GB2317740A - Reinforcement apparatus of a cathode ray tube - Google Patents

Abstract

To reinforce a CRT and/or resist its implosion, a film 10 is applied over the face panel 6, the skirt area 7 and curved region 14 therebetween. A first film portion covers the face panel 6 and a second film portion, which as shown may comprise four parts overlapping the first film portion, is adhered to the curved region 14 and the skirt area 7 over a reinforcing band 3. The second film portion is of a different material from the first film portion, may be thicker than the first film portion, and may for example comprise poly-p-terephthalamide or polybenzamide mixed with aromatic polyamide system fibres. The first film portion may be antireflective or antistatic.

Description

REINFORCEMENT APPARATUS FOR CATHODE RAY TUBE The present invention relates to a reinforcement apparatus for a cathode ray tube, suitably applicable to a tube body of a cathode ray tube whose face panel is flattened, for the purpose of reinforcement and/or resisting explosion.

Types of explosion-proof apparatus for reinforcing the tube body of a cathode ray tube (hereinafter referred to as a CRT) are known. For example, there are know a band-reinforced type in which a steel band is wound around a skirt portion of a panel of the tube body to fasten it tight; a rim-reinforced type in which a metal shell (rib) is fitted on a peripheral portion of the cathode and hardened with an injected liquid resin; and a panel-reinforced type in which a reinforced glass plate whose curvature is similar to that of a face portion in front of the panel is arranged with a predetermined space thereto and hardened by injecting a flexible and transparent liquid resin, etc. into the space.

Recently, almost all manufactured CRTs use the bandreinforced type of these types of explosion-proof apparatus.

FIG. 1 shows a perspective view of a band-reinforced type CRT.

As shown in FIG. 1, a tube body 1 is comprised of a panel part 2 and a funnel body 5. The panel part 2 is comprised of a face panel 6 forming a tube screen and a skirt area 7, which together form a box of almost rectangular shape. The funnel body 5 includes a funnel portion 8 and a neck portion 9, which together form a shape close to a funnel.

After a protecting tape made of polyethylene or the like is applied around an outer circumference near a mould match region of the skirt area 7 and a frit seal portion which joins end faces of the panel part 2 and the funnel body 5 of the tube body 1 each other through a frit glass, a steel band 3 is fitted on the tape by a quenching fit or the like. Thus, a surface stress during an exhaust of the CRT is reduced by an external force F of the band 3 directed to the interior of the tube body 1. Further, in FIG. 1, reference numeral 4 denotes each of metal fittings fixed integrally to each of corner portions of the band 3 by welding and the like.

Moreover, such a cathode ray tube is also known from Patent Application Laying-open No. 52-87355 which discloses a plastic film 10 of nearly rectangular form subjected to a processing for the prevention of reflection, the prevention of electrification and the like being applied on the face panel 6 of the panel part 2, thereby providing an explosion-proof role which prevents the glass of the panel part 2 from being scattered to the front.

As to a method of measuring a safety strength of the tube body 1 which can be compensated by the explosion-proof apparatus of a CRT as described above relating to the prior art, various safety standards are prescribed in each country. In Japan, there is a shock test in which a ball of predetermined diameter and weight is bumped against the face panel 6 with an impact energy of 5.5 J (joule) i.e. 5.5J ball impact test. 7J ball impact test issued in U.S.A. The safety standards are thus prescribed in a manner that when a definite impact is applied to the face panel 6 made of glass, the tube bode 1 should not implode.

There is also carried out a breaking test in which a CRT is completely broken down. In Japan, there is a thermal shock test, as the standard breaking test, in which the surface of the face panel 6 is flawed and a liquid nitrogen, etc. is blown against it. In U.S.A., there is a breaking test in which the surface of the face panel 6 is flawed beforehand to a predetermined depth by a diamond cutter or the like and then a warhead shaped steel block is bumped against it with the impact energy of 20J. The safety standards prescribe that a large quantify of glass fragments should not scatter to the front of the face panel 6 if the tube body 1 is broken down, when performing such a breaking test.

The conventional explosion-proof apparatus of a CRT as described above have heretofore passed the foregoing various shock and breaking tests.

However, with the recent larger sizes of CRT, it is desirable to decrease a thickness of the tube body 1 for reducing its weight. Furthermore, a tube body of CRT with a cylindrical screen having a curvature R along the longitudinal direction of the face panel 6 is proposed, and the face panel surface thereof is made close to flat by making the curvature R large, say, 8000 mmR to 15000 mmR.

With the explosion-proof apparatus of CRT whose face panel 6 of the tube body 1 is made substantially flat, it is difficult to reduce the vacuum deformation of the face panel 6 only with the band 3 for preventing explosion as is seen from FIG. 1. Accordingly, there arise a need to make the glass of the tube body 1 extremely thick or to use another explosion-proof method simultaneously.

In the tube body 1 of CRT shown in FIG. 1, since the functional film 10 is applied on the surface of the face panel 6 in addition to the band reinforcement, this functional film 10 is also useful for preventing implosion and plays a part of a flaw preventer and a shock absorber.

In tests, when the band 3 was fitted on the skirt area 7 of the panel part 2 of a wide CRT of 66cm, and at the same time an almost rectangular polyethylene terephthalate film with 188 m thick was applied to the face panel 6 through a transparent adhesive, and then the above-mentioned 5.5J ball impact test was performed against the face panel 6, the shock-proof property was improved about twice or more.

However, in case of the breaking test where a 20J missile warhead shaped steel block is bumped onto the flawed surface of the face panel 6, the tube body 1 of CRT was caused to implode, such that the functional film 10 and the face panel 6 were sucked into the tube body 1 and broken down by colliding against each other within the funnel body 5. As a result, they rebound out again to the front. At this time, the film 10 does not play the part of suppressor of the glass scatter. In particular, since an R portion called blend R portion ranging from the face panel 6 surface to the skirt area 7 has no film 10 applied, there has been a problem in which fragments of that portion springing out to the front increase significantly in quantity. In order to solve this problem, it has been proposed to make the film 10 large enough to be applied from the skirt area 7 of the tube body 1 to the band portion 3. However, the film which is processed for preventing reflection and electrification is very expensive and so it is impractical for the film to be applied even to the skirt area.

According to the present invention there is provided an explosion-proof apparatus comprising a film applied over the range from a face panel to a skirt area of a tube body of the CRT, as its example is shown in FIG. 2, in which a film portion of the film applied to the face panel and a film portion of the film applied over the range from a blend R portion to the skirt area are made of different materials, respectively.

With embodiments of the explosion-proof apparatus for a CRT according to the present invention, fragments of the face plate and the blend R portion may scatter to the front less if the face panel and so on are imploded in the breaking test.

Since a film whose surface is not processed or a thick film can be applied on four sides over the range from the blend R portion to the skirt area, it is possible to obtain the apparatus which is low in price and of less scatter to the front.

Therefore, the present invention is capable of providing to an explosion-proof apparatus for a CRT whose face panel is made flat without increasing the thickness of the face panel of the tube body.

Merely by way of non-limitative example, an embodiment of the explosion-proof apparatus for CRT according to the present invention will be described below with reference to the accompanying drawings, in which: FIG. 1 is a perspective view of a band-reinforced type of explosion proof apparatus; FIG. 2 is a perspective view of an embodiment of the explosion-proof apparatus of CRT according to the present invention; FIG. 3 is a partial sectional view taken along an A A' line of FIG. 2; and FIG. 4 is a plan view of the film applied to the tube body of the CRT shown in FIGS. 2 and 3.

Referring to FIGS 2 to 4, a tube body 1 of a CRT is constructed as one body by joining a panel part 2 comprising a face panel 6 and a skirt area 7 made of an almost rectangular box shaped glass to an almost funnel form glass comprising a funnel body 5 and a neck portion 9 with a frit glass at a frit seal portion 11.

Of the face panel 6, the blend R (or bend) portion (between the face panel 6 and the skirt area 7) 14 and the skirt area 7 which form the panel part 2 of the tube body 1, around a outer circumference of a mould match region 12 of the skirt area 7, a protecting tape 13 with an adhesive made of polyethylene or the like for protection is applied. A metal fitting 4 is fixed integrally at four corners of the protecting tape 13. A band 3 made of, e.g., steel. of an almost rectangular shape is fitted on the tape 13 by, e.g., a quenching fit, so that the deforming strain of the face panel 6 due to the atmospheric pressure when the tube body 1 is exhausted to vacuum can be compensated with the fastening band 3.

In this example, a rectangular film portion 10A whose four corners are round off as shown in FIG. 4 is prepared first and then a multilayer film made of SiO2, ITO, etc. is formed on the surface of the film portion l0A with effects so as to prevent reflection and electrification. The film portion 10A thus processed is applied to the face panel 6 as shown in FIG. 2 and FIG. 3. Thereafter, a sticking piece lOB made of a rectangular film is applied to four sides of the panel in such a manner that, as illustrated in FIG. 4, a part of the rectangular film portion lOB is overlapped on the rectangular film portion lOA from the blend R portion 14 to the skirt area 7, as is shown in FIG. 2 as an overlap lOF.

The film of the sticking piece lOB is not subjected to any surface processing. In addition, the thickness of the sticking film piece lOB may be selected appropriately, but preferably selected to be thicker than that of the rectangular film portion 10A. Furthermore, it is preferable for the sticking piece lOB to be a film of poly-p-phenylene terephthalamide or polybenzamide which is mixed with aromatic polyamide system fibre having good tensile property and heatresistance.

According to the present invention, due to the effect of the films applied to the four sides, the suction of the face panel together with the film into the tube on implosion is prevented and at the same time the scatter of the blend R portion is prevented, which in turn leads to a substantial improvement of the explosion-proof performance.

Moreover, the formation of the reflection-free film requires much costs and so it is necessary to reduce its use amount as much as possible. However, according to the present invention, the film applied to the skirt area is subjected to no processing, thereby enabling its costs to be reduced to a minimum. Furthermore, by increasing the film of the sticking piece lOB in the thickness and the strength relative to the rectangular film portion lOA, the scatter of the blend R portion can further be prevented without failure.

According to the explosion-proof apparatus of CRT of the present invention, since the non-processed film is applied over the range from the blend R portion to the skirt area in addition to the functional film applied to the face panel, the explosion-proof performance will substantially be improved.

Moreover, since the fragments of the face panel does not scatter in the breaking test even in case of the tube body of CRT which is made flat by making a curvature R of the curved surface formed cylindrical in the long sid direction of the face panel large, it is possible to make the thickness of the face panel glass to be thin and thus to reduce a weight of the entire CRT.

Having described a preferred embodiment of the present invention with reference to the accompanying drawings, it is to be understood that the present invention is not limited to the above-mentioned embodiment and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope of the present invention as defined in the appended claims.

Claims (11)

1. A reinforcement apparatus for a cathode ray tube in which a film is applied over a range from a face panel to a skirt area of a tube body of a cathode ray tube, wherein a first film portion applied to the face portion and a sticking film portion applied over the range from a blend R portion to the skirt area are made of different materials, respectively.

2. A reinforcement apparatus according to claim 1, wherein the sticking film portion overlaps the first film portion.

3. A reinforcement apparatus according to claim 1 or 2, wherein the sticking film portion comprises separate portions applied to the four sides of the panel portion of the cathode ray tube.

4. A reinforcement apparatus according to any one of the preceding claims, wherein the sticking film portion is thicker than the first film portion.

5. A reinforcement apparatus according to any one of the preceding claims, wherein the first film portion is a multilayer film.

6. A reinforcement apparatus according to any one of the preceding claims, wherein a band is fitted around the skirt area of the cathode ray tube.

7. A reinforcement apparatus according to claim 6, wherein the band is fitted over a protective tape.

8. A reinforcement apparatus according to claim 6 or 7, wherein the sticking film portion is applied over the band.

9. A reinforcement apparatus according to any one of the preceding claims, wherein the first film portion but not the sticking film portion has been subjected to surface processing.

10. A cathode ray tube having applied thereto a reinforcement apparatus according to any one of the preceding claims.

11. A reinforcement apparatus constructed substantially as hereinfore described with reference to FIGS. 2 to 4 of the accompanying drawings.