JPH0435871B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a flat cathode ray tube used in color image display devices such as color television receivers and computer terminal displays.

Structure of Conventional Example and Its Problems FIG. 1 is a perspective view of a conventional flat cathode ray tube that performs deflection by changing the voltage applied to each electrode of a divided deflection plate.

The electron beam 12 emitted from the electron source 11 is
The beam modulated by the modulation electrode 13 and not cut off comes to the deflection system formed by the deflection plate 14 and the fluorescent surface 15, and travels directly to the electrode 14a having the same voltage as the fluorescent surface 15. , as it approaches the electrode 14b to which a voltage several tens of volts lower than the potential of the fluorescent surface 15 is applied, it is deflected under the influence of the electric field and enters the fluorescent surface 15.

In the conventional example described above, even if either the voltage of the deflection plate 14 or the voltage of the fluorescent surface 15 fluctuates, the position and angle of arrival at the fluorescent surface 15 change depending on the amount of the fluctuation. Therefore, especially in flat cathode ray tubes for color television receivers, the fluorescent surface 15
The accuracy of the position reached is required to be about 1/10 of the field scanning line width, so the voltage applied to the deflection plate 14 and the fluorescent surface 15 is required to have extremely high accuracy. This will become extremely difficult both in terms of space and cost.

Purpose of the Invention The present invention is intended to solve the above-mentioned problems, and its purpose is to obtain an electron beam spot with uniform properties in which the arrival position and arrival angle of the electron beam do not change even if the vertical deflection voltage varies. shall be.

Structure of the Invention The present invention comprises a portion that forms a horizontally long band-shaped electron beam, a plurality of deflection electrodes that deflect the band-shaped electron beam in the vertical direction, and a face portion in which a phosphor is formed in a predetermined pattern. It is composed of
This is a flat cathode ray tube in which the voltage of each deflection electrode is sequentially switched between a voltage equal to the cathode voltage and a voltage higher than the cathode voltage.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a sectional view of a flat cathode ray tube according to an embodiment of the present invention.

Electron beam 2 emitted from linear cathode 20
1 is formed by the focus electrode 25 and the shield electrode 26, the amount of which is controlled by the electric field formed by the back electrode 22 and the beam extraction electrode 23, and the divergence is suppressed by the pre-focus electrode 24. The light passes through the focusing system and goes straight to the deflection system formed by the deflection electrode 27 and the modulation electrode group 28. It is assumed that the central axis of the band-shaped electron beam and the central axis of the deflection space are in the same plane. However, it is not limited to this. The deflection electrode 27 is composed of a stripe-shaped electrode divided into at least the same number as one field scanning line in the traveling direction of the electron beam, and the deflection is achieved by sequentially switching the potential of each electrode to the cathode potential. Then, field scanning is performed. Regarding the direction of vertical deflection, the first case is to deflect the electrons in a direction away from the electron source (from the left side to the right side in Figure 2), and the second case is to deflect the electrons from a place far from the electron source towards the electron source side. In the case of (from right to left in Figure 2)
Two ways can be considered: only the divided electrode 27a of the deflection electrode 27 closest to the shield electrode 26 is set at a voltage higher than the cathode voltage, and the other divided electrodes 27b,
27c... is set to the cathode voltage, and by sequentially switching the voltage of the divided electrodes 27b, 27c... to a voltage higher than the cathode voltage, the first deflection direction is obtained. Only the divided electrode 27z furthest from the shield electrode 26 is set to cathode voltage, and the other divided electrodes 27y, 27x...
The second deflection direction can be obtained by setting voltage 27a higher than the cathode voltage and sequentially switching the divided electrodes 27y, 27x, . . . to the cathode voltage. At least the electrode on the first deflection electrode side of the modulation electrode group 28 is set to a voltage higher than the cathode voltage. The deflected electron beam passes through the modulation electrode group 2
8, each pixel is modulated and the phosphor is applied to a phosphor surface 29 coated with a predetermined pattern.

In FIG. 3, the potential of the electrodes 27a, 27b...27j closer to the electron source than the electrode 27k where the deflection electrode 27 is located is V, and the potential of the electrodes 27m, 27n...27z after the electrode 27l adjacent to the electrode 27k _{is VD.} The modulation electrode group 28 when these voltages are changed as
The upward beam arrival position and arrival angle were determined by solving the equation of motion governing the electron beam. Here, the beam arrival position is the distance from the center of the linear cathode along the central axis of the deflection space, and the beam arrival angle is the electrode when the electron beam is incident on the electrode on the deflection electrode side of the modulation electrode group 28. and the tangent to the electron beam trajectory.
At this time, the electrode potential on the deflection electrode side of the modulation electrode group 28 is assumed to be equal to V, and the cathode potential V _k is -
It is 30V.

In FIG. 3, the deflection voltage V _D with respect to the voltage V
The ratio of the difference between the deflection voltage V D and the voltage V (V _D - V) is the deflection voltage V _D
When is a large negative voltage, the smaller the voltage V is, the larger the voltage becomes. When the deflection voltage V _D is a large positive voltage, the larger the voltage V is, the larger the voltage is. Therefore, when the voltage V is small, the electrons accelerated by the voltage V are strongly influenced by the deflection electric field, and the deflection voltage V _D is negative because the ratio (V _D - V) is large. As V _D increases,
When the influence of the deflection electric field weakens and the deflection voltage V _D becomes positive and large, the ratio (V _D -V) decreases, and the influence of the deflection electric field reverses and becomes weaker. That is, when the voltage V is small and the deflection voltage V _D is negative and large, the beam arrival position will be short and the beam arrival angle will be large. The reason why the curves indicating the beam arrival position or beam arrival angle intersect at approximately V _D =V _k when the voltage V is changed is that when electrons are emitted from the cathode, the curves indicate the beam arrival angle due to the cathode voltage V _k . In order to be drawn out, the voltage V when V _D = V _k
It can be explained that the beam arrival angle and the beam arrival position are converged to a constant value even if the beam arrival angle and the beam arrival position are different. FIG. 3 quantitatively shows the above qualitative explanation.
From FIG. 3, it can be seen that when the deflection voltage V _D is equal to the cathode potential V _k , the arrival position and arrival angle of the beam do not change even if the voltage V changes. Therefore, by making the deflection voltage V _D equal to the cathode voltage V _k , even if the voltage V changes, the beam arrival position and arrival angle do not change, and a uniform and stable electron beam spot can be obtained. becomes possible. As a result, the electron beam always lands at the same position on the fluorescent surface 29 at the same angle regardless of fluctuations in the voltage V, so that a very stable scanning line can be obtained.

Effects of the Invention As described above, the present invention divides the deflection electrode arranged facing the fluorescent surface into at least the same number as the number of field scanning lines, and sets the deflection voltage applied to each divided electrode to a certain voltage higher than the cathode voltage. V and cathode voltage
This is a flat cathode ray tube that deflects a band-shaped electron beam incident in a direction parallel to a fluorescent surface in a direction perpendicular to that surface by sequentially changing the voltage _V. The electron beam can always be incident at the same position and at the same angle.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an example of a conventional flat cathode ray tube, FIG. 2 is a sectional view showing an embodiment of the flat cathode ray tube according to the present invention, and FIG. 3 is an electronic diagram of the flat cathode ray tube shown in FIG. FIG. 3 is a diagram showing beam characteristics. 11, 20... Linear cathode, 12, 21...
Electron beam, 13... Modulation electrode, 14... Deflection plate, 15... Fluorescent surface, 22... Back electrode, 23...
... Beam extraction electrode, 24 ... Prefocus electrode, 25 ... Focus electrode, 26 ... Shield electrode, 27 ... Deflection electrode, 28 ... Modulation electrode group, 29 ... Fluorescent surface.

Claims (1)

[Claims] 1. A fluorescent surface, a deflection electrode disposed opposite to the fluorescent surface, and means for making a band-shaped electron beam enter a deflection space between the fluorescent surface and the deflection electrode. The deflection electrode is divided into at least the same number as the number of field running lines in the traveling direction of the electron beam, and a first voltage equal to the cathode voltage and a second voltage higher than the cathode voltage are applied to each divided deflection electrode. A flat plate cathode ray tube that is characterized by sequentially switching the voltage. 2. The electron beam incidence means as set forth in claim 1, wherein the electron beam incidence means is provided in an extension part in the direction along the surface direction of the fluorescent surface, and the central axis of the band-shaped electron beam and the center of the deflection space coincide with each other. Flat plate cathode ray tube. 3. A flat plate cathode ray tube according to claim 1, wherein the electron beam incidence means is sequentially switched from the first voltage to the second voltage from the nearest deflection electrode to the farthest deflection electrode. 4. A flat plate cathode ray tube according to claim 1, wherein the second voltage is sequentially switched to the first voltage from the deflection electrode furthest to the nearest deflection electrode to the electron beam incidence means.