JPH07111878B2 - Cathode ray tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention has a cathode ray tube, particularly a brazing type electron gun configuration, and a cathode ray tube having a magnetic field type electron lens (magnet focusing) type configuration using a permanent magnet. Involved in pipes.

[Outline of Invention]

The present invention adopts a brazing type electron gun configuration, is a combination lens configuration of an electrostatic prefocus lens and a magnetic main focus lens, and further is small in size, high in brightness, and high in resolution by specifying the electrode dimensions and the wiring relationship. Of the cathode ray tube.

[Conventional technology]

An electron gun in a conventional cathode ray tube, for example, a television picture tube has a structure in which a plurality of metal electrode bodies are connected to each other by insulating rods or beading glass as disclosed in FIG. 1 of Japanese Patent Publication No. 58-31696. Are connected to each other while maintaining a predetermined positional relationship.

On the other hand, in recent years, for example, in cathode ray tubes used for portable projectors, projection type cathode ray tubes for terminal displays of computers, and the like, there is an increasing demand for smaller, smaller diameter, and lighter weight cathode ray tubes. In this case, in order to construct an electron gun with an electron lens having a small aberration in a small-diameter tube body, it is desirable to make the diameter of the metal electrode body constituting this electron gun as large as possible. The technique of avoiding the use of the body and mechanically connecting the electrode bodies to each other by interposing an insulating ring spacer between the electrode bodies and brazing each metal electrode body to this with silver brazing or the like is adopted. There is a direction to use it to increase the diameter of the electron gun in the arrangement space.

Further, there has been proposed a cathode ray tube in which the main focus lens is composed of a magnetic lens made of a magnet arranged outside the tube body.

[Problems to be solved by the invention]

Originally, the magnetic focus lens is focusing by the spiral orbit of electrons as well known, so that it has the advantage of high resolution because the mutual repulsion effect of electrons is small, but it is difficult to assemble and adjust it. When a permanent magnet is used for magnetic focusing, it has the advantage of lowering the power consumption, but it is difficult to adjust due to the effect of bias magnetization. Precision is required.

On the other hand, in a cathode ray tube for a projector and a projection type cathode ray tube for a terminal display of a computer, there is a strong demand for high accuracy and high resolution, but generally, improvement in brightness and improvement in resolution are mutually exclusive.

[Means for solving problems]

A cathode ray tube according to the present invention will be described with reference to FIGS. 1 and 2.

Reference numeral (1) is a cathode ray tube body, and a fluorescent surface (3) is formed on the inner surface of a front panel (2) thereof. The neck portion (4) of the tube body (1) has a small outer diameter φ of 13 mm or less, and the electron gun (5) is housed on the tube axis in the neck portion (4). The electron gun (5) has a cathode K and a grid metal electrode body, in this example, first, second and third grid metal electrode bodies (hereinafter, referred to as first, second and third grids) G ₁ and G.
₂ and G ₃ .

The first and second grids G ₁ and G ₂ are cup-shaped,
The first grid is arranged so that the end faces face each other.
A ring-shaped insulating spacer (6) between the outer periphery of the end plate of G ₁ and the flange formed at the front end of the second grid G _2.
For example, a ceramic spacer is interposed, and the end face plate of the first grid G ₁ and the flange portion of the second grid G ₂ are brazed to the both end faces of the spacer (6). This brazing is carried out by applying a conductive layer of Mo, Mn or the like on the both end surfaces of the spacer (6) in advance by metallizing, and then, on the metallizing layer, the end face plate of the first grid G ₁ and the first plate that abuts against the metallizing layer. 2 a flange portion of the grid G ₂ is brazed by silver solder. By doing this, the first and second
The grids G ₁ and G ₂ are mechanically connected in a state where they are set in a predetermined positional relationship. Further, the cathode side of the third grid G ₃ small diameter portion is provided, the small-diameter portion is adapted to enter in a spaced relationship by a required distance thereto within the second grid G _2, the third grid G ₃ Similarly, a ring-shaped insulating spacer (7), for example, a ceramic spacer, is interposed between the shoulder portion generated between the small diameter portion and the large diameter portion and the flange portion of the second grid G ₂ , and the spacer is also formed. The flange portion of the second grid G ₂ and the shoulder portion of the third grid G ₃ are brazed to the metallized layers formed on both end faces to mechanically connect them.
In this way, the first to third grids G _{1 to} G ₃ are mechanically connected to each other in a required positional relationship. Further, the cathode K is held in the first grid G ₁ .

(11) is a terminal pin penetratingly embedded in a stem (12) welded to the end of the neck portion of the tubular body (1).
1) Each electrode of the electron gun (5), for example, the first to third grids G _{1 to} G ₃ , the cathode K, a heater (not shown), etc. are electrically connected to each other and the machine of the electron gun (5) Support is made. In this electron gun (5), for example, the free end of the elastic piece (23) provided on the ring (13) fitted to the third grid G ₃ collides with the tube wall of the neck portion of the tube (1). By being combined, they are arranged coaxially with the pipe body (1).

As described above, in the electron gun (5), the electrodes are mechanically connected by brazing and the use of the beading glass described at the beginning is avoided, so that electrons are generated in the neck portion (4) of the tube body (1). selecting each electrode G ₁ ~G ₃ gun (5) as far as possible a large diameter.

Then, from the neck portion (4) of the tubular body (1) to the inner peripheral surface of the funnel portion (14) where the front panel of the tubular body (1) is sealed by frit attachment, the final part of the electron gun (5) is The third grid G ₃ of the step extends from the outer periphery of the end opposite to the fluorescent surface (3), that is, the rear end, to the position close to or to the fluorescent surface (3), for example, from a carbon coating film. A conductive film (15) consisting of is deposited. Then, for example, a high voltage anode voltage is applied from the high voltage supply terminal (26) led out from the frit attachment portion between the funnel portion (14) and the front panel (2) to the fluorescent surface (3) and the internal conductive film (15). Eb is applied.

Then, the internal conductive film (15) and a part of the electrodes of the electron gun (2) form a bipotential electrostatic prefocus lens PL. That is, the prefocus lens PL is formed by the third grid G ₃ made of a metal electrode body and the internal conductive film (15) as the fourth grid G _4, for example. Then, the inner conductive film (15), the end portion, and the rear end of the electrode body of the third grid G ₃ are made to face each other over a required length l. In this way, for example, a part of the electron beam of the electron gun impacts the glass wall of the neck portion (4) and secondary electron emission occurs, so that the tube wall of this part is unstablely charged and the electron beam The electric field is disturbed in the passage of
In particular, since the prefocus lens PL is affected and the focus characteristic fluctuates, such an inconvenience is avoided by providing the facing portion having the length l.

On the other hand, a magnetic field generating means (16) for forming a required magnetic main focus lens ML in the electron beam passage is provided on the outer circumference of the neck portion (4) of the tube body (1). As a result, a large-diameter electron lens is formed. The magnetic field generating means (16) each have a ring shape and are composed of a pair of permanent magnets (16A) and (16B) that are NS-magnetized in the thickness direction, and are arranged so that magnetic poles of the same polarity face each other. It will be done. Also (1
7) is astigmatism correction means by forming quadrupole to octupole, (1
8) is a deflection yoke for registration correction, (19)
Shows the horizontal and vertical deflection yokes of the electron beam.

The electron beam crossover point P depends on the cathode K-grid G ₁ , G ₂ system lens of the electron gun (2).
To the center of the main focus lens ML (that is, the center between both magnets (16A) and (16B)) is a, and the distance from the center of the main focus lens ML to the fluorescent surface (3) is b B / a is less than 3, that is, the apparent image magnification m is m <3.

With such a configuration, the electron beam from the electron gun (5) is focused on the fluorescent surface (3) by the electrostatic prefocus lens PL and the magnetic main focus lens ML.

In the present invention, this prefocus lens
When the diameter of the electrode of the electron gun (5) that constructs PL in cooperation with the internal conductive film (15), that is, the third grid G ₃ is D and the total length is L, L / D is selected to be 0.5 to 1.5. To do.

[Action]

As described above, in the present invention, m = b / a <3 is set, and thereby the beam spot size Vss on the fluorescent surface (3) is reduced. That is, as shown in the curve (30) in FIG. 3, the apparent image magnification m and the beam spot size Vss on the fluorescent surface are measured, and Vss is satisfied when m <3.
It can be seen that is less than 0.1 mm. In the curve (30), Vss increases when m becomes a certain value or less. This is because when m is too small, Vss becomes large due to the influence of spherical aberration of the lens system. In the present invention, if this m is small, Vs in the range
The increase in s is compensated by setting L / D to 0.5 to 1.5.

To explain this, first, regarding the focal length f _m of the magnetic main lens ML, (K is proportional constant (= 0.22), z is axial distance (cm), B
(Z) is represented by the magnetic flux density (gauss) on the axis.

Also, the focal length f of the electrostatic prefocus lens PL
_P is (V (z) is an axial ponsial, and V ″ (z) is its second derivative).

That is, from the equation (1), if the anode voltage Eb is constant, the focal length f _m of the main lens ML can be selected by changing B (z), and B (z)
Is capable of adjusting the distance between the magnets (16A) and (16B). Specifically, if the distance G is increased,
f _m is small.

On the other hand, assuming that the prefocus lens PL has a bipotential type lens configuration including the above-described third grid G ₃ and the internal conductive film (15) in the equation (2), (Where A is a proportional constant, E _C3 is the voltage applied to the third grid G ₃ ) and the focal length of the prefocus lens PL is the ratio L / D of the diameter D and the length L of the third grid G _3. , Or the voltage applied to it.

Then, in the present invention, as described above, the effect of suppressing the increase of Vss due to the spherical aberration can be exerted even in the range where m is small. That is, in the present invention, the divergence angle of the beam in the pre-focus lens PL is made small so that the electron beam is incident on the main focus lens ML in the paraxial region, thereby further reducing the spherical aberration in the main focus lens ML.
That is, the combined focal length f of the combination lens composed of the prefocus lens PL and the main focus lens ML is (However, t is given here by the distance between the principal surfaces of both lenses PL and ML). And, here, f is uniquely determined if the dimensions of the cathode ray tube are determined. In the present invention, this f is determined by changing the sharing ratio of the prefocus lens PL and the main focus lens ML, and as described above, the spherical aberration can be reduced by using the paraxial region of the main focus lens ML. It is made to come off. The share ratio of the play focus lens is calculated by the formula (2 '), specifically, the third grid.
You can vary the lens effect by changing the applied voltage E _C3 to G _3, the voltage E to the third grid G ₃
As described above, _C3 is supplied from the terminal pin (11) side, and this terminal pin (11) is connected to the tubular body (1).
As to the neck portion of the aperture (4) and the small, the mutual spacing of the terminal pins (11) is narrowed, the breakdown voltage between the terminal pin (11), the breakdown voltage or the like of the stem (12), this E _C3 is There are restrictions. Actually, the breakdown voltage between such terminal pins (11),
Due to the safety of the stem (12) such as withstand voltage, the maximum applied voltage E _C3 max to the third grid G ₃ and the outer diameter φ of the neck (4)
It is required that the ratio E _C3 max / φ to be 0.3 (KV / mm) or less.

However, in the present invention, this prefocus lens
The L / D of the third grid G ₃ as an electrode that constitutes the PL is 0.5
By setting it to ~ 1.5, Vss could be improved with low E _C3 . The broken line curve (4
0) shows the result of measuring the minimum electron beam spot size Vss on the fluorescent surface (3) that can be obtained when this L / D is changed. In addition, this measurement is performed when Eb = 12 KV, cathode electrode I _K = 20 μA, cutoff voltage E _CO = 50 V, and image magnification m = 1.7. In addition, the solid line (41) in the figure is f _m = ∞ in the equation (3).
Is the value of the applied voltage E _C3 nm to the third grid G ₃ when each minimum Vss is obtained by f = f _P.

According to this, there is a possibility that Vss can be made small when L / D is 0.5 to 1.5. Moreover, even if all the prefocus lenses share the predetermined focus condition, the third
The applied voltage E _C3 to the grid G ₃ can be kept below 1.4 KV.

Then, the magnet gap G is adjusted so as to fall within the range of E _C3 nmE _{C3 C3} max, and f _m is set.

Fine adjustment of focus is performed by adjusting E _C3 .

〔Example〕

An example of a case where the neck portion (4) is a cathode ray tube having a small diameter of 13 mm in the configuration described in FIGS. 1 and 2 will be described. In this case, the anode voltage Eb = 12KV,
The voltage E _C3 of the third grid G ₃ = 2.63 KV. By the way, the maximum voltage E _C3 max that can be taken as the voltage E _C3 at φ = 13 mm in this example is E _C3 max / φ = 0.3 (KV / m) as described above from the problem of withstand voltage of terminal pins. It is 3.9KV. The third grid G ₃ has a diameter D = 7.7 mm, a length L = 7.5 mm, and L / D = 0.97. Also, a = 32.7mm, b = 84.4m
m and m = b / a = 2.58. At this time, magnets (16A) and (1
6B), the gap G was set to 0.95 mm, and a magnet having a central magnetic flux density B (z) max of 600 Gauss was used. At this time Vss ＝
It became 0.08 mm.

〔The invention's effect〕

As described above, according to the present invention, the diameter of the cathode ray tube is reduced,
Therefore, even when the weight is reduced, the beam spot Vss on the fluorescent surface can be made sufficiently small, so that the resolution is improved and the high brightness is achieved. The benefit is great when used as a cathode ray tube for a display.

[Brief description of drawings]

FIG. 1 is a side view of an example of a cathode ray tube according to the present invention, FIG. 2 is a cross-sectional view of the main part thereof, FIG. 3 is a curve diagram showing the relationship between beam spot size and image magnification, and FIG. It is a curve figure which shows the relationship between the dimension of a grid, a prefocus voltage, and a beam spot size. (1) is a tubular body, (3) is a fluorescent surface, (4) is a neck part,
(5) an electron gun, K is the cathode, G ₁ ~G ₃ the first to third grids, (15) inner conductive film (16) is a magnetic field generating means,
PL is a prefocus lens and ML is a main focus lens.

Front page continuation (72) Inventor Isamu Kawashima 6-735 Kitashinagawa, Shinagawa-ku, Tokyo Sony Corporation (72) Inventor Tsuneo Whip 6-735 Kitashinagawa, Shinagawa-ku, Tokyo Sony Corporation Shares In-house (56) References JP 55-37747 (JP, A) JP 58-128640 (JP, A)

Claims (1)

[Claims] 1. An electron gun in which a cathode and a plurality of grid metal electrode bodies facing the cathode and a first grid and below are mechanically held in a predetermined positional relationship and connected by brazing means are housed and arranged in a cathode ray tube tube. A magnetic field generating means for forming a magnetic main focus lens is arranged outside the tube body, and electrostatically formed by a part of the grid metal electrode of the electron gun and an inner conductive film formed on the inner peripheral surface of the tube body. When the length of the grid metal electrode forming the prefocus lens is L and the diameter is D,
A cathode ray tube characterized in that L / D is selected to be 0.5 to 1.5.