JPH0523010B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an electron gun for color picture tubes, and particularly to an in-line electron gun for color picture tubes with improved focus characteristics.

[Background of the invention]

Generally, the main lens aperture of an electron gun for a color picture tube has a great influence on focus characteristics, and it is desirable to make the main lens aperture as large as possible in order to obtain suitable focus characteristics.

FIG. 1 is a cross-sectional configuration diagram of essential parts showing an example of a conventional bipotential focusing type in-line electron gun. In the figure, 1A, 1B, and 1C are cathodes that each emit three electron beams from the top surface, 2 is a first grid that controls the electron beams, and 3 is a cathode that emits three electron beams from the top surface.
4 is a second grid that accelerates the electron beam, and 4 is a lower third grid that focuses the electron beam.
2A, 2B, 2C, 3A, 3B, 3C and 4A, 4B, 4C are electron beam passage holes for three electron beams, respectively. 5 is the upper third grid, 6
is the fourth grid, and this upper third grid 5
and the fourth grid 6 are three aperture holes 5A, 5B, 5C and 6 provided opposite to each other on the bottom surface.
A, 6B, and 6C form three main lenses corresponding to three electron beams.

In this case, the operating voltage of the electron gun is OV for the first grid 2, about 700 V for the second grid 3, about 7 KV for the upper third grid 4 and lower third grid 5, and about 7 KV for the fourth grid 6. Approximately 25KV is applied.

In such an electron gun configuration, the three electron beams A, B, and C, each of which has its amount controlled by the signal potential applied to the three cathodes 1A, 1B, and 1C, are connected to the second grid 3. and lower third
After receiving a slight focusing effect by the brief focus lens formed between each hole facing the grid 4,
The respective main lenses formed by the upper third grid 5 and the fourth grid 6 receive a focusing action so that an image is formed on the fluorescent surface of a picture tube (not shown). At the same time, the electron beams A and C on both sides are tilted at an angle by known means to slightly eccentrically eccentrically the beam passing holes 6A and 6C of the fourth grid 6 outward with respect to the beam passing holes 5A and 5C of the upper third grid 5. A tilt of θ is given to make the three electron beams A, B, and C converge to one point. Therefore, it is impossible to use the same part for the upper third grid 5 and the fourth grid 6, and there is a problem that the number of types of parts increases. Furthermore, the assembly jig becomes complicated as it requires an eccentric core metal. Note that 7 is a convergence electrode.

In an electron gun configured in this way, the size of the image point on the fluorescent surface of the picture tube, that is, the focus characteristic, affects the sharpness of the image, so it is desirable to make it as small as possible. In order to improve focus characteristics, the aperture of the main lens is generally increased.

FIG. 2 is a plan view of essential parts showing the upper surface of the third upper grid 5. As shown in FIG. In the figure, three electron beam passing holes 5A, 5B, and 5C each having a diameter D are arranged in a straight line with an interval S between them.
As a means of improving focus characteristics, it is necessary to increase the diameter D of the electron beam passage holes 5A, 5B, and 5C in order to enlarge the main lens aperture. However, the electron beam passing holes 5A, 5B of the upper third grid 5 are formed by pressing a non-magnetic metal such as a stainless steel plate with a thickness of about 0.3 mm.
5C needs to have an aperture hole structure in order to improve the withstand voltage characteristics with the fourth grid 6 shown in FIG. Furthermore, in order to prevent deterioration of the rotational symmetry of the main lens electric field, the aperture depth l must be at least 1/2 of the diameter D of the hole.
Restricted to 0.8~1.0mm smaller dimensions. In addition, increasing the hole spacing S increases the convergence error at each point on the phosphor surface during operation of the picture tube, and also increases the horizontal direction between the upper third grid 5 and the fourth grid 6 that form the main lens. There was a problem in that as the dimension L increased, the voltage resistance characteristics deteriorated as the electron gun came close to the inner wall of the valve neck in which the electron gun was housed.

Furthermore, in order to obtain good focus characteristics, it is said that the roundness error (major axis - minor axis) of the electron beam passing holes 5A, 5B, 5C, etc. is desirably about 0.5% or less of the hole diameter D. Therefore, to assemble the electron gun, each electrode component is held on a jig (not shown) equipped with three core metals passing through each electron beam passage hole, and the heated multiform glass 8 is attached to the support 9. It is done by crimping. In this case, the three core metals have errors in the hole pitch S and hole diameter D of each electrode component, so
The hole diameter is set to be approximately 0.02 to 0.03 mm smaller than the hole diameter D.
Therefore, the deformation of the cup-shaped body due to errors in manufacturing each electrode component and stress during pressure bonding of the multiform glass 8 spreads to the electron beam passage holes 5A, 5B, and 5C formed by the aperture holes, and is cured. The roundness error measured when removed from the tool is approximately 0.05 mm in extreme cases, or approximately 1.3% when hole diameter D = 3.9 mm.
may reach. This reduction in roundness distorts the electric field of the main lens, causing astigmatism in the electron beam, resulting in a serious drawback in that focus characteristics are impaired.

[Purpose of the invention]

Therefore, the present invention has been made in view of the various drawbacks of the prior art described above, and its purpose is to reduce or eliminate the aforementioned side effects, expand the main lens aperture, and improve the efficiency of electron guns. An object of the present invention is to provide an electron gun for a color picture tube with improved assembly accuracy and improved focus characteristics.

[Summary of the invention]

In order to achieve such an object, the present invention provides a main lens-forming electrode for electron beam focusing, in which oblong thick plates each having three electron beam passing holes arranged in-line in the major axis direction are arranged facing each other with an interval. , the electron beam passing holes on both sides are semicircular in the outward direction, and the inward direction is an irregularly shaped hole in which semi-ovals are connected with the major axis in the short axis direction of the oval thick plate, and the central electron beam passing hole is in the oval thickness. The short axis direction of the plate is an elliptical hole with the long axis direction, and each electron beam passing hole has a wide gap with the counter electrode, leaving a peripheral edge of the oval thick plate at the short diameter part of the adjacent electron beam passing hole. A groove is formed on the bottom surface of each electrode, and the electron beam is focused on both sides of the electron lens between the second grid and the third grid by decentering the electron lens associated with the electron beam. It is.

[Embodiments of the invention]

Next, embodiments of the present invention will be described in detail using the drawings.

FIG. 3a is a plan view of a main part of an upper third grid constituting a main lens showing an embodiment of an electron gun for a color picture tube according to the present invention. In the same figure, the upper third grid 50 is composed of an oblong plate with a thickness of about 2 mm, and the central electron beam passage hole 50B is an elliptical hole with a major axis Dl and a minor axis Ds, and electron beam passage holes 50A on both sides. and 50C each have a radius on the outside
The hole is a semicircle of Dl/2, and the inner side is a concatenation of half ellipses of the same size as the central hole 50B, and the centers of each hole are arranged at an interval S. By making the short axis direction of the elliptical upper third grid 50 the long axis direction of the electron beam passage holes, the long axis Dl can be made larger than the hole pitch S. Also, unlike conventional aperture holes, the electron beam passing holes 50A, 50
The dimensions of the bridge between B and 50C and the dimensions of the holes 50A and 50C on both sides and the major diameter end of the outside are also approximately
Since it can be made as small as 0.5 mm, there is no need to increase the horizontal dimension L. Further, electron beam passing holes 50A, 50B forming the main lens,
By forming 50C into an elliptical shape and a hole having different diameters in which a semicircle and a semiellipse are connected, astigmatism occurs in which each electron beam is strongly focused in the minor axis direction. For this correction, as shown in the cross-sectional view of FIG. 3a in FIG. 3b, the central electron beam passing hole 50 is
Electron beam passing holes 50A, 5 on both sides from the center of B
The major axis Dl and the minor axis h over the range of the center of 0C
An elliptical groove 50D is provided.

FIG. 4 shows a main lens according to the present invention in which a fourth grid 60 having the same structure as the upper third grid 50 is disposed opposite to each other, and both sides of an electron lens formed between the second grid 30 and the lower third grid 40. This is a cross-sectional view of a main part of an electron gun that combines an electron beam concentration method in which an electron lens related to the electron beam is decentered. In the figure, the aperture of the main lens is determined by the elliptical grooves 50D and 60D because the distance between the short diameter sides of the electron beam passage holes 50A to 50C and 60A to 60C is widened by the elliptical grooves 50D and 60D.
By selecting the depth h of D and 60D to appropriate values, a substantially rotationally symmetrical electric field is formed in the main lens aperture in the range through which the electron beam passes, corresponding to the major axis Dl.

In FIG. 4, the electron gun consists of an upper third grid 50 and a fourth grid 60.
There is a limit of approximately 2 mm to the plate thickness for punching 0A to 50C and 60A to 60C with high precision, so the hole diameter is approximately 4 mm.
If the thickness is more than 1/2 mm, the thickness of about 1/2 or more cannot be satisfied, so the holes 50A to 50C of the upper third grid 50 and the holes 60 of the fourth grid 60 are
Auxiliary electrode 5 with only punched holes equivalent to A to 60C
Supports 52 and 62 are stacked on the back surfaces of 1 and 61.

According to such a configuration, the mechanical strength of the main lens constituent electrode is strengthened, so that the shape of the hole will not be deformed even by stress caused by pressure bonding of the multiform glass during assembly of the electron gun. Therefore, the main lens aperture is equivalently enlarged, variations are extremely small because the same parts are used, and assembly accuracy is improved, making it possible to obtain an electron gun with improved focus characteristics. .

In addition, the convergence of the electron beams on both sides is
As shown in FIG. 5, the -' cross _section in FIG. Hole 40A, 40
The electron beam passing hole 20 is made by increasing the hole spacing _S2 of C.
A, 30A and 20C, 30C are eccentrically set to the outside to give an inclination angle of θ.

Figure 6 shows the holes 40 on both sides of the lower third grid 40'.
Although A' and 40C' are formed as horizontally elongated holes, electron beams on both sides can be converged similarly.

In addition, if there is a difference in the shape of the central electron beam B and the electron beams A and C on both sides, the short diameter of the central elliptical holes 50B and 60B of the upper third grid 50 and the fourth grid 60, as shown in FIG. The three electron beams can be adjusted to be round by selecting appropriate values for Ds and the minor axis Ds'/2 of the inner half-ellipse of the holes 50A, 50C, 60A, and 60C on both sides.

In addition, in order to avoid deterioration of the image quality around the fluorescent surface due to the electron beam shape being collapsed into a horizontally long shape around the fluorescent surface due to deflection aberration, the upper third grid 500 sets the electron beam shape to be vertically long in advance.
Another embodiment is shown in FIG. In the same figure, the holes 500A and 500C on both sides have a major axis Dl, and the outside has a larger short axis than the inside.The central hole 500B is an elliptical hole with a major axis Dl. By providing an elliptical groove as in FIG. 3b, the three electron beams can be adjusted to be round.

In the above-described embodiment, the cross-sectional shape of the groove for correcting astigmatism is semi-elliptical, but it may also be formed with a plurality of curved lines and straight lines that approximate an ellipse, as shown in the cross-section in FIG. Rectangular groove shape 50
Almost the same effect can be obtained with 0D'.

In recent years, the diameter of the neck tube of color picture tubes has become smaller in order to reduce the deflection power, and as the electron gun housed inside the tube has become smaller, the diameter of the main lens has become smaller and the focus characteristics have deteriorated. , there is an extremely high demand for its improvement. For this reason, the diameter of the nets currently produced is approximately 22.5 mm.
The main lens dimensions of the electron gun are hole pitch S = 4.75mm,
The hole diameter D = 3.9 mm, but in the main lens of the present invention, the upper third grid 50 and the anode 60 have hole pitch S = 4.50 mm, major axis Dl = 5.0 mm, and minor axis Ds = 4.0.
mm, groove depth h=1.2mm and equivalent main lens aperture is 5.0
mm, which is approximately 1.3 times larger than that of a conventional electron gun, has improved the focus characteristics to approximately the same as a color picture tube with a large net diameter of approximately 29 mm.

In the above embodiments, a bipotential focusing electron gun has been described, but the present invention is not limited thereto, and may be applied to the main lens forming electrode of an electron gun such as a unipotential type or a multistage focusing electron gun. Of course, even if applied, the same effect as described above can be obtained.

〔Effect of the invention〕

As explained above, according to the electron gun for color picture tube according to the present invention, the main lens aperture can be enlarged without problems in electrode processing or side effects such as withstand voltage characteristics, so that the focus can be improved. It has an extremely excellent effect of improving characteristics and producing images with high sharpness.

[Brief explanation of drawings]

Figure 1 is a sectional view of the main parts showing the structure and operating state of a conventional in-line electron gun, Figure 2 is a plan view of the main parts showing the conventional upper third grid, and Figures 3a and b.
4 is a plan view of a main part showing the upper third grid of the electron gun for a color picture tube according to the present invention, and a cross-sectional view of the main part thereof. FIG. 5 and 6 are plan views of main parts for explaining the electron beam concentration method combined with the electron gun according to the present invention, and FIG.
FIG. 8 is a plan view of essential parts showing another embodiment of the upper third grid of the electron gun according to the present invention, and FIG. 8 is a sectional view of essential parts showing another embodiment of the upper third grid of the electron gun according to the present invention. be. 20...First grid, 20A, 20B, 20
C... Electron beam passing hole, 30... Second grid, 30A, 30B, 30C... Electron beam passing hole, 40... Lower third grid, 40A, 40
A', 40B, 40B', 40C, 40C'...Electron beam passing hole, 50...Third upper grid, 50
A, 50B, 50C...Electron beam passing hole, 50
D... Groove, 500, 500'... Upper third grid, 500A, 500B, 500C... Electron beam passing hole, 500D, 500D'... Groove.

Claims (1)

[Scope of Claims] 1. An in-line type electronic device in which a plurality of grids each having three electron beam passing holes arranged in-line are arranged in the tube axis direction and an electron lens is formed by each of the opposing electron beam passing holes. In a color picture tube equipped with a gun, the grid forming the electron lens has a plurality of oval thick plate electrodes arranged facing each other at intervals, and the electron beam passing hole in the center of the oval thick plate electrode is An elliptical hole whose major axis is the short axis direction of the oval thick plate, and each of the electron beam passing holes on both sides is a semi-ellipse whose long axis is the short axis direction of the oval thick plate in the inner direction, and the semi-ellipse in the outer direction. The irregularly shaped holes are made larger than the short axis of the adjacent electron beam passing hole and are connected so that the distance between each electron beam passing hole and the opposing electrode is widened by leaving the peripheral edge of the oval thick plate at the short axis of the adjacent electron beam passing hole. A color picture tube characterized by being equipped with an in-line electron gun configured as follows. 2. The color image receiving device according to claim 1, wherein grooves are formed on opposing sides of a plurality of oblong thick plate electrodes arranged at intervals in the electron lens forming grid. tube. 3. The color picture tube according to claim 1, wherein the groove is deepest in the central portion of the oval thick plate in the short axis direction thereof. 4. The in-line electron gun includes at least a first grid and a second grid having three electron beam passing holes.
The grid and the third grid are arranged sequentially in the tube axis direction, and the electron beam passing holes on both sides of the third grid are
From the electron beam passing holes on both sides of the second grid,
2. The color picture tube according to claim 1, wherein the color picture tube is eccentric to the outside. 5 The distance from the center of the main lens that converges the electron beams on both sides to the center of the main lens that converges the central electron beam is smaller than the distance from the center of the hole at the center of the second grid to the center of the holes on both sides. A color picture tube according to claim 1, characterized in that: