JPH11135012A - Stud coating and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cathode-ray tube enhancing color cathode-ray tube performance reliability, reducing manufacturing costs, and minimizing arc discharge surrounding a stud coating. SOLUTION: A stud coating forms electric connection between an aluminum film and a stud in a face plate of a color picture tube. The coating contains colloid graphite capable of passing through a lacquer layer below the aluminum film and dispersing in acrylic resin solution, the solvent in the coating is burnt away together with the lacquer layer in the baking process of the tube, and the electric connection is in a flexible state capable of resisting flaking.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates generally to color television picture tubes and, more particularly, to improved stud coating compositions and color picture tube shadow masks and screened faceplates. A method for providing an electrical path.

[0002]

2. Description of the Related Art A cathode ray tube of a color television includes a glass bulb.
A faceplate sealed to the flared end of the funnel. An electron gun is mounted on the neck of the funnel to provide one or more electron beams. The faceplate has a substantially flat inner surface onto which the phosphor groups excited by the electron beam are deposited. Shadow masks provide color selection by masking phosphor groups so that they can be excited by only one of the electron beams. The shadow mask is precision mounted to the faceplate by a plurality of suspension springs that removably engage metal studs extending from the faceplate. A conductive coating of colloidal graphite is applied to the inner surface of the funnel and a high voltage is imposed through the anode button on the funnel wall.

[0003] It is common practice to aluminize phosphor screens by applying an electron transmissive film of aluminum onto the phosphor screen. This film acts as a mirror and increases the brightness of the display by reflecting backward traveling light generated by the phosphor. A film of an organic material such as a lacquer is applied on the phosphor deposit before the application of aluminum. The organic film fills the non-uniform areas of the phosphor deposit to provide a smooth surface on which the aluminum film can be deposited, which inherits the smooth nature of the lacquer.

It is essential that an anode voltage on the funnel coating be imposed on the shadow mask and the aluminum film. The electrical path for accomplishing this includes one or more springs extending from the shadow mask to engage the funnel coating. The anode potential of the shadow mask is transmitted to the aluminum film through the shadow mask suspension spring and metal support studs. To obtain an electrical path to the aluminum film, the metal support studs are painted with a conductive "mustache" that extends to the aluminum film. This material, including the conductive mustache, is commonly referred to as stud coating.

Prior art conductive materials that were previously widely used as stud coatings include water-soluble silicates in a form suitable for brush application. The water is removed in a subsequent tube baking process, leaving a hard, conductive film between the stud and the aluminum film. The aqueous solution generally contained either potassium silicate or sodium silicate as a binder and did not always properly "wet" and did not adhere to the part. As a result, debris from the coating flaked off (flaked off) from the studs and glass area, and blocked one or more apertures in the shadow mask, which often resulted in unacceptable tubes. Such particles in the gun area can also cause inter-electrode arc discharge and / or cathodic poisoning. The aqueous solution coating required an extra baking cycle after aluminization and before the stud Dag.

[0006] In the name of the inventor, and Zenith Elect
U.S. Patent No. 4,289,800 assigned to ronics Corporation
No. 4,301,041 solved the above prior art problem by eliminating the need for an additional baking step after aluminization, and introduced significant cost savings to the manufacturing process. These patents are incorporated herein by reference. These patents disclose a stud coating composition comprising a mixture of glass frit particles and colloidal graphite in a volatile solvent for a lacquer film (underneath the aluminum film) and a thickener to provide a coatable viscosity. And methods are disclosed. The solvent passed through the lacquer layer through the porous aluminum film and was removed during the Lehr (furnace) tube baking cycle. The stud coating solutions and methods described in these patents are widely used in industry and have worked very well for many years.

The glass frit type stud coatings described in the above-mentioned patents clearly show defects during the hindrance or interruption of the manufacturing process. In particular, problems arise when the tubes are exposed to high Lehr temperatures for extended periods of time, such as when a production line is shut down. The lead oxide in the glass frit reacts with the carbon in the graphite, producing carbon dioxide and lead, and destroying the conductivity of the stud coating. In many instances, by watching Lehr's thermal control during production line outages, this problem can be avoided, but during prolonged outages, it may be difficult. The problem is that the tube often does not suffer from a sufficient amount of stud coating to pass the final inspection and testing, but is prone to repeated arcing in the electric field and ultimately failure. Combined with facts. Although this problem is not large in number, it is fatal for picture tubes, and the problem is obviously expensive for consumers as it does not appear during routine testing of picture tubes, and Is inconvenient for people.

[0008]

SUMMARY OF THE INVENTION It is a main object of the present invention to improve the performance reliability of a color cathode ray tube. Another object of the present invention is to reduce the cost of manufacturing a color cathode ray tube. It is a further object of the present invention to provide a cathode ray tube that minimizes arcing associated with stud coating.

[0009]

As described above, a color cathode ray tube has a phosphor-containing imaging faceplate having a lacquer film and an aluminum film in turn on the faceplate. The shadow mask is secured adjacent to the face plate by a plurality of metal studs extending from the face plate. An electrical bridge is provided between the shadow mask and the aluminum film via studs and stud coating, and the aluminum film is maintained at anodic potential. (As is well known, shadow masks are used to connect the faceplate of the picture tube to the funnel. A spring connecting the non-conductive glass frit seal between them electrically connects to the anode voltage on the coating inside the funnel).

[0010] An improved bake-hard enable solution according to the present invention for providing stud-coated electrical bridges or mustaches.
Essentially comprises a mixture of graphite particles in the micron size range. The particles are in suspension in a volatile solvent for the lacquer film. The suspension contains a sufficient amount of a thickener to provide a coatable viscosity for brush application. When applying this solution between the suspension stud and the aluminum film, this solution
As the tube is baked, it passes through the lacquer film and the solution cures to provide a permanent conductive bridge between the mask and the aluminum film.

[0011] The solution may have a viscosity ranging from 200 to 800 centipoise, and is preferably about 550 centipoise. After baking, the solution may have an electrical resistivity in the range of 100-500 ohms / scare. The conductive stud coating of the present invention can be formulated as follows (producing 1 gallon). Equivalent materials that can be supplied from other sources may be used.

Purified grade butyl cellosolve (ethylene glycol monobutyl ether) (Fisher Scientifi)
c Co. E179) Acrylic resin (Elva in 2025 grams)
Dissolve 225 grams of cite2044-ICI Acrylics) to obtain an acrylic resin raw material solution. Suitable container (2000ml
In a beaker) weigh 225 grams of butyl cellosolve. To this, N-butyl acetate (Fisher Scienti
675 grams of fic Co. B-396) and resin binder 6
Add 30 grams and stir the solution until homogeneous to produce a resin binder solution. About 8 kneading media
The following ingredients are added to a ball mill containing 000 grams.

Ingredient Amount Weight% Range Graphite HPN-2 630 g 14 36 144 Graphite LN 1052 (Grapfo Colloids) 90 g 2 35797 Acrylic resin raw material solution 2250 g 50 45 to 55 Resin binder solution 1530 g 34 30 to 38

Rotate the ball jar for 22 to 24 hours,
Then pour the kneaded coating suspension into a 1 gallon container. The preparation of the coating should be performed in a well-ventilated area with appropriate and careful procedures, such as personnel wearing rubber gloves, respirator masks, lab coats, hair nets and shoe covers. Care must also be taken for the flammability of the N-butyl acetate and resin binder solutions.

[0015] The stud coatings prepared and used according to the present invention obviate the above-mentioned problems associated with the use of stud coatings based on glass frit. The main features of this new stud coating are:
Flexible (after processing), which improves resistance to flaking. In addition, the stud coating of the present invention has the advantage that it is less expensive and furthermore does not require an extra baking cycle for the picture tube.

In testing, a prior art frit-based stud coating was applied to the stud and aluminum film and subjected to a temperature of 450 ° C. for 2 hours. Coating resistance from 300 ohms to 73,
Rose to 2,000 ohms. With the new stud coating, under the same conditions, the resistance remained at 300 ohms.

In operation of a color picture tube production line, stud arc discharge defects were as high as 0.3% with the prior art frit-based stud coating, but with the stud coating of the present invention. No defective products were found.

A novel stud coating composition and method have been described that solves the problem of studs on aluminum film conductivity in color picture tubes. It will be appreciated that many modifications may be made by those skilled in the art in the described embodiments of the invention without departing from the spirit and scope of the invention. The present invention should be limited only as defined in the appended claims.

Claims (9)

[Claims] 1. Providing a colloidal graphite mixture, preparing an acrylic resin solution that can pass through a lacquer film of an aluminized picture tube faceplate, preparing a resin binder solution, and Kneading a solution of and a graphite mixture,
And a method for producing a stud coating. 2. The method of claim 1, wherein said acrylic resin solution is prepared by dissolving an acrylic resin in ethylene glycol monobutyl ether. 3. The method of claim 2, wherein said resin binder solution is prepared by making a homogeneous mixture of ethylene glycol monobutyl ether, N-butyl acetate and a resin binder. 4. The weight percentage of the stud coating solution is approximately: colloidal graphite, 16%; resin (binder),
14%; acrylic resin, 5%; N-butyl acetate,
The method according to claim 3, wherein the ethylene glycol monobutyl ether is 50%. 5. A stud coating for forming an electrical connection between an aluminum film and a stud on a face plate of a color picture tube, wherein the acrylic resin solution can pass through a lacquer layer below the aluminum film. Wherein the solvent in the coating is burned off with the lacquer layer during a tube baking step and the electrical connection is in a state that is flexible enough to withstand flaking. coating. 6. The coating according to claim 5, comprising an acrylic resin solution and a resin binder solution. 7. The coating of claim 6, wherein said acrylic resin solution comprises an acrylic resin dissolved in a solution of ethylene glycol monobutyl ether. 8. The coating of claim 7, wherein said resin binder solution comprises a resin binder, N-butyl acetate and ethylene glycol monobutyl ether. 9. The weight percentage of the coating is approximately: colloidal graphite, 16%; resin (binder);
14%; acrylic resin, 5%; N-butyl acetate,
9. The coating of claim 8, wherein the coating is 15%; ethylene glycol monobutyl ether, 50%.