US 3558818 A
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United States Patent Inventor Floris DeBoer Emmasingle, Eindhoven, Netherlands a  AppLNo. 696,238
 Filed Jan. 8,1968
 Patented Jan. 26, 197]  Assignee U. S. Philips Corporation New York, N.Y.
a corporation of Delaware  Priority Jan. 18, 1967 [3 3 Netherlands [3 l 6700756  METHOD OF STRENGTHENING A TELEVISION DISPLAY TUBE 3 Claims, 1 Drawing Fig.
52 us. Cl l78/7.82, 220/2. 1  Int. Cl ..H01j 29/28, HOlj 61/50, H0lk1/28  Field ofSearch l78/7.82;
 References Cited UNITED STATES PATENTS 3,220,592 1 1/1965 Powell l78/7.82 3,412,203 1 III 968 DAngelo 220/2.1A
Primary ExaminerRobert L. Griffin Assistant ExaminerHoward W. Britton Attorney-Frank R. Trifari ABSTRACT: A method of strengthening a cathode-ray tube against implosion in which a metal band and the conical portion of the cathode-ray tube adjoining the window are provided with an adhesive layer containing a reducing agent compatible with a redox system used to harden a combination of a polyester and a monomer. The metal band is placed around the conical portion of the tube and the space therebetween filled with a polyester, a monomer, a redox system, and a filler The polyester mass is subsequently hardened at ambient tem peratures.
'PATENTEU JAN 25 1971 INVENTOR.
FLORIS DE BDER BY v METHOD OF STRENGTHENING A TELEVISION DISPLAY TUBE This invention relates to a method of strengthening a television display tube with a substantially rectangular screen for the purpose of reducing the risk of implosion. More particularly in accordance with the invention the transition region between thewindow and the cone of the completed tube is surrounded by a metallic band so as to obtain a space of substantially wedge-shaped section between the whole or part of the inner surface of the band and the outer surface of the transition regions. Thereafter this space is filled with a mixture consisting of an unsaturated polyester resin, a monomer which is polymerisable therewith and a filler. Subsequently, the mixture is hardened at room temperature in a manner as is usable for this mixture with the aid of a redox system. Part of the metallic band may be surrounded by further metallic bands under stress.
When using this method it is of essential importance for obtaining the desired protection against implosion that satisfactory adhesion of the polyester mass to the surface of the metallic band and to the surface of the glass forming the transition region is obtained. Only under these conditions is it ensured that in case of cracks occurring in the window owing to an external, mechanical cause, a mechanical stress exists or develops in the polyester-metallic band envelope wi which sufficiently counteracts the implosion.
ln practice it has been been found that the difference between the coefficients of expansion of the-metallic band and of the glass of the transition region upon great variation in temperature cannot be bridged, unless use is made of expensive polyester resins specially developed for this purpose.
For this reason the inner surface of the metallic band and the surface of the glass forming the transition region have previously been provided with an adhesive layer of a thermoplastic synthetic material, more particularly polyvinylacetate.
In practice it is found that in this way a slight improvement is obtained.
However, upon close investigation it was found that with great variation in temperature, more particularly with cooling to temperatures down to -40 C., such as may occur during transport and storage in winter at higher degrees of latitude, the polyester mass locally loosens, resulting in superficial deterioration of the surface of the glass.
An object of the present invention is to provide a solution to this problem.
Mixtures of unsaturated polyester resins and monomers, such as styrene, which are polymerisable therewith, are hardened at room temperature with the aid of a redox system consisting of an organic oxide and usually a metal soap or an amine as a reducing agent.
According to the invention the problem of obtaining satisfactory adhesion was solved by using an adhesive layer containing a reducing agent of the kind which is also used in the redox system for hardening the polyester mass.
As such it is known to incorporate either the peroxide or the reducing agent in a primer layer which is covered with a layer of a mixture consisting of an unsaturated polyester and a monomer which is polymerisable therewith and contains the other component of the redox system. However, the primary object of this method is to prevent premature polymerisation of the mixture of unsaturated polyester and monomer polymerisable therewith. If better adaptation of the shape of an injection-moulded mass to the shape of the mould or better adhesion of lacquer layers should in this case be obtained, then the beginning of the polymerisation of the mass at the surface covered with primer layer is responsible for this.
However, in the method according to the invention, the polymerisation takes place in the whole of the mass at the same time. Also, a contraction of the mass in the direction of the metal and glass surfaces does not occur. This contraction causes cracks in the mass, but such cracks do not occur when the method according to the invention is used.
The invention will now be described with reference to the accompanying drawing, the sale FlG. of which shows a part section of the marginal region of a television display tube, and to the example to be described hereinafter.
ln the sole FlG. the transition region between the conical part 2 and the window 3 is indicated by l. A metallic band with a flanged part 5 for fastening purposes is indicated by 4.
Starting with a 23 inch tube, the inner surface of the metallic band 4, (which is, for example, of aluminum) and the outer surface of the transition region 1 are covered with 30 gm. of a polyvinyl acetate solution consisting of 150 gm. of polyvinyl acetate, 1.5 liters of water to which 1 percent by weight of dimethyl paratoluidine has been added. After the adhesive layers have been dried in air, the metallic band is placed in a holder (now shown). Subsequently the completed television display tube is placed in the metallic band in the manner shown in the FIG. The space of slightly wedge-shaped section between the band 4 and the marginal region 1 is filled with a mass consisting of a mixture having the composition:
100 gm. of unsaturated polyester (for example type S 523) from Synres Ltd. at Hook of Holland;
25 gm. of styrene;
90 gm. of filler (CaCO 5 gm. of benzyl peroxide;
0.35 gm. of dimethyl paratoluidine.
This composition may be used at a temperature of the working space between 20 C. and 22C. At a higher temperature the amount of dimethyl paratoluidine is reduced proportionately.
Comparative tests gave the following results:
If a polyvinyl acetate adhesive was used without an addition of a dimethyl paratoluidine, the adhesion between the glass and the resin at the comers of a substantially rectangular window was broken in more than percent of the cases even during the hardening of the polyester resin.
If dimethyl paratoluidine to an amount of 1 percent by weight was added to the polyvinyl acetate adhesive, the said percentage decreased below 1 percent.
The polyester resin used was of the general purpose type and consisted substantially of polyglycol-isophthalatemaleinate and styrene.
By the use of the invention a similar result was obtained as seemed possible before only by using expensive polyesters, for example, on the basis of neopentyl-glycol, which are specially manufactured for this purpose.
The behavior of the tubes when cracks are caused in the glass by the action of liquid air, during shock tests with a steel ball and in cooling tests down to 40 C. was similar to that of tubes in which a polyester resin on the basis of neopentyl glycol had been used.
It will be evident that the invented method is not limited to the constructions described nor to the specified combinations Evident modifications of the construction described in the example will be, for instance;
a. The band 4 can embrace the tube over part of its width under stress.
b. The band 4, which may possibly consist of two parts can be surrounded by a clamping band after the resin has been poured in and hardened.
c. The band 4 may be positioned so that the aperture of the wedge-shaped space 6 lies adjacent the window side 3 of the tube.
f. Other peroxides and accelerators can be used.
1. A method of strengthening a television display tube having a substantially rectangular window closing one end of a conical portion for the purpose of reducing the risk of implosion comprising the steps of applying to a surface of a metallic band and the surface of the conical portion adjoining the window an adhesive layer containing a reducing agent for hardening a polyester mass, surrounding the conical portion covered with said adhesive layer with said metallic band leaving a space therebetween, filling said space between the metallic band and the conical portion with a mixture consisting of an the adhesive layer is the same as that in the redox system. unsalumtcfj Polyester a monomer which pllymcrlsa' 3. A method of strengthening a television display tube as ble therewith, a redox system and a filler, and hardening the v claimed |n claim 2 m WhlLh the reduemg agent is dimethyl mixture at room temperature. urlnoluidinc 2. A method of strengthening a television display tube as 5 p i claimed in claim I in which the reducing agent contained in