JPH0414459B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a color picture tube equipped with multiple electron guns, and particularly to a color picture tube in which the multiple electron guns are configured to emit electron beams substantially in parallel in an undeflected state. This relates to the deflection yoke of a picture tube.

Technical Background of the Invention A conventional color picture tube will be explained with reference to the drawings.
As shown in Figure 1, the conventional so-called shadow mask or in-line color picture tube has a phosphor layer that emits red, green, and blue colors on its inner surface in a regular dot-like or band-like manner by the impingement of an electron beam. A face plate 1 on which an array of fluorescent surfaces 2 is adhered and formed.
and a plurality of panel pins 5 embedded in the inner wall of the side wall portion 1-1 of the face plate 1, a spring 6, and a large number of electrons arranged oppositely at a predetermined distance from the fluorescent surface 2 via the mask frame 4. A shadow mask 3 with an opening 12 that serves as a beam passage hole
and inner shield 1 installed as necessary.
4, a color picture tube main body connected to a net 9 which houses an electron gun 10 through a funnel 7 on the side wall portion 1-1; a deflection device 8 mounted via a wedge 8-2 between the
The adjustment magnet 11 is attached to the outer wall of the net 9. In such a color picture tube, the electron beam 1 emitted from the electron gun 10
3 causes a predetermined phosphor layer of the phosphor surface 2 to emit light through the opening 13 of the shadow mask 3 while being subjected to focusing, acceleration and deflection effects.

The electron gun 10 is usually red, green, and blue (hereinafter R, G, B).
It forms three R, G, and B electron beams that cause each phosphor to emit light. Among these color picture tubes, which are generally called three-beam shadow mask tubes, electron guns in which three electron guns are arranged horizontally in a row, called in-line electron guns, are currently the mainstream. In a color picture tube using such an in-line electron gun,
The electron beams (hereinafter referred to as R, G, and B beams) that cause R, G, and B color phosphors to emit light are emitted from the electron gun 1 when the deflection yoke 8 is not operated and there is no deflection.
It is designed to concentrate at one point on the fluorescent surface 2 due to the dimensions of the focusing electrode. However, in reality, the electron gun 2 and the shadow mask 3 are not accurately focused due to assembly errors, etc., so the adjustment magnet 11 is used for fine adjustment.

Furthermore, in the in-line electron gun, by appropriately designing the magnetic field of the deflection yoke 8, it is possible to simultaneously pass the R, G, and B3 beams during deflection at one point of the shadow mask 3. In color picture tubes with in-line electron guns, such a so-called dynamic convergenceless magnetic field design is possible, and compared to those with delta-type electron guns, there is no need for a convergence yoke, and complicated adjustments are required. Most current color picture tubes use in-line electron guns because of the many advantages such as no need for an in-line electron gun. An example of a dynamic convergenceless magnetic field will be explained with reference to FIG.
In the dynamic convergenceless magnetic field, as shown by the solid line, the vertical deflection magnetic field 23 becomes a so-called barrel magnetic field whose strength decreases as it moves away from the center, and the horizontal deflection magnetic field 22, shown by the broken line, decreases as it moves away from the center. This is a so-called pink tension magnetic field, where the magnetic field strength increases. In this way, a dynamic convergence magnetic field is realized by distorting the magnetic field from the same so-called uniform magnetic field regardless of the distance from the center. moreover,
A method in which pattern distortion, which was conventionally corrected by a circuit, is removed by a deflection magnetic field is becoming common, and such a magnetic field tends to further intensify the distortion of the deflection magnetic field.

Problems with the Background Art By the way, when the distortion of the deflection magnetic field becomes strong in this way, good convergence or pattern distortion characteristics can be obtained, but problems appear in other aspects.
That is, by distorting the deflection magnetic field, the spot of the electron beam becomes increasingly distorted. Therefore, when deflected, the electron beam spreads, so-called "bleeding" increases, and the resolution at the periphery of the screen is significantly reduced, making it impossible to obtain a satisfactory screen. Furthermore, when the electron beam spot around the screen expands, the electron gun design has to compromise between the center of the screen and the periphery of the screen, which is a major obstacle in terms of electron gun design.

Further, Japanese Patent Publication No. 57-4061 describes a dynamic convergence device using a color television receiver using a video signal delay device. According to this invention, the three electron beams are not concentrated at one point on the shadow mask in a state where the deflection yoke is not operated, that is, in a non-deflected state,
A color picture tube is designed in a state of so-called static convergence deficiency. As a result, the R, G, and B3 beams are not concentrated on the screen, resulting in color shift in the three-color pattern. In Figure 3, if the R, G, and B3 beams are accurately focused, a correct screen will be reproduced.
If the R, G, and B3 beams lack so-called static convergence, the pattern will be 31B, 31G, 31R, 32B, 32G, as shown in Figure 3.
32R, resulting in an image with color shift.
This color shift is corrected by giving a delay to some signals of the R, G, and B3 beams to correctly reproduce the image. Therefore, if the correct delay is given to the image signal, 31R, 31G, 31B and 32R, 3
2G and 32B match and a correct image is reproduced.

A color television using a delay circuit will be explained based on the drawings. Here, all the numbers in the drawings after FIG. 4 are the same as those in FIG. 1 and indicate the same members.

In FIG. 4, a signal source 41 generally supplies signals for driving the R, G, and B color electron guns. 42G and 42B are delay circuits, which are inserted in pairs in the signals that drive the G beam and B beam in FIG. It may be configured to delay one or two arbitrary colors. Alternatively, a signal whose delay is controlled in advance may be generated from the signal source 41 without using the delay circuits 42G and 42B. Reference numeral 43 indicates R, G, and B three-color electron beams, which are approximately parallel in FIG. 4, but may be tilted to some extent. That is, a substantially parallel electron beam is one having an inclination within 1/2 of the concentration angle of a conventional color picture tube.

Now, FIG. 4 shows the state of the electron beam in a state where the electron beam is not deflected. Here, it is most preferable that the delay circuit 42 provides a constant delay time, and if the deflection magnetic field is formed in this way, a suitable result can be obtained. That is, in order to make the delay time variable, the delay circuit itself becomes complicated, and an additional circuit for controlling the delay circuit is required, which is undesirable from both a cost and technical standpoint. Therefore, in a color picture tube having an in-line array electron gun, for example, when a white grid is displayed on the screen and the delay circuit is not operated, the fifth
As shown in the figure, it is necessary that the positional deviations Δx of the three colors R, G, and B are all the same on the entire screen. Furthermore, the fifth
In the figure, the horizontal lines are expressed as a single line, assuming that they match.

By the way, according to a 1957 paper by Johann, Hernthes, Gerritt, Jan, Ruthben et al., Philips Research Report, Vol. 12, pp. 46-48, the convergence error is expressed as follows. This will be explained below with reference to the drawings.

Of the coordinate axes that are perpendicular to each other in Figure 6, Z
The axis indicates the axis of the picture tube, the positive Z direction indicates the traveling direction of the electron beam, and the X direction and Y direction each indicate the deflection direction of the electron beam. In FIG. 6, R,
G and B electron beams are generated from three electron guns respectively, R,
It is assumed that each color of G and B is hit by a phosphor, and Z=Zo
Now let us assume that it has not yet been deflected. here,
Let the incident position of Z = Zo of the electron beam be xs and ys at the X and Y coordinate positions, respectively, and the incident angle is
Assuming xs' and ys' in the direction and Y direction, respectively, the deviation from the so-called Gaussian deflection, that is, the deflection error in the general sense △x (X direction) and △y (Y direction) are expressed as follows. .

△x=A ₁・Xs ³ +(A ₂ +B ₃ )・Xs・Ys ² +(A ₄・Xs ² +B
_{5 Ys} ² _{) _} ^_ _{_} ^_ _{_}
・^ys ′+(A _{9 Xs} ² +B ₁₀ Ys ² ₎ xs +(B ₁₁ +A ₁₂ )XsYsys ⁺ A _13
5 Ysxsys＋A ₁₆ Xs・xsxs′ ＋B ₁₇・Ys・ysxs′＋A ₁₈・Xs・ys・ys′＋B ₁₈ Ysxsy
s'(1-a) △y=B ₁ Ys ³ + (B ₂ + A ₃ ) Xs ²・Ys+ (B ₄ Ys ² + A ₅ Xs ² )
ys _′ + ^{( A} _{6 + B 6 )}
^{2 +} _{A 10 _ _} ^_ _{_} ^_ _{_ _}
Ys・ys・ys′ +A ₁₇ Xs・xs・ys′+B ₁₈ Ys・xs・xs′ (1−b) However, An and Bn (n=1,..., 18) are each a function of the strength of the magnetic field. and a function of deflection,
Xs is the magnitude of deflection in the X direction on the plane Z=Zs,
Ys is the magnitude of deflection in the Y direction on the plane Z=Zs,
Zo and Zs represent the Z coordinate of the deflection start point on the tube axis and the Z coordinate of the screen position, respectively, and indicate the coordinate values shown in FIG. 6, respectively. Here, in the present invention, we mainly deal with the case where the R, G, and B3 electron beams are almost parallel, and since the R, G, and B3 electron beams are arranged in a straight line in the horizontal direction,
It is important to set xs'=0, ys'=0, and ys=0, and by substituting these values into equations (1-a) and (1-b), △x=A ₁・Xs ³ + (A ₂ +B ₃ )・Xs・Ys ² +(A ₉・Xs ² +B
₁₀・Ys ² )・xs+A ₁₃・Xs・xs ² …(2-a) △y=B ₁・Ys ³ +(B ₂ +A ₃ )・Xs ²・Ys+(A ₁₁ +B ₁₂ )
・Xs・Ys・xs＋B ₁₄・Ys・xs ² … (2-b) Here, in both equations (2-a) and (2-b), the first
The second term is a term representing linearity distortion and figure distortion, and is unrelated to the convergence term, so if it is excluded, △x=(A ₉ Xs ² +B ₁₀・Ys ² )×xs+A ₁₃・Xs・xs ²
...(3-a) △y=(A ₁₁ +B ₁₂ )・Xs・Ys・xs+B ₁₄・Ys・xs ²
...(3-b) It is expressed as.

Here, each coefficient A ₉ of equations (3-a) and (3-b),
B ₁₀ , A ₁₃ , A ₁₁ +B ₁₂ , and B ₁₄ are expressed as follows.

A ₉ ＝2K∫ ^Zs _Z0 dS∫ ^S _Z0 H _o2・X／X _s ²・dZ…(4) B ₁₀ ＝−K∫ ^Zs _Z0 dS∫ ^S _Z0 H′ ₁₀・Y′／Y _s ² dZ−
2K∫ ^Zs _Z0 dS∫ ^S _Z0 H ₁₂・Y／Y _s ² dZ…(5) A ₁₁ ＋B ₁₂ =−2K∫ ^Zs _Z0 dS∫ ^Zs _Z0 H _o2・Y／X _s・Y _s dZ−2
K∫ ^Zs _Z0 ds∫ ^S _Z0 H ₁₂・X／X _s・Y _s dZ＋K∫ ^Zs _Z0 H′ ₁₀・X
/X _s・Y _s・dZ…(6) A ₁₃ =K∫ ^Zs _Z0 dS∫ ^S _Z0 H〓 ₂ /Y _s dZ…(7) B ₁₄ =−K∫ ^Zs _Z0 dS∫ ^S _Z0 H2/Y _s dZ+1/2K∫H′
0/Y _s dZ …(8) H〓 _X represents the strength of the vertical deflection magnetic field in the X direction in the plane where It is shown as follows.

_{H〓 _ _} ^_ _{_ _} The second-order coefficient of the vertical deflection magnetic field, Z=Zo indicates the deflection start point, and Z=Zs indicates the Z coordinate of the deflection end point, that is, the screen position. In addition, K is a proportionality constant, Y and Y' are the degree of deflection (trajectory) and deflection change (differential) of the beam in the Y direction, respectively, where Y=Y(z) and Y'=dY/dZ, and when Z=Zo, is Y=Y'=
It is 0.

Further, H 〓 _Y represents the strength of the horizontal deflection magnetic field in the Y direction in the plane where Y=0, and is expanded to the power of X on the x axis, and is expressed as the following equation (10).

H〓 _Y = H〓 ₀ +H〓 ₂・x ² +… …(10) However, H〓 ₀ : A function of Z, the zero-order coefficient of the horizontal deflection magnetic field on the tube axis H〓 ₂ : A function of Z The second-order coefficients X and X' of the horizontal deflection magnetic field are X=X(z) and X'=
The degree of deflection (trajectory) and change in deflection (differential) of the beam in the X direction is dX/dZ, and when Z=Z0, X=X'=0.

The subscripts and subscripts indicate the vertical deflection magnetic field and the horizontal deflection magnetic field, respectively. Xs and Ys are respectively the X of the beam at Z=Zs
and the Y coordinate position.

Note that H′〓 ₀ represents the differential of H〓 ₀ with respect to Z. That is, H′〓 ₀ = dH〓 ₀ /dZo Here, in order to make the deflection error zero, A ₉ ,
Since B ₁₀ , A ₁₃ , A ₁₁ +B ₁₂ , and B ₁₄ can all be set to zero, the conditions can be written out as follows.

Transforming equations (4) and (7) using partial integration, A ₉ = 2K∫ ^Zs _Z0 dS∫ ^S _Z0 H〓 ₂・X/X _s ²・dZ=−2K∫
^Zs _Z0 (Z−Z _s )・H〓 ₂・X/X _s ² dZ=0…(11) A ₁₃ ＝K∫ ^Zs _Z0 dS∫ ^S _Z0 H〓 ₂ /X _s dZ=−K∫ ^Zs _Z0 ( Z
−Z _s )・H〓 ₂ /X _s dZ=0…(12) In order for equations (11) and (12) to hold true regardless of the amount of deflection of X, H〓 ₂ =0…(13) holds. There must be. That is, the horizontal deflection magnetic field must be uniform. However, in practice, there is no problem as long as it is substantially uniform, and it has been experimentally confirmed that there is almost no error if |H〓 ₂ |≦5.0 oersted per square centimeter. Then, the horizontal deflection magnetic field is said to be uniform. Using the condition of equation (13), B ₁₀ = −K∫ ^Zs _Z0 dS∫ ^S _Z0 H′〓 ₀・Y′／Y _s ²・d
Z−2K∫ ^Zs _Z0 dS∫ ^S _Z0 H〓 ₂・Y／Y _s ² dZ =K∫ ^Zs _Z0 (Z−Z _s ) (H′〓 ₀・Y′＋2H〓
₂・Y)/Y _s ² dZ=0…(14) A ₁₁ +B ₁₂ =−2K∫ ^Zs _Z0 dS∫ ^S _Z0 H〓 ₂・X/X _s
・Y _s dZ＋K∫ ^Zs _Z0 H′〓 ₀・X／X _s・Y _s・dZ =K∫ ^Zs _Z0 2(Z−Z _s )・H〓 ₂ +H′〓 ₀ /X
_s・Y _s・X・dZ=0...(15)

What is important here is that each electron beam 5 in FIG.
1, 52, and 53, the three colors R, G, and B are drawn as if they are the same in the horizontal direction, but in reality there is a considerable deflection error, and this deflection error is △
Expressed as a y error. △ like this
If a y error exists, the delay circuit must provide a delay time for several horizontal deflection scanning lines. In addition, since the amount of △y changes depending on the amount of deflection, the delay time must be controlled variably, and the unit of this variable time is controlled in terms of how many scanning lines, so even if it is possible, the image quality will be affected. Significantly decreased. However, such control is not possible in practice. In other words, it is clear that this method is not suitable for practical use because the scanning lines are discontinuous, resulting in misalignment on the screen.

Therefore, it is especially essential that equation (15) holds true. Therefore, 2(Z−Zs)H〓 ₂ +H′〓 ₀ =0 (16) must hold. What is particularly important in the convergence characteristics of color picture tubes of this type is the error △y in the Y direction rather than the error △x in the X direction.
It is. Therefore, the condition of equation (5) that does not involve Δy is not required in this case. Also, if equation (16) holds, equation (8) will also be transformed as follows, so at the same time
The condition of equation (8) is also satisfied.

B ₁₄ =−K∫ ^Zs _Z0 dS∫ ^S _Z0 H〓 ₂ /Y _s dZ＋1/2K∫H′〓 ₀ /
Y _s dZ =K/2∫ ^Zs _Z0 2(Z-Z _s )H _I2 +H _I0 /Y _s dZ=0 It is clear from the above explanation that at this time △y=0 and good convergence can be obtained. .

As shown in Figures 7 and 8, the magnetic fields that satisfy the above conditions are: the horizontal deflection magnetic field is a so-called uniform magnetic field, the direct deflection magnetic field is a so-called pink tension magnetic field on the electron beam entrance side, and a so-called barrel magnetic field on the electron beam exit side. It's good to have.

Thereby, as an example, the condition of equation (16) can be approached, and good convergence can be obtained. This will be explained using drawings.
Figure 12a shows an example of H′〓 ₀ , and Figure 12b shows (Z
-Zs), and Fig. 12c shows H〓 ₂ when the incident side of the electron beam is a so-called pincushion type magnetic field and the exit side is a so-called barrel type magnetic field. In this case, the first term on the left side of equation (16), 2(Z-Zs)H〓 ₂ , becomes as shown in Figure 12d, and the left side of equation (16) |2
(Z−Zs)·H〓 ₂ +H′〓 ₀ | can be brought close to zero according to FIGS. 12a and 12d.

Furthermore, if the horizontal deflection magnetic field is formed into a so-called uniform magnetic field, a very good screen can be formed.

By making the horizontal deflection magnetic field a so-called uniform magnetic field, it is possible to approach the condition of H〓 ₂ =0 in equation (13), and good convergence can be obtained. However, in FIG. 7, the horizontal deflection magnetic field is shown by a broken line. If the deflection direction is positive, the vertical deflection magnetic field will be negative due to the way the coordinate axes are taken, but here, for ease of understanding, the direction of the magnetic field is assumed to be positive.

However, even if good convergence is obtained with this method, the vertical deflection magnetic field seen in the tube axis direction becomes a pincushion magnetic field on the electron gun side and a barrel magnetic field on the phosphor screen side, and as a result, the magnetic field is also distorted. Beam spot distortion still remains.

Furthermore, since permanent magnet pieces are used, the deviation of the deflection yoke is large, which is extremely problematic from a practical point of view.

Further, US Pat. No. 2,764,628 discloses a color television in which multiple electron guns are formed in parallel when not deflected, but there is no mention of the deflection magnetic field, so it is natural for such a system to do so. Otherwise, a good screen will not be formed.

OBJECTS OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a deflection yoke magnetic field that provides good spot distortion characteristics in a color television device using a delay circuit or the like.

Summary of the Invention The present invention is equipped with a multiple electron gun, which emits electron beams almost in parallel, with a uniform horizontal deflection magnetic field, a pink tension magnetic field on the electron gun side of the vertical deflection magnetic field, and a barrel magnetic field on the screen side. In a color picture tube, by locating the maximum value of the vertical deflection magnetic field on the tube axis closer to the screen than the maximum value of the horizontal deflection magnetic field on the tube axis, the beam spot on the screen can be focused with less spread and distortion. It is intended to be as small as possible.

Embodiments of the Invention By the way, if a deflection magnetic field has the above-mentioned magnetic field distribution, good convergence and a relatively good electron beam spot shape on the screen surface can be obtained in a so-called parallel beam type color picture tube. Although it is understood that this method alone is not enough to obtain a sufficiently small beam spot. Therefore, next we will consider the spread of the electron beam spot on the screen surface.
The spread of the electron beam spot due to deflection is formally treated in the same way as the convergence error, and is expressed as follows. In other words, since the spread of the electron beam spot on the screen surface is considered to be the dispersion of the beam's advancing angle, △x=(A ₄ Xs ² +B ₅・Ys ² )・xs′+(A ₆ +B ₆ )・Xs・
Ys・ys′＋＋A ₇・Xs・xs′ ² +A ₈・Xs・ys′ ² +2B ₈ Ys・xs′・ys′…(17) △y=(B ₄・Yg ² +A ₅ Xs ² )・ys′ +(A ₆ +B ₆ )・Xs・
It can be expressed as Ys・xs′＋＋B ₇・Ys・ys′ ² +B ₈・Ys・xs′ ² +2A ₈・Xs・xs′・ys′ (18).

Also, consider separately the case of only horizontal deflection and the case of only vertical deflection, and in case of only horizontal deflection,
Since Ys=0, △x=A ₄・Xs ²・xs′+A ₇・Xs・xs′ ² +A ₈・Xs・ys′ ² …(19) △y=A ₅・Xs ²・ys′+2・B ₈・Xs・xs′・ys′
…(20) becomes.

Here, in an actual color picture tube, the main error in △x is astigmatism, so if we express the main term of the error with the subscript domi (the same applies hereafter), (△x)domi=A ₄・Xs ²・xs′ …(21) A ₄ = 3/2∫X′ ² /X _s ²・dz＋2k∫ds∫H〓 ₂ (Z−Z ₅ )
・X/X _s ²・dz=3/2∫X' ² /X _s ² dz−2k∫H〓 ₂・(Z
−Z ₅ ) ²・X/X _s ²・dz = 3/2∫X′ ² /X _s ² dz (∵H〓 ₂ =0) …(22).

Also, the main term in △y is astigmatism due to ys′, (△y) domi=A ₅・Xs ²・ys′ …(23) A5=1/2∫X′ ² /X _s ² dz+k∫ ds∫H′〓 ₀・X′
・(Z−Z _s )/X _s ² dz−2k∫ds∫H〓 ₂ X(Z−Z _s )/X _s ²
dz = 1/2∫X′ ² /X _s ² dz−k∫H′〓 ₀・X′・(
Z−Zs) ² /X _s ² dz (∵H〓 ₂ =0) (24).

Here, since the first term of equation (24) is always positive, the second term
term must also be positive. It is also known that in an actual color picture tube, X'.(Z-Zs) ² has a distribution as shown in FIG. 9 (provided that the deflection is to the horizontal end of the color picture tube). Therefore, (2
4) The numerator of the integrand in the second term of the equation has a distribution as shown in FIG. Also, in order to make equation (24) zero, the second term should be made negative, and for that purpose,
It is sufficient to bring H′〓 ₀ closer to the electron gun side.

Next, in the case of only vertical deflection, Xs=0, △x=B ₅・Ys ²・xs′+2B ₈・Ys・xs′・ys′ …(25) △y=B ₄・Ys ²・ys ′+B ₇・Ys・ys′ ² +B ₈・Ys・xs′ ² …(26).

Next, the main term of △y is (△y) domi=B ₇・Ys・ys′ ² …(27) B ₇ = 3/2 + k∫ds∫H′〓 ₂・(Z−Z _s ) ² /X _s dz = 3/2 (∵H〓 ₂ = 0) ...(28).

Therefore, considering the next largest term (△y) sud, (△y)sub=B ₄・Ys ²・ys′ …(29) B ₄ =3/2∫Y′ ² /Y _s ² dz+2k ∫ds∫H〓 ₂・(Z−Z _s )
・Y/Y _s ² dz = 3/2∫Y′ ² /Y _s ² dz−2k∫H〓 ₂・(Z−Z _s ) ²・Y
/Y _s ² dz …(30)

Here, if the second term of equation (30) is made positive, △y becomes close to zero. The integrand of the second term in equation (30) is the first
1a to d. That is, it is sufficient to make the integrand function positive, but it is clear that for this purpose, the vertical deflection magnetic field should be brought closer to the screen side, opposite to the horizontal deflection magnetic field.

That is, when the vertical deflection magnetic field is brought closer to the screen side, the integrand of the second term of equation (30) becomes like the dotted lines in FIGS. 11a to 11d. Therefore, the absolute value of the maximum value of the negative part of the integrand H〓 ₂ (Z−Zs) ² is also
The absolute value of the maximum value of the positive part also decreases, but this integrand is shown in Figure 11b (Z-
Since it is a product of Zs) ² , a function that decreases rapidly along Z, the decrease in the negative part of this integrand is greater than the decrease in the positive part. Therefore, this integrand as a whole changes in the positive direction.

In addition, in FIGS. 11a to 11d, the Y deflection direction is set to be positive, so H ₀ is in the negative direction.

In the case of only vertical deflection, Δx is almost zero, so there is no need to consider it in practice.

As described above, by bringing the magnetic field distribution of the vertical deflection magnetic field closer to the screen side than the magnetic field distribution of the horizontal deflection magnetic field, the beam spot on the screen when deflected can be kept in a good condition.

In practice, as shown in Figure 13, the Z coordinate of the maximum value of the vertical deflection magnetic field, that is, the maximum value of the magnetic field strength along the Z direction on the tube axis (Z axis), is determined from the Z coordinate of the maximum value of the horizontal deflection magnetic field. It has been experimentally confirmed that it is possible to achieve the objective by moving it closer to the screen.

By using a deflection magnetic field having such a magnetic field distribution, it is possible to realize a color picture tube with less color shift and, in particular, less spread of the beam spot on the screen during deflection, making it possible to reproduce high-quality images.

However, the term "substantially parallel electron beam" in the present invention refers to one having an inclination within 1/2 of the concentration angle of a conventional color picture tube.

Effects of the Invention As described above, according to the present invention, it is possible to realize a color picture tube that uses nearly parallel electron beams and has less distortion of the beam spot on the screen, which has great industrial value. .

[Brief explanation of drawings]

Figure 1 is a schematic cross-sectional view for explaining a conventional color picture tube, Figure 2 is a schematic diagram for explaining the magnetic field distribution of a conventional color picture tube, and Figure 3 is a schematic diagram for explaining convergence error. 4 is a schematic cross-sectional view showing a color picture tube using a parallel electron beam, FIG. 5 is a schematic diagram showing the screen of a color picture tube using a parallel electron beam, and FIG. 6 is a schematic diagram showing a color picture tube using a parallel electron beam. A conceptual diagram for explaining the deflection error, Figure 7 is a qualitative diagram showing the distribution of the horizontal deflection magnetic field, Figure 8 is a qualitative diagram showing the distribution of the vertical deflection magnetic field, Figures 9 and 10.
11a to 11d are qualitative diagrams representing integrand terms representing beam spot distortion of horizontal and vertical deflection magnetic fields, and FIGS. 12a to 12d are deflection magnetic fields of embodiments of the present invention, respectively. A diagram explaining
FIG. 13 is a diagram illustrating the magnetic field distribution of the present invention. 1... Face plate, 2... Fluorescent surface, 3...
...Shadow mask, 4...Mask frame, 5...
...Panel pin, 6...Spring, 7...Funnel, 8...Deflection yoke, 9...Net, 10...
...electron gun, 11...adjustment magnet, 12...21...
Around the screen, 22... Horizontal deflection magnetic field, 23... Vertical deflection magnetic field, 31... Image, 32... Image, 41...
... Signal source, 42 ... Delay circuit, 43 ... Electron beam, 51, 52, 53 ... Grid image, 61, 6
2, 67, 70...Mask periphery, 63...Horizontal deflection axis, 64...Vertical deflection axis, 65...Horizontal deflection meridional concentration point, 66...Horizontal deflection spherical concentration point, 6
8... Vertical deflection spherical focal point, 69... Vertical deflection meridian concentrated point.

Claims (1)

[Claims] 1. In a color picture tube equipped with multiple electron guns, in which electron beams are emitted almost parallel from the multiple electron guns, the horizontal deflection magnetic field is uniform, the vertical deflection magnetic field is set as a pincushion magnetic field on the electron gun side, and as a barrel magnetic field on the screen side. . A color picture tube, characterized in that the position of the maximum value of the vertical deflection magnetic field on the tube axis is located closer to the screen than the position of the maximum value of the horizontal deflection magnetic field on the tube axis.