JP2000243322A - Cathode-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a completely round beam spot on a fluorescent screen and to improve resolution by forming the aperture of the electrode of an electron beam driving system on the cathode side than a main lens system electrode of an electron gun into an ellipse. SOLUTION: The electrode of an electron beam driving system for extracting an electron beam from a cathode K, e.g. first and second grids G1, G2, is formed into a bottomed cylindrical shape, an aperture 16 is bored at the center position of the bottom in an oblong elliptic shape, thereby the prescribed electrode of an electron gun is made astigmatic, and the magnifying power of an image in the Y-axis direction can be reduced. No electric control is required for making an electron beam astigmatic by merely forming the aperture 16 of the electrode of the electron beam driving system such as the first grid G1 or/and the second grid G2 into the oblong elliptic shape. An oblong elliptic spot 17 is formed on a virtual vertical plane 13, however a completely round spot 18 is obtained on an inclined fluorescent plane 5 due to astigmatism, and resolution can be improved.

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 (hereinafter referred to as "CRT") suitable for use in a flat tube, and more particularly to an improvement in an electron gun for a flat picture tube.

[0002]

2. Description of the Related Art A flat tube is well known as a CRT in which an electron beam is incident obliquely on an incident surface such as a fluorescent screen.

FIG. 5 is a plan view of a conventional flat tube, and FIG. 6 is a view for explaining the operation of a main part of the conventional flat tube. Hereinafter, the flat tube will be described with reference to FIGS. 5 and 6. The outline of is explained. As shown in the plan view of the appearance in FIG.
The flat tube 1 is formed of a substantially fan-shaped flat glass tube 2, and the glass tube 2 includes a neck portion 3 and a screen panel portion 4.

The screen panel section 4 is composed of a phosphor screen 5 and a transparent electrode 6 as shown in the side sectional view of FIG. 6, and a cylindrical first grid G _{1 to a} fourth grid G are formed in the neck section 3. electron gun 7 connected held so as to become a predetermined positional relationship with each other to secure the G ₄ Bee dengue glass through the pin is fixed.

Reference numeral 8 denotes an electromagnetic horizontal deflection yoke, which uses a ferrite 8a or the like to increase the magnetic flux utilization rate because the maximum horizontal deflection angle is large. The vertical deflection angle θ is relatively small and 1
Since the angle is about 0 degrees, the vertical deflection is generally performed by an electrostatic deflection method using a vertical deflection electrode 9 such as a ferrite.

[0006] Of the first to fourth grids G _{1 to} G ₄ constituting the electron gun 7, the first grid G ₁ is used as a crossover point formation and modulation electrode, and the second grid G ₂ is used as a cathode K Operates as an accelerating electrode for accelerating the electron beam 11 from the third axis G in the axial direction.
₃ and the fourth grid G ₄ are formed a main lens 10, functions as a focusing electrode, to form a bi-potential lens system made so as to focus the electron beam 11 on the phosphor screen.

[0007] The electron beam 11 emitted from the electron gun 7 of the flat tube 1 is applied to the first grid G _{1 to} the fourth grid G ₁ of the electron gun 7.
The light passes through the perfect circular aperture 12 of the grid G ₄ , is modulated, accelerated and focused, is deflected in the horizontal and vertical directions by the horizontal deflection yoke 8 and the vertical deflection electrode 9, and is
And into the screen panel section 4 between the transparent electrodes 6.

As shown in FIG. 6, the electron beam 11 is always incident on the fluorescent screen 5 which is the incident surface of the electron beam 11 from an oblique direction, and the fluorescent light is generated by an electric field formed between the transparent electrode 6 and the fluorescent screen 5. Light is emitted by landing on the surface 5.

The first grid G constituting the above-mentioned electron gun 7
_{The first to} fourth grids G ₄ are usually formed in a bottomed cylindrical shape,
An aperture 12 is formed at the center of the bottomed portion, and the aperture shape is a perfect circle.

[0010]

As described above, if the central axis of the electron gun 7 and the incident surface of the electron beam 11 are substantially perpendicular to the electron beam incident surface (phosphor screen) as in a normal CRT, As shown in FIG. 7, the optical lens system of the electron gun
The ratio between the optical image magnifications in the axial (horizontal) direction and the Y-axis (vertical) direction is ideally 1: 1 in the X-axis and Y-axis directions.

That is, in FIG. 7, the image magnification a of the X-axis and the Y-axis from the position of the object point (cathode K) to the position of the main lens 10 composed of the third grid G ₃ and the fourth grid G ₄ of the electron gun 7. And the X-axis and Y-axis image magnifications b from the main lens 10 to the image point (the fluorescent screen 5) have a relationship of a = b.

However, when the electron beam 11 is arranged at an angle of θ degrees from the XY axis plane with respect to the phosphor screen 5 as shown in FIG. The spot after the electron beam 11 has passed through a perfect circular aperture 12 formed in the center of the bottom of the bottomed cylindrical shape of the first grid G ₁ and a similar perfect circular aperture 12 of the second grid G ₂ becomes a virtual vertical plane 13. 7, a perfect circular beam spot 14 is formed as shown in FIG. 7. However, when the beam spot 14 is incident on the phosphor screen 5 inclined by θ degrees, the beam spot becomes a vertically long ellipse and the vertically elongated beam spot 15 is formed on the phosphor screen 5. Will be projected.

If the beam spot diameter on the phosphor screen 5 becomes vertically long in this way, the resolution in the vertical direction and the resolution in the horizontal direction greatly differ, and the entire screen on the phosphor screen 5 becomes a blurred image.

An object of the present invention is to provide a CRT which has solved the above-mentioned problems, and has a beam incident on a phosphor screen by making an aperture of an electrode of an electron beam driving system of an electron gun elliptical. The objective is to obtain a CRT with a spot made a perfect circle and improved resolution.

[0015]

SUMMARY OF THE INVENTION The present invention is a CRT in which an electron beam is obliquely incident on an incident surface,
The aperture of the electrode of the electron beam driving system closer to the cathode than the main lens system electrode is formed in an elliptical shape among a plurality of electrodes arranged in the electron gun constituting the CRT.

According to the CRT of the present invention, even if the electron beam 11 is obliquely incident on the incident surface, the electron beam spot on the incident surface can be made a perfect circle, and the resolution can be improved. Can be.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to FIGS. FIG. 1 is an explanatory view of an electron beam spot of the present invention, FIG. 2 is a schematic side sectional view of a CRT showing one embodiment of the present invention, and FIG. 3 is a CRT showing one embodiment of the present invention.
FIG. 4 is a diagram showing an optical lens system when an electron gun used in the present invention is stigmatized.

In the present invention, a configuration of a flat tube will be described with reference to FIGS. 2 and 3 as a CRT in which an electron beam is obliquely incident on an incident surface such as a fluorescent screen 5.

3 (A) and 3 (B) are external views showing a substantially linear side surface and a flat surface of the flat tube 1 according to the present invention. The fan-shaped glass tube 2 has a substantially flat rectangular parallelepiped shape. The cylindrical neck portion 3 is welded to the lower end portion of the screen panel portion 4 to be integrated.

An electron gun 7 to be described later is provided at a sealed end of the neck portion 3. The electron gun 7 is configured such that a plurality of electrodes and a cathode are fixed to beading glass so as to accurately maintain a predetermined positional relationship with each other.

The electron beam 11 emitted from the cathode K of the electron gun 7 is applied to the phosphor screen (incident surface) 5 of the screen panel unit 4.
Is incident at an angle θ with respect to the emission direction.

FIG. 2 schematically shows the inside of the neck portion 3 and the screen panel portion 4 of the flat tube 1 of FIG. 3. The screen panel portion 4 is composed of a phosphor screen 5 and a transparent electrode 6, 5 is provided with a high-voltage electrode 19 on the glass side,
A high voltage for generating an electric field that deflects the electron beam 11 toward the fluorescent screen 5 is applied to the high-voltage electrode 19 and the transparent electrode 6.

The electron gun 7 in the neck 3 is a bipotential electron gun composed of a first grid G _{1 to a} fourth grid G ₄ having a cylindrical shape. Of course, a con-potential type, an increased number of electrodes, or an electron gun configuration provided with auxiliary electrodes or the like may be used.

In the first grid G ₁ , R (red), G
The respective cathodes K corresponding to (green) and B (blue) are arranged in-line or in a data form.
Will be described.

Of the first to fourth grids G _{1 to} G ₄ constituting the electron gun 7, the first grid G ₁ is used as a crossover point formation and modulation electrode, and the second grid G ₂ is used as a cathode K The first and second grids G ₁ and G ₂ constitute an electrode group for extracting the electron beam 11 of the electron beam driving system from the cathode K. The third grid G ₃ and the fourth grid G ₄ form the main lens 10, function as focusing electrodes, and
Is focused on the phosphor screen.

Reference numeral 8 denotes an electromagnetic horizontal deflection yoke, and reference numeral 9 denotes an electrostatic vertical deflection electrode.

In the flat tube 1 having the above structure, the viewer 2
Numeral 0 indicates that the reflected light from the fluorescent screen 5 is viewed from the transparent electrode 6 side opposite to the fluorescent screen 5.

The electron beam 11 emitted from the cathode K of the electron gun 7 of the flat tube 1 passes through the apertures 16 of the first to fourth grids G _{1 to} G ₄ of the electron gun 7 to modulate, accelerate, The light is focused, deflected in the horizontal and vertical directions by the horizontal deflection yoke 8 and the vertical deflection electrode 9, and is incident on the screen panel unit 4 between the phosphor screen 5 and the transparent electrode 6.

As shown in FIG. 3, the electron beam 11 is always incident on the phosphor screen 5 which is the incident surface of the electron beam 11 at an angle θ degrees from an oblique direction. The light is emitted by landing on the phosphor screen 5 by the formed electric field.

The first grid G constituting the above-mentioned electron gun 7
_{The first to} fourth grids G ₄ are usually formed in a bottomed cylindrical shape,
An aperture 16 is formed at the center of the bottomed portion, and the aperture shape is an elliptical shape as shown in FIG.

[0031] Figure 1 is intended to explain the flat-type CRT electron beam spot of the present invention, the first grid G ₁ and the second
Elliptical apertures both oblong elliptical shape to the grid G ₂ 1
Shows the case where bored 6, may be as bored only to either of the first grid G ₁ and the second grid G _2. Preferably bored an elliptical holes only in the second grid G ₂ side, the first grid G ₁ side of the aperture 16 may be a perfect circle.

The shape of the elliptical aperture 16 is not limited to an elliptical ellipse, but may be a horizontally elongated slit or a horizontally elongated rectangular aperture.

Further, the first grid G ₁ and / or the second grid G ₁
Bottom portion of the grid G _2, or elliptical aperture 16 bored in the auxiliary electrode and the pore size of the X-axis direction having a pore diameter of> Y axis direction as shown in A-A 'arrow view of FIG. 1, X-axis The major axis and the minor axis are selected to be about 3: 1.

As described above, the electron beam 11 from the cathode K
Electrodes of the electron beam driving system for extracting
And the second grids G ₁ , G ₂ ) have a horizontally long elliptical shape, so that a predetermined electrode of the electron gun 7 is stigmatized, and as shown in the optical lens system of FIG. The magnification can be reduced.

According to the flat tube of the present invention, the first grid G ₁
Or / and since the second aperture 16 of the electron beam driving system electrodes such as the grid G ₂ is only an elliptical, electrical control for the electron beam 11 to the astigmatic is not necessary,
The addition of a new electrode or the like can be omitted.

Further, according to the present invention, the same effect as when the concave lens 21 is inserted between the main lens 10 in the Y-axis direction and the object point (cathode K) as shown in the optical lens system of FIG. Therefore, the image magnification is reduced accordingly. That is,
Image magnification b 'in the Y-axis direction compared to image magnification b / a in the X-axis direction
/ A 'is reduced and the ratio of the minor axis to the major axis of the ellipse (flattening ratio)
Is 3: 1 in the above description, but this flatness is
It has been found that the ratio of the minor axis to the major axis of the ellipse increases as the incident angle increases, depending on the incident angle θ to the incident surface of No. 1.

As described above, in the present invention, the elliptical beam spot 17 is horizontally long on the imaginary vertical plane 13 as shown in FIG.
8, the electron beam spot characteristics can be improved without increasing the cost because only the shape of the aperture is changed, and the resolution is improved by making the electron beam spot obliquely incident on the incident surface into a perfect circle. improves.

By changing the flattening ratio (ratio of minor axis to major axis), even if the incident angle of the electron beam is changed, the larger the incident angle becomes, the more the electron beam spot shape becomes a perfect circle.
It becomes possible to increase the flattening rate and control.

[0039]

According to the cathode ray tube of the present invention, the characteristics of the electron beam spot can be improved, the electron beam spot obliquely incident on the incident surface can be made a perfect circle, the image blur can be improved, and the horizontal direction can be improved. The resolution can be improved.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an electron beam spot showing one embodiment of a cathode ray tube of the present invention.

FIG. 2 is a schematic side sectional view showing one embodiment of a cathode ray tube according to the present invention.

FIG. 3 is an external view showing one embodiment of a cathode ray tube of the present invention.

FIG. 4 is a diagram showing an optical lens system when an electron gun used in the present invention is stigmatized.

FIG. 5 is a plan view of a conventional flat tube.

FIG. 6 is an explanatory diagram of an operation of a main part of a conventional flat tube.

FIG. 7 is a diagram showing an optical lens system showing an ideal state of the electron gun.

FIG. 8 is an explanatory view of a conventional electron beam spot.

[Explanation of symbols]

G _{1 to} G ₄ {first to fourth grids, K} cathode, 1 flat tube, 5 phosphor screen (incident surface), 7 electron gun, 16 aperture

Claims (3)

[Claims] 1. A cathode ray tube in which an electron beam is obliquely incident on an incident surface, wherein a plurality of electrodes arranged in an electron gun constituting the cathode ray tube are closer to a cathode than a main lens system electrode. A cathode ray tube, wherein an aperture of an electrode of an electron beam driving system has an elliptical shape. 2. The cathode ray tube is a flat tube, wherein the electrode of the electron beam driving system is a crossover point forming electrode, a modulation electrode, or an accelerating electrode for accelerating an electron beam, and at least one of these electrodes. 2. The cathode ray tube according to claim 1, wherein the major axis direction of the elliptical shape formed in the electrode is parallel to the X axis of the incident surface of the beam. 3. The cathode ray tube is a flat tube, and the ratio of the major axis to the minor axis of the elliptical aperture formed in the electron beam driving system electrode increases as the incident angle of the electron beam on the incident surface increases. 3. The cathode ray tube according to claim 1, wherein the cathode ray tube is made larger.