JPH02135651A - Antistatic cathode-ray tube - Google Patents

Abstract

PURPOSE:To prevent the induction of static electricity upon the external surface of a face-plate by separately forming a second conductive film having its resistivity smaller than that of a first conductive film on the first conductive film, and electrically connecting this second conductive film to both the first conductive film and an implosion preventing means. CONSTITUTION:After a first conductive film 9 is dried, a second conductive film 10 made of graphite is coated such that the first conductive film 9 and a reinforcing band 8 are mutually contacted to make a mutual electric connection, so that the electric connection of the first conductive film 9 to a cushioning material 7 and also to the reinforcing band 8 may be ensured. Subsequently, these films 9, 10 are respectively heated for the sake of improving the mechanical strengths thereof and of reducing the resistance values thereof. Then, the second conductive film 10 is coated such that it is overlapped by about 5 square centimeters upon the first conductive film for being connected as far as to the reinforcing band 8.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to antistatic treatment for cathode ray tubes used in television picture tubes, terminal display devices, and the like.

[Conventional technology]

Since a high voltage of several tens of kV is normally applied to the phosphor screen on the inner surface of the faceplate of a cathode ray tube, static electricity will be induced on the outer surface of the faceplate and it will become charged if no measures are taken. In particular, at the moment when a high voltage is applied or erased, it becomes charged to a large value, reaching a high voltage of several tens of kV. This static electricity gradually disappears, but during that time, it can cause shocks when touched with hands, collect dirt, become dirty, and cause dust to fly away, causing an S effect. Various measures have been proposed to form a first conductive film and ground it to release the charge. A method has been proposed in which an aluminum tape is separately provided and the first conductive coating is electrically connected to the implosion prevention metal member. Usually, a metal fitting for attaching the cathode ray tube to a cabinet or the like is fixed to the implosion prevention metal member, and is connected to a ground potential section through this metal fitting. However, the resistance value of the first conductive film is generally high, and if this grounding method is insufficient, it will be charged to a large value the moment a high voltage is applied or erased, resulting in a high voltage of several tens of kV. It will also happen.

In addition, in order to solve this problem, the applicant filed a patent application in 1986.
No. 3-141715 proposed a structure in which a conductive metal strip (including aluminum tape) is folded back at an intermediate portion that almost touches the end of the insulating member on the side closer to the outer surface of the panel. This method simplifies the work and makes it possible to obtain a cathode ray tube that can fairly reliably prevent various problems caused by charging on the panel surface.

However, even with this method, it was still insufficient to narrow down the ratio by using a more strict charge decay time. That is, the first conductive film on the panel surface is reliably coated up to the skirt portion,
This is because there was a possibility that there were portions that were not in reliable contact with the conductive metal strip.

According to experiments conducted by the present inventors, when the air-conditioned environment during operation of the horizontal line tube is at a relative humidity of 40% or less, -instantaneous (1 sec or less)
In a cathode ray tube of size 14, the condition that there is no charge is that the surface resistivity of the first conductive film is I x 1
It was found that this could not be achieved unless the electric charge was set to 0'Ω/h or less and the electric charge was reliably grounded over almost the entire circumference of the panel.

Furthermore, immediately after manufacturing, the first conductive coating and the conductive metal strip were in contact with each other, but during long-term use,
After a high-voltage switch is turned on and off, the membrane at its contact area may be damaged, resulting in poor continuity.
All conventional techniques were insufficient.

[Problem to be solved by the invention]

The present invention provides a method for sufficiently electrically connecting the first conductive coating described above to an implosion-preventing metal member.

[Means to solve the problem]

This invention is an antistatic type panel having a first conductive coating formed on the face plate portion of the panel or from the face plate portion to the skirt portion, and having implosion prevention means for pressurizing the skirt portion with a metal member through a cushioning material. In a cathode ray tube, a second conductive film having a specific resistance lower than that of the first conductive film is separately provided, and this second conductive film is electrically connected to both the first conductive film and the implosion prevention means. A grounding means is provided, which is characterized by being connected to.

[Effect]

Since a high voltage of several tens of kV is normally applied to the phosphor screen on the inner surface of the faceplate of a cathode ray tube, static electricity will be induced on the outer surface of the faceplate and it will become charged if no measures are taken. In particular, at the moment when a high voltage is applied or erased, it becomes charged to a large value, reaching a high voltage of several tens of kV. However, the resistance value of the first conductive film is generally high, and if this grounding method is insufficient, it will be charged to a large value and cannot fully exhibit its effect. In this invention, a second conductive film having a lower specific resistance than the first conductive film is further used, and this second conductive film is electrically connected to both the first conductive film and the implosion prevention means. By connecting the faceplate to the faceplate, static electricity is hardly induced on the outer surface of the faceplate.

〔Example〕

Embodiment 1 Hereinafter, one embodiment of the present invention will be described with reference to FIGS. 1 to 3.

First, as shown in the figure, a tube body 3 is constructed by frit-sealing a panel 1 with a phosphor screen formed on its inner surface to a funnel 2. After that, an electron gun 5 is inserted into the neck 4, and the electron gun 5 is inserted into the neck 4. Connect the stem 6 provided at the base of the gun 5 to the neck 4.
After welding to the end of the panel 1, a cushioning material 7, for example, a glass fiber tape, is wrapped around the entire circumference around the skirt of the panel 1 or on the frit seal portion between the panel 1 and the funnel 2. After wrapping this tape around the front outer periphery of the cathode ray tube as shown in Fig. 1, a reinforcing band 8 is tightened on top of the cushioning material 7. In this case, the reinforcing band 8 is made by welding both ends of the metal band. This reinforcing band 8 is formed in advance into a ring shape according to the outer peripheral shape and size of the tube body of the part to be tightened, and this ring-shaped reinforcing band 8 is heated and expanded to make it non-combustible and conductive. It is fitted onto the buffer material 7, cooled and tightened to constitute implosion prevention means.

After that, exhaust treatment is performed. This exhaust treatment is performed by an exhaust pipe 12 provided through the glass stem 6.
After exhausting air, tip it off to make it airtight. This evacuation is performed with the tube body 3 placed in a heating furnace and heated at, for example, 400° C. as usual.

After evacuation, the tube body 3 is taken out from the heating furnace, and the tube body 3 is removed from the heating furnace.
When the temperature reaches approximately 80° C., the face plate portion 11 of the panel 1 is cleaned and a transparent first conductive film 9 is applied by, for example, a spin cord method. At this time, it is desirable that the first conductive film 9 contacts and electrically connects with the cushioning material 7 and the reinforcing band 8.
For example, the dispersion medium evaporates and the first conductive film 9 dries. After that, in order to ensure the electrical connection between the first conductive film 9 and the cushioning material 7 and reinforcing band 8, a layer of graphite made of graphite, for example Hitazol LT-4B manufactured by Hitachi Powder Metallurgy Co., Ltd. As shown in FIG. 2, the second conductive film 10 is applied so that the first conductive film 9 and the reinforcing band 8 are in contact and electrically connected. After that, the first conductive film 9 and the second conductive film 10 are formed.
It is preferable to heat these at about 160° C. for 30 minutes in order to improve the mechanical strength and lower the resistance value.

However, when the first conductive film is formed by applying a solution in which fine particles of tin oxide doped with antimony are made into a sol with ethyl silicate and alcohol,
The resistance value was on the order of 107 ohms/hole, and if the second conductive film was formed by applying a liquid in which graphite was dispersed with lacquer, the resistance value was on the order of 103 ohms/hole. . In this case, if the second conductive coating lO is not applied, the cathode ray tube will have a 25k
When operated with a voltage of V applied, a voltage of 3.5 kV was induced. Then, in order to establish an electrical connection between the first conductive film 9 and the reinforcing band 8, the second conductive film 10 and the first conductive film 9 are overlapped by about 2" and connected up to the reinforcing band 8. However, a voltage of 2 kV was induced as indicated by aa of the small area earth in FIG.

Therefore, when the second conductive coating 10 was applied so as to overlap the first conductive coating 9 by about 5 am'' and connect to the reinforcing band 8, the large-area ground line in Fig. 3 was reversed as shown above. Only a very small voltage of polarity was induced.

The reason for this is that since the first conductive film 9 has a high resistance value, if the small area overlaps, the resistance value between the second conductive film 10 and the first conductive film 9 will increase. . Therefore,
The larger the overlap between the second conductive film 10 and the first conductive film 9, the better. Ideally, as shown in FIG. conductive coating 9
It is best to apply it around the entire circumference. In addition, in FIG. 3, line C indicates the conventional No. 1. The line d shows the characteristics of the case without the second conductive coating, and the line d shows the characteristic of the case with only the first conductive coating.

Embodiment 2 FIG. 4 is a schematic sectional view of another embodiment of the present invention, FIG. 5 is an enlarged detailed view of circle A in FIG. 4, and FIG. 6 is an explanatory diagram of the manufacturing method of the same embodiment. . Note that illustrations of components other than the metal back film and shadow mask group are omitted. In these figures, 41 is a transparent first conductive coating, and 42 is a glass panel.

43 is a fluorescent screen, 44 is a metal reinforcement, 45 is a glass tape, 46 is a metal foil, 46a is a folded portion thereof, 47 is a second
, and 48 is a valve.

Next, the manufacturing method will be explained with reference to FIG. With respect to the main body of the cathode ray tube which has undergone the exhaust process and has almost all cathode ray tube functions, a metal foil 46, for example, an aluminum foil is placed on the side wall of the skirt of the panel 42 of the bulb 47 (step (1)).

In this state, an explosion-proof adhesive glass tape 45 is wrapped around the entire circumference of the skirt side wall of the valve panel 42 according to normal reinforcement specifications. The metal foil 46 may be placed all around the circumference, or may be placed partially, ie, with a length of several cm to several tens of cm, at several locations as necessary (step (2)). Next, metal foil 4
The outer edge of the panel 6 is folded back at the folding part 46a to wrap around the glass tape 45 (step (3)
), the glass tape 45 may be adhesive on both sides.

Next, the metal reinforcing body 44 is wrapped five times from above (
Tension band method) or shrink fitting (shrink fitting method).

Finally, if necessary, the metal foil 46 may be cut to the same length. A transparent first conductive film is formed on the outer surface and skirt portion of the panel 42 of the cathode ray tube body that has undergone the above reinforcement process by spin coating or dip coating. The conductive material solution sufficiently enters the gap 49 between the metal reinforcing body 44 and the panel 42 to ensure that the metal foil 46 and the first conductive coating 41 come into contact with each other.
], and the metal reinforcing body 44 at ground potential are ensured to be electrically conductive (step (4)). Next, gap 4
For example, lacquer-based graphite (Hitachi Powder Metallurgical Co., Ltd. [Hitasol LT-4BJ)] is applied to 9 with a brush to form the second conductive film 47. The second conductive film 47 may be applied over the entire circumference, or may be partially applied at several locations with a length of several Qm to several tens of square meters (step (5)).
).

After coating, the first conductive film 41 and the second conductive film 47 are baked at around 160° C. for 30 minutes.

The second conductive film 47 does not necessarily require firing, but may be fired at 160°C.

That is, the second conductive film may be applied after the first conductive film is applied and fired.

Further, it is also possible to apply the second conductive film in advance before coating and forming the first conductive film. Completed prevention cathode ray tube.

In such a configuration, the difference in antistatic effect between when the second conductive film 47 is coated all around and when it is not coated at all is determined by the decay rate of the charged voltage on the surface of the 14-inch cathode ray tube panel (applied voltage Table 1 below shows a comparison of the time it takes for the charged voltage on the panel surface to drop below Ov after switching on and off at 23 kV and the instantaneous charged voltage. As is clear from this table, by carrying out the present invention, the antistatic effect becomes very good, and it can be seen that there is almost no static charge even momentarily. Even when I placed a piece of paper in front of the cathode ray tube and turned the first switch on and off, it did not budge at all.

On the other hand, in a cathode ray tube that is not coated with the second conductive coating 47, the piece of paper moves for a fraction of a second.

Of course, in cathode ray tubes that do not undergo any treatment or have incomplete antistatic functions, the pieces of paper will be attracted to the front panel and will not let go, even for several minutes.

This also shows that the application of the second conductive film 47 is very effective.

In the above embodiments, a color cathode ray tube has been described, but the present invention is of course not limited to this.Although a band reinforcement structure has been described for reinforcement, other examples such as P
Of course, it is also possible to use -0-P reinforcement. Of course, the metal foil may be replaced with various conductive members, such as Cu foil, as long as the purpose of the present invention is met.

Although lacquer-based graphite was used as the graphite, other types of graphite may be used as long as they meet the above purpose. The water-soluble graphite that is currently coated on the outer wall of cathode ray tubes, or any graphite suitable for the above purpose may be used.

In this way, electrical continuity is reliably established between the transparent first conductive coating covering the panel surface and the metal reinforcement. As a result, the charge that has been accumulated on the panel surface for a long period of time disappears instantaneously. It should be noted that it is not necessary to insert gold [f] over the entire circumference of the skirt, but it can be done partially, for example, in a total of 8 locations, 2 locations each on the long and short sides, with a length of several Qm to several tens of cm. good. However, as long as the second conductive film ensures continuity over the entire circumference, it may be sufficient to apply the second conductive film to one location, and it is better to apply the second conductive film to the entire circumference as much as possible.

The dimensions of the second conductive film are adjusted by selecting the surface resistance value of the first conductive film, the size of the cathode ray tube, how much the decay time needs to be shortened, whether it should not be charged even momentarily, etc. I don't mind if you do that.

In the above embodiment, graphite was used as the second conductive coating, but this graphite was selected because it is relatively inexpensive and has a proven track record of being used as graphite for the exterior of cathode ray tubes. It is. In addition, it can maintain chemical, mechanical and adhesive strength, is quick drying, has good wettability for simultaneous application, and has excellent workability. In addition, it is flexible, so long-term switch o
n/.

This is because it is extremely flexible against mechanical damage and electrical damage during ff.

However, it goes without saying that the present invention is not limited to this graphite, and for example, silver paste or the like may also be used.

〔Effect of the invention〕

As described above, in the present invention, the first conductive film is formed on the face plate portion of the panel or from the face plate portion to the skirt portion, and the implosion is applied to the skirt portion by applying pressure with a metal member through a cushioning material. In an antistatic cathode ray tube provided with a prevention means, a second conductive film having a lower resistivity than the first conductive film is further provided, and this second conductive film is combined with the first conductive film and implosion. By electrically connecting both of the prevention means, induction of static electricity on the outer surface of the faceplate is almost eliminated. Therefore, even if a high voltage of several tens of kV is applied to the cathode ray tube, there will be no negative effects such as getting a shock when touching it, collecting dust and getting dirty, or blowing dust away. It has excellent features such as a good working environment.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway side view of an example of a cathode ray tube for explaining the structure of the cathode ray tube according to the present invention. FIG. 2 is an enlarged partially cutaway side view of the main part of FIG. 1, FIG. 3 is a diagram showing the antistatic effect, FIG. 4 is a schematic sectional view of another embodiment of the present invention, and FIG. FIG. 6, an enlarged detailed view of the circle A in the figure, is an explanatory view of the manufacturing method of the same embodiment. 1: panel, 2: funnel, 3: tube body, 4: neck,
5: Electron gun, 6: Stem, 7: 1/i! ! Shock material, 8: Reinforcement band, 9: Transparent conductive film, 10: Graphite, 11: Face plate part, 12: Exhaust pipe, 13 Varnishing part, 41... (transparent) conductive film, 42. ... Glass panel, 43 ... Fluorescent screen, 44 ... Metal reinforcement, 45.
...Glass tape, 46...Metal foil, 46a...Folded portion, 47...Second conductive coating, 48...Bulb, 49...Gap.゛Figure 1 4q = Psr, i Muscle 4 Figure 4 Cow Rule 5 Togo 6cL: NL 496 No. 60 49' 4

Claims (1)

[Claims] 1. A first conductive coating provided on the face plate portion of the panel or from the face plate portion to the skirt portion, and implosion prevention means for pressurizing the skirt portion with a metal member via a cushioning material. In the antistatic cathode ray tube, the first conductive film and the implosion prevention means are electrically connected, the second conductive film having a specific resistance lower than that of the first conductive film. An antistatic cathode ray tube, characterized in that a coating is electrically connected to both the first conductive coating and implosion prevention means. 2. The antistatic cathode ray tube according to claim 1, wherein the overlapping area of the first and second conductive films is 5 cm^2 or more. 3. In the antistatic cathode ray tube according to claim 1, the resistance value of the first conductive film is 10^5 to 10.
＾9kΩ/□, the resistance value of the second conductive film is 10＾5k
An antistatic cathode ray tube characterized by a resistance of Ω/□ or less. 4. In the antistatic cathode ray tube according to claim 3, the first conductive film is formed by applying a solution in which fine particles of tin oxide doped with antimony are made into a sol with ethyl silicate and alcohol. An antistatic cathode ray tube characterized by: 5. The antistatic cathode ray tube according to claim 3, wherein the second conductive film is formed by applying a liquid in which graphite is dispersed with lacquer. . 6. Implosion prevention by having a first conductive coating on the outer surface of a panel of a glass bulb and applying pressure with a metal member through an insulating member placed from around the skirt portion of the panel to the middle of the skirt portion. In the cathode ray tube, the cathode ray tube has an intermediate portion which is sandwiched between the panel skirt portion and the insulating member and between the insulating member and the metal member, respectively, and which is substantially in contact with the end of the insulating member on the side closer to the outer surface of the panel. In an antistatic cathode ray tube in which a folded thin conductive metal strip is disposed and the first conductive coating and the conductive metal strip are electrically connected, An antistatic cathode ray tube, characterized in that a second conductive coating having a low specific resistance is electrically connected to both the first conductive coating and the conductive metal strip. 7. The antistatic cathode ray tube according to claim 6, wherein the first and second conductive coatings have an overlapping area of 5 cm^2 or more. 8. In the antistatic cathode ray tube according to claim 6, the resistance value of the first conductive film is 10^5 to 10
＾9kΩ/□, the resistance value of the second conductive film is 10＾5k
An antistatic cathode ray tube characterized by a resistance of Ω/□ or less. 9. In the antistatic cathode ray tube according to claim 8, the first conductive film is formed by applying a solution in which fine particles of tin oxide doped with antimony are made into a sol with ethyl silicate and alcohol. An antistatic cathode ray tube characterized by: 10. The antistatic cathode ray tube according to claim 8, wherein the second conductive film is formed by applying a liquid in which graphite is dispersed with lacquer. .