JPH0430704B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an in-line integrated electron gun assembly, and more particularly to improving focus characteristics.

[Conventional technology and its problems]

The deflection magnetic field of a color cathode ray tube using an in-line electron gun consists of a horizontal deflection magnetic field, a pink tension magnetic field,
Because a nonuniform magnetic field using a barrel magnetic field is used for the vertical deflection magnetic field, it is known that a beam spot that is perfectly circular in the center of the screen becomes laterally collapsed when moved to the periphery of the screen. .

This will be explained according to the diagram. Figure 1 shows an example of a conventional electron gun.The auxiliary electrodes 5 and 8 arranged inside the G3 and G4 electrodes in Figure 1 have the function of correcting astigmatism, and the main lens formed also , a nearly axisymmetric magnetic field is formed. For this reason, the electron beam that is imaged on the screen has an almost perfect circular shape with no distortion, so when this electron beam is deflected toward the periphery of the screen, it becomes horizontally crushed due to the influence of deflection aberration. This causes a deterioration of the focus level. This is a fatal drawback, especially in high-resolution tubes that require full focus. To prevent focus deterioration in the periphery of the screen due to horizontal beam collapse, shaping the beam spot in the center of the screen into a vertically elongated shape will greatly reduce horizontal beam collapse when the beam is deflected to the periphery of the screen. This makes it possible to prevent focus deterioration in the peripheral area of the screen.

In order to increase the number of display dots and vertical resolution in color display tubes, raster scan systems require an increase in the number of scan lines. For example, to form 600 scan lines without interlacing at a frame frequency of 60Hz, the horizontal operating frequency would be 36KHz. Further, the video signal frequency at this time is approximately 30MHz. In order to increase the resolution by increasing the horizontal frequency in this way, it is necessary to increase the video signal frequency band, which is becoming difficult in terms of circuit design and cost.

The easiest way to solve this problem is to lower the frame frequency, but if this is done, flicker will appear due to the afterglow characteristics of the phosphor. In current color TV picture tubes, the afterglow properties of the red, blue, and green phosphors are all several hundred microseconds, and flickering can be prevented at a frame frequency of 60Hz. In order to solve the above problem, phosphors with long afterglow properties have come to be used to solve the problem of flicker development. However, a phosphor with a long afterglow property has a lower luminous efficiency than a phosphor with a short afterglow property, and in order to obtain the same brightness, the cathode current per single electron gun must be increased. The current value required to obtain a specified brightness is I _s when using a phosphor with short afterglow property, and I _L when using a phosphor with long afterglow property, then I _s < I _L There is a relationship between For this reason, the focus characteristic deteriorates due to the increase in current, which is disadvantageous when the same electron gun is used with a display tube using a short afterglow phosphor. Also, red,
It is not always the case that phosphors with the same afterglow properties are used for all three colors, such as green and blue, but the afterglow properties and luminous efficiency are usually different for each of the three colors. Therefore, the current ratio of the three electron guns to obtain a predetermined brightness differs depending on the phosphor used, and also differs between the three colors.

In the past, various methods have been proposed in which the beam shape at the center of the screen is modified to be slightly elongated in order to obtain uniformity of focus characteristics across the screen, but all of these methods require almost the same current for the three colors. The major prerequisite is to use it. However, in display tubes using phosphors with long afterglow properties, the current ratio used differs for each of the three colors red, green, and blue, resulting in differences in the focus characteristics of the three colors. The current ratio used may be more than double the maximum current value and the minimum current value.

[Means to solve the problem]

In order to make the beam spot imaged at the center of the screen vertically elongated and to make the focus characteristics of the entire screen uniform, the present invention provides an electron gun for use in a color display tube that uses different current ratios for each of the three colors. In order to obtain the optimum focus condition with the current value, the distance from the main lens facing surface of the auxiliary electrode, which has a hole diameter different from the main lens hole diameter and is placed inside the main lens constituent electrode, is determined by the current value of each of the three colors. It is characterized in that it is determined to be in an optimal focus state. This makes it possible to provide a color display tube with uniform focus characteristics.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 2 is a cross-sectional view perpendicular to the in-line surface of an in-line integrated electron gun assembly showing one embodiment of the present invention, and FIG. 3 is a cross-sectional view including the in-line surface. Furthermore, what is an in-line integrated electron gun structure?
It is an integrated system in which red, blue, and green electron guns are arranged in-line. In order to make the electron beam imaged on the screen into a vertically elongated shape and to prevent the influence of this deflection aberration, the G3 electrode 16 and the G4 electrode 17 that constitute the main lens are integrated inside, as shown in Fig. 2. Electron beam passing hole diameter φ _S of auxiliary electrodes 15 and 18
is smaller than the main lens hole diameter φ _M , and as shown in Figure 3, the distance from the tip of the main lens opening of the three red, blue, and green electron guns to the tip of the integrated auxiliary electrode.
By adjusting L _G for each electron gun so as to obtain the optimum focus characteristic, the aspect ratio of the electron beam formed on the screen is adjusted. When the range of L _G is changed within the range of 0≦L _G ≦φ _M , the aspect ratio of the beam spot imaged on the screen is changed to 1.
It becomes possible to change it within the range of ~3. In addition, in the figure, 11 is a cathode, 12 is a G1 electrode,
13 is the G2 electrode.

In the present invention, in a color display tube electron gun that uses different current values for three colors, taking advantage of the above characteristics, each L _G is adjusted so that the optimum focus state can be obtained at the current value corresponding to each of the three colors. Using the method described above, for each of the three color electron guns,
By selecting L _G , even if the current values differ among the three colors, it is possible to set the optimum focus state corresponding to each current value.

〔Effect of the invention〕

If this method according to the present invention is used, it is possible to easily change the vertical length of the electron beam that is imaged on the screen by simply changing L _G , so the range of application is extremely wide. Further, since the main lens constituent electrode openings and the auxiliary electrodes 15 and 18 openings are circular in shape, the parts can be manufactured easily.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a conventional in-line electron gun equipped with an auxiliary electrode arranged inside the main lens constituent electrode to correct astigmatism of the beam spot, and Fig. 2 is an embodiment of the present invention. FIG. 3 is a cross-sectional view perpendicular to the in-line plane of an in-line electron gun with an auxiliary electrode according to an example; FIG. 3 is a cross-sectional view including the in-line plane; 1, 11... cathode, 2, 12... G1 electrode, 3,
13...G2 electrode, 6,16...G3 electrode, 7,1
7... G4 electrode, 5, 8... Conventionally used integrated auxiliary electrode for astigmatism correction, 15, 1
8... Integrated auxiliary electrode provided to correct the beam spot imaged on the screen into a vertically elongated shape, 9, 19... Equipotential lines.

Claims (1)

[Claims] 1 Inside each of the pair of electrodes that make up the main lens part, auxiliary electrodes are provided inside the electrodes in red, blue, and green, at positions that are set back by L _G from the surface facing the main lens into the electrodes for the purpose of correcting astigmatism. In an in-line integrated electron gun structure in which three electron guns are arranged in-line, the electron beam passing hole diameter of the electrode constituting the main lens is φ _M , and the hole diameter of the auxiliary electrode is φ _S
, the relationship φ _S < φ _M is satisfied, and the value of L _G for each electron gun is different for each electron gun so that the optimum focus characteristic can be obtained at a given current value used. In-line integrated electron gun structure.