JPH03250541A - Projection type cathode-ray tube - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a projection cathode ray tube, and particularly to the shape of a panel and funnel constituting a glass bulb.

[Prior Art] Projection displays obtain images by enlarging and projecting the light emitted from a cathode ray tube with a relatively small phosphor screen onto a relatively large screen through an adjacent optical lens system. High-intensity light output is desired, and various improvements have been made. Among these, an example is known in which the inner curved surface of the panel is a curved surface that is convex toward the funnel side (Japanese Patent Laid-Open No. 61-273837). This is because the light emitted from the phosphor screen has a cosine distribution according to Lambert's law, so by making the curved surface inside the panel convex toward the funnel side, the normal line at any point on the phosphor screen can be adjusted to the direction of the optical lens system. By crossing the optical axis, the amount of light sent to the optical system increases. In addition, the concave lens in the optical lens system, which is located just in front of the cathode ray tube, corrects the image curvature that occurs because the screen is usually flat, but as the screen becomes larger, this adjustment becomes less possible. , making the inner curved surface of the panel convex toward the funnel side means that
known to be effective. In this case, the convex inner curved surface is not limited to a spherical surface, and may be an aspherical surface that deviates from a spherical surface according to a certain rule. FIG. 2 shows an example of the conventional structure and optical system of a projection cathode ray tube using a panel having a convex curved surface on the funnel side. The glass bulb 1 is composed of a panel 2 having a convex inner curved surface 5, a funnel 3 welded to this panel at the sealing surface, and a neck 4 welded to the smaller diameter side of the funnel opposite to the panel. When the electron gun 40 is sealed to this neck, the pressure inside the glass bulb is reduced to create a vacuum.

The shape of the panel generally has an outer surrounding part called a skirt part 13, as shown in FIG. This is because the molten glass is highly efficient (for press molding, and because it has a shape suitable for withstanding the pressure difference between the inside and outside of the cathode ray tube. For this reason, the sealing surface 9 is generally the inner curved surface 5 of the panel. It is located far away from the funnel and on the same plane perpendicular to the tube axis lO.

Further, the effective light emitting surface 7 corresponding to the range obtained as an image on the projection display is approximately rectangular as shown in FIG. 4, and its aspect ratio is generally from 1:1 to 9:16. By making the contour of the sealing surface 9 substantially similar to this, the volume of the cathode ray tube can be minimized in response to the miniaturization of projection display devices.

However, the curvature accuracy of the inner curved surface of a panel made by pressure molding method etc. is 50 to 200 μm, and it is difficult to achieve the same accuracy as an optical lens. Therefore, the necessary curvature accuracy can be obtained by mechanically polishing the inner curved surface 5 of the panel, but since the sealing surface 9 is placed close to the effective light emitting surface 7, the polishing jig may hit the skirt portion 13. Therefore, in order to sufficiently polish the entire effective light emitting surface, the skirt portion must be significantly separated from the effective light emitting surface, which significantly increases the volume of the cathode ray tube. The example shown in Figure 2 has been proposed.The difference from the example in Figure 2 is that
The outer surrounding part is not a skirt shape, and the sealing surface 9 is an inner curved surface 5.
It consists of a flange part 14 provided so as not to protrude to the funnel side from the curved surface extending from the curved surface, and the side wall part of the funnel is extended by that much to the panel flange part.

As a result, sufficient curvature accuracy can be obtained by mechanically polishing the inner curved surface of the panel.

In a projection cathode ray tube having a skirt portion, as shown in the example shown in Figure 2, the operation for joining the panel and funnel is a welding operation in which the sealing surfaces of both sides and their vicinity are directly melted with flame. However, in the case of the example shown in Fig. 3, the flame reaches the face 8 of the panel 2 or the effective diameter end 7-a of the inner curved surface, making the surface uneven. The process is called frit sealing, which is used in cathode ray tubes such as color televisions.

Frit sealing involves applying a frit (powdered glass) in the form of a highly viscous slurry to the arrival surface of the funnel and overlapping it with the arrival surface of the panel, thereby melting only the powdered glass without affecting the glass in the panel or funnel. This is an operation to join the sealing surfaces by melting at a temperature of do.

[Problems to be Solved by the Invention] When frit sealing is performed in the example shown in FIG. 3, the shape of the frit protruding portion becomes as shown in FIGS. 7(A) and CB) depending on the shape of the flange portion of the panel. .

When d in Fig. 7(A) is small, Fig. 7(C
), the frit protrusion 11 comes into contact with the side wall 15 of the step, and during the process of reducing the pressure inside the glass bulb to vacuum, stress concentration occurs at this contact area, and the glass bulb cannot withstand the pressure difference between the inside and outside. It may be destroyed. Similarly, θ(0"〈θ〈90°
) is small, as shown in FIG. 7 (DJ), the part of the frit protrusion 11 that is not in contact with the bulb becomes sharp, and the glass bulb may break due to stress concentration in this part. Importantly, in order to prevent the aforementioned stress concentration, it is necessary to avoid contact with the stepped sidewalls or sharpening of the protrusions over the entire contour of the sealing surface; however, this depends on the flatness of the arrival surface. It is also influenced by
If the gap formed when the two sealing surfaces are overlapped is large, the frit will protrude less (and the part with no gap will protrude more).
This is to become. Including this factor, d in the case of FIG. 7(A) needs to be 4 mm or more. In addition, the probability that the glass bulb will break in the case of Fig. 7 (B) is 80% when θ is 45°, 30% when 55°, and 5% when 60'. ° or more is desirable.

By the way, the shape of the flange portion shown in FIG. 7 is also restricted by the following conditions. The flange wall thickness t must be at least the minimum thickness determined from the guarantee that X-rays generated from the phosphor will not leak to the outside of the glass bulb and the pressure resistance. It should not protrude beyond the extension surface of the inner curved surface 5 toward the funnel side.

If the desirable values of d and θ mentioned above are adopted, the outer diameter of the panel will increase, which goes against the idea of minimizing the volume of the cathode ray tube, but it is necessary to consider the flange wall thickness and mechanical polishing conditions. In some cases, depending on how the wall thickness of the central part of the panel and the radius of curvature are selected, inconsistencies may occur, such as the absence of a shape that satisfies these conditions.

The present invention solves the above-mentioned inconsistencies in the prior art, and creates a projection shape that provides sufficient optical curvature accuracy of the panel's inner curved surface, maintains a pressure-resistant structure, and minimizes the volume of the cathode ray tube. Our goal is to provide anode ray tubes.

[Means for Solving the Problems] The present invention provides a panel in which the entire inner surface on the funnel side is a convex curved surface, and a sealing portion corresponding to the peripheral edge of the curved surface of the panel has a shape that corresponds to the peripheral edge. The present invention provides a projection type anode ray tube comprising a funnel having a curved shape so as to be brought into close contact with the projection type anode ray tube.

Here, the face surface of the panel is not only a flat surface but also a convex curved surface,
The shape may be a concave curved surface or the like.

[Example] Next, embodiments of the present invention will be described using the drawings.

FIG. 1 is a side sectional view of the maximum diameter of a projection type anode ray tube showing an embodiment of the present invention. The glass bulb 1 has a phosphor screen 6 on an outer flat face 8 and a convex inner curved surface 5.
A panel 2 having a diameter of 100 mm and a funnel 3 having a neck 4 welded to its small diameter side are frit-sealed with a sealing surface 9 on a curved surface, and an electron gun 40 is sealed on the open end side inside the neck 4. It consists of:

The phosphor screen 6 is formed on the inner curved surface 5 of the panel using a coating technique such as a slurry method or a precipitation method. This prevents the negative influence of the end effect at the effective end 7-a, which is the outline of the effective light emitting surface. In the conventional technology, the sealing surface between the panel and the funnel is almost an exception (
Although they were on the same plane, the feature of this example is that by providing this sealing surface on a curved surface, the panel does not require an outer enclosure, and the shape of the sealing surface of the funnel is curved. This brings about the following three advantages.

The first is that the curvature accuracy can be improved by mechanically polishing the inner curved surface of the panel. Since it does not have the skirt portion 3 unlike the prior art example shown in FIG. 2, the inner curved surface can be sufficiently polished into a predetermined shape over the entire surface, although the example shown in FIG. 3 is also similar.

The second one. Thirdly, the shape of the glass bulb has a pressure-resistant structure against the pressure difference due to the vacuum inside, and the fact that it can be made smaller as the main body of a projection display device, that is, the volume of the cathode ray tube can be reduced. It is to be as small as possible.

In the example of the prior art shown in FIG. 3, FIG. 7(A)
By increasing d in FIG. 7 and θ in FIG. 7B, the pressure-resistant structure can be maintained, but at the same time, the volume of the cathode ray tube increases.

Here, it will be confirmed whether or not the same destruction as shown in FIG. 7CB) occurs in the frit protruding portion on the inside of the sealing surface in the example of the present invention.

In FIG. 6, θ of the inner portion of the sealing surface 9 can be considered in the same way as θ discussed in FIG.

Therefore, θ is desirably 60 @ or more, but θ in this example is 65” to 85°, and the glass bulb does not break due to the sharpening of the frit protrusion, so there is no problem as a pressure-resistant structure.

Further, the volume of the cathode ray tube depends on the width of the portion not used for images between the effective end and the inner side of the arrival surface.

If the protruding part of the frit comes into contact with the phosphor, there is still a possibility that the glass bulb will be destroyed, but in this example, the sealing surfaces of both the panel and the funnel were mechanically polished to eliminate irregularities from the designed curved surface. Since the deviation can be 0.2 m+n or less, the distance between the inner side of the sealing surface and the end of the phosphor screen can be 2+ nm or more in the direction perpendicular to the tube axis, unlike the example shown in FIG.

The distance between the effective end and the end of the phosphor screen should be 1 mm or more to prevent the end effect of the phosphor screen, and therefore the distance from the effective end to the inner side of the arrival surface should be 3 mm or more in the direction perpendicular to the tube axis.

Therefore, the outer diameter of the sealing surface of this embodiment can be made the same or as small as 6m+n compared to the example of the prior art shown in FIG. Therefore, it can be reduced by about 5 to 20%.

[Effects of the Invention] As described above, in the present invention, by sealing a funnel having a similarly curved arrival surface shape on the curved surface of the periphery of a panel provided with a convex curved surface, the convex inner curved surface is Optical curvature accuracy can be obtained by mechanical polishing, and the structure has sufficient pressure resistance, and the volume of the cathode ray tube can also be made smaller or equal to that of conventional cathode ray tubes.

[Brief explanation of drawings]

FIG. 1 is a side sectional view of the main part of an embodiment of the present invention, FIG. 2 is a side sectional view of the main part of a conventional cathode ray tube and optical system, and FIG. 3 is a side sectional view of the main part of a conventional cathode ray tube. Figure 4 is a panel plan view, Figure 5
The figure is a side sectional view of a glass bulb showing a normal frit sealing part, FIG. 6 is a side sectional view of a frit sealing part of an embodiment of the present invention, and FIG. 7 is a frit sealing part of a conventional cathode ray tube. FIG. ■...Glass bulb 3...Funnel 5...Inner curved surface 7...Effective light emitting surface 8...Face lO...Tube axis 12...Inner curved surface extension surface 14...Flange portion 2 Panel 4 Neck 6 Fluorescent screen 7-a Effective end 9 Sealing surface 11 Frit protrusion 13 Skirt 15 Stepped wall Part ■ Figure 4 Figure α Part (C) (C) (B) (D)

Claims (3)

[Claims] (1) A panel whose entire inner surface on the funnel side is a convex curved surface, and a sealing portion corresponding to the periphery of the curved surface of the panel is curved so as to fit closely to the periphery. A projection type cathode ray tube comprising a funnel. (2) The projection cathode ray tube according to claim 1, wherein the convex curved surface on the inner surface of the panel is mechanically polished to provide a lens with sufficient optical precision. (3) A bulb for a projection cathode ray tube comprising the panel and funnel according to claim 1 or 2.