JP2848388B2 - Cathode ray tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention prevents the front outer surface on which an antireflection film is formed from being charged to a high voltage.
The present invention relates to a cathode ray tube that can be easily produced.

[0002]

2. Description of the Related Art In a cathode ray tube, a fluorescent surface (metal back film) is maintained at a high voltage anode potential in order to scan a fluorescent surface formed on the back surface of a glass bulb with an electron beam.
Therefore, the front surface of the panel of the glass bulb is also charged to a high potential, which gives a user an electric shock, and has an adverse effect such as a malfunction at a nearby electronic device due to a discharge at that time.

[0003] Many countermeasures have been proposed for such problems. For example, Japanese Utility Model Application Laid-Open No. 62-1313
No. 56 discloses that an anti-reflection film (directly reflected light from the film surface and light reflected once at the interface with the next medium and returned to the film surface) interferes with the front surface of the cathode ray tube panel. A relatively thin transparent plate (the AR film requires vacuum deposition when forming it, so it is separate from the cathode ray tube body) It is economically advantageous to form it, and this plate is hereinafter referred to as a tele panel. On the back surface where the AR film is not formed, a transparent conductive film (hereinafter, referred to as an ITO film because it is usually formed of indium or tin oxide). It is disclosed that the ITO film is grounded to prevent the front outer surface of the cathode ray tube from having a high potential. However, this method requires the formation of thin films on the front and back of the telepanel, which increases the cost and is disadvantageous in terms of antireflection characteristics.

[0004]

As a means for preventing the front outer surface of a cathode ray tube with an AR film from being charged and becoming a high voltage, an ITO film is first formed on the front surface of a tele panel to be adhered to the front surface of a valve panel. Then, an AR film is formed thereon, and the ITO film is grounded (grounding in this case means so-called circuit grounding, and does not necessarily mean only connection to a cable embedded in the ground. Circuit grounding. In this case, it is advantageous in terms of antireflection characteristics and manufacturing cost. However, in the above structure, since the ITO film is entirely covered with the AR film which is an insulator, there is a problem how to form an electrode for grounding the ITO film and releasing the charged electric charge as a current. .

The present invention solves the above-mentioned conventional problems, and a tele panel in which an ITO film and an AR film are sequentially formed only on the front surface (a panel of a cathode ray tube bulb itself may be used if economically permitted or necessary. Another object of the present invention is to provide a means for easily forming an electrode for releasing the charged electric charge as a current.

[0006]

In order to achieve the above object, according to the present invention, an electrode made of a conductive substance is arranged in close contact with the AR film surface in a peripheral portion which does not hinder image observation of a (tele) panel. Then, the charged electric charge is released as a current through a capacitor formed between the electrode and the ITO film.

By employing the above means, there is no need to perform a complicated operation such as arranging an electrode by removing a part of the AR film formed on the ITO film, and the electrode forming process is extremely simple. Also, if graphite or the like having a small particle size is used as a conductive substance dispersed in a conductive paste used for forming an electrode, the conductive fine particles enter the pinholes of the AR film, and the electrode and the ITO film are separated. The space between the electrodes becomes electrically conductive, and even if the electric charge is once accumulated in the capacitor formed between the electrode and the ITO film, the electric charge is finally discharged and finally becomes zero. In addition, for high frequency, the ITO film is grounded by a capacitor formed between the electrode and the ITO film. Therefore, by appropriately selecting the sheet resistance of the ITO film,
The effect of suppressing unnecessary radiation from the cathode ray tube surface is also obtained.

[0008]

FIG. 1 is a schematic sectional view of a main part of an embodiment of the present invention. In the figure, 1 is a tele panel, 2 is ITO
Membrane, 3 is an AR film, 4 is an electrode, 5 is a reinforcing band, 6 is a conductive adhesive tape, 7 is a valve panel, 8 is a resin for bonding a tele panel to a valve panel, 9 is a valve funnel, 10 Is exterior graphite. As shown, the reinforcing band 5 and the exterior graphite 10 are grounded, and the electrodes and the reinforcing band are connected by a conductive adhesive tape or the like.

FIG. 2 shows an equivalent circuit. In this figure, C ₁ is the capacitance formed between the ITO film 2 and the anode, and R ₁ is the ITO
The resistance of the film, the current i ₂ flowing through the film, the current to release the charged charge, V ₀ is the power supply voltage, R ₀ is the internal resistance of the power supply, and C ₂ is I
The capacitance formed between the TO film 2 and the electrode 4, R ₂ is ITO
The leak resistance between the film 2 and the electrode 4 and C ₃ is the capacity of the exterior graphite. Capacitor C ₂ formed by ITO film 2 and electrode 4
And the voltage V ₂ applied is too large intermediate AR film cause dielectric breakdown, ITO film is also destroyed. In FIG. 2, components other than C ₂ and R ₂ are determined by the cathode ray tube and the set. Therefore it is necessary to lower the maximum value of V ₂ by suitably selecting the C ₂ and R _2.

In FIG. 2, the transient phenomenon when the switch S is closed is solved for V _2.

[0011]

(Equation 1)

The initial condition is that at t = 0

[0013]

(Equation 2)

FIG. 3 shows the result of solving this equation for various values of the parameters C ₂ and R ₂ .
₂ (this voltage appears on the front outer surface of the cathode ray tube) and time. R ₂ is a leak resistance between the electrode and the ITO film, and does not become a very small value. Here, the minimum value of R ₂ is set to 200Ω, and the other constants are examples in the case of a 14-inch cathode ray tube. As can be seen from FIG. 3, C ₂ is a particularly important factor, and the maximum value of V ₂ is almost determined by the value of C ₂ . R ₂ defines the time from when charged C ₂ gradually discharges to when V ₂ becomes zero. However, if C ₂ is sufficiently large, the potential of V ₂ becomes low, so that even if R ₂ → ∞, no practical problem occurs.

FIG. 4 shows how the current i ₂ for releasing the charged charge changes with time when the switch is closed. This figure shows the case where C ₂ = 0.1 μF and R ₂ = 20 kΩ, which is a general example when graphite is used for the electrode. As seen, the current miss charged charge Most flow capacity C _2, R ₂ is seen that the C ₂ is after being charged, it has a role of discharging. As described above, the present invention is missed charges charged by capacitance and leakage resistance between the electrode and the ITO film, in particular a capacitor C ₂ plays an important role.

The electrodes forming the capacitor C ₂ are A
Any material can be used as long as it is in close contact with the R film and has sufficient capacity. For example, various graphite pastes (dispersed graphite in epoxy, phenol, silicone, acrylic resin, etc.), silver paste, aluminum paste, etc. may be used.
Here, the silver paste and the aluminum paste are obtained by dispersing silver powder and aluminum powder in the above resin. Above all, graphite paste can be used to reduce the size of graphite particles.
It is particularly advantageous in that it can be electrically connected to the O film and can discharge the electric charge accumulated in the capacitor. If the conductive paste contains conductive fine particles having a size of 1 μm or less, depending on the properties of the AR film, the conductive fine particles can reach the ITO film through a pinhole of the AR film. Can be electrically connected between the ITO film and the electrode even after the electrode is formed by coating and drying. The resistance between the electrode thus formed and the ITO film is 10
It is desirable to be ⁸ Ω or less. However, conduction essential role does not have, the present invention method if you have a required value capacitor C ₂ is operated without problems. The electrodes may be formed in the state of the telepanel, or may be formed simultaneously in a heating step of bonding the telepanel to the cathode ray tube.
However, the resin for bonding the telepanel and the cathode ray tube generally has a low viscosity before thermosetting and may mix with the conductive paste. Therefore, it is preferable to apply, dry and cure the conductive paste in the state of the telepanel.

In order to ground the electrode formed on the AR film, it is convenient to connect it to a reinforcing band (in this case, of course, the reinforcing band must ultimately be grounded). It is convenient to use a conductive adhesive tape for connecting the reinforcing band and the electrode. There are various types of conductive pressure-sensitive adhesive tapes, such as those obtained by applying a conductive pressure-sensitive adhesive to a copper foil and those applied to an aluminum foil. If a plurality of conductive adhesive tapes are used, the capacity can be increased and the reliability can be improved. Of course, other than the conductive adhesive tape, a conductive tape or wire may be used.

In FIG. 2, the value of V ₂ when R ₂ → ∞ is a value when the power supply voltage V ₀ is divided in series by C ₁ and C ₂ . That is, V ₂ = (C ₁ V ₀ ) / (C ₁ + C ₂ ),
C ₂ is the smaller the value of V ₂ is smaller larger than the C _1. Specifically, the value of V ₂ is required to be lower than the breakdown voltage of the AR film. For example, if the AR film thickness is 3000
The dielectric breakdown onset voltage is about 120V. Thus increasing the value of C ₂ to be less than此voltage, i.e., it is necessary to'll spread the electrode area. In practice, the value of C ₂ is preferably set to more than 20 times the value of C _1. If the conduction resistance R ₂ is sufficiently small, the maximum voltage of V ₂ can be reduced as shown in FIG.

The cathode ray tube with a telepanel has been mainly described above, but it goes without saying that the same applies to the case without a telepanel.

FIG. 5 is a front view showing an example in which the present invention is applied to a 14-inch cathode ray tube. In the illustrated example, the electrodes 4 are formed on the short sides on both sides of the panel.
It may be formed at four corners or all around.

When the electrode is formed of graphite, its thickness may be such that it does not cause peeling and does not impair the appearance. However, when forming the graphite electrode, it is desirable to apply it by a printing method in order to make the appearance, the film thickness and the film surface uniform.
In this case, an appropriate film thickness is about 3 to 50 μm.

As shown in FIG. 4, since this system operates at a high speed, it has a shielding effect against unnecessary electromagnetic radiation radiated from the cathode ray tube surface. For example, in the example shown in FIG.
Since the operation is almost completed in μs, it has a shielding effect against electromagnetic radiation up to 500 kHz. This is because a capacitor is formed in the electrode portion, and it is very effective that the resistance of the electrode portion becomes almost zero for high frequency. In the present invention, the C ₂ is the sufficiently larger than C _1, the current to prevent the unwanted radiation is thus determined mostly by the sheet resistance R ₁ of C ₁ and the conductive film. C ₁ is determined by the structure of the cathode ray tube, but the sheet resistance R _{1 of the} conductive film is determined.
, The frequency of the unnecessary radiation to be prevented can be changed. If it is desired to raise the frequency of the electromagnetic wave to be shielded to a higher range, the sheet resistance of the ITO film may be reduced. 1KΩ sheet resistance if ITO film is used
/ □ is possible. By setting the product of the capacitance of the capacitor formed between the conductive film on the panel surface and the anode and the sheet resistance of the conductive film on the panel surface to 10 ⁻⁶ ΩF / □ or less, unnecessary radiation of higher frequency can be achieved. Can be prevented.

As described above, the present invention has a great effect of shielding unnecessary high-frequency radiation as well as an effect of simply preventing electrostatic charge.

[0024]

As described above, according to the present invention, a highly reliable cathode-ray tube in which the front outer surface is prevented from being charged to a high voltage can be produced at a low cost by an extremely simple operation. I can do it.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a main part of an embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram for explaining the operation of the present invention.

FIG. 3 is a diagram showing a relationship between a voltage V ₂ appearing on an electrode according to the present invention and time when values of parameters C ₂ and R ₂ are variously changed.

FIG. 4 is a diagram showing how a current i ₂ for releasing charged electric charge changes with time when a switch is closed in one embodiment of the present invention.

FIG. 5 is a front view showing an example in which the present invention is applied to a 14-type cathode ray tube.

[Explanation of symbols]

1 Tele panel, 2 ITO film, 3 AR
Membrane, 4 ... Electrode, 5 ... Reinforcement band, 6 ... Conductive adhesive tape, 7 ... Valve panel, 8 ... Resin for bonding the tele panel to the valve panel, 9 •
... of the valve funnel, 10 ... exterior graphite, R ₁ ·
··· Resistance of ITO film, i _2: current for releasing charged electric charge, V _0: power supply voltage, R ₀ : internal resistance of power supply, C
₂ ... Capacity formed between ITO film and electrode, R ₂
・ Leakage resistance between the ITO film and the electrode, C ₃ ...

Claims (7)

(57) [Claims] A reinforcing band is provided on a side surface of the panel, an anode including a fluorescent screen to which a high voltage is applied is formed on an inner surface of the panel, and a conductive film is formed on an outer surface of the panel.
In the cathode ray tube in which the conductive film is covered with an insulating film, a capacitor is formed around the outer surface of the panel with the insulating film interposed therebetween, the capacitor is connected to the reinforcing band, and the reinforcing band is grounded to a circuit. A cathode ray tube characterized by the above-mentioned. 2. A reinforcing band is provided on a side surface of the panel, an anode including a phosphor screen to which a high voltage is applied is formed on an inner surface of the panel, and a conductive film is formed on an outer surface of the panel.
The conductive film is coated with an insulating film, and in a cathode ray tube in which exterior graphite is formed outside a funnel connected to the panel, a capacitor is formed by sandwiching the insulating film around an outer surface of the panel, A cathode ray tube, wherein a capacitor is connected to the reinforcing band, and the reinforcing band is connected to an outer graphite of the funnel. 3. The value of the high voltage is V ₀ , the capacitance of the capacitor formed around the outer surface of the panel is C ₂ ,
When the capacitance between the conductive film formed on the anode and the panel outer surface which is formed on the inner surface of the panel was _{C 1, V 0 × C 1} /
_2. The cathode ray tube according to claim 1, wherein a value of (C ₁ + C ₂ ) is lower than a dielectric breakdown voltage of the insulating film. 4. The capacitance of the capacitor formed on the periphery of the outer surface of the panel is C _2, and the capacitance of the anode formed on the inner surface of the panel and the conductive film formed on the outer surface of the panel is C 2.
When set to _1, the cathode ray tube according to claim 1 to 3, characterized in that a C ₂ ≧ 20C _1. 5. The conductive film formed on the outer surface of the panel is
The cathode ray tube according to claim 1, wherein the cathode ray tube is TO. 6. The cathode ray tube according to claim 1, wherein a sheet resistance of said ITO is 1 KΩ / □ or less. 7. The cathode ray tube according to claim 1, wherein the insulating film formed on the conductive film formed on the outer surface of the panel is an anti-reflection film.