JPH1092345A - Cathode-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an AC power field in a super-low frequency wave VLF bandzone and provide a cathode-ray tube that satisfies TCO specifications by increasing electrostatic capacity in a horizontal deflection frequency zone by means of a band-shaped conductive member for electrically connecting between a transparent conductive film and an explosion-proof band. SOLUTION: In a cathode-ray tube 10, there is electrically connected on at least one side of a long side or short side of a panel between a display region shield mechanism due to a transparent conductive film 21 and an explosion-proof band 22 by means of a conductive band-shaped member 24 in which longitudinal dimensions are 50% or more of the screen effective dimensions. Thereby, electrostatic capacity between outer and inner faces in the panel increases, potential variation of a phosphor screen is restrained, a shield is formed in a gap between an explosion-proof band 22 connected to an earth and a transparent conductive film 21 on a face surface, and a pulse- shaped AC electric field from a horizontal deflection coil to be radiated on a front face of an image display device between cathode rays and a saw-wave shaped AC electric field due to potential variation of a phosphor screen can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode ray tube, and more particularly, to a cathode ray tube provided with means for suppressing an alternating electric field radiated to the outside.

[0002]

2. Description of the Related Art In recent years, personal computers and the like have been remarkably popularized, and the chances of using an image display apparatus equipped with a cathode ray tube at a relatively short distance and for a long time have increased.
Under these circumstances, there is a concern that a low-frequency AC electric field radiated from a cathode ray tube image display device may have an adverse effect on a human body, and a technique for suppressing the adverse effect is important. In particular, Scandinavian countries have set standards for AEF (Alternating Electric Field) to regulate so-called unnecessary radiation electric fields.

[0003] As a representative example of the standard relating to AEF, MPR-2 established in Sweden is widely known, and the TCO guideline of the Swedish Central Labor Council is a stricter version of the MPR-2 standard. . According to the TCO guidelines, an electric field value of 1.0 [V / m] or less (30 cm in front of the cathode ray tube surface and 50 cm around the surface) for a VLF (Very Low Frequency) band having a frequency of 2 kHz to 400 kHz, and a frequency of 5 Hz to 2 kHz. The ELF (Extremely Low Frequency) band has an electric field value of 10 [V / m] or less (30 cm in front of the cathode ray tube surface).

An image display apparatus using a cathode ray tube causes a horizontal deflection current and a vertical deflection current of a sawtooth waveform to flow through a horizontal deflection coil and a vertical deflection coil, respectively, to generate a magnetic field, deflect and scan an electron beam, and perform fluorescent scanning. An image is displayed on the screen. Normally, the vertical deflection current is several tens of H
Very low frequency with z. On the other hand, the horizontal deflection current has a relatively high frequency of usually several tens of kHz, and a pulse voltage as high as about 1 kV is applied to the horizontal deflection coil during the flyback period to generate a sawtooth current. An AC electric field in the VLF band is radiated from the horizontal deflection coil by this pulse voltage.

A cathode ray tube image display device such as a display monitor can easily shield an unnecessary radiated electric field from the radiation of the AC electric field by using a metal plate or the like on the surface other than the image display surface (front), for example, on the back and side surfaces. Can be. However, since it is a part for displaying an image only at the front, it cannot be shielded with an opaque metal plate.

Further, it has been found that a sawtooth alternating electric field is emitted from the phosphor screen in a horizontal deflection cycle. This is usually the case for phosphor screens in cathode ray tubes.
A high voltage of 5 kV to 30 kV is applied to accelerate the electron beam toward the phosphor screen. However, during the screen display period, the potential of the phosphor screen gradually decreases due to the impact of the electron beam, ie, the negative charge. This is considered to be due to the phenomenon that the potential returns to the positive side because the electron beam does not come during the flyback period.

In order to reduce the unnecessary radiated electric field leaking from the image display surface of the cathode ray tube, there is a method of forming a transparent conductive film on the surface of the cathode ray tube and connecting the conductive film to the ground. However, a method of forming a transparent conductive film having a low resistance sufficient to satisfy the TCO standard has a problem in terms of cost.

Therefore, as in Japanese Patent Application Laid-Open No. Hei 4-24936, a conductive tape is applied over the transparent conductive film formed on the face surface of the cathode ray tube along the periphery of the face surface, and the end of the tape is attached. There is a method of equivalently lowering the resistance value of the transparent conductive film by connecting to an explosion-proof band attached to the cathode ray tube side wall and connected to the ground.

On the other hand, as a first method for reducing a pulse-like electric field radiated from a horizontal deflection coil, as disclosed in Japanese Patent Application Laid-Open No. 5-74374, a graphite conductive material generally applied to the outer surface of a funnel body of a cathode ray tube is used. Some shields are formed by extending the film to a cone portion and a neck portion where the deflection coil is mounted and connected to the ground.

As a second method, Japanese Patent Laid-Open No. 4-31
As in 5741, a so-called reverse pulse voltage having a polarity opposite to that of the pulse voltage is generated, and a reverse pulse voltage is applied to an electrode disposed near the periphery of the front surface of the cathode ray tube to radiate a reverse pulse electric field, Some cancel or reduce the pulse electric field radiated from the deflection coil.

As a third method, Japanese Patent Application Laid-Open No.
As in 2008, a reverse pulse voltage is applied to an electrode disposed between the graphite conductive film on the outer surface of the funnel connected to the ground and the opening of the deflection coil to radiate a reverse pulse electric field, and the pulse electric field radiated from the horizontal deflection coil is applied. There is something to offset or reduce.

[0012]

However, according to the method of equivalently lowering the resistance value of the transparent conductive film with the conductive tape, the screen is not sufficiently attached to the conductive tape until the resistance becomes sufficiently low. May be narrow.

In the method of extending the graphite conductive film to the cone portion and the neck portion where the deflection coil is mounted, in order to prevent a discharge from being generated between the deflection coil and the graphite conductive film, it is necessary to extend from the cone portion to the neck portion. It is necessary to cover with an insulating sheet, and the workability is remarkably deteriorated, for example, the insulating sheet is turned up when a wedge is inserted for fixing the deflection coil.

In the method of disposing the reverse pulse electrode near the periphery of the front surface of the cathode ray tube, the pulse electric field can be effectively reduced in the front direction of the cathode ray tube. However, only the reverse pulse electric field is emitted, and the regulation value may not be satisfied. Also,
In order to place the electrodes, the cabinet structure of the monitoring device must be special.

In the method in which the reverse pulse electrode is arranged between the graphite conductive film on the outer surface of the funnel of the cathode ray tube and the opening of the deflection coil, the position of the reverse pulse electrode is far from the image display surface of the cathode ray tube and is applied to the deflection coil. It is necessary to supply a reverse pulse of a rather high voltage, though not equal to the pulse voltage to be applied.

The sawtooth alternating electric field radiated from the phosphor screen is formed by a method of extending a graphite conductive film to a cone portion and a neck portion where a deflection coil is mounted, or by a reverse pulse electric field from a reverse pulse electrode. This cannot be solved by canceling the pulsed electric field.

As means for stabilizing the high voltage potential in the cathode ray tube, an inner conductive film and an outer conductive film oppose each other with a funnel glass interposed therebetween in the funnel portion, and have a capacitance. Since a relatively high-resistance material such as a pin doug is interposed between the conductive film and the phosphor screen, it does not sufficiently contribute to stabilizing the potential of the phosphor screen.

In view of the above problems, the present invention effectively suppresses both the pulse electric field emitted from the horizontal deflection coil and the sawtooth wave electric field emitted from the phosphor screen, and satisfies the TCO standard. It is an object of the present invention to provide a cathode ray tube image display device.

[0019]

In order to solve the above-mentioned problems, the present invention provides a screen formed on an inner surface of the screen, which emits light by the impact of an electron beam emitted from an electron gun, and a transparent conductive film on an outer surface. A panel comprising a formed face portion and a rectangular frame-shaped skirt portion extending from the end of the face portion, a neck containing an electron gun for emitting an electron beam for exciting the screen, and an outer periphery of the skirt portion. A cathode ray tube having an explosion-proof band provided, wherein a means for increasing capacitance in a horizontal deflection frequency band is provided on an outer surface of a panel.

As the capacitance increasing means, there is a band-shaped conductive member provided on at least one of the long side and the short side of the panel and electrically connecting the transparent conductive film and the explosion-proof band.

Further, the conductive strip-shaped member includes a long side of the panel,
It is provided on at least one of the short sides, and the longitudinal dimension is at least 50% of the screen effective dimension of the side.

Further, the transparent conductive film has a resistance per unit area of 1 × 10 ⁴ Ω / □ or less.
In the present invention, an alternating electric field is suppressed by a transparent conductive film and a belt-shaped conductive member.

First, a transparent conductive film is formed on the outer surface of the face portion of the cathode ray tube for the purpose of reducing the pulsed AC electric field radiated from the deflection coil, particularly the horizontal deflection coil. The membrane is electrically connected to the explosion-proof band by a conductive strip. Since the explosion-proof band is at the ground potential, the AC electric field radiated in the front direction of the cathode ray tube is shielded to some extent by the transparent conductive film.

In addition, for an AC electric field having a sawtooth waveform caused by a potential fluctuation of the phosphor screen, a conductive band-shaped member is provided from the vicinity of the front end of the explosion-proof band on the skirt portion of the panel of the cathode ray tube to the periphery of the outer surface of the face portion. Paste on both sides or one side of at least one of the long side or short side,
A capacitance is formed between the phosphor screen and the conductive tape connected to the ground. As a result, the capacitance can be increased at the panel portion, which is electrically closest to the explosion-proof band and the phosphor screen connected to the ground, and stabilizes the potential of the phosphor screen.

As described above, when the cathode ray tube of the present invention is used, a pulse-like AC electric field is shielded, and the potential fluctuation of the phosphor screen is stabilized against the sawtooth-like AC electric field.

[0026]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of a cathode ray tube and its peripheral device according to the present invention, and FIG. 2 shows a partial cross section of a panel portion of FIG.

The cathode ray tube 10 includes a panel 13 in which a phosphor screen 12 is formed on the inner surface of a substantially rectangular face portion 11, and an electron gun (not shown) for emitting an electron beam toward the phosphor screen 12. And a funnel 15 connecting the panel 13 and the neck 14. panel
13 has a skirt portion 16 extending from the periphery of the face portion 11 to the funnel 15 side, and the skirt portion 16 and the funnel 15 are joined by a frit 17. The inner conductive film 18 is formed on the inner surface of the funnel, and the outer conductive film is formed on the outer surface.
19 are formed, and an anode terminal 20 for applying an anode potential to the internal conductive film is provided. The external conductive film 19 is for forming a capacitance between itself and the internal conductive film 18 to stabilize the potential, and is formed so as to avoid the anode terminal 20.

On the outer surface of the face portion 11 of the panel 13, a transparent conductive film 21 is formed. In addition, the skirt of the panel
An explosion-proof band 22 made of metal is provided on the outer periphery of 16, and conduction between the explosion-proof band 22 and the transparent conductive film 21 is established by a conductive member 23. Further, a strip-shaped conductive member 24 provided along the long side of the panel and the strip-shaped conductive member 24 are provided.
And a conductive member 25 that connects between the explosion-proof band 22 and the explosion-proof band 22.

A deflecting device 27 is mounted outside the funnel 15. The deflection device 27 includes a horizontal deflection coil that generates a horizontal deflection magnetic field that deflects the electron beam in the horizontal direction;
Usually, the horizontal deflection coil is constituted by a pair of upper and lower saddle-type deflection coils, and the vertical deflection coil is constituted by a pair of left and right saddle-type deflection coils. A saddle-saddle type is common. Then, a predetermined voltage waveform 31 that changes at a predetermined cycle from the high-voltage / deflection circuit 30 is applied to the horizontal deflection coil and the vertical deflection coil to generate a deflection magnetic field. In the case of a horizontal deflection coil, a pulse-like voltage waveform of several hundreds to 1 kV is usually obtained.

As described above, the compensating electrode 26 and the conductive strip member tape 24 have the explosion-proof band 22 sandwiched by the skirt portion on the long side of the panel 13, the compensating electrode 26 on the neck 14 side, and the conductive strip member on the face side. Installed to be 24. External conductive film 19 made of graphite outside explosion-proof band 22 and funnel 15
Is connected to ground.

An alternating electric field having a waveform as shown in FIG. 3A is leaking from the cathode ray tube device. The cause of the leakage is considered as follows. First, the first factor is due to the potential fluctuation of the deflection device. This is because when a deflection voltage that fluctuates in time in synchronization with the deflection frequency is supplied, a spatial change in the potential in the deflection coil occurs from the high voltage side to the low voltage side, and this potential is ground potential, that is, with respect to the ground. , Which creates a fluctuating electric field with the ground. The AC electric field leaking from the deflecting device when a deflecting voltage is applied to such a deflecting device has a waveform that changes substantially in synchronization with the deflecting voltage waveform as shown in FIG.

It is also known that the second factor is a potential fluctuation of the phosphor screen. That is, in the horizontal deflection cycle, the electron beam, which is a negative charge emitted from the electron gun, collides with the phosphor screen during the image display period and gradually lowers the potential. This is caused by stopping the emission of the beam and restoring the potential of the phosphor screen, as shown in FIG.
This is a sawtooth-like potential fluctuation phenomenon as shown in FIG.

The first and second factors overlap, and an alternating electric field having a waveform as shown in FIG. 3A leaks from the cathode ray tube device. In the present invention, the capacitance between the inner and outer surfaces of the panel is increased to suppress the potential fluctuation of the phosphor screen,
Further, it shields a gap between the explosion-proof band connected to the ground and the transparent conductive film on the face surface.

Hereinafter, the configuration for that will be described in detail.
In this embodiment, in order to compensate for a leakage AC electric field, as shown in FIG. 1, a display area shield mechanism by a transparent conductive film 21 and a conductive member electrically connected to an explosion-proof band 22 by a conductive member 25 are provided. And a capacitance increasing mechanism including the band-shaped member 24.

The present invention is particularly effective when the transparent conductive film on the surface is formed by spin coating. This is because, according to the spin coating method, the transparent conductive film is formed on the face surface up to the peripheral edge portion, but the coating liquid does not easily reach the skirt portion, so that the transparent conductive film is not formed near the front end of the explosion-proof band. . That is, JP-A-4
When it is attached to the periphery of the face surface as in -249036, the effect of increasing the capacitance is small especially when a low-resistance transparent conductive film is formed because the conductive film is originally present, Attaching the conductive tape to the part where the conductive film is not formed and connecting it to the ground forms a shield in a place where there is no electric field shield, and the horizontal deflection coil radiated to the front of the cathode ray tube image display device The effect of reducing both the pulsed AC electric field from the light source and the sawtooth AC electric field caused by the potential fluctuation of the phosphor screen is increased.

The inventors conducted an experiment using a 41 cm cathode ray tube image display device. 5 on the face of the face of the cathode ray tube
A transparent conductive film of × 10 ³ Ω / □ was formed, and a 30 mm square aluminum tape was attached to the short side to electrically connect to an explosion-proof band. An aluminum tape having a width of 15 mm and a length of 240 mm was attached to the vicinity of the skirt portion on the long side, and this was also electrically connected to the explosion-proof band with a 30 mm square aluminum tape.

By providing the long-side aluminum tape, the unnecessary radiation electric field intensity at a position 30 cm from the front of the cathode ray tube was reduced from 1.3 [V / m] to 0.7 V / m.
In addition, the waveform of the unnecessary radiation electric field changes from the state shown in FIG. 4A to the state shown in FIG. 4B, so that the sawtooth alternating electric field due to the potential fluctuation of the phosphor screen is suppressed and the horizontal deflection The pulsed AC electric field emitted from the coil was reduced by almost half.

FIG. 5 shows the results of the measurement of the capacitance between the explosion-proof band and the anode terminal before and after the application of the aluminum tape as the belt-shaped conductive member on the long side. As is apparent from this figure, the horizontal deflection frequency of a signal output from a computer display or the like is 31.5 kHz to 11
It can be seen that the capacitance is increased in a frequency band above 0 kHz, that is, a frequency band that contributes to the suppression of the potential fluctuation of the phosphor screen generated in the horizontal deflection cycle.

The strip-shaped conductive member attached to the long side in the above embodiment may be attached to the short side, or may be attached to both the long side and the short side. Further, as the conductive member, 1 × 10 ⁴ per unit area is used instead of aluminum tape.
A graphite conductive film or a transparent conductive film of Ω / □ or less may be applied and formed.

[0040]

As described above, according to the present invention,
An AC electric field in the VLF band can be effectively reduced, and a cathode ray tube image display device satisfying the TCO standard can be provided.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one embodiment of a main part of a cathode ray tube image display device according to the present invention.

FIG. 2 is a sectional view showing a main part of FIG. 1;

FIG. 3 is a diagram showing a waveform of an AC electric field leaking from a conventional cathode ray tube image display device.

FIG. 4 is a diagram illustrating waveforms of a pulse voltage applied to a horizontal deflection coil and a reverse pulse voltage generated by a reverse voltage supply unit and applied to a compensation electrode.

FIG. 5 is a diagram showing a frequency distribution of capacitance between an explosion-proof band and an anode terminal.

[Explanation of symbols]

 10 ... Cathode tube 13 ... Panel 14 ... Neck 15 ... Funnel 20 ... Anode terminal 21 ... Transparent conductive film 22 ... Explosion proof band 27 ... Deflecting device 23,25 ... Conductive member 24 ... Strip conductive member 30 ... High voltage / deflection circuit

Claims (4)

[Claims] A screen which emits light by the projection of an electron beam emitted from an electron gun is formed on an inner surface thereof, and a face portion having a transparent conductive film formed on an outer surface thereof and a frame extending from an end of the face portion. A cathode ray tube having a panel consisting of a skirt portion, an electron gun for emitting an electron beam for exciting the screen, and an explosion-proof band provided on the outer periphery of the skirt portion. A cathode ray tube provided with means for increasing capacitance in a deflection frequency band. 2. A conductive band-shaped member provided on one of a long side and a short side of the panel, and configured to electrically connect a transparent conductive film and an explosion-proof band. The cathode ray tube according to claim 1, wherein: 3. The panel according to claim 2, wherein the conductive strip is provided on at least one of a long side and a short side of the panel, and a longitudinal dimension thereof is 50% or more of an effective screen size of the side. 2. The cathode ray tube according to 2. 4. The cathode ray tube according to claim 1, wherein the transparent conductive film has a resistance per unit area of 1 × 10 ⁴ Ω / □ or less.