DE2404402A1 - PROCESS FOR MANUFACTURING COLOR SELECTIVE ELECTRODES FOR SHADOW MASK COLOR TUBES - Google Patents

Description

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81-22.105P 30. -1. 1974

HITACHI, LTD., TOKYO (Japan)

Process for producing color-selective electrodes for shadow mask color picture tubes

The invention relates to a method for producing a color-selective electrode for color picture display tubes (color picture tubes for short) to obtain images of high color purity.

In general, a post-etch treatment of a color-selective electrode such as e.g. B. a shadow mask is required when the fluorescent screen of a color picture tube by photographic etching with a large number of luminous dots

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the diameter of which is smaller than that of holes in the shadow mask; this applies in particular to Color picture tubes with a black body (matrix) or refocusable tubes. With these color picture tubes, the training of luminous dots of smaller diameter than that of holes in a color-selective electrode used, so that when using a color-selective electrode to form luminous dots, the electrode receives holes which be formed by an etching process and have the same diameter how the luminous dots have; Then the hole diameters are enlarged by a further etching process. This process is called re-etching.

In conventional post-etching processes, however, The main problem that the operation of the color picture tube is impaired by the fact that the thickness of the Shadow mask tube is reduced so that its mechanical strength deteriorates and the control of the Hole diameter is made difficult. Refocusing color picture tubes are used to effectively suppress secondary electron emission from the shadow mask to prevent the color purity from deteriorating due to the scattering of the secondary electrons, the surfaces of the shadow mask with a substance having a small secondary electron emission ratio coated; the surfaces of the shadow mask are therefore coated with graphite or carbon bromide after the post-etching. The object of the invention is to create a manufacturing method for the color-selective electrode of a Color picture tube in which the above-mentioned difficulties are overcome.

The invention thus specifies a method for manufacturing a color-selective electrode for a black base body (matrix) or another color picture tube, wherein parts of the main surfaces having holes

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Fig. la until Id Fig. 2a until 2d

Electrode plate can be coated with an etch-resistant substance, so given dimensions for holes of larger diameter to limit, and then the holes are enlarged by post-etching and get their given dimensions.

The invention is explained in more detail below with reference to the drawing
explained. Show it:

Cross-sections to explain the previously customary process steps for producing a shadow mask; and

Cross-sections to explain the method steps according to the invention.

According to Fig. Ia-Id 1 holes 6 are formed in an electrode plate, and it is coated with a blackening film 2 to prevent rust formation (Fig. La). Then the blackening film 2 is removed by pickling (Fig. Ib), and then the
Holes enlarged by re-etching, so that üöcher 6 arise
(Fig. Ic). Finally, the electrode plate 1 is through
chemical treatment with an anti-rust blackening film
2 'so that a shadow mask 1' is obtained
(Fig. Id).

However, the main component of the blackening film 2 is iron oxide, which has a high secondary electron emission ratio. As a result, in a post-focus type color picture tube, the electrode plate becomes post-focus instead of the blackening film
the hole enlargement is coated with a secondary electron emission suppressing film. Thus, the production of the shadow mask, including the re-etching, requires great technical effort; nevertheless, no predetermined performance is achievable because of the required control of the
Hole size or the low mechanical strength, which results as a result of the reduction in the thickness of the shadow mask after re-etching, or because of the difficulties in attaching

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bring the necessary secondary electron emission suppressing film.

The invention will now be explained with reference to Figures 2a-2d. To simplify the description, it is assumed that the color selective electrode is a shadow mask, but of course it can be any other color selective Electrode, e.g. B. one with strip-shaped holes act.

According to Fig. 2a, parts of the main surfaces of a perforated electrode 1 and walls of holes 3 in the electrode plate with a material 4, for. B. a photoresist coated. The holes 3 were formed by etching. The partial covering of the main surfaces of the electrode plate 1 and the walls of the holes 3 is used to determine predetermined dimensions D- and Dp for holes to be formed in a finished color-selective electrode or shadow mask, and is therefore carried out photographically. Then a secondary electron emission suppressing material 5 such as C, CBr, CBr_, CBr "or CW z. B. applied by ionization or electroplating. The material 5 must be etch-resistant (e.g. against iron (III) chloride) for subsequent post-etching treatment. Its layer thickness is 1-4 μm. The photoresist 4 is then removed from the electrode plate 1 (FIG. 2c). The electrode plate according to FIG. 2c is subjected to a post-etching treatment to enlarge the holes 3, so that holes 3a defined _{by D 1} and D _{2 are obtained;} a shadow mask according to FIG. 2d is thereby completed. The walls of the holes 3a can, if necessary, additionally be subjected to an anti-rust treatment, e.g. B. electrolytic smoothing. It should be noted that the holes 3 to be enlarged are etched since they are not coated with an etch-proof secondary electron emission suppressing film while the

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other parts are not etched because they are coated with such a film; this eliminates the control of the Hole size when re-etching, and there is no reduction in the thickness of the shadow mask.

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Claims (5)

- ο - Claims before Method for manufacturing a color selective electrode for a color picture display tube with a fluorescent screen which has a plurality of luminous points, the dimensions of which are smaller than those of first holes in the color selective electrode, with a number of second Holes is formed by etching in an electrode plate, the two communicating with each other through the holes has standing major surfaces, and the dimensions of the first holes are smaller than those of the second holes, and wherein the electrode plate obtained is subjected to a post-etching process to enlarge the first holes by means of a Etchant, whereby the second holes in the electrode plate are obtained, marked by it. et that before re-etching parts of the surfaces of the electrode plate (l) with a secondary electron emission suppressing, with respect to the post-etching agent, etch-resistant material (5) are coated, whereby this predetermined Hole dimensions limited. 2. The method according to claim 1, characterized by coating the hole walls and those parts of the main surfaces with Photoresist (4) which are exposed to the post-etching, application of the secondary electron emission suppressing Materials (5) on the main surfaces, and removing the photoresist (4). 3. The method according to claim 1 or 2, characterized in that that after the re-etching, the hole walls of the color-selective electrode (1) are subjected to a rust protection treatment. 409845/0692 4. The method according to claim 1, 2 or -3, characterized in that the secondary electron emission suppressing material (5) which is resistant to the etchant. C, CBr, CBr ₂ , CBr ₃ or CW. 5. The method according to any one of the preceding claims, characterized in that all holes (3, 3a) are circular are. Blank page