JPS59141150A - Shadow mask-type color picture tube - Google Patents

Abstract

PURPOSE:To prevent the occurrence of color drift by providing the supporting points of a shadow mask to an envelope at positions apart from the center axises of the shadow mask and providing the fixing points between springs and the frame further outward from the said supporting points in relation to the center axises. CONSTITUTION:A shadow mask 3 arranged oppsite to a phosphor screen 2 formed inside the panel section of an envelope 1 has a mask section 5 provided with many fine holes and forming a nearly rectangular shape and a frame 6 supporting and reinforcing the mask section 5. The supporting points of the mask 3 to the envelope 1, i.e., the positions of pins 9, are provided at the same distance A from geometrical center axises X, Y of the mask 3 in the same direction. In addition, the fixing points between springs 8 and the frame 6 are provided at the same distance B further outward from the positions of the pins 9 in relation to the center axises. Accordingly, displacement between an electron beam and the phosphor due to the thermal expansion of the mask is corrected and a color picture tube with no color drift can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a shadow mask type color picture tube, and in particular, to prevent color shift due to thermal expansion of the shadow mask.

As shown in Figs. 1 and 2, the shadow mask type color picture tube has an envelope (1) and a fluorescent surface (2) formed on the inner surface of the panel of the envelope (1) facing the fluorescent surface (2). It has a shadow mask (3) having a large number of holes arranged through which electron beams pass, and an electron gun (4) disposed behind the shadow mask (3) for emitting an electron beam. .

In addition, the shadow mask (3) has a mask portion (
5) and a frame (6) that supports and reinforces the mask part (5).
, a bimetal (7) whose one end is fixed to the frame (6) to compensate for thermal expansion of the shadow mask (3) that occurs during operation of the color picture tube, and a shadow mask (3) whose one end is fixed to the bimetal (7). It is composed of a plurality of springs (8) fixedly supporting the envelope fi+.

In such a configuration, the electron beam emitted from the electron gun (4) passes through the pores of the mask part (5) and causes the fluorescent surface (2) to emit light. The hole area is about 20% of the surface area of the mask part (5), and most of the electron beams collide with the surface of the mask part (5) and heat the mask part (5). When this was measured using a 20-inch color picture tube, the high voltage was 24KV.

Under the condition of a beam current of 1000 μA, the mask part (5
) had a remarkable temperature rise in the first 10 minutes, and reached saturation in about 60 minutes, with a temperature rise of about 40°C.

On the other hand, the temperature of the frame (6) gradually increases to about 1
Although the temperature reaches a saturated state over time, such temperature rise causes color shift in the mask portion (5) due to thermal expansion, which will be explained below. That is, the mask portion (5), which was in the state A immediately after the start of operation in FIG. 6, undergoes thermal expansion due to a rapid temperature rise and changes to the state B. Therefore, on the fluorescent surface (2), it is the 4th area).

As shown in (B), the electron beam moves toward the center and causes adjacent phosphors of other colors to emit light, making it impossible to obtain a normal color image.

Note that a bimetal/I/(γ) is provided to compensate for the thermal expansion of the mask portion (5), but the effect is not as the temperature rise of the frame (6) is small during the first 10 minutes. Almost no light appears, and when the temperature of the bimetal (7) rises, the mask part (5) becomes a fluorescent surface (
2) Since it acts to move G, it produces an effect opposite to the direction of correcting the initial thermal expansion.

Further, even if the shadow mask (3) is almost saturated in terms of temperature, a similar phenomenon may occur depending on the type of image, as shown in FIG. In other words, when a screen is created where most of the background is dark and only one part is bright,
Since the temperature of the mask portion (3) corresponding to the bright portion rises significantly compared to the surrounding area, a phenomenon of local swelling occurs.

This type of image occurs particularly when graphics such as graphs are partially displayed on high-resolution color picture tubes used in computer terminal displays.

Now, the above phenomenon is collectively called the doming phenomenon because the mask part (5) swells, but in order to improve this doming phenomenon, the mask part (5) of the shadow mask (3) is made of a low-expansion metal. material, e.g. amber 1'
(36% Ni, balance Fe) etc. However, as is well known, the mask portion (5) usually has a thickness of 0.
It is thin with a thickness of 10 to 0.20 mm, and the mask part (5)
If only the mask part (5) is made of low expansion metal, it will be deformed by the thermal expansion of the frame (6).
) is made of low expansion metal, the frame (6) must also be made of low expansion gold. By making the mask part (5) and the frame (6) from low expansion metal in this way,
It has been found that although it becomes possible to greatly improve the doming phenomenon, it also causes the problems described below.

Figure 6 particularly shows the support part of the shadow mask (3) - (5) is the mask part, (6) is the frame, f8)t;
The j spring (9) is a support pin installed on the side wall of the envelope (1), and the mask portion (5) and frame (6) are both made of low expansion metal. In this case, the thermal expansion of the mask part (5) and frame (6) itself will be very small, so the bimetal (A) shown in Fig. 2 will be used.
is not necessary. In addition, the spring (8) plays a very important role in accurately supporting the entire weight of the shadow mask (8) on the envelope (1), and requires spring properties and heat resistance. Made of heat-resistant stainless steel spring material.

Now, when a color picture tube is operated with such a configuration, the amount of thermal expansion of the spring (8) is much larger than that of the mask portion (5) and the plate (6). As a result, the spring (8) pushes the shadow mask (3) away from the central axis X (in the direction of the arrow in FIG. 6). For this reason, for example, as shown in FIG. 2, the support point of the envelope (11 and spring (8)
If there are Y, , C, and the directions of the springs (8) are the same in the rotational direction, the rise in temperature of the shadow mask (3) causes the shadow mask (3) to move in the direction of the spring (
8) and the fixed point of the frame (6), and as a result, the electron beam causes a shift in the direction of the arrow in FIG. 7 with respect to the phosphor.

Of course, if the spring (8) is made of the same low expansion material as the mask part (5) and frame (6), the above problem will not occur, but as an excellent heat resistant spring material and a low expansion metal material, There are currently no matching items found.

This invention was made to eliminate the above-mentioned drawbacks, and by separating the support point between the spring and the envelope from the central axis of the shadow mask, it is possible to produce a color picture tube with excellent quality and no color shift. is intended to provide.

Embodiments of the present invention will now be described in detail based on the drawings. FIG. 8 shows a color picture tube according to an embodiment of the present invention. Part of FIG. 8 differs greatly from FIG. 2 in that the support point between the spring (8) and the envelope (1), that is, the position of the bottle (9), is in the shadow mask (3).
This means that they are shifted in the same direction by the same distance 14 from the geometrical central axes X and Y of. Now the pin (9) is the center axis x
, y is the distance A, and the distance from the bin (9) to the fixed point of the spring +83 and the frame (6) is B. Assuming that the thermal expansion coefficients of the frame (6) and the spring (8) are αF and α8 toshi, respectively, and the rising temperatures are TygTs, respectively, the spring (8) and the frame (6)
) Shadow mask (3) caused by the difference in thermal expansion of
The amount of deviation Δ is Δ=αθ・Ta−B−αy, T7・(A
+B). For example, in a 20-inch color receiving tube, the mask part (5) and the frame part (6) are made of amber material (coefficient of thermal expansion 1.2X10), and the spring (8) with a real length of 60 cm is made of 5us3Q1. When using spring material (thermal expansion coefficient 1.2 x 10 1, high pressure 2
4, when operated with a current of 1000 μA, the mask part (5
) and the frame (6) rise to about 40°C, and the spring (8) experiences a temperature rise of about 60°C.

Therefore, in the case of the conventional structure where the bin (9) is on the central axes X and Y, Δ=1.2X10X50X50-1.2X10X
40X50! ; o, o 09 (+mn), but if the device of bottle (9) is separated by 70 degrees from the central axes X and Y, Δ=1.2
X10 X30X30-1.2X10 X40X (30
+701=0.005(,ll,l) 1 , and the amount of deviation of the shadow mask (3) is reduced to about 4.

FIG. 9 shows another embodiment of the invention. A feature of the configuration shown in FIG. 9 is that the bottle (9) and the spring (8) are each cut in two places on the long side symmetrically with the Y axis. With such a configuration, by increasing the distance A' from the center axis Y, it is possible to almost completely correct the deviation, and even if there is a remainder, it is possible to compensate for it. Since the directions of deviation are opposite to each other on the left and right sides of the Y axis, there is an advantage that they cancel each other out. Of course, it is clear that the same effect can be obtained even if two support points are provided on each short side symmetrically with the X axis.

As described above, according to the present invention, the heat of the shadow mask can be reduced by simply shifting the supporting point of the shadow mask to the envelope from the central axis of the mask without complicating the structure in any way. The deviation between the electron beam' and the phosphor due to expansion can be almost completely corrected, and a high-quality color picture tube without color deviation can be obtained. In particular, the spread of high-resolution color picture tubes used for special purposes such as computer terminal displays has been remarkable in recent years, but at the same time performance requirements have become increasingly strict. The dedication of the invention can be said to be extremely large.

[Brief explanation of the drawing]

Figure 1 is a partially cutaway side view showing the configuration of a shadow mask type color picture tube, Figure 2 is a cross-sectional front view taken along ■-■ in Figure 1, and Figure 6 is for explaining the doming phenomenon of the shadow mask. Figure 4 (A) * (B) is a diagram for explaining the misalignment between the phosphor and the electron beam, Figure 5 is a front view showing the state in which the image is projected on the color picture tube, FIG. 6 is a detailed view of the support portion of the shadow mask, FIG. 7 is a diagram for explaining the direction of deviation of the electron beam, and FIG. 8 is a cross-sectional front view showing an embodiment of the shadow mask type color picture tube of the present invention. , FIG. 9 is a cross-sectional front view showing another embodiment of the shadow mask type color picture tube of the present invention. 6(1)...envelope, (3)...shadow mask, (5)... ··mask! , (e)...Frame, (8)...Spring, (9)...Pin, X, Y...Central axis. Note that the same reference numerals in the figures indicate the same or corresponding parts. Agent Makoto Kuzuno - 1 person other than C) is1 figure - 12 figure 3 figure 4 (A) (B) figure 5 figure 6 figure 7 figure 8

Claims (3)

[Claims] (1) A mask portion having a substantially rectangular shape with a large number of pores at its edges, and supporting and reinforcing this mask portion. 11) A shadow mask type with a fixed Max. In the color picture tube, the support point of the shadow mask to the envelope is located at a position apart from the central axis of the shadow mask, and the point at which the spring and frame are fixed is located at a position farther from the support point with respect to the central axis. A shadow mask type color picture tube that is featured in the SaukJi4. (2) The supporting points are present in two locations on at least one pair of opposing sides of the shadow mask, and the distances between the two supporting points from the central axis are approximately the same. A shadow mask type color picture tube according to claim 1, characterized in that: (3) The shadow mask type color picture tube according to claim 1 or 2, wherein the mask portion and the frame are made of an invar material.