US 3166211 A
Description (OCR text may contain errors)
Jan. 19, 1965 M. STEL ETAL 3,166,211
GLASS CATHODE RAY TUBE FOR REPRODUCING IMAGES Filed oct. 9. 1961 INVENTORS CONSTANTIUS J-W. PANIS MARINUS ST EL 53' E55? J" ELSS? l BY AGEN United States Patent 3,166,211 GLASfi CATHQDE RAY TUBE FOR REPRQDUCING IMAGES Mai-inns Ste], Pieter Harm Fennerna, Wilicrn Foidro Nienhuis, and (Ionstantius Johannes Waltheflrs Penis, all of *Eindhoven, Netherlands, assignors to North Arnericm Phiiips Company, Inc., New York, N31, a corporafion of Delaware Filed Oct. 9, 1961, Ser. No. 143,893 Claims priority, application Netherlands Nov. 3, 1960 5 Claims. (Cl. 220--2.1)
The invention relates to glass cathode ray tubes for reproducing images, more particularly to large-sized tubes, esspecially television display-tubes.
In such cathode ray tubes there is a risk that implosion may occur as a result of injury to or aging of the glass. Particularly in large-sized display tubes, implosion may have serious consequences for persons happening to be about, and the material damage may also be considerable. This applies especially to tubes having a substantially rectangular window.
Various endeavours have been made to mitigate the consequences of implosion or'to reduce the risk of implosion to a minimum.
To limit the consequences of implosion, a protective sheet is arranged in front of the display screen in the cabinet of the receiver of which the cathode ray tube forms part. However, this precaution does not effectively protect the persons having to assemble the receiver.
It is also known to cover the window and, if required, the cone of a cathode ray tube with a coating of a synthetic resin, by which in the case of implosion the fragments are held together. The synthetic resin maybe slipped in the form of a hood over the window and the adjoining part of the cone and then shrunk on. Since generally in the junction between the window and the cone and in the portion of the window surrounding the image area, tensile stresses may be produced in the glass, glass aging may occur in this zone, so that the risk of collapse of the glass wall here is a maximum.
It has been found that the known means are capable of materially reducing the consequences of implosion, but they require a coating of synthetic resin covering the entire image area. However, a suitable synthetic resin generally tends to discolour, is readily scratched and soiled by smoke and dust particles.
It has proved possible substantially to preclude the occurrence of implosion and in any case to render the consequences of implosion quite harmless, if in a cathode ray tube for image display, the glass-Wall of which is coated at least in part with synthetic resin, according to the invention this coating contains fibrous material, at least in an area in which this coating covers the zone which adjoins the image area of the window and extends over part of the cone.
it was surprising to find that, even if a crack was mechanically produced in the glass Wall, this crack does not run further. This even applies to a crack produced in the image area of the window not covered by the fibrous layer. The vessel is slowly filled with air. Hence, it is of importance that the fibre containing layer of synthetic resin should have satisfactory adherence to the glass. To this end, the glass may previously be covered with a separate intermediate layer consisting of a substance having a better adherence to the glass and to the fibre containing synthetic resin than this latter layer has to the glass, so that the intermediate layer acts as a glue.
The fibre-containing synthetic resin layer according to the invention preferably contains glass fibres, which are embedded in the synthetic resin preferably as short lengths of, for example, a few centimetres. Apparently, by the 3,lfifi,2ll Patented Jan. 19, 1965 addition of the fibres the strength of the synthetic resin layer is increased so that the glass fragments cannot separate any further, so that a crack does not run on.
Since this layer is opaque, it obviously cannot be applied to the image area of the window. However, this has proved unnecessary, since the mere presence of such a layer on the zone outside the image area, in which tensile stresses may be produced in the glass, is sufiicient to provide the desired effect in the image area also.
Such a clear intermediate layer applied to the glass in order to improve the adherence may also be used in any known manner to obtain certain optical effects, e.g. the avoidance of light reflections of nearby light sources or increase of the contrast. The fibre containing layer according to the invention may also be used in combination with means for strengthening the surface of the glass, e.g. the provision of a layer of glaze, as has already been suggested in prior applications. The term image area is to be understood to mean the window portion used for display. This is generally defined by the luminescent layer applied to the inner surface, but frequently it is defined by a mask provided on the outer surface of the tube or in the cabinet and, in the case under consideration, may be constituted by the fibre containing layer.
The invention will now be described more fully with reference to a drawing, in which FIGS. 1, 2 and 3 show various embodiments of cathode ray tubes in accordance with the invention.
In FIG. 1, a cone 1 of a cathode ray tube has fused to it a neck 2 and a window 3, to the inner surface of which a luminescent screen 8 is applied. Tensile stresses may be produced in the glass in a zone 4. According to the invention, at least that part of this zone 4 adjoining the image area is covered with a robust layer 5 of synthetic resins having a thickness of a few mms. and consisting of a mixture of glass fibres having a length of from 1 to 3 cm. and a hardened unsaturated polyester resin having satisfactory adherence to the glass. This mixture may consist of 3 parts by weight of glass fibres and 7 parts by weight of a solution of an unsaturated polyester in, for example, styrene and may be applied to the glass surface by spraying and pressed to this surface by means of a roller.
The unsaturated polyester may be obtained by polycondensation of an 0:, 18 unsaturated dicarboxylic acid and a polyvalent alcohol. The polyester may be modified with saturated and/or halogen containing dicarboxylic acids. The polyvalent alcohols may be glycols or glycerol.
Solutions of from 50 to 70 percent by weight of unsaturated polyester in styrene are very suitable.
Hardening may take place under the influence of known combinations of catalysts, such as benzoyl peroxide, methyl ethyl ketone peroxide and the like, and of accelerators, such as cobalt naphthenate or dimethyl aniline.
To prevent premature hardening of the polyester, shortly before the application of the synthetic resin, a solution of the catalyst in a part of the polyester styrene mixture may be mixed with a solution of the hardening accelerator in the remainder of the polyester styrene mixture.
The unsaturated polyester solution may also contain dyes and pigments and fillers, such as titanium dioxide (TiO in order to counteract shrinking and cracking of the layer during the hardening process.
The glass fibres may consist of substantially any glass which is readily workable. Glasses having a low alkaline content are highly suitable.
In FIG. 2, a glass cord 6 is wound on the tube envelope during the process of spraying the glass surface with polyester resin, the assembly being pressed to the glass, so that a continuous fibre containing layer is produced having satisfactory adherence to the glass.
It has been found that it is not necessary to restrict the image area to within the zone in which tensile stresses may occur in the glass. In most cases, it is sufficient to cover the part of this zone forming the sharply bent junction between the image area and the sealing area and the cone.
In FIG. 3, the envelope is previously covered with an intermediate layer 7, which may consist of polyvinyl acecoating comprising a layer of strongly adherent synthetic resin containing wire-like fibres, an intermediate layer of synthetic resin between the implosion resistant coating and the portions of the tube covered thereby for promoting adherence of the coating to the tube.
3. A cathode-ray tube comprising a transparent window portion and a cone portion adjoining said window portion and an implosion resistant noncompressive coattate and has satisfactory adherence, the fibre containing layer 5 of synthetic resin being applied on said intermediate layer.
The synthetic resin layer may also serve to provide the envelope with lugs for securing the tube in a cabinet.
The wall thickness of the envelope and hence the weight of the tube may be materially reduced, since the strength of the envelope is increased by the coating according to the invention and also, owing to the fact that implosion of fracture of the envelope now is completely harmless, the safety factor may be lower.
If the outside surface of the cone has to be covered with a conductive layer, this maybe provided on the synthetic resin layer. Alternatively, however, the synthetic resin layer itself may be rendered conductive by the addition of particles of metal or graphite, or by incorporating conductive fibres of metal gauze in this layer.
What is claimed is:
1. A cathode-ray tube comprising a transparent window portion and a cone portion adjoining said window portion and an implosion resistant noncompressive coating covering a zone adjoining the Window portion and extending over a portion of the cone, said implosion resistant coating comprising a layer of strongly adherent synthetic resin containing wire-like fibers.
2. A cathode-ray tube comprising a transparent window portion and a cone portion adjoining said window portion, an implosion resistant noncompressive coating covering a zone adjoining the window portion and extending over a portion of the cone, said implosion resistant ing covering a zone adjoining the window portion and extending over a portion of the cone, said implosion resistant coating comprising a layer of strongly adherent synthetic resin containing Wire-like glass fibers having a length of about 1 to 3 cms.
4. A cathode-ray tube comprising a, transparent window portion and a cone portion adjoining said window portion and an implosion resistant noncompressive coating covering a zone adjoining the window portion and extending overa portion of the cone, said implosion resistant coating comprising a wound cord of glass fibers embedded in a synthetic resin strongly adherent to the surface of the ,tube to which it is applied.
5. A cathode-ray tube comprising a transparent window portion and a cone portion adjoining said window portion and an implosion resistant noncompressive coating covering a zone adjoining the window portion and extending over a portion of the cone, said implosion resistant coating comprising a layer of strongly adherent hardened unsaturated polyester resin containing wire-like fibers.
References Cited in the file of this patent UNITED STATES PATENTS 2,293,529 Bedford Aug. 18, 1942 2,734,142 Barnes Feb. 7, 1956 2,785,820 Vincent et a1. Mar. 19, 1957 2,859,109 Hawley et a1. Nov. 4, 1958 2,873,226 Davies et a1. Feb. 10, 1959 2,963,612 Thorington Dec. 6, 1960