JPS59191239A - Projection type cathode-ray tube - Google Patents

Abstract

PURPOSE:To realize miniaturization of a projection television without deteriorating the brilliancy by disposing the deflection coils inside the cathode-ray tube and the core outside the tube and by establishing the potential of the internal conductive film within the active range of the deflecting field lower than the anode potential. CONSTITUTION:After winding the vertical deflection coils 54 and the horizontal deflection coils 55 in spiral form, the entire surfaces are covered by glass material in the vacuum for the purpose of preventing gas generation and improving the anti-potential characteristics between wires. Moreover, the length in Z direction is made short, at the same time the entire body is shifted towards the phosphor surface 3 side and the deflection center is shifted towards the front side. Outside the neck tube 7, a ferrite core 51 is disposed to improve the sensitivity of the deflecting magnetic field. By means of such a structure, the effective F number can be made small as the deflecting system shields the light flux passing through the lens 4 very little. Also, the anode potential is applied to the phosphor surface 3 and the 4th electrode 15 of an electron gun through the introducing entrance 10, and the deflection sensitivity is improved, as the internal conductive film 8, the nesa film 9 and the 3rd electrode 14 are applied with the lower potential than the anode potential.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a projection type cathode ray tube for enlarging and projecting television images etc. onto a screen by optical means. In order to realize large-screen televisions with projection type cathode ray tubes of 40 to 70 inches, currently a magnifying projection lens is placed in front of the plastic tube to enable the realization of projection televisions. The mainstream is a system that enlarges the image by about 7 to 15 times and projects it onto a screen. The reason for this is that it has become possible to design and manufacture an inexpensive and bright magnifying projection lens with a small F number, and that the overall configuration can be made relatively simple.

However, on the other hand, the volume of the main body of the set is currently not compact enough to be accepted by ordinary households, and there is a strong demand for compactness.

FIGS. 1 and 2 are schematic longitudinal sectional views showing conventional projection televisions, respectively. In these figures, 9
Reference numeral 1 represents a reflecting mirror, and reference numeral 92 represents a projection lens 93 representing a projection type cathode ray tube. Conventionally, as shown in FIGS. 1 and 2, the number and arrangement of reflecting mirrors 91 have been devised to achieve compactness. However, even this is not sufficient to meet the requirements (even if it were possible, as shown in Figure 2, as the number of reflecting mirrors increases,
A loss of 31 degrees was unavoidable.

[Purpose of the invention]

The purpose of the present invention is to improve the problems of the prior art described above,
To provide a projection type cathode ray tube that can realize a compact projection television without deteriorating brightness.

[Summary of the invention]

In order to achieve the above object, the present invention provides a projection type cathode ray tube in which the phosphor screen is a concave surface, the phosphor screen is a reflection type viewed from the beam incidence side, and the funnel portion forms a convex lens, and a deflection coil molded with a glass material is used. The core is placed inside the cathode ray tube and the core is placed outside the tube, and the internal conductive film of the cathode ray tube is divided, and the internal conductive film potential in the area covered by the deflection magnetic field is similar to the conductive film potential of the phosphor screen to which the anode voltage is applied. It is characterized by being set low.

FIG. 3 is a diagram illustrating the principle of the projection type cathode ray tube according to the present invention, in which the deflection yoke is particularly mounted outside the neck tube.

In FIG. 3, 1 is an electron gun, 2 is an electron beam, 3 is a fluorescent screen, 4 is a convex lens made of glass, 5 is a deflection yoke, and 6 is a convex lens made of glass.
is an aberration correction lens, 7 is a neck portion, 8 is an internal conductive film, 9
10 indicates a Nesa membrane, and 10 indicates a high pressure inlet. The light beam emitted from the phosphor screen 6 by the electron beam 2 passes through a convex lens 4 and an aberration correction lens 6, and forms an image on a screen (not shown). When this projection type cathode ray tube is used, the embedding of the projection television body into a compact structure is a basic element that determines the volume of the set. This is because the distance from the screen to the tip of the neck of the cathode ray tube can be made shorter by the total length of the cathode ray tube (= length from the phosphor screen to the tip of the neck) compared to previous models. Figure 4 shows a schematic vertical cross-sectional view of a set using the projection type cathode ray tube shown in Figure 3. The product of depth and height is reduced by approximately 20%.

However, as a practical matter, in the projection type cathode ray tube shown in FIG. It is not possible to display the 6 stars on the fluorescent screen. For this reason, the compactness, which is an original advantage, is significantly impaired.

This is because the distance from the fluorescent screen to the screen (TC'L)
) is shown as a rough approximation in the formula below.

TCL': rM xf - (11M: Projection magnification f: Lens system magnification In other words, as mentioned above, since the size of the Lascue cannot be increased, M will inevitably become large and the above formula f) 1''CL
It has no choice but to become larger. As an example of a solution to this problem, it is possible to increase the diameter of the tip of the convex lens 4 on the phosphor screen side, but the effective F number increases and the brightness decreases. Also, it is good to design the center of the deflection magnetic field formed by the deflection yoke 5 to be close to the phosphor screen side, but if designed in this way, the outer diameter of the deflection yoke 5 becomes large, and as a result of blocking the light flux, the lapsed I゛The number becomes large.

Therefore, it is necessary to devise a rounding method to improve these problems.

[Embodiments of the invention]

FIG. 5 is a schematic sectional view showing one embodiment of the present invention. In the figure, the same strange rocks are attached to those that have the same function as in Figure 3. Also, Fig. 6 shows A- in Fig. 5.
A' cross-sectional view is shown.

The major difference between FIG. 5 and FIG. 6 is that the deflection coil 54.
55, the contents of the entire neck tube 7 are installed, and the potential inside the cathode ray tube is divided by the funnel section 17. In other words, the anode voltage is applied to the fluorescent screen 3 through the inlet 10.
is applied to the fourth electrode 15 of the electron gun, and the internal conductive film 8,
A voltage lower than the anode voltage is applied to the Nesa membrane 9 and the third electrode 14 through the inlet 16. Also, the deflection coil 54
．． 55 (in the Z direction) is shortened, and at the same time, the entire structure is moved to the phosphor screen 39111, and the center of deflection is shifted to the front side. In this way, the desired raster size can be obtained without the electron beam 2 hitting the convex lens 4, which was a problem in FIG. The explanation will be given below.

Generally, when the electron beam 2 passes through a deflection magnetic field, it is subjected to a deflection action expressed by the following equation (deflection angle=θ).

k: Constant Le・L: Ampere turn i of the deflection coil, ,: Effective length of the deflection magnetic field in the Z direction Dm = Effective aperture E: Potential in the area affected by the deflection magnetic field, that is, the deflection angle θ is approximated! 1, D, , (
It can be seen that B is inversely proportional to. On the other hand, it is clear from a light railway perspective that the deflection center of the deflection coil is approximately at the center of the deflection coil. Therefore, in the present invention, in order to bring the center of deflection closer to the phosphor screen 3 side, 11. pm as much as possible
To compensate for this, Dl and Eb are slightly reduced and the deflection angle θ is
We are improving this. Below is the deflection coil 54゜5
Let's talk about 5.

The vertical deflection coil 54 and the horizontal deflection coil 55 are spirally wound as shown in FIG. 7, and then their entire surfaces are covered with a glass material 52 in a vacuum for the purpose of suppressing gas generation and improving line-to-line voltage resistance. . Furthermore, in order to maintain insulation from the internal conductive film 8, a cylindrical insulating glass 53 is inserted between the internal conductive film 8 and the deflection coils 54, 55, as shown in FIG.

Further, since the voltage applied to the internal conductive film 8 is not a high anode voltage as in the conventional case, sufficient breakdown voltage characteristics can be obtained with the above structure. A ferrite core 51 is arranged outside the neck tube 7 as shown in FIG. 5 in order to improve the sensitivity of the deflection magnetic field, and current is introduced into the deflection coil by the neck pin 18 of the neck tube 7.

Therefore, when the neck tube of the present invention is structured as described above, not only is the effective radius reduced, but also the diameter of the neck tube can be increased compared to the conventional one. There is also the benefit of improving focus.

However, as described above, the deflection coils 54 and 55 are molded with a glass material and are placed inside the neck tube in a vacuum, so the heat dissipation efficiency of the coils is relatively poor. Therefore, the deflection current generator is limited, and it becomes impossible to obtain the desired deflection angle shown by equation (2).

On the other hand, as is clear from Fig. 5, the potential CE) in the region affected by the deflection magnetic field is set to a potential p lower than the anode voltage, so the deflection sensitivity is improved from the relationship shown in equation (2). I understand that As a result, the deficiency in the deflection angle resulting from the above-mentioned limitations of the deflection current generator can be compensated for by lowering the internal potential of the neck tube of the present invention.

The relationship between the voltage E at the internal conductive film and the anode voltage E is preferably expressed by the following equation from the viewpoint of breakdown voltage characteristics and focus characteristics.

0.2≦E/E≦07 Also, because the potential gradient at the potential dividing portion of the funnel portion 17 causes the electron beam to be incident on the phosphor screen almost at right angles even in the periphery, there is also the advantage of improving the peripheral brightness.
Ru.

Furthermore, in FIG. 5, the anode voltage is applied to the phosphor screen and the fourth electrode, and the focus voltage is applied to the internal conductive film 8, the NESA film, and the third electrode 14, but the sixth electrode 14 is applied to the NESA film 9 and the internal conductive film. There is no problem even if a voltage different from 8 is supplied.

〔Effect of the invention〕

As described above, the present invention provides a projection type cathode ray tube that makes it possible to realize an extremely compact projection television without deteriorating the F-number.

[Brief explanation of the drawing]

Figures 1 and 2 are longitudinal sectional views showing conventional projection televisions, Figure 3 is a diagram explaining the principle of a projection type cathode ray tube according to the present invention, and Figure 4 is a projection type of the type shown in Figure 3. A schematic vertical sectional view of a set using a cathode ray tube, FIG. 5 is a schematic sectional view showing an embodiment of the present invention, FIG. 6 is a sectional view taken along line AA' in FIG. 5, and FIG. FIG. 3 is a perspective view of a deflection coil. Symbol Explanation 1......Electron gun 2...Electron beam 3...
...... Fluorescent screen 4 ...... Convex lens 5 ...... Deflection yoke 6 ...
......Aberration correction lens 7...
・Neck part 8 ・・・・・Inner conductive film 9 ・・・・Nesa membrane 10 ・・・・High pressure inlet 17 ・・・・...Funnel portion 51...Core 52...Glass material 56...Cylindrical insulating glass 54...
...Horizontal deflection coil 55...Vertical deflection coil Fig. 3 Fig. 1 Fig. 7 Fig. 2 Ward sheath 5 Fig. E Fig. 6

Claims (1)

[Claims] 1) The concave phosphor screen is a reflection type phosphor screen with the beam incident side serving as the image display surface, and in a projection type cathode ray tube in which a part of the funnel part forms a convex lens, the deflection □ coil is placed inside the cathode ray tube, and the core is placed outside the tube, and the internal conductive film of the cathode ray tube is divided, and the internal conductive film potential in the area covered by the deflection magnetic field is equal to the conductive film potential of the phosphor screen to which the anode voltage is applied. A projection type cathode ray tube characterized by a low beam angle.