DE69823284T2 - Production method of a contact bolt layer - Google Patents

Description

general State of the art

The The present invention relates generally to color television picture tubes and in particular, an improved stick coating composition and a method for establishing an electrical path between the color picture tube hole mask and the shielded windscreen.

The Color television cathode ray picture tube has a glass bulb consisting of a funnel and a windscreen which is sealingly connected to the flared end of the funnel is. In the neck part of the funnel an electron gun is mounted, to one or more electron beams available put. The windscreen has an almost flat inner surface, on which groups of phosphors are deposited by the Be excited electron beams. The shadow mask ensures color selection, by masking groups of phosphors so that they only can be excited by one of the electron beams. attached is the shadow mask in exact relation to the windscreen with the help several suspension springs, the solvable assembled with protruding from the windshield metal pins become. On the inner surface of the Funnel is an electrically conductive coating of colloidal Graphite applied to the over an anode button in the funnel wall a high voltage applied becomes.

Usually The luminescent screen is aluminized by placing on it an electron-permeable aluminum film is applied. The film acts as a mirror and increases the brightness the ad by doing that through. the phosphors generated, backward Light reflected. Before the aluminum is applied, a film is formed of organic material, such as a paint, on the phosphor deposits applied. The organic film fills uneven areas of the phosphor deposits out and take care of a smooth surface on the the aluminum film can be deposited, so the smooth texture of the paint.

It is absolutely necessary, the anode voltage of the funnel coating to put on the shadow mask and the aluminum film. The one to be produced electrical path has one or more springs extending from the shadow mask to the hopper coating, in engagement with the same, extend. The forwarding of the anode potential on the shadow mask to the aluminum film takes place through the Lochmaskenaufhängefedern and the metal pins. To complete the electrical path To the aluminum film, the metal pins are coated with a conductive "mustache", the reaches to the aluminum film. The material that makes up the conductive mustache is commonly referred to as a pencil coating.

One earlier in big Scope used as a pencil coating conductive material from the prior Technique contains a water-soluble Silicate in a suitable for application by means of a brush Shape. The water was expelled in a subsequent tube baking process, creating a hard, electrically conductive film between the pins and the aluminum film remained. The aqueous solutions contained in general either potassium silicate or sodium silicate as binder, and neither their wetting behavior nor their adhesion to components always met the requirements. As a result, it often came to peel of coating fragments from the pins and the glass surface, the then one or more openings blocked the shadow mask, which is often an unacceptable Tube led. Such particles in the cannon area could also electrode flashovers and / or Cathode poisoning result. The water-soluble coatings required An additional Burn-in operation after aluminizing and before application of conductive pen graphite plating.

By in the name of the inventor, Zenith Electronics Corporation transferred US patents. Nos. 4,289,800 and 4,301,041 are discussed above Problems solved by the prior art and the cost of the manufacturing process considerably reduced by the need for additional Burning step after aluminizing eliminated. These patents disclosed a method and a stick coating composition comprising a Mixture of glass frit particles and colloidal graphite in one vaporizable solvent for the Paint film (under the aluminum film) and a thickener for Achievement of a spreadable viscosity contains. The solvent penetrated the paint layer through the porous aluminum film and was during of the tube baking process expelled in the teaching oven. The procedure and the pen coating solution, such as as described in these patents find wide use in the art Application and have had quite a success over the years.

The glass frit type pencil coating described in U.S. Patent Nos. 4,130,347 and 5,457,800, issued to the patents discussed above, is found to be deficient in the event of a disruption or interruption of the manufacturing process. In particular, a problem arises when tubes are exposed to the high teaching temperatures for a long time, such as when the production line comes to a standstill. The lead oxide in the glass frit reacts with the carbon in the graphite to form carbon dioxide and lead, thereby destroying the conductivity of the pin coating. In many cases, the problem can be addressed by careful teach temperature control at standstills, but the difficulties may still exist during longer downtime. Often, the problem is compounded by the fact that so much of the pen coating can be preserved that the tube passes the final inspection and final inspection, even though it tends to be subject to recurring flashover and eventual failure. While not a serious issue in terms of numbers, it is catastrophic for the picture tube and results in obvious expense and inconvenience to the customer, as it is not always apparent during the routine inspection of the picture tube.

Tasks of invention

A The main object of the invention is to increase the reliability of the performance of color cathode ray tubes improve.

Farther It is the object of the invention to increase the production costs of color cathode ray tubes reduce.

Further It is an object of the present invention, a cathode ray tube with with minimal pen coating flashovers put.

description the preferred embodiment

As already mentioned, have color cathode ray tubes one after another of a paint film and an aluminum film superimposed, the phosphor carrying, imaging front screen. The windscreen adjacent is by means of several metallic, protruding from the windscreen Pins attached a shadow mask. Between the shadow mask and the Aluminum film is over the pins and a pin coating made an electrical bridge, to keep the aluminum film at anode potential. (As is known, the shadow mask is electrical with the on the coating inside connected to the hopper anode voltage present through springs, which the non-conductive glass frit seal between the picture tube front panel and bridge the funnel.)

A according to the invention, by Bake hardenable solution for making the electric bridge or mustache in Contains mold of the pen coating essentially according to the claims a mixture of graphite particles in the micrometer range. The particles are in suspension in a vaporizable solvent for the Paint film in front. The suspension also contains a thickener in order to obtain a spreadable viscosity in order Application by brush sufficient amount. Will this solution be between the suspension pins and applied to the aluminum film, the solution penetrates into the paint film. When the tube is burned in, the solution hardens to create a tube permanent electrically conductive Bridge between the mask and the aluminum film.

The solution can be a viscosity in the range of 0.2 to 0.8 Pa · s (200-800 Centipoise), and preferably about 0.55 Pa · s (550 centipoise). After firing, the solution may be an electrical resistance in the range of 100 to 500 ohms per Square. This inventive electrically conductive pencil coating can be put together as follows (gives 3.75 l (one gallon)). Equivalent, materials supplied by other companies.

you solve 225 Grams of acrylic resin (Elvacite 2044, from ICI Acrylics) in 2025 grams Butyl cellosolve "purified" (E179 of the company Fisher Scientific Co.) and receives so the acrylic resin stock solution.

In a suitable vessel (2000 ml beaker) 225 grams of butyl cellosolve are weighed. You add 875 grams n-butyl acetate (B-396 from Fisher Scientific Co.) and 630 grams of the resin binder and stir, until the solution is homogeneous and is a resin binder solution.

The following Ingredients are contained in about 8000 grams of media ball mill brought in:

The Ball drum will be 22-24 Rolled for hours and the ground coating suspension in one 3.75 l (one gallon) large container cast.

The Preparation of the coating should be in a well-ventilated area and the personnel involved take appropriate precautions such as rubber gloves, respirators, lab coats, hair nets and wear protective shoe covers. Beware too, given the flammability of n-butyl acetate and the resin binder solution offered.

By the inventively prepared and pen coating used becomes the above problem in connection with the use of a glass frit-based pen coating Fixed. An essential feature of the new pen coating is their flexibility (after processing), by their resilience against peeling elevated becomes. moreover is the pen coating according to the invention less expensive and yet offers the advantage of no additional Burning operation for the picture tube too require.

In In a test, the frit - based pen coating was removed from the Prior art applied to pen and aluminum film and two Exposed for hours to a temperature of 450 degrees Celsius. The specific one Resistance of the coating increased from 300 ohms to 73,000 ohms. With the new pen coating, the specific resistance remained under the same conditions to a value of 300 ohms.

at a production line series of color picture tubes the committee concluded from pen rollovers the frit-based pin coating of the prior art to 0.3% while with the pen coating according to the invention no pencil overdraft Committee incurred.

described became a new pen coating composition and a new one Method by which the problem of conductivity between pen and Aluminum film in color picture tubes solved becomes. Limited the invention is only insofar as this described in the claims is.

Claims (8)

Method for producing a pencil coating, including the provision of a colloidal graphite mixture; the Preparation of an aluminized to penetrate the paint film CRT windscreen suitable acrylic resin solution; the Preparation of a resin binder solution; as well as the grinding of the solutions and the graphite mixture. The method of claim 1, wherein the acrylic resin solution by Solve one Acrylic resin is produced in butyl cellosolve. The method of claim 2, wherein the resin binder solution is characterized by Prepare a homogeneous mixture of butyl cellosolve, n-butyl acetate and resin binder is produced. Method according to claim 3, wherein the parts by weight the pen coating solution on about 16% colloidal graphite, 14% resin (binder), 5% Acrylic resin, 15% n-butyl acetate, as well 50% butyl cellosolve, amount. Pen coating for the production of an electrical Connection between the pins and the aluminum film in a color picture tube front panel, the: in one to penetrate under the aluminum film paint layer dispersed suitable acrylic resin solution and resin binder solution colloidal graphite contains; in which the solvents in the coating together with the paint layer during one Röhreneinbrennarbeitsgangs be heated, and the conductive Compound remains flexible and so resistant to peeling. A coating according to claim 5, wherein the acrylic resin solution is a in a butylcellosolve solution dissolved acrylic resin includes. The coating of claim 6, wherein the resin binder solution comprises Resin binder, n-butyl acetate, and butyl cellosolve. Method according to claim 7, wherein the parts by weight the coating is on approx 16% colloidal graphite, 14% Resin (binder), 5% acrylic resin, 15% n-butyl acetate, as well 50% cellosolve amount.