JPH0439651Y2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Field of Industrial Application The present invention relates to a flat cathode ray tube suitable for use in small, flat-screen television receivers.

(b) Prior art In general, cathode ray tubes used in television receivers, etc. have an electron gun mounted on an axis perpendicular to the phosphor surface, and irradiate the phosphor surface with an electron beam through a metal backing film. scanning. Therefore, the head of the cathode ray tube has become larger, and the depth has been longer, so the receiver itself, which is approximately determined by the area of the cathode ray tube's fluorescent surface and its depth, which differs in capacity, has also become larger, resulting in a small and thin television receiver. This has become a major problem when doing so.

For this reason, a flat cathode ray tube in which the phosphor surface is inclined with respect to the central axis of the electron beam to flatten the cathode ray tube is described in Japanese Patent Publication No. 1973-5294, and the following documents are described in this document. The flat type cathode ray tube will be explained below.

Figure 2 shows the cross-sectional structure of a flat cathode ray tube, where 1 is a flat glass tube body, 2 is a neck portion 3
4 is a deflection coil provided in the neck portion 3; 5 is an anode cap; 6 is a conductive coating layer; 7 is a fluorescent surface provided inside the conductive coating layer 6; Yes, the fluorescent surface 7 emits an electron beam 8
The central axis 8' (beam central axis when not deflected) is inclined with respect to the central axis of the neck portion 3,
The image reproduced on the fluorescent surface 7 is displayed on the viewing panel section 9.
It is something that is observed through.

In the case of a cathode ray tube constructed as described above, the electron beam produces a trapezoidal raster as shown by crosshatching in FIG. 3 due to electromagnetic deflection by the deflection coil 4. It can be easily corrected to a rectangular raster using a deflection current waveform, a correction magnet, etc. Furthermore, 1
0 is a centering magnet, which is used to align the center of the electron beam with the center of the fluorescent surface.

Next, a conventional phosphor surface shape in a flat cathode ray tube as described above will be explained.

In Fig. 4, A is the main lens position of the electron gun;
B is the center of deflection, and C and D are both ends of the fluorescent surface 7, respectively. Now, if we draw a circle a passing through points B, C, and D (center I), and let the intersection of this circle a and the perpendicular bisector of the line segment CD be J K, then a line segment JC with point J as the center is drawn.
An arc CD having a radius of (or JD) is drawn, and this arc CD, P is the vertical cross-sectional shape of the fluorescent surface 7.

Now, assuming that the difference in spot diameter due to the difference in travel distance of the electron beam is small, in order to obtain the same resolution at both ends C and D of the fluorescent surface 6, the beam incidence angles must be equal at CD. .

By the way, the arc CD⌒ at points C and D in Figure 4,
If the tangents to P are T and T', respectively, C,
The incident angle of the electron beam at point D is ∠
BCT.∠BDT′.

However, ∠BCT=90°−∠BCJ ∠BDT=90°−∠BDJ Also, since ∠BCJ=∠BDJ ∠BCT＝∠BDT′ becomes.

Therefore, the beam incidence angles at both ends C and D of the fluorescent surface 7 are equal, and the resolution of the fluorescent surface can be made substantially equal.

However, the resolution on the fluorescent surface becomes approximately equal only when the difference in spot diameter due to the difference in the traveling distance of the electron beam is small; Therefore, the spot diameters differ. Therefore, with the fluorescent surface of the shape described above, in a flat cathode ray tube equipped with a general electron gun,
It is difficult to make the differences in local resolution on the fluorescent surface approximately equal.

(c) Problems to be solved by the invention The invention aims to reduce as much as possible the difference in resolution caused by the change in beam spot diameter due to the difference in travel distance of the electron beam.

(d) Means for solving the problem The present invention tilts the phosphor surface with respect to the central axis of the electron beam, and makes the cross-sectional shape of the phosphor surface perpendicular to the phosphor surface and including the central axis of the electron beam. , the point farthest from the fluorescent surface among the intersections of the perpendicular bisector of the line connecting both ends of the fluorescent surface with the circle passing through the three points, both ends of the cross section of the fluorescent surface and the center of deflection, and the three points mentioned above. A point located at a predetermined position excluding the farthest point and the center of the circle on the line connecting the center of the circle passing through, and a length connecting the point located at the predetermined position and one end of the fluorescent surface. It is an arc whose radius is .

(e) Effect With the above configuration, changes in beam spot diameter due to differences in travel distance of the electron beam can be minimized as much as possible.

(F) Embodiment An embodiment of the present invention will be described below with reference to FIG. 1 for explaining the vertical cross-sectional shape of the fluorescent surface of a flat cathode ray tube. and FIG. 3, so the explanation thereof will be omitted.
In FIG. 1, the same parts as in FIG. 4 are given the same reference numerals.

The beam travel distances at points C and D, which correspond to the ends of the fluorescent surface, are + and +, respectively, and +<+, so the beam spot diameter at point C is smaller than that at point D. This is clear from the gun's magnification.

Therefore, in the present invention, an arc CD⌒ (this arc CD⌒ is assumed to be q) is drawn with the point L on the line segment JI as the center and the radius as LC (or LD). If this arc q is the cross-sectional shape of the fluorescent surface 7 in FIG. 2, and the tangents to the arc q at points C and D are U and U', then C
The incident angles of the electron beam at point and point D are respectively ∠BCU.∠BDU'.

However, ∠BCU=90°−∠BCJ−∠LCJ ∠BDU′=90°−∠BDJ+∠LDJ Also, ∠LCJ=∠LDJ ∠BDJ＝∠BCJ And 90°−∠BCJ=ψ ∠LCJ=θ Then, ∠BCU=ψ−θ ∠BDU′=ψ+θ becomes.

That is, ∠BCU<∠BDU', and if the above circular arc q is the fluorescent surface, the incident angle of the point C where the beam travel distance is the minimum on the fluorescent surface CD is the point D where the beam travels the maximum distance.
is smaller than the angle of incidence of Therefore, depending on the characteristics of the focal vibration of the electron gun, ∠LCJ (or ∠LDJ)
change. That is, by appropriately selecting the position of point L on the perpendicular bisector JI of line segment CD, the angle of incidence at both ends of the fluorescent surface can be increased or decreased equally, and the resolution of the fluorescent surface can be made approximately equal. be able to.

For example, in the case of an electron gun in which the beam spot diameter is proportional to the beam travel distance, when the beam incidence angle is constant over the entire fluorescent surface, the resolution ratio at points C and D is mainly determined by the beam travel distance.
AB + BD / AB + BC. Conversely, if the beam spot diameter is assumed to be constant depending on the beam travel distance, C
The ratio of the resolutions at points C and D is sin(ψ-θ)/sin(ψ+θ) from the angle of incidence of the beam on the fluorescent surface (arc q). Therefore, to make the resolutions at points C and D equal, θ
The following condition must be satisfied:

AB+BD/AB+BC・sin(ψ+θ)/sin(ψ−θ)=1
...(1) In other words, when calculating θ that satisfies equation (1), θ=
Since ∠LCJ, point L can be uniquely determined, and if the fluorescent surface is an arc with radius of LC (or LD) centered on point L, a fluorescent surface with approximately equal resolution can be obtained. .

(g) Effects of the invention According to the invention, differences in resolution caused by changes in beam spot diameter due to differences in travel distance of electron beams can be minimized as much as possible.

[Brief explanation of the drawing]

Fig. 1 is a diagram for explaining the shape of the fluorescent surface of the cathode ray tube of the present invention, Fig. 2 is a cross-sectional view of a flat cathode ray tube, Fig. 3 is a plan view of the same, and Fig. 4 is a conventional cathode ray tube. FIG. 2 is a diagram for explaining the shape of a fluorescent surface. 3...Network part, 7...fluorescent surface, 8...electron beam.

Claims (1)

[Scope of utility model registration request] The fluorescent surface is tilted with respect to the central axis of the electron beam, and the shape of the cross section of the fluorescent surface that is perpendicular to the fluorescent surface and includes the center axis of the electron beam is determined at three points: both ends of the cross section of the fluorescent surface and the center of deflection. Among the points of intersection between the circle passing through and the perpendicular bisector of the line connecting both ends of the fluorescent surface, the farthest point on the line connecting the center of the circle passing through the three points above and the point that is farthest from the fluorescent surface. A flat cathode ray tube whose center is a point at a predetermined position excluding the center of the circle and whose radius is the length connecting the point at the predetermined position and one end of the fluorescent surface.