fritted surface is immersed accordingly.

After the film former has dried at the point (s) to be protected the inner layer is made by one of the known processes, e.g. painting, brushing, Pouring, filling or spraying, applied and also dried. Finally the paint film and together with it the inner layer on it is washed off. The washing process can be carried out by applying mechanical force, e.g. with a bristle or by means of a suitable / shaped jet nozzle.

The following can be used as film images: - Materials that are before and after Drying are soluble in water, e.g. polyvinyl acetate, polyvinylpyrrolidone, casein, Starch, glue, cellulose, preferably gelatin or polyvinyl alcohol.

- Materials that are before and after drying in organic solvents are soluble, e.g. polymethacrylate, polystyrene, nitrocellulose, polyester, solvent-based paints.

- Materials that are after film formation with aqueous chemicals E.g. diluted alkalis or acids are redispersible, e.g .: polyacrylates.

The inner layer applied to the paint film should be the same b @ nets, otherwise at the transition between areas protected by the lacquer film and unprotected places numbness of the inner layer can occur, which in turn to an uneven transition between coated and uncoated areas would roar.

Claims (5)

Method for applying a layer in cathode ray tubes Claims Method of applying a cathode ray tube interior of the envelope partially covering magiletic and / or electrically conductive layer with sharp, smooth dividing lines between covered and uncovered areas, characterized by that the remaining areas are first covered with a paint film that then the conductive layer (4) is applied and that finally the paint film is washed off with the part of the conductive layer located on it. 2) Method according to claim 1, characterized in that the remaining free Areas are covered with a water-soluble paint film. 3) Method according to claim 1, characterized in that the to be released Areas covered with an irl organic solvent-soluble lacquer film will. ) The method according to claim 1, characterized in that the remaining free Areas can be covered with a redispersible paint film. 5) Method according to claim 1, characterized in that the paint film with the part of the conductive layer on it supported by application mechanical force is washed off.