DE2122258A1 - Process for producing an opaque cover layer on a glass surface - Google Patents

Description

7167-71 / Dr.vB / Ro.
RCA 61,758
US Ser. No. 34.689
Filed: May 5, 1970

RCA Corporation, Mew York, NY, V.St.A.

Process for producing an opaque cover layer on a glass surface.

The present invention relates to a method for producing an opaque, firmly adhering cover layer on a Glass surface.

A main field of application of the invention is in the luminescent screens of color television picture tubes. However, the invention is not limited to this area of application but can be used wherever an opaque, firmly adhering cover layer is required on a glass surface, e.g. in the production of projection or copy masks, optical scales, crosshairs etc.

U.S. Patents 2,842,697 and 3,146,368 disclose color television picture tubes known, the luminescent screen contains a plurality of light-emitting phosphor areas, which of a light-absorbing matrix are surrounded. The light-absorbing matrix is located on the inside of the front panel of the Tube and has a plurality of holes, each of which is filled by a phosphor area.

It is known the light absorbing matrix both before as well as after the fluorescent areas on the inside of the front panel to raise. However, in all known methods at least one additional photographic exposure except for those used to apply the phosphor areas required, required. Provide photographic processes

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Although satisfactory results but they are relatively labor intensive and it is therefore desirable to take such a comparison _t and the required handling to a minimum'maß limit.

The invention is accordingly based on the object of providing an opaque, firmly adhering cover layer on a glass surface by a simple non-photographic process.

This object is achieved according to the present invention by ^; solved that a layer of nickel and / or cobalt and / or copper is deposited electrolessly on the glass surface and then converted into a dark-colored oxide.

When applying the invention to the production of a luminescent screen for a cathode ray tube, the inside of the glass front plate of the cathode ray tube is first activated for the electroless (chemical) deposition of the desired metal by causing an agent promoting the deposition on the inner surface of the glass front plate of the cathode ray tube for absorption will. A point-like pattern of blue-, green- and red-emitting phosphors is then applied in a known manner with a polymeric binder, the area between the point-like areas remaining uncoated. Using the point-like phosphor areas as a template, the uncoated surface is now electrolessly plated with at least one of the metals nickel, cobalt and copper. Subsequently, the arrangement within the usual further processing is heated in air to about 440 ⁰ C, whereby the expelled organic components and the deposited metal, before-I preferably cobalt, is oxidized to substantially black compounds.

The production process described has the advantage that there are no photographic process steps for the production of the Light absorbing matrix is needed because the shape of the matrix is determined by the shape of the electroless or chemically deposited Metal layer and this in turn is determined by the previously deposited phosphor-containing areas. The fluorescent part

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surfaces in the luminescent screen are created by the electroless deposition the metal layer is not affected.

In the following, exemplary embodiments of the invention are explained in more detail with reference to the drawing, which show:

Fig. La to Ie a sectional view of part of the front panel a cathode ray tube during various steps in the manufacture of a phosphor screen using the method according to the invention; and

Fig. 2 is a plan view seen through the front panel on the luminescent screen according to Fig. Ie.

When applying an embodiment of the present invention to the manufacture of the phosphor screen for a Color television picture tube is a front plate 21 (Fig. La) of the picture tube on the inside 23 after careful cleaning coated with an activator material. Then the inside of the front panel is used for at least one minute a 10% aqueous solution of fluoroboric acid rinsed to leach out the glass surface and make it hydrophilic. Then the surface is rinsed with a solution of a stannous salt, e.g. an acidic stannous chloride solution, stannous ions being adsorbed on the leached surface. The surface 23 is then washed with water, to remove excess stannous chloride, and then with a palladium salt solution, e.g. an aqueous, acidic one Palladium chloride solution, rinsed and washed again with water. The palladium ions take the place of those on the surface 23 adsorbed stannous ions and are reduced to palladium atoms, which are shown as layer 25 in FIG. the Palladium atoms probably do not form a coherent layer because the amount of adsorbed palladium is less than it is for a monoatomic covering of the surface would be necessary. Of course, there is enough palladium available to later to enable electroless or chemical deposition of cobalt.

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Green-emitting phosphor areas 27, blue-emitting phosphor areas 29 and red-emitting phosphor areas 31, which are substantially circular, by a direct photographic Down proceedings. The treated surface is coated with blue-emitting particles, e.g. by pouring a dispersion on it Phosphor coated in a binder made of bichromated polyvinyl alcohol, the layer thus formed exposed with a corresponding Iluster, for which the perforated mask of the tube and one arranged at a predetermined point can serve approximately punctiform light source. As a result of the exposure, point-like areas 27 of the layer become water-insoluble. The layer is then developed by rinsing with water, removing the unexposed areas and creating an iluster the blue-emitting phosphor particles remain from point-like areas which consist of binder that has been made insoluble contains. The process is then repeated with green-emitting phosphor to produce the green-emitting regions 29 and finally, using red-emitting phosphor particles, respective red-emitting areas are grounded 31 manufactured.

A cobalt layer 33 is now applied to the parts of the surface 23 that have remained free, the pattern from the punctiform areas 27, 29 and 31 serves as a template. That This is because metallic cobalt is only deposited on the surface between the regions 27, 29 and 31, as shown in FIG. 1d is because the nucleating palladium atoms are only not there

i are covered. For electroless deposition of the cobalt layer ! the surface can be treated with an aqueous solution,

which contains 50 g of CoSO ₄ .7H ₂ O, 70 g of sodium pyrophosphate, 1.5 g of dimethylamine borane and 7.5 ml of concentrated ammonium hydroxide per liter. The pH of the solution is about 10.0 to 10.5 and the temperature of the solution is maintained at about 32 to 38 ^° C (90 to 100 ^° F). A layer of about 1.3 µm (0.05 mil) per hour will typically deposit.

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"~ 5 ™"

In the present example, the plating solution is allowed to act for about 6 minutes so that it becomes about 0.13 µm (0.005 mil) thick cobalt layer.

The plating solution is then removed and the plated surface is rinsed with water and dried. The arrangement is then vaporized with an aluminum layer and then heated in air at around 440 ° C. During the Bakeout removes organic materials through evaporation and oxidation. In addition, the metallic cobalt oxidized to a substantially black material which is a or contains several cobalt oxides. The end product, which is shown in Fig. Ie and in Fig. 2 in partial view, consists of one practically black matrix 35 between the point-like areas 27, 29 and 31 on the surface of the glass front plate 21.

The activation layer 25 remains on the surface, but it has practically no influence on the function of the tube, because it is not even an atomic layer thick and therefore appears completely transparent to the viewer.

The described exemplary embodiment of the present method can be modified in the most varied of ways. In the present application and corresponding similar For the purposes of (A) the surface in question is activated to generate metal atoms or nuclei for the initiation of electroless plating to create, (B) a desired pattern is applied to the treated surface, e.g. a pattern of phosphor-binder layers, to form a mask or stencil for the later electroless deposition of the metal, j (C) Electrolessly or chemically deposit an oxidizable metal on the areas that have remained free, preferably for which purpose Cobalt, copper or nickel can be used, and then (D) to convert the deposited metal into a dark colored material .

The metal used for the electroless plating is preferably copper, cobalt, or nickel, or combinations of these metals, or combinations of one or more of these

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Metals with other metals such as iron, manganese and tungsten. Any metal or metal combination that is electroless or chemically precipitate and convert into a dark colored material lets can be used. The process steps (A) and (C) given above are obviously dependent on one another and one can proceed according to the teachings of U.S. Patents 2,968,578 and 3,446,657, for example.

The application of the pattern serving as a stencil, e.g. the leuco-binding agent precipitates according to the process step (B) can be carried out by any known method, in particular luminescent screen production methods, e.g. offset printing, Screen printing or photo printing. The fluorescent powder can at the time the preparation of the pattern can be mixed with the binder, or a pattern can be made from the binder first and then make the phosphor adhere to it. Fluorescent screens of cathode ray tubes are preferably by Direct photographic process produced directly on the inside of the front plate of the cathode ray tubes in question. Processes described in US Pat. Nos. 3,406,068, 3,364,054 and 3,269,838 are particularly suitable for this purpose.

The conversion of the electrolessly deposited metal into the dark-colored material according to process step (D) can be carried out by oxidizing or sulfating or otherwise converting the metal into a metal compound or a mixture of compounds which, as a whole, appear dark-colored, preferably black. {Nickel and cobalt form black oxides and sulfides. However, nickel j also forms green oxides. In some cases, when nickel sulfide is heated in air, a light colored compound is formed. ι Copper forms black sulphides and red oxides. The metals mentioned are all capable of forming dark-colored compounds and materials, i.e. a compound or mixtures of compounds that result from the chemical reaction of the metal. The reaction can be carried out by heating in a suitable gaseous atmosphere or by chemical reaction in a liquid medium.

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After making the phosphor pattern and the light absorbing Matrix, a reflective metal layer can be applied to the luminescent screen arrangement in the usual way, the phosphor areas 27, 29 and 31 and the matrix 35 covered. A suitable method for this is e.g. in the work "Emulsion Filming for Color Television Screens" by T.A. Saulnier, Jr. published in "Electrochemical Technology" 4; 31-34 (1966). The aluminized screen becomes then baked out and processed into a picture tube together with the shadow mask in the usual way.

With regard to the implementation of the present procedure, the following should also be pointed out:

1.) If the plating bath is used at room temperature, the layer thickness may not grow all parts of the surface at the same speed. Noisy if the plating bath is set to about 30 to 40 °, this problem does not arise. Presumably it will be at the increased bath temperature any resistance to knockdown has been overcome.

2.) At the certain critical thickness of the plated metallic cobalt there is a risk that the plated Metal layer peeling off the surface. This problem can be eliminated by having one under the initiator layer 25 additionally used a thin promoter layer. The promoter layer can be made of a chemical material such as heat treated Tin oxide, or by changing the surface, e.g. by leaching and / or hydration. The danger The peeling can also be reduced or eliminated by keeping the internal stresses in the depressed Metal decreases, which can be done by appropriate choice of the parameters of the plating process.

3.) Under certain circumstances, the plating bath can penetrate through pores in the phosphor areas, so that undesirable Make metal precipitates. In order to avoid this, the phosphor deposits should contain as few pores as possible and be as hydrophobic as possible. This can be done in a number of ways.

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be sufficient, for example by heating the deposited phosphor areas for about 10 minutes to about 150 ^° C. or introducing an organic filler such as an acrylate copolymer which makes the phosphor areas water-repellent. The best way to make the precipitated areas as pore-free as possible is to use a film-forming binder.

4.) The efficiency of most particulate phosphors is severely affected by impurities and foreign ions. Ions of cobalt, nickel, copper etc. have an effect often as poisons when they diffuse into the fluorescent particles. Experiments with cobalt metal have shown, however, that the use of a film-forming binder is sufficient Protection of the fluorescent areas against those when the power is off Plating existing ions ensured, so that the efficiency of the phosphor particles is practically not impaired will. In this context, too, a minimum of porosity should be aimed for, since the efficiency of the phosphor is higher can be affected less than there are pores. After the binder is removed, the phosphor particles become practically not influenced in the following operations of the tube production.

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Claims (1)

Q _ Claims .) Process for producing an opaque, firmly adhering cover layer on a glass surface, characterized in that a layer of at least one a dark connection forming metal, especially from minidesten one of the metals nickel, cobalt and copper, deposited electrolessly and then turned into a dark-colored material ■ is converted. • 2.) The method according to claim 1, characterized in that the conversion by heating in a I containing oxygen and / or sulfur or hydrogen sulfide Atmosphere takes place. 3.) The method according to claim 1, characterized in that the conversion is carried out by heating in air ¹ to a temperature of the order of 440 C. 4.) The method according to claim 1, characterized that on a glass plate of a picture reproduction ■ device, in particular a color television picture tube, a pattern is applied from areas that have a forming binder and contain phosphor particles and that on the surface between the regions at least one of the metals nickel, cobalt and copper is deposited electrolessly and then chemically; converted into a dark-colored connecting material, I5.) The method according to claim 4, characterized in (characterized that the phosphor particles with the binding agent be mixed before the areas (27, 29, 31) are applied will. 6.) Method according to claim 4 or 5, characterized in that g e that the phosphor particles are mixed with an organic hydrophobic filler. 7.) The method according to claim 4, 5 or 6, characterized in gel that the knocked down metal 109847/1334 'Umged into the dark-colored connecting material by oxidation is changing. 8.) The method according to claim 4, 5 or 6, characterized in that the deposited metal is converted into the dark-colored material by the action of sulfur or a sulfur compound or by sulfurization. 9.) Process according to one of the preceding claims, characterized in that the surface is first treated in particular prior to the application of any a concealing 'areas, with an adsorbable initiator material (25). 10.) The method according to claim 9, characterized that atomic palladium is adsorbed as initiator material on the surface (23). 11.) The method according to claim 10, characterized in that that the adsorption of atomic palladium! on the surface is caused by the fact that this is done first with an aqueous solution of an etano salt and then treated with an aqueous solution of a palladium salt will. 12.) The method according to claim 10, characterized in that that the adsorption of atomic palladium on the surface is caused by the surface is treated first with an acidic stannous chloride solution and then with an acidic palladium chloride solution. 10 9 8 4 7/1334