JPH0129298B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a high-resolution cathode ray tube device suitable for graphical display, kanji display, etc.

Conventional configurations and their problems A particularly high resolution is required for cathode ray tube devices used for graphical display, kanji display, etc. However, if you increase the anode voltage or increase the electron gun diameter to improve resolution,
This not only increases X-ray radiation and deflection power but also increases costs.

The cathode ray tube device disclosed in Japanese Patent Application Laid-Open No. 57-30247 adopts a double-crossing method in which the electron beam crosses over near the prefocus lens and then crosses over again toward the main lens. High resolution is achieved by reducing spherical aberration in the lens. However, since it is only the outer electron beam part (outer peripheral surface part) that forms the outer shell of the electron beam that intersects the gun axis twice, high resolution can only be obtained in the large beam current region where the brightness is high. The resolution in the small beam current region where the brightness is low is not improved, but rather deteriorates.

OBJECTS OF THE INVENTION The present invention provides a cathode ray tube device that employs the above-described two-crossing method and can obtain high resolution even in a small beam current range.

Structure of the Invention In the present invention, a G _2s electrode is provided with a potential lower than the G ₂ electrode potential and which changes depending on the amount of deflection between the front triode and the main lens generating electrode.
An electrode is provided so that most of the electrons emitted from the electron emitting surface of the cathode cross the gun axis twice, and the outer peripheral surface of the focused electron beam is cut off by a trimming electrode, details of which are shown in the drawings below. This will be explained together with the embodiment shown in .

DESCRIPTION OF THE EMBODIMENTS In FIG. 1, an electron gun 1 includes a cathode 3 having an electron emitting surface 2, a _G1 electrode 4 as a control electrode, a _G2 electrode 5 as a shielding electrode, and a G2 electrode 5 as an auxiliary shielding electrode.
G _2s electrode 6, G ₃ electrode 7 as first anode, G ₄ electrode 8 as focusing electrode and G ₅ as second anode
The G ₅ electrode 9 has a trimming electrode 10 inside thereof. G ₁ electrode 4, G ₂ electrode 5
The diameters of the electron beam passage holes 11, 12, and 13 provided on each main surface of the G _2s electrode 6 are all 0.4 mm.
φ, the thickness of the main surface of G ₁ electrode 4 is 0.065 mm, the thickness of the main surface of G ₂ electrode 5 is 0.25 mm, the thickness of the main surface of G _2s electrode 6 is 0.2 mm, and the thickness of the main surface of G ₄ electrode 8 is 0.065 mm. The inner diameter is 8.7 mmφ, the distance between the electron emission surface 2 and the G ₁ electrode 4 is 0.07 mm, and the distance between the G ₁ electrode 4 and the electron emitting surface 2 is 0.07 mm.
The effective distance between the G ₂ electrode 5 and the G ₂ electrode 5 is 0.43 mm.
The distance between the G _2s electrode 6 and the G 3 electrode 6 is 0.4 mm, the distance between the G _2s electrode 6 and the G ₃ electrode 7 is 3.2 mm, and the diameter of the trimming hole 14 of the trimming electrode 10 is 0.8 mmφ. Also,
The distance Z _k between the electron emitting surface 2 of the cathode 3 and the center of the main lens is 17.27 mm, and the distance Z _s between the trimming center and the phosphor screen surface is 213.4 mm. G _2s electrode 6
, there is a dynamic voltage V _g2s which is lower than the voltage V _g2 applied to the _G2 electrode 5 and which changes depending on the vertical or horizontal deflection amount as shown in a and b in Fig. 2.
is given, and the electron travels within the trajectory shown by the curve in Figure 3.

A cathode ray tube device configured in this manner can improve resolution by about 25% compared to a cathode ray tube device with a conventional configuration, and this point will be explained next using a phase diagram.

A phase diagram is a convenient method for understanding the state of an electron beam, and includes emittance and acceptance. The former is suitable for understanding the state of the rotationally symmetrical electron beam traveling from the cathode to the main lens, and the latter is suitable for understanding the performance of the main lens. Furthermore, by overlapping and matching both phase diagrams, the size of the beam spot (bright spot) can be estimated.

Before explaining the present invention, an application example of such a phase diagram will be explained. As shown in FIG. , intersects the gun axis Z only once and heads toward the main lens 16. The virtual radiation point 17 is located at the intersection of the gun axis Z and an extension line 18 that is a linear return of the trajectory immediately before entering the main lens 16. The off-axis distance r at the intersection of the extension line 18 and the electron emission surface 2, and the inclination angle r' of the extension line 18 (r'=
dz/dz) is plotted at a large number of equally divided points, an emittance diagram as shown in FIG. 5 is obtained. In addition, 19 is a fluorescent screen surface,
ρ indicates spherical aberration on the screen surface.

Figure 6 is an acceptance diagram, where given a certain main lens position and screen surface position,
The spherical aberration ρ on the screen surface is determined by the electron beam incident on the main lens. The orbit of the spherical aberration ρ is calculated by changing the off-axis distance r and the inclination angle r' on the electron emission surface, and many combinations of the r value and the r' value such that ρ=0.5 mm are determined, for example. Then, as shown in Figure 6, this combination is ρ=+0.5mm.
The contour lines are expressed as contour lines of ρ and calculated under the condition of ρ = −0.5 mm.
=A diagram depicting a constant line is acceptance.

Next, emittance and acceptance are superimposed and matched. When all emittances fall within the acceptance range of ρ=±0.5 mm, the diameter of the beam spot is estimated to be 1.0 mmφ. Similarly, the diameter of the beam spot when it falls within the acceptance range of ρ=±1.0 mm is estimated to be 2 mmφ.

If the emittance is unevenly distributed in the positive region of ρ, as shown in FIG. 7a, the beam spot will become abnormally large. This means that the focusing voltage is too high and the main lens action is weak. Conversely, when the emittance is unevenly distributed in the negative region of ρ, as shown in FIG. 7b, it means that the focusing voltage is too low. In the optimal convergence state, the emittance is located approximately midway between the positive and negative regions of ρ, as shown in FIG. 7c. Therefore, if we prepare various acceptance diagrams with different focusing voltages and select the acceptance diagram that best matches them, we can achieve the following:
The optimal focusing voltage and beam spot diameter at that time can be estimated.

FIG. 8 is an emittance diagram drawn by calculating the trajectory of the cathode ray tube device according to the present invention shown and explained in FIGS. 1 to 3, and a and a' indicate trimming holes of the trimming electrode. In this cathode ray tube device, almost all of the electrons emitted from the electron emitting surface 2 of the cathode 3 (excluding the electrons emitted from the center of the electron emitting surface) pass along a trajectory that intersects the gun axis Z twice. , when the off-axis distance r is a positive value, all angles r' are negative values, and when the off-axis distance r is a negative value, the angle
All r' values are positive values, which is significantly different from the emittance diagram of a conventional general electron gun device shown in FIG.

In addition, since the trimming electrode 10 having a trimming hole of 0.8 mmφ is provided, the electron beam portion (outer peripheral surface portion) where r'≧0.04 is the trimming electrode 10.
The effective electron beam that is ablated by 0 and directed from the main lens to the screen surface is approximately 54% of the total cathode current _Ik .
% (=beam transmittance). Therefore, the cathode current I _k is determined to be 100 μA, which is twice the 50 μA of the conventional device using a bipotential electron gun.

FIG. 9 is an emittance diagram when V _g2s is changed. If V _g2s is low, the divergence angle of the electron beam becomes large and the transmittance of the electron beam passing through the trimming electrode becomes low, so it is better to make V _g2s as high as possible. However, at Z _k = 17.27 mm, the V _g2s value that can minimize the beam spot diameter is 100~
Since it is 150V, here it is set as V _g2s =150V (at a deflection amount of 0).

Figure 10 is a diagram that matches the emittance and acceptance at V _g2s = 150V, and the emittance regulated by the trimming electrode is ρ = ±
Within the acceptance range of 0.175, V _g2s
= The diameter of the beam spot is 0.35 under the condition of 150V
mmφ, and extremely high resolution can be obtained.

In addition, in the conventional configuration in which most of the electrons emitted from the electron emitting surface intersect the gun axis only once, many electrons travel parallel to the gun axis, which means that r has a non-zero value in the emittance diagram. This means that r'=0 when In other words, the emittance crosses the r-axis at a point below 0. As can be seen from the acceptance diagram in FIG. 7, even if the focusing voltage is changed, the point where the curve of ρ=±0.25 mm crosses the r-axis hardly changes. Therefore, under conditions where the emittance crosses the r-axis at a point other than 0, the emittance is set to ρ = ±0.25 mm.
It is difficult to keep the beam spot within the range of , and it is difficult to obtain a beam spot with a small diameter. Therefore, in the present invention, as described above, almost all of the electrons emitted from the electron emitting surface are made to intersect the gun axis twice. Also, V _g2 =
As you can see from the 600V emittance diagram, V _g2s is V _g2
If it is close to , the amount of electrons traveling parallel to the gun axis will increase, so set V _g2s to a value lower than V _g2 . Furthermore, in the present invention, a trimming electrode is provided to cut off the outer peripheral surface portion of the electron beam directed from the main lens to the screen surface, but if the same trimming as in the present invention is performed on a conventional structure, the c As can be seen from the figure, since the electron beam is ablated from the side with the larger r' value, the electrons that should be concentrated at the center of the beam spot are ablated, leaving the beam spot diameter unchanged and the brightness distribution worsening.

Note that although the above has described an example in which the present invention is applied to a unipotential type electron gun configuration,
The present invention can be similarly applied to an electron gun configuration such as a bipotential type, in which case the G ₂ electrode operates as an accelerating electrode, and the G _2s electrode operates as an auxiliary accelerating electrode.

Effects of the Invention Since the cathode ray tube device of the present invention is constructed as described above, a beam spot with a small diameter can be obtained regardless of the large beam current range or the small beam current range, and exhibits good resolution characteristics. Furthermore, since the amount of change when changing the voltage to the G _2s electrode according to the amount of deflection is as low as about 35 V, there is an advantage that the circuit configuration does not become too complicated.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of the electron gun section of a cathode ray tube device embodying the present invention, and a and b in Fig. 2 are G _2s of the electron gun.
3 is a cross-sectional view showing the state of the electron beam in the electron gun section, FIG. 4 is a diagram illustrating the trajectory of the electron beam in a conventional cathode ray tube device, and FIG. 5 is a waveform diagram of the voltage applied to the electrode. Figure 4 is an emittance diagram of the electron beam, Figure 6 is an acceptance diagram of the same device, Figure 7 a, b, and c are matching diagrams of emittance and acceptance, and Figures 8 to 10 are diagrams for implementing the present invention. FIG. 2 is an emittance diagram, an acceptance diagram, and a matching diagram of the device. 3... cathode, 4... G ₁ electrode, 5... G ₂ electrode,
6...G _2s electrode, 10...Trimming electrode, 16
... Main lens, 19 ... Fluorescent screen surface.

Claims (1)

[Claims] 1. A _G2s electrode that is provided with a potential that is lower than the _G2 electrode potential and that changes depending on the amount of deflection between the front triode consisting of the cathode, G1 electrode, and _G2 electrode and _the main lens generation electrode. is installed, and most of the electrons emitted from the cathode and heading towards the main lens are transferred to the gun axis and 2.
A cathode ray tube device characterized in that, while the electron beam crosses back and forth, the outer peripheral surface portion of the electron beam directed from the main lens toward the phosphor screen surface is cut off by a trimming electrode.